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Abstract: A series of Zr-based metal-organic frameworks (UiO-66) supported CuO-CeO2 catalysts with various total metal loadings and various Cu/Ce ratios were prepared by using a co-impregnation method. The catalytic activities of the catalysts for low temperature oxidation of carbon monoxide were compared with that supported on the ZrO2 and mesostructured cellular foam silica. The results show that the catalysts supported by UiO-66 are expected to give the best catalytic activity, which should be attributed to the special construction of UiO-66. The samples were further characterized by XRD, TEM, N2 adsorption-desorption, H2-TPR, XPS, and in situ DRIFT. And the catalyst with a bimetallic loading of 50 wt% and Cu/Ce ratio of 3:7 (wt/wt) has the highest catalytic activity, which can be attributed to the larger amount of finely dispersed Cu species strongly interacting with CeO2, the highest amounts of oxygen vacancies and Cu+ species on the catalyst surface.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract: The effect of titanium promotion on the catalytic performance of Rh-Mn-Li catalyst supported on PVP-modified SiO2 for C2+ oxygenates synthesis from CO hydrogenation was investigated. The highest selectivity toward C2+ oxygenates (51.3%) was achieved over the RML/0.5Ti/SiO2 catalyst. Characterization results indicates that the addition of Ti promotes the adsorption of geminal CO and the formation of Rh+, which is favorable for the CO insertion into metal-CHx band, and finally increases the selectivity of C2+ oxygenates.Graphical Abstract: The effect of titanium promotion on the catalytic performance of Rh-Mn-Li catalyst supported on PVP-modified SiO2 for C2+ oxygenates synthesis from CO hydrogenation was investigated. The highest selectivity toward C2+ oxygenates (51.3%) was achieved over the RML/0.5Ti/SiO2 catalyst [ABSTRACT FROM AUTHOR]

It has been reported widely that Rh-Mn-Li/SiO 2 catalysts can exhibit high selectivity to C 2 + oxygenates during CO hydrogenation, with promoters of Mn and Li playing an important role in this behavior. In this study, a series catalysts of Rh-Mn-Li/SiO 2 with different amounts of Mn and Li were prepared, and the new insights into the effects of Mn and Li on the mechanistic pathway for C 2 + oxygenates synthesis from syngas were investigated. The XPS analysis showed that Rh existed mainly as metallic Rh after reduction, however partially positively charged Rh δ+ atoms appeared on the surface of Mn-containing catalyst due to the interaction of Rh-Mn. The results of H 2 -TPR indicated that both of Li and Mn can inhibit the reduction of Rh 2 O 3 . With the increase in the ratio of Mn/Rh, the most effective interaction, associated to the presence of two reduction centers of Rh 2 O 3 , was obtained when the ratio of Mn/Rh = 1. In situ -FTIR was used to probe the effects of Mn and Li on CO absorption and hydrogenation. With regards to the CO adsorption, the doping of Mn can enhance the CO adsorption ability of Rh and weaken the CO-Rh bond strength very effectively when the amount of Mn reached 1.5 wt.%. Improved capacity of CO adsorption is conducive to increase of CO conversion, while the weakening of CO-Rh bond is beneficial to the CO insertion reaction, thus contributing to the generation of C 2 + oxygenates. Moreover, the low amount of Li (≤0.075 wt.%) can also enhance the CO adsorption, resulting in the improvement of reactivity. On the other hand, Mn and Li promoted dissociation of H 2 , which is favorable to an increase in the rate of hydrogenation. But an opposite effect appeared at high content of Mn (>1.5 wt.%). As the optimized results, when Rh, Mn, Li content was 1.5 wt.%, 1.5 wt.% and 0.075 wt.%, the catalyst for CO hydrogenation of C 2 + oxygenates achieved the best performance of C 2 + oxygenates synthesis. [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]

Abstract: Rh-Mn-Li catalysts supported on SiO2, ZrO2 and SiO2-ZrO2 mixed oxides with various molar ratios of Si/Zr were prepared and tested for the synthesis of C2-oxygenates from syngas. Compared with pure SiO2 and ZrO2 supported catalysts, catalysts supported on SiO2-ZrO2 mixed oxides showed higher activity and C2-oxygenates selectivity, in which Rh-Mn-Li/SiO2-ZrO2 (molar ratio of Si/Zr=1:3) exhibited the best yield of C2-oxygenates. The effect of the support on the performance of the Rh-based catalysts was investigated comprehensively by XRD, N2 adsorption-desorption, H2 and CO uptakes, FT-IR, XPS, H2-TPR, TPSR and CO-TPD techniques. The results indicated that the chemical state of Rh, CO adsorption species, dispersion of Rh and the ability of CO hydrogenation varied over catalysts supported on SiO2, ZrO2 and SiO2-ZrO2 mixed oxides, which led to the diverse catalytic activity toward C2-oxygenates synthesis. [Copyright &y& Elsevier]

Abstract: The effect of calcination temperature of the monodispersed SiO2 synthesized by the Stöber method on the catalytic performance of Rhph name="sbnd" />Li/SiO2 for CO hydrogenation to C2 oxygenates was investigated. The means of N2 adsorption-desorption, in-situ FT-IR, H2-TPD, H2-TPR, CO-TPD, and TPSR were used to characterize the physico-chemical properties of SiO2 supports and the corresponding Rhph name="sbnd" />Li/SiO2 catalysts. The results showed that the amount of surface Si-OH groups on SiO2 affects the Rh dispersion and Rhction. The increase in the number of Si on the SiO2 was favorable for the Rh dispersion and CO adsorption, further enhanced the activity of the catalyst. In addition, an appropriate amount of surface Si on the SiO2 calcined at 350°C can gain a moderate Rhction. This interaction is conducive to achieve the right hydrogenation ability, which is favorable for the CO insertion into metal-CHx band, and ultimately increases the selectivity of C2 oxygenates. [Copyright &y& Elsevier]

Abstract: A novel SiO2 synthesized by the Stöber method was studied as the support for Rh–Mn–Li catalyst, and better performance for C2 oxygenate synthesis via CO hydrogenation was achieved compared with the counterpart using commercial SiO2 as the support. The investigation based on the catalytic performance and characterizations of the catalysts suggests that the hydroxyl–metal interaction over the catalyst supported on SiO2 prepared by the Stöber method results in a change in the CO adsorption on Rh particles, which promotes the CO dissociation and CO insertion, leading to higher CO conversion and C2 oxygenate selectivity. [Copyright &y& Elsevier]

Abstract: A series of HZSM-5 zeolites modified with various contents of magnesium oxide (0–10 wt%) were prepared with an incipient impregnation technique and characterized by X-ray diffraction, N2 adsorption, temperature-programmed desorption of NH3 and CO2, 27Al MAS NMR, and FT-IR. The modified HZSM-5 zeolites were mixed physically with methanol synthesis components (CuO–ZnO–Al2O3) to perform the direct synthesis of dimethyl ether (DME) from syngas under pressurized fixed-bed continuous-flow conditions. The results indicated that modification of HZSM-5 with a suitable amount of MgO significantly decreased the selectivities for undesired by-products like hydrocarbons and CO2 from 9.3 and 37.1% to less than 0.4 and 31%, respectively, through the removal of unselective strong Brønsted acid sites and hence enhanced the selectivity for DME from 49% to more than 64%, whereas the conversion of carbon monoxide was scarcely affected. However, when the MgO contents were equal to or higher than 5 wt%, both the conversion of CO and selectivity for DME decreased markedly because of the decreased activity for methanol dehydration. A mechanism for methanol dehydration to DME involving both acidic and basic sites on the HZSM-5 zeolites modified with MgO has been proposed based on the results obtained. [Copyright &y& Elsevier]

A series of M 3 Co 16 O x (M = Cr, Ti, Zr, Fe, Mn) oxide catalysts wrapped by polymer nanofilm were developed by the solid-phase method, and the catalytic activities were investigated for low temperature oxidation of carbon monoxide under moisture-rich condition. The catalysts were characterized by HR-TEM, FT-IR, XRD, N 2 adsorption-desorption, H 2 -TPR, CO-TPD and XPS techniques. The results reveal that the M 3 Co 16 O x composite oxides are high-dispersive mesoporous materials coated by polymer nanofilm with an average thickness in the scope of 4–7 nm. The percentages of surface oxygen vacancy and lattice oxygen on the catalysts decrease in the following order: Mn 3 Co 16 O x > Fe 3 Co 16 O x > Zr 3 Co 16 O x > Ti 3 Co 16 O x > Cr 3 Co 16 O x , which is consistent with their catalytic performances. Among all the prepared catalysts, the polymer nanofilm wrapped Mn 3 Co 16 O x nanoparticles possess the highest Co 3+ /Co 2+ ratio (1.56), the highest percentage of surface oxygen vacancy (17.5%) and lattice oxygen (62.2%), resulting in the best catalytic activity, such as, 100% conversion at 55 °C under moisture-rich condition (∼0.6 vol.%). Moreover, the Mn 3 Co 16 O x catalyst also exhibits long-term catalytic stability (>one month) even at a very high water vapor level (3.1 vol.%) and considerably low temperature (85 °C). [ABSTRACT FROM AUTHOR]

Abstract: Co/CuZnO is known as a base metal catalyst active for C2+ oxygenate synthesis. This study probed the interactions of the different components of Co/CuZnO catalysts on CO hydrogenation using Fischer–Tropsch synthesis (250°C, H2/CO=2) and SSITKA. Only combination of all three metal components produced a catalyst with relatively high C2+ oxygenate selectivity, but with much lower activity compared to that for Co/Al2O3. In situ reaction characterizations, albeit at somewhat different conditions than alcohol synthesis, helped explain interaction of the components. SSITKA, under methanation conditions, indicated that the most striking feature for the combination of Co with ZnO and/or Cu was a much decreased amount of reaction intermediates. Ethane hydrogenolysis results suggested that the different components for these catalysts were in close contact and few or no large ensembles (n ⩾12) of Co atoms existed, confirming that ZnO and/or Cu covered/blocked a substantial number of active sites on Co for CO hydrogenation. [Copyright &y& Elsevier]