Recent Advances in the Catalytic Conversion of Cellulose

Concerns about the depletion of fossil fuel reserves, the impact of anthropogenic CO2 emissions, and increasing energy demands have encouraged the exploration of new catalytic procedures for converting cellulosic biomass into valuable platform chemicals and renewable fuel components. The development of these sustainable catalytic transformations could potentially provide a long-term solution to the industrial dependence on fossil carbon, requiring in 2025 production of up to 30% of raw materials for the chemical industry from renewable resources. With an abundance of approximately 720 billion tonnes, that is, 40% of the annual net yield of photosynthesis, cellulose is the world’s largest organic raw material resource. Whereas nature renews 40 billion tonnes every year, no more than 200 million tonnes of this nonedible biomass are processed, mainly as a raw material for paper and packaging industry. The blueprints of the “new” cellulose chemistry are based on some key elements, namely controlled depolymerization of the biopolymer and catalytic cascade reactions (e.g. , hydrogenation, hydrogenolysis, oxidation), which, when put together, yield a pool of molecules that can be used for the synthesis of industrial intermediates and fine chemicals. One of the methods for chemical degradation of cellulose is the acid-catalyzed hydrolytic cleavage into its glucose monomers, which are, for example, of high interest for further fermentation into bioethanol. 6] An excellent review on cellulose hydrolysis as an entry point into biorefinery schemes has recently been published by Rinaldi and Sch th. Also as an introduction, we recommend more general reviews on the challenges and issues involved in the catalytic processing of biomass. In this Minireview, we focus on the impressive scope of recent catalytic advances in the conversion of cellulose over solid acid and multifunctional catalysts, the direct conversion into furan-based or valeric biofuels, liquid alkenes, alkyl glycosides, and cellulose dissolution and processing in ionic liquids. Particular emphasis will be on concepts known from heterogeneous and multistep catalysis. Before the different catalytic strategies are discussed, structural aspects as well as specific chemical and physical properties of cellulose will be briefly addressed, as this knowledge is a prerequisite for the rational design of new catalytic transformations.