Aromatic Product Selectivity of Template free and Template Synthesized ZSM-5 Catalysts in Methanol to Hydrocarbon Conversion

Template-free ZSM-5 zeolites with the SiO2/Al2O3 ratios of 28, 50, and 80 were synthesized and compared with template preparation. The resulting zeolites were characterized by IR, XRD, XRF, SEM, and BET analyses. The template-free and SDA (synthetic directing agent, or with template) zeolites manifested similar physical and chemical characteristics. In addition, their catalytic performances were tested for methanol to hydrocarbon (MTH) as an industrial process in which methanol produced from any source can be converted to a wide range of hydrocarbons (from olefins to gasoline and aromatic hydrocarbons) in a fixed-bed reactor. The zeolites showed methanol conversions of 93.5 and 92.6% for the SiO2/Al2O3 ratio of 50 with the template HZ-50T and template-free HZ-50, respectively. Further, their product selectivity was also similar; nonetheless, eliminating the templates in the preparation of the zeolites had little effect on the conversion and selectivity of the products. The ratio of aromatic to aliphatic decreased with an increase in the SiO2/Al2O3 ratio. Furthermore, raising the SiO2/Al2O3 ratio (from 28 to 80) reduced the gaseous product from 54.1% to 52.1%.