Overview
At present, there have been literature reports on the preparation of tetrahydroxymethylphosphorus sulfate by absorbing the tail gas phosphine produced by the production of sodium hypophosphite through a suction spray absorption tower reaction, such as CN101224378, publication date 2008.07.23; CN101143877, publication date 2008.03.19. Among them, CN101224378 introduces the method of waste gas treatment in the production process of sodium hypophosphite. The process steps are as follows: collecting and storing phosphine; formulating formaldehyde, sulfuric acid or hydrochloric acid into an aqueous solution at a molar ratio of: 8.1-8.2:1; the aqueous solution Use a corrosion-resistant pump to pump it into the absorption tower, spray it downward from the top of the tower, use an air pump to send the phosphine gas in the tank into the absorption tower, and react and synthesize it at a temperature of 40-50°C to prepare Tetrakis hydroxymethyl phosphorus sulfate or tetrakis hydroxymethyl phosphorus chloride aqueous solution. However, the traditional spray tower absorption tower has a slow reaction speed, is prone to clogging, and is inconvenient to clean.
Absorption towers are divided into three categories according to the gas-liquid phase contact form. The first type is plate towers, bubble absorption towers, and stirring bubble absorption towers in which gas is dispersed in the form of bubbles in the liquid phase; the second type is ejector, venturi, and spray in which liquid is dispersed in the gas phase in the form of droplets. Tower; the third category is the packed absorption tower and falling film absorption tower in which the liquid contacts the gas phase in a film-like motion. The gas-liquid two-phase flow in the tower can be countercurrent or cocurrent. Countercurrent operation is usually adopted. The absorbent is added at the top of the tower and flows from top to bottom, contacting the gas flowing from bottom to upward. The liquid that has absorbed the absorbent is discharged from the bottom of the tower, and the purified gas is discharged from the top of the tower.
Content of the invention
The technical problem to be solved by the present invention is to provide a preparation method of tetrahydroxymethylphosphorus sulfate, which is simple, low in cost, fast in reaction speed, does not cause clogging, and is suitable for industrial production of waste gas reuse.
The reaction formula of the present invention is as follows:
2PH3+8HCHO+H2SO4→(HOCH2)4PSO4O(CH2OH)4
The preparation method of tetrahydroxymethylphosphorus sulfate of the present invention includes:
Add sulfuric acid and formaldehyde into the reaction kettle, turn on the gas-liquid circulation mixing reaction pump, add phosphine into the gas-liquid circulation mixing reaction pump, and absorb phosphine through the gas-liquid circulation mixing reaction device at 50-60°C , the phosphine that has not been fully absorbed enters the next gas-liquid circulation mixing reaction pump (the two gas-liquid circulation mixing reaction devices are the same, but are connected in series, which is more conducive to the utilization of phosphine), and passes the central control detection The formaldehyde content determines the end point of the reaction. After the reaction is completed, it is concentrated under reduced pressure to obtain tetrahydroxymethylphosphorus sulfate.
The mass ratio of sulfuric acid and formaldehyde is 1:7.0-7.1.
The phosphine described is the phosphine-containing tail gas generated during the production of sodium hypophosphite, which has been purified.
Beneficial effects:
The present invention circulates the reaction in the reaction device through a gas-liquid circulation mixing reaction pump, and at the same time introduces phosphine gas to carry out the absorption reaction. The gas-liquid circulation mixing reaction pump has liquid and gas inlets, and the flow rate of the pump can Reaching 30m2/h, the maximum allowable silicone elastomer content is 40%. The phosphine gas and the reaction liquid are strongly mixed through the pump and then absorbed and reacted. Compared with the traditional spray tower absorption method, this reaction device is simple, There will be no blockage, the reaction speed can be increased by about 40%, and the equipment is simple to install and operate, making it suitable for industrial production of waste gas reuse.
Production method
Add sulfuric acid (98%) and formaldehyde (37%) into reactor 1, turn on the gas-liquid circulation mixing anti-oxidant pump 2, and purify the phosphine-containing hydrogen produced in the production of sodium hypophosphite. (About 80%) the tail gas is added to the gas-liquid circulation mixing reaction pump 2 through the gas inlet, and phosphine is absorbed through the gas-liquid circulation mixing reaction device at 50-60’C, and the phosphine that is not completely absorbed enters the next stage of reaction. Sign, and determine the end point of the reaction by detecting the formaldehyde content in the central control. After the reaction is completed, the reaction is concentrated under reduced pressure to obtain tetrahydroxymethylphosphorus sulfate. The mass ratio of sulfuric acid and formaldehyde is 1:7.0-7.1.
The main content of the product is 75-77%, the available phosphorus content is 11.0-12.0%, PH3.0-5.0, iron ion <0.0015%, viscosity <50cps, chroma <100APHA, specific gravity 1.370-1.g/ml.
