Jun Zhao

Methanation of Carbon Dioxide over a Highly Dispersed Ni/La2O3 Catalyst

The methanation of carbon dioxide on a Ni/La2O3 catalyst containing 10 wt% Ni prepared by the impregnation method was studied. The space-time yield of methane was 3000 g/(kg·h) at conditions of 350 °C, GHSV of 30000 h−1, 1.5 MPa pressure, and H2/CO2 molar ratio of 4. The selectivity for methane was 100% with different CO2 conversions. Combined with X-ray diffraction and H2 temperature-programmed reduction analyses, this suggested that the reaction mechanism on Ni/La2O3 may be different from that on Ni/γ-Al2O3. The formation of lanthanum oxycarbonate (La2O2CO3) can play an important role in the activation of CO2.

Selective Conversion of Methane to C2 Hydrocarbons Using Carbon Dioxide over Mn-SrCO3 Catalysts

The combination of Mn with SrCO3 leads to effective catalysts for the selective conversion of CH4 to C2 hydrocarbons using CO2 as an oxidant; C2 selectivities approach 88 and 79.1% with a C2 yield of 4.3 and 4.5% over catalysts with an Mn/Sr ratio of 0.1 and 0.2, respectively. It is assumed that the Mn3+/Mn2+ couple formed in the reaction plays an important role in the activation of CO2 and CH4.

Characterization and performance of Cu/ZnO/Al2O3 catalysts prepared via decomposition of M(Cu, Zn)-ammonia complexes under sub-atmospheric pressure for methanol synthesis from H2 and CO2

Abstract Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M(Cu, Zn)-ammonia complexes (DMAC) at various temperatures. The catalysts were characterized in detail, including X-ray diffraction, N2 adsorption-desorption, N2O chemisorption, temperature-programmed reduction and evolved gas analyses. The influences of DMAC temperature, reaction temperature and specific Cu surface area on catalytic performance are investigated. It is considered that the aurichalcite phase in the precursor plays a key role in improving the physiochemical properties and activities of the final catalysts. The catalyst from rich-aurichalcite precursor exhibits large specific Cu surface area and high space time yield of methanol (212 g/(Lcat · h); T = 513 K, p = 3 MPa, SV = 12000 h−1).

Preparation of a Cu–Ce–O Catalyst by Urea Combustion for Removing CO from Hydrogen

Abstract A urea combustion method was used for the preparation of the Cu–Ce–O catalyst without the need for a binder or additional calcination steps. The catalytic performance of the catalyst for preferential oxidation of CO was investigated under dry and humid feed gas conditions, and the catalyst was also examined for CO removal at the operating temperature of the PEMFC anode. A 99.3% CO conversion and 75% selectivity for CO 2 could be achieved at 130°C in the presence of H 2 O and CO 2 . The results of XRD and SEM characterizations indicated that copper oxides were highly dispersed on the catalyst and formed nanoparticles.

Electrochemical Behavior of a Polydopamine Nanofilm

Polydopamine is a multifunctional polymer that has recently been employed for surface modification. However, the mechanism of polydopamine formation is not well understood. In this communication, electrochemistry was employed to study the polymerization of dopamine. The behavior of polydopamine nanofilms on an indium-tin oxide (ITO) glass surface was investigated by cyclic voltammetry and electrochemical impedance spectroscopy through the self-polymerization of dopamine in basic conditions. The chemical components and the redox behavior were analyzed and showed the presence of noncovalent dopamine in the nanofilms and the dopamine/dopaminequinone redox peak was maximal in pH 7.0 buffer. The study provides fundamental information regarding the chemical components and electrochemical behavior of polydopamine.

Morphological effect of lanthanum-based supports on the catalytic performance of Pt catalysts in crotonaldehyde hydrogenation

Rod-like and particle-like La2O2CO3 and La2O3 were obtained via morphology-preserved thermal transformation of the La(OH)3 precursors. La2O2CO3- and La2O3-supported Pt catalysts were prepared by impregnation method and tested in the liquid-phase crotonaldehyde hydrogenation reaction. The textural and physicochemical properties of the samples were studied by a series of techniques including XRD, TG-DSC, N2 adsorption–desorption, TEM and HRTEM, IR spectrum, H2-TPD, and H2-TPR. Even after 600xa0°C reduction, Pt particles of about 0.8–2.8xa0nm interplayed with support surface to form Pt-doped interface, thereby preventing the catalysts from migration and affording a high dispersion of platinum. The specific exposed crystal-facets and surface oxygen species depending on the shape of the support affected the preferential deposition of Pt species and the metal-support interaction. Thus, Pt catalysts performed different physicochemical properties and catalytic performance relying on the morphology and structure of the supports. During the cycle experiment, severe deactivation was observed for NP-supported catalysts with an increased selectivity due to the aggregation and growth of Pt particles. Meantime, the NR-supported catalysts retained relatively high reactivity as a consequence of the crystal-facet confinement of rod-shaped lanthanum supports.

One-pot synthesis of ordered mesoporous transition metal–zirconium oxophosphate composites with excellent textural and catalytic properties

A series of ordered mesoporous transition metal–zirconium oxophosphate composites (M–X–ZrPO, X = Cr, Mn, Fe, Co, Ni, Cu, Zn) were designed and synthesized via a facile and general one-pot evaporation-induced self-assembly (EISA) method. N2-physisorption and TEM characterization showed that all the final materials possessed ordered mesoporous structure accompanied by large specific surface area (170–220 m2 g−1), big pore volume (0.2–0.4 cm3 g−1) and uniform pore size (5.6–7.8 nm). Moreover, the introduced transition metals homogeneously dispersed in the mesoporous skeleton and effectively improved the mesostructure. The catalytic performance of M–X–ZrPO was evaluated in the liquid phase oxidation of ethylbenzene. The introduced transition metals obviously enhanced the catalytic performance of M–ZrPO. M–Mn–ZrPO showed excellent catalytic activity with 91.6% conversion of ethylbenzene and 87.0% selectivity of acetophenone. After five cycles, there was no notable decrease in catalytic activity. Therefore, it was a promising catalyst for the oxidation of ethylbenzene.

Effective and stable CeO2-W-Mn/SiO2 catalyst for methane oxidation to ethylene and ethane

Abstract CeO 2 -W-Mn/SiO 2 catalyst is found to be effective for the oxidative coupling of methane (OCM); ca. 30of C 2 + and 22of C 2 H 4 yields have been obtained in single pass at 800 °C. During the 500 h continuous reaction, no significant decrease of activity and selectivity is observed.

Insight into the structure and molybdenum species in mesoporous molybdena–alumina catalysts for isobutane dehydrogenation

The relationship between the structure and Mo species in mesoporous molybdena–alumina catalysts and their catalytic performance for isobutane dehydrogenation has been investigated in detail. Characterization by XRD, HAADF-STEM, EDX, FT-IR, and N2 physisorption illustrated that ordered mesoporous catalysts (OM-Al, MoAl(F), and MoAl(C)) possessed an amorphous alumina phase and non-ordered mesoporous catalysts (M-Al and MoAl) exhibited a γ-Al2O3 phase. Mo species were highly dispersed over all the catalysts because Mo surface densities were about 1.0 Mo nm−2. Moreover, XPS and ICP-OES showed that Mo species were uniformly distributed over MoAl(F) with the Mo species confined in the ordered mesoporous structure. Higher dehydrogenation stability and a lower coke formation rate, albeit lower catalytic conversion, was obtained over MoAl(F) in comparison with those of MoAl(C) and MoAl on account of its stronger metal–support interaction, as shown by H2-TPR technique. The catalyst with a γ-Al2O3 phase exhibited stronger acidity and higher activity than the corresponding catalyst with an amorphous phase. The acidity of the catalysts was greatly enhanced by the addition of Mo species, according to the NH3-TPD characterization. However, not all the acid sites were active sites for dehydrogenation activity. The moderately and strongly acidic sites and the Mo species, including Mo6+ and lower valence Mo species, probably contributed to the dehydrogenation reactivity. Moreover, deactivation of the catalysts was mainly due to coke formation over the spent catalysts.

Precursor effect on the property and catalytic behavior of Fe-TS-1 in butadiene epoxidation

The effect of iron precursor on the property and catalytic behavior of iron modified titanium silicalite molecular sieve (Fe-TS-1) catalysts in butadiene selective epoxidation has been studied. Three Fe-TS-1 catalysts were prepared, using iron nitrate, iron chloride and iron sulfate as precursors, which played an important role in adjusting the textural properties and chemical states of TS-1. Of the prepared Fe-TS-1 catalysts, those modified by iron nitrate (FN-TS-1) exhibited a significant enhanced performance in butadiene selective epoxidation compared to those derived from iron sulfate (FS-TS-1) or iron chloride (FC-TS-1) precursors. To obtain a deep understanding of their structure-performance relationship, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Temperature programmed desorption of NH3 (NH3-TPD), Diffuse reflectance UV–Vis spectra (DR UV–Vis), Fourier transformed infrared spectra (FT-IR) and thermal gravimetric analysis (TGA) were conducted to characterize Fe-TS-1 catalysts. Experimental results indicated that textural structures and acid sites of modified catalysts as well as the type of Fe species influenced by the precursors were all responsible for the activity and product distribution.