A series of sulfonated mesoporous carbon‐based catalysts with intact silica template (MC) were prepared through incomplete carbonization of sucrose followed by sulfonation. The MC catalysts were characterized by use of Fourier Transform‐infrared spectra, N2 adsorption–desorption, and titration method. The effects of preparation conditions such as carbonization temperature, amount of carbon precursor, sulfonation time, and temperature on the structural and acidic properties of the catalysts were investigated. Preparation conditions such as amount of carbon precursor, sulfonation time, and temperature significantly influenced the surface area and acidic properties of MC catalysts. The activity of prepared catalysts in saccharification was tested using cellulose and rice straw as substrates and high saccharification yield can be obtained using these catalysts. In saccharification of cellulose without pretreatment, the highest yield of 25.2% of C6 monosaccharide can be attained after reaction at 180°C for 3 h. In saccharification of rice straw, the total monosaccharide yield of 43.4% can be achieved after reaction at 150°C for 1 h. In addition, it was found that despite the versatility of mesoporous structure in varied chemical reactions has been confirmed, acid amount was the most important property that determined the effectivity of cellulose saccharification. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 574–581, 2016
A series of mesoporous carbon‐based solid acid catalysts were prepared using tannic acid (C76H52O46), a polyphenol compound, as starting carbon materials and SBA‐15 as silica template. The tannic acid catalysts were characterized by use of N2 Adsorption‐Desorption Isotherm, XRD, FTIR, XPS, and titration method. Phenolic hydroxyl group with weak acidity was confirmed as main functional groups in these catalysts based on characterization using FT‐IR and XPS. The catalysts were tested in saccharification of cellulose. Effects of different preparation parameters of catalyst were correlated to its saccharification activity: (a) oxidation using H2SO4 was important factor determined the high catalytic activity of catalysts, proved by comparison of catalytic activity of catalysts after treatment in concentrated H2SO4 and parent materials lacking the functionalization, (b) higher carbon coating also promoted good catalytic activity since it has higher relative percentage of acid functional groups based on XPS measurement, and (c) catalyst that treated by short oxidation time (2 h) could exhibit higher catalytic activity compared with catalysts that treated by longer oxidation time. With a ratio of catalyst/substrate: 0.5/1 (g/g) at 180°C for 1 h, glucose yield and conversion of 31.45 and 53.86% could be obtained. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 850–860, 2018
To establish an efficient bioethanol production system, a solid-acid catalyst-based saccharification of rice straw in two steps was developed. It was rarely concerned so far that many biomass species contain a significant amount of nonstructural carbohydrates (NSCs, free sugars and starch). NSCs, including hemicellulose, are readily hydrolyzed but also susceptible to overreaction with byproducts. In the developed process, the first step is intended to effectively hydrolyze the significant sugar source of NSCs and HC in rice straw under a mild condition, and the second step is addressed to hydrolyze the cellulose in the residue obtained under a harsh condition. For each step, several catalysts were screened and reaction condition were investigated. For the first step, an appropriate catalyst was Amberlyst 35 Dry, at 130 °C for 30 min in which high yields of C6 monosaccharide, 47.2%, and C5 monosaccharide, 10.8%, were obtained. For the second step, the most active catalyst was a sulfonated mesoporous carbon that provided a maximum yield of C6 sugar (52.5%) at 220 °C for 0 min. A test with the sequential two-step saccharification provided a 65% yield of sugars. From the investigations, the most studied modified pathways of dilute-acid catalyzed hydrolysis of HC and cellulose were also likely to occur with a solid-acid catalyst with an additional pathway of direct hydrolysis of NSCs to C6. To support the observed phenomena, the characteristics of the RS before and after saccharifications were analyzed using SEM and XRD. Thus, this process represents a method to increase the cost-effectiveness of bioethanol production system in an environmentally sound way.
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