Catalytic selective oxidation in biomass conversion

Speaker: Professor Yanhui YANG, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore

In the global attempt to reduce carbon footprint, the Chemical and Petrochemical Industry faces the problem to replace the currently used fossil feedstock with renewable resources, reduce energy consumption and to intensify and integrate the processes to be more carbon efficient. In all three issues, catalysis will be the key to a successful transformation. Knowledge-based development and implementation of catalytic technology will help to process the novel feedstock, reduce the energy required for maintaining the desired process and improve the carbon efficiency of the targeted synthesis routes. In this seminar, two examples will be discussed to illustrate our efforts in the last few years in biomass transformation. The first example is a classic heterogeneous catalysis approach in which an integrated experimental and computational investigation reveals that the surface lattice oxygen of copper oxide activates the formyl C–H bond in glucose and incorporates itself into the glucose molecule to oxidize it to gluconic acid. The reduced CuO catalyst regains its structure, morphology and activity upon re-oxidation. The activity of lattice oxygen is shown to be superior to that of the chemisorbed oxygen on the metal surface and the hydrogen abstraction ability of the catalyst is correlated with the adsorption energy. Based on the present investigation, it is suggested that surface lattice oxygen is critical for the oxidation of glucose to gluconic acid, without further breaking down the glucose molecule into smaller fragments, due to C–C cleavage. Using CuO as the catalyst, excellent yield of gluconic acid is also obtained for the direct oxidation of cellobiose and polymeric cellulose, as biomass substrates. The selective oxidation can be effectively catalyzed using noble metal nanoparticles. Choosing an appropriate support with well-defined structure and suitable surface chemistry is a feasible and effective approach to make metal nanoparticles with specific size, shape, structure, and to avoid agglomeration leading to catalytic deactivation. With the intention of successfully synthesizing more efficient heterogeneous catalysts for the selective oxidation, it is extremely important to elucidate the effect of metal nanoparticle configuration, the novel nano-structured support on the catalytic activity for selective oxidation with particular highlights on the interactions between both metal-metal and metal-support. The second example shows the Au-Pd bimetallic catalyst and its application in selective oxidation of HMF to FDCA . The unique structure of selected support is found to improve the stabilization of the metals in the preparation as well as the reaction process. Furthermore, surface chemistry (metal-support interaction) and synergetic effect in the case of metal alloy catalysts (metal-metal interaction) play a crucial role in controlling the catalytic performance of as-prepared catalysts. Various characterizations will be carefully conducted to look into the insights of these catalysts’ physicochemical properties.

This talk is part of the Chemical Engineering and Biotechnology Departmental Seminars series.