Abstract: On-spec phthalic anhydride is prepared by distillative purification of crude phthalic anhydride by a process in which crude phthalic anhydride is fed to a distillation column which is operated at reduced pressure, the low boilers are removed at the top or in the vicinity of the top of the distillation column and the on-spec phthalic anhydride is removed from the column via a side take-off.

Abstract: The invention relates to a method for producing shell catalysts for the catalytic vapor-phase oxidation of aromatic carboxylic acids and/or carboxylic acid anhydrides comprised of a supporting core and of catalytically active metal oxides which are deposited in a shell-shaped manner on said supporting core. The inventive catalysts are obtained by spraying an aqueous active mass suspension, said suspension containing the active metal oxides, at higher temperatures onto the hot supporting material which has a temperature ranging from 50 to 450° C. The aqueous active mass suspension contains 1 to 10 wt. %, with regard to the solid content of the active mass suspension, a binding agent comprised of A) a polymerizate obtained by radical polymerization, containing 5 to 100 wt. % of monomers (a) in the form of ethylenically unsaturated acid anhydrides or ethylenically unsaturated dicarboxylic acids whose carboxyl groups can form an anhydride and containing 0 to 95 wt.

Abstract: Phosphorus-containing calixarenes of the general formula I ##STR1## and a process for their preparation are described. Additionally, a process for the preparation of aldehydes by the hydroformylation of C.sub.3 -C.sub.20 -olefins by means of rhodium or ruthenium carbonyl complexes, in which the phosphorus-containing calixarenes of the formula I are used as ligands, is described.