SHAPE-SELECTIVE ISOPROPYLATION OF NAPHTHALENE OVER DEALUMINATED MORDENITES - INCREASING BETA-SUBSTITUTION SELECTIVITY BY ADDING WATER

Isopropylation of naphthalene was examined over two dealuminated H-mor denites (HM) having SiO2/Al2O3 molar ratio of 38 (HM38) and 74 (HM74). Experiments were done in batch reactors at 200 degrees C. With propyl ene as the alkylating agent, selectivity for beta-substitution of naph thalene increased when water was added, and reached a maximum with a w ater-to-catalyst mass ratio of 0.80 (ca. 45 mmol water/g-cat). Of part icular importance was the increase in beta beta-selectivity to 2,6- an d 2,7-diisopropylnaphthalene (2,6-DIPN and 2,7-DIPN) with added water. Without added water, beta beta-selectivities were 56 and 77% for HM38 and HM74, respectively. Selectivities to the highly desired 2,6-DIPN isomer were 37 and 54%, respectively. With added water, beta beta-sele ctivities increased to 90 and 95%, and 2,6-DIPN selectivities increase d to 60 and 70% for HM38 and HM74, respectively. A large amount of add ed water always decreased the activity; however, mixed effects were ob served for intermediate amounts of added water. Sorption of water on t he catalyst surface seems to explain changes in isomer selectivity and catalytic activity. Coke deposits on the catalysts also decreased whe n water was added. Furthermore, it was shown that higher beta beta-sel ectivity could be obtained with isopropanol (i-PrOH) as the alkylating agent, rather than propylene, under the same conditions. Comparison e xperiments showed that this was due to water formed from i-PrOH.