Abstract: In a process for the preparation of aliphatic .alpha.,.omega.-diols of 4 to 12 carbon atoms from aliphatic .alpha.,.omega.-dicarboxylic acids of 4 to 12 carbon atoms, an oligo ester is first of all formed from diol and dicarboxylic acid and is subsequently subjected to catalytic hydrogenation in the liquid phase. The hydrogenation is carried out continuously at from 180.degree. to 250.degree. C. and at an H.sub.2 pressure of from 100 to 400 bar over a catalyst in piece form comprising compressed powders of Cu, Zn and Al oxides which do or do not contain at least one oxide of metals of the iron group of the Periodic Table of the Elements (Mendeleev) or of manganese. The quantity of H.sub.2 is from 20 to 100 times the stoichiometrically required quantity.

Abstract: In a distillation column with vaporous sidestream removal, the vaporous product removed is condensed in a condenser. The vapor pipe provided for the removal of product opens into a dip tank of which the upper end is connected to the condenser while its lower end is connected to a discharge pump. Inert gas present in the condensate is returned to the column above the sidestream removal through an inert gas pipe arranged at the upper end of the condenser.

Abstract: In a process for the preparation of aqueous formaldehyde solutions consisting of the following steps:(a) reaction of a methanol/water/air mixture in vapor form at elevated temperature over a catalyst,(b) absorption of the reaction mixture in one or more successive absorption stages with the formation of a methanol-containing aqueous formaldehyde solution and(c) removal by fractional distillation of a fraction esentially containing methanol and water,the methanol/water/air mixture which is required for the reaction is evaporated by means of heat which is withdrawn by indirect heat exchange from the formaldehyde solution being formed in the absorber and/or at least some of the vapors obtained by fractional distillation are condensed by means of liquid water. This condensate is fed together with fresh methanol and with air into the evaporator which is upstream from the catalyst stage.

Abstract: The invention relates to a vanadium/phosphorus mixed oxide catalyst, a process for its preparation and its use for the preparation of maleic anhydride.The catalyst according to the invention is prepared by reacting a vanadium(V) compound with phosphoric acid and/or a compound forming phosphoric acid with heating, optionally in the presence of water, and subsequently treating the product obtained after the reaction with organic solvents and/or diluents having reducing activity, optionally in the presence of a promoter, at an elevated temperature.

Abstract: An improvement in the process for the preparation of formaldehyde by oxidative dehydrogenation of methanol with air in the presence of a silver catalyst at an elevated temperature wherein into the reactor in which the methanol is charged there is passed a stream of gas containing a halogen or halogen compound.