We report a reaction network detailing the mechanistic origins of 20 C2–C6 byproducts observed during the oxidation of propylene to acrolein at 623 K on a molybdenum-based catalyst promoted with cobalt and nickel used in the industrial production of acrolein. The carbon backbone of propylene is preserved in the sequential oxidation of propylene to allyl alcohol, acrolein, and acrylic acid, as well as propylene oxidation to acetone and propanal via water-mediated pathways. Transient kinetic measurements in conjunction with co-feed experiments of C2 and C3 aldehydes and carboxylic acids show that decarbonylation and decarboxylation reactions, reactions of organic compounds with surface-adsorbed oxygen species, and total combustion reactions are the three mechanisms for C–C bond cleavage. C–C bond formation reactions that result in C4–C6 byproducts occur via: (i) the addition reaction of a propylene-derived surface allyl species with formaldehyde to form C4 products and with propylene and allyl alcohol to form C6 products, or (ii) the addition reaction of an acrolein (acrylic acid)-derived surface ethenyl intermediate with propylene to form pentadiene and with acrolein to form C5 cyclic oxygenates.
Bibliographical noteFunding Information:
The authors acknowledge financial support from The Dow Chemical Company. The authors also acknowledge Dr. Joseph DeWilde, The Dow Chemical Company, and Mr. Andrew Hwang, University of Minnesota, for helpful technical discussions.
© 2017 Elsevier B.V.
Copyright 2017 Elsevier B.V., All rights reserved.
- Mechanistic network
- Propylene oxidation