Calcium oxide pressure

Zinc oxide is a common activator in mbber formulations. It reacts during vulcanization with most accelerators to form the highly active zinc salt. A preceding reaction with stearic acid forms the hydrocarbon-soluble zinc stearate and Hberates water before the onset of cross-linking (6). In cures at atmospheric pressure, such as continuous extmsions, the prereacted zinc stearate can be used to avoid the evolution of water that would otherwise lead to undesirable porosity. In these appHcations, calcium oxide is also added as a desiccant to remove water from all sources. 

DihydroxyanthraquiQone (anthranifin) [117-12-4] (47) is an important iatermediate for manufacturiag disperse blue dyes, eg. Cl Disperse Blue 73 (113), and is prepared from anthraquiQone-l,5-disulfonic acid by heating with an aqueous suspension of calcium oxide and magnesium chloride under pressure at 200—250°C (67). Alternative methods have been proposed, ie, direct replacement of the NO2 groups of 1,5-dinitroanthraquiaone (49) (68) or the route via 1,5-dimethoxyanthraquiaone [6448-90-4] (48) and subsequent hydrolysis (69). 

Pressure rising. Calcium oxide and carbon dioxide forming-... 

The stability of ceramic materials at high temperatures has made them useful as furnace liners and has led to interest in ceramic automobile engines, which could endure overheating. Currently, a typical automobile contains about 35 kg of ceramic materials such as spark plugs, pressure and vibration sensors, brake linings, catalytic converters, and thermal and electrical insulation. Some fuel cells make use of a porous solid electrolyte such as zirconia, Zr02, that contains a small amount of calcium oxide. It is an electronic insulator, and so electrons do not flow through it, but oxide ions do. 

As it has been mention in preceding section, the vast effect of the mechanism of adsorption-caused change in electrophysical characteristics of adsorbent is provided by availability of defects [32]. However, various admixtures play similarly important role on effects of properties of oxides including the sensitivity of their electrophysical properties to adsorption [4, 5]. Small amounts of admixtures (of the order of 0.5 -1 mol.-%) can both increase the sensitivity of oxide for instance to oxygen (addition of Y2O3 to calcium oxide over pressure interval lO -10 Torr [189]) and decrease it (addition of Ga203 to ZnO [190]), or can result in insensitivity of electric conductivity on the pressure of the gas in question (as it is the case with respect to O2 while adding 0.5 -1 mol.-% of lithium to NiO [190]). 

The presence of impurities can cause a shift in the dissociation point. It implies that the equilibrium temperature and pressure of the carbonate decomposition reaction are shifted. The effect of silica is particularly illustrative in the case of limestone. If silica is present as an impurity, it lowers the decomposition point of limestone. The acid anhydride silica slags combines with the basic calcium oxide according to following ... 

Solid calcium carbonate decomposes to produce solid calcium oxide and carbon dioxide gas. The value of AG° for this reaction is 130.24 kJ/mole. Calculate AG at 100°C for this reaction if the pressure of the carbon dioxide gas is 1.00 atm. 

Ding and Alpay also studied sorption-enhanced reforming with K-HTC as sorbent [28], using a commercial Ni-based catalyst. They found that the SER process benefits from higher pressures and that lower steam to methane ratios can be used than in ordinary reforming. Reijers et al. [25] have shown that K-HTC is an effective sorbent between 400 and 500 °C, with an C02 uptake of approx. 0.2 mmol g 1. This capacity is low compared with calcium oxides and lithium zirconates. Above 500 °C, the C02 sorption capacity of K-HTC decreases rapidly to zero [36]. 

Stage III The decomposition of calcium carbonate to calcium oxide, which is a function of the partial pressure of the C02 in contact with the sample. The endothermal band for the carbonate decomposition is sharply peaked spread over a relatively narrower temperature range in an atmosphere of C02. 

The total pressure of a mixture of sulfur dioxide and nitrogen gases at 25°C in a 5.00 X 102-mL vessel is 1.09 atm. The mixture is passed over warm calcium oxide powder, which removes the sulfur dioxide by the reaction CaO(s) + S02(g) —> CaS03(s). It is then... 

This reaction can go in either direction, depending on the temperature and pressure used. This reaction is an important industrial process and takes place in a lime kiln (Figure 13.7). In excess of 60 million tonnes of calcium oxide are produced worldwide every year. 

Commercial dimethyl sulphate may be purified by, (a) allowing it to stand over anhydrous potassium carbonate until it is neutral to Congo red paper, or (b) by washing, just before use, with an equal volume of ice-water, followed by one-third of its volume of cold, saturated sodium hydrogen carbonate solution, and finally drying over calcium oxide. In both cases the purified dimethyl sulphate is fractionally distilled under reduced pressure from calcium oxide and the fraction having b.p. 72-73 °C/13 mmHg collected. 

This can be dried with Linde-type sieves 4A or 13X, by prolonged contact and by passage through a column of the material, then distilled under reduced pressure. Other drying agents include calcium hydride, calcium oxide, barium oxide and calcium sulphate. It can also be fractionally crystallized by partial freezing. 

The concept of a reversible chemical reaction may be illustrated by the decomposition of calcium carbonate, which when heated forms calcium oxide and carbon dioxide gas. At equilibrium, this system exerts a definite decomposition pressure of C02 for a given temperature. When the pressure falls below this value, CaCOj decomposes. Assume now that a cylinder is fitted with a frictionless piston and contains CaC03, CaO, and C02 in equilibrium. It is immersed in a constant-temperature bath, as shown in Fig. 2.5, with the temperature adjusted to a value such that the decomposition pressure is just sufficient to balance the weight on the piston. The system is in mechanical equilibrium, the temperature of the system is equal to that of the bath, and the chemical reaction is held in balance by the pressure of the COj. Any change of conditions, however slight,... 

If the product contains chlorine as indicated by the alcoholic silver nitrate test, it may be purified by adding a small amount of anhydrous calcium oxide (0.5 g. per 50 g. of product) and redistilling under reduced pressure. 

The temperature required for the reduction of cobalt oxides to the metal appears to be somewhat higher than for the reduction of nickel oxide. The catalyst with a higher catalytic activity is obtained by reduction of cobalt hydroxide (or basic carbonate) than by reduction of the cobalt oxide obtained by calcination of cobalt nitrate, as compared in the decomposition of formic acid.91 Winans obtained good results by using a technical cobalt oxide activated by freshly calcined powdered calcium oxide in the hydrogenation of aniline at 280°C and an initial hydrogen pressure of 10 MPa (Section... 

The dissociation pressure of calcite reaches 0.101 kPa (1 atm) at 894°C (S20) and the decarbonation reaction is highly endothermic (Section 3.1.4). The rate of decarbonation becomes significant at 500-600°C if a sufficiently low partial pressure of COj is maintained or if the calcite is intimately mixed with materials, such as quartz or clay mineral decomposition products, that react with the calcium oxide. Even in a precalciner, such mixing occurs, aided by agglomeration caused by the presence of low-temperature sulphate melts. 

Bukowinski, M. S. T. (1982). Pressure effects on bonding in calcium oxide comparison with magnesium oxide. J. Geophys. Res. 87B, 303-19. 

Figure 17.6 Scheme of the industrial pilot plant for the pyrolysis of 5000 t/yr plastics or tires. Z cyclone Q quench cooler K cooler DW high-pressure quench cooler KM compressor WT heat exchanger F flare G excess gas R carbon black P plastic feed K calcium oxide, LS low-boiling oil HS high-boiling oil... 

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