Evidence of Preferential\nAluminum Site Loss during\nReaction-Induced Dealumination

Understanding the\nmechanism of steam-induced dealumination\nof\nzeolite catalysts is of high relevance for tuning their performance\nand stability in multiple industrial processes. A combination of <sup>27</sup>Al and <sup>1</sup>H–<sup>1</sup>H double-quantum\nsingle-quantum magic angle spinning nuclear magnetic resonance and\ndiffuse-reflectance ultraviolet–visible spectroscopies identified\na preferential dealumination of tetrahedral aluminum sites in H-ZSM-5\nzeolites. Framework aluminum atoms facing channels display reactivity\ntoward steam higher than that of those in their intersections. Dealumination\nrandomly occurs on isolated and proximate sites. However, the concentration\nof the latter sites decays more prominently. These findings contribute\nto a better understanding of the stability of zeolite catalysts in\nthe presence of steam.