Study On Methanol To Aromatics On Fixed Bed Catalyzed By HZSM-5 Zeolites

Modern chemical industry depending on gas, coal or other fossil fuels that are disappearing will face a severe test. In contrast, methanol has an extensive source, such as transformation from coal, natural gas, coal bed methane, and biomass. With the further development of technology, methanol is expected from carbon dioxide in the air through the use of wind, solar, nuclear power and other sustainable energy. "Carbon" neutral cycle is just around the corner with such a great possibility and feasibility. The development of methanol and its derivatives industry, such as methanol to olefins, methanol to aromatics prospected, to some extent, can reduce the dependence on crude oil and maintain the energy security, sustainable economic and social development. It is significantly important to the safety of those countries that are shortage of crude oil but coal-rich, for example, China.To our best knowledge, more reliable products composition division and precise contents weight were got by chromatographic jointly employed that were operated under operating conditions optimized. This analytic technique provided us exact contents weight of H2, CO, CO2, benzene, toluene, xylene and its isomers. The catalysts were prepared by hydrothemeral treatment or modified by metals. The catalyst crystal structure, surface acidity, specific surface area and Al species were characterized, respectively, by XRD, FT-IR, BET and 27AlMAS NMR. Methanol to aromatics reaction carried on fixed bed reactor catalyzed by 2.5%Zn-HZSM-5 under changing reaction conditions of temperature, pressure, gas space velocity, or catalyzed by HZSM-5 hydrothemerally treated or modified by metals. The catalyst bed temperature changes were investigated by diluting catalyst, changing the molar ratio of methanol in methanol aqueous and changing the partial pressure of nitrogen in the gas phase.The results demonstrated that hydrothermal treatment reduces specific surface area, total acidity, acid strength and BTX selectivity on MTA reaction of HZSM-5. Compared to steaming HZSM-5, HTNaZSM-5 has higher concentration of acid sites and better performance in MTA reaction. Citric acid washing can remove some non-framework aluminum, increase external surface area, and extend catalyst life. The optimal zinc loading weight ratio of zinc-modified HZSM-5 was 2%-3% (wt%). Among all the HZSM-5 modified by 2% (wt%) of K, Cr, Mn, Cu, Zn, Cd, respectively, ZnHZSM-5 had the highest BTX selectivity of 37.84%. Compared with 2% Zn-HZSM-5,1% (wt%) Mg, Fe, Cu, Cr and 1% (wt%) zinc, respectively, modified HZSM-5 raised the BTX selectivity from 37.84% to 41.58%,38.45%,39.06%,42.43%, respectively. Optimal conditions for 2.5% Zn-HZSM-5 were atmospheric pressure,400℃-430℃, methanol weight hourly space velocity less than 2h"’. The rising temperature of catalyst bed can be reduced by catalyst dilution, increasing the molar ratio of methanol in aqueous methanol, and decreasing the nitrogen partial pressure in the gas phase space velocity.