Key Roles of Lewis Acid-base Pairs on ZnxZryOz in Direct Ethanol/Acetone to Isobutene Conversion
Abstract
The effects of surface acidity on the cascade ethanol-to-isobutene conversion were studied using ZnxZryOz catalysts. The ethanol-to-isobutene reaction was found to be limited by the secondary reaction of the key intermediate, acetone, namely the acetone-to-isobutene reaction. Although the catalysts with coexisting Brønsted acidity could catalyze the rate-limiting acetone-to-isobutene reaction, the presence of Brønsted acidity is also detrimental. First, secondary isobutene isomerization is favored, producing a mixture of butene isomers. Second, undesired polymerization and coke formation prevail, leading to rapid catalyst deactivation. Most importantly, both steady-state and kinetic reaction studies as well as FTIR analysis of adsorbed acetone-d6 and D2O unambiguously showed that a highly active and selective nature of balanced Lewis acid-base pairs was masked by the coexisting Brønsted acidity in the aldolization and self-deoxygenation of acetone to isobutene. As a result, ZnxZryOz catalysts with only Lewis acid-base pairs were discovered, on which nearly a theoretical selectivity to isobutene (~88.9%) was successfully achieved, which has never been reported before. Moreover, the absence of Brønsted acidity in such ZnxZryOz catalysts also eliminates the side isobutene isomerization and undesired polymerization/coke reactions, resulting in the production of high purity isobutene with significantly improved catalyst stability (< 2% activity loss after 200 h time-on-stream).more »
- Authors:
- Publication Date:
- Research Org.:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Org.:
- USDOE
- OSTI Identifier:
- 1236308
- Report Number(s):
- PNNL-SA-114858
Journal ID: ISSN 0002-7863; 48772; KC0302010
- DOE Contract Number:
- AC05-76RL01830
- Resource Type:
- Journal Article
- Journal Name:
- Journal of the American Chemical Society
- Additional Journal Information:
- Journal Volume: 138; Journal Issue: 2; Journal ID: ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
- Subject:
- Lewis acid-base pair; ethanol; acetone; isobutene; ZrxZnyOz; Environmental Molecular Sciences Laboratory
Citation Formats
Sun, Junming, Baylon, Rebecca A., Liu, Changjun, Mei, Donghai, Martin, Kevin J., Venkitasubramanian, Padmesh, and Wang, Yong. Key Roles of Lewis Acid-base Pairs on ZnxZryOz in Direct Ethanol/Acetone to Isobutene Conversion. United States: N. p., 2016.
Web. doi:10.1021/jacs.5b07401.
Sun, Junming, Baylon, Rebecca A., Liu, Changjun, Mei, Donghai, Martin, Kevin J., Venkitasubramanian, Padmesh, & Wang, Yong. Key Roles of Lewis Acid-base Pairs on ZnxZryOz in Direct Ethanol/Acetone to Isobutene Conversion. United States. https://doi.org/10.1021/jacs.5b07401
Sun, Junming, Baylon, Rebecca A., Liu, Changjun, Mei, Donghai, Martin, Kevin J., Venkitasubramanian, Padmesh, and Wang, Yong. 2016.
"Key Roles of Lewis Acid-base Pairs on ZnxZryOz in Direct Ethanol/Acetone to Isobutene Conversion". United States. https://doi.org/10.1021/jacs.5b07401.
@article{osti_1236308,
title = {Key Roles of Lewis Acid-base Pairs on ZnxZryOz in Direct Ethanol/Acetone to Isobutene Conversion},
author = {Sun, Junming and Baylon, Rebecca A. and Liu, Changjun and Mei, Donghai and Martin, Kevin J. and Venkitasubramanian, Padmesh and Wang, Yong},
abstractNote = {The effects of surface acidity on the cascade ethanol-to-isobutene conversion were studied using ZnxZryOz catalysts. The ethanol-to-isobutene reaction was found to be limited by the secondary reaction of the key intermediate, acetone, namely the acetone-to-isobutene reaction. Although the catalysts with coexisting Brønsted acidity could catalyze the rate-limiting acetone-to-isobutene reaction, the presence of Brønsted acidity is also detrimental. First, secondary isobutene isomerization is favored, producing a mixture of butene isomers. Second, undesired polymerization and coke formation prevail, leading to rapid catalyst deactivation. Most importantly, both steady-state and kinetic reaction studies as well as FTIR analysis of adsorbed acetone-d6 and D2O unambiguously showed that a highly active and selective nature of balanced Lewis acid-base pairs was masked by the coexisting Brønsted acidity in the aldolization and self-deoxygenation of acetone to isobutene. As a result, ZnxZryOz catalysts with only Lewis acid-base pairs were discovered, on which nearly a theoretical selectivity to isobutene (~88.9%) was successfully achieved, which has never been reported before. Moreover, the absence of Brønsted acidity in such ZnxZryOz catalysts also eliminates the side isobutene isomerization and undesired polymerization/coke reactions, resulting in the production of high purity isobutene with significantly improved catalyst stability (< 2% activity loss after 200 h time-on-stream). This work not only demonstrates a balanced Lewis acid-base pair for the highly active and selective cascade ethanol-to-isobutene reaction, but also sheds light on the rational design of selective and robust acid-base catalyst for C-C coupling via aldolization reaction.},
doi = {10.1021/jacs.5b07401},
url = {https://www.osti.gov/biblio/1236308},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 2,
volume = 138,
place = {United States},
year = {Wed Jan 20 00:00:00 EST 2016},
month = {Wed Jan 20 00:00:00 EST 2016}
}