Quick-quenching

GTP is a safe operation. A runaway polymerization can be quickly quenched with a protonic solvent. Since the group transfer polymerization goes to completion, no unwanted toxic monomer remains the silicone group on the living end after hydroxylation is removed as inactive siloxane. The living polymer in GTP is costlier than traditional polymerization techniques because of the stringent reaction conditions and requirements for pure and dry monomers and solvents. It can be used in fabrication of silicon chips, coating of optical fibers, etc. 

In an early stage of warning for a runaway reaction, emergency cooling should be applied in an attempt to control the situation. This often is not sufficient to be a fully preventive measure, particularly if the runaway initiation was not identified quickly. Quenching of the reaction is the usual next step to take. The reaction can be quenched by using one or more of the following procedures ... 

Why does this pathway occur instead of the Robinson annulation when the seemingly trivial change of increasing the concentration of NaOH is made Good question. It is not clear. It seems likely that the Robinson annulation does occur first (because quick quenching helps to increase the quantity of Robinson product), but the Elcb elimination at the end of the annulation mechanism is reversible in the presence of NaOH as base. It seems likely, then, that if NaOEt were used as base instead, only the Robinson product would be observed regardless of the quantity of catalyst. 

When mechanical vibration of bis(pyridinium) salts (see Scheme 5.5) was conducted with a stainless steel ball in a stainless steel blender at room temperature under strict anaerobic conditions, the powdery white snrface of the dicationic salts turned deep blue-purple (Kuzuya et al. 1993). Single-line ESR spectra were recorded in the resnlting powder. No ESR spectra were observed in any of the dipyridinium salts when mechanical vibration was conducted with a Teflon-made ball in a Teflon-made blender nnder otherwise identical conditions. When observed, the ESR signals were quickly quenched on exposnre to air and the starting dicationic salts were recovered. Each of the resulting powders was dissolved in air-free acetonitrile, and the ESR spectra of the solution were recorded after the material had been milled nnder anaerobic conditions. Analysis of the signal hyperflne structure confirmed the formation of the corresponding cation-radicals, which are depicted in Scheme 5.5. 

The single crystals thus far prepared are too small for many physical property measurements. Also, the two techniques described for preparation of powders result in fine grained (and not sintered) materials which are also not appropriate for many measurements. A different technique, however, was recently developed which produces near theoretical density polycrystalline pellets (56). Stoichiometric mixtures of BaO, K02 and Bi2Os are mixed and melted in N2 gas and quickly quenched onto a copper block under the N2 atmosphere. The process must be performed... 

Staff. "Quick-Quenching Steels." Pttp. Met liurtics. 18 lOclober 1990). 

When observed, the ESR signals were quickly quenched on exposure to air to recover the starting dications. 

However, droplet systems can enable much higher energy input (via gas phase pressure drop in cocurrent systems) and, as a result, dominate applications where a quick quench is needed. See Examples 21 and 22. Conversely, droplet systems can also be designed for very low pressure drop which is advantageous in applications such as vacuum condensers. 

This very rapid response of the concentrated solutions suggests a reasonable kinetic behavior in the melt. However, for future applications, there is also the possibility of quickly quenching the solutions under an applied electric field. This would freeze the structure at any desired microdomain spacing. 

The other two processes, by Rockwell/Cities Service and Bell Aerospace, are based on Rocket Tehcnology. They both utilize high mass flux reactors in which finely powdered coal is rapidly fixed with high velocity, hot gas. The mixture is then quickly quenched to give very short reaction times. The Rockwell Process... 

On raising the temperature, both emissions are reduced and eventually die out (the emission from the Z state being much more quickly quenched by rise in temperature). This occurs parallel with an increase in the primary quantum yield. 

For our system we chose the simplest approach — a fast sample conduit with quick quench into an evacuated sample container. For temperature measurements we used a similar probe outfitted with platinum/6% rhodium-platinum/30% rhodium thermocouple. For pressure measurements the same general type probe mentioned was employed but without extracting samples. This probe had one hole opening perpendicular to the longitudinal axis of the probe such that when inserted into the reactor it could be rotated 360°. In this manner the pressures were read from a precision pressure gauge with the opening facing 0°, 90°, 180°, and 270° relative to the direction of flow in the reactor. 

In all cases where the warm drift was studied, the calorimeter had been quickly quenched. It can then be assumed that the system is sufficiently far away from equlibrium that, during the process of observing the drifts at various tern-... 

Ways to mitigate the emission of pollutants from incinerators include the capture of particulates by installing filters and systems to quickly quench hot exiting gases in order to decrease dioxin formation, and the use of sensors to constantly monitor the emitted gases so as to obtain timely feedback for the control of the pertinent process parameters. 

This chapter discusses four methods of gas phase ceramic powder synthesis by flames, fiunaces, lasers, and plasmas. In each case, the reaction thermodynamics and kinetics are similar, but the reactor design is different. To account for the particle size distribution produced in a gas phase synthesis reactor, the population balance must account for nudeation, atomistic growth (also called vapor condensation) and particle—particle segregation. These gas phase reactors are real life examples of idealized plug flow reactors that are modeled by the dispersion model for plve flow. To obtain narrow size distribution ceramic powders by gas phase synthesis, dispersion must be minimized because it leads to a broadening of the particle size distribution. Finally the gas must be quickly quenched or cooled to freeze the ceramic particles, which are often liquid at the reaction temperature, and thus prevent further aggregation. 

Polymers (olefins) were formed In small amounts when alkylate leaving a reactor was quickly quenched with a caustic solution (1). When, however, the acid and hydrocarbon phases were allowed to separate by decanting, few If any olefins were detected. 

RQL Combustion Rich Burn—Quick Quench—Lean Burn... 

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