Selective synthesis of cyclohexylcyclohexanone on bifunctional zeolite catalysts. Influence of the metal and of the pore structure

The transformation of cyclohexanone into cyclohexylcyclohexanone was carried out on various Pt or Pd zeolite catalysts with Si/Al (or Si/Ga) ratios around 40 under the following conditions : now reactor, 473 K, pressures of cyclohexanone and hydrogen equal to 0.25 and 0.75 bar. The effect of the percentages of platinum or of palladium (from 0.1 to 0.5 wt%) was shown with series of Pt and PdHFAU catalysts. The initial activity first increased with metal content then remained constant for metal contents greater than or equal to 0.2 wt%, which is typical of bifunctional catalyzed processes. The initial activity did not depend on the metal but the selectivity to cyclohexylcyclohexanone was much higher with the PdHFAU sample (75% against 47% with PtHFAU, at a cyclohexanone conversion of 30%). The catalytic properties of,various 0.2 wt% Pt or Pd zeolite catalysts with average or large pore size (HMFI alumino and gallosilicates, HBEA, HMOR and HFAU) were compared. The higher selectivity to cyclohexylcyclohexanone was found with all the Pd zeolites while the initial activities of 0.2 wt% PtHMFI and PtHMOR were greater than those of the corresponding Pd samples. The initial activities and the selectivities of 0.2 wt% Pd zeolites depended on the zeolite pore structure. The PdHFAU catalyst which has the largest pores was the more active and the more selective to cyclohexylcyclohexanone.