Xylene is a colorless, volatile, sweet-smelling, flammable liquid that is insoluble in water and remains on its surface when mixed with water. Xylene consists of two methyl groups attached to the six-carbon ring of benzene, therefore it is also called dimethylbenzene.
This material is mainly used as a solvent and is used in the printing, rubber, and leather industries and can replace toluene in places where slower drying is required. This chemical is primarily a synthetic chemical. However, it occurs naturally in oil, and coal, and is produced during forest fires.
Xylene is an aromatic hydrocarbon widely used as a solvent in industry and medical technology. The chemical formula of this compound is C6 H4 (CH 3) 2. This compound is found in small amounts in jet fuel, gasoline, and cigarette smoke.
Features of xylene
The chemical and physical properties of xylene are different according to the respective isomers. The melting point of this compound varies from -47.87°C (m-Xylene) to 13.26°C (p-Xylene). Typically, the melting point of the para isomer is much higher because it easily fits into the crystal structure. The boiling point of each isomer is around 140°C (284°F).
The density of each isomer is about 0.87 g/ml, and as a result, it has a lower density than water. This chemical in the air can be identified by the smell in concentrations from 0.08 to 3.7 ppm, and in water with a concentration of 0.53 to 1.8 ppm, its sweet taste can be recognized.
Specific applications of xylene
Xylene, often called xylol, is a powerful chemical solvent. This substance is derived from petroleum and therefore has certain advantages over other similar products.
It may seem odd, but solvents are chemical composites that are molecularly similar to the substances they are designed to dissolve. Since xylene is made from petroleum, it is especially good at removing paints, wood stains, and other synthetic products without damaging surfaces. It also acts as a solvent with compounds used on metals to prevent rust. Other materials that xylene will dissolve include a variety of adhesives and putty, as well as grease, glazes, resins, and waterproofing materials.
This compound is widely used as a starting material (or building block) for the production of other industrial chemicals, especially terephthalic acid (TPA), pure terephthalic acid (PTA), and dimethyl terephthalate (DMT). TPA, PTA, and DMT are used to produce polyethylene terephthalate (PET) polyesters, a type of plastic.
Bottles made of PET plastic are widely used as containers for water, soft drinks, and other beverages because PET is light, shatter-resistant, and strong. In addition, PET helps retain gas in carbonated beverages as it has strong carbon dioxide-blocking properties.
General applications of xylene
Xylene is used in laboratories for dry ice baths to cool reaction vessels and as a solvent to remove synthetic immersion oils from the microscopic field. This material can react with strong acids and oxidizing agents.
Xylene is also used to remove paraffin from microscopic slides before staining microscopic sections. Xylene is used in histology laboratories for tissue processing, staining, and in dentistry in root canal treatment. The high dissolution coefficient of this compound in histology makes it a good alternative to alcohol because it makes the tissue transparent and increases the penetration of paraffin. In coloring methods, its excellent degradability and cleaning ability helps to shine the slides.
Although conversion to terephthalate acid is the dominant chemical reaction of xylene, these compounds are also precursors of other chemical compounds. For example, chlorination of both methyl groups or monobromination of this compound is done to produce other products.
In the oil industry, xylene is one of the usual components of paraffin solvents that are used when the pipe is clogged with paraffin wax. For similar reasons, this substance is used in commercial products used to remove earwax (cerumen or earwax).
Production of xylene
In the recent past, the use of xylene has been important in industries and domestic and agricultural applications. Global demand for xylene is increasing. Therefore, the increase in its demand has created a challenge that must be considered in the industrial sector.
Xylenes are obtained industrially from the methylation of toluene and benzene. It is also worth mentioning that xylenes are considered part of BTX aromatics (benzene, toluene, and xylene) and are produced through processes such as catalytic reforming and carbonization of coal in the production of coke fuel.
Mixed xylenes are produced by heavy catalytic reforming of naphtha, from which the C8 stream contains ortho, meta, and Para-Xylenes and ethylbenzene. Xylenes are also obtained from the pyrolysis gasoline stream in a naphtha steam cracker with toluene disproportionation. Conventional PX technology is based on the isomerization of mixed xylenes. High-purity products can be obtained by crystallization or separation of the selective adsorbent such as UOP’s Parex and IFP’s Eluxyl processes.
Toluene disproportionation offers an alternative route with the latest catalysts capable of producing a PX-rich stream, but this route co-produces benzene. Processes have also been developed using zeolite catalysts for the alkylation of toluene with methanol to produce PX without the benzene byproduct.
Environmental pollution of xylene
This substance often enters the environment from industrial sources, car exhaust, and during use as a solvent. Therefore, workers engaged in paint factories and garages are exposed to a large amount of this chemical. Because xylene is a liquid, it can easily enter the soil, surface water, or underground water. This substance evaporates quickly and breaks down into less harmful chemical compounds under the influence of sunlight. If xylene gets into the groundwater, it may contaminate the water for several months before it breaks down.
Complications and dangers of xylene for humans
Xylene is mainly an industrial chemical. Therefore, humans are more exposed to it in industrial facilities. This compound is flammable, so it should be kept away from possible sources of ignition and the ventilation of storage areas should be controlled.
Exposure to xylene occurs through inhalation, ingestion, eyes, or skin. This substance can affect health acutely or chronically based on the amount of exposure. The type and severity of the effects of this chemical depend on various factors, including the number of chemicals at the time of exposure and the length of time you have been exposed to it. People also react differently to different levels of exposure.
This primary chemical is metabolized in the liver by oxidation of a methyl group and its combination with glycine to yield methyl hippuric acid, which is excreted in the urine. Smaller amounts are eliminated unchanged through exhaled air, so this substance has little potential for accumulation in the body. Inhaling the vapor of this chemical mainly affects the central nervous system and causes symptoms such as headache, dizziness, nausea, and vomiting.
The effects mentioned begin with exposure to about 100 ppm of this substance. These side effects are reversible and can be significant and severe as the duration of exposure to xylene increases. This Chemical is heavier in density than air, and its pleasant, sweet smell is a warning of its toxic nature. This smell can be detected at a concentration of one part per million of air (PPM)!
Purchase of xylene
The xylene buying and selling market should be divided into two periods before 2013 and after. Until 2013, due to the need for this material and the lack of production, the global price of this material was increasing. Since this year, with the increase in p-Xylene production worldwide, the market of this product has become saturated, and this has caused the production capacity of this material to decrease in 2014. This saturation on the one hand and the decrease in the price of crude oil on the other hand led to changes in the price of xylene this year and in 2015.
With the decrease in the price of crude oil, the consumption of gasoline and, as a result, gasoline additives such as xylene and toluene increased, and this caused the price of p-Xylene to increase once again at the global level.
To consult and purchase xylene you can contact our experts on Iran Petroleum. Do not hesitate to call us, we are available 24/7.