Coalescence-adsorption coupling treatment instead of alkaline washing-water washing process for efficient removal of sulfuric acid and sulfates

Abstract

C4 alkylate oil is an ideal blending component of automotive gasoline, and the green removal of sulfuric acid and sulfates from the high-temperature sulfuric acid alkylation reaction products (SAARP) has always been a hot issue in the field of clean alkylation production. In this paper, a novel coalescence separation-depth adsorption (CS-DA) coupling dry separation technique is introduced to efficiently separate acid-hydrocarbon emulsions, with the aim to supersede the alkaline washing-water washing (AW-WW) process in alkylation unit. Lateral line tests were conducted on the coupling treatment of the alkylation reaction products (ARP) produced in the STRATCO alkylation unit of Sinopec Tianjin Branch. The sulfur morphology analysis shows that the sulfides in the ARP mainly come from C4 feedstocks and alkylation reaction, including mercaptans, thioethers, thiophenes, trace hydrogen sulfide and sulfur dioxide. The mechanism of coalescence separation reveals that the efficient removal process of sulfuric acid by fiber coalescence separation also has a function similar to "pickling extraction" to remove sulfates. In addition, we investigated the influence of CS-DA coupling treatment on the total sulfur and sulfuric acid content in the ARP and performed the copper corrosion and water-soluble acid assays. The research findings indicated that the back sideline of the acid coalescer had the most outstanding separation effect relative to the front and rear lateral lines of the heat exchanger. The total sulfur content in the ARP after separation can be reduced to less than 5 mg/L, without water-soluble acid and copper corrosion (1a). The industrial application shows that the CS-DA coupling dry separation technique can completely replace the AW-WW process, which makes the various indicators of alkylate oil strictly controlled and the sulfur content up to the industrial standard. The novel dry separation technique provides a promising alternative for solving the difficulties in the emulsion treatment of high-temperature sulfuric acid alkylation and promoting the clean production of alkylation.