Activities of MFI-Supported Rhenium Catalysts for the Aromatization of Methane: Effect of Cationic Form of the Inorganic Carrier

Abstract

MFI type inorganic carrier was used in two different cationic forms, hydrogen and calcium respectively. MFI-supported molybdenum and rhenium catalysts were prepared. The activities of the catalysts were compared for the aromatization reaction of methane. Higher activity values were attained with the catalysts supported on HZSM-5. Aromatics were also observed with the catalysts supported on CaZSM-5, despite their deficiency in acid sites. Highly dispersed rhenium is expected to be formed with the use of the inorganic carrier in calcium form. On the other hand, lower reaction rates were observed with rhenium supported on CaZSM-5, in spite of the improved dispersion of the active rhenium species on this catalyst. This was interpreted in terms of the critical role of the acid sites in the conversion of methane to aromatics, compared to the improved dispersion of the active metal.

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

“…Other catalysts, such as Mo supported on ZSM-5 containing Ga [22,60] [63−65], have also been investigated. All showed much lower activity for methane conversion and lower selectivity to benzene, compared with Mo supported on HZSM-5.…”

“…The effect of zeolite type was described in Section 2. Researchers have found that catalysts such as unsupported Mo 2 C [93−95], unmodified HZSM-5 [64,69], and Mo supported on carriers without Brønsted acid sites, including Na-ZSM-5 [16,64], Cs-ZSM-5 [96], Ga-ZSM-5 [60], and TiO 2 [97], show low or no activity towards benzene formation. However, hybrid catalysts that are physical mixtures, such as Mo/SiO 2 +HZSM-5 or Mo 2 C+HZSM-5, exhibit remarkable activity, giving yields of benzene and naphthalene that are 100-300 times greater than either component alone [30].…”

“…Some researchers [32,151] studied the dealumination of MCM-22 zeolite by refluxing in an aqueous solution of 6 M HNO 3 at 100 • C for 10 h. The strong Brønsted acid sites were effectively removed, and the catalytic performance of the dealuminated Mo/HMCM-22 in MDA was significantly enhanced. Treatment of the zeolite support in a stream of N 2 [152,153], with an aqueous solution of NH 4 F [154,155], or with oxalic acid [52,156], has also been proven to be successful in preparing dealuminated Mo/zeolite catalysts that are more active and more stable in MDA. Migration and location of Mo species, as crucial factors in MDA, are closely related to the number of Brønsted acid sites.…”

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

“…This process is also favored at high calcination temperatures. Besides the Si/Al ratio and Mo loading, the size [50] and morphology [51] of the HZSM-5 crystallites also play a role in catalyst performance.…”

SiOxNanowires Produced on Molybdenum-Coated Si Substrates

“…In this communication, we report the production of SiO x nanowires by the simple heating of molybdenum (Mo)-coated Si substrates. Although Mo-based catalysts have been utilized in various chemical reactions [5,6] and in fabricating carbon nanotubes [7], to our knowledge, synthesis of any inorganic 1D nanomaterial on the Mo substrate has not been reported to date.…”