Synthesis and characterization of fibrous HFZSM-5 for alkylation of benzene

Abstract

The global demand of toluene is expected to increase at an annual rate of 1.5% from 1995 to 2020. Thus, it is important to increase the yield of toluene by upgrading the productivity of benzene methylation process without constructing a new plant. One of the alternatives is by modifying the catalysts that are commonly used in industry to provide a better catalytic activity and performance. During the synthesis, the oil phase was varied using benzene (HFZSM-5-B), toluene (HFZSM-5-T) and xylene (HFZSM-5-X). All catalysts were characterized with X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), N2 physisorption, Fourier transform infrared (FTIR), and electron spin resonance. The acidic property was determined by lutidine adsorbed FTIR spectroscopy, while the catalytic activity was carried out in a microcatalytic pulse reactor in the reaction temperature range of 423-673 K. The XRD, FESEM and N2 physisorption results have confirmed the structure of all HFZSM-5 type catalysts with a spherical dendrimer silica fiber possessing high surface area of HFZSM-5-B (717 m2/g), HFZSM-5-T (691 m2/g) and HFZSM-5-X (307 m2/g). The 2,6 - lutidine adsorbed in FTIR revealed that HFZSM-5-B has abundant strong Bronsted and Lewis acid sites, followed by HFZSM-5-T and HFZSM-5-X. At a low temperature of 423 K, all HFZSM-5 type catalysts possessed excellent conversion of more than 90%. HFZSM-5-X gave the highest yield of toluene (35.27%) which attributed from its controllable micropores area in inter-dendrimer structure and reduction amount of Bronsted and Lewis acid sites. Meanwhile, it was noted that HFZSM-5-T revealed the highest yield of C8 (71%) due to high mesopore area (647 m2/g).