Experimental studies on a two-step fast pyrolysis-catalytic hydrotreatment process for hydrocarbons from microalgae (Nannochloropsis gaditana and Scenedesmus almeriensis)

Two microalgae species (marine Nannochloropsis gaditana, and freshwater Scenedesmus almeriensis) were subjected to pyrolysis followed by a catalytic hydrotreatment of the liquid products with the objective to obtain liquid products enriched in hydrocarbons. Pre-dried microalgae were pyrolyzed in a mechanically stirred fluidized bed reactor (380 and 480 degrees C) with fractional condensation. The heavy phase pyrolysis oils were hydrotreated (350 degrees C and 15 MPa of H-2 pressure for 4 h) using a NiMo on alumina catalyst. The pyrolysis liquids after pyrolysis and those after catalytic hydrotreatment were analyzed in detail using GC-MS, GC x GC-MS, and 2D HSQC NMR. The liquid products are enriched in aromatics and aliphatic hydrocarbons and, as such have a considerably lower oxygen content (1.6-4.2% w/w) compared to the microalgae feeds (25-30% w/w). The overall carbon yield for the liquid products was between 15.6 and 19.1% w/w based on the initial carbon content of the algae feedstock

Micro-pyrolysis of lignin-rich digested stillage from 2nd generation bioethanol production: Investigation to determine the catalytic effect of its natural ash

Lignin-rich digested stillage from a sequence of 2nd generation bioethanol production followed by anaerobic digestion is a unique feedstock for fast pyrolysis process. The feedstock contains a high amount of lignin (62 wt. % d.b), ash (9.97 wt. % d.b), residual polysaccharide and microbial biomass portions. Qualitative analysis using a micro-pyrolyser for this feedstock indicates that the pyrolysis vapours exhibit similarity with chemical compounds in pyrolysis vapours from alkali lignin, organosolv lignin and kraft lignin. Detailed analyses confirm the presence of several types of phenolic compounds, ketones, benzenes, furans, and aromatic hydrocarbons typically found in pyrolysis vapours of feedstock with a high hemicellulose-lignin fraction. Further analysis of the feedstock ash reveals a high concentration of alkaline earth metals (e.g. calcium and magnesium), transition metals (e.g. iron) and posttransitional metals (e.g. zinc), commonly used for doping zeolite catalysts (e.g. ZSM-5). Using the feedstock’s natural ash as a fast-pyrolysis catalyst could provide additional value and better economics by enabling alternative utilization pathways for these otherwise discarded materials. This work aims at investigating the effects of original ash as a catalyst for fast pyrolysis of lignin-rich digested stillage using a micro-pyrolyser. In-situ catalytic micro-pyrolysis experiments have been conducted in quadruplets using the Frontier Laboratories Multi-Shot tandem pyrolyser EGA/PY-3030D coupled with a TRACE GC Ultra and ISQ Single Quadrupole MS. Proximate and ultimate analyses, gross calorific value, acid-insoluble lignin content, and elemental content were carried out to fully characterize the feedstock. Changes in the concentrations of pyrolysis key vapour components (e.g. phenolics, furans, benzenes) were assessed by calculating the ratio of peak areas (relative to the per sample weight) in original-ash catalysed micro-pyrolysis over those of non-catalytic micro-pyrolysis. A value below one indicates a decrease in abundance of a particular compound while a value higher than one suggests an increase in the formation of that compound upon the addition of ash to the lignin digestate pyrolysis. The results of this ratio calculation suggest some significant changes in the pyrolysis vapour composition. Carbon dioxide and methoxyeugenol increase by a factor of almost two while p-creosol, o-cresol, methanol, chloromethane, pyrrole, and benzene on the other hand are decreased. Several newly formed ketones and methylated compounds such as 2-butanone, butyrolactone, 2, 3-butanedione, 2-methylfuran, and 2-methyl 2- cyclopenten-1-one were detected in the vapours derived from ash-catalyzed micro-pyrolysis. The changes suggest that natural ash has the potential to alter fast-pyrolysis vapours of lignin-rich digested stillage by augmenting decarboxylation, methylation, aldol condensation and retro-aldol reactions

Micro-pyrolysis of lignin-rich digested stillage from 2^nd generation bioethanol production:Investigation to determine the catalytic effect of its natural ash

Lignin-rich digested stillage from a sequence of 2nd generation bioethanol production followed by anaerobic digestion is a unique feedstock for fast pyrolysis process. The feedstock contains a high amount of lignin (62 wt. % d.b), ash (9.97 wt. % d.b), residual polysaccharide and microbial biomass portions. Qualitative analysis using a micro-pyrolyser for this feedstock indicates that the pyrolysis vapours exhibit similarity with chemical compounds in pyrolysis vapours from alkali lignin, organosolv lignin and kraft lignin. Detailed analyses confirm the presence of several types of phenolic compounds, ketones, benzenes, furans, and aromatic hydrocarbons typically found in pyrolysis vapours of feedstock with a high hemicellulose-lignin fraction. Further analysis of the feedstock ash reveals a high concentration of alkaline earth metals (e.g. calcium and magnesium), transition metals (e.g. iron) and posttransitional metals (e.g. zinc), commonly used for doping zeolite catalysts (e.g. ZSM-5). Using the feedstock’s natural ash as a fast-pyrolysis catalyst could provide additional value and better economics by enabling alternative utilization pathways for these otherwise discarded materials. This work aims at investigating the effects of original ash as a catalyst for fast pyrolysis of lignin-rich digested stillage using a micro-pyrolyser. In-situ catalytic micro-pyrolysis experiments have been conducted in quadruplets using the Frontier Laboratories Multi-Shot tandem pyrolyser EGA/PY-3030D coupled with a TRACE GC Ultra and ISQ Single Quadrupole MS. Proximate and ultimate analyses, gross calorific value, acid-insoluble lignin content, and elemental content were carried out to fully characterize the feedstock. Changes in the concentrations of pyrolysis key vapour components (e.g. phenolics, furans, benzenes) were assessed by calculating the ratio of peak areas (relative to the per sample weight) in original-ash catalysed micro-pyrolysis over those of non-catalytic micro-pyrolysis. A value below one indicates a decrease in abundance of a particular compound while a value higher than one suggests an increase in the formation of that compound upon the addition of ash to the lignin digestate pyrolysis. The results of this ratio calculation suggest some significant changes in the pyrolysis vapour composition. Carbon dioxide and methoxyeugenol increase by a factor of almost two while p-creosol, o-cresol, methanol, chloromethane, pyrrole, and benzene on the other hand are decreased. Several newly formed ketones and methylated compounds such as 2-butanone, butyrolactone, 2, 3-butanedione, 2-methylfuran, and 2-methyl 2- cyclopenten-1-one were detected in the vapours derived from ash-catalyzed micro-pyrolysis. The changes suggest that natural ash has the potential to alter fast-pyrolysis vapours of lignin-rich digested stillage by augmenting decarboxylation, methylation, aldol condensation and retro-aldol reactions.</p