Reaction scale-down

Miniaturization of reaction scale-down to the level of a single bead in SP reduces the amount of precious reagents and solvents used. 

All of this careful addition is to keep the reaction from starting before the bomb is sealed. It is also important to note that the chemist must scale up or scale down the amount of reactants so that the total amount of all the ingredients consumes no less than 90 of the volume space of her particular pipe bomb. Too much head space with its atmospheric air will lower the yield. The bomb is heated in an oil bath or oven at 105-115°C for 18-24 hours and the contents are then distilled with the 1,3 benzodioxole coming over at about 170-175°C with no vacuum, Alternatively, the chemist can only distill off the methanol, wash with dilute NaOH solution and extract with ether, etc. 

Figure 2.3.1 (Wachtel, et al, 1972) shows the ARCO reactor that tried to simulate the real reaction conditions in a fluid cracking unit. This was a formal scale-down where many important similarities had to be sacrificed to get a workable unit. This unit was still too large for a laboratory study or test unit, but instead was pilot-plant equipment that could still give useful empirical results Since this serves a very large industry, it may pay off to try it, even if it costs a lot to operate.

When reacting two phases that are not very soluble in each other, for example when carrying out nucleophilic substitution reactions, phase transfer catalysts should be considered when scaling down from equipment with poor mixing characteristic, rather than buying new equipment. 

The relative percentage yields of products at 135-7°C are (A) ll-l, (B) 1-3, (C) 45-7, (D) 32-1, (E) 9-8. The yield of isoprene has been scaled down by a factor of 2 since the decomposition of one molecule of the cyclobutane yields two molecules of isoprene. The products and rates of reaction of this cyclobutane and the previous one discussed are both consistent with the reaction paths already mentioned. 

Another Methodfor 5 5-Diethyl Barbituric Acid. (This is a scaled down version.) 16 g of clean sodium is dissolved in 300 g of absolute ethanol. To this cooled solution is added 20 g of dry urea and 50 g of diethyl malonic ester (diethyl diethyl malonate). The mixture is heated in an autoclave (pressure cooker, very strong) for 4 to 5 hours at 100-110°. After removing from the autoclave, the mixture is cooled. Upon cooling, the sodium salt of diethyl barbituric acid separates, is filtered off, dissolved in water, and the free acid precipitated by the addition of hydrochloric acid. The acid is filtered and recrystallized from water, using decolorizing carbon, if necessary. Yield Depends on your ability to exclude H2O from the beginning of reaction. 

The majority of preparations can be scaled down provided that microware is available. Most preparations are already scaled down and can be used as described. Reactions run on a large scale by a laboratory class pose a disposal problem, which is very costly. 

If only 50ml of alcohol are used in the precipitation the yield is decreased to 88g and the use of 250ml of water for the reaction drops the yield to T7g. The reaction may be readily scaled down to give proportionate yields. 

The protocols are for 0.5 mg of antigen in a 0.5-mL reaction volume, but if the antigen is in short supply, it may be possible to scale down both weight and volume by using a smaller Sephadex column or replacing it with a microspin column (check to ensure that the same separation is obtained). 

The reaction can be either scaled up or scaled down proportionally. 

The principle of the scale-down methodology, using a reaction calorimeter, is as follows ... 

Zuflerey, B. (2006) Scale-down Approach Chemical Process Optimisation Using Reaction Calorimetry for the Experimental Simulation of Industrial Reactors Dynamics, EPFL, n°3464, Lausanne. 

For systems involving fast reactions where reactor performance has been established at one scale and equal performance is required at different scales, the criteria for scale-up/scale-down are ... 

An interpretation of the results for catalytic reaction kinetics on active supported nanoparticles on the scale down to 10nm has been obtained by the MC technique [285]. The technique allows the peculiarities of the reaction performance on the nanometer scale, including the inherent heterogeneity of metal crystallites as well as spontaneous and adsorbate-induced changes of the shape and degree of dispersion of supported catalysts. 

It is important to note that most large-scale SCWO reactors are designed to be turbulent flow. In addition, some of the reactors (e.g., transpiring wall reactor) are not possible to scale down for laboratory-scale experiments. The method given here is a generic approach for understanding the reaction kinetics of pollutants under SCWO conditions. 

Electrolysis may be particularly well suited to meeting the early-stage fueling needs of a fuel cell vehicle market. Electrolyzers scale down reasonably well the efficiency of the electrolysis reaction is independent of the size of the cell or cell stacks involved. And the balance of plant costs in an electrolyzer are also fairly scalable. 

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