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-Al 2 O 3 , 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-Al 2 O 3 , 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 H 2 /MEK molar ratio, butane selectivity increased. However, when this ratio was decreased, hydrogenation of butene was reduced, but dimerization to C 8 alkenes and alkane began to be favored. The main products over 20% Cu-Al 2 O 3 were butene and butane, and a maximum selectivity of butene (87%) was achieved at an H 2 /MEK molar ratio of five. The lowest selectivity of butene was obtained using Cu-ZYH, reaching ∼40%. All catalysts were characterized by (NH 3 -TPD), (CO 2 -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.