Effect of Surface Fluorination with CCIF3 on Catalytic Activity of SiO2–Al2O3 for Alkylation of Benzene with Propene

For surface modification, the vapor-phase fluorination of SiO2–Al2O3 with CCIF3 was carried out at various temperatures ranging from 350 to 550°C in a conventional flow reactor. It was found that surface fluorination at about 400°C was especially effective for the enhancement of both the catalytic activity and the maintenance of the catalytic activity for the vapor-phase alkylation of benzene with propene. Ammonia–TPD revealed that the surface acidity of SiO2–Al2O3 could be somewhat increased by surface fluorination at about 400°C. The vapor-phase adsorption of water, hexane, propene, benzene, and cumene showed that the SiO2–Al2O3 surface became hydro- and lipo-phobic after surface fluorination. Thus, an enhancement of catalytic activity maintenance was assignable to a decrease in the affinity of the catalyst surface to reaction products.