CN111187192A

CN111187192A - Method for improving yield of methomyl

Info

Publication number: CN111187192A
Application number: CN201911379169.1A
Authority: CN
Inventors: 李子平; 李金元; 严峰
Original assignee: Andomai Co Ltd
Current assignee: Andomai Co Ltd
Priority date: 2019-12-27
Filing date: 2019-12-27
Publication date: 2020-05-22

Abstract

The invention discloses a method for improving yield of methomyl, and belongs to the technical field of fine chemical engineering. The methomyl is a high-quality methomyl with the purity of more than 98.7 percent, which is prepared by reacting methomyl with methyl isocyanate to prepare a crude methomyl product, putting the crude methomyl product into a heating kettle filled with water, adding activated carbon, heating to 60-70 ℃, transferring into a filtering device for filtering after full adsorption, and sending filtrate into a crystallization kettle for normal recrystallization, filter pressing and drying; the target product obtained by the method not only has improved yield, but also has good crystal form and bright white color.

Description

Method for improving yield of methomyl

Technical Field

The invention relates to recycling of a target product, belongs to the technical field of fine chemical engineering, and particularly relates to a method for improving yield of methomyl.

Background

The methomyl is a systemic carbamate broad-spectrum insecticide with contact killing and stomach toxicity, is suitable for controlling aphids, moths, cutworms and other pests of cotton, tobacco, fruit trees and vegetables, and is a good substitute variety for controlling drug-resistant cotton aphids at present. The methomyl can also be used as an intermediate of thiodicarb, is a broad-spectrum and quick-acting insecticide, is effective on various pests such as aphids, cotton bollworms and the like, and can be used for crops such as grains, cotton, vegetables, tobacco, fruits and the like.

The domestic pesticide methomyl is a target product directly synthesized by the reaction of methylthioacetaldoxime and methyl isocyanate at the temperature of 5 ℃, and is generally produced by adopting a kettle type reactor and an intermittent method at present. The side reaction is more, the reaction temperature is not easy to control, the reaction time is long, and the product quality can not be guaranteed. The selection and yield of chemical synthesis reaction are not high, and the yield is not high.

For example, the Chinese patent application (application publication No. CN103524389A, application publication date:

2014-01-22) discloses a preparation method of a pesticide methomyl, which comprises the steps of adding water into methylthio acetaldoxime, pulping, adding methyl isocyanate dropwise into the methylthio acetaldoxime pulping liquid for reaction according to the mass ratio of the methylthio acetaldoxime to methyl isocyanate of 1: 1.0-1.3, controlling the reaction temperature to be 5-15 ℃ and the reaction time to be 1.5-3 h; then cooling and crystallizing after microporous filtration, and then filtering and drying. The method has the advantages of convenient operation, safe and controllable production, reduced generation of by-products, improved yield and quality, reduced energy consumption, reduced production cost, improved production site environment, further improved reaction solubility and safety, and reduced discharge of three wastes.

For another example, the chinese patent application (application publication No. CN 104529846a, application publication date: 2015-04-22) discloses a method for increasing the yield of methomyl produced by reacting methomyl with methyl isocyanate to obtain an aqueous solution of methomyl, which comprises the steps of: after the reaction is finished, controlling the temperature of the methomyl aqueous solution at 5-10 ℃, adding NaCl to separate the methomyl out, and filtering to obtain the solid methomyl. The method of the invention separates the methomyl in the water solution by using a salting-out method, improves the yield of the methomyl production, reduces the discharge amount of pollutants in the wastewater and is beneficial to environmental protection. The method is simple and low in cost, and the obtained methomyl product has high purity, good quality and strong practicability.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for improving the yield of methomyl, and the target product obtained by the method not only has improved yield, but also has good crystal form and bright and white color.

In order to achieve the purpose, the invention discloses a method for improving the yield of methomyl, which is characterized in that the methomyl is a crude methomyl product prepared by reacting methomyl with methyl isocyanate, and the method comprises the steps of placing the crude methomyl product in a heating kettle filled with water, adding activated carbon, heating to 60-70 ℃, fully adsorbing, transferring to a filtering device for filtering, and sending filtrate into a crystallization kettle for normal recrystallization, filter pressing and drying to obtain high-quality methomyl with the purity of more than 98.7%;

and a filtering carbon rod is arranged in the filtering device, and the aperture of the filtering carbon rod is 0.5 mm.

Further, the filtering device also comprises a jacket positioned outside the device for heat preservation, and water vapor is introduced into the jacket.

Further, air is introduced into the heating kettle to improve the filtering rate of the filtering device.

Further, the crude methomyl is prepared by reacting methomyl with methyl isocyanate to prepare a methomyl aqueous solution, and then heating, recrystallizing, filter-pressing and drying the solution, wherein the purity of the crude methomyl is lower than 98.2%.

Furthermore, in the process of preparing the crude methomyl product, the methomyl mother liquor obtained by pressure filtration is metered and then added with a certain proportion of industrial sodium chloride, the difference of solubility is utilized to separate out the methomyl crystal, and then the crude methomyl product is obtained by suction filtration and drying.

The beneficial effects of the invention are mainly embodied in the following aspects:

the invention utilizes the salting-out method to separate out the methomyl in the aqueous solution to obtain the crude methomyl, and the crude methomyl is subjected to full decoloration and impurity removal recovery to improve the production yield and quality of the methomyl, thereby not only saving the production cost, but also reducing the discharge amount of wastewater, being beneficial to environmental protection, having simple method and low cost, and obtaining the methomyl with high purity and good quality, and having strong practicability.

Drawings

FIG. 1 is a schematic view of the recovery process of the present invention.

Detailed Description

The invention discloses a method for improving the yield of methomyl, wherein the methomyl is a high-quality methomyl with the purity of more than 98.7 percent, which is prepared by reacting methomyl with methyl isocyanate, the methomyl crude product is placed in a heating kettle filled with water, activated carbon is added, the temperature is raised to 60-70 ℃, the mixture is transferred into a filtering device for filtering after being fully absorbed, and filtrate is sent into a crystallization kettle for normal recrystallization, filter pressing and drying; as can be seen from fig. 1, more than one carbon filter rod is disposed in the filter device, and the pore diameter of the carbon filter rod is 0.5 mm. The carbon rod can completely intercept the adsorbed activated carbon and impurities in the crude product, the obtained filter residue is discharged through a residue discharge port arranged at the bottom of the filtering device, and when the carbon rod reaches the service life of the carbon rod, the carbon rod can be taken out and replaced by a new carbon rod.

Further, the filtering device also comprises a jacket positioned on the outer side of the device and used for heat preservation, and water vapor is introduced into the jacket to realize heat preservation of the heating kettle.

In order to better explain the invention, the following further illustrate the main content of the invention in connection with specific examples, but the content of the invention is not limited to the following examples.

Example 1

The embodiment discloses a method for preparing a crude methomyl product by reacting methomyl with methyl isocyanate to prepare a methomyl aqueous solution, then heating, recrystallizing, filter-pressing and drying, wherein the filter-pressed mother liquor is recycled and salted out once, the methomyl mother liquor obtained by filter-pressing is measured again, then industrial sodium chloride is added in proportion, the difference of solubility is utilized to separate out the methomyl crystal, and then the crude methomyl product is obtained by suction filtration.

Example 2

Putting 1.7-1.8 t of the crude methomyl product obtained in the example 1 into a heating kettle with prepared fresh water, putting 20kg of activated carbon adsorption decolorant, heating to 60-70 ℃, fully adsorbing for 1.5-2.0 h, and adsorbing impurities in the crude methomyl product through the special filtering device,

the device is a precision filter, 5 groups of precision filtering carbon rods are arranged in the device, the through hole diameter is 0.5 mesh, the adsorbed activated carbon and impurities in a crude product can be completely intercepted, especially 2 groups of carbon rods are arranged at the bottom of the filtering device, filtrate in the filtering device can be completely filtered, and then dry filter residues are discharged from a residue discharge hole at the bottom, so that the activation and regeneration of the carbon rods can be facilitated, and the influence on the filtering efficiency caused by blockage due to excessive solid residues can be prevented, and the specific process flow is illustrated in attached figure 1; transferring the materials to a crystallization kettle for normal recrystallization, performing filter pressing and drying to obtain the high-quality methomyl with the content of more than 98.7 percent, and improving the total yield by 3 percent compared with the total yield of the crude methomyl treated by a water washing method.

The research finds that the mother liquor for treating the crude methomyl can be recycled only once, and if the mother liquor is recycled, a small amount of high-quality methomyl product can be obtained, which is shown in the conditions of low content, yellow or gray color, poor crystal form and easy agglomeration of the product, so the recycling is not recommended.

The invention mainly achieves the effects of decoloring and removing impurities of the crude methomyl product by adding a set of special adsorption and filtration equipment, the purity of the prepared recovered methomyl can reach 98.7 percent, the methomyl in the mother solution is fully recovered, and the yield and the quality of the product are improved. The methomyl produced by the method has low one-time investment cost, greatly reduces the ton wastewater discharge of the product, realizes cost reduction and efficiency improvement, lightens the environmental protection pressure of the company, and has strong practicability.

The above examples are merely preferred examples and are not intended to limit the embodiments of the present invention. In addition to the above embodiments, the present invention has other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.

Claims

1. The method for improving the yield of methomyl is characterized in that the methomyl crude product is placed in a heating kettle filled with water, activated carbon is added, the temperature is raised to 60-70 ℃, the mixture is transferred into a filtering device for filtering after being fully absorbed, and filtrate is sent into a crystallization kettle for normal recrystallization, filter pressing and drying to obtain high-quality methomyl with the purity of more than 98.7 percent;

2. The method for improving methomyl yield according to claim 1, wherein the filtration device further comprises a jacket for holding temperature outside the device, and water vapor is introduced into the jacket.

3. The method for increasing methomyl yield of claim 1 further comprising introducing air into the heated kettle to increase the filtration rate of the filtration device.

4. The method for improving the yield of methomyl according to any one of claims 1 to 3, characterized in that the crude methomyl is prepared by reacting methomyl with methyl isocyanate to prepare an aqueous solution of methomyl, and then heating, recrystallizing, pressure filtering, and drying, wherein the purity of the crude methomyl is lower than 98.2%.

5. The method for improving the yield of methomyl according to claim 4, characterized in that the methomyl crude product is obtained by metering the methomyl mother liquor obtained by pressure filtration in the process of preparing the methomyl crude product, then adding a certain proportion of industrial sodium chloride, crystallizing and separating the methomyl by utilizing the difference of solubility, and then carrying out suction filtration and drying.