Adsorption of carbon dioxide

Farmer, V.C. (1975) Adsorption of carbon dioxide on goethite (a-FeOOH) surfaces, and its implications for anion adsorption. J. 

The adsorption of carbon dioxide or oxygen on praseodymium samples was measured by a constant-volume method using a calibrated Pirani vacuum gauge. Praseodymium oxide was heated in oxygen (4 kPa) at 775°C for 1 h, then evacuated at 750°C for 0.5 h just before the measurement. The sample of praseodymium oxychloride was prepared from praseodymium chloride by heating under oxygen flow... 

Adsorption of Carbon Dioxide and Oxygen on Praseodymium Samples. 

Adsorption of carbon dioxide or oxygen on the praseodymium samples was carried out in the pressure range of 1-40 Pa to evaluate the number of chemisorption sites on the samples. Praseodymium oxide irreversibly adsorbed 9.5 x 10" mol g of carbon dioxide. The amount of oxygen irreversibly adsorbed on the sample was 15.2 x 10" mol g Carbon dioxide or oxygen was not adsorbed on the samples containing chlorine, i.e., praseodymium chloride and praseodymium oxychloride prepared from the chloride by heating under oxygen flow at 750°C for 1 h. 

The Surface Properties of the Praseodymium Compound. Although the efficiency of catalysts in methane conversion has been ascribed to a variety of properties, a number of researchers have demonstrated the importance of basicity of the catalysts employed in this process (14-16). Thus estimates of basicity, such as may be obtained from the adsorption of carbon dioxide, are of some value in characterizing the catalysts. It is obvious that the surface state of a working catalyst at 750°C is different from that at room temperature. However, measurements of the adsorption of carbon dioxide at the latter temperature provide semiquantitative information on sites capable of donating electrons. 

No adsorption of carbon dioxide or oxygen was observed on either praseodymium chloride or oxychloride. This finding is consistent with the XPS results. The main peaks at 529 eV in the spectra for praseodymium oxychloride samples are also attributed to the lattice oxygen of the oxychloride while the peaks at 531 eV are assignable to O Is for praseodymium oxide, suggesting that the surfaces of the oxychloride samples are partially oxidized to praseodymium oxide. The 3d binding energy of 933 eV for praseodymium in the chloride and oxychloride implies that the valence of praseodymium is 3+, while the shoulder at 928 eV could be attributed to metallic praseodymium (77). 

To reduce to the simple rate Equation (2), it is necessary that some of the steps in the general scheme occur at a negligible or an extremely fast rate. It has been observed (37) that carbon monoxide gas is an immediate product of the chemisorption of carbon dioxide on carbon and that the adsorption of carbon dioxide is not reversible to give immediate desorption of carbon dioxide. Therefore, it may be assumed that the lives of CCCOs) and C(CO)x are short. Consequently, the general expressions can be simplified to... 

As for NiO (200), the adsorption of C02 does not change the electrical conductivity of the sample. On both oxides, the adsorption of carbon dioxide is mostly irreversible. 

Carbon dioxide adsorption causes changes in the sizes of all the zeolites studied similar to the variation observed for faujasite-type zeolites after water adsorption (Figure 6). For all zeolites, an increase in the adsorption of carbon dioxide leads to contraction this reached a minimum in the adsorption range 3-5.5 mM/gram. The final length of the pellets is below the initial value up to a relative pressure of p/ps 0.7 for zeolites CaA, CaY, and NaY while for NaA and NaX the contraction passes to an expansion, reaching 0.11% of the initial length at p/ps = 0.66 for NaX and 0.32 for NaA. 

Yong Z, Mata V, Rodrigues ArE (2002) Adsorption of carbon dioxide at high temperature—a review. Sep Purif Technol 26(2-3) 195-205... 

Figure 5. Relationship between the pressure at which maximum differential adsorption of carbon dioxide occurs and the mean pore diameter of activated carbons.

The carbon dioxide sorbent, calcium oxide, serves three functions in the process. First, the adsorption of carbon dioxide by calcium oxide to produce calcium carbonate is an exothermic chemical reaction that also delivers energy to the reforming reactions in the form of chemical potential energy. During the air regeneration step, the process of decomposing the calcium carbonate to calcium oxide largely absorbs heat released by oxidation of nickel, and... 

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. 

All of the differences between the specific surfaces obtained by adsorption and small-angle scattering therefore cannot be explained by the existence of pores with restricted entrances. Instead, since the specific surfaces from adsorption of carbon dioxide at room temperature are always much greater than those obtained from the scattering data, there must be a large number of pores for which smallest pore dimensions do not satisfy (4). 

Large E contributions were also reported by Barrer (1978, p. 188) for the adsorption of carbon dioxide, ammonia and water vapour on NaX. Indeed, in the case of water, over 90% of the low-coverage adsorption energy was attributed to tp. With these highly polar molecules it is likely that the cation-adsorbate interaction provides a major contribution to E. ... 

Ozdemir, E. (2004) Ph.D. thesis Chemistry of the adsorption of carbon dioxide by argorme premium coals and a model to simulate CO2 sequestration in coal seams. University of Pittsburg, Pittsburgh. 

Yong Z., Meta V. and Rodrigues A E., Adsorption of carbon dioxide onto hydrotalcite-like compounds (HTis) at high temperatures. Ind. Eng. Chem. Res. 40 (2001) pp. 204-209. 

Our experiments on the blocking of adsorption centers (i.e., zeolite cations) by preadsorbed water molecules serve to substantiate the physical meaning of Equation 9. For the adsorption of carbon dioxide on dehydrated crystals of zeolite NaX, 0 = 3470 cal/mole, n = 3, Goh = 2.90 mmole/gram, and 3 = 5200 cal/mole, the second term of Equation 9 expressing adsorption on active centers, which amount to 2.90 mmole/ gram. Water is adsorbed energetically on active centers (n = 4, 4 = 9150 cal/mole), and as a result of preadsorption of 3.5 mmole/gram of... 

The adsorption of carbon dioxide on DD3R amounts to 40.5 % of the adsorption on zeolite Na-A (7.62 wt% and 18.8 wt% respectively). It is dear that the preference of zeolite Na-A for adsorption of polarizable gases is larger than that of DD3R Charged frameworks as well as the presence of cations in the framework stmcture can induce dipoles within the adsorbate molecule, resulting in stronger interactions with the adsorbent. 

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