【Ten Years of Great Development in Chemical Equipment】1945–2024: Yangnong Group’s independent development of the caprolactam-based hexamethylenediamine production process
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Safety first. Prevention first: Let’s praise and encourage the achievements in China’s chemical engineering technology and equipment. **********************【Ten Years of Great Development in Chemical Engineering Equipment】A continuously updated summary post is available; feel free to join the discussions at https://bbs.hcbbs.com/thread-3576046-1-1.html (Source: Haichuan Chemical Engineering Forum) ***************** Among the wide range of nylon materials, nylon 66 is one of the key members alongside nylon 6; thanks to its superior overall performance compared to nylon 6, it is being used more and more often, becoming an important strategic material that impacts national economy and people’s livelihoods. However, due to the extremely high technical challenges associated with the production of upstream raw materials such as adiponitrile/adipamide, and the long-term reliance on imports for these materials, domestic nylon 66 manufacturers often find themselves in a situation where they have to \"buy the ingredients to make the product\". Is there a way to produce nylon 66 without being constrained by adiponitrile? Jiangsu Yangnong Chemical Group Co., Ltd. provides an affirmative answer with its independently developed process for producing hexamethylenediamine using caprolactam. Recently, this technology was included in the Petrochemical Industry Federation’s “List of Green and Low-Carbon Processes in the Petrochemical Industry (2024 Edition)”. An innovative approach to the manufacturing process: In 2005, Yangnong Group began exploring production technologies for adiponitrile/adipamide. At that time, the production technologies for hexamethylenediamine/hexamethylenecarbonitrile in the world could be roughly divided into three types, but none of them involved domestic technologies. The first is the direct hydrocyanation of butadiene. This process is the mainstream method for producing adiponitrile, but it has drawbacks such as a long production process, high technical barriers related to catalysts, and the fact that hydrocyanic acid is highly toxic and prone to polymerization. The second is the electrolytic dimerization of acrylonitrile. The core of this process is electrolytic organic synthesis, and it is necessary to overcome technical challenges such as electrolyte formulation, electrode materials, and electrolyzer structure; scaling up the equipment poses difficulties. Third is the adipic acid-catalyzed amination method. This process has a low technical threshold, but high production costs, and it generates characteristic impurities that can easily affect product quality. This path is not good; find another way. In 2019, Ding Kehong, General Manager of the Innovation Center of Sinochem’s Chemicals Division and former Chief Scientist at Yangnong Group, observed the growing surplus of caprolactam production capacity in China. He decided to find an alternative approach: using the bulk chemical caprolactam as a raw material, he proceeded with a two-step reaction to directly produce hexamethylenediamine, thereby bypassing the long-term monopoly held by multinational companies over the technology and supply of adiponitrile, the key raw material for nylon 66. “At that time, faced with the ‘three lacks’ of no experience, no data, and no external support, we started from scratch. After countless days and nights of hard work, numerous experiments and explorations, as well as comprehensive comparisons, we finally determined the process for producing adipic acid from caprolactam. ”Ding Kehong recalled. With this idea in mind, from July 2019 to October 2020, within just over a year, the project team led by Ding Khong overcame one process challenge after another, successfully developing a catalyst with excellent performance. They completed pilot-scale production on a scale of hundreds of tons, and the product quality met the top-tier standards of the industry; it also passed the verification tests for nylon 66 polymerization. In May 2022, the plant for producing 40,000 tons of nylon 66 and 25,000 tons of hexamethylenediamine per year was brought online successfully in one go, completing the industrial implementation of this technology. In April 2024, the development and industrialization of key technologies for high-quality hexamethylenediamine produced via the caprolactam method passed the evaluation of scientific and technological achievements by the China Petroleum and Chemical Industry Federation. The experts present agreed that this project enables the stable production of high-quality hexamethylenediamine, with the overall technology reaching an internationally leading level.
Excellent product quality The approach of using caprolactam to produce hexamethylenediamine instead of adiponitrile is correct; in practice, not only are the raw materials readily available, but the quality of the products manufactured is also superior. ”Ding Kehong said. The previous process of preparing hexamethylenediamine via the hydrogenation of adiponitrile introduced adiponitrile isomer impurities, and the high-reactivity imine intermediates formed during the hydrogenation of adiponitrile further increased impurities such as cyclized compounds. “This impurity is like rat droppings; it can degrade the quality of nylon 66. ”Ding Kehong explained that, for example, if the level of the impurity trans-1,2-diaminocyclohexane (DCH) is too high, it can cause the polymer chains to break, thereby affecting properties such as the strength and toughness of nylon 66 sheets. This is manifested in an increase in the breakage rate and waste yarn rate during spinning, as well as impacts on the dyeing performance and color uniformity of nylon 66 fibers. Therefore, many downstream companies using hexamethylenediamine strictly limit the DCH content. By bypassing adiponitrile, this process reduces the formation of various cyclic diamine impurities at the source, resulting in excellent product quality with a purity level consistently above 99.995%. Green and low-carbon production Another advantage of this process is its green and low-carbon nature, which is reflected in the fact that the raw materials are not highly toxic, and there is less waste generation. The three existing production processes for hexamethylenediamine/hexamethylenecarbonitrile involve either highly toxic raw materials or corrosive materials, posing dangers during the production process. For example, hydrocyanic acid, the main raw material in the butadiene process, cannot be underestimated; it is a highly toxic chemical that can be rapidly absorbed by the human body through the skin and respiratory tract, potentially leading to immediate coma ； The same is true for the acrylonitrile method; its main raw material, acrylonitrile, is also a highly toxic chemical ； The main raw material in the adipic acid method is adipic acid. Although it is not highly toxic, adipic acid is a weak acid while ammonia is a weak base; during the production process, the ionization equilibrium of ammonium adipate results in a small amount of adipic acid remaining in the high-temperature reactor, which can lead to equipment corrosion. This process avoids these problems. “Our technology uses low-toxicity caprolactam and liquid ammonia as raw materials, avoiding the use of highly toxic chemicals, and thus replaces the toxic, harmful, and corrosive raw materials used in existing technologies. ”Ding Kehong explained. Furthermore, reducing the generation of \"three wastes\" is also one of the highlights of this process. This process has developed coupled technologies for reducing and recycling \"three wastes.\" By analyzing the composition of these wastes and their formation mechanisms, separation techniques for high-melting-point and thermosensitive materials have been developed, thereby achieving reduction in the generation of these \"three wastes\" at the source. “For some of the waste materials that have already been generated, we will also find ways to recycle them as resources. ”According to Ding Khonghong, this process has led to the development of technologies such as tar recycling by analyzing the results of element flow assessments, thereby further reducing the emission of \"three wastes\". “After several years of strenuous efforts, we have finally identified a research and development direction for greener and lower-carbon manufacturing processes; in the future, we will continue to work along this path. ”Looking to the future, Ding Khong is full of anticipation.
【Ten Years of Rapid Development in Chemical Engineering Equipment】Asia’s Largest Annual 600-Ton CO2 Direct Air Capture (DAC) Facility, 1946–2024 https://bbs.hcbbs.com/thread-5668824-1-1.html (Source: Haichuan Chemical Industry Forum)
4 Yangnong Group has independently developed a production process for hexamethylenediamine using the caprolactam method [
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