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A kind of on-line depolymerization method of by-product paraformaldehyde in the synthesis reaction of trioxane

A technology of paraformaldehyde and paraformaldehyde, which is applied in the preparation of organic compounds, carbon-based compounds, chemical instruments and methods, etc., can solve the problem of unblocking tubes, long maintenance and recovery time, and increased thermal resistance of heat exchanger fouling Large, large loss of raw materials and other problems, to achieve considerable economic and social benefits, reduce economic losses, the effect of mild reaction temperature

Active Publication Date: 2019-04-16
YANKUANG GRP CO LTD
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AI Technical Summary

Problems solved by technology

[0012] (1) The synthesis reaction system of paraformaldehyde is a strong acid environment. Adding strong alkaline sodium hydroxide will cause the reaction of paraformaldehyde to change from acidic environment to neutral or alkaline. Under neutral or alkaline conditions, paraformaldehyde will be synthesized The reaction is terminated, the whole reactor liquid is polluted, and the acidic reaction liquid must be re-prepared before the production can be resumed, and the loss of raw materials is large.
[0013] (2) The heat release of the acid-base neutralization reaction is too fast, the reaction temperature cannot be controlled, and side reactions are prone to generate high-polymer paraformaldehyde precipitation or high-molecular polymers, and it is easier to block the reboiler tubes of the reactor. As a result, the tubes of the reboiler are hardened and agglomerated, scrapped, etc., and it takes a long time to clear and repair the blocked tubes, usually more than one month; in addition, the reboiler of the reactor is made of zirconium, and once the equipment is damaged, the economic loss will be large
[0014] (3) The salts generated during acid-base neutralization adhere to the tubes of the heat exchanger at high temperature, causing the thermal resistance of the heat exchanger dirt to increase, the heat exchange efficiency to decrease, and the cleaning is difficult, and the cleaning time is 7 days The above is not conducive to the long-term operation of production
[0015] In summary, the existing methods cannot solve the problem that the by-product paraformaldehyde precipitation that occurs during online production of paraformaldehyde affects the production of paraformaldehyde. Therefore, it is necessary to study a method for on-line depolymerization of paraformaldehyde

Method used

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  • A kind of on-line depolymerization method of by-product paraformaldehyde in the synthesis reaction of trioxane
  • A kind of on-line depolymerization method of by-product paraformaldehyde in the synthesis reaction of trioxane
  • A kind of on-line depolymerization method of by-product paraformaldehyde in the synthesis reaction of trioxane

Examples

Experimental program
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Effect test

Embodiment 1

[0055] The paraformaldehyde synthesis reaction solution to be depolymerized: the main components are 65.5wt% formaldehyde and 8.5wt% paraformaldehyde, the reaction temperature is 120°C, the catalyst sulfuric acid concentration is 4.32wt%, the heating steam is 0.3MPa, take the reaction kettle liquid and let it stand The volume content of the by-product paraformaldehyde precipitation is 80Vol%.

[0056] Such as figure 1 Shown, the on-line depolymerization method of by-product paraformaldehyde in a kind of trioxane synthesis reaction comprises the steps:

[0057] (1) Increase the concentration of sulfuric acid in the above-mentioned reaction solution to 6wt%, and calculate the amount of fresh sulfuric acid added according to the total amount of the reaction kettle liquid. It is necessary to exchange heat and transfer heat with circulating water through a graphite heat exchanger, store it in a dilute acid storage tank after mixing, and transport it to a paraformaldehyde synthesis...

Embodiment 2

[0063] The paraformaldehyde synthesis reaction solution to be depolymerized: the main components are 62.1wt% formaldehyde and 7.2wt% paraformaldehyde, the reaction temperature is 120°C, the catalyst sulfuric acid concentration is 4.55wt%, the heating steam is 0.3MPa, and the reaction kettle liquid is taken to stand The volume content of the by-product paraformaldehyde precipitation is 75 Vol%.

[0064] Such as figure 1 Shown, the on-line depolymerization method of by-product paraformaldehyde in a kind of trioxane synthesis reaction comprises the steps:

[0065] (1) the sulfuric acid concentration in the above-mentioned reaction solution is brought up to 8wt%, and method is with embodiment 1;

[0066] (2) After adding sulfuric acid, continuously add desalted water to the reaction solution to dilute the formaldehyde concentration, and control the flow rate of desalted water at 5m 3 Between / h, at the same time, the amount of 0.3MPa steam added to the reactor reboiler is increa...

Embodiment 3

[0071] The paraformaldehyde synthesis reaction liquid to be depolymerized: the main components are 63.5wt% formaldehyde and 6.5wt% paraformaldehyde, the reaction temperature is 115°C, the catalyst p-toluenesulfonic acid concentration is 4.95wt%, the heating steam is 0.3MPa, and the The precipitated paraformaldehyde content of the product was 70 Vol%.

[0072] Such as figure 1 Shown, the on-line depolymerization method of by-product paraformaldehyde in a kind of trioxane synthesis reaction comprises the steps:

[0073] (1) The p-toluenesulfonic acid concentration in the above-mentioned reaction solution is increased to 7.51wt%, and the method is the same as in Example 1;

[0074] (2) After adding p-toluenesulfonic acid, continuously add desalted water to the reaction solution to dilute the formaldehyde concentration, and control the flow rate of desalted water at 5m 3 Between / h, at the same time, the amount of 0.3MPa steam added to the reactor reboiler is increased by 5t / h, ...

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Abstract

The invention relates to an online depolymerization method of a by-product paraformaldehyde in the synthetic reaction of trioxymethylene, and belongs to the technical field of polyformaldehyde. The method comprises the steps that (1) the concentration of a strong acid catalyst in the synthetic reaction of trioxymethylene is increased to be 6wt%-8wt%, the speed of formaldehyde generating trioxymethylene in the strong acid condition is increased, and the reaction going from paraformaldehyde to formaldehyde direction is facilitated; (2) demineralized water is taken as a diluent to be supplementedinto the trioxymethylene synthetic reaction system, the concentration of monomer formaldehyde is decreased to be 40wt% or below, the reaction going from paraformaldehyde to formaldehyde solution depolymerization direction is facilitated, and online depolymerization of paraformaldehyde is achieved; and (3) the reaction temperature is increased and controlled to be between 130-150 DEG C, and depolymerization of paraformaldehyde is conducted. The by-product paraformaldehyde generated in the synthetic reaction of trioxymethylene is transformed to be formaldehyde under the conditions of high temperature, diluted formaldehyde and strong acid, accordingly online depolymerization of paraformaldehyde in the operation period of a production device is achieved, the method is easy and convenient to operate, the processing time is short, and the effect is outstanding.

Description

technical field [0001] The invention relates to the technical field of paraformaldehyde preparation, in particular to a method for on-line depolymerization of by-product paraformaldehyde generated during the synthesis reaction of paraformaldehyde. Background technique [0002] The production process of paraformaldehyde generally uses 50wt%-70wt% formaldehyde solution as raw material to synthesize paraformaldehyde under the catalysis of strong acids such as sulfuric acid or p-toluenesulfonic acid. The reaction equation is as follows: [0003] [0004] [0005] [0006] [0007] When the formaldehyde concentration is too high and the reaction temperature is low during the synthesis reaction, paraformaldehyde precipitation will be generated. The reaction equation is as follows: [0008] [0009] [0010] In actual enterprise production, the appearance of paraformaldehyde precipitation during on-line preparation of paraformaldehyde will not only prevent the ge...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07D323/06C07C45/55C07C47/045
CPCC07C45/55C07D323/06C07C47/04
Inventor 龙厚坤李志远张华娄兰亭王广义何闯沈祺王霜霜江在成叶墨香
Owner YANKUANG GRP CO LTD
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