Temperature carbon adsorption

Chlorine can be removed by either activated carbon adsorption or by reaction with olefins such as ethylene over-activated carbon at temperatures of 30—200°C (44). Addition of Hquid high boiling paraffins can reduce the chlorine content in the HCl gas to less than 0.01% (45). 

Thermal Desorption. Thermal desorption is an innovative treatment that has been appHed primarily to soils. Wastes are heated to temperatures of 200 to 600°C to increase the volatilization of organic contaminants. Volatilized organics in the gas stream are removed by a variety of methods including incineration, carbon adsorption, and chemical reduction. 

The value of r can be estimated as that of saturated liquid at the same temperature or related to supercritical properties at temperatures above critical. Critoph [2] found that for the practical purposes of modelling ammonia - carbon adsorption cycles, using experimentally determined porosity data, that the complexity of estimating both r and p at sub and supercritical levels was not justified. The measured porosity data could be fitted to a much simpler version of the equation with no loss of accuracy, as follows ... 

Engineering Considerations To effect the good engineering design of an activated carbon adsorption system, it is first necessary to obtain information on the following the actual cubic feet per minute (ACFM) of air to be processed by the adsorber, the temperature of gas stream, the material(s) to be absorbed, the concentration of the material to be adsorbed, and if the intended application is air pollution control such as odor control - then the odor threshold of the material to be adsorbed. In addition, data is needed on the presence of other constituents in the gas stream, and whether or not solvent recovery is economical. 

From an isotherm test it can be determined whether a particular organic material can be removed effectively. It will also show the approximate capacity of the carbon for the application and provide a rough estimate of the carbon dosage required. Isotherm tests also afford a convenient means of studying the effects of pH and temperature on adsorption. Isotherms put a large amount of data into concise form for ready evaluation and interpretation. Isotherms obtained under identical conditions using the same contaminated groundwater for two or more carbons can be quickly and conveniently compared to determine the relative merits of the carbons. 

The pore size distribution in highly activated carbon HSGD measured with low temperature nitrogen adsorption shows absence of the curve maximum in the range of 75-900 A (Fig. 29.6). In comparison with the pore distribution of SCN hemosorbent, HSGD has predominantly meso- and small macroporous structure, with some... 

Fig. 23. 75.4-MHz 13C MAS spectra of 2-bromopropane-2-13Creacting on Lewis superacids AlBr3 and SbF5. Spectrum a shows the formation of an adsorption complex (89 ppm for C2 and 29 ppm for the methyl carbons) with AlBr3 at 298 K. Note that 13C label scrambling from C2 to Q is complete in the adsorption complex as indicated by the 2 1 intensity ratio of the 29 ppm to 89 ppm peaks. Spectrum b shows a completely 13C scrambled isopropyl cation (320 and 52 ppm) and a partially 13C scrambled adsorption complex with SbF5 (92 and 26 ppm) at 233 K. (c) Upon raising the temperature, the adsorption complex was completely converted to the isopropyl cation.

The introduction of hydrogen at 100 torr on solid C produced an increase of the oh bands, which are now well resolved (3640-3540 cm-1) (Figure 5). The intensity of these bands increased slowly with the time the maximum value was reached after 6 hours at the same time, the water formation was detected by its 5h2o band at 1640 cm 1. After evacuation of hydrogen at room temperature, the adsorption of carbon monoxide generated bands at 2135, 2110, 2100, 1935, and 1895 cm 1. The last three bands were pressure dependent. Evacuation at 25 °C produced a partial removal of the 2100 cm 1 band, and the 1935-1895 cm-1 bands dis-... 

The equilibration time for the adsorption in some microporous materials, like CMS and carbonized chars, may be extremely long that may be a source of error for the evaluation of microporosity. For example, this occurs for N2 at 77 K in samples with narrow microporosity (size below 0.7 nm), where the size of the adsorbate molecule is similar to the size of the pore entrance. In this case, contrary to the exothermic nature of the adsorption process, an increase in the temperature of adsorption leads to an increase in the amount adsorbed. In this so-called activated diffusion process, the molecules will have insufficient kinetic energy, and the number of molecules entering the pores during the adsorption equilibrium time will increase with temperature [9,23],... 

Setoyama N, Kaneko K, and Rodrfguez-Reinoso F. Ultramicropore characterization of microporous carbons by low temperature helium adsorption. J. Phys. Chem., 1996 100(24) 10331-10336. 

In Table 1 we list the sum of the specific surfaces of the macropores and transition pores and also the specific surfaces obtained by low temperature nitrogen adsorption and by adsorption of carbon dioxide at room temperatures. The nitrogen and carbon dioxide specific surfaces are taken from the PSOC data bank, except for coal PSOC 105. Since the specific surfaces in the data bank for this coal appeared questionable, they were remeasured by R. G. Jenkins at Pennsylvania State University. 

In view of the above points, the first choice was titanium dioxide powder, and then the various partially graphitized carbon blacks. Titanium dioxide is a nonporous material which can be obtained with a high specific surface area, and has been the object of considerable study (9, 14, 18, 29), so that not only is it known that reproducible and precise surface areas can be obtained by low temperature gas adsorption, but, in addition, the heats and entropies of adsorption by nitrogen and other gases are known. The same may be said of various carbon blacks (9, II, 17, 21, 25). These are prepared by various types of pyrolytic decomposition of... 

In view of the difference of a factor of 10 or more in peak delay between butene and thiophene at similar temperatures, butene adsorption was checked to see that chemisorption was in fact occurring below 200° C. Using the 50-foot propylene carbonate column, it was found that some butane was formed in spite of the H2S present down to 150° C. (without H2S butene was almost completely hydrogenated at this temperature) and both cis-trans and double bond isomerization of the butenes went to completion at temperatures below 100° C., indicating that chemisorption of butene must have occurred. It is therefore felt that extrapolation of the butene sorption results obtained to the temperature range of the desulfurization reaction (above 200° C.) should be valid. 

Equilibrium capacity for adsorption of organic solutes on carbon can be predicted to increase with decreasing temperature since adsorption reactions are exothermic. The differential heat of adsorption, AH, is defined as the total amount of heat evolved in the adsorption of a definite quantity of solute on an adsorbent. Heats of vapor phase adsorption... 

The estimate of the surface area of chromatographic silica support is a complicated issue. It is usually performed via the BET method using low temperature nitrogen adsorption (N2.- sorptometry). The total surface area of the adsorbent is the product of the number of adsorbed molecules and the surface area per molecule. However, if the pore size distribution is not very narrow, an estimate of bonding density on the basis of carbon load and surface area may yield a large error because the smallest pores are not available for derivatization and the calculated bonding density is lower than the actual one. 

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