Adsorption of cyclic amines on graphitized thermal carbon black

Thermodynamic characteristics of adsorption (TCA) for aniline and its methyl derivatives on the surface of graphitized thermal carbon black (GTC, Carbopack C HT trade mark) were determined using equilibrium gas adsorption chromatography in the range of the lowest adsorbate concentrations in the gas phase. A series of relationships relating the TCA of the studied amines to their physicochemical parameters was obtained. The theoretical values of entropy of adsorption were calculated in the framework of the model of two-dimensional ideal gas and compared with the corresponding experimental values, which allowed one to reveal specific features of the molecular structure of the adsorbates. A similarity between the thermal component of entropy of the studied compounds in the adsorbed state and that of the entropy of the pure liquid adsorbates made it possible to refine the physical state and mobility of the adsorbate molecules in the force field of the adsorbent. The regression equation relating the heats of adsorption on the GTC to such molecular constants of adsorbates as polarizability, molecular surface area, and molecular weight were proposed for the first time. A high predictive power of the equations derived in the work for the preliminary estimation of the adsorption characteristics of alkylanilines and alkylbenzenes on the GTC was shown.     

Adsorption of adamantanol isomers on graphitized thermal carbon black

The thermodynamic characteristics of adsorption of some adamantanol isomers on graphitized thermal carbon black were calculated and determined experimentally. The parameters of the potential function for the intermolecular interaction between hydroxyl oxygen and carbon of the graphite basis plane were determined for the first time. The adsorption properties of adamantanols are largely determined by electron density distribution in the adamantane cage, which are related to the cage effect.     

Gas chromatographic investigation of adsorption equilibria on graphitized thermal carbon black

Summary Retention volumes and heats of adsorption at low surface coverages of graphitized thermal carbon black (GTCB) for C₆–C₁₄ aromatic hydrocarbons have been determined. The dependence of heats of adsorption of these molecules on their structure and the number of carbon atoms in the molecule have been investigated. Substitution in the ring in methylbenzenes is not equivalent to the lengthening of the side-chain in the isomers of n-alkylbenzenes and gives rise to a much greater increase in the retention volumes and heats of adsorption.     

Adsorption behavior of Vulkan-7H graphitized carbon black

The adsorption behavior of Vulkan-7H carbon black graphitized at 3073 K was studied. Benzene adsorption isotherms at 293 K were measured by the static method and by gas chromatography. It was shown that Vulkan-7H carbon black may be considered as a supermicroporous adsorbent with a pore size of 1.05 nm.The sample was provided by N. N. Lezhnev.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1544–1546, September, 1993.     

Adsorption of benzyl alcohol and 1-phenylethanol on graphitized thermal carbon black

The adsorption of benzyl alcohol and 1-phenylethanol on graphitized thermal carbon black at 300 K is investigated. Thermodynamic characteristics of the adsorption of conformers stable in the gas phase and in the adsorbed state are determined by a molecular statistics method. The geometry of the molecules is optimized using the MP2 and B3LYP methods with a 6-311++G(d,p) basis set. Using the PBE0/6-31G(d) method, it is established that, in the adsorption of benzyl alcohol, two types of interactions, CH…O and OH…π_GTCB, occur. It is shown that, in 1-phenylethanol, intramolecular interactions are maintained.     

Adsorption equilibria of binary ethylmercaptan/hydrocarbon mixtures on a NaX zeolite

We present here coadsorption data of ethylmercaptan with n-heptane or toluene on NaX at 298 K in the aim to use this adsorbent for removing mercaptans from natural gas. Results show that NaX has an adsorption affinity for sulphur compound strong enough to perform a deep desulphurization. NaX adsorbs preferentially ethylmercaptan over a large domain of pore filling. A displacement of n-heptane by ethylmercaptan is even observed. However, toluene becomes preferentially adsorbed at high filling. The dependence of filling and composition on selectivities and failed prediction of coadsorption equilibria by the IAS Theory indicate that the adsorbed mixture behaves as a non-ideal solution. Calorimetric measurements of coadsorption heats show that the coadsorption process is not governed by enthalpic effects but by entropic effects consecutive to steric hindrance of molecules in confined spaces.     

Adsorption and separation of isomeric methyl- and dimethylaminoadamantanes on graphitized thermal carbon black

The thermodynamic characteristics of adsorption (TCA) of isomeric molecules of methyl- and dimethylaminoadamantanes on the surface of the basis face of graphite were determined experimentally and calculated by the molecular statistical method. A relationship between the geometric structure of adsorbate molecules and the values of their TCA on graphitized thermal carbon black was established. The data obtained were used for the gas chromatographic identification of the amination products of a mixture of Z,E-isomers of 1,4-dimethyladamantane and 1,3-dimethyladamantane.     

Adsorption of n-alkanes on a graphitized carbon black and its activation products in dry air

Summary Adsorption of n-alkanes (n-heptane to n-decane) on a graphitized carbon black and its activation products in dry air was carried out by a gas chromatographic technique. Adsorption runs were performed at finite surface coverage, to obtain the surface area and the London component of the surface free energy of the solids from the adsorption isotherms. On the other hand, the adsorption of n-alkanes carried out at zero surface coverage gave the differential heats of adsorption. The results show that, after the activation in dry air of the graphitized carbon black used, the surface area has a linear relationship with the degree of activation, whereas the surface heterogeneity changes in a parabolic fashion.     

Adsorption of isomeric aryl- and diadamantane molecules on the surface of graphitized thermal carbon black

The thermodynamic characteristics of adsorption of isomeric molecules of 1,1??-, 1,2??-, and 2,2??-diadamantanes, 1- and 2-phenyladamantanes, and 1-cyclohexyladamantane on the surface of graphitized thermal carbon black (GTC) were experimentally determined. The influence of the molecular structure of adsorbates on their adsorption on the basis face of graphite was considered. A high selectivity of the GTC surface for the gas chromatographic separation of mixtures of the considered structural isomers was shown.     

Adsorption of molecules of different structure on graphitized thermal carbon black IV. Gas chromatographic investigation of adsorption of aldehydes,ketones and alcohols on hydrogen-treated graphitized thermal carbon black

Summary Retention volumes (Henry constants) and differential molar change of internal energy at low surface coverages on hydrogen-treated graphitized thermal carbon black (HTGTCG) for aldehydes, ketones and alcohols have been determined. An additional hydrogen treatment of graphitized thermal carbon black at 1000°C (GTCB) was undertaken to remove chemical inhomogeneity of the surface. After this treatment the peaks of oxygenated hydrocarbon derivatives became more symmetrical. Reduction of retention volumes after this treatment was observed only for substances with short hydrocarbon chains. The dependence during adsorption on the structure of, and number of carbon atoms in, aldehydes, ketones and alcohols has been investigated. The Kovats' indices for the chromatography on HTGTCB were obtained and used for identification.     

Liquid-liquid-vapor phase equilibria behavior of certain binary carbon dioxide + n-alkylbenzene mixtures

The liquid-liquid-vapor loci for the binary mixtures CO₂ + n-hexylbenzene, n-heptylbenzene, and n-octylbenzene were experimentally studied. The compositions and molar volumes of the liquid phases are reported along with the pressure and temperature. For these three alkylbenzenes, the nature of the liquid-liquid-vapor loci experiences a transition, with the CO₂ + n-heptylbenzene mixture exhibiting two separate liquid-liquid-vapor branches.     

Vapor-liquid equilibria for binary mixtures of carbon dioxide and fatty acid ethyl esters

Vapor-liquid equilibria were measured and correlated using the Peng-Robinson equation of state for five binary systems of carbon dioxide and fatty acid ethyl esters (ethyl stearate, ethyl oleate, ethyl linoleate, ethyl eicosapentanoate, ethyl docosahexanoate) at 313.15 K, 323.15 K and 333.15 K. Solubility in CO₂ of fatty acid ethyl esters of equal chain length but of various degrees of unsaturation was compared. Although there was no distinct difference in solubility at lower pressures, at higher pressures (more than 15 MPa), those with a higher degree of unsaturation showed a slightly higher solubility. When the solubility in CO₂ of methyl esters and the corresponding ethyl esters were compared, it was noted that the former showed a slightly higher solubility at all system pressures measured in this work.