CN1445232A - New technique for synthesizing dialkyl ester phosphorous acid - Google Patents
New technique for synthesizing dialkyl ester phosphorous acid Download PDFInfo
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Abstract
A process for synthesizing dialkyl phosphite from PCl3 and C1-C8 alkyl monool features that its high-boiling-point by-product containing monoalkyl phosphite and phosphorus acid can be converted to dialkyl phosphite, so increasing the output rate to 98-99.9%.
Description
Technical Field
The present invention relates to an improvement in the art of dialkyl phosphite production, and more particularly to the synthesis of dialkyl phosphites from phosphorous acid-containing by-products produced during the dialkyl phosphite production process.
The background art containsOr(R is alkyl, such as methyl, ethyl, phenyl, etc.) is called dialkyl phosphite ester, and this kind of material, especially dimethyl phosphite and diethyl phosphite, is an important chemical material and intermediate, and it is widely used in organic phosphoric acid type corrosion inhibitor, synthetic plastic adjuvant, dye additive, flame retardant and pesticide preparation industry. The water quality corrosion and scale inhibitor of organic phosphoric acid type and organic phosphonic acid-carboxylic acid type prepared by it is widely used for industrial and chemical circulating water treatment; the phosphite compounds prepared by the method are widely used as phosphorus additives with different functions in the plastic industry and additives in the dye industry and oil products; meanwhile, it is also an important intermediate for preparing organophosphorus pesticides such as trichlorphon, dichlorvos, fenoxanil, omethoate, glyphosate and the like. The domestic yield of dialkyl phosphite ester reaches 20 million tons.
There are many methods for producing dialkyl phosphorites, and there are two main methods currently in commercial use: the first is solvent method or solvent-free method with phosphorus trichloride and corresponding alcohol (such as methanol, ethanol, etc.) as raw materials; the other is an esterification method using phosphorous acid and corresponding alcohol (such as methanol, ethanol, etc.) as raw materials. The preparation of dialkyl phosphite by direct reaction of phosphorus trichloride and alcohol is the most studied subject at home and abroad, and the industrial production technology is comprehensively divided into the following two cases (taking dimethyl phosphite as an example):
1) industrial production technology in which the reaction is carried out in an organic medium.
The technique is generally characterized in that phosphorus trichloride directly reacts with methanol to prepare dimethyl phosphite at a lower temperature (generally less than or equal to 10 ℃) in an inert or halogenated organic solvent in the absence or presence of an acid-binding agent (organic amine or ammonia). The industrial production includes a batch method and a continuous method. The method has mild reaction conditions and safe and easily-controlled operation, but the yield is unstable due to the influence of a plurality of factors. The yield is usually 65-90% based on phosphorus trichloride, and the recycling of the solvent increases the operating cost.
2) Continuous industrial production technology without solvent
In the industrial production technology, some of the industrial production technologies are carried out by gas phase reaction, and the yield of the dimethyl phosphite is about 90 percent; some are liquid phase reactions with yields of about 86-93%. The solvent-free production method has the common advantages that the production speed is high, the product yield is high and the product purity can reach 98.9 percent as long as the control is proper. And because no solvent is used in the production process, the production cost and the operation cost are low. Compared with the gas phase method and the liquid phase method, the former method has large equipment and large production investment, and the latter method has much less production investment. However, the solvent-free process has high requirements for the raw materials, especially methanol. This method is now accepted by manufacturers at home and abroad.
The above-mentioned commonly employed dialkyl phosphite production method has disadvantages in that the industrial yield is less than 93%, and by-products (viscous substances having a high boiling point remaining in the product purification) are generated, the main components of which are monoalkyl phosphite, phosphorous acid and their polymers or copolymers.
For such by-products, the invention patent application No. 97123386 discloses a method for producing industrial phosphorous acid by using it, which changes the by-products discarded before into valuable things and is a very good method, but the added value of phosphorous acid is not high because of the low value of phosphorous acid when the by-products are treated by this method.
The method provided by the invention well solves the problems, improves the existing dialkyl phosphite production process, and enables the yield to reach 98-99.9%.
Disclosure of Invention
In order to make the description of the invention more clear and concise, the invention is described by taking dimethyl phosphite as an example, but the technology is also applicable to all dialkyl phosphite preparation processes, and the invention comprises all processes for preparing dialkyl phosphite by reacting phosphorus trichloride with monohydric alcohol with 1-8 carbon atoms.
The reaction process of direct contact of phosphorus trichloride and methanol to synthesize dimethyl phosphite is that phosphorus trichloride reacts with methanol to form trimethyl phosphite:
in order to reduce the side reaction, the existing process is to rapidly remove the generated hydrogen chloride from the system by adopting a vacuum and heating method in the reaction process (called deacidification process), the material at the end of the deacidification process is called crude ester, but the acidolysis reaction of the tri (mono, di) phosphite is rapid, a considerable amount of monomethyl phosphite and phosphorous acid are generated and dissolved in the crude ester, and the main reaction yield is not high. The generated monomethyl phosphite and phosphorous acid generate polymers containing P-O-P bonds at high temperature (100-170 ℃) in the product refining (adopting a rectification method), and the byproducts are collectively called high-boiling point byproducts in the invention. In the prior art, it produced about 5-20% of the total product.
The high boiling point by-product produced in the production process of dimethyl phosphite comprises the following components: 0.1-70% of monomethyl phosphite, 10-95% of phosphorous acid, 0.1-20% of polymer and 1-10% of dimethyl phosphite.
In the process of synthesis and rectification in the dimethyl ester production process, low boiling point substances accounting for 1-20% of the total product are separated under the vacuum degree of 10-200mmHg, called low boiling point by-products, wherein the low boiling point by-products contain methanol and trimethyl phosphite, and can be returned to a synthesis system before the deacidification procedure in the prior art to react with hydrogen chloride in the system to generate dimethyl phosphite and by-products of monomethyl phosphite and phosphorous acid.
The invention analyzes the composition of materials generated in each process in the production process of dimethyl phosphite, and creatively provides an improved method, so that the yield of dimethyl phosphite reaches 98-99.9% which is not existed before, and hardly generates unpleasant high-boiling byproducts (the weight of which is not more than 5% of the target product) for the whole reaction system.
The method adopted by the invention is to return the high-boiling point byproduct to a synthesis system to react with intermediate trimethyl phosphite as follows:
in the reaction system, phosphorus trichloride and methanol are contacted to generate phosphorus trimethyl ester, the reaction speed of the phosphorus trimethyl ester, phosphorous acid and monomethyl phosphite is very high, and the high boiling point by-product is added into the reaction system, so that the concentration of the phosphorus phosphite and the monomethyl phosphite in the system can be improved, the phosphorus trichloride and the methanol are quickly reacted with the trimethyl phosphite which is just generated to form a target product, and the yield of the target product is improved. The concentration of trimethyl phosphite is highest at the instant of contacting phosphorus trichloride with methanol, and it is a preferred method to dissolve it in the mixed feed of methanol in order to promote the conversion of high boiling by-products, which are present in concentrations of 0.1 to 20% by weight. Or adding the high-boiling point by-product into a deacidification process, and reacting with unconverted trimethyl phosphite to generate a target product.
Another method for treating the high-boiling-point by-product is to mix the high-boiling-point by-product with 0.5-6.0 times of trimethyl phosphite by weight, control the reaction temperature at 0-110 deg.C, and then return the reaction liquid to the rectification process of dimethyl phosphite production or directly separate to obtain the target product. Of course, it is not economical to use commercial trimethyl phosphite from the viewpoint of cost, and the low boiling point by-product generated in the production process of dimethyl phosphite may be used in place of or in part of trimethyl phosphite, and the low boiling point by-product and the high boiling point by-product are mixed and then fed into the above-mentioned rectification process for separation or directly refined.
In actual production, because the high boiling point by-product contains polymer, has dark color and contains mechanical impurities, before returning the high boiling point by-product to the synthesis system, water with the weight of 1-10% of that of the high boiling point by-product is added for hydrolysis, and then the high boiling point by-product is filtered, but the added water quantity is strictly controlled, if the water is excessive, the water is introduced into the system, and the high boiling point by-product reacts with the raw material phosphorus trichloride or phosphite ester to form phosphorous acid. Considering that the amount of water added depends on the amount of the polymer in the high-boiling by-products, the detection of the polymer is very difficult, and water may be added in an excessive amount in order to prevent the addition of water, so that since the polymer cannot be converted into dimethyl phosphite, a small amount of high-boiling by-products is also produced for the whole production system, that is, the yield of the objective product will not reach a level close to 100% in theory.
The phosphorous acid or monomethyl phosphite produced in the dimethyl phosphite synthesis and deacidification process is dissolved in the crude ester, and another method is to convert all or part of the crude ester into the target product before rectification or distillation, which is the most economical method. Because the reaction between trimethyl phosphite and phosphorous acid or monomethyl phosphite is fast and can be carried out at relatively low concentration, the method can be adopted that a compound containing trimethyl phosphite is added into crude ester to react with phosphorous acid and monomethyl phosphite to generate dimethyl phosphite, and then rectification or distillation is carried out to separate low boiling point materials such as methanol and trimethyl phosphite and a small amount of unreacted high boiling point byproducts. The amount of trimethyl phosphite containing compound added should be determined based on the content of the phosphorous acid or monomethyl phosphite in the crude ester, and is typically from 5% to 20%, and the amount of trimethyl phosphite containing compound added is from 0.25% to 120% by weight of the crude ester. Of course, the commercial use of trimethyl phosphite is uneconomical from an economic point of view, and low-boiling by-products formed during the production of dimethyl phosphite can be used instead of trimethyl phosphite or as a mixture of the two in any proportion.
Detailed Description
The examples of the invention take the synthesis of dimethyl phosphite as an example, but do not indicate that the scheme is only applicable to the preparation of dimethyl phosphite, and the technical scheme applied to the synthesis of other dialkyl phosphites is also included in the invention.
Example 1: weighing 72g of industrial methanol (99 percent), placing the industrial methanol into a four-neck flask which is provided with a cooling medium and a spherical condenser and is stirred, and taking frozen brine as a cooling medium; 100g of industrial phosphorus trichloride (99%) was weighed, and continuously charged into the flask under a vacuum of-0.09 MPa, and the reaction temperature was controlled to 40 ℃ or lowerby the charging speed. After the reaction, the temperature was raised at a vacuum degree of-0.09 MPa, and the fraction at 90 ℃ or lower (called low boiling point by-product) and the fraction at 90-140 ℃ (main product) were collected, and the high boiling point by-product remained at the end, and weighed separately.
Example 2: as in example 1, 10g of the high-boiling by-product obtained in example 1 was added simultaneously with the reaction.
Example 3: as in example 1, the starting material was 18g of the high-boiling by-product obtained in example 1 dissolved in 72g of methanol.
Example 4: in the same manner as in example 1, 1g of water was added to 10g of the high boiling point by-product obtained in example 1, and the mixture was thoroughly mixed and added simultaneously during the reaction.
Example 5: 15g of the high boiling point by-product obtained in example 1 and 20g of trimethyl phosphite were mixed and reacted, and the reaction mixture was added to the reaction mixture obtained in example 1, followed by distillation under reduced pressure under the conditions of example 1.
Example 6: in the same manner as in example 5, trimethyl phosphite was replaced with 10g of the low-boiling by-product obtained in example 1.
Example 7: the same procedure as in example 1, but with the addition of 8g of trimethyl phosphite before the collection of the 90-140 ℃ fraction, was followed by distillation.
Example 8: the same procedure as in example 7, but using 10g of the low-boiling by-product obtained in example 1 in place of trimethyl phosphite.
List of experimental results
| Batch number | Main product | Content of major product | High boiling point by-products | Yield of | Remarks for note |
| g | ％ | g | ％ | ||
| 1 | 69.8 | 96.7 | 10.3 | 85.2 | Comparative example |
| 2 | 80.8 | 96.4 | 11.4 | 98.3 | |
| 3 | 81.0 | 96.9 | 13.5 | 99.1 | |
| 4 | 80.2 | 97.2 | 10.1 | 98.4 | |
| 5 | 82.6 | 95.8 | 0.5 | 99.9 | |
| 6 | 81.6 | 96.6 | 2.8 | 99.5 | |
| 7 | 80.8 | 96.7 | 5.4 | 98.6 | |
| 8 | 80.5 | 96.5 | 6.7 | 98.1 |
Claims (15)
1. A process for synthesizing dialkyl phosphite from phosphorus trichloride and alkyl alcohol features that the high-boiling by-product generated in reaction is used to generate dialkyl phosphite.
2. The process according to claim 1, wherein the alkyl alcohol is a monohydric alcohol having 1 to 8 carbon atoms, preferably methanol or ethanol.
3. The process of claim 1 wherein said dialkyl phosphite is of the structure
OrWherein R is an alkyl group having 1 to 8 carbon atoms, preferably a methyl group and an ethyl group.
4. The process of claim 1, wherein said high boiling by-product is characterized by comprising one or a mixture of two or more of monoalkyl phosphites, phosphorous acids, polyphosphoric acids, or polyphosphites.
5. The process as set forth in claim 1, characterized in that said high-boiling by-products are returned to the process for the preparation of dialkyl phosphites.
6. The process as claimed in claim 5, wherein the feed is carried out by dissolving the high-boiling by-products in the starting alkyl monoalcohol, the concentration by weight of the high-boiling by-products being 0.1 to 20%.
7. The process as set forth in claim 1, wherein the high-boiling by-products are reacted by mixing with a trialkyl phosphite-containing material, and the reaction mass is returned to the dialkyl phosphite production process.
8. The process of claim 7, wherein the trialkyl phosphite-containing material is a mixture of low boiling by-products produced during the production of trialkyl or dialkyl phosphites or in any proportion.
9. The process according to claim 7 or 8, wherein the weight ratio of the high-boiling by-products to the trialkyl phosphite-containing material is 1: 0.5-6.
10. A process according to claim 5, 6 or 7, characterized in that the high-boiling by-products are partially or completely hydrolysed by mixing them with water or a solution containing water.
11. The process as claimed in claim 10, wherein the amount of water added is from 1 to 10% by weight based on the high-boiling by-products.
12. The process as claimed in claim 1, wherein the high-boiling by-products are not separated from the system and a trialkyl phosphite-containing material is added to the system to convert the trialkyl phosphite into dialkyl phosphite. Preferably to the crude ester.
13. The process according to claim 12, wherein the trialkyl phosphite-containing material is added in an amount of 0.25 to 120% by weight of the crude ester.
14. The process according to claim 12 or 13, wherein the trialkyl phosphite-containing material is a low boiling point byproduct produced during the production of trialkyl phosphite or dialkyl phosphite, or a mixture thereof in any proportion.
15. The process as claimed in claim 1, wherein the weight of the high-boiling by-products discharged is not more than 5% of the target product, based on the total dialkyl phosphite preparation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 02150012 CN1215074C (en) | 2002-10-10 | 2002-10-10 | New technique for synthesizing dialkyl ester phosphorous acid |
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| CN 02150012 CN1215074C (en) | 2002-10-10 | 2002-10-10 | New technique for synthesizing dialkyl ester phosphorous acid |
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| CN1215074C CN1215074C (en) | 2005-08-17 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108003188A (en) * | 2017-12-25 | 2018-05-08 | 长春吉大天元化学技术股份有限公司 | A kind of new purification process of alkyl phosphoric acid esters compound |
| CN109824720A (en) * | 2019-03-29 | 2019-05-31 | 山东泰和水处理科技股份有限公司 | A kind of dimethylphosphite is continuously synthesizing to method and device |
| CN109912647A (en) * | 2019-03-20 | 2019-06-21 | 山东泰和水处理科技股份有限公司 | A kind of synthetic method of dimethylphosphite |
-
2002
- 2002-10-10 CN CN 02150012 patent/CN1215074C/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108003188A (en) * | 2017-12-25 | 2018-05-08 | 长春吉大天元化学技术股份有限公司 | A kind of new purification process of alkyl phosphoric acid esters compound |
| CN109912647A (en) * | 2019-03-20 | 2019-06-21 | 山东泰和水处理科技股份有限公司 | A kind of synthetic method of dimethylphosphite |
| CN109824720A (en) * | 2019-03-29 | 2019-05-31 | 山东泰和水处理科技股份有限公司 | A kind of dimethylphosphite is continuously synthesizing to method and device |
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| CN1215074C (en) | 2005-08-17 |
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