Method for preparing highly-pure phosphoric acid by flow chromatographic crystallization method

Abstract

The invention discloses a method for preparing a highly-pure phosphoric acid by a flow chromatographic crystallization method, in particular a production method for preparing the highly-pure phosphoric acid from an industrial phosphoric acid, which relates to highly-pure phosphoric acid preparation technology. The method comprises the following steps: (1) filtering the raw material phosphoric acid for crystallization with a film of 0.1 to 0.5 mu m for later use; (2) filling the phosphoric acid in a crystallizer, keeping the phosphoric acid at 12 to 20 DEG C and adding phosphoric acid seed crystals into the crystallizer, and standing for 1 to 20 minutes or acting on the stood phosphoric acid for 10 to 30 minutes by using an external sound field of 20 to 40 KHz; (3) keeping the phosphoric acid at 12 to 20 DEG C in a phosphoric acid thermostatic bath, pumping the phosphoric acid into the crystallizer by using a pump for circulation, making a crystal layer grow for 1 to 2 hours at a crystallization temperature of minus 15 to 2 DEG C and discharging the raw material phosphoric acid from the crystallizer; (4) melting and distilling the phosphoric acid crystal layer in the crystallizer at the temperature of 0 to 25 DEG C, wherein discharged distillate accounts for 40 to 50 percent of the mass of the crystal layer; (5) cleaning the surface of the crystal layer with spray highly-pure water; and (6) melting the cleaned phosphoric acid crystal layer at the temperature of 35 to 55 DEG C and diluting the melted phosphoric acid crystal layer with the highly-pure water to produce the highly-pure phosphoric acid product. The highly-pure phosphoric acid product produced by the method of the invention can be applied in the fields of chip wet-process cleaning and wet-process etching, silicon wafer surface cleaning, glass optical fiber production and the like.

Description

technical field [0001] The invention relates to high-purity phosphoric acid preparation technology, in particular to a production method for preparing high-purity phosphoric acid from industrial phosphoric acid. Background technique [0002] High-purity phosphoric acid is a special electronic chemical used in the manufacturing process of large-scale integrated circuits and semiconductor devices. It is mainly used in wet cleaning and wet etching of chips, surface cleaning of silicon wafers, and production of optical fiber glass. Insoluble solid particles and metal impurity ions in phosphoric acid will lead to a decrease in the withstand voltage of electronic products and a decrease in the withstand voltage of the P-N junction, seriously affecting the yield, electrical performance and reliability of electronic products. Therefore, the high-purity phosphoric acid used in the electronics industry has extremely high requirements for insoluble solid particles and metal impurity io...

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Problems solved by technology

The process of this method is long, the process control is difficult, the production cost is high, and it is difficult to form an industrial scale with competitive advantages

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