Process for producing purified terephthalic acid

A technology of terephthalic acid and its manufacturing method, which is applied in the direction of oxidative preparation of carboxylic acid, chemical instruments and methods, preparation of organic compounds, etc., can solve the problems of inability to separate two phases, decrease in dehydration energy, and inability to extract acetic acid, etc. The cost of equipment and machinery, the cost of maintenance and management, and the effect of reducing the frequency of failures

Inactive Publication Date: 2017-01-04
HITACHI LTD
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  • Abstract
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Problems solved by technology

[0027] However, as described in the above-mentioned Patent Document 5 or Patent Document 6, an acetic acid solution with a low water content (that is, a high-concentration acetic acid solution) and an extractant ( Entrainer) mixed in the extraction separation method described in Patent Document 7, the mixed solution is a homogeneous solution, the two phases cannot be separated, and acetic acid cannot be extracted with the entrainer (extractant)
Therefore, it can be seen that the extraction and separation method of water separation is suitable for the high-concentration acetic acid solution derived from the oxidation reaction, but the dehydration energy reduction technology described in Patent Document 7, which is combined with the dehydration distillation method, cannot be applied as described.

Method used

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  • Process for producing purified terephthalic acid
  • Process for producing purified terephthalic acid
  • Process for producing purified terephthalic acid

Examples

Experimental program
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Effect test

Embodiment 2

[0146] Use a perforated plate extraction tower with an inner diameter of 60 mm, a height of about 2600 mm, and a plate count of 25 plates (a perforated plate tower with a perforated plate with a stainless steel downcomer sandwiched between a short pipe (90 mm) with an acrylic flange) , 15% by mass aqueous acetic acid solution was supplied from the top of the tower at a rate of 170 g / min. On the other hand, butyl acetate as an extractant was continuously supplied at a ratio of 526 g / min (3.1 times by mass as a solvent ratio to the aqueous acetic acid solution) from the bottom of the column (countercurrent extraction). Then, the acetic acid extraction solution was discharged from the top of the tower, and the extraction raffinate was discharged from the bottom of the tower, and a continuous extraction test of acetic acid using butyl acetate was implemented. In addition, the average temperature of the extraction tower in which the test was carried out was about 35°C.

[0147] Th...

Embodiment 3

[0152] Use the perforated plate type extraction tower of embodiment 2, the 10 mass % acetic acid aqueous solution is from tower top with the ratio of 100g / minute, in addition, as the isobutyl acetate of extractant with the ratio of 300g / minute (as the solvent with respect to acetic acid aqueous solution The ratio is 3 mass times) to be supplied continuously from the bottom of the tower. Then, in the same manner as in Example 2, a continuous extraction test of acetic acid was implemented. In addition, the average temperature of the extraction tower in which the test was carried out was about 35°C. The results are shown in Table 4.

[0153] 【Table 4】

[0154] Discharge (g / min) Acetic acid content (mass%) Acetic acid extract (organic phase) 317 3.1 Extraction raffinate (water phase) 83 0.3

[0155] As shown in Table 4, the acetic acid content contained in the acetic acid extract was 3.1% by mass. From this result, it was found that the extracti...

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Abstract

The invention relates to a preparation method for refining terephthalic acid, and concretely provides a no-dry technology that drying of moist crystals prepared from crude terephthalic acid are dried and preparation into crystal powder are not needed and refining is carried out as an aqueous solution staying the same economically. Thus, recycle of acetic acid from crude terephthalic acid crystals by utilization of water washing is carried out efficiently and in an energy saving manner. Crystals are separated from a crude terephthalic acid crystal slurry and washed, crystals which do not containing acetic acid are recycled, and discharge water after water washing is recycled. Then the washing discharge water is subjected to extraction of acetic acid by extractants without dehydration distillation. After water is separated, the acetic acid extract is supplied to a dehydration distillation column of acetic acid and acetic acid is recycled. Then the effective relation of the acetic acid content of the washing discharge water and the amount of the extractants is calculated, and the easy water washing method reducing acetic acid loss and energy is discoveried.

Description

[0001] 【Technical field】 [0002] The present invention relates to an improvement in a method for producing purified terephthalic acid in which crude terephthalic acid is produced from p-xylene as a raw material, followed by a step of refining the crude terephthalic acid by hydrogenation. [0003] 【Background technique】 [0004] In the production of crude terephthalic acid prior to the purification of crude terephthalic acid, the raw material p-xylene is oxidized in the liquid phase, and the crude terephthalic acid produced in the acetic acid solvent is recovered at a high yield crystallization. On the other hand, the solvent acetic acid separated from the crystallization of crude terephthalic acid is also recovered, and by recycling while reducing the loss of acetic acid during recovery, an economical (specifically, production cost reduction) production method in industrial production is desired. . [0005] In a general process for producing purified terephthalic acid, first...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07C63/26C07C51/265C07C51/487
CPCC07C51/265C07C51/487C07C63/26C07C51/16C07C51/42
Inventor 原徳明伊藤悦嗣山崎初太郎
Owner HITACHI LTD
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