Читать книгу Handbook of Biomass Valorization for Industrial Applications - Группа авторов - Страница 20

Usually, photocatalysis depends on the substrate type present on the surface of semiconductor. In primary steps of photocatalysis, several observations are important such as generation of charge carrier, solar incident photon radiation or its absorption, charge separation and charge trapping. Many researchers reported that the separation of product and less stability of photons in homogeneous systems are tough to analyze. Although the predictability about the interaction between reactants and heterogeneous photocatalysts is easy than interaction of the heterogeneous photocatalysts with reactants the efficiency and applicability are higher in heterogeneous systems [5]. So, the focus has been created on heterogeneous systems which consist of rare metal ions with organic materials for a wide range of applications in technical ways. Heterogeneous surfaces are chosen for handling multiple and complex reaction pathways in which a variety of reactions such as oxidation, reduction, and redox-neutral reactions. Moreover, photocatalysis is pre-treatment process for converting biomass substrates as cellulose and lignin into high value added chemicals such as alcohols, diols, and acids by fermentation process; HMF and Furfural by hydrolysis; and alkanes by aqueous phase reforming [14].

Lignocellulosic materials consist of dry waste obtained from plants and trees which have three main ingredients as lignin, cellulose, and hemicelluloses. Before processing into valuable chemicals, purification and separation processes are quite challenging tasks. A classic way to utilize lignocellulosic biomass material is the photocatalytic pre-treatment to achieve simple structured products and photo-reforming for the production of hydrogen. Basically, the conversion of lignocellulosic materials provide a variety of products such as Arabinose, Erythrose, HMF, hydrogen, ethanol, carbon dioxide, glucose, syringaldehyde pyrocatechol raspberryketon, vanillic acid, guaiacol, and vanillin 4-phenyl-1-buten-4-ol.

Many carbohydrates are converted into high value added chemicals under ultraviolet and visible lights with fine selectivity of products such as glucaric acid, gluconic acid, Arabitol, Erythrose, glyceraldehydes, formic acid, hydrogen, fructose, xylitol, formate, etc. In this process of converting carbohydrates into products, mostly TiO₂ catalyst with combination of other materials is used.

The conversion of HMF provides FDC and FDCA with basic and acidic attributes through photocatalytic valorization under ultraviolet, visible, and natural solar lights. Moreover, glycerol, methanol, ethanol, and toluene are converted into hydrogen and other chemical products under specific operating conditions via photocatalytic reforming.