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Oxidative coupling of methane over unsupported and alumina-supported samaria catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
40474 45855 2013 15 PDF Available
Title
Oxidative coupling of methane over unsupported and alumina-supported samaria catalysts
Abstract

Being the shortest unsaturated hydrocarbon, ethylene is a valuable feedstock gas for synthesizing longer chain hydrocarbon products. Using the oxidative coupling of methane to produce ethylene and ethane (C2 products) has been studied extensively over the past few decades. In this work, samaria nanoparticles (NPs) and alumina-supported samaria catalysts were prepared using different methods (water/toluene reverse microemulsion, metal-oleate high temperature decomposition, and incipient-wetness impregnation followed by calcination) and various types of alumina supports (high and low surface area nanoparticle alumina [n-Al2O3(+), n-Al2O3(−)] and a porous gamma alumina support [p-Al2O3]). The highest product yields were obtained over Sm2O3 NPs synthesized using the metal-oleate high temperature decomposition and a nitrate precursor. Using a chloride precursor in the preparation of the Sm2O3 NPs resulted in less active and selective catalysts, and should be avoided. While the C2 selectivities were lower over the Sm2O3/Al2O3 catalysts, the yield per gram of Sm2O3 were higher compared with the Sm2O3 NPs. The best supported catalyst was the Sm2O3/n-Al2O3(−) prepared using incipient wetness impregnation of a nitrate precursor, since this leads to the smallest Sm2O3 particles as well as the largest coverage of the acidic Al2O3 support. XRD analysis revealed that high-temperature calcinations form SmAlO3 on the Al2O3-supported catalysts. While this reduced the near surface Sm2O3 concentration, it had beneficial effects as it also lowered the Al2O3 content. Therefore, Al2O3-supported Sm2O3 warrants further investigation, as surface modifications of the Al2O3 can reduce its acidity and lead to higher C2 selectivities in the oxidative coupling of methane over these catalysts.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (115 K)Download as PowerPoint slideHighlights► Smallest Sm2O3 nanoparticles yield highest OCM activity per unit weight of catalyst. ► Incipient wetness impregnation using Sm(NO3)3 best method for Sm2O3/Al2O3. ► Sm2O3/n-Al2O3(−)-IM produces the highest yield at 5.6% for supported catalysts. ► Yield per gram of Sm2O3 is higher for Sm2O3/n-Al2O3(−) than Sm2O3 NPs.

Keywords
Samarium oxide nanoparticles; Alumina-supported samaria; Methane coupling activity and selectivity; XRD; XPS
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Oxidative coupling of methane over unsupported and alumina-supported samaria catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 454, 15 March 2013, Pages 100–114
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