[Chemical Knowledge]：The nature, use, upstream and downstream raw materials, storage methods of o-xylene, what is the critical amount of o-xylene.

o-Xylene Properties

Ortho-xylene (o-Xylene) is an aromatic hydrocarbon with the molecular formula C8H10, and its chemical structure consists of a benzene ring and two adjacent methyl groups. It is a colorless and transparent liquid at room temperature with an aromatic odor. o-Xylene has a density of 0.88g/cm³, a boiling point of 144°C and a melting point of -25°C. It is insoluble in water, but miscible with organic solvents such as ethanol and ether. Ortho-xylene has high volatility and flammability, its vapor and air can form an explosive mixture, and the explosion limit is between 1.1% and 7.0%.

Ortho-xylene use

O-xylene is widely used in chemical industry. The main use is as a raw material for the production of phthalic anhydride (PA), which is an important intermediate for the production of plastic plasticizers. Ortho-xylene is also used in the synthesis of coatings, resins, dyes and pesticides. As a solvent, o-xylene also has important applications in coatings, inks and adhesives. Due to its good dissolution properties, it is widely used as a cleaning agent and solvent in laboratory and industrial production.

Upstream raw materials

The production of o-xylene mainly depends on petrochemical raw materials. Oil or natural gas through cracking, reforming and other processes can be obtained mixed xylene (Mixed Xylene), which contains o-xylene, p-xylene, m-xylene and ethylbenzene. High purity o-xylene can be separated from mixed xylene by distillation separation technology. Olefin compounds generated in the cracking process are also the basic raw materials for the production of o-xylene.

Downstream Products

The main downstream product of o-xylene is phthalic anhydride (PA), which is an important chemical intermediate used in the production of plasticizers such as dioctyl phthalate (DOP) and dibutyl phthalate (DBP). These plasticizers are widely used in the production of plastics such as PVC to improve their flexibility and ductility. Phthalic anhydride is also used in the manufacture of unsaturated polyester resins, alkyd resins, etc., which are widely used in the coatings and adhesives industry. Phthalic anhydride is also used in the synthesis of dyes and pesticides.

O-Xylene Production Process

The main process for the production of o-xylene is the production of mixed xylenes by cracking oil or natural gas, which are then separated by distillation. The cracking reaction is usually carried out under high temperature and high pressure conditions, and mixed xylenes with higher yield can be obtained by catalytic cracking or steam cracking. The separation process includes a series of distillation columns. By controlling the temperature and pressure, high purity o-xylene can be effectively separated. Adsorptive separation techniques, such as the use of zeolite adsorbents, can also be used to separate different xylene isomers by changing the polarity and pore size of the adsorbent.

storage method

The storage of o-xylene requires attention to fire prevention, explosion prevention and leakage prevention. It should be stored in a cool, ventilated and dry place, avoid direct sunlight and heat source contact. The storage tank should use explosion-proof equipment, and it is strictly forbidden to use ignition sources and tools that produce sparks. Due to its high volatility, the storage tank should be well sealed to prevent vapor leakage. During transportation, tank cars that meet the standards should be used, equipped with fire prevention facilities, and protective measures should be taken during loading and unloading to prevent static electricity from causing fire or explosion.

Safety and environmental impact

O-xylene is harmful to human health and environment. Inhalation of its vapors may cause symptoms such as headache, dizziness and nausea, and long-term exposure may cause liver and kidney damage. Skin contact can cause irritation and allergic reactions. For the environment, o-xylene has certain toxicity and bioaccumulation, and has toxic effects on aquatic organisms after entering the water body. Therefore, in the process of production and use, it is necessary to strictly control its emissions and take effective waste gas and wastewater treatment measures to reduce environmental pollution.

Market Analysis

The market demand for o-xylene is mainly driven by the demand for downstream products. In recent years, with the development of plastics, coatings and resin industries, the demand for o-xylene is gradually increasing. Asia is the world's largest consumer market for o-xylene, especially China, which has benefited from the rapid industrialization and urbanization process, and the demand for o-xylene is growing rapidly. On the other hand, with the increasingly stringent environmental protection regulations, the environmental protection issues in the production and use of o-xylene have also become the focus of the industry. In the future, green production technology and environmental protection technology will become an important direction of development.

Summary

As an important chemical raw material, o-xylene is widely used in modern industry. Its production relies on petrochemical raw materials, and high-purity products are separated by distillation and other processes. Downstream products are mainly concentrated in the fields of plastic plasticizers, coatings and resins. The storage and transportation of o-xylene requires special attention to fire and explosion protection to ensure safety. With the growth of market demand and the improvement of environmental protection requirements, the o-xylene industry is facing new challenges and opportunities, and green production technology will become an important direction for future development.