CHARACTERIZATION OF SURFACE ACIDIC STRENGTH FOR SOLID ACID CATALYST THROUGH TEMPERATURE PROGRAMMED DESORPTION

The surface acidic strength for solid acid catalyst was characterized through temperature programmed desorption.Based on determination of the kinetic model equation of TPD,a new simulation method used to characterize the surface acid strength was developed by using one group of TPD experimental data.The results of simulation for the TPD data with one desorption peak or two desorption peaks indicated that the desorption activation energies of solid acid catalysts were correspond to the temperatures of desorption peaks.Based on the desorption kinetic model,the characterization of catalyst surface acidic strength was developed from qualitative characterization of desorption peak temperature to mathematical characterization of desorption activation energy.The kinetic parameters for TPD model were determined through n-propylamine TPD experiment and model parameter estimation.The simulation results of TPD data obtained from the catalysts activated under different temperature showed that the acid strength of the catalyst changed from rise to drop with the rise of catalyst activation temperature and reached maximum at 350℃.Compared with kinetic model of many groups of desorption peak temperatures at different TPD heating rates,the kinetic model of one group of TPD data was simpler and more reliable to determine the desorption activation energy of solid acid catalyst.