Water vapor desorption

The water vapor desorption can be measured as shown in the scheme in Figure 1.85.1 and be calculated by... 

Figure 16 Simulated temperature profiles along a reactor with and without "desorptive" cooling at various times for the oxidation of CO on a Pt catalyst with water vapor desorption from 3A zeolite in a fixed bed comprising equal proportions of catalyst and adsorbent. The solid curves give the simple regenerative behavior and the dotted curves describe the desorptively cooled case. Initial reactor temperature is 125°C, initial adsorbent loading 0.12 kg/kg, inlet CO-concentration 0.2 mol/l, gas loading 6000 h-1.

Fig. XVI-7. Dielectric isotherms of water vapor at 15°C adsorbed on a-FeiOa (solid points indicate desorption). A complete monolayer was present at P/P = 0.1, and by P/P = 0.8 several layers of adsorbed water were present. (From Ref. 110.)...

Fig. 10. Adsorption ( , O)"desorption (A, A) isotherms of water vapor on poly(vinylidene chloride) (PVDC) carbon before (filled symbols) and after...

Desorption of the dissolved gases formed bubbles of gas and a limited amount of bubbles containing gas-water vapor mixture. Under these conditions, during flow boiling of water boiling incipience occurred at channel wall temperatures below that of saturation temperature. Addition of surfactants led to an increase in wall temperature. In this case the boiling occurred in the range of heat flux of 5.2-21 W/cm at wall temperatures of 107-121 °C. 

Desorption of the dissolved bubbles formed bubbles of gas and a limited amount of bubbles containing gas-water vapor mixture. As a result, boiling incipience oc-... 

In an open sorption storage system air is transporting water vapor and heat in and out of the packed bed of solid adsorbents (see Figure 235) or a reactor where the air is in contact with a liquid desiccant. In desorption mode a hot air stream enters the packed bed or the reactor, desorbs the water from the adsorbent or the salt solution and exits the bed cooler and saturated. In adsorption mode the previously humidified, cool air enters the desorbed packed bed or the... 

For the second point of the linear approximation the maximum A T has to be found. Assuming that the highest temperature Tout max can be reached after a complete desorption and that all of the water vapor within the air stream will be adsorbed ( Ax = x n), Tmax can be written as... 

Figure 241 shows the shape of two thermal breakthrough curves for Zeolite and Silicagel in adsorption. The adsorption is following a desorption using 130 °C and the inlet air is saturated with water vapor at 25 °C. 

Table 16-4 shows the IUPAC classification of pores by size. Micropores are small enough that a molecule is attracted to both of the opposing walls forming the pore. The potential energy functions for these walls superimpose to create a deep well, and strong adsorption results. Hysteresis is generally not observed. (However, water vapor adsorbed in the micropores of activated carbon shows a large hysteresis loop, and the desorption branch is sometimes used with the Kelvin equation to determine the pore size distribution.) Capillary condensation occurs in mesopores and a hysteresis loop is typically found. Macropores form important paths for molecules to diffuse into a par-... 

The most fundamental manner of demonstrating the relationship between sorbed water vapor and a solid is the water sorption-desorption isotherm. The water sorption-desorption isotherm describes the relationship between the equilibrium amount of water vapor sorbed to a solid (usually expressed as amount per unit mass or per unit surface area of solid) and the thermodynamic quantity, water activity (aw), at constant temperature and pressure. At equilibrium the chemical potential of water sorbed to the solid must equal the chemical potential of water in the vapor phase. Water activity in the vapor phase is related to chemical potential by... 

Fig. 3 Water vapor sorption and desorption isotherms for ipratropium bromide at 20°C ( ), 2 month sorption (A), 5 month sorption ( ), 2 and 5 month desorption [Note All 2 month sorption results, except at 53% and 63% relative humidity, were verified at 5 months.]...

Fig. 4 Water vapor sorption ( ) and desorption (A) isotherms for microcrystalline cellulose at 20°C.-----, GAB fit to sorption data ------, GAB fit to desorption data.

By using 22.4 103 L mbar corresponding to 18 g HzO, mbar L can be converted into g. This relationship is accurate enough as the temperature of the water vapor depends on several factors and will also be modified by a change of Tsh The desorption process can be best illustrated by using the desorption rate (DR), which measures the desorbed amount of water in % of the solids of the product per hour. 

The desorption isotherm describes, under equilibrium conditions, the amount of water absorbed on the product at a given temperature as a function of water vapor pressure, as shown in Fig. 1.96. To approximate the equilibrium at a given temperature in a short time, the pressure during SD should be small compared with the equilibrium vapor pressure,... 

The merit of Malinin s work is the comparative study of water content of bones by reproducible methods. The measurement of water vapor pressure during the drying cannot be used dirctly to determine the RM, as Malinin correctly states. Measurement of the description rates (DR) provide a means to follow quantitatively the course of desorption drying. The method is described in Section 1.2.2, but cannot be applied in an installation used by Malinin because the condenser cannot be separated from the chamber by a valve. By using the data given in the paper of Malinin it is possible to estimate the freeze drying process of bone transplants as follows ... 

The amounts of water absorbed as function of relative water vapor pressure (relative humidity) for HA and its esters are reported in Tables 1-4. HA absorbed the highest amount of water at all humidity levels compared to its esters. The ethyl ester (Hyaff ) absorbs more water than the other two, and the dodecyl ester (Hyaff73) absorbs more water than the benzyl ester (Hyaffll). A small percentage of water absorption hysteresis, between sorption and desorption, was found for the four different materials analyzed. No significant differences in the percentage of hysteresis was found among the HA and the three esters. 

Duplessix et al. used water vapor pressure isotherm (i.e., water uptake vs external relative humidity) data combined with simultaneous isotherm differential microcalorimeter analysis to determine the average heat of absorption per water molecule for 1200 EW acid form samples. Hysteresis was seen between sorption and subsequent desorption curves at 25 °C, and nonzero water content remained at zero relative humidity, indicating the presence of tightly... 

Three series of LaCoi. CuxOs, LaMni.xCuxOs, LaFei x(Cu, Pd)x03 perovskites prepared by reactive grinding were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed desorption (TPD) of O2, NO + O2, and CsHg in the absence or presence of H2O, Fourier transform infrared (FTIR) spectroscopy as well as activity evaluations without or with 10% steam in the feed. This research was carried out with the objective to investigate the water vapor effect on the catalytic behavior of the tested perovskites. An attempt to propose a steam deactivation mechanism and to correlate the water resistance of perovskites with their properties has also been done. 

The adsorption-desorption process is of interest in many systems (such as with cement). The water vapor may condense in the pores after adsorption under certain conditions. This may be studied by analyzing the adsorption-desorption data... 

---