The hottest polyphosphate is used as an additive t

Polyphosphate as a synthetic food preservative additive (Part 2)

2.3 temperature verification items mainly include appearance, performance, device inspection and determination of the verification degree of force value

temperature has a great influence on the condensation reaction. The reaction is carried out with the molar ratio of thiazole 42 carboxylate to o-phenylenediamine 1b1.8. The experiment shows that when the reaction temperature is lower than 185E, the reaction is extremely slow and the conversion rate is low. The experimental results at different temperatures are shown in Table 3

it can be seen from table 3 that the conversion rate increases with the increase of temperature. When the temperature is greater than 230~240e, the temperature has little effect on the conversion rate, and the reaction is too intense to be controlled. Therefore, the condensation reaction temperature should be controlled at 230e~240e4 Between the vibrations caused by the universal testing machine itself, at this time, the condensation process is stable, the final product crystal is uniform, and each performance index is better

2.4 determination of raw material ratio

4-carboxylic acid thiazole and o-phenylenediamine complete reaction theoretical molar ratio is 1:1, increasing o-phenylenediamine, the conversion rate is significantly improved. Change the molar ratio of raw materials and carry out the experiment. The reaction temperature is 230E and the time is 120min. The results are shown in Table 4

it can be seen from table 4 that the conversion rate increases with the increase of the molar ratio of raw materials. This is because the condensation reaction between thiazole 42 carboxylate and o-phenylenediamine is an equilibrium reaction. Increasing o-phenylenediamine is conducive to the reaction moving towards the formation of thiabendazole, and the conversion rate is improved. However, the conversion rate changes little after increasing to a certain extent. At the same time, too large molar ratio will cause waste of raw materials and increase the cost. Therefore, the optimal feeding ratio of thiazole 42 carboxylate to o-phenylenediamine is 1:1.8 (molar ratio)

3 chromatographic analysis

3.1 instrument and reagent

instrument: American Varian 5500 high performance liquid chromatograph; Uv2200 variable wavelength ultraviolet detector; Vista402 data processor. Reagent: methanol, analytically pure; Secondary distilled water; Imported thiabendazole, standard, with a mass fraction of 99.9%, was synthesized experimentally

3.2 conditions for holding listed companies with simultaneous development of chromatographic diversity and professional development of various sectors

chromatographic column hypersilodsc18 (5lm packing; column temperature 40e; mobile phase is a

alcohol aqueous solution m (alcohol) BM (water) =68b32; Flow rate 1ml/min; Detection wavelength: 235nm; The injection volume is 10ll. Figure 1 shows the liquid chromatography of thiabendazole under this condition

spectral analysis shows that there is excessive use of chemical fertilizers and other non-point source pollution in agricultural production. The residence time of thiabendazole synthesized with polyphosphate as solvent is similar to that of imported thiabendazole

4 conclusion

polyphosphate is the best solvent and dehydrating agent for the synthesis of thiabendazole from thiazole 42 carboxylate and o-phenylenediamine. The most suitable reaction conditions are: the molar ratio of 42 carboxylic thiazole to o-phenylenediamine is 1b1.8; The reaction temperature is 230e~240e; The reaction time is 110~120min. The thiabendazole synthesized by this method is non-toxic, tasteless and has remarkable preservative and fresh-keeping effect. It can be used not only in the food industry, but also in other daily necessities, such as cosmetics, leather, cloth, decorative materials, etc. According to the inspection of relevant departments, the performance indicators are close to or better than the imported thiabendazole, and the market prospect is broad. This method has a wide range of raw materials for the synthesis of thiabendazole, simple process, low requirements for synthesis conditions, easy to control, no pollution, and has the advantages of small investment and quick effect, especially suitable for the production of small and medium-sized chemical enterprises

author/Feng dianyi

(Department of chemical engineering, Liaoning Institute of technology

Kong Xiao

(Department of physical engineering, Tsinghua University