Rotary reaction techniques

Solvated metal atoms and aggregates can also be made by liquid phase rotary reaction techniques.(36-39) Depending on the reactivity of the medium, clustering of metal atoms may occur immediately... 

Thus cooling-warming cycles, suitably induced, allowed temporal resolution of the reaction, step by step. The absorption, optical rotary dispersion, and electron spin resonance (ESR) spectra of pure compounds I and II were then recorded and found to be similar to those obtained under fast-reaction conditions (Douzou et al., 1970 Douzou and Leter-rier, 1970). Additional interesting observations were made possible by the low-temperature technique for instance, instead of making the time scale of reactions feasible exp>erimentally by increasing the substrate concentrations as in fast techniques, reactions at low temperatures could be performed with stoichiometric concentrations of enzyme. Such con-... 

Because the initial rotary evaporation is faster with the organic solvent, we have usually prepared DHA in 95% ethanol. In methanol the reaction gives up to 10-20% of a methanol complex of DHA that is only partly reconverted to free DHA on repeated evaporations from water. Extensive rotary evaporation with repeated additions of diethyl ether, followed by lyophilization, yields a more manageable, semisolid product. DHA in the syrup or semisolid form is stable for many weeks when stored at —10° to —20°C. Analysis of the products prepared as described above was done by NMR, one of the few analytical techniques that gives unambiguous results on the purity and identity of this compound. 

Pump and Purge. A key objective of cannula techniques is to achieve very low partial pressures of oxygen without the use of time consuming high vacuum techniques, and this is achieved by repeated pump and purge cycles. Even a heavily used rotary pump will give an ultimate vacuum of 1 x 10 2 mm Hg, and will rapidly reduce the pressure in a small reaction vessel to 1 m Hg. In a typical example a 224 mL reaction vessel contains approximately 2 mmol of O2, and evacuation to 1 mm Hg reduces the quantity of 02 to 2 x 10 3 mmol. If the vessel is refilled and the cycle repeated the quantity of O2 reduces to 2 x 10 mmol, and it is clear that relatively poor vacuums are sufficient to provide very low effective partial pressures of O2 after 2 or 3 pump/purge cycles. 

Diol linseed fatty amide is treated with TDI at room temperature in a one shot technique to obtain polyurethane, using a minimal amount of xylene as the solvent and without any chain extender or catalyst. The reaction is stopped when it has reached the desired hydroxyl value and the solvent is removed through a rotary vacuum evaporator to obtain poly(urethane amide) resin. 

Crude vermiculite ore produces the basic material used in the manufacture of fire protection and industrial insulation products. The process equipment consists of three rotary furnaces for heating and reaction. Torftech Ltd. (UK) replaced these with a single toroidal fluidized bed (Torbed) furnace of 1-m diameter with a capacity of 2 ton/hr. This led to a reduction in overall energy consumption and in vermiculite wastage and maintenance costs. The new process resulted in a payback period of 16 months. Now 11 plants are operational in Europe with this Torbed technology. This technique is also commercialized to produce silica from rice husk and roasting of sulphide ores, etc. 

Work-Up and Isoiation Transfer the reaction mixture to a small separatory funnel. Add 5 mL of water and separate the layers. Extract the aqueous layer with two separate 10-mL portions of diethyl ether. Wash the combined organic layers sequentially with two 10-mL portions of water and two 10-mL portions of saturated brine, and dry them over several spatula-tips full of anhydrous sodium sulfate. Add additional portions of anhydrous sodium sulfate if the liquid remains cloudy. Filter or decant the dried solution into a dry 50-mL round-bottom flask and remove the volatile solvents by simple distillation. Alternatively, rotary evaporation or other techniques may be used to remove the solvents. The final traces of solvents may be removed by attaching the flask to a vacuum source... 

Work-Up and Isolation Remove the gas trap, separatory funnel, condenser, and Claisen adapter from the reaction flask. Add 15 mL of 2.5 M aqueous sodium hydroxide to the stirred solution and continue stirring for 15 min swirl the flask if necessary to dissolve all of the white solid. Transfer the reaction mixture to a separatory funnel, separate the layers, and remove the lower aqueous layer. Wash the organic layer with 15 mL of cold3 M hydrochloric acid, venting as necessary, and then with 15 mL of cold water. Dry the organic layer over several spatula-tips full of anhydrous sodium sulfate." Filter or carefully decant the solution into a tared round-bottom flask and remove most of the ether by simple distillation. Alternatively, use rotary evaporation or other techniques to concentrate the solution. The final fraces of solvent may be removed by conneoting the cool stillpot to a vacuum source. Determine the yield of crude producf." ... 

The raw batch calcination can be accomplished in almost any kind of furnace. Tunnel kilns, box kilns, shuttle kilns, and rotary kilns have been used for many years, each with its own advantages, disadvantages, and limitations. In some instances, patents have been issued for the calcination technique Special firing profiles have been developed for some pigments to guide the reaction chemistry. 

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