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Transformations of alkyl aromatics over delaminated MCM-22 zeolites and their composites with mesoporous MCM-41 silicate

Paper ID Volume ID Publish Year Pages File Format Full-Text
41742 45899 2011 12 PDF Available
Title
Transformations of alkyl aromatics over delaminated MCM-22 zeolites and their composites with mesoporous MCM-41 silicate
Abstract

Small (S)- and large (L)-crystalline zeolite MCM-22 precursors with the same Si/AlF ratio of 17, were synthesized and either converted to zeolites MCM-22(S/L) or delaminated. From the delaminated zeolite MCM-22 precursors delaminated zeolites MCM-22 (dl-MCM-22(S/L)) were prepared. Delaminated zeolite precursors were admixed to the synthesis mixture of mesoporous silica MCM-41 to obtain the respective dl-MCM-22/MCM-41(S/L) composite materials. The preparations were characterized by XRD, N2 adsorption measurements, scanning electron microscopy. FT-IR spectroscopic studies of pyridine (Py) and 2,4-dimethylquinoline (2,4-DMQ) adsorption were used for determination of total (Brønsted and Lewis acidity) and external Brønsted acidity, respectively. It was found that the crystallite size of the MCM-22 precursors strongly influenced the structural, acidic and catalytic properties of the delaminated and composite materials. The effectiveness of the delamination procedure for the zeolite MCM-22(S) precursor having smaller and thinner particles is higher. At same synthesis gel compositions, the amount of mesoporous fraction in the composite materials was different. In dl-MCM-22/MCM-41(S) composite the formation of the mesoporous component was suppressed. Moreover, delamination resulted, for both delaminated and composite materials, in a similar decrease in the Brønsted acidity.The reduction in toluene disproportionation activity confirmed the above structural and acidity changes. 2,4-DMQ adsorption results proved that both the dl-MCM-22 samples and the composites possess higher amount of external Brønsted acid sites than zeolite MCM-22. The enhanced external acidity and accessibility of the active sites of these preparations appeared favorable when more basic and bulkier reactant, such as 1,2,4-trimethylbenzene was transformed.

Graphical abstract.Figure optionsDownload full-size imageDownload high-quality image (108 K)Download as PowerPoint slideResearch highlights▶ The crystallite size of zeolite MCM-22 precursor is crucial for the effectiveness of its delamination and insertion in a composite with MCM-41. ▶ The lamellae structuring defines the acidity and catalytic performance of the delaminated and composite materials. ▶ Delamination and preparation of composites consisting of zeolite MCM-22 and MCM-41 silicate are beneficial for catalytic transformations of more basic and bulkier alkylaromatic reactants.

Keywords
Small- and large-crystalline MCM-22; Delaminated MCM-22; MCM-22/Si-MCM-41 composite; Toluene disproportionation; 1,2,4-Trimethylbenzene transformation
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Transformations of alkyl aromatics over delaminated MCM-22 zeolites and their composites with mesoporous MCM-41 silicate
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 393, Issues 1–2, 15 February 2011, Pages 59–70
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us