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Applied Catalysis
Elsevier
Applied Catalysis

Elsevier

0926-860X

Applied Catalysis/Journal Applied Catalysis
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    Active site structure and methane oxidation reactivity of bimetallic Pd and Pt nanoparticles

    Yang, YifeiLee, JaekyoungDorakhan, RohamNie, Haoyu...
    13页
    查看更多>>摘要：Kinetic, oxygen uptake, microscopic, and spectroscopic studies shed light on the structural dynamics of PdPt bimetallic catalysts and their methane oxidation rates. Reductive treatments lead to Pd0Pt0 nanoparticles distributed in sizes and Pt:Pd ratios. Oxidative treatments, including treatments in CH4-O2 reaction mixture, lead the Pd, as the more oxophilic metal, to migrate onto the surfaces and undergo bulk oxidation, forming a thin PdO shell covering the underneath Pt-rich core. Residing on the PdO shell are Pd2+-O2- site pairs that are highly effective for C-H activation in methane-the CH4 turnover rates are the highest at 0.3 Pt:Pd ratio and the C-H activation barrier decreases from 64 to 37 kJ mol-1 as the Pt:Pd ratio increases from 0 to 1. H2O and SO2 impurities increase the effective barrier to 58 and 116 kJ mol-1, respectively, but such effects remain much smaller than on unpromoted PdO.
      原文链接:
    • NSTL
    • Elsevier

    Grafted nickel-promoter catalysts for dry reforming of methane identified through high-throughput experimentation

    Ferrandon, Magali S.Byron, CarlyCelik, GokhanZhang, Yuying...
    15页
    查看更多>>摘要：High-throughput synthesis of a series of monometallic and bimetallic catalysts (45 bimetallic and 50 mono-metallic samples) consisting of nickel and one of nine different metal promoters (B, Co, Cu, Fe, Mg, Mn, Sn, V and Zn) supported on one of five different metal oxides (alumina, ceria, magnesia, silica and titania) is carried out via organometallic grafting using a robotic platform. The catalysts are evaluated for their activity and selectivity for the dry reforming of methane at a feed ratio of CH4:CO2 of 1 at 650-800 degrees C in a parallel flow reactor system. The type of oxide support prevails over the type of additive for both catalyst activity and stability. On Al2O3 and MgO, Fe was found to be the best promoter; on SiO2, Cu is the best promoter at 700 degrees C and higher, while on TiO2, Mn is found to enhance the conversion at 800 degrees C. On CeO2, all additives except Fe have beneficial effects. Twenty-five catalysts show > 90% methane conversion with ten catalysts showing > 95% conversion at 800 degrees C with the H-2:CO ratios ranging from 0.8 to 1.2. Amongst the ten highest performers, NiFe/Al2O3 and NiFe/MgO are more active than Ni/Al2O3 and Ni/MgO, respectively and were stable over a period of 25 h at 800 degrees C. Characterization on the as-prepared samples reveals highly dispersed phase, while after reduction in H-2, highly dispersed and reduced nickel particles up to 10 nm are formed. The particles do not increase in size under dry reforming reaction conditions at 800 degrees C. An increased hydrogen consumption observed during H-2-TPR of the nickel particles is positively correlated with methane conversion for Al2O3-based catalysts. The resistance to deactivation by coking and variation in coke structure are investigated by spectroscopic and microscopic methods to identify the relationship between metal promoters, alloy formation, and type of surface carbon deposits. Carbon whiskers were observed on the ten selected spent samples and are preferentially deposited on Ni rather than on the promoters. Carbon nanotube formation and metal particle removal from support were not observed to cause deactivation while amorphous carbon formation was clearly linked to catalyst deactivation, as amorphous carbon could encapsulate Ni, either on the support or at the end of the carbon nanotube. The organometallic grafting technique is an efficient and suitable technique for synthesizing highly dispersed and homogeneous phases which lead to high conversion and high durability for dry reforming of methane.
      原文链接:
    • NSTL
    • Elsevier

    Improved catalyst formulations for the conversion of glycerol to bio-based aromatics

    He, SongboKramer, Thomas SjoukeKlein, Frederike Gerda HiltjeChandel, Anshu...
    13页
    查看更多>>摘要：The catalytic conversion of glycerol to aromatics (GTA, e.g., benzene, toluene, and xylenes, BTX) over a shaped H-ZSM-5/Al2O3 (60/40 wt%) catalyst was investigated in a continuous fixed-bed reactor to study the addition of the Al2O3 binder in the catalyst formulation on catalyst performance. The experiments were performed under N2 at 550 degrees C, a WHSV of glycerol (pure) of 1 h(-1), and atmospheric pressure. The spent H-ZSM-5/Al2O3 catalysts were reused after an oxidative regeneration at 680 degrees C and in total 5 reaction-regeneration cycles were performed. Catalyst characterization studies show that the addition of the Al2O3 binder does not affect the surface area and crystallinity of the formulation, but increases the total pore volume (mesopores in particular) and total acidity (Lewis acidity in particular). The H-ZSM-5/Al2O3 (60/40 wt%) catalyst shows a considerably prolonged catalyst life-time (8.5 vs. 6.5 h for H-ZSM-5), resulting in a significant increase in the total BTX productivity (710 vs. 556 mg g-1 H-ZSM-5). Besides, the addition of the Al2O3 binder retards irreversible deactivation. For instance, after 3 regenerations, catalyst performance is comparable to the fresh one. However, after 4 regenerations, some irre-versible catalyst deactivation occurs, associated with a reduction in total pore volume, crystallinity, and acidity (Bronsted acidity in particular), and meso-porosity of the Al2O3 binder. This study shows that both the stability and reusability of H-ZSM-5-based catalysts for GTA are remarkably enhanced when using a suitable binder.
      原文链接:
    • NSTL
    • Elsevier

    Clays catalyzed cascade Prins and Prins-Friedel-Crafts reactions for synthesis of terpenoid-derived polycyclic compounds

    Sidorenko, A. YuKurban, Yu M.Kravtsova, A., VIl'ina, I., V...
    14页
    查看更多>>摘要：The Prins/Friedel-Crafts cascade reactions of the terpenoid trans-4-hydroxymethyl-2-carene (synthesized from 3-carene) with aromatic aldehydes were systematically studied for the first time on acidic mesoporous clays (halloysite, illite, montmorillonites). Both the reaction rate and selectivity to the desired polycyclic product with tetrahydrofuran moiety increased with an increase in the catalyst acidity and their drying temperature, indicating that relatively strong Brunsted and Lewis acid sites favored their formation. The best activity and selectivity (up to 97%) was demonstrated over commercial montmorillonite K-10 with acidity of ca. 100 mu mol/g. In contrast, on strongest acids (resin Amberlyst-15), dehydration/aromatization of the substrate was observed. It was shown, that mesopomsity of the catalyst is one of the key factors governing catalytic behavior. The presence of at least one an electron-donor substituent at the meta-position of benzaldehyde is critical for the Prins-Friedel-Crafts reaction. Overall, available montmorillonites are an effective replacement for homogeneous catalysts for the Prins/Friedel-Crafts cascade reactions.
      原文链接:
    • NSTL
    • Elsevier

    Combination of piezoelectric additives and ball milling for high-efficiency degradation of organic dye in solid state

    Zhou, ShuzhenHao, JingyiZhou, MengjieQiao, Xiaoguang...
    7页
    查看更多>>摘要：The combination of piezoelectric material and ball milling leads to new frontiers in catalysis research. Here we used piezoelectric BaTiO3 nanoparticles as the additive for the degradation of dye pollutant in solid state in ball milling process. With the assistant of ppm level CuBr2 and H2O2, high degradation conversion (> 99%) of dyes can be achieved in short time (10 min). BaTiO3 nanoparticles became temporarily highly polarized particles during BM process and generated electron-hole. These particles exhibited strong reducing properties and reduced Cu(II) into the active Cu(I) species which can catalyze H2O2 to generate highly active .O2- to enhance the dye degradation. In addition to the general applicability for different dyes and larger scales, this BaTiO3 assist BM process was deduced to be a promising powerful platform for organic pollutant treatment in solid states.
      原文链接:
    • NSTL
    • Elsevier

    Synthesis of phosphate-bridged g-C3N4/LaFeO3 nanosheets Z-scheme nanocomposites as efficient visible photocatalysts for CO2 reduction and malachite green degradation

    Ai, BohanZaman, SaeedKhan, IltafLuo, Mingsheng...
    10页
    查看更多>>摘要：In this novel study, phosphate bridged p-type LaFeO3 nanosheets and n-type g-C(3)N(4 )nanosheets Z-scheme nanocomposites are successfully designed. Herein, our results confirmed that LaFeO3 nanosheets and g-C3N4 nanosheets have excellent performances as compared to nanosized LaFeO3 and g-C3N4 nanoparticles respectively. Based on TEM, HRTEM with elemental mapping, XRD, DRS, XPS, TR-PL, FTIR, TPD, PEC, BET and FS spectra related to center dot OH amount have confirmed that the fabrication of g-C3N4 nanosheets has successfully enhanced the charge separation and enlarged the surface area of LaFeO3 nanosheets. Correspondingly, the interfacing of phosphate bridge (P-O) with strong shuttling ability worked as linker and facilitator for photogenerated charge transfer and enhancement. In contrast to pristine LaFeO3 nanosheets (LFONS), the amount optimized resulting 15CNNS-3P-LFONS nanocomposites have 6-fold and 3.5-fold improvement in activities for CO2 reduction and malachite green degradation respectively. Based on scavenger experiments related to active species and photocatalytic pollutants degradation pathway mechanism, it is confirmed that h(+) and center dot O-2(-) is the vital species for malachite green degradation. Finally, we believe that our current novel research studies will open a new gateway for the synthesis of p-LaFeO3 and n-g-C3N4 type based Z-scheme and its utilization for energy production and environmental remediation.
      原文链接:
    • NSTL
    • Elsevier

    Efficient nickel and copper-based catalysts supported on modified graphite materials for the hydrogen production from formic acid decomposition

    Faroldi, B. M.Conesa, J. M.Guerrero-Ruiz, A.Rodriguez-Ramos, I...
    9页
    查看更多>>摘要：Ni, Cu and Ni-Cu catalysts supported on high surface area graphite were synthesized by incipient wet impregnation. Also, the effect of doping the graphite support with alkali oxides (Li, Na and K) was studied. The catalysts were tested in the formic acid decomposition reaction to produce hydrogen. The bimetallic Ni-Cu catalyst doped with K showed the best catalytic performance with 100% conversion of formic acid at 130 degrees C and a 95% of selectivity to hydrogen. The turnover frequency (TOF) of the catalysts follows the order: Ni-Cu/K > NiCu/Na > Ni-Cu > Ni-Cu/Li. While the order for the apparent activation energy values is: Ni-Cu > Ni-Cu/Li > Ni-Cu/Na > Ni-Cu/K. The mechanism of the reaction is approached by programmed temperature surface reaction (TPSR) experiments and attenuated total reflectance (ATR). The greater catalytic activity of the Ni-Cu catalyst doped with potassium is ascribed to the lower stability of the formate, bicarbonate and carbonate species on its surface.
      原文链接:
    • NSTL
    • Elsevier

    CH2Cl2 catalytic oxidation over Ce-Ti-Zr mixed oxide catalysts

    Pan, JunWang, YangyangXia, HangqiGao, Xiaohui...
    12页
    查看更多>>摘要：Ce-Ti-Zr mixed oxide catalysts prepared by sol-gel method were used in catalytic combustion of CH2Cl2. The characterization reveals that the incorporation of Ce and Zr into TiO2 anatase or Ti and Zr into CeO2 fluorite promotes hydroxyl groups, Lewis acidity and surface oxygen through the formation of Ti-O-Zr, Ti-O-Ce and Ce-OZr species. Ce-Ti-Zr catalysts show high activity for CH2Cl2 oxidation with the rate of 5.66 x 10-3-6.45 x 10-3 mu mol s(-1) m(-2) at 250 degrees C and high stability for 50 h. The substitution of surface oxygen for Cl maintains the availability of Ti-OH and thus promotes Cl removal as HCl, which is verified by a great increase in the stable activity of physically closely contacted mixture of separated CeO2 and TiO2 or Ti9Zr1 particles. In situ FT-IR shows that CH2Cl2 interacts with Ti-OH to form -O-CH2-O-, which is quickly rearranged into formate. Finally, formate is oxidized with surface oxygen into CO or CO2.
      原文链接:
    • NSTL
    • Elsevier

    Influence of framework Al distribution in HZSM-5 channels on catalytic performance in the methanol to propylene reaction

    Hu, XiaoyanZhou, MinYan, ZifengFeng, Rui...
    15页
    查看更多>>摘要：Nanosized and microsized ZSM-5 samples were prepared using a two-stage crystallization method in the presence of glucose and additional post-treated by acid leaching, tetrapropylammonium hydroxide, or ammonium fluorosilicate. The characterization results show that for synthesizing ZSM-5 zeolites, glucose inhibits the position of Al atoms in the channel intersections, thus forming additional single Al atoms and making more Al pairs at the straight and sinusoidal channels rather than channel intersections. The catalytic performance in the methanol conversion reaction shows that nanosized ZSM-5 catalysts are enriched in Al pairs in the channel intersections and exhibit higher ethylene and aromatics selectivity via the aromatic-based cycle, whereas microsized ZSM-5 catalysts have multiple single Al sites and low Al pairs in the channel intersections and exhibit higher propylene selectivity but lower aromatics selectivity via olefinic-based cycle. It provides a facile method to prepare the ZSM-5 zeolite with improved catalytic performance in the MTP reaction.
      原文链接:
    • NSTL
    • Elsevier

    Fischer-Tropsch synthesis: Towards a highly-selective catalyst by lanthanide promotion under relevant CO2 syngas mixtures

    Guilera, JordiAntonio Diaz-Lopez, JoseBerenguer, AntonioBiset-Peiro, Marti...
    9页
    查看更多>>摘要：The role of lanthanides as promoters on cobalt-based catalysts for Fischer-Tropsch synthesis was evaluated under relevant biomass-derived syngas mixtures. Cerium, lanthanum and a combination of them were impregnated on an industrial cobalt-based micro-catalyst. Lanthanide incorporation did not affect significantly the morphology of the catalyst, although it reduced the available surface cobalt. Catalytic tests revealed that both the presence of carbon dioxide in the feed and lanthanides in the catalyst led to similar outcomes; higher selectivity to long-chain hydrocarbons, at the expense of reactivity. Reaction experiments were well aligned with in-situ DRIFTS measurements, which evidenced the modification of the initial reaction mechanism, CO2 conversion and the presence of lower CO-cobalt coverages. This work reports two relevant findings for FTS development. Firstly, the presence of carbon dioxide is beneficial for long-chain hydrocarbon production. Secondly, the incorporation of lanthanides increases the production of gasoline, kerosene and diesel fractions.
      原文链接:
    • NSTL
    • Elsevier