fulltext.study @t Gmail

Ammoxidation of ethylene over low and over-exchanged Cr–ZSM-5 catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
41149 45878 2012 9 PDF Available
Title
Ammoxidation of ethylene over low and over-exchanged Cr–ZSM-5 catalysts
Abstract

Catalytic performances of Cr–ZSM-5 catalysts (5 wt.% of Cr, Si/Al = 26), prepared by solid-state reaction and aqueous exchange, from Cr nitrate and Cr acetate precursors, were evaluated in the selective ammoxidation of ethylene into acetonitrile in the temperature range 425–500 °C. Catalysts were characterized by chemical and thermal analysis, XRD, N2 physisorption, 27Al MAS NMR, TEM, UV–vis DRS, Raman, DRIFTS and H2-TPR. Characterization results shown that solid-state exchange was favorable for Cr2O3 formation, while exchanging chromium in aqueous phase led, essentially, to Cr(VI) species. Catalysts were actives and selectives in the studied reaction, and among them, those, prepared from aqueous exchange, exhibited the highest acetonitrile yields (23 ± 0.5%, at 500 °C). Improved catalytic properties can be correlated with the chromium species nature. In fact, mono/di-chromates and/or polychromate species, sited in the charge compensation positions, were definitively shown, as being, the active sites. Furthermore, during solid-state reaction, the agglomeration of Cr2O3 oxide should be avoided since these species inhibit the catalyst activity.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (148 K)Download as PowerPoint slideHighlights► Cr–ZSM-5 solids were tested in the ammoxidation of ethylene into acetonitrile. ► Cr(VI) ions and Cr(III) oxide species coexist. ► Solid-state exchange is favorable for Cr2O3 formation. ► Aqueous exchange catalysts showed better catalytic performances. ► Cr(VI) species are actives in the ammoxidation, while Cr2O3 oxide should be avoided.

Keywords
Cr–ZSM-5; Ammoxidation; Acetonitrile; Solid-state exchange; Aqueous exchange
First Page Preview
Ammoxidation of ethylene over low and over-exchanged Cr–ZSM-5 catalysts
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
Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volumes 415–416, 16 February 2012, Pages 132–140
Authors
, , , , , ,
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