fulltext.study @t Gmail

Deactivation mechanism of Pd supported on ordered and non-ordered mesoporous silica in the direct H2O2 synthesis using CO2-expanded methanol

Paper ID Volume ID Publish Year Pages File Format Full-Text
55627 47059 2012 8 PDF Available
Title
Deactivation mechanism of Pd supported on ordered and non-ordered mesoporous silica in the direct H2O2 synthesis using CO2-expanded methanol
Abstract

The deactivation mechanism of Pd supported on silica and mesoporous silica (SBA-15) using CO2-expanded methanol as solvent was studied in the direct synthesis of H2O2 in batch and semi-continuous batch reactor tests as well as its hydrogenolysis. Fresh and used catalysts were characterized by TPR and CO chemisorption. The results evidence the presence of deactivation, which can be correlated to the loss of accessible active metal surface area due to sintering of Pd, but there is also an effect of the presence of the ordered mesoporous structure and of the reaction conditions. The higher concentration of H2 in solution in semi-continuous batch reactor tests with respect to batch reactor tests leads to a more relevant deactivation in Pd-SiO2 with respect to Pd-SBA-15, but a higher initial activity, due to the fact that H2 accelerates the reduction of the Pd species which are less reducible in Pd-SiO2 than in Pd-SBA-15. Pd-SBA-15 shows a higher H2O2 selectivity and productivity with respect to Pd-SiO2 in batch reactor tests, related to the presence of easier reducible Pd species. Another difference is related to the different mechanism of sintering. On the SBA-15 support, due to the presence of the ordered mesoporosity, the Pd particles migrate into the SBA-15 channels forming elongated 1D-type particles. In Pd-SiO2 catalyst, instead, the sintering of the Pd particles leads to large aggregates of Pd particles in the range of 20–25 nm.

Graphical abstractThe deactivation mechanism of Pd supported on silica and mesoporous silica (SBA-15) using CO2-expanded methanol as solvent was studied in the direct synthesis of H2O2 in batch and semi-continuous batch reactor tests as well as its hydrogenolysis. The results will be discussed in terms of catalysts deactivation correlated to the loss of accessible active metal surface area of Pd particles due to sintering which is different on the two silica supports.Figure optionsDownload full-size imageDownload high-quality image (215 K)Download as PowerPoint slide

Keywords
H2O2; Palladium; Silica; SBA-15; Deactivation; CO2-expanded methanol
First Page Preview
Deactivation mechanism of Pd supported on ordered and non-ordered mesoporous silica in the direct H2O2 synthesis using CO2-expanded methanol
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: Catalysis Today - Volume 179, Issue 1, 5 January 2012, Pages 170–177
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