CN101870712B - Production method of dimethyl phosphite - Google Patents

Abstract

The production method of dimethyl phosphite uses phosphorus trichloride and methanol as raw materials to react. In the reaction chamber space with various raw material injection structures with cross injection angles, the phosphorus trichloride and methanol measured at a molar ratio of 1: (3.0 to 3.1) are respectively passed through the respective injection structures by the corresponding pumping mechanisms. The continuous injection is sent into the reaction chamber space to mix and react with each other, and then the reaction material is introduced into the centrifugal cyclone separation device along the tangential direction with a pressure lower than the reaction chamber space, so that the non-condensable gas and the condensed liquid product are subjected to centrifugal cyclone separation, collected along the centrifugal The liquid dimethyl phosphite product descending on the inner wall of the type cyclone separation device. The method can quickly complete the reaction and separate products, effectively reduce the contact between HCl and dimethyl phosphite, suppress the occurrence of side reactions, improve the yield and quality of products, and greatly reduce energy consumption.

Description

The production method of dimethyl phosphite

technical field

What the present invention relates to is a kind of production method of improved dimethyl phosphite.

Background technique

Dimethyl phosphite is an important product in fine chemical industry. It is not only an intermediate for the production of glyphosate, trichlorfon, rice blast, omethoate and other pesticides, but also a raw material for organophosphorus corrosion inhibitors, dye additives, plastic additives and flame retardants, and can be used for synthetic water treatment It can also be used as a methylating agent to synthesize quaternary ammonium salt fungicides, antistatic agents, softeners and other products.

Dimethyl phosphite is generally produced by reacting phosphorus trichloride and methanol in industry:

PCl ₃ +3CH ₃ OH→(CH ₃ O) ₂ POH+2HCl↑+CH ₃ Cl↑

The reaction process and mechanism are:

PCl ₃ +CH ₃ OH→CH ₃ OPCl ₂ +HCl↑ (1)

CH ₃ OPCl ₂ +CH ₃ OH→(CH ₃ O) ₂ PCl+HCl↑ (2)

(CH ₃ O) ₂ +CH ₃ OH→(CH ₃ O) ₃ P+HCl↑ (3)

(CH ₃ O) ₃ P+HCl→(CH ₃ O) ₂ POH+CH ₃ Cl↑ (4)

In the reaction process, the trimethyl phosphite in (3) formula is extremely unstable, as long as HCl exists, it can react to generate dimethyl phosphite. And the existence of HCl also very easily makes product dimethyl phosphite continue to take place following side reaction simultaneously:

(CH ₃ O) ₂ POH+HCl→CH ₃ OP(OH) ₂ +CH ₃ Cl↑

CH ₃ OP(OH) ₂ +HCl→H ₃ PO ₃ +CH ₃ Cl↑

The higher the temperature and/or the longer the time during the reaction, the more side reactions. Since the above-mentioned reaction of phosphorus trichloride and methanol is a transient reaction with strong exotherm, the key to ensure the smooth progress and completion of the reaction is to create conditions that allow the two reactants to fully contact, shorten the reaction time, and effectively remove the reaction. heat, and remove HCl in the reaction product as much as possible to suppress the occurrence of side reactions.

At present, the industrial production of dimethyl phosphite has been using the batch method of single-pot reaction and single-pot rectification. The reaction materials are fed through the high-level tank, and the measurement control is difficult, and the reaction needs to be controlled below 55°C. , frequent operations, high labor intensity, long production cycle and low equipment capacity. At the same time, the heat of reaction needs to be removed by freezing during the reaction process, and the material needs to be heated during deacidification, so the energy utilization rate in the production process is low.

Contents of the invention

For above-mentioned situation, the present invention will provide a kind of new dimethyl phosphite production method, to solve the above-mentioned problem.

The production method of dimethyl phosphite of the present invention, still reacts with phosphorus trichloride and methyl alcohol as raw material. The specific process is that in the reaction chamber space with various raw material injection structures with cross-type injection angles, phosphorus trichloride and methanol measured at a molar ratio of 1: (3.0-3.1) are respectively passed through their respective injection structures. Each corresponding pumping mechanism continuously sprays and sends them into the reaction chamber space to mix and react with each other. Because the reaction raw materials are sprayed, especially after high-speed spraying, the atomization can make them dispersed into fine droplets, which is conducive to the rapid, sufficient and uniform mixing of the raw materials, and the contact and collision with each other with a large contact area. , so that the reaction can be carried out rapidly and fully within a few seconds (for example, 3 to 5 seconds) and completed. Then the reactant material is introduced tangentially into the centrifugal cyclone separation device whose pressure is lower than that of the reaction chamber space. Since the reaction is a strong exothermic reaction, the reaction material after the mixed reaction is introduced into the centrifugal cyclone separation device in the process of rapid volume expansion, can make full use of the reaction heat to complete the vaporization, and then pass along the cyclone separation device In the internal circular motion, the heat exchange is completed between the interfaces of the substances. Among them, non-condensable gases such as HCl and methyl chloride are heated by reaction heat and then separated from the condensed and liquefied dimethyl phosphite product, and form an internal spiral upward airflow, which is discharged from the top and sent to the next step for processing; The condensed and liquefied dimethyl phosphite descends in a spiral manner and forms a descending liquid film on the inner wall of the device to be collected. Therefore, the gaseous components such as HCl and the condensed and liquefied dimethyl phosphite can be separated and removed quickly, and the occurrence of side reactions is effectively suppressed.

After testing, in the above-mentioned method, the phosphorus trichloride and methanol two reaction raw materials that collide and mix with each other in the space of the reaction chamber in a cross-jet manner are used to form a jet stream at an angle of 40 to 120°. The effect of mutual mixing reaction is more preferable.

As mentioned above, in addition to shortening the contact time of the reaction raw materials as much as possible so that they can be quickly mixed to complete the reaction, the reaction temperature is also an influencing factor that should be paid attention to. According to the current method, it is permissible to control the reaction temperature at no more than 55°C. It is better to control the mixed reaction temperature of phosphorus trichloride and methanol in the space of the above reaction chamber to be no higher than 45°C.

Because the two reaction raw materials are sent into the reaction chamber space for mixed reaction in the way of injection with a relatively high speed, the running speed of the materials is correspondingly relatively fast. In order to ensure that the two raw materials can have sufficient mixing reaction time, according to actual needs, the reaction materials in the reaction chamber space can be introduced into the centrifugal cyclone separation device through a pipeline reaction extension structure of appropriate length, so as to facilitate The material continues to fully complete the reaction during the operation of the centrifugal cyclone separation device.

When a centrifugal cyclone separation device is used to separate the mixed materials, the cyclone separation chamber of the cyclone separation device should generally have a relatively low pressure. For further improving the separation effect to reaction material, through test, in above-mentioned method, to adopt the pressure that makes said centrifugal cyclone separation device not higher than gauge pressure-0.075MPa, and/or make said It is more preferable that the reaction material is introduced into the centrifugal cyclone separation device along the tangential direction at a speed of 5-10 m/s.

In order to minimize the unfavorable side reactions of the reaction materials under the influence of HCl that has not been completely separated during the separation process, it is better to control the temperature of the centrifugal cyclone separation of the reaction materials at 60°C to 80°C.

For the benefit of controlling and regulating the temperature of the mixed reaction and/or centrifugal cyclone separation process, the above-mentioned mixed reaction and/or centrifugal cyclone separation are preferably to adopt temperature control such as commonly used jacketed insulation layers. /Accommodating structure of reaction chamber space and/or centrifugal cyclone separation device. For example, for the above-mentioned strong exothermic reaction of the present invention, the corresponding required temperature can be controlled/adjusted by passing a cooling medium such as ice brine into the jacket.

According to different production scales, the above-mentioned production method of the present invention can have different specific operation modes. For example, the raw material phosphorus trichloride and methanol can be fed into the same reaction chamber at one time according to the molar ratio to complete the reaction.

The above-mentioned production method of the present invention can also adopt the mode of two-stage reaction, make said phosphorus trichloride and methyl alcohol complete reaction through the two-stage said reaction chamber space that is arranged continuously respectively by said molar ratio. When adopting the two-stage reaction mode, in the first-stage reaction chamber space, the methanol of the total amount of phosphorus trichloride and 1/2 to 3/4 amount is mixed and reacted with each other in the said spraying manner, and through the said centrifuge After the cyclone separation, the collected separation product and the remaining amount of methanol are sent to the reaction chamber space of the second stage in the same injection manner to carry out the mixing reaction, and the subsequent centrifugal cyclone separation is carried out. According to the aforementioned reaction process and mechanism, especially for large-scale production, the use of this two-stage reaction method can obtain more ideal results.

The test shows that the above-mentioned production method of the present invention can greatly shorten the reaction time, effectively avoid the acidolysis side reaction of dimethyl phosphite, improve the effective conversion rate of raw materials, and the yield of dimethyl phosphite can reach 90%. Above, the hydrogen chloride removal rate in the crude ester product can reach 98%. However, if traditional methods are used for production, the yield of dimethyl phosphite is generally 80-88%, and the removal rate of HCl is about 90%. The load on the device is large, and the removal of HCl is not timely, which also brings the problem of many side reactions. In addition, the above-mentioned method of the present invention can realize the continuous production of dimethyl phosphite, which provides a great development space for the improvement of production capacity and the further reduction of operation cost.

The above contents of the present invention will be further described in detail below in conjunction with the specific implementation manners of the embodiments shown in the accompanying drawings. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following examples. Without departing from the above-mentioned technical idea of the present invention, various replacements or changes made according to common technical knowledge and customary means in this field shall be included in the scope of the present invention.

Description of drawings

Fig. 1 is a schematic diagram of a reaction/separation apparatus applicable to the production method of the present invention.

Detailed ways

Example 1

In the device shown in Figure 1, 810kg/h of methanol and 1160kg/h of phosphorus trichloride are respectively metered by their respective metering pumps 1 and then continuously sprayed into them through high-pressure nozzles 2 at an angle of 70° Reaction chamber space 3 with reaction extension tube and cooling jacket structure. Under the action of the injection of the high-pressure nozzle 2, the pressure of the raw material entering the chamber space 3 of the reaction section is controlled at a gauge pressure of -0.085 to -0.090 MPa. Collide and mix with each other in a spray mode, and make the reaction materials enter the centrifugal cyclone (wind) separator 4 with a pressure of -0.090～0.092 (gauge pressure) along the reaction extension pipe at a speed of 8.5m/s along the tangential direction. Separation of liquid phase product dimethyl phosphite crude product and non-condensable gases such as HCl and methyl chloride at ~70°C. In the dimethyl phosphite crude product obtained after being separated by the centrifugal cyclone separator 4, the removal rate of hydrogen chloride reaches 95%, and the yield of the dimethyl phosphite after the crude product is rectified is 89.1%.

Example 2

The two-stage reaction process is composed of two identical devices with the structure shown in Figure 1 . The raw materials are 890kg/h of methanol and 1257kg/h of phosphorus trichloride, and after being metered by respective metering pumps 1, the full amount of phosphorus trichloride and 594kg of methanol are sprayed into the reaction chamber space 3 of the first-stage device. The included angle of the jet stream is 120°. The pressure of the primary reaction device is controlled at gauge pressure -0.075~-0.080MPa, the reaction temperature is controlled at 48~50°C, the speed of entering the cyclone (wind) separator is 5.5m/s, and the inner temperature of the cyclone separator is controlled at 75±1°C. The gauge pressure of the second-stage reaction device is -0.085～-0.090MPa, the included angle of the jet flow is 90°, the reaction temperature is 50～53°C, the velocity entering the cyclone (wind) separator is 7.5m/s, and the inner temperature of the cyclone separator Control 65±1℃. The separated liquid collected from the second stage reaction device. After testing, the removal rate of HCl reaches 98%, and the yield of the crude product after distillation and purification is 91.5%.

Claims (8)

1. the production method of dimethyl phosphite, reacts with phosphorus trichloride and methyl alcohol as raw material, it is characterized in that in the reaction chamber space that is provided with each raw material injection structure with cross type injection angle, molar ratio 1 : (3.0～3.1) Metered phosphorus trichloride and methanol are sent into the reaction chamber through continuous injection by each corresponding pumping mechanism through their respective injection structures, and then mixed and reacted with each other, and then the reaction materials are introduced into the reaction chamber along the tangential direction with a pressure lower than that of the reaction chamber. The centrifugal cyclone separation device in the space, the non-condensable gaseous components and the condensed liquid products are subjected to centrifugal cyclone separation at 60 ° C ~ 80 ° C, and the liquid dimethyl phosphite product that descends along the inner wall of the centrifugal cyclone separation device is collected. 2. the production method of dimethyl phosphite as claimed in claim 1 is characterized in that in said reaction chamber space, phosphorus trichloride and methyl alcohol collide with each other and mix with the jet flow that becomes 40～120 ° of angles reaction. 3. the production method of dimethyl phosphite as claimed in claim 1 is characterized in that the mixed reaction temperature of phosphorus trichloride and methyl alcohol in said reaction chamber space is not higher than 45 ℃. 4. the production method of dimethyl phosphite as claimed in claim 1 is characterized in that the reaction material in the said reaction chamber space is introduced into the centrifugal cyclone separation device through the pipeline reaction extension structure. 5. the production method of dimethyl phosphite as claimed in claim 1 is characterized in that the pressure of said centrifugal cyclone separation device is not higher than gauge pressure-0.075MPa. 6. the production method of dimethyl phosphite as claimed in claim 1 is characterized in that said reaction material is introduced into centrifugal cyclone separation device along tangential direction with the speed of 5～10m/s. 7. as the production method of the described dimethyl phosphite of one of claim 1 to 6, it is characterized in that said phosphorus trichloride and methyl alcohol are once in same said reaction chamber space by said molar ratio Sexual feeding completes the reaction. 8. as the production method of the described dimethyl phosphite of one of claim 1 to 6, it is characterized in that said phosphorus trichloride and methyl alcohol are respectively through the two-stage said reaction of continuous arrangement by said molar ratio The chamber space completes the reaction. In the first-stage reaction chamber space, the total amount of phosphorus trichloride and 1/2 to 3/4 amount of methanol are mixed with each other in the spray mode, and the centrifugal cyclone After the separation, the collected separation product and the remaining amount of methanol are sent to the reaction chamber space of the second stage in the same injection manner to carry out the mixed reaction, and the subsequent centrifugal cyclone separation is carried out.

Images