Efficient One-Pot Cellulosic Ethanol Production Over PdZn@Silicalite-1 Catalysts with Metal-Acid “Restricted Adjacency” Structures

Abstract

Direct hydrogenolysis of cellulose to produce ethanol is a promising way to efficiently utilize biomass resources, contributing significantly to low-carbon energy development and greenhouse gas reduction. However, this process is challenging due to intricate cascading reactions. In this study, PdZn@S-1 catalysts featuring metal-acid “restricted adjacency” structures for direct cellulose conversion are developed. This unique structure allows acidic sites and metal nanoparticles to be in close proximity in a microscopic space, leading to changes in the electronic states of the metal sites, and an increase in the number of acidic sites. This configuration fosters synergistic and balanced interaction between the two types of sites. As a result, the PdZn_0.5@S-1 catalyst demonstrates exceptional performance, achieving an ethanol yield of 69.2% at 245 °C and 4.5 MPa H₂ within 4 h. The remarkable catalytic activity and selectivity are attributed to the formation of Lewis acid sites through Pd^δ+─O(H)─Si coordination, which facilitates the cleavage of C─C bonds, while the adjacent PdZn alloy provides an effective site for the hydrogenation of C─O bonds. This work introduces a novel approach by successfully integrating metal@zeolite catalysts into the catalytic conversion of biomass macromolecules, offering new insights for the direct utilization of biomass resources.