Dehydration of methanol to light olefins upon zeolite/alumina catalysts: Effect of reaction conditions, catalyst support and zeolite modification

Hajimirzaee, Saeed; Ainte, Mohammed; Soltani, Behdad; Behbahani, Reza Mosayebi; Leeke, Gary A.; Wood, Joseph

doi:10.1016/j.cherd.2014.05.011

Cited by 47 publications

(19 citation statements)

References 55 publications

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“…With increasing methanol partial pressure, dissociation of the H-bonded methanol is reported to be less favorable due to this dimer formation. 42 The dehydration of methanol to DME may also yield methane and coke as byproducts, 43,44 which could cause catalyst deactivation at long times on stream (≫11 h). Methanation occurs when methoxy species strongly bond to acidic surface sites, creating surface formates, which decompose to form CO, H 2 and CH 4 .…”

Section: ■ Discussionmentioning

confidence: 99%

Hydrogenation of CO₂ to Dimethyl Ether over Brønsted Acidic PdZn Catalysts

Bahruji

Armstrong

Esquius

et al. 2018

Ind. Eng. Chem. Res.

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Eschewing the common trend toward use of catalysts composed of Cu, it is reported that PdZn alloys are active for CO 2 hydrogenation to oxygenates. It is shown that enhanced CO 2 conversion is achievable through the introduction of Brønsted acid sites, which promote dehydration of methanol to dimethyl ether. We report that deposition of PdZn alloy nanoparticles onto the solid acid ZSM-5, via chemical vapor impregnation affords catalysts for the direct hydrogenation of CO 2 to DME. This catalyst shows dual functionality; catalyzing both CO 2 hydrogenation to methanol and its dehydration to dimethyl in a single catalyst bed, at temperatures of >270°C. A physically mixed bed comprising 5% Pd 15% Zn/TiO 2 and H-ZSM-5 shows a comparably high performance, affording a dimethyl ether synthesis rate of 546 mmol kg cat −1 h −1 at a reaction temperature of 270°C . ■ INTRODUCTIONMethanol is ubiquitous within the chemical industry, with global demand exceeding 57 Mt/annum. The majority of this is met through a two-step process whereby synthesis gas is produced via methane steam reforming and then reacted over a Cu/ZnO/Al 2 O 3 catalyst to prepare methanol. The energy consumption of this process is estimated to exceed 1 exajoule (1 × 10 18 J)/annum globally, with a significant carbon footprint (ca. 88 Mt GHG eq). 1 In line with political and social pressure to decrease society's dependence on fossil fuels, there is growing interest in producing methanol through more sustainable routes. One promising route is catalytic CO 2 hydrogenation. The process, however, is restricted by thermodynamic equilibrium; with the reverse water gas shift reaction (RWGS) dominating the reaction at high temperatures. Indeed, methanol is thermodynamically favored at lower temperatures. Unfortunately, because of the relatively low reactivity of CO 2 , high reaction temperatures and/or pressures are required for its activation. To maximize yields of valueadded products, it is important that CO 2 hydrogenation be carried out near equilibrium. One approach toward circumventing RWGS at elevated reaction temperatures is removal of the product, methanol, from the catalytic system. This can be achieved through dehydration to dimethyl ether (DME), typically over a solid acid catalyst. DME is a key feedstock for production of methylating agents for organic synthesis. 2 DME has also been identified as an environmentally friendly fuel, with low associated emissions of NO x , hydrocarbons, CO and SO x . 3 Through the methanol to gasoline (MTG) process, methanol is catalytically converted to yield an equilibrium mixture containing methanol, DME and water. This is then converted to hydrocarbons. 4 Being both exothermic and reversible, methanol dehydration is subject to thermodynamic limitation, though effectively not so under methanol synthesis conditions. 4 Integrating methanol dehydration into CO 2 hydrogenation reaction systems might increase hydrogenation yields, by intercepting the methanol through dehydration to DME, therefore shifting the reactio...

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Section: ■ Discussionmentioning

confidence: 99%

Hydrogenation of CO₂ to Dimethyl Ether over Brønsted Acidic PdZn Catalysts

Bahruji

Armstrong

Esquius

et al. 2018

Ind. Eng. Chem. Res.

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“…The addition of Al into HBZ resulted in decreased amount of weak acid site, but increased moderate to strong acid sites as well as total acidity. This can be attributed to the addition of Al possibly alter the acid distribution with different Si/Al ratios of catalysts [21]. Furthermore, the slight difference in total acidity of HBZ and Al-HBZ perhaps results from only slightly different Si/Al ratios.…”

Section: Fig 4 Sem Images Of All Catalystsmentioning

confidence: 99%

“…In other words, the Si/Al ratio of HBZ was the highest. The decreased Si/Al ratio is perhaps related to the decrease in weak acid sites, but increased strong acid sites as well as increased total acidity [21]. Thus, the acid properties of catalysts were determined using NH3-TPD.…”

Section: Fig 4 Sem Images Of All Catalystsmentioning

confidence: 99%

A Comparative Study of Different Al-based Solid Acid Catalysts for Catalytic Dehydration of Ethanol

Kamsuwan¹,

Jongsomjit²

2016

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Abstract. In this present study, the catalytic dehydration of ethanol over three different Al-based solid acid catalysts including H-beta zeolite (HBZ), modified H-beta zeolite with γ-Al2O3 (Al-HBZ) and mixed γ-χ phase of Al2O3 (M-Al) catalysts was investigated. The ethanol dehydration reaction was performed at temperature range of 200 to 400 o C. It revealed that all catalysts exhibited higher ethanol conversion with increased temperatures. At low temperatures (ca. 200 to 250 o C), diethyl ether (DEE) was obtained as a major product for all catalysts. However, with increased temperatures (ca. 300 to 400 o C), ethylene was a major product. Among all catalysts, HBZ exhibited the highest ethanol conversion giving the ethylene yield of 99.4% at 400 o C. This can be attributed to the largest amount of weak acid sites present in HBZ, which is related to the Brønsted acid. It should be mentioned that HBZ also rendered the highest catalytic activity for every reaction temperature. As the results, HBZ catalyst is promising to produce ethylene and DEE from ethanol, which is considered as cleaner technology.

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“…(1) Reducing the Brønsted acidity (in terms of both site density and strength) of zeolite catalysts 6,7 in order to limit/ inhibit the side reactions. The approaches include: adjusting the Si/Al ratio of the zeolite, [8][9][10] post-synthesis modication, [11][12][13][14][15][16] and isomorphous substitution of heteroatoms for zeolite. 5,[17][18][19][20][21] (2) Modifying the porosity of the zeolite and thereby inuencing the transition state shape selectivity, such as by using zeolites with different topologies [22][23][24][25][26][27][28][29][30] or tailoring their pore size by post-synthesis modication.…”

Section: Introductionmentioning

confidence: 99%

Bi₂O₃ modification of HZSM-5 for methanol-to-propylene conversion: evidence of olefin-based cycle

et al. 2017

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Dehydration of methanol to light olefins upon zeolite/alumina catalysts: Effect of reaction conditions, catalyst support and zeolite modification

Cited by 47 publications

References 55 publications

Hydrogenation of CO₂ to Dimethyl Ether over Brønsted Acidic PdZn Catalysts

Hydrogenation of CO₂ to Dimethyl Ether over Brønsted Acidic PdZn Catalysts

A Comparative Study of Different Al-based Solid Acid Catalysts for Catalytic Dehydration of Ethanol

Bi₂O₃ modification of HZSM-5 for methanol-to-propylene conversion: evidence of olefin-based cycle

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Dehydration of methanol to light olefins upon zeolite/alumina catalysts: Effect of reaction conditions, catalyst support and zeolite modification

Cited by 47 publications

References 55 publications

Hydrogenation of CO2 to Dimethyl Ether over Brønsted Acidic PdZn Catalysts

Hydrogenation of CO2 to Dimethyl Ether over Brønsted Acidic PdZn Catalysts

A Comparative Study of Different Al-based Solid Acid Catalysts for Catalytic Dehydration of Ethanol

Bi2O3 modification of HZSM-5 for methanol-to-propylene conversion: evidence of olefin-based cycle

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Hydrogenation of CO₂ to Dimethyl Ether over Brønsted Acidic PdZn Catalysts

Hydrogenation of CO₂ to Dimethyl Ether over Brønsted Acidic PdZn Catalysts

Bi₂O₃ modification of HZSM-5 for methanol-to-propylene conversion: evidence of olefin-based cycle