Comparison of ethylene with propylene hydroformylation over a Rh-Y zeolite catalyst under atmospheric pressure

Abstract

Hydroformylation of ethylene and propylene over the Rh-Y zeolite was carried out in a continuous-flow system under atmospheric pressure. The activity of the catalyst used for the formation of propionaldehyde and butyraldehyde was observed to be constant for a period of over 1 month. Pretreatment of the catalyst with HeH 2 (10%) at 127 °C considerably affected the steady-state rate ( r PA) and the apparent activation energy ( E PA) for the propionaldehyde formation. On the Rh-Y zeolite with a rhodium content of less than 110 × 10 −6 mol/g cat (1.13 wt%), the enhancement in r PA was observed with no appreciable change in E PA. On the other hand, on the Rh-Y zeolite (No. 6) with a rhodium content of 280 × 10 −6 mol/g cat (2.88 wt%), r PA was somewhat reduced by the pretreatment while E PA was considerably enhanced i.e., 40 kJ/mol on the untreated catalyst and 56 kJ/mol on the pretreated one. In the propylene hydroformylation, the pretreatment of the Rh-Y (No. 6) remarkably reduced r BA compared with r PA, but it enhanced the n-isomer selectivity ( S n-BA ). The enhancement in S n-BA is closely related to the enhancement in E PA. On the basis of the results obtained, it is concluded that (1) the active sites formed either at the entrance of the pore or the external surface can effectively catalyze both the hydroformylation of ethylene and propylene and (2) the active sites formed in the pore at a very short distance from the entrance can catalyze the hydroformylation of ethylene but not propylene.