Original title: Introduction and market analysis of downstream products of xylene
Introduction: Aromatic hydrocarbons are important basic raw materials for the petrochemical industry. Among the total of about 8 million known organic compounds, aromatic compounds account for about 30%, of which aromatic hydrocarbons (Benzene, Toluene, Xylene) are called Primary basic organic raw materials. In petrochemical industry, naphtha is used as raw material to produce benzene, toluene and xylene (BTX) through continuous reforming, aromatic extraction, adsorption separation and other equipment. The downstream products and current market of aromatic xylene in aromatics. Brief description of the situation.
1. Downstream products of mixed xylene
The largest amount of xylene is p-xylene, and p-xylene is oxidized to produce terephthalic acid, which is esterified with ethylene glycol or the like to form ethylene terephthalate, which is a raw material for producing polyester fibers and films. O-xylene produces phthalic anhydride, and phthalic anhydride is a raw material for the production of plasticizers, alkyd resins, unsaturated polyester resins, etc., and most of the xylene isomerized to para-xylene. Oxidation to isophthalic acid instead of phthalic anhydride as a raw material for unsaturated polyesters and alkyd resins.
Ethylbenzene in mixed xylene is mainly used for the production of styrene, and is also used to produce products such as phenylethyl alcohol. However, ethylbenzene separated from mixed xylene only accounts for a very small part of the total production capacity of ethylbenzene. The main source should be It is the alkylation of benzene and ethylene.
Xylene derivative use:
1. A small amount of xylene sulfonation to produce a surfactant (ammonium xylene sulfonate, sodium xylene sulfonate);
2. Ammonia oxidation of m-xylene to produce isophthalonitrile;
3. Meta-xylene produces m-phenylenediamine, which can be used to produce fibers, produce diisocyanate, and be used as an epoxy resin curing agent;
4. Industrially, xylene-formaldehyde resin (XF resin) is also produced from xylene;
5. Para-xylene can be synthesized in the gas phase to synthesize poly(p-methylenebenzene), which can be used as a high insulating film and coating.
Second, the downstream product market and process technology status of mixed xylene
1. Separation of p-xylene by mixed xylene
1) Analysis of market prospects
Paraxylene (PX) is an organic basic chemical raw material mainly used for oxidative synthesis of terephthalic acid (PTA). Terephthalic acid can be esterified to synthesize dimethyl terephthalate (DMT). Polyethylene glycol is polymerized to obtain polyester. Polyester is widely used in fiber production and resin preparation due to its excellent properties. Therefore, para-xylene has become an important chemical raw material for synthetic plastics and fibers.
Due to the rapid development of China's polyester industry, the consumption of PTA has soared, resulting in a rapid increase in the consumption of PX. In 2017, the total production capacity of China's PX reached 13.99 million tons. Compared with the domestic PX in 2016, there is no actual new capacity. Only Shanghai Petrochemical's 250,000 tons of equipment may have a re-engineering plan. Fuhua Group has invested in Tenglong Aromatics. At present, the distribution of domestic PX capacity is still dominated by Sinopec and PetroChina, with a small share of private capital, only Lidong, Fujia, Fujian United and Sinopec. In 2018, China National Petrochemical's second phase of 1.6 million tons of equipment will be put into operation. By then, the annual domestic PX production capacity will reach 15.59 million tons. In the future, with the installation of several large-scale installations such as Zhejiang Petrochemical, Fujian Quanzhou and Dalian Hengli, PX Will gradually become self-sufficient.
2) Paraxylene product technology route
At present, there are mainly three kinds of PX production methods, namely, a xylene isomerization process (conversion between C8 aromatic hydrocarbons), a toluene methanol alkylation process, and a toluene selective disproportionation process.
2. Separation of meta-xylene by mixed xylene
1) Meta-xylene use
The application of m-xylene to m-xylene mainly has the following applications: one is used as a raw material for isomerization to produce para-xylene and ortho-xylene; the other is used as a solvent or a component of blending gasoline; the third is used to produce resin. And fine chemical products, the following focuses on the application of meta-xylene in resins and fine chemicals.
Used as a modified intermediate for resin materials
The meta-xylene can be obtained by liquid phase oxidation reaction to produce isophthalic acid. Isophthalic acid can improve the strength and toughness of resin materials, anti-fatigue and corrosion resistance. Its biggest use is to produce unsaturated polyester resin. This resin can be applied in the field of building transportation and other applications. Coating, which can react with polyhydric alcohol to form polyester resin, used on polyester and urethane surface coatings, small amount can also be used in alkyd resin, using isophthalic acid instead of phthalic acid to improve surface The hydrolytic stability of the coating has higher durability and weather resistance. Another main use of isophthalic acid is to produce a modified polyester resin as a comonomer, which can lower the melting point of the resin and slow down the crystallization rate, thereby expanding the processing parameters of the resin and improving the coloration of the pigment. Formic acid modified polyesters are widely used in the packaging industry.
Isophthalic acid can also be used to produce sulfonated isophthalate, which is used in the manufacture of polyester fibers. A small amount of isophthalic acid is also used to make special products, such as polyamide fiber liquid crystalline polymer polyarylate and other less demanding products.
The meta-xylene is first oxidized and then reacted with phosgene to produce isophthaloyl chloride. The poly(m-phenylene diphenyl) synthesized from isophthaloyl dichloride and m-phenylenediamine can be made into a fiber film and A coating, an aramid fiber (i.e., aramid) made of such a resin has excellent heat resistance dimensional stability and electrical insulation.
The meta-xylene is used as a raw material to react with carbon monoxide to synthesize m-dimethylbenzaldehyde, and then oxidative dehydration to obtain trimellitic anhydride. Trimellitic anhydride is an important raw material for the development of new materials, mainly used in the production of polyvinyl chloride heat-resistant plasticizer trimellitic acid trioctyl ester polyimide engineering plastic water-soluble alkyd resin coating and epoxy resin curing agent and other fine chemicals Especially in the electromechanical industry, the polyamide diimide prepared by the synthesis of trimellitic anhydride and aromatic diamine has high heat resistance and good insulating properties, and is used for the production of heat-resistant wire insulating paint, which can be used at 220 ° C. Used for a long time.
Used as a fine chemical intermediate for pesticides, pharmaceutical dyes, etc.
Meta-xylene can be used to prepare isophthalonitrile, which is an intermediate material for high-efficiency broad-spectrum, low-toxicity and low-residue fungicide chlorothalonil. It is also an intermediate for the production of sulfhydryl resin and m-xylylenediamine. And used to produce epoxy resin curing agent. Due to the increased demand for chlorothalonil and the increase in demand for isophthalonitrile in the field of synthetic fiber plastics, isophthalonitrile is in short supply on the international market.
Meta-xylene can be obtained by air oxidation to obtain m-methylbenzoic acid, which is mainly used as an intermediate of the drug toluene diethylamine. It can also be used as a raw material for the hygienic insecticide "Deterophosamine", and can also be used for the production of polyvinyl chloride. A stabilizer for the resin and a raw material for the polymer monomer.
M-xylaniline can be obtained by using meta-xylene as raw material, by nitrification, isomer separation and liquid phase hydrogenation of nickel catalyst. m-Dimethylaniline is an important intermediate for the synthesis of pesticides and veterinary drugs and dyes. 2,4 dimethylaniline is mainly used in the production of pesticides and medicines, especially the production of pesticide monomethyl hydrazine, amitraz and acaricide; 2,6-dimethylaniline is an intermediate for the synthesis of pesticide dyes, such as the highly effective fungicides "metalaxyl", "吠霜灵" and "benz cream", the herbicides "isobutachlor" and "Terido" .
The meta-xylene is sulfonated and alkali-soluble to obtain a phenolic product, which is a raw material for various pesticides, and is also used for producing an azo dye, a plasticizer, a rubber antioxidant, an epoxy resin curing agent, and the like.
2) Market analysis of domestic meta-xylene
Domestic demand for meta-xylene is mainly divided into two categories: production of isophthalic acid and non-isophthalic acid. In recent years, the production capacity of domestic chlorothalonil, aniline, m-xylylenediamine, m-methylbenzoic acid and perfume has expanded rapidly, and the strong demand has caused the domestic xylene market to be in short supply.
China's xylene is mainly used to produce isophthalic acid products. The market demand for m-xylene is directly dependent on the isophthalic acid market. The international market also affects the domestic market demand for xylene. In addition to dicarboxylic acid, other fields are mainly “BaiChuqing”, “Mealaxyl” and “Mosquito Repellent”, and these products are mainly exported. Therefore, fluctuations in international market conditions also affect the market of meta-xylene. The main drivers of future xylene consumption growth include: the rapid increase in demand for 1 phthalic acid, and the increase in demand for isophthalic acid is an important driver for the increase in demand for xylene in the future. Among the total consumption of isophthalic acid in China, unsaturated polyester accounts for about 50%, copolymer resin accounts for about 34%, alkyd resin accounts for about 12%, and other accounts for about 4%. In 2017, the total demand for isophthalic acid in China will reach about 350,000 tons, of which unsaturated polyester resin and copolyester resin will remain the two main consumption areas. 2 In addition to isophthalic acid, the export of m-xylene downstream products such as isophthalonitrile will continue to grow steadily, thus driving the consumption of m-xylene; consumption in other application areas has also increased, but The ratio will decrease to varying degrees.
3) Main route of m-xylene production
At present, the main domestic production route of xylene includes two kinds of meta-xylene production processes, such as C8 aromatic isomerization-liquid phase adsorption separation process and o-xylene isomerization-gas phase adsorption separation process.
Aromatic isomerization-liquid phase adsorption separation of meta-xylene
In order to maximize the production of meta-xylene, Sinopec has developed a C8 liquid phase adsorption separation process for aromatics isomerization. The process consists of a C8 aromatic isomerization unit and a simulated moving bed adsorption separation unit, including a matching rectification system. The adsorption separation unit adopts R-, one of the R-AS aromatics adsorption separation process technologies developed by Sinopec. AS-m-xylene process. The R-AS-m-xylene process is similar to the p-xylene adsorption separation process, except that the process uses a RAX-II type adsorbent that preferentially adsorbs meta-xylene, and toluene is used as a desorbent, so the operation of the two processes The parameters and associated fractionation systems are also different.
O-xylene isomerization-multicolumn series gas phase adsorption separation process
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