Abstract: A process for heterogeneously catalyzed gas phase partial oxidation of an organic starting compound over a fixed catalyst bed freshly installed into a reaction chamber, in which the reduction in the quality of the fixed catalyst bed is restored with increasing operating time by replacing a portion of the fixed catalyst bed by a replacement fixed catalyst bed part whose volume-specific activity is lower than the volume-specific activity of the replaced fixed catalyst bed part in its freshly installed state.

Abstract: A process for the long-term operation of a heterogeneously catalyzed gas phase partial oxidation of at least one organic compound over a catalyst bed, in which, in order to counteract the deactivation of the catalyst bed, the working pressure in the gas phase is increased during the operating time of the catalyst bed.

Abstract: Apparatus for the long-term operation of a heterogeneously catalyzed gas phase partial oxidation of at least one organic compound over a catalyst bed, in which, in order to counteract the deactivation of the catalyst bed, the working pressure in the gas phase is increased during the operating time of the catalyst bed.

Abstract: A process for heterogeneously catalyzed gas phase partial oxidation of an organic starting compound over a fixed catalyst bed freshly installed into a reaction chamber, in which the reduction in the quality of the fixed catalyst bed is restored with increasing operating time by replacing a portion of the fixed catalyst bed by a replacement fixed catalyst bed part whose volume-specific activity is lower than the volume-specific activity of the replaced fixed catalyst bed part in its freshly installed state.

Abstract: A process for the long-term operation of a heterogeneously catalyzed gas phase partial oxidation of at least one organic compound over a catalyst bed, in which, in order to counteract the deactivation of the catalyst bed, the working pressure in the gas phase is increased during the operating time of the catalyst bed.

Abstract: A process for working up residues from the preparation of pyrrolidone and/or N-vinylpyrrolidone comprises subjecting the residues to a thermolysis.

Abstract: The present invention relates to a process for the dissociation of allophanates, in which a thermal dissociation is carried out in a reaction vessel and the gaseous dissociation products obtained are removed from the reaction vessel using an inert carrier gas or the vapor of a liquid as stripping medium and are condensed.

Abstract: A process for working up residues from the preparation of pyrrolidone and/or N-vinylpyrrolidone comprises subjecting the residues to a thermolysis.

Abstract: The present invention relates to a process for the dissociation of allophanates, in which a thermal dissociation is carried out in a reaction vessel and the gaseous dissociation products obtained are removed from the reaction vessel using an inert carrier gas or the vapor of a liquid as stripping medium and are condensed.

Abstract: Organic diurethanes and/or polyurethanes are prepared by reacting organic diamines and/or polyamines (a) with urea and/or alkyl cabamates (b) and alcohols (c) in the presence of soluble zirconium compounds, preferably zirconium alkoxides, zirconium acetate or zirconium acetylacetonate, as catalyst (d). They can be used for preparing diisocyanates and/or polyisocyanates by thermal dissociation.

Abstract: Organic diurethanes and/or polyurethanes are prepared by reacting organic diamines and/or polyamines (a) with urea and/or alkyl cabamates (b) and alcohols (c) in the presence of soluble zirconium compounds, preferably zirconium alkoxides, zirconium acetate or zirconium acetylacetonate, as catalyst (d). They can be used for preparing diisocyanates and/or polyisocyanates by thermal dissociation.

Abstract: Stable (cyclo)aliphatic polyisocyanate compositions obtainable by phosgene-free methods, preferably by thermal cleavage of (cyclo)aliphatic polycarbamates, are stabilized with carbon dioxide, advantageously in an amount of up to 0.3% by weight.

Abstract: (Cyclo)aliphatic polyisocyanate compositions which have a long shelf life, are obtainable by phosgene-free methods, preferably by thermal cleavage of (cyclo)aliphatic polycarbamates, and, for stabilization, contain at least one primary stabilizer (2a), preferably a sterically hindered phenol and/or an aromatic amine, or at least one secondary stabilizer (2b), preferably an organic phosphite and/or a thioether, or at least one acidic stabilizer (2c), preferably a carboxylic acid, an acyl chloride, an inorganic acid, an inorganic acid chloride and/or a diester of phosphoric acid, or a stabilizer system comprising at least 2 of the stabilizers (2a) to (2c), a process for the preparation of the (cyclo)aliphatic polyisocyanate compositions and their preferred use for the preparation of isocyanurate-containing polyisocyanates.

Abstract: A process for the preparation of 3-cyano-3,5,5-trimethylcyclohexanone by the reaction of isophorone with hydrogen cyanide in the presence of quaternary ammonium catalysts at temperatures ranging from 80.degree. to 180.degree. C. and pressures ranging from 0.5 to 20 bar, in which the ammonium catalysts used are salts of the general formula I ##STR1## in which R.sup.1, R.sup.2, R.sup.3, R.sup.4 denote C.sub.1 -C.sub.18 alkyl, C.sub.5 -C.sub.8 cycloalkyl, aryl, C.sub.7 -C.sub.18 aralkyl or C.sub.2 -C.sub.18 hydroxyalkyl andX denotes HCO.sub.3 or ##STR2## with the proviso that R.sup.4 stands for C.sub.1 -C.sub.

Abstract: Polyisocyanates containing isocyanurate groups are prepared by a partial trimerization of (cyclo)aliphatic diisocyanates in the presence of at least one trimerization catalyst selected from the group consisting of tetraalkylammonium alkyl carbonates of the formula (I) ##STR1## (quaternary ammonioalkyl) carbonates having a betaine structure of the formula (II) ##STR2## and the preferred use of the polyisocyanates containing isocyanurate groups which are obtainable in this way is aspolyisocyanate component in polyurethane finishes.