CATALYTIC PROPERTIES OF THE GALLOPHOSPHATE CLOVERITE .2. GAS-PHASE FORMATION OF ETHYL-TERT-BUTYL ETHER

The catalytic gas phase etherification of isobutene by ethanol over th e gallophosphate molecular sieve cloverite was studied within the temp erature range 345-405 K, and at molar ratios of isobutene to ethanol f rom 0.5 to 2. A maximum ethanol conversion of 20% is achievable at tem peratures of 365-375 K and at a space velocity (WHSV) of 4.9 h(-1), wi th a selectivity higher than 90% for the primary product ethyl-tert.-b utyl ether. It is shown for the first time, that an additional etherif ication of di-isobutene oligomers (2,4,4-trimethyl-pent-1-ene and 2,4, 4-trimethyl-pent-2-ene) takes place by ethanol leading to 2,4,4-trimet hyl-2-ethoxy-pentane. This reaction is not relevant for medium pore ze olites but can obviously proceed on cloverite owing to its large cavit y size. It is further shown that cloverite after in situ template remo val at 685 K still contains fluoride (which is an imperative ingredien t of the synthesis recipe) that intensifies the acid properties thus p romoting the etherification reaction at low reaction temperatures.