Title: Mixed Alcohol Dehydration over Bronsted and Lewis Acidic Catalysts

Abstract

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. Here, we describe 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 highestmore » 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.« less

Authors:

Nash, Connor P. ^[1]; Ramanathan, Anand ^[2]; Ruddy, Daniel A. ^[3]; Behl, Mayank ^[1]; Gjersing, Erica ^[1]; Griffin, Michael ^[1]; Zhu, Hongda ^[2]; Subramaniam, Bala ^[2]; Schaidle, Joshua A. ^[1]; Hensley, Jesse E. ^[1]

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+ Show Author Affiliations

1. National Renewable Energy Lab. (NREL), Golden, CO (United States). National Bioenergy Center
2. Univ. of Kansas, Lawrence, KS (United States). Center for Environmentally Beneficial Catalysis
3. National Renewable Energy Lab. (NREL), Golden, CO (United States). Chemistry and Nanoscience Center

Publication Date:

Tue Dec 01 00:00:00 EST 2015

Research Org.:

National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Bioenergy Technologies Office (BETO)

OSTI Identifier:

1235230

Alternate Identifier(s):

OSTI ID: 1400013

Report Number(s):

NREL/JA-5100-65042
Journal ID: ISSN 0926-860X

Grant/Contract Number:  

AC36-08GO28308; AC36-080GO28308

Resource Type:

Accepted Manuscript

Journal Name:

Applied Catalysis. A, General

Additional Journal Information:

Journal Volume: 510; Journal ID: ISSN 0926-860X

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

09 BIOMASS FUELS; 59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; mixed alcohols; dehydration; olefin; SAPO-34; syngas