GB855421A - Purification of gases - Google Patents

Abstract

855,421. Purifying gases. HUMPHREYS & GLASGOW Ltd. Aug. 16, 1957 [Aug. 24, 1956], No. 26020/56. Class 55 (2). Hydrogen sulphide is removed from a gas by washing it with a solution of chelated iron in the ferric state, the chelated iron being able to exist dissolved in the solution in both the ferric and the ferrous states, and when in solution being reducible by hydrogen sulphide from the ferric to the ferrous state and readily oxidizable from the ferrous to the ferric state, the solution after contacting the gas being regenerated by oxidation for re-use. The chelating agents may be amino acids such as polyamino polycarboxylic acids in which the amino groups are separated from each other by at least two carbon atoms. The amino acid may be of the type in which at least two of the groups X are selected from the class consisting of acetic acid and propionic acid residues and in which R is an alkyl group with at least two carbon atoms in the chain. Alternatively R may be cyclohexane, the nitrogen atoms being attached to the ring in the 1.2 positions. In another form, R is a benzene ring, the nitrogen atoms being substituted for hydrogen atoms in the 1.2 positions and chlorine or a methyl group being substituted for hydrogen in at least one of the positions 3 and 6 in the ring. Examples of suitable amino acids are ethylene diamine tetra acetic acid, ethylene diamine tetra propionic acid, 1.2 diaminocyclohexane N.N<SP>1</SP>-tetra acetic acid, 1.2 diaminocyclohexane N.N<SP>1</SP>-tetra propionic acid, di-ethylene triamine penta acetic acid, N-hydroxyethyl ethylene diamine triacetic acid. In preparing the solution of chelated iron, salts such as alkali metal salts of the acids may be used. The chelated iron solution may be alkaline or not, the hydrogen ion concentration being adjusted by the addition of bases, such as secondary or tertiary aliphatic amines and amino alcohols, or acids such as sulphuric acid.