SHAPE-SELECTIVE ALKYLATION OF BIPHENYL OVER MORDENITES - EFFECTS OF DEALUMINATION ON SHAPE-SELECTIVITY AND COKE DEPOSITION

To understand the relationships between shape-selectivity and coke dep osition in the alkylation of biphenyl over H-mordenite (HM), thermogra vimetric analyses were examined for the catalyst after the reaction. T he coke deposition during the catalysis was very severe over HM with l ow SiO2/Al2O3 ratio, however, dealumination enhanced the decrease of c oke deposition. Over highly dealuminated HM, volatile organic compound s, mainly biphenyl derivatives, were observed in addition to carbonace ous deposits. The deposits are produced from biphenyl derivatives on a cid sites in the HM pore, and the ease of their formation is governed by acid site density and acid strength. The decrease of carbonaceous d eposits and the increase of encapsulated biphenyl derivatives are rela ted with the increase of both selectivity and yield of 4,4'-diisopropy lbiphenyl (4,4'-DIPB). The increase of reaction temperature up to 250- degrees-C enhanced the catalysis over highly dealuminated HM, however, further increase of the temperature resulted in extensive decrease of the selectivity of 4,4'-DIPB. Coke deposition also increased with the temperature although its level was low. The composition of 4,4'-DIPB in encapsulated DIPB isomers remained as high as 80% in spite of a cha nge of the distribution of bulk products.