Liquefaction of lignocellulosic biomass through fast pyrolysis, to yield fast pyrolysis bio-oil (FPBO), is a technique that has been extensively researched in the quest for finding alternatives to fossil feedstocks to produce fuels, chemicals, etc. Properties such as high oxygen content, acidity, and poor storage stability greatly limit the direct use of this bio-oil. Furthermore, high coking tendencies make upgrading of the FPBO by hydrodeoxygenation in fixed-bed bed hydrotreaters challenging due to plugging and catalyst deactivation. This study investigates a novel two-step hydroprocessing concept; a continuous slurry-based process using a dispersed NiMo-catalyst, followed by a fixed bed process using a supported NiMo-catalyst. The oil product from the slurry-process, having a reduced oxygen content (15 wt%) compared to the FPBO and a comparatively low coking tendency (TGA residue of 1.4 wt%), was successfully processed in the downstream fixed bed process for 58 h without any noticeable decrease in catalyst activity, or increase in pressure drop. The overall process resulted in a 29 wt% yield of deoxygenated oil product (0.5 wt% oxygen) from FPBO with an overall carbon recovery of 68%.

Reducing the use of fossil fuels is an ongoing and important effort considering the environmental impact and depletion of fossil-based resources. The combination of ablative fast pyrolysis and hydroprocessing is explored as a pathway allowing bio-based intermediates (BioMates) integration in underlying petroleum refineries. The proposed technology is validated in industrially relevant scale, identifying pros and cons towards its commercialization. Straw from wheat, rye and barley was fed to ablative fast pyrolysis rendering Fast Pyrolysis Bio-Oil (FPBO) as the main product. The FPBO was stabilized via slurry hydroprocessing, rendering a stabilized FPBO (sFPBO) with 49 % reduced oxygen content, 71 % reduced carbonyl content and 49 % reduced Conradson carbon residue. Fixed bed catalytic hydroprocessing of sFPBO resulted in the production of BioMates, a high bio-content product to be co-fed in established refinery units. Compared to the starting biomass, BioMates has 83.6 wt% C content increase, 92.5 wt% O content decrease, 93.0 wt% water content decrease, while the overall technology has 20 wt% conversion yield (32 wt% carbon yield) from biomass to BioMates. © 2022 The Author(s)

Lignocellulosic biomass from energy crops, i.e., short rotation coppice willows such as Salix spp., can be used as feedstock for production of transportation biofuels. Biomass conversion via fast pyrolysis followed by co-refining with fossil oil in existing refinery infrastructure could enable a fast introduction of large-scale production of biofuels. In this study, Salix was first liquefied using ablative fast pyrolysis in a pilot scale unit. The resulting pyrolysis oil, rich in oxygenates, was thereafter co-refined in 20 wt% ratio with fossil feedstock using two separate technologies, a fluidized catalytic cracking (FCC) laboratory unit and a continuous slurry hydroprocessing pilot plant. In the FCC route, the pyrolysis oil was cracked at 798 K using a commercial FCC catalyst at atmospheric pressure, while in the hydroprocessing route, the oil was processed at 693 K and a hydrogen pressure of 15 MPa in the presence of an unsupported molybdenum sulfide catalyst. Both routes resulted in significant deoxygenation (97 wt% versus 93 wt%). It is feasible to co-refine pyrolysis oil using both methods, the main difference being that the hydroprocessing results in a significantly higher biogenic carbon yield from the pyrolysis oil to liquid and gaseous hydrocarbon products (92 wt%) but would in turn require input of H2. In the cracking route, besides the liquid product, a significant part of the biogenic carbon ends up as gas and as coke on the catalyst. The choice of route depends, among other factors, on the available amount of bio-oil and refining infrastructures. © 2023 The Authors

Kraft lignin is an abundantly available and largely underutilized renewable material with potential for production of biobased fuels and chemicals. This study reports the results of a series of slurry hydroprocessing experiments with the aim of converting solid Kraft lignin to liquid products suitable for downstream refining in more conventional reactors. Experiments reported in this study were conducted by feeding a lignin slurry to an already hot, liquid-filled reactor to provide momentaneous heating of the lignin to the reaction temperature. This modified batch procedure provided superior results compared to the regular batch experiments, likely since unwanted repolymerization and condensation reactions of the lignin during the heating phase was avoided, and was therefore used for most of the experiments reported. Experiments were performed using both an unsupported Mo-sulfide catalyst and Fe-based catalysts (bauxite and hematite) at varied reaction temperatures, pressures, and catalyst loadings. The use of Mo-sulfide (0.1% Mo of the entire feed mass) at 425 °C and 50 bar resulted in complete conversion of the Kraft lignin to nonsolid products. Very high conversions (>95%) could also be achieved with both sulfided bauxite or hematite at the same temperature and pressure, but this required much higher catalyst loadings (6.25% bauxite or 4.3% hematite of the total feed mass), and around 99% conversion could be achieved at higher temperatures but at the expense of much higher gas yields. Although requiring much higher loadings, the results in this study suggest that comparatively nonexpensive Fe-based catalysts may be an attractive alternative for a slurry-based process aimed at the hydroconversion of solid lignin to liquid products. Possible implementation strategies for a slurry-based hydroconversion process are proposed and discussed. © 2022 The Authors.

Co-refining of fast pyrolysis bio-oil together with fossil oil in existing refinery infrastructure is an attractive and cost-efficient route to conversion of lignocellulosic biomass to transportation fuel. However, due to large differences in properties between the two oils, special notice is needed to reduce process-related issues. Here, fast pyrolysis bio-oil produced from lignocellulosic biomass was co-refined with vacuum gas oil at a 20:80 weight ratio in continuous operation in a pilot-scale slurry hydrocracker in order to investigate the impact of process parameters on product quality and process performance. Mass balances together with product characterization were used to investigate product yields, product composition, and hydrodeoxygenation. Best conversion and hydrodeoxygenation of the fast pyrolysis bio-oil was achieved using an unsupported catalyst loading of 900 ppm Mo with either a low temperature (410 °C) and long residence time (2 h) or higher temperature (435 °C) and shorter residence time (1 h). These settings resulted in about 94% hydrodeoxygenation but also led to highest yield of biogenic carbon to gas phase (40-43 wt %) and lowest yield of biogenic carbon to oil fractions (53-56 wt %) as well as the water fraction (3-5 wt %). Successfully, coke yield remained low at around 0.07-0.10 wt % for all performed runs, which was comparable to the insoluble particle content in the feed due to the presence of particles in the untreated fast pyrolysis bio-oil. Co-processing pyrolysis oil with fossil oil in a slurry hydrocracker seems to be a robust process with regard to coke formation, which should lead to reduced plugging issues compared to fixed bed hydrotreaters. Although this study gives a brief understanding of the effect of process parameters on the processing of fast pyrolysis bio-oil, further research is required to find optimal process parameters and to fully comprehend the possibilities and limitations for production of transportation fuels from fast pyrolysis bio-oil using this technology.

Integration of renewable raw materials in existing refineries is most likely the shortest way for the successful, large-scale introduction of biofuels in the transport sector in the short term and medium term. One possible renewable raw material for this application is fast pyrolysis bio-oil (FPBO), which in this study has been coprocessed (at 0 and 20 wt %) with vacuum residue (VR, 50 wt %) and vacuum gas oil (VGO, balance) in a continuous, as well as a semibatch, slurry hydrocracking process. Experiments both with and without FPBO were performed at 450°C and 150 bar with a continuous hydrogen flow through the reactor. Oil-soluble molybdenum hexacarbonyl and molybdenum 2-ethylhexanoate were used as catalyst precursors, to be sulfided in situ. The continuous trials resulted in reactor walls completely free of coking, and they resulted in a low overall coke yield (about 1 wt %). The hydrodeoxygenation reached almost 92%, and the total acid number was reduced by nearly 99% in the FPBO experiment A mass balance of the renewable carbon from FPBO, based on the performed experiments, showed that the fossil CO2 emissions can be lowered by 1.35 kg per kg of processed FPBO if all renewable carbon in gaseous and liquid hydrocarbons is used to replace its fossil counterparts, and all methane formed from FPBO is used to produce hydrogen. Semibatch experiments gave less successful results when upgrading FPBO-containing feedstock, with a high coke yield (8 wt %) as well as a high gas yield (24 wt %). The results of this study demonstrate that FPBO can be successfully coprocessed with heavy fossil oils in a continuous slurry hydrocracking process without neg. affecting the processing of the fossil components of the feed and that a continuous process is preferred over batch or semibatch processes when studying coprocessing of bio-oils.