The Influence of Modification on the Properties of High-Silica TsVM Zeolite in the Benzene Alkylation Reaction with Ethanol

Abstract

The influence of the nature of a modifying metal (Sc, La, Gd, Yb) on the physicochemical and catalytic properties of a high-silica zeolite of the TsVM type in the alkylation reaction of benzene with ethanol has been studied in a plug-flow- reactor unit in the temperature range of 350–450°C. It has been found that the activity and selectivity of the catalyst depend on the nature of the modifying metal. The maximum yield of ethylbenzene is achieved over the Yb-loaded zeolite to be 40.7 wt % with the selectivity of 56.1%. The modified catalysts are ranked as follows with respect to the yield of ethylbenzene: Yb–HTsVM > La–HTsVM > Gd–HTsVM > Sc–TsVM. The highest ethylbenzene selectivity (59.5%) is obtained on the La-promoted zeolite. The modified catalysts are arranged as follows with respect to the ethylbenzene selectivity: La–HTsVM > Gd–HTsVM > Yb–HTsVM > Sc–HTsVM. There are substantial of amounts xylenes and di- and triethylbenzenes formed in the presence of Sc–HTsVM, leading to a decrease in the ethylbenzene selectivity. As opposed to other modifiers, the micropore volume and average pore diameter of the zeolite increase in the case of modification by Sc. It has been found that the increase in the ethylbenzene selectivity of the catalysts modified with La, Gd, and Yb is associated with the nature of the modifying metal, a decrease in the strength and concentration of strong acid sites, and a decrease in the specific surface area and total pore volume of the zeolite as a result of its chemical modification.