Effect of the Formation of Secondary Pores in Zeolite ZSM-5 on the Properties of Molybdenum–Zeolite Catalysts for Methane Aromatization

摘要

A study is performed of 4% Mo/ZSM-5 (30) catalysts for methane aromatization prepared by solid-phase synthesis with mechanical mixing of a zeolite with MoO_3 followed by calcination at 550°C. Zeolite etched with sodium hydroxide solutions and dealuminated with aluminum nitrate solutions is used as a support. Catalytic studies of the catalysts are conducted. The effect of treating the initial zeolite on the properties of catalysts in methane aromatization is determined. The effect subsequently treating a zeolite support has on the acid sites of a catalyst is confirmed by means of temperature-programmed reduction and the temperature-programmed desorption of NH_3. The formation of molybdenum ions in the +5 oxidation state during catalysis and the presence of graphitized carbon deposits on a spent catalyst's surface are confirmed by EPR and temperature-programmed oxidation.