Catalytic Conversion Of Biomass Into Carboxylic Acids

Economic and geopolitical factors (high oil prices, environmental concerns, and supply instability) have certainly played a role in reviving interest in renewable resources. Biomass is currently the only renewable carbon source in the field of new energy. Therefore, the generation of liquid fuels and chemicals from it is currently a hot research topic. This paper focuses on the study of the utilization of biomass, especially lignocellulosic biomass to generate a number of commodity chemicals and biofuel platform molecules. In the first chapter, we first introduce the concept of biomass and biomass platform molecules, and we emphasize carboxylic acids is a key member of biomass platform molecules. Then we briefly introduce three carboxylic acids, levulinic acid, formic acid and acetic acid. Levulinic acid maybe is the most important biomass platform molecules. We primarily state the industrial technology for its generation, and then its conversion into liquid fuels and advanced fuel additives. Secondly, we briefly describe the industrial commodity chemical, formic acid. The reversible transformation of formic acid and carbon dioxide, hydrogen has emerged a hot area for fuel cell, and we propose that the production hydrogen from biomass with formic acid as intermediate is an important process in the future. Finally, we describe the industrial bulk chemical, acetic acid. Introduce the problems existing in the industrial generation of acetic acid will assist us developing industrial production of acetic acid from biomass.Currently, generation of formic acid from biomass needs harsh reaction conditions and/or the additional use of base. In the second chapter, for the first time, we achieve the generation of formic acid from biomass-derived carbohydrates under mild reaction conditions by the use of H5PV2Mo10O40. The highest yield of formic acid for glucose oxidation was55%when oxidized by oxygen and52%when oxidized by air. The X-ray photoelectron spectra and reactions of possible intermediates indirectly revealed the reaction mechanism to be electron and oxygen transfer processes. H5PV2Mo10O40can also be used as a bifunctional catalyst for the conversion of cellulose into FA at443K in9h with35%yield when using air as the oxidant.Then we reported the integrated conversion of lignocellulosic biomass to levulinic acid in a biphasic system consisting of THF and NaCl aqueous solution. The one-step hydrolysis of C6and C5carbohydrates in the lignocellulosic biomass was firstly achieved to give a product solution that contained furfural, formic acid, levulinic acid and lignin, and the hydrolysis process was operated with both model substrates and biomass raw materials. The yields of the hydrolysis products are comparable to values obtained in the literature using a mixed solvent of GVL and water. In contrast to processes using the high boiling point solvent GVL, the utilization of THF allowed a one-step distillation of the product solution into three fractions:furfural and formic acid; levulinic acid; lignin. This separation step not only removed the solid residue from the desired product effectively, but it also let us investigate the hydrogenation of furfural with by-product formic acid without any interference. The hydrogenation process was eventually achieved and the product furfuryl alcohol was finally hydrolyzed to levulinic acid to achieve the integrated conversion of lignocellulosic biomass to levulinic acid. The highest mass yield of levulinic acid was27.7%, which was promoted by68.9%with the additional conversion of the hemicellulose fraction. Thus, the utilization of a lower boiling point solvent, THF, not only achieves the simultaneous hydrolysis of C6and C5carbohydrates in lignocellulosic biomass, but as compared to GVL, it also offers an alternative operation procedure for the integrated conversion of biomass to levulinic acid.Finally, we develop a method for preparing a high yield with high selectivity of acetic acid from lignocellulosic biomass. While using sulfuric acid as the acid catalyst, oxygen as the oxidant, a variety of biomass materials can be converted to acetic acid with a highest mass yield of21.3%and highest liquid product selectivity of90%. The transformation of the components of the biomass feedstock demonstrated that the carbohydrates, especially hexoses are the main source of acetic acid, and levulinic acid is the main intermediate. Ultimately, we focus on the recycle of catalyst and the purification of acetic acid which are important factors in industrial processes for acetic acid production.