Acrylonitrile (ACN) is a chemical compound that serves as a foundational building block for a wide array of industrial and consumer products. This organic compound is primarily used as a monomer, a small molecule that links together to form long polymer chains. The resulting synthetic materials, which include various plastics, resins, and synthetic rubber, are integral to modern manufacturing. Acrylonitrile imparts desirable properties like durability and chemical resistance to these end products.
Chemical Identity and Characteristics
Acrylonitrile is chemically defined by the molecular formula C3H3N, featuring a distinct structure that links a vinyl group to a nitrile group. This compound is also known by its systematic name, 2-propenenitrile, or its common alias, vinyl cyanide. In its pure state, acrylonitrile is a colorless, volatile liquid that is less dense than water. It possesses a pungent odor, often described as similar to garlic or onions, although commercial samples may appear pale yellow due to trace impurities.
Acrylonitrile has a low boiling point of approximately 77 degrees Celsius, making it highly volatile and prone to vaporization at room temperature. It is moderately soluble in water and readily mixes with most common organic solvents. The presence of the nitrile group contributes to its high reactivity, which makes it valuable in polymer chemistry.
Manufacturing Acrylonitrile
Industrial production of acrylonitrile is overwhelmingly dominated by a single, high-efficiency method known as the Sohio process. This process, developed by the Standard Oil of Ohio, is a catalytic ammoxidation of propylene. It is a single-step, vapor-phase reaction that accounts for virtually all global acrylonitrile output. The primary raw materials for this process include propylene, a hydrocarbon derived from petroleum refining, ammonia, and air as the source of oxygen.
The reaction is performed in a fluidized bed reactor at high temperatures, typically between 350 and 510 degrees Celsius, and relatively low pressure. A specialized solid catalyst, often based on bismuth phosphomolybdate, is used to facilitate the reaction. Because the reaction is exothermic, meaning it releases heat, careful temperature management is required within the reactor to maintain process control. The resulting product stream contains acrylonitrile along with byproducts such as acetonitrile and hydrogen cyanide, which must be subsequently separated through absorption and distillation steps to achieve high purity.
Major Consumer and Industrial Applications
Acrylonitrile’s utility lies in its ability to serve as a monomer for creating polymers and co-polymers with a range of beneficial material properties. The largest volume application is in the production of acrylic and modacrylic fibers, which are spun into textiles for use in clothing, carpets, and upholstery. These synthetic fibers are valued for their softness, warmth, and resistance to fading and chemicals. Acrylic fibers also function as a precursor material in the manufacture of specialized carbon fibers used in aerospace and high-performance automotive parts due to their light weight and strength.
Acrylonitrile is a component in the creation of several engineering plastics. Acrylonitrile Butadiene Styrene, commonly known as ABS plastic, is a robust terpolymer that combines the strength of acrylonitrile, the rubbery resilience of butadiene, and the rigidity of styrene. ABS is widely used in automotive parts, appliance housings, and children’s toys because of its superior impact resistance and durability.
Another important copolymer is Styrene Acrylonitrile (SAN) resin, a transparent plastic prized for its rigidity, clarity, and resistance to heat and chemicals, making it suitable for household goods and packaging. Acrylonitrile is also used in the synthesis of nitrile rubber, a synthetic elastomer known for its excellent resistance to oil and fuel, which is used for manufacturing protective gloves and fuel hoses.
Toxicity and Exposure Management
Acrylonitrile is recognized as a toxic substance that poses significant health risks upon exposure, and it is categorized as a probable human carcinogen by several international health agencies. Exposure can occur via inhalation of its volatile vapors or through direct skin contact with the liquid, as it is readily absorbed through the skin. Acute exposure to high concentrations can rapidly irritate the eyes, respiratory tract, and mucous membranes. Immediate symptoms often include headache, dizziness, nausea, and feelings of apprehension.
A concern with acrylonitrile is its metabolic conversion within the body, which can release free cyanide. This leads to effects similar to cyanide poisoning that target the central nervous system. Chronic exposure can result in long-term effects, including nervous system dysfunction and an increased risk of certain cancers, such as lung and bladder cancer.
In industrial settings, managing this risk involves strict adherence to closed-system handling procedures to minimize vapor release. Workers must use appropriate personal protective equipment, including chemical-resistant gloves and respirators. They must also undergo regular training to ensure safe handling and emergency response protocols are followed.