英语论文网

ion. However, the micro reactor’s production capacity at any time is too small, but we can build reaction chamber with a large scale of continuous flow reactors where the total production capacity will be much greater10.
In the fluid flow system, pressure drop is defined as the different in pressure between fluids at two locations of channels. The pressure drop is caused by the frictional forces which resistance to flow in the channels. The pressure drop increases proportional to the frictional forces in the channels. In the continuous flow system, mixing of the reagents will enhance interfacial area and increased the pressure drop in fluid flow. The high pressure drop, highfrictional forces in the channels, which means low flow capacity, and a tendency to block in the channels, are the common problems in the micro reactors. The fluid flow system is difficult to keep cleaning and dismantle frequently. It is difficult to overcome this problem nowadays10.
The continuous flow synthesis technology is applied in the organic molecular synthesis in the recent years.
1. Liquid-liquid phase reaction
1.1 Nitration reactions
Nitration is a chemical process to introduce a nitro group into an organic molecular by using concentrated nitric and sulphuric acid. Nitration of organic synthesisis usually carried out in the liquid-liquid phase reactions. And the reactions are fast, extremely exothermic, and the reaction reagents could be hearten up to a very high temperature very soon. It’s hard to control the temperature of nitration reactions in traditional batch reactors. In order to overcome this problems, the continuous flow system is considered to apply on the nitration reactions because of its excellent temperature controlling and heat delivery.
Amol A et al. have reported nitration of salicylic acid in theSS316 tubular micro reactor(Fig.1). The HNO3 and AcOH reagents were transported by electroosmotic flow in the channel network, mixed and conversed to salicylic acid in the micro reactors. Under specific reaction conditions, the complete process of salicylic acid production was achieved in less than 7 min. Compared to the bath reactors, the continuous flow reactors produces only monitor derivatives with a higher selectivity of 5NSA, which is required for the salicylic acid production, and lower amount of acetic acid (3NSA), which is detrimental wastes. The results showed a positive relationship between the selectivity of 5NSA and temperatures11.

1.2 Oxidation reactions
The swern oxidation is a chemical reaction using oxalyl chloride, DMSO and an organic base as oxidants to make a primary or secondary alcohol transmit into an aldehyde or ketone. The swern oxidation is a highly exothermic and active reaction. The swern oxidation can be accomplished by using a batch reactor at temperatures between -50℃ and -78℃. Tatsuya Kawaguchi et al. have found the continuous flow reactors enable to accurately control the reactive intermediates in the swern oxidation process, and facilitate the swern oxidation reaction at higher temperatures between -20℃and 20℃ in micro reactors12 (Fig.2).

The continuous flow system has great advantage on Nef oxidation reaction. Jorg Sedelmeier et al. used KMnO4 as an oxidant and made an efficient and easily transformation of alcohols and aldehydes to carboxylic acids and nitroalkane derivatives, and further transformed into