TRANSALKYLATION OF DIETHYLBENZENE WITH BENZENE IN SUPERCRITICAL CARBON DIOXIDE: INFLUENCE OF STRUCTURE AND ACIDITY OF ZEOLITIC CATALYSTS

摘要

Ethylbenzene (EB) is commercially one of the largest volume derivates of benzene. The worldwide production of EB is 23 million metric tons per year with a 4% annual growth. The 90% of EB world's production is employed in the manufacture of styrene, the other 10% is used in other applications like paint solvents and pharmaceuticals [1]. EB is mostly synthesized by benzene (B) ethylation over acidic catalysts. This reaction is accompanied by the formation of many polyalkylates, mainly isomers of diethylbenzene (DEB), and also cumene, butylbenzenes and ethylene oligomers. In order to transform these by-products in more valuable ones, the transalkylation reaction between B and DEB to obtain EB is carried out. However, transalkylation requires higher acid strength and more severe reaction conditions than alkylation, which becomes unselective at those conditions [2]. Since 1950s, the synthesis of EB was performed using Friedel-Crafts catalysts like AlCl_3. Nevertheless, the operating costs associated with the corrosivity, safe handling and disposal of this type of catalysts as well as a higher environmental conscience during the last decades, have made the industry to move towards a zeolite based technology, making the process cleaner, less corrosive and more economically competitive.