Trend and Progress in Catalysis for Ethylene Production from Bioethanol Using ZSM-5

Advancing technologies for the conversion of bioethanol (ET) to ethylene (ETY) holds significant potential for enhancing the production of numerous tertiary chemicals, which are currently derived from fossil-based resources. This review explores the feasibility of producing ethylene from bioethanol and underscores its growing importance in the global market. It focuses on breakthroughs in ZSM-5-based catalysts, compared to conventional ones, with particular attention to two key aspects: (i) the remodulation of ZSM-5 properties to establish a clear catalyst structure–reactivity–selectivity relationship in ET conversion and (ii) the identification of major factors influencing ZSM-5 stability and reusability. State-of-the-art approaches for ZSM-5 modification and regeneration are thoroughly examined with an emphasis on the role of active sites in ETY formation. The impact of key reaction parameters (such as temperature, space velocity, pressure, and feed composition (including impurities and water)) on ET-to-ETY reaction kinetics is systematically evaluated. The review shows that the formation of undesirable C3+ hydrocarbons is promoted by the contribution of strong Brønsted acid sites at elevated temperatures. In contrast, pathways favoring the formation of ETY or diethyl ether (DEE) are driven by the individual or synergistic effects of weak Lewis and strong Brønsted acid sites at milder temperatures. The integration of ET-to-ETY conversion within compact biorefineries and polyolefin manufacturing chains, alongside in situ regeneration of ZSM-5 catalysts through controlled cofeeding of H2O at moderate temperatures, presents a promising strategy for intensifying the ET-to-ETY process. This Perspective expects to provide a comprehensive overview of recent developments in ET-to-ETY catalysis, particularly at lower temperatures, with the goal of improving process efficiency in terms of energy consumption, cost, and CO2 emissions.