Abstract: A process for removing acid gases from natural or synthesis gases by absorption, comprising the following stages:(a) cooling the natural or synthesis gas to be purified to condense part of the CO.sub.2 contained in said gas;(b) feeding the cooled and partly condensed gas to an absorption column in order to reduce the acid gas content to the required value;(c) regenerating the solvent or solvents used in the acid gas absorption, the solvent or solvents used being chosen from esters, alcohols and ethers of low molecular weight.

Abstract: A cryogenic process for removing acid gases from natural or synthesis gases, comprising the following stages:(a) feeding the natural or synthesis gas to a first absorption column in order to absorb the H.sub.2 S;(b) cooling the substantially H.sub.2 S-free gas to condense part of the CO.sub.2 contained in said gas;(c) feeding the cooled and partly condensed gas to a second absorption column in order to reduce the CO.sub.2 content to the required value;(d) regenerating the solvent or solvents used in the acid gas absorption, the solvent or solvents used being chosen from esters, alcohols or ethers, of low molecular weight.

Abstract: A process is described for stripping acidic gases, mainly hydrogen sulphide and carbon dioxide, from natural gas or synthesis gas, especially when the percentages of such acidic gases are high and the conventional processes become economically objectionable.The process is based on the use of a number of selective solvents, generally belonging to the class of esters, ethers, mixed ester-ethers and lactones, in combination with sequential absorbing cycles which start from the stripping of hydrogen sulphide, and comprise the regeneration of the solvents used by several expansion cycles: H.sub.2 S and CO.sub.2 are recovered and the regenerated solvents recycled.

Abstract: Low temperature treatments are combined with solvent treatments using particularly selective solvents for stripping acidic gases such as carbon dioxide and hydrogen sulphide from natural gas or from synthetic gases.The preferred solvents are a wide range of compounds having an esteric or an etheric function in their molecule, but there are also examples of compounds which have the two functions simultaneously.The stripping process is comparatively simple, is efficient, especially for high contents of acidic gases in the raw gas streams, and is economically acceptable.

Abstract: A method for separating benzene, toluene, xylenes and higher aromatics from admixtures containing them is disclosed, said method being based on the use of a solvent which is a 5-atom cyclic derivative of urea in which at least one of the nitrogen atoms is bound to an alkyl.Representative of this class of selective solvents is N,N'-dimethyl ethylene urea.Procedure details and examples are given.

Abstract: A diolefin (isoprene or butadiene) is separated from a mixture thereof with other hydrocarbons by feeding the mixture to an extractive distillation column at a point intermediate its ends and also feeding to that column, at a point adjacent its upper end, an imidazole derivative, such as N-methyl imidazole, which is a solvent for the diolefin, withdrawing substantially all of the other hydrocarbons from the upper end of the column and withdrawing the solvent, substantially all of the diolefin and the balance of the other hydrocarbons as bottom product from that first extractive distillation column. That bottom product is then fed to a second extractive distillation column, the diolefin is withdrawn from its upper end in substantially pure form, the balance of the other hydrocarbons are withdrawn in vapor phase and the solvent is withdrawn from the lower end of the second extractive distillation column for recycle to the first and second extractive distillation columns.

Abstract: Styrene of exceptional purity is separated from a mixture of hydrocarbons including it, xylenes, saturated and olefinic hydrocarbons and ethyl benzene by means of a two-step extractive distillation process through the use of a high boiling polar solvent such as N-formyl morpholine in admixture with an amount of water in the range of from 1% to 30% by weight.