Enterprise standard of terephthalic acid dianhydride

Production technology, market and development trend of trimellitic anhydride

Release date: 2022/10/1216: 43: 23.

background

Trimellitic anhydride is abbreviated as trimellitic anhydride, and its chemical name is 1, 2,4-trimellitic anhydride, abbreviated as TMA. Metaanhydride is a white block or granular solid with molecular formula of C9H4O5, molecular weight of 192. 12, melting point of 168℃ and boiling point of 390℃. It is easily soluble in water, acetone, ethyl acetate and N, N- dimethylformamide, and slightly soluble in carbon tetrachloride, ether and dimethyl formamide. Because the molecular structure of partial anhydride contains bifunctional groups-carboxylic acid and anhydride groups, it has bifunctional chemical properties and high reactivity. It can be used to produce a series of valuable special chemicals and is an important chemical raw material for modern new materials [1].

The active chemical properties of partial anhydride make it an important raw material for organic synthesis, which can be used to synthesize more environmentally friendly fine chemical products with high added value, and has a wide range of applications [2]:

The trimellitic acid ester plasticizer synthesized by esterification of (1) dianhydride and monohydric alcohol has excellent electrothermal properties, and is widely used as a heat-resistant and environment-friendly plasticizer for polyvinyl chloride (PVC), such as wire and cable materials with heat resistance grades of 90℃ and 105℃ and high pressure of 6kV and 10kV.

(2) Polyamide-imide polymer is polymerized from dianhydride and phenyl diisocyanate, which has good high-temperature environment performance, solvent solubility resistance, impact resistance, radiation resistance and creep resistance, and is widely used in motor trunking equipment and insulating paint for wires and cables.

(3) Alkyd resin has excellent stability and is often used as a primer for electrophoretic coating. The fire resistance time and flame spread rate of alkyd resin materials have reached the first-class standard.

(4) Polyester epoxy powder coating is made of polyester resin synthesized from dianhydride and then mixed with epoxy resin according to a certain formula. The powder can also be melted into a film, which has the advantages of environmental protection and construction.

(5) The block polymer rubber synthesized from dianhydride has good weather resistance, flexibility and light stability; Sodium trimellitate can be prepared by the reaction of trimellitic anhydride with higher fatty alcohols such as dodecanol and octadecanol. It is an excellent anionic surfactant.

Production technology of 1 meta-anhydride

Early partial anhydride was found in the by-product of the synthesis of pyromellitic dianhydride by air oxidation of gas-phase durene. Industrial production methods of trimellitic anhydride [3-5] include liquid-phase nitric acid oxidation of trimellitic toluene, liquid-phase air oxidation of m-xylene benzaldehyde and liquid-phase air oxidation of trimellitic toluene, which are collectively called liquid-phase oxidation method and gas-phase air oxidation method of trimellitic toluene (belonging to gas-phase oxidation method).

Liquid phase oxidation of trimethylbenzene with nitric acid

The nitric acid oxidation method of trimethylbenzene takes trimethylbenzene as raw material. Under the conditions of 180℃ ~ 205℃ and 1.5 ~ 3.0 MPa, trimellitic acid was oxidized step by step with nitric acid, then evaporated and crystallized, separated from solid and liquid, washed with solvent and dried to obtain trimellitic anhydride. The process is easy to operate, the process is simple and the product yield is high, but the nitric acid method has some problems such as high cost, serious corrosion, high requirements for equipment and materials, and serious pollution.

Liquid-phase air oxidation of 1.2 m m m-xylene benzaldehyde

Liquid-phase air oxidation of m-xylene benzaldehyde is a production process disclosed by Mitsubishi Gas Chemical Company of Japan in 1985. Metaanhydride is synthesized from m-xylene and formaldehyde, so it is also called MGC method. On the basis of summarizing the previous methods, this method developed a new route: under the complexation of strong acid catalyst HF-BF3, m-xylene and carbon monoxide were formylated to prepare 2,4-dimethylbenzaldehyde, and then trimellitic acid was prepared by air oxidation in aqueous solution, then dehydrated to anhydride to obtain trimellitic anhydride, and finally refined and sliced to obtain the finished product.

The reaction process of continuous method takes water as solvent, and the raw materials are easily available, the product yield and purity are high, the automation is easy to operate and implement, there is almost no volatilization loss, the explosion risk can be minimized, and the by-product treatment is relatively easy; However, this method uses strong acid catalyst HF-BF3, and the core equipment of oxidation part needs to be made of expensive alloys such as Ni-Ti-Zr, which leads to high production cost and increased investment in factory construction. Because the catalyst used is super strong acid HF-BF3, it causes serious corrosion to other equipment, which has potential safety and environmental protection risks, and the total production cost is too high, so it is impossible to maintain the operation of its production device for a long time.

1.3 air oxidation of gaseous trimethylbenzene

In the air oxidation method of gas-phase trimellitic acid disclosed by Japan's catalyst chemical industry, metallic and nonmetallic compounds containing vanadium, titanium, phosphorus, iron, chromium, manganese, silicon and halogen are used as catalysts to synthesize trimellitic acid by catalytic oxidation, and then it is dehydrated into anhydride to generate trimellitic anhydride, or the trimellitic acid can be oxidized to V-P-Ti-Mo by V-Cu-Mo system.

The method for synthesizing trimellitic acid has the advantages of simple process, less equipment investment and convenient operation. However, in industrial production, the catalyst used in this process cannot be recovered, resulting in catalyst waste and great environmental pollution. Moreover, for the target product, the yield is low and there are many by-products, so continuous production cannot be realized. In the post-treatment process, more water will be consumed and a lot of waste will be produced. These waste water and waste residue have caused great pressure on the environment and management.

Liquid phase air oxidation of 1.4 trimethylbenzene

At present, the widely used production process of 1, 2,4-trimellitic anhydride is trimethylbenzene liquid-phase air oxidation. 1, 2,4-trimethylbenzene was used as raw material, high purity acetic acid as solvent and cobalt manganese bromide as catalyst, and 1.4 ~ 1.6 MPa was synthesized by air liquid phase oxidation at 220℃ ~ 230℃.

This method was developed by American medieval company, and then improved by Amoco company to realize industrial production, so it is called AMOCO method for short. The oxidant of the process is air, the main catalyst is cobalt manganese acetate, and the cocatalyst is tetrabromoethane or hydrobromic acid. The oxidation reaction was carried out in acetic acid solution to produce 1, 2,4-trimellitic acid, and after dehydration, 1, 2,4-trimellitic anhydride was produced. At the beginning of 1990, Amoco company improved the process by adding cobalt, manganese and bromine composite catalysts to the air oxidation process of trimethylbenzene, which greatly enhanced the catalytic effect and shortened the reaction time. After further treatment and catalyst recovery in the later stage of the reaction, the energy consumption and material consumption were reduced, the product yield was improved, and the economy of the process was greatly improved. At present, the main method of producing metathesis anhydride at home and abroad is continuous or intermittent liquid-phase air oxidation.

Comparative analysis of the production processes of 2- trimellitic anhydride by batch method and continuous method [6-7]

The main difference between domestic and foreign processes for producing trimellitic anhydride by liquid-phase air oxidation is that trimellitic acid is purified first in foreign countries, while many domestic processes are one-step processes. The reason is that because trimellitic acid is not crystallized and purified, the metal ions brought by the catalyst remain in trimellitic acid, and then dehydrate into anhydride at high temperature, and the refining process is prone to side reactions. Part of trimellitic acid is converted into trimellitic acid, and the other part of trimellitic acid is further decarboxylated and disproportionated, and finally converted into o/m/terephthalic acid and benzoic acid.

In view of the harsh production conditions, easy blockage and equipment corrosion, it is difficult to realize the whole process automation. In general, the production of partial anhydride mostly adopts batch method or semi-continuous method or a combination of the two. Because of the amplification effect in the process of anhydride generation and crystallization, intermittent operation is mostly used at present, while continuous distillation process is used for acetic acid recovery.

2. 1 intermittent oxidation method and continuous oxidation method

2. 1. 1 batch oxidation method

The intermittent oxidation production process is as follows: firstly, the prepared mixture of mesitylene, acetic acid and catalyst is put into a reaction kettle; when the temperature and pressure are raised to the oxidation reaction conditions, air is introduced for oxidation reaction; after the reaction is completed, the air is stopped; then the discharge is cooled under reduced pressure; and then the oxidation reaction process of the second kettle is repeated, and so on.

2. 1.2 continuous oxidation method

Continuous oxidation process is a process in which materials are continuously pumped in, compressed air is continuously introduced and the other side is continuously discharged under certain reaction conditions such as temperature and pressure.

2.2 process comparison and analysis

2.2. 1 Advantages and disadvantages of intermittent oxidation process

Advantages: simple process flow, intermittent operation of oxidation reaction unit, low technical requirements for employees and low equipment investment.

Disadvantages:

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(2) The process of repeatedly initiating and discharging materials into the reaction kettle for several hours is characterized by high energy consumption, frequent and complicated control of the reaction process, easy leakage, low product yield and unstable product quality, which is 65,438+00% ~ 65,438+05% lower than that of the continuous oxidation method and 20% ~ 30% higher energy consumption.

(3) The output is not large, which is not suitable for large-capacity industrial production.

2.2.2 Advantages and disadvantages of continuous oxidation production process

Advantages:

(1) continuous oxidation production process is to feed and discharge at the same time under a constant oxidation condition, without feeding one kettle at a time for reciprocating oxidation reaction, so the automation degree is high, the reaction process is stable, the fatigue of metal equipment is reduced, the safety of equipment use is increased, and the service life of equipment is prolonged.

(2) low reaction temperature, small reactor volume, stable reaction process, stable product quality, low energy consumption and high product yield, and is suitable for large-scale industrial production.

Disadvantages: Due to the high degree of automation and technical difficulty, it requires a lot of one-time investment and requires high quality of workers.

3 Development Status and Market Analysis of Metaanhydride [8- 1 1]

3. 1 foreign production status

The earliest research on metathesis anhydride abroad was in 1950s. 1962, the liquid-phase air oxidation of trimethylbenzene was adopted by American Amoco company for the first time and industrialized production was realized. In 1990s, Amoco upgraded the existing process. By improving the catalyst and adopting metal compounds, the catalytic effect was significantly enhanced, the reaction time was greatly shortened, the product yield was improved and the energy consumption was reduced. Amoco was once the world's largest producer of trimellitic anhydride, with two overseas plants in Illinois, Belgium and Malaysia, with production capacity of 65,000 tons/year, 23,000 tons/year (discontinued) and 55,000 tons/year (discontinued) respectively. 1985 Mitsubishi gas chemical co., ltd. of Japan built a set of maleic anhydride production equipment with10.5 million tons/year MGC process in the waterway; At the same time, Japan Distillery Industry Co., Ltd. and Mitsui East Asia Co., Ltd. seized the opportunity to build production facilities with an annual output of 1000 tons (discontinued) respectively. 1995, Italian company Lonza independently developed a set of equipment for producing trimellitic anhydride by liquid-phase air oxidation, with an annual output of 20,000 tons (discontinued). Sasas of Italy plans to build a production plant with an annual output of 50,000 tons of meta-anhydride in Belgium (discontinued). Up to now (2065438+the end of 2008), the foreign manufacturers of meta-anhydride are mainly distributed in the United States and Europe, among which the production capacity of FHR Company in the United States is 65,000 tons/year, and that of Polynt Company in Italy is 20,000 tons/year.

3.2 Domestic production situation

In 1980s, Harbin Petrochemical Plant cooperated with Heilongjiang Petrochemical Research Institute to successfully develop and build a maleic anhydride plant with a capacity of 300 tons/year, and the production capacity of 1993 was expanded to 3000 tons/year. 1997 jiangyin changjing acetic acid factory in Wuxi, Jiangsu province improved the original domestic technology and developed a new production scale of 2000 tons/year. On this basis, the production scale was expanded to 5000 tons/year in 2000. At the end of 2002, the company also built a set of production equipment with a production capacity of10.5 million tons/year by introducing Italian technology, bringing the total production capacity of the group company to 20,000 tons. In addition, according to the market demand and taking into account the scale advantage, our local company organized scientific research and technical strength, and after unremitting efforts and repeated research, independently developed a continuous oxidation process with intellectual property rights, which filled the domestic gap and won three national patents for technological inventions. In June 2003, a set of continuous production equipment with a production capacity of 654.38+500,000 tons/year was completed and put into operation. Up to now (202 1), the domestic companies that produce partial anhydride mainly include Zheng Dan in Jiangsu, Baichuan in Wuxi, Bolin in Changzhou and TEDA in Anhui. Its production capacity of meta-anhydride is 654.38+10,000 tons/year, Wuxi Baichuan 40,000 tons/year, Changzhou Bolin 20,000 tons/year (production suspension and relocation) and Anhui TEDA 20,000 tons/year respectively.

3.3 Market analysis

At present, the production facilities of the world's partial anhydride are mainly concentrated in China, the United States and Europe, among which China is the world's largest producer of partial anhydride, accounting for more than 70% of the world's total production capacity. At present, there is no modification and expansion project of metaanhydride abroad, and the newly added capacity mainly comes from China. In recent years, the world consumption market of trimellitic anhydride is mainly concentrated in Asia, North America and Europe, accounting for 58.2%, 27.8% and 12.7% respectively. The consumption of trimellitic anhydride in South America is at the level of 1000 tons, while that in Central and Eastern Europe, the Middle East, Africa and Oceania is only at the level of1000 tons. Its main consumer market is the production of environmental plasticizer TOTM. Followed by powder coatings, advanced insulating materials and high-temperature curing agents, and a small number of products are used in aircraft engine lubricating oil additives, film flocculants and sodium trimellite anionic surfactants.

4. The future development prospect of the trimellitic anhydride industry

In the past few years, the main problem faced by trimellitic anhydride industry is that the production process is relatively backward, mostly batch process and semi-continuous process, which is unfavorable to the development and competition of trimellitic anhydride market [12- 18]. Therefore, efforts should be made to develop continuous oxidation production technology, and enterprises with small scale, small production capacity and backward production technology should be eliminated or merged one by one. At the same time, expand production scale and improve product quality. Enterprises in the same industry should strengthen technical exchanges, promote the technical upgrading and sustained and healthy development of China's metathesis anhydride industry, improve the competitive advantage of China's metathesis anhydride products in the international market, and further expand the market share.

Trioctyl trimellitate (TOTM) is an important nontoxic and environment-friendly plasticizer product downstream of trimellitic anhydride in plastic additives industry, which has the characteristics of high temperature resistance, corrosion resistance, aging resistance, migration resistance and excellent insulation performance, and has been fully affirmed and developed in plasticizer industry. In particular, ROHS directive and EU REACH regulations have raised the requirements for environmental protection standards, which proves that TOTM will gradually replace DOP, a non-environmental plasticizer widely used in plasticizer industry.

In the powder coating industry, the application of dianhydride is increasing day by day, especially for powder coatings with excellent performance and environmental protection. With the rapid development of light household appliances and other products in China, the requirements for the output, variety, quality and performance of coating products have been greatly improved, especially the demand for environmentally friendly coatings has increased rapidly.

In addition, some anhydrides can also be used to synthesize special engineering plastics such as polyamideimide and polyester imide, which can be used not only as insulating materials, but also to manufacture plastic molded parts such as bearings, valve parts, electronic components and jet engine parts. At present, this field needs further development in China, which will provide a broad market and strong impetus for the development of metathesis anhydride industry.

Metaanhydride can also be used to produce epoxy resin high temperature curing agent. China coating industry is developing in the direction of environmental protection, non-toxicity and high flame retardancy. A new type of water-soluble resin coating was obtained by using water-soluble resin coating, which was used as electrophoretic coating primer for automobiles, refrigerators and washing machines.

With the country's increasingly strict requirements for environmental protection, environmental protection is the cornerstone of enterprise development. The chemical industry consumes a lot of energy and causes serious pollution. In the specific production process, for the waste water, waste gas and solid waste generated, the resource utilization rate will be improved within the allowable range. The waste generated in the upstream is recycled as raw materials for downstream production, and a perfect resource utilization cycle is gradually formed.

Therefore, for the production of trimellitic anhydride, the demand of downstream products for environmental protection is increasing. In view of the imperfect treatment facilities of "three wastes" and the substandard discharge of wastewater, enterprises should carry out rectification and guide the whole industry to develop in a large scale and concentration when necessary.

5 conclusion

To sum up, trimellitic anhydride has a great development prospect. Make full use of heavy aromatic hydrocarbon resources at home and abroad, and encourage the comprehensive utilization of c9 aromatic hydrocarbon industrial chain resources. On the one hand, expand the production scale of trimellitic anhydride, and ease the contradiction between supply and demand in the market; On the other hand, make full use of the complementary advantages of nitrogen and carbon dioxide produced by oxidation tail gas, and the strong chain effect of mesitylene and mesitylene produced by mesitylene alkylation, and by-products mesitylene and mesitylene to enhance the comprehensive competitiveness of the whole C9 industry. In a word, the continuous oxidation process of trimethylbenzene will be the development trend of the industry. At the same time, we will strengthen technology research and development, increase capital investment, make a breakthrough in the continuous process of crystallization-centrifugation-anhydride, and realize the full continuous production of trimellitic anhydride as soon as possible.

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