The review focuses on the advancements in the methylation of p-xylene from toluene, highlighting the significant role of surface acidity and pore size of ZSM-5 and modified ZSM-5 catalysts in this process. It analyses the characteristics of the toluene methylation mechanism, examining various synthesis strategies for catalysts and methods to enhance shape selectivity. Additionally, the discussion includes the influence of reaction temperature and pressure, as well as the reaction kinetics involved in alkylation reactions, providing a comprehensive understanding of the factors that affect the efficiency and selectivity of the methylation process.

Abstract

p-Xylene is a key industrial chemical with increasing demand due to the shift in global markets toward petrochemicals. Although most p-xylene is currently produced through naphtha cracking or naphtha reforming, alternative and cost-effective manufacturing techniques are needed. Catalytic methylation of toluene using shape selective catalysts is a potential route to yield xylenes with great para selectivity. Recent research has focused on modifying catalysts to increase surface acidity, pore channels, and crystallinity, improving para selectivity and toluene conversion. However, challenges remain in designing effective shape selective catalysts without sacrificing catalytic activity and maximizing methanol utilization for increased p-xylene productivity. This review discusses recent developments in catalyst design and modification strategies for improved shape selectivity, including the influence of reaction conditions, kinetics, mechanism, and catalyst deactivation. The review concludes with a forward-looking perspective on developing, designing, and modifying catalysts to address gaps in the related research field.