Известия Томского политехнического университета: Инжиниринг георесурсов (May 2019)
Non-oxidative methane conversion over Mo-containing zeolites
Abstract
The regulations on burning natural and oil-gas in the production site are becoming more severe, which calls for new environmentally-friendly technologies of recycling gaseous hydrocarbons. An alternative method of natural gas utilization is a non-oxidative conversion of methane, the main natural gas component, into useful aromatic hydrocarbons. The development of new catalytic systems for conversion is an urgent task for oil and gas industry. The aim of the work is to study the effect of the process of producing ZSM-5 structure zeolite being used as a support for preparing Mo-containing catalyst on its physical-chemical and catalytic properties in non-oxidative conversion of methane into aromatic hydrocarbons. Methods of investigation: the zeolites under study were synthesized using different templates (hexamethylenediamine, ammonium bicarbonate, and polyethylenepolyamine). The bifunctional catalytic systems were produced from the resulting zeolites by dry mechanical mixing with nano-sized electroexplosive molybdenum powders. Their physical-chemical characteristics were investigated by the methods of X-ray structure analysis, IR- spectroscopy, atomic absorption analysis, low-temperature nitrogen desorption, SEM and temperature-programmed desorption of ammonia. The non-oxidative conversion of methane (99,9 % purity) was performed in a flow reactor at 750 °С at a feed space velocity of 1000 h-1 and atmospheric pressure. The reaction products were analyzed by gas chromatography. Results: The Mo-containing zeolite catalysts for non-oxidative methane conversion have been produced using nano-sized Mo powder. The paper demonstrates the effect of the nature of the structure-forming additive used in the synthesis of zeolites on the activity and stability of Mo-containing catalysts. It was found out that the highest activity and stability were exhibited by the Mo-containing catalyst prepared using a zeolite synthesized with hexamethylenediamine (GMDA) as a structure-forming additive. It was shown that the differences in catalytic reactivity of the resulting catalysts are caused by the acid and structural characteristics of the zeolites used as carriers for preparing Mo-containing systems.
