Method for recovering organic acid and cobalt-manganese metal in terephthalic acid oxidized residues

Abstract

The invention belongs to the technology for recovering organic acid and catalyst from terephthalic acid oxidized residues, which includes the steps of firstly, discharging high-temperature oxidized residues from a pure terephthalic acid (PTA for short) production device, controlling the solid content within the range from 20% to 45% and implementing primary filtering separation within the temperature range from 55 DEG C to 90 DEG C, and directly vending separated solid for manufacturing resin or paint or returning the separated solid to an oxidation reactor for use, wherein primary filtrate is treated according to the process: (I) adding oxalic acid to obtain cobalt-manganese oxalate precipitation, obtaining cobalt-manganese oxalate by means of filtering separation, further cooling the filtrate by means of filtering separation, utilizing the separated solid for extracting benzoic acid and delivering the filtrate to a waste water treating device; or (II) directly cooling the primary filtrate for secondary filtering separation, utilizing the separated solid for extracting benzoic acid, adding oxalic acid into secondary filtrate to obtain cobalt-manganese oxalate precipitation, obtaining cobalt-manganese oxalate by means of filtering separation and delivering the filtrate to a waste water treating device; and secondly, carrying out reaction of the cobalt-manganese oxalate obtained from (I) or (II) with oxidant such as hydrogen peroxide, peroxyacetic acid, bromine, manganate, permanganic acid, manganese dioxide or / and hydrobromic acid, utilizing cobalt acetate aqueous liquor, cobalt bromide aqueous liquor, manganese acetate aqueous liquor, manganese bromide aqueous liquor, acetic acid or / and pure water as dissolvent, then carrying out reaction of the cobalt-manganese oxalate with metallic cobalt, metallic manganese or / and hydrobromic acid after the cobalt-manganese oxalate is completely dissolved, and obtaining homogeneous phase liquor containing cobalt-manganese bromide ions by means of purification and filtration, wherein the mixed liquor can be directly mixed with cobalt acetate, manganese acetate, cobalt bromide, manganese bromide, acetic acid or water to serve as oxidation catalyst for the terephthalic acid.

Description

technical field [0001] The invention relates to the technical field of recovery and reuse of organic acids and cobalt-manganese metals in terephthalic acid (PTA for short) oxidation residues. In more detail, the residue containing organic acids and cobalt-manganese metals removed from the mother liquor evaporator of the PTA unit is filtered to separate the water-insoluble organic acid solids, and the filtrate is further processed to recover organic acids, cobalt-manganese compounds and the recovered cobalt-manganese compounds. The homogeneous treatment returns to the field of recycling of the PTA oxidation system. Background technique [0002] At present, the production method of PTA is to use cobalt-manganese-bromine compounds as catalysts to oxidize p-xylene through high-temperature liquid phase air. These cobalt-manganese-bromine compounds include cobalt acetate, cobalt bromide, manganese acetate, manganese bromide, hydrogen Bromic acid, tetrabromoethane, etc. In order ...

AI Technical Summary

Problems solved by technology

[0005] The disadvantages of the method of Mitsui Chemicals are: only about 70% of the cobalt and manganese catalysts are recovered, and the energy consumption is high, the equipment is many, the pipelines are easy to block, and the waste of water is large; there are iron, nickel and other impurity ions in the recovered cobalt-manganese catalysts The accumulation of cobalt and manganese ions has defects such as unstable valence state and reduced activity; in addition, all organic acids are sent to incineration, which pollutes the environment; the ion exchange method has complex treatment devices and treatment processes, introduces a large number of other chemical substances, and increases waste emissions , increased waste water treatment, high cost and other defects, the instability of PTA residue composition also increases the difficulty and complexity of ion exchange pretreatment, this method does not mention the recovery of organic acids

[0006] The defect of the oxalate recovery method adopted by DuPont is that oxalic acid or aqueous solution is directly added to the mother liquor extracted from the PTA device, and the precipitate generated by oxalic acid and cobalt manganese is mixed with the insoluble organic acid in the residue liquid to form a A viscous substance is separated by a finned centrifuge. The viscous substance is easy to adhere to the separation equipment and is not easy to separate, and the pipeline and equipment are also easily blocked. At the same time of separation, more than 90% of the separated liquid needs to be separated. Return to flush, so the actual efficiency of the separation equipment is very low, and the solid mixture of cobalt-manganese oxalate and organic acid is obtained. When the mixture is dispersed in aqueous acetic acid solution, it is mixed with fresh catalyst to form a heterogeneous solution. During application, only The purpose of reuse can be achieved by increasing the temperature of the PTA oxidation reactor and reducing the circulation volume of the recovered dispersion liquid. This is also the reason why DuPont PTA technology uses high-temperature oxidation at present, but the increase in temperature will make the raw material PX (p-xylene) used in the manufacture of PTA abbreviation) and acetic acid consumption increased significantly, and the side reactions were significantly intensified; in addition, the process still uses incineration to treat the residues after the separation of cobalt manganese oxalate and acetic acid, which causes environmental pollution