GB417379A - Improvements in the removal of weak gaseous acids from gases - Google Patents

Abstract

Weak gaseous acids and readily volatile liquids in the vaporous phase are simultaneously removed from gases containing them by washing the gases with true solutions, or colloidal solutions or emulsions or suspensions of difficulty volatile strong organic bases, or of salts of strong bases with weak acids, in organic solvents preferably of high boiling point. The weak gaseous acids referred to are hydrogen sulphide, carbon dioxide and cyanogen compounds such as hydrogen cyanide. The readily volatile liquids referred to are benzene, benzine, carbon disulphide alcohol, ether or acetone. Suitable organic solvents are mineral oils, tar oils, ordinary or low temperature tars, high boiling oils obtained in the destructive hydrogenation of coal &c. and alcohols of high boiling point, preferably not below 160 DEG C. Suitable bases or basic compounds are alkylamines such as dibutylamine, dodecylamine, ethylene diamine or the amine mixture obtainable by the catalytic reduction of the amides of coconut fatty acids; alkylolamines such as diethanolamine, triethanolamine or butanolamine; arylamines such as phenylenediamine or methylmetaphenyldiamine; alkylalkylolamines such as methylethanolamine, ethyldiethanolamine or butylmonoethanolamine; quinoline and its homologues or crude quinoline bases; pyridines such as pyridine, crude pyridine bases or piperidine or its homologues; quaternary ammonium bases such as tetrabutyl-ammonium hydroxide, or basic salts of strong inorganic or organic bases with weak acids, such as piperidine borate, tetramethylammonium borate, sodium phosphates, the sodium salt of alanine, sodium stearate, or alkali metal salts of amino- or nitro-phenols or amino- or nitro-naphthols or of boric acid, or salts of phenols. Aniline is too weakly basic to be suitable. The gases may be washed at room temperature and atmospheric, increased or reduced pressure, the absorbed constituents being expelled by heating. Carbon dioxide is not so readily absorbed by the solutions &c. so that it is possible to remove from gases containing, in addition to readily volatile liquids, small amounts of hydrogen sulphide with large amounts of carbon dioxide, a comparatively large proportion of only the hydrogen sulphide. In the regeneration of the solvents by heating e.g. by direct contact with steam, the liquids of low boiling point are separated in the liquid state by condensation while the gases are recovered as such. The weak gaseous acids dissolved in the condensed liquids may be expelled by heating. The weak gaseous acids may be freed from the volatile liquids by washing with oil. Examples are given which describe the treatment of coal distillation gas and coke oven gas. The Provisional Specification describes also butyldiethanolamine and the alkali metal salts of aliphatic or aromatic carboxylic acids as being suitable basic compounds. Specifications 341,584, 391,780, and 391,786 are referred to.