Silicon tetrachloride

Silicon tetrachloride (CAS 10026-04-7) is without doubt a substance without which it is difficult to imagine the modern world. The development of modern technologies and widespread computerisation would not have been possible without this compound. Although the end-uses of SiCl₄-based products vary, ensuring an uninterrupted supply of this raw material, which is an intermediate product in many sectors of the economy, is fundamental to guaranteeing global development.

Chemical and physical properties of silicon tetrachloride

SiCl₄ is the chemical formula of silicon tetrachloride. It is a substance characterised by a number of properties that are extremely important for the industrial use of this raw material.

• Liquid silicon tetrachloride is a non-flammable, highly volatile liquid with a low boiling point of 57 degrees Celsius;
• at temperatures below 650 degrees Celsius, the substance does not spontaneously ignite. It is not explosive and it does not oxidise;
• The density of silicon (IV) chloride is48 g/cm3, which means it is greater than the density of water. When working with this substance, it is important to bear in mind that it reacts violently with water and is corrosive and toxic. Therefore, special caution should be exercised;
• On contact with water or damp air, it decomposes with high heat release, producing silicic acid and hydrochloric acid;
• It causes corrosion of metals in humid environments;
• It mixes very well with many organic solvents, e.g., toluene, benzene, chloroform, carbon tetrachloride, petroleum ether, and hydrochloric acid.

What is the difference between technical silicon tetrachloride and 6N silicon tetrachloride?

Silicon tetrachloride, often called tetrachlorosilane, offered by the PCC Group is available in two variants: as technical silicon tetrachloride and 6N silicon tetrachloride. What are the differences between them?

Technical silicon tetrachloride

Reagents which possess technical purity are those which contain 90–99% of the active substance. They are of high importance for industry. Distributors of technical grade silicon tetrachloride offer a product which is contaminated with a small amount of free chlorine. Usually its amount in the final product does not exceed 0.2%. It can be successfully used as a raw material or intermediate product in the manufacturing of metallurgical silicon, silica or other silicon-based substances.

Silicon tetrachloride 6N

A raw material which, unlike technical SiCl₄, is characterised by a unique purity of 99.9999%. Ultra pure silicon (IV) chloride is obtained by rectification of technical silicon tetrachloride. Manufacturers declaring purity as high as 99.9999% provide an excellent raw material for the production of top quality glass fibres for signal conduction and high-speed data transfer. 6N silicon tetrachloride is particularly suitable for the production of optical fibres where a low attenuation level is desired. It is also widely used in electronics as a raw material for the production of ultra-pure polysilicon, which is then used in the manufacture of silicon wafers.

Situation on the raw materials market

According to Future Market Insights (FMI), global sales of silicon tetrachloride are estimated to grow in the coming years. They will increase by 4.5% during the period 2022–2027. The market is expected to reach a value of over USD 2.846 million by the end of the forecast period. FMI has published a new study entitled “Silicon Tetrachloride & Derivatives Market: Global Industry Analysis 2012–2021 and Opportunity Assessment 2022–2027”. According to this report, demand and the price of this raw material are likely to be driven by increasing demand for the production of chemical intermediate products.

High-purity silicon (IV) chloride is the main raw material used in the production of optical cable preforms are a basis of currently popular optical fibres. Recently, supported by the development of 4G, 5G, LTE, FFTx and loT technologies, there has been a significant increase in the demand for optical cables worldwide. China, the US and Japan account for about 80% of the total production of optical cable preforms, and in terms of consumption, China accounted for nearly 58% of the total optical fibre preforms in 2021. The steadily growing demand for optical cables will lead to an increase in the demand for optical cable preforms, which in turn will drive the silicon tetrachloride market during the forecast period.

The increasingly frequent use of SiCl₄ in China can be attributed to the lucrative growth of the solar industry in that region. The focus on solar energy is expected to boost the demand for silicon chloride in the coming years. In addition, the snowball effect of the semiconductor industry and growing advances in the field of industrial paints and coatings will only strengthen this effect.

The price of silicon tetrachloride is influenced by factors such as the high demand for smartphones and other portable multimedia devices, development of advanced communication devices, growing use of optical fibres in the aerospace, oil and gas industries and the launch of 5G services. The development and growing importance of this raw material depends on the integration of the latest production technologies with dynamic investments on a global scale.

In which industries can we find tetrachlorosilane?

Silicon (IV) chloride is widely used in many industries. Its various applications include the production of many silica-based materials with high added value, such as foamed silica, optical fibres and ethyl silicate.

Other uses include the following areas:

• SiCl₄ as a by-product of the processing of metallurgical grade silicon is used to obtain polysilicon. 3-4 tonnes of tetrachlorosilane are required for every tonne of polysilicon. Polysilicon manufacturers further process silicon tetrachloride waste and reuse it after processing. This saves energy and raw material costs, but requires an expensive set of machines which process the waste.
• Large amounts of tetrachlorosilane produced worldwide are used to manufacture high-quality fumed silica.
• The product is also a precursor in the production of orthosilicate acid esters, including tetraethoxysilane (TEOS) and tetramethoxysilane (TMOS).
• Pure silicon obtained from silicon chloride is used in the manufacture of semiconductors as well as silicon anodes.

Silicon tetrachloride is used only under highly controlled laboratory and industrial conditions, where specific safety rules must be created and followed. The production and use of SiCl₄ does not pose any significant risk to humans or the environment if the instructions contained in the safety data sheet, as well as applicable legal requirements, are followed.

Silicon tetrachloride in the production of optical fibres

Fibre optic technologies are becoming more and more popular every year. Few of us realise that the Internet, which we use everyday, is a source of enormous pollution of the environment. Thanks to optical fibres, it is possible to significantly increase the range of data transmission compared with traditional techniques. Also, by eliminating a number of devices, we limit the creation of waste, save energy and reduce the emission of greenhouse gases.

One of the most important ingredients in the production of optical fibres is high-purity silicon tetrachloride, usually 6N. It has recently been included in the portfolio of the PCC Group. Its quality has a significant impact on the final product. It is estimated that about 85% of optical fibres are produced from imported raw material. Purification of this compound with the chemical formula SiCl₄ is not an easy task. Many countries have developed methods to effectively remove impurities such as metallic ions. But the same methods are not effective if we want to get rid of hydrogen impurities.

Optical fibres consist mainly of the element silicon, although a number of other substances are often added. In the outdated crucible method, highly purified, powdered silica was used. Today, liquid silicon tetrachloride is the primary source of silicon. It is deposited in the gas phase method, in a gaseous stream of pure oxygen. Other chemicals, such as germanium tetrachloride (GeCl₄) and phosphorus oxychloride (POCl₃), can be used to produce core fibres and outer coatings, or cladding, with function-specific optical properties.

Producing optical fibres of unique quality requires every stage of production to be conducted at the highest level. It is important to provide high-quality raw materials and semi-finished products. Therefore, we should choose manufacturers and distributors who can guarantee this. Quality control of any optical fibre manufacturing process starts with the suppliers of the chemicals used as the raw materials for the substrate rods, chemical reactants and fibre coatings. Suppliers of specialty chemicals provide detailed chemical analyses of the components, which are constantly monitored by computerised analysers connected to process vessels.

Silicon (IV) chloride manufacturer in the PCC Group

PCC Rokita SA is one of the largest chemical companies in Poland as well as Central and Eastern Europe. Its activity includes the production of chloroalkali, polyether polyols, polyalkylene glycols and phosphorus derivatives. PCC Rokita S.A., as a distributor and supplier of ultra-pure silicon tetrachloride, guarantees products with very high effectiveness and low CO₂ emission. The carbon footprint of the production technology is minimised, which helps to protect the environment.