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Mixed alcohol dehydration over Brønsted and Lewis acidic catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
39021 45801 2016 15 PDF Available
Title
Mixed alcohol dehydration over Brønsted and Lewis acidic catalysts
Abstract

•Brønsted acidic sites were more active for alcohol dehydration than Lewis acidic sites.•SAPO-34 achieved the highest olefin yields below 350 °C compared to Zr-KIT-6, Al-MCM-41 and HZSM-5.•SAPO-34 produced olefin yields comparable to the MTO process, at lower temperature.•The olefin product distribution over SAPO-34 was tunable by the composition of the alcohol feed mixture.

Mixed alcohols are attractive oxygenated products of biomass-derived syngas because they may be catalytically converted to a range of hydrocarbon products, including liquid hydrocarbon fuels. Catalytic dehydration to form olefins is a potential first step in the conversion of C2–C4 alcohols into longer-chain hydrocarbons. We describe here the physical and chemical characterization along with catalytic activity and selectivity of 4 Brønsted and Lewis acidic catalysts for the dehydration of two mixed alcohol feed streams that are representative of products from syngas conversion over K-CoMoS type catalysts (i.e., ethanol, 1-propanol, 1-butanol and 2-methyl-1-propanol). Specifically, a Lewis acidic Zr-incorporated mesoporous silicate (Zr-KIT-6), a commercial Al-containing mesoporous silicate (Al-MCM-41), a commercial microporous aluminosilicate (HZSM-5), and a commercial microporous silicoaluminophosphate (SAPO-34) were tested for mixed alcohol dehydration at 250, 300 and 350 °C. The zeolite materials exhibited high activity (>98% ethanol conversion) at all temperatures while the mesoporous materials only displayed significant activity (>10% ethanol conversion) at or above 300 °C. The turnover frequencies for ethanol dehydration at 300 °C decreased in the following order: HZSM-5 > SAPO-34 > Al-MCM-41 > Zr-KIT-6, suggesting that Brønsted acidic sites are more active than Lewis acidic sites for alcohol dehydration. At 300 °C, SAPO-34 produced the highest yield of olefin products from both a water-free ethanol rich feed stream and a C3+-alcohol rich feed stream containing water. Post-reaction characterization indicated changes in the Brønsted-to-Lewis acidic site ratios for Zr-KIT-6, Al-MCM-41 and HZSM-5. Ammonia temperature programmed desorption indicated that the acid sites of post-reaction samples could be regenerated following treatment in air. The post-reaction SAPO-34 catalyst contained more aromatic, methylated aromatic and polyaromatic compounds than its zeolite counterpart HZSM-5, while no aromatic compounds were observed on post-reaction Al-MCM-41 or Zr-KIT-6 catalysts. Olefin yield at 300 °C over SAPO-34 (>95%) was comparable to published values for the methanol-to-olefins process, indicating the potential industrial application of mixed alcohol dehydration. Furthermore, the olefin product distribution over SAPO-34 was tunable by the composition of the alcohol feed mixture.

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Keywords
Mixed alcohols; Dehydration; Olefin; SAPO-34; Syngas
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Mixed alcohol dehydration over Brønsted and Lewis acidic catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 510, 25 January 2016, Pages 110–124
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Don't Miss Today's Special Offer
Price was $35.95
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Price after discount Only $4.95
100% Money Back Guarantee
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