Correlation between properties of supported RhCu catalysts and procedure of preparation

Zauwen, M.N.; Crucq, A.; Degols, L.; Liénard, Georges; Frennet, Alfred; Mikhalenko, N. N.; Grange, Paul

doi:10.1016/0920-5861(89)80029-x

Cited by 9 publications

(4 citation statements)

References 18 publications

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“…Some extra adsorption sites must have been created at initial additions of copper to the Rh/Al 2 O 3 monometallic sample. From the isosteric heats of hydrogen adsorption on a sample of Cu−Rh/SiO 2 , Frennet et al suggested that new active sites were formed from an electronic interaction between rhodium and copper and have a chemisorption stoichiometry larger than 2.…”

Section: Resultsmentioning

confidence: 99%

“…Isotherms of hydrogen adsorption for the alumina support and the 3.8% Cu/Al2O3 sample at 300 K, where the lines a, b, and c represent the total uptake for alumina, the total uptake for Cu/Al2O3, and the reversible uptake for Cu/Al2O3, respectively. 16 suggested that new active sites were formed from an electronic interaction between rhodium and copper and have a chemisorption stoichiometry larger than 2.…”

Section: Figurementioning

confidence: 99%

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Adsorption of Hydrogen on Dispersed Copper−Rhodium Bimetallic Crystallites

1997

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Supported bimetallic Rh−Cu/A12O3 samples of different X Cu [N Cu/(N Cu + N Rh) atomic ratios] were prepared by impregnating a 3.8 wt % Rh/A12O3 sample with different amounts of Cu(NO3)2 solution and characterized with techniques of hydrogen chemisorption and 2H NMR spectroscopy. The irreversible hydrogen uptake of the bimetallic samples, measured from the chemisorption, increases upon impregnating a small amount of copper but decreases as the X Cu becomes larger than 0.1. Deuterium atoms adsorbed on the bimetallic samples exhibit only a single 2H NMR peak. However, both the line width (Δυ) and the chemical shift (δ) of this peak vary significantly with the X Cu ratio. Phenomena observed from chemisorption and NMR spectroscopy may be explained satisfactorily by the formation of two alloy phases, i.e., a rhodium-rich phase [(Rh), X Cu ≈ 0.05] and a copper-rich phase, [(Cu), X Cu ≈ 0.8], on the surface of bimetallic crystallites. Detected variations in the Δυ and the δ suggest a fast chemical exchange of the deuterium atoms adsorbed on the surfaces of these two alloy phases. The rate constant of this exchange process is estimated from the variation of Δυ to be k ex = (1.4 ± 0.6) × 106 exp(−8.6 ± 0.8 kJ mol-1/(RT)) s-1. From the average X Cu calculated from the δ of 2H NMR and the X Cu of the bulk composition estimated from ICP-MS, a surface enrichment of copper on supported Cu−Rh crystallites was indicated.

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Section: Resultsmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Adsorption of Hydrogen on Dispersed Copper−Rhodium Bimetallic Crystallites

1997

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“…The rhodium electronic modification has notable chemical implications. Let us mention, for instance, that the thermodynamics of hydrogen chemisorption is strongly altered 31 and, consequently, H/Rh ratios of Table 1 cannot be considered as indicators of Rh dispersion. Other chemical effects can be deduced from the interaction of CO with the 0.14RhCu sample.…”

Section: Discussionmentioning

confidence: 99%

Genesis of Surface and Bulk Phases in Rhodium−Copper Catalysts

et al. 1999

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The temperature-programmed reduction of four copper-rich, Rh−Cu/Al2O3 bimetallic catalysts was studied using X-ray absorption near-edge spectroscopy (XANES), infrared spectroscopy using CO as a probe molecule, and electron paramagnetic resonance (EPR). In the initial, fully oxidized state, copper and rhodium do not form mixed oxide phases; that is, only copper aluminates and rhodium oxide are detected. The nature of the copper aluminate is controlled by the Rh loading and pH of the preparation solution. Below 1.0 wt % of rhodium charge, there is extensive formation of a superficial copper aluminate phase, which is coreduced with rhodium oxide to yield an alloyed phase. The bimetallic particles formed have a heterogeneous composition with a Rh-rich core and a surface enriched in copper. Rh is electronically perturbed in these binary particles in relation to a metallic reference and shows a net positive charge. The analysis of the genesis mechanism of the zerovalent phases provides evidence of the critical role of the support and superficial interactions between oxidized phases in alloy formation.

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“…Also, reductive depolymerization of lignin in the presence of hydrogen and several late transition metals, 3d and 4d, (e.g., Fe, Co, Ni, Cu, Ru, Rh, Pd, and Ag) has been studied . A previous investigation showed that mixed noble–transition metal catalysts (e.g., Ru–Co, Rh–Cu, and Rh–Ag) have been applied . Alumina-supported catalysts have been known to be active in the hydrodeoxygenation process; however, they promoted coke formation and deposition on the surface of the catalyst and, as a result, caused catalyst deactivation .…”

Section: Introductionmentioning

confidence: 99%

Reductive Hydroprocessing of Hydrolysis Lignin over Efficient Bimetallic Catalyst MoRu/AC

Tymchyshyn

Rezayan

Yuan

et al. 2020

Ind. Eng. Chem. Res.

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The fast-growing demand for renewable fuels and chemicals, together with environmental concern, has inspired the study of lignin. However, the valorization of lignin is challenged by its large molecular structure and oxygen content. Catalytic hydroprocessing of lignin is the effective depolymerization for producing fuels and chemicals. The aims of this work were the implementation and study of the role of a novel and inexpensive bimetallic catalyst, MoRu/AC, in the reductive depolymerization (hydroprocessing) of hydrolysis lignin. The increase in the reaction temperature, between 200 and 340 °C, dramatically enhanced the hydrogen content of the bio-oils relative to the feed. The MoRu/AC catalyst exhibited excellent activity in the hydrogenation and produced bio-oils with a substantially increased H/C ratio, suggesting enhanced hydrodeoxygenation activity of the MoRu/AC. The catalyst at optimum temperature, 340 °C, significantly promoted the hydrogenation, and the H content in the bio-oil was 1.5 times of that in the feed. The results demonstrated that the phenolic compounds were the main component in all the produced biooils. This confirms that hydrolysis lignin can be easily depolymerized at the temperature range of 200−340 °C in the presence of the MoRu/AC catalyst.

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Correlation between properties of supported RhCu catalysts and procedure of preparation

Cited by 9 publications

References 18 publications

Adsorption of Hydrogen on Dispersed Copper−Rhodium Bimetallic Crystallites

Adsorption of Hydrogen on Dispersed Copper−Rhodium Bimetallic Crystallites

Genesis of Surface and Bulk Phases in Rhodium−Copper Catalysts

Reductive Hydroprocessing of Hydrolysis Lignin over Efficient Bimetallic Catalyst MoRu/AC

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