Abstract: In order to widen the range of SINOALKY sulfuric acid alkylation unit feedstock, improve the yield of alkylated oil and solve the problem of high vapor pressure of gasoline in summer, a petrochemical company has carried out the industrial practice of adding a small amount of gas-fractionated C₅ fraction into the alkylation unit. In August 2021, it was found that the pressure difference in the reaction feed pipeline of the alkylation unit was abnormally increased by 0.6 MPa. The site pressure measurement showed that the blockage was in the reaction feed pipeline of the alkylation unit and the related equipment. Through the detection and analysis of various analysis methods, it was determined that the main reason for the increase of pressure difference in the feed pipelines and equipment of the alkylation reactor was that there were trace impurities of N-methyldiethanolamine in the C₅ fraction. Those trace impurities reacted with the sulfur dioxide in the circulating isobutane to form a brownish-yellow amine sulfite salt, resulting in the clogging of the feed pipeline and equipment. Through the innovation of process facilities, the addition of gas-fractionated C₅ water washing and agglomeration dewatering process, the production practice has proved that this gas-fractionated C₅ processing method had a good effect on removing impurities. The mass concentration of nitrogen in the washing water and the total outlet of the neutralization tank was controlled at 126.2 mg/L and 47.5 mg/L, respectively. The pH of water samples from the total discharge of the neutralization tanks was stable at 6-7. At the same time, the quality of the alkylated oil product was also up to the standard, and the continuous blending of gas-fractionated C₅ has been successfully realized. It provides a strong theoretical support for the research and application of this method.

Key words: alkylation catalyzed by sulfuric acid, gas-fractionated C₅, raw materials, impurities, clogging, water washing