Aromatization of dilute ethylene over Ga-modified ZSM-5 type zeolite catalysts

Choudhary, Vasant R.; Devadas, P.; Banerjee, Subhabrata; Kinage, Anil K.

doi:10.1016/s1387-1811(01)00385-7

Cited by 101 publications

(83 citation statements)

References 25 publications

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“…Our earlier studies on the alkane and alkene aromatization over Ga-modified ZSM-5 zeolites also revealed that the zeolitic protons and nonframework gallium oxide species work in cooperation with each other. [22] Methyl cations are likely to be produced through the formation of pentacoordinated carbocations II, similar to that proposed earlier by Olah. [23] As no methane conversion is observed in the absence of methanol and/or the bifunctional sites, activation of the HÀ CH 3 bond and formation of the pentacoordinated carbocations II are expected to be facilitated by the nonframework metal oxide species in the presence of oxonium cations I and/ or carbenium ions formed from the olefins produced from methanol.…”

Section: Angewandte Chemiesupporting

confidence: 61%

Simultaneous Conversion of Methane and Methanol into Gasoline over Bifunctional Ga‐, Zn‐, In‐, and/or Mo‐Modified ZSM‐5 Zeolites

2005

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In response to increased energy demands, worldwide efforts have been made over the past 2-3 decades to develop alternative methods for the conversion of methane (a main constituent of natural gas, coal-bed gas, and biogas) into value-added products. These include ethylene (by oxidative coupling of methane), [1][2][3] syngas (by partial oxidation with or without simultaneous steam-and/or CO 2 -mediated methane reformation), [4][5][6][7][8] and gasoline/liquid hydrocarbon fuels [9][10][11][12][13][14] that involve either oxidative [1][2][3][4][5][6][7][8][9][10] or nonoxidative [11][12][13][14][15] methane activation. As methane and carbon dioxide are key greenhouse gases responsible for global warming, the current industrial practice of emission and/or flaring of produced methane will be banned in the near future. The methane produced in remote places must therefore be converted into easily transportable energy sources like liquid hydrocarbon fuels at the sites of methane production. The most important approach for the transformation of methane into liquid hydrocarbons is the well-established and already commercially proven route: [16] methane!syngas!methanol!gasoline, based on the methanol-to-gasoline (MTG) process developed by Mobil. [16][17][18] In 1985, Mobil successfully operated a commercial plant in New Zealand for MTG conversions. However, its operation had to be discontinued as a result of unfavorable process economics. [18][19][20] The cost of the syngas production step (by steam reforming) is about twice the cost of the MTG production step.The MTG process could become economically viable if it were possible to convert a significant portion of the methane into gasoline without the intermediate steps of conversion into syngas and methanol. Herein, we show that this very difficult goal can be met through the nonoxidative activation of methane and its simultaneous conversion with methanol into gasoline-range hydrocarbons over bifunctional Ga-, In-, Zn-, and/or Mo-modified ZSM-5 type zeolites that have both dehydrogenation and acid functions. We also show that the amount of methane converted can be equimolar to the amount of methanol converted in this novel process, depend-

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Section: Angewandte Chemiesupporting

confidence: 61%

Simultaneous Conversion of Methane and Methanol into Gasoline over Bifunctional Ga‐, Zn‐, In‐, and/or Mo‐Modified ZSM‐5 Zeolites

2005

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“…Due to its higher acidity, better shape selectivity and diffusibility, ZSM-5 zeolite has shown very good catalytic performance in light hydrocarbon aromatization [5][6][7][8][9]. However, this zeolite usually loses its activity during aromatization due to relatively rapid coking, which is viewed as a difficult problem in aromatization.…”

Section: Introductionmentioning

confidence: 99%

Effect of acidity and diffusibility on coke deactivation over nano-sized HZSM-5 zeolites

Sun

Wang

Li³

et al. 2010

Reac Kinet Mech Cat

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Four series of nano-sized HZSM-5 zeolite catalysts were prepared with different steaming and HNO 3 leaching processes. These samples were studied by XRD, NH 3 -TPD, FT-IR, n-hexane and cyclohexane adsorption, and fixed-bed aromatization of C 4 liquefied petroleum gas (C 4 LPG). Results show that, with the steaming temperature increasing, the acidity of catalyst decreased gradually, which was attributed to the removal of Al species from the framework of the zeolite. When steaming is combined with acid leaching, we found that acid leaching-steam catalysts exhibit stronger acidity than steam-acid leaching catalysts. Besides, acid leaching also played an important role in enhancing the diffusibility of catalysts. Catalysts which underwent acid leaching twice exhibit the best microporous diffusibility. Through correlating the acidity and diffusibility of the catalysts with their aromatization performance, it is found that the product distribution of aromatization is mainly determined by catalyst acidity rather than diffusibility. On the other hand, the average coking speed of the catalysts is not only influenced by the acidity of the catalyst, but also by its microporous diffusibility. The improvement of microporous diffusibility remarkably favors suppressing the coking deactivation of nano-sized ZSM-5 zeolite in C 4 LPG aromatization.Electronic supplementary material The online version of this article (

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“…Meanwhile, the Brönsted acid sites of the HZSM-5 zeolite are responsible for aromatization of the C 2 species [7][8][9][10][11][12][13]. Since either ethylene or ethane aromatization proceeds easily in the temperature range 573-873 K on HZSM-5 or transition metal (Zn, and/or Ga) modified HZSM-5 [14][15][16][17][18][19], such a bifunctional description of the Mo/HZSM-5 catalysts also suggests that methane dehydrogenation and However, more detailed descriptions of the bifunctionality of the Mo/HZSM-5 catalyst are missing, or still under debate. Since ammonium heptamolybdate (AHM) is generally used as the starting material, most of the Mo species are supposed to locate on the external surface during impregnation, while part of the Mo species would migrate into the channels during calcination.…”

Section: Introductionmentioning

confidence: 99%

Methane dehydroaromatization over Mo/HZSM-5 catalysts: The reactivity of MoCx species formed from MoOx associated and non-associated with Brönsted acid sites

Shen

Bao

et al. 2005

Applied Catalysis A: General

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Aromatization of dilute ethylene over Ga-modified ZSM-5 type zeolite catalysts

Cited by 101 publications

References 25 publications

Simultaneous Conversion of Methane and Methanol into Gasoline over Bifunctional Ga‐, Zn‐, In‐, and/or Mo‐Modified ZSM‐5 Zeolites

Simultaneous Conversion of Methane and Methanol into Gasoline over Bifunctional Ga‐, Zn‐, In‐, and/or Mo‐Modified ZSM‐5 Zeolites

Effect of acidity and diffusibility on coke deactivation over nano-sized HZSM-5 zeolites

Methane dehydroaromatization over Mo/HZSM-5 catalysts: The reactivity of MoCx species formed from MoOx associated and non-associated with Brönsted acid sites

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