Microchemicals: From "Bigger is better" to "small and efficient"

As one of the important means of chemical process strengthening, microchemical technology has the advantages of both process strengthening and miniaturization, and has the characteristics of strong heat mass transfer performance, good safety, easy control and direct amplification of the process, which can significantly improve the safety and production efficiency of the process, and quickly promote the practical process of laboratory results. Microreaction can subvert the traditional thinking mode of "bigger is better" of chemical process, and provide important inspiration for the reform of chemical industry development mode. This is the conclusion given by the experts at the 2017 Workshop on Microchemical process Optimization Engineering Design and Equipment Application held in Nanjing, Jiangsu Province, on November 16 to 17.

1. Strengthen the reaction process

At present, China's environmental safety supervision is becoming increasingly strict, especially the State Administration of Work Safety has strengthened the focus on the supervision of 18 types of dangerous processes, and put forward higher safety requirements for chemical production. Dr. Ma Bing, general manager of Shanghai Huihe Huide Biotechnology Co., LTD., said that compared with traditional process technology, micro-reaction technology can reduce the reactor volume by 1000 times, increase the reactor heat transfer efficiency by 1000 times, increase the mass transfer by 100 times, the reaction time can be precisely controlled, and there is no amplification effect from the laboratory to industrial production. Help chemical production to achieve safety, environmental protection and high efficiency.

Professor Xu Jianhong, a researcher at the Department of Chemistry of Tsinghua University, said that in the traditional chemical industry, the synthesis of pharmaceuticals, fine chemicals and chemical intermediates is mostly carried out in the batch or semi-batch reactor, but it has obvious defects. Such as loading, unloading and other auxiliary operations time-consuming, process discontinuous; Due to the weak heat and mass transfer ability of the traditional reactor, the quality stability of the product is poor and the control ability of the strong exothermic reaction is poor. The characteristic scale of the channel inside the microreactor is in the microscale range (10 ~ 500μm), which is much smaller than the characteristic size of the traditional reactor, with large specific surface area, good heat and mass transfer effect, accurate control of reaction conditions, improve product quality and yield, etc., providing important support for realizing the efficient and safe chemical process and key technological innovation of fine chemical products.

"Chemical systems with microchemical equipment as the core can operate chemical processes in micron or submillimeter confined Spaces, strengthen mixing, transfer and reaction processes by reducing the flow or dispersion scale of the system, improve process efficiency and safety, and quickly and reliably apply laboratory results to industrial processes." It has the advantages of fast heat and mass transfer rate, high internal safety, low process energy consumption, high integration, small amplification effect, strong controllability, fast technology update, fast product upgrade, low cost, good safety, and has been widely used in machinery, electronics, materials, biology, medicine, chemistry and other fields." Xu Jianhong told reporters.

2. Suitable for multiple reactions

Zhang Yuecheng, a professor at the School of Chemical Engineering, Hebei University of Technology, believes that microreaction technology is an effective way to reduce waste liquid emissions, strengthen process safety and reduce energy consumption. For most of the 18 types of hazardous processes under key supervision, intrinsic safety can be well achieved by using microreaction technology. The modular, intelligent and flexible continuous flow microreaction process combines the advantages of continuous reaction and intermittent reaction, and promotes the chemical reaction to be faster. The amount of chemicals in the reactor is small, which is easy to control, and makes the chemical process safer. Fast and effective mixing, precise control of residence time and reaction temperature, improve the conversion rate and selectivity of chemical reaction; At the same time, the microreaction process is strengthened and the solvent usage is reduced. Such as azide reaction, Grigeldahl reaction, nitrification reaction, oxidation reaction, series reaction, aldol condensation reaction and other processes, can use continuous flow micro-reaction process, to achieve high efficiency, economy, safety and environmental protection.

Chen Guangwen, a researcher at the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences and winner of the National Natural Science Outstanding Youth Fund, said that the development and progress of chemical process strengthening technology has injected new impetus and vitality into the related chemical industry. As an effective process strengthening technology, microreaction technology has been successfully applied at home and abroad. In foreign countries, Germany Bayer, BASF, Switzerland Lonza, Corning and other companies have set up departments dedicated to microchemical technology, research and development and promotion of their microchemical equipment products. In China, the micro-channel reaction technology developed by Dalian Chemical Institute has achieved industrial operation of 80,000 tons/year of ammonium dihydrogen phosphate production, 5,000 tons/year of magnesium hydroxide flame retardant pilot test and industrial demonstration operation test of 10,000 tons of petroleum sulfonate production. The State Key Laboratory of Chemical Engineering of Tsinghua University has successfully developed a 10,000-ton membrane dispersion micro-structure reactor for the preparation of monodisperse nano-calcium carbonate and 150,000 tons/year of wet phosphoric acid purification equipment. These fully prove the feasibility and superiority of microchemical technology in industrial scale application.

3. Technical difficulties remain

Chen Guangwen said that although the development of microchemical technology has been very rapid in the past decade, it is also necessary to be sobering to realize that although for some reaction processes, microreactors are the preferred device, there are still some reactions that are not suitable for microchemical systems. As a new field, there are still many problems that need to be further studied, such as structure optimization design and advanced manufacturing technology of micro-reaction system, system automatic control technology, anti-corrosion and anti-clogging technology of micro-reactor, industrial application and so on. "The application of microreactors is conditional, which is closely related to the principle of chemical reaction, as well as the control of reaction conditions such as temperature and flow rate, not as long as the use of microreactors can improve production efficiency, better selectivity, reduce 'three wastes', and no safety problems." The horseman stressed.

"This requires in-depth and substantive cooperation among relevant enterprises to carry out long-term industrial application demonstration operations for different types of chemical processes or reaction types, accumulate experience, and provide theoretical basis for the design, scale-up and operation of microchemical technology." Chen Guangwen said that during the "13th Five-Year Plan" period, in order to strengthen the strength to overcome the difficulties of micro-reaction technology, relevant enterprises need to vigorously strengthen the basic and applied basic research of micro-chemical engineering and technology, and solve the key common scientific problems in the field of micro-chemical engineering and technology. At the national level, more efforts should be made to recommend and promote micro-reaction technology and other advanced chemical technology that can achieve chemical process strengthening, process safety and energy saving and emission reduction.