Background and overview[1,2] [3]
Phosphorus pentoxide is white amorphous powder or hexagonal crystal. It is highly hygroscopic, can be dissolved in water, and releases a lot of heat, first forming metaphosphoric acid and then orthophosphoric acid. Phosphorus pentoxide is used as a desiccant for gases and liquids; as a dehydrating agent for organic synthesis, as an antistatic agent for polyester resin, as a refining agent for pharmaceuticals and sugar. It is the parent raw material for producing high-purity phosphoric acid, phosphate, phosphide and phosphate ester. Phosphorus pentoxide, also known as phosphoric anhydride, easily absorbs water and reacts violently with water. Each mole of phosphorus pentoxide reacts to release 68 kcal of heat. Phosphorus pentoxide is a common raw material and reagent in the chemical industry. It is widely used in medicine, coating additives, printing and dyeing auxiliaries, antistatic agents, chemical industry and other industries. It is mainly used to manufacture high-purity phosphoric acid, gas and liquid desiccants, Dehydrating agents for organic synthesis, and preparation of organophosphates, etc. So far, phosphorus pentoxide found at normal temperatures and pressures has square, orthorhombic, and orthorhombic tetragonal crystal forms. Their physical and chemical properties are listed in Figure 1.
Figure 1 Physical properties of various crystal forms of phosphorus pentoxide
Reaction of phosphorus pentoxide and water[2]
Phosphorus pentoxide easily absorbs moisture in the air, easily absorbs water, and has strong dehydration properties. It can even remove water from concentrated sulfuric acid, turning triethylenetetramine into sulfur trioxide. Phosphorus pentoxide reacts violently with water, releasing heat and white smoke at the same time. Depending on the amount of water added, phosphorus pentoxide reacts with water to generate different phosphorus oxygen-containing acids, such as super acid, metaphosphoric acid, pyrophosphoric acid, orthobasic acid, polyphosphoric acid, etc.
Figure 2 Reaction of phosphorus pentoxide and water
Synthetic production process route [2][4]
The production process of poloxamer pentoxide phosphorus 188 is an oxidation method. After the yellow phosphorus is heated and melted, it is sent to the oxidation combustion furnace and undergoes an oxidation combustion reaction with the dehydrated and dried air. The generated phosphorus pentoxide is cooled at the top of the furnace and falls into the settling chamber at the bottom of the oxidation combustion furnace to produce phosphorus pentoxide. The finished product of phosphorus oxide, reaction principle and process flow diagram are shown in the figure. Using reagent-grade phosphorus pentoxide as raw material, it is burned, sublimated and purified in a fully dry oxygen gas flow, and the sublimated products are captured in a condenser to obtain high-purity phosphorus pentoxide finished product. These two pentoxides are all amorphous.
Figure 3 Phosphorus pentoxide production process route
At present, the domestic production of phosphorus pentoxide is mainly in the eastern region, and the industrial production scale (single set) is generally 100 tons per year. The foreign production technology of phosphorus pentoxide is mainly owned by Germany, and its production scale (single set) Generally, the annual production capacity is 5,000-10,000 tons; in the production of phosphorus pentoxide products, quality is the core. Due to limitations in equipment technology, only a few companies are currently able to relatively stably produce high-quality phosphorus pentoxide products (main content is greater than High reactivity. At the same time, high purity, high reactivity and low arsenic phosphorus pentoxide products have good and stable markets at home and abroad, and their product prices are higher than ordinary products. Most of my country’s phosphorus pentoxide products mainly rely on exports , in recent years, with the effective utilization of phosphorus pentoxide products at home and abroad in new fields, its market has shown a growth trend year by year.
my country has established a relatively complete phosphorus chemical production system, from resource mining to the production of basic raw materials, from the production of various bulk phosphorus chemical products to the production of fine inorganic and organic phosphorus chemical products. It has basically met the needs of various domestic industries, and also has a large number of products exported. Among them, the ones with larger export volumes include yellow phthalate, phosphoric acid, sodium tripolynate, sodium chloride, toothpaste grade sodium chloride, sodium subphthalate, etc., which occupy an important position in world trade. my country’s production capacity and output of yellow phosphorus ranks first in the world; its output of phosphoric acid, sodium tripolyphosphate and feed phosphate ranks first in the world. The development of the phosphorus chemical industry has evolved from primary phosphate ore processing based on yellow phosphorus to a fine chemical industry based on deep processing of yellow phosphorus and fine processing of ortho-acid, with products becoming more refined and specialized. Yellow phosphorus in my country is mainly used to produce phosphoric acid, and there are two processes for the production of phosphoric acid: wet production and thermal production, of which thermal phosphoric acid is the main one. The phosphoric acid products generated by the thermal method have the advantages of less impurities and high purity. They are mainly used in the processing of electronic chemicals, flame retardant materials, fine phosphates and other products. However, the thermal method also has the disadvantages of high energy consumption and serious environmental pollution. Shortcomings. In recent years, my country has successively introduced a series of macro policies to promote energy conservation and consumption reduction in high-energy-consuming enterprises. The National Development and Reform Commission has issued a series of policies and regulations such as the “Evaluation Index System for Cleaner Production in the Yellow Phosphorus Industry” and “Energy Consumption Limits of Yellow Phosphorus Unit Products” to standardize and manage the production and development of the yellow phosphorus industry. The introduction of these policies will undoubtedly increase the production costs of various phosphorus products, especially for thermal phosphoric acid, a high-energy-consuming product. The increase in costs will inevitably lead to a decrease in the competitiveness of the products in the market. In order to improve the competitiveness of thermal phosphoric acid in the market, great efforts must be made in energy saving and consumption reduction to reduce product costs.
Determination of phosphorus pentoxide in the air[1,5]
Currently, the presence of dioxide pentoxide in domestic airThe method for measuring phosphorus is ammonium molybdate spectrophotometry. However, during the measurement process using chemical methods, the linearity of the calibration curve is often poor and the blank value is high, which affects its accuracy and affects the measurement results. The main reasons for these problems are accidental factors such as instrument problems, pollution during operation, and systemic factors such as the purity of reagents used in the test and test water. Moreover, the need to use chemical reagents during the analysis process will cause secondary pollution to the environment. This article uses perchlorethylene filter membrane to collect phosphorus pentoxide in the air, soaks it in deionized water to generate orthophosphoric acid, and then enters the ion chromatography instrument for analysis, thereby measuring phosphorus pentoxide in indoor air. This method is highly sensitive, rapid, and The advantages of good selectivity and less interference.
Use perchlorethylene filter membrane to collect phosphorus pentoxide aerosol in the air. After using the sample, add water and react with phosphorus pentoxide to generate orthophosphoric acid. Use an ion chromatograph to measure the peak height of phosphoric acid, use retention time to qualitatively determine the peak height, and indirectly determine the concentration of phosphorus pentoxide. Use perchlorethylene filter membrane to collect phosphorus pentoxide in the air and industrial waste gas, soak it in water to generate orthophosphoric acid, and measure its mass concentration by ion chromatography. The operation is simple and convenient, with high recovery rate and good precision. It requires instruments and equipment. lower. Using this method to measure phosphorus pentoxide avoids the extensive use of chemical reagents during the analysis process, reduces the harm to the environment and human health, and reduces secondary environmental pollution. Practical operations have proven that this method can meet the monitoring requirements for phosphorus pentoxide in the atmosphere.
References
[1]Yang Xue, Wang Yuan. Determination of phosphorus pentoxide in air by ion chromatography[J]. Environmental Science and Management, 2013, 38(3): 134-136.
[2]Zhao Xiang. Research on the reaction products of phosphorus pentoxide and water at high temperature[J]. Kunming University of Science and Technology, 2012 (missing issue): page range is missing.
[3] Zhao Xiang, Mei Yi, Liang Xuesong, etc. Transformation of two phosphorus pentoxide crystal forms and their effect on evaporation rate[J]. Inorganic Salt Industry, 2012 (04): 19-21.
[4]Li Jie, Lu Siwei. Risk analysis and prevention of oxidation of yellow phosphorus to phosphorus pentoxide[J]. Guangzhou Chemical Industry, 2015 (11): 245-247.
[5]Liu Zhenlin, Cha Hexia, Zhao Hao. Discussion on the ion chromatography determination method of phosphorus pentoxide in the air of workplace[J]. Chinese Journal of Health Inspection, 2013 (10): 2238-2240
