III International Conference

PP-II-74STUDY OF METHANE DEHYDROAROMATIZATIOM ON IMPREGNATEDMo/ZSM-5 CATALYSTS IN RECYCLE CONDITIONSMatus E.V., Ismagilov I.Z., Sukhova O.B., Tsikoza L.T., Litvak G.S., Kerzhentsev M.A.,Ismagilov Z.R.Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaE-mail: matus@catalysis.ruThe study of methane dehydroaromatization over a series of impregnated Mo/ZSM-5catalysts is performed in flow and recycle conditions. It is shown that if methanedehydroaromatization is carried out in recycle conditions the benzene formation rate isessentially improved. The oxidative treatment conditions of carbonized Mo/ZSM-5 catalystsproviding stable operation of the catalysts under multiple reaction-oxidative treatment cycleshave been selected.During the past few years methane has been often seen as perspective source to producevaluable chemicals [1]. But it is a very stable organic molecule and new approaches ofeffective activation for profitable utilization of methane are needed. Mo/ZSM-5 catalystsprovide high activities in methane dehydroaromatization, which is the alternative way ofmethane conversion to aromatic hydrocarbons and hydrogen [2].The methane dehydroaromatization is characterized by a not great single-pass conversion.Earlier we have shown [3], that the maximum catalytic activity (CH 4 conversion ~ 14%) andbenzene formation selectivity (70 %) were observed for the samples with 2-5 % Mo. Theactivity and selectivity were improved when Si/Al in H-ZSM-5 zeolite was changed from 45to 17. To increase overall methane conversion we performed multiple recycling of CH 4 withseparation of aromatic product. It is shown that if the reaction is carried out in recycleconditions the benzene formation rate (mgС 6 H 6 /gcat.·h) is essentially improved. The benzeneyield is increased when the circulating factor is increased.The main problem for methane dehydroaromatization on Mo/ZSM-5 catalysts is theformation of carbonaceous deposits which block the active surface of the catalysts and lead totheir fast deactivation. Thus, the dependencies of the concentration and condensation degree(C/H ratio) of the carbonaceous residues on the catalyst synthesis conditions (Moconcentration = 1-10%, Si/Al ratio in the initial H-ZSM-5 = 17-45) and reaction conditions(feed flow rate = 405-1620 h -1 , methane concentration = 90-98 %, reaction temperature = 720-780°C) have been investigated. The oxidative treatment conditions of carbonized Mo/ZSM-5catalysts providing stable operation of the catalysts under multiple reaction-oxidativetreatment cycles have been selected.299