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۱Conventional hydrothermal synthesis of H–ZSM–5 catalysts using various templates for light olefins production from methanol
نویسنده(ها): ، ، ،
اطلاعات انتشار: پانزدهمین کنگره ملی مهندسی شیمی ایران، سال
تعداد صفحات: ۴
High–silica H–ZSM–5 catalysts were successfully synthesized using the conventional hydrothermal method under a static condition in the presence of tetrapropyl ammonium hydroxide (TPAOH), tetrapropyl ammonium bromide (TPABr), n–butyl amine (NBA) and morpholine (MOR) as the structure–directing agents. The influences of the templates on the crystal size, surface area, pore volume, morphology and surface acidity of H–ZSM–5 catalysts were characterized by XRD, SEM, BET and NH3–TPD techniques. The catalytic performances of the H–ZSM–5 samples in themethanol to olefins (MTO) reaction were conducted in a fixed–bed reactor at 480 °C, atmospheric pressure and methanol WHSV of 0.9 h–1 using methanol to water weight ratio of unity in the feed. The SEM micrographs revealed that only ZSM–5 samples prepared with TPAOH and TPABrexhibited the MFI–typical hexagonal and spherical–shaped morphologies. The XRD patterns indicated higher crystallinity for the catalyst synthesized using TPABr. Also, this catalyst exhibited the highest acidity and an acceptable surface area. All the samples illustrated activity inthe MTO reaction but the products selectivities especially for the propylene and other light olefins were extremely different. The prepared sample with TPABr as the template displayed the highest methanol conversion (99.37%) and propylene selectivity (37.59%).results.<\div>

۲Methanol–to–hydrocarbons reaction over SAPO–34 and ZSM–5 catalysts: A thermodynamic equilibrium simulation
نویسنده(ها): ، ، ،
اطلاعات انتشار: پانزدهمین کنگره ملی مهندسی شیمی ایران، سال
تعداد صفحات: ۴
The equilibrium conversion and selectivity of methanol to oxygenates and hydrocarbons reaction over SAPO–34 and ZSM–5 catalysts was studied. The equilibrium compositions were calculated using constrained Gibbs free energy minimization. The effect of catalyst type was considered by setting upper limits to products carbon number due to shape selectivity according to catalyst cage size; that is, n5 for SAPO–34 and n6 for aliphatic and n10 for aromatic compounds over ZSM–5. The equilibrium selectivity of paraffins is negligible over SAPO–34 system while that of olefins is very small over ZSM–5 both consistent with experimental results. Within temperature range of 250–450 °C, the equilibrium selectivity to ethylene and propylene increases with temperature over SAPO–34 whereas that of butenes and C5 hydrocarbons decreases. However, the main product selectivities are little affected over ZSM–5. The equilibrium selectivities of individual components showed fair agreement with experimental results for SAPO–34. For ZSM–5, the lumped product composition showed reasonable agreements. However, the products are mostly methane and benzene. The elimination of methane, and ethane from calculations by additional considerations, e.g., mechanism and kinetic evidences, significantly improved the results.<\div>
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