Use of CONTIN for calculation of adsorption energy distribution

The CONTIN method for in inverting noisy linear operators was used to calcu late the adsorption distribution function from both simulated and experimen tal adsorption isotherms. Simulated isotherms allowed us to estimate the re solving power of the method and the influence of errors on the distribution function, while experimental isotherms enabled us to validate the adsorpti on model and its parameters. It was shown that calculation within the conde nsation approximation region gives perfect recovering of the original distr ibution if sufficient information is inherent in the input data, that is, i n the case of a large data set over a wide range of relative pressures. Whe n only a window of data is available on the adsorption isotherm, it is poss ible to calculate the distribution restricted to the condensation approxima tion (CA) region. The influence of peaks outside the CA region may be elimi nated by introducing the constant background term in the calculation. The l evel of error on the isotherm does not affect the resulting distribution up to 10% in the case of a large data set and up to 5% in the case of a small data set. On the basis of analysis of the randomness of the residuals of t he fit to the data, it was possible to establish a true parameter of the la teral interaction constant. This approach applied to experimental data has led to the value k(1)(mob) = 5.5-5.6 for the HdB mobile adsorption model an d k(1)(loc) = 3 for the FG localized adsorption model. On the basis of the fact that optimal value of k(1)(mob) is closer to the theoretical value, th e mobile adsorption model is preferred. The CONTIN method applied to graphi tized carbon black revealed four peaks on the adsorption energy distributio n function. The peak constrained analysis allowed us to confirm the existen ce of all original peaks. The distributions calculated from standard nitrog en adsorption data showed that although reference carbons are heterogeneous in different ways, they possess common peaks at 4.9, 6.8, and 8.8 kJ/mol c haracteristic to graphitized carbon black Sterling FT. Analysis of the hete rogeneity of synthetic carbons revealed the changes in adsorption energy di stributions (AEDs) that occur during CVD from methane.