The aromatization of n hexane and mixed C 4 hydrocarbon was investigated under microwave heating over ZnNi/HZSM 5 catalyst of lower activity in order to compare with that under the conventional heating. For the n hexane aromatization, the selectivity for benzene and toluene by the microwave heating at 450 ℃ increases by 4% and 5%, respectively, and the aromatics yield by the microwave heating at 480℃ increases by 4% , compared with those by the conventional heating. For the mixed C 4 olefine aromatization, the BTX yield by the microwave heating at 400 ℃ increases by 17 08% and the aromatics selectivity is also higher than that by the conventional heating.
Effect of different alkali metal salts on the crystal size and the crystallization rate of ZSM 5 zeolite was detailedly investigated in this paper. The samples prepared by adding the different alkali metal salts were characterized by using XRD, TEM, TG DSC, BET and IR techniques. The XRD results showed that, for the nanosized ZSM 5 zeolite, the characteristic peaks broadened on the XRD patterns in comparison with the microsized ZSM 5 zeolite. The SEM results verified that the crystal size of zeolites prepared by adding different alkali metal salts had different results, and adding NaCl, NaC2H3O2 and KCl showed the better effect of reducing crystal size, which are about of 40～ 60nm size. The crystallization curve of adding the different alkali metal salts suggested that the crystallization rate was significantly affected by the anions in the alkali metal salt besides the cations. Moreover, the crystal size likewise depended on the anion in the alkali metal salt. In addition, the BET results suggested that the nanosized ZSM 5 zeolite possessed a larger outer surface area in comparison with the microsized ZSM 5 zeolite. The thermostability of the samples was determined by TG DSC technique, indicating that the nanosized ZSM 5 zeolite had a poor thermostability as compared with the microsized ZSM 5 zeolite. The possible difference of the samples with different crystal sizes on IR spectra was also given.
