Improvement of the methanol-to-hydrocarbons catalytic performance for one-dimensional zeolites obtained by post-synthetic modifications

Abstract

The relatively short lifetime of unidimensional 10-ring zeolite catalysts in the methanol to hydrocarbons reaction is improved by a factor of ~20 by introducing mesoporosity in the zeolites via sequential desilication and acid post-synthetic treatments. The catalytic selective production of high quality low-aromatics gasoline precursors is improved. By using two morphologically distinct starting ZSM-22 samples and three desilication methods, the study concludes that the conditions of the treatment need to be adjusted depending on the properties of the starting material in order to produce more efficient MTH catalysts. Particularly, the parent zeolite morphology is the most influential parameter for the mesopore generation. The influence of the starting material on the change in the catalyst properties (composition, acidity, porosity) is also reflected in the catalytic improvement, which is explained based on a more efficient use of the hierarchical catalyst crystal, allowing longer operation of the alkene cycle during MTH. Operando XRD experiments provided insights into the ZSM-22 deactivation mechanism as a function of the applied post-synthetic method and co-feeding experiments.