THE EFFECT OF PROPYLENE PRESSURE ON SHAPE-SELECTIVE ISOPROPYLATION OFBIPHENYL OVER H-MORDENITE

The effect of propylene pressure on the isopropylation of biphenyl was investigated over highly dealuminated H-mordenite. The selectivity of 4,4'-diisopropylbiphenyl (4,4'-DIPB) in liquid phase products was ach ieved up to 90% under a high propylene pressure of 0.8 MPa, whereas th e decrease of the selectivity of 4,4'-DIPB by the isomerization to 3,4 '-DIPB was observed under low pressure of 0.1 MPa. However, the format ion of IPBP isomers was not influenced by the pressure. The yield of 4 -isopropylbiphenyl (4-IPBP) reached a maximum at 50-60% conversion of biphenyl, whereas that of 3-IPBP increased monotonously. The isomeriza tion of 4,4'-DIPB occurred extensively under low propylene pressure, b ut decreased with the increase of the pressure, No significant isoprop ylation of 4,4'-DIPB was observed even under high pressure, The select ivities of 4,4'-DIPB encapsulated in the catalysts were more than 90% in both cases for the isopropylation of biphenyl and for the isomeriza tion of 4,4'-DIPB under every pressure. These results of the isopropyl ation and the isomerization suggest that selective formation of 4,4'-D IPB occurred in the pores, and that high selectivity under high pressu res is due to the prevention of the adsorption of 4,4'-DIPB at externa l acid sites because of preferential adsorption of propylene. The isom erization of 4,4'-DIPB under low pressures occurred on external acid s ites where no propylene was adsorbed.