Monday, November 12, 2018
4701 N. Cumberland Avenue
Professor Friedeike Jentoff
Chemical Engineering Department
Univ of Massachusetts
Aldol reactions are important for C-C bond formation in chemical synthesis, with a wide range of applications in basic and fine chemicals, and potential for upgrading of carbonyl compounds in biomass-derived pyrolysis oils to longer carbon chain compounds. In cross aldol condensations, particularly when involving unsymmetrical ketones, there are many possibilities for product formation. While a high level of selectivity is achievable using homogeneous catalysis with elaborate strategies, not much research has been dedicated to controlling selectivity using solid catalysts.
We have investigated the potential of solid catalysts for regioselectivity control, using the aldol condensation of benzaldehyde and 2-butanone as a test reaction. An advantage of this reaction is the stability of the intermediate aldols, which allows analysis of selectivity in the individual reaction steps (addition and dehydration). Solid catalysts include ordered mesoporous silicas and resins functionalized with sulfonic acid or amine groups, sulfated zirconia, and various zeolites and zeotypes. The effect of the following parameters on selectivity will be discussed: nature of the sites (acid vs base), acid/base strength, surface hydrophobicity, and spatial constraints .
An interesting side reaction in the aldol chemistry is the formation of cleavage products. This pathway has drawn attention as an intermediate step in the synthesis of isobutene from ethanol via acetone and its aldol condensation [2,3]. We have identified catalysts and conditions that favor this fission pathway for other reactants .
1. Tuning solid catalysts to control regioselectivity in cross aldol condensations with unsymmetrical ketones for biomass conversion, K. Ponnuru, J.C. Manayil, H.J. Cho, A. Osatiashtiani, W. Fan, K. Wilson, F.C. Jentoft, Molecular Catalysis 458B (2018) 247-260.
2. Direct conversion of bio-ethanol to isobutene on nanosized ZnxZryOz mixed oxides with balanced acid-base sites, J. Sun, K. Zhu, F. Gao, C. Wang, J. Liu, C.H. Peden, Y.Wang, J. Am. Chem. Soc. 133 (2011) 11096-11099.
3. Selective conversion of acetone to isobutene and acetic acid on aluminosilicates: Kinetic coupling between acid-catalyzed and radical- mediated pathways, S. Herrmann, E. Iglesia, Journal of Catalysis 360 (2018) 66–80.
4.Intraparticle diffusional effects vs. site effects on reaction pathways in liquid-phase cross aldol reactions, K. Ponnuru, J.C. Manayil, H.J. Cho, W. Fan, K. Wilson, F.C. Jentoft, ChemPhysChem 19 (2018) 386 – 401.
Friederike C. Jentoft is Professor of Chemical Engineering at the University of Massachusetts Amherst, USA. She studied Chemistry in Tübingen and at Ludwig-Maximilians-Universität München, where she received her Dr. rer. nat. (1994) under the guidance of Helmut Knözinger. After working as a postgraduate researcher in Bruce Gates’ group at the University of California in Davis, she led a research group for 12 years at the Fritz Haber Institute of the Max Planck Society in Berlin. She assumed a faculty position at the University of Oklahoma in Norman in 2008 and moved to UMass Amherst in 2015. Jentoft received the Award for Young Scientists of the German Society for Petroleum and Coal Science and Technology (1996) and a Young Scientists Prize from the International Association of Catalysis Societies (2000), was named Anadarko Petroleum Corporation Presidential Professor (2014), and was given the Excellence in Catalysis Award of the Catalysis Society of Metropolitan New York (2018). From 2009 to 2015, she served as Associate Editor and Editor of Advances in Catalysis. She also was member and chair (2009-2013) of the Acid-Base-Catalysis Board of Directors. Jentoft has authored more than 90 papers and several book chapters. Her main research interests are in acid-base catalysis and spectroscopic analysis of surface reactions.