Polymerization inhibitor and method for prolonging polymerization inhibition time of polymerization inhibitor in carboxylic acid vinyl ester rectification process

Abstract

The invention discloses a polymerization inhibitor for rectification of carboxylic acid vinyl ester. The polymerization inhibitor is a composite polymerization inhibitor composed of a polyphenol polymerization inhibitor, a nitroxide free radical compound and an arylamine polymerization inhibitor. The composite polymerization inhibitor prepared by the invention has good solubility in a carboxylic acid vinyl ester system; the polymerization inhibition efficiency in the induction period is high, and meanwhile, the induction period is prolonged, that is, the polymerization inhibition lasting validity period of the polymerization inhibitor in a carboxylic acid vinyl ester rectification process is long.

Description

Technical Field

[0001] The present invention relates to a method for preparing vinyl carboxylate in the field of organic chemistry, and in particular to a composite polymerization inhibitor for vinyl carboxylate distillation and a method for increasing the polymerization inhibition time in the vinyl carboxylate distillation process. Background Art

[0002] Vinyl carboxylates are a very important class of organic chemical raw materials. Existing methods for producing vinyl carboxylates involve the addition of carboxylic acids to alkynes. However, during the distillation process after the initial synthesis of vinyl carboxylates, the vinyl carboxylates monomers readily polymerize, leading to blockage of the distillation column trays and heat exchangers, requiring frequent production stops for cleaning, significantly reducing production efficiency. Therefore, after the initial synthesis of vinyl carboxylates, during the distillation process, an appropriate polymerization inhibitor is added to inhibit polymerization.

[0003] Chinese patent document CN111100001A discloses a composite polymerization inhibitor for vinyl acetate distillation and its use method. The inhibitor is composed of three components: 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide, N,N-diphenyl-p-phenylenediamine, and 2,4-dimethyl-6-sec-butylphenol, compounded in a specific ratio. This composite polymerization inhibitor cleverly utilizes the synergistic effect between its components, overcoming the respective shortcomings of retarders and true inhibitors, resulting in a significantly improved polymerization inhibition effect compared to the individual components. Furthermore, the inhibitor is highly efficient and has low toxicity, effectively improving the yield of vinyl acetate distillation.

[0004] Although the existing technology improves its polymerization inhibition efficiency, its polymerization inhibition duration is short. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide an inhibitor for the distillation of vinyl carboxylate, which produces a synergistic effect in the distillation process, has high inhibition efficiency and a long effective period of inhibition. The inhibitor is a composite inhibitor composed of a polyphenol inhibitor, a nitrogen oxide free radical compound and an aromatic amine inhibitor.

[0006] Furthermore, the mass ratio of the polyphenol polymerization inhibitor, the nitroxide free radical compound and the aromatic amine polymerization inhibitor is 2-6:1.5-5:2-5.

[0007] Furthermore, the polyphenol polymerization inhibitor is selected from p-tert-butylcatechol.

[0008] Furthermore, the nitroxide free radical compound is selected from 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical.

[0009] Furthermore, the aromatic amine polymerization inhibitor is selected from one or more of diphenylamine sulfide, toluidine, benzidine, p-phenylenediamine and N-nitrosodiphenylamine.

[0010] Furthermore, the polymerization inhibitor is a composite polymerization inhibitor of p-tert-butylcatechol, 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical and diphenylamine sulfide.

[0011] Furthermore, the content of the composite polymerization inhibitor in the vinyl carboxylate distillation system is 1-150 ppm.

[0012] In a second aspect, the present invention provides a method for increasing the inhibition time in a vinyl carboxylate distillation process, comprising: using the above-mentioned inhibitor.

[0013] The present invention has the following beneficial effects:

[0014] (1) The composite polymerization inhibitor prepared by the present invention has good solubility in the vinyl carboxylate system, has high inhibition efficiency during the induction period, and prolongs the induction period, that is, the polymerization inhibitor has a long effective period of inhibition in the vinyl carboxylate distillation process.

[0015] (2) The composite polymerization inhibitor prepared by the present invention has high polymerization inhibition efficiency during the induction period, can significantly reduce the polymerization reaction rate, and prevent the explosion phenomenon caused by heat accumulation.

[0016] (2) The composite polymerization inhibitor prepared by the present invention can reduce the blockage and scaling of production equipment such as distillation towers, pipelines, and storage tanks during the refining process, thereby ensuring the stable and normal operation of the process and thus not affecting production and product quality.

[0017] (3) Compared with the polymerization inhibitors p-benzoquinone and hydroquinone currently used in industry, the polymerization inhibitor provided by the present invention reduces the amount of highly toxic substances used, reduces toxicity, improves the polymerization inhibition efficiency of the polymerization inhibitor, and has good social benefits. DETAILED DESCRIPTION

[0018] The examples are provided to better illustrate the present invention, but are not intended to limit the present invention to the examples. Therefore, non-essential improvements and adjustments to the embodiments made by those skilled in the art based on the above-mentioned invention still fall within the scope of protection of the present invention.

[0019] Preferably, the mass ratio of the polyphenol polymerization inhibitor, the nitroxide free radical compound and the aromatic amine polymerization inhibitor of the present invention is 30-60:15-35:25-45.

[0020] The polyphenol polymerization inhibitor of the present invention is selected from p-tert-butylcatechol, which is a substance known in the prior art and can be purchased commercially.

[0021] The nitroxide free radical compound of the present invention is selected from 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical, etc., which are substances known in the prior art and can be commercially obtained.

[0022] The induction period of the present invention refers to the initial stage of polymerization, when some impurities with polymerization inhibition and retardation effects exist in the system, and the primary free radicals terminate with these impurities, and polymerization does not occur on the surface, and the polymerization rate is zero.

[0023] Example 1

[0024] Polymerization inhibitor: a compound obtained by mixing 4-tert-butylcatechol (4-TBC), 2,2,6,6-tetramethyl-4-hydroxypiperidinyl nitroxide free radical compound (ZJ-701) and diphenylamine sulfide (PTZ).

[0025] Add a certain amount of refined vinyl acetate to a test tube, then add 0.1% of the weight of vinyl acetate as the initiator azobisisobutyronitrile, and 45ppm of the inhibitor, mix well, place the test tube in a constant temperature water bath at 65°C, start timing, stop timing when vinyl acetate starts bubbling, and record the time when polymerization begins, which is the polymerization induction period.

[0026] Examples 2-7

[0027] Except for the contents in Table 1 below, everything else is the same as in Example 1.

[0028] Table 1 Inhibition effect of different ratios of inhibitors

[0029]

[0030] Example 8 and Comparative Examples 1-2

[0031] Polymerization inhibitor: a compound obtained by mixing 4-tert-butylcatechol (4-TBC), 2,2,6,6-tetramethyl-4-hydroxypiperidinyl nitroxide free radical compound (ZJ-701) and diphenylamine sulfide (PTZ) in a ratio of 3.6:2.4:2.0.

[0032] Add a certain amount of refined vinyl acetate to a test tube, then add 0.1% of the initiator azobisisobutyronitrile by weight of vinyl acetate and 0.27 μmol / g of polymerization inhibitor relative to vinyl acetate, mix well, place the test tube in a constant temperature water bath at 65°C, start timing, stop timing when vinyl acetate starts bubbling, and record the time when polymerization begins, which is the polymerization induction period.

[0033] Table 2 Comparison of the inhibition effects of different inhibitors

[0034]

[0035]

[0036] As shown in Table 2, the induction period of existing benzoquinone and hydroquinone as polymerization inhibitors is 4124-4730s, while the induction period of the composite polymerization inhibitor described in the present invention is 6102s. This proves that the composite polymerization inhibitor prepared by the present invention has a long effective period of polymerization inhibition and high inhibition efficiency, and the toxicity of the carboxylic acid vinyl ester distillation inhibitor used is significantly reduced.

[0037] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A polymerization inhibitor for the distillation of vinyl carboxylate, characterized in that: The polymerization inhibitor is a composite polymerization inhibitor consisting of a polyphenol polymerization inhibitor, a nitrogen oxide free radical compound and an aromatic amine polymerization inhibitor.

2. The polymerization inhibitor according to claim 1, characterized in that: The mass ratio of the polyphenol polymerization inhibitor, the nitroxide free radical compound and the aromatic amine polymerization inhibitor is 2-6:1.5-5:2-5.

3. The polymerization inhibitor according to claim 1 or 2, characterized in that: The polyphenol polymerization inhibitor is selected from p-tert-butylcatechol.

4. The polymerization inhibitor according to any one of claims 1 to 3, characterized in that: The nitroxide free radical compound is selected from 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical.

5. The polymerization inhibitor according to any one of claims 1 to 4, characterized in that: The aromatic amine polymerization inhibitor is selected from one or more of sulfided diphenylamine, toluidine, benzidine, p-phenylenediamine and N-nitrosodiphenylamine.

6. The polymerization inhibitor according to claim 1 or 2, characterized in that: The polymerization inhibitor is a composite polymerization inhibitor composed of p-tert-butylcatechol, 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical and diphenylamine sulfide.

7. The polymerization inhibitor according to claim 6, characterized in that: The content of the composite polymerization inhibitor in the vinyl carboxylate distillation system is 1-150 ppm.

8. A method for increasing the inhibition time in a vinyl carboxylate distillation process, characterized in that: The polymerization inhibitor according to any one of claims 1 to 7 is used.

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