Derivatizing of Fast Pyrolysis Bio-Oil and Coprocessing in Fixed Bed Hydrotreater

Abstract

In several countries forest-based biofuels are being developed and to some extent also deployed. Fast pyrolysis bio-oil produced from, for example, sawdust, has now been coprocessed in fluid catalytic cracking refinery units in a number of commercial trials. However, this application is limited to about 10% of the total feed, and coprocessing in conventional fixed bed hydrotreaters is necessary to reach the high potential with this feedstock. Feeding and upgrading of fast pyrolysis bio-oil in a fixed bed reactor configuration is still problematic due to the inherent bio-oil properties. Stabilization of reactive compounds in fast pyrolysis bio-oil and mild hydrotreatment in a separate refining unit prior to refinery integration has therefore been developed the past decade. Another approach, presented here, involves complete dewatering of fast pyrolysis bio-oil by azeotropic distillation using mesityl oxide as the solvent, followed by conversion of the abundant hydroxyl compounds via mixed anhydride esterification methodology using an external source of mixed carboxylic acids of different chain lengths originating from renewable tall oil fatty acids, providing a lipophilic feed component. Dewatering and derivatizing were carried out in reactors up to 50 dm3 with a mass ratio of fast pyrolysis bio-oil to tall oil fatty acid of 10:13. The produced lipophilic oils were miscible with a petroleum light gas oil fraction and exhibited superior stability even after accelerated aging at elevated temperature (80 °C). The derivatized oils were thus mixed with light gas oil, with a proportion of 30 wt % derivatized oil in final blends and hydrotreated continuously in pilot fixed bed reactors for 14 days at 4 operating conditions without plugging or excessive exotherms. The test conditions were varied; the reactor pressure was either 55 or 80 bar, temperature 380 or 400 °C, and liquid hourly space velocity either 1 or 2 h–1 during the hydrotreatment. Successful hydrodeoxygenation and desulfurization were accomplished, whereas an increasing nitrogen concentration could be observed in the liquid products with the particular catalyst and reaction conditions employed. The observed hydrogen consumption (15–20 g/kg feed) was compared with the stoichiometric consumption for direct deoxygenation and with typical consumptions for industrial hydrotreated vegetable oil processing. The measured biogenic carbon content in hydrotreated liquid products (26.7%) agreed extremely well with the calculated biogenic carbon content in the hydrotreating feed (26.6%) that consisted of the blend of derivatized oil and petroleum light gas oil. The overall results are very promising since simple unit operations can be used to produce derivatized fast pyrolysis bio-oils that do not need additional standalone hydrotreating units but can be coprocessed in existing ones.

Removal of Inorganic Impurities in the Fast Pyrolysis Bio-oil Using Sorbents at Ambient Temperature

“…The most abundant compound group present in FPBOs is hydroxyls, which include carboxylic acids (4–15 wt %), phenolics (17–35 wt %), sugars (20–35 wt %), and water (20–30 wt %). , GCxGC-MS analysis provided information regarding the monomeric fraction present in the FPBO, including volatile and semivolatile compounds. The average molecular weight of FPBO produced from sawdust 554 g mol –1 (an average reported on a FPBO sample of the same feedstock from the same producer by gel permeation chromatography using tetrahydrofuran (THF) as a mobile phase) indicates the presence of large compounds. Although extensive characterization of bio-oils and method development of GCxGC analysis have been reported for FPBOs in the literature, variations in the biomass feedstock, the pyrolysis process and GC analysis methods, and precision make comparing results challenging. − Therefore, in this paper, some typical functional groups have been categorized by GCxGC analysis (marked 1–5 in Figure a), and a few of the most typical compounds were selected in these groups, namely, isopropanol, lactic acid (1), hydroxy acetone (2), furfural (3), guaiacol (4), and levoglucosan (5); their chemical structures and peaks are shown in Figure b.…”

Virtual Special Issue of Recent Advances in Biofuel Production via Co-refining Route

“…Lutz et al 11 studied the effect of hydrotreatment on process performance and gasoline quality when wood-derived FPBOs are used as co-feed in an FCC pilot plant and concluded the potentiality of the co-FCC process as a possible near-future pathway to ensure high biofuel contents in commercially available fuels. Janosik et al 12 presented an approach that involves complete dewatering of FPBO, followed by esterification. The overall results are promising because simple unit operations can be used to produce derivatized FPBOs that do not need additional standalone hydrotreating units but can be co-processed in existing units.…”

Determination of Biomass-Coal Blending Ratio during Indirect Cocombustion by the 14C-Liquid Scintillation Count Method

“…There are also research studies focused on enhancing accuracy and identifying sources of CO 2 contamination, , particularly pertaining to air CO 2 pollution caused by various pathways. In recent years, there has been a growing application of the 14 C method in determining the ratio of mixed utilization of biogenic and fossil fuel, including the determination of biomass-coal blending ratios, , the biogenic carbon content of biobased liquid blended fuel, ,− and the biogas-natural gas blending ratios …”