Microreactors as the new way of intensification of heterogeneous processes

Microstructure reactors (microreactors) in recent decades became one of the most actively studied subjects of the reaction equipment aimed at intensification of chemical processes and increase in their safety. It is not surprising because due to miniature dimensions of microstructures which do not exceed 2 mm microreactors contribute to minimization of the material at their production as well as raw material and energy in the process of exploitation. Moreover, due to acceleration of heat and mass transfer the productivity of equipment with microreactors in a range of cases is significantly higher than classical batch reactors applied in industry. The brief overview of the modern development and achievements of microreactor technology is given in this article by an example of heterogeneous reaction systems which are different by their nature and occur in different types of microreactors: phase-transfer catalysis, biocatalysis, and synthesis of nanoparticles. A special attention in the article is paid to the aspects of intensification of the considered processes because exactly the possibility of intensification makes microreactor technology attractive for the industry.     

Experimental study and simulation of kinetics of acetophenone hydrosilylation with diphenylsilane in the presence of rhodium complexes in a microreactor

The hydrosilylation of acetophenone with diphenylsilane in a microreactor in the presence of complexes [Rh(cod)Cl]₂ and [Rh(CO)₂(μ-Cl)]₂ and (R)-(-)-cis-mirtanyl- and (R)-(+)-bornylamine in situ was studied, the kinetics simulation of the process was performed, and the multicriteria optimization of the process was carried out. The influence of the micro-mixing effect on the reaction rate was revealed. Best results in the microreactor were obtained for the [Rh(cod)Cl]₂-BornylNH2 catalytic system. It was established that the formation of 1-phenylethanol and related enol silyl ethers are simultaneous competing reactions.     

Microstructural reactors: Concept, development and application

In the recent years owing to growing necessity of raw material and energy economy and solution of ecological problems, a significant interest by the chemistry thechnologists is paid to the microsystem technology. One of directions in the development of microsystem technology is creation and application of microstructural reactors (microreactors). Currently world market proposes many samples of microstructural installations and even full-value chemical units for, in part, of organic synthesis. In Russia the microsystem technology is included to the list of priority directions of development of science and technology in 2001–2010 years.     

Hydrosilylation of acetophenone with diphenylsilane in the presence of rhodium(I) complexes with chiral amines

New chiral rhodium complexes cis-[Rh(CO)₂(RNH₂)Cl] [RNH₂ = (R)-(−)-cis-MyrtNH₂, (R)-(−)-MenthylNH₂, (R)-(+)-BornylNH₂] were synthesized and their catalytic properties in reactions of hydrosilylation of acetophenone with diphenylsilane were studied. It was shown that the reaction products were diphenyl-1-phenylethoxysilane, diphenyl-1-phenylvinyloxysilane and 1,1,3,3-tetraphenyldisiloxane. The best catalytic activity displayed (−)-cis-[Rh(CO)₂(MenthNH₂)Cl]. The hydrosilylation of acetophenone with diphenylsilane in the presence of [Rh(CO)₂(μ-Cl)]₂ and [Rh(cod)Cl]₂ and amines in situ was studied. The best ratio amine:complex = 5:1 was established. With the catalytic systems based on [Rh(cod)Cl]₂ or [Rh(CO)₂(μ-Cl)]₂ the activity increased in the series of amines: (R)-(−)-cis-MyrtNH₂ < (R)-(−)-MenthylNH₂ < (R)-(+)-BornylNH₂, and (R)-(−)-MenthylNH₂ < (R)-(+)-BornylNH₂ < (R)-(−)-cis-MyrtNH₂, respectively. The chemoselectivity maximum was observed in the presence of [Rh(cod)Cl]₂ with (R)-(−)-MenthylNH₂ and [Rh (CO)₂(μ-Cl)]₂ with (R)-(+)-BornylNH₂; maximum asymmetric induction was 43.5% ee at the use of [Rh(CO)₂ (μ-Cl)]₂ and (R)-(+)-BornylNH₂.