Effect of Composition of Iron-Cobalt Oxide Catalyst and Process Parameters on The Hydrothermal Liquefaction of Sugarcane Bagasse

Abstract

Development of catalyst with high deoxygenation activity and optimum process parameters are the key for getting the highest biooil yield with the least oxygen content by hydrothermal liquefaction. With this view, iron-cobalt oxides of Co/Fe ratio 0.33, 1.09, 2.35, and 3.52 were prepared by co-precipitation method, and characterized by XRD, BET surface area, chemical composition by EDX method, and evaluated for hydrothermal liquefaction of sugarcane bagasse in a high-pressure batch reactor under subcritical conditions using CO as process gas to find the optimum Co/Fe ratio and process parameters. Optimum Co/Fe ratio was found to be 1.09 as it gave the highest bio-oil yield of 57.6% with the least oxygen content of 10.8%, attributed to the cobalt ferrite, the major phase present in it. The optimum temperature, initial CO pressure, water/biomass ratio, catalyst/biomass ratio and reaction time for the highest oil yield with the least oxygen content were found to be 250 °C, 45 bar, 28, 0.4, and 120 min, respectively. From the effect of reaction time, it was found that much of the hydrolysis of lignocellulose to water soluble oxygenates, its deoxygenation to bio-oil and its deoxygenation to low oxygen containing bio-oil took place in initial 15 min, 15 to 60 min, and from 30 to 120 min, respectively. Total oil yield (%) was lower by 21% and % oxygen in total oil was higher by 9.9% for spent catalyst compared to fresh catalyst indicating the erosion in the deoxygenation activity of catalyst and thus need for improving its hydrothermal stability. Copyright © 2020 BCREC Group. All rights reserved

Studies on the catalytic hydrothermal liquefaction of sugarcane bagasse to bio-oil, over cobalt oxide

“…Gaseous products from the reactor were passed through the CO incinerator and then vented out. Rest of the product was separated and quantified as Oil 1, Oil 2, water soluble organics (WSO), Oil 3, Solid Residue (SR) using the procedure reported earlier [12]. Conversion, yield of the products, and yield of Total Oil were calculated using the equations reported thereof.…”

“…This was in accordance with the reported finding that the conversion of sugarcane was owing to the depolymerization of lignocellulose to WSO viz. xylose, mannose, glucose, galactose, p-coumaryl alcohol, coniferyl alcohol, sinapyl alcohol [12] catalyzed by OHand H + furnished by sub-critical water [19], independent of the externally added catalyst. Whereas the conversion of WSO to water immiscible oil was due to the deoxygenation activity of catalyst [12].…”

“…xylose, mannose, glucose, galactose, p-coumaryl alcohol, coniferyl alcohol, sinapyl alcohol [12] catalyzed by OHand H + furnished by sub-critical water [19], independent of the externally added catalyst. Whereas the conversion of WSO to water immiscible oil was due to the deoxygenation activity of catalyst [12]. Percentage of total oil yield increased when the catalyst/biomass (C/B) weight ratio was increased from 0 to 0.4, mainly due to the increase in the yield of oil 2 and 3.…”

“…KOH, K 2 CO 3 which increased the conversion and bio-oil yield by 10-15% compared to non-catalytic HTL IOP Publishing doi:10.1088/1755-1315/1042/1/012007 2 [11]. A study with the heterogeneous catalyst of iron-cobalt oxide, reported an increase in the bio-oil yield by 22% compared to non-catalytic HTL [12]. Formation of bio-oil by the HTL of sugarcane bagasse first involves the depolymerization of lignocellulose to water soluble oxygenates (WSO) such as phenols and sugars by acid-base catalyzed hydrolysis, followed by the deoxygenation of WSO to bio-oil.…”

“…Hot compressed water used in HTL was reportedly having ionic product 500 times as that of ambient water, thus the H + and OHfurnished by it, acted as acid and base catalysts respectively [13]. The second step and thus the bio-oil yield depends upon the activity of the externally added catalyst and the process parameters [12]. Soni et al reported that the cobalt oxide catalyst was effective for the deoxygenation of jatropha and palm oil to hydrocarbons [14].…”