Conversion of methyl ethyl ketone to butenes over bifunctional catalysts

Abstract

The direct conversion of methyl ethyl ketone (MEK) to butene over supported copper catalysts was investigated in a fixed bed reactor over Cu-Al2O3, Cu-zeolite Y sodium (Cu-ZYNa) and Cu-zeolite Y hydrogen (Cu-ZYH). In this reaction, MEK is hydrogenated to 2-butanol over metal sites which is further dehydrated on acid sites to produce butene. Experimental results showed that the selectivity of butene was the highest over Cu-ZYNa, and it was improved by finding the optimum reaction temperature, hydrogen pressure and the percentage of copper loaded on ZYNa. The highest selectivity of butene (97.9%) was obtained at 270 °C and 20 wt% Cu-ZYNa. Over Cu-Al2O3, the selectivity of butenes was less than Cu-ZYNa since subsequent hydrogenation of butene occurred to produce butane. It was also observed that with increasing H2/MEK molar ratio, butane selectivity increased. However, when this ratio was decreased, hydrogenation of butene was reduced, but dimerization to C8 alkenes and alkane began to be favored. The main products over 20% Cu-Al2O3 were butene and butane, and a maximum selectivity of butene (87%) was achieved at an H2/MEK molar ratio of five. The lowest selectivity of butene was obtained using Cu-ZYH, reaching ∼40%. All catalysts were characterized by (NH3-TPD), (CO2-TPD), XPS and TPR to probe catalyst acidity, basicity and the reducibility of Cu loaded on the supports. It was found that the amount of acidity in Cu-ZYH is much higher than in Cu-ZYNa. This could have caused the selectivity of butene to decrease as a result of dimerization, oligomerization and cracking reactions.