Preparation of hierarchical HZSM-5 zeolites with combined desilication with NaAlO/tetrapropylammonium hydroxide and acid modification for converting methanol to propylene.

In the present work, mesoporosity is introduced into highly siliceous HZSM-5 zeolites (SiO/AlO = 400) by a two-step path including desilication using NaAlO and TPAOH (tetrapropylammonium hydroxide) mixtures, followed by acid washing treatment. The physicochemical properties of conventional microporous HZSM-5 and all treated samples were characterized by ICP-OES, XRD, FE-SEM, BET and NH-TPD methods. The catalytic performance of the HZSM-5 samples was determined in methanol to propylene conversion reaction at 460 °C and methanol WHSV of 0.

Mesoporosity based classification of ZSM-5 nano catalysts using DRIFT spectroscopy and chemometrics.

DRIFT spectra were used for classification of ZSM-5 catalysts according to their mesopore volumes. The spectra were pretreated by Savitzky-Golay smoothing and standard normal variate (SNV) algorithms prior to outlier detection by Hotelling T statistic technique. Supervised classification was applied to the spectra using partial least squares-discriminant analysis (PLS-DA) and soft independent modelling of class analogies (SIMCA) algorithms.

Application of diffuse reflectance near-infrared spectrometry and chemometrics in characterization of micro and mesoporous ZSM-5 zeolites.

Evaluation of porosity type of zeolites is one of the critical topics in catalysis science. The relationship between external surface area and diffuse reflectance (DR) spectra in the near-infrared spectral region has been employed to propose a method for estimation of micro or mesoporosity in ZSM-5 zeolite samples. Linear discriminant analysis (LDA) was utilized to estimate degree of porosity based on near-infrared diffuse reflectance spectra.