Abstract: A catalyst for the hydrogenation of C4-dicarboxylic acids and/or their derivatives, preferably maleic anhydride, in the gas phase comprises from 5 to 100% by weight, preferably from 40 to 90% by weight, of copper oxide and from 0 to 95% by weight, preferably from 10 to 60% by weight, of one or more metals or compounds thereof selected from the group consisting of Al, Si, Zn, Pd, La, Ce, the elements of groups III A to VIII A and groups I A and II A as active composition applied in the form of a thin layer to an inert support material.

Abstract: A hydrogenation catalyst which is suitable, in particular, for the hydrogenation of maleic anhydride and its derivatives to THF or its derivatives comprises copper oxide and at least one further metal or compound thereof, preferably an oxide, selected from the group consisting of Al, Si, Zn, La, Ce, the elements of groups IIIA to VIIIA and the elements of groups IA and IIA and having a pore volume of ≧ 0.01 ml/g for pore diameters of >50 nm and a ratio of the pore volume of macropores having a diameter of >50 nm to the total pore volume for pores having a diameter of >4 nm of >10%.

Abstract: In a process for the continuous fractional distillation of mixtures comprising tetrahydrofuran, &ggr;-butyrolactone and/or 1,4-butanediol to give at least three fractions, the fractionation is carried out in an assembly of distillation columns comprising at least one dividing wall column or at least one assembly of thermally coupled conventional distillation columns.

Abstract: In a process for preparing 1,4-butanediol, tetrahydrofuran and &ggr;-butyrolactone by oxidation of butane to give a product stream comprising maleic anhydride, absorption of maleic anhydride from the product stream using a high-boiling alcohol to give a liquid absorption product comprising monoesters and diesters of maleic acid and also high-boiling alcohol, after-esterification of the liquid absorption product and subsequent hydrogenation of the after-esterified product in the liquid phase, the high-boiling alcohol is a polyhydric alcohol having a boiling point at atmospheric pressure of above 233° C. and the after-esterified product has an acid number of less than 30 mg KOH/g and a water content of less than 1% by weight.

Abstract: A process for preparing 1,4-butanediol and, if desired, &ggr;-butyrolactone and THF by oxidizing butane or benzene to form a product stream including maleic anhydride, absorbing maleic anhydride from the product stream with a high-boiling inert solvent in an absorption stage to give a liquid absorption product, esterifying the liquid absorption product with a C1-C5 esterifying alcohol in an esterification stage to form an esterification product comprising the corresponding diester and high-boiling inert solvent, then hydrogenating the esterification product to give a hydrogenation product which comprises the products of value, 1,4-butanediol and, if desired, &ggr;-butyrolactone and tetrahydrofuran and the esterifying alcohol and which is separated by distillation into the products of value and the esterifying alcohol, and recycling the esterifying alcohol to the esterification zone, which comprises separating the esterification product into the diester and the inert solvent by distillation under reduced press

Abstract: Process for producing butyrolactones of the general formula I where R1 and R2 are each hydrogen, alkyl, hydroxyalkyl, substituted or unsubstituted aryl or substituted or unsubstituted trialkylsilyl, by reacting alkynes of the general formula II where R1 and R2 are each as defined above, with carbon monoxide and water in the presence of a rhodium catalyst under pressures from 20 to 300 bar and hydrogenating the unhydrogenated 2(5H)-furanone intermediates comprises a) reacting the carbonylation reaction mixture with hydrogen at from 150 to 250° C. and from 100 to 300 bar, b) removing the precipitated catalyst and returning it into the carbonylation reaction, and c) subjecting the catalyst-free reaction mixture to a distillation to recover the butyrolactone.

Abstract: The invention relates to a process for the separation of maleic anhydride from the maleic anhydride-containing reactor offgases from the preparation of maleic anhydride by the oxidation of hydrocarbons, in which this gas stream is brought into contact with a high-boiling, inert absorbent for maleic anhydride and maleic anhydride is separated from the resultant liquid absorbate phase by vapor stripping, where the stripping agent used is an alcohol, and at least some of the maleic anhydride is reacted with the alcohol to give the ester.

Abstract: In a process for isolating &agr;-ethynyl carbinols from the liquid reaction mixture from the addition of acetylene onto &agr;,&bgr;-unsaturated carbonyl compounds by distillation, the distillation is carried out continuously, the feed stream is introduced into the middle section of a distillation column (K), the major part of the water is distilled off azeotropically together with the solvent at the top of the column, and the &agr;-ethynyl carbinol target product is taken off below the feed point to the column.

Abstract: In a process for carrying out an exothermal reaction, selected from the addition reaction of organomagnesium halide compounds to carbonyl compounds and the ensuing hydrolysis of the addition product, a considerable fraction of the heat liberated during the reaction is removed by evaporation of the solvent.

Abstract: Vinyl formate containing formic acid, acetaldehyde and water following synthesis is separated from formic acid and water in a first distillation stage and from acetaldehyde in a second stage to give pure vinyl formate.