Recently, a new clean production process for 356-trichloro-2-pyridine phenol sodium (referred to as trichloropyridine phenol sodium), an important intermediate used in the production of organophosphorus pesticides such as diazinon, methyl diazinon, and the herbicide Green Grass, has passed the scientific and technological achievement appraisal organized by the China Petroleum and Chemical Industry Federation in Shandong, China.

According to the developer of this new process, Shandong Qiancheng Industrial and Trade Technology Co., Ltd., the traditional production processes of trichloropyridine phenol sodium abroad and at home have the characteristics of high energy consumption and high pollution. The new process adopts an innovative pyridine bidirectional synthesis method, which has low energy consumption, less "three-waste" emissions, and outstanding advantages such as high conversion rate, high selectivity, and product purity greater than 99%.

The innovation points of this project are mainly reflected in the following aspects:

First, a new type of photochlorination reactor was independently developed, increasing the conversion rate of pyridine from 90% to over 99%; the reaction products are one-chloropyridine and two-chloropyridine, with the proportion of 26-dichloropyridine reaching over 60%.

Second, a solvent with catalytic function was used, enabling the one-step quantitative conversion of 26-dichloropyridine to 6-chloro-2-pyridine phenol sodium. The reaction conditions are mild, the separation process is simple, and the yield is over 99%.

Third, using sodium hypochlorite as an electrophilic substitution reagent for β-directional substitution at the β-position of 6-chloro-2-pyridine phenol sodium directly generates 356-trichloro-2-pyridine phenol sodium, with a yield of 80%.

The appraisal expert group observed on site that the 10,000-ton/year demonstration production line built by Qiancheng Company using this new process has been operating stably for two years. All process steps are at atmospheric pressure, the process is simple, and the energy-saving effect is obvious. The process water is achieved in a closed circuit, meeting environmental protection requirements. User usage reports show that the quality of the products produced by this device is significantly better than that of the traditional process.

It is learned that the Chinese government attaches great importance to safety, energy conservation, and environmental protection issues. The successive withdrawal of highly toxic and highly residual pesticides has brought a broad market space and development opportunities for diazinon. It is expected that China's diazinon production will account for about 45% of the global production in 2015. One of the key factors for the rapid increase in diazinon production capacity is the development and innovation of the synthesis process for trichloropyridine phenol sodium.