Applications of pure pyridine [Overview]
Pure pyridine (Pgridine) is a six-membered heterocyclic compound formed by replacing a nitrogen atom on the benzene ring. It is an important member of the downstream products of formaldehyde. Pyridine is one of the “chips” for the synthesis of fourth-generation heterocyclic pesticides, and is mainly used to synthesize the pesticides and herbicides paraquat, diquat and the insecticide chlorpyrifos.
Applications of pure pyridine [Physical and chemical properties]
Pyridine is a colorless or light yellow hygroscopic liquid with a special bitter odor. Melting point – 42℃, boiling point 115.56℃, soluble in water, alcohol, ether and various organic solvents.
Figure 1 shows pure pyridine
Application of pure pyridine [preparation method]
The pure pyridine production process uses the crude light pyridine produced in the recycling workshop as raw material, dehydrates and distills it in the crude pyridine tower to obtain a 105°C ~ 120°C pyridine fraction, and then uses the pyridine fraction as the raw material to distill again to obtain pure pyridine product.
Application of pure pyridine [Measurement method]
Gas chromatography method to determine the purity of pyridine: 1. Analyze the sample. Use a balance to accurately weigh analytically pure pyridine (mass fraction 99.9%) and a small amount of pure benzene and distilled water to prepare a series of solutions of different concentrations; the industrial pyridine to be measured. 2. Chromatography analysis conditions Carrier gas: Nitrogen vaporization temperature: 120℃ Chromatography temperature: 80℃ Gas velocity: 20 mL/min Pre-column pressure: 1.2 kg/cm Injection volume: 1μL Bridge flow: 120 mA Sensitivity: 100 Attenuation Ratio: 1:1 Chromatographic column: dinonyl phthalate 3. Analysis and comparison method: After chromatographic analysis of the prepared solutions, the respective response factors are obtained, and then the analytically pure pure ethoxycarbonyl phenylboronic acid and pyridine are Use chromatographic analysis to conduct chromatographic analysis of the industrial products to be tested, and use titration method to analyze and compare the industrial products to verify the feasibility of the analysis method.
Applications of pure pyridine [Application]
1. The application of pyridine in the clean production of chlorpyrifos. Chlorpyrifos is one of the top three pesticides consumed in the world market. It is also the main alternative after China banned 5 highly toxic ammonium bicarbonate pesticides in 2007. The product is synthesized from sodium pyridine and ethyl chloride as raw materials. The output of chlorpyrifos in 2011 was 41,900 tons. There are currently two production processes for sodium pyridine. One is the route using pyridine as raw material. The pyridine is processed by Chlorination yields tetrachloropyridine, which is further reacted to form sodium trichloropyridinol; the other is the cyclization route, which uses trichloroacetyl chloride and acrylonitrile as raw materials to synthesize sodium trichloropyridinol through a cyclization reaction. Foreign companies use the pyridine raw material route, while most domestic companies use the ring method route.
2. New downstream applications of pyridine. In addition to tetrachloropyridine introduced above, which is an important intermediate for the synthesis of chlorpyrifos, 2,3-dichloropyridine has also become an important pesticide intermediate and can be used to synthesize chlorantraniliprole. Amide. Chlorantraniliprole is a new generation of insecticide developed by DuPont. Its 20% suspension is sold under the trade name “Kangkuan”. The market development of chlorantraniliprole has grown rapidly in recent years, and it is a new pesticide market worthy of attention downstream of pyridine.
Applications of pure pyridine [Main reference materials]
[1] Jiang Zhenhai. Application and development prospects of pyridine in pesticides in my country [J]. Shanghai Chemical Industry, 2014, 39(11):31-33.
[2]Wang Haiquan, Guo Ruiwei. Research on improving the quality of pure pyridine[J]. Fuel and Chemical Engineering, 2007(03):58-59.
[3]Hu Yanfang. Determination of pyridine purity by gas chromatography[J]. Journal of Qingdao University (Engineering Technology Edition), 2001(01):85-86.
