Selective Oxygen Removal from Oxygenates

Selective Oxygen Removal from Oxygenates
Maria Eugenia Sad Department of Chemical Engineering University of California at Berkeley Financial Support: BP 19 November 2009

Selective Removal of O by C instead of H
Premises and Context: ……….. feedstocks and streams have low H/(C,O) ratios … a problem best addressed by reacting the C with the O CO/H2O mixtures as sources of “H” CO O* H2O O* O* O* O* CO2 H* O* H2 H* Selective removal of oxygen using carbon monoxide instead of hydrogen This is a new research thrust in which we pose and propose to address broad and fundamental questions about how oxygen atoms within molecules can be removed via (i) intermolecular reactions with CO or ii) reactions of C-atoms within oxygenates or within co-reactant molecules. These activities reflect the premise that X-to-liquids scenarios are evolving into H-poorer and C/O-richer contexts, as coal and biomass are increasingly introduced into carbon feedstock pools; they also reflect an expected benefit of forming concentrated CO2 streams, for conversion or sequestration purpose, in the economics of conversion processes within carbon-constrained scenarios. We stress that forming CO2 is unavoidable for the conversion of these H-deficient feedstock pools, whether by the selective use of excess C and CO directly or indirectly or by the production of H2 required for stoichiometric balance via endothermic gasification of carbon-rich feedstocks. One component of the proposed research addresses the use of CO to extract oxygen from H2O with H2 as the desired by-product, a process that in its conventional catalytic context is known as the water-gas shift reaction. Our initial studies will address the mechanism for this reaction –widely studied but yet unclear- and the specific role of O2-assisted pathways in increasing rates and improving the thermodynamics of H2 generation from CO/H2O mixtures. We propose to then transfer these insights and knowledge into novel strategies for the removal of oxygen and/or the in situ regeneration of H2. Some of these proposed strategies are: in-situ formation of H2 or hydrogen-rich transfer species from H2O/CO mixtures during the upgrading of molecules with high C or O content derived from coal or biomass direct use of CO to remove oxygen from biomass-derived oxygenates (e.g. glycerol, carbohydrates) and the use of C atoms within these molecules (instead of their H atoms) to remove excess oxygen while preserving hydrogen use of CO to remove O directly or to form H2 in situ during methanol/DME homologation via direct routes or intervening water-gas shift pathways exploit redox water-gas shift routes by decoupling these elementary steps into thermochemical cycles that form separate high-purity H2 and CO2 streams via temporal cycling of H2O and CO reactants direct or indirect (via in situ water-gas shift) reactions of CO with excess O atoms in coal of lignite origin These projects share a need for precise understanding of the catalyst requirements and pathways by which O atoms are removed intermolecularly and intramolecularly by carbon versus hydrogen active species Our previous elucidation of the mechanism and site requirements for selective oxidation of CO in the presence of excess H2 and for removal of H2 via selective reaction with O2 during alkane dehydrogenation have led to precedents for our ability to design catalysts to control the selectivity of oxygen removal. Our on-going collaborations with Matt Neurock in theoretical studies of reactions of chemisorbed oxygen with diverse reactants provide also essential foundations for rapid progress in an area critical to address the severe H/C/O imbalances prevalent in conversion scenarios tackling alternate sources of carbon. O* “CHxOy” catalytic water-gas shift (or the thermochemical cycle analogs) in situ generation of “H” during upgrading of aromatics and oxygenates (methanol/DME/biomass/glycerol)

Selective Removal of O by C instead of H
Premise and Context: ……….. feedstocks and streams have low H/(C,O) ratios … a problem best addressed by reacting the C with the O “Direct” Reactions of CO with O CO O* O* O* O* O* Selective removal of oxygen using carbon monoxide instead of hydrogen This is a new research thrust in which we pose and propose to address broad and fundamental questions about how oxygen atoms within molecules can be removed via (i) intermolecular reactions with CO or ii) reactions of C-atoms within oxygenates or within co-reactant molecules. These activities reflect the premise that X-to-liquids scenarios are evolving into H-poorer and C/O-richer contexts, as coal and biomass are increasingly introduced into carbon feedstock pools; they also reflect an expected benefit of forming concentrated CO2 streams, for conversion or sequestration purpose, in the economics of conversion processes within carbon-constrained scenarios. We stress that forming CO2 is unavoidable for the conversion of these H-deficient feedstock pools, whether by the selective use of excess C and CO directly or indirectly or by the production of H2 required for stoichiometric balance via endothermic gasification of carbon-rich feedstocks. One component of the proposed research addresses the use of CO to extract oxygen from H2O with H2 as the desired by-product, a process that in its conventional catalytic context is known as the water-gas shift reaction. Our initial studies will address the mechanism for this reaction –widely studied but yet unclear- and the specific role of O2-assisted pathways in increasing rates and improving the thermodynamics of H2 generation from CO/H2O mixtures. We propose to then transfer these insights and knowledge into novel strategies for the removal of oxygen and/or the in situ regeneration of H2. Some of these proposed strategies are: in-situ formation of H2 or hydrogen-rich transfer species from H2O/CO mixtures during the upgrading of molecules with high C or O content derived from coal or biomass direct use of CO to remove oxygen from biomass-derived oxygenates (e.g. glycerol, carbohydrates) and the use of C atoms within these molecules (instead of their H atoms) to remove excess oxygen while preserving hydrogen use of CO to remove O directly or to form H2 in situ during methanol/DME homologation via direct routes or intervening water-gas shift pathways exploit redox water-gas shift routes by decoupling these elementary steps into thermochemical cycles that form separate high-purity H2 and CO2 streams via temporal cycling of H2O and CO reactants direct or indirect (via in situ water-gas shift) reactions of CO with excess O atoms in coal of lignite origin These projects share a need for precise understanding of the catalyst requirements and pathways by which O atoms are removed intermolecularly and intramolecularly by carbon versus hydrogen active species Our previous elucidation of the mechanism and site requirements for selective oxidation of CO in the presence of excess H2 and for removal of H2 via selective reaction with O2 during alkane dehydrogenation have led to precedents for our ability to design catalysts to control the selectivity of oxygen removal. Our on-going collaborations with Matt Neurock in theoretical studies of reactions of chemisorbed oxygen with diverse reactants provide also essential foundations for rapid progress in an area critical to address the severe H/C/O imbalances prevalent in conversion scenarios tackling alternate sources of carbon. CO2 H* O* -(CHx)- H* Water-gas shift H-O-H + CO O-C-O + H-H Alkanol-gas shift R-O-H + CO O=C-O R-H O* “CHxOy”

Selective Removal of O by Forming New C-C and C-O bonds
Premise and Context: ……….. feedstocks and streams have low H/(C,O) ratios … a problem best addressed by reacting C and O O* O* O* O* O* … concentrated … but unavoidable CO2 H* O* -(CHx)- H* O* Selective removal of oxygen using carbon monoxide instead of hydrogen This is a new research thrust in which we pose and propose to address broad and fundamental questions about how oxygen atoms within molecules can be removed via (i) intermolecular reactions with CO or ii) reactions of C-atoms within oxygenates or within co-reactant molecules. These activities reflect the premise that X-to-liquids scenarios are evolving into H-poorer and C/O-richer contexts, as coal and biomass are increasingly introduced into carbon feedstock pools; they also reflect an expected benefit of forming concentrated CO2 streams, for conversion or sequestration purpose, in the economics of conversion processes within carbon-constrained scenarios. We stress that forming CO2 is unavoidable for the conversion of these H-deficient feedstock pools, whether by the selective use of excess C and CO directly or indirectly or by the production of H2 required for stoichiometric balance via endothermic gasification of carbon-rich feedstocks. One component of the proposed research addresses the use of CO to extract oxygen from H2O with H2 as the desired by-product, a process that in its conventional catalytic context is known as the water-gas shift reaction. Our initial studies will address the mechanism for this reaction –widely studied but yet unclear- and the specific role of O2-assisted pathways in increasing rates and improving the thermodynamics of H2 generation from CO/H2O mixtures. We propose to then transfer these insights and knowledge into novel strategies for the removal of oxygen and/or the in situ regeneration of H2. Some of these proposed strategies are: in-situ formation of H2 or hydrogen-rich transfer species from H2O/CO mixtures during the upgrading of molecules with high C or O content derived from coal or biomass direct use of CO to remove oxygen from biomass-derived oxygenates (e.g. glycerol, carbohydrates) and the use of C atoms within these molecules (instead of their H atoms) to remove excess oxygen while preserving hydrogen use of CO to remove O directly or to form H2 in situ during methanol/DME homologation via direct routes or intervening water-gas shift pathways exploit redox water-gas shift routes by decoupling these elementary steps into thermochemical cycles that form separate high-purity H2 and CO2 streams via temporal cycling of H2O and CO reactants direct or indirect (via in situ water-gas shift) reactions of CO with excess O atoms in coal of lignite origin These projects share a need for precise understanding of the catalyst requirements and pathways by which O atoms are removed intermolecularly and intramolecularly by carbon versus hydrogen active species Our previous elucidation of the mechanism and site requirements for selective oxidation of CO in the presence of excess H2 and for removal of H2 via selective reaction with O2 during alkane dehydrogenation have led to precedents for our ability to design catalysts to control the selectivity of oxygen removal. Our on-going collaborations with Matt Neurock in theoretical studies of reactions of chemisorbed oxygen with diverse reactants provide also essential foundations for rapid progress in an area critical to address the severe H/C/O imbalances prevalent in conversion scenarios tackling alternate sources of carbon. “CHxOy” …… intramolecular reactions of C with O in CHxOy …… C-C bond formation with O-removal as H2O or CO2 …… O-removal as H2O in etherification/dehydration… C-O bonds form

…… in fact, it is the precursor to low rank coals
The major challenge with all biomass conversion strategies is how to efficiently remove the oxygen and form molecules with the appropriate combustion or chemical properties. Effective hydrogen-to-carbon ratio (H/Ceff) H/Ceff ratios of carbohydrates, sorbitol, and glycerol (all biomass-derived compounds) are 0, 1/3, and 2/3. H/Ceff ratios are ∼2 for highly paraffinic crudes to ~ 1 for aromatic residues. In this respect, biomass can be viewed as a hydrogen-deficient molecule compared with petroleum-based feedstocks …… in fact, it is the precursor to low rank coals

Abstract Propanediol, propanol and propanal are used as reactants to probe oxygen removal pathways involving intramolecular decarbonylation, direct reactions with CO, and hydrodeoxygenation and hydrogenolysis using H2 formed in situ from CO-H2O mixtures on supported metal clusters. Group VIII and Ib metals catalyze these reactions, as well as the aldol condensation and esterification of reactants and intermediates and form larger molecules (C4+ alkanes, alkenes, and oxygenates) with fewer O-atoms than oxygenate reactants. Specifically, these C3 oxygenates form C-C bonds on metal clusters and 3-pentanone as the initial product via aldol-type condensation steps that remove O-atoms as CO and preserve valuable H-atoms within reaction products. CO reacts directly with alkanols via steps analogous to those involved in water-gas shift to form alkanes at rates much higher that for alkanol hydrogenolysis with H2 as co-reactant. These C-C and C-O activation reactions occur predominantly via monofunctional pathways on metal surfaces; rates and selectivities are influenced by the size of metal clusters but not by the identity of the support, as aresult of the monofunctional nature of the reactions on Cu and other metal surfaces.

Alternatives to remove O from biomass-derived compounds
Oxygen could be removed via: intramolecular use of C-atoms, e.g. decarbonylation, decarboxylation intermolecular reactions with CO (or concurrent formation of C-C and H2O use of CO to extract H from H2O via water gas shift as alternative to the on-purpose generation WGS shift is the simplest manifestation of the selective removal of oxygen from the simplest “oxygenate” … H2O. -(CHx)- O* H* “CHxOy” CO/H2O CO none …. increase H/(C,O) ratio

Selecting appropriate surrogates for biomass-derived molecules
OH Tb = 287 C C-O, C-C and O-H bonds Glycerol OH Tbl = 214 C C-O, C-C and O-H bonds 1,3 propanediol (1,3PD) ….. diols and their derivatives as prototypical molecules with higher vapor pressures than triols, carbohydrates and glycerides, but with the C-O, C-H, and O-H moieties in such molecules

Catalysts: Exploratory studies led us to choose Cu
…. but Fe, Pt, Pd,… show similar “catalytic characteristics” CuO/ZnO/Al2O3 Cu/SiO2 Cu Vary Cu content and cluster size Cu is a well-know catalyst used for WGS reaction at low temperatures. ZnO and Al2O3 act as structural promoters that may not be catalytically innocent …….. incipient wetness impregnation Cu/C co-precipitation Carbon is an inactive support incipient wetness impregnation

Reactions that require H2
1,3 Propanediol Reaction Pathways OH C3H8O2 1,3 PPD Reactions that do not require co-reactants Reactions that require H2 -H2O OH O H C3H6O allyl alcohol C3H4O acrolein propanal -H2 +H2 +H2 C3H8O propanol Propanal formation does not require H2 because it can be obtained by ismoerization (keto-enol tautomerism) of allyl alcohol previously formed from dehydration of 1,3PPD. However, allyl alcohol formation is thermodynamically disfavored under our experimental conditions. Propanol formation does require H2 and for this reason its formation rate is higher when H2 or CO and H2O are fed than when only 1,3PPD reacts over Cu/ZnO/Al2O3 keto-enol tautomerism -H2O +H2 C3H6 propene C3H8 propane Allyl alcohol isomerization to propanal is favored by thermodynamics (∆G=-57 kJ mol-1)

Reactions of H2 with 1,3 propanediol
Hydrogenation of 1,3 propanediol complete coversion to propanol and propanal. Equilibrium line …. no propane detected Diol hydrogenation CuO/ZnO/Al2O3 OH C3H8O2 1,3 PDD -H2O O H +H2 OH Only 1,3PPD X=100%, Spropanal=85% C3H6O propanal C3H8O propanol [503 K, 0.8 kPa 1,3 PPD, residence time = 216 g ks mol-1]

Example: Hydrogenation of 1,3 propanediol
Propanal 10 kPa H2 20 kPa H2 40 kPa H2 Propanol Conversion CuO/ZnO/Al2O3 1,3 propanediol propanal propanol More H2, larger propanol/propane ratios [503 K, 0.8 kPa 1,3 PPD, residence time = 216 g ks mol-1]

1,3 Propanediol Reaction Pathways OH C3H8O2 1,3 PPD Reactions that do not require co-reactants Reactions that require H2 -H2O OH O H C3H6O allyl alcohol C3H4O acrolein propanal + H2 -H2 +H2 C3H8O propanol Propanal formation does not require H2 because it can be obtained by ismoerization (keto-enol tautomerism) of allyl alcohol previously formed from dehydration of 1,3PPD. However, allyl alcohol formation is thermodynamically disfavored under our experimental conditions. Propanol formation does require H2 and for this reason its formation rate is higher when H2 or CO and H2O are fed than when only 1,3PPD reacts over Cu/ZnO/Al2O3 keto-enol tautomerism -H2O +H2 C3H6 propene C3H8 propane

H2 formation rates on Cu/ZnO/Al2O3 without co-feed 1,3 propanediol
In situ H2 formation via WGS reaction H2 formation rates on Cu/ZnO/Al2O3 without co-feed 1,3 propanediol Presure [kPa] Residence time [g ks mol CO-1] Rate H2 formation by WGS [μmoles g-1 s-1] CO H2O H2 1,3PPD Initial 3 h 8 21 19.7 12 3 80 30.5 7.6 10 30 64.9 0.8 6.3 1.9 19 5 7.1 7 H2O-CO co-feed caused deactivation …. some H2 stabilized WGS rates (for 100 h)

H2 formation rates on Cu/ZnO/Al2O3 with and without 1,3 propanediol
In situ H2 formation via WGS reaction H2 formation rates on Cu/ZnO/Al2O3 with and without 1,3 propanediol Presure [kPa] Residence time [g ks mol CO-1] Rate H2 formation by WGS [μmoles g-1 s-1] CO H2O H2 1,3PPD Initial 3 h 8 21 19.7 12 3 80 30.5 7.6 10 30 64.9 0.8 6.3 1.9 19 5 7.1 7

residence time = 216 g ks mol-1]
In situ H2 formation via WGS reaction Equilibrium line Diol hydrogenation CuO/ZnO/Al2O3 Only 1,3PPD, 100% conversion, Spropanal=85% [503 K, 0.8 kPa 1,3 PPD, residence time = 216 g ks mol-1]

In situ H2 formation via WGS reaction Equilibrium line Diol hydrogenation In situ H2 formation via WGS CuO/ZnO/Al2O3 3 h time initial 3 h time [503 K, 0.8 kPa 1,3 PPD, residence time = 216 g ks mol-1]

1,3 Propanediol Reaction Pathways OH C3H8O2 1,3 PPD Reactions that do not require co-reactants Reactions that require H2 -H2O OH O H C3H6O allyl alcohol C3H4O acrolein propanal + H2 -H2 +H2 C3H8O propanol Propanal formation does not require H2 because it can be obtained by ismoerization (keto-enol tautomerism) of allyl alcohol previously formed from dehydration of 1,3PPD. However, allyl alcohol formation is thermodynamically disfavored under our experimental conditions. Propanol formation does require H2 and for this reason its formation rate is higher when H2 or CO and H2O are fed than when only 1,3PPD reacts over Cu/ZnO/Al2O3 keto-enol tautomerism -H2O +H2 C3H6 propene C3H8 propane

Primary and secondary pathways: 1,3 propanediol/CO/H2O reactants
Propanal and acrolein form as “primary” products because required intermediates are present at undetectable levels (PSSH) even at short residence times Propanol and propane act as secondary products formed from propanal and acrolein [503 K, 0.8 kPa 1,3 PPD, 80 kPa H2O, 8 kPa CO]

Reactions that required H2
Primary and secondary products in 1,3 PPD reactions OH Propanal and acrolein appear to be primary products because any possible intermediates are in undetectable concentrations and reach steady-satate values even at very low residence times primary products since their precursor (allyl alcohol was not detected in these experiments). Propanol and propane appera to be secondary products. C3H8O2 1,3 PPD Reactions that do not required co-reactants Reactions that required H2 -H2O OH O H C3H6O allyl alcohol C3H4O acrolein propanal -H2 +H2 +H2 C3H8O propanol -H2O keto-enol tautomerism +H2 C3H6 propene C3H8 propane reactive intermediate [503 K, 0.8 kPa 1,3 PPD, 80 kPa H2O, 8 kPa CO]

Effect of CO on 1,3 propanediol reactions Equilibrium line Diol hydrogenation In situ H2 formation via WGS Diol hydrogenation +18 kPa CO CuO/ZnO/Al2O3 [503 K, 0.8 kPa 1,3 PPD, residence time = 216 g ks mol-1]

… but H2 did not form propane.
Effect of CO on 1,3 propanediol reactions Equilibrium line Diol hydrogenation In situ H2 formation via WGS Diol hydrogenation +18kPa CO CO (10-50 kPa) does not influence propanol/propanal equilibrium, but … …surprisingly forms propane !!! OH O H Propanol/propanal Propane/propanol CO [kPa] … suggestive of direct reactions of CO with propanol or propanal in which O-atoms are removed as CO2. … but H2 did not form propane. CuO/ZnO/Al2O3 [503 K, 0.8 kPa 1,3 PPD, residence time = 216 g ks mol-1]

Alkanol-gas shift reaction
CO + HOH CO2 + H Water-gas shift reaction CO + ROH CO2 + RH Alkanol-gas shift reaction OH C3H8O propanol +CO -CO2 -H2O +H2 C3H6 propene C3H8 propane

Esterification and aldol condensation reactions
Alkanol-gas shift reaction CO + HOH CO2 + H Water gas shift reaction CO + ROH CO2 + RH Alkanol gas shift reaction Alkanol Water R O H H O H R ---- OH RO ---- H H ---- OH HO ---- H RH CO2 OH R CO CO2 OH H CO H2 R=O + H2 Esterification and aldol condensation reactions

……… focus on propanol/propanal reactions in what follows
Since 1,3 propanediol to equilibrium propanol/propanal mixtures is easy 1,3 propanediol/He on CuZnAl catalyst X=100% , Spropanal=85 % Propane can be formed from propanol using CO to remove the O add H2 vary propanal-propanol ratios consider them as an equilibrated pool of reactants OH C3H8O propanol ……… focus on propanol/propanal reactions in what follows …….. H2 O H C3H6O propanal

5. Propanol/propanal reactions
Experiments feeding propanol, propanal-H2, propanol-H2, or propanal OH C3H8O propanol H2 O H C3H6O propanal

Propanol/propanal reactions
OH C3H8O propanol H2 O H C3H6O propanal

+H2 +H2 -H2O AGS -H2O Cα - CO - H2 - CO - H2 Cβ +H2 H2 -H2O C=O + O OH
propene C3H8 propane +H2 -H2O AGS 3 pentanone - H2 - CO O OH 2 methyl pentanal 2 methyl 3-pentanone +H2 -H2O Cα OH - H2 - CO O OH +H2 -H2O hexanal 3 hexanone Cβ C3H8O propanol H2 O H O propylpropionate propanol propionic acid OH + C=O C3H6O propanal

20 % wt. Cu/SiO2 +H2 +H2 -H2O AGS -H2O Cα - CO - H2 - CO - H2 Cβ +H2
propene C3H8 propane +H2 -H2O AGS 3 pentanone - H2 - CO O OH 2 methyl pentanal 2 methyl 3-pentanone +H2 -H2O Cα Propylpropionate 3-Pentanone 2-Methylpentanal Propene Propane 2-Methyl 3-pentanone Pool conversion [20wt% Cu/SiO2, 503 K, 0.64 kPa propanol, 50 kPa H2, residence time = 1623 g ks mol-1] 20 % wt. Cu/SiO2 OH - H2 - CO O OH +H2 -H2O hexanal 3 hexanone Cβ C3H8O propanol H2 O H O propylpropionate propanol propionic acid OH + C=O C3H6O propanal

+H2 +H2 -H2O AGS +H2 -H2O -H2O Cα - CO - H2 - CO - H2 Cβ H2 +H2 -H2O
propene +H2 -H2O C3H8 propane OH O 2 methyl 3-pentanone AGS O +H2 -H2O O OH -H2O 2 methyl pentanal Cα OH - CO - H2 O - CO C3H8O propanol - H2 3-pentanone Cβ H2 O OH +H2 -H2O O O H hexanal +H2 -H2O C3H6O propanal OH O O C=O 3 hexanone O OH O OH + propylpropionate propionic acid propanol

+H2 -H2O Only when CO is present AGS +H2 -H2O Cα - CO - H2 H2
C3H8 propane AGS Only when CO is present O +H2 -H2O OH O 2 methyl 3-pentanone O +H2 -H2O O OH 2 methyl pentanal Cα OH - CO - H2 O C3H8O propanol 3-pentanone H2 Aldol products O H C3H6O propanal Ester C=O O OH O OH + propylpropionate propionic acid propanol

H2 Primary products O ester O 3-pentanone 2-methylpentanal OH propene
2-methyl 3-pentanone propane O 2 methyl 3-pentanone O 2 methyl pentanal OH O C3H8O propanol 3-pentanone H2 O H Aldol products Primary products C3H6O propanal O Ester propylpropionate

Supports are not required for condensation, esterification, alkanol-gas shift …. Cu does it
10% Cu/SiO2 20%Cu/SiO2 50%Cu/ZnO/Al2O3 10% Cu/C Residence time(c) 2125 3400 4250 1700 Pool conversion(a) 2.0 10.4 5.4 1.8 Selectivity (b) Propylpropionate 75 43 47 66 3-Pentanone 21 32 6 12 2-Methyl 3-pentanone 4 13 28 8 2-Methylpentanal 5 Propane Co-feeding CO (10 kPa) 8.6-6 1.7-1 Selectivity (c) 50-62 37-47 37-45 55-76 11-15 18-28 3 14-17 17 27-30 5-7 27-16 15-3 25-8 17-6 Hydrogenation of propanol over Cu based catalysts produces mainly condensation products (C5 and C6) and no propene/propane. Usually, condensation reactions are carried out using base catalyst… Here, we found that also metallic catalysts (Cu) can formed these compounds. (a) pool conversion (propanal + propanol) (b) calculated as carbon-selectivity (c) defined as: moles Cu s (moles propanol in)-1 [503 K, 0.64 kPa propanol, 10 kPa H2]

Supports are not required for condensation, esterification, alkanol-gas shift …. Cu does it
10% Cu/SiO2 20%Cu/SiO2 50%Cu/ZnO/Al2O3 10% Cu/C Residence time(c) 2125 3400 4250 1700 Pool conversion(a) 2.0 10.4 5.4 1.8 Selectivity (b) Propylpropionate 75 43 47 66 3-Pentanone 21 32 6 12 2-Methyl 3-pentanone 4 13 28 8 2-Methylpentanal 5 Propane CO (10 kPa) 8.6-6 1.7-1 50-62 37-47 37-45 55-76 11-15 18-28 3 14-17 17 27-30 5-7 27-16 15-3 25-8 17-6 [503 K, 0.64 kPa propanol, 10 kPa H2]

Propanal Kinetic Study (Cu/SiO2)
[10 wt % Cu/SiO2 (5.5% dispersion), 503 K] these products are formed from the aldehyde

Propanal Kinetic Study (Cu/SiO2)
Aldol Ester [10 wt % Cu/SiO2 (5.5% dispersion), 503 K]

Effect of Cu dispersion and cluster size
Site-time yield vs Cu dispersion for propanol/propanal reactions Esterification Aldol Condensation Surface of large Cu crystallites most effective at C-C and C-O bond formation

Effect of Cu dispersions and average crystallite diameters
Site-time yield vs Cu dispersion for propanol/propanal reactions on 10wt% Cu/SiO2 samples Propene and propane formation The propene+propane selectivity was always lower than 10%. Light hydrocarbons formation experiences no significant geometric effect.

Conclusions O-atoms can be removed via: (i) intramolecular use of C-atoms (ii) intermolecular reactions between the oxygenate compound with CO and (iii) using CO to extract H from H2O via water gas shift. (in addition to hydrodeoxygenation) Cu-based catalysts work (and Pt, Pd, Fe, ……). in situ generated H2 via water gas shift reaction can be used to form propanol and propanal at their equilibrium ratio from 1,3 propanediol. significant amounts of propane do not form 1,3 propanediol or propanol/propanal reactants when H2 is used, but do form via alkanol-gas shift reactions with CO. Cu metal surfaces form C-C and C-O bonds and large clusters have more “active” surfaces (for aldol condensation and esterification) Rate equations are consistent with bimolecular surface reactions

Selective Oxygen Removal from Oxygenates

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