Zibo Tianchen Qixiang starts operations; domestic production project for adiponitrile comes online

It is said that a project investment of 20 billion has been made, with the design firm Tiancheng Company also participating in the investment; this could lead to better results

The raw material for adiponitrile is butadiene; I am not very familiar with this manufacturing process.

There are several production processes. Adiponitrile (AND) is a colorless oily liquid with a slight odor; it is slightly soluble in water and ether, but soluble in alcohol. It serves as an important raw material for the production of nylon 66 salts, and this represents its most significant industrial use. In recent years, with the advancement of technology and the expansion of its application areas, it can be used in insecticides, rubber accelerators, rust inhibitors, raw materials for rockets, as a spinning solvent for terpolymers of methacrylonitrile and methyl methacrylate, as solvents for wet and dry spinning of polyvinyl chloride fibers, as a coloring agent for polyamides, as an additive in fabric bleaching agents, as plasticizers for butyrate and mixed esters, and as an extractant for aromatic hydrocarbon extraction.

In the early 1970s, DuPont developed a new method for producing adiponitrile: the direct cyanation of 1,3-butadiene (BD). The process consists of three steps: 1,3-butadiene cyanation (primary cyanation), isomerization of 2-methyl-3-butenonitrile, and hydrocyanation of pentenonitrile (secondary cyanation). In the primary hydrocyanic acid production stage, in addition to the most important intermediate, 3-pentenecyanide (3PN), by-products such as 2-methyl-3-butenecyanide (2M3BN), 2-methyl-2-butenecyanide (2M2BN), and 2-pentenecyanide (2PN) are also produced, as shown in Figure 1. After the first-stage cyanation reaction, the 3-pentenenitrile that has been separated and purified enters the second-stage cyanation stage. At this point, the presence of 2-pentenenitrile is undesirable, as it poisons the catalyst system and reduces its activity, thereby lowering the conversion rate of 3-pentenenitrile and the selectivity for adiponitrile during the cyanation process. Therefore, the higher the purity of 3-pentenenitrile in the primary cyanation products, and the lower the content of 2-pentenenitrile, the more favorable it is for the hydrocyanation of pentenenitriles. The challenge in the first-stage cyanide production section is the separation and purification of 3-pentenecyanide from 2-pentenecyanide.

In the 1970s, CNPC’s Liaoyang Petrochemical Company acquired the patent from the French company Rhône-Poulenc for the process of producing adiponitrile through the ammonolysis and dehydration of adipic acid. With design support from the French company Spécim Ingénierie, China’s first adiponitrile production facility was built. The core of the production process for hexanitrile via the ammonolysis of adipic acid is to react adipic acid with ammonia and then undergo dehydration to produce hexanitrile. The reaction process involves each carboxyl group combining with ammonia and losing one molecule of water to form an amide; further loss of a second molecule of water then completes the conversion of the carboxyl group into a nitrile group. The adiponitrile production unit at Liaoyang Petrochemical has been operating poorly since it was put into use in 1981; the reactors suffered severe coking and corrosion, with 3 reactors breaking down within two years. The entire unit could operate continuously for only 100 days. To produce 1 ton of adiponitrile, 1.6 tons of adipic acid were required, which is far higher than the theoretical value of 1.35 tons. The molar yield was only 85%. Under the pressure of high raw material costs, the adiponitrile production unit at CNPC Liaoyang Petrochemical was shut down in 2002.

25% of the raw materials are involved in side reactions. Adipic acid is ammoniated in very low-temperature water, and the salt formation rate of the resulting adipic acid diamine salt is 99.9%, with almost no side reactions occurring. The technical challenge in producing adiponitrile through the ammonolysis and dehydration of adipic acid lies in the numerous side reactions that occur during dehydration. These side reactions mainly include the decarboxylation and dehydration of adipic acid. Molten adipic acid tends to decompose, producing cyclopentene, water, carbon dioxide, and other substances. When adipic acid undergoes decarboxylation at high temperatures, the resulting cyclopentene undergoes self-condensation at the reaction temperature, generating large amounts of tar. δ-Cyanovaleric acid and valeramide cyclize at high temperatures to form secondary amines, namely adipimide, which are then converted into adipic anhydride. Prolonged heating or localized overheating can lead to the formation of adiponitrile dimers. Carbonylation and Raney catalyst poisoning occur because there is a certain amount of acidic substances in crude hexanenitrile; during distillation, these acidic substances cause carbonylation and coking. The condensation of carboxyamides results in the formation of highly unstable imiamides when the amides undergo partial thermal decomposition to release water, and these imiamides quickly decompose into nitriles and carboxylic acids or rearrange to form secondary amides. Adipamide undergoes strong resinification in the presence of dehydrating catalysts such as phosphoric acid, and adiponitrile is sensitive to temperature, also tending to resinify at high temperatures. The isomers of adiponitrile contain conjugated compounds such as 1-imino-2-cyanocyclopentane or 1-aminо-2-cyanocyclopentene. The isomers will continue to react during subsequent hydrogenation steps to form amines, which then condense on the surface of the hydrogenation catalyst, leading to catalyst poisoning. Furthermore, during the polymerization process of nylon 66 salts, these residual amines react with adipic acid to form acid salts, which affect the color and stability of the nylon 66 salts and cause chain scission in the polymer during polymerization. The nitrification reactor is one of the key equipment in the production facility for manufacturing adiponitrile via the ammonolysis and dehydration of adipic acid. This facility primarily uses bubble column reactors; the temperature in the tube section is high, which leads to numerous side reactions. The adipic acid concentration in the tube section used for dehydration is too high, and the mixing within the bubble tower results in an excessive residence time of the reactants in the reaction zone. Additionally, the high temperatures cause severe coking in the tube section. Connecting a bubbling pre-reactor in series before the reactor does not fundamentally solve the problem of reducing the adipic acid concentration entering the reactor’s tube section. The ammoxidation and dehydration of adipic acid to produce adiponitrile results in 250 kilograms of adipic acid being wasted as a by-product per ton of adiponitrile produced, along with 100–150 kilograms of waste, **increasing the raw material consumption.

New growth is possible only by breaking free from existing technical constraints. To revitalize the process of converting adipic acid into hexanitroacid, it is necessary to break away from the limitations imposed by the existing process designs and equipment technologies; thinking outside the boundaries of these conventional processes and equipment is essential in order to overcome the issues that hinder the operation of such systems, so that the process of converting adipic acid into hexanitroacid can truly become competitive. Purified adiponitrile is obtained through the ammonolysis and dehydration of adipic acid. The fewer by-products and intermediate compounds present in the reaction products, the better; otherwise, the separation costs increase. For example, the content of cyanoiminocyclopentane needs to be kept between 200–250 ppm. It is possible to reduce this level to below a few dozen ppm, but this requires high separation costs. By optimizing the processes and equipment, as well as by redesigning new nitrification reactors during the reaction process, it is possible to reduce the formation of impurities at the source. Therefore, to break free from the existing frameworks of technology and equipment design for producing adiponitrile using the adipic acid method, new methods and new equipment are needed, even special processes and devices. Minor adjustments and partial reforms alone cannot resolve the technical constraints that existed 17 years ago. Only by breaking free from the existing technical constraints can the drawbacks associated with the production of adiponitrile using the adipic acid method be largely eliminated, the consumption of adipic acid can be significantly reduced, the formation of tar and dimers can be prevented, solid waste can be greatly decreased, the quality of adiponitrile can be improved, equipment coking and corrosion can be basically avoided, the content of cyaniminocyclopentane in the product can be kept low, and the facility can operate for a long time. Only in this way can the advantages of the process for synthesizing adiponitrile through the ammonolysis and dehydration of adipic acid – namely, its wide range of raw material sources, lower investment costs, and relatively low environmental impact – be fully utilized. Moreover, as there is an oversupply of adipic acid and its prices drop, these advantages become even more evident.

Luo Yufeng, Secretary of the Shanzhou District Party Committee, said in his speech that this signing marks a solid step forward in the cooperation between Shanzhou District and Swedish International Chemical Technology Company, and it also initiates a period of deeper collaboration between the two parties. Shanzhou District should regard this project as an important pillar for development and growth, intensify its efforts to attract investment, seek partners, and create the best possible environment along with top-notch services. It is hoped that Swedish International Chemical Technology Company will make full use of its strengths, continue to deepen cooperation between the two parties, ensure the smooth implementation of the project, and exert its leading role at an early stage. At the signing ceremony, the representatives of the Swedish company specializing in chemical technologies and Henan Xiaguang Polymer Materials Company presented information on the project and their respective companies, and signed an agreement regarding the process licensing and engineering details for a project aimed at producing 50,000 tons of adiponitrile per year. It is understood that the process licensing and project implementation for this newly signed project, which has an annual production capacity of 50,000 tons of adiponitrile, are being led by ** in Shanzhou District. The aim is to establish a long industrial chain in the field of high-tech fine chemicals; this chain can extend upwards to the petrochemical industry and downwards to areas such as nylon fibers, engineering plastics, and new types of polyurethane materials. This will help address the constraints facing the development of the nylon industry and end the reliance on imported adiponitrile in China. Today’s Shaanzhou New Media