Methanol dehydration over alkali-modified H-ZSM-5; effect of temperature and water dilution on products distribution

A sample of HZSM-5 catalyst with gel SiO2/Al2O3 molar ratio of 38 was synthesized and its diffusion properties were improved by controlled desilication with 0.2 Molar NaOH solution at 80 °C for 3 h. X-ray fluorescence (XRF) test of the final treated sample showed SiO2/Al2O3 molar ratio had been decreased to 31.5. The modified catalyst was employed in methanol to hydrocarbon reaction as a promising route to convert low valuable hydrocarbons or renewable carbon-containing resources into high-octane gasoline and light olefins. The reaction was performed with weight hourly space velocity (WHSV) of 5 h−1 and at temperatures of 375, 425 and 475 °C. Based on the amounts of valuable products and catalyst life time, 425 °C was known as the optimum temperature. At this temperature, effects of water addition to the feed on control of reactor heat, products distribution and catalyst life time were assessed and the feed with 50 wt% of water showed to make three times more catalyst life time, better thermal stability and acceptable selectivity to desired products.