• Energy Research

Abstract A fully controlled, continuously operated mini-plant has been designed and constructed based on auger reactor technology. Three types of biomass fast pyrolysis experiments were performed in this set-up, viz. non-catalytic, in situ catalytic fast pyrolysis and ex situ upgrading of non-catalytic fast pyrolysis vapours by means of a downstream, moving-bed catalytic reactor. Pine wood was selected as the reference biomass feedstock. The mini-plant enables variation of the catalyst loading and contact times while producing larger samples suitable for full characterization in continuous operation. Due to short catalyst residence times and the fact that the biomass fed to the reactor is always brought into contact with fresh catalyst (in case of in situ catalysis) or the pyrolysis vapours always contact with fresh catalyst in the moving bed catalytic reactor (in case of ex situ catalysis), catalyst deactivation and coking are prevented ensuring improved experimental repeatability in catalytic pyrolysis experiments. The performance of the system was verified by in- and ex situ application of a single type of heterogeneous ZSM-5 based acidic catalyst while the non-catalytic results were taken as reference. Catalytic fast pyrolysis results in more effective oxygen removal from the bio-oil in the form of water, and resulting in lower yields of the organic fraction. Moreover catalytic decarbonylation reactions gave rise to increased gas yields. With in- and ex situ catalysis, increases in the char yields were observed as well as coke deposition on the catalyst surface. GC × GC-FID and GC × GC-TOF-MS analysis of the produced bio-oils showed that the use of in- and ex situ catalysis causes conversion of high molecular weight compounds to lower ones. Disappearance of detectable sugars and aldehydes, a decrease of the yield of acids, formation of phenols, and favoured aromatics production were the other catalytic effects observed.

Abstract A fully controlled, continuously operated mini-plant has been designed and constructed based on auger reactor technology. Three types of biomass fast pyrolysis experiments were performed in this set-up, viz. non-catalytic, in situ catalytic fast pyrolysis and ex situ upgrading of non-catalytic fast pyrolysis vapours by means of a downstream, moving-bed catalytic reactor. Pine wood was selected as the reference biomass feedstock. The mini-plant enables variation of the catalyst loading and contact times while producing larger samples suitable for full characterization in continuous operation. Due to short catalyst residence times and the fact that the biomass fed to the reactor is always brought into contact with fresh catalyst (in case of in situ catalysis) or the pyrolysis vapours always contact with fresh catalyst in the moving bed catalytic reactor (in case of ex situ catalysis), catalyst deactivation and coking are prevented ensuring improved experimental repeatability in catalytic pyrolysis experiments. The performance of the system was verified by in- and ex situ application of a single type of heterogeneous ZSM-5 based acidic catalyst while the non-catalytic results were taken as reference. Catalytic fast pyrolysis results in more effective oxygen removal from the bio-oil in the form of water, and resulting in lower yields of the organic fraction. Moreover catalytic decarbonylation reactions gave rise to increased gas yields. With in- and ex situ catalysis, increases in the char yields were observed as well as coke deposition on the catalyst surface. GC × GC-FID and GC × GC-TOF-MS analysis of the produced bio-oils showed that the use of in- and ex situ catalysis causes conversion of high molecular weight compounds to lower ones. Disappearance of detectable sugars and aldehydes, a decrease of the yield of acids, formation of phenols, and favoured aromatics production were the other catalytic effects observed.

AbstractIn fast pyrolysis of cellulose, levoglucosan is often reported as the most abundant primary decomposition product. Char, the solid residue of pyrolysis is thought to catalyze secondary reactions that decompose levoglucosan into water and additional, secondary char. A CDS Analytical Pyroprobe 5200 was used to pyrolyze pure cellulose to levoglucosan and the generated vapors were passed through a temperature‐controlled tubular reactor filled with material to be tested for catalytic activity and then to a GC‐FID for analysis. Carbonaceous materials included as‐received and acid‐washed char derived from pyrolysis of red oak and, pure graphite. Acid‐washed red oak char and pure graphite had little effect on levoglucosan decomposition compared with the empty tubular reactor for the range of tubular reactor temperatures studied (200–400°C). In contrast, unwashed red oak char significantly reduced the amount of levoglucosan when the tubular reactor was operated above 300°C. These results suggest that metals—which are removed through the procedure of acid washing—rather than the fixed carbon in the char, catalyze the decomposition of levoglucosan in the vapor phase. © 2012 American Institute of Chemical Engineers Environ Prog, 2012

AbstractIn fast pyrolysis of cellulose, levoglucosan is often reported as the most abundant primary decomposition product. Char, the solid residue of pyrolysis is thought to catalyze secondary reactions that decompose levoglucosan into water and additional, secondary char. A CDS Analytical Pyroprobe 5200 was used to pyrolyze pure cellulose to levoglucosan and the generated vapors were passed through a temperature‐controlled tubular reactor filled with material to be tested for catalytic activity and then to a GC‐FID for analysis. Carbonaceous materials included as‐received and acid‐washed char derived from pyrolysis of red oak and, pure graphite. Acid‐washed red oak char and pure graphite had little effect on levoglucosan decomposition compared with the empty tubular reactor for the range of tubular reactor temperatures studied (200–400°C). In contrast, unwashed red oak char significantly reduced the amount of levoglucosan when the tubular reactor was operated above 300°C. These results suggest that metals—which are removed through the procedure of acid washing—rather than the fixed carbon in the char, catalyze the decomposition of levoglucosan in the vapor phase. © 2012 American Institute of Chemical Engineers Environ Prog, 2012

Lignin-rich digested stillage from second-generation bioethanol production is a unique biomass-derived feedstock, not only because it contains high amounts of lignin but also due to its residual amounts of cellulose and hemicellulose. In this study, catalytic hydrotreatment experiments were conducted on pyrolysis liquids obtained from the lignin-rich feedstock using sulphided NiMo/Al2O3 and CoMo/Al2O3 catalysts. The aim was to obtain a high conversion of the initial pyrolysis feed into a hydrotreated oil with a high phenolics and aromatics fractions. Experiments were carried out in a stirred batch reactor at 350 degrees C and 10 MPa of H-2 (initial pressure). Product oils were obtained in about 60-65% w/w, the remainder being an aqueous phase (12-14% w/w), solids (7-8% w/w) and gas phase components (all on initial pyrolysis oil feed basis). The product oils were characterised in detail using various techniques (elemental composition, GCxGC-FID, GPC, and 2D HSQC NMR). The oxygen content was reduced from 23% w/w in the pyrolysis oils to 7.5-11.5% in the hydrotreated oils, indicative of the occurrence of hydrodeoxygenation reactions. This was also evident from the chemical composition, showing an increase in the amounts of low molecular weight aromatics, alkylphenolics, alkanes and cycloalkanes in hydrotreated oils. Performance of the two catalysts was compared, and a higher degree of deoxygenation was observed for the NiMo catalyst. The implications of the findings for the valorisation of second-generation bioethanol residues are also discussed.

Lignin-rich digested stillage from second-generation bioethanol production is a unique biomass-derived feedstock, not only because it contains high amounts of lignin but also due to its residual amounts of cellulose and hemicellulose. In this study, catalytic hydrotreatment experiments were conducted on pyrolysis liquids obtained from the lignin-rich feedstock using sulphided NiMo/Al2O3 and CoMo/Al2O3 catalysts. The aim was to obtain a high conversion of the initial pyrolysis feed into a hydrotreated oil with a high phenolics and aromatics fractions. Experiments were carried out in a stirred batch reactor at 350 degrees C and 10 MPa of H-2 (initial pressure). Product oils were obtained in about 60-65% w/w, the remainder being an aqueous phase (12-14% w/w), solids (7-8% w/w) and gas phase components (all on initial pyrolysis oil feed basis). The product oils were characterised in detail using various techniques (elemental composition, GCxGC-FID, GPC, and 2D HSQC NMR). The oxygen content was reduced from 23% w/w in the pyrolysis oils to 7.5-11.5% in the hydrotreated oils, indicative of the occurrence of hydrodeoxygenation reactions. This was also evident from the chemical composition, showing an increase in the amounts of low molecular weight aromatics, alkylphenolics, alkanes and cycloalkanes in hydrotreated oils. Performance of the two catalysts was compared, and a higher degree of deoxygenation was observed for the NiMo catalyst. The implications of the findings for the valorisation of second-generation bioethanol residues are also discussed.

Algae are an interesting feedstock for producing biofuel via hydrothermal liquefaction (HTL), due to their high water content. In this study, algae slurries (5-7 wt% daf) from different species were liquefied at 250 and 375 °C in batch autoclaves during 5 min. The aim was to analyze the influence of strain-specific parameters (cell structure, biochemical composition and growth environment) on the HTL process. Results show big variations in the biocrude oil yield within species at 250 °C (from 17.6 to 44.8 wt%). At 375 °C, these differences become less significant (from 45.6 to 58.1 wt%). An appropriate characterization of feedstock appeared to be critical to interpret the results. If a high conversion of microalgae-to-biocrude is pursued, near critical conditions are required, with Scenedesmus almeriensis (freshwater) and Nannochloropsis gaditana (marine) leading to the biocrude oils with lower nitrogen content from each growth environment.

Algae are an interesting feedstock for producing biofuel via hydrothermal liquefaction (HTL), due to their high water content. In this study, algae slurries (5-7 wt% daf) from different species were liquefied at 250 and 375 °C in batch autoclaves during 5 min. The aim was to analyze the influence of strain-specific parameters (cell structure, biochemical composition and growth environment) on the HTL process. Results show big variations in the biocrude oil yield within species at 250 °C (from 17.6 to 44.8 wt%). At 375 °C, these differences become less significant (from 45.6 to 58.1 wt%). An appropriate characterization of feedstock appeared to be critical to interpret the results. If a high conversion of microalgae-to-biocrude is pursued, near critical conditions are required, with Scenedesmus almeriensis (freshwater) and Nannochloropsis gaditana (marine) leading to the biocrude oils with lower nitrogen content from each growth environment.