Resource utilization method of isooctyl thioglycolate rectification waste

Abstract

The invention belongs to the technical field of fine chemical engineering, and discloses a resource utilization method of isooctyl thioglycolate rectification waste, which comprises the following steps: adding a proper amount of mercaptoethanol into the rectification waste to carry out reduction reaction, adding a certain amount of water to wash after the reaction is finished, standing for a period of time, separating out an upper organic phase, and drying to obtain the isooctyl thioglycolate rectification waste. And then carrying out continuous flash evaporation to obtain the isooctyl thioglycolate. The recovered isooctyl thioglycolate meets the synthesis requirements of tin mercaptide and ester tin, and has the characteristics of short process chain, simple operation, mild reaction conditions, environmental protection and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, and more specifically to a method for reducing and recovering isooctyl thioglycolate from the rectification waste of isooctyl thioglycolate under metal-free conditions. Background Art

[0002] Isooctyl thioglycolate (IOTG) is an important chemical raw material and chemical intermediate, which is widely used in industries such as chemicals, light industry, pharmaceuticals, oil extraction, and mineral processing. With the widespread use of various non-toxic mercaptan tin PVC heat stabilizers, the demand for isooctyl thioglycolate is increasing continuously. It is reported that there are mainly two process routes for synthesizing isooctyl thioglycolate: "thiolation first and then esterification" and "esterification first and then thiolation". However, no matter which process route, the final product isooctyl thioglycolate is very easy to oxidize and polymerize, forming high-boiling polymers such as isooctyl monothiodiacetate and isooctyl dithiodiacetate. During the rectification and purification of isooctyl thioglycolate, due to the high boiling points and low volatility of these compounds, they are enriched in the rectification residue. This not only reduces the product yield, increases the production cost, but also causes environmental hazards. Therefore, how to recycle these rectification wastes is one of the effective ways to reduce production costs and environmental pollution.

[0003] Wang Yanjun proposed a method for recovering isooctanol from the rectification waste of isooctyl thioglycolate after saponification, but a large amount of organic wastewater was generated during the washing process. Zhang Guangjun published a method for reducing the rectification waste of isooctyl thioglycolate with zinc powder to recover isooctyl thioglycolate. This method requires a large amount of zinc powder, bringing problems of zinc mud solid waste treatment. However, the reduction with zinc powder can significantly improve the yield of isooctyl thioglycolate, indicating that it is feasible to recover isooctyl thioglycolate by breaking the -S-S- bond.

[0004] Therefore, it is an urgent problem for those skilled in the art to develop a method for reducing the rectification waste of isooctyl thioglycolate to isooctyl thioglycolate under metal-free conditions. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for resource utilization of the rectification waste of isooctyl thioglycolate, which reduces the rectification waste of isooctyl thioglycolate to isooctyl thioglycolate under metal-free conditions. Starting from the specific breaking effect of mercaptoethanol on the -S-S- bond, mercaptoethanol is used to reduce the main component isooctyl dithiodiacetate in the rectification waste of isooctyl thioglycolate to recover the target product isooctyl thioglycolate, which can significantly improve the yield of isooctyl thioglycolate, reduce the production cost, relieve the burden on the ecological environment, and realize resource recycling.

[0006] To achieve the above purpose, the present invention provides a method for resource utilization of the rectification waste of isooctyl thioglycolate, including the following steps:

[0007] (1) Reduction reaction: Appropriate amount of mercaptoethanol is added to the rectification waste of isooctyl thioglycolate for reduction reaction;

[0008] (2) Washing and phase separation: After the reaction is completed, appropriate amount of water is added to the reaction mixture, washed and allowed to stand for layering to obtain the organic phase;

[0009] (3) Purification: The organic phase is continuously flash distilled to obtain isooctyl thioglycolate.

[0010] Furthermore, the rectification waste of isooctyl thioglycolate is the high-boiling bottom residue in the purification process of isooctyl thioglycolate, and the main component is isooctyl dithiodiglycolate containing disulfide bond.

[0011] More preferably, the content of isooctyl dithiodiglycolate is 68%.

[0012] Furthermore, in step (1), the mass ratio of mercaptoethanol to the rectification waste of isooctyl thioglycolate is 2.5:10 - 3.5:10.

[0013] Preferably, the mass ratio of mercaptoethanol to the rectification waste of isooctyl thioglycolate is 3.0:10.

[0014] Furthermore, in step (1), the time of the reduction reaction is 30 - 90 min, and the temperature is 25 - 35 °C.

[0015] Preferably, the time of the reduction reaction is 65 min, and the temperature is 30 °C.

[0016] Furthermore, in step (2), the amount of water added is 1 / 3 - 1 / 2 of the mass of the reaction mixture.

[0017] Preferably, the amount of water added is 2 / 5 of the mass of the reaction mixture.

[0018] Furthermore, in step (2), the washing time is 10 - 20 min, and the standing time is 15 - 30 min.

[0019] Furthermore, in step (3), the flash distillation temperature is 155 - 215 °C, and the flash distillation time is 1.5 - 2.0 min.

[0020] Preferably, the flash distillation temperature is 200 °C, and the flash distillation time is 2.0 min.

[0021] The main chemical reaction equation involved in the present invention is:

[0022] 2HSCH2CH2OH + C8H 17OOCCH2-S-S-CH2COOC8H 17 →2HSCH2COOC8H17+HOCH2CH2-S-S-CH2CH2OH

[0023] The technical concept of the present invention is as follows:

[0024] For the -S-S- bond, mercaptoethanol has strong reducibility, and the reducibility of mercaptoethanol comes from the mercapto (-SH) group in its molecule. Mercaptoethanol can react with the disulfide bond to reduce it to thiol. By virtue of its characteristics, it is an ideal treatment approach to use mercaptoethanol to reduce the distillation waste of isooctyl thioglycolate to recover the target product. This method has mild reaction conditions, simple process, and easily available reducing agent, can improve the yield of isooctyl thioglycolate, and at the same time reduce the production cost of isooctyl thioglycolate, which has positive significance for environmental protection and waste recycling.

[0025] It can be seen from the above technical solutions that, compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0026] The present invention uses the method of reduction with mercaptoethanol to treat the distillation waste of isooctyl thioglycolate, and after treatment, the target product isooctyl thioglycolate is recovered, improving the yield of isooctyl thioglycolate. This treatment method has the characteristics of short process chain, easy operation, mild reaction conditions, environmental protection, and high efficiency.

[0027] The isooctyl thioglycolate recovered by the present invention meets the synthesis requirements of thiol tin and ester tin. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0029] Figure 1 It is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] Example 1

[0032] Place 100.0 g of the rectification waste of isooctyl thioglycolate in a reaction flask, add 25.0 g of mercaptoethanol, stir and react at 25 °C for 30 min, then add 50.0 g of water for washing, wash for 15 min, pour into a separatory funnel and let it stand for phase separation. After standing for 20 min, separate the upper organic phase. The organic phase is continuously flash distilled at 195 °C for 2.0 min to obtain 58.4 g of isooctyl thioglycolate product with a purity of 99.5 wt% and a chromaticity <5.

[0033] Example 2

[0034] Place 100.0 g of the rectification waste of isooctyl thioglycolate in a reaction flask, add 35.0 g of mercaptoethanol, stir and react at 35 °C for 80 min, then add 60.0 g of water for washing, wash for 20 min, pour into a separatory funnel and let it stand for phase separation. After standing for 20 min, separate the upper organic phase. The organic phase is continuously flash distilled at 210 °C for 2.0 min to obtain 62.8 g of isooctyl thioglycolate product with a purity of 99.6 wt% and a chromaticity <5.

[0035] Example 3

[0036] Place 100.0 g of the rectification waste of isooctyl thioglycolate in a reaction flask, add 30.0 g of mercaptoethanol, stir and react at 30 °C for 60 min, then add 50.0 g of water for washing, wash for 20 min, pour into a separatory funnel and let it stand for phase separation. After standing for 15 min, separate the upper organic phase. The organic phase is continuously flash distilled at 205 °C for 1.5 min to obtain 61.8 g of isooctyl thioglycolate product with a purity of 99.4 wt% and a chromaticity <5.

[0037] Example 4

[0038] Place 100.0 g of the rectification waste of isooctyl thioglycolate in a reaction flask, add 35.0 g of mercaptoethanol, stir and react at 30 °C for 60 min, then add 65.0 g of water for washing, wash for 20 min, pour into a separatory funnel and let it stand for phase separation. After standing for 15 min, separate the upper organic phase. The organic phase is continuously flash distilled at 210 °C for 2.0 min to obtain 62.6 g of isooctyl thioglycolate product with a purity of 99.5 wt% and a chromaticity <5.

[0039] Example 5

[0040] Place 100.0 g of the rectification waste of isooctyl thioglycolate in a reaction flask, add 33.0 g of mercaptoethanol, stir and react at 28 °C for 80 min, then add 60.0 g of water for washing, wash for 20 min, pour into a separating funnel and let it stand for phase separation. After standing for 15 min, separate the upper organic phase. The organic phase is continuously flash distilled at 200 °C for 1.5 min to obtain 62.4 g of isooctyl thioglycolate product with a purity of 99.5 wt% and a chromaticity <5.

[0041] Example 6

[0042] Place 100.0 g of the rectification waste of isooctyl thioglycolate in a reaction flask, add 30.0 g of mercaptoethanol, stir and react at 30 °C for 65 min, then add 52.0 g of water for washing, wash for 15 min, pour into a separating funnel and let it stand for phase separation. After standing for 20 min, separate the upper organic phase. The organic phase is continuously flash distilled at 200 °C for 2.0 min to obtain 63.2 g of isooctyl thioglycolate product with a purity of 99.6 wt% and a chromaticity <5.

[0043] Comparative Example 1

[0044] Place 100.0 g of the rectification waste of isooctyl thioglycolate in a reaction flask, add 22.0 g of mercaptoethanol, stir and react at 30 °C for 80 min, then add 60.0 g of water for washing, wash for 20 min, pour into a separating funnel and let it stand for phase separation. After standing for 15 min, separate the upper organic phase. The organic phase is continuously flash distilled at 210 °C for 2.0 min to obtain 52.6 g of isooctyl thioglycolate product with a purity of 98.4 wt% and a chromaticity <5.

[0045] Comparative Example 2

[0046] Place 100.0 g of the rectification waste of isooctyl thioglycolate in a reaction flask, add 40.0 g of mercaptoethanol, stir and react at 32 °C for 70 min, then add 55.0 g of water for washing, wash for 20 min, pour into a separating funnel and let it stand for phase separation. After standing for 15 min, separate the upper organic phase. The organic phase is continuously flash distilled at 205 °C for 1.5 min to obtain 63.0 g of isooctyl thioglycolate product with a purity of 99.4 wt% and a chromaticity <5.

[0047] Comparative Example 3

[0048] Place 100.0 g of the rectification waste of isooctyl thioglycolate in a reaction flask, add 35.0 g of mercaptoethanol, stir and react at 50 °C for 60 min, then add 50.0 g of water for washing, wash for 20 min, pour into a separating funnel and let it stand for phase separation. After standing for 15 min, separate the upper organic phase. The organic phase is continuously flash distilled at 205 °C for 1.5 min to obtain 54.5 g of isooctyl thioglycolate product with a purity of 99.2 wt% and a chromaticity <5.

[0049] Comparative Example 4

[0050] Put 100.0 g of the rectification waste of isooctyl thioglycolate into a reaction flask, add 33.0 g of mercaptoethanol, stir and react at 70 °C for 80 min, then add 50.0 g of water for washing, wash for 15 min, pour it into a separatory funnel and let it stand for phase separation. After standing for 20 min, separate the upper organic phase. The organic phase is continuously flash-evaporated at 200 °C for 2.0 min to obtain 46.7 g of isooctyl thioglycolate product with a purity of 98.8 wt% and a chromaticity of <5.

[0051] Comparative Example 5

[0052] Put 100.0 g of the rectification waste of isooctyl thioglycolate into a reaction flask, add 35.0 g of mercaptoethanol, stir and react at 15 °C for 120 min, then add 50.0 g of water for washing, wash for 20 min, pour it into a separatory funnel and let it stand for phase separation. After standing for 20 min, separate the upper organic phase. The organic phase is continuously flash-evaporated at 205 °C for 2.0 min to obtain 49.2 g of isooctyl thioglycolate product with a purity of 99.0 wt% and a chromaticity of <5.

[0053] Comparative Example 6

[0054] Put 100.0 g of the rectification waste of isooctyl thioglycolate into a reaction flask, add 35.0 g of mercaptoethanol, stir and react at 28 °C for 80 min, then add 25.0 g of water for washing, wash for 30 min, pour it into a separatory funnel and let it stand for phase separation. After standing for 20 min, separate the upper organic phase. The organic phase is continuously flash-evaporated at 210 °C for 2.0 min to obtain 62.3 g of isooctyl thioglycolate product with a purity of 98.2 wt% and a chromaticity of <5.

[0055] Comparative Example 7

[0056] Put 100.0 g of the rectification waste of isooctyl thioglycolate into a reaction flask, add 35.0 g of mercaptoethanol, stir and react at 30 °C for 60 min, then add 50.0 g of water for washing, wash for 20 min, pour it into a separatory funnel and let it stand for phase separation. After standing for 15 min, separate the upper organic phase. The organic phase is continuously flash-evaporated at 240 °C for 1.5 min to obtain 59.8 g of isooctyl thioglycolate product with a purity of 97.8 wt% and a chromaticity of =14.

[0057] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

Claims

1. A method for resource utilization of isooctyl thioglycolate distillation waste, characterized in that: The following steps are involved: (1) adding an appropriate amount of mercaptoethanol to the isooctyl thioglycolate distillation waste to carry out a reduction reaction; (2) After the reaction is completed, add an appropriate amount of water to the reaction mixture, wash, and stand for stratification to obtain an organic phase; (3) continuously flashing the organic phase to obtain isooctyl thioglycolate.

2. The method for resource utilization of isooctyl thioglycolate distillation waste according to claim 1, characterized in that: The isooctyl thioglycolate distillation waste is a high-boiling-point kettle bottom residue in the process of purifying isooctyl thioglycolate, and its main component is isooctyl dithiodiacetate.

3. The method for resource utilization of isooctyl thioglycolate distillation waste according to claim 1, characterized in that: In step (1), the mass ratio of the mercaptoethanol to the isooctyl thioglycolate distillation waste is 2.5:10-3.5:

10.

4. The method for resource utilization of isooctyl thioglycolate distillation waste according to claim 1, characterized in that: In step (1), the reduction reaction time is 30-90 min and the temperature is 25-35°C.

5. The method for resource utilization of isooctyl thioglycolate distillation waste according to claim 1, characterized in that: In step (2), the amount of water added is 1 / 3-1 / 2 of the mass of the reaction mixture.

6. The method for resource utilization of isooctyl thioglycolate distillation waste according to claim 1, characterized in that: In step (2), the washing time is 10-20 minutes and the standing time is 15-30 minutes.

7. The method for resource utilization of isooctyl thioglycolate distillation waste according to claim 1, characterized in that: In step (3), the flash evaporation temperature is 155-215° C., and the flash evaporation time is 1.5-2.0 min.

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