GB1306449A - Selective sulphide removal process - Google Patents

Abstract

1306449 Purifying natural gas CHEVRON RESEARCH CO 20 Aug 1970 [21 Aug 1969] 40249/70 Heading C5E [Also in Division C1] Gaseous sulphides are removed from natural gas by contacting the gas with a solution comprising a substituted aromatic nitrile having a substituent at least as strong electron attracting as fluorene and a hydrosulphide of K, Na, Li, NH 4 or dimethyl ammonium, or compounds which form such hydrosulphides under the reaction conditions in a substantially hydroxylfree solvent. Suitable substituents include CN, COOH, Cl, Br, I, F and exemplified nitriles include o- and p-iodo benzonitrile, p- and mbromobenzonitrile, o- and p-chlorobenzonitrile and m- and p-cyanobenzonitrile. Suitable solvents include piperidones, cyclotetramethylene sulphones, lower alkylene carbonates, dialkyl ethers of polyethylene glycol, and preferably pyrrolidones in particular N-methyl-2-pyrrolidone. The gas stream is preferably dehydrated by contacting with the solvent prior to the sulphide removal step. The absorption solution may be regenerated by first heating and flashing to a lower pressure to release any dissolved gases such as CO 2 and light hydrocarbons, then heating to a higher temperature to decompose the sulphide-nitrile reaction products. Alternatively the reaction products and the solvent may be separated by adding water to the spent absorbent to precipitate the degradation products and recovering the solvent in aqueous solution, from which it may be separated by distillation.