What Is a Microreactor?

A microreactor is a three-dimensional structural element that can be used to carry out chemical reactions on a solid substrate with the help of special micromachining techniques. Microreactors usually contain small channel sizes (equivalent diameters less than 500 µm) and channel diversity, and fluids flow in these channels and require the required reactions to occur in these channels. This results in a very large surface area / volume ratio in microstructured chemical equipment.

Chinese name: Microreactor
Foreign name: Micro-reactor

Also known as: Microchannel reactor
Classification: Micromixers, microheat exchangers and microreactors

Microreactor definition

Micro-reactors, that is, micro-channel reactors, are manufactured using precision processing technology with micro-reactors with a characteristic size between 10 and 300 microns (or 1000 microns). The "micro" of a micro-reactor indicates that the channels of the process fluid are at the micron level , Not the small size of the micro-reaction equipment or the small output of the product. Microreactors can contain millions of tens of millions of microchannels, so high yields are also achieved.

Microreactor development history

The United States Dupont company first carried out the basic research on the application of micro-chemical systems in the production of hazardous chemicals in the early 1990s, and successfully developed a miniature chemical device for synthesizing methyl isocyanate. The United States PNNL (Pacific Northwest National Lbaoratory) mainly conducts research on the miniaturization of hydrogen source systems for fuel cells. The main structure of the reactor is a cross-flow microchannel heat exchanger. Compared with traditional, the same processing capacity, the reactor volume can be reduced. ~ 2 orders of magnitude. Microreactors have shown great advantages in terms of mass transfer, heat transfer, and constant temperature. Since their introduction, they have quickly attracted the interest and attention of experts in related fields ^[1] .

Bayer-Erfeld Mikrotechnik BTS (EMB) is the world's leading supplier of microreactor technology. In the field of chemical and fine chemical product production, Miprowa series microreactors developed by EMB have been used in process development and production by major chemical companies in the world; in the field of pharmaceutical production, in 2010, EMB cooperated with Lonza to market Launched the Flowplate series of microreactors that meet GMP certification requirements. ^[1]

Microreactor use

Micro-reactor equipment can be subdivided into micro-mixers, micro-heat exchangers and micro-reactors according to their main uses or functions. Because of its internal microstructure, the microreactor equipment has a large specific surface area, which can reach hundreds or even thousands of times the specific surface area of the stirred tank. Microreactors have excellent heat and mass transfer capabilities, which can achieve instant and uniform mixing of materials and efficient heat transfer. Therefore, many reactions that cannot be achieved in conventional reactors can be achieved in microreactors.

At present, microreactors have been widely used in the research and development of chemical processes, and applications in commercial production are increasing. Its main application areas include organic synthesis processes, preparation of micro and nano materials, and production of daily chemicals. In chemical production, the latest Miprowa technology can already achieve a flow of tens of thousands of liters per hour. ^[1]

Disadvantages of microreactors

The biggest disadvantage of the microstructure of the microreactor is that the solid materials cannot pass through the microchannels. If a large amount of solids are generated in the reaction, the microchannels are easily blocked, resulting in continuous production.

At present, this problem is mainly solved by improving the design of the reactor. For example, the valve mixer (reactor) developed by Bayer-Elfeld Microtechnology can be used for rapid precipitation reactions. Based on this technology, Bayer has successfully developed a commercial production process for producing high-performance micron Materials and nanomaterials. ^[1]

Microreactor China related

In China, micro-reaction technology is in the research and development stage. Although many universities are engaged in research on micro-reaction technology, no mature domestic equipment has yet appeared.

Microreactor applications

The unique structure of the microreactor has brought it a series of high-quality properties, so it has been applied to many fields. For small-scale photochemical processes, for example, the use of a transparent microreactor can facilitate the thin fluid layer close to the radiation source. The Mainz Institute for Microtechnology in Germany has developed an electrochemical microreactor with a parallel disc structure. With this device, the selectivity of the reaction for the synthesis of p-methoxybenzaldehyde from 4-methoxytoluene is improved.
Due to the high heat transfer efficiency of the microreactor, the temperature of the reaction bed is almost constant, which is conducive to the progress of various chemical reactions. Wan et al. Oxidized aniline to azobenzene in a microreactor. DelSman et al. Studied the selective oxidation of carbon monoxide in a microsystem. At the same time, microreactors have also been applied to hydrogenation reactions, ammonia oxidation, methanol oxidation to formaldehyde, A series of reactions such as water gas shift and photocatalysis. In addition, microreactors can also be used for the on-site production of certain toxic substances, for the study of intrinsic kinetics of strong exothermic reactions, and for high-throughput screening of combinatorial chemistry such as catalysts, materials, and drugs. ^[1]

Prospects and Prospects of Microreactors

So far, domestic and foreign academic circles have conducted extensive research on microreactors, and have a better understanding of its principles and characteristics, and have made gratifying achievements in microreactor design, manufacturing, integration and amplification. Grades. However, the research on it is not mature enough. The traditional theory of "three passes and one inversion" must be revised, supplemented and innovated. Some principles of the reaction have not been explored clearly, and a lot of work is needed. In addition, there are many technical difficulties in its manufacture, catalyst wall loading, and automatic control of the system. It is necessary to conduct in-depth research on surface and interface phenomena, transfer laws, reaction characteristics, and amplification integration in microreaction systems.
In the 21st century, due to a series of problems such as environmental degradation and energy depletion, the chemical industry is facing unprecedented opportunities and challenges. Due to the many advantages shown by microreactors, the scientific community is committed to exploring new reaction paths to make chemical production more economical and environmentally friendly. So we need to believe that microreactors will play a huge role in the chemical industry. ^[1]