Deoxygenation of oleic acid: Influence of the synthesis route of Pd/mesoporous carbon nanocatalysts onto their activity and selectivity (original) (raw)
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Modified mesoporous materials as Pd scavengers and catalyst supports
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The use of mesoporous molecular sieves (MMSs) modified by mercaptopropyl trimethoxysilane (MPTMS) to scavenge Pd is described. The ordered mesoporous material displays excellent ability to remove Pd from organic and aqueous solutions. After only one treatment, a 500-ppm solution of PdCl 2 in water can be reduced to 1 ppb. In addition, the resulting material is an effective, leach-proof catalyst for the Suzuki-Miyaura and Mizoroki-Heck reactions. Thus, the Suzuki-Miyaura reaction can be conducted in water at 80 °C with as little as 3 ppb Pd leaching. Hot filtrations and three-phase tests confirm that the catalyst acts without leaching Pd from the surface.
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Selective production of octadecane through the hydrodeoxygenation of oleic acid in hexane containing pressurized CO 2 , a green reaction media, using a mesocellular foam (MCF) supported Fe-Pd-Ni/MCF catalyst was demonstrated in this study. In addition to hexane containing pressurized CO 2 playing a key role in directing the hydrotreatment of oleic acid towards hydrodeoxygenation over decarboxylation/decarbonylation, the use of MCF as the support helped achieve higher selectivity for octadecane, the major hydrodeoxygenation product while at the same time completely negating heptadecane, the decarboxylation/decarbonylation product. Negligible diffusion resistance aided by the 3-dimensional cage like structure and large pore opening of MCF, plus a better dispersion of the catalyst were identified as major reasons for enhancement of octadecane yield. An octadecane yield of 93% at 4 h was achieved through an optimization of temperature to 278°C and a H 2 pressure to 40 bars, while the CO 2 pressure was kept constant at 20 bars. The activation energy for the hydrodeoxygenation of stearic acid to octadecane was observed to be a 43.6% reduction over the existing literature. An increased spillover of H 2 onto the surface of Fe nanoparticles, triggered by an increased sticking capability of H 2 on Pd-Ni alloy patches formed on the top Fe nanoparticles, was proposed as the major reason for this acceleration. The proposed catalyst could not only avoid production of undesired decarbonized product heptadecane but also reduce energy requirement to achieve higher yield over reported data due to the lowering of temperature and time, indicating its superiority.
Preparation and characterization of Pd/C catalyst obtained in NH3-mediated polyol process
Journal of Power Sources, 2007
Vulcan XC-72R carbon supported Pd nanoparticles was obtained in a NH 3 -mediated polyol process without any protective agent and characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM) techniques. The added NH 3 species is found to have a strong complex ability to Pd, which not only avoids the formation of Pd hydroxide precipitate resulted from Pd hydrolysis, but also restrains the further complete reduction of Pd. Temperature-programmed reduction equipped with a mass spectrometry (TPR-MS) is employed to study the reductive behavior of unreduced Pd complex in Pd/C catalyst and the results show that the post-treatment in a reductive atmosphere at higher temperature is needed to ensure the complete reduction of Pd. XRD patterns show the heat-treated Pd/C sample in a reductive atmosphere has a face centered cubic crystal structure and TEM image indicates that the dispersion of Pd nanoparticles on the carbon support is uniform and in a narrow particle size range. Thermodynamic data analysis is carried out to elucidate the possible reaction pathway for the preparation of Pd/C catalyst in this process. The obtained Pd/C catalyst shows high activity to formic acid oxidation and high selectivity to oxygen reduction reaction (ORR) with the presence of methanol. acid fuel cell (DFAFC) due to their high catalytic activity to formic acid oxidation at lower temperature . The anodic oxidation of formic acid on Pd-based catalysts has been proposed to occur via a direct pathway, in which formic acid is directly oxidized to form the final product of CO 2 without forming CO like intermediate. In comparison with Pt-based catalysts, on which formic acid is oxidized to CO 2 with poisoning CO as the main reactive intermediate, the adoption of Pd catalyst could enhance the formic acid oxidation activity and decrease CO poisoning of the electrode catalyst, and thus to enhance cell performance of a DFAFC greatly . Another interesting property of Pd catalyst is its high sensitivity to oxygen reduction reaction (ORR) in acid solution with the presence of methanol. The methanol crossover is considered to be one of the biggest problems for the further development of direct methanol fuel cell (DMFC) technology. The crossover methanol in the cathode side is well known to depolarize the cathode greatly and 0378-7753/$ -see front matter
Catalysts, 2019
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Industrial & Engineering Chemistry Research, 2005
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Enantioselective hydrogenations with highly mesoporous carbon supported Pd catalysts
Journal of Molecular Catalysis A: Chemical, 2004
Highly mesoporous carbon supported Pd catalysts were prepared using sodium formate and hydrogen for the reduction of the catalyst precursors. These catalysts were tested in the enantioselective hydrogenation of isophorone and of 2-benzylidene-1-benzosuberone. The support and the catalysts were characterized by different methods such as nitrogen adsorption, hydrogen chemisorption, SEM, XPS, and TPD.
Chemical Engineering Science, 2018
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