Benzene hydrogenation on nickel/honeycomb catalysts

Monolithic supported nickel catalysts were investigated in benzene hydrogenation between 100 and 280 °C. The conversion of benzene to cyclohexane reaches a maximum around 210 °C with a maximum yield at a ratio p^oH₂/p^oBz=3. The experimental results and some kinetic aspects are discussed.

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100 280 °C. 210 °C p^oH₂/p^oB=3. .

     

New high-selectivity hydrogenation catalysts prepared from bimetallic acetate complexes

The catalytic properties of new Pd-Zn/Al₂O₃ catalysts in selective acetylene hydrogenation in an acetylene-ethylene mixture at 30–120°C and atmospheric pressure are reported. The catalysts prepared from the bimetallic complex Pd-Zn(OOCMe)₄(OH₂) are much more selective than the catalysts prepared by simultaneously supporting the homonuclear complexes Pd₃(OOCMe)₆ and Zn(OOCMe)₂ · 2H₂O. It is demonstrated by diffuse reflectance IR spectroscopy of adsorbed CO that the heat treatment of the supported bimetallic complex at 250°C in flowing H₂ yields a Pd-Zn alloy on the surface. It is this alloy that ensures the high selectivity of the Pd-Zn/Al₂O₃ catalysts.     

Hydrodesulfurization and hydrogenation activities of carbon supported bimetallic catalysts

Carbon-supported noble metals are tailored for hydrodesulfurization reaction by adding iron, in such a manner that undesirable hydrogenation reactions are prevented without decrease of the catalytic activity.

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, , , .

     

NiFe双金属催化剂用于月桂酸甲酯加氢的研究

负载型Ni Fe/γ-Al₂O₃双金属催化剂的物理化学性质明显受还原温度的影响,进而影响月桂酸甲酯的加氢活性和产物选择性。金属Ni活性中心主要促进脱羰/脱羧(DOC)反应,Fe的加入能促进月桂酸甲酯发生加氢脱氧反应,促进C₁₂烷烃化合物生成。H₂-TPR、XRD、H₂-TPD和BET结果表明,高的还原温度有利于金属或合金活性中心形成,NiFe双金属催化剂的加氢活性取决于金属Ni、Fe和NiFe合金的含量;NiFe双金属催化剂吸附与活化H₂分子的能力明显受还原温度的影响。在研究的温度范围内,Ni活性中心具有优异的加氢和裂解性能,Fe物种的引入能有效抑制裂解性能。双金属催化剂的加氢活性顺序:NF420>NF360>NF450>NF300,在420℃下经H₂还原制得的NF420催化剂具有最佳的月桂酸甲酯加氢性能,在反应温度为380℃时,月桂酸甲酯加氢转化率和烷烃化合物选择性分别高达93.3%和90.0%。     

Dynamics of CO hydrogenation for bimetallic Co-Fe/Carrier catalysts

Bimetallic catalysts based a Co-Fe/carrier system are prepared via the consecutive and combined deposition of metals on Al₂O₃ and MgO · Al₂O₃. The dynamics of CO hydrogenation at 300°C is studied.     

CO2 hydrogenation on iron-containing mono- and bimetallic catalysts

The effect of chemical composition of supported, ironcontaining mono- and bimetallic catalysts on the mechanism of CO₂ adsorption and hydrogenation has been studied. It is shown that at 673 K the conversion degree of CO₂ decreases in the sequence Co/Al₂O₃> Co–Ni/Al₂O₃>Ni/Al₂O₃.

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CO₂. , 673 Co/Al₂O₃> Co–Ni/Al₂O₃>Ni/Al₂O₃ .

     

Synergic effect of palladium-based bimetallic catalysts for the hydrogenation of nitroaromatics

Bimetallic catalysts, PdCl₂-MX_n and PdCl₂(PhCN)₂-Mx_n (MX_n=FeCl₃, Fe(acac)₃, Co(OAc)₂, CoCl₂, Co(acac)₂, NiCl₂, Ni(OAc)₂, RuCl₃, Cu(OAc)₂, CuCl₂), exhibit remarkable synergic effect which can obviously increase the activity of the monometallic Pd catalyst for the hydrogenation of nitroaromatics, whereas MX_n alone is not catalytically active under the same reaction conditions.     

Selective hydrogenation of citral over Au-based bimetallic catalysts in supercritical carbon dioxide

Selective hydrogenation of citral was investigated over Au-based bimetallic catalysts in the environmentally benign supercritical carbon dioxide (scCO₂) medium. The catalytic performances were different in citral hydrogenation when Pd or Ru was mixed (physically and chemically) with Au. Compared with the corresponding monometallic catalyst, the total conversion and the selectivity to citronellal (CAL) were significantly enhanced over TiO₂ supported Pd and Au bimetallic catalysts (physically and chemically mixed); however, the conversion and selectivity did not change when Ru was physically mixed with Au catalyst compared to the monometallic Ru/TiO₂, and the chemically mixed Ru-Au/TiO₂ catalyst did not show any activity. The effect of CO₂ pressure on the conversion of citral and product selectivity was significantly different over the Au/TiO₂, Pd-Au/TiO₂, and Pd/TiO₂ catalysts. It was assumed to be ascribed to the difference in the interactions between Au, Pd nanoparticles and CO₂ under different CO₂ pressures.     

Preparation and catalytic performance of monolayer-dispersed Pd/Ni bimetallic catalysts for hydrogenation

Pd/Ni bimetallic catalysts were prepared by replacement reactions, characterized by X-ray diffraction, CO chemisorption and H₂ temperature-programmed desorption, and evaluated for hydrogenation of cyclohexene, styrene and acetone. The results show that Pd atoms are monolayer-dispersed on the Ni surface in these Pd/Ni catalysts. Consequently, Pd/Ni catalysts are much more active than Pd/Ni and Pd/c-Al₂O₃ with the same Pd loading prepared by the conventional impregnation method. __________ Translated from Chinese Journal of Catalysis, 2007, 28(8): 676–680 [译自: 催化学报]     

n-Hexane hydrogenolysis on bimetallic platinum-palladium catalysts

Alumina supported platinum, palladium and bimetallic platinum-palladium catalysts have been investigated in the hydrogenolysis of n-hexane. Results show that, compared with platinum, the activity of bimetallic catalysts is several times lower while the selectivity to hydrogenolytic products increases from 72 to 100%.

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, , , -. , , , 72 100%.

     

Insight into the role of iron in platinum-based bimetallic catalysts for selective hydrogenation of cinnamaldehyde

Selective hydrogenation of cinnamaldehyde (CAL) toward cinnamyl alcohol (COL) is an extremely important and challenging reaction. Herein, a series of Pt_xFe_y-Al₂O₃ bimetallic catalysts with varied Pt to Fe ratios were prepared by incipient wetness impregnation method. The introduction of Fe significantly modifies the electronic and surface properties of Pt, which clearly enhances the C=O hydrogenation selectivity. Among all the catalysts, Pt₃Fe-Al₂O₃ displays the best catalytic performance and the conversion of CAL is 96.6% with 77.2% selectivity of COL within 1 h. In addition, Pt₃Fe-Al₂O₃ had excellent reusability with 76% COL selectivity after five runs of the recycle process. Further characterization of the fresh, used and cycled catalysts revealed that the structure and electronic state of the synthesized Pt_xFe_y-Al₂O₃ are unchanged after hydrogenation reaction. The identical-location transmission electron microscopy (IL-TEM) results revealed that the interaction between the nanoparticles and the supports was strong and the catalyst was relatively stable.     

Nanoscale bimetallic catalysts: are they really bimetallic?

The existence of bimetallic particles (and their reducibility and location on/or in the support) in Ru–Co/NaY and Pt–Co/NaY samples has been studied by in situ X-ray adsorption spectroscopy (XAS). It is established that in Ru–Co/NaY the monometallic clusters maintain their identity, whereas in Pt–Co/NaY the existence of small bimetallic particles can be established. In both cases the results are supported by other techniques, such as XPS and temperature-programmed reduction. Copyright © 2002 John Wiley & Sons, Ltd.     

Ni基双金属催化剂加氢脱氧性能的研究

考察了Ni-M/γ-Al2O3（M＝Co、Cu、Fe、La）双金属催化剂对醇、酸、酮有机含氧化合物（丁醇、丁酸、丁酮）的加氢脱氧性能,并对其中间产物进行了考察。通过TPR、XRD表征手段对Ni基催化剂的还原性能、表面分散度等特性进行了研究。结果表明,Ni基催化剂中第二活性组分相对不同有机含氧化合物表现出不同的加氢活性和选择性。对于丁酸,在Ni基催化剂中加入Fe表现出较好的活性;对于丁醇,加入La有较好的加氢脱氧性能;而对于丁酮,加入Cu更有利于提高催化剂的脱除性能。醇和酯是有机酸在Ni/γ-Al2O3催化剂上加氢转化的中间产物。     

Benzene hydrogenation on sulfide catalyst under unsteady-state conditions

A kinetic model of benzene hydrogenation on a sulfide hydropurification catalyst (Ni,Mo)/Al₂O₃ has been developed. The model describes well the experimental data obtained under unsteady-state conditions and relies on the assumption that the catalyst surface contains only one type of active sites, i.e., Ni atoms in the sulfide bimetallic complex, and makes allowance for the transition of active sites into inactive sites. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanism and kinetics of the hydrogenation of CO to saturated hydrocarbons and alcohols on supported bimetallic catalysts containing rhodium

The mechanism of the simultaneous formation of methane, ethane, propane, methanol, ethanol, and propanol from carbon monoxide and hydrogen over supported bimetallic catalyst, Rh-M/Al₂O₃, has been established on the basis of kinetic and adsorption data. The experimental data are described quantitatively by kinetic and thermodynamic parameters calculated using the kinetic model.L. V. Pisarzhevskii Institute of Physical Chemistry, Ukraine National Academy of Sciences, Ukraine, 252039 Kiev, Nauki Prosp. 31. D. V. Sokol'skii Institute of Organic Catalysis and Electrochemistry, Kazakhstan National Academy of Sciences, Kazakhstan, 480110 Alma Ata, D. Kunaev Street, 142. Translated from Teoreticheskeskaya i Éksperimental'naya Khimiya, Vol. 32, No. 2, pp. 97–101, March–April, 1996. Original article submitted May 23, 1995.     

Enhanced catalytic performance of Pd‐Ga bimetallic catalysts for 2‐ethylanthraquinone hydrogenation

A series of Pd and Pd‐Ga bimetallic catalysts were prepared by a co‐impregnation method for 2‐ethylanthraquinone (EAQ) hydrogenation to produce hydrogen peroxide. Compared with 0.6Pd catalyst, the hydrogenation efficiency of 0.6Pd1.2Ga catalyst (11.9 g L^?1) increases by 32.2%, and the stability of 0.6Pd1.2Ga catalyst is also higher than that of 0.6Pd catalyst. The structures of the samples were determined by N₂ adsorption–desorption, ICP, XRD, CO chemisorption, TEM, H₂‐TPR, in situ CO‐DRIFTS and XPS. The results suggest that incorporation of Ga species improves Pd dispersion and generates a strong interaction between Ga₂O₃ and Pd interface or between Pd and support. DFT calculation results indicate that the strong adsorption of carbonyl group on Ga₂O₃/Pd interface facilitates the activation of EAQ and promotes the hydrogenation efficiency.     

Enantioselective hydrogenation on heterogeneous metal catalysts

The rate of formation of the excess of one enantiomeric product in the enantioselective hydrogenation of ethyl acetoacetate (EAA) and acetylacetone (acac) on a Raney copper catalyst modified with chiral aminoacids (AmA) correlates with the formation constants of the mixed complexes [CU EAA AmA] and [Cu acac AmA].

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() - () , () [Cu··] [Cu··].