GB1005096A - Process for the removal of hydrogen sulphide from gases - Google Patents

Abstract

Gases, e.g. natural gas or refinery gas, are purified from hydrogen sulphide by absorption of the hydrogen sulphide in a solvent containing water, at least one sulphone, at least one ferrous salt and at least one chelating agent for ferrous ions, and the hydrogen sulphide-containing solvent is treated with SO2, whereby water and sulphur are formed. The water content of the solvent is preferably 2-20% by weight. The sulphone, at least 50% by weight, is preferably a hydrocarbyl sulphone, e.g. methyl ethyl, diethyl, di-n-propyl, dibenzyl or ditolyl sulphone, or tetrahydrothiophene-1,1-dioxide or 2,3-dihydrothiophene-1,1-dioxide, or substitution derivatives of these containing not more than four alkyl groups per molecule, e.g. the 2,3-dimethyl, 2,4-dimethyl, 2,5-dimethyl, 3-ethyl or 2-methyl-5-propyl derivatives of tetrahydrothiophene-1,1-dioxide. Hydroxyamino- or keto-sulphones may also be utilized. The ferrous salt, 0.5-10% by weight, may be ferrous nitrate, chloride or sulphate. The chelating agent, 0.1-5% by weight, or 0.1-1 molecule for each ferrous ion present, is any compound capable of forming one or more complexes with ferrous ions, the negative logarithm of the dissociation constant of the complexes being preferably in the range 0.2-10 in the temperature range - 1 to 150 DEG C., and suitable agents include alkyleneamine carboxylic acids, amine carboxylic acids, dicarboxylic acids, polyamines, amino acids and pyrridine carboxylic acids. Salts of these acids may also be used. The SO2 required may be obtained from part of the H2S absorbed in the solvent, e.g. by flashing off 35% of the H2S and oxidizing with air, or by oxidizing part of the sulphur produced in the process, or, at least partly, from SO2 which may be present in the gas to be treated. The gas is contacted in countercurrent with the solvent under a pressure of 70 atm. absolute, and treatment of the H2S-containing solvent is carried out at a pH between 0 and 8, and at a temperature between 26 DEG and 163 DEG C. This treatment may take place simultaneously with or subsequent to, the absorption. The solvent, after removal of sulphur and water equivalent to that formed in the reaction, is recycled.ALSO:Hydrogen sulphide in admixture with another gas, e.g. hydrogen and/or low boiling hydrocarbons, is absorbed in a solvent containing water, at least one sulphone, at least one ferrous salt and at least one chelating agent for ferrous ions, and the hydrogen sulphide-containing solvent is treated with SO2, whereby water and sulphur are formed. The water content of the solvent is preferably 2-20% by weight. The sulphone, at least 50% by weight, is preferably a hydrocarbyl sulphone, e.g. methyl ethyl, diethyl, di-n-propyl, dibenzyl or ditolyl sulphone, or tetrahydrothiophene-1, 1-dioxide or 2,3-dihydrothiophene - 1,1 - dioxide, or substitution derivatives of these containing not more than four alkyl groups per molecule, e.g. the 2,3-dimethyl, 2,4-dimethyl, 2,5-dimethyl, 3-ethyl or 2 - methyl - 5 - propyl derivatives of tetrahydrothiophene - 1,1 - dioxide. Hydroxyamino-or keto-sulphones may also be utilized. The ferrous salt, 0.5-10% by weight, may be ferrous nitrate, chloride or sulphate. The chelating agent, 0.1-5% by weight, or 0.1-1 molecule for each ferrous ion present, is any compound capable of forming one or more complexes with ferrous ions, the negative logarithm of the dissociation constant of the complexes being preferably in the range 0.2-10 in the temperature range -1 DEG to +150 DEG C., and suitable agents include alkyleneamine carboxylic acids, polyamines, amino acids and pyridine carboxylic acids. Salts of the acids may be used. The SO2 required may be obtained from part of the H2S absorbed in the solvent, e.g. by flashing off 35% of the H2S and oxidizing with air, or by oxidizing part of the sulphur produced in the process, or, at least partly, from SO2 which may be present in the gas to be treated. H2S is absorbed in countercurrent at 70 atm. abs., and treatment of the H2S-containing solvent is carried out at a pH between 0 and 8, and at a temperature between 26 DEG C. and 163 DEG C. This treatment may take place simultaneously with, or subsequent to, the absorption. The solvent, after removal of sulphur and water equivalent to that formed in the reaction, is recycled.