Micromixers reactions

The possibility of reaching higher selectivity in micromixed reaction mixtures also contributes to greener chemistry because this saves reactants, which are not converted to undesired by-products that have to be removed from the product. In addition waste removal or deposition can be reduced. 

Integrated Microdevices for Medical Diagnostics, Fig. 2 (Left) Schematic diagram of a blood typing biochip. The device contains flow splitting microchannels, a serpentine micromixer, reaction microchambers, and detection microfilters. The reaction chamber holds 3 pi... 

Absorption of CO Micro-bubble column with a static micromixer, reaction platelet and a microheat exchanger Conversion increased by a factor of 2.5 with a residence time of 0.1 s... 

As the flow of a reacting fluid through a reactor is a very complex process, idealized chemical engineering models are useful in simplifying the interaction of the flow pattern with the chemical reaction. These interactions take place on different scales, ranging from the macroscopic scale (macromixing) to the microscopic scale (micromixing). 

Each stage of particle formation is controlled variously by the type of reactor, i.e. gas-liquid contacting apparatus. Gas-liquid mass transfer phenomena determine the level of solute supersaturation and its spatial distribution in the liquid phase the counterpart role in liquid-liquid reaction systems may be played by micromixing phenomena. The agglomeration and subsequent ageing processes are likely to be affected by the flow dynamics such as motion of the suspension of solids and the fluid shear stress distribution. Thus, the choice of reactor is of substantial importance for the tailoring of product quality as well as for production efficiency. 

Baldyga, J. and Bourne, J.R., 1984b. A fluid mechanical approach to turbulent mixing and chemical reaction. Part II Micromixing in the light of turbulence theory. Chemical Engineering Communications, 28, 243-258. 

Bourne, J.R. and Yu, S., 1994. Investigation of micromixing in stirred tank reactors using parallel reactions. Industrial and Engineering Chemistry Research, 33, 41-55. 

Fournier, M.-C., Falk, L. and Villermaux, J., 1996. A new parallel competing reaction system for assessing micromixing efficiency - experimental approach. Chemical Engineering Science, 51, 5053-5064. 

Garside, J. and Tavare, N.S., 1985. Mixing, reaction and precipitation limits of micromixing in an MSMPR crystallizer. Chemical Engineering Science, 40, 1485-1493. 

Does this model give us a practical solution for the synthesis of monosubstitution products in high yields The model teaches us that reactions are not disguised by micromixing if the intrinsic rate constant (in Scheme 12-84 k2o and k2v>) is significantly less than 1 m-1s-1. As discussed in Section 12.7, the intrinsic rate constant refers to unit concentrations of the acid-base equilibrium species involved in the substitution proper, not to analytical concentrations. Therefore, if the azo coupling reaction mentioned above is not carried out within the range of maximal measured rates (i.e., with the equilibria not on the side of the 1-naphthoxide ion and... 

A microreactor was also applied to this reaction. The slit interdigital micromixer was purchased from IMM (Mainz, Germany). The width of the interdigital channels is 25 pm. HPLC pumps were used to feed the two reaction solutions. One is a mixture of Boc-AMP and 1.2 molar equivalents of r-BocaO. The other is a 50% aqueous KOH solution. The microreactor was immersed in a temperature controlled cooling bath at 15 °C. The product was quenched with an acid, and samples were taken for HPLC analysis. 

Hessel, V., Lowe, H., Hofmann, C., ScHONFELD, F., WeHLE, D., WeRNER, B., Process development of a fast reaction of industrial importance using a caterpillar micromixer/tubular reactor set-up, in Proceedings of the 6th International Conference on Microreaction Technology, IMRET 6, pp. 39-54 (11-14 March 2002), AIChE Pub. 

Eheeeld, W., Golbig, K., Hessel, V., Lowe, H., Richter, T, Characterization of mixing in micromixers by a test reaction single mixing units and mixer arrays, Ind. Eng. Chem. Res. 38, 3... 

Establishing the process sensitivity with respect to the above-mentioned factors is crucial for further scale-up considerations. If the sensitivity is low, a direct volume scale-up is allowed and the use of standard batch reactor configurations is permitted. However, many reactions are characterized by a large thermal effect and many molecules are very sensitive to process conditions on molecular scale (pH, temperature, concentrations, etc.). Such processes are much more difficult to scale up. Mixing can then become a very important factor influencing reactor performance for reactions where mixing times and reaction times are comparable, micromixing also becomes important. 

When the half-life time of reaction and the half-life time of micromixing in the absence of chemical reaction are of the same order or the former is less than the latter, the role of micromixing may become crucial. For instance, nitration or bromination of resorcinol, even when the ratio of moles of resorcinol to moles of bromine is high, can lead to predominantly disubstituted product contrary to the general belief. In such cases, in many respects, the theory of coupling between reaction and micromixing has parallels with the formalism of theory of mass transfer with chemical reaction (Bourne, 1983). 

The reaction can be slow compared to micromixing but fast or instantaneous compared to meso-or macromixing. 

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