Overview
Potassium pyrophosphate is a white powder or block. The apparent density is above 0.3g/cm3. Melting point 1100℃. Soluble in water, insoluble in alcohol, water solution is alkaline. Slightly hygroscopic. Trihydrate loses two molecules of crystal water at 180°C and loses all crystal water at 300°C. There are four types of hydrated crystals: 1 hydrate, 3 hydrate, 3.5 hydrate and no crystal water. The anhydrous substance of K4P2O7 is widely used in industry. Potassium pyrophosphate is a white powder or agglomerate. Relative density 2.534. Melting point 1109℃. Soluble in water, insoluble in ethanol. Aqueous solutions are alkaline. The solubility in 100g of water at 25℃ is 187g. The pH value of an aqueous solution with a concentration of % is 10.2. Potassium pyrophosphate has all the properties of condensed phosphate. The solid at equilibrium in a saturated solution is K4P2O7•3H2O. Anhydrous potassium pyrophosphate has two configurations. The transition temperature from type I to type II is 278°C.
Main applications
Potassium pyrophosphate is mainly used for cyanide-free electroplating, industrial and household applications Dimethyl silicone emulsifiers are used as detergent additives, especially as liquid detergents, which have broad market prospects. In addition, it is used as a dispersant and buffer for ceramic clays, synthetic rubbers, dyes, soaps and pigments. In the bleaching and dyeing industry, it is used to remove a small amount of ferric ions in water to improve the quality of dyeing and bleaching. In the food industry, it is used as an emulsifier, texture improver, and chelating agent. It is also used as a raw material for alkaline water used in flour products. It is often used in combination with other condensed phosphates. It is usually used to prevent struvite formation in canned aquatic products and prevent discoloration of canned food in fruit shops. Improve the expansion of ice cream, the yield of ham and sausage, and the water holding capacity of ground fish; improve the taste of hydroxybutyl acrylate in noodles and increase the yield, prevent aging of cheese, etc.
Production method
Neutralization and calcination method uses phosphoric acid and potassium hydroxide as raw materials to produce potassium pyrophosphate. The reaction formula is as follows:
H3PO4+2KOH→K2HPO4+ 2H2O
2K2HPO4→K4P2O7+ H2O
React potassium hydroxide and phosphoric acid to generate dipotassium hydrogen phosphate solution, spray-dry the powder to obtain the powder, and then roast it in a rotary kiln at 350-℃. Product, if a solution product is required, the powder can be prepared by dissolving the powder in deionized water. Food-grade potassium pyrophosphate requires food-grade phosphoric acid as raw material.
