HETEROPOLYACID-BASED CATALYSIS - DAWSON ACID FOR MTBE SYNTHESIS IN GAS-PHASE

The Wells-Dawson acid was studied as a catalyst for producing methyl t ert-butyl ether (MTBE) from methanol and isobutylene in the gas phase at 373 K. Thus, pure Wells-Dawson acid was synthesized and characteriz ed by P-31 NMR, XRD, FTIR and TGA-DTA measurements. The results indica ted that the Dawson acid keeps its heteropolyoxoanion structure up to 873 K. The samples were active and very selective (close to 100%) for MTBE production and showed stable behavior during the reaction period of 3 h. The conversion observed on reference catalyst Amberlyst 15-wet under the same conditions was significantly lower. The acid was also tested in methanol dehydration to dimethyl ether at 373 K. For both re actions, the catalytic activity depends on the pretreatment temperatur e of the acid. The activity was approximately constant up to 473 K; th en activity decreased steadily until becoming null when pretreatment t emperature was 673 K. The catalytic results were explained using the p seudoliquid phase behavior concept. (C) 1998 Elsevier Science B.V. All rights reserved.