Conversion of Biomass-Derived Methyl Levulinate to Methyl Vinyl Ketone

A high-throughput screening exercise testing 60 different catalysts resulted in 5 wt % Pt on sulfided carbon as the best catalyst in the conversion of biobased methyl levulinate (ML) to methyl vinyl ketone (MVK) in a gas-phase continuous process. Up to 18% yield of MVK was obtained, but fast catalyst deactivation was observed. For a better understanding of the reaction mechanism, the potential reaction intermediates [alpha-angelica lactone (alpha-AL), gamma-valerolactone, methyl ethyl ketone (MEK), and levulinic acid (LA)] were also fed as starting materials under the same reaction conditions as those used for ML. Of the different pathways possible, the route via AL seems to be the most likely route. Since the side product methanol led to the hydrogenation of MVK to MEK, LA is a better substrate in this reaction toward MVK at a medium reaction temperature. Herein, we report the highest yield of MVK (>50%) from LA at 350 degrees C. However, this knowledge of the reaction pathway via AL also opened up the possibility of a high-temperature conversion process of ML to MVK. It was found that ML could be converted to MVK in 71% selectivity at 600 degrees C using 40% CaO on gamma-Al2O3 as the catalyst. Here, the catalyst merely serves to accelerate the ring closure of ML to AL, which undergoes an electrocyclic reaction under extrusion of CO to form MVK.