Amit Gokhale - Profile on Academia.edu (original) (raw)
Papers by Amit Gokhale
Atomic-Scale Design of Iron Fischer-Tropsch Catalysts: A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach
Efforts during this second year focused on four areas: (1) continued searching and summarizing of... more Efforts during this second year focused on four areas: (1) continued searching and summarizing of published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) investigation of CO adsorption/desorption and temperature programmed hydrogenation (TPH) of carbonaceous species after FTS on unsupported iron and alumina-supported iron catalysts; (3) activity tests of alumina-supported iron catalysts in a
Green Chemistry, 2016
Self-condensation of biomass-derived methyl ketones catalyzed by solid bases or acids produces co... more Self-condensation of biomass-derived methyl ketones catalyzed by solid bases or acids produces corresponding cyclic trimers exclusively in excellent yields. Hydrogenated versions of such trimers can be good lubricants.
Catalysis Science & Technology
Spectroscopic, kinetic and theoretical insights guide the design of PdCu dehydrogenation catalysts.
Hybrid Biological–Chemical Approach Offers Flexibility and Reduces the Carbon Footprint of Biobased Plastics, Rubbers, and Fuels
ACS Sustainable Chemistry & Engineering
Accounts of Chemical Research
CONSPECTUS: Growing concern with the environmental impact of CO 2 emissions produced by combustio... more CONSPECTUS: Growing concern with the environmental impact of CO 2 emissions produced by combustion of fuels derived from fossil-based carbon resources has stimulated the search for renewable sources of carbon. Much of this focus has been on the development of methods for producing transportation fuels, the major source of CO 2 emissions today, and to a lesser extent on the production of lubricants and chemicals. First-generation biofuels such as bioethanol, produced by the fermentation of sugar cane-or corn-based sugars, and biodiesel, produced by the transesterification reaction of triglycerides with alcohols to form a mixture of long-chain fatty esters, can be blended with traditional fuels in limited amounts and also arise in food versus fuel debates. Producing molecules that can be drop-in solutions for fossil-derived products used in the transportation sector allows for efficient use of the existing infrastructure and is therefore particularly interesting. In this context, the most viable source of renewable carbon is abundantly available lignocellulosic biomass, a complex mixture of lignin, hemicellulose, and cellulose. Conversion of the carbohydrate portion of biomass (hemicellulose and cellulose) to fuels requires considerable chemical restructuring of the component sugars in order to achieve the energy density and combustion properties required for transportation fuelsgasoline, diesel, and jet. A different set of constraints must be met for the conversion of biomass-sourced sugars to lubricants and chemicals. This Account describes strategies developed by us to utilize aldehydes, ketones, alcohols, furfurals, and carboxylic acids derived from C 5 and C 6 sugars, acetone−butanol−ethanol (ABE) fermentation mixtures, and various biomass-derived carboxylic acids and fatty acids to produce fuels, lubricants, and chemicals. Oxygen removal from these synthons is achieved by dehydration, decarboxylation, hydrogenolysis, and hydrodeoxygenation, whereas reactions such as aldol condensation, etherification, alkylation, and ketonization are used to build up the number of carbon atoms in the final product. We show that our strategies lead to high-octane components that can be blended into gasoline, C 9 −C 22 compounds that possess energy densities and properties required for diesel and jet fuels, and lubricants that are equivalent or superior to current synthetic lubricants. Replacing a fraction of the crude-oil-derived products with such renewable sources can mitigate the negative impact of the transportation sector on overall anthropogenic greenhouse gas (GHG) emissions and climate change potential. While ethanol is a well-known fuel additive, there is significant interest in using ethanol as a platform molecule to manufacture a variety of valuable chemicals. We show that bioethanol can be converted with high selectivity to butanol or 1,3-butadiene, providing interesting alternatives to the current production from petroleum. Finally, we report that several of the strategies developed have the potential to reduce GHG emissions by 55−80% relative to those for petroleum-based processes.
Chem
Renewable resources and bio-based feedstocks may present a sustainable alternative to petrochemic... more Renewable resources and bio-based feedstocks may present a sustainable alternative to petrochemical sources to satisfy modern society's ever-increasing demand for energy and chemicals. However, the conversion processes needed for these future bio-refineries will likely differ from those currently used in the petrochemical industry. Biotechnology and chemocatalysis offer routes for converting biomass into a variety of molecules that can serve as platform chemicals. While a host of technologies can be leveraged for biomass upgrading, condensation reactions are significant because they have the potential to upgrade these bio-derived feedstocks while minimizing the loss of carbon and the generation of by-products. This review surveys both the biological and chemical catalytic routes to producing platform chemicals from renewable sources and describes advances in condensation chemistry and strategies for the conversion of these platform chemicals into fuels and high-value chemicals.
Sustainable Energy Fuels
We describe catalytic sequences for converting biomass-derived carboxylic acids, to fuels and lub... more We describe catalytic sequences for converting biomass-derived carboxylic acids, to fuels and lubricants that are compatible with the existing energy infrastructure.
ChemCatChem, 2017
Supporting informationand the ORCID identification number(s) for the author(s) of this article ca... more Supporting informationand the ORCID identification number(s) for the author(s) of this article can be found underh ttp://dx.doi.org/10.1002/ cctc.201601507. This manuscript is part of aS pecialI ssue to celebrate the 50 th annual meeting of the GermanC atalysis Society.
Mechanism of the Water Gas Shift Reaction on Pt: First Principles, Experiments, and Microkinetic Modeling
The Journal of Physical Chemistry C, 2008
The research described in this product was performed in part in the Environmental Molecular Scien... more The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We present a microkinetic model as well as experimental data for the low-temperature water gas shift (WGS) reaction catalyzed by
Carbonaceous material for purifying lignocellulosic oligomers
Journal of Crystal Growth, May 1, 2007
The role of Sb and Bi as surfactants in GaN growth is investigated using first-principles, period... more The role of Sb and Bi as surfactants in GaN growth is investigated using first-principles, periodic, self-consistent, density functional theory calculations. It is shown that N diffuses much slower than Ga on the Ga-rich GaN(0 0 0 1) surface. Surfactants such as Sb and Bi are considerably more mobile on this surface and they react with N to produce SbN and BiN intermediates. The diffusion of these intermediates on the Ga-rich GaN(0 0 0 1) surface is more facile than that of atomic N. Therefore, this intermediate-mediated transport mechanism would increase the effective diffusion length for N. As a result, Sb and Bi would improve step edge incorporation of N, leading to a reduction in the average surface roughness of the GaN samples. While the barrier for BiN diffusion on GaN(0 0 0 1) is only slightly lower than that of N, the calculated difference in the diffusion barriers of SbN and N on that surface is significant and this would cause the preferential sidewall facets to change from ð11 0 1Þ and ð1 12 2Þ to the vertical ð1 12 0Þ facets during lateral epitaxial overgrowth (LEO). Additional calculations show that Sb and Bi can act as surfactants on the GaNð1 12 0Þ surface too. However, the adsorption of all the species on GaNð1 12 0Þ is significantly weaker and the diffusion barriers of SbN and BiN are considerably higher compared to the GaN(0 0 0 1) surface. Consequently, the surfactant effect of Sb and Bi on the GaNð1 12 0Þ surface should be less pronounced compared to that on the GaN(0 0 0 1) surface.
Journal of the American Chemical Society, 2016
Condensation reactions such as Guerbet and aldol are important since they allow for C−C bond form... more Condensation reactions such as Guerbet and aldol are important since they allow for C−C bond formation and give higher molecular weight oxygenates. An initial study identified Pdsupported on hydrotalcite as an active catalyst for the transformation, although this catalyst showed extensive undesirable decarbonylation. A catalyst containing Pd and Cu in a 3:1 ratio dramatically decreased decarbonylation, while preserving the high catalytic rates seen with Pd-based catalysts. A combination of XRD, EXAFS, TEM, and CO chemisorption and TPD revealed the formation of CuPd bimetallic nanoparticles with a Cu-enriched surface. Finally, density functional theory studies suggest that the surface segregation of Cu atoms in the bimetallic alloy catalyst produces Cu sites with increased reactivity, while the Pd sites responsible for unselective decarbonylation pathways are selectively poisoned by CO.
Purification Methods and Systems Related to Renewable Materials and Biofuels Production
Method for extracting organic compounds from aqueous mixtures
Proceedings of the National Academy of Sciences, 2015
Decarbonizing the transportation sector is critical to achieving global climate change mitigation... more Decarbonizing the transportation sector is critical to achieving global climate change mitigation. Although biofuels will play an important role in conventional gasoline and diesel applications, bioderived solutions are particularly important in jet fuels and lubricants, for which no other viable renewable alternatives exist. Producing compounds for jet fuel and lubricant base oil applications often requires upgrading fermentation products, such as alcohols and ketones, to reach the appropriate molecular-weight range. Ketones possess both electrophilic and nucleophilic functionality, which allows them to be used as building blocks similar to alkenes and aromatics in a petroleum refining complex. Here, we develop a method for selectively upgrading biomass-derived alkyl methyl ketones with >95% yields into trimer condensates, which can then be hydrodeoxygenated in near-quantitative yields to give a new class of cycloalkane compounds. The basic chemistry developed here can be tailor...
Role of lignin in reducing life-cycle carbon emissions, water use, and cost for United States cellulosic biofuels
Environmental science & technology, Jan 5, 2014
Cellulosic ethanol can achieve estimated greenhouse gas (GHG) emission reductions greater than 80... more Cellulosic ethanol can achieve estimated greenhouse gas (GHG) emission reductions greater than 80% relative to gasoline, largely as a result of the combustion of lignin for process heat and electricity in biorefineries. Most studies assume lignin is combusted onsite, but exporting lignin to be cofired at coal power plants has the potential to substantially reduce biorefinery capital costs. We assess the life-cycle GHG emissions, water use, and capital costs associated with four representative biorefinery test cases. Each case is evaluated in the context of a U.S. national scenario in which corn stover, wheat straw, and Miscanthus are converted to 1.4 EJ (60 billion liters) of ethanol annually. Life-cycle GHG emissions range from 4.7 to 61 g CO2e/MJ of ethanol (compared with ∼ 95 g CO2e/MJ of gasoline), depending on biorefinery configurations and marginal electricity sources. Exporting lignin can achieve GHG emission reductions comparable to onsite combustion in some cases, reduce li...
This work focuses on (1) searching/summarizing published Fischer-Tropsch synthesis (FTS) mechanis... more This work focuses on (1) searching/summarizing published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) preparation and characterization of unsupported iron catalysts with/without potassium/platinum promoters; (3) measurement of H 2 and CO adsorption/dissociation kinetics on iron catalysts using transient methods; (3) analysis of the transient rate data to calculate kinetic parameters of early elementary steps in FTS; (4) construction of a microkinetic model of FTS on iron, and (5) validation of the model from collection of steady-state rate data for FTS on iron catalysts.
Atomic-Scale Design of Iron Fischer-Tropsch Catalysts: A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach
Efforts during this second year focused on four areas: (1) continued searching and summarizing of... more Efforts during this second year focused on four areas: (1) continued searching and summarizing of published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) investigation of CO adsorption/desorption and temperature programmed hydrogenation (TPH) of carbonaceous species after FTS on unsupported iron and alumina-supported iron catalysts; (3) activity tests of alumina-supported iron catalysts in a
Green Chemistry, 2016
Self-condensation of biomass-derived methyl ketones catalyzed by solid bases or acids produces co... more Self-condensation of biomass-derived methyl ketones catalyzed by solid bases or acids produces corresponding cyclic trimers exclusively in excellent yields. Hydrogenated versions of such trimers can be good lubricants.
Catalysis Science & Technology
Spectroscopic, kinetic and theoretical insights guide the design of PdCu dehydrogenation catalysts.
Hybrid Biological–Chemical Approach Offers Flexibility and Reduces the Carbon Footprint of Biobased Plastics, Rubbers, and Fuels
ACS Sustainable Chemistry & Engineering
Accounts of Chemical Research
CONSPECTUS: Growing concern with the environmental impact of CO 2 emissions produced by combustio... more CONSPECTUS: Growing concern with the environmental impact of CO 2 emissions produced by combustion of fuels derived from fossil-based carbon resources has stimulated the search for renewable sources of carbon. Much of this focus has been on the development of methods for producing transportation fuels, the major source of CO 2 emissions today, and to a lesser extent on the production of lubricants and chemicals. First-generation biofuels such as bioethanol, produced by the fermentation of sugar cane-or corn-based sugars, and biodiesel, produced by the transesterification reaction of triglycerides with alcohols to form a mixture of long-chain fatty esters, can be blended with traditional fuels in limited amounts and also arise in food versus fuel debates. Producing molecules that can be drop-in solutions for fossil-derived products used in the transportation sector allows for efficient use of the existing infrastructure and is therefore particularly interesting. In this context, the most viable source of renewable carbon is abundantly available lignocellulosic biomass, a complex mixture of lignin, hemicellulose, and cellulose. Conversion of the carbohydrate portion of biomass (hemicellulose and cellulose) to fuels requires considerable chemical restructuring of the component sugars in order to achieve the energy density and combustion properties required for transportation fuelsgasoline, diesel, and jet. A different set of constraints must be met for the conversion of biomass-sourced sugars to lubricants and chemicals. This Account describes strategies developed by us to utilize aldehydes, ketones, alcohols, furfurals, and carboxylic acids derived from C 5 and C 6 sugars, acetone−butanol−ethanol (ABE) fermentation mixtures, and various biomass-derived carboxylic acids and fatty acids to produce fuels, lubricants, and chemicals. Oxygen removal from these synthons is achieved by dehydration, decarboxylation, hydrogenolysis, and hydrodeoxygenation, whereas reactions such as aldol condensation, etherification, alkylation, and ketonization are used to build up the number of carbon atoms in the final product. We show that our strategies lead to high-octane components that can be blended into gasoline, C 9 −C 22 compounds that possess energy densities and properties required for diesel and jet fuels, and lubricants that are equivalent or superior to current synthetic lubricants. Replacing a fraction of the crude-oil-derived products with such renewable sources can mitigate the negative impact of the transportation sector on overall anthropogenic greenhouse gas (GHG) emissions and climate change potential. While ethanol is a well-known fuel additive, there is significant interest in using ethanol as a platform molecule to manufacture a variety of valuable chemicals. We show that bioethanol can be converted with high selectivity to butanol or 1,3-butadiene, providing interesting alternatives to the current production from petroleum. Finally, we report that several of the strategies developed have the potential to reduce GHG emissions by 55−80% relative to those for petroleum-based processes.
Chem
Renewable resources and bio-based feedstocks may present a sustainable alternative to petrochemic... more Renewable resources and bio-based feedstocks may present a sustainable alternative to petrochemical sources to satisfy modern society's ever-increasing demand for energy and chemicals. However, the conversion processes needed for these future bio-refineries will likely differ from those currently used in the petrochemical industry. Biotechnology and chemocatalysis offer routes for converting biomass into a variety of molecules that can serve as platform chemicals. While a host of technologies can be leveraged for biomass upgrading, condensation reactions are significant because they have the potential to upgrade these bio-derived feedstocks while minimizing the loss of carbon and the generation of by-products. This review surveys both the biological and chemical catalytic routes to producing platform chemicals from renewable sources and describes advances in condensation chemistry and strategies for the conversion of these platform chemicals into fuels and high-value chemicals.
Sustainable Energy Fuels
We describe catalytic sequences for converting biomass-derived carboxylic acids, to fuels and lub... more We describe catalytic sequences for converting biomass-derived carboxylic acids, to fuels and lubricants that are compatible with the existing energy infrastructure.
ChemCatChem, 2017
Supporting informationand the ORCID identification number(s) for the author(s) of this article ca... more Supporting informationand the ORCID identification number(s) for the author(s) of this article can be found underh ttp://dx.doi.org/10.1002/ cctc.201601507. This manuscript is part of aS pecialI ssue to celebrate the 50 th annual meeting of the GermanC atalysis Society.
Mechanism of the Water Gas Shift Reaction on Pt: First Principles, Experiments, and Microkinetic Modeling
The Journal of Physical Chemistry C, 2008
The research described in this product was performed in part in the Environmental Molecular Scien... more The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We present a microkinetic model as well as experimental data for the low-temperature water gas shift (WGS) reaction catalyzed by
Carbonaceous material for purifying lignocellulosic oligomers
Journal of Crystal Growth, May 1, 2007
The role of Sb and Bi as surfactants in GaN growth is investigated using first-principles, period... more The role of Sb and Bi as surfactants in GaN growth is investigated using first-principles, periodic, self-consistent, density functional theory calculations. It is shown that N diffuses much slower than Ga on the Ga-rich GaN(0 0 0 1) surface. Surfactants such as Sb and Bi are considerably more mobile on this surface and they react with N to produce SbN and BiN intermediates. The diffusion of these intermediates on the Ga-rich GaN(0 0 0 1) surface is more facile than that of atomic N. Therefore, this intermediate-mediated transport mechanism would increase the effective diffusion length for N. As a result, Sb and Bi would improve step edge incorporation of N, leading to a reduction in the average surface roughness of the GaN samples. While the barrier for BiN diffusion on GaN(0 0 0 1) is only slightly lower than that of N, the calculated difference in the diffusion barriers of SbN and N on that surface is significant and this would cause the preferential sidewall facets to change from ð11 0 1Þ and ð1 12 2Þ to the vertical ð1 12 0Þ facets during lateral epitaxial overgrowth (LEO). Additional calculations show that Sb and Bi can act as surfactants on the GaNð1 12 0Þ surface too. However, the adsorption of all the species on GaNð1 12 0Þ is significantly weaker and the diffusion barriers of SbN and BiN are considerably higher compared to the GaN(0 0 0 1) surface. Consequently, the surfactant effect of Sb and Bi on the GaNð1 12 0Þ surface should be less pronounced compared to that on the GaN(0 0 0 1) surface.
Journal of the American Chemical Society, 2016
Condensation reactions such as Guerbet and aldol are important since they allow for C−C bond form... more Condensation reactions such as Guerbet and aldol are important since they allow for C−C bond formation and give higher molecular weight oxygenates. An initial study identified Pdsupported on hydrotalcite as an active catalyst for the transformation, although this catalyst showed extensive undesirable decarbonylation. A catalyst containing Pd and Cu in a 3:1 ratio dramatically decreased decarbonylation, while preserving the high catalytic rates seen with Pd-based catalysts. A combination of XRD, EXAFS, TEM, and CO chemisorption and TPD revealed the formation of CuPd bimetallic nanoparticles with a Cu-enriched surface. Finally, density functional theory studies suggest that the surface segregation of Cu atoms in the bimetallic alloy catalyst produces Cu sites with increased reactivity, while the Pd sites responsible for unselective decarbonylation pathways are selectively poisoned by CO.
Purification Methods and Systems Related to Renewable Materials and Biofuels Production
Method for extracting organic compounds from aqueous mixtures
Proceedings of the National Academy of Sciences, 2015
Decarbonizing the transportation sector is critical to achieving global climate change mitigation... more Decarbonizing the transportation sector is critical to achieving global climate change mitigation. Although biofuels will play an important role in conventional gasoline and diesel applications, bioderived solutions are particularly important in jet fuels and lubricants, for which no other viable renewable alternatives exist. Producing compounds for jet fuel and lubricant base oil applications often requires upgrading fermentation products, such as alcohols and ketones, to reach the appropriate molecular-weight range. Ketones possess both electrophilic and nucleophilic functionality, which allows them to be used as building blocks similar to alkenes and aromatics in a petroleum refining complex. Here, we develop a method for selectively upgrading biomass-derived alkyl methyl ketones with >95% yields into trimer condensates, which can then be hydrodeoxygenated in near-quantitative yields to give a new class of cycloalkane compounds. The basic chemistry developed here can be tailor...
Role of lignin in reducing life-cycle carbon emissions, water use, and cost for United States cellulosic biofuels
Environmental science & technology, Jan 5, 2014
Cellulosic ethanol can achieve estimated greenhouse gas (GHG) emission reductions greater than 80... more Cellulosic ethanol can achieve estimated greenhouse gas (GHG) emission reductions greater than 80% relative to gasoline, largely as a result of the combustion of lignin for process heat and electricity in biorefineries. Most studies assume lignin is combusted onsite, but exporting lignin to be cofired at coal power plants has the potential to substantially reduce biorefinery capital costs. We assess the life-cycle GHG emissions, water use, and capital costs associated with four representative biorefinery test cases. Each case is evaluated in the context of a U.S. national scenario in which corn stover, wheat straw, and Miscanthus are converted to 1.4 EJ (60 billion liters) of ethanol annually. Life-cycle GHG emissions range from 4.7 to 61 g CO2e/MJ of ethanol (compared with ∼ 95 g CO2e/MJ of gasoline), depending on biorefinery configurations and marginal electricity sources. Exporting lignin can achieve GHG emission reductions comparable to onsite combustion in some cases, reduce li...
This work focuses on (1) searching/summarizing published Fischer-Tropsch synthesis (FTS) mechanis... more This work focuses on (1) searching/summarizing published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) preparation and characterization of unsupported iron catalysts with/without potassium/platinum promoters; (3) measurement of H 2 and CO adsorption/dissociation kinetics on iron catalysts using transient methods; (3) analysis of the transient rate data to calculate kinetic parameters of early elementary steps in FTS; (4) construction of a microkinetic model of FTS on iron, and (5) validation of the model from collection of steady-state rate data for FTS on iron catalysts.