University of Twente Student Theses


The effect of ethanol/water on lignocellulosic biomass and cellulose liquefaction

Murti, G.W. (2017) The effect of ethanol/water on lignocellulosic biomass and cellulose liquefaction.

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Abstract:Biomass and cellulose, as potential renewable alternative resources, were liquefied in the presence of ethanol and water. The aim of this work is to study the effects of ethanol/water mixture on direct liquefaction of biomass and cellulose. The experiments were conducted in a 45-ml batch autoclave at high temperature and elevated pressure. The parameters include feedstock (wood and cellulose), ethanol concentration (0 – 100 wt%), reaction temperature (250 – 350 oC), and reaction time (0 – 90 min). The products were analyzed by GC-MS, Karl Fischer titration, GPC, HPLC, and LC-MS. The optimum operating condition for biomass liquefaction was achieved in the ethanol/water mixture of 60/40 (w/w) at a reaction temperature of 300oC, and a holding time of 30 min. Above 300oC, the solid residue yield increased significantly due to re-polymerization. Furthermore, prolonged reaction time more than 1 h led to high solid residue yield. During recovery, the bio-crude oil tended to be entrained through a filter when employing ethanol in the liquefaction process. It was revealed that bio-crude oil was partly dissolved in the ethanol/water mixture. The solubility of the hydrophobic-bio-crude oil increased proportionally to the amount of ethanol concentration. Cellulose liquefaction was also conducted by varying the concentration of ethanol. The results showed a similar trend to those from biomass liquefaction. The same operating condition gave the lowest solid residue yields. Some degradation products of cellulose in the aqueous phase such as levulinic acid, acetic acid, formic acid, and ethyl levulinate were observed by HPLC and LCMS. Then, the analyses were also applied to the aqueous phase from biomass liquefaction in which the compounds were also found. In summary, ethanol and water mixture showed a synergistic effect on liquefaction process. Water accelerates the decomposition reaction, and simultaneously, ethanol may dissolve the heavy molecular weight compounds from the solid matrix. GPC analyses demonstrated that the average of molecular weight of the oil from biomass liquefaction increased gradually by increasing amount of ethanol in the medium. Nevertheless, in cellulose liquefaction, the average molecular weight decreased by an increase in ethanol. It indicated that charring might be avoided by using ethanol as a solvent. Also, ethanol reacts with the intermediate product and produces light molecular weight compounds. Our work confirmed that in a water-rich medium, the reaction occurred quickly toward the degradation products and charring; however, an addition of ethanol could decrease the reaction rate as well as protect the glucose into further degradation products, and eventually, levulinic ester was found as a stable product at the end of the reaction.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:58 process technology
Programme:Chemical Engineering MSc (60437)
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