Low-Temperature Nonoxidative Activation of Methane over H -Galloaluminosilicate (MFI) Zeolite

Abstract

Conversion of methane to higher hydrocarbons by its low-temperature activation without forming undesirable carbon oxides is of great scientific and practical importance. Methane can be highly activated, yielding high rates of conversion to higher hydrocarbons and aromatics (10 to 45 percent) at low temperatures (400° to 600°C), by its reaction over H-galloaluminosilicate ZSM-5 type (MFI) zeolite in the presence of alkenes or higher alkanes. The methane activation results from its hydrogen-transfer reaction with alkenes.

Recent progress in methane dehydroaromatization: From laboratory curiosities to promising technology

“…Choudhary and co-workers [198] found that when relatively large amounts of alkenes and/or higher alkanes were added into methane, the temperature required to activate methane was reduced. In addition, higher methane conversion (20%-50%) with high aromatics selectivity (>90%) was achieved.…”

Non-oxidative methane aromatization by bimetallic (La, Co, Pd and Pt) M-Zn/HZSM-5: Impact of propane addition

“…Co-feeding methane with other hydrocarbons resulted in higher yields of methane conversion than thermodynamic equilibrium conversion [5,6]. For example, adding only a small percent of ethane caused a remarkable increase in benzene formation over the Mo/HZSM-5 catalyst at 998 K (The formation rate of benzene was enhanced by a factor of 1.68 for an ethane content of 6.3%).…”

“…The carbenium ion reacts with the pre-activated methane on metal oxide, yielding CH 2 species by hydride transfer. Subsequent dimerization of the CH 2 species results in ethylene which, upon oligomerization and dehydrocyclization, converts into aromatics [6]. More recently, Luzgin et al [13] used 13 C labeled methane and found that methane was not involved in the aromatization reaction, but it was involved in methylation of aromatics that formed exclusively from propane in a temperature range of 823-873 K. Subsequent intramolecular rearrangements resulted in the involvement of methane carbon in the aromatic ring.…”

“…Given the conflicting literature concerning the role of higher hydrocarbons in methane-toaromatics conversion [5,6,11,12] led to the present work, which investigated the coaromatization of a mixture of methane and propane on different catalysts under the conventional reaction conditions. The catalysts were prepared by impregnating the parent Zn/HZSM-5 catalyst with a second promoter (La, Pt, Co, and Pd) and performing co-aromatization reactions.…”

High-throughput screening of HZSM-5 supported metal-oxides catalysts for the coupling of methane with CO to benzene and naphthalene

“…Choudhary et al [1] first reported the activation of methane over H-GaAlZSM-5 in the presence of either alkenes or higher alkanes at low temperatures, yielding higher hydrocarbons and aromatics at high-rate conversions. Subsequently, other researchers demonstrated that the conversion of methane could be remarkably improved by the coupling reaction of methane with ethylene over Ag/Y or HZSM-5 ion-exchanged with various metal cations [2], and that the transformation of methane into aromatic hydrocarbons was activated with liquefied-petroleum-gas (LPG) over Zn/ZSM-11 zeolite [3] under mild conditions.…”