Heterogeneous Catalysis for Today’s Challenges: Synthesis, Characterization and Applications (RSC Green Chemistry)

Book Preface

The usage of fossil fuels causes serious problems like the energy crisis and global warming. In order to solve these problems, so far much attention has been paid to the development of renewable energies such as solar or wind energy. Biofuel produced from biomass is one of the potential alternatives. First-generation biofuels (i.e. biodiesel) produced from corn and soybean oil have proved that biomass to-biofuel conversion is possible; however, the use of edible agriculture as a source will cause other problems such as food deficiency.1 Therefore, second-generation biofuels generated from nonedible lignocellulosic biomass have attracted more attention recently.

Lignocellulosic (or so-called ‘wood-based’) biomass consists of three major components: cellulose (41%), hemicellulose (28%), and lignin (27%).2 Generally, cellulose and hemicellulose can be used to produce bioethanol, and lignin offers a broad spectrum of conversion (thermal cracking, fast pyrolysis, and complete gasification) to achieve valuable chemicals and transportation fuels.3 So far, a great deal of effort has been put toward the degradation of cellulose with enzymes,4 mineral acids,5 bases,6 and supercritical water.7 The enzymatic hydrolysis of cellulose is effective, but the system is sensitive to contaminants originating from other biomass components. Furthermore, pre-treatment of cellulose (e.g., ammonia or steam treatments in a high-pressure process or mechanical milling) is typically required to increase the accessible area of cellulose for a reasonable rate of enzymatic hydrolysis.8 Mineral acids have been extensively investigated to catalyze hydrolysis at a variety of acid concentrations and temperatures. A rather high temperature (180–230 1C) has been used in order to obtain an acceptable rate of cellulose hydrolysis. Furthermore, degradation of the resulting glucose becomes an issue at such high temperatures.