Calcium phosphate catalyst prepn. - by reacting calcium salt with phosphoric acid salt under mol. ration and pH control

摘要

Ca phosphate catalysts are prepd. by reacting Ca salts, (I), with phosphoric acid salts, (II), in an aq. ammonia medium, sepg. the ppte. formed from the reaction mixt., shaping the bottom sediment and drying. Novelty consists in (a) reacting (I) and (II) in (I) : (II) mol. ratio 1.5 : 1 to 5 : 1 (2.5 : 1); and (b) treating the reaction mixt. with H3PO4 soln. to pH 5-7 (5.5-6) before sepg. the ppte. The catalysts are used in isoprene prepn. from isobutylene and HCHO and in alcohol dehydration, esp. in the dissociation of 1,3-dioxans, partic. 4,4-dimethyl-1,3-dioxan, (A), to isoprene. Mol. ratio control (a) and pH control (b) in catalyst prepn. increase catalyst activity, lower operating temp., increase efficiency, catalyst life and isoprene selectivity and also lower coke deposition in (A)-dissociation. E.g. catalyst selectivity to isoprene is increased to 84-85.8 mol.%, i.e. by 3.8-6.6 mol.%. At 320 deg.C, conversion is increased by 20-25%, e.g. to 96-96.6% and catalyst activity is 0.8 t isoprene/cu.m.catalyst.hr. Catalyst life can reach 1500 hrs.