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Synthesize 2-methylpyrazine using aqueous glycerol and ethylenediamine over zinc oxide–zinc chromite catalysts: Structure–activity relationship

Paper ID Volume ID Publish Year Pages File Format Full-Text
40779 45865 2012 11 PDF Available
Title
Synthesize 2-methylpyrazine using aqueous glycerol and ethylenediamine over zinc oxide–zinc chromite catalysts: Structure–activity relationship
Abstract

ZnO–ZnCr2O4 mixed oxides (Zn–Cr–O) were obtained by decomposition of Zn–Cr hydrotalcite precursors synthesized by co-precipitation method at pH ∼ 7 and 9, with a constant Zn/Cr ratio of 2. Based on the product distribution, mechanisms were proposed. The differences in dehydrocyclization activity of Zn–Cr–O mixed oxides were established based on adsorption and spectroscopic data that emphasized changes in the structural properties of Zn–Cr–O obtained at different pHs. X-ray photoelectron (XPS) lines indicated Cr6+ and these species were reduced to Cr3+ during H2-temperature programmed reduction (H2-TPR) analysis. The higher NH3 and O2 uptakes of Zn–Cr–O (pH ∼ 7) than Zn–Cr–O (pH ∼ 9) are attributed to the presence of Cr6+ ions on the catalyst surface. Disorder in the cubic ZnCr2O4 sub-lattice may result in multiple Raman bands appeared in the Zn–Cr–O samples. The characteristic bands of Lewis and Bronsted acid sites at 1450 and 1540 cm−1 assigned by FT-IR spectra of pyridine adsorbed on Zn–Cr–O samples, and their relative peak intensities corresponding to Lewis and Bronsted suggested higher ratios for Zn–Cr–O (pH ∼ 7) than for Zn–Cr–O (pH ∼ 9). It is demonstrated that the dehydrocyclization reaction proceeds on ZnO and/or ZnCr2O4 resulting in 2MP synthesis, and catalysts that possess mainly acid sites show intermolecular cyclization of EDA leading to high selectivity of pyrazine.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (92 K)Download as PowerPoint slideHighlights► Dehydrocyclization of EDA and glycerol produce 2-methylpyrazine over ZnO–ZnCr2O4. ► Nature of ZnO–ZnCr2O4 plays an important role on selectivity of 2MP and pyrazine. ► Intermolecular cyclization of EDA is predominant over crystalline Cr2O3.

Keywords
Dehydrocyclization; 2-Methylpyrazine; Raman; NH3 uptake; UV–DRS
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Synthesize 2-methylpyrazine using aqueous glycerol and ethylenediamine over zinc oxide–zinc chromite catalysts: Structure–activity relationship
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volumes 441–442, 28 October 2012, Pages 108–118
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