CO2 to fuels and chemicals course material final version

NCCR Online Course Series
Dr. Balasubramanian Viswanathan
National Centre of Catalysis Research (NCCR)
IIT Madras
NCCR

National Centre for Catalysis Research
Online Course Series
For further information:
http://www.eprints.iitm.ac.in/

Dr. Balasubramanian Viswanathan
Carbon Dioxide to
Fuels and Chemicals
Course Materials

COURSE OUTLINE
1. CO2 Conversion – Relevance and Importance
1.1. Introduction (CO2 Utilization for Global
Sustainability)
1.2. CO2 as a Raw Material for Fuels
1.3. CO2 as a Raw Material for Organic
Chemicals
1.4. Overview on Conversion Processes
1.5. Prospects
2. Surface chemistry of CO2
2.1. Thermodynamic and Kinetic Considerations
2.2. Bonding in CO2
2.3. Adsorption of CO2 on Metal Surfaces
2.3.1. Adsorption of CO2 at sp- Metal Surfaces
2.3.2. Interaction of CO2 with Single Metal
Crystals
2.3.3. Adsorption of CO2 at Copper Surfaces
2.4. Chemisorption of CO2 at Oxide Surfaces
2.5. Reactions of Adsorption of CO2 with Co-
adsorbed Species
2.6. Alkali Metal Activation of CO2 at Metal
Surfaces
3. CO2 - Capture and Storage
3.1. Introduction and Role in Mitigating Climate
Change
3.2. CO2 - Capture
3.2.1. Conventional Chemical Absorptions
3.2.2. Emerging Methods in CO2 Capture
3.2.3. New Materials for CO2 Capture
3.2.4. Opportunities and Challenges

3.3. CO2 - Storage
3.3.1. Options and Characteristics
3.3.2. Current Status and Storage Possibilities
3.3.3. Technical and Economical Potentials
3.3.4. Implications - Local Health, Safety and
Environmental
3.4. Perspectives
4. Hydrogenation of CO2
4.1. Introduction
4.2. Homogeneous Hydrogenation of Carbon
Dioxide
4.2.1. Producing Formic Acid or Formate Salts
4.2.1.1. Via Carbon Monoxide
4.2.1.2. Via Carbonate
4.2.1.3. Via Normal CO2 Insertion into M-H
Bond
4.2.1.4. Via Abnormal CO2 Insertion into M-
H Bond
4.2.1.5. Via Hydride Transfer
4.2.2. Producing Methanol, Methane and
Carbon Monoxide
4.2.3. Producing Alkyl Formates from
Alcohols
4.2.3.2. Via Formic Acid
4.2.3.3. Methanolysis
4.2.4. Producing Alkyl Formates from Alkyl
Halides
4.2.5. Producing Formamides or
Methylamines from Amines
4.2.5.2. Via Formic Acid
4.2.5.3. Aminolysis

4.2.5.4. Via Carbamates or Carbonates
4.2.5.5. Formation of Methylamine
4.2.6. Producing diols and diol formates from
Oxiranes
4.2.7. Homogeneous Hydrogenation of
Supercritical CO2
4.2.8. Perspectives
4.3. Heterogeneous Hydrogenation of Carbon
Dioxide
4.3.1. Introduction
4.3.2. Synthesis of carbon monoxide via
reverse water gas shift reaction
4.3.2.1. Metal Based Heterogeneous
Catalysts
4.3.2.2. Reactor Aspects
4.3.2.3. Reaction Mechanism
4.3.3. Methanation of Carbon Dioxide
4.3.3.1. Metal Based Heterogeneous
Catalysts
4.3.4. Synthesis of Hydrocarbons
4.3.5. Production of Methanol
4.3.5.1. Limitation in Methanol Formation
4.3.5.3. Catalysts and Performances
4.3.5.4. Addition of Precursors
4.3.5.5. Water as an Exhibitor
4.3.5.6. Theoretical Studies
4.3.6. Synthesis of Dimethyl Ether
4.3.6.1. Hybrid Oxide-Based Catalysts
4.3.6.2. Theoretical Studies
4.3.7. Synthesis of Higher Alcohols
4.3.8. Concluding Remarks and Perspectives
5. Biochemical reduction of CO2

5.1. Introduction
5.2. CO2 Fixation
5.3. Computational Studies on CO2 Fixation
5.4. Hydrogen Utilization
5.5. CO2 Capture
5.6. Host Development
5.7. Prospects and Concluding Remarks
6. Photochemical reduction of CO2
6.1. Introduction
6.2. Basics of CO2 Photo reduction Systems
6.3. Typical Mechanisms
6.4. Limiting Steps and Strategies for
Enhancement
6.5. Comparison between different Systems
6.5.1. Biological Systems
6.5.2. Semiconductor Systems
6.5.2.1. TiO2 Based Systems
6.5.2.2. Other Semiconductors
6.5.2.3. Metal-Organic Complexes
6.5.2.4. Hybrid Systems
6.6. Summary and Outlook
7. Photoelectrochemical reduction of CO2
7.1. Introduction
7.2. Principles and Mechanisms
7.3. Homogeneous PEC reduction
7.4. Heterogeneous PEC reduction
7.4.1. Aqueous Media
7.4.2. Non-aqueous Media
7.5. The Mechanism of CO2 Reduction on
Semiconductor Surfaces
7.6. PEC Reduction of CO2 at
Semiconductor/Molecular Catalyst Junctions

7.7. Homogeneous PEC Reduction of CO2 at
Semiconductor/Molecular Catalyst Junctions
7.8. Heterogeneous PEC Reduction of CO2 by
Molecular Catalysts anchored to
Semiconductor Surface
7.9. Challenges and Prospects
8. Electrochemical reduction of CO2
8.1. Introduction
8.2. Direct Electrochemical Reduction at Inert
Electrodes
8.3. Basic Principles and Fundamentals
8.3.1. Redox and Chemical Catalysis
8.3.2. Overpotential and Turnover Frequency
in Homogeneous and heterogeneous
Cataysis
8.3.3. Understanding Catalytic Responses
through Cyclic voltammetry
8.4. Homogeneous Catalysis of Reduction of CO2
8.5. Heterogeneous Catalysis of Reduction of CO2
8.6. Bioelectrochemical Reduction of CO2
8.7. Product Selectivity in the Electrocatalytic
Reduction of CO2
8.8. Catalyst Stability, Activity Degradation and
Mitigation Strategies
8.9. Technological Challenges in Electroreduction
of CO2
8.10. Summary and Prospects
References
9. Perspectives - CO2 Conversion to fuels and
Chemicals

TABLE OF CONTENTS
Lectures (Page No) Topics
Lecture 1 (1) Introduction
Lecture 2 (6) Attempts at Carbon Dioxide
Reduction
Lecture 3 (14) Hydrogenation of Carbon
Dioxide to CO, CH3OH,CH4
Lecture 4 (35) Metal Cathodes employed for
Photoreduction of Carbon
Dioxide
Lecture 5 (58) Photoelectroreduction of
Carbon Dioxide
Lecture 6 (79) Reforming of Carbon Dioxide
with Methane for Synthesis
Gas
Lecture 7 (112) The concept of Trireforming
Lecture 8 (147) Carbon as a stock for
Chemicals and Fuels
Lecture 9 (172) Fundamentals of
Electrocatalytic Redution of
CO2 metal surfaces only to
small molecules and fuels.
Basic Information
Lecture 10 (215) Fundamentals of
Electrocatalytic Reduction of
CO2 on Surfaces to Molecules
and Fuels
Lecture 11 (241) The Question on
Electrocatalytic Reduction on
CO2
Lecture 12 (268) Synthesis of Linear
Carbamates

Lecture 13 (290) Reflection on the
Electrochemical Reduction of
Carbon dioxide on Metallic
Surfaces
Lecture 14 (319) Electrocatalytic Reduction of
Carbon Dioxide
Lecture 15 (351) Bocarsly’s work on CO2
reduction from 1994
Lecture 16 (368) Photocatalytic Reduction of
Carbon Dioxide by Metal
complexes : Single Component
System
Lecture 17 (390) Muticomponent Systems for
Carbon dioxide Reduction
Lecture 18 (411) Carbon Dioxide Reduction on
Semiconductors
Lecture 19 (435) Reflections on Heterogeneous
Photocatalysis
Carbon Dioxide : Product
Analysis and Systematics
Carbon Dioxide: Product
Analysis and Systematics.
Continuation
Lecture 22 (500) Why Titanium Dioxide
Receives Maximum Attention?
Lecture 23 (524) Other Semiconductors Used
for Carbon Dioxide
Conversion
Lecture 24 (541) Biochemical Routes For
Carbon Dioxide Reduction :
An Introduction
Lecture 25 (571) Concluding Remarks

CARBON DIOXIDE TO FUELS AND
CHEMICALS – INTRODUCTION
LECTURE 1
• WHY THIS NEW COURSE ?
• WHAT WILL BE THE COVERAGE?
• WHAT WILL NOT BE CONSIDERED IN THIS AREA?
• WHAT WILL BE THE PARTICIPANT GET?
• COVERAGE LEVEL- MOSTLY UP-TO-DATE AND
CURRENT SCIENTIFIC LITERATURE
1

CARBON DIOXIDE TO FUELS AND
CHEMICALS
• SOME FUNDAMENTAL KNOWLEDGE ASSUMED
1. CHEMISTRY
2. PHYSICS
3. ELECTRONIC STRUCTURE OF SOLIDS
4. ELECTRONICS
5. MATERIALS
6. REACTOR DESIGNS
7. PROCESS CONTROL 2

POSSIBLE COVERAGE
(MAY INCLUDE OTHER ASPECTS)
• INTERFACES WITH RESPECT TO SEMICONDUCTOR
• PRINCIPLES OF PEC AND ITS RELEVANCE TO PHOTOCATALYTIC
REDUCTION
• MATERIALS FOR PHOTOCATALYSIS
• POSSIBLE PHOTOCATALYTIC REACTIONS
• PHOTOSYNTHESIS AND RELATED AREAS
• ELECTROCATALYSIS
• REFORMING
• BIOCHEMICAL REDUCTION
3

TENTATIVE SYLLABUS FOR THE COURSE
• Chapter 1: Introduction and analysis of carbon dioxide sources. Harnessing
carbon dioxide methods. Carbon dioxide is a waste or wealth for carbon dioxide
conversion. (2-3L)
• Chapter 2: Reforming Carbon dioxide possibilities and features (2-3L)
• Chapter 3: Electrochemical reduction of carbon dioxide to chemicals (4-5L)
• Chapter 4: Photochemical conversion of carbon dioxide (2-3L)
• Chapter 5: Photo electrochemical/ Photocatalytic conversion of carbon dioxide
(4-5L)
• Chapter 6: Biochemical Possibilities (1-2L)
• Chapter 7: Future possibilities (1-2L)
WARNING: THE COURSE WILL COVER THIS ASPECTS IN ABOUT 20-25
LECTURES THERE ARE OTHER ASPECTS WHICH WILL NOT BE
COVERED. KINDLY NOTE THIS. 4

CARBON DIOXIDE TO FUELS AND CHEMICALS
ATTEMPTS AT CARBON DIOXIDE REDUCTION
LECTURE 2
FEBRUARY 14
6

Course on Carbon dioxide to Chemicals
and Fuels
PRESENTATION - THREE
17TH February 2014
On Line Course of NCCR
(Total Number of Projections for this Lecture is 21)
14

The thermodynamics are neutral or favorable because of the production
of water from hydrogen but economics are unfavorable for the same
reason
Hydrogenation of CO2 → CO, CH3OH, CH4
P.G.Jessop, Chem. Rev. 95 (2), (1995) 259
CO2(aq) + H2(aq) -------- CO(aq) + H2O(l)
ΔG 0 = 11 KJ/mol; ΔH 0 = 11KJ/mol;ΔS0 = - 8 J/(mol.K)
15

Diols and Diol Formates from Oxiranes
CO2 with methyloxirane in the presence of H2 →1,2- diols & their formates
in addition to cyclic carbonate
P.G.Jessop, Chem. Rev. 95 (2), (1995) 259
16

Catalytic Hydrogenation of CO2 in Supercritical CO2
in the presence of Additional substrates
The hitherto solely highly selective catalytic C–C coupling reaction
using CO2 as substrate can also be realized in compressed CO2
17

Cycloco-Oligomerisation of CO2 & Alkynes in compressed
Carbon Dioxide
Styrene or Cyclooctene react in a catalytic system → Epoxidation as
well as the reaction to cyclic carbonates
18

• The potential of this types of catalytic reaction is by
no means yet explored.
• The field of homogeneous catalysis in compressed
CO2 will attract major interest in future.
• The development of new CO2 soluble catalysts,
understanding how to prevent deactivation
reactions with CO2 as well as the control of the fine
tuning of the reaction parameters in supercritical
CO2 are starting points to discover new selective
catalysis in supercritical CO2.
19

If pure hydrogen from renewable sources
(e.g. hydroelectric power) is available, an
easiest method for converting it to methanol
with CO2 is to combine both gases in a
thermal reactor at about 220 °C under
moderate pressure (20 - 50 bar).
A. Bill, A. Wokaun, Energy Convers. Mgmt. 38,
(1997) 415
20

Catalyst: Fe supported on MY-zeolite (M=Li, Na, K, Rb)
Hydrogenation of CO2 to hydrocarbons over group VIII metals proceeds in two
steps.
1. Partial reduction of CO2 to CO by reverse water gas shift (RWGS) reaction
2. Subsequent F-T synthesis
S.S. Nam et al., Applied Catalysis A: General 179 (1999) 155
21

S.S. Nam et al., Applied Catalysis A: General 179 (1999) 155
22

(Cu-La2 Zr207 ) → Alcohols & HC from CO + H2 & CO2 + H2
feeds
Addn. oxides, e.g., ZnO or ZrO2 → Good MeOH selectivity
Addn. trans. metal promoter like Co → C2 + alcohols & C2 +
hydrocarbons
Cu-La2 Zr207 + HY zeolite → Mainly C2 + hydrocarbons
Hydrogenation of CO & CO2 → Methanol, Alcohols & HC
R. Kieffer et al., Catalysis Today 36 (1997) 15
23

CO2 to Hydrocarbons
Fe promoted with Cr & Mn → Conversion of CO2 ↑& Selectivity of C2 - C4 alkenes↑
Zn promoted iron catalyst → Unusually very high selectivity for C2- C4 alkenes
With smaller ratio of Zn in Fe:Zn → Alkene selectivity↑
S.S. Nam et al., Energy Convers. Mgmt. 38, (1997) 397
24

CO2 to Hydrocarbons
Zn promoted iron catalyst → Unusually very high selectivity
for C2- C4 alkenes
With smaller ratio of Zn in Fe:Zn → Alkene selectivity↑
S.S. Nam et al.,
Energy Convers. Mgmt. 38, (1997) 397
25

CO2 –Hydrogenation to Ethanol
Well balanced multi-functional FT-type composite catalysts
Fe-based Cu-based Pd/Gd addition
↓ ↓ ↓
CO2 to CO C–C bond formation Stabilize optimum
reductive –OH group formation state of catalyst
Difference in alcohol distribution for different catalysts
T.Inui et al., Applied Catalysis A: General 186 (1999) 395
26

Electrochemical Reduction of CO2
M. A. Scibioh & B. Viswanathan, Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004.
27

Reduction of CO2 under Protic, and Aprotic Conditions
Protic
Aprotic
Aq. solutions leads to formic acid production (C1 products)
M. A. Scibioh & B. Viswanathan, Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004. 28

Reduction of CO2 under Partially aprotic conditions
Aprotic solvents favor dimerization of CO2 leading to Cn products
M. A. Scibioh & B. Viswanathan, Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004. 29

Variation of solubility of CO2 with pressure for several solvents at T = 293K and 333K
Solubility of CO2
30

Solubility of CO2 with temperature for several solvents
used in electrochemistry
Solubility of CO2
31

CO2 Electro-reduction on sp Metal Electrodes
(kindly read next three slides together)
M. Jitaru, J. Appl. Elec. Chem 27 (1997) 875
32

(kindly read this slide with the previous slide)
M. Jitaru, J. Appl. Elec.Chem 27 (1997) 875
33

M. Jitaru , J. Appl. Elec. Chem. , 27 (1997) 875
(kindly read this slide with previous two)
34

and Fuels
PRESENTATION - FOUR
20TH February 2014
(Total Number of Projections for this Lecture is 22 )
35

Periodic Table for CO2 Reduction Products
At –2.2 V /SCE in low temperature, 0.05 M KHCO3 solution
Y Hori et al., J. Chem. Soc. Chem. Commun, (1987) 728 36

Summary of Metal Cathodes Employed for
Electroreduction of CO2
M. A. Scibioh & B. Viswanathan, Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004
38

Influence of Pressure on Mechanism – An Example
Comparative mechanism of high-pressure CO2 electroreduction (A) &
Electroreduction of CO2 at atmospheric pressure (B) on Ni cathode
M. Jitaru, J. Appl. Elec.Chem ., 27 (1997)875
39

Electro-catalytic Reduction of CO2
(a) Molecular electrocatalysts in solution; (b) Cathodic materials modified by
surface deposition of molecular electrocatalysts
M. A. Scibioh & B. Viswanathan, Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004
40

Electrochemical reduction of carbon dioxide in
copper particle suspended methanol
Adopted from the publication of S.Kaneco et al
41

Electrochemical reduction of carbon dioxide in copper
particle suspended methanol
Reproduced from the publication of S.Kaneco et al 42

• Phthalocyanine complexes
• Porphyrin complexes
• Metal complexes of 2,2’-bipyridine & related
ligands
• Phosphine complexes
• Metal clusters and polymetallic complexes
• Biphenanthroline hexaazacyclophane complexes
• Azamacrocylic complexes
• Macrocyclic ligands related to macromolecular
functions
J.P. Collin & J.P. Sauvage, Coord. Chem. Rev. 93 (1989) 245
Transition Metal Complexes – Electro-catalysts to reduce CO2
43

Transition metal complexes – Electrocatalysts to reduce CO2
Porphyrins and phthalocyanines Tetraaza macrocyclic complexes
44

J. Costamagna et al., Coord. Chem. Rev.: 148 (1996) 221
Fuels from the reduction of CO2
45

Coordination Compounds with Acyclic Ligands
General cycle for the generation of CO2 reduction products with various complexes of
acyclic ligands as electro-catalysts [Also valid for electro-catalysis with macrocyclic
ligands]
46

Coordination compounds with macrocyclic ligands
Cyclam & cyclam derivatives
47

Porphyrin and phthalocyanine derivative complexes
48

• Binding of CO2 to a metal centre leads to a net electron transfer from
metal to LUMO of CO2 & thus leads to its activation.
• Hence, coordinated CO2 undergoes reactions that are impossible for
free CO2.
• Many stoichiometric & most catalytic reactions involving CO2
activation proceed via formal insertion of CO2 into highly reactive
M–E bonds → formation of new C–E bonds.
• These reactions might not necessarily require strong coordination of
CO2 as in stable complexes, but are generally initiated by
nucleophilic attack of E at Lewis acidic carbon atom of CO2.
• Weak interaction between the metal & the lone pairs of one oxygen
atom of CO2 may play a role in supporting the insertion process.
• Although we are more knowledgeable about CO2 activation, the
effective activation of CO2 by transition metal complexes is still a
goal!
CO2 Activation by Metal Complexes- Perception
49

Direct photo-reduction of CO2
At the surface of
semiconducting materials; p-
Si, p-CdTe, p-InP, pGaP, n-
GaAs
Direct photo-reduction of CO2
Three principles of photo-
catalytic cycles of CO2
reduction
D. Walther et al.,Coord Chem Rev 182 (1999) 67 50

Photo-reduction of CO2
T. Xie et al., Mater Chem Phy 70 (2001) 103
Energy band modes of an n-type
semiconductor with a Schottky-type barrier:
(a) band–band transition;
(b) surface state population transition. Vs
and Vs0,
surface potential difference; CB, conduction
band; VB, valence band; Et, surface state
level; EF, Fermi level.
Pd/RuO2/TiO2 photoreduction of CO2
51

L. G. Wang et al., Phy. Rev Let. 89 (7) (2002) 075506-1
Role of the Nanoscale in Surface Reactions: CO2 on
CdSe
Electron transfer from surfaces or
nanocrystals to the CO2 molecule. The
localized energy level near the valence band
edge is caused by a Se vacancy
The total energy of a CO2 molecule
chemisorbed in a Se vacancy on the CdSe (1010)
surface as a function of the vertical distance
between C atom & ideal truncated surface
52

Photocatalytic reduction of CO2
Photocatalytic reduction of CO2 with H2O on the anchored
titanium oxide
M. Anpo, J.Electroanal Chem 396 (1995) 21
53

Photocatalytic reduction of CO2 : Formation of MeOH
Reaction time profiles:
To produce CH4 (a) &
CH3OH (b) on TiO2/Y-
zeolite
Product distribution: Photocatalytic reduction
.
The yields of CH4 and
CH3OH in the Photo-
catalytic reduction of CO2
with H2O TiO2 powder (a),
TS-1 (b), Ti-MCM-41 (c),
Ti-MCM-48 (d), Pt-loaded
Ti-MCM- 48 (e)catalysts.
H. Yamashita et al., Catalysis Today 45 (1998) 221
CO2 with H2O: anatase TiO2
powder (a),Imp-Ti-oxide/Yzeolite
(10.0 wt% as TiO2) (b), Imp-Ti
-oxide/Y-zeolite (1.0 wt% as TiO2)
(c), Ex-Ti-oxide/Y-zeolite
(1.1 wt% asTiO2) (d),Pt-loaded
ex-Ti-oxide/Y-zeolite (e) catalysts
Photocatalytic reduction of CO2 : Formation of MeOH
54

PHOTOCHEMICAL REDUCTION OF CO2
Formation of HCOOH Formation of Methane
55

J.P. Collin & J.P. Sauvage ,Coord. Chem. Rev. 93 (1989) 245
HOMOGENEOUS SYSTEM MICROHETEROGENEOUS SYSTEM
Light driven catalytic cycle reducing CO2.
Light reaction: terphenyl (TP) -
photocatalyst, triethylamin (TEA) -
reductive quencher (electron donor).
Dark reaction: cyclam cobalt complex -
electron relay (a) oxidising - terphenyl
radical anion & (b) reducing CO2.
Light driven carboxylation of lactic acid to
form malic acid (MV2+ , methylviologen
dication, FNR, ferredoxin-NADPreductase;
ME, malic enzyme).
56

Photo-reduction of CO2 - Perception
Unsolved Problems!
• TON (mol reduction product of CO2 / mol catalyst) are still low
• Efficiencies of the reactions is unsatisfactory-both the amount of reduction products of CO2
(usually C1 products) & oxidation products of the sacrificial donor
• The tuning of the single components w.r.t. their redox potentials, life times and selectivity is
not well understood.
• Necessary to device systems which do not require sacrificial donors light energy is also used
for degradation of sacrificial donors, influencing the energy balance of the reactions unfavorably
• Macro-cyclic complexes of transition metal ions- satisfy the requirements of a useful relay.
They may play a dual role as a catalysts and relays
• Even with transition metal complexes – Reduction products have not been of great economic
value (usually only C1 products)
• Multicomponent systems containing photoactive center, electron relays and/or molecular
electro-catalysts in addition to possible micro-heterogeneous systems will be discovered. 57

and Fuels
PRESENTATION - FIVE
24TH February 2014
58

PHOTOELECTROREDUCTION OF CO2
Principle An Example
Appealing Approach!
An important energy input contribution from light might be
expected, thus diminishing electricity consumption
59

A study on photo-electro-reduction of CO2
Possible Mechanistic Route
By insitu-IR
J, O‘M. Bockris & J. C. Wass, Mater Chem Phys, 22 (1989) 249
Photovoltomogram, λ= 560 nm (0.5 mW cm2)
60

Metal islet catalysts deposited on a p-CdTe
electrode in DMF-0.1 M TEAP/5% H20
MPc catalysts adsorbed on a p-CdTe electrode
in DMF-0.1 M TEAP/5% H 0
Product analysis results for CO2 reduction on phthalocyanine/p-CdTe
Study on photo-electro-reduction of CO2
61

Current-potential curves for trinuclear carbonyl catalysts
adsorbed on a p-CdTe electrode in DMF-0.1 M TEAP/5%
H20.
Product analysis results for CO2 reduction on carbonyl/p-CdTc
Iron carbonyl is the best among the three carbonyls studied
Study on Photo-electro-reduction of CO2
62

Product analysis results
Current-potential curves for crown ether catalysts added to the electrolyte for a p-CdTe
electrode in DMF-0.1 M TEAP/S% H20
Study on photo-electro-reduction of CO2
63

Catalytic shift (ΔE) times the CO faradaic
efficiency for metal catalysts on p-CdTe as a
function of M-O bond energy
For metal-phthalocyanine catalysts on p-
CdTe as a function of M-O bond energy
ΔE values for CO production are linear
Catalytic shift (ΔE)
J, O‘M. Bockris & J. C. Wass
Mater Chem Phys, 22 (1989) 249
64

For trinuclear carbonyl catalysts on p-CdTe
as a function of M-C bond energy
Catalytic Shift (ΔE)
65

• Fertilization of open waters to increase primary
production & hence to absorb more carbon in
fixed form
• Disposal of captured carbon dioxide directly
into oceanic waters
• Injection of captured CO2 into sub-seabed
geological formations
CARBON MANAGEMENT
66

• High cost of capturing, processing, &
transporting anthropogenic CO2
• Incomplete understanding of reservoir
processes
• Underdeveloped monitoring & verification
technologies
• Unclear emissions trading regulations
• Potential conflicts of interest between
sequestration & EOR or natural gas recovery
Barriers to wider implementation
CO2 sequestration
67

The technology is in its infancy and unproven
• The technology is too costly
• Not enough is known about the long-term storage of
CO2
• The capture and storage of CO2 are seen as being
energy intensive
• The option presents an enormous engineering and
infrastructure challenge
• It is not a long-term solution
Barriers can only be overcome by research and design
& effective demonstration of the technology
Public Perception
CO2 Sequestration
68

Perceptions: Large-Scale CO2 Utilization &
Sequestration
69

Utilization
TRASPORTATION COST
71

WHAT HAS BEEN COVERED SO FAR
The electronic structure of Carbon dioxide
72

CHEMICAL REDUCTION OF
CARBONDIOXIDE
ADDING HYDROGEN AND ELIMINATING WATER
M. A. Scibioh & B. Viswanathan,Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004.407-462
73

The possible electrochemical Reactions and the corresponding
potentials
REACTION E0 ΔG0 (Kcal/mol)
H2O to H2(g)+ 0.5O2(g) 1.23 56.7
CO2 + H2 to HCOOH 5.1
CO2 + H2O to HCOOH + 0.5O2 1.34 61.8
CO2 + H2 to CO + H2O 4.6
CO2 to CO + 0.5O2 1.33 61.3
CO2 + 3H2 to CH3OH + H2O -4.1
CO2 + 4H2 to CH3OH + 2 H2O -31.3
CO2 + 2 H2O to CH3OH + 1.5O2 1.20 166
CO2 + 2 H2O to CH4 + 2 O2 1.03 195 74

SECTOR % COMPOSITION
Land Use and Forestry 17
Industry 19
Residential and Commercial 8
Buildings
Transportation 13
Power 26
Waste and Waste Water 3
Sector-wise contribution of CO2 emissions
75

Scheme.1.Chemical Transformations of CO2 76

(1) the magnitude of environmental consequences,
(2) the economic costs of these consequences,
(3) options available that could help avoid or diminish the
damage to our environment and the economy
(4) the environmental and economic consequences for each
of these options
(5) an estimate of cost for developing the technology to
implement these options and
(6) a complete energy balance which accounts for energy
demanding steps and their costs.
Barriers for Further Progress
77

Suggested Some References
1. A Beher, Carbon Dioxide Activation by Metal Complexes VCH, Weinheim (1988)
2. Catalytic Activation of Carbon Dioxide (ACS Symp Ser) (1988) 363
3. M. Aulice Scibioh and V.R. Vijayaraghavan, J. Sci. Indus. Res., 1998, 57, 111-123.
4. M. Aulice Scibioh and B. Viswanathan, Proc. Indn. Natl. Acad.Sci., 70 A (3), 2004, 407-462
5. M. Aulice Scibioh and B. Viswanathan, Editor. Satoshi Kaneco, Japan, Photo/ Electrochemistry
and Photobiology for Environment,Energy and Fuel, 2002, 1- 46, ISBN: 81-7736-101-5.
6. F. Bertilsson and H. T. Karlsson, Energy Convers. Mgmt Vol. 37,No. 12, pp. 1725-1731, 1996
7. I. Omae, Catalysis Today 115 (2006) 3352
8. M. Gattrell, N. Gupta and A. Co, J. Electroanal Chem, 594, (2006),1-19.
9. Enzymatic and Model Carboxylation and Reduction Reaction for Carbon Dixoide Utilization
(NATO ASF Ser C 314 (1990)
10. Electrochemical and Electrocatalytic Reaction of Carbon Dioxide (Eds B P Sullivan, K Krist and
H E Guard) Elsevier Amsterdam (1993)
11. M M Halmann Chemical Fixation of Carbon Dixoide CRC Boca Raton (1993) D Walther Coord
Chem Rev 79 (1987) 135.
12. P. G. Jessop, F. Jo, C-C Tai, Coordination Chemistry Reviews 248 (2004) 2425-2442
78

and Fuels
PRESENTATION - SIX
27TH February 2014
79

FOCUS
This Lecture mainly deals with
reforming of carbon dioxide with
methane for synthesis gas
80

COVERAGE
THERMODYNAMICS
TEMPERATURE RANGE
CATALYST SYSTEMS
ROLE OF THE COMPONENTS
OTHER RELEVANT REACTIONS
REACTORS
81

Reproduced from Hongyan Ma presentation 82

Halmann, Martin M. (1993). "Carbon Dioxide Reforming". Chemical fixation of carbon dioxide: methods for recycling CO2
into useful products. CRC Press. ISBN 978-0-8493-4428-2
Carbon dioxide reforming (dry reforming) is for
producing synthesis gas by the reaction of CO2 with
hydrocarbons especially methane. Synthesis gas is
conventionally produced via the steam reforming of
naphtha. This has relevance to the concern on the
greenhouse gases to global warming. It is a method
of replacing steam as reactant with carbon dioxide.
The methane carbon dioxide reforming reaction is:
CO2 + CH4 → 2H2 + 2CO
Halmann, Martin M. (1993). Carbon di oxide reforming. Chemical
fixation of carbon dioxide: methods for recycling CO2 into useful
products. CRC Press. ISBN 978-0-8493-4428-2
DRY REFORMING OF CARBON DIOXIDE
83

Mun-Sing Fan et al., ChemCatChem, 1,192 (2009)
Catalyst Technology for carbon dioxide reforming with methane to synthesis gas
84

Carbon dioxide Reforming Scheme
• O=C=O Methane
Catalyst(?)
SYN GAS (CO /H2)
TRANSPORT SECTOR
AUTOMOBILES,
DIESEL ENGINES
AEROPLANES
STORAGE
Gas stations
Storage in gas
Pressure vessels
85

RELEVANT REACTIONS
• (1) CH4+ CO2 ↔ 2CO + 2H2 ΔH0
298=247 ΔG0=61770-67.3T
• (2) CH4+H2O ↔CO + 3H2 =206;
• (3) CH4↔ C + 2H2 75; 2190-26.5T
• (4) 2CO↔CO2+ C -171; 39810+40.9T
• (5) CO2+ H2 ↔ CPO + H2O 41; -8545+7.84T
• (6) CO + H2↔ C + H2O -131
• The first figure refer to the ΔH0
298 in kJ/mol
• The second figure refer to ΔG0
• Reaction T (K)
• DRM 913
• Methane cracking (3) 830
• Boudouard Reaction (4) 973
• RWGS (5) 1093
• Limiting temperatures for different reactions DRM 86

Catalyst component Proposed mechanism
Metal active site (M(as)) CH4 + 2M(as)↔CH3-M(as)+ H-M(as)
CH3-M(as)+ M(as)↔CH2-M(as) + H-M(as)
CH2-M(as) + M(as)↔CH-M(as)+H-M(as)
CH-M(as) + M(as)↔C-M(as) + H-M(as)
2h-M(as)↔ H2(g) +2M+(as)
Catalyst component and corresponding proposed mechanism
87

Catalyst component Proposed Mechanism
Support ( Acidic support)
Support ( BASIC SUPPORT)
CO(g)↔CO2(metal)
CO2(metal)↔CO(metal) + O(metals)
CO(metal)↔CO(g)
CO2(g) ↔ CO2(support)
CO2(support) + O2-
(support) ↔CO3(support)
2-
2H(metal)↔ 2H(support)
CO3(support)
2-
+2H(support)↔HCO3
-
(s) + OH-
(s)
CO(support)↔CO(g)
88

Catalyst component Proposed Mechanism
Promoter CO(g)↔CO(support)+ O(promoter)
O(promoter) + C(metal) ↔CO(g)
89

Catalyst Temp.
(K)
Conversion % Remarks
NiO/CaO/CoO-MgO/MgO 873-1123 80-100(CH4) High selectivity
Ru/SiO2/MgO/TiO2 973-1073 28-35 deactivation
Co/SiO2/MgO-SiO2 873 41-46(CH4) Better than Ni
Ir/Al2O3 873 18-50 preparation
Different types of catalysts used for the DRM reaction
90

Characterization of DRM reaction catalysts
Catalyst type Techniques Aspects
Monometallic supported catalysts
Ni/CeO2,Pt/Al2O3,Ni/SiO2,Ru/SiO2,Ir/Al2O3
XRD,TPR,XPS,EPR,TPO,TPH Metal dispersion,
reducibility, coke
Bimetallic supported catalysts Ni-Co, Ni-
Rh
XRD,XRF,XPS,TG,DTA,
chemisorption
Composition,
phase, coke, metal
dispersion
Metal oxide supported catalysts CoO-
MgO/CeO2
TPO, XRD,XPS Resistance to C,
phases
Promoted supported catalysts on
alumina
Ni-K,Ni-Sn,Ni-Ca,Ni-Mn
TG,TPH,TPR,XRD,TEM,TPO Carbon, active
sites, reduction
behaviour
Perovskite catalysts, LaNiOx, LaNiMgOx,
LaNiCoOx, LaSrNiOx,LaCeNiOx
XRD,TPR,TPO,TEM,SEM Calcination temp,
structure, phases,
reversibility,
sintering
91

92

94

96

97

CO2 reforming on Ni/Cu catalyst
• Factors like addition of copper to supported Ni system
surface geometry, electronic structure, the extent of CH2
species, and hydrogen spill over contribute to Ni-Cu/support
catalyst in CO2 reforming.
1. 1 wt% Cu , 8 wt% Ni/SiO2 stability >7600C
2. active site is stabilized by Cu
3. Carbon formation same as Ni and Ni/Cu
4. Cu-Ni species inhibit the C formation
5. Cu addition promotes CH4 cracking and inactive Coke does
not accumulate on Cu/Ni catalyst
• H-W Chen et al., Catalysis Today 97,173 (2004) 98

• TD favours carbon formation
• Noble metals and Ni alleviate this problem
99

Summary of Catalytic Reforming of CO2/CH4
Catalyst
CO2/CH4 conversion (%) Temp (K)
Ni/NaY 1:1 84.0 873
Ni/Al2O3 1:1 36.3 873
Ni/SiO2 1:1 14.9 873
Pd/NaY 1:1 29.2 873
Pt/NaY 1:1 156.3 873
KNiCa/Al2O3 1:1 17 923
KNiCa/SiO2 1:1 21 923
KNiCa/ZSI 1:1 78 923
Rh/TiO2 1:1 88.2 893
Rh/SiO2 1:1 5.1 893
Rh/Al2O3 1:1 85.1 893
Ni/Al2O3 1:1 80−90 1050
Pd/Al2O3 1:1 70−75 1050
Ru/Al2O3 1:1 60−70 1050
Rh/Al2O3 1:1 85−90 1050
Ir/Al2O3 1:1 85−90 1050
Wang et al, Energy & Fuels, 10,896 (1996) 100

Catalyst Conversion % Temperature, K
Ni/NaY/Al2O3/SiO2/ 15-85 873
Pd/NaY/Al2O3/MgO 29, 70-75,84 873,1050,963
Pt/NaY/MgO 156,85 873,963
Rh/TiO2/SiO2/Al2O3 88,5,85 893
Ni/Al2O3/MgO-Al2O3/CaO-Al2O3/CaO-TiO2Al2O3 75,,100,86,88,100 1050,1213
Ru/Al2O3/Eu2O3/MgO 60,75,90, 1050,923,963
Ir/Eu2O3/Al2O3/ 88,85 1000,1050
Table Catalytic reforming of CO2/CH4 with 1:1 mixture on various
catalysts collected from literature
101

Co,MgO/C 1:1 65−75 923
Ni/CaO-MgO 1:1 80 1123
Rh/Al2O3 1:1 85 1073
Ru/Al2O3 1:1 83 1073
Ru/Eu2O3 1:1 75 923
Ir/Eu2O3 1:1 88 1000
Ru/MgO 1:1 90 963
Rh/MgO 1:1 88 963
Pt/MgO 1:1 85 963
Pd/MgO 1:1 84 963
Ni/Al2O3 2.38:1 100 1213
Ni/MgO−Al2O3 2.38:1 86 1211
Ni/CaO−Al2O3 2.01:1 88 1211
Ni/CaO−TiO2−Al2O3 2.01:1 100 1223
Summary of Catalytic Reforming of CO2/CH4
Wang et al, Energy & Fuels, 10,896 (1996)
102

metal activity metal loading (wt %) temp (K)
1. Al2O3
Rh > Pd > Ru > Pt > Ir 1 823
Rh>Pd>Pt>Ru 0.5−1 823−973
Ir > Rh > Pd > Ru 1 1050
Ni>Co >>Fe 9 773−973
Ni>Co>> Fe 10 1023
Ru > Rh 0.5 873
Ru > Ru 0.5 923−1073
2. SiO2
Ru > Rh > Ni > Pt > Pd 1 973
Ni > Ru > Rh >Pt > Pd >> Co 0.5 893
3. MgO
Rh > Ru > Ir > Pt > Pd 0.5 1073
Ru > Rh > Ni > Pd > Pt 1 973
Ru> Rh ~Ni > Ir > Pt > Pd 1 823
Ru > Rh > Pt > Pd 1 913
4. Eu2O3
Ru > Ir 1−5 873−973
5. NaY
Ni > Pd > Pt 2 873
Catalytic Activities of Metals on Various Supports
Wang et al, Energy & Fuels, 10,896 (1996) 103

Effect of Support on Catalyst Activity
activity order
temp (K) metal loading (wt %)
Ru
Al2O3 > TiO2 > SiO2 893 0.5
TiO2 > Al2O3 > SiO2 893 0.5
Pd
TiO2 > Al2O3 > NaY > SiO2 > MgO > Na-ZSM-5 773 5
TiO2 > Al2O3 > SiO2 > MgO 773 1
Rh
YSZ > Al2O3 >TiO2 >SiO2>> MgO 923 0.5
Al2O3 > SiO2 > TiO2 > MgO 773 1
Ni
Al2O3 > SiO2 800−1000 40
Al2O3 > SiO2 873 10
NaY > Al2O3 > SiO2 873 2
SiO2 > ZrO2 > La2O3 > MgO > TiO2 823 4
Wang et al, Energy & Fuels, 10,896 (1996)
104

Synthesis gas over Ni/ZrO2-SiO2
• Helium treatment –generate
distribution of active Ni sites
• Heterogeneity of Ni sites on
hydrogen treatment
• CO treatment carbon covered
metallic sites deactivation
Dapeng Liu, Yifan Wang, Daming Shi, Xinli Jia, Xin Wang, Armando Borgna,
Raymond Lau and Yanhui Yang, Internationl Journal of Hydrogen energy,37,10135 (2012) 105

CO2 reforming on Co-Pd/Al2O3
• Co containing promoted by noble
metal (Pd) with respect to activity,
selectivity, resistance to carbon
formation Co-Pd/Al2O3 depend on
composition and process
conditions. Oxygenates are
produced.
Sh.S.Itkulova et al., Bull Korean chem.soc., 26,2017 (2005) 106

Stable CO2 reforming over modified Ni/Al2O3
• Ni/Al2O3 promotedby
C,Cu,Zr,Mn,Mo,Ti,Ag and Sn
• Cu,Co,Zr improved Mn reduces
carbon formation
Jae-Sung Choi, Kwang-ik Moon, Young Gul Kim, Jae Sung Lee, Cheol-Hyun Kim, and
David L.Trim, catalysis Letters, 52,43 (1998)
107

Table 2. Catalyst component and corresponding proposed mechanism.
Catalyst component Proposed mechanism
Metal active site (M(as)) CH4+2 M(as)⇌CH3-M(as)+H-M(as)
CH3-M(as)+M(as)⇌CH2-M(as)+H-M(as)
CH2-M(as)+M(as)⇌CH-M(as)+H-M(as)
CH-M(as)+M(as)⇌C-M(as)+H-M(as)
2 H-M(as)⇌H2(g)+2 M(as)
Support Acidic support:
CO2(g)⇌CO2(metal)
CO2(metal)⇌CO(metal)+O(metal)
CO(metal)⇌CO(g)
Basic support:
CO2(g)⇌CO2(support)
CO2(support)+O 2-
(support) ⇌ CO3
2-
(support)
2 H(metal)⇌2 H(support)
CO3
2-
(support) +2 H(support)⇌ HCO3
-
(support) + OH-
(support)
CO(support)⇌CO(g)
Promoter CO2(g)⇌O(promoter)+CO(support)
O(promoter)+C(metal)⇌CO(g)
Mun-Sing Fan et al., ChemCatChem.,1,192 (2009)
108

Processes occurring in the catalytic membrane reactor during the combined POM/DRM reaction
109

In this work, we have performed first principle calculations to study the
adsorption of hydrogen on combined TM-decorated B-doped graphene
surface. We found that transition metals Ni, Pd and Co show the great
advantage of both hydrogen adsorption and H spill over method in the
hydrogen storage process. Our results show that all the calculated
activation barriers are sufficiently low for the H diffusion along the Ni-
Pd and Pd-Co paths, indicating that a fast H diffusion on the substrate
can be achieved under ambient conditions. Moreover, the calculated
desorption energies of the hydrogen molecules on these TM decorated
B-doped surface are close to the energies required to obtain reversible
storage at room temperature and hence the proposed TM decorated
boron doped graphene surface will be a good candidate to enhance the
reversible hydrogen storage capacity.
110

Different isotope dependences on reaction kinetics have been observed during RBM
of pure Mg powder and Mg–Ti powder mixtures. For pure Mg, gas absorption
depends on the isotope nature and the rls is assigned to H(D)-diffusion in MgH2
phase. In contrast, in presence of Ti, the diffusion lengths in MgH2 phase are
strongly shortened due to the abrasive properties of TiH(D)2. Thus, gas absorption
turns to be isotope independent and the rls is assigned to the milling efficiency.
Analysis of hydrogen and deuterium kinetic curves under isothermal conditions
(548 K) has highlighted outstandingly fast reaction rates for the nanocomposite.
Absorption is diffusion controlled whereas desorption depends on the Mg/MgH2
interface displacement.
Finally, we have shown by means of HP-DSC the superior cycling stability of
0.7MgH2–0.3TiH2 nanocomposite over 100 cycles. Though, the crystallite growth
associated to cycling at moderate temperatures (<650 K) induces modifications in
the absorption mechanism, which changes on cycling from extended MgH2
nucleation at Mg/TiH2 interfaces to H-diffusion across the MgH2 layer.
Nevertheless, the composite material exhibits excellent kinetics and cycling
properties as compared to pure Mg.
111

and Fuels
PRESENTATION - SEVEN
3rd MARCH 2014
(Total Number of Projections for this Lecture is )
112

The concept of tri Reforming
• A novel tri-reforming process - involves a synergetic
combination of CO2 reforming, steam reforming, and partial
oxidation of methane in a single gasification reactor for
effective production of useful synthesis gas for use in F-T
Process.
• The novel tri-reforming concept represents alternate way of
thinking for both conversion and utilization of CO2 and CH4
without separation that can be applied to industrial flue gas as
well.
• The Novel tri-reforming catalytic system can not only produce
biomass synthesis gas (CO + H2) with H2/CO ratios (1.5–2.0),
but also could eliminate carbon formation which is usually a
serious problem in the CO2 reforming of methane and biomass
gasification.
• This area has assumed importance in the last 10-15 years.
113

Advantages of Tri
Reforming
• Therefore, the proposed tri-reforming can solve two
important problems that are encountered in individual
processing.
• The incorporation of low partial pressures of O2 in the
partial oxidation reaction generates heat in-situ that can be
used to increase energy efficiency and O2 also reduces or
eliminates the carbon formation on the reforming catalyst.
The selection of catalyst support is critical.
114

.
Z.Jiang et al, Phil.Trans.Roy.Soc., A368,3343 (2010)
115

Song and colleagues have pioneered a novel process centred on the
unique advantages of directly utilizing flue gas, rather than pre-
separated and purified CO2 from flue gases, for the production of
hydrogen-rich syngas from methane reforming of CO2 (so-called ‘dry
reforming’). The overall process, named ‘tri-reforming’, couples the
processes of CH4/CO2 reforming, steam reforming of CH4, and partial
oxidation and complete oxidation of CH4. The reactions involved are
itemized in the table above together with the corresponding enthalpies
of reaction (298 K).
.
116

Coupling CO2 and H2O can give syngas with the desired H2/CO ratios
for methanol and dimethyl ether synthesis and higher-carbon Fischer–
Tropsch synthesis of fuels.
CH4→ C + 2H2O
2CO→ C + CO2
It also helps to avoid the formation of particulate (solid) carbon
deposits arising from reactions such as Experimental studies have
shown that the introduction of the CO2 tri-reforming reaction may also
enhance the durability and lifetime of metal nanoparticle catalysts
owing to the addition of oxygen (and consequent oxidation of carbon
deposits).
117

It is possible to achieve up to 95 per cent methane conversion by this
process at equilibrium temperatures in the range 1073–1123 K. To
achieve effective conversion (of both CO2 and CH4), the flue gas is
combined with natural gas and used as chemical feedstocks for the
production of syngas (CO+H2) with desired H2/CO ratios. In addition,
the process makes use of ‘waste heat’ in the power plant and heat
generated in situ from partial oxidation of methane (POM) with the
O2 present in the flue gas (above table). In effect, the two endothermic
reactions noted in the table above are thermally sustained by the waste
heat content of the exhaust gases, and the partial combustion of the
primary methane fuel
.
118

The main advantages of Tri reforming
1.Prevention of carbon deposit
2.appropriate CO/H2 ratio
3.more autothemic reaction enthalpy
than dry reforming
.
119

Reaction Stoichiometry ∆H0
298 (kJ/mol)
enthalpy
CO2 reforming of methane (DRM) CH4 +CO2↔2CO +2H2 +247.3 (endo)
Steam reforming of methane (SRM) CH4 + H2O↔CO + 3H2 +206.3 (endo)
Partial oxidation of methane (POM) CH4 + 1/2O2↔CO + 2H2 -35.6 (exo)
Catalytic combustion of
methane(CCM)
CH4+ 2O2↔CO2+2H2O -880 (exo)
Main reactions for syngas production by tri reforming of natural gas
120

Table 1 Reaction steps of methane tri-reforming process
1. Reaction steps
a. CH4(g)+ CO2(g) → 2CO(g)+ 2H2(g)
b. CH4(g) + H2O(g) → CO(g) + 3H2(g)
c. CH4(g) + _O2(g) → CO(g) + 2H2(g)
d. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
e. CH4(g) → C(s) + 2H2(g)+. 2CO(g) + C(s) → CO2(g)
g. CO2(g) + H2(g) → CO(g) + H2O(g)
h. C(s) + H2O(g) → CO(g) + H2(g)
m. C(s) + O2(g) → CO2(g)
n. 5CH4(g) + 7/2O2(g) → 9H2(g) + 4CO(g) + CO2(g)+ H2O(g)
2. Observed reaction steps
I. CH4(g) + 5/8O2(g) → CO(g) + 7/4H2(g) + _H2O(g)
II. CH4(g) → C(s) + 2H2(g) (Methane Cracking)
III. 2CO(g) →2 C(s) + CO2(g) (Boudouard Reaction)
IV. CO2(g) + H2(g) → CO(g)+ H2O(g) (Reverse Water Gas)
121

Steam Reforming
−H0
298(kJ/mol)
1. CH4 + H2O CO + H2 −206
2. CnHm + nH2O nCO + (n + m/2) H2 −1175 (for nC7H16)
3. CO + H2O CO2 + H2 (WGS) +41
CO2 (dry) reforming
4. CH4 + CO2 2CO + 2H2 −247
Auto Thermal Reforming (ATR)
5. CH4 + 1. O2 CO + 2H2O +520
6. CH4 + H2O CO + 3H2 −206
7. CO + H2O CO2 + H2 +41
Catalytic Partial Oxidation (CPO)
8. CH4 + 1/2O2 CO + 2H2 +38
Total oxidation
9. CH4 + 2O2→ CO2 + 2H2O +802
Boudouard reaction
10. 2CO C + CO2 +172
The main chemical products from natural gas are summarized
122

REFORMING –STEAM-DRY-BI-TRI
 STEAM REFORMING
CnHm + nH2O → nCO + (n+0.5m)H2 ∆Ho
298 =206kJ/mol
 Dry Reforming
CH4 + CO2→ 2CO + 2H2 ∆Ho
298 =247kJ/mol
 Water Gas Shift (WGS)
CO + H2O → CO2 + H2 ∆H0
298 = -41 kJ/mol
 Boudouard Reaction
2CO→ C + CO2 ∆H0
298 = -173 kJ/mol
 Methane Decomposition
CH4 → C + 2H2 ∆H0
298 = 75 kJ/mol 123

TRI REFORMING A NEW PROCESS FOR REDUCING
CARON DI OXIDE EMISSIONS
CO2 separated, recovered and purified by absorption,
adsorption or membrane separation. Refer database
But require energy input in power plants nearly 20%
May be possible to reduce this
Tri reforming (Penn State University)is a three step process
avoids separation step, can be cost efficient for synthesis gas
production
124

CO2 Emissions from different sectors in USA
( in Million Metric Tons of Carbon)
Emissions Source 1980 1985 1990 1995 1997
Residential sector 248 246 253 270 286
Commercial sector 178 190 207 218 237
Industrial Sector 485 425 454 465 483
Transportation Sector 378 384 432 459 473
End use total 1289 1245 1346 1412 1479
Electric Utilities 418 439 477 495 523
125

Top 10 Countries
• Canada
• China
• Germany
• India
• Italy
• Japan
• Russia
• South Korea
• UK
• USA
• Alphabetical order 126

Typical Flue Gas Composition
•Flue gas 8-10% CO218-20% H2O,2-3% O2, 67-72%
N2 from natural gas fired power plants
•12-14% CO2, 8-10% H2O,3-5% O2,72-77% N2, coal
based boilers
127

TRI REFORMING PROCESS
• CH4 + CO2→ 2CO + 2H2 247.3 kJ/mol
• CH4 + H2O →CO + H2 206.3 kJ/mol
• CH4 + 1/2O2 → CO + 2H2 -35.6kJ/mol
• CH4 + 2O2→CO2 + 2H2O -880kJ/mol
• Coupling CO2 reforming with steam reforming will give synthesis gas
fit for FT H2/CO =2
• Dry reforming is endothermic
• Carbon formation a major problem
128

OTHER REACTIONS
• CH4 → C + 2H2 74.9 kJ/mol
• 2CO→C + CO2 -172kJ/mol
• C + CO2→2CO 172kJ/mol
• C + H2O → CO + H2 131 kJ/mol
• C+O2 → CO2 -393kJ/mol
• Steam reforming
• Syngas desired H2/CO mitigate carbon formation heat is also
generated
• NG or flue gas waste heat
129

Electric power plant Coal, NG fired IGCC
Glue gas CO2,O2,H2O, N2
O2CO2-H2O reforming of CH4
NG input Process waste heat exchange
Syngas CO+H2+ unreacted gas
Fuels Chemicals Electricity
Proposed CO2 based tri generation concept
IGCC Integrated gasification combined cycle
130

PICTORIAL REPRESENTATION OF ROLE OF SUPPORT AND
PROMOTER 131

The energy sector, which is the largest source of CO2 emissions, is responsible
for approximately 25% of global CO2 emissions. Great efforts have been
conducted in the past to use carbon dioxide as a chemical raw material with a
very low or even negative cost rather than as a waste, e.g. CO2 reductions under
photoirradiation, or under electrolytic conditions, or production of synthesis gas
by reforming natural gas. However, many of these reactions produce rather
simple molecules such as carbon monoxide and formic acid. CO2 has the
advantages of being nontoxic, abundant, and economical, attractive as an
environmentally
friendly chemical reagent, especially useful as a phosgene substitute. The
largest obstacle for establishing industrial processes based on CO2 as a raw
material is its low energy level. In other
words, a large energy input is required to transform CO2. There are several
methodologies to transform CO2 into useful chemicals, such as the use of high-
energy starting materials such as hydrogen, unsaturated compounds, small-
membered ring compounds, and organometallics; the choice of oxidized low-
energy synthetic targets such as organic carbonates or the supply of physical
energy such as light or electricity. Selecting appropriate reactions can lead
to a negative Gibbs free energy of the reaction .
Ioana et al., Catalysis Today 189,212(2012) 132

Carbon di oxide to fuels have been studied largely as a complementary
technology to carbon sequestration (CSS) and storage. CSS requires the
minimization of hydrogen consumption to produce fuels.
From this perspective, the preferable option is to produce alcohols (preferably
≥C2) by use of solar energy to produce the protons and electrons necessary for
CO2 reduction. The chemical transformation of CO2 includes a reverse water–
gas shift reaction and hydrogenation to produce hydrocarbons, alcohols,
dimethyl ether and formic acid, a reaction with hydrocarbons to syngas (such as
dry reforming of methane), and photo- and electro-catalytic and
thermochemical conversions.
CO2 can be used as a building block in organic syntheses to obtain valuable
chemicals and materials has been discussed in many reports and review articles.
The main applications of CO2 as chemical raw materials are syntheses of
polycarbonates and polyurethanes.
Ioana et al., Catalysis Today 189,212(2012)
133

Organic carbonates are roughly categorized into cyclic and linear carbonates, which both
compounds have three oxygens in each molecule, and are suitable from a thermodynamic
point of view as synthetic targets starting from CO2. Four industrially important organic
carbonates are ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate
(DMC), and diphenyl carbonate (DPC). EC, DMC and DPC are useful intermediates for
manufacturing polycarbonates through a non-phosgene process . In addition, EC, PC and
DMC are employed as electrolytes in lithium ion batteries and are widely used as aprotic
polar solvents. Furthermore, the excellent properties of DMC as a fuel additive have attracted
much attention. DMC can be synthesised from methanol and CO2, over homogeneous
catalysts or heterogeneous such as
solid acid catalysts of zirconia modified by Ce and acid additives such as phosphoric acid, or
as a support for heteropolyacids, or via cyclic carbonates (CO2 with epoxides), the
cycloaddition of oxiranes and oxetanes and CO2 over e.g. CeO2–ZrO2 or homogeneous metal
complexes catalysts, or coplymerisation of CO2 and oxiranes on metal complexes, the
synthesis of urea (CO2 + NH3) and urethane derivatives, e.g. CO2 + secondary or primary
amines giving carbamic acid which reacts with organic halides or alcohols giving carbamates
(urethanes) or are dehydrated to isocyanate without using phosgene, the synthesis of
carboxylic acids, e.g. acrylic acid, the synthesis of esters and lactones by combining CO2 with
unsaturated
compounds such as vinyl ethers, the hydrogenation and hydroformylation of alkenes by CO2
and H2, and so forth
134

Currently, the utilization of CO2 as a chemical feedstock is limited
to a few processes, such as the synthesis of urea (for nitrogen
fertilizers and plastics), salicylic acid (a pharmaceutical ingredient)
and polycarbonates (for plastics). It is worth noting that the actual
use of CO2 corresponds to a small percentage of the potential CO2
that is suitable to be converted into chemicals; thus, a chemical
transformation of CO2 may significantly contribute to a reduction
of its emissions, in particular for the fuel pool, the worldwide
consumption of which is two orders of magnitude greater than that
of chemicals. Note that CO2 transformation requires energy, which
may produce CO2. Thus, the importance of the transformation of
CO2 into useful chemicals should be closely related to the
importance of utilizing a renewable feedstock .
135

Different options exist in heterogeneous catalysis for the conversion of CO2. The
hydrogenation of CO2 to form oxygenates and/or hydrocarbons are the most intensively
investigated area of CO2 conversion. Methanol synthesis from CO2 and H2 has been investigated
at the pilot-plant stage with promising results.
An alternative possibility is the production of DME, which is a potential diesel substitute.
Ethanol formation, either directly or via methanol homologation, and the conversion of CO2 to
formic acid are also potentially interesting routes. Methanol, ethanol, and formic acid may also
be used as feedstocks in fuel cells, which provide a route to store energy from CO2 and then
produce electricity.
The hydrogenation of carbon dioxide to hydrocarbons consumes much more hydrogen (per unit
of product) than the formation of oxygenates. Therefore, this route is, in principle, only valuable
when hydrogen is made primarily from renewable or non-fossil resources; however, other
thermodynamic aspects must also be considered. The dry reforming of methane with CO2 is a
known technology that is available on a nearly industrial scale, although the positive impact on
CO2 emissions is questionable.
Specifically, it is important to ensure that CO2 emissions due to energy consumption are not
greater than the amount of CO2 consumed in the reaction. An improvement in the positive
direction is tri-reforming, which operates autothermically and does not require a pure CO2 feed
stream; however, large-scale demonstration units are necessary. The conversion of CO2 at room
temperature and atmospheric pressure using solar light represents a highly challenging approach
to close the CO2 cycle and develop approaches that mimic photosynthesis. An interesting
solution could be a photo-electrochemical (PEC) reactor that operates in the gas phase and uses
nanoconfined electrodes that differ from those used in conventional PEC systems.
136

CH4/CO2/H2O/O2/Ar Temp K conversion % Mole ratio H2/CO
CH4 CO2 H2O
1/0.475/0.475/0.1/7.5
973 90.9 75.9 73.4 2.13
1/0.475/0.475/0.1/15 973 95.6 80.6 78.6 2.13
1/0.475/0.475/2.75/15 973 99.5 16.5 9.4 1.85
1/0.475/0.475/2.0/15 813 65 28 2.42
Results of thermodynamic calculations for equilibrium conversion of the reagents in the
methane tri reforming process
Data from S.A.Solov’ev et al.,Theoretical and Experimental Chemistry, 48,199 (2012)
137

Catalyst component composition Temp K Conversion % H2/CO Yield %
CH4 CO2 O2 H2O Ar CH4 CO2 H2 CO
NiAl 1 0.9 0 0.65 13 983 99.8 68 1.59 80 70
NiLaAl 1 0.95 0 0.7 14.5 878 88 65 1.46 69 65
NiCeAl 1 0.7 0 0.65 14.5 978 98 74 1.71 76 70
1 0.7 0.4 0.7 14.5 833 85 9 2.02 57 45
Ni2CeAl 1 0.45 0.2 0.55 15 888 91 16 1.73 78 75
1 1 0.2 0.55 15 888 94 34 1.42 64 72
Parameters of methane Trireforming in Ni-Al2O3 catalysts modified by
rare earth oxides on structured cordierite supports.
Data from S.A.Solov’ev et al.,Theoretical and Experimental Chemistry,
48,199 (2012)
138

A generic energy cycle using captured or sequestered CO2 and sustainable or renewable
hydrogen to yield carbon-neutral or renewable carbonaceous fuels (courtesy of M. L.
Jiang Z et al. Phil. Trans. R. Soc. A 2010;368:3343-3364©2010 by The Royal Society
139

Some Experimental Observations
Aerogel Co/Al2O3 catalysts for CH4–CO2 reforming. (a) (i) Conventional and (ii) magnetic
fluidized bed. (b) Conversions of (i) CH4 and (ii) CO2. (c) Microstructure of the catalysts after
20 h operation: (i) magnetic fluidized bed, (ii) fluidized bed and (iii) fixed bed. Note that in
the fluidized-bed operation mode, (i), carbon deposition is mainly of particulates, while in the
fixed-bed mode, (iii), we see extensive filamentous, graphitic carbon, causing deactivation of
the catalyst. Symbols: (b) (i) filled squares, magnetic fluidized bed; filled triangles, fluidized
bed; filled inverted triangles, fixed bed; dotted line, equilibrium conversion; (ii) open squares,
magnetic fluidized bed; open triangles, fluidized bed; open inverted triangles, fixed bed;
dotted line, equilibrium conversion..
Reproduced fromZ.Jiang et al, Phil.Trans.Roy.Soc., A368,3343 (2010)
140

Gibbs free energy of formation for selected chemicals (data compiled and calculated from
NIST database, http://webbook.nist.gov/chemistry/name-ser.html).
141

The enthalpy of reaction for syngas production and Fischer–Tropsch (FT)
synthesis of methanol and dimethyl ether.
142

The interest for tri-reforming process is:
1. The attractive possibility of potential integration of this technology into gas-
turbine-based electric power cycles, having very low overall CO2 emissions.
2. Detailed experimental studies, computational analysis and engineering
evaluations are being carried out on the tri-reforming process.
3. The CO2 in power plant exhausts could be used directly in catalytic
processes to generate a syngas suitable for ultimately delivering energy
fuels (and a variety of chemical products).
143

The Development of Catalysts
The majority of developments are directed on the CH4–CO2 reforming
component of the tri-reforming process.
Both Ni and Co have frequently been employed as active metal components
owing to their high intrinsic catalytic activities, wide availability and
(relatively) low costs .
The drawback of these catalytic materials centres on serious carbon deposition
in the industrial CO2reforming of methane.
This leads to rapid catalyst deactivation and reaction inhibition
Carbon deposition was strongly influenced by the precise mode of operation of
the chemical conversion process.
Fluidized-bed reforming leads to significant enhancement in the
CH4 conversion process and a considerably reduced carbon deposition when
compared with the fixed-bed operation process Further optimization of the
fluidized-bed configuration has taken the form of innovative approaches using a
fluidized bed assisted by an external, axial magnetic field.
Ref: Z.Jiang et al, Phil.Trans.Roy.Soc., A368,3343 (2010) 144

Hao et al. (2008) have recently reported studies of CH4–CO2 reforming on
aerogel Co/Al2O3 nanoparticulate catalysts in a magnetic fluidized bed. In their
study, Co was introduced as the active catalyst component for the reforming
process; here, they have taken advantage of the high Curie temperature of Co
(ca 1120°C) that makes it ideally suited for the high operating temperatures of
between 700 and 1000°C necessary for the reforming process. In addition, the
influence of an external magnetic field on the catalytic activity and stability of
these catalyst systems was investigated in detail and compared with data for a
conventional fluidized bed and a static bed. These impressive studies are
summarized in figure 9, which is a compilation of conversion efficiencies for
both CH4 and CO2. Also shown are images of the operating catalysts that
clearly demonstrate that carbon deposition is considerably reduced through
improving the gas–solid efficiency by the use of the external magnetic field.
For these ferromagnetic particulate catalysts, it is quite clear that magnetic-
field enhancement of operating process properties may be a most important
avenue for future, major studies.
145

Reaction Stoichiometry ∆H0
298 (kJ/mol)
enthalpy
CO2 reforming of methane (DRM) CH4 +CO2↔2CO +2H2 +247.3 (endo)
Steam reforming of methane (SRM) CH4 + H2O↔CO + 3H2 +206.3 (endo)
Partial oxidation of methane (POM) CH4 + 1/2O2↔CO + 2H2 -35.6 (exo)
Catalytic combustion of
methane(CCM)
CH4+ 2O2↔CO2+2H2O -880 (exo)
Main reactions for syngas production by tri reforming of natural gas
146

and Fuels
PRESENTATION - EIGHT
6 MARCH 2014
147

CARBON DIOXIDE AS FEEDSTOCK FOR
CHEMICALS AND FUELS
• The objective is to develop new industrial processes
for fuels like gasoline, diesel, jet fuel and industrial
chemicals.
• This places a condition that carbon dioxide has to
captured from the sources like flue gas and
purified.(tri reforming possibly avoids this step)
• Different technologies for separation keeping cost in
mind are (i) use of basic solids like zeolites, polymeric
amines, new materials or liquids Monoethanolamine
(MEA) and water
148

Most common chemicals
from carbon dioxide
• Sodium bicarbonate (NaHCO3) and sodium carbonate
(Na2CO3) by Solvay process
• Urea and salycilic acid by thermal process
• Methanol production through the syngas or
carboxylation of ethene epoxide ( direct methanol
production from carbon dioxide is under development
which we will see subsequently)
149

THE STARTING POINT IN DIRECT CARBON DIOXIDE
STARTED FROM THE OBSERVATION THAT IN 1975, IT WAS
SHOWN THAT TRANSITION METAL COMPLEXES CAN
ACTIVATE THIS INERT MOLECULE
Aresta et al., New nickel-carbon dioxide complex: synthesis properties,
and crystallographic characterization of (carbon dioxide)-
bis(tricyclohexylphosphine)nickel, J Chem.Soc., Chem.commun.,636-
637 (1975)
This leaves us to a question why do we concentrate on certain complexes
like nitrogen, phosphorus containing ligands this has to be linked with
the coordinating ability and also the nature of coordination as compared
with other ligands containing coordinating species like oxygen, sulphur
and other such species.
150

The Situation Now
Carbon dioxide is used now for the production of urea,
organic and inorganic carbonates, salicylic acid and in
food conservation.
However the total use of carbon dioxide is only 0.6% of the
anthropogenic CO2 emissions which is around 33 Gt.y-1
Out of this only 200 Mt/y is used for these chemicals.
151

Possible Processes
Homogeneous, heterogeneized, heterogeneous and enzymatic
are the possibilities.
Carbon dioxide can be considered to be in the potential well
stable molecule
Two ways of activating this molecule
Low energy process where CO2 is incorporated in the organic
or inorganic substrates.
High energy process ( where oxidation state of carbon from 4
to upto a minimum of -4.
152

CaCO3 (s) −1130
C2O4
2-(aq) −671
HCO3
-(aq) −586
CO3
2-(aq) −528
CO2 (g) −394
HCOOH(l) −361
CH3OH(l) −166
CO(g) −137
CH3C(O)CH3 (g) −113
HC(O)H(l) −102
CH4 (g) −51
C6 H14 (I) −4
C2H4 (g) +68
C6H6 (I) +124
C6H6( g) +130
Gibbs free energy of formation (∆G0
f)
for some C1 and Cn compounds(kJ/mol)
CO2 insertion (exoergonic)
C1 reduced H and increased H
require energy (endoergonic)
153

Homogeneous Catalysis
Production of carbonates, carbamates, urethanes, lactones,
pyrones formic acid and derivatives –homogeneous catalysts
are better than heterogeneous catalysts.
154

Heterogeneous Catalysis
Dimethyl carbonate
Cyclic carbamates
Synthesis gas ( already discussed in reforming)
Methanol by CO2hydrogenation
155

Synthesis of Methanol
• CO2 + 3H2 → CH3OH + H2O
90 methanol plants – 75Metric tons
Methanol to formaldehyde (resin) PET PTA
3CH4 + CO2 +2H2 O→ 4CO + 8H2 to methanol
Olah Metgas (CO-2H2)
Another is tri reforming which we have already discussed the three reactions
Dry reforming, steam reforming and POM
CH4+ CO2 →2CO + H2 247 kJ/mol
• CH4 + H2O →CO + H2 206.3 kJ/mol
• CH4 + 1/2O2 → CO + 2H2 -35.6kJ/mol
• Coupling CO2 reforming with steam reforming will give synthesis gas for methanol H2/CO =2
• Dry reforming is endothermic
• Carbon formation a major problem which is avoided in tri reforming
• Methanol to dimethyl carbonate dimethyl ether fuel additive.
• Homogeneous catalyst low temperature Ru phosphine complex TON 221 at 413K
156

Factors for heterogeneous catalysts
• The metal and catalyst structure
• The uniform particle size of metal
• The distribution of the metal on support
• The surface area
• The active sites
• The stability and long term operation
• The type of promoter and support
• The growth of the metal particle
• Cu/ZnO – Cu/ZnO/ZrO2
• Al2O3,TiO2 Ga2O3-Vox, MnOx MgO
• MTO (ethylene and propylene) TOTAL Honeywell and china Dow Union Carbide
157

Catalytic Hydrogenation of CO2
Key issue: H2 sources
Since molecular hydrogen does not naturally exist in its pure form, it is typically derived
from natural gas, oil, coal, biomass, and water by means of various chemical, physico-
chemical, photolytic, electrolytic or biological transformations. From an environmental
viewpoint, it is crucial that its production is also CO2 emission free. Since hydrogen can
actually substitute fossil fuels, it opens the possibility to even have a positive CO2 balance,
i.e. reducing overall CO2 production, when generating heat and energy upon hydrogen
combustion yielding H2O as the only product. Hydrogen can be produced from fossil
fuels water and biomass. The emphasis will be on their environmental impact and
economy in CO2 hydrogenation to value-added chemicals.
Steam reforming of methane
CH4+ H2O→ 3H2 +CO
H2O + CO → CO2 + H2 (WGS)
Energy intensive endothermic
CO2 (from fossil fuel ) autothermal reforming
Economic needs, H:CO ratio, deactivation air separation required
Biomass can also be converted through liquefaction, pyrolysis, gasification
Gasification requires sulphur and carbon tolerant catalysts and separation technologies
CxHyOz + H2O → H2 + CO + CO2+ CnHm +tar
Water electrolysis will be dealt with separately subsequently
158

CO2 Hydrogenation by Heterogeneous Catalysts
Hydrogen and methane are two high-energy materials, which can be used
for the large-scale transformation of carbon dioxide to valuable products.
Fig. illustrates the most attractive
heterogeneously catalyzed routes. It is important to highlight that the H2-
based routes directly yield fuels or chemical building blocks, while the
CO2 conversion with CH4 results in syngas, which can be converted to
the above products in an additional process step. From an economic
point of view, the direct transformation of CO2 is preferable.
159

Conversion of CO2 to hydrocarbons
The hydrogenation of CO2 to CH4 is highly important from an
industrial viewpoint. There are several uses of methane
1. Steam reforming of methane
2. Heat and electricity generation
3. As substitute for gasoline, diesel or liquid petroleum
Audi AG builds windmill electricity and hydrogen to convert biomass
based carbon dioxide
Projected production is 1 kt of methane will consume 2.8kt of CO2
Catalysts employed are given in table 1
CO2 to CH4 is exothermic and low temperature operation favourable to
suppress WGS
100% yield of methane at 453 K on Ru/TiO2
New experiments are necessary smaller nanoparticles usage
160

FT Process
Carbon dioxide hydrogenated to HC by FT cobalt
catalyst does not give Schulz-Flory distribution low
activity for RWGS.
Iron based catalysts are not selective
Mn, Cu, K, Ce promoters
Mn,Cu improve reducibility of iron
K is better for increased adsorption of CO2
Ce selectivity advantage to C2-C5
161

FT Process
Fe catalyst activity methane formation has to be
addressed
The process economics has to be addressed
capture
conversion
classical FT shown in Fig
162

Formation of oxygenates from CO2
CO2 to methanol Lurgi 30 years ago
2011 carbon recycling international (CRI) 4Kt
(40Kt) methanol no details are available
Lurgi and air liquide forschung and others
commercial methanol synthesis catalyst
CO-CO2 based water formation, alcohol, HC,
Esters and ketones
163

Di-methyl ether (DME) a substitute to
diesel when a methanol catalyst is
coupled with an acid catalyst like
alumina
Lurgi MegaDME heat integration
methanol formation and subsequent
dehydration
169

Catalysts
Cu/ZnO the role of ZnO is to keep
morphology and stabilize copper species.
Promoter like ZrO2,SiO2, Al2O3, La2O3
dispersion of copper
direct relation of TON with monoclinic
ZrO2
morphology and nano state play a role
170

Carbon dioxide to Chemicals and Fuels
PRESENTAION NINE
NCCR on line course
10th March 2014
(this presentation contains projections)
172

FUNDAMENTALS OF
ELECTROCATALYTIC REDUCTION
OF CARBON DIOXIDE ON METAL
SURFACES ONLY TO SMALL
MOLECULES AND FUELS
Basic information
173

Why CO2 appears important today?
• Increase of CO2 one of the causes of green house effect and global
warming issues
• Electro-catalytic reduction of CO2 to liquid fuels
• Carbon balance by recycling into usable fuels
• There are other reasons for utilizing carbon dioxide – these will be
subsequently taken up
174

1.Carbon dioxide is a stable molecule
Produced by fossil fuel combustion and respiration
2. Returning CO2 to useful state on the same scale as its
current production rates is beyond our current scientific
and technical ability
No commercial available process for the conversion of
CO2 to fuels and chemicals – challenges are great
potential rewards enormous .Fundamental knowledge for
activation of CO2
3.Require catalysts that operate near TD equilibrium
potentials and high rates
3. novel catalyst systems are required multi-active site
systems complex process like C-O,C-C,C-H multi-step,
multi electron, charge and atom transfer reactions
175

Increase of Carbon dioxide in the
atmosphere
electro-catalytic reduction is one possible
way to mitigate the carbon balance
No commercial process for conversion of
carbon dioxide to selective product
176

Understanding of the chemistry of
activation of carbon dioxide
multi-functional catalysts
C-O bond activation C-H and C-C
bond formation
energy input and reasonable selectivity
are the main objectives
177

Electrochemical conversion of CO2
+ is reverse of
electrochemical reactions taking place at anode of
fuel cells at the anode of the fuel cell fuel is
oxidized to carbon dioxide and water.
a process of converting electrical energy to
chemical energy though high selectivity may be
possible, the reactions involve Gibbs free energy is
always positive due to overvoltage is >1 V in
aqueous medium, water reduction is a competing
process – high Hydrogen overvoltage metals like
Hg suppress H2 evolution leads to HCOO- at high
over-potentials
178

Copper different from other metals
CO2 to HC- CH4 or C2H4 - 5-10
mA/cm2
Current efficiency >69%
copper single crystals, ad-atom cu, cu
alloys, H2 ,CH4,C2H4 and CO
Hythane combined fuel can be
produced in aqueous electrolyte
179

CO2 reduction in gas phase GDE or
SPE
Isopropanol and C4 oxygenates in
GDE CNT-encapsulated metal
catalysts although small amounts but
can open up new avenues for electro-
catalytic conversion to liquid fuels
180

Current knowledge
metal electrodes GDE, SPE
Homogeneous catalysis is efficient
we have considered it before and
hence it is not included in this
presentation
181

Liquid fuels like HCOOH,
isopropanol, HC and fuel precursor
CO The equilibrium potentials are
negative with respect to hydrogen
evolution (HER) in aqueous
electrolyte solutions
182

Fundamental challenges
The primary reactions at pH = 7 at
298 K against NHE
CO2+H2O+2e→HCOO- + OH- (-
0.43V)
CO2 +H2O+2e=CO+ 2OH-(-0.52V)
CO2+6H2O=8e=CH4+8OH-(-0.25V)
2CO2+8H2O +12e=C2H4 +12OH-(-0.34V)
2CO2+9H2O+12e= C2H5OH +12OH- (-0.33V)
3CO2+13H2O+18e=C3H7OH+18OH-(-0.32V)
2H2O+2e= 2OH- +H2 (-0.41V)
183

However reduction of CO2 does not
occur at equilibrium values more
negative potentials
since single electron reduction
CO2 + E = CO2
- (-1.90 V) due to
large reorganizational energy
between the linear molecule and bent
radical anion first step
CO2 + e === CO2.(-1.90V)
184

The equilibrium potential that is
considered is dependent on pH
CO2+8H+ +8e=CH4 +2H2O (+0.17V)
at pH = 0 while it changes with pH
shown in Fig.1.
185

BASIC ELECTROCHEMISTRY
Potential scale
Negative values
Positive values
186

REACTIONS AT ELECTRODE
FOLLOWS
SO CALLED NERNST
EQUATION
IF TRUE THERMODYNAMIC
EQUALIBRIUM WERE TO
EXIST
IF NOT DEVIATIONS POSSIBLE
187

OVER VOLTAGE
CONVENTIONALLY THE DEVIATION
FROM EQUILIBRIUM POTENTIAL
OHMIC
concentration
ACTIVATION and many more possible
Many of these concepts are seemingly not fully understood
Why
Full picture of Electrode/Electrolyte can be
described with all precision
188

Even though the potentials for various
reactions in CO2 are known the actual
values at which these reactions will
occur depends on the medium that is
used ( ionic strength influence) and the
changes that can take place – so called
pH dependence
concentration even though solubility
data are known
189

In general the electrode/electrolyte
interface is less defined why?
190

What is CO2 reduction?
Assembling nuclei formation of chemical
bonds to convert the simple molecule into
more complex and energetic molecules
kinetic control since low equilibrium
potentials
TD Methane and ethylene should occur at
less cathodic potential than hydrogen,
kinetically does not happen
192

The product distribution for CO2
on Cu is shown as a function of
potential in Fig.2.
1. Initially CO and HCOO at -1.12V
then hydrocarbon first ethylene and
methane form- these potential
dependent and predominates at around -
1.35 V. So both TD and kinetics are
important
193

HER in aqueous electrolyte competes
with CO2 reduction
HER predominates in acid and CO2
does not exist in basic and hence most
of the measurements have to be done in
neutral medium
194

The product selectivity depends on
many factors
concentration, electrode potential ,
temperature, electro-catalyst material,
electrolyte
product on electro-catalyst material if
other factors are remain the same.
195

Four groups
1st group
Pb Hg, In,Sn,Cd,Tl, Bi high hydrogen
overvoltage negligible CO adsorption
high overvoltages for CO2 to CO2
radical ion weak stabilisation of the
CO2 radical ion. Major product is
formate
196

Second group
Au,Ag,Zn
medium hydrogen overvoltage,
weak CO adsorption major product
is CO C-O bond break and desorb
CO
197

Third group Ni, Fe,Pt,Ti low
hydrogen overvoltage strong CO
adsorption major product is H2
198

Fourth group
Cu Unique more reduced species
like methane ethylene
199

Under potential deposition copper -
1.44 V Co selectivity is 60% while
that of Cd and Pd adatom modified
Cu is 82% and 0 respectively.
201

Reaction mechanism
limited from charge transfer
coefficients and reaction orders
202

CO2 adsorbed as CO2
δ-
promoted by defects alkali metals and irraditions
CO2 is amphoteric - both acidic and basic
to adsorb as CO2
δ-
depends on electrode surface carbon or oxygen
or mixed coordination anion radical is first step
where is the excess charge on C as a nucleophilic
agent Std potential -1.9vs SHE or -2.21 C vs
SCE Transfer coefficient is 0.67 in aqueous and
non aqueous solutions CO2
-
Two main pathways to CO or formate depends
on metal Fig 4
203

on Hg the major product is formate
CO2 by one electron transfer to for CO2
.-
at the negative potential of -1.6 V it will take a
proton from water H will not be bonded to
oxygen atom since the pKa I 1.4 formate radical
is reduced to formate ion subsequently The steps
CO2
.- (ads) + H2O === HCOO. + OH- -
HCOO. + e == HCOO-
or directly
CO2
.- + Hads=== HCOO-
205

The reaction scheme is suitable to
other metal electrodes like Ag, Au,
Cu and Zn. Sequence of CO
selectivity follows the electrode
potential only that stabilizes carbon
dioxide anion radical CO is main
product - weak CO adsorption
207

HER side reaction for CO2 reduction in
aqueous medium
pH dependent in acid and independent in
alkaline medium
H+ + e-
→ Hads
2Hads → H2
Hads + H+ + e-
→ H2
Hads. H+ are the hydrogen source for CO2
reduction
Pt/Fe/Ni/Ti CO is strongly adsorbed and
major product is H2
208

Cu Based electro-catalysts
CO2 → CH4 /C2H4/alcohols
At low over potential CO/COO- yield
appreciable at -1.1V C2H4 increases
CO/HCOO- precursors to HC/alcohols
CO linear adsorbed at -0.6 V Coverage high
heat (17.7 kcal/mol) appropriate.
So subsequent reduction CO to HC/alcohols
209

COads to HC
CH4 more negative potential than C2H4 (1.22 to 1.12V)
C2H4, CH4 through different reactions CO bond is broken
since alcohol is not formed
CH4 CO anion radical Cu-C bond decrease C-O bond
increase
Two Paths
Co anion radical proton and second electron transfer
CH4 formation irreversible (5b)
Co anon radical + adsorbed hydrogen C----O H addition
(5c)
C2H4 associated pair
Ch2ads two dimerise
Or CO-CH3 (Fig.6)
210

Crystal face (100) for copper Pi-CO two oxygen
atoms close to Cu
(111) CH4 formation more negative potential
(110) 2/3 carbon product
different over potential
Surface treatment Cu Alloy
CH3 OH intentional peroxide
Alloy Cu-Ni, Cu-Fr, hydrogen increases and CH4
C2H4 decrease
Cu-Cd CH4, ethylene
other alloys CO and formate
Cu-Au majority is CO
212

Carbon dioxide to Chemicals and Fuels
PRESENTATION TEN
NCCR on line course
13th March 2014
(This Presentation Contains
Projections)
215

FUNDAMENTALS OF
ELECTROCATALYTIC REDUCTION
OF CARBON DIOXIDE ON
SURFACES TO MOLECULES AND
FUELS
216

Under potential deposition copper -
1.44 V Co selectivity is 60% while
that of Cd and Pd adatom modified
Cu is 82% and 0 respectively.
218

Reaction mechanism
limited from charge transfer
coefficients and reaction orders
219

on Hg the major product is formate
CO2 by one electron transfer to for CO2
.-
at the negative potential of -1.6 V it will take a
proton from water H will not be bonded to
oxygen atom since the pKa I 1.4 formate radical
is reduced to formate ion subsequently The steps
CO2
.- (ads) + H2O === HCOO. + OH- -
HCOO. + e == HCOO-
or directly
CO2
.- + Hads=== HCOO-
220

The reaction scheme is suitable to
other metal electrodes like Ag, Au,
Cu and Zn. Sequence of CO
selectivity follows the electrode
potential only that stabilizes carbon
dioxide anion radical CO is main
product - weak CO adsorption
222

HER side reaction for CO2 reduction in
aqueous medium
pH dependent in acid and independent in
alkaline medium
H+ + e-
→ Hads
2Hads → H2
Hads + H+ + e-
→ H2
Hads. H+ are the hydrogen source for CO2
reduction
Pt/Fe/Ni/Ti CO is strongly adsorbed and
major product is H2
223

Cu Based electro-catalysts
CO2 → CH4 /C2H4/alcohols
At low over potential CO/COO- yield
appreciable at -1.1V C2H4 increases
CO/HCOO- precursors to HC/alcohols
CO linear adsorbed at -0.6 V Coverage high
heat (17.7 kcal/mol) appropriate.
So subsequent reduction CO to HC/alcohols
224

COads to HC
CH4 more negative potential than C2H4 (1.22 to 1.12V)
C2H4, CH4 through different reactions CO bond is broken
since alcohol is not formed
CH4 CO anion radical Cu-C bond decrease C-O bond
increase
Two Paths
Co anion radical proton and second electron transfer
CH4 formation irreversible (5b)
Co anon radical + adsorbed hydrogen C----O H addition
(5c)
C2H4 associated pair
Ch2ads two dimerise
Or CO-CH3 (Fig.6)
225

Crystal face (100) for copper Pi-CO two oxygen
atoms close to Cu
(111) CH4 formation more negative potential
(110) 2/3 carbon product
different over potential
Surface treatment Cu Alloy
CH3 OH intentional peroxide
Alloy Cu-Ni, Cu-Fr, hydrogen increases and CH4
C2H4 decrease
Cu-Cd CH4, ethylene
other alloys CO and formate
Cu-Au majority is CO
227

GDE/SPE
CO2 to fuel precursor CO
CO2 to CO 2nd group Au Ag H2O to H2
CO2+H2O to CO + H2 (1:2) GDE
Au/Ag Cathode (Fig8)
Time dependent
229

CO2 to C1-C2 fuels
CO2 to HCOOH Pb impregnated GDE
CO2 to higher than C2 SPE
Copper catalyst Cation/anion exchange
membrane (CEM/AEM
Only 20-25% current efficienty
Product depends on CEM/AEM
CO2 long chain HC
Challenge Upto C6 Cu electrode
FT distribution
230

Product distribution
IPA, Acetone, Ethanol,
acetaldehyde
and methanol in Fe encapsulated
CNT
231

1.CO2 is stable
2.Electrocatalytic method high potential
3.Energy efficiency TD/rate
4.Mechanism limited knowledge
5.Beyond current ability
6.New methods approaches of activating
7.Novel catalysts multi-site
8.C-O bond cleavage C-C and C-H
9.Multi step, multi-electron transformations
10.Space restrictions intermediates
11.Model catalysts single crystals, ad-atom, electro-
deposited
232

ELECTROCATALYTIC HYDROGENATION
OF CARBON DIOXIDELong history since 19th century
Homogeneous catalysts can facilitate
Cell design to be such that analysis of products must be possible
Electrodes Products
CO2 reduction Copper HC
Au,Ag,Zn CO
Pb,Hg,In,Sn,Cd,Tl HCOO-
Ni,Fe,Pt,Ti,Ga H2
233

OF CARBON DIOXIDE
• Why this classification (adsorption and over potential)
• Inactive metals C,Al,Si,V,Cr,Mn,Nb,Mo,Rh,Ru,Hf,Ta,W,Re and Ir
• Different faces (100) favour ethylene, (111) methane(110) alcohols
234

OF CARBON DIOXIDE
• High overpotential
• Low solubility
• The formation of mixture of products
• The fouling and deactivation of the electrodes
• GDE
235

OF CARBON DIOXIDE
1.Modifying the metal electrode with oxide
2.Operating at high temp molten or solid electrolyte
3. Using ionic liquids water free conditions preventing hydrogen
evolution
4.Biological microorganisms or photons
236

OF CARBON DIOXIDE
• Modification – electrodeposition of thin layer of cuprous
oxide HC to methanol
• Sn/SnO2 CO HCOOH 3-4 times stabilization of CO2 radical
ion
• Low Faradaic efficiencies, current densities mechanism not
better understood
237

Laboratory cells used for electrochemical CO2 conversion: (a) two-compartment cell, (b)
cell with electrodes separated by an H+ conducting membrane, and (c) cell with a gas
diffusion electrode
238

Comparison of the energy efficiencies and current densities for CO2
reduction to formic acid ( ), syngas ( ), and hydrocarbons ( ).
This figure is from JPC letters,2010,1,3451.
239

OF CARBON DIOXIDE
Solid oxide electrodes
High temperature >673 K
TD and kinetically more attractive
Molton carbonate or solid electrolyte Zirconia stabilized by
Yttrium oxide
Cofeeding of hydrogen was required
Proton conducting electrolyzers
BaCeO0.5 Zr0.3Y0.16 Zn0.04 O3-δ to convert to CO and methane
Co is more than methane hydrogen transport limited
240

The question on electro-catalytic
reduction of carbon-di-oxide
Four groups of metals for CO2 reduction based on high hydrogen
overvoltage, CO adsorption strength, high hydrogen producing metals
and HC forming Copper
The three class of metals are understandable but why copper behaves
differently and also why this metal shows phase specificity
What makes copper to promote C-C coupling reaction
The answer is not yet known
241

Cyclic Carbonates
Ethene carbonate (EC) propene carbonate (PC),
Styrene carbonate solvents, precursor for
polycarbonates, electrolyte in Li batteries,
Pharmaceuticals and chemical reaction raw materials.
The reaction shown is atom economy and green
process carboxylation of epoxides example
Reproduced from J Chem Technol.Biotechnol,89,334 (2014) 245

Other attempts include starting
from olefins without intermediate
formation of epoxide
DMF dialkylacetamide (DAA) is
used as solvent since promote
carboxylation
Pd catalyzed fixation of CO2 cobalt
complexes coupling of CO2 with
epoxide
Reproduced from J Chem Technol.Biotechnol,89,334 (2014)
246

Use of ionic liquids
thermal and chemical stability
selective solubility for org and inorg
reusability of catalyst
carbon dioxide solubility
water Lewis base catalysts show high
activity
247

Super critical carbon dioxide
another reaction medium no flammability,
non toxic, absence of gas liquid phase
boundary and easy work up
metalloporphrins reusable
Triazine high nitrogen centres to inorganice
carbonates
polymer supported IL epoxide to cyclic
carbonates

Cobalt complex active for cyclic carbonate
and polycarbonate synthesis.

Other options for cyclic carbonate synthesis are the
reactions of CO2 with cyclic ketals, propargylic alcohols,
diols and the direct oxidative carboxylation of olefins. The
latter appears to be a very interesting synthetic methodology
to synthesize cyclic carbonates
starting from cheap and easily available reagents such as
CO2 and O2
250

The direct oxidative carboxylation of olefins has great
potential and has many advantages. It does not require
carbon dioxide free of dioxygen. This feature makes it
attractive because of the purification cost of carbon
dioxide, which may discourage its use. Moreover, the
direct oxidative carboxylation of olefins can couple
two processes, the epoxidation of the olefins and the
carboxylation of the epoxides. The process makes
direct use of olefins which are available on the market
at a low price, and are abundant feedstock.
251

Only a few examples are reported in the literature of
the direct oxidative carboxylation of olefins such as
the direct functionalization of propene and styrene.
Using RhClP3 as catalyst, under homogeneous
conditions, it was demonstrated that two classes of
compounds are formed: the first one is due to ‘one
oxygen’ transfer to the olefin with formation of
epoxide and its isomerization products and carbonate
; the second class of products is due to ‘two oxygen’
transfer to the olefin with formation of aldehydes, as
effect of the addition of the oxygen to the C–C double
bond with cleavage of the double bond of the olefin,
and the relevant acids 252

Using heterogeneous conditions it has been demonstrated that oxidation
of the olefin does not follow the peroxocarbonate pathway, more likely
it is a radical process which can be started by the catalyst which plays a
very important role in the carbonation step. The carbonate yield depends
on the catalyst used. The selectivity of the process (that reaches a
maximum of 50% with respect to the olefin) is still affected by the
formation of by-products such as benzaldehyde, benzoic acid,
acetophenone, phenylacetaldehyde, 1,2-ethanediol-1-phenyl and
a benzoic acid ester. After a short induction time, benzaldehyde is
formed in higher amounts than the epoxide which becomes the
predominant product after 45 min. The carbonate formation starts after 1
h and steadily increases with time, while the concentration
of the epoxide and benzaldehyde reach a steady status. The life of the
catalyst is of days and the catalyst is easily recovered at the end of the
catalytic run.
253

By reacting cyclic ketals with carbon dioxide under supercritical conditions in organic solvents a
cyclic carbonate has been obtained under relatively mild conditions (10 MPa and 370 K)
using a suitable catalyst
254

The coproduct cyclohexanone may react with 1,2-ethane-diol in the presence of FeCl3 to
afford, with almost quantitative yield, the cyclic ketal (Equation 16) which can be reused.
255

Several metal systems were tested, either oxides [ZnO, Nb2O5, ZrO2, TiO2], or metal
halides [ZnCl2, FeCl2], or else metal complexes [FeCl2 · 1.5 THF], CuL2, FeClL.
The most active catalysts have been found to be CuL2 and FeClL (L=C11H7F4O2), i.e.
those bearing perfluoro alkyl groups, which are soluble in sc-CO2 under the reaction
conditions
256

Cyclic carbonates have also been synthesized from propargylic alcohol derivatives and CO2
as the starting materials. This synthetic approach (Equation 17) is based on the cyclization
of the propargylic carbonate moiety (HC≡CCH2OCO2 –) into the corresponding α-alkylidene
cyclic carbonate in the presence of a suitable catalyst such as ruthenium, cobalt,
palladium,copper, or phosphine.
257

Ikarya has reported the use of imidazolin-2-ylidenes with N-alkyl and N-aryl
substituents and their CO2 adducts as catalyst of the carboxylative cyclization of
internal and terminal propargylic alcohols. The reaction of internal propargyl alcohols
with CO2 has been carried out also under supercritical conditions. Ikariya et al. have
developed a synthetic process to afford Z-alkylidene cyclic carbonates promoted by
P(n-C4H9)3 with high efficiency.
258

Oxidative carboxylation of styrene under homogeneous conditions.
259

Ionic liquid (1-butyl-3-methylimidazolium
benzene sulfonate ([BMIm][PhSO3])) has also
been used as reaction medium for the synthesis
of α-methylene cyclic carbonates from CO2
and propargyl alcohols using transition metal
salts as catalyst
260

Among the catalysts used, CuCl was revealed to be
the most efficient. On the contrary, when Pd(II),
Rh(III), Ru(III), and Au(III) salts were used as
catalysts no carbonate was produced, also if the
substrate has been converted. This is due to the
formation of the kind of polymer (black tar is
found on the inner wall of the reactor) that occurs
when the noble metal salts/ [BMIm] [PhSO3]
systems are used. In the absence of metal salt as
catalyst, the reaction did not yield any product even
after a long reaction time

Starting from propargyl alcohols using
supercritical carbon dioxide in the presence
of bicyclic guanidines as catalysts
α-methylene cyclic carbonates is obtained
262

Cyclic carbonates can be produced from diols
and carbon dioxide in the presence of suitable
catalysts
The thermodynamics of this reaction are not very favourable
and the major drawback is related to the coproduction of
water, which may involve modification or deactivation of the
catalyst with negative effects on the conversion rate.
263

Ceria based catalysts and CeO2–ZrO2 solid
solution catalysts have been reported to be very
efficient catalyst for the synthesis of ethene
carbonate and propene carbonate by reaction of
CO2 with ethene glycol and propene glycol,
respectively.
The catalytic activity has been shown to be
dependent on the composition and the
calcination temperature of catalysts
264

Different metallic acetates have been used in acetonitrile
which acts not only as solvent but also as dehydrating agent to
eliminate the effect of the water produced during the reaction.
In this way, the thermodynamic equilibrium is shifted and the
yield of cyclic carbonates improved. Organic super bases such
as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-
diazabicyclo[4.3.0]non-5-ene (DBN), or 1,5,7-
triazabicyclo[4.4.0]dec-5-ene (TBD) have also been used as
effective promoters in the synthesis of propene carbonate
from propene glycol and carbon dioxide in the presence of
acetonitrile (yield 15.3%, selectivity 100% under the optimal
conditions)
265

The reaction of polyols with urea is a recent
strategy to afford cyclic carbonates. Efficient
catalysts have been used for the synthesis of
glycerol carbonate that has been used as
platform molecule for the synthesis of several
chemicals, including epichlorohydrin.
266

SYNTHESIS OF LINEAR CARBONATES
267

Caution:
This presentation has a great limitation since the presenter
has very limited and possibly very little knowledge of Organic
Chemistry and the ramifications of this wonderful scientific
field.
268

Important ones are dimethyl carbonate
(DMC), Monomer for polymers and for
trans esterification for preparation of
other carbonates or alkylating agent,
carboxylating agent agrochemical and
Pharmaceuticals and additive to
gasoline
(need can increase) using phosgene or
oxidative carbonylation of methanol
Journal of Chemical Technology and Biotechnology, Volume 89, Issue 3, pages 334–353, March 2014 269

other carbonates of importance are:
diethyl carbonate (DEC) and diphenyl
carbonate (DPC). How carbon dixoide and
alcohol can be used for forming these
chemicals will be considered – meets the
requirements of green chemistry
thermodynamically not feasible one has to
chose conditions to favour the products to
make industrially attractive
Journal of Chemical Technology and Biotechnology, Volume 89, Issue 3, pages 334–353, March 2014
270

Important reaction
2CH3OH + CO2→ MeOC(O)OMe +
H2O
Both homogeneous and heterogeneous
catalysts are employed
n-dibutyldialkoxy stannaes (n-
Bu2Sn(OR)2 ( R = Me, Et,n-butyl) and
other alkoxides of Ti(IV) and group 5
metals are catalytic precursors
271

Table . DMC or DEC yields in the direct carboxylation of alcohols using
homogeneous metal alkoxides. (Yields are determined with respect to
alcohol)
Catalysts DMC Yield % DEC Yield % Pressure Mpa Temperature K Time h
Bu2Sn(OMe)2 0.17 6.6 423 6
Bu2Sn(OEt)2 0.19 6.6 423 6
Bu2Sn(OBu)2 0.43 6.6 423 6
Sn (OEt)4 0.45 6 423 6
Ti (OEt)4 0.17 6 423 6
Ti (OBu)4 0.4 6 423 6
Nb(OEt)5 1.6 5.5 410 30
Nb(OMe)5 1.8 5.5 423 30
VO(OiPr)3 0 5.5 410 30
Ta(OEt)5 0.1 5.5 410 30
Bu2Sn(OR)2 with R = -Bu gave better performance than shorter chain alkoxides
Recovery of final product is difficult;
272

The catalytic species is
hemicarbonate formed by reaction
of the monomeric penta-alkoxo
species with CO2
273

CO2 to fuels and chemicals course material final version

CO2 to fuels and chemicals course material final version

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Andere mochten auch

Andere mochten auch (9)

Ähnlich wie CO2 to fuels and chemicals course material final version

Ähnlich wie CO2 to fuels and chemicals course material final version (20)

Mehr von Hariprasad Narayanan

Mehr von Hariprasad Narayanan (6)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

CO2 to fuels and chemicals course material final version