Regulation of Al Distribution in ITR Zeolites by Boron Modification to Enhance Catalytic Performance in Methanol to Propylene
ITR zeolites exhibited excellent performance in methanol to propylene (MTP), where an important factor was the Al distribution of the ITR zeolites. However, optimization of the Al location in ITR zeolites in the conventional synthesis is challenging. In this work, the Al distribution in the ITR zeolites was efficiently adjusted by adding boron species in the synthesis gels due to the competitive occupancy of T sites in zeolites between boron and aluminum species. The obtained ITR with different boron content zeolites displayed similar nanosheet morphology, textural parameters, and strong acidic concentration but characterizations of Al distribution showed that the addition of boron species led to more Al species distributed in a relatively small sinusoidal channel and less Al species located in an intersection cavity. As a result, the aromatic cycle would be effectively suppressed due to the steric configuration of large aromatic cycle intermediates, whereas the alkene cycle will be enhanced correspondingly. As expected, catalytic tests in the conversion of MTP showed that the new ITR zeolites exhibited enhanced propylene selectivity and catalyst lifetime with the incorporation of boron species, which was attributed to different Al distribution in these ITR zeolites.
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