Overview of Adipic Acid

Adipic acid
1. Physical and chemical properties of adipic acid
Adipic acid is commonly known as fatty acid, with a molecular formula of C6H10O4 (ADOH) and a molecular weight of 146. Adipic acid is a white crystalline substance with a slightly sour taste and a bone burning odor.
. Melting point 153C, boiling point 322.7C, flash point: 210C (open cup), relative density 1.36Q, explosion limit: 3.94% to 7.9%. Slightly soluble in water, easily soluble in most organic solvents such as alcohol and ether. Has slight toxicity and corrosiveness. Adipic acid has good stability in air, is prone to static electricity, and can soften and clump at high temperatures, even deteriorating. When the oxygen content is higher than 15%, adipic acid is prone to static electricity and ignition, so the oxygen content must be controlled during operation. Adipic acid is an important fatty dicarboxylic acid that can undergo condensation reactions with compounds with multiple functional groups, such as hexamethylenediamine. In industry, nylon 66 salt (abbreviated as AH salt) is produced by the condensation reaction of adipic acid and hexamethylenediamine. Nylon 66 salt can be further condensed to obtain nylon 66 resin. In addition, adipic acid can also react with alcohols to produce adipic acid esters, which are used as plasticizers, synthetic lubricants, and polyester polyols. It can also be used to produce advanced lubricants, food additives, pharmaceutical intermediates, essence and spice control agents, new single crystal materials, plastic foaming agents, coatings, adhesives, pesticides, dyes, etc.
The main technical parameters of adipic acid include important indicators such as moisture, ash content, iron content, and nitric acid content. The analysis of nitric acid content, iron content, and ash content are important control indicators. Polyester polyols are sensitive to metal ions in production reactions, and the reaction is intense (influenced by trace metal elements). Imported goods such as Asahi Kasei and Rhodia mainly have the advantages of low iron ion content, stable indicators, and small fluctuations;
Domestic products: Liaohua products have the most stable indicators, while other peers have slightly lower relative indicators. The price of the main production process for imported goods is higher than that of domestically produced goods. Due to the complex manufacturing process of adipic acid, its production technology has always been monopolized by chemical industry giants. Manufacturers with proprietary technology and routes include DuPont, Asahi Kasei, BASF, and others. The main distribution area of global adipic acid production capacity is North America, with 1.172 million t • a-1, of which 1.002 million t • a-1 is in the United States; The European production capacity is 1.124 million t • a-1, including 320000 t • a-1 in France, 408000 t • a-1 in Germany, and 270000 t • a-1 in the UK; The production capacity in the Asia Pacific region is 568000 t • a-1, including 197000 t • a-1 in China, 122000 t • a-1 in Japan, 135000 t • a-1 in South Korea, and 114000 t • a-1 in Singapore. NVIDIA Corporation in the United States is the world's largest producer of adipic acid, with a production capacity of 805000 t • a-1, accounting for 37% of the global total production capacity; Next is the French company Rodia, which accounts for approximately 18.5% of the global production capacity.
3.1 International Production Status of Adipic Acid Up to now, there are four production methods for adipic acid in the world. Phenol method, before the 1950s, adipic acid production used phenol as raw material. Phenol hydrogenation generates cyclohexanol, which is then oxidized by nitric acid to produce adipic acid. The phenol method is a relatively classical method, which has the advantages of high product purity, mature production technology, and low demand for stainless steel materials. However, phenol resources are limited and expensive, and the product cost is high. Currently, it has been basically eliminated.
The butadiene process was developed by BASF in Germany. The biggest advantage of this method is that it can use mixed C4 from refineries as raw materials, and the production cost is low. Its disadvantages are long process, multiple steps, and the need for high-voltage equipment.

According to relevant information, this method produces adipic acid at a lower cost. The process route of producing adipic acid from straight chain olefins is more reasonable in terms of principle and energy consumption utilization than the route of producing adipic acid from benzene as raw material. The prospects for large-scale industrial production and application in the future are promising. However, it is currently undergoing trial operation and does not yet have the conditions for large-scale industrial production.
The other two methods are the relatively mature process routes used in industrial production today, namely the cyclohexane method and the cyclohexene method.
The cyclohexane method is currently the main method used in the production of adipic acid worldwide. The main manufacturers of adipic acid in the world include DuPont, Monsanto in the United States, and Rhodia in France, all of which use this process technology. The output accounts for more than 90% of the total output, and the raw material is benzene. The main advantages are mature technology, complete localization of catalysts and chemicals, high product yield and purity, but the process is complex and requires a large amount of nitric acid.
The fourth process route for producing adipic acid using cyclohexene method is a new process developed by Asahi Kasei Corporation in Japan in the 1990s, which uses benzene as raw material. This method uses benzene as the raw material, selectively hydrogenates benzene to produce cyclohexene, hydrates it to produce cyclohexanol, and then oxidizes it with nitric acid to produce adipic acid. Pingdingshan Shenma Group in Henan Province began introducing its production process for nylon 66 salt in 1993, and the production line was completed and put into operation in 1996. This route has the characteristics of high yield and good safety, but it also has a variety of catalysts, high prices, difficult localization, and generates a large amount of waste residue that needs to be buried and treated (tens of tons per year).
At present, for the production of adipic acid in the world, except for the yet to be developed butadiene method, whether it is the phenol method or the cyclohexane and cyclohexene method, the raw materials are nitric acid and cyclohexanol, or a mixture of nitric acid and cyclohexanol and cyclohexanone. The difference between the two process routes mainly lies in the different raw material production routes. The production process of adipic acid in the later stage is similar. This process was first developed and industrialized by the French company Rodia. However, according to literature reports, the cyclohexanol process route produces more nitrous oxide gas as a byproduct, and the essence of the two process routes is the same. Especially in recent years, the two process routes have borrowed from each other and continuously improved, and the process routes are basically the same.
3.2 Domestic Production of Adipic Acid

Currently, the main production facilities for adipic acid in China are Liaoyang Petrochemical Branch

In the 1970s

, a 56000 ton/year adipic acid plant was introduced from Rhodia, France (now expanded to 140000 tons) and Pingdingshan

In the early 1990s, a 38000 ton/year adipic acid plant was introduced from Asahi Chemical Company in Japan.
. Liaoyang Petrochemical's adipic acid unit adopts the cyclohexane production route, while Pingdingshan's adipic acid unit adopts the cyclohexene process route. The raw material production routes of the two sets of adipic acid plants are different: cyclohexanol used in the cyclohexene method is generated from cyclohexene water, and the key to the process is the use of water and catalyst. Due to the fact that this process was developed and industrialized by Asahi Kasei Corporation in Japan, this catalyst is also its patented product. In other words, if this raw material route is adopted, the technology should be imported. The raw material used in the cyclohexane process route is a mixture of alcohols and ketones. This process route adopts non catalytic oxidation technology, and the chemicals and catalysts used in the subsequent reactions can be localized. 90% of the manufacturers producing adipic acid in the world use this process. But the process route of the subsequent adipic acid production plant is basically the same.

Tianchen Company has accumulated years of engineering experience and has digested and absorbed the production process technology of adipic acid plants at home and abroad. The localization of the process technology route has been completed.

Currently, domestic production enterprises include CPC Liaohua with 150000 tons, Shandong Hongye with 140000 tons, Shandong Haili with 225000 tons, and Tianli High tech with 70000 tons.

4.1.3 Conclusion of Process Technology Selection

The process route of this project adopts the domestically produced cyclohexane to produce adipic acid production route, and the original

materials are alcohol ketone and nitric acid.
. In selecting the recommended process technology scheme, various reasons were comprehensively considered, especially in the localization and introduction of technology routes, drawing on past engineering experience. Previous engineering experience has shown that adipic acid is currently in high demand, and various suppliers are actively competing for the market. At the same time, technological barriers are constantly being set up. Introducing technology often comes with strict conditions, high costs, and high investment. At present, Tianchen Company has mature domestic technology (cyclohexane process route) and rich practical experience of Xinjiang Tianli High tech. It can be expected that the process route produced in China will be feasible in the engineering design and implementation process in the future; Through engineering design optimization and advanced engineering management system, the adipic acid plant has reached or approached the current international advanced level in terms of process flow, operation, environmental protection, energy conservation and consumption reduction. 4、 Main sources of pollution and major pollutants
2.1 Waste gas: The waste gas in this project mainly comes from the exhaust emissions of various production facilities. Its main pollutants are NOx and trace amounts of CO, adipic acid, etc.
2.2 Wastewater
The wastewater discharged from this project can be divided into acidic and alkaline wastewater, organic wastewater, domestic sewage, and clean sewage according to their properties. 2.3 Waste residue (liquid)
During the production process, the waste catalysts from each unit are returned to the manufacturing plant for recycling. After draining the water from waste activated carbon, waste adsorbent, and waste resin, they should be disposed of in a landfill.
There is still a small amount of waste liquid in this project, mainly consisting of waste oil from the alcohol ketone unit. The main pollutants are organic heavy components and cyclohexanol, cyclohexane, cyclopentane, benzene, tert butanol, etc., which are incinerated in the incinerator. 2.4 Noise. The continuous noise of the proposed project mainly comes from various pumps such as compressors, air coolers, vacuum pumps, centrifuges, fans, etc., and its noise value is controlled below 85dB (A).
(Some of the content in this document is sourced from the internet. If there is any infringement, please inform us to delete it. The document can be edited and modified by yourself for reference. Thank you for your cooperation and support.)