MCM-36 is a catalytically active material made by swelling and subsequent pillaring of a layered zeolite precursor, MCM-22(P). However, the swelling procedures lead to significant destruction of layer structure and alteration of framework silicon/aluminum (Si/Al) ratio, which are likely to influence the acidity and catalytic activity of the final materials. We report a milder swelling and pillaring process to prevent such structural destruction. The resulting pillared materials show higher crystallinity and improved retention of the zeolitic layer structure when compared to the ones prepared by the previously reported methods involving more aggressive treatments. Implications of such structural preservation on the physicochemical, acidic and catalytic properties of the materials have been investigated using a variety of characterization methods. The milder swelling results in catalytic materials with stronger acid sites and, at similar Si/Al ratios, higher acid site density and higher catalytic activity when compared to the MCM-36 materials produced using the previously reported more aggressive swelling process.
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We gratefully acknowledge Sandeep Kumar for the TEM images and Dr. Sonjong Hwang for the NMR spectra of the MCM-36 materials. We thank Professor Frank Bates for his input since the early stages of this work and Professor Aditya Bhan for suggestions during the writing of this manuscript. This work was made possible with the financial support from the NSF (CBET-0403574 (NIRT) and 0327811), and PROMETEO and Consolider from Generalitat Valenciana and Ministerio de Ciencia e Innovación. Parts of this work were carried out in the University of Minnesota I.T. Characterization facility, which receives partial support from the NSF through the NNIN program. M.T. Portilla gratefully acknowledges CSIC for JAE fellowship.
- Layered zeolites
- MWW zeolite
- Xylene isomerization