In addition, literature [17] developed a new manufacturing technology of PFS with an atomization method, that is, under the conditions of normal pressure and heating, the atomization drip of ferrous sulfate was contacted with nitrogen dioxide in circulation state. The aim of this process was to raise the contact area between nitrogen dioxide and ferrous sulfate solution, quicken reaction velocity, and shorten production cycle. The process pioneered a new way for the production of PFS. Of course, this will also increase the difficulty of technology and the investment of equipment.

    Moreover, it was reported that the best kind of catalyst had been found^[18] already up to now. This catalyst was not only high effective but nonpoisonous. When it was used in the oxidizing reaction of ferrous sulfate, the reaction could be completed in two hours. We hope it can be used in the industrial production of PFS early.

    In the manufacturing process of PFS above-mentioned, the reaction of ferrous and nitrogen oxides belongs to a reaction between liquid and gas. In order to increase their contact area and quicken the reaction speed, some measures, such as heating, high-pressure, strong stirring, and spraying, were often used. So, the technology of the method is complicated and the investment cost of equipment is also higher.

    Besides, in other report, potassium chlorate or hydrogen peroxide were used as a substitute for air or oxygen in the system of sodium nitrite. Although this can quicken the speed of catalysis oxidizing reaction, it increases the product cost, too.

1.3 Effect of catalyst promoter on the reaction of catalyzed oxidation

    Because the oxidizing reaction is a rate controlling step in the manufacturing process of PFS, shortening the reaction time has already become a focal point concerned. So people had made thorough studies^[3,6,18] at the aspects of oxidizer, catalyst, and catalyst promoter. Literature [3] had made some detailed studies on the kind and the addition of catalysts, the selection of catalyst promoters, the temperature and the acidity of reaction system. This literature thought that sodium iodide as a catalyst promoter could quicken the reaction speed. At the same time, it also thought that controlling the PH of the reaction system was a key to quicken the speed of oxidizing reaction. It discussed how sodium iodide quickens the speed of the oxidizing reaction, too.

     On the basis of inspecting t

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