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1.
《Applied catalysis》1982,2(1-2):75-86
The hydrodesulfurization of dibenzothiophene (DBT) is investigated at 240°C, under one atmosphere pressure of H2 + DBT, in a DBT conversion range giving rise to a H2S concentration between 30 and 200 ppm. The turnover number (TN) of platinum slightly decreases as the dispersion of platinum (Ptins) to Pt ratio = D (Pt)) increases from 0.01 to 0.7, whatever support (α-Al203, SiO2, chlorinated γ-Al2O3, SiO2-Al2O3, montmorillonite) was used. Furthermore, the TN is much lower for highly dispersed Pt/γ-Al2O3-C1 (D(Pt) = 0.9; ø (Pt) = 1.0 nm). Pt/TiO2 (D(Pt) = 0.06 or D(Pt) = 0.34) reduced or re-reduced at 240°C has a higher TN than the preceding catalysts. Reduction or re-reduction of Pt/TiO2, at 500°C results in only a relatively small decrease in the catalytic activity, in spite of the appearance of a strong metal-support interaction observed by several workers. For different supported metals on Al2O3, the TN follows the sequence: Pt > Ir > Ru > Re. Alloying Ir or Ru (25 to 30 at %) with Platinum results in a relatively small decrease in the TN (per one (Pts + Irs or Rus ) atom).The activity, per unit weight of catalyst, of an industrial Co-Mo/γ-Al2O3 sulfided catalyst (HR 306) is equivalent to that of 1 % Pt/γ-Al303 (D(Pt) = 0.7). The present platinum supported catalysts have a very low selectivity in hydrogenation (production of phenylcyclohexane, PCH < 1 %), except when supported by silica, SiO2-Al2O3 or montmorillonite; the Co-Mo/γ-Al203 catalyst has a selectivity which is intermediate between Pt/γ-Al2O3 and Pt/SiO2-Al2O3 or montmorillonite. The deactivation (decrease in activity versus the time en-stream) is lower for Co-Moγ-Al303 than for Pt/γ-Al3O3, but the addition of Ge to Pt/γ-Al2O3 gives rise to a more stable catalyst. 相似文献
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《Applied catalysis. B, Environmental》2001,29(2):115-123
Heterogeneous catalytic wet oxidation of aqueous p-chlorophenol (p-CP) solution was investigated at 453 K and 2.6 MPa in a slurry reactor. The performance of noble metal catalysts was compared with that of traditional manganese catalysts. Activated carbon supported catalysts showed significant higher activities for total organic carbon (TOC) reduction than those supported on alumina or cerium oxide. Pt was found to be the most active metal for p-chlorophenol oxidation. The activities of noble metal catalysts were found to correlate with heat of formation of metal oxides. CO2 is the predominant oxidation product with formation of minor p-benzoquinone and acetic acid as intermediate compounds. Possible reaction pathway was also discussed. 相似文献
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The influence of altervalent cation doping of TiO2 carriers on the chemisorptive and catalytic properties of supported Pt and Rh crystallites has been investigated. It was observed that doping of the carrier with higher valence cations leads to suppression of the H2 and CO chemisorption capacity of Pt catalysts, while their activity in hydrogenation and oxidation reactions is significantly reduced. The opposite effects were observed in the case of Rh catalysts supported on higher valence doped TiO2. These catalysts were found to possess higher activity in CO and CO2 hydrogenation, in aromatics hydrogenation and in CO and C2H4 oxidation. Their stability characteristics were also found to be superior to those of the undoped Rh/TiO2 catalyst. These effects are believed to originate from an electronic type interaction at the metal-support interface, induced by doping, which results in electron transfer from the support to the metal crystallites. 相似文献
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Wilfrid Jochum Dominik Eder Gernot Kaltenhauser Reinhard Kramer 《Topics in Catalysis》2007,46(1-2):49-55
Hydrogen treatment of Pt/TiO2 leads to an exceptional increase in electric conductivity even at moderate temperature presumably due to the formation of
donor electrons during a superficial reduction process. Interestingly, after cooling to lower temperatures that are typically
applied for catalytic reactions the observed high conductivity was largely preserved. The enhanced charge carrier density
in titania is assumed to cause a considerable charge transfer between support and metal. In this work we show that this charge
transfer is correlated with typical catalytic parameters (e.g. hydrogen adsorption capacity and catalytic activity for a hydrocarbon
skeleton reaction). Based on these observations we suggest and discuss a modified charge transfer mechanism in addition to
the decoration mechanism as a possible reason for the SMSI effect occurring during hydrogen treatment already at moderate
temperatures.
Dedicated to Konrad Hayek. 相似文献
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Deoxygenation of methyl esters and triglycerides was studied for production of either α-olefins or diesel components. The reactions were carried out in a reactive distillation fashion in which products are quickly removed from the reaction mixture in flowing He. The effects of He flow rate, reaction temperature, active component and support were studied. PtSnK supported on silica was found to be the best catalyst for selective production of α-olefins. Palm kernel oil and coconut oil were also deoxygenated to produce α-olefins or diesel components, depending on reaction conditions. 相似文献
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《Applied catalysis. B, Environmental》2005,55(1):1-10
Catalytic wet air oxidation (CWAO) of stearic acid was carried out in a batch reactor over noble metals (Ru, Pd, Pt, Ir) catalysts supported on ceria. The influence of reaction conditions such as temperature, oxygen pressure and stearic acid concentration were investigated. The reaction occurs via a complex mechanism. The molecule of stearic acid can be oxidized by successive carboxy–decarboxylation (RnCOOH + O2 → Rn−1COOH +CO2) yielding essentially CO2 (route A). It may also be oxidized after CC bond rupture within the alkyl chain, which gives rise to significant amounts of acetic acid besides CO2 (route B). Pt/CeO2 is a very active catalyst in the conversion of stearic acid and extremely selective to carbon dioxide (route A), while the mechanism via CC bond splitting is much more marked on Ru/CeO2. The catalyst characterization indicates that both noble metal and CeO2 particles remain stable during the reaction. 相似文献
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Dimitris K. Liguras Dimitris I. Kondarides Xenophon E. Verykios 《Applied catalysis. B, Environmental》2003,43(4):345-354
The catalytic performance of supported noble metal catalysts for the steam reforming (SR) of ethanol has been investigated in the temperature range of 600–850 °C with respect to the nature of the active metallic phase (Rh, Ru, Pt, Pd), the nature of the support (Al2O3, MgO, TiO2) and the metal loading (0–5 wt.%). It is found that for low-loaded catalysts, Rh is significantly more active and selective toward hydrogen formation compared to Ru, Pt and Pd, which show a similar behavior. The catalytic performance of Rh and, particularly, Ru is significantly improved with increasing metal loading, leading to higher ethanol conversions and hydrogen selectivities at given reaction temperatures. The catalytic activity and selectivity of high-loaded Ru catalysts is comparable to that of Rh and, therefore, ruthenium was further investigated as a less costly alternative. It was found that, under certain reaction conditions, the 5% Ru/Al2O3 catalyst is able to completely convert ethanol with selectivities toward hydrogen above 95%, the only byproduct being methane. Long-term tests conducted under severe conditions showed that the catalyst is acceptably stable and could be a good candidate for the production of hydrogen by steam reforming of ethanol for fuel cell applications. 相似文献
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《Journal of Industrial and Engineering Chemistry》2014,20(6):3947-3959
A variety of metal oxides catalysts are used in heterogeneous catalysis for chemical processes and have now been developed for their catalytic performance and durability. The heterogeneous catalysis is the most important technology in chemical industry as well as other environmental, energy applications, etc. This review examines recent advances at the preparation and applications of metal oxide particles, especially pertaining to catalytic enhancements for current and future chemical process such as Fischer–Tropsch process, alkylation, and transesterification and environmental applications such as the oxidation of volatile organic compounds and the reduction of NOx. 相似文献
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Catalysts used for high-temperature combustion of light hydrocarbons must maintain high activity over long time intervals by avoiding excessive sintering and deactivation in the hot and corrosive combustion environment. The sintering resistance and chemical stability of catalytically active phases is a key technical problem that must be solved for the development of commercially viable combustion catalysts. All noble metals and transition metal oxides that are catalytically active rapidly sinter at temperatures required for high combustion rates. Advanced materials used in the development of stable catalysts include highly sintering-resistant hexaaluminate supports for dispersion of noble metals, chemically and thermally stable supporting oxides for active transition metal oxides, and single-phase, substitutionally activated, sintering-resistant complex metal oxides. This paper will review deactivating phenomena, such as sintering and vapor transport and assess recent progress in the development of durable combustion catalysts. 相似文献
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Hydrodeoxygenation of guaiacol on noble metal catalysts 总被引:4,自引:0,他引:4
Hydrodeoxygenation (HDO) performed at high temperatures and pressures is one alternative for upgrading of pyrolysis oils from biomass. Studies on zirconia-supported mono- and bimetallic noble metal (Rh, Pd, Pt) catalysts showed these catalysts to be active and selective in the hydrogenation of guaiacol (GUA) at 100 °C and in the HDO of GUA at 300 °C. GUA was used as model compound for wood-based pyrolysis oil. At the temperatures tested, the performance of the noble metal catalysts, especially the Rh-containing catalysts was similar or better than that of the conventional sulfided CoMo/Al2O3 catalyst. The carbon deposition on the noble metal catalysts was lower than that on the sulfided CoMo/Al2O3 catalyst. The performance of the Rh-containing catalysts in the reactions of GUA at the tested conditions demonstrates their potential in the upgrading of wood-based pyrolysis oils. 相似文献
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Ferric hydroxide supported Pd catalyst prepared by a simple co-precipitation method without calcinations at elevated temperatures and only reduced at 50 °C possessed unexpectedly higher activity for CO oxidations even compared with that of supported Au catalysts. XRD and TEM results showed that the support was mixture of Fe(OH)x and Fe3O4 and Pd was highly dispersed on it. XPS results showed that Pd existed as mixture of oxidation and metal state. The large amount of OH group on the supports may play an important role in O adsorption and activation. 相似文献
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Catalytic decomposition of nitrous oxide over perovskite type solid oxide solutions and supported noble metal catalysts 总被引:2,自引:0,他引:2
The catalytic decomposition of nitrous oxide to nitrogen and oxygen has been investigated over various solid oxide solutions (SOS), La0.8Sr0.2MO3– (M=Cr, Fe, Mn, Co or Y), La1.8Sr0.2CuO4– and supported Pd, Pt catalysts. The reaction was carried out in a gradientless recycle reactor at 1 atm pressure with a feed gas containing about 0.5% N2O (in helium). Among the various solid solutions, La0.8Sr0.2CoO3– showed a maximum N2O conversion of 90% at 600C. The order of activity observed for N2O decomposition was La0.8Sr0.2CoO3–>La0.8Sr0.2FeO3–>La1.8Sr0.2CuO4–> La0.8Sr0.2MnO3–La0.8Sr0.2CrO3–La0.8Sr0.2YO3–. The activity of La0.8Sr0.2CoO3– was compared with supported Pd, Pt and also with unsubstituted LaCoO3 catalysts under similar reaction conditions. Among all the catalysts tested in this study, Pd/Al2O3 showed the lowest light-off temperature for N2O decomposition. The activity of La0.8Sr0.2CoO3– was found to be comparable to Pd/Al2O3 catalyst at temperatures above 500 C. The influence of added oxygen (about 4%) in the feed was examined over La0.8Sr0.2CoO3– and Pd/Al2O3 catalysts and only in the case of cobalt catalyst was the conversion of N2O decreased by 13%. By choosing varied sintering conditions, La0.8Sr0.2CoO3– of different BET surface areas were prepared and the light-off temperature was found to decrease with increase in surface area. The results obtained over solid solutions are discussed on the basis of the cation mixed valency and oxygen properties of the catalyst. 相似文献
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受“水俣公约”和环境保护政策约束,研究和开发新型无汞催化剂是保障我国乙炔法制备聚氯乙烯未来发展的核心环节。无汞催化剂包括贵金属催化剂、非贵金属催化剂和非金属催化剂,其中贵金属催化剂被认为是最具有工业化应用前景的催化剂。本文概述了近年来国内外乙炔氢氯化贵金属Au、Ru、Pd和Pt催化剂的研究进展,重点综述了不同催化剂的活性组分、催化机理及催化剂的改性方法等方面的研究,分析了不同改性方法的作用机制及不同催化剂改性的研究方向。研究表明,添加助剂或多金属复配、配体和离子液体的使用及载体改性均使贵金属催化剂的催化活性和稳定性得到一定程度提高,从而进一步增加了贵金属催化剂工业化应用的可能性。 相似文献
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The thiophene hydrodesulfurization (HDS) activity of Pt/ASA, Pt/SiO2, Ir/ASA and Ir/SiO2 catalysts at thiophene concentrations of 300 ppm has been studied at 573 K and 20 bar. Pt/ASA showed the highest HDS activity. Nitrogen tolerance was investigated by co-feeding ammonia in gas phase concentrations from 10 to 1000 ppm. The amorphous silica alumina (ASA) supported catalysts were similarly strongly inhibited by the presence of ammonia, with even 10 ppm of ammonia causing a significant drop in activity, despite widely different dispersions. The SiO2 supported catalysts were less severely affected by the presence of ammonia. 相似文献
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Shailesh J. Patil 《Chemical Engineering Communications》2019,206(5):605-618
Jatropha oil is a promising nonedible feedstock for producing renewable diesel. In this work, the hydrotreatment processing of jatropha oil was investigated. Instead of using conventional alumina-supported Co–Mo, Ni–Mo, and Ni–W catalysts that need sulfidation pretreatment, noble metals such as Pd and Ru were chosen. Trials were performed in an isothermal trickle-bed reactor and the reaction conditions were as follows: temperature 603–663?K, weight hourly space velocity (WHSV) 1 to 4/h, pressure 1.5–3?MPa, and H2/oil ratio 200–800 (v/v). Yield of n-C15 to n-C18 hydrocarbons was maximized (70.3 and 43.8% for Pd/Al2O3 and Ru/Al2O3, respectively) at the following conditions: T?=?663 K, WHSV?=?2/h, P?=?3?MPa, and H2/oil ratio?=?600 (v/v). Since Ru favored cracking reactions to a larger extent than Pd, the yield of C15 to C18 hydrocarbons over Ru/Al2O3 was lowered. Using simple first-order plots for oil conversion, activation energies for the hydrotreating process over Pd/Al2O3 and Ru/Al2O3 were found and they were equal to 109 and 121?kJ/mol, correspondingly. 相似文献