Aqueous solutions Partial pressure

Deleye and Froment (1986) have reported the data on absorption of CO2 in aqueous solution of monoethanol amine (MEA) in a packed bed absorber. Gas containing CO2 at a partial pressure of 2 atm is to be purified by absorption into an aqueous solution of MEA in a packed bed filled with 5 cm diameter steel pal rings. Assuming excess concentration of MEA in the solution, the reaction between CO2 and MEA is treated as pseudo-first order reaction with rate constant k = 7.194 x 1(P s L A quantity of 6500 rcF/h of gas is treated with 1000 m /h of MEA solution. Partial pressure of CO2 is to be reduced to 0.02 bar. Column diameter is 2 m and it is operating at a pressure of 14.3 bar and a temperature of 315 K. Calculate the height of the bed. The following data are reported. 

Deliquescence and efflorescence. A substance is said to deliquesce (Latin to become liquid) when it forms a solution or liquid phase upon standing in the air. The essential condition is that the vapour pressure of the saturated solution of the highest hydrate at the ordinary temperature should be less than the partial pressure of the aqueous vapour in the atmosphere. Water will be absorbed by the substance, which gradually liquefies to a saturated solution water vapour will continue to be absorbed by the latter until an unsaturated solution, having the same vapour pressure as the partial pressure of water vapour in the air, is formed. In order that the vapour pressure of the saturated solution may be sufficiently low, the substance must be extremely soluble in water, and it is only such substances (e.g., calcium chloride, zinc chloride and potassium hydroxide) that deliquesce. 

Increasing or decreasing the partial pressure of a gas is the same as increasing or decreasing its concentration. The effect on a reaction s equilibrium position can be analyzed as described in the preceding example for aqueous solutes. Since the concentration of a gas depends on its partial pressure, and not on the total pressure of the system, adding or removing an inert gas has no effect on the equilibrium position of a gas-phase reaction. 

The reactors were thick-waked stainless steel towers packed with a catalyst containing copper and bismuth oxides on a skiceous carrier. This was activated by formaldehyde and acetylene to give the copper acetyUde complex that functioned as the tme catalyst. Acetylene and an aqueous solution of formaldehyde were passed together through one or more reactors at about 90—100°C and an acetylene partial pressure of about 500—600 kPa (5—6 atm) with recycling as required. Yields of butynediol were over 90%, in addition to 4—5% propargyl alcohol. 

Significant disciepancies in fomialdehyde partial pressures above aqueous solutions (22,23) can occur due to nonequilibrium conditions in the liquid phase. However, these problems have been overcome and consistent results obtained (8,18,22,24—26). 

Figure 2 shows the vapor pressures of anhydrous hydrazine (AH), monomethyUiydrazine [60-34-4] (MMH), and unsymmetrical dimethyUiydrazine [57-14-7] (UDMH) as a function of temperature (2). The partial pressures of N2H4 over aqueous solutions of various concentrations are plotted in Figure 3. 

Fig. 3. Hydrazine partial pressure over aqueous solutions containing (-------) 64, (— - —) 54.4, and (—) 35 wt % hydrazine.

Partial Pressures of Water over Aqueous Solutions of HCl, , 2-76... 

TABLE 2-10 Partial Pressures of HCI over Aqueous Solutions of HCI ... 

Partial Pressures of H O and SO2 over Aqueous Solutions of Sulfur Dioxide ... 

TABLE 2-12 Water Partial Pressure, bar, over Aqueous Sulfuric Acid Solutions ... 

TABLE 2-16 Partial Pressures of HNO3 and H O over Aqueous Solutions of HNO3... 

TABLE 2-18 Partial Pressures of HI over Aqueous Solutions of HI at 2S C... 

TABLE 2-23 Partial Pressures of NH3 over Aqueous Solutions of NH3 ... 

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