Showing papers in "Catalysis Letters in 2009"
TL;DR: In this paper, the authors showed that carbon nanotubes (CNTs) were the most efficient support of Ru for cellulose conversion, and the mean size of Ru nanoparticles over CNT was ~8.8nm.
Abstract: Cellulose samples with different crystallinities (33–85%) were prepared by treating a commercial cellulose (crystalline, 85%) with phosphoric acid under different conditions. Supported Fe, Co, Ni, Pd, Pt, Rh, Ru, Ir, Ag, and Au catalysts were examined for the conversion of cellulose with a crystallinity of 33% in water medium in the presence of hydrogen, and Ru was found to be the most effective catalyst for the formation of sorbitol. We demonstrated that carbon nanotubes (CNTs) were the most efficient support of Ru for cellulose conversion, and the mean size of Ru nanoparticles over CNT was ~8.8 nm. NH3-TPD and H2-TPD characterizations suggest that plenty of acid sites and unique hydrogen species over the Ru/CNT are important for sorbitol formation through hydrolysis and hydrogenation of cellulose. A 40% yield of hexitols (including 36% of sorbitol) could be achieved over the Ru/CNT catalyst for the conversion of the commercial cellulose (crystalline, 85%), and this yield was the highest one reported to date for the direct conversion of cellulose into sugar alcohols.
277 citations
TL;DR: In this paper, the synthesis of palladium (Pd) nanoparticles incorporated poly-(3,4)ethylenedioxythiophene (PEDOT) matrix in aqueous medium and its catalytic performance towards 4-nitrophenol reduction was reported.
Abstract: We report here the synthesis of palladium (Pd) nanoparticles incorporated poly-(3,4)ethylenedioxythiophene (PEDOT) matrix in aqueous medium and its catalytic performance towards 4-nitrophenol reduction. This simple one-pot synthesis involving a redox reaction between 3,4-ethylenedioxythiophene and palladium chloride (PdCl2) precursor, leads to the formation of Pd nanoparticles supported on particulate PEDOT. Pd nanoparticles of size 1–9 nm were found to distribute uniformly over the PEDOT matrix. Morphology of the Pd–PEDOT nanocomposite was characterized by field emission-scanning electron microscopy and transmission electron microscopy and the crystallographic details obtained using X-ray diffraction. The chemical nature of the PEDOT support matrix was analyzed using Fourier transform-infra red (FT-IR) spectroscopy. The catalytic activity of the composite was demonstrated using a model reaction, i.e., reduction of 4-nitrophenol to 4-aminophenol. The value of the apparent rate constant, ca. 65.8 × 10−3 s−1 obtained using UV visible spectroscopy of the reduction of 4-nitrophenol at the Pd–PEDOT nanocomposite is comparable to those reported for other catalytic systems.
187 citations
TL;DR: In this article, the deoxygenation of methyl octanoate and methyl stearate over alumina-supported Pt was studied in both the vapor phase in a flow reactor and in the liquid phase in the semibatch reactor.
Abstract: The deoxygenation of methyl octanoate and methyl stearate over alumina-supported Pt was studied in both the vapor phase in a flow reactor and in the liquid phase in a semibatch reactor. The conversion of both methyl esters resulted in hydrocarbons with one carbon less than the fatty acid of the corresponding ester as the dominant products. In the vapor phase, acid and other oxygenates were observed in low concentrations, but they were not detected when the reaction was conducted in the liquid phase. Under He, condensation products (from esterification and ketonization) were observed. By contrast, under H2, mostly paraffins were obtained. These results show promise to directly produce standard diesel components from biodiesel.
165 citations
TL;DR: In this article, the catalytic activity of colloid platinum nanoparticles synthesized with different organic capping layers was investigated for CO oxidation on several platinum nanoparticle systems capped with various organic molecules.
Abstract: We report the catalytic activity of colloid platinum nanoparticles synthesized with different organic capping layers. On the molecular scale, the porous organic layers have open spaces that permit the reactant and product molecules to reach the metal surface. We carried out CO oxidation on several platinum nanoparticle systems capped with various organic molecules to investigate the role of the capping agent on catalytic activity. Platinum colloid nanoparticles with four types of capping layer have been used: TTAB (Tetradecyltrimethylammonium Bromide), HDA (hexadecylamine), HDT (hexadecylthiol), and PVP (poly(vinylpyrrolidone)). The reactivity of the Pt nanoparticles varied by 30%, with higher activity on TTAB coated nanoparticles and lower activity on HDT, while the activation energy remained between 27 and 28 kcal/mol. In separate experiments, the organic capping layers were partially removed using ultraviolet light-ozone generation techniques, which resulted in increased catalytic activity due to the removal of some of the organic layers. These results indicate that the nature of chemical bonding between organic capping layers and nanoparticle surfaces plays a role in determining the catalytic activity of platinum colloid nanoparticles for carbon monoxide oxidation.
164 citations
TL;DR: In this paper, a series of mesoporous metal oxides with highly crystalline walls were characterized by PXRD, TEM, N2 adsorption and evaluated as CO oxidation catalysts.
Abstract: Crystalline mesoporous metal oxides have attracted considerable attention recently, but their catalytic applications have rarely been studied. In this work, a series of crystalline three-dimensional mesoporous metal oxides (i.e., CeO2, Co3O4, Cr2O3, CuO, Fe2O3, β-MnO2, Mn2O3, Mn3O4, NiO, and NiCoMnO4) were prepared using the mesoporous silica KIT-6 as a hard template. These ordered mesoporous metal oxides with highly crystalline walls were characterized by PXRD, TEM, N2 adsorption and evaluated as CO oxidation catalysts. These mesoporous materials, except for mesoporous Fe2O3, exhibit much higher catalytic activities than their bulk counterparts. In particular, mesoporous Co3O4, β-MnO2, and NiO show appreciable CO oxidation activity below 0 °C, and the catalytic activities of mesoporous β-MnO2, and NiO are even higher than those of their nanoparticulate counterparts with large surface areas. β-MnO2 is particularly interesting because it combines low cost and low toxicity with high activity (T 50 = 39 °C).
150 citations
TL;DR: In this paper, Fe-doped titanate nanotubes (Fe/TiO2 NTs) with high photocatalytic activity were obtained by the combination of sol-gel process with hydrothermal treatment.
Abstract: Fe-doped titanate nanotubes were prepared by the combination of sol–gel process with hydrothermal treatment. After a further calcinations process, Fe-doped TiO2 nanotubes (Fe/TiO2 NTs) with high photocatalytic activity were obtained. The prepared catalysts were characterized by XRD, TEM, and XPS. The photocatlytic activity of Fe/TiO2 NTs was evaluated through the photodegradation of aqueous methyl orange. The experiments demonstrated that the 0.5% Fe/TiO2 NTs calcined at 300 °C possessed the best photocatalytic activity. Compared with pure TiO2 nanotubes, the doping with Fe significantly enhanced the photocatalytic efficiency.
147 citations
TL;DR: In this article, a sulfonated (SO3H-bearing) carbon catalyst with mesoporous structure and high specific surface area is successfully prepared by impregnating the cellulosic precursor (wood powder) with ZnCl2 prior to activation and sulfonation.
Abstract: A sulfonated (SO3H-bearing) carbon catalyst with mesoporous structure and high specific surface area is successfully prepared by impregnating the cellulosic precursor (wood powder) with ZnCl2 prior to activation and sulfonation. The specific surface area of the porous carbon catalyst thus prepared is also found to increase with carbonization temperature to a maximum of 1,560 m2 g−1 at ca. 773 K. Structural analyses reveal that the porous carbon catalysts carbonized at temperatures higher than 723 K contain high densities of micro- and mesopores. The porous carbon catalyst exhibits high catalytic performance for the esterification of acetic acid (343 K), the activity for which is dependent only on the acid density. The porous carbon catalyst also exhibits high catalytic activity for the benzylation of toluene, whereas non-porous sulfonated carbon has very limited activity for this reaction. The activity for the benzylation of toluene is dependent on both the specific surface area and the acid density of the sulfonated porous carbon catalyst.
139 citations
TL;DR: In this article, a simple method for preparing nanocrystalline C-N-codoped TiO2 photocatalyst was developed by annealing titanium carbonitride.
Abstract: A simple method for preparing nanocrystalline C–N-codoped TiO2 photocatalyst was developed by annealing titanium carbonitride. The prepared C–N-codoped TiO2 powders were characterized by TGA, XRD, XPS, UV–Vis, PL, SEM, and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic degradation of methylene blue in an aqueous solution under visible-light radiation. Results showed that the annealing temperatures and time affected the crystal composition and structure and activity of the catalyst. The most promoting effect of C–N-codoping in activity was obtained over C–N-codoped TiO2 prepared by annealing titanium carbonitride at 400 °C for 8 h. The high photocatalytic activity could be attributed to the synergetic effects in light absorption and the suppression of recombination of electrons/holes pairs.
138 citations
TL;DR: In this paper, the authors investigated the catalytic properties of Co3O4, CeO2, and Co 3O4-CeO2 mixed oxides and compared with a conventional Pt(1/Al2O3) catalyst.
Abstract: The catalytic oxidation of toluene, chosen as VOC probe molecule, was investigated over Co3O4, CeO2 and over Co3O4–CeO2 mixed oxides and compared with the catalytic behavior of a conventional Pt(1 wt%)/Al2O3 catalyst. Complete toluene oxidation to carbon dioxide and water was achieved over all the investigated systems at temperatures below 500 °C. The most efficient catalyst, Co3O4(30 wt%)–CeO2(70 wt%), showed full toluene conversion at 275 °C, comparing favorably with Pt/Al2O3 (100% toluene conversion at 225 °C).
132 citations
TL;DR: Using a SiO2 supported copper and H4SiW12O40 catalyst, the authors showed that glycerol can be directly converted to 1,3-Propanediol (1-3-PD) through vapor-phase process under pressure below 0.54 MPa, without employing environmentally harmful organic solvent.
Abstract: Using a SiO2 supported copper and H4SiW12O40 catalyst, it is demonstrated that glycerol can be directly converted to 1,3-Propanediol (1,3-PD) through vapor-phase process under pressure below 0.54 MPa, without employing environmentally harmful organic solvent. The formation of 1,3-PD is proved to proceed through the designed reaction pathway: (step 1) dehydration of glycerol to 3-hydroxypropanal on acid site of supported H4SiW12O40 (step 2) hydrogenation of 3-hydroxypropanal on supported copper metal. The effect of temperature, weight hourly space velocity, pressure, and initial water content was investigated to obtain the optimum conditions. The glycerol conversion and products distribution greatly depended on these factors. Both the 1,3-PD and 1,2-Propanediol selectivity improved with increasing hydrogen pressure. At 210 °C, 0.54 MPa and 83.4% conversion, the selectivity of 1,3-PD was up to 32.1%, together with a 22.2% selectivity of 1,2-Propanediol. The cyclic acetal, an important kind of byproducts, was identified by Gas Chromatogram–Mass Spectrometer (GC–MS).
128 citations
TL;DR: In this paper, a series of mesoporous composite photocatalysts for photoreduction of CO2 with H2O to methanol were synthesized by sol-gel synthesis.
Abstract: A series of mesoporous TiO2/SBA-15, Cu/TiO2 and Cu/TiO2/SBA-15 composite photocatalysts were prepared by sol–gel synthesis for photoreduction of CO2 with H2O to methanol. It was found that optimum amount of titanium loading of TiO2/SBA-15 was 45 wt% which exhibited higher photoreduction activity than pure TiO2. An addition of copper on TiO2 or TiO2/SBA-15 catalyst as cocatalyst was found to enhance the catalytic activity because copper serves as an electron trapper and prohibits the recombination of hole and electron.
TL;DR: In this article, a WO3/ZrO2 solid heterogeneous catalysts in a continuous flow fixed bed reactor were used to de-hydrate glycerol to acrolein.
Abstract: Dehydration of glycerol to acrolein was performed on WO3/ZrO2 solid heterogeneous catalysts in a continuous flow fixed bed reactor. A maximum of 75% acrolein selectivity was achieved at 100% conversion of glycerol. The acrolein selectivity correlates with the concentration of weak acidic sites of the WO3/ZrO2 catalysts that were free of basic sites.
TL;DR: In this paper, the deoxygenation experiments of different reactants, i.e., pure palmitic acid, stearic acid and a technical grade stearric acid containing a mixture of 59% of palmitics and 40% of stearics, were successfully performed over 4 wt% Pd/C mesoporous catalyst at 300 °C under 17 bar of 5% H2 in argon.
Abstract: The deoxygenation experiments of different reactants, ie, pure palmitic acid, stearic acid, and a technical grade stearic acid containing a mixture of 59% of palmitic and 40% of stearic acid were successfully performed over 4 wt% Pd/C mesoporous catalyst at 300 °C under 17 bar of 5% H2 in argon The main product in catalytic deoxygenation of saturated fatty acids, C16 and C18, were aliphatic chain length hydrocarbons containing one less carbon than the corresponding acid Additionally it was found that the deoxygenation rates of different reactant were independent on carbon chain length of its fatty acids
TL;DR: In this article, a novel one-step fabrication of Ag-deposited Fe2O3 nanoparticles and their application for the catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH4 was investigated.
Abstract: In this work, we have investigated a novel one-step fabrication of Ag-deposited Fe2O3 nanoparticles and their application for the catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH4. To deposit Ag onto them, Fe2O3 particles were dispersed in a reaction mixture consisting of ethanolic AgNO3 and butylamine, and then the reaction mixture was incubated and shaken for 40 min at 45 °C. With this simple and surfactant-free fabrication of Ag-deposited Fe2O3 nanoparticles, we can avoid contamination in the final product, which makes them suitable for further catalytic applications. Since the magnetic particles are readily recovered from the solution phase without centrifugation and/or filtering, the Ag-deposited Fe2O3 nanoparticles prepared in this work have been exploited as solid phase catalysts for the reduction of 4-nitrophenol in the presence of NaBH4. At the end of the reaction, the Ag-deposited Fe2O3 catalyst particles still remain active. They can thus be separated from the product, 4-aminophenol, simply using a neodium magnet and can be recycled a number of times.
TL;DR: In this article, the conversion of ethanol to propylene over ZSM-5 zeolites was investigated and the catalytic performance of H-ZSM-4 (Si/Al2 = 30, 80, and 280) and ZSM5 (Si /Al 2 = 80) modified with various metals was investigated.
Abstract: In this work, we studied the conversion of ethanol to propylene over ZSM-5 zeolites. The catalytic performance of H-ZSM-5 (Si/Al2 = 30, 80, and 280) and ZSM-5 (Si/Al2 = 80) modified with various metals was investigated. H-ZSM-5(Si/Al2 = 80) afforded high propylene yield, which indicates that a moderate surface acidity favored propylene production. Zr-modified ZSM-5(80) gave the highest yield (32%) of propylene at 773 K. Furthermore, the catalytic stability of the zeolite was improved by the modification of zirconium. The surface acidity and the presence of metal ions played important roles on the production of propylene.
TL;DR: In this article, the authors explore a path starting with the hydrogenation of the surface, which liberates iron 4-fold sites for adsorption and dissociation of CO. The reaction cycle to methane resembles the Mars-van Krevelen mechanism for oxidation reactions.
Abstract: Computational chemistry is used to explore a mechanism for CO hydrogenation to methane on iron carbides. As CO dissociation is endothermic on carbon terminated Fe5C2 (100) cuts, we explore a path starting with the hydrogenation of the surface, which liberates iron 4-fold sites for adsorption and dissociation of CO. The reaction cycle to methane resembles the Mars-van Krevelen mechanism for oxidation reactions.
TL;DR: In this article, a series of HBeta, HZSM-5, Al2O3, MgO and hydrotalcite precursor supported Pt catalysts were prepared and used for glycerol hydrogenolysis to 1,2propanediol (1,2-TPD) in a base-free aqueous solution.
Abstract: A series of HBeta, HZSM-5, Al2O3, MgO and hydrotalcite precursor supported Pt catalysts were prepared and used for glycerol hydrogenolysis to 1,2-propanediol (1,2-TPD) in a base-free aqueous solution. XRD, TEM, CO2-TPD and H2-TPD characterizations concluded that the activity for glycerol hydrogenolysis of the tested catalysts depends mainly on their alkalinity and particle size of Pt. A hydrotalcite precursor supported Pt catalyst with strong alkalinity and highly dispersed Pt particles exhibited the predominant performance for the desired reaction (with a 93.0% selectivity of 1,2-PDO at a conversion of 92.1%) in a base-free aqueous solution at lower pressure, and can be recycled simply by filtration.
TL;DR: In this article, the photocatalytic reforming of glycerol to hydrogen over palladium and gold modified TiO2 catalysts was reported and the rate of hydrogen production exceeds that measured for the photoreforming of methanol over both catalysts with the palladium catalyst performing approximately four times better than gold.
Abstract: The photocatalytic reforming of glycerol to hydrogen over palladium and gold modified TiO2 catalysts is reported. The rate of hydrogen production exceeds that measured for the photoreforming of methanol over both catalysts with the palladium catalyst performing approximately four times better than the gold. The reaction occurs under ambient conditions and neither system suffered from poisoning after extensive testing. This therefore offers a potentially attractive route by which one of the major waste products from the manufacture of biodiesel can be converted into a useful product.
TL;DR: In this paper, the photocatalytic activities of the NaNbO3 samples were evaluated for the H2 evolution from CH3OH/H2O solution under UV light irradiation.
Abstract: NaNbO3 nanowires and cubes were synthesized by means of a facile surfactant-assisted hydrothermal process. The NaNbO3 nanowires were single-crystalline and showed uniform size with a diameter of about 100 nanometers in width and length of up to several tens of micrometers in length. The NaNbO3 cubes displayed edges of several hundred nanometers. Meanwhile, the possible growth mechanism of NaNbO3 nanowires was proposed. In addition, the photocatalytic activities of the NaNbO3 samples were evaluated for the H2 evolution from CH3OH/H2O solution under UV light irradiation. Compared with the cubes-NaNbO3 and a NaNbO3 sample prepared by solid state reaction method, NaNbO3 nanowires showed a much higher photocatalytic activity.
TL;DR: In this paper, it was shown that the conversion of ethanol to gasoline over an HZSM-5 catalyst yields essentially the same product distribution as for methanol-to-gasoline performed over the same catalyst.
Abstract: It is shown that the conversion of ethanol-to-gasoline over an HZSM-5 catalyst yields essentially the same product distribution as for methanol-to-gasoline performed over the same catalyst. Interestingly, there is a significant difference between the identity of the hydrocarbon molecules trapped inside the HZSM-5 catalyst when ethanol is used as a feed instead of methanol. In particular, the hydrocarbon pool contains a significant amount of ethylsubstituted aromatics when ethanol is used as feedstock, but there remains only methyl-substituted aromatics in the product slate.
TL;DR: In this article, a three-component reaction of aldehydes, dimedone, malononitrile in 20% ethanol using anhydrous potassium phosphate as a catalyst at room temperature is described.
Abstract: An efficient, rapid, one-pot synthesis of tetrahydrobenzo[b]pyran is achieved via a three-component reaction of aldehydes, 1,3-diketone, malononitrile in 20% ethanol using anhydrous potassium phosphate as a catalyst at room temperature. The key advantages are the short reaction time, high yields, simple work-up, inexpensive catalyst and purification of products by non-chromatographic methods, i.e. by simple recrystallization from ethanol. An efficient, rapid, one-pot synthesis of tetrahydrobenzo[b]pyran is achieved via a three-component reaction of aldehydes, dimedone, malononitrile in 20% ethanol using anhydrous potassium phosphate as a catalyst at room temperature. The key advantages are the short reaction time, high yields, simple work-up, inexpensive catalyst and purification of products by non-chromatographic methods, i.e. by simple recrystallization from ethanol.
TL;DR: In this paper, a series of Ru/SBA-15 catalysts (0.5 − 6.0 ) are prepared by impregnation method and the catalytic activities were evaluated for the vapor phase hydrogenation of nitrobenzene.
Abstract: A series of Ru/SBA-15 catalysts (0.5–6.0 wt%) are prepared by impregnation method. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), CO-chemisorption, surface area and pore-size distribution measurements. The catalytic activities were evaluated for the vapor phase hydrogenation of nitrobenzene. The dispersion measured by CO-uptake values suggests decrease in dispersion with increasing Ru loading on SBA-15. These findings are well supported by the crystallite size measured from XRD and TEM measurements. XPS study reveals the formation of Ru0 after reduction at 573 K for 3 h. The catalysts exhibit high conversion/selectivity at 4.5 wt% Ru loading during hydrogenation reaction. The particle size measured from CO-chemisorption and TEM analysis related to the TOF during the hydrogenation reaction. Ru/SBA-15 catalysts are found to show higher conversion/selectivities during hydrogenation of nitrobenzene than Ru/SiO2 and Ru/Al2O3 catalysts.
TL;DR: In this article, the selectivity and activity for the hydrogenation of crotonaldehyde to crotyl alcohol and butyraldehyde was studied over a series of Pt nanoparticles (diameter of 1.7, 2.9, 3.6, and 7.1 nm).
Abstract: The selectivity and activity for the hydrogenation of crotonaldehyde to crotyl alcohol and butyraldehyde was studied over a series of Pt nanoparticles (diameter of 1.7, 2.9, 3.6, and 7.1 nm). The nanoparticles were synthesized by alcohol reduction of a Pt salt in the presence of poly(vinylpyrrolidone) (PVP), followed by incorporation into mesoporous SBA-15 silica. The rate of crotonaldehyde hydrogenation and selectivity towards crotyl alcohol both increase with increasing particle size. With an increase in particle size from 1.7 nm to 7.1 nm, the selectivity towards crotyl alcohol increases from 13.7% to 33.9% (8 Torr crotonaldehyde, 160 Torr H2 and 353 K). The turnover frequency increases from 2.1 × 10−2 s−1 to 4.8 × 10−2 s−1 with increasing particle size. Additionally, the decarbonylation pathway to form propene and CO is enhanced over smaller nanoparticles. The apparent activation energy remains constant (~16 kcal mol−1 for the formation of butyraldehyde and ~8 kcal mol−1 for the formation of crotyl alcohol) as a function of particle size as does the reaction order in H2, which is unity. In the presence of 130–260 mTorr CO, the reaction rate decreases for all products with a CO reaction order of −1 to −1.4 for crotyl alcohol and butyraldehyde. Hydrogen reduction at 673–723 K results in increased activity and selectivity relative to reduction at either higher or lower temperature; this is discussed with respect to the organic capping agent, PVP.
TL;DR: In this article, the NaOH solutions of various concentrations (0.05 − 1 m) were used as a desilicating agent for α-pinene isomerization.
Abstract: Limited information is available on the isomerization of α-pinene proceeding on zeolites and related desilicated materials. We wish therefore to report on the title reaction proceeding over ZSM-5, ZSM-12 and MCM-22 type zeolites, parent and modified by the sodium hydroxide treatment. The NaOH solutions of various concentrations (0.05–1 M) were used as a desilicating agent. Such treatments with basic solutions were applied: (i) under atmospheric pressure, and (ii) under hydrothermal conditions. It was shown that ZSM-12 was more resistant towards the basic solutions treatment, and its structure was retained over a whole range of NaOH concentrations studied. Nitrogen sorption revealed strong influence of the desilication process on the pore structure of modified materials—the mesopores system was formed in the zeolite crystals. Finally, catalytic studies were carried out using ZSM-5, ZSM-12, MCM-22, their desilicated derivatives and a ZSM-12/MCM-41 composite material. Catalytic properties of the samples studied were affected to a large extent by the NaOH treatment.
TL;DR: In this paper, the effect of ceria promotion over Ni/Al2O3 catalysts on the catalytic activity and coke formation was investigated in combined steam and carbon dioxide reforming of methane (CSCRM) to produce synthesis gas (H2/CO = 2) for gas to liquid (GTL) process.
Abstract: The effect of ceria promotion over Ni/Al2O3 catalysts on the catalytic activity and coke formation was investigated in combined steam and carbon dioxide reforming of methane (CSCRM) to produce synthesis gas (H2/CO = 2) for gas to liquid (GTL) process. Ce-promoted Ni/Al2O3 catalysts were prepared by co-impregnation method. It has been found that the Ce promotion over Ni/Al2O3 catalyst is beneficial to catalytic activity and coke resistance. As a result, the catalyst promoted with 6 wt% Ce exhibits the highest activity as well as high coke resistance due to the improvement of Ni dispersion and high oxygen storage capacity of CeO2.
TL;DR: In this article, the role of the positive charge in CuO 2 x 1 center and the negative charge in the center in photo-induced charge transfer was investigated and the results indicated that the positive charges in Cu 2 x 2 center affect photo-dependent charge transfer significantly.
Abstract: The fabrication of different CuO
x
species (Cu(0), Cu(I) and Cu(II) species) over TiO2 has been accomplished and their roles in photoinduced hydrogen generation have been investigated. The results indicate that the positive charge in CuO
x
center affect photo-induced charge transfer significantly. Cu(I) species seems promote photocurrent generation while the Cu(II) species inhibits the photocurrent generation. Photoactivity order follows the similar sequence. Lower temperature calcination helps the formation of Cu(I) species and higher temperature treatment leads to the formation of Cu(II) species. At the lower loading level, the Cu content increase leads to the activity increase, but over loading of copper resulted in the decrease of activities for hydrogen generation. Detail analysis indicates that too much copper loading induces more Cu(II) center formation, as a results, the activity for hydrogen generation decreases. The species of Cu(0) does no affect the activity obviously at low loading level and shows detrimental effect at high loading level. The optimal loading amount of copper is 1.0Cu (wt%).
TL;DR: In this paper, the effect of potassium doping on N2O decomposition over Co3O4 was analyzed by work function measurements and DFT calculations and the optimal surface loading was found to be 1.8 atoms/nm2.
Abstract: The beneficial effect (decrease of the half conversion temperature by 100 °C) of potassium doping, in the range of 0–5 atoms/nm2, on N2O decomposition over Co3O4 was analyzed by work function measurements and DFT calculations. The optimal potassium surface loading was found to be 1.8 atoms/nm2. The effect was explained in terms of electronic promotion gauged by lowering of the catalyst work function by 0.48 eV (for K2CO3 precursor) and 0.44 eV (for KOH). The promotional effect is discussed in relation to the theoretical and experimental surface dipoles determined from Hirshfeld atomic charges and geometry of the postulated potassium adspecies and from the Topping model, respectively.
TL;DR: In this paper, a 20-40 mol% Ni/ZrO2 catalysts doped with Ce and Sm were synthesized by an ultrasound-assisted method and characterized by a number of physico-chemical methods (XRD, HR TEM, BET, XPS) and demonstrated that the synthesized catalysts had a mesoporous structure.
Abstract: About 20–40 mol% Ni/ZrO2 catalysts doped with Ce and Sm were synthesized by an ultrasound-assisted method and characterized by a number of physico-chemical methods (XRD, HR TEM, BET, XPS) It was demonstrated that the synthesized catalysts had a mesoporous structure, where ca 10 nm size Ni nanoparticles were incorporated into the rare earth metal modified tetragonal zirconium oxide The Ni particles formed during the reduction treatment could support the porous structure in the supports, and thus the porous properties of the catalysts were related to the Ni-loading The maximum porous volume and size were obtained for the catalyst with a 30 mol% Ni loading, which coincidentally exhibited the highest catalytic activity for the methanation of CO2 After an oxidation–reduction pretreatment, the catalytic activity could be further improved The increase in the catalytic activity was attributed to the formation of additional active centers on the catalysts’ surface
TL;DR: In this article, a tetrakis-soluble tetrameric Pd(II)-phthalocyanine complex was used for olefin (styrene, 1-octene, trans-2 octene and cyclohexene) hydrogenation with molecular hydrogen in an organic/fluorous biphasic system.
Abstract: A fluoroalkene-soluble tetrakis[heptadecafluorononyl]-substituted Pd(II)-phthalocyanine complex has been studied for olefin (styrene, 1-octene, trans-2-octene and cyclohexene) hydrogenation with molecular hydrogen in an organic/fluorous biphasic system [n-hexane/perfluoromethylcyclohexane (PFMCH)]. The palladium complex was found to be an active catalyst for styrene (100% conversion, TON = 634) and 1-octene (92%, TON = 596) at 80 °C and 15 bar of H2 after 6 h of reaction time. The catalyst was recycled in nine consecutive reactions for the hydrogenation of styrene without the loss of activity or metal contamination.
TL;DR: In this paper, the physicochemical properties of the La-HZSM-5 catalyst were characterized and the stability test showed that ethanol conversion and selectivity over this catalyst could be maintained above 98% for more than 950 h.
Abstract: Ethylene production from petroleum or natural gas is an energy intensive process. Bio-ethanol catalytic dehydration to ethylene is an attractive alternative for oil based ethylene. Catalytic dehydration conversion of bio-ethanol to ethylene using HZSM-5 modified by 3 wt% rare earth metal (lanthanum) was carried out in a laboratory bioreactor. The physicochemical properties of the catalyst were characterized. The stability test showed that ethanol conversion and selectivity over this catalyst could be maintained above 98% for more than 950 h. The regenerated catalyst also displayed high reactivity and stability of up to 830 h can be obtained. The effects of temperature, liquid hourly space velocity, particle size of catalyst, and bio-ethanol partial pressure on products formation rate were investigated. The external and internal diffusion resistances were eliminated and the kinetic control range was identified. An apparent kinetics model was used to describe the dehydration reaction of ethanol over 3 wt% La-HZSM-5 catalyst, and the kinetic parameters were determined.