Propylene oxide/styrene co-production technology (RHPOSM)
Propylene oxide is the third largest propylene derivative after polypropylene and acrylonitrile. It is mainly used in the production of polyether and propylene glycol. Its derivatives are widely used in industries such as automobiles, construction, food, tobacco, medicine and cosmetics. . Nearly 100 kinds of downstream products have been produced, which are important raw materials for fine chemical products.
In industry, propylene oxide production technology mainly includes chlorohydrin method and indirect oxidation method. The characteristics of the production of propylene oxide by the chlorohydrin method are that the process is relatively short, the process is mature, and the construction investment is small; but the production of propylene oxide by the chlorohydrin method will produce a large amount of waste water containing calcium chloride, and the environmental pollution is very serious. Since 2011, the approval of the new chlorohydrin process propylene oxide plant has been suspended.
At present, all domestic propylene oxide plants using indirect oxidation process adopt foreign technology. Changzhou Ruihua Chemical has incorporated indirect oxidation propylene oxide technology into the scope of research and development from the beginning of the company. After five years of development, it has successfully developed propylene oxide/styrene co-production (PO/SM) and propylene oxide/benzene. The complete process technology of ethylene co-production (PO/AMS) has made up for the blank of domestic indirect oxidation propylene oxide technology.
The process of propylene oxide/styrene co-production includes four parts: ethylbenzene peroxidation, epoxidation, phenethyl alcohol dehydration and acetophenone hydrogenation.
The ethylbenzene peroxidation reaction is carried out in three bubble column reactors. The liquid phase ethylbenzene enters the first reactor, and the air enters the three middle reactors respectively. The ethylbenzene reacts in the reactor to produce ethylbenzene hydrogen peroxide. After reaching a certain concentration, it enters the next reactor. After three reactors, the ethylbenzene hydrogen peroxide content in the material is about 11~13%, and then it enters the concentration tower to increase the peroxide concentration and then enters the epoxidation reactor for reaction.
The epoxidation reactor is a series of horizontal reactors. The liquid propylene enters from the first reactor, and then enters the next reactor in turn, while the ethylbenzene hydrogen peroxide enters each reactor separately. In the epoxidation reactor, propylene is oxidized to propylene oxide, and ethylbenzene hydrogen peroxide is converted to phenethyl alcohol and acetophenone. After the epoxidized product is recovered from propylene, crude propylene oxide is separated, and then after light-removal, heavy-weight, and extraction separation, polymer-grade propylene oxide is obtained.
The acetophenone produced by epoxidation is hydrogenated to produce phenethyl alcohol, which is dehydrated to produce styrene. After the crude styrene is refined and separated, polymer-grade styrene is obtained.
The raw material ethylbenzene used in the POSM process must be produced by the alkylation of ethylene benzene, and the purity of ethylbenzene>=99.8%; the raw material propylene must meet the requirements of high-quality products in GB 7716-2002.
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