Brønsted Acid-Triggered Fast Synthesis Pathway of Furfural to Ethyl Levulinate by PtZn Supported on ZSM-5 Nanosheets
Longbin Deng, Zongyuan Wang, Xin Yu, Congzhen Qiao, Shuaishuai Zhou, Qiang Deng, Yong Zhao, Yajie Tian
Abstract
Furfural (FUR) is widely used to synthesize alkyl levulinate (AL), an important biomass-derived compound for industrial use. Traditional synthesis pathways, including hydrogenation, etherification, and hydrolysis, are slow due to high activation energy requirements. This study presents a pathway using ethyl levulinate (EL) as a model AL. The process starts with the acetalization of FUR to produce 2-(diethoxymethyl)furan (DEMF) using a Brønsted acid–based ZSM-5 nanosheet-supported PtZn (PtZn/ZSM-NS) catalyst. DEMF is then hydrogenolyzed to form 2-(ethoxymethyl)furan (EMF), which is hydrolyzed to produce EL at a rate of 29.8 mmol·g –1 h –1, over 20 times faster than with a Lewis acid–based catalyst. In the initial step, Brønsted acid sites on the PtZn/ZSM-NS activate ethanol to generate an acetate-like intermediate (COO θ ), which facilitates the acetalization of FUR to produce DEMF. This step is crucial for efficiently producing EL using the PtZn/ZSM-NS catalyst. Subsequently, EMF is easily formed through the hydrogenolysis of DEMF instead of through the etherification of furfuryl alcohol. Additionally, highly dispersed PtZn alloys on PtZn/ZSM-NS are essential for optimizing the adsorption strength, thereby accelerating the overall reaction. Using this pathway, the PtZn/ZSM-NS catalyst achieves an EL yield of up to 89.5 wt % at 200 °C in just 1 h.