| In view of increasing shortage of petroleum resource and high price of crude oil, the utilization of the relatively abundant natural gas, composed mainly of CH4, has attracted significant attention. The catalytic conversion of natural gas into aromatic hydrocarbons via bromomethane as intermediate is a desirable way to develop effectively natural gas industry and enhance its added-value, which opens up a novel and feasible synthetic route for aromatic hydrocarbon and provides new raw materials for aromatics. This paper try to develope highly efficient catalysts for the conversion of methyl bromide into aromatics, clarify the structure-catalytic efficiency relationship of the catalysts and make a preliminary study on the reaction mechanism and catalysts deactivation mechanism.The catalytic conversion of CH3Br to aromatics was firstly investigated over PbO-modified commercial HZSM-5 catalyst. The effects of supports, modifying components, calcination conditions and reaction conditions on catalytic performance were studied. It was found that HZSM-5 is better than SiO2, A12O3, ZrO2 or HSAPO-34 as support. PbO is superior to the other metal oxides selected to modify HZSM-5, and the most suitable PbO loading and SiO2/Al2O3 ratio are 5wt.% and 70, respectively. The 5wt.%-PbO/HZSM-5 calcined at 450℃for 8 h performs the best. Also, The characterization results indicate that (i) the PbO species is highly dispersed on the HZSM-5 support, which leads to a significant decrease in the density of the surface moderate intensity acidity and a slight increase in the density of the strong and weak intensity acidity of the catalyst, (ii) the role of PbO is to promote hydrocarbon aromatization, and (iii) the acid sites of HZSM-5 are indispensable for CH3Br conversion into aromatics. (iiii) the deactivation of catalyst is due to pore blocking by carbonaceous deposits on the surface of catalysts.In order to obtain more efficient catalyst, H-ZMS-5 zeolite was prepared by hydrothermal crystallization method, using n-butylamine (BTA) as template. The as-prepared materials were evaluated for the conversion of CH3Br into aromatics in the fixed-bed reactor. The effects of batch SiO2/Al2O3 ratio, alkalinity, NaCl/Al2O3 ratio, seed crystals and crystallization time on the yield, physico-chemical properties and catalytic performance of ZSM-5 zeolites were systematically studied. The structure-catalytic efficiency relationships of the catalysts were also clarified by the characterization techniques of XRD,SEM and NH3-TPD. Using the optimum sol (SiO2/Al2O3=70, BTA/SiO2= 0.2847, Na2O/SiO2= 0.1237, H2O/SiO2= 37.4, NaCl/Al2O3= 60, and Seed crystals/SiO2= 5wt.%), and the preferable crystallization conditions of 100℃/24h-170℃/24h, HZSM-5 zeolites with high crystallinity and a small size of 0.3μm-0.7μm were obtained and found to exhibit better activity, selectivity and stability towards the CH3Br conversion into aromatics, the aromatic yield reach up to 44.2%. It can be deduced that higher crystallinity or smaller crystal size will favor the improvement of the catalytic performance of HZSM-5 zeolites. Moreover, efficient conversion of methyl bromide into aromatics can be obtained only when the surface acidity of the HZSM-5 zeolite is moderate.
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