Many desirable organic reactions are accompanied by side reactions and undesired by-products, which waste raw materials and complicate product work-up and isolation. By enhancing the competition between reactions to obtain more selective syntheses, ecological and economic benefits may be expected. The most effective way to do this is usually catalysis. Recently, however, more has been learned about the role of "reactive mixing", which refers here to bringing reagents together on the molecular scale. When chemical knowledge (especially reaction kinetics and physical organic chemistry) is combined with that of mixing, significant improvements to the selectivity of some syntheses can be achieved. This review offers an introduction to understanding how mixing influences those single-phase and two-phase reactions which are sufficiently fast that mixing cannot fully homogenize their reactants. It includes theoretical principles, typical experimental results, worked examples, and literature references for further study. Reactive mixing is treated in very few textbooks (refer to section 1), is unknown to many chemists, and is unfamiliar to many chemical engineers. It is hoped that its wider recognition will lead others to become intellectually fascinated by its structure and to value its practical applications.
The emergence of worldwide communications networks and powerful computer technologies has redefined the concept of distance learning and the delivery of engineering education content. This article discusses the Sloan Consortium’s quest for quality, scale, and breadth in online learning, the impact on both continuing education of graduate engineers as well as degree-seeking engineering students, and the future of engineering colleges and schools as worldwide providers of engineering education.
Biological denitrification of drinking water was studied in a fluidized sand bed reactor using a mixed culture. Hydrogen gas was used as the reaction partner. The reaction kinetics were calculated with a double Monod saturation function. The K(s) value for hydrogen was below 0.1% of saturation. No appreciable biofilm diffusion effects were detected. Reactor performance was a function of the culture's past history. Batch experiments always exhibited an accumulation of NO(2) (-), but continuous experiments with a sufficiently long residence time always resulted in complete nitrogen removal. Rates of up to 23 mg N/L h, 25 mg N/g DW h, and 7.9 mg H(2)/L h were achieved. Residence times of 4.5 h would be required for complete denitrification of water containing 25 mg NO(3) (-)-N/L or approximately 1 h for every 5 mg/L.
The emergence of worldwide communications networks and powerful computer technologies has redefined the concept of distance learning and the delivery of engineering education content. This article discusses the Sloan Consortium's quest for quality, scale, and breadth in online learning, the impact on both continuing education of graduate engineers as well as degree‐seeking engineering students, and the future of engineering colleges and schools as worldwide providers of engineering education.
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