Impact of activation on properties of carbon-based solid acid catalysts for the hydrothermal conversion of xylose and hemicelluloses

Abstract

Activation plays an important role in improving the pore structure of the carbon materials preparation. For carbon-based solid catalysts, activation could provide the high specific surface area and porosity. In this work, non-activated, KOH-activated, ZnCl2-activated treatments were comparatively discussed to prepare carbon-based solid acid catalysts for furfural production from xylose and hemicelluloses. These prepared catalysts were characterized by SEM, FT-IR, elemental analysis, Raman, N2 adsorption-desorption and Boehm titration. The results showed that the chemical activated treatment could significantly improve the specific surface area of carbon-based solid catalysts, but also had an important influence on the distribution of surface functional groups especially for decreasing of the SO3H density and the enhancement of the phenolic OH and COOH density. For the highest SO3H density of non-activated carbon-based catalyst, it displayed higher catalytic activity in the conversion of xylose to furfural than other catalysts. Meanwhile, using non-activated carbon-based catalyst in the aqueous solution, the maximum furfural yield of 50% was obtained from hemicelluloses at 200 °C for 2.5 h, the maximum xylose yield of 55% was achieved at 200 °C for 1.5 h. While KOH-activated carbon-based catalyst exhibited the excellent catalytic performance to produce xylooligosaccharide with the highest yield of 62% at 180 °C for 1.5 h.