Meerwein-Ponndorf-Verley Reduction of Crotonaldehyde over Supported Zirconium Oxide Catalysts Using Batch and Tubular Flow Reactors

The authors studied Meerwein-Ponndorf-Verley (MPV) reduction of crotonaldehyde using batch and tubular flow reactors. Various ZrO₂/SiO₂ catalysts prepared from commercially available carriers and precursors were subjected to activity testing using autoclave batch reactors. To determine the degree of Zr dispersion in the ZrO₂/SiO₂ catalysts, X-ray photoelectron spectroscopy (XPS) measurements and the benzaldehyde-ammonia titration (BAT) method were carried out. The results suggested a positive correlation between Zr dispersion and crotonaldehyde conversion. Durability tests using tubular flow reactors were performed with the most suitable catalyst, which was selected through batch reactions and catalyst characterizations. Almost no degradation of the catalytic activity was observed over 2,200 h in a liquid-phase reaction, while catalyst durability was short in a gas-phase reaction. It was surmised that in the liquid-phase, 2-propanol (hydrogen donor) in the feed had dissolved the reaction byproducts to purge from the catalyst. In addition, a continuous process flow design that includes 2-propanol regeneration was proposed for industrial production.