Method for purifying terephthalic acid from waste material

Abstract

The invention discloses a method for purifying terephthalic acid from waste materials, which comprises the following process steps: first washing terephthalic acid or alkali weight reduction waste to form a suspension, adding alkali compounds, and filtering to obtain a filtrate, Add a compound finishing agent to the filtrate, and then filter to obtain the filtrate; add an acid compound to the filtrate for acidification, and then wash the filter material with water. After the filter material is dried, it is a crude product of terephthalic acid with a terephthalic acid content of 98%. , and then add a compound solvent to the crude product of terephthalic acid to dissolve it at a temperature of 110-120°C to form a saturated solution, crystallize and precipitate terephthalic acid crystals after cooling down, then add sprinkles for washing, filter and dry , to obtain a refined product of terephthalic acid with a content of more than 99.5%. The dual treatment method has relatively simple process, small investment scale, strong applicability, easy mastery and control of process technology, high utilization rate of solvent, low economic operation cost, and remarkable economic and social benefits.

Description

technical field [0001] The invention relates to a method for purifying waste materials, in particular to a method for purifying terephthalic acid from chemical waste materials. Background technique [0002] Purified terephthalic acid is an important chemical industry raw material, which is widely used in the production of chemical fibers, coatings, plastics, polyester chips and plasticizers and other products. In the process of preparing terephthalic acid, due to various reasons, part of terephthalic acid will leak into the waste water pool along with the by-products generated in the reaction process, and the average total weight of waste materials leaked into the wastewater tank accounts for about 1%-2% of the total weight of phthalic acid, because terephthalic acid is insoluble in water, and deposits to form sludge waste, these precipitated sludge waste contains an average of 50-80%% terephthalic acid,. With the continuous expansion of the production scale of terephthalic...

AI Technical Summary

Problems solved by technology

These wastes have been treated by deep burial or mixed combustion with other fuels, and a large amount of black dust will be produced after mixed combustion. Therefore, this treatment not only wastes the important terephthalic acid materials in the waste, but also seriously pollutes the environment. , does not comply with relevant national policies

At present, the treatment methods for the above-mentioned terephthalic acid wastes are mainly to salvage regularly and irregularly, and then dry naturally after a period of time to form solid black sludge wastes. The content of terephthalic acid in this black sludge wastes is only 50-80%, it can only be used as a raw material for the production of fireworks for export, and has an obvious sour smell, and cannot be used in industrial production such as coatings, plastics, polyester chips and plasticizers

With the continuous development of chemical science and technology, there are new improvements in the treatment methods of this terephthalic acid waste. The new treatment methods roughly include the following types: the first category belongs to the crude method, mainly including water washing method, lye acid analysis method and solvent dissolution method; the second category belongs to the refining method, mainly including rotary vacuum washing method, pressurized multi-stage countercurrent washing method and rotary pressure washing transition method, and the water washing method and lye acid analysis method in the first category of treatment methods Although the treatment process is relatively simple, the content of the purified terephthalic acid is lower than 95%, the ash content is high, and the organic impurities in the waste cannot be removed, and it is only suitable for purifying the sludge discharged during the preparation of terephthalic acid Waste materials cannot be used to purify alkali and reduce waste materials. Although the solvent dissolution method in the first type of treatment method has high purification precision, it cannot remove harmful impurities. The purification process is long and must be repeatedly dissolved and washed. The use of solvents consumes Large amount and high purification cost; although the second type of treatment method has high purification precision and can reach the polymerization level, the plant equipment used for purification is huge, the investment scale is large, water and electricity consumption is quite large, and the process technology is not easy to control

For example, Yangzi Petrochemical Kangtai Industrial Co., Ltd. applied for a patent application with the application number 2004100138821. There are two main problems in the method for purifying terephthalic acid in this invention patent. One is that the treatment process is long and the equipment costs a lot; The content of terephthalic acid extracted from terephthalic acid sludge waste is generally about 90%, and the highest is not more than 96%. It can only be used as plasticizer, anti-aging agent and tanning agent in low- and medium-level industries. The use of solvents; and the fatty saponification multiple distillation method developed by Tsinghua University, and the acid-base method developed by Tianjin University. Their common characteristics are that the process is relatively simple and the investment scale is small, but the purification from terephthalic acid sludge waste The content of terephthalic acid is less than 96%, and the scope of use is also subject to some restrictions