Background and overview[1]
Sodium phosphate is a hygroscopic white powder or crystalline granule, odorless. It can absorb carbon dioxide and moisture in the air to generate disodium hydrogen phosphate and sodium bicarbonate. The aqueous solution is strongly alkaline. Sodium phosphate dodecahydrate is a colorless trigonal crystal. Odorless. Hygroscopic. Dehydration at 55～65℃ can produce decahydrate, dehydration at 65～100℃ can produce hexahydrate, 100～120℃ Dehydration at 121 ~ 200℃ can produce hemihydrate, and continued dehydration at 121 ~ 200℃ can produce anhydrous. Insoluble in carbon disulfide and ethanol, soluble in water: 1.5 at 0℃, 28.3 at 15℃, 157 at 70℃. The aqueous solution is strongly alkaline, with pH=11.9 at 1.0% and pH=11.5 at 0.1%. Rat oral LD507mg/kg.
Purpose[1]
Sodium phosphate is used as a food additive. It is a moisture retaining agent for food permitted by my country’s GB2760-1996. It is also used as an emulsifier, buffer, nutritional supplement, metal chelating agent; sugar juice purifier; brine raw material; Bacterial culture fluid, etc. ADI0～70mg/kg.
Preparation method[2-4]
Method 1: Add a stoichiometric amount of sodium hydroxide to the disodium hydrogen phosphate solution for neutralization to prepare a sodium phosphate solution. After filtration and concentration, sodium phosphate can be obtained.
Method 2: After diluting phosphoric acid with water, neutralize it with sodium carbonate to generate an aqueous solution of sodium phosphate, filter to remove impurities, concentrate, and crystallize to produce sodium phosphate. After careful heating, sodium phosphate can be produced.
Method 3: A method for preparing pentaerythritol to co-produce zinc formate and sodium phosphate. The raw material is the waste liquid obtained from the condensation of formaldehyde and acetaldehyde to produce pentaerythritol, including the following steps:
Step A: The waste liquid obtained by condensing formaldehyde and acetaldehyde to produce pentaerythritol is distilled under reduced pressure into a saturated solution of pentaerythritol, and then cooled. Pentaerythritol crystallizes out and is separated by filtration to obtain pentaerythritol crystals and filtrate 1; filtrate 1 is further distilled under reduced pressure. It is a saturated solution of sodium formate, and then cooled, the sodium formate crystals are precipitated by Japan Mitsubishi, and separated by filtration to obtain sodium formate crystals and filtrate II;
Step B: Wash, dry and pulverize the pentaerythritol crystals obtained above to obtain the pentaerythritol product;
Step C: Dissolve the sodium formate crystals obtained above in water, and then react with the zinc phosphate solution at a molar ratio of the pure substances of sodium formate and zinc phosphate to 6:0.8-1.2 to produce Zinc formate and sodium phosphate are filtered to remove a small amount of filter residue to obtain filtrate three containing zinc formate and sodium phosphate;
Step D: The third filtrate is distilled under reduced pressure into a saturated solution of zinc formate, and cooled to 10°C. At this time, the saturation of sodium phosphate is 8.2g, and the saturation of zinc formate is 4.3g. , therefore, zinc formate crystallizes out, while sodium phosphate is still in the solution, and is separated by filtration to obtain formic acid antioxidant price zinc crystals and filtrate 4; filtrate 4 is further distilled under reduced pressure into a supersaturated sodium phosphate solution, and is cooled to10 ℃At this time, a large amount of sodium phosphate crystallizes out to obtain sodium phosphate crystals; the sodium phosphate crystals and zinc formate crystals are washed, dried and pulverized respectively to obtain sodium phosphate products and zinc formate products respectively. Its chemical reaction equation:
Method 2: A preparation method of sodium phosphate,
1) Preparation of sodium orthophosphate:
First, wash the crude sodium pyrophosphate with water until the NaCI content is less than 1%. Fully mix the crude sodium pyrophosphate, water and wet phosphoric acid, add the impurity remover and decolorizing agent, and control the temperature to 135 by steam. The hydrolysis reaction is carried out at ℃, the pressure of the hydrolysis reaction is 0.2MPa, let it stand, until the hydrolysis is complete, the sodium pyrophosphate reacts completely to form sodium orthophosphate;
2) Preparation of disodium phosphate and trisodium phosphate:
After filtering and removing impurities from the material liquid obtained in step 1) (because the crude sodium pyrophosphate contains impurities such as carbon black, the dissolved liquid is filtered to remove impurities such as carbon black, and the filtered carbon black is washed with a little water (the filter residue is sold as an accessory product), after sedimentation and natural cooling to 30-40℃, purified wet phosphoric acid is added for further hydrolysis. When the pH is adjusted to 7.5, the complete reaction generates disodium phosphate. Then cool to less than 18℃ to obtain the corresponding Na2PO4·12H2O crystal;
3) Preparation of sodium tripolyphosphate;
Add the disodium phosphate prepared in step 2) into the neutralization tank, heat and dissolve it, then mix it with wet phosphoric acid, control the pH to 6.5, add sodium nitrate at 70-80°C, and neutralize After the reaction is complete, the material liquid is placed in a polymerization furnace for polymerization to obtain tripolyphosphate sodium salt.
Method 3: A method for producing sodium phosphate salt from glyphosate by-product disodium hydrogen phosphate, including the following preparation steps: (1) heating disodium hydrogen phosphate to 60-90°C Melting; (2) Add hydrogen peroxide to the molten disodium hydrogen phosphate to form a mixture, in which the mass ratio of disodium hydrogen phosphate to hydrogen peroxide is 1:0.03; (3) Add activated carbon to the mixture, the mass ratio of the mixture to activated carbon The ratio is 1000:1, filter to obtain a sodium phosphate solution; (4) Add an appropriate amount of phosphoric acid, adjust the pH value of the sodium phosphate solution to 3.5, concentrate and crystallize to obtain the product.
Main reference materials
[1] Practical Fine Chemical Dictionary
[2] CN201010611564.0 A method for preparing pentaerythritol to co-produce zinc formate and sodium phosphate
[3] CN201510177885.7 Preparation method of sodium phosphate salt
[4] CN201710587631.1 A method for producing sodium phosphate from glyphosate by-product disodium hydrogen phosphate
