Isolation of a chloride-capped cerium polyoxo nanocluster built from 52 metal ions

Four cerium compounds - (HPy)2[CeCl6]·2(HPyCl) (Ce1-1), (HPy)2[CeCl6] (Ce1-2), (HPy)m[Ce38O56-x(OH)xCl50(H2O)12]·nH2O (Ce38), and (HPy)m[Ce52O80-x(OH)xCl59(H2O)17]·nH2O (Ce52) - were crystallized from acidic aqueous solutions using pyridinium (HPy) counterions. The latter consists of two unique cerium oxide nanoclusters that are built from 52 metal ions and represents the largest chloride capped {CeIII/IVO} and/or {MIVO} (M = Ce, Th, U, Np, Pu) nanocluster that adopts the fluorite-type structure of MO2 that has been reported.

Cerium Oxide Nanoparticles Confined in Doped Mesoporous Carbons: A Strategy to Produce Catalysts for Imine Synthesis

A group of (doped N or P) carbons were synthesized using soluble starch as a carbon precursor. Further, ceria nanoparticles (NPs) were confined into these (doped) carbon materials. The obtained solids were characterized by various techniques such as N2 physisorption, XRD, TEM, SEM, XPS, and XAS. These materials were used as catalysts for the oxidative coupling between benzyl alcohol and aniline as the model reaction. Ceria immobilized on mesoporous-doped carbon shows higher activity than the other materials, benchmark catalysts, and most of the previously reported catalysts. The control of the ceria NP size, the presence of Ce3+ cations, and an increment in the disorder in the ceria NP structure caused by a support-ceria interaction could increase the number of oxygen vacancies and improve its catalytic performance. CN-meso/CeO2 was also used as the catalyst for a rich scope of substrates, such as substituted aromatic alcohols, linear alcohols, and different types of amines. The influence of various reaction parameters (substrate content, reaction temperature, and catalyst content) on the activity of this catalyst was also checked.

Fabrication and catalytic application of tandem reactor module using Au nanoparticles-coated glass beads as packing materials

A tandem reactor module using Au nanoparticles (NPs)-coated glass beads as packing materials is designed and fabricated for the catalytic reduction of 4-NP. Au NPs-coated glass beads are firstly prepared...

Nanoscale Cerium Oxide: Synthesis, Biocatalytic Mechanism, and Applications

Nanoscale cerium oxide has excellent catalytic performance due to its unique surface properties and has very important applications in various fields. In this paper, the synthesis methods, catalytic mechanism and activity regulation of nanoscale cerium oxide in recent years are reviewed. Secondly, the application of cerium oxide in the detection of organic and inorganic molecules is summarized, and its latest progress and applications in antibacterial, antioxidant and anticancer are discussed. Finally, the future development prospect of nanoscale cerium oxide is summarized and prospected.

A structured catalyst with high dispersity of Au species based on hollow SiC foam with porous walls for acetylene hydrochlorination

It is essential to improve the catalytic stability of Au-based catalysts for acetylene hydrochlorination. In this study, a novel hollow SiC foam with porous walls (HSFp) is proposed to modify the Au catalyst distribution on the foam-based structured catalyst. The scanning electron microscopy and 3D X-ray tomography results showed that the hollow structure and the porous ceramic wall of HSFp were successfully obtained. An Au/AC/HSF structured catalyst was prepared by the slurry-coating and impregnation method. Then the effects of the wall pore structure of HSFp on the distribution of Au species and the stability of the catalyst were studied by comparison with a hollow SiC foam with compact walls (HSFc). The HSFp with 3D interconnected hollow channel structure was demonstrated to have a promotion effect on the reaction stability due to its ability to refine the catalyst particles during the impregnation and drying processes. The result indicates that the time on stream of acetylene conversion above 90% over the Au/AC/HSFp structured catalyst reaches about 380 h at an acetylene gaseous hourly space velocity of 130 h-1, which is much longer than that of the Au/AC/HSFc. In addition, a bidirectional diffusion effect that can enhance the catalyst distribution by the porous wall of HSF was proposed in this paper. This may have positive significance in the field of preparation of structured catalysts.

Ce(OH)2Cl and lanthanide-substituted variants as precursors to redox-active CeO2 materials

The cerium(iii) hydroxide chloride Ce(OH)2Cl crystallises directly as a polycrystalline powder from a solution of CeCl3·7H2O in poly(ethylene) glycol (Mn = 400) heated at 240 °C and is found to be isostructural with La(OH)2Cl, as determined from high-resolution synchrotron powder X-ray diffraction (P21/m, a = 6.2868(2) Å, b = 3.94950(3) Å, c = 6.8740(3) Å, β = 113.5120(5)°). Replacement of a proportion of the cerium chloride in synthesis by a second lanthanide chloride yields a set of materials Ce1-xLnx(OH)2Cl for Ln = La, Pr, Gd, Tb. For La the maximum value of x is 0.2, with an isotropic expansion of the unit cell, but for the other lanthanides a wider composition range is possible, and the lattice parameters show an isotropic contraction with increasing x. Thermal decomposition of the hydroxide chlorides at 700 °C yields mixed-oxides Ce1-xLnxO2-δ that all have cubic fluorite structures with either expanded (Ln = La, Gd) or contracted (Ln = Pr, Tb) unit cells compared to CeO2. Scanning electron microscopy shows a shape memory effect in crystal morphology upon decomposition, with clusters of anisotropic sub-micron crystallites being seen in the precursor and oxide products. The Pr- and Tb-substituted oxides contain the substituent in a mixture of +3 and +4 oxidation states, as seen by X-ray absorption near edge structure spectroscopy at the lanthanide LIII edges. The mixed oxide materials are examined using temperature programmed reduction in 10%H2 in N2, which reveals redox properties suitable for heterogeneous catalysis, with the Pr-substituted materials showing the greatest reducibility at lower temperature.

Divergent influence of {1 1 1} vs. {1 0 0} crystal planes and Yb3+ dopant on CO oxidation paths in mixed nano-sized oxide Au/Ce1−xYbxO2−x/2 (x = 0 or 0.1) systems

In this paper, the fundamental information on interactions in systems concerning nanocrystalline gold disperses on the shaped (octahedron-like or cube-like) Ce_1−xYb_xO_2−x/2 (x = 0 or 0.1) support has been discussed.

Metal-free catalytic oxidation of benzylic alcohols for benzaldehyde

Metal-free catalytic oxidation of benzylic alcohols for benzaldehyde and process intensification by using a rotating packed bed reactor were demonstrated.