Pilot Study On Freezing Treatment Of Spherical Catalyst Mother Liquor

A series of spherical catalyst belongs to the fourth generation Ziegler-Natta spherical catalyst for polypropylene, which is now widely used in Spheripol polypropylene technology and loop process of Sinopec. Meanwhile, spherical catalyst is one of the major polyolefin catalysts that hold the largest sales volume. The catalyst was developed by the Beijing Chemical Industry Research Institute and produced by Sinopec Catalyst Co., Ltd. Beijing Aoda Branch(referred as Aoda), which performed the largest production among all products.Titanium tetrachloride was one of the major raw materials for industrial production process of spherical catalyst, which was easily taking reaction with air and water to produce corrosive gas of hydrochloric acid. Therefore, increasing the recovery of titanium tetrachloride during production process will lead to higher economic and social benefits for Aoda’s production.The study started with distillation process of mother liquor, which was the largest consumption session of titanium tetrachloride during the production process. After careful research and analysis as well as organization of lab trials and pilot study, we finalized the new process route of mother liquor treatment including cooling of mother liquor, washing and drying of precipitated solids and further distillation of coolant.The way of cooling impurity on mother liquor improved the recovery of titanium tetrachloride in mother liquor as well as avoided the risk of coking and scaling of concentrate in the bottom of reactor via original high temperature distillation technology. Freezing precipitation under the optimum condition was able to achieve resource utilization without hydrolysis treatment, which resulted in cost reduction of environmental treatment on waste acid produced by hydrolysis.