| 摘要 |
A catalyst particularly applicable for the selective production of para dialkyl substituted benzenes is provided comprising a porous crystalline aluminosilicate zeolite which has undergone modification by deposition thereon of a coating of silica extensively covering, and residing substantially exclusively on the external surface thereof as a result of contact with a silicone compound of a molecular size incapable of entering the pores of the zeolite and subsequent heating in an oxygen-containing atmosphere to a temperature in excess of 300 DEG C. but below a temperature at which crystallinity of the zeolite is adversely affected at a rate such that the silicone compound does not volatilize prior to undergoing oxidation to silica. The zeolite is characterized by an activity, in terms of alpha value, of between about 2 and about 5000, a xylene sorption capacity greater than 1 gram/100 grams of zeolite and an ortho-xylene sorption time for 30 percent of said capacity of greater than 10 minutes, said sorption capacity and sorption time being measured at 120 DEG C. and a xylene pressure of 4.5 +/- 0.8 mm. of mercury.
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