In-situ hydrothermal synthesis of Al-rich Cu@ZSM-5 catalyst for furfuryl alcohol upgrading to pentanediols

Abstract

Bifunctional metal-acid catalysts have been widely used in the process of upgrading the molecules of biomass. As an important bifunctional catalyst, metal @ zeolite exhibits excellent sintering resistance and efficient catalytic performance, which is significant for improving practical applications. While the development of Al-rich zeolite-confined nanocluster catalysts is still a considerable challenge. In this paper, Cu@ZSM-5 (SiO2/Al2O3 = 40) catalyst with Al-rich ZSM-5 zeolite-confined copper nanoclusters were designed and synthesized by the in-situ ligand-assisted hydrothermal crystallization method. The average size of the encapsulation metal clusters was only 2.3 nm after treatment at 400°C for 2 h in a hydrogen environment, which exhibits excellent thermal stability. 27Al MAS NMR and Pyridine-adsorbed IR (Py-IR) spectra confirmed that Al was successfully introduced into the zeolite framework. The intimate metal- Brønsted acidic site distribution enables complete conversion of furfuryl alcohol and 92.1 % selectivity of pentanediols. DFT calculations revealed that the high catalytic activity in catalyzing the ring opening of furfuryl alcohol to pentanediols could be attributed to the unique electronic effect in the Al-rich catalyst Cu@ZSM-5 (SiO2/Al2O3 = 40). The in-situ ligand-assisted hydrothermal crystallization method will be very attractive regarding the simplicity required for industrial production. The Al-rich Cu@ZSM-5 (SiO2/Al2O3 = 40) catalyst was endowed with rich and dense metal-Brønsted acidic sites by a simple in-situ synthesis method, providing a practical and feasible path for the high-value utilization of biomass molecules.