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In-situ ATR-IR investigation of methylcinnamic acid adsorption and hydrogenation on Pd/Al2O3

Paper ID Volume ID Publish Year Pages File Format Full-Text
50963 46824 2012 5 PDF Available
Title
In-situ ATR-IR investigation of methylcinnamic acid adsorption and hydrogenation on Pd/Al2O3
Abstract

The adsorption and hydrogenation of C = C in α-methylcinnamic acid in dichloromethane over the concentration range 2–16 mM have been studied on Al2O3 and Pd/Al2O3 using in-situ attenuated total reflection infrared (ATR-IR) spectroscopy. For Al2O3, the spectra reveal that the acid adsorbs both molecularly and dissociatively, while for 1 wt.% Pd/Al2O3 only the latter is observed. In the case of molecular adsorption, C = O stretching vibrations arising from adsorbed monomer (1710 cm− 1) and dimer (1684 cm− 1) species were observed. In the case of dissociatively adsorbed carboxylate, the typical asymmetric (1522 cm− 1) and symmetric (1378 cm− 1) vibrations are observed. No changes in adsorbed species were observed in the presence of solution-phase H2 over alumina, whereas significant changes occurred for Pd/Al2O3. While bands associated with monomer/dimer and carboxylate species still persist on the surface in the presence of H2, new vibrational features associated with adsorbed product (i.e., α-methylhydrocinnamic acid) are detected. The results demonstrate that the product is strongly adsorbed under hydrogenation conditions, which likely influences the catalytic performance of this system.

► Acid adsorbs molecularly and dissociatively on Al2O3, but only dissociatively on Pd. ► Adsorbed monomer/dimer acid species and bridging bidentate carboxylate are observed. ► Hydrogenation product is strongly adsorbed on catalyst surface.

Keywords
Enantioselective hydrogenation; α-methylcinnamic acid; Pd/γ-Al2O3; ATR-IR; Heterogeneous catalyst
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In-situ ATR-IR investigation of methylcinnamic acid adsorption and hydrogenation on Pd/Al2O3
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Communications - Volume 17, 5 January 2012, Pages 13–17
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
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Any Questions? feel free to contact us