Bromination of aromatic hydrocarbons is one of the most important unit reactions in fine organic synthesis, and it is also a widely studied chemical reaction. Brominated products are important intermediates or starting materials for the synthesis of fine chemicals such as pharmaceuticals, pesticides, dyes, flame retardants, fire extinguishing agents, etc. Brominated reagents used in traditional bromination reactions include bromine, N-bromosuccinimide (NBS), cbrcl3, CuBr2, br-/br2, etc. this method has outstanding shortcomings: each molecule of brominated product is obtained, a molecule of hydrogen bromide by-product will be formed. This by-product is not only corrosive, but also causes the utilization rate of bromine atoms in bromine raw materials to be less than 50%. Therefore, it not only has low atomic economy, but also causes environmental pollution, which is not in line with the development trend of modern organic synthesis greening.
Oxidative bromination seems to be able to solve the problem of low utilization of bromine atoms, that is, adding oxidants to the reaction system to oxidize the byproduct of hydrogen bromide into reactive bromine in situ. In recent years, the oxidative bromination method using hydrogen bromide and bromine anion of inorganic bromide salt as bromine source has achieved some results, but there are still some deficiencies, such as the need for a certain catalyst and solvent; Secondly, in order to avoid the danger caused by the violent reaction between hydrogen peroxide and hydrogen bromide, it is generally overcome by dropping, which is not conducive to industrial application.
The research of micro chemical technology began around 1996. Lerous and ehrfeld, respectively, systematically elaborated the application principle and unique advantages of micro reactors in the field of chemical engineering. Subsequently, micro chemical technology has developed rapidly. In the past few years, it has been increasingly applied in the fields of fine chemical products, drugs, intermediate synthesis and free radical polymerization, and has become one of the priority development directions in the field of chemical engineering. The research shows that due to the miniaturization of the characteristic scale of the reactor, the heat transfer coefficient and mass transfer performance are significantly enhanced, and the fluid flow uniformity can be better guaranteed, so that the conversion and selectivity of the reaction are significantly improved. These advantages make the micro chemical technology an effective means to realize the high efficiency, energy saving, safety and cleaning of chemical and chemical processes. It has been paid attention to in the field of chemical and chemical engineering, and also provides a possible path for the safe implementation of oxidative bromination reaction and even industrial application. Taking hbr-h2o2 as the oxidative bromination system, it is of positive significance to study the oxidative bromination of toluene in a microchannel reactor.