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1.
The hydrogenolysis of dimethyl disulfide in the presence of Ni,Mo and Co,Mo bimetallic sulfide catalysts was studied at atmospheric pressure and T = 160–400°C. At T ≤ 200°C, dimethyl disulfide undergoes hydrogenolysis at the S-S bond, yielding methanethiol in 95–100% yield. The selectivity of the reaction decreases with increasing residence time and temperature due to methanethiol undergoing condensation to dimethyl disulfide and hydrogenolysis at the C-S bond to yield methane and hydrogen sulfide. The specific activity of the Co,Mo/Al2O3 catalyst in hydrogenolysis at the S-S and C-S bonds is equal to or lower than the total activity of the monometallic catalysts. The Ni,Mo/Al2O3 catalyst is twice as active as the Ni/Al2O3 + Mo/Al2O3 or the cobalt-molybdenum bimetallic catalyst.  相似文献   

2.
Ni‐based magnetic catalysts exhibit moderate activity, low cost, and magnetic reusability in hydrogenation reactions. However, Ni nanoparticles anchored on magnetic supports commonly suffer from undesirable agglomeration during catalytic reactions due to the relatively weak affinity of the magnetic support for the Ni nanoparticles. A hierarchical yolk–shell Fe@SiO2/Ni catalyst, with an inner movable Fe core and an ultrathin SiO2/Ni shell composed of nanosheets, was synthesized in a self‐templating reduction strategy with a hierarchical yolk–shell Fe3O4@nickel silicate nanocomposite as the precursor. The spatial confinement of highly dispersed Ni nanoparticles with a mean size of 4 nm within ultrathin SiO2 nanosheets with a thickness of 2.6 nm not only prevented their agglomeration during catalytic transformations but also exposed the abundant active Ni sites to reactants. Moreover, the large inner cavities and interlayer spaces between the assembled ultrathin SiO2/Ni nanosheets provided suitable mesoporous channels for diffusion of the reactants towards the active sites. As expected, the Fe@SiO2/Ni catalyst displayed high activity, high stability, and magnetic recoverability for the reduction of nitroaromatic compounds. In particular, the Ni‐based catalyst in the conversion of 4‐nitroamine maintained a rate of over 98 % and preserved the initial yolk–shell structure without any obvious aggregation of Ni nanoparticles after ten catalytic cycles, which confirmed the high structural stability of the Ni‐based catalyst.  相似文献   

3.
Oxidative desulfurization (ODS) of organic compounds containing sulfur element from a model oil was performed using tungsten oxide catalysts supported on mesoporous silica with cubic Ia3d mesostructure, well-defined mesopores (7.2 nm), high surface area (719 m2/g), and three-dimensional pore network (WO x /KIT-6). The prepared WO x /KIT-6 catalysts (5–20 wt% WO x ) were characterized by X-ray diffraction analysis, N2 sorption measurements, electron microscopy, H2-temperature programmed reduction, Raman spectroscopy, and thermogravimetric analysis. Among the mesoporous catalysts, 10 wt% WO x /KIT-6 exhibited the best catalytic performance. Sulfur-containing organic compounds, such as dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene, were completely (100 %) removed from the model oil over 10 wt% WO x /KIT-6 catalyst in 2 h. In addition, the catalyst could be reused several times with only slight decrease in catalytic activity.  相似文献   

4.
采用浸渍法制备了Ni掺杂的Cu-ZnO催化剂,采用多种物理化学手段研究了其化学物理性质及甘油加氢制取1,2-丙二醇反应催化性能。结果发现,金属Ni助剂的引入可以进一步优化Ni-Cu-ZnO催化剂的甘油加氢生成1, 2-丙二醇的反应活性。少量金属Ni的加入,Ni-Cu-ZnO催化剂的甘油转化率变化不大,生成1, 2-丙二醇的选择性明显增加。而进一步增加Ni含量到nNi/nCu=0.5,Ni含量过高会导致Ni-Cu-ZnO催化剂中实际Cu原子的量减少,从而导致甘油转化率下降。Ni掺杂的Cu-ZnO催化剂甘油加氢性能稳定性较好,在反应102 h后没有明显变化。  相似文献   

5.
The structure and catalytic characteristics of a series of Pd–Cu/α-Al2O3 catalysts with Pd: Cu ratio varied from Pd1–Cu0.5 to Pd1–Cu4 were studied. The use of α-Al2O3 with a small surface area (Ssp = 8 m2/g) as a support made it possible to minimize the effect of diffusion on the catalytic characteristics and to study the structure of Pd–Cu nanoparticles by X-ray diffraction (XRD) analysis. The XRD analysis and transmission electron microscopy (TEM) data indicated the formation of uniform bimetallic Pd–Cu nanoparticles (d = 20–60 nm), whose composition corresponded to a ratio between the metals in the catalyst, and also the absence of monometallic Pd0 and Cu0 nanoparticles. The study of catalytic properties in the liquid-phase hydrogenation of diphenylacetylene (DPA) showed that the activity of the catalysts rapidly decreased with the Cu content increase; however, in this case, the yield of a desired alkene compound significantly increased. The selectivity of alkene formation on the catalysts with the ratios Pd: Cu = 1: 3 and 1: 4 was superior to the commercial Lindlar catalyst.  相似文献   

6.
采用浸渍法制备了Ni掺杂的Cu-Zn O催化剂,采用多种物理化学手段研究了其化学物理性质及甘油加氢制取1,2-丙二醇反应催化性能。结果发现,金属Ni助剂的引入可以进一步优化Ni-Cu-Zn O催化剂的甘油加氢生成1,2-丙二醇的反应活性。少量金属Ni的加入,Ni-Cu-Zn O催化剂的甘油转化率变化不大,生成1,2-丙二醇的选择性明显增加。而进一步增加Ni含量到nNi/nCu=0.5,Ni含量过高会导致Ni-Cu-Zn O催化剂中实际Cu原子的量减少,从而导致甘油转化率下降。Ni掺杂的Cu-Zn O催化剂甘油加氢性能稳定性较好,在反应102 h后没有明显变化。  相似文献   

7.
The effect of Ce-promotion on 50 wt% Ni-based catalysts during the prereforming of n-tetradecane and its optimum content were investigated. The Ni catalyst was synthesized by deposition–precipitation method. Next, various amounts of Ce (0–13 wt%) were loaded on the Ni catalyst by impregnation. The characteristics of the prepared catalysts were analyzed by XRD, H2-TPR, BET, BJH, and H2-chemisorption analyses. The prepared catalysts were tested under the prereforming conditions (temperature = 400 °C, GHSV = 3000 h?1, and S/C = 3 and 4). The Ni catalyst was easily deactivated under the following conditions: temperature = 400 °C, GHSV = 3000 h?1, and S/C = 4. The stability of all Ce-promoted Ni catalysts was improved as compared to that of the Ni catalyst. Among the Ce-promoted catalysts, 5 wt% Ce/50 wt% Ni/MgO–Al2O3 catalyst showed excellent stability even under the severe condition of S/C = 3. SEM, TEM, and TG analyses were performed in order to identify the main factor responsible for the rapid deactivation of the Ni catalyst. In the case of 0Ce/50Ni, Ni particles were encapsulated by many folds of coke and it was related to the rapid catalyst deactivation. However, after Ce promoted on the Ni catalyst, the thickness of the coke layers and the number of encapsulated Ni particles decreased and the deposited amount of coke on the catalyst also decreased.  相似文献   

8.
负载型钌催化剂催化山梨醇氢解制乙二醇(英)   总被引:1,自引:0,他引:1  
Supported Ru catalysts were prepared by wet impregnation to evaluate the role of different oxide supports(Al2O3,SiO2,TiO2,ZrO2) in sorbitol hydrogenolysis to glycols.X-ray diffraction,transmission electron microscopy,hydrogen chemisorption,X-ray photoelectron spectroscopy,and NH3temperature-programmed desorption were used to characterize the catalysts,which were active in the hydrogenolysis of sorbitol.The support affected both the physicochemical properties and catalytic behavior of the supported Ru particles.The characterization results revealed that the Ru/Al2O3catalyst has a high surface acidity,partially oxidized Ru species on the surface,and a higher surface Ru/Al atomic ratio,which gave it the highest selectivity and yield to glycols.  相似文献   

9.
A series of Ni based catalysts with different supports and basic additives were prepared by sequential impregnation method. The catalysts were characterized by XRD, BET, H2-TPR and CO2-TPD techniques. It was found that the introduction of basic additives enhanced the basicities of catalyats and promoted the dispersities of Ni particles by strong interaction between Ni2+ and basic additives. Among the Ni based catalysts, 10%Ni/10%La2O3/ZrO2 showed the superior performance in sorbitol hydrogenolysis. The synergistic effect of Ni and La2O3 was proven to play an essential role in selective synthesis of EG and 1,2-PG. In the optimal reaction condition, the catalyst presented 100% sorbitol conversion and over 48% glycols (EG and 1,2-PG) yield. The kinetics study of polyols (sorbitol, xylitol and glycerol) hydrogenolysis showed that polyols with more hydroxyl number have higher activity and products distribution was final results of kinetic balance, which could give us some inspiration about how to change the products selectivity.  相似文献   

10.
A series of Ir1–xNixO2–y (0 ≤ x ≤ 0.5) composite oxides have been prepared by a simple pyrolysis method in ethanol system and used as the electrocatalysts for OER in acidic medium. The materials have been characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM). The electrochemical performances of these Ir1–xNixO2–y composite catalysts are evaluated by cyclic voltammetry (CV) and steady-state measurements. The resulting oxides with the Ni content (x) less than 0.3 have a complex nature of metal Ir and rutile structure IrO2 which is similar to the Ir oxide prepared by the same approach and possess the contracted lattice resulted from the Ni-doping. Although the addition of Ni reduces the electroactive surface areas due to the coalescence of particles, the catalytic activity of the Ir1–xNixO2–y (0 < x ≤ 0.3) catalysts is slightly higher than that of the pyrolyzed Ir oxide. Regardless of the surface area difference, the intrinsic activity first increases and then decreases with the Ni content in Ir1–xNixO2–y catalysts, and the intrinsic activity of Ir0.7Ni0.3O2–y catalyst is about 1.4 times of the Ni-free Ir oxide mainly attributed to the enhancement of conductivity and a change of the binding energy as increasing amount of the incorporated Ni with respect to the pure IrO2. The Ir0.7Ni0.3O2–y catalyst shows a prospect of iridium-nickel oxide materials in reducing the demand of the expensive Ir oxide catalyst for OER in acidic water electrolysis.  相似文献   

11.
A novel and simple method to synthesize supported Ni2P/Na(x)-MCM-41 catalysts (where x is the mass fraction of Na-to-MCM-41 in terms of percentage) at a lower reduction temperature by incorporation of Na was described. The catalysts were characterized by H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), N2 adsorption–desorption, CO uptake, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The effect of Na on the structure of catalysts and catalytic properties for the dibenzothiophene (DBT) hydrodesulfurization (HDS) was investigated, which confirmed that a suitable amount of Na can promote highly dispersed Ni2P particles. The Na preferentially interacts with phosphate to generate the sodium phosphate and therefore suppresses the formation of stronger P–O–P bonds, which enables the phosphide catalyst to be easily formed at a lower reduction temperature. Compared with conventional phosphate (973–1273 K), the reduction temperature of Ni2P/Na(x)-MCM-41 catalyst was relatively low (773 K). The Ni2P/Na(x)-MCM-41 catalyst with x?=?1.0 showed the maximum DBT conversion of 91.6%, which is higher than that of Ni2P/M41 without Na (80.3%).  相似文献   

12.
The direct conversion of ethanol into the linear primary alcohols C n H2n+1OH (n = 4, 6, and 8) in the presence of the original mono- and bimetallic catalysts Au/Al2O3, Ni/Al2O3, and Au–Ni/Al2O3 was studied. It was established that the rate and selectivity of the reaction performed under the conditions of a supercritical state of ethanol sharply increased in the presence of Au–Ni/Al2O3. The yield of target products on the bimetallic catalyst was higher by a factor of 2–3 than that reached on the monometallic analogs. Differences in the catalytic behaviors of the Au, Ni, and Au–Ni systems were discussed with consideration for their structure peculiarities and reaction mechanisms.  相似文献   

13.
This review paper reports the recent progress concerning the application of nickel–alumina–zirconia based catalysts to the ethanol steam reforming for hydrogen production. Several series of mesoporous nickel–alumina–zirconia based catalysts were prepared by an epoxide-initiated sol–gel method. The first series comprised Ni–Al2O3–ZrO2 xerogel catalysts with diverse Zr/Al molar ratios. Chemical species maintained a well-dispersed state, while catalyst acidity decreased with increasing Zr/Al molar ratio. An optimal amount of Zr (Zr/Al molar ratio of 0.2) was required to achieve the highest hydrogen yield. In the second series, Ni–Al2O3–ZrO2 xerogel catalysts with different Ni content were examined. Reducibility and nickel surface area of the catalysts could be modulated by changing nickel content. Ni–Al2O3–ZrO2 catalyst with 15 wt% of nickel content showed the highest nickel surface area and the best catalytic performance. In the catalysts where copper was introduced as an additive (Cu–Ni–Al2O3–ZrO2), it was found that nickel dispersion, nickel surface area, and ethanol adsorption capacity were enhanced at an appropriate amount of copper introduction, leading to a promising catalytic activity. Ni–Sr–Al2O3–ZrO2 catalysts prepared by changing drying method were tested as well. Textural properties of Ni–Sr–Al2O3–ZrO2 aerogel catalyst produced from supercritical drying were enhanced when compared to those of xerogel catalyst produced from conventional drying. Nickel dispersion and nickel surface area were higher on Ni–Sr–Al2O3–ZrO2 aerogel catalyst, which led to higher hydrogen yield and catalyst stability over Ni–Sr–Al2O3–ZrO2 aerogel catalyst.  相似文献   

14.
The unique physicochemical properties of ordered mesoporous transition metal oxides have attracted more and more attention. The hydrolysis process of metal oxide precursors is difficult to control, and it is difficult to synthesize an ordered mesoporous transition metal oxide material using the conventional template method. Ordered mesoporous Pt/Fe3O4–CeO2 heterostructure gel materials with excellent catalytic properties were successfully prepared using aerogel technology and the chemical deposition method. The Pt/Fe3O4–CeO2 material was an n–n combined heterostructured semiconductor material which consisted of a magnetic Fe3O4 layer, a CeO2 core and Pt noble metal doped nanoparticles. A layer of Fe3O4 thin film was formed on the surface of ordered mesoporous Pt/CeO2 gel matrix material using the chemical deposition method. The intriguing heterostructural features could facilitate reactant diffusion and exposure of active sites which could enhance synergistic catalytic effects between the Pt nanoparticles and CeO2 nanoparticles. Compared with Pt/CeO2, the prepared Pt/Fe3O4–CeO2 showed enhanced catalytic activity in the reduction of 4-nitrophenol at room temperature. The catalytic activity of the heterostructure catalysts was systematically investigated using 4-nitrophenol reduction as a model reaction. The results showed that the Pt (0.1%)/Fe3O4–CeO2 sample exhibited the optimal catalytic performance toward catalytic reduction of 4-nitrophenol to 4-aminophenol. The study provided a method for the preparation of heterostructure nanocatalysts with high efficiency, which would be effective for application in various catalytic reactions.  相似文献   

15.
《Comptes Rendus Chimie》2015,18(3):293-301
Dry reforming of methane has been carried out on SBA-15 catalysts containing 5 wt% Ni and 6 wt% Ce. The effect of the order of Ni and Ce impregnation on the catalytic activity has been studied. Both metals were added using the “two-solvent” method that favors metal dispersion inside the pores. Characterizations by XRD (low and high angles), N2 sorption, SEM and TEM of the materials after metal addition and calcination indicate good preservation of the porosities and high NiO and CeO2 dispersion inside the porous channels. Reduction was carried out before the catalytic tests and followed by TPR measurements. The most active reduced catalyst was the Ni–Ce/SBA-15 sample prepared by impregnating cerium first, then nickel. All catalysts were highly active and selective towards H2 and CO at atmospheric pressure. Full CH4 conversion was obtained below 650 °C. The higher performances compared to those reported in the literature for mesoporous silica with supported Ni and Ce catalysts are discussed.  相似文献   

16.
Using mesoporous N-doped carbons (NCs) derived from glucose and melamine as the supports, a series of Pd/NC catalysts were prepared, in which Pd nanoparticles with average size<2.0 nm were uniformly distributed on the supports. It was indicated that the resultant Pd/NC catalysts were effective for N-formylation of amines with CO2 and H2 in ethanol without any additives. Especially, the catalyst Pd/NC-800-6.9% containing quaternary N showed the best performance, affording a series of formylamides in good or even excellent yields. Further investigation reveals that the interaction between the Pd nanoparticles and quaternary nitrogen in the NC support was responsible for the good performance of the catalyst.  相似文献   

17.
Hydrogen was produced by Aqueous Phase Reforming (APR) of 10% (w/w) sorbitol using mono- and bi-metallic catalysts of Ni and Pt supported on alumina nano-fibre (Alnf), mesoporous ZrO2 and mixed oxides of ceria–zirconia–silica (CZxS) with varying concentration of silica (where x is silica concentration). X-ray diffraction, TEM/EDS and temperature programmed reduction were also carried on these catalysts to study the surface properties. It was observed that co-impregnation of Pt and Ni in atomic ratio 1:12 increased the reducibility of Ni by forming an alloy. However, sequential impregnation of Ni followed by Pt does not form the bi-metallic particles to increase the Ni reducibility. Reduction peak of co-impregnated Ni–Pt/Alnf was found to be 270 °C lower than the sequentially impregnated Pt/Ni/Alnf. The presence of silica at high concentration in CZxS support decreased the reducibility of ceria by forming an amorphous layer on CexZr1?xO2 crystals, which also decreased Ni reducibility. The rate of H2 formation from aqueous phase sorbitol reforming was found to be highest for co-impregnated Ni–Pt catalysts followed by sequentially impregnated Pt/Ni and monometallic Ni catalyst. The H2 activity decreased in the following order of the supports: Alnf > ZrO2 > CZ3S > CZ7S.  相似文献   

18.
A series of Ce–MnO x /TiO2 catalysts were prepared using a novel sol–gel template method and investigated for low-temperature selective catalytic reduction (SCR) of NO with NH3 at temperatures ranging from 353 to 473 K. The 0.07Ce–MnO x /TiO2 catalyst showed the highest activity and best resistance to SO2 poisoning. The structure and properties of the catalysts were characterized using X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), thermogravimetry (TG)–differential scanning calorimetry (DSC)–mass spectroscopy (MS), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) measurements, H2-temperature-programmed reduction (TPR), and NH3-temperature-programmed desorption (TPD). The superior catalytic activity of the 0.07Ce–MnO x /TiO2 catalyst was probably due to a change in the active components, an increase in surface active oxygen and surface acid sites, and lower crystallinity and larger surface area with Ce doping. Furthermore, the reduction ability also became stronger. The SO2 poisoning resistance of the 0.07Ce–MnO x /TiO2 catalyst improved because doping with Ce can effectively decrease the formation of ammonium salt on the catalyst surface and the sulfation of MnO x . In situ diffuse-reflectance infrared Fourier-transform (DRIFT) spectroscopy experiments indicated that addition of Ce could promote adsorption of NH3 and inhibit generation of some nitryl species. The SCR reactions over the catalysts mainly followed the Eley–Rideal mechanism accompanied with a partial Langmuir–Hinshelwood mechanism.  相似文献   

19.
This work is a continuation of the studies devoted to the synthesis of nanostructured carbon (NSC) as a result of the pyrolysis of a mixture of H2 + C3–C4 alkanes on supported Ni catalysts. Mesoporous alumina (γ-Al2O3) and titania (TiO2), on which Ni(II) compounds are deposited by impregnation or homogeneous precipitation, are studied as carriers. Using the methods of thermogravimetric analysis and scanning electron microscopy, it is shown that the activity of Ni catalysts (carbon yield) and the morphology of synthesized NSC are largely determined by the chemical nature of the support. It is found that the synthesis of NSC in the form of carbon nanofibers with a pronounced filamentary structure proceeds only on a Ni catalyst supported on titanium dioxide. The mesoporous carbon–mineral supports obtained after catalytic pyrolysis were studied in the adsorptive immobilization of the enzyme such as Thermomyces lanuginosus lipase. The adsorption properties of the supports, as well as the enzymatic activity and stability of the prepared biocatalysts in the esterification of saturated fatty acids (capric, C10: 0) with aliphatic alcohols (isopentanol, C5) in the non-aqueous media of organic solvents (hexane and diethyl ether) at ambient temperature, are studied. Biocatalysts prepared by lipase adsorption on NSC/TiO2 show the maximum esterification activity of 100 EA/g, which is 20–45 times higher than the activity of lipase adsorbed on NSC/Al2O3.  相似文献   

20.
Bimetallic Co–Ni catalysts in the composition range Co(1?x)Nix with x?=?0.0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8 and 1.0, with total metal loading of 15% w/w and supported on TiO2-P25, have been prepared by chemical reduction of the metal acetates by glucose in aqueous alkaline medium and characterized by XRD, TEM, TPR, XPS and H2-TPD techniques. Selective hydrogenation of cinnamaldhyde (CAL) to hydrocinnamaldehyde (HCAL), cinnamyl alcohol (COL) and hydrocinnamyl alcohol (HCOL) has been investigated at 20 bar pressure, in the temperature range 120–140 °C. Co/Ni crystallite sizes in the range 6.0?±?1 nm are observed by TEM. TPR and XPS results indicate the formation of nanoscale Co–Ni alloys, which tend to weaken M–H bond strength, as revealed by H2-TPD measurements. Ni/TiO2 displays very high conversion of CAL (86.9%) with high selectivity (78.7%) towards HCAL formation at 140 °C. Co/TiO2, on the other hand, exhibits relatively lower CAL conversion (55%) and higher selectivity (61.3%) for COL formation at the same temperature. However, bi-metallic Co–Ni catalysts in the composition range x?=?0.3–0.6 display very high conversion (>?98%) due to alloy formation and weakening of M–H bonds. Bimetallic Co0.7Ni0.3 catalyst displays high conversion of CAL (98.1%) and high selectivity (82.9%) towards HCOL. Overall CAL hydrogenation activity at 140 °C, when expressed as TOF, displays a maximum value at the composition Co0.5Ni0.5. Activity and selectivity patterns have been rationalized based on the reaction pathways observed on the catalysts and the influence of Co–Ni alloy formation and M–H bond strength. Thus, a synergetic effect, originating from an appropriate composition of base metal catalysts and reaction conditions, could result in hydrogenation activity comparable with noble metal based catalysts.  相似文献   

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