No abstract

No abstract

In this work, carbon xerogels with a high pore volume and surface area (up to 2.58 cm 3 /g and 3200 m 2 /g respectively) have been synthesized using the sol-gel polycondensation of resorcinol (R) with formaldehyde (F) in a basic medium of monoethanolamine (MEA), followed by drying and pyrolysis. This medium (MEA) has not been used in previous investigations. The effect of activation with CO 2 on the pore size distribution and the chemical functional groups has been investigated using N 2 (77 K) adsorption, FTIR and elemental analysis techniques. A series of experiments has been conducted to investigate the effect of activation time and activation temperature. Activation of the samples was carried out at 850, 900 and 980°C for times ranging from one to three hours. Within the range of activation conditions, an increase in activation time at 850°C results in a continuous steady rise of the BET surface area and total pore volume. However, at the two higher temperatures, the surface area shows a maximum when plotted against activation time. FT-IR results show that the use of MEA as a catalyst leads to the formation of nitrogen functional groups in the surface of the resin.

No abstract

A new method to determine binary adsorption isotherms from a set of binary chromatographic retention-time experiments is proposed. It differs from existing methods in two main ways. The first is that a functional form is assumed for the isotherms. The second is that it does not require supplementary measurements to be made. The isotherm parameters are found by a computer search. Any other available data may be incorporated into the method. The method is tested on retention-time data for the coadsorption of nitrogen and argon on 5A molecular sieves and of ethane and ethylene on 13X molecular sieves. Very precise experimental data are required if the isotherms are to be reconstructed solely from retention data.

No abstract

The polynomial-fitting method is used to determine the adsorption isotherms of binary gas mixtures. The method involves measuring retention times in a chromatographic column at different compositions; a polynomial is then fitted to a specific function of the retention time versus composition data. An algebraic expression can be obtained for each isotherm, with the coefficients depending on the polynomial coefficients. In this paper we examine the detailed working of the method assuming perfect experimental data is available. We use hypothetical systems that obey the binary-Langmuir theory. Starting with the hypothetical system, the set of retention times is calculated, and these are used in the polynomial-fitting method to estimate the binary isotherms. Comparison of the original and estimated isotherms allows a direct assessment of the precision of the method. The results show that the method is best suited to systems where both binary isotherms are close to linear.

No abstract