In-situ evaluation for upgrading of biomass over noble metal catalysts by isotopic tracing and NMR monitoring

Abstract

One of the key challenges in studying the upgrading processes for the conversion of biomass is developing an understanding of the underlying conversion mechanism at the atomic scale. This study proposed an innovative high pressure in situ NMR monitoring approach for an isotopic traced upgrading process, which demonstrated a powerful capability to identify key products and provide insights into the reaction structure. The investigations for ring opening of two basic model compounds – methylcyclopentane (MCP) and cyclohexane (CH) on Ir, Pt, Ru and Pd/γ-Al2O3 at 55 and 110 °C have been accomplished. For the study performed at 110 °C on Ir, Pt and Ru catalysts, the trend of H/D exchange rates were clearly dependent on the position on the ring with the highest exchange rate for the unhindered (or open side) and the lowest rate with the methyl group. However, Pd could perform almost equally efficient H/D exchanges for all sides, which may indicate that the “turnover” reactions could also occur on Pd. For both MCP and CH, Ru performed the most efficient H/D exchanges (C–H bond activation), and ring opened products were only observed with the Ru catalyst at 110 °C suggesting it is the most promising ring opening catalyst.