Sodium Cyanide: An Indispensable Material from Industrial Synthesis to Fine Chemicals

Introduction

Sodium cyanide, with the chemical formula NaCN, is a white crystalline powder. It is highly soluble in water and has a faint bitter almond odor. As a crucial basic chemical raw material, Sodium cyanide plays an irreplaceable role in various industrial fields, especially in industrial synthesis and Fine chemicals.

Physical and Chemical Properties

Sodium cyanide is a cubic crystal system. It is highly soluble in water and easily hydrolyzes to produce hydrogen cyanide, with its aqueous solution showing strong alkalinity. Its melting point is 563.7 °C, and its boiling point is 1496 °C. It has a density of 1.595 g/cm³. Sodium cyanide is extremely toxic, and even a trace amount of contact through skin wounds, inhalation, or ingestion can lead to death. This high toxicity is mainly due to the cyanide ion (CN⁻) in it, which can combine with the ferric ions in blood cells, causing the blood cells to lose their oxygen-carrying function, and ultimately leading to rapid death of the organism due to hypoxia.

Industrial Synthesis Methods

1. Andrussow Process: This method uses natural gas, ammonia, and air as raw materials, with a platinum-rhodium alloy as the catalyst. The reaction occurs at high temperatures. Natural gas (mainly methane) reacts with ammonia and oxygen in the presence of a catalyst to produce hydrogen cyanide, and then hydrogen cyanide reacts with sodium hydroxide solution to obtain Sodium Cyanide. The overall reaction can be simply expressed as: CH₄ + NH₃ + 1.5O₂ → HCN + 3H₂O, HCN + NaOH → NaCN + H₂O. This method has relatively high production efficiency and is suitable for large-scale industrial production. However, it requires high reaction conditions and strict control of raw material ratios and reaction parameters.

2. Light Oil Pyrolysis Method: Liquid ammonia is vaporized and then mixed with light oil in a mixer and preheated. The preheated mixed gas enters the cracking furnace, where a cracking reaction occurs at a high temperature (about 1450 °C). Petroleum coke is used as a carrier, and nitrogen is used as a protective gas to prevent oxidation. The cracking gas contains hydrogen cyanide. After processes such as ammonia removal, water absorption, rectification, and condensation, hydrogen cyanide is obtained, and then it reacts with sodium hydroxide solution to get liquid sodium cyanide. Liquid sodium cyanide can be further concentrated and crystallized to obtain solid sodium cyanide. Although this process has mature technology, it also has problems such as difficult desulfurization and impurity removal of hydrogen cyanide, high product energy consumption, great difficulty in "three wastes" treatment, and relatively high production costs.

3. Acrylonitrile By - product Method: In the process of producing acrylonitrile by ammoxidation of propylene, hydrogen cyanide gas is produced as a by - product (the amount is equivalent to 4% - 10% of the acrylonitrile production). The gas from the reactor contains excess ammonia. After removing ammonia with dilute sulfuric acid, the reaction gas enters a water absorption cooling tower to absorb acrylonitrile, hydrogen cyanide, acetonitrile, and acrolein, etc. The absorption liquid undergoes further separation and purification processes such as resolution and rectification to obtain high - purity acrylonitrile products and by - product hydrogen cyanide. The by - product hydrogen cyanide is then absorbed by an alkali solution to produce sodium cyanide. The products obtained by this method have fewer impurities and a low sulfur content. However, it is limited by the acrylonitrile production capacity. Currently, the acrylonitrile production in China has approached saturation, and its output is difficult to increase significantly.

Applications in Fine Chemicals

1. Pharmaceutical Industry: Sodium cyanide is widely used in the synthesis of pharmaceutical intermediates. For example, in the synthesis of some common drugs such as penicillin, ibuprofen, vitamin B6. folic acid, guanine, acyclovir, barbiturates, norfloxacin, caffeine, and berberine, sodium cyanide is an essential raw material. It participates in key reactions in the synthesis route, helping to construct the molecular structure of the drug and playing a crucial role in the entire drug synthesis process.

2. Pesticide Industry: It is also an important raw material in the production of pesticides. Common pesticides such as glyphosate, paraquat, cyanazine, phenthoate, and isoprothiolane all require the use of sodium cyanide in their manufacturing processes. Sodium cyanide is involved in the synthesis of pesticide active ingredients, endowing pesticides with specific chemical structures and pesticidal properties, which is of great significance for ensuring agricultural production and preventing and controlling agricultural pests.

3. Dye and Pigment Industry: In the dye industry, sodium cyanide is used to manufacture important intermediates such as cyanuric chloride. Cyanuric chloride is an important intermediate for reactive dyes and is also a raw material for the production of optical brighteners. It participates in the synthesis of dyes, endowing dyes with excellent coloring properties and color fastness, and promoting the development of the dye industry.

4. Synthesis of Special Organic Compounds: Sodium cyanide can be used to synthesize a variety of special organic compounds, such as cyanobenzyl and its derivative series products, iminodiacetonitrile, iminodiacetic acid (ester), chelating agent series products (EDTA, DTPA, NTA) and their metal salt products, glycine, hydroxyacetonitrile (acid), etc. These organic compounds have wide applications in fields such as chemical analysis, water treatment, and organic synthesis. For example, chelating agents can be used to bind metal ions, playing an important role in water softening and metal ion separation processes.

Safety and Environmental Considerations

Due to its high toxicity, strict safety measures must be taken in the production, transportation, storage, and use of sodium cyanide. In the production process, operators need to wear appropriate personal protective equipment, including gas - tight suits, respirators, and protective gloves, to prevent contact with sodium cyanide. Production facilities should be equipped with advanced ventilation and exhaust systems to ensure that the workplace air meets safety standards. During transportation, sodium cyanide must be packaged in accordance with relevant regulations, usually in sealed steel drums, and transported by specialized hazardous chemical transport vehicles. Transportation routes should be carefully planned to avoid densely populated areas and water sources. In storage, it should be stored in a dedicated warehouse with good ventilation, away from heat sources, ignition sources, and incompatible substances such as acids and oxidants. The warehouse should be equipped with leak - proof and anti - theft facilities, and implement a "double - lock" management system.

In terms of environmental protection, the "three wastes" generated in the production of sodium cyanide must be properly treated. Wastewater containing cyanide should be treated by chemical oxidation or other appropriate methods to decompose cyanide ions into non - toxic substances before being discharged. Waste gas containing hydrogen cyanide should be purified through absorption or combustion treatment to reduce its impact on the atmosphere. Solid waste containing cyanide should be safely landfilled or treated by specialized hazardous waste treatment facilities to prevent pollution of soil and groundwater.

Conclusion

Sodium cyanide, despite its high toxicity, is an indispensable material in modern industry. From industrial synthesis to fine chemicals, it has made important contributions in various fields. With the continuous development of technology, on the one hand, more efficient and environmentally friendly production methods of sodium cyanide are being explored; on the other hand, in the application process, efforts are being made to improve the utilization rate of sodium cyanide and reduce its negative impact on human health and the environment. In the future, sodium cyanide will continue to play an important role in the development of the industrial economy while better balancing safety, environmental protection, and production needs.