Combination method for increasing yield of p-xylene in aromatic hydrocarbon production

Abstract

The invention relates to a combination method for increasing the yield of p-xylene in aromatic hydrocarbon production, which mainly ensures that the problems of low concentration of p-xylene in mixed xylenes, large aromatic hydrocarbon processing circulating amount, high requirements on reaction raw materials, high energy consumption and the like in aromatic hydrocarbon production are solved. The technical scheme of the method is as follows: mixed raw materials separated from a reforming unit are adopted; C-9 aromatic hydrocarbon and a third flow of benzene, which are separated from the reforming unit, enter into a benzene and C-9 aromatic hydrocarbon alkyl transfer unit so as to be subjected to dealkylation reaction to generate a second flow of benzene, a second flow of toluene and a second flow of C-8 aromatic hydrocarbon; toluene selectivity disproportionated reaction is carried out in all toluene selectivity disproportionation units to generate C-8 aromatic hydrocarbon containing p-xylene and benzene flows, thus obtaining a third flow of C-8 aromatic hydrocarbon, a third flow of toluene and a third flow of benzene, wherein the third flow of benzene is returned to the toluene selectivity disproportionation units; the C-8 aromatic hydrocarbon and the second flow of C-8 aromatic hydrocarbon, which are separated from the reforming unit are mixed and then delivered to an absorptive separation unit so as to obtain a fifth flow of C-8 aromatic hydrocarbon; and the third flow of C-8 aromatic hydrocarbon and the fifth flow of C-8 aromatic hydrocarbon are delivered to a crystallization separation unit so as to obtain a fourth flow of C-8 aromatic hydrocarbon and pure p-xylene, wherein the fourth flow of C-8 aromatic hydrocarbon is returned to the absorptive separation unit. The problems of the prior art can be solved, and the combination method can be used for p-xylene industrial production.

Description

technical field

[0001] The invention relates to a combined method for increasing the production of p-xylene in the production of aromatic hydrocarbons. Background technique

[0002] P-xylene is one of the main basic organic raw materials in the petrochemical industry. It is widely used in many chemical production fields such as chemical fibers, synthetic resins, pesticides, medicines, and plastics. The typical production method of p-xylene is from the thermodynamically balanced xylene containing ethylbenzene, that is, C8 aromatics generated by catalytic reforming of naphtha, through multi-stage cryogenic crystallization separation or molecular sieve simulated moving bed adsorption separation (adsorption separation for short) Technology to separate p-xylene from a mixture of isomers with similar boiling points. For the treatment of ortho- and meta-xylene, C 8 A isomerization (referred to as isomerization) technology to isomerize it into p-xylene. In order to increase the p...

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