Patent ID: 7595035

Claim:
Process for the recovery of sulfuric acid comprising: (a) contacting a stream containing sulfuric acid vapor and/or sulfur trioxide in an absorption stage with a ionic liquid absorbent, wherein the ionic liquid absorbent comprises a mixture of bisulfate and sulfuric acid, said bisulfate comprising at least one of the salts from the group R 3 NH HSO 4 , LiHSO 4 , NaHSO 4 , KHSO 4 , RbHSO 4 , CsHSO 4 , where R═H—, alkyl, aryl and wherein the content of sulfuric acid in the mixture is 5 to 90 wt %, (b) withdrawing a gas substantially free of sulfuric acid vapor and/or sulfur trioxide from said absorption stage, (c) withdrawing a stream comprising the ionic liquid absorbent from said absorption stage, in which said ionic liquid absorbent contains sulfuric acid, (d) recovering sulfuric acid from said ionic liquid absorbent by passing the stream of step (c) through a separation stage, (e) withdrawing from the separation stage (d) a stream rich in sulfuric acid, (f) withdrawing from the separating step (d) a ionic liquid absorbent stream in which said ionic liquid absorbent contains sulfuric acid and returning said stream to the absorption step (a).