The effect of support on methane activation over Pt catalysts in the presence of MoO3

Abstract

It is reported the role of different supports (silica, alumina and zirconia) on the non-oxidative conversion of methane, through the isothermal two-step reaction, on Pt-loaded catalysts, with or without the presence of MoO3. The activated chemisorption of methane, followed by reaction of the carbon adspecies with hydrogen was conducted in pulse and continuous modes, in the temperature range of 473–673 K. It was observed by using pulse mode that evolutions of H2, CO and CO2 occurred simultaneously with the pulses of methane without the formation of higher hydrocarbons. The reactivity, regarding the CH4 conversion, with or without MoO3, follows the sequence Pt/Al2O3 ≈ Pt/ZrO2 > Pt/SiO2. Also the hydrogenation of carbon residues produced only methane. The presence of MoO3 had a positive influence concerning the reactivity of carbon residues, on zirconia and especially on alumina supported catalysts. In the flow mode operation, methane chemisorption is followed by the evolution of H2, plus C2, C2, C3=, and C3, depending on the nature of the support. The hydrogenation of carbon residues produced mainly methane, but ethane and propane were also detected specially in the presence of MoO3 which improves the mobility of CHX adspecies, favoring the CC nucleation.