N-butene is a crucial link in the C4 chemical industry chain. As a basic organic chemical raw material, it connects the upstream petroleum refining and the downstream polymer materials and fine chemicals. This article will comprehensively introduce the knowledge about N-butene from its definition and properties, industrial production methods, application fields, as well as safety storage and transportation aspects.
N-butene, usually referred to as 1-butene (chemical formula: C₄H₈, structural formula: CH₃CH₂CH=CH₂), is an important basic organic chemical raw material. At normal temperature and pressure, it is a colorless gas, slightly soluble in water, and easily soluble in organic solvents such as ethanol and ether. It usually has a faint aromatic odor.
1.Chemical Family and Physical Properties
N-butene is one of the four isomers of butene. The other three are 2-butene (which is further divided into cis and trans forms) and isobutylene. The key physical constants of isobutene are as follows:
Molecular weight: 56.1
Melting point: -185.3℃
Boiling point: -6.3℃
Density: 0.5951 g/cm³ (at 20/4℃), heavier than air as a gas (about 1.93 times that of air).
Flash point: -80℃ (closed cup), classified as an extremely flammable substance.
2. Industrial Production Method: Source and Production Process
The n-butene used in industry is mainly obtained through the separation of the C4 fraction, and it can also be produced using specific synthetic processes.
C4 fraction separation (main source): The C4 fraction obtained from petroleum catalytic cracking or ethylene cracking is the main source of butene. For example, the C4 fraction obtained from catalytic cracking contains approximately 13% 1-butene and 25% 2-butene (sum of cis-trans isomers). In industry, butadiene and isobutene are usually extracted first from it, and then high-purity (>99%) 1-butene is obtained through distillation and other means.
Ethylene dimerization (synthesis method): In the presence of a catalyst (such as titanium ester and triethylaluminum), ethylene undergoes a dimerization reaction, selectively generating high-purity 1-butene. This is an important supplementary route in addition to the separation method.
By-product recovery: In some emerging processes such as methanol-to-olefins (MTO) projects, 1-butene also emerges as a by-product.
3. Application fields: From plastics to fine chemicals
Tetradecene serves as a bridge connecting basic petrochemicals and high-end materials. Its applications are mainly divided into two directions: as an intermediate for the production of other chemicals and as a monomer for polymers.
Polymers and copolymers:
Linear low-density polyethylene (LLDPE) copolymer monomer: This is one of the most important applications of 1-butene. It is copolymerized with ethylene, which can improve the environmental stress cracking resistance, flexibility and other properties of polyethylene, and is widely used in the production of films, packaging materials, etc.
Poly 1-butene (PB): 1-butene can be polymerized by itself to form poly 1-butene. This is a high molecular material with excellent high-temperature creep resistance, wear resistance and stress cracking resistance, and is mainly used in the field of pipe materials.
Organic synthetic intermediates:
Production of butadiene: Through catalytic oxidation and dehydrogenation, n-butene can be used to produce butadiene, which is the core raw material for synthetic rubber (such as cis-butadiene rubber and styrene-butadiene rubber).
Preparation of isobutanol and butanone: N-butene (usually a mixture of 1-butene and 2-butene) can be hydrolyzed to produce isobutanol, and then dehydrogenated to form methyl ethyl ketone (butanone). Butanone is an excellent industrial solvent and is widely used in the paint, adhesive, and ink industries.
Preparation of epoxycyclobutane: Through catalytic oxidation reaction, n-butene can be used to produce epoxycyclobutane, which can then be further converted into other fine chemicals.
Other fine chemicals:
Isomerization to produce propylene: Under the action of a specific catalyst, 2-butene (which is often regarded as the target for the conversion of normal butene) can undergo a translocation reaction with ethylene to form propylene. This is an important technology for regulating the balance of olefin production capacity.
Oxidation to adipic acid: N-butylene can also be used in catalytic oxidation to produce adipic acid (adipone), which is a raw material for the production of unsaturated polyester resins and food additives (such as malic acid).
4. Safety and Storage/Transportation
Due to the highly flammable nature of n-butene, its safety precautions are of utmost importance.
Hazard: When mixed with air, it can form an explosive mixture. The explosive limit is approximately 1.6% to 10.0% (by volume). The gas is heavier than air and tends to accumulate in low-lying areas. It will catch fire and backfire upon encountering a source of ignition. Additionally, contact of liquid n-butylene with the skin can cause frostbite.
Toxicity: N-butylene is classified as a low-toxicity substance. It mainly has effects such as simple asphyxiation, mild anesthesia, and mild irritation. Exposure to high concentrations may cause dizziness, drowsiness, and even coma.
Storage requirements: It should be stored in a cool, well-ventilated warehouse specifically designated for flammable gases, kept away from fire sources and heat sources, and stored separately from oxidants and acids. During transportation, usually use pressure-resistant steel cylinders or dedicated tanker trucks, and take anti-static measures.
5. Current State of the Market and Industry
N-butene is a crucial link in the carbon four industrial chain. With the enhancement of global ethylene cracking and catalytic cracking capabilities, the total amount of C4 resources is abundant. Currently, the industry trend focuses on the high-value utilization of 2-butenes (such as for the production of propylene) as well as the in-depth development of polymer-grade 1-butenes in the field of high-performance materials.
As a fundamental molecule in the field of chemistry, n-butene, through various chemical reaction pathways, has given rise to products such as plastics, rubber, and solvents that are closely related to daily life. Understanding its properties and applications is not only essential knowledge for chemical professionals but also helps us understand how modern industries efficiently convert petroleum resources into high-value materials.
