NONOXIDATIVE DEHYDRO-AROMATIZATION OF MET HANE OVER STRONG ACID-PROMOTED W HZSM-5-BASED CATALYSTS/

Highly active and heat-resisting strong acid-promoted W/HZSM-5-based c atalysts, W-Zn(La,Nb)-H2SO4/HZSM-5, for non-oxidative dehydro-aromatiz ation of methane have been developed. Over a W-Zn-H2SO4/HZSM-5 catalys t and under the reaction conditions of 1 123 K, 0.1 MPa, and GHSV=1 50 0 mL/h per gram cat., methane conversion (X-CH4) reached 23%, with a s electivity to benzene at 97% and an amount of coking for 3 h operation at 0.02% of the weight of the catalyst used. During a stability test at 1 073 K for 3 h, X-CH4, had been maintaind at about 21.5% over the W-Zn-H2SO4/HZSM-5 catalyst, whereas dropped gradually to 13% from 19% in the initial stage over the Mo-Zn-H2SO4/HZSM-5, demonstrating that t he former has a better heat-resisting peculiarity than the latter. The results of investigation of optimization of the catalyst composition showed that the optimal W-loading on the HZSM-5[n(Si)/n(Al)=38] zeolit e support was about 2.5%, and that an optimal match-ratio existed amon g the W and the promoters, Zn(or La or Nb) and H2SO4. The experimental results also indicated that the promoting effects of Zn and La were m ore pronounced than Nb.