Dehydrogenation of Light Alkanes Over Rhenium Catalysts on Conventional and Mesoporous MFI Supports

Abstract

Recently, Re/HZSM-5 (Si/Al = 15) was shown to be an efficient catalyst for ethane dehydrogenation and aromatization at 823 K and atmospheric pressure. In this reaction, the major initial products were benzene, toluene and xylene (BTX), but increasing amounts of ethene were produced with time on stream due to deactivation of the catalyst. We show that by use of rhenium impregnated MFI supports with very few or no acidic sites (Si/Al > 500), highly selective ethane dehydrogenation catalysts are obtained with ethene selectivities of 98%. By use of mesoporous MFI supports (Si/Al >500) the lifetime of the catalyst appears to be slightly improved compared to conventional MFI crystals. The beneficial effect of a mesoporous MFI support is convincingly demonstrated in propane dehydrogenation, where both conversion and selectivities on the mesoporous MFI (Si/Al > 500) impregnated with Re are significantly higher than on Re supported on a comparable conventional MFI support.

Enhanced Catalytic Performance of Zn‐containing HZSM‐5 upon Selective Desilication in Ethane Dehydroaromatization Process

“…[13,14] In order to directly convert alkanes to aromatics, a bifunctional catalyst is required, which in addition to the acid function comprises the dehydrogenation functionality of metal such as Ga, Zn, Mo, Re or Pt. [15][16][17][18][19][20][21][22][23] Numerous studies demonstrated that incorporation of Lewis acid metals such as Zn into zeolites modifies the surface acidity and enhances selectivity to BTX in light alkane dehydroaromatization. [7,15,18,[24][25][26][27] However, only a few studies have been dedicated to the performance and catalytic life-time enhancement of Zn-containing zeolite catalyst for ethane direct conversion to aromatics.…”

“…In order to directly convert alkanes to aromatics, a bi‐functional catalyst is required, which in addition to the acid function comprises the dehydrogenation functionality of metal such as Ga, Zn, Mo, Re or Pt . Numerous studies demonstrated that incorporation of Lewis acid metals such as Zn into zeolites modifies the surface acidity and enhances selectivity to BTX in light alkane dehydroaromatization .…”

Synergetic effect between Pd2+ and Ir4+ species promoting direct ethane dehydrogenation into ethylene over bimetallic PdIr/AC catalysts

“…were employed as catalyst supports. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Miller et al prepared a Pt-In intermetallic alloy and found that the Pt 3 In phase exhibited a superior ethane turnover rate (TOR) of 5.3 s −1 and 99% ethylene selectivity at 600 °C, and this catalyst exhibited little deactivation in 5 h. Compared with a monometallic Pt catalyst, the electronic changes and geometric changes were responsible for the higher TOR and ethylene selectivity of the PtIn alloy. 1 Wang et al deposited Pt and Sn over hydrotalcite materials (MgGaAlO) and found that the presence of Ga enhanced the interaction of the Sn-support and Pt-Sn, maintaining the oxidized Sn species and improving the EDH activity.…”

Titanium Silicalite-1 Nanosheet-Supported Platinum for Non-oxidative Ethane Dehydrogenation

“…In order to form stable Pt-based NDE catalysts, the support should be thermally stable, have a sufficiently high specific surface area, be free of Brønsted acidity for hosting undesirable side reactions, and have Lewis acidity and amphoteric silanol (−OH) groups to contribute to optimum metal dispersion. , In search of a suitable support material, metal oxides such as alumina (Al 2 O 3 ) or aluminate (e.g., MgAl 2 O 4 ) have been used for Pt-based catalysts. ,, Zeolite-based materials are ideal alternatives to metal oxide supports due to their high surface area, uniform micropores, and tunable acidity by adding alkaline cations and/or isomorphous substitution of Lewis acidity centers. For example, the aluminosilicate zeolite with an MFI (Mobil-type five) framework structure (i.e., ZSM-5, Zeolite Socony Mobil-5) has been used as the support for rhenium (Re), − molybdenum (Mo), and iron (Fe) species for NDE reactions, in which metal species were loaded by the wetness impregnation approach. In order to enhance metal dispersion and modulate zeolite acidity, the heteroatom (i.e., Fe and gallium (Ga))-isomorphously substituted ZSM-5 zeolites were reported.…”