Alloys reaction vessel

Figure 1. High-pressure oxygen apparatus A Rene alloy reaction vessel B safety rupture disk C pressure gauge D high-pressure capillary tubing E two-way valve F gas inlet G thermocouple recess H tube furnace I plunger.

Oxychlorination of Ethylene or Dichloroethane. Ethylene or dichloroethane can be chlorinated to a mixture of tetrachoroethylene and trichloroethylene in the presence of oxygen and catalysts. The reaction is carried out in a fluidized-bed reactor at 425°C and 138—207 kPa (20—30 psi). The most common catalysts ate mixtures of potassium and cupric chlorides. Conversion to chlotocatbons ranges from 85—90%, with 10—15% lost as carbon monoxide and carbon dioxide (24). Temperature control is critical. Below 425°C, tetrachloroethane becomes the dominant product, 57.3 wt % of cmde product at 330°C (30). Above 480°C, excessive burning and decomposition reactions occur. Product ratios can be controlled but less readily than in the chlorination process. Reaction vessels must be constmcted of corrosion-resistant alloys. 

Thus nickel and nickel-copper alloy films evaporated in vacuo onto the inner walls of the reaction vessel have been chosen for further investigations. The films were deposited onto the inner wall of a glass tube kept at 450°C their thickness amounted to approximately 2000 A. After annealing at the same temperature in vacuo they were transferred into the side-arm of the Smith-Linnett apparatus in order for the recombination coefficients to be determined. The bulk homogeneity of alloy films prepared in this way was confirmed by X-ray diffraction (65, 65a, 66). 

Materials. Ethylene Oxide (EO) and pivalolactone (PVL) were dried over calcium hydride for a day before use. EO was further dried on a sodium mirror prior to passing into the reaction vessel. Dried PVL was sealed into ampules under high vacuum (I0"° mm Hg). Succinic anhydride (SA) was dried in a vacuum oven for a day and sublimed under high vacuum into ampules. Dry THF was obtained by refluxing THF on Na/K (1 1) alloy for six hours, distilling over the alloy and degassing under high vacuum in the... 

According to the data in Table III, the value of the ratio P)Mm is approximately the same for the metals Au, Fe, Co, Ni, and Pd. Binary alloys formed from any pair of these metals can therefore be expected to evaporate without substantial fractionation. On the other hand, films evaporated from Ag-Pd and Cu-Ni alloys can be expected to be enriched in Ag and Cu, respectively. These predictions are largely confirmed by experiment. For example, the composition of Pd-Au films was found to be the same as the wires which were evaporated (46), but in the case of Pd-Ag, evaporation of a 30% Ag-Pd alloy ware yielded a 50% Ag-Pd alloy film (47)- Alexander and Russell evaporated a number of alloys from pellets in the reaction vessel as shown in Fig. 5 (48) The alloy pellet was placed in a small quartz cup with its surface equidistant from the hemispherical top of the reaction vessel. The pellet was evaporated by... 

Fig. 5. Reaction vessel, in the dome of which, alloy films are deposited by evaporation from an alloy pellet subjected to induction heating (.48).

With due regard to the lateral variations in composition which can arise as a consequence of source geometry and positioning (discussed in Section II), it is vise to analyze the alloy film at a number of representative points. For example, if a catalytic reaction was carried out over an alloy film deposited inside a spherical vessel maintained at a constant temperature over its entire area, then the mean alloy composition (and the uniformity of composition) is required. A convenient procedure is to cut glass reaction vessels carefully into pieces at the end of the experiment and to determine the composition by X-ray fluorescence analysis of a number of representative pieces. Compositions of Pd-Ag alloy films (40) determined at 12 representative parts of a spherical vessel from the intensities of the AgK 12 and PdKau fluorescent X-ray emissions are shown in Table V mean compositions are listed in the first column. (The Pd and Ag sources were separate short concentric spirals.) In other applications of evaporated alloy films to adsorption and catalytic studies, as good or better uniformity of composition was achieved. Analyses of five sections of a cylindrical... 

The most important applications of nickel metal involve its use in numerous alloys. Such alloys are used to construct various equipment, reaction vessels, plumbing parts, missile, and aerospace components. Such nickel-based alloys include Monel, Inconel, HasteUoy, Nichrome, Duranickel, Udinet, Incoloy and many other alloys under various other trade names. The metal itself has some major uses. Nickel anodes are used for nickel plating of many base metals to enhance their resistance to corrosion. Nickel-plated metals are used in various equipment, machine parts, printing plates, and many household items such as scissors, keys, clips, pins, and decorative pieces. Nickel powder is used as porous electrodes in storage batteries and fuel cells. 

When the crucible has cooled down, the system is thoroughly evacuated, and water, or heavy water (ca. 10 ml.), allowed to drip slowly onto the alloy. The progress of the reaction can be followed by observing the manometer. When no more gas is formed, the products are condensed successively in the traps 1, 2, and 3 and in the collection vessel. The tap A is closed when the pressure drops below ca. 10 mm. to keep to a minimum the amount of water that distills over. The reaction vessel is evacuated, filled with N2 or Ar, and removed to a fume hood. 

Equipment using high pressures with reactive gases has been developed mainly for fundamental scientific research. The stabilization of unusual oxidation states of transition elements is one area of research involving such equipment. Specific reaction vessels with external heating have been developed to synthesize oxides which require high temperatures (Fig. 7.11). Due to the large decrease of the mechanical properties of alloys with temperature, only a limited pressure-temperature domain is available (Fig. 7.12). 

Hydrogen fluoride attacks silica glass (equation 8.36) thereby corroding glass reaction vessels, and it is only relatively recently that HF has found applications as a non-aqueous solvent. It can be handled in polytetrafluoroethene (PTFE) containers, or, if absolutely free of water, in Cu or Monel metal (a nickel alloy) equipment. 

The preparation of the alloys can proceed by two essentially different methods. Vacuum melting in an induction furnace is the more common method. First, Fe and B are melted in alumina crucibles under purified argon gas. Subsequently, the reaction vessel is degassed under vacuum and Nd metal is added to the melt after the latter has reached a temperature only slightly above the Fe-B liquidus temper-... 

---