In the field of chemical synthesis, there are various methods for the synthesis of hydroxylamine hydrochloride. Hydroxylamine hydrochloride is an important organic compound with wide-ranging applications including pharmaceuticals, pesticides, and dyes. Its synthesis methods are crucial for improving yield, reducing costs, and minimizing waste emissions. This article aims to inspire readers' interest in hydroxylamine hydrochloride and further expand research and applications in related fields.
Hydroxylamine hydrochloride, with the molecular formula NH2OH·HCl, is an important organic synthetic intermediate used in various fields such as pharmaceuticals, pesticides, and electronic chemicals. It serves as a key raw material for synthesizing oxime groups in pharmaceuticals, pesticides, and dyes. Electron-grade free hydroxylamine is used as a cleaning agent in integrated circuits. Isomeric hydroxamic acids prepared by the reaction of hydroxylamine and carboxylic esters act as specific metal chelating agents for rare earths, copper, and others. Additionally, hydroxylamine hydrochloride is utilized as an important analytical reagent for the analysis of aldehydes, ketones, etc.
The hydroxylamine hydrochloride formula is NH2OH·HCl. This formula indicates the combination of one molecule of hydroxylamine (NH2OH) with one molecule of hydrochloric acid (HCl) through an ionic bond.
The structural formula of hydroxylamine hydrochloride displays the arrangement of atoms in the molecule. It can be decomposed as follows:
In the combined molecule, the hydrogen atom (H) from the hydroxyl group (OH) in hydroxylamine dissociates and forms an ionic bond with the chlorine atom (Cl) in hydrochloric acid. This produces the positively charged hydroxylammonium ion (NH3OH+) and the negatively charged chloride ion (Cl?), which attract each other to form hydroxylamine hydrochloride.
Initially produced in the EU, US, Japan, and other places, hydroxylamine hydrochloride has high added value. The main production processes include nitromethane method, nitric oxide reduction method, and oxime acid decomposition method. China introduced the nitromethane method, which has been continuously improved and used to date, but the production capacity is generally small. There have been reports of domestically produced hydroxylamine hydrochloride using the oxime acid decomposition method, but the oxime is mainly prepared by the Raschig process, resulting in high actual production costs. In recent years, with the advancement of oxime compound synthesis technology, the HPO method and hydrogen peroxide ammonia oxidation method have greatly simplified the synthesis process. Oxime compounds can be used as raw materials for preparing hydroxylamine hydrochloride, reducing the cost of hydroxylamine hydrochloride preparation by oxime acid decomposition method, which is more advantageous than the nitromethane method. Recently, the industrialization of using oxime-based silane by-products to prepare ketoxime hydrochloride has further reduced the cost of hydroxylamine hydrochloride and made it more environmentally friendly.
The process of preparing hydroxylamine hydrochloride by oxime acid decomposition has been reported in the literature. The previous process involved preparing hydroxylamine sulfate by the Raschig process, then reacting hydroxylamine sulfate with a ketone to produce ketoxime, and finally, using ketoxime acid decomposition to prepare hydroxylamine hydrochloride. Compared to the nitromethane method, the Raschig process is complex, costly, and equipment-prone to corrosion, thus unable to achieve large-scale production. In recent years, due to the reduction in oxime preparation cost by the titanium-silicate molecular sieve hydrogen peroxide ammonia oxidation method, the overall cost of hydroxylamine hydrochloride preparation by this method has also decreased. Therefore, some manufacturers have re-examined the oxime acid decomposition method for preparing hydroxylamine hydrochloride. This process uses oxime and hydrochloric acid as raw materials, and hydroxylamine hydrochloride solution and ketone are obtained through reaction and fractional distillation. After concentration, crystallization, and drying treatment, hydroxylamine hydrochloride product is obtained, while the by-product ketone can be recycled for oxime production. The reaction is as follows:
There is extensive research on the raw material ketones, such as acetone oxime, butanone oxime, and cyclohexanone oxime, with reported yields of over 90%. Currently, butanone oxime is the most commonly used raw material in industrial production.
The reaction of ketoxime salt hydrolysis is as follows:
This method further improves the process of preparing hydroxylamine hydrochloride by oxime acid decomposition. By using oxime-based silane and water as raw materials to prepare hydroxylamine hydrochloride, this process has unique advantages. Firstly, it can exceed the upper limit of hydrochloric acid content because ketoxime hydrochloride is a complex of ketoxime and hydrochloric acid with a molar ratio of 1:1, and the hydrolysis process achieves zero wastewater generation. At the same time, the free acid content is controlled at a lower level, reducing equipment corrosion. Secondly, this process can efficiently utilize the by-products of oxime-based silane. After the by-product ketoxime hydrochloride of the original oxime-based silane production unit is separated by high-value ammonia neutralization, ketoxime can be used to continue producing oxime-based silane, while low-value ammonium chloride is produced as a by-product. This process allows the by-product butanone oxime hydrochloride to be used to prepare high-value hydroxylamine hydrochloride, achieving effective resource utilization and reducing production costs.
Hydroxylamine hydrochloride is prepared by the nitromethane hydrolysis method. Nitromethane, dilute hydrochloric acid, and water are heated and refluxed together, then subjected to vacuum concentration, crystallization, and purification to obtain high-quality hydroxylamine hydrochloride.
The specific steps are as follows: nitromethane, distilled water, and hydrochloric acid are added to the batching tank in a certain proportion, mixed, and then placed into the reaction kettle. The temperature is raised, and the reaction is carried out under the condition of maximum jacket steam pressure ≤ 0.08 MPa for 48 hours, with the final temperature below 110°C, resulting in hydroxylamine hydrochloride and formic acid. Then, the liquid in the reaction kettle is transferred to the hydroxylamine hydrochloride concentration tank for vacuum concentration. Formic acid, water, and residual HCl are distilled out, condensed and cooled, and placed into the formic acid tank for production. After crystallization and negative pressure filtration of the material in the concentration tank, hydroxylamine hydrochloride crystal crude product is obtained. The hydroxylamine hydrochloride crystals are washed with ethanol to remove impurities and improve purity and whiteness. Then, they are dried in a boiling dryer. The hydroxylamine hydrochloride dried in the dryer is placed into packaging bags through the discharge port at the bottom of the dryer. During the drying and packaging process, the generated exhaust gas is collected by the gas hood and treated by the induced draft fan into the cyclone dust collector and water absorption tower. The dust (hydroxylamine hydrochloride) collected by the cyclone dust collector is sold as hydroxylamine hydrochloride substandard products.
In conclusion, this article summarizes the synthesis and preparation methods of hydroxylamine hydrochloride, emphasizing its importance in various industries and the necessity of safety precautions. As an important organic compound, hydroxylamine hydrochloride finds wide applications in pharmaceuticals, pesticides, dyes, etc., thus safety requirements in its production and use are crucial. We encourage readers to further explore the applications of hydroxylamine hydrochloride in various industries and consider the potential value and innovation brought by products containing hydroxylamine hydrochloride. By gaining a deeper understanding of the characteristics and uses of hydroxylamine hydrochloride, readers can better apply this compound and contribute to the development of relevant fields.
[1]https://pubchem.ncbi.nlm.nih.gov/compound/Hydroxylamine-Hydrochloride
[2]https://www.dcfinechemicals.com/en/products/analytical-reagents/hydroxylamine-hydrochloride-detail/
[3]CN106829892A
[4] Zhou Liyang, Zhang Chaoqun, Zhou Qiang. Synthesis and production method of hydroxylamine hydrochloride [J]. Chemical Production and Technology, 2021, 27(06): 12-14+8.
[5]US2319669A
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