Abstract: Process for oligomerizing an alkene stream over a solid catalyst comprising sulfur and nickel, in which the oligomerization is carried out in two or more successive catalyst zones and the molar ratio of sulfur to nickel in the first catalyst zone is less than 0.5 and that in the last catalyst zone is 0.5 or more and, in the case of further catalyst zones between the first and last catalyst zones, the molar ratio of sulfur to nickel in each catalyst zone is not less than that in the immediately preceding catalyst zone, based on the main flow direction of the feed stream.

Abstract: Process for oligomerizing an alkene stream over a solid catalyst comprising sulfur and nickel, in which the oligomerization is carried out in two or more successive catalyst zones and the molar ratio of sulfur to nickel in the first catalyst zone is less than 0.5 and that in the last catalyst zone is 0.5 or more and, in the case of further catalyst zones between the first and last catalyst zones, the molar ratio of sulfur to nickel in each catalyst zone is not less than that in the immediately preceding catalyst zone, based on the main flow direction of the feed stream.

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.