M-phenylenediamine microchannel reaction complete process package

It’s suggested to expose certain parts to the sun :P

Comparison of Process Technical Solutions 5.1 Selection of Process Technical Solution: There are two methods for the production process of mixed ***benzene (DNB): batch nitration and continuous nitration. Intermittent nitration involves the stepwise nitration of benzene to obtain ***; after separating *** from the waste acid, *** is further nitrated to produce mixed *** benzene (DNB). After neutralization and washing, mixed *** benzene (DNB) is obtained as the final product. Its advantages are few devices, low inventory, and simple control ； The disadvantages include low yield and complex operation; in particular, when producing ***benzene, the addition of reaction materials must be done via drip feeding, which makes it susceptible to human error. Automated control is relatively difficult to achieve, thus posing risks to safe production. Continuous nitration involves the continuous nitration of benzene to form ***, which is then further nitrated to yield ***benzene; after separation, a mixture of ***benzenes (DNB) is obtained. Following pre-washing, neutralization, and washing, the final product, DNB, is achieved. Its advantages are high yield, simple operation, and suitability for safe production. This device is intended to use a continuous nitration process with microchannel reactors. Originated in Europe in the 1990s, microchannel reactors feature channel sizes on the order of microns to millimeters; as a result, molecular diffusion distances are short, mass transfer occurs rapidly, and they possess intrinsically safe properties. 5.2 Technical advantages of microchannel reactors: This project utilizes the state-of-the-art microchannel reactors available internationally for the nitration reaction. These reactors consist of upper and lower heat exchange layers along with a reaction layer in the middle; their internal structure is shown in Figure 5-1. The flow channels in the reaction layer have a heart-shaped design, which prevents mixing of materials back together, thereby ensuring the sustainability and safety of the process from the very beginning. A diagram of these channels is shown in Figure 5-2. Compared to traditional batch reactors, microchannel reactors offer the following advantages: 1. High mass transfer efficiency – thorough mixing can be achieved within milliseconds to microseconds, which reduces reaction time, decreases the size of the equipment, and enables continuous production to enhance efficiency ； 2. It has good heat transfer efficiency, and the reactor has a large specific surface area, which is 100 to 200 times that of ordinary industrial equipment ； The heat transfer efficiency is 10 to 20 times that of laboratory equipment, and 100 to 200 times that of industrial equipment. 3. Precise automatic control and accurate regulation of reaction conditions enhance the reaction process, improving conversion rate, selectivity, and yield ； 4. Small reaction volume, low-flux reactions, high safety performance ； Energy and resource conservation, with a significant reduction in the use of toxic and polluting solvents ； 5. The amplification effect is low; the number of channels increases, which reduces the need for pilot-scale testing and shortens the process development cycle. Based on these characteristics, microchannel reactors have been widely used in industrial installations; Figure 5-3 shows the applications of microchannel reactors

A. Comparison of mass transfer efficiency: Table 5-1 Comparison of mass transfer efficiency. Sequence Number, Type of gas-liquid reactor, Mass transfer coefficient (KL×10-5/m·s^-1), Relative surface area (a/m2·m^-3), Mass transfer rate (KL·a/s^-1). 1. Bubble column: 10–40, 50–600, 0.005–0.24; 2. Cooter-Taylor flow reactor: 9–20, 200–1200, 0.03–0.21; 3. Impingement jet absorber: 29–66, 90–2050, 0.025–1.22; 4. Co-current packed tower: 4–60, 10–1700, 0.004–1.02; 5. Spray column: 12–19, 75–170, 0.015–0.022; 6. Static mixer: 100–450, 100–1000, 0.1–2.5; 7. Reactor vessel: 0.3–80, 100–2000, 0.03–0.4; 8. Microchannel reactor: 40–160, 3000–9000, 0.3–21. It can be seen from the table above that microchannel reactors have the best mass transfer efficiency. B. Comparison of heat transfer efficiency: Traditional kettle-type equipment uses jacketed heat exchange; its specific surface area is around 2–10, and the uneven heat transfer leads to a decrease in reaction selectivity. The addition of reactants involved in vigorous reactions can only be done via dropwise addition. The heat transfer specific surface area of microchannel reactors ranges from 500 to 4,000, which is one hundred to one thousand times that of conventional reactors, resulting in a significant improvement in heat transfer efficiency. Therefore, for reactions that generate a large amount of heat, such as nitration and hydrogenation reactions, the use of microchannel reactors enables the heat generated by the reaction to be removed promptly, thus keeping the temperature of the reaction system under control. Reduce reaction risks and fundamentally address the safety issues associated with exothermic reactions. Based on the above comparison, this project plans to use microchannel reactors, with each reactor holding no more than 2 L of liquid and a reaction time of no more than 20 seconds ； The traditional kettle-type continuous reactor has a liquid holdup of 18,000 L and a reaction time of 36,000 s. The specific parameter comparisons are as follows: Table 5-2 Comparison between microchannel reactors and batch reactors. Sequence Number, Parameter, Microchannel Reactor, Batch Continuous Reactor, Remarks: 1, Number of reactors, 4, 4; 2, Liquid holding capacity per reactor (L), 2,4500; 3, Total liquid holding capacity (L), 8,18000; 4, Reaction time per reactor (s), 10, 6000; 5, Total reaction time (s), 20, 36000; 6, Area occupied by the reactor (m²), 20, 120

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