6,440 research outputs found
Activity of Rh-containing catalysts in Naphthalene Hydrogenation under Pressure
No full textThree Rh-containing catalysts were investigated in the vapor-phase hydrogenation of naphthalene at 6.0 MPa: i) 1.0 wt.% in a MCM41-type mesoporous aluminosilicate (Si/Al=20 as atomic ratio, a.r) (CAT1); ii) 2.0 wt.% in a HMS-type mesoporous aluminosilicate (Si/Al=20 a.r.) (CAT2); iii) 2.0 wt.% on a microporous Al/Ce/Mg pillared layer montmorillonite (CAT3). The following order of hydrogenation activity for weight unit of Rh was detected: CAT1>CAT3>CAT2, while the hydrogenolysis/ring-opening activity followed the order: CAT1>CAT2>CAT3. The catalytic activity improved significantly upon alloying Rh with Pd (1:2 as atomic ratio), although the thio-tolerance remained low
Synthesis and Structures of Mononuclear 3,4-Bis(Trifluoromethyl)Pyrrolyl Complexes of Rh(I) and Ni(II)
No full textNew mononuclear complexes of the 3,4-bis(trifluoromethyl)pyrrolyl ligand (3,4-(CF3)(2)-Pyr(-)) with Rh(I) and Ni(II) are reported. Reaction of 3,4-(CF3)(2)-PyrNa with [Rh(COD)Cl](2) produces [Rh(PMe3)(3)(3,4-(CF3)(2)(-)Pyr)] (1) while reaction of 3,4-(CF3)(2)-PyrH with [Ni(PMe3)(2)Me-2] (2) or [Ni(PMe3)(2)Ph-2] (4) gives [trans-Ni (PMe3)(2) (3,4-(CF3)(2)-Pyr)(CH3)] (3) or [trans-Ni(PMe3)(2)(C6H5)(3,4-(CF3)2-Pyr)] (5) respectively. Complexes 1, 3 and 5 have been characterized spectroscopically and all five compounds have been structurally characterized by single crystal X-ray diffraction studies.Welch Foundation F-816Petroleum Research Fund 47014-ACSNSF 0741973Chemistr
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Dinuclear Rh(II) Pyrazolates As CVD Precursors for Rhodium Thin Films
No full textNew dinuclear rhodium(II) pyrazolate (Pz) complexes of formula Rh(2)(3-R, 5-R'Pz)(4)center dot 2L (R = R' = CF(3), L = H(2)O (1), CH(3)CN (2)) and Rh(2)(3-R, 5-R'Pz)(4) (R = R' = (t)Bu (3); R = CF(3), R' = tBu (4)) have been synthesized from the interaction of the lithium salt of the corresponding pyrazole with Rh(2)(OAc)(4) in diethyl ether. The complexes were characterized by X-ray crystallography and spectroscopic methods. They were further evaluated as precursors for the chemical vapor deposition (CVD) of Rh thin films using H(2) as the carrier gas. The resulting films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).Welch Foundation F-816Petroleum Research Fund 47014-ACSNSF 0741973Chemistr
Unveiling the Structure Sensitivity for Direct Conversion of Syngas to C2-Oxygenates with a Multicomponent-Promoted Rh Catalyst
No full textAbstract: Mn and Li promoted Rh catalysts supported on SiO2 with a thin TiO2 layer were synthesized by stepwise incipient wetness impregnation approach. The thin TiO2 layer on the surface of SiO2 was proved to stabilize those small Rh nanoparticles and hinder their agglomeration. The reducibility of Rh on these catalysts depends on Rh particle size as well as the position of manganese oxide, and large Rh nanoparticles with MnO on Rh nanoparticles can be only reduced at an elevated temperature. Catalyst with large Rh particles exhibits a higher CO conversion and higher products selectivity towards long chain hydrocarbons and C2-oxygenates at the expense of decreasing methane formation than a similar catalyst with smaller Rh particles. This was attributed to the synergistic effect of Mn and Li promotion and molar ratio between Rh0 and Rhδ+ sites on the surface of Rh nanoparticles. Moreover, Rh nanoparticles on MnO are proved to be more efficient in promoting hydrogenation of acetaldehyde to ethanol than its counterpart with MnO on Rh nanoparticles. Finally, in order to target high C2-oxygenates selectivity, low reaction temperature together with a low H2/CO ratio in the feed is recommended. Graphic Abstract: [Figure not available: see fulltext.].ChemE/Catalysis EngineeringChemE/O&O groe
Computational Exploration of Rh-III/Rh-V and Rh-III/Rh-I Catalysis in Rhodium(III)-Catalyzed C-H Activation Reactions of N-Phenoxyacetamides with Alkynes
No full textThe selective rhodium-catalyzed functionalization of arenes is greatly facilitated by oxidizing directing groups that, act both as directing groups and internal oxidants. We report density functional theory (B3LYP and M06) investigations on the mechanism of rhodium(III)-catalyzed redox coupling reaction of N-phenoxyacetamides with alkynes. The results elucidated the role of the internal oxidizing directing group, and the role of Rh-III/Rh-I and Rh-III/Rh-V catalysis of C-H functionalizations. A novel Rh-III/Rh-V-Rh-III cycle successfully rationalizes recent experimental observations by Liu and Lu et al. (Liu, G. Angew. Chem. Int. Ed. 2013, 52, 6033) on the reactions of N-phenoxyacetamides with alkynes in different solvents. Natural Bond Orbital (NBO) analysis confirms the identity of Rhy intermediate in the catalytic cycle.National Natural Science Foundation of China [21133002, 21203004]; Shenzhen Peacock Program [KQTD201103]; National Science Foundation of the USA [CHE-1361104]; National Science Foundation under the CCI Center for Selective C-H Functionalization [CHE-1205646]; National Science Foundation [OCI-1053575]SCI(E)[email protected]; [email protected]
Marlène Leroux interviewée par Awen Jones dans le dernier numéro d'ArchiBat RH
No full textAyant tous deux commencé leurs études à l'Ecole Nationale Supérieure d'Architecture de Lyon et diplômé à l'EPFL, Marlène Leroux et Francis Jacquier expliquent leur parcours professionnel et l'installation de leur agence, archiplein, en Chine.I
Limiting Conditions of Muckenhoupt and Reverse Hölder Classes on Metric Measure Spaces
No full textFunding Information: Open Access funding provided by Aalto University. The author was supported by the Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters. Publisher Copyright: © 2023, The Author(s).The natural maximal and minimal functions commute pointwise with the logarithm on A∞. We use this observation to characterize the spaces A1 and RH∞ on metric measure spaces with a doubling measure. As the limiting cases of Muckenhoupt Ap and reverse Hölder classes, respectively, their behavior is remarkably symmetric. On general metric measure spaces, an additional geometric assumption is needed in order to pass between Ap and reverse Hölder descriptions. Finally, we apply the characterization to give simple proofs of several known properties of A1 and RH∞, including a refined Jones factorization theorem. In addition, we show a boundedness result for the natural maximal function.Peer reviewe
Solvent effects in heterogeneous selective hydrogenation of acetophenone: differences between Rh/C and Rh/Al2O3 catalysts and the superiority of water as a functional solvent
No full textSelective hydrogenation of acetophenone (AP) to 1-phenylethanol (PhE) was investigated over Rh/Al2O3 and Rh/C catalysts in 13 solvents including water and conventional organic solvents. Strong solvent effects on the overall rate of AP conversion were observed in different manners depending on the catalysts used. The conversion obtained is correlated with hydrogen-bond-donation (HBD) capability for Rh/C but with hydrogen-bond-acceptance (HBA) capacity for Rh/Al2O3. The solvent effects should result from interactions between the carbonyl group of AP and the solvent molecules through hydrogen bonding for Rh/C and from those between the solvent molecules and the catalyst surface for Rh/Al2O3 having HBD hydroxyl groups on its surface. Water is the most effective functional solvent in the selective hydrogenation of AP for C and Al2O3-supported Rh catalysts due to its high HBD capability (a) and low HBA capability (beta), respectively. For the hydrogenation with Rh/Al2O3 in water, its large polarity/polarizability index (pi*) may contribute to the high selectivity to PhE
Adverse effects of potassium on NO<sub>x</sub> reduction over Di-Air catalyst (Rh/La-Ce-Zr)
No full textThe influence of potassium in Rh on a lanthium promoted zirconia stablised ceria (CZ) catalysts was studied toward NOxreduction reactivity and selectivity. The results are compared with a Rh/CZ catalyst. The samples were characterised by N2 adsorption, XRD, SEM, ICP, and H2-TPR. The study highlighted the importance of stored NOx regeneration over potassium in determining the overall performance of the Rh/K/CZ catalyst. The NOx stored over Rh/K/CZ in the previous NO gas stream cannot be regenerated sufficiently during the C3H6 gas stream, and stored NOxgradually decreased from one cycle to the next, resulting in deteriorating performance of Rh/K/CZ. Besides, problem of NOx slip, the formation of both NH3 and N2O (selectivities up to 30% for each side product) were observed by the addition of potassium into the Rh/CZ catalyst system, depending on the reaction conditions applied and the severity of the catalyst deactivation.</p
Rh promoted In2O3 as a highly active catalyst for CO2 hydrogenation to methanol
No full textSynthesis of methanol with high selectivity and productivity through hydrogenation of CO2 is highly attractive. This work uses a Rh doped In2O3 catalyst to achieve a high methanol productivity of 1.0 g(MeOH) h(-1) g(cat)(-1) while maintaining the intrinsic high selectivity of pure In2O3. Rh facilitated the dissociation of H-2 leading to creation of oxygen vacancies over the In2O3 surface. In addition, Rh atoms also participated in the activation of CO2 to produce formate species with a low activation barrier as evidenced by DFT calculation. Rh species were atomically dispersed in the In2O3 matrix and were stable during a long term reaction. Under reaction conditions, the surface Rh atoms were reduced and were stabilized by charge transfer from neighbouring In atoms. Our results show that incorporation of atomic Rh species in In2O3 can lead to high methanol productivity by creation of oxygen vacancies as well as Rh centred active sites for CO2 activation
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