Microchannel reactor for nitration reaction process

Nitration reactions mainly include:

1. Alkyl nitration, synthesis of nitroalkanes. This type of reaction is a high-temperature free radical reaction, mostly occurring in the gas phase. Although there are patents and literature reports, it is not a typical case of micro-reaction nitration;

2. Hydroxyl, amino, urea, etc. Nitration, synthesis of nitrate esters, etc. This type of reaction is extremely active, fast, and highly exothermic, which is very suitable for microchannel reaction technology;

3. Benzene ring and heterocyclic nitration. There are a large number of aromatic ring nitration reactions in the fine chemical industry. Due to the different electron cloud densities on the aromatic ring (electron-rich, electron-deficient, etc.), the activity of the nitration reaction is also very different. The applicability of microchannel reactor technology in aromatic ring nitration is relatively complex, and targeted analysis is required for different substrates and different reaction systems.

The applicability of aromatic ring nitration reaction in microchannel reactor needs to be considered comprehensively through multiple factors. These include reaction system fluidity, nitration substrate activity, sulfuric acid and nitric acid concentration, dehydration value, etc. Among them, the activity of nitration substrate directly affects the speed of reaction. The nitration activity index (NAI: nitration activity index) is based on the calculated electron cloud density of the nitration substrate reaction site, and combined with the value obtained by correcting the empirical parameters of multiple factors. It can relatively accurately judge whether a certain nitration reaction is suitable for microchannel reaction technology. The smaller the NAI value, the stronger the nitration activity, and vice versa, the weaker the nitration activity. When NAI>2.76, it indicates that the nitration activity is too low, and the feasibility of nitration of the substrate in the microreactor is not high. By calculating the NAI values of more than 40 mononitration and dinitration cases and comparing them with experimental data, it is shown that microchannel reactor technology has a wide range of applications in nitration reactions.

In addition, some raw materials or products of nitration reactions cannot be dissolved in the reaction system and have poor fluidity, so microchannel reactor technology cannot be used.

Microchannel reactor technology has been used on a certain scale in the industrial production of nitration processes. For example, the industrial production of isooctyl nitrate, a diesel cetane number improver, currently uses the microchannel reactor process as the mainstream process. This process is continuous and highly automated, and its safety is significantly better than the traditional batch process. At the same time, there are also a certain number of nitration processes in China that are currently in the process of applying for industrial production.

The significance of microchannel reactor technology in nitration production

01 Safety:

Under the same production capacity, the liquid holding volume of the microchannel reactor is only 1/1000 of that of the reactor and 1/10 to 1/100 of that of the pipeline reactor. Even if the reaction section is out of control, there are few instantaneous reaction materials and little harm;

02 Continuity:

Continuous and automated production reduces labor and is in line with the trend of industry upgrading and transformation;

03 Process improvement:

Through the redevelopment of the microchannel reaction process, there is the possibility of improving the yield, selectivity and environmental protection level.