Conversion of Methane over Ag+-exchanged Zeolite in the Presence of Ethene

Abstract

Methane is shown to react with ethene over silver-exchanged zeolites at around 673 K to form higher hydrocarbons. Methane conversion of 13.2% is achieved at 673 K over Ag-ZSM)5 catalyst. Under these conditions, H-ZSM)5 does not catalyze the methane conversion, only ethene being converted into higher hydrocarbons. Zeolites with extra-framework metal cations such as In and Ga also activate methane in the presence of ethene. Using 13 C-labeled methane as a reactant, propene is shown to be a primary product from methane and ethane. 13 C atoms were not found in benzene molecules produced, indicating that benzene is entirely originated from ethane. On the other hand, in toluene, 13 C atoms are found in both the methyl group and the aromatic ring. This implies that toluene is formed by the reaction of propene with butenes formed by the dimerization of ethene, and also by the reaction of benzene with methane. The latter path was confirmed by direct reaction of 13 CH 4 with benzene. In this case, 13 C atoms are found only in methyl groups of toluene produced. The heterolytic dissociation of methane over Ag + -exchanged zeolites is proposed as a reaction mechanism for the catalytic conversion of methane, leading to the formation of silver hydride and CH 3 d+ species, which reacts with ethene and benzene to form propene and toluene, respectively. The conversion of methane over zeolites loaded with metal cations other than Ag + is also described. The reaction of methane with benzene over indium-loaded ZSM)5 afforded toluene and xylenes in yields of up to 7.6% and 0.9% at 623 K when the reaction was carried out in a flow reactor.

Recent advances in heterogeneous selective oxidation catalysis for sustainable chemistry

“…129 Furthermore, CH 4 could react with ethylene to produce propylene (eqn ( 23)) over (LiCl + NaCl)/MgO or Ag + -exchanged zeolite catalysts. 130,131 This article will not include these C-C couplings of CH 4 with other molecules.…”

Nature of the Surface Intermediates Formed from Methane on Cu-ZSM-5 Zeolite: A Combined Solid-State Nuclear Magnetic Resonance and Density Functional Theory Study

“…Methane being a major component of natural gas is cheap and a widely accessible raw material . The conversion of methane to higher hydrocarbons or oxygenates over zeolite-based catalysts has attracted considerable attention from the scientific community as a basis for future efficient gas-to-liquid technologies. − Despite the great potential of methane as the feedstock for the chemical industry, there are several important challenges hampering the efficient chemical processing of methane to such versatile chemical intermediates as, for example, methanol . The key challenges are related to the low intrinsic reactivity of methane in combination with the higher reactivity of the products of its conversion.…”

Propylene production technology: Today and tomorrow

“…The direct conversion of methane (route E) is considered much more rarely. It can be carried out by performing the oxi dative condensation or pyrolysis [181,182], including reactions in the absence of the oxidant [183].…”