Deactivation mechanisms and regeneration of a bimetallic hydrodechlorination catalyst

Heinrichs, Benoı̂t; Noville, Francis; Schoebrechts, Jean‐Paul; Pirard, Jean-Paul

doi:10.1016/s0167-2991(99)80492-3

Cited by 11 publications

(24 citation statements)

References 5 publications

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“…PA-0 and PA-150 showed particles within 4−5 nm of diameter, while more contribution of particles larger than 9 nm was observed in PA-150. Major mobility of the active phase with increasing of the Pd particle size has been reported for HDC reactions in acid media and has been attributed to possible formation of Pd−Cl species. , This behavior was not observed in the PA-0 sample, which has a similar Pd particle size as the other used catalyst samples. Moreover, the Pd−Cl species was not detected by XPS, vide infra.…”

Section: Resultsmentioning

confidence: 74%

The Effect of NaOH on the Liquid-Phase Hydrodechlorination of Dioxins over Pd/γ-Al₂O₃

2008

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The effect of sodium hydroxide on the-liquid phase hydrodechlorination (LPHDC) of polychlorinated dibenzo- p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) over 2% Pd/gamma-Al 2O 3 was evaluated. Reactions were carried out using 2-propanol both as a hydrogen donor and as a solvent. Fresh and used catalyst samples were characterized by BET, hydrogen chemisorption, TEM/EDS, XPS, and TPR. When the reaction mixture contained no NaOH, active-phase leaching and Pd-C formation were observed even after 10 min of reaction. Therefore, sodium hydroxide appears to be required to maintain surface metal clusters on the support and avoid binding of carbon species to the active metal. On the other hand, excess NaOH in the reaction mixture led to deposition of organic and inorganic solid residues on the catalyst surface, blocking the active sites. Under the conditions of this study, the addition of 30 mg of NaOH maintained the basicity of the system and diminished deposition of solid residues on the catalyst samples, and almost 100% detoxification was reached after a 3 h reaction.

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Section: Resultsmentioning

confidence: 74%

The Effect of NaOH on the Liquid-Phase Hydrodechlorination of Dioxins over Pd/γ-Al₂O₃

2008

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“…Cu and Pd can originate from ordered Cu 3 Pd, CuPd, or CuPd 3 phases below 900 K or disordered alloys over a wide range of composition at high temperatures. 13−22 To determine the surface composition of the alloyed nanoparticles formed in our study, we followed the procedure reported by Heinrichs et al 23 and Venezia et al 24,25 It is relevant to mention that we considered only Pd and Cu atoms present in alloyed particles in the calculation. In the mathematical developments, Pd atoms present in pure Pd particles were not considered.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Most investigations performed affirm that during the reduction process, Pd−Cu alloys are formed with Cu segregated onto the surface of the nanoparticles, 2,13,23,24,27,28 which is related to the lower surface free energy of Cu, the exothermicity of the Pd−Cu alloy formation process, and the strain resulting from the difference in the atomic radii of Cu and Pd. It has also been reported that the degree of surface segregation of Cu depends on the Cu content of the alloy nanoparticles.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Nature and Distribution of Cu and Pd Species in CuPd/TiO₂–Na Bimetallic Catalysts for Glycerol Hydrodeoxygenation

2020

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We demonstrated recently that CuPd/TiO 2 –Na bimetallic catalysts synthesized by sequential wet impregnation are active, selective, and stable for the hydrodeoxygenation (HDO) of glycerol into propylene glycol at low H 2 pressure. The present study reports on the nature and distribution of Cu and Pd surface species in CuPd/TiO 2 –Na bimetallic catalysts using different scanning transmission electron microscopy techniques that supply cluster-specific alloying details. In particular, we used atomic-resolution Z -contrast imaging, X-ray energy-dispersive spectroscopy, and electron energy-loss spectroscopy. We also include X-ray photoelectron spectroscopy results. Our analysis shows that the metallic nanoparticles adopt mainly five different structures according to how the Cu and Pd atoms coordinate among themselves: a homogeneous CuPd alloy structure (45–61%), a Cu shell/CuPd core (15–23%), a smaller number of particles formed by Cu on the surface and Pd in the nucleus (10–17%), and there are also nanoparticles formed only by Pd (4–7%) or by Cu (8–13%). We determined that there is a inhomogeneous distribution of Cu and Pd in the bimetallic nanoparticles, with Cu being predominant on the surface (between 76 and 90% of the total area analyzed for each particle). Most bimetallic nanoparticles have sizes below 6 nm, the Pd monometallic nanoparticles are in the 2–4 nm range, whereas the monometallic Cu nanoparticles are larger than 8 nm. Bimetallic nanoparticles with sizes smaller than 6–7 nm are fundamentally made up of Cu 0 –Pd 0 and Cu 1+ –Pd 0 . The nanoparticles with sizes greater than 7 nm consist of Cu 2+ and Cu 2+ –Pd 2+ . Our obtained results also help describe reports about the activation of HDO by Pd–Cu in the absence of H 2 , an effect apparently not observed with other bimetallic systems.

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“…Accordingly, Pd/ SiO 2 samples with palladium dispersed in very small size may be prepared by a sol-gel (SG) method. 17,18 The SG method allows reaction 1 at the stage of gel formation when the extent of reaction 2 is low.…”

Section: Introductionmentioning

confidence: 99%

Chemical Activity of Palladium Clusters: Sorption of Hydrogen

Huang

Chang

et al. 2006

J. Phys. Chem. B

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Samples of Pd/SiO2 with average cluster size of palladium (d(Pd)) ranging from 1 to 10 nm were prepared by different methods, such as incipient wetness impregnation (IW), ion exchange (IE), and sol-gel (SG). The dispersion (D(Pd)) for prepared Pd/SiO2 samples varied with the method of preparation and showed a trend of IW < IE < SG. Chemical interaction between the dispersed nanopalladium and hydrogen gas was calorimetrically studied as a function of hydrogen uptake. Measured profiles of interaction energy vary with the d(Pd) of studied samples. The initial heat of hydrogen chemisorption (Q(Hi)) also steeply increases for particles with d(Pd) smaller than 2 nm.

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Deactivation mechanisms and regeneration of a bimetallic hydrodechlorination catalyst

Cited by 11 publications

References 5 publications

The Effect of NaOH on the Liquid-Phase Hydrodechlorination of Dioxins over Pd/γ-Al₂O₃

The Effect of NaOH on the Liquid-Phase Hydrodechlorination of Dioxins over Pd/γ-Al₂O₃

Nature and Distribution of Cu and Pd Species in CuPd/TiO₂–Na Bimetallic Catalysts for Glycerol Hydrodeoxygenation

Chemical Activity of Palladium Clusters: Sorption of Hydrogen

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Deactivation mechanisms and regeneration of a bimetallic hydrodechlorination catalyst

Cited by 11 publications

References 5 publications

The Effect of NaOH on the Liquid-Phase Hydrodechlorination of Dioxins over Pd/γ-Al2O3

The Effect of NaOH on the Liquid-Phase Hydrodechlorination of Dioxins over Pd/γ-Al2O3

Nature and Distribution of Cu and Pd Species in CuPd/TiO2–Na Bimetallic Catalysts for Glycerol Hydrodeoxygenation

Chemical Activity of Palladium Clusters: Sorption of Hydrogen

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The Effect of NaOH on the Liquid-Phase Hydrodechlorination of Dioxins over Pd/γ-Al₂O₃

The Effect of NaOH on the Liquid-Phase Hydrodechlorination of Dioxins over Pd/γ-Al₂O₃

Nature and Distribution of Cu and Pd Species in CuPd/TiO₂–Na Bimetallic Catalysts for Glycerol Hydrodeoxygenation