Study of Fourier transform infrared-temperature-programmed desorption of benzene, toluene and ethylbenzene from H-ZSM-5 and H-Beta zeolites

In the present study, an infrared (IR) high temperature cell was used, in combination with a Fourier transform infrared (FTIR) spectrometer for the development of an alternative temperature-programmed desorption (TPD) procedure. Three different adsorbates, i.e., benzene, toluene and ethylbenzene were non-isothermally desorbed from two zeolites H-ZSM-5 and H-Beta. The FTIR-TPD profiles were fitted with the help of the complementary error function. The fitting process was carried out with the help of a computer program which allows us to calculate two parameters, the temperature, T₀ (K) and the temperature range ΔT (K), which, in conjunction with the complementary error function, characterizes the FTIR-TPD profile. Was found that the parameter T₀ is linked with the adsorption energy of the adsorbate in the zeolite and the parameter ΔT was correlated with the transport process of the desorbed molecules inside the zeolites during the desorption process and with the presence of more than one type of adsorption sites. In conclusion, was confirmed that the FTIR-TPD methodology is appropriate for in situ observation of adsorbed molecules on zeolites, and that this technique makes available information concerning the adsorbed state of guest molecules in non-isothermal desorption.