Catalytic ketonization over oxide catalysts, part IV. Cycloketonization ofdiethyl hexanodiate

Activity of 20 wt.% MO2/S catalysts, where M = Mn, Ce and Th, and S = Al2O3 or SiO2, has been studied in cycloketonization of diethyl hexanodiate at t he temperature range 573-698 K in a flow system. Only moderate yields of cy clopentanone (<35%) were achieved. The highest yields of ketone were obtain ed over MnO2/Al2O3 and MnO2/SiO2 catalysts - 33 and 27%, respectively. ThO2 containing catalysts were the most active, whereby ester transformations w ere detected below 573 K. In the presence of all catalysts the formation of the main product was accompanied by various amounts of 2-ethylcyclopentano ne, cyclopent-2-en-1-one, cyclopentene, 2-cyclopentylidenecyclopentanone an d numerous unidentified by-products.