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Maintaining high conversion under the premise of high oxygenates selectivity in syngas conversion is important but a formidable challenge in Rh catalysis. Monometallic Rh catalysts provide poor oxygenate conversion efficiency, and efforts have been focused on constructing adjacent polymetallic sites; however, the one‐pass yields of C2+ oxygenates over the reported Rh‐based catalysts were mostly <20 %. In this study, we constructed a monometallic Rh catalyst encapsulated in UiO‐67 (Rh/UiO‐67) with enhanced proximity to dual‐site Rh1,2‐Rhn ensembles. Unexpectedly, this catalyst exhibited high efficacy for oxygenate synthesis from syngas, giving a high oxygenate selectivity of 72.0 % with a remarkable CO conversion of 50.4 %, and the one‐pass yield of C2+ oxygenates exceeded 25 %. The state‐of‐the‐art characterizations further revealed the spontaneous formation of an ensemble of Rh single atoms/dimers (Rh1,2) in the proximity of ultrasmall Rh clusters (Rhn) confined within the nanocavity of UiO‐67, providing adjacent Rh+‐Rh0 dual sites dynamically during the reaction that promote the relay of the undissociated CHO species to the CHx species. Thus, our results open a new route for designing highly efficient Rh catalysts for the conversion of syngas to oxygenates by precisely tuning the ensemble and proximity of the dual active sites in a confined space. [ABSTRACT FROM AUTHOR]

A series of CuO-ZnO-ZrO2 catalysts was prepared by a facile microwave-assisted hydrothermal synthesis method and used for the direct synthesis of methanol by CO2 hydrogenation in a fixed-bed reactor at 240 °C, 3.0 MPa, CO2/H2=1:3 ( v/ v), and space velocity of 2400 mL gcat−1 h−1. The effects of the hydrothermal synthesis temperature (80-150 °C) on the physicochemical properties and catalytic activity of the CuO-ZnO-ZrO2 catalysts were investigated by using several techniques, including XRD, N2 adsorption, reactive N2O adsorption, SEM with energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction by H2, and the temperature-programmed desorption of adsorbed CO2 and H2. The catalyst prepared at 120 °C possessed a high surface area, a high dispersion of Cu species, a high adsorption capacity for CO2 and H2, and thus exhibited a high CO2 conversion and methanol selectivity. The surface area of metallic Cu ( SCu) is the critical factor in determining the activity of the CuO-ZnO-ZrO2 catalyst. [ABSTRACT FROM AUTHOR]

The tetragonally double alkaline rare earth molybdates NaRe(MoO4)2 (Re = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Er) micro-particles in aqueous solution of Re(NO3)3 and Na2MoO4 were prepared hydrothermally by a facile and effective EDTA-assisted method, and investigated by XRD, SEM, FE-SEM, photoluminescence (PL) excitation and emission spectra. The results showed that the radii of Re ions, pH and the molar ratio of Re(NO3)3/Na2MoO4 in the synthesis solution play an important role in controlling sizes, morphologies and luminescent properties of the final products. And the possible formation mechanism for the bipyramid-like structure and role of EDTA were discussed in detail. The microstructure and PL property of NaYxLa1-x(MoO4)2:10%Eu3+ was investigated, and it showed that NaY0.5La0.5(MoO4)2 exhibited regular sphere-like morphology and emitted the stronger red emission with better color purity than other products. When Tm3+, Dy3+ and Eu3+ with appropriate concentrations were used as dopants to modify this bipyramid NaY(MoO4)2 material, the white light emission material of NaY(MoO4)2:1%Tm3+-11%Dy3+-0.6%Eu3+ was successfully synthesized and its CIE chromaticity coordinates is (0.33, 0.33), which is the standard white light point. These novel white-light-emitting NaY(MoO4)2:1%Tm3+-11%Dy3+-0.6%Eu3+ with single phase would be a promising material in the WLED field. [ABSTRACT FROM AUTHOR]

A series of CuO-ZnO-TiO2 catalysts with various TiO2 loadings were prepared by using a co-precipitation method. The prepared catalysts were characterized by using X-ray diffraction (XRD), N2 adsorption, reactive N2O adsorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), hydrogen temperature programmed desorption (H2-TPD), and CO2-TPD techniques, and tested the extent of methanol synthesis from carbon dioxide (CO2) hydrogenation. The results indicate that the addition of TiO2 to the CuO-ZnO catalyst makes the copper species exist in an amorphous-like structure or in much smaller crystallites, which promotes the reduction of CuO. Upon increasing the TiO2 loading, the metallic Cu surface area ( SCu) of the catalyst rises first and then decreases, exhibiting a maximum at a TiO2 loading of 10 %. The results of the catalytic experiments reveal that the addition of TiO2 favors the production of methanol, and an optimum catalytic activity is obtained at a TiO2 loading of 10 %. Moreover, the methanol yield increases linearly with the SCu of the catalysts, thereby indicating that the addition of TiO2 enhances the SCu but not the intrinsic activity. [ABSTRACT FROM AUTHOR]

HZSM-5 zeolites modified with various alkaline earth oxides (MgO, CaO, and BaO) were prepared by using impregnation and mixed physically with Cu/ZnO/Al2O3 to perform the direct synthesis of dimethyl ether (DME) from syngas in a pressurized fixed-bed under continuous flow conditions. The results indicated that the modification effectively enhanced the DME selectivity; MgO and CaO are more effective modifiers than BaO and they improved the DME selectivity up to 67 % as compared to only 54 % over the parent HZSM-5. Moreover, the catalyst prepared from magnesium nitrate exhibits higher DME selectivity than those prepared from magnesium acetate and chloride. The enhancement in the DME selectivity resulted from the effective suppression of hydrocarbon and CO2 formation, which can be attributed to the significant decline in the amount of strong acid sites of the HZSM-5 zeolite resulting from the modification. [ABSTRACT FROM AUTHOR]

A tandem cycle ride: The catalytic reaction mechanism of CO oxidation over Pd‐Cu‐Clx/γ‐Al2O3 is proposed based on DFT studies. There are two catalytic cycles in the CO oxidation process, the palladium cycle (— (green)) and the copper cycle (— (red)). [ABSTRACT FROM AUTHOR]