Background and overview[1][2]
Phosphate is currently the most widely used food quality improver in various countries around the world. In various fields of food production, phosphate plays an irreplaceable role in improving food quality. Especially in the meat industry, it has significantly improved meat quality. The role of product quality. Disodium hydrogen phosphate, a colorless and transparent monoclinic prismatic crystal, generally exists in the form of 12 crystal waters, with a density of 1.52g/cm3 and a melting point of 34.6℃. It is easily weathered in the air and is extremely easy to Five molecules of crystal water are lost to form heptahydrate (Na2HPO4·7H2O). Soluble in water, insoluble in alcohol, the aqueous solution shows a slightly alkaline reaction (the pH of 0.1-1N solution is about 9.0), and loses crystal water at 100℃ to become anhydrous, 250 It decomposes into sodium pyrophosphate at ℃. There is an increasing demand for high-purity disodium hydrogen phosphate products in functional materials, biotechnology, agricultural technology, etc. Therefore, high-purity disodium hydrogen phosphate has better economic and social benefits. Due to the influence of factors such as the origin, grade, and price of raw materials, the production processes used by different manufacturers are also different, and the purity of their products also varies greatly. The production methods of disodium hydrogen phosphate mainly include neutralization method, extraction method, Ion exchange method, metathesis method, direct method, crystallization method and electrolysis method, etc. The direct method is mainly used to prepare disodium hydrogen phosphate with higher purity. Disodium hydrogen phosphate is a precursor required for the preparation of products such as sodium pyrophosphate and sodium tripolyphosphate, so research on the preparation of disodium hydrogen phosphate is of great significance.
Apply[1,3-4]
Disodium hydrogenphosphate (antioxidant manufacturer) is a precursor required for the preparation of sodium pyrophosphate and sodium tripolyphosphate. At the same time, disodium hydrogenphosphate can also be used as a food additive, medical reagent, and water treatment agent. etc., it also has its use value in textile, leather, paint and other fields.
1. Modification effect of disodium hydrogen phosphate on water glass. Water glass is an inorganic binder for castings. It is colorless, odorless, non-toxic and low-priced. It produces no smoke, no irritating or harmful substances during the casting process, such as no resin sand and green sand when pouring. Dioxins and furans have no black pollution and are a pollution-free and clean mold binder. They are currently widely used in the production of steel castings and are one of the main mold binders that meet environmental protection requirements. However, the poor disintegrability (sand production) of water glass sand and the difficulty of regeneration and reuse limit the possibility of further expanding its application.
Research has found that disodium hydrogen phosphate can improve the bonding strength of water glass and reduce the high-temperature residual strength. It is one of the commonly used modifiers to improve the disintegration of water glass (sand). Disodium hydrogen phosphate can improve the disintegration of water glass sand. Hardening strength after blowing CO2; disodium hydrogen phosphate and water glass can form [PO4, [SiO4] composite glass network; during the cooling process, due to the precipitation of beta detergent-Na2Si2O5, γ from the [PO4, [SiO4] composite glass network) – Crystals such as Na3PO4 and 5Na2O·P2O5·4SiO2 destroy the integrity of the water glass adhesive film, and the huge difference in shrinkage between phosphate glass and silicate glass causes the adhesive film to crack, making water glass (sand) High temperature disintegration is improved.
2. Produce sodium phosphate. Includes the following preparation steps:
(1) Heat disodium hydrogen phosphate until melted;
(2) Add an oxidant to the molten disodium hydrogen phosphate to form a mixture. The mass ratio of disodium hydrogen phosphate to the oxidant is 1:0.005-0.03;
(3) Add activated carbon to the mixture, the mass ratio of the mixture to activated carbon is 1000:1-3, filter to obtain sodium phosphate solution;
(4) Adjust the pH value of the sodium phosphate solution to 3.5-13.5.
Preparation [1-2,5-6]
Method 1: Add a certain amount of food-grade phosphoric acid to the reaction device, and under stirring, add a certain concentration of sodium carbonate solution dropwise into the reaction vessel through a peristaltic pump, neutralize it with the phosphoric acid, and use a precision acidimeter to Control the pH value and ensure that the reaction is carried out at a certain constant temperature. When pH=8.34 is reached, it is the end point of the reaction. The reaction-completed liquid is evaporated and crystallized, and then placed in an oven to dry before being weighed. The optimal process conditions for the above preparation of disodium hydrogen phosphate are: selecting the solution concentration as 25%, the temperature as 25°C, and the feeding rate as 20 mL/min. The product produced under this process condition has a high yield of 93.3% and can meet the standards of food-grade additives.
Method 2: A method for preparing high-purity disodium hydrogen phosphate, including the following steps:
A. Slowly add sodium bicarbonate (NaHCO3) to the phosphoric acid (H3PO4) solution to perform a neutralization reaction. The reaction temperature is controlled at 80~100℃ for 2 hours, and the pH value is controlled at 8.7 -9.2, and then naturally cool down to obtain disodium hydrogen phosphate solution. Chemical reaction formula:
B. Centrifuge and dehydrate the obtained disodium hydrogen phosphate solution, evaporate and concentrate, then quickly rinse the product with deionized water to remove adsorbed impurity molecules on the precipitated surface, and then centrifuge and dehydrate to obtain disodium hydrogen phosphate crystals.
C. Send the obtained disodium hydrogen phosphate crystals to a rake dryer for drying. The drying conditions are the inlet air temperature 120°C, the fluidizing gas flow rate 0.3m3/s, and the drying time 15 minutes. , finally stable: the purity of potassium dihydrogen phosphate obtained after process conditions is 99.6%.
Method 3: A production method for ultra-low iron anhydrous disodium hydrogen phosphate, including the following steps:
1) Stir disodium hydrogen phosphate dodecahydrate and pure water.�� to 60-90℃, completely dissolved, filter;
2) Cool the above filtrate to 30-60℃, stir and add calcium chloride aqueous solution, stir thoroughly for 10-20 minutes, pH 8.8-9.2;
3) 40℃ let stand for 1 hour;
4) Hot filtration, concentration of the filtrate, and crystallization at room temperature;
5) Suction filtration to obtain crystals, rinse with a small amount of pure water 2-5 times, and drain;
6) Crystallize, air dry, and then dry at 120-140°C to obtain anhydrous disodium hydrogen phosphate finished product.
Method 4: A method for preparing food-grade anhydrous disodium hydrogen phosphate. The steps are: filter the raw material phosphoric acid alkali and adjust the temperature and concentration; add phosphoric acid and liquid alkali to the neutralization kettle, and control the addition of liquid alkali. speed, after the liquid alkali is completely added, control the reaction temperature and the reaction end point, and mature. The neutralized clear liquid is concentrated; dehydrated; fluidized bed drying is used to obtain food grade anhydrous disodium hydrogen phosphate. The above method first effectively ensures the yield and purity of the synthetic product by controlling the processing, neutralization process and parameters of the raw materials, and then realizes the process from concentration to crystallization to one-step drying through the fluidized bed process, thereby solving the problem of the ordinary two-step method. Problems in Preparing Anhydrous Disodium Hydrogen Phosphate. Effectively save human resources, save energy consumption, effectively increase output and stabilize product quality.
Main reference materials
[1] Li Baosheng, Wang Xiujun, Qiu Shuyi, et al. Research on the preparation process of food additive disodium hydrogen phosphate [J]. China Food Additives, 2009 (6).
[2] CN201210526009.7 A method for preparing high-purity disodium hydrogen phosphate
[3] Qu Yinhu, Xing Jiandong, Gao Yimin. Research on the modification effect of disodium hydrogen phosphate on water glass[J]. Casting, 2003, 52(9): 668-671.
[4] CN201710587631.1 A method for producing sodium phosphate from glyphosate by-product disodium hydrogen phosphate
[5] CN201310446174.6 A production method of ultra-low iron anhydrous disodium hydrogen phosphate
[6] CN201810333000.1 A preparation method of food-grade anhydrous disodium hydrogen phosphate
