Distribution and Characterizations of Liquefaction of Celluloses in Sub- and Super-Critical Ethanol

Abstract

Effects of reaction conditions (temperature, retention time, and cellulose/ ethanol ratio) on biomass liquefaction in sub-and super-critical ethanol were investigated in this work. The liquefaction system was divided into the following fractions: a volatile organic compounds fraction, a gas fraction, a heavy oil fraction, a water-soluble oil fraction, and a solid residue fraction. Results showed that for three samples, the SR yield of microcrystalline cellulose was highest compared with corn stalk cellulose and rice straw cellulose at the same temperature, while the HO yield was lowest in the liquefaction process. At the same retention time in supercritical ethanol, the SR yield of microcrystalline cellulose was highest, suggesting that the microcrystalline cellulose was difficult to liquefy. The effect of different samples on liquefaction in ethanol with various cellulose/ethanol ratios can be clearly seen from the distribution yields. The FT-IR analysis of the solid residues showed that the structure of celluloses changed after liquefaction. The GC-MS analysis showed that the volatile organic compounds, water-soluble oil, and heavy oil comprised a mixture of organic compounds, which mainly included furfural, acids, furans, esters, and their derivatives. XRD analysis revealed that the decomposing reaction primarily occurred within amorphous zones of the celluloses at the low temperatures. Keywords: Liquefaction; Cellulose; FT-IR; XRD; GC-MS INTRODUCTONThe demand for energy has been increasing dramatically due to the rapid increase in the world's population and developing technologies. Meanwhile the current energy resources have limited reserves and are decreasing (Ozcimen and Karaosmanoglu 2004). Today, biomass is considered a renewable resource with high potential for energy production. Biomass can be converted to various forms of energy through numerous thermo-chemical conversion processes, depending upon the type of energy desired (Yanik et al. 2007).Among the many thermo-chemical procedures, biomass liquefaction into liquid fuel is a promising one, during which the common products are gas, liquid, and char. Liquefaction has many advantages such as, (1) The presence of solvent dilutes the concentration of the products, thus tending to minimize cross-linked reactions and reverse reactions, and (2) The processing temperature is relatively low (less energy consumption) in comparison with other thermo-chemical processes (such as pyrolysis and gasification) (Liu and Zhang 2008). Some articles have reported on the liquefaction of biomass; the presence of solvents has been shown to effectively lower the viscosity of heavy oil derived from biomass liquefaction (Demirbas 2000).

Metal oxide-catalyzed hydrothermal liquefaction of Malaysian oil palm biomass to bio-oil under supercritical condition

“…The generation of bio-oil based on mechanisms such as biomass depolymerisation, cleavage of C C bond in biomass structure, dehydration, decarboxylation, deamination and finally the recombination of reactive fragments [7]. Liquefaction requires lower operating temperature (approximately 250-400 • C) and higher pressure (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) MPa) compared to pyrolysis (temperature at 500-800 • C) [6]. Therefore, it is expected that the energy consumption of liquefaction should be lower compared to pyrolysis.…”

“…Therefore, it is expected that the energy consumption of liquefaction should be lower compared to pyrolysis. The use of solvent in liquefaction dilutes the concentration of products, thus capable of preventing cross-linking and recombination reactions from occurring [8]. Liquefaction method is able to convert wet biomass without the need of drying compared to pyrolysis [4].…”

A Comprehensive Review on Hydrothermal Carbonization of Biomass and its Applications

“…Rice-husk To characterize morphology and crystalline structure [17,146] a temperature lower than 200 °C would give a higher yield of hydrochar rather than temperature beyond 200 °C [195]. Thermodynamic properties of the hydrochar have revealed that its yield and properties can be expressed as a function of dose-response, and hence there occur significant variations in the properties and yield by a change in the temperature [56,58,189,[192][193][194].…”

“…The hydrochar modification is performed on the basis of the type of contaminants to be removed. [195]. Various effects of different parameters and modifications over hydrochar yield have been summarized in Table 5.…”

A review on conversion of biomass to biofuel by nanocatalysts

“…Mixed solvents (ethanol-water) and also other pure solvents (ethanol) (Zheng et al, 2013) have been used in thermochemical conversion of biomass. However, these solvents increase the operating costs of the biomass conversion.…”