Preparation method of ultra-pure sulfuric acid

Abstract

The invention discloses a preparation method of ultra-pure sulfuric acid. Fuming sulfuric acid is used as a raw material. The preparation method includes following steps: (1), distilling; (2), purifying and filtering; (3), separating sulfur trioxide liquid; (4), second evaporation; (5), multistage absorption; (6), impurity removal through a stripping tower; (7), obtaining a finished product. In the ultra-pure sulfuric acid, concentration of particles greater than or equal to 0.5 um is less than 5 p / ml, concentration of particles greater than or equal to 0.2 um is less than 100 p / ml, content of single metal ions is less than 0.1 ppb, and content of sulfuric dioxide is less than 3 ppm. The preparation method is simple in process and low in energy consumption; the ultra-pure sulfuric acid of ppt grade is obtained through a reasonable purification impurity removal process to obtain sulfur trioxide gaspure and then through multistage absorption and steam stripping, so that content of trace sulfur dioxide impurities in the ultra-pure sulfuric acid is controlled effectively and a foundation is laid for producing new-generation ultra-pure sulfuric acid.

Description

technical field [0001] The invention relates to the technical field of preparation of ultra-pure chemicals, in particular to a method for preparing ultra-pure sulfuric acid with ultra-low sulfur dioxide content. Background technique [0002] Ultra-pure sulfuric acid, also known as high-purity sulfuric acid and electronic-grade sulfuric acid, belongs to ultra-clean and high-purity reagents. It is one of the eight ultra-pure chemical materials commonly used in the semiconductor industry and one of the indispensable key basic chemical reagents in the development of microelectronics technology. The consumption of ultra-pure sulfuric acid ranks first in the IC industry. It is widely used in the assembly and processing of semiconductors and ultra-large-scale integrated circuits. It is mainly used in the diffusion, corrosion, and cleaning of silicon wafers, which can effectively remove impurity particles on the wafers. , inorganic residues and carbon deposits. The purity and clean...

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Problems solved by technology

Among them, the rectification method consumes a lot of energy and costs, and some impurities are difficult to remove. The waste gas and acid mist produced are harmful to the human body and are not conducive to environmental protection. They are only suitable for small-scale production

The gas absorption method is to purify sulfur trioxide gas, and then absorb it with ultrapure water or wash sulfuric acid to obtain ultra-pure sulfuric acid. This method can effectively avoid the above-mentioned shortcomings of the rectification method, but the existing gas absorption method cannot effectively remove sulfur dioxide. Gas, so that the prepared sulfuric acid contains a certain amount of trace sulfur dioxide impurities, affecting the performance of sulfuric acid

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