We report here on an experimental study to produce refinery-ready fuel blendstocks via catalytic ... more We report here on an experimental study to produce refinery-ready fuel blendstocks via catalytic hydrodeoxygenation (upgrading) of pyrolysis oil using several biomass feedstocks and various blends. Blends were tested along with the pure materials to determine the effect of blending on product yields and qualities. Within experimental error, oil yields from fast pyrolysis and upgrading are shown to be linear functions of the blend components. Switchgrass exhibited lower fast pyrolysis and upgrading yields than the woody samples, which included clean pine, oriented strand board (OSB), and a mix of piñon and juniper (PJ). The notable exception was PJ, for which the poor upgrading yield of 18% was likely associated with the very high viscosity of the PJ fast pyrolysis oil (947 cp). The highest fast pyrolysis yield (54% dry basis) was obtained from clean pine, while the highest upgrading yield (50%) was obtained from a blend of 80% clean pine and 20% OSB (CP 8 OSB 2). For switchgrass, reducing the fast pyrolysis temperature to 450 °C resulted in a significant increase to the pyrolysis oil yield and reduced hydrogen consumption during hydrotreating, but did not directly affect the hydrotreating oil yield. The water content of fast pyrolysis oils was also observed to increase linearly with the summed content of potassium and sodium, ranging from 21% for clean pine to 37% for switchgrass. Multiple linear regression models demonstrate that fast pyrolysis is strongly dependent upon the contents lignin and volatile matter as well as the sum of potassium and sodium.
Efficient conversion of all components in lignocellulosic biomass is essential to realizing econo... more Efficient conversion of all components in lignocellulosic biomass is essential to realizing economic feasibility of biorefineries. However, lignin cannot be fermented using biochemical routes. Furthermore, high lignin and high ash residues from simultaneous saccharification and fermentation (SSF) is difficult to thermochemically process due to feed line plugging and bed agglomeration. In this study a corn stover SSF digester residue was thermally pretreated at 300°C for 22.5 minutes and gasified in a fluidized bed gasifier to study the effect of thermal pretreatment on its processing behavior. Untreated, pelletized SSF residue was gasified at the same conditions to establish the baseline processing behavior. Results indicate the thermal pretreatment process removes a substantial portion of the polar and non-polar extractives, with a resultant increase in the concentration of lignin, cellulose, and ash. Feed line plugging was not observed, although bed agglomeration occurred at similar rates for both feedstocks, suggesting that overall ash content is the most important factor affecting bed agglomeration. Benzene, phenol, and polyaromatic hydrocarbons in the tar were present at higher concentrations in the treated material, with higher tar loading in the product gas. Total product gas generation is lower for the treated material, although overall gas composition does not change.
Residues high in lignin and ash generated from the simultaneous saccharification and fermentation... more Residues high in lignin and ash generated from the simultaneous saccharification and fermentation of corn stover were thermally pretreated in an inert (N 2) atmosphere to study the effect of time and temperature on their softening points. These residues are difficult to feed into gasifiers due to premature thermal degradation and formation of reactive liquids in the feed lines, leading to plugging. The untreated and treated residues were characterized by proximate and ultimate analysis, and then analyzed via TGA, DSC, 13 C NMR, Py-GC-MS, CHNO/S, and TMA. Interpretation of the compositional analysis indicates that the weight loss observed during pretreatment is mainly due to the thermal decomposition and volatilization of the hemicelluloses and amorphous cellulose fractions. Fixed carbon increases in the pretreated material, mostly due to a concentration effect rather than the formation of new extra poly-aromatic material. The optimal processing time and temperature to minimize the production of carbonyl groups in the pretreated samples was 300 • C at a time of 30 min. Results showed that the softening point of the material could be increased from 187 • C to 250 • C, and that under the experimental conditions studied, pretreatment temperature plays a more important role than time. The increase in softening point was mainly due to the formation of covalent bonds in the lignin structures and the removal of low molecular weight volatile intermediates.
This research investigates the bed agglomeration phenomena during the steam gasification of a hig... more This research investigates the bed agglomeration phenomena during the steam gasification of a high-lignin residue produced from the simultaneous saccharification and fermentation (SSF) of corn stover in a bubbling fluidized bed. The studies were conducted at 895°C using alumina as bed material. Biomass was fed at 1.5 kg/h, while steam was fed to give a velocity equal to 2.5 times the minimum fluidization velocity, with a steam/carbon ratio of 0.9. The pelletized feedstock was co-fed with a cooling nitrogen stream to mitigate feed line plugging issues. Tar production was high at 50.3 g/Nm 3 , and the fraction of C10+ compounds was greater than that observed in the gasification of traditional lignocellulosic feedstocks. Carbon closures over 94% were achieved for all experiments. Bed agglomeration was found to be problematic, indicated by pressure drop increases observed below the bed and upstream of the feed line. Two size categories of solids were recovered from the reactor: +0.25 mm and −0.25 mm. After 2.75 h of experiment, 61.7 wt % was recovered as −0.25 mm particles and 38.2 wt % of the recovered reactor solids were +0.25 mm. A sizable percentage (31.8 wt %) was +0.841 mm. The −0.25 mm particles were mainly formed by the initial bed material (Al 2 O 3). Almost 50 wt % of the +0.841 mm particles was found to be formed by organics. The unreacted carbon remaining in the reactor resulted in a low conversion rate to product gas. Inductively coupled plasma−atomic emission spectroscopy (ICP-AES), scanning electron microscopy−energy-dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) confirmed that the large agglomerates (+0.841 mm) were not encapsulated bed material but rather ungasified feedstock pellets with sand particles attached to it.
Feedstock composition can affect final fuel yields and quality for the fast pyrolysis and hydrotr... more Feedstock composition can affect final fuel yields and quality for the fast pyrolysis and hydrotreatment upgrading pathway. However, previous studies have focused on individual unit operations rather than the integrated system. In this study, a suite of six pure lignocellulosic feedstocks (clean (no bark) pine, whole-tree (including bark) pine, tulip poplar, hybrid poplar, switchgrass, and corn stover) and two blends (equal weight percentages whole-tree pine/tulip poplar/switchgrass and wholetree pine/clean pine/hybrid poplar) were prepared and characterized. These materials then underwent fast pyrolysis and hydrotreatment. Although some feedstocks showed a high fast pyrolysis bio-oil yield, such as tulip poplar at 60%, high yields in the hydrotreater were not always observed. Results showed overall fuel yields of 17% (switchgrass), 20% (corn stover), 24% (tulip poplar, blend 1, blend 2), 25% (whole-tree pine, hybrid poplar), and 27% (clean pine). Simulated distillation of the upgraded oils indicated that the gasoline fraction varied from 39% (clean pine) to 51% (corn stover), while the diesel fraction ranged from 40% (corn stover) to 46% (tulip poplar). Little variation was seen in the jet fuel fraction at 11−12%. Hydrogen consumption during hydrotreating, a major factor in the economic feasibility of the integrated process, ranged from 0.051 g/g dry feed (tulip poplar) to 0.070 g/g dry feed (clean pine).
In this study the aqueous phases resulting from the hydrothermal liquefaction (HTL) of biomass an... more In this study the aqueous phases resulting from the hydrothermal liquefaction (HTL) of biomass and the hydrotreatment (HT) of fast pyrolysis bio-oils were analyzed via TC, COD, GC-MS, GC-FID, HPLC, and ICP-OES to determine the organic and inorganic species present and the quantitative amounts of each. This work is necessary to address a significant knowledge gap in the literature related to the aqueous phases from thermochemical processes. Results showed that water from the hydrotreatment of eight different bio-oils contained less than 1 wt% total carbon, in many cases less than 0.2%. Negligible organic carbon was observed. HTL samples contained between 1-2 wt% carbon. Due to the large volume of water added to the HTL feedstock and the dilute samples generated, this accounts for 34-45% of the total carbon sent to the reactor. The majority of this carbon was present as acids, with glycolic acid and acetic acid having the highest concentrations. Alcohols, specifically methanol and ethanol, were also present. Numerous ketones were observed, consisting of mainly acetone and cyclopenta-ones. The amount of the total carbon identified and quantified in the HTL samples ranged from 64-82%. Inorganic species present in the HT samples were sodium, silicon, and sulfur. The highest levels of sulfur were observed in the grasses and agricultural residue (corn stover). The HTL samples exhibited much higher inorganic content, with very high levels of sodium and potassium. Alkali and alkali earth metals, as well as sulfur, were also present at levels high enough to raise concerns for the use of catalysts in downstream upgrading or reforming processes.
Catalytic microchannel reactors were designed for in situ propellant production for Mars explorat... more Catalytic microchannel reactors were designed for in situ propellant production for Mars exploration. In the reactor system, the Sabatier and the reverse water–gas-shift (RWGS) reactions were carried out for methane and oxygen production using carbon dioxide and ...
Large-scale, cost-competitive deployment of thermochemical technologies to replace petroleum oil ... more Large-scale, cost-competitive deployment of thermochemical technologies to replace petroleum oil with domestic biofuels will require inclusion of high volumes of low-cost, diverse biomass types into the supply chain. However, a comprehensive understanding of the impacts of feedstock thermo-physical and chemical variability, particularly inorganic matter (ash), on the yield and product distribution
ABSTRACT Feedstock composition can affect final fuel yields and quality for the fast pyrolysis an... more ABSTRACT Feedstock composition can affect final fuel yields and quality for the fast pyrolysis and hydrotreatment upgrading pathway. However, previous studies have focused on individual unit operations rather than the integrated system. In this study, a suite of six pure lignocellulosic feedstocks (clean (no bark) pine, whole-tree (including bark) pine, tulip poplar, hybrid poplar, switchgrass, and corn stover) and two blends (equal weight percentages whole-tree pine/tulip poplar/switchgrass and whole-tree pine/clean pine/hybrid poplar) were prepared and characterized. These materials then underwent fast pyrolysis and hydrotreatment. Although some feedstocks showed a high fast pyrolysis bio-oil yield, such as tulip poplar at 60%, high yields in the hydrotreater were not always observed. Results showed overall fuel yields of 17% (switchgrass), 20% (corn stover), 24% (tulip poplar, Blend 1, Blend 2), 25% (whole-tree pine, hybrid poplar) and 27% (clean pine). Simulated distillation of the upgraded oils indicated that the gasoline fraction varied from 39% (clean pine) to 51% (corn stover), while the diesel fraction ranged from 40% (corn stover) to 46% (tulip poplar). Little variation was seen in the jet fuel fraction at 11 to 12%. Hydrogen consumption during hydrotreating, a major factor in the economic feasibility of the integrated process, ranged from 0.051 g/g dry feed (tulip poplar) to 0.070 g/g dry feed (clean pine).
We report here on an experimental study to produce refinery-ready fuel blendstocks via catalytic ... more We report here on an experimental study to produce refinery-ready fuel blendstocks via catalytic hydrodeoxygenation (upgrading) of pyrolysis oil using several biomass feedstocks and various blends. Blends were tested along with the pure materials to determine the effect of blending on product yields and qualities. Within experimental error, oil yields from fast pyrolysis and upgrading are shown to be linear functions of the blend components. Switchgrass exhibited lower fast pyrolysis and upgrading yields than the woody samples, which included clean pine, oriented strand board (OSB), and a mix of piñon and juniper (PJ). The notable exception was PJ, for which the poor upgrading yield of 18% was likely associated with the very high viscosity of the PJ fast pyrolysis oil (947 cp). The highest fast pyrolysis yield (54% dry basis) was obtained from clean pine, while the highest upgrading yield (50%) was obtained from a blend of 80% clean pine and 20% OSB (CP 8 OSB 2). For switchgrass, reducing the fast pyrolysis temperature to 450 °C resulted in a significant increase to the pyrolysis oil yield and reduced hydrogen consumption during hydrotreating, but did not directly affect the hydrotreating oil yield. The water content of fast pyrolysis oils was also observed to increase linearly with the summed content of potassium and sodium, ranging from 21% for clean pine to 37% for switchgrass. Multiple linear regression models demonstrate that fast pyrolysis is strongly dependent upon the contents lignin and volatile matter as well as the sum of potassium and sodium.
Efficient conversion of all components in lignocellulosic biomass is essential to realizing econo... more Efficient conversion of all components in lignocellulosic biomass is essential to realizing economic feasibility of biorefineries. However, lignin cannot be fermented using biochemical routes. Furthermore, high lignin and high ash residues from simultaneous saccharification and fermentation (SSF) is difficult to thermochemically process due to feed line plugging and bed agglomeration. In this study a corn stover SSF digester residue was thermally pretreated at 300°C for 22.5 minutes and gasified in a fluidized bed gasifier to study the effect of thermal pretreatment on its processing behavior. Untreated, pelletized SSF residue was gasified at the same conditions to establish the baseline processing behavior. Results indicate the thermal pretreatment process removes a substantial portion of the polar and non-polar extractives, with a resultant increase in the concentration of lignin, cellulose, and ash. Feed line plugging was not observed, although bed agglomeration occurred at similar rates for both feedstocks, suggesting that overall ash content is the most important factor affecting bed agglomeration. Benzene, phenol, and polyaromatic hydrocarbons in the tar were present at higher concentrations in the treated material, with higher tar loading in the product gas. Total product gas generation is lower for the treated material, although overall gas composition does not change.
Residues high in lignin and ash generated from the simultaneous saccharification and fermentation... more Residues high in lignin and ash generated from the simultaneous saccharification and fermentation of corn stover were thermally pretreated in an inert (N 2) atmosphere to study the effect of time and temperature on their softening points. These residues are difficult to feed into gasifiers due to premature thermal degradation and formation of reactive liquids in the feed lines, leading to plugging. The untreated and treated residues were characterized by proximate and ultimate analysis, and then analyzed via TGA, DSC, 13 C NMR, Py-GC-MS, CHNO/S, and TMA. Interpretation of the compositional analysis indicates that the weight loss observed during pretreatment is mainly due to the thermal decomposition and volatilization of the hemicelluloses and amorphous cellulose fractions. Fixed carbon increases in the pretreated material, mostly due to a concentration effect rather than the formation of new extra poly-aromatic material. The optimal processing time and temperature to minimize the production of carbonyl groups in the pretreated samples was 300 • C at a time of 30 min. Results showed that the softening point of the material could be increased from 187 • C to 250 • C, and that under the experimental conditions studied, pretreatment temperature plays a more important role than time. The increase in softening point was mainly due to the formation of covalent bonds in the lignin structures and the removal of low molecular weight volatile intermediates.
This research investigates the bed agglomeration phenomena during the steam gasification of a hig... more This research investigates the bed agglomeration phenomena during the steam gasification of a high-lignin residue produced from the simultaneous saccharification and fermentation (SSF) of corn stover in a bubbling fluidized bed. The studies were conducted at 895°C using alumina as bed material. Biomass was fed at 1.5 kg/h, while steam was fed to give a velocity equal to 2.5 times the minimum fluidization velocity, with a steam/carbon ratio of 0.9. The pelletized feedstock was co-fed with a cooling nitrogen stream to mitigate feed line plugging issues. Tar production was high at 50.3 g/Nm 3 , and the fraction of C10+ compounds was greater than that observed in the gasification of traditional lignocellulosic feedstocks. Carbon closures over 94% were achieved for all experiments. Bed agglomeration was found to be problematic, indicated by pressure drop increases observed below the bed and upstream of the feed line. Two size categories of solids were recovered from the reactor: +0.25 mm and −0.25 mm. After 2.75 h of experiment, 61.7 wt % was recovered as −0.25 mm particles and 38.2 wt % of the recovered reactor solids were +0.25 mm. A sizable percentage (31.8 wt %) was +0.841 mm. The −0.25 mm particles were mainly formed by the initial bed material (Al 2 O 3). Almost 50 wt % of the +0.841 mm particles was found to be formed by organics. The unreacted carbon remaining in the reactor resulted in a low conversion rate to product gas. Inductively coupled plasma−atomic emission spectroscopy (ICP-AES), scanning electron microscopy−energy-dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) confirmed that the large agglomerates (+0.841 mm) were not encapsulated bed material but rather ungasified feedstock pellets with sand particles attached to it.
Feedstock composition can affect final fuel yields and quality for the fast pyrolysis and hydrotr... more Feedstock composition can affect final fuel yields and quality for the fast pyrolysis and hydrotreatment upgrading pathway. However, previous studies have focused on individual unit operations rather than the integrated system. In this study, a suite of six pure lignocellulosic feedstocks (clean (no bark) pine, whole-tree (including bark) pine, tulip poplar, hybrid poplar, switchgrass, and corn stover) and two blends (equal weight percentages whole-tree pine/tulip poplar/switchgrass and wholetree pine/clean pine/hybrid poplar) were prepared and characterized. These materials then underwent fast pyrolysis and hydrotreatment. Although some feedstocks showed a high fast pyrolysis bio-oil yield, such as tulip poplar at 60%, high yields in the hydrotreater were not always observed. Results showed overall fuel yields of 17% (switchgrass), 20% (corn stover), 24% (tulip poplar, blend 1, blend 2), 25% (whole-tree pine, hybrid poplar), and 27% (clean pine). Simulated distillation of the upgraded oils indicated that the gasoline fraction varied from 39% (clean pine) to 51% (corn stover), while the diesel fraction ranged from 40% (corn stover) to 46% (tulip poplar). Little variation was seen in the jet fuel fraction at 11−12%. Hydrogen consumption during hydrotreating, a major factor in the economic feasibility of the integrated process, ranged from 0.051 g/g dry feed (tulip poplar) to 0.070 g/g dry feed (clean pine).
In this study the aqueous phases resulting from the hydrothermal liquefaction (HTL) of biomass an... more In this study the aqueous phases resulting from the hydrothermal liquefaction (HTL) of biomass and the hydrotreatment (HT) of fast pyrolysis bio-oils were analyzed via TC, COD, GC-MS, GC-FID, HPLC, and ICP-OES to determine the organic and inorganic species present and the quantitative amounts of each. This work is necessary to address a significant knowledge gap in the literature related to the aqueous phases from thermochemical processes. Results showed that water from the hydrotreatment of eight different bio-oils contained less than 1 wt% total carbon, in many cases less than 0.2%. Negligible organic carbon was observed. HTL samples contained between 1-2 wt% carbon. Due to the large volume of water added to the HTL feedstock and the dilute samples generated, this accounts for 34-45% of the total carbon sent to the reactor. The majority of this carbon was present as acids, with glycolic acid and acetic acid having the highest concentrations. Alcohols, specifically methanol and ethanol, were also present. Numerous ketones were observed, consisting of mainly acetone and cyclopenta-ones. The amount of the total carbon identified and quantified in the HTL samples ranged from 64-82%. Inorganic species present in the HT samples were sodium, silicon, and sulfur. The highest levels of sulfur were observed in the grasses and agricultural residue (corn stover). The HTL samples exhibited much higher inorganic content, with very high levels of sodium and potassium. Alkali and alkali earth metals, as well as sulfur, were also present at levels high enough to raise concerns for the use of catalysts in downstream upgrading or reforming processes.
Catalytic microchannel reactors were designed for in situ propellant production for Mars explorat... more Catalytic microchannel reactors were designed for in situ propellant production for Mars exploration. In the reactor system, the Sabatier and the reverse water–gas-shift (RWGS) reactions were carried out for methane and oxygen production using carbon dioxide and ...
Large-scale, cost-competitive deployment of thermochemical technologies to replace petroleum oil ... more Large-scale, cost-competitive deployment of thermochemical technologies to replace petroleum oil with domestic biofuels will require inclusion of high volumes of low-cost, diverse biomass types into the supply chain. However, a comprehensive understanding of the impacts of feedstock thermo-physical and chemical variability, particularly inorganic matter (ash), on the yield and product distribution
ABSTRACT Feedstock composition can affect final fuel yields and quality for the fast pyrolysis an... more ABSTRACT Feedstock composition can affect final fuel yields and quality for the fast pyrolysis and hydrotreatment upgrading pathway. However, previous studies have focused on individual unit operations rather than the integrated system. In this study, a suite of six pure lignocellulosic feedstocks (clean (no bark) pine, whole-tree (including bark) pine, tulip poplar, hybrid poplar, switchgrass, and corn stover) and two blends (equal weight percentages whole-tree pine/tulip poplar/switchgrass and whole-tree pine/clean pine/hybrid poplar) were prepared and characterized. These materials then underwent fast pyrolysis and hydrotreatment. Although some feedstocks showed a high fast pyrolysis bio-oil yield, such as tulip poplar at 60%, high yields in the hydrotreater were not always observed. Results showed overall fuel yields of 17% (switchgrass), 20% (corn stover), 24% (tulip poplar, Blend 1, Blend 2), 25% (whole-tree pine, hybrid poplar) and 27% (clean pine). Simulated distillation of the upgraded oils indicated that the gasoline fraction varied from 39% (clean pine) to 51% (corn stover), while the diesel fraction ranged from 40% (corn stover) to 46% (tulip poplar). Little variation was seen in the jet fuel fraction at 11 to 12%. Hydrogen consumption during hydrotreating, a major factor in the economic feasibility of the integrated process, ranged from 0.051 g/g dry feed (tulip poplar) to 0.070 g/g dry feed (clean pine).
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