Continuous Catalytic Production of Methyl Acrylates from Unsaturated Alcohols by Gold: The Strong Effect of C=C Unsaturation on Reaction Selectivity

Journal Article · Tue Feb 02 00:00:00 EST 2016 · ACS Catalysis

DOI:https://doi.org/10.1021/acscatal.5b02902· OSTI ID:1414356

Zugic, Branko ^[1]; Karakalos, Stavros ^[1]; Stowers, Kara J. ^[1]; Biener, Monika M. ^[2]; Biener, Juergen ^[2]; Madix, Robert J. ^[3]; Friend, Cynthia M. ^[4]

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1. Harvard Univ., Cambridge, MA (United States). Dept. of Chemistry and Chemical Biology
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nanoscale Synthesis and Characterization Lab.
3. Harvard Univ., Cambridge, MA (United States). School of Engineering and Applied Sciences
4. Harvard Univ., Cambridge, MA (United States). Dept. of Chemistry and Chemical Biology, School of Engineering and Applied Sciences

We demonstrate the gas-phase catalytic production of methyl acrylates by oxygen-assisted coupling of methanol with the unsaturated alcohols allyl alcohol and methylallyl alcohol over nanoporous gold (npAu) at atmospheric pressure. Analogous investigations on O-activated Au(110) exhibit the same pattern of reactivity and are used to establish that the competition between methoxy and allyloxy (or methallyloxy) reaction intermediates for adsorption sites, mediated by the reactants themselves, determines the selectivity of reaction. These results clearly show that the C=C bond substantially increases the binding efficacy of the allyloxy (or methallyloxy), thus requiring extremely high methanol mole fractions (>0.99) in order to achieve comparable surface concentrations of methoxy and produce optimum yields of either methacrylate or methyl methacrylate. Allyloxy and methallyloxy were favored by factors of ~100 and ~450, respectively, vs methoxy. These values are more than 1 order of magnitude greater than those measured for competitive binding of ethoxy and 1-butoxy vs methoxy, demonstrating the strong effect of the carbon–carbon bond unsaturation. The 4.5-fold increase due to the addition of the methyl group in methylallyl alcohol vs allyl alcohol indicates the significant effect of the additional van der Waals interactions between the methyl group and the surface. Gas-phase acidity is also shown to be a good qualitative indicator for the relative binding strength of the alkoxides. This work then provides insight into the control of reaction selectivity for coupling reactions and demonstrates the value of fundamental studies on single crystals for establishing key principles governing reaction selectivity. Notably, these oxygen-assisted coupling reactions occur without oxidation of the C=C bond.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Integrated Mesoscale Architectures for Sustainable Catalysis (IMASC); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: AC52-07NA27344; SC0012573
• OSTI ID: 1414356
• Report Number(s): LLNL-JRNL--737635
• Journal Information: ACS Catalysis, Journal Name: ACS Catalysis Journal Issue: 3 Vol. 6; ISSN 2155-5435
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
esterification
green catalysis
methyl acrylate
methyl methacrylate
nanoporous gold
selective alcohol oxidation