SYNTHESIS, CHARACTERIZATION AND CATALYTIC ACTIVITY OF SAPO-34 OBTAINED WITH PIPERIDINE AS TEMPLATING AGENT

The synthesis of SAPO-34 in the presence of a new templating agent, na mely piperidine, was investigated. The effects of the gel composition, the template concentration, the time and temperature of crystallizati on on the degree of crystallinity and the purity of the crystalline ph ase were examined. It was found that SAPO-34 and SAPO-20 are competing phases at high piperidine concentrations, whereas SAPO-34, SAPO-17 an d SAPO-35 are the phases present at low template concentrations. Pure SAPO-34 with high crystallinity was obtained at a piperidine/Al2O3 rat io of 1.1:1.0. An optimal synthesis procedure giving an homogeneous SA PO-34 framework without Si islands, consists of heating a gel of compo sition .0Al(2)O(3)/0.6P(2)O(5)/1.1Pip./0.8SiO(2)/100H(2)O at 200 degre es C for 4-8 days. Such a reproducible procedure gives rise to an acid ic catalyst active in the aldol condensation of acetaldehyde with form aldehyde. (C) 1997 Elsevier Science B.V.