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Methanol to gasoline over zeolite H-ZSM-5: Improved catalyst performance by treatment with NaOH

Paper ID Volume ID Publish Year Pages File Format Full-Text
43323 45964 2008 8 PDF Available
Title
Methanol to gasoline over zeolite H-ZSM-5: Improved catalyst performance by treatment with NaOH
Abstract

This work outlines how treatment of zeolite H-ZSM-5 (Si/Al = 46) with NaOH may improve the catalytic performance in the conversion of methanol to gasoline. The zeolite was treated with 0.05 or 0.20 M NaOH solution for 2× 4 h at 75 °C. XRD confirmed the retention of crystallinity. The Si/Al ratio of the catalyst decreased as a consequence of the treatment, in particular for the more severely treated sample, but the total acidity determined by NH3-TPD was not altered, showing that the treated samples contain significant amounts of Al not giving rise to acidity. The BET surface area increased from 313 to 419 m2/g as a consequence of the desilication, and the N2 adsorption measurements indicated mesopore generation. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) indicated presence of Lewis acidity in the treated samples. Methanol conversion was carried out in a fixed bed reactor at 370 °C and WHSV = 8 g g−1 h−1. The catalyst lifetime, quantified as the total conversion capacity, increased by a factor of 3.3 as a consequence of the most severe treatment. The procedure led to a moderate increase in the initial activities. Further, the product selectivities were altered dramatically. The selectivity towards the gasoline fraction (C5+) was at best increased by a factor of 1.7. Hydrogen transfer reactions became faster and led to more aromatic and paraffinic compounds in the products. Increases in the propene/ethene ratios were observed at moderate conversion. The results are well rationalized by alterations of acidic properties, mesopore formation, and improved diffusivity.

Graphical abstractThe catalytic performance of alkaline-treated zeolite H-ZSM-5 in the conversion of methanol to gasoline has been studied. After treatment with 0.20 M NaOH, the total conversion capacity increased by a factor of 3.3, and the selectivity towards the gasoline fraction increased by a factor of 1.7. Physical characterization indicated the formation of mesopores and improved crystallinity. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Zeolite; Methanol; ZSM-5; Desilication; Post-synthesis; Methanol to gasoline (MTG); Methanol to hydrocarbons (MTH)
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Methanol to gasoline over zeolite H-ZSM-5: Improved catalyst performance by treatment with NaOH
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 345, Issue 1, 31 July 2008, Pages 43–50
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