Absorption rates, hydrogen

The absorption is carried out by countercurrent passage of ethylene through 95—98% sulfuric acid in a column reactor at 80°C and 1.3—1.5 MPa (180—200 psig) (41). The absorption is exothermic, and cooling is required (42) to keep the temperatures down and thereby limit corrosion problems. The absorption rate increases when ethyl hydrogen sulfate is present in the acid (43—46). This increase is attributed to the greater solubiUty of ethylene in ethyl hydrogen sulfate than in sulfuric acid. 

The inhibitor should not decompose during the life of the pickle nor decrease the rate of scale removal appreciably. Some highly efficient inhibitors, however, do reduce pickling speed a little. It would be expected that since the hydrogen evolution is reduced the amount of hydrogen absorption and embrittlement would also be reduced. This is not always the case thiocyanate inhibitors, for example, actually increase the absorption of hydrogen. 

Carbon dioxide is absorbed in water from a 25 per cent mixture in nitrogen. How will its absorption rate compare with that from a mixture containing 35 per cent carbon dioxide, 40 per cent hydrogen and 25 per cent nitrogen It may be assumed that the gas-film resistance is controlling, that the partial pressure of carbon dioxide, at the gas-liquid interface is negligible and that the two-lilm theory is applicable, with the gan film thickness the same in the two cases. 

The absorption of hydrogen occurred smoothly at a rate which could be followed by the rise of water in the bottle containing hydrogen. When this rate suddenly decreased it was known that two atoms of hydrogen had been added to the triple bond. The hexenetetrol, which was formed in excellent yield, melted at 80-82°. 

The rapid rate of stirring desirable for maximum reaction rate often causes spraying of fine droplets of mercury from the seal. This can be prevented by a layer of paraffin oil over the mercury. It is important for the gas-inlet tube to extend below the surface of the stirred liquid, for absorption of hydrogen occurs chiefly at the rapidly agitated surface. 

Note. (1) Rapid stirring is desirable in order to obtain the maximum reaction rate absorption of hydrogen occurs chiefly at the rapidly agitated surface. 

The decrease of the free-carrier absorption upon hydrogenation can be associated with localization of free carries near C-H bonds in SWNTs, or increase in the rate of their scattering by these defects. The complete removal of hydrogen by vacuum annealing at 700°C only partly restored the intensity of the... 

A solution of 2.6 grams of an above prepared acetate in 50 ml of hexane was stirred under hydrogen with 1.56 grams of 5 % Pd on CaC03 at 22°C. Absorption of hydrogen ran at about 6.0 ml/min. At the theoretical end-point, 176 milliliters of hydrogen at 22°C, the rate of absorption had fallen to 0.8 ml/min. The catalyst was filtered off and the hexane removed under vacuum. The product was a light yellow oil the yield was 2.52 g. 

Experiments are carried out at atmospheric pressure on the absorption into water of ammonia from a mixture of hydrogen and nitrogen, both of which may be taken as insoluble in the water. For a constant mole fraction of 0.05 of ammonia, it is found that the absorption rate is 25 per cent higher when the molar ratio of hydrogen to nitrogen is changed from 1 1 to 4 1. Is this result consistent with the assumption of a steady-state gas-film controlled process and, if not, what suggestions have you to make to account for the discrepancy ... 

And again the residual stresses change the symmetry of the task the diffusion process in the hollow cylinder obeys the law of flat symmetry. The hydrogen absorption rate increases from the side of the outer boundary. Acceleration of the process kinetics is caused by reducing the compression stresses in the radial direction, which are changed with the tensile stresses. The solution of tasks (5) and (6) is well known. Thus, it is not difficult to obtain the solution of task (4). This solution describes the hydrogen absorption kinetics from the two surfaces of the hollow cylinder at given character of the residual stresses distribution... 

Gas/liquid contacting is frequently encountered in chemical reaction and bioprocess engineering. For reactions in gas/liquid systems (oxidation, hydrogenation, chlorination, and so on) and aerobic fermentation processes (including biological waste water treatment), the gaseous reaction partner must first be dissolved in the liquid. In order to increase its absorption rate, the gas must be dispersed into fine bubbles in the liquid. A fast rotating stirrer (e.g. a turbine stirrer), to which the gas is supplied from below, is normally used for this purpose (see the sketch in Fig. 34). 

As the equilibrium partial pressure of hydrogen chloride over a 35.2 per cent hydrochloric acid is only pxHci = 135 mm Hg the gas under partial pressure Phci = 228 mm Hg will be readily absorbed in the acid (the difference in pressures pHci — Pan — AB determines the absorption rate). 

Figure 3. Hydrogen absorption rates effect of hydrogen content of solvent. The asterisk indicates where the reaction was stopped and the reactor was vented and repressured with fresh hydrogen.

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