Reaction Network and Mechanistic Assessment of Acrolein Oxidation on an Industrial Oxide Catalyst

Partial oxidation of acrolein at 498 K in the presence of oxygen and water over a proprietary mixed metal oxide industrial catalyst achieved ~98% selectivity to acrylic acid in a gradientless, gas-phase recirculating batch reactor. Formation of nearly 20 hydrocarbon and oxygenate side products ranging in carbon number from one to seven was also observed. Acrolein partial oxidation in either oxygen- or water-deficient conditions decreased acrolein selectivity and increased selectivity to total combustion products. Independent studies in which partial and total oxidation products were co-processed with with acrolein, water, and oxygen revealed:

• Production of formaldehyde, acetaldehyde, methyl vinyl ketone, furan, furfural, and benzaldehyde from acrylic acid
• Distinct mechanistic routes for CO and CO₂ production
• Participation of both acrolein and acrylic acid in carbon-carbon bond formation and carbon-carbon bond scission reactions

These and other side product co-processing experiments have allowed for the formulation of a network connectivity scheme explaining formation of all side products with selectivity exceeding 0.01C%. A power law kinetic model quantitatively describes product evolution over time and reveals connectivity of side products in the reaction network. ¹³C isotopic labeled co-processing experiments confirm the presence and role of of C₁, C₂, C₃, and C₄ reactive surface intermediates on the catalyst surface. A detailed network of reactions involving hypothesized surface intermediates explaining production of acrolein oxidation side products on the catalyst surface will also be presented.