Organotemplate-free, seed-directed, and rapid synthesis of Al-rich zeolite MTT with improved catalytic performance in isomerization of m-xylene

•MTT zeolite has been synthesized via the seed-directed and organotemplate-free route.•Seed-directed and organotemplate-free synthesis has very fast crystallization rate.•The Al-rich MTT zeolites contain stable aluminum species in the framework.•The Al-rich MTT zeolites show superior catalytic activity in m-xylene isomerization.

m-xylene isomerization over zeolites is of great importance because of the shortage of p-xylene currently. Here, we show an organotemplate-free, seed-directed, and rapid synthesis of Al-rich zeolite MTT (denoted as ZJM-6) with improved catalytic performance in isomerization of m-xylene to p-xylene. Physicochemical characterizations including XRD, SEM, Ar sorption isotherms, 27Al NMR, and NH3-TPD show that the zeolitic product has good crystallinity, uniform crystals, high surface area, tetrahedral Al3+ species, and abundant acidic sites. Interestingly, the crystallization of ZJM-6 takes very short time (5 h at 170 °C), compared with conventional MTT zeolites (20 h at 170 °C). Very importantly, catalytic tests for m-xylene isomerization show that H-form of ZJM-6 zeolite exhibits superior performance, which could be potentially important for industrial applications of ZJM-6 zeolite as a candidate in the future.

Graphical abstractAn organotemplate-free, seed-directed, and rapid synthesis of Al-rich MTT zeolite designated as ZJM-6 has been demonstrated. Catalytic tests in m-xylene isomerization show that H-form of ZJM-6 exhibits much higher activity than conventional ZSM-23 zeolite synthesized in the presence of organic template.Figure optionsDownload full-size imageDownload as PowerPoint slide