Processes for the purification of bis(2-hydroxyethyl)terephthalate
A technology for di-terephthalic acid and crude terephthalic acid is applied in the preparation of carboxylic acid esters, chemical instruments and methods, preparation of organic compounds, etc., and can solve the problems of difficult separation and removal, degradation of BHET quality, etc.
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Embodiment 1
[0155] (Preparation of starting materials)
[0156] (Pre-depolymerization)
[0157] The used PET bottles (bottles made of polyethylene terephthalate) mixed with 10% by weight of colored PET bottles were crushed into pieces with an average size of 8mm square, and 57kg of the used PET bottles (bottles made of polyethylene terephthalate) -Hydroxyethyl) ester (BHET) and 25 kg of the mixture of its oligomers were put into an 800L autoclave with a stirrer, and pre-depolymerization was carried out under normal pressure and 250°C.
[0158] (Depolymerization)
[0159] Next, 418 kg of ethylene glycol (EG) and 0.23 kg of sodium hydroxide as a depolymerization catalyst were added to the pre-depolymerized polymer, and the depolymerization reaction was carried out under the conditions of a pressure of 0.15 MPa and a temperature of 220° C. to obtain 500 kg of a depolymerization reaction solution.
[0160] (Removal of solid foreign matter)
[0161] The solution was cooled to 180°C, and solid fore...
Embodiment 2
[0174] (Preparation of starting materials)
[0175] The same method as in Example 1 was performed.
[0176] (Crystallization process)
[0177] Except that the crystallization temperature was 15°C, the same method as in Example 1 was performed. The average particle size of the precipitates was 61 μm.
[0178] (Solid-liquid separation process)
[0179] The same method as in Example 1 was carried out to obtain a filter cake.
[0180] As a result, 150 kg of a filter cake containing 61% by weight of crude BHET (a collection rate of 30% by weight) and 350 kg of a filtrate with a solid content concentration of 2.5% by weight (a collection rate of 70% by weight) were obtained. This filter cake contains 2.3% by weight of DEG ester.
[0181] From these facts, generally, lowering the crystallization temperature can be expected to increase the crystallization efficiency. In the present invention, it is confirmed that the solid content concentration in the filtrate and the solid content concen...
Embodiment 3
[0198] (Preparation of starting materials)
[0199] The same method as in Example 1 was performed. The obtained deionization treatment solution was purified by the distillation process shown in FIG. 1 and used as a raw material.
[0200] (The first stage evaporation process)
[0201] The starting material was supplied to the falling film evaporator in the first stage at a supply rate of 138 kg / h, and low boiling point components were evaporated under the conditions of a temperature of 150°C and a pressure of 500 Pa. The evaporation treatment time was 3.6 hours, the amount of the first condensate produced by cooling the low-boiling components was 109 kg / h, and the production amount of the first molten liquid was 29 kg / h.
[0202] Table 2 shows the total amount of EG and free DEG and the oligomer content in the first molten liquid.
[0203] (The second stage evaporation process)
[0204] Next, the first molten liquid was supplied to the falling film evaporator of the second stage at...
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Abstract
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