Utilizing high-boiling residues from isoprene mfr - by decomposition with water over alumina then calcium phosphate catalysts

摘要

The high b.pt. residues (A) produced in the first stage of the synthesis of isoprene (I) by the dioxan process, to give (I), isobutylene (II) and HCHO (III), are processed by catalytic decompsn. of (A) in presence of water at wt. ratio (A): water of 1:1-2 in 2 stages, over an Al2O3 catalyst at 250-290 degrees C to give a vapour mixt. which is then cleaved at 315-360 degrees over a Ca phosphate catalyst. (I), (II) and (III) are recycled e.g. for synthesis of rubber. The process gives better yields of (I) than single-stage decompsn. over either catalyst alone and fouling of the Ca phosphate catalyst by carbonaceous deposits is avoided.