Patent GB-597655-A (GB)
Title: Conversion of hydrosulphides to neutral sulphur substances
IPC: C07B45/00
Filed: 1945-05-22
Abstract: Hydrosulphides including hydrogen sulphide are oxidised in aqueous alkaline solutions to neutral sulphur substances by contacting the hydrosulphides with an oxidising agent in the presence of an oxidising catalyst consisting of an aromatic compound containing at least one nitro group as a nuclear substituent in a benzene ring and in addition thereto, preferably in the same ring, at least two radicals each selected from the group consisting of the hydroxy radical and the amino radical -NH2 which may be mono-substituted by a hydrocarbon or acyl radical; the catalysts may also contain in the benzene ring other substituents such as alkyl, alicyclic, aryl, halogen, carboxyl, sulphonyl and phosphonyl radicals and are preferably nitro diamino-, nitro dihydroxy- or nitro amino hydroxy-benzenes.  The process may be applied to the regeneration of alkaline solutions employed in treating sour hydrocarbons and comprise extracting hydrosulphides from hydrocarbon mixtures containing them with an aqueous alkaline solution which may contain a solubility promoter for the hydrosulphides, separating the aqueous alkaline phase and treating it with an oxidising agent in the presence of one of the above mentioned catalysts to precipitate neutral sulphur substances such as sulphur and organic disulphides, removing these sulphur substances, for example, by filtration, decantation, settling or solvent extraction and recycling the resulting regenerated alkaline solution for the treatment of more sour hydrocarbons.  To prevent oxidation of the catalyst itself, it is preferred to leave some mercaptan or inorganic sulphide sulphur in the aqueous solution.  The hydrosulphides may be derived from such sources as hydrogen sulphide or mercaptan containing petroleum or coal tar liquids or gases, such as natural or coke-oven gas, gasolines and kerosenes.  The aqueous alkaline solutions for the treatment of hydrogen sulphide may comprise alkali metal and alkaline earth metal hydroxides, carbonates, phosphates, borates, arsenates, phenolates and various organic amines and for mercaptans, alkali metal hydroxides.  Solubility promoters specified comprise certain alkanols, alkanolamines, aliphatic polyamines, hydroxy and amino ethers, naphthenes, phenols and carboxylic acids.  Suitable oxidising agents are peroxides, permanganates, manganese dioxide, hypochlorites, oxygen and air.  Examples describe the regeneration of spent aqueous caustic soda containing mercaptan and sulphide sulphur extracted from gasoline, using air as the oxidising agent and picramic acid as catalyst.  Other catalysts specified are 3 and 4 nitro pyrocatechol, nitro pyrogallols, nitro-bromopyrogallols, nitro-chloro-hydroquinones, 2-forking lever 9 secured near its middle to a 3-nitro-phenol, 4-nitro-o-phenylene diamine, 2-nitro-p-phenylene diamine, 5-nitro-3-amino salicylic acid and 2-amino-4-nitro naphthol. The Specification as open to inspection under Sect. 91 is not restricted to oxidation in alkaline solution and mentions nitro-naphthazarin and nitro-anthrahydroquinone as additional examples of catalysts.  This subject-matter does not appear in the Specification as accepted.ALSO:Hydrosulphides, including hydrogen sulphide, aliphatic mercaptans and thiophenols are oxidised in aqueous alkaline solutions to neutral sulphur substances by contacting the hydrosulphides with an oxidizing agent in the presence of an oxidizing catalyst consisting of an aromatic compound containing at least one nitro group as a nuclear substituent in a benzene ring and in addition thereto, preferably in the same ring, at least two radicals each of which is selected from the group consisting of the hydroxy radical and the amino radical -NH2 which may be mono-substituted by a hydrocarbon or acyl radical; the catalysts may also contain in the benzene ring other radicals such as alkyl, alicyclic, aryl, halogen, carboxyl, sulphonyl and phosphonyl radicals and are, preferably, nitro diamino-, nitro dihydroxy- or nitro amino hydroxy-benzenes.  The process may be applied to the regeneration of alkaline solutions employed in treating sour hydrocarbons and comprise extracting hydrosulphides from hydrocarbon mixtures containing them with an aqueous alkaline solution which may contain a solubility promoter for the hydrosulphide, separating the aqueous alkaline phase and treating it with an oxidizing agent in the presence of one of the above-mentioned catalysts to precipitate neutral sulphur substances such as sulphur and organic disulphides removing these sulphur substances, for example, by filtration, decantation, settling or extraction with a suitable solvent, and recycling the resulting regenerated alkaline solution for the treatment of more sour hydrocarbons.  To prevent oxidation of the catalyst itself, it is preferred to leave some mercaptan or inorganic sulphide sulphur in the aqueous treating solution.  The hydrosulphides may be derived from such sources as hydrogen sulphide and/or mercaptan containing petroleum or coal tar liquids or gases such as natural and coke oven gases, gasolines and kerosenes.  The aqueous alkaline solutions for the treatment of hydrogen sulphide may comprise alkali metal and alkaline earth metal hydroxides, phosphates, carbonates, phenolates, borates, arsenates and various amines and for mercaptans, alkali metal hydroxides.  Solubility promoters specified comprise certain alkanols, alkanolamines, aliphatic polyamines, hydroxy and amino ethers, naphthenes, phenols and carboxylic acids.  Suitable oxidizing agents are peroxides, permanganates, manganese dioxide, hypochlorites, oxygen and air. Examples describe the regeneration of a spent aqueous caustic soda solution containing mercaptan and sulphide sulphur extracted from gasoline, using picramic acid as catalyst and air as the oxidizing agent.  Other catalysts specified are 3-and 4-nitro pyrocatechol, nitro-pyrogallols, nitro - bromo - pyrogallols, nitro - chloro - hydroquinones, 2-amino, 3-, 4-, 5- or 6-nitrophenol, 4-amino 2- and 3-nitro phenol, 4-nitro-o-phenylene diamine, 2-nitro-p-phenylene di-amine, 5-nitro-3-amino salicyclic acid and 2-amino-4-nitro naphthol.  The Specification as open to inspection under Sect. 91 is not restricted to oxidation in alkaline solution and mentions nitro-naphthazarin and nitro anthrahydroquinone as also being suitable catalysts.  This subject-matter does not appear in the Specification as accepted.