Catalytic Transformation of Methane over In-Loaded ZSM-5 Zeolite in the Presence of Ethene

Abstract

Methane is shown to react with ethene over In-loaded ZSM-5 to higher hydrocarbons such as propene and toluene at around 673 K. Such methane conversion is not catalyzed by proton-exchanged ZSM-5 (H-ZSM-5) under the same conditions, only C2H4 being converted to higher hydrocarbons. By using 13C-labeled methane (13CH4) as a reactant, the reaction paths for the formation of propene, benzene and toluene were examined. 13C-labeled propene (13CC2H6) is formed by the reaction of 13CH4 with C2H4. The lack of 13C-labeled benzene revealed that propene is not transformed to benzene, which instead originates entirely from C2H4. The 13C atom is inserted both into the methyl group and benzene ring in the toluene formed. This indicates that toluene is formed by two reaction paths; the reaction of 13CC2H6 with butenes formed by the dimerization of C2H4 and the reaction of benzene with 13CH4. The existence of the latter path was proved by the direct reaction of 13CH4 with benzene. The reaction of methane with benzene was also carried out in a continuous flow system over In-loaded ZSM-5. The reaction afforded 7.6% and 0.9% yields of toluene and xylenes, respectively, at 623 K.

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

“…The results of 13 CH4 conversion in the presence of ethene at 673 K using various metal cation-exchanged ZSM-5 zeolites are shown in Table 3 47), 48) . The main product in all cases is propene, and 13 C was found in propene to varying extents.…”

“…In the case of In _ ZSM-5 (In/Al＝0.7), ethene conver sion reached 13％, and ethane (17％), propene (23％), benzene (41％), and toluene (19％) were observed as gaseous hydrocarbon products (values in parenthesis denote selectivities in mol％) 48) . Among these hydro carbons, 13 C-labeled ethane ( 13 CCH6 and 13 C2H6) and 13 C-labeled benzene ( 13 CC5H6) are negligible, with mole fractions of only 2％ and 7％, respectively (close to natural abundances).…”

“…The formation of 13 C-labeled toluene ( 13 CC6H8) and the absence of 13 C-labeled benzene suggest that a frac tion of the toluene is formed by reaction between meth ane and benzene 48) . Reaction of benzene over In _ ZSM-5 under 39.8 kPa of 13 CH4 and 1.63 kPa of benzene at 673 K produced only toluene and hydrogen as reaction products.…”

“…This result is reasonable, since indium cations are more resistant to reduction than silver cations. The catalytic activity of In _ ZSM-5 is also dependent on the temperature of catalyst calcination and hydrogen pre treatment: continuous methane conversion of 11.8％ is achieved over In _ ZSM-5 at 673 K when the catalyst is pretreated with hydrogen at 723 K after calcination at 903 K 48) .…”

Advanced Catalysts Based on Micro‐ and Mesoporous Molecular Sieves for the Conversion of Natural Gas to Fuels and Chemicals

“…Besides CH 4 homologation (self-coupling), nonoxidative cross-coupling of methane with olefins and aromatics is catalyzed by metal-zeolite catalysts. In this respect, it has been demonstrated that the conversion of CH 4 in the presence of ethylene or benzene in a continuous flow system at temperatures in the range 300-500 • C can be accomplished by using Ag and In-exchanged NH 4 -ZSM-5 catalysts [30][31][32]. Continuous nonoxidative alkylation of benzene with methane has also been recently outlined, employing a bifunctional Pt/H-ZSM-5 [33], and it has been claimed the synergistic effect of both metallic and acidic sites in the formation of toluene.…”