Antimony trioxide is widely used in various fields (1)

With the development of science and technology, the application fields of antimony trioxide are constantly expanding. Based on the understood and mastered information, the main fields of antimony are as follows:

   (1) Flame retardants used in rubber and textile industries

The largest area of antimony use is antimony compounds used as flame retardants in the rubber and textile industries. Relevant data reports that in the mid-1990s, the amount of native antimony used for flame retardants in the United States and Japan accounted for 64.5% and 89.4% of their total antimony consumption, respectively. In 1986, the total amount of antimony trioxide used for flame retardants in the United States, Japan, and Western Europe reached 40,230 tons, with 15,930 tons, 8,300 tons, and 16,000 tons respectively. In 1990, the United States used 20,000 tons of antimony trioxide for flame retardants.

The main varieties of antimony-based flame retardant synergists are antimony trioxide, antimony pentoxide, and sodium antimonate. The most important and largest in use is antimony trioxide. The flame retardant synergistic mechanism of antimony trioxide is described later. It is particularly noteworthy here that its use with halogen-based flame retardant products not only has the advantage of significantly reducing costs, but also greatly reduces the mechanical damage caused by the large amount of organic halogen flame retardants added to the polymer matrix on the impact resistance, bending resistance, and tensile properties.

In addition to indicators such as composition, whiteness, black spots, and crystal form, the particle size and surface properties of antimony trioxide used in the flame retardant field are also emphasized. Particle size has a significant impact on the color and mechanical strength of the organic polymer matrix, while surface properties affect whether antimony trioxide can be uniformly dispersed in the organic polymer and obtain the optimal flame retardant synergistic effect. Generally, antimony trioxide with smaller particle size has higher coloring power, and vice versa. For the production of white or light-colored flame-retardant polymer products, antimony trioxide with good whiteness and fine particle size should be selected. For the production of dark-colored flame-retardant polymer products, antimony trioxide with low coloring power can be selected to reduce pigment consumption and lower production costs; for the production of transparent or translucent flame-retardant polymer products, antimony trioxide with an average particle size of less than 0.05 µm should be selected. Particle size also has a significant impact on the mechanical strength of the polymer; the larger the particle size, the greater the damage to the mechanical strength of the polymer. Particle size also has a great impact on the flame retardant efficiency; the finer the particle size, the higher the degree of dispersion in the polymer, the larger the reaction surface area, and the better the flame retardant effect.

    (2) Application of antimony (Sb2O3) in plastic additives - heat stabilizers

1. Concept and mechanism of heat stabilizers

Heat stabilizers are one of the indispensable important categories of plastic additives. They are mainly used in the processing of polyvinyl chloride (PVC) resin to improve the thermal stability of plastics during processing and use, and to prevent plastic aging.

Pure PVC resin is extremely sensitive to heat. When the heating temperature reaches about 90℃ or higher, thermal decomposition reaction occurs. When the heating temperature reaches 120℃, significant thermal decomposition reaction occurs, leading to the breakage of macromolecular chains. To prevent the thermal decomposition of PVC, heat stabilizers must be added during PVC processing (wires, cables, etc. are all PVC materials).

2. Main classifications of PVC heat stabilizers

Lead-based:

Metal-based:

Organotin-based:

Rare earth-based:

Antimony-based:

3. Thiolantimony heat stabilizers are a new type of heat stabilizer

This type of heat stabilizer is currently considered the best substitute for organotin, and the most widely researched are antimony carboxylates, thiolantimony, and mercaptocarboxylate antimony. Its characteristics are high thermal stability efficiency and non-toxicity, but poor light resistance. Literature reports that the composite of barium thiolate heat stabilizer and thiolantimony can enhance the interaction between the heat stabilizer and PVC, exhibiting a synergistic effect. The ratio of the two is 3:1.

Due to the abundant antimony and rare earth resources in China, the development of antimony-based and rare earth-based heat stabilizers in China has accelerated in recent years. The development of antimony heat stabilizers is accelerating. Antimony heat stabilizers are mainly used in PVC rigid, transparent sheets and plastic transparent pipes, as well as PVC drainage pipes. Because antimony heat stabilizers are low in price, have strong transparency, good weather resistance, storage stability, and high consumption ratio, they can completely replace some expensive tin stabilizers. It is a new type of PVC antimony-based stabilizer. It is a colorless or light yellow transparent liquid with an antimony content of about 13-16%. It has excellent initial color and color retention. In some aspects, its thermal stability is superior to organotin stabilizers. Central South University and Hunan Yiyang Nitrogen Fertilizer Factory in my province have made full use of Hunan's antimony resources to develop antimony-based organic heat stabilizers. Dongtai in Jiangsu, Zouping in Shandong, Pudong in Shanghai, and the Additive Research Institute in Beijing have respectively used metallic antimony and antimony trioxide to produce antimony-based heat stabilizers (also known as thiolantimony or organic antimony), with antimony consumption exceeding 100 tons and organic antimony production reaching 1500 tons.

4. Current status of heat stabilizers at home and abroad

The consumption of heat stabilizers in the United States, Japan, and Western Europe reached 350,000 tons in 2000. The rapid development of China's PVC industry. According to relevant statistics, in 1997, China's demand for heat stabilizers reached 97,000 tons, and it developed at an annual growth rate of 14%, with nearly 100 manufacturers and the ability to produce 50 to 60 kinds of various stabilizers. The main categories are lead salts, metal stearates, and organotin.

  (3) The status and role of antimony trioxide-based metal passivators in deep petroleum processing

1. Concept of passivators

Metal passivators are transparent liquids mainly composed of antimony (other raw materials mainly include hydrogen peroxide, tartaric acid, ethanol, etc.) produced by heating reaction in a reaction tank.

2. The role of metal passivators

In the petroleum refining industry, due to advancements in catalytic cracking technology and the need for deep petroleum processing, a large amount of residual oil needs to be processed during catalytic cracking. Domestic residual oil contains a large amount of heavy metals such as nickel (Ni), vanadium (V), sodium (Na), and iron (Fe). These heavy metals can cause catalyst poisoning during the catalytic cracking process. This leads to increased H2 low-carbon gas and coke, affecting the reduction of light oil yield and resulting in poor economic efficiency. To solve this problem, Chinese petroleum chemical researchers developed a series of products called metal passivators in the mid-1980s. The main function of this product is to add a certain proportion of passivator to the catalyst feed oil to passivate the heavy metals such as nickel on the catalyst surface, thereby reducing the gas and coke yield, inhibiting the generation of hydrogen and coke, and increasing the yield of gasoline and other light oils.

3. Passivation Principle of Passivator

After the nickel compounds in the catalytic cracking feedstock decompose in the reactor, they generate nickel hydride, nickel aluminate, or nickel aluminate. Nickel can be evenly dispersed on the catalyst and has a strong dehydrogenation reaction. Therefore, nickel poisoning leads to increased dehydrogenation activity of the catalyst, increased coke and hydrogen yield, and decreased light oil yield. However, nickel has little effect on the catalyst activity.

The passivator designed based on the poisoning mechanism of nickel uses organic compounds of antimony, bismuth, and tin. After entering the lift reactor, the passivator decomposes, and the compounds of antimony or bismuth and tin form larger aggregated particles of SB-NI or SB/SI-NI, BI-NI alloy with nickel, preventing the dispersion of nickel and thus reducing the activity of nickel.

4. Form, Main Raw Materials, Antimony Content, and Other Aspects of Passivator

The passivator has a light yellow, brown, or dark blue, milky white transparent liquid appearance (the most commonly used in refineries are light yellow and brown liquids, density 20℃ g/cm³). The main raw materials are antimony trioxide, hydrogen peroxide, tartaric acid, and ethanol. Different specifications of catalysts are selected according to the different heavy metal contents in the residual oil of each refinery. The existing antimony content of the passivator is 12.5%, 24%, 26%, 33%, 39%, etc., with multiple series of products with different antimony contents. In recent years, passivators based on bismuth, tin, and antimony/tin bimetallic have also been developed.

The research and development of passivators in China started in the 1980s and developed rapidly in the 1990s. From the original three companies (Beijing Research Institute of Petroleum, Luoyang Refining Institute, Yixing Refinery Additives Factory), it has grown to more than 20 companies, covering 10 provinces and cities across the country. Among them, the largest scale, highest output, and best influence are Yixing Hangguang Group, Luoyang Longpu, Hebei Renqiu Jingkai Chemical Factory, Yixing Xingda Chemical Factory, Yixing Petrochemical Additives Factory, and Shandong Dongying Zhuorun Company. The quality of domestic passivators has reached the level of foreign companies such as Philips and Nalco, basically replacing expensive imported passivators. The output has also increased from the initial 20-30 tons to 500 tons in the mid-1990s. According to incomplete statistics, the production capacity of domestic passivators in 2001 reached more than 3,000 tons.

(IV) Application of Antimony Trioxide as a Catalyst in the Production of PET Polyester in Chemical Fiber Production

So far, the production of PET polyester must use antimony trioxide (catalyst type), antimony acetate, or ethylene glycol antimony as a polymerization catalyst (from the perspective of environmental protection, titanium dioxide and silicon dioxide products have been developed to gradually replace antimony catalysts). Different PET polymerization processes are used, and the types of catalysts used are also different. For example, some use antimony trioxide, while others use antimony acetate and ethylene glycol antimony. However, the mechanism is the same, which is to use antimony ions to accelerate the catalytic reaction.

The amount of catalyst added in PET polyester is approximately 3.5-4 tons of antimony per 10,000 tons of polymer when using antimony trioxide as a catalyst, and 4.8-6 tons of antimony acetate per 10,000 tons of polymer when using antimony acetate as a catalyst.

The PET polymerization process has very high requirements for the physicochemical properties of antimony trioxide. In addition to the strict limitations on the impurity content (solubility requirements) of antimony trioxide (i.e., tartaric acid insolubles), there are also strict requirements for the main component, whiteness, crystal form, lead, and arsenic.

Appendix: Antimony Acetate Manufacturer's Requirements for Antimony Trioxide

(V) Application of Antimony Trioxide as a Clarifying Agent and Decolorizing Agent in the Field of Television Glass Shells and Glass

Antimony trioxide's primary function in television glass shells and glass melting is as a clarifying agent and decolorizer. The glass shell industry directly uses sodium antimonate, while most of the glass industry uses antimony trioxide; however, antimony trioxide is ultimately converted into sodium antimonate. Therefore, sodium antimonate can be used not only as a flame retardant synergist but also as a glaze material for high-grade ceramics and enamel, but more importantly and in larger quantities, as a clarifying agent and decolorizer in the glass and glass shell industries.

The ferrous oxide, which is a bluish-green pigment in glass, is a harmful substance that affects the color and transparency of glass products if not removed. Antimony trioxide has a high density, and its decomposition temperature is very close to the glass clarifying temperature. It sinks to the bottom of the molten glass in the crucible. During the heating process, high-pressure antimony trioxide vapor is formed. At 1400℃, the rising antimony trioxide vapor releases absorbed oxygen, converting ferrous oxide into ferric oxide. This effectively removes bubbles and discoloration from the glass solution, resulting in a highly clarified glass with high transparency and good quality. Therefore, antimony trioxide acts as both a clarifying agent and a decolorizer in glass production. It is widely used in the electronics and glass industries as a clarifying agent for electronic tube glass shells and high-grade, high-quality optical glass. In glass shell melting, the proportion is approximately 0.4%. This industry has very high requirements for the quality and fluidity of antimony trioxide and sodium antimonate, with strict control over impurities and content.