Abstract: Gases containing CO.sub.2 and/or H.sub.2 S in a first absorption stage, at from 40.degree. to 100.degree. C., with an aqueous absorption liquid containing from 20 to 79% by weight of methyldiethanolamine, the gas obtained at the top of the first absorption stage is fed to a second absorption stage in which, it is treated at from 30.degree. to 90.degree. C. with an aqueous absorption liquid which contains from 20 to 79% by weight of methyldiethanolamine and has a lower content of CO.sub.2 and/or H.sub.2 S than the absorption liquid fed into the first absorption stage, the treated gas is taken off at the top of the second absorption stage, the aqueous absorption liquid obtained at the bottom of the second absorption stage and preladen with CO.sub.2 and/or H.sub.2 S is fed to the top of the first absorption stage, the aqueous absorption liquid obtained in the lower part of the first absorption stage and laden with CO.sub.2 and/or H.sub.

Abstract: But-2-enes are obtained from C.sub.4 -hydrocarbon mixtures which contain but-1-ene and may or may not contain but-2-enes by catalytic isomerization of the but-1-ene to but-2-enes in an isomerization zone at elevated temperatures by a process in which the isomerization is carried out in combination with a distillative separation zone, the said hydrocarbon mixture being fed to the isomerization zone and/or distillative separation zone, the isomerization mixture obtained from the isomerization zone is passed into the distillative separation zone, a but-1-ene-containing fraction is removed above the lower third of the distillative separation zone and passed into the isomerization zone, and the but-2-enes or a fraction containing these are or is removed in the lower third of the distillative separation zone.

Abstract: Isoprene is recovered from a C.sub.5 -hydrocarbon mixture containing isoprene, penta-1,3-diene and cyclopentadiene by separating the said mixture by liquid-liquid extraction or extractive distillation with the aid of a selective solvent, in combination with a distillation upstream or downstream from the liquid-liquid extraction or extractive distillation, by a method in which a stream containing penta-1,3-diene and cyclopentadiene is separated off in the upstream or downstream distillation and is catalytically hydrogenated, and the hydrogenated stream is fed to the upper part of the liquid-liquid extraction or extractive distillation.

Abstract: A C.sub.4 -hydrocarbon mixture which essentially contains n-butenes and butanes is separated by a process in whichthe mixture is reacted with a carboxylic acid in the presence of an acidic catalyst to form a butyl carboxylate,the reaction mixture obtained from the esterification zone is distilled to give, as the top product, a fraction containing the butanes, and, as the bottom product, a fraction containing the resulting butyl carboxylate,the butyl carboxylate is decomposed at elevated temperatures to give the carboxylic acid and n-butenes, andthe mixture of n-butenes and carboxylic acid is then distilled, the n-butenes being obtained as the top product, and the carboxylic acid as the bottom product.

Abstract: CO.sub.2 and/or H.sub.2 S are removed from gases which contain CO.sub.2 and/or H.sub.2 S by a process in which the said gas is treated, in an absorption stage at from 40.degree. to 100.degree. C., with an aqueous absorption liquid containing from 20 to 70% by weight of methyldiethanolamine, the treated gas is taken off at the top of the absorption stage, the aqueous absorption liquid laden with CO.sub.2 and/or H.sub.

Abstract: CO.sub.2 and/or H.sub.2 S are removed from gases which contain CO.sub.2 and/or H.sub.2 S by means of an aqueous absorption liquid containing an alkanolamine, by a process wherein the said gas is treated, in an absorption stage, at from 40.degree. to 100.degree. C., with an aqueous absorption liquid containing from 20 to 70% by weight of methyldiethanolamine, the treated gas is taken off at the top of the absorption stage, the aqueous absorption liquid laden with CO.sub.2 and/or H.sub.2 S is taken off at the bottom of this stage and is regenerated by being let down in two or more flash stages, and the final flash stage is operated under reduced pressure and the regenerated absorption liquid is recycled to the absorption stage.

Abstract: CO.sub.2 and, where relevant, H.sub.2 S are removed from natural gases which contain CO.sub.2 and may or may not contain H.sub.2 S by a process in which the said natural gases are treated, in an absorption stage at from 40.degree. to 100.degree. C., with an aqueous absorption liquid containing from 20 to 70% by weight of methyldiethanolamine, the treated natural gases are taken off at the top of the absorption stage, the aqueous absorption liquid laden with CO.sub.2 and, where relevant, H.sub.2 S is taken off at the bottom of the absorption stage and then regenerated in one or more flash stages, and the regenerated absorption liquid is recycled to the absorption stage.

Abstract: A process for isolating isobutene from C.sub.4 -hydrocarbon mixtures containing isobutene by reacting the mixture with a primary alcohol in the presence of an acid condensing agent, to form the tertiary ether, separating off the unconverted hydrocarbons and decomposing the tertiary ether in the presence of an acid catalyst at an elevated temperature, wherein a primary C.sub.3 - or C.sub.4 -alcohol is used and the temperature at which the reaction mixture leaves the etherification stage, in which the tertiary ether is formed, is lower than the mean temperature in the etherification stage.

Abstract: A process for removing condensable aliphatic hydrocarbons and acidic gases such as H.sub.2 S, CO.sub.2 and COS from natural gas containing these, wherein the natural gas is initially treated with polyethylene glycol dialkyl ethers, as the solvent, in a first absorption stage to effect absorption of the condensable aliphatic hydrocarbons; the natural gas drawn off from the first absorption stage is then treated with polyethylene glycol dialkyl ethers, as the solvent, under superatmospheric pressure in a second absorption stage, the acidic gases being completely or partly absorbed; the solvent charged with the condensable aliphatic hydrocarbons which is obtained from the first absorption stage is treated with water in an extraction stage, to form a hydrocarbon phase containing the condensable aliphatic hydrocarbons and an aqueous dialkyl ether phase, and the hydrocarbon phase is separated from the aqueous dialkyl ether phase.

Abstract: An aqueous solution containing from 0.81 to 1.3 moles of piperazine per liter is used as a washing agent for removing impurities such as H.sub.2 S, CO.sub.2 and COS from gases. Piperazine can also be used, in amounts of up to 0.8 mole per liter, together with physical or chemical solvents, to accelerate the absorption of H.sub.2 S, CO.sub.2 and COS. The washing process is used for natural gases, coke-oven gases, gases from the gasification of coal and synthesis gases, of any origin.

Abstract: Acid constituents, eg. H.sub.2 S and CO.sub.2 or their mixtures, are removed from industrial gases or natural gases by means of a washing agent which contains the methyl isopropyl ethers of polyethylene glycols. The washing can be carried out with simultaneous drying of the gas, especially in the case of natural gases, since the anhydrous ethers are able to absorb water.

Abstract: A process for conjointly preparing methyl tert.-butyl ether and obtaining isobutene from an isobutene-containing C.sub.4 -hydrocarbon mixture. In the process the C.sub.4 -hydrocarbon mixture is reacted, in one or more etherification stages, with methanol and a primary C.sub.3 - or C.sub.4 -alcohol in the presence of an acid condensing agent, the resulting reaction mixture or mixtures are then separated into a fraction containing the unconverted hydrocarbons, the methyl tert.-butyl ether and a fraction containing the C.sub.3 - or C.sub.4 -alkyl tert.-butyl ether. Thereafter, the C.sub.3 - or C.sub.4 -alkyl tert.-butyl ether is decomposed at an elevated temperature, in the presence of an acid catalyst, into isobutene and primary C.sub.3 - or C.sub.4 -alcohol.

Abstract: A process for isolating a conjugated diolefin from a C.sub.4 - or C.sub.5 -hydrocarbon mixture containing the diolefin, by single-stage or multi-stage extractive distillation using a selective solvent, wherein the selective solvent is a solvent mixture which comprises(a) from 50 to 99 percent by weight of a selective solvent boiling at from 140.degree. C. to 260.degree. C. and(b) from 1 to 50 percent by weight of an organic solvent boiling at from 45.degree. C. to 125.degree. C.

Abstract: A process for simultaneously removing water and hydrogen sulfide from gases containing both of these by treating the gases, in an absorption zone under superatmospheric pressure, with polyethylene glycol dialkyl ethers as a solvent, stripping the hydrogen sulfide from the loaded solvent, obtained from the absorption zone, in a desorption zone, removing the water, taken up in the absorption zone, from the solvent and recycling the regenerated solvent to the absorption zone, wherein the solvent additionally contains from 0.01 to 20% by weight, based on the solvent mixture, of an alcohol or ether boiling in the range from 50.degree. to 140.degree. C.

Abstract: A process for isolating butadiene, with the aid of a selective solvent, from a C.sub.4 -hydrocarbon mixture which contains butadiene and small amounts of styrene and may contain oxygen, hydrocarbons more soluble than butadiene in the selective solvent and hydrocarbons less soluble than butadiene in the selective solvent, in which process the C.sub.4 -hydrocarbon mixture is separated by extractive distillation into a distillate which contains the less soluble hydrocarbons, a stream of butadiene and a stream containing the more soluble hydrocarbons, and in which a mixture of styrene and C.sub.4 -hydrocarbons is removed from the C.sub.4 -hydrocarbon mixture in a distillation zone upstream of the extractive distillation, the top product of the said distillation zone being fed to the extractive distillation.

Abstract: A process for obtaining isobutene from a C.sub.4 -hydrocarbon mixture containing isobutene, by reacting the mixture with a primary alcohol in the presence of an acid condensing agent and decomposing the resulting tertiary ether in the presence of an acid catalyst at an elevated temperature, wherein a primary C.sub.3 - or C.sub.4 -alcohol is used.

Abstract: A process for isolating a conjugated diolefin from a C.sub.4 - or C.sub.5 -hydrocarbon mixture containing the diolefin, by single-stage or multi-stage extractive distillation using a selective solvent, wherein the selective solvent is a solvent mixture which comprises(a) from 1 to 99 percent by weight of an N-alkyl-substituted lower aliphatic acid amide or of an N-alkyl-substituted alicyclic acid amide having 5 ring members and(b) from 1 to 99 percent by weight of an aliphatic or alicyclic ether boiling at from 30.degree. C. to 200.degree. C.

Abstract: A process for isolating a conjugated diolefin from a C.sub.4 - or C.sub.5 -hydrocarbon mixture containing the diolefin, by single-stage or multi-stage extractive distillation using a selective solvent, wherein the selective solvent is a solvent mixture which comprises(a) from 1 to 99 percent by weight of an N-alkyl-substituted lower aliphatic acid amide or of an N-alkyl-substituted alicyclic acid amide having 5 ring members and(b) from 1 to 99 percent by weight of an lower aliphatic carboxylic acid ester or carbonic acid ester boiling at from 30.degree. C. to 200.degree. C.

Abstract: A process for isolating 1,3-butadiene by means of a selective solvent from a C.sub.4 -hydrocarbon mixture which contains 1,3-butadiene, propyne, hydrocarbons which are more soluble than 1,3-butadiene in the selective solvent and hydrocarbons which are less soluble than 1,3-butadiene in the selective solvent, wherein the C.sub.4 -hydrocarbon mixture is separated, using one or more extractive distillation zones, into a distillate containing the less soluble hydrocarbons, a stream of 1,3-butadiene and a stream containing the more soluble hydrocarbons, and the propyne is separated off either by distillation of the C.sub.

Abstract: A process for isolating butadiene by means of a selective solvent from a C.sub.4 -hydrocarbon mixture which contains butadiene, small amounts of oxygen, hydrocarbons which are more soluble than butadiene in the selective solvent and hydrocarbons which are less soluble than butadiene in the selective solvent, wherein the C.sub.4 -hydrocarbon mixture is separated, by extractive distillation, into a distillate containing the less soluble hydrocarbons, a stream of butadiene and a stream containing the more soluble hydrocarbons, a mixture of oxygen and C.sub.4 -hydrocarbons is separated out of the C.sub.4 -hydrocarbon mixture in a distillation zone upstream of the extractive distillation, and the bottom product is fed to the extractive distillation.