Steam cracking of green diesel (C12) to BTX and olefins over silane-treated hierarchical BEA

Abstract

Commercial BEA zeolite was modified under the radiation of microwave labstation with different modification strategies. Catalytic properties and textural properties were manipulated by desilication using sodium hydroxide or tetrapropyl ammonium hydroxide solution. It was found that sodium hydroxide can lead to very fragile textural properties and low catalytic activity. While tetrapropyl ammonium hydroxide is highly recommended for the improvement of textural properties, especially at long desilication time. Parent and desilicated samples were further modified by octadecyltrichlorosilane (OTS) in order to add the silane functionality to the zeolitic materials. This addition led to minimizing the textural properties of the silane-treated BEA zeolites and consequentially led to a reduction in the catalytic activity. Recovering and improving the catalytic activity and textural properties were then performed by calcining the silane-treated catalyst to combust the long-chain alkyl groups, which facilitate the formation of silica layer. Another modification strategy was found that the desilicated BEA sample can enhance the catalytic activity and catalytic stability when it treated with a low concentration of nitric acid after desilication. This modification strategy led to improving the catalytic conversion from 29% to 76%.