Propene Production from Ethene and Methane Using Silver- and Proton-exchanged Zeolite Catalysts

Abstract

Two new methods for the catalytic synthesis of propene using solid acid catalysts are presented. The first approach is a new method for the activation of methane, involving conversion of methane to propene over silver-exchanged zeolite in the presence of ethene. In the second method, ethene conversion proceeds directly and selectively over proton-exchanged zeolite under the control of a molecular sieving effect.
The heterolytic dissociation of methane over silver cationic clusters (Ag_n⁺) in Ag⁺-exchanged zeolites, leading to the formation of silver hydride (Ag_n-H) and CH₃^δ+ species, which reacts with ethene to form propene around 673 K. Using ¹³C-labeled methane as a reactant, propene is shown to be a primary product from methane and ethene. Thus, a significant proportion of propene was singly ¹³C-labeled (¹³CC₂H₆).
Under these reaction conditions, H⁺-exchanged zeolites, such as H-ZSM-5 do not catalyze the methane conversion, only ethene being converted into higher hydrocarbons, such as propene. Ethene is selectively converted to propene over SAPO-34 at 723 K with a yield of 52.2% and selectivity of 73.3% at ethene conversion of 71.2%. The high and selective propene yields achieved over SAPO-34 can be attributed to a shape selectivity effect of the small-pore SAPO-34.