Vapor quenching

Reactor vapor quench. LCO, naphtha, or other quench streams can be used to quench reactor vapors to minimize thermal cracking. 

The structure of a vapor-quenched alloy may be either crystalline, in which the periodicity of the unit cell is repeated within the crystallites, or amorphous, in which there is no translational periodicity even over a distance of several lattice spacings. Mader (64) has given the following criteria for the formation of an amorphous structure the equilibrium diagram must show limited terminal solubilities of the two components, and a size difference of greater than 10% should exist between the component atoms. A ball model simulation experiment has been used to illustrate the effects of size difference and rate of deposition on the structure of quench-cooled alloy films (68). Concentrated alloys of Cu-Ag (35-65%... 

Vapor quenching provides a method of bridging the miscibility gap which exists in many alloy systems, and makes a range of novel alloys available for study. Such films, of course, would not be ideal for catalytic studies. They could not be used at high temperatures, and indeed the heat of reaction might be sufficient to induce a transformation to a more stable structure. In addition, characterization by X-ray diffraction would be difficult, even for the crystalline films, because of line broadening by the small crystallites. Nevertheless, alloy films which are metastable above room temperature can be prepared, and their high surface area would... 

There is now available a substantial amount of information on the principles and techniques involved in preparing evaporated alloy films suitable for adsorption or catalytic work, although some preparative methods, e.g., vapor quenching, used in other research fields have not yet been adopted. Alloy films have been characterized with respect to bulk properties, e.g., uniformity of composition, phase separation, crystallite orientation, and surface areas have been measured. Direct quantitative measurements of surface composition have not been made on alloy films prepared for catalytic studies, but techniques, e.g., Auger electron spectroscopy, are available. 

An improved riser terminator can lower delta coke, reduce dry gas up to 40%, lower regenerator temperature and allow more feed or higher conversion. Adding post-riser vapor quench can independently reduce dry gas, increase gasoline and reduce diolefins in the alkylation stream and the FCC gasoline. 

Operational problems with the freshwater vapor quenching system may cause high particulate emissions. 

U. Stolz, R. Kirchheim, J.E. Sadoc, and M. Laridjani. Hydrogen in liquid-quenched and vapor-quenched amorphous PdgoSi20- J- Less-Common Mater., 103(1)r81—90, 1984. 

Cr-MCM-41 MoO,/Si02 Dehydration Reduction in ethanol or methanol vapor, quenching" during ethanol or methanol oxidation... 

One of the features shown by vapor-quenched (VQ) non-crystalline solids is their high configurational enthalpies compart to those of liquid-quenched (LQ) solids. Figure 5 draws... 

Figure 5 (Left) Molar heat capacity and (right) configurational enthalpy of butyronitrile prepared by vapor-quenching (V(j) and liquid-quenching (LQ).

In 1979, White [3.2] observed that, by milling elemental Nb and Sn powders, the distinct X-ray diffraction peaks of the elements disappeared and typical diffuse peaks of an amorphous pattern showed up. But these samples did not show the superconducting transition temperature of vapor-quenched amorphous Nb-Sn alloys. In 1983, Koch et al. reported on the Preparation of amorphous Ni60Nb40 by mechanical alloying [3.3]. After the detection of amorphization by solid-state reaction in evaporated multilayer films by Schwarz and Johnson [3.4] (see also Chap. 2), Schwarz et al. [3.5] proposed after investigating glass formation in Ni-Ti alloys, that amorphization by mechanical alloying is also based on the solid-state reaction process. Within the last couple... 

Ramshom riser termination (S W), Direct coupled cyclones (Texaco), Post-riser vapor quench (Amoco)... 

Visible immediately, without preceding exposure in ammonia vapor Quenching fluorescence... 

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