What is PX (p-xylene / para-xylene)?

Tell you a real PX (p-xylene or para-xylene)

In recent years, PX, a common chemical term, has continuously entered the public eye in various ways, deriving various problems, and constantly carrying the public's environmental anxiety. But in fact, how much do we know about PX (p-xylene)?

 

What exactly is PX and what field is it mainly used for? What are its functions? What is its toxicity and hazard? How advanced is the domestic PX process technology? How about the equipment process safety and supporting safety measures? We must have an objective and scientific Cognition.

 

　　 Qingliang and Coke bottles are all from PX (para-xylene)

　　PX is the abbreviation of p-xylene in English, and the Chinese name is p-xylene. As an aromatic product, it is mostly used in oil refining and ethylene plants and is one of the very common chemicals in petrochemical production. 

PX comes from petroleum products, which can be produced on a large scale with relatively low production costs. Therefore, it can ensure that people can enjoy high-quality and inexpensive polyester textiles and clothing, and play a beautiful life.

 

p-xylene and allied

　　 In modern life, PX has a wide range of uses and is closely related to our daily lives. PX is an important organic chemical raw material, which is ultimately used to produce clothes, beverage bottles, edible oil bottles, etc., which people wear. 

For example, what people commonly call "zhenliang" is the product of PX, and PET beverage bottles made of PX are the earliest It was introduced to the market by Coca-Cola and Pepsi. 

In industrial applications, PX is mainly used as a raw material for the production of polyester fibers and resins, coatings, dyes and pesticides. It also has a wide range of applications in the production of spices, medicines, pesticides, inks, adhesives and other fields.

 

　　PX is the initial raw material for textiles and garments

 As the supply of natural fibers is limited by land, it is difficult to grow. Therefore, the development of synthetic fibers meets our needs for all kinds of clothing. 

In 2012, the global consumption of synthetic fibers was about 55 million tons, of which most of them were polyester fibers. Polyester fiber is produced by PX through multiple processes. 

In 2012, the global PX output was about 34 million tons, of which about 98% was used to produce polyester. my country is a big country of chemical fiber, and synthetic fiber production needs a lot of PX.

 

　　PX is the raw material of packaging products. Part of the polyester is used to make beverage bottles. The cola, soda, and juice we consume every day can be packaged in polyester bottles.

 

　　PX is also one of the components of gasoline

　　 In addition, there are about 600,000 tons of p-xylene used in paints, coatings and solvents in the world every year, but this way of utilization is becoming less and less. PX is also used to produce other chemicals in relatively small quantities.

 

　　 There has been no major pollution accident so far

　　PX is mainly derived from naphtha, an intermediate product in the petroleum refining process. After catalytic reforming or ethylene cracking, reformed gasoline and pyrolysis gasoline are obtained, and then mixed xylene is obtained through aromatic extraction process, and then prepared by adsorption separation. 

At present, the typical PX production processes in the world mainly include the production processes developed by UOP in the United States and IFP in France. 

Domestic Sinopec also overcome the difficulties in the entire process of PX in 2011 and became one of the main PX technology patents.

 

　　 The above-mentioned processes have overcome the safety production and environmental protection barriers, and can ensure that PX is produced in a safe environment. 

Using these advanced technologies, in the history of PX production, humans have not had a major pollution accident that caused serious harm to the environment and residents so far. 

Since the introduction of PX production technology in my country in the 1970s, PX has been produced for more than 30 years. Up to now, 13 domestic PX companies have not had serious pollution incidents.

 

In recent years, PX, a common chemical term, has continuously entered the public eye in various ways, deriving various problems, and constantly carrying the public's environmental anxiety. But in fact, how much do we know about PX?

 

　　 Japan’s PX (p-xylene) device is separated from the community all the way

　　 The entire production process of PX is basically a physical separation process, except for a small part of the chemical reaction process. The operating temperature is about 350°C to 420°C, and the operating pressure is about 10 atmospheres to 30 atmospheres. 

Compared with the synthetic ammonia production equipment for the production of nitrogen fertilizer and the petroleum refining production process for the production of gasoline and diesel, the process conditions are relatively mild.

 

　　PX production device is a modern production process system. The materials and processes are closed. Its production process is very similar to petroleum refining. Unlike the gasoline that we can touch daily, PX is inaccessible to the public from raw materials to products. 

Today with highly developed information technology, PX production is completely completed by equipment monitoring systems, operating operating systems, and safety precautionary instrument systems, avoiding errors caused by human operations and ensuring timely predictions before and during accidents. 

Also, prevention, including automatic shutdown, parking, and even chain parking. Therefore, this large-scale modern refining and chemical project already has the guarantee of safety and health.

 

　　According to actual measurement and research, under normal production and operation conditions, PX projects around the world have very little impact on air pollution in the city where they are located, and will not affect the health of citizens. 

So far, PX devices in all countries in the world have not had any safety accidents that caused major environmental impacts. Regarding the safe distance between PX production and residential areas, the PX device of the Yokohama NPRC refinery is only separated from the residential area by a highway. 

The PX device of the ExxonMobil refinery on Jurong Island in Singapore is 2.6 kilometers away from the residential area of ​​Singapore’s main island, and the PX device in Houston, USA It is also only 1.2 kilometers away from the city.

 

　　 In fact, the sanitary protection distance for petrochemical projects in my country should be more than 800 meters according to the national standard "Petroleum Processing Industry Sanitary Protection Distance" (GB8195-2011).

 

　　PX and gasoline belong to Category 3 dangerous goods

　　According to documents such as the "Global Unified Classification and Labeling System of Chemicals", PX is a low-toxic chemical substance. At high concentrations, when inhaled by the human body, it has an anesthetic effect on the human central nervous system. But under normal conditions, PX is a colorless and transparent liquid, which is not volatile.

 

In terms of hazard, PX and gasoline belong to the third category in my country's hazard category classification-flammable liquids. Their vapors can form explosive mixtures with air, and will cause combustion and explosion when exposed to open flames and high heat. 

In terms of poisoning performance, Both poisoning can cause headache, dizziness, nausea, vomiting, neurasthenia and other symptoms. It can be seen that the flammability, explosion risk, and toxicity of PX are similar to gasoline. 

However, from the perspective of daily life, PX is far less frequent than gasoline and people. What we are exposed to is only the downstream product of PX-the chemically stable polyester fiber (polyester).

 

In recent years, PX, a common chemical term, has continuously entered the public eye in various ways, deriving various problems, and constantly carrying the public's environmental anxiety. 

How much do we know about PX (p-xylene)? 

　　 Inhalation: The poisoned person should be quickly moved to a place with fresh air. Keep the airway open. If breathing is difficult, give oxygen. Breathing and heartbeat stop, immediately perform CPR. Seek medical attention.

 

　　 Eye contact: Immediately separate the eyelids and rinse thoroughly with running water or saline. Seek medical attention.

 

　　 Skin contact: Take off contaminated clothing immediately, and rinse thoroughly with soap and water. Seek medical attention.

 

　　 Ingestion: Rinse mouth, drink as much water as possible, and don't induce vomiting. Seek medical attention. Avoid adrenaline to avoid ventricular fibrillation.

  

　　 In the past few years, global PX production capacity has gradually shifted to concentrated consumption areas. Asia is the fastest growing region for PX, followed by the Middle East. As resources and markets are not dominant, the capacity growth in North America and Western Europe is very limited, and there is basically no development in Central and South America and Central and Eastern Europe. 

By 2012, the global PX production capacity reached 38.48 million tons, and the consumption volume was 34.1 million tons. China's PX production capacity and consumption accounted for 23% and 41% of the global share respectively.

 

Japan: As one of the first countries in the world to produce PX, Japan basically completed the construction and layout of production capacity before 2010. However, due to the lack of downstream labor-intensive industries, more than 80% of its PX products are used for export, especially China accounts for more than 60% of its exports.

 

　　 During the "March 11" earthquake in Japan, approximately 1.2 million tons of PX installations in Ibaraki and Chiba were affected and shut down. Afterwards, the plant resumed production smoothly and the load continued to increase.

 

South Korea: South Korea’s PX industrial production capacity has increased from only 260,000 tons in 1990 to 5.25 million tons at present, of which downstream demand has stabilized at about 4 million tons, and exports accounted for about 40% of total output. South Korea will continue to expand its PX in the future.

 

Singapore: As an island country, Singapore attaches great importance to environmental protection and safety. The country had its first PX device in 1992, and by 2000 the capacity was expanded to 850,000 tons. 

As the demand gap in mainland China continues to expand, Singapore’s Jurong Aromatics Group invested US$2.4 billion to build a new 800,000-ton PX device, which was put into operation in 2014, and all products are exported to China.