Exploration of the Promoting Effect of Nanoscale Copper Powder on Properties of Mo/ZSM-5 Catalyst in Methane Dehydroaromatization Reaction

The dry mechanical mixing of ZSM-5 catalyst with nanoscale powders (NSP) of molybdenum and copper produced Cu-Mo/ZSM catalysts. The Mo and Cu contents therein were 4.0 mass % and 0.05-1.0 mass %, respectively. In order to carry out comparison tests, Cu-Mo/ZSM-5 systems were prepared by impregnation of 4.0 % Mo/ZSM-5 catalyst with a Cu(NO 3) 2 solution and by its mechanical mixing with CuO. Acid characteristics of the resulting samples were investigated by ammonia temperature programmed desorption. The acid sites concentration and strength of catalysts were determined. It was found that that the addition of 0.1 % copper nanopowder to 4.0 % Mo/ZSM-5 catalyst resulted in a reduced concentration of strong acid sites to 140 mu mol/g. Whereas, a further increase in copper NSP concentration leads to their concentration growth to 153 mu mol/g. Herewith, the activity of catalysts in methane conversion is reduced compared to 0.1 % Cu NSP sample. Methane conversion degree for 20 min of the reaction over Mo/ZSM-5 and 0.1% Cu-4.0 % Mo/ZSM-5 catalysts is 16.1 and 18.9 %, correspondingly. As demonstrated by research on methane conversion temperature in the presence of 0.1 %.u-4.0 % Mo/ZSM-5 catalyst, an increase in temperature from 650 to 750 degrees C is accompanied by increasing methane conversion. For example, the latter is 7.9 and 18.9 % over the first 20 min of reaction at 650 and 750 degrees C, respectively. It was determined that the maximum methane conversion degree over 0.1 % Cu-4.0 % Mo/ZSM-5 catalyst was reached at 1000 h-1 space velocity of gas raw materials.