Experimental (XAS, STEM, TPR, and XPS) and Theoretical (DFT) Characterization of Supported Rhenium Catalysts

Bare, Simon R.; Kelly, Shelly D.; Vila, Fernando D.; Boldingh, Edwin P.; Karapetrova, Evguenia; Kas, J.J.; Mickelson, George E.; Modica, Frank S.; Yang, Ning; Rehr, J. J.

doi:10.1021/jp1105218

Cited by 90 publications

(107 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…5−12 The nature of the surface Re 7+ oxide species on alumina has recently come into question because of reported contradictory conclusions. 12,13 Bare et al concluded that isolated trioxo (O) 3 Re−O−Al species are present for calcined supported rhenia/alumina catalysts 12 mainly from EXAFS analysis. In contrast, Scott et al postulated isolated penta-coordinated dioxo (O) 2 Re(−O-Al) 3 from XANES/ EXAFS measurements and DFT calculations employing cluster models.…”

Section: Introductionmentioning

confidence: 99%

Surface ReO_x Sites on Al₂O₃ and Their Molecular Structure–Reactivity Relationships for Olefin Metathesis

et al. 2015

View full text Add to dashboard Cite

Supported ReO x /Al 2 O 3 catalysts were investigated for propylene metathesis as a function of surface rhenia loading and extensively characterized with in situ UV−vis, Raman, IR, XANES/EXAFS, and isotopic 18 O− 16 O exchange studies. The experimental studies were complemented with DFT calculations using realistic models of the alumina surface. The surface ReO x sites were found to be isolated surface dioxo (O) 2 ReO 2 species, which represent the most stable surface rhenia structures on alumina as shown by DFT. Two distinct surface ReO 4 species, however, were found to be present and only slightly differ in their bridging Re−O−Al bond lengths brought about by anchoring at different sites of the Al 2 O 3 support. The deformed surface ReO 4 −I species preferentially anchor at more basic μ 1 Al IV and μ 1 Al VI sites and are difficult to activate for propylene metathesis. The surface ReO 4 −II species are formed at more acidic μ 2 Al VI and μ 3 Al VI sites and are the catalytic active sites for propylene metathesis. The surface ReO 4 −II sites were readily activated by propylene while the deformed surface ReO 4 −I sites were almost not affected by propylene, with only a few sites being activated. The steady-state propylene metathesis reaction rates are much higher for the surface ReO 4 −II sites than the deformed surface ReO 4 −I sites. The formation of the less reactive deformed surface ReO 4 −I species could be blocked by occupation of the μ 1 Al IV sites with sacrificial surface TaO x species that resulted in catalysts exclusively containing the more active surface ReO 4 −II sites on alumina. This is the f irst study to demonstrate that the surface ReO 4 −II sites are the precursors for the catalytic active sites for propylene metathesis by supported ReO 4 /Al 2 O 3 catalysts and to molecularly design olefin metathesis catalysts that exclusively contain isolated surface ReO 4 −II sites.

show abstract

Section: Introductionmentioning

confidence: 99%

Surface ReO_x Sites on Al₂O₃ and Their Molecular Structure–Reactivity Relationships for Olefin Metathesis

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Moreover, the CO DRIFT spectrum of the calcined DCS catalyst after reduction contains a strong peak assigned to linearly adsorbed CO on Re nanoparticles. We infer that PdO and perrhenate anions that spread across the support [18,20]. In contrast, the supported PdO species agglomerate during calcination yielding large Pd particles upon reduction [61,62].…”

Section: Discussionmentioning

confidence: 94%

“…Most preparations of PdRe/Al 2 O 3 catalysts include a calcination step, whether the catalysts are prepared by co-impregnation using a single solution containing both precursors [14] or by sequential impregnation using separate solutions [15][16][17]. During calcination, [ReO 4 ] À species wet the support surface forming up to a monolayer of AlAOAReO 3 surface complexes [10,11,[18][19][20]. There is also evidence that Re 2 O 7 may sublime and then re-adsorb on the support contributing to the mobility of Re 7+ species under oxidizing conditions [19,21].…”

Section: Introductionmentioning

confidence: 99%

Catalysts for selective hydrogenation of furfural derived from the double complex salt [Pd(NH3)4](ReO4)2 on γ-Al2O3

Thompson

Lamb

2017

Journal of Catalysis

View full text Add to dashboard Cite

a b s t r a c tThe double complex salt [Pd(NH 3 ) 4 ](ReO 4 ) 2 was employed as precursor of supported bimetallic catalysts for selective hydrogenation of furfural. Direct reduction of [Pd(NH 3 ) 4 ](ReO 4 ) 2 on c-Al 2 O 3 in flowing H 2 at 400°C yields bimetallic nanoparticles 1-2 nm in size that exhibit significant interaction between the metals, as evidenced by temperature-programmed hydride decomposition (complete suppression of b-PdH x formation), extended X-ray absorption fine structure spectroscopy at the Pd K and Re L III edges (PdARe distance = 2.72 Å), and scanning transmission electron microscopy with energy dispersive X-ray analysis. In contrast, calcination of [Pd(NH 3 ) 4 ](ReO 4 ) 2 on c-Al 2 O 3 at 350°C in air and subsequent reduction in H 2 at 400°C results in metal segregation and formation of large (>50 nm) supported Pd particles; Re species cover the Pd particles and c-Al 2 O 3 support. A PdRe 1:2 catalyst prepared by sequential impregnation and calcination using HReO 4 and [Pd(NH 3 ) 4 ](NO 3 ) 2 has a similar morphology.The catalyst derived by direct reduction of [Pd(NH 3 ) 4 ](ReO 4 ) 2 on c-Al 2 O 3 exhibits remarkably high activity for selective hydrogenation of furfural to furfuryl alcohol (FAL) at 150°C and 1 atm. Suppression of H 2 chemisorption via elimination of Pd threefold sites, as evidenced by CO diffuse-reflectance infrared Fourier transform spectroscopy, correlates with increased FAL selectivity.

show abstract

“…Formal valences of rhenium range from −1 to +7 and the stability of this very high oxidation state has rendered this element particularly relevant for the production of catalysts [25]. The most stable ionic state is 4+ and the ionic radius of Re 4+ (0.72 Å) is close to the radii of Mo and W 4+ (both around 0.70 Å) [26], thus favouring a random substitution by rhenium in the isostructural minerals molybdenite (MoS 2 )-the common molybdenum ore component recognized as the main Re-carrier-and tungstenite (WS 2 ), a very rare mineral isostructural with molybdenite but usually carrying much less rhenium.…”

Section: Rhenium Position In the Periodicmentioning

confidence: 99%

Molybdenite as a Rhenium Carrier: First Results of a Spectroscopic Approach Using Synchrotron Radiation

Pereira¹,

Maria-Ondina²,

Oliveira³

et al. 2013

JMMCE

View full text Add to dashboard Cite

The chemical and physical properties of rhenium render it a highly demanded metal for advanced applications in important industrial fields. This very scarce element occurs mainly in ores of porphyry copper-molybdenum deposits associated with the mineral molybdenite, MoS 2 , but it has also been found in granite pegmatites and quartz veins as well as in volcanic gases. Molybdenite is a typical polytype mineral which crystal structure is based on the stacking of [SMo-S] with molybdenum in prismatic coordination by sulphide anions; however, it is not yet clearly established if rhenium ions replace Mo 4+ cations in a disordered way or else, if such replacement gives rise to dispersed nanodomains of a rhenium-rich phase. As a contribution to clarify this question, an X-ray absorption spectroscopy (XANES) study using synchrotron radiation was performed at the Re L 3 -edge of rhenium-containing molybdenite samples. Obtained results are described and discussed supporting the generally accepted structural perspective that rhenium is mainly carried by molybdenite through the isomorphous replacement of Mo, rather than by the formation of dispersed Re-specific nanophase(s).

show abstract

Experimental (XAS, STEM, TPR, and XPS) and Theoretical (DFT) Characterization of Supported Rhenium Catalysts

Cited by 90 publications

References 49 publications

Surface ReO_x Sites on Al₂O₃ and Their Molecular Structure–Reactivity Relationships for Olefin Metathesis

Surface ReO_x Sites on Al₂O₃ and Their Molecular Structure–Reactivity Relationships for Olefin Metathesis

Catalysts for selective hydrogenation of furfural derived from the double complex salt [Pd(NH3)4](ReO4)2 on γ-Al2O3

Molybdenite as a Rhenium Carrier: First Results of a Spectroscopic Approach Using Synchrotron Radiation

Contact Info

Product

Resources

About

Experimental (XAS, STEM, TPR, and XPS) and Theoretical (DFT) Characterization of Supported Rhenium Catalysts

Cited by 90 publications

References 49 publications

Surface ReOx Sites on Al2O3 and Their Molecular Structure–Reactivity Relationships for Olefin Metathesis

Surface ReOx Sites on Al2O3 and Their Molecular Structure–Reactivity Relationships for Olefin Metathesis

Catalysts for selective hydrogenation of furfural derived from the double complex salt [Pd(NH3)4](ReO4)2 on γ-Al2O3

Molybdenite as a Rhenium Carrier: First Results of a Spectroscopic Approach Using Synchrotron Radiation

Contact Info

Product

Resources

About

Surface ReO_x Sites on Al₂O₃ and Their Molecular Structure–Reactivity Relationships for Olefin Metathesis

Surface ReO_x Sites on Al₂O₃ and Their Molecular Structure–Reactivity Relationships for Olefin Metathesis