Читать книгу Handbook of Biomass Valorization for Industrial Applications - Группа авторов - Страница 53

The dependence on fossil fuel is increasing due to over population and industrialization to sustain the overgrowth of the population. The depletion of fossil reserves limits the availability of resources to sustain mankind. Hence, immediate measures are required to solve the long-term persisting problem of depletion of fossil fuels and increased emission of greenhouse gases as a result of rapid industrialization [1]. Research focusing on deriving chemicals and fuels from the renewable resources has been tremendously increased over a few decades. Biomass can be used as a renewable resource as it can be replenished using carbon dioxide, water and sunlight following the process of photosynthesis. This makes the process carbon neutral [2, 3]. Biomass can be obtained from forest waste, waste from animal farming, algae, solid waste, organic municipal solid waste and paper industrial sludge waste [4, 5]. Lignocellulosic biomass is one of the most readily available renewable resources for the sustainable development of chemicals and fuels as it doesn’t compete with the supply of food supply. Lignocellulose is composed of cellulose (34–54%), hemicellulose (19–34%) and lignin (11–30%). Cellulose is made up glucose units linked together by b-1,4-glycosidic bonds. The two units of fibrils are interconnected with the inter and intra molecular hydrogen bonding. Hemicellulose is the polymer of five to six carbon sugars, such as xylose and glucose. Hemicellulose and cellulose can be hydrolyzed using acid catalyst in the presence of electronegative atoms such as chloro group to break the inter and intra molecular hydrogen bonding [6–8]. Lignin is the polymer of phenylpropane units having different hydrophobicity and aromatic properties. Lignin on depolymerization and fractionation results phenol derivatives such as (p-hydroxyphenyl), (guaiacyl), and (syringyl) [9]. Biofuels and various value-added chemicals can be produced based on the reactivities of different components of biomass and their mode of transformation. Different processes involved are pyrolysis, gasification and aqueous phase reforming as explained in Figure 3.1. Pyrolysis involves heating of biomass at high temperature at higher heating rate to produce biooils [10], gasification on heating produces the gases, ash and solid reminiscent [11], Aqueous phase reforming involve chemical transformation of sugars obtained from the hydrolysis of cellulose or hemicellulose to platform chemicals such as levulinic acid and furfural which can be further upgraded to value added chemicals and fuels [12–14].