Oxidative methylation of toluene with methane using X zeolite catalyst modified with alkali earth oxides

Abstract

Oxidative methylation of toluene with methane was used to study the catalytic activity, selectivity and yield of C 8 hydrocarbons (ethylbenzene and styrene) of X zeolites, modified with different alkali earth oxides (MgO, CaO, SrO and BaO). It was found that SrO and BaO modified zeolites are more favorable for conversion and C 8 yield than MgO and CaO modified ones. C 8 selectivity is slightly affected by the nature of alkali earth oxide, used for zeolite modification. The effect of temperature, contact time and time-on-stream on the catalytic activity, selectivity and yield of C 8 hydrocarbons were also studied. Basicity results reveal that strong basic sites are generated by introduction of alkali earth oxides. The amount of basic sites increases with oxide molecular size. The nature of alkali earth oxide also affects the amount of crystal phase detectable by X-ray diffraction (XRD). BaO/NaX is the catalyst with the best represented oxide phases. Infrared spectroscopy (IRS) results point to a preserved crystal structure of the zeolite, regardless of the nature of the modifying alkali earth oxide.