Main application background and overview of pyridones
Pyridone is an intermediate in the production of sodium 3,5,6-trichloropyridinol. It is an important chemical raw material and is mainly used in the production of the pesticide chlorpyrifos and Class A chlorpyrifos. Pesticide intermediates. At present, the most valuable method for preparing pyridones is the trichloroacetyl chloride method. This method involves the reaction of trichloroacetyl chloride and acrylonitrile under the action of a catalyst, and the resulting product is then subjected to ring closure, crystallization, and centrifugation to obtain pyridone. One of the most important raw materials of this method is trichloroacetyl chloride, and the final yield of pyridone is measured by trichloroacetyl chloride, because its price is the most expensive among the main raw materials. The existing methods of preparing pyridones using trichloroacetyl chloride start with trichloroacetyl chloride as raw material, resulting in the need to outsource trichloroacetyl chloride in actual large-scale production, which not only consumes manpower and material resources, but also Increased freight and storage costs, etc., virtually increase the production cost of pyridone and reduce the competitiveness of the enterprise.
Main applications of pyridone
Pyridones are a type of organic compound skeleton with important biological activity and medicinal value, which are used to synthesize the diuretic drug torsemide or other drug intermediates; therefore, it is important to develop simple and efficient methods to realize the functionalization of pyridones. It has great research significance and application value; its application examples are as follows:
1) Preparation of pyridone-modified cellulose adsorbent. Pyridone compounds have good ion binding ability, and pyridone macrocyclic compounds also show good ion selectivity: five-membered macrocyclic compounds can selectively adsorb Cs+, K+ and Ag+ from a mixed solution of 19 kinds of metal ions. . A new type of pyridone functionalized cellulose adsorbent has been synthesized. The structure and surface morphology of the adsorbent were characterized by infrared spectroscopy and scanning electron microscopy, respectively, and its adsorption performance as an adsorbent for heavy metal ions was studied. The results show that the surface of the cellulose adsorbent becomes rough and the specific surface area increases after modification by pyridonedioic acid. The adsorbent has strong effects on Cu2+, Pb2+, The maximum adsorption capacities of Cd2+ and Co2+ reach 146.52mg/g, 233.05mg/g, 192.08mg/g, and 258.13mg/g respectively; for metal ions The adsorption behavior is consistent with the pseudo-second-order kinetic model and the Langmuir isothermal adsorption model; through infrared spectral research on the adsorbent before and after adsorption of metal ions, it was found that the ketone carbonyl group and carboxylic acid group of pyridone participated in the adsorption process of metal ions at the same time.
2) Preparation of pyridone-type benzotriazole ultraviolet absorber. Studies have used thiourea dioxide as a reducing agent to reduce C.I. Disperse Yellow 119 into pyridone-type benzotriazole ultraviolet absorber UV-1. The reduction was verified by analytical means such as ultraviolet-visible spectroscopy, infrared spectroscopy, hydrogen nuclear magnetic spectroscopy, and mass spectrometry. The molecular structure of the product. Research results show that the maximum absorption wavelength of ultraviolet absorber UV-1 in ethanol solution is 329nm, and the molar extinction coefficient is high. UV absorber UV-1 has certain dyeing ability on polyester fabrics and is suitable as a UV absorber for polyester.
3) Production of chlorpyrifos by pyridone aqueous method. The chemical name of chlorpyrifos is 0,0-diethyl-0-(3,5,6,-trichloro-2-pyridyl)phosphorothioate. It is a high-efficiency, broad-spectrum, medium-low-toxic, safe organophosphorus insecticide and acaricide. It is one of the better products to replace highly toxic pesticides and can effectively control borers on vegetables, corn, tea, fruit trees and flowers. , leaf rollers, leaf miners, cotton bollworms, armyworms, scale insects, aphids, thrips, leafhoppers and various mites. It can also control underground pests and parasites outside livestock. It has broad application prospects and is an alternative. The first type of highly toxic pesticide. The preparation is as follows: 1) Mix 3-4 parts by weight of water, 0.8-1.2 parts by weight of pyridone, 0.2-0.25 parts by weight of sodium chloride, and 0.04-0.06 parts by weight of caustic soda (the pH value of the system is adjusted to 8- 10), 0.03-0.04 parts by weight of boric acid, 0.001-0.003 parts by weight of emulsifier and 0.0005-0.0008 parts by weight of phase transfer catalyst are sequentially put into the condensation kettle and stirred evenly, then slowly add 0.7-0.9 parts by weight of 0,0 -Diethylphosphorothioate chloride. Because heat is released during the reaction, the system temperature will rise by itself, and the reaction temperature must be controlled at 45 to 50°C. After the ethyl chloride is added dropwise, continue the insulation reaction for 1 hour, then stop stirring in the condensation kettle, control the temperature to 50±2°C, keep it for 2 hours and then separate into layers. The lower layer (oil phase) is introduced into the filter aid kettle to prepare for filtration, and the upper layer ( Aqueous phase) is introduced into the extraction kettle for extraction. 2) Add a certain amount of desalted water to the filter aid kettle and add filter aid. After stirring for a certain period of time, start filtering at 60±3°C. The filtrate is introduced into the stratifier, the temperature is controlled at 60±3°C, kept warm for 2 hours and then separated into layers. The lower layer (oil phase) is introduced into the dehydration kettle, and the upper layer (water phase) is introduced into the condensation kettle for use in the next condensation. 3) The crude oil introduced into the dehydration kettle is dehydrated. The entire dehydration process requires a vacuum degree of ≥0.08MPa and a temperature of 60±3°C until the water content in the crude oil is qualified. The dehydrated oil phase undergoes filtration, cooling, crystallization, centrifugal separation, and drying to obtain chlorpyrifos raw powder with a purity greater than 99%.
Main Application Preparation of Pyridone
Method 1: Pyridone is prepared as follows:
(1) Mix the newly distilled trichloroacetyl chloride, acrylonitrile, and solvent at a certain molar ratio, then react under the action of cuprous chloride catalyst at 90-120°C, and remove it by operating under reflux conditions PlaceThe produced hydrogen chloride gas generates a dilute solution of 2,2,4-trichloro-4-cyanobutyryl chloride.
(2) Distill the 2,2,4-trichloro-4-cyanobutyryl chloride mixture under reduced pressure, recover unreacted raw materials (mainly acrylonitrile, trichloroacetyl chloride and some solvents), and filter The catalyst is taken out, and the filtrate is a concentrated solution of 2,2,4-trichloro-4-cyanobutyryl chloride.
(3) Add an appropriate amount of solvent to the concentrated solution of 2,2,4-trichloro-4-cyanobutyryl chloride at a gauge pressure of 30-150KPa, a temperature of heavy calcium carbonate of 30-100°C and a catalyst. The reaction proceeds under the influence of pyridinone solution. The pyridone solution is cooled, crystallized and separated to obtain dry pyridone.
Method 2: A method of preparing pyridones using chloroacetic acid waste liquid with wide sources of raw materials and low industrial production costs, including the following steps:
(1) Introduce the chloroacetic acid waste liquid into the reaction kettle and start distillation. The temperature is between 100 and 180°C. The fraction is discharged in 0 to 3 hours. After 3 hours, take a sample to test the moisture. If the moisture is less than 30%, remove the fraction. Collect it into the fore distillation tank, continue distillation until the instantaneous sample moisture is less than 1% to 3%, stop distillation, cool to 50°C, and introduce it into the mother liquor mica storage tank.
(2) Adjust the temperature of the main kettle to 65~75℃ and the auxiliary kettle to 50~60℃ according to the reflux flow. In the later stage of the reaction, samples are taken to determine the boiling range. If the high boiling content is 5% to 10%, it is the end point, and the reaction time is 7 to 15 hours.
(3) During the chlorination reaction, the temperature of the main kettle is 85°C and the auxiliary kettle is 75°C. During the reaction process, the chlorine flow rate is optimal when the condenser of the main kettle is slightly green and the upper air pipe condenser of the auxiliary kettle is pure white. When the content of mixed acid chloride (monochloroacetyl chloride and dichloroacetyl chloride) is less than 3%, the reaction reaches the end point and chlorine flow is stopped.
(4) After introducing the chlorination completed liquid into the distillation tower, adjust the steam pressure. Mining stops when there is almost no gold left at the top of the tower. During the production process, the reflux ratio is strictly controlled and the steam pressure is stable.
(5) Trichloroacetyl chloride and acrylonitrile are added to each other at 90 to 120°C. The catalyst used in the addition process is cuprous chloride, and its mass is 0.33% of the mass of trichloroacetyl chloride. Reflux for 10 to 30 hours and cool to 50 to 60°C; the molar ratio of the reaction raw materials used is acrylonitrile: trichloroacetyl chloride: solvent = 1: 1.5 to 2.0: 4.3.
(6) The solvent used is chlorobenzene, and the desolvation temperature is controlled within 80 to 120°C to avoid the formation of tetrachloropyridine.
(7) The catalyst used in the closed-loop process is zinc chloride, and its mass is 0.012% of the total solution. The temperature of the closed loop is 68~78℃.
