Effects of Composition and Structure of Mg/Al Oxides on Their Activity and Selectivity for the Condensation of Methyl Ketones

Handle URI:
http://hdl.handle.net/10754/622395
Title:
Effects of Composition and Structure of Mg/Al Oxides on Their Activity and Selectivity for the Condensation of Methyl Ketones
Authors:
Shylesh, Sankaranarayanapillai; Kim, Daeyoup; Gokhale, Amit A.; Canlas, Christian; Struppe, Jochem O.; Ho, Christopher R.; Jadhav, Deepak; Yeh, Alice; Bell, Alexis T.
Abstract:
The effects of chemical composition and pretreatment on Mg–Al hydrotalcites and alumina-supported MgO were evaluated for the gas-phase, self-condensation reaction of C3–C5 biomass-derived methyl ketones. We show that the selectivity toward the acyclic dimer enone and the cyclic enone trimer can be tuned by controlling the temperature of hydrotalcite calcination. Methyl ketone cyclization is promoted by Lewis acidic sites present on the hydrotalcite catalysts. XRD and thermal decomposition analysis reveal that the formation of periclase MgO starts above 623 K accompanied by complete disappearance of the hydrotalcite structure and is accompanied by an increase in hydroxyl condensation as the formation of well-crystallized periclase. 27Al MQMAS and 25Mg MAS NMR show that at progressively higher temperatures, Al3+ cations diffuses out of the octahedral brucite layers and incorporate into the tetrahedral and octahedral sites of the MgO matrix thereby creating defects to compensate the excess positive charge generated. The oxygen anions adjacent to the Mg2+/Al3+ defects become coordinatively unsaturated, leading to the formation of new basic sites. A kinetic isotope effect, kH/kD = 0.96, is observed at 473 K for the reaction of (CH3)2CO versus (CD3)2CO, which suggests that carbon–carbon bond formation leading to the dimer aldol product is the rate-determining step in the condensation reaction of methyl ketones. We also show that acid–base catalysts having similar reactivity and higher hydrothermal stability to that of calcined hydrotalcites can be achieved by creating defects in MgO crystallites supported alumina as a consequence of the diffusion of Al3+ cations into MgO. The physical properties of these materials are shown to be very similar to those of hydrotalcite calcined at 823 K.
KAUST Department:
KAUST NMR Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
Citation:
Shylesh S, Kim D, Gokhale AA, Canlas CG, Struppe JO, et al. (2016) Effects of Composition and Structure of Mg/Al Oxides on Their Activity and Selectivity for the Condensation of Methyl Ketones. Industrial & Engineering Chemistry Research 55: 10635–10644. Available: http://dx.doi.org/10.1021/acs.iecr.6b03601.
Publisher:
American Chemical Society (ACS)
Journal:
Industrial & Engineering Chemistry Research
Issue Date:
22-Sep-2016
DOI:
10.1021/acs.iecr.6b03601
Type:
Article
ISSN:
0888-5885; 1520-5045
Sponsors:
This work was supported by the Energy Bioscience Institute. STEM-EDS mapping was performed at the National Center for Electron Microscopy at the Molecular Foundry, Lawrence Berkeley National Laboratory. Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. We gratefully acknowledge the contributions of Dr. Benjamin Keitz and Dr. Gregory Johnson to the characterization section of the manuscript.
Additional Links:
http://pubs.acs.org/doi/abs/10.1021/acs.iecr.6b03601
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Full metadata record

DC FieldValue Language
dc.contributor.authorShylesh, Sankaranarayanapillaien
dc.contributor.authorKim, Daeyoupen
dc.contributor.authorGokhale, Amit A.en
dc.contributor.authorCanlas, Christianen
dc.contributor.authorStruppe, Jochem O.en
dc.contributor.authorHo, Christopher R.en
dc.contributor.authorJadhav, Deepaken
dc.contributor.authorYeh, Aliceen
dc.contributor.authorBell, Alexis T.en
dc.date.accessioned2017-01-02T09:28:28Z-
dc.date.available2017-01-02T09:28:28Z-
dc.date.issued2016-09-22en
dc.identifier.citationShylesh S, Kim D, Gokhale AA, Canlas CG, Struppe JO, et al. (2016) Effects of Composition and Structure of Mg/Al Oxides on Their Activity and Selectivity for the Condensation of Methyl Ketones. Industrial & Engineering Chemistry Research 55: 10635–10644. Available: http://dx.doi.org/10.1021/acs.iecr.6b03601.en
dc.identifier.issn0888-5885en
dc.identifier.issn1520-5045en
dc.identifier.doi10.1021/acs.iecr.6b03601en
dc.identifier.urihttp://hdl.handle.net/10754/622395-
dc.description.abstractThe effects of chemical composition and pretreatment on Mg–Al hydrotalcites and alumina-supported MgO were evaluated for the gas-phase, self-condensation reaction of C3–C5 biomass-derived methyl ketones. We show that the selectivity toward the acyclic dimer enone and the cyclic enone trimer can be tuned by controlling the temperature of hydrotalcite calcination. Methyl ketone cyclization is promoted by Lewis acidic sites present on the hydrotalcite catalysts. XRD and thermal decomposition analysis reveal that the formation of periclase MgO starts above 623 K accompanied by complete disappearance of the hydrotalcite structure and is accompanied by an increase in hydroxyl condensation as the formation of well-crystallized periclase. 27Al MQMAS and 25Mg MAS NMR show that at progressively higher temperatures, Al3+ cations diffuses out of the octahedral brucite layers and incorporate into the tetrahedral and octahedral sites of the MgO matrix thereby creating defects to compensate the excess positive charge generated. The oxygen anions adjacent to the Mg2+/Al3+ defects become coordinatively unsaturated, leading to the formation of new basic sites. A kinetic isotope effect, kH/kD = 0.96, is observed at 473 K for the reaction of (CH3)2CO versus (CD3)2CO, which suggests that carbon–carbon bond formation leading to the dimer aldol product is the rate-determining step in the condensation reaction of methyl ketones. We also show that acid–base catalysts having similar reactivity and higher hydrothermal stability to that of calcined hydrotalcites can be achieved by creating defects in MgO crystallites supported alumina as a consequence of the diffusion of Al3+ cations into MgO. The physical properties of these materials are shown to be very similar to those of hydrotalcite calcined at 823 K.en
dc.description.sponsorshipThis work was supported by the Energy Bioscience Institute. STEM-EDS mapping was performed at the National Center for Electron Microscopy at the Molecular Foundry, Lawrence Berkeley National Laboratory. Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. We gratefully acknowledge the contributions of Dr. Benjamin Keitz and Dr. Gregory Johnson to the characterization section of the manuscript.en
dc.publisherAmerican Chemical Society (ACS)en
dc.relation.urlhttp://pubs.acs.org/doi/abs/10.1021/acs.iecr.6b03601en
dc.titleEffects of Composition and Structure of Mg/Al Oxides on Their Activity and Selectivity for the Condensation of Methyl Ketonesen
dc.typeArticleen
dc.contributor.departmentKAUST NMR Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabiaen
dc.identifier.journalIndustrial & Engineering Chemistry Researchen
dc.contributor.institutionEnergy Biosciences Instituteen
dc.contributor.institutionDepartment of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United Statesen
dc.contributor.institutionBASF Coorporation, 33 Wood Avenue South, Iselin, New Jersey 08830, United Statesen
dc.contributor.institutionBruker Biospin Coorporation, Billerica, Massachusetts 01821, United Statesen
kaust.authorCanlas, Christianen
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