GB676606A - Process for the purification of spent sulphuric acid - Google Patents

Abstract

Carbon and carbonaceous material are removed from spent sulphuric acid, e.g. that derived from a process for producttion of alcohols from olefins, by mixing with not more than 15 per cent by weight of a water-soluble anionic surface-active agent, blowing a non-reactive gas, e.g. air, nitrogen, carbon dioxide, or furnace gases, through the resulting mixture, allowing the acid to settle and separating the lower layer of cleaned acid from the upper layer of carbonaceous sludge. Surface-active agents, usually present to about 0.2 per cent by weight, may be longchain alkyl acid esters of inorganic oxygen-containing polybasic acids, particularly secondary alkyl acid esters of sulphuric acid described in Specifications 459,078, 459,079, 459,080, and 459,117, [all in Group IV], or salts therof, alkyl aryl sulphonic acids or salts thereof such as dodecyl cumene and dodecyl benzene sulphonic acids, sulphonic acids or salts thereof, produced in the treatment of hydrocarbon oils with sulphuric acid or oleum, soaps such as alkalic metal stearates, oleates, or naphthenates, and sulphonated fatty acids, fatty acid esters and glycerides. About 1 per cent of an oleophilic organic liquid, e.g. liquid hydrocarbons such as a spindle oil or aromatic extract from refining mineral lubricating oils, an alcohol or ester, by-product polymers which separate on diluting or neutralizing alkyl sulphuric acid ester crude products, residues from distillation of methyl-isobutyl ketone, diisobutyl ketone, hexylene glycol, mesityl oxide, and amyl and higher alcohols, may be added to coalesce the carbon particles. The acid should be of strength 45-50 per cent by weight and treatment temperatures up to 100 DEG C may be used. Sludge from previous batches may be added to subsequent batches or in a continuous process some sludge may be recycled. Before the sludge is discarded it is diluted with water, allowed to settle, and cleaned diluted acid separated which is either used to dilute spent acid to the required strength or passed to a concentrator.