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How to increase the selectivity of Pd-based catalyst in alkynol hydrogenation: Effect of second metal

Paper ID Volume ID Publish Year Pages File Format Full-Text
39687 45831 2014 8 PDF Available
Title
How to increase the selectivity of Pd-based catalyst in alkynol hydrogenation: Effect of second metal
Abstract

•We developed a Pd-based catalyst for industrial hydrogenation of C20-alkynol.•The first step comprised a modification of Pd nanoparticles (NPs) with Ag or Cu.•Bimetallic nanocatalysts showed superior selectivity to alkenol than unmodified Pd.•On the second step, the NPs were deposited on the structured ZnO-coated support.•The developed catalyst demonstrated high selectivity to alkenol (96%) and stable activity.

The development of selective Pd-based catalyst for semi-hydrogenation of dehydroisophytol (DIP), a C20-alkynol, is reported. A series of unsupported mono- (Pd) and bimetallic (Pd-M) nanoparticles (NPs) with Pd/M molar ratios of 1.5 - 5.0 (M = Ag or Cu) were examined as model systems. The Pd-Ag and Pd-Cu NPs with controlled crystal sizes of ∼3.3 nm were prepared by Ag (Cu) electroless deposition on pre-formed poly(N-vinyl-2-pyrrolidone)-stabilized Pd0 colloids. Bimetallic Pd-Ag NPs adopted a core (Pd)-shell (Ag) structure whereas a mixed alloy was attained in the Pd-Cu nanocrystals. A (partial) Pd surface segregation induced by reaction with H2 was in evidence for the Pd-Ag NPs. A significant increase in selectivity up to 97% (at XDIP = 99%) to the target alkenol was demonstrated following the incorporation of a second metal. This result is attributed to the dilution of the surface Pd-sites by Ag (Cu) and a modification of the Pd electronic properties. Pd-Ag NPs, having shown the highest selectivity, were further deposited on a structured support based on sintered metal fibers (SMF) coated with ZnO. The improved selectivity achieved over the unsupported Pd-Ag colloidal NPs was retained over the structured catalytic system. The bimetallic Pd5.0Ag/ZnO/SMF (SIP = 93%) demonstrated a drastic increase in IP selectivity relative to the monometallic Pd/ZnO/SMF (SIP = 78%) and state-of-the-art Lindlar catalyst (SIP = 62%) at DIP conversion ≥99% with the stable activity during 50 h, suggesting catalyst feasibility for selective semi-hydrogenation of long chain alkynols with important applications in the manufacture of vitamins and fine chemicals.

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Keywords
Partial hydrogenation; Dehydroisophytol; Isophytol; Pd nanoparticles; Sintered metal fibers; ZnO; Pd-Cu; Pd-Ag
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 478, 20 May 2014, Pages 186–193
Authors
, , , , ,
Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
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Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us