Preparation process for synthesizing phosphorous acid by hydrolyzing phosphorous trichloride

Abstract

The invention belongs to the field of chemical industries, and in particular relates to a preparation process for synthesizing phosphorous acid by hydrolyzing phosphorous trichloride. The preparation process comprises the specific steps of: adding hydrochloric acid into a hydrolysis reaction kettle, dripping phosphorous trichloride into the hydrolysis reaction kettle, pumping a phosphorous acid mixture synthesized by hydrolysis reaction into a distillation and deacidification kettle with a stirrer through a pump to perform negative-pressure distillation concentration, cooling and crystallizing a concentration solution to prepare a crystallized phosphorous acid product; and absorbing an HCL gas generated through reaction through a protective trough and a hydrochloric film type absorbing system in sequence to obtain hydrochloric acid. According to the preparation process disclosed by the invention, a bubble absorbing trough (the protective trough) is additionally provided before a hydrolysis reaction film reducing hydrochloric acid absorbing system so that the HCL gas generated through reaction is more rapidly discharged, and thus the effects on the dripping quantity and the speed of the phosphorous trichloride in the hydrolysis reaction are greatly reduced. The mechanical stirrer is used in the distillation and deacidification kettle so as to implement the mechanical transmission stir, carry out the reduced-pressure distillation, enhance the heat transfer, improve the heat transfer efficiency and accelerate the deacidification speed, and thus the deacidification time is shortened and the capacity is increased.

Description

technical field [0001] The invention belongs to the field of chemical industry and relates to a preparation process for synthesizing phosphorous acid by hydrolyzing phosphorus trichloride. Background technique [0002] Phosphorous acid is one of the series of phosphorus species, and it is the main raw material for chemical production. It is often used to manufacture phosphite, pesticide intermediates, polyester stabilizers, polyester resins, water treatment agents and other products. [0003] At present, most domestic phosphorous acid production methods use phosphorus trichloride as raw material to prepare phosphorous acid by hydrolysis. Its production process is usually to add a certain amount of water or a small amount of saturated phosphorous acid solution in proportion to the hydrolysis reactor, slowly add phosphorus trichloride solution to it, and strictly control the dropping speed and reaction temperature of the phosphorus trichloride solution. The produced hydrogen ...

AI Technical Summary

Problems solved by technology

The disadvantages of this process are as follows: (1) Phosphorus trichloride is added dropwise into the hydrolysis reactor to react with water. In the initial stage of the reaction, the reactants release heat in a large amount, and the temperature rises sharply in an instant, and the requirements for temperature control are relatively high.

(2) The generated hydrogen chloride gas needs to pass through several stages of series-connected water bubbling absorption devices to produce by-product hydrochloric acid, and the resistance of the absorption system is large

It makes it difficult to discharge the hydrogen chloride gas produced by the reaction immediately, which seriously restricts the amount and speed of phosphorus trichloride dripping in the hydrolysis reaction

(3) The distillation deacidification kettle does not have agitation, and only relies on the jacket to heat, and the heat is slowly transferred to the material through the kettle wall. The deacidification takes a long time, which affects the increase in production capacity.

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