Applied Catalysis A, General (v.401, #1-2)
Editorial Board (CO2).
Hydrodesulphurization and hydrodenitrogenation of light gas oil using NiMo catalyst supported on functionalized mesoporous carbon by N. Prabhu; A.K. Dalai; J. Adjaye (1-11).
Display Omitted► Effect of nitric acid functionalization on mesoporous carbons and NiMo catalysts. ► Optimum between functional groups and textural properties is established. ► NiMo over 6 M HNO3 treated mesoporous carbon exhibits highest HDS & HDN activity. ► Lower support metal interaction helps to form active, Type-II like NiMoS phase. ► HDS & HDN activity of NiMo/mC ≫ NiMo/γ-Al2O3 under industrial operating conditions.The effect of functionalization on the hydrotreating activity of NiMo catalysts supported on mesoporous carbon supports (mC) was studied. mC support was prepared by volume templating of alkali modified SBA-15 using sucrose as carbon source. The mC supports were functionalized using nitric acid of various concentrations (upto 8 M HNO3). The supports and catalysts were characterized by N2 physisorption, SAXS, XRD, FTIR, TGA, Raman spectroscopy, SEM, TEM, and HRTEM. SAXS results showed the changes in structural orderliness of virgin and functionalized mC supports. Physisorption analysis indicated progressive reduction in surface area (SA) and pore volume with the increase in nitric acid concentration. Enhancement of surface functional groups after functionalization was observed through FTIR. SEM images showed that the carbon supports retain needle like morphology even after nitric acid etching. As seen by HRTEM, qualitatively Type-II like NiMoS phase (lower support metal interaction (SMI)) is generated on functionalized mC supported catalysts, which is active for hydrotreating. Hydrotreating activity study of these NiMo catalysts were carried out under industrial operating conditions in a laboratory trickle bed reactor using coker light gas oil feed and it was found that NiMo supported on 6 M acid treated mC showed the highest activity. Based on equal catalyst mass, the hydrodesulphurization and hydrodenitrogenation activities of NiMo/mC catalyst were higher than that of NiMo/γ-Al2O3 owing to lower SMI and higher SA. This study reveals that the functionalized mCs can become potential alternative catalyst support to conventional γ-Al2O3, for the hydrotreating of gas oil feedstocks.
Keywords: Hydrodesulphurization; Mesoporous carbon; NiMo; Functionalization; Gas oil;
Performance of Cu-promoted Pd catalysts prepared by adding Cu using a surface redox method in acetylene hydrogenation by Seok Ki Kim; Ji Hoon Lee; In Young Ahn; Woo-Jae Kim; Sang Heup Moon (12-19).
Display Omitted► Cu was selectively deposited onto Pd using a surface redox method. ► Cu was deposited particularly on the low-coordination sites of Pd. ► Added Cu promoted the ethylene selectivity of Pd in acetylene hydrogenation. ► Activity for acetylene hydrogenation was higher for Pd–Cu than for Pd–Ag.Cu-promoted Pd/Al2O3 catalysts were prepared by selectively depositing Cu onto the Pd surface using a surface redox (SR) method, and their performance in the selective hydrogenation of acetylene was compared with that of Ag-promoted catalysts prepared by both the SR and the conventional impregnation method. The Cu-promoted catalysts prepared by SR showed higher ethylene selectivity and activity than Ag-promoted catalysts, particularly with small amounts of added promoter. The above results were obtained because Cu added by SR was deposited preferentially onto the low-coordination sites of Pd, which were detrimental to ethylene selectivity but took a small fraction of the Pd surface that was responsible for acetylene conversion, and also because Cu had an intrinsic activity for hydrogenation. The advantages of Cu-promoted catalysts prepared using Cu as a promoter and the SR process as the promoter-addition method were conclusively demonstrated in the present study.
Keywords: Acetylene hydrogenation; Pd; Cu; Surface redox method; Ethylene selectivity;
Combustion synthesis of Ni, Fe and Cu multi-component catalysts for hydrogen production from ethanol reforming by A. Kumar; A.S. Mukasyan; E.E. Wolf (20-28).
Display Omitted► Ni1Fe0.5Cu1 is the most active composition. ► The activity–selectivity of Cu, Ni and Fe varied with T. ► Ni is selective for H2 and CH4, Cu for CH3CHO and H2, and Fe for H2 and C2H6.Solution combustion synthesis was used to prepare multi-component catalysts containing Ni, Fe, and Cu using a controlled volume combustion method. A series of catalysts containing the selected metals in different molar ratios were analyzed for their activity and hydrogen selectivity for ethanol decomposition and ethanol partial oxidative reforming reactions. The most active and selective catalyst was found to be Ni1Fe0.5Cu1 yielding ∼80% conversion and ∼42% hydrogen selectivity at the relatively low temperature of ∼415 °C for the ethanol decomposition reaction. Decreasing the oxygen concentration in the feed increased the H2 selectivity at lower temperature. In the absence of oxygen, i.e. during ethanol decomposition, hydrogen production starts at 120 °C and gives a selectivity of ∼40% at about 380 °C. Studies with monometallic catalysts show that Ni at lower temperature was the most active and selective for hydrogen and methane, Cu was selective for acetaldehyde and Fe was selective for CO2 and ethane. Hydrogen selectivity was found to be highest for Fe at high temperature.
Keywords: Solution combustion synthesis; Ethanol partial oxidation; Ethanol decomposition; Multi-component Ni; Fe; Cu catalyst;
Understanding the effects of sulfur on Mo2C and Pt/Mo2C catalysts: Methanol steam reforming by Adam C. Lausche; Joshua A. Schaidle; Levi T. Thompson (29-36).
Display Omitted► Mo2C and Pt/Mo2C catalysts highly active for methanol steam reforming. ► Mo2C was partially tolerant to sulfur exposure and fully regenerable. ► Methanol decomposition sites appeared to be sulfur tolerant but water gas shift sites intolerant.To enhance our understanding of the effects of sulfur on the properties of Mo2C and Pt/Mo2C catalysts, methanol steam reforming rates were measured in the absence and presence of 5 ppm H2S. Exposure to H2S quickly deactivated the Mo2C catalyst, although 60% of the initial rates were retained. Deactivation of the Pt/Mo2C catalyst was more gradual and the pseudo-steady state rates approached those for the Mo2C catalyst. Treatment in 15% CH4 in H2 at 590 °C for 4 h restored ∼100% and ∼15% of the initial rates for the Mo2C and Pt/Mo2C catalysts, respectively. X-ray photoelectron spectroscopy indicated domains of Mo2C, MoS2 and S-Mo on the Pt/Mo2C catalyst surface, but no sulfur was observed on the Mo2C catalyst surface. The results suggested that sulfur selectively poisoned some but not all of the active sites on Mo2C, and irreversibly poisoned the Pt sites producing inactive PtS.
Keywords: Molybdenum carbide; Methanol steam reforming; Water–gas shift; Sulfur poisoning; H2S; Platinum;
Epoxidation of alkenes and their derivatives over Ti-YNU-1 by Xiaohua Shen; Weibin Fan; Yue He; Peng Wu; Jianguo Wang; Takashi Tatsumi (37-45).
Display Omitted► Ti-YNU-1 are highly active and selective for epoxidation of alkenes and their derivatives. ► The catalytic properties of Ti-YNU-1 depend on the reaction conditions and the electronic and geometric features of substrates. ► Acid-treatment conditions greatly influence the structure and framework Ti content of Ti-YNU-1. ► The activity and selectivity of titanosilicates could be controlled by adding another type of alkene.The catalytic properties of Ti-YNU-1 for the epoxidation of various alkenes and their derivatives have been investigated in detail, and further were made a comparison with those of Ti-Beta. The much higher efficiency of Ti-YNU-1 than Ti-Beta was observed in catalyzing the epoxidation of alkenes and their electron-rich analogues. Although it was less active in the epoxidation of α,β-unsaturated ketones, it showed much higher stability. In contrast, Ti leaching from the framework sites occurred to Ti-Beta, and the leaching degree increased with the carbon number of ketones. It was also shown that the catalytic conditions, including the Ti content in samples, H2O2/substrate ratio, reaction temperature and time, acid washing and catalyst amount, significantly influenced the activity, selectivity and H2O2 efficiency. Co-oxidation of different alkenes led to the activity and epoxide selectivity being different from those obtained in the oxidation of single olefin as a result of the differences in adsorption properties of substrates over various titanosilicates, which affected the diffusion of substrate molecules and accounted for the unique shape-selectivity of Ti-YNU-1.
Keywords: Alkene; Epoxidation; Titanosilicate; Ti-YNU-1; Unsaturated ketone;
Study on the preparation of Cu/ZnO catalyst by sol–gel auto-combustion method and its application for low-temperature methanol synthesis by Lei Shi; Kai Tao; Ruiqin Yang; Fanzhi Meng; Chuang Xing; Noritatsu Tsubaki (46-55).
Display Omitted► For the first time, a novel sol–gel auto-combustion method was proposed to prepare the metal and metallic oxide catalyst (Cu/ZnO) without additional reduction. ► Cu particle size was strongly influenced by the initial M/CA molar ratio. ► More carbon residues were left with the increased citric acid amount. ► The methanol selectivity increased with the decreased Cu particle size.A series of the as-burnt and the burnt Cu/ZnO catalysts were prepared by a sol–gel auto-combustion method using metal nitrates with the mole ratio of Cu/Zn = 1/1 (noted as M, M = Cu + Zn) and citric acid (noted as CA). When the xerogels were burnt in the argon atmosphere, H2 and CH4 which were came from the decomposition of the citric acid, were the reducing agents and were used in the redox process for synthesizing metallic Cu from Cu2+ in the chelated compound. The XRD patterns revealed that all the as-burnt catalysts with different M/CA molar ratios were converted into pure Cu and ZnO species. TPR analysis of the as-burnt catalyst illustrated that almost no hydrogen was consumed. It proved that Cu2+ in the chelated compound was absolutely reduced to metallic Cu in the as-burnt catalyst. The effects of M/CA molar ratio on the properties of catalysts were studied by TG-DTA, FT-IR, Raman spectrum, XRD, SEM-EDS, BET, and N2O chemisorption techniques. The activity of the as-burnt catalysts without reduction was investigated for low-temperature methanol synthesis from syngas containing CO2 using ethanol as a promoter at 443 K and 5.0 MPa for 12 h. The total carbon conversion increased with increasing the content of citric acid and reached a maximum for the as-burnt Cu/ZnO catalyst C0.8 with M/CA = 1/0.8, and then decreased. The variation trend was in accordance with that of the copper (Cu0) surface area. Comparing with the burnt catalyst C0.8-air after reduction, the methanol selectivity of the as-burnt Cu/ZnO catalyst was much lower owing to lower hydrogenation activity of the ethyl formate. The as-burnt catalyst C0.8 was also used in continuous low-temperature methanol synthesis at 443 K and 5.0 MPa for 40 h. The total carbon conversion was stable after 15 h and no obvious deactivation during 40 h reaction, but the methanol selectivity was still not high.
Keywords: Low-temperature; Methanol synthesis; Auto-combustion; Cu/ZnO; Metallic catalysts;
Selective hydrogenation of citral over Pt/KL type catalysts doped with Sr, La, Nd and Sm by J. Álvarez-Rodríguez; I. Rodríguez-Ramos; A. Guerrero-Ruiz; A. Arcoya (56-64).
Display Omitted► La, Nd, Sm and Sr as promoters of Pt/KL catalysts for hydrogenation of citral. ► Lanthanides favor the Pt dispersion and formation of electron-deficient Pt species. ► Lanthanides enhance formation of unsaturated alcohols and inhibit that of citronellal. ► Sr difficults the Pt dispersion and promotes formation of electron-rich Pt species. ► Sr improves the formation of geraniol + nerol and enhances that of citronellol.The effect of Sr and some lanthanides (La, Nd, Sm) as promoters of Pt/KL supported catalysts is analyzed in the selective hydrogenation of citral in the liquid phase. Characterization of the catalysts by XRD, N2 adsorption, H2 chemisorption, TPD of NH3, XPS and competitive hydrogenation of benzene/toluene mixtures shows that impregnation of KL zeolite with Sr(NO3)2 in aqueous solution, followed by calcination prior to the incorporation of Pt, increases the surface basicity of the zeolite, which hinders the dispersion of Pt and promotes the formation of electron-rich platinum nanoparticles (Ptδ−). Ion exchange of K+ by rare earth cations (La3+, Nd3+ and Sm3+) increases the surface acidity of the zeolite and favors the dispersion of Pt, but with preferential location at the external surface of the zeolite. Furthermore, acidity promotes the formation of electron-deficient metal species (Ptδ+). Catalytic performances for the citral hydrogenation at 323 K and 5 MPa show that strontium addition enhances the hydrogenation activity of Pt, thus favoring the formation of citronellol as main reaction product (S = 80%) and increasing the yield to geraniol and nerol. Lanthanides as countercations diminish the overall hydrogenation activity of Pt/KL catalysts, but improve their selectivity towards unsaturated alcohols. Selectivity towards the reaction products is related to the mode and strength of the electronic interactions of the conjugated unsaturated bonds of citral reactant molecules with the metal surface species Pt0, Ptδ+ or Ptδ− on the zeolite.
Keywords: Pt/KL catalysts; Selective hydrogenation; Citral; Geraniol; Nerol, Promoters, Sr, La, Nd, Sm;
The role of lithium tetrahydroaluminate in the formation of nanodimensional nickel hydrogenation catalysts by L.B. Belykh; Yu.Yu. Titova; V.A. Umanets; A.V. Rokhin; F.K. Schmidt (65-72).
.Display Omitted► Formation of nickel hydrogenation catalysts under the action of LiAlH4. ► Nanoparticles formed in the system Ni(acac)2–LiAlH4 are inactive in the hydrogenation. ► LiAlH4 is reducing agent, stabilizer of nanoparticles and catalytic poison. ► The promoting effect of proton containing compounds. ► Strategy for synthesis of the highly effective hydrogenation nickel catalysts.The principal stages of formation and the nature of nanoparticles of the reduced nickel formed in the system Ni(acac)2–LiAlH4 and catalytically active in hydrogenation catalysis are established. The reduction of Ni(II) to Ni(0) under the action of LiAlH4 is shown; the Ni(0) atoms form clusters whose growth results in the formation of nanoparticles of the average size of 2–3 nm. Being adsorbed on the surface, the tetrahydroaluminate anions act as stabilizers of the nickel nanoparticles. Besides, the tetrahydroaluminate anions and the products of catalytic decomposition of LiAlH4 (Li n Al n+2H2n+2), by occupying free positions on the surface, can be active as catalytic poisons. Highly efficient hydrogenation catalysts with well reproduced properties are obtained by the reaction of the products formed in the system Ni(acac)2–LiAlH4 with proton-donating compounds (water, alcohols, weak acids). Alcoholysis (hydrolysis) of the surface compounds results in their dissolution, release of the centers of the catalytically active nickel nanoparticles and their stabilization.
Keywords: Hydrogenation; Nickel catalysts; Lithium tetrahydroaluminate;
Selective oxidation of glucose to gluconic acid over Pd–Te supported catalysts by I. Witońska; M. Frajtak; S. Karski (73-82).
Display Omitted► Pd–Te/support catalysts show high activity and selectivity in the glucose oxidation. ► After catalyst activation in H2 the formation of PdTe and PdTe2 phases was observed. ► The best activities show the systems for which the presence of only PdTe phase was proved ► Intermetallic Pd x Te y compounds can modify the catalytic properties of studied systems. ► 5%Pd–1%Te/SiO2 system is characterized by high stability in the glucose oxidation.The effect of tellurium introduction on the activity and selectivity of home-made supported palladium catalysts in the oxidation of glucose to gluconic acid was studied. Bimetallic Pd–Te/SiO2 and Pd–Te/Al2O3 catalysts containing 5 wt.% of Pd and 0.3–5 wt.% of Te are characterized by both high activity and high selectivity to gluconic acid. However, catalysts 5%Pd–8%Te/support show lower conversion but their selectivity to gluconic acid is still high. The activation of bimetallic Pd–Te/support catalysts at 300 °C in hydrogen atmosphere leads to the formation of PdTe and PdTe2 compounds. The presence of intermetallic phase Pd x Te y on the surface of studied catalysts probably modifies their catalytic properties. The catalysts, for which the existence of PdTe was proved, show high activity and selectivity in the studied reaction. The existence of those compounds on the surface was confirmed by XRD, SIMS-ToF, XPS and TPR techniques. Moreover, another important feature of the bimetallic Pd–Te/support catalysts is their high stability in the process of glucose oxidation in the liquid phase.
Keywords: Glucose oxidation; Pd–Te/support catalysts; Intermetallic compounds;
Structural and chemical states of palladium in Pd/Al2O3 catalysts under self-sustained oscillations in reaction of CO oxidation by E.M. Slavinskaya; O.A. Stonkus; R.V. Gulyaev; A.S. Ivanova; V.I. Zaikovskii; P.A. Kuznetsov; A.I. Boronin (83-97).
СО + О2 mixture in the self-oscillation regime of the CO oxidation stimulates the formation of core–shell structures in Pd/Al2O3 catalysts.Display Omitted► The SO regime of CO oxidation stimulates the formation of core–shell structures. ► Two types of core–shell structures were observed. ► Pd/Al2O3-1000 sample contains PdO particles with the shell formed by Pd0 clusters. ► Pd/Al2O3-1200 sample contains Pd0 particles with the shell formed by PdO layer.Pd/Al2O3 supported catalysts, differed in the initial structural and chemical states of palladium, were examined for the possible existence of self-sustained oscillations in the reaction of CO oxidation under temperature-programmed and isothermal modes using plug flow reactor at ambient pressure and CO and O2 concentration of 0.2 and 1.0 vol%, respectively. The supported samples after the action of reaction mixture were characterized using the HRTEM and XPS methods. The catalysts, calcined at relatively low temperatures 450 °C, cannot induce the self-sustained oscillation phenomena in the reaction of CO oxidation. The calcination at 800 °C yields highly dispersed particles of Pd0 and PdO in the catalysts with sizes varying between 2–3 and 10–20 nm, respectively. In this case self-sustained oscillations (SO) of the CO oxidation appeared in the region of middle CO conversions. In the catalyst calcined at 1000 °C, PdO is formed as large particles with sizes 20–100 nm. During prolonged self-sustained oscillations under isothermal conditions with varying CO concentrations in the reaction mixture, particles with “core–shell” structures are formed, where the cores are PdO and the shells are a Pd0 clusters ordered along a specific direction due to an epitaxy on PdO. Calcination at 1200 °C results in the formation of large Pd0 particles with sizes ≥200 nm. During prolonged self-sustained oscillations with varying CO concentrations under isothermal conditions, the reaction mixture causes destruction of the above particles to yield palladium particles with core–shell structures; in this case the cores are Pd0, and the shells are PdO layers.
Keywords: CO oxidation; Self-sustained oscillations; Palladium; Alumina; Catalysis; Core–shell structure; XPS; HRTEM;
Experimental and theoretical studies of Fe-doped TiO2 films prepared by peroxo sol–gel method by Diana V. Wellia; Qing Chi Xu; Mahasin Alam Sk; Kok Hwa Lim; Tuti Mariana Lim; Timothy Thatt Yang Tan (98-105).
Display Omitted► The current work describes an easy and “organic” free approach to synthesize cation Fe-doped TiO2 films. ► The Fe-doped TiO2 thin films are transparent, uniform, crack-free and visible-light active. ► Density of States (DOS) calculations reveal that band gap narrowing of Fe-doped TiO2 results in enhanced visible light photocatalytic activity.Transparent, uniform, crack-free and visible light activated Fe-doped TiO2 thin films have been prepared by an organic-free approach using titanium tetrachloride (TiCl4), Fe3+ and ammonium hydroxide solutions to form yellow aqueous peroxo titanic acid (PTA) solution. Pure glass was made superhydrophilic after heating at 550 °C for 1 h and was used as the coating substrate. The PTA solution dispersed uniformly on the superhydrophilic glass by forming a thin film, resulting in a crack-free Fe-doped TiO2 film as observed under FESEM. XRD results confirmed the presence of only anatase phase for all samples after calcination at 550 °C. The Fe-doped TiO2 films exhibited slight red-shift in absorbance and enhanced absorbance in the visible-light region compared with undoped TiO2, attributed to bandgap narrowing by successful Fe3+ doping into TiO2, which is supported by DOS calculations. Photodegradation of stearic acid (SA) revealed that Fe3+ doping increased visible light photocatalytic activity four-fold compared to undoped TiO2 at optimal Fe-doped TiO2 (1 wt% Fe3+) film. At higher Fe ions concentrations, the existence of increased charge recombination sites and segregated iron oxide phase suppressed the photoactivity.
Keywords: Peroxo titanic acid (PTA); Visible light; Fe-doped TiO2; Density functional theory (DFT);
Mild, single-pot hydrocarboxylation of linear C5–C9 alkanes into branched monocarboxylic C6–C10 acids in copper-catalyzed aqueous systems by Marina V. Kirillova; Alexander M. Kirillov; Armando J.L. Pombeiro (106-113).
.Display Omitted► Inert C n alkanes are directly transformed into branched C n+1 carboxylic acids. ► Alkane hydrocarboxylations with CO and H2O proceed at low temperature and in H2O/MeCN medium. ► Important features are the mild and acid-solvent-free conditions, high selectivity and efficiency. ► Homogeneous catalysis with an aqua-soluble tetracopper(II) complex.A single-pot method has been developed for the hydrocarboxylation of the liquid C5–C9 alkanes (n-pentane, n-hexane, n-heptane, n-octane, n-nonane and 3-methylhexane) into the branched monocarboxylic C6–C10 acids bearing one more carbon atom. This method is characterized by a direct, selective and low-temperature (60 °C) hydrocarboxylation reaction of the alkane with carbon monoxide, water (which acts as a reagent besides being a solvent component) and potassium peroxodisulfate, in H2O/MeCN medium. The hydrocarboxylations are markedly enhanced in the presence of a tetracopper(II) triethanolaminate complex as a homogeneous catalyst precursor. Total yields (based on alkane) of carboxylic acids up to 46% (with 97–99% overall selectivity) have been achieved, which are remarkable in the field of alkane functionalization under mild conditions, especially for a C–C bond formation reaction in aqueous acid-solvent-free medium. The regio- and bond selectivity parameters have been determined and a free radical mechanism has been proposed.
Keywords: Alkanes; C–H activation; Carboxylation; C–C bond formation; Carboxylic acids; Homogeneous catalysis; Aqueous medium; Copper;
Controlled atmosphere 13C and 1H MAS NMR study of reforming route of methane with carbon dioxide over Rh/SBA-15 by Linping Qian; Yu Ren; Hui Yu; Yu Wang; Bin Yue; Heyong He (114-118).
Display Omitted► CH4 reforming with CO2 over Rh/SBA-15 was studied by 13C and 1H MAS NMR. ► Isotopic scrambling and dry reforming reaction were observed by 13C MAS NMR. ► CH3O* and CH2O* species were found by 1H MAS NMR. ► Three crucial steps in the reforming route were found.The mechanism of methane reforming with carbon dioxide over 1.0 wt.% Rh/SBA-15 catalyst has been studied by the 13C and 1H magic-angle spinning (MAS) NMR spectroscopies under controlled atmosphere condition using 13CH4 + 12CO2 and 12CH4 + 13CO2 as reactants. The effect of temperature in the region of 298–1023 K on the reaction was investigated and the contents of various 13C and 1H species were obtained quantitatively by the NMR technique. When treated at 573 K, the carbon exchange between methane and carbon dioxide can be observed. With the temperature rising to 773 K, the adsorbed CH3O* species is formed but no reforming reaction occurs. In the high temperature range of 873–1023 K, the reforming reaction was observed with concomitant appearance of the adsorbed CH2O* species and the intensity of both CH3O* and CH2O* increases with increasing temperature, indicating that the decomposition of CH3O* to CH2O* occurs and the products of dry reforming are formed from decomposition of the adsorbed CH2O* species.
Keywords: Methane; Carbon dioxide; Dry reforming; Rh/SBA-15; MAS NMR;
Homogeneous and heterogeneous catalytic behavior of Ni-porphyrines immobilized in SBA-15 for the esterification of DMT by M. Espinosa; S. Pacheco; S. Vargas; M. Estevez; M.E. Llanos; R. Rodríguez (119-123).
.Display Omitted► New porphyrin-based hybrids heterogeneous catalysts were synthesized and tested. ► These catalysts were supported in the SBA-15 mesoporous material. ► These were tested in the esterification reaction of DMT with EG to produce PET. ► The conversions and activities were slightly lower respect to homogeneous. ► But high enough to be considered as good candidates for industrial application.New porphyrin-based hybrids materials, (SBA-15)-O-Si-(CH2)3-NH-CO-(CH2)2-OC-HN-5m-Etio-III-Ni2+ and (SBA-15)-O-Si-(CH2)3-NH-CO-(CH2)2-OC-HN-2-pyrrolic-m-5,10,15,20-TPP-Ni2+, were used as heterogeneous catalysts in the esterification reaction of dimethyl terephthalate (DMT) with ethylene glycol (EG) in semi-batch conditions. These results were compared with those obtained for homogeneous catalysis using pure unsupported porphyrins, Etio-III-Ni2+ and m-5,10,15,20-TPP-Ni2+. The catalytic activity for all systems was determined by measuring the amount of methanol produced during the reaction. The kinetic parameter K was obtained for both processes resulting for the heterogeneous catalyst activation energies of 15.39 kJ/mol for SBA-15-Etio-III-Ni2+ and 23.77 kJ/mol for SBA-15-TPP-Ni2+, while for homogeneous catalysis the activation energies were 10.49 kJ/mol for Etio-III-Ni2+ and 23.45 kJ/mol for TPP-Ni2+. The catalytic efficiencies were determined for both processes resulting that the conversions and the activities were slightly higher for homogeneous processes respect to the heterogeneous ones.
Keywords: Porphyrins; Nickel; Succinic anhydride; Amino-propyl; SBA-15; Glycolysis;
Co/ZrO2 catalysts coated on cordierite monoliths for CO preferential oxidation by Leticia E. Gómez; Inés S. Tiscornia; Alicia V. Boix; Eduardo E. Miró (124-133).
.Display Omitted► Monoliths washcoated with Co/ZrO2 catalysts were studied for the COProx reaction. ► The one prepared with Nyacol showed 95% of CO conversion and 60% of selectivity at 230 °C. ► The open structure of the Nyacol favored the diffusion process towards the active sites. ► The Co3O4 phase exhibited a high redox capacity, an important property for CO oxidation.Cordierite monoliths washcoated with Co/ZrO2 catalysts were studied for the CO preferential oxidation reaction (COProx). CO oxidation experiments (COTox) were also performed for the sake of comparison. Different procedures were employed to prepare the structured catalysts, using Nyacol and/or monoclinic powder as ZrO2 sources. The slurries used to perform the washcoatings were prepared with different solid concentrations and different solvents in order to study the influence of these conditions on catalytic activity and mechanical stability. Among the monolithic catalysts under study, the one prepared with Nyacol showed the higher activity for the preferential oxidation of CO (PROx), yielding 95% of CO conversion and 60% of selectivity at 230 °C. Only a small deactivation was observed during 100 h of time-on-stream. The better catalytic performance of this catalyst could be ascribed to the more open structure of the ZrO2 coating, which favored the diffusion process of the reactives towards the active sites. LRS characterization of powder and monolithic catalysts showed the formation of the spinel Co3O4 phase which exhibited a high redox capacity, an important property for CO oxidation reaction. EDX characterization also showed an even distribution of the cobalt oxide in monolithic samples. However, UV–vis spectroscopy results suggest that the spinel was not well developed, and that the formation of a pre-spinel structure containing Co2+ species in octahedral coordination probably occurred. Nevertheless, TPR results indicate that the Co3O4 phase can be totally reduced at relatively low temperatures.
Keywords: Co/ZrO2; Monolithic catalysts; CO preferential oxidation; Co3O4;
One-pot synthesis of aniline derivatives from nitroarenes under mild conditions promoted by a recyclable polymer-supported palladium catalyst by Maria Michela Dell’Anna; Piero Mastrorilli; Antonino Rizzuti; Cristina Leonelli (134-140).
.Display Omitted► A polymer supported Pd(II) complex (Pd-pol) was synthesized and characterized ► Good activity of Pd-pol in the one-pot reductive amination with nitroarenes ► Pd leaching was negligible ► The catalyst could be reused at least eight times with unchanged activity ► The active species were palladium nanoparticles with size of ca. 5 nm.This work describes the one-pot direct reductive amination of carbonyl compounds with nitroarenes promoted by a polymer supported palladium catalyst, in the presence of molecular hydrogen as the reductant. This methodology is applicable, with slight differences, to both aliphatic and aromatic aldehydes. The operational simplicity, the mild reaction conditions, the high yields and the good recyclability of the supported catalyst are major advantages of this method. TEM observations of the catalyst showed that the active species are palladium nanoparticles having a size distribution centered at 5 nm within the polymeric support.
Keywords: One-pot reductive amination; Palladium nanoparticles; Supported catalysis; TEM;
Microencapsulated rhodium/cross-linked PVP catalysts in the hydroformylation of 1-hexene by Maija-Liisa Kontkanen; Liubov Vlasova; Sari Suvanto; Matti Haukka (141-146).
.Display Omitted►Active Rh/P4VP-25% microcapsules as a catalyst. ► Uniform spherical morphology of Rh/P4VP-25% with good recyclability, and catalytic activity ► Partial protection of the air sensitive catalyst by microencapsulation.A rhodium complex Rh(acac)(CO)2 microencapsulated into poly(4-vinylpyridine) (P4VP) cross-linked with 2% or 25% divinylbenzene (DVB) was developed as a catalyst for the hydroformylation of 1-hexene. A study was made of the catalytic activity, recyclability, and effect of DVB content of the Rh/P4VP-25% and Rh/P4VP-2% systems. The best yields of hydroformylation products were achieved with the Rh/P4VP-25% as a catalyst. With a high DVB content and regular, spherically shaped particles, Rh/P4VP-25% was an efficient heterogeneous catalyst for the hydroformylation of 1-hexene. The recyclability was good and the 1-hexene conversion high.
Keywords: Microencapsulation; Rhodium; Cross-linked PVP; Hydroformylation;
Synthesis of light hydrocarbons from syngas in near-critical phase by Qianwen Zhang; Peng Liu; Yuya Fujiyama; Chun Chen; Xiaohong Li (147-152).
Display Omitted► Hybrid catalysts based on the Cu–Zn oxide and Pd-β zeolite has been prepared. ► Light hydrocarbons were directly synthesized from syngas in a near-critical phase. ► Introduction of near-critical fluid remarkably decreased the yield of CO2 by suppressing the water–gas shift reaction. ► Efficiently removing reaction heat increased the stability of the catalysts and selectivity of light hydrocarbons.Selective synthesis of light hydrocarbons from synthesis gas (syngas) over hybrid catalysts based on the Cu–Zn oxide and Pd-β zeolite in a near-critical phase was investigated. Light hydrocarbons were directly synthesized from syngas over the catalysts through an intermediate of methanol or DME. Introduction of near-critical fluid remarkably decreased the yield of CO2 by suppressing the water–gas shift reaction. Differences in activity, CO2 selectivity, hydrocarbon distributions, catalyst stability and heat transfer between near-critical and conventional gas phase light hydrocarbons synthesis were compared. Efficient removal of reaction heat increased the stability of the catalysts and selectivity of light hydrocarbons in the reaction.
Keywords: Near-critical phase; Light hydrocarbons; Synthesis gas; Methanol; DME;
Synthesis of glycerol carbonate by transesterification of glycerol with dimethyl carbonate over Mg/Al/Zr catalysts by M. Malyaadri; K. Jagadeeswaraiah; P.S. Sai Prasad; N. Lingaiah (153-157).
Synthesis of glycerol carbonate by transesterification of glycerol with dimethyl carbonate over Mg/Al/Zr catalysts.Display Omitted► Mg/Al/Zr mixed oxides are efficient catalysts for glycerol transesterification. ► The yield of glycerol carbonate varies with the basicity of the catalysts. ► Basicity relate to mole ratio of metal ions and pretreatment temperature. ► The glycerol carbonate yield also depends on reaction parameters.Glycerol carbonate was synthesized by transesterification of glycerol with dimethyl carbonate using Mg/Al/Zr mixed oxide base catalysts. A series of Mg/Al/Zr catalysts were prepared with different molar ratios by using co-precipitation method and calcining at different temperatures. The catalysts were characterized by FT-infrared spectroscopy, X-ray diffraction and temperature-programmed desorption of CO2. The transesterification activity depends on the Mg/Al/Zr molar ratio and the catalyst with Mg/Al/Zr molar ratio of 3:1:1 showed excellent activity. The catalyst activity depends on the pretreatment temperature, structure and basicity of the catalysts. The transesterification activity of catalysts was correlated with the structural aspects and the amount of basicity. Various parameters such as reaction temperature, catalyst concentration and molar ratio of dimethyl carbonate to glycerol were studied to optimize the reaction conditions.
Keywords: Glycerol; Dimethyl carbonate; Transesterification; Glycerol carbonate; Mg/Al/Zr catalysts;
RETRACTED: Preparation of carbon-based catalysts for PEFC cathodes from aromatic polyamide with Fe compound by Masayuki Chokai; Libin Wu; Yuta Nabae; Shigeki Kuroki; Teruaki Hayakawa; Masa-aki Kakimoto; Seizo Miyata (158-162).
This article has been retracted at the request of the Authors.The authors have stated that the manuscript contains fictitious data. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.
In situ synthesis of solid base catalysts for the regeneration of degradation products formed during the anthraquinone process for the manufacture of hydrogen peroxide by Zitian Guo; Junting Feng; Yongjun Feng; David G. Evans; Dianqing Li (163-169).
Display Omitted► MgAl-LDHs was synthesized on the surface of γ-Al2O3 as a catalyst precursor. ► Calcination of MgAl-LDHs/γ-Al2O3 precursor, LDO/γ-Al2O3 catalyst was obtained. ► The surface basicity of the catalysts increased with increasing LDO loading. ► LDO/γ-Al2O3 exhibits high efficiency of anthraquinone degradation regeneration.MgAl–CO3-layered double hydroxides (MgAl-LDHs) have been synthesized on the surface of spherical γ-Al2O3 by an in situ synthesis technique using urea as a precipitant. After calcination, LDH crystallites are transformed into complex metal oxides (LDO) with high homogeneity and MgAl-LDO/γ-Al2O3 solid base catalysts containing different LDO content were obtained. X-ray diffraction, scanning electron microscopy, and surface area measurements using the Brunauer–Emmett–Teller method indicated that the MgAl-LDO/γ-Al2O3 catalysts possess high specific surface area and rich mesoporous structure. The MgAl-LDO/γ-Al2O3 catalysts were used to regenerate anthraquinone degradation products formed in the anthraquinone process for the manufacture of hydrogen peroxide. The efficiency of regeneration of the anthraquinone degradation products was found to increase with increasing LDO loading in the catalysts. Compared with commercial catalysts of NaOH/γ-Al2O3 and MgO/γ-Al2O3 prepared by the impregnation method, MgAl-LDO/γ-Al2O3 catalysts exhibited not only higher activity but also longer life.
Keywords: In situ synthesis; LDHs; MgAl-LDO; Anthraquinone degradation; Regeneration;
Porous nickel based catalysts for partial oxidation of methane to synthesis gas by V.A. Kirillov; Z.A. Fedorova; M.M. Danilova; V.I. Zaikovskii; N.A. Kuzin; V.A. Kuzmin; T.A. Krieger; V.D. Mescheryakov (170-175).
Display Omitted► The texture of Ni catalysts supported on porous Ni with MgO underlayer was studied. ► In reduced Ni catalysts phases of Ni and solid solution of NiO in MgO were observed. ► A considerable part of nickel crystallites is epitaxially bound with MgO. ► The activity of Ni catalysts decreased slightly after 100 h of testing in POM. ► No carbon deposition was detected by TEM in tested samples.The phase composition and texture of nickel catalysts supported on ribbon porous nickel with a magnesium oxide underlayer were investigated by X-ray diffraction, low-temperature nitrogen adsorption, and electron microscopy combined with energy dispersive X-ray microanalysis. The MgO underlayer was obtained by impregnation the porous nickel with a Mg(NO3)2 solution followed by calcination at 550 °C; nickel was supported additionally by impregnation with a Ni(NO3)2 solution followed by calcination at 450 °C. In the supported reduced nickel catalysts (800–900 °C, H2) the phases of Ni and a solid solution of NiO in MgO were observed; a considerable part of nickel crystallites was epitaxially bound with MgO. The partial oxidation of methane to synthesis gas (800 °С, O2/C = 0.65, GHSV = 127 L/g h) over porous nickel based catalysts was studied. The activity of initial nickel support decreased considerably during the partial oxidation of methane; the value of methane conversion decreased slightly after 100 h of testing on the supported nickel catalysts.
Keywords: Nickel catalysts; Partial oxidation of methane; Synthesis gas;
Trichloroisocyanuric acid in 98% sulfuric acid: A superelectrophilic medium for chlorination of deactivated arenes by Gabriela Fonseca Mendonça; Mônica Rufino Senra; Pierre M. Esteves; Marcio C.S. de Mattos (176-181).
Display Omitted► TCCA is safe, stable, and easily available reagent with high atom economy. ► TCCA is monoprotonated by 98% H2SO4. ► DFT calculations support the formation of a superelectrophilic species. ► TCCA in 98% H2SO4 can chlorinate arenes, even strongly deactivated substrates. ► The reactivity of TCCA is regulated by the acid strength of the medium.Trichloroisocyanuric acid (TCCA) reacts with arenes and its reactivity is highly affected by the acid strength of the reaction medium. Deactivated arenes are efficiently chlorinated by TCCA in H2SO4. Our results, along with DFT calculations and 13C NMR spectrometry suggest the formation of a monoprotonated TCCA superelectrophile as the reactive species that can efficiently transfer electrophilic Cl+ to even very weak nucleophiles, such as m-dinitrobenzene.
Keywords: Trichloroisocyanuric acid; DFT Calculations; Arenes; Superelectrophilic species; Aromatic chlorination;
Influence of Al3+ insertion in the stannosilicate MFI framework on the catalytic performance in vapor phase aniline N-methylation by P.S. Niphadkar; P.N. Joshi; S.S. Deshpande; V.V. Bokade (182-188).
Display Omitted► Investigation of synergetic effect of Lewis and Brønsted acid sites in Sn-MFI. ► Isomorphous substitution of Al in place of Sn in Sn-MFI framework. ► Al-Sn-MFI showed higher aniline conversion compared to their monometallic counterparts. ► Increase of stronger acid sites was found to decrease aniline conversion.Silica-based Sn-MFI, Al-MFI and Al-Sn-MFI molecular sieves were synthesized by hydrothermal crystallization of gels having molar compositions SiO2:xSnO2:yAl2O3:0.23 (TPA)2O:35H2O, where x ranges from 1/0 to 1/200 and y from 1/0 to 1/400. Keeping molar Si/(Al + Sn) = 50, the amount of tin and aluminum in hydrogel was varied (Sn:Al molar ratios = 1:0, 1:0.33, 1:1, 1:3, 0:1) to investigate the synergy between Lewis and Brønsted acid sites in acid catalyzed aniline N-methylation reaction. Catalyst characterization was done by Powder X-ray diffraction, DRUV–vis spectroscopy, temperature programmed ammonia desorption (TPAD) and FTIR spectroscopy. An increase in the Al3+ insertion in Sn-MFI framework resulted in the increase in the stronger acid sites. Al-Sn-MFI showed higher aniline conversion than their monometallic counterparts. A sample having B/L ratio in between 0.67 and 0.91 was found to be optimum for maximizing the NMA yield, indicating the existence synergistic properties of Al-Sn-MFI. Upon process parameter optimization, the optimum sample M50 [Si/Al = 50.2, Si/Sn = 93.8, Si/(Al + Sn) = 43.2] showed the maximum aniline conversion (67%) and NMA selectivity (81%) at reaction temperature = 220 °C, weight hourly space velocity (WHSV) = 3 h−1, molar ratio (aniline to methanol) = 1:8 and TOS = 4 h.
Keywords: Al-Sn-MFI; Brønsted and Lewis acid; Aniline; Methanol; N-methylaniline;
Selective epoxidation of methyl soyate over alumina-supported group VI metal oxide catalysts by Jitendra K. Satyarthi; D. Srinivas (189-198).
Display Omitted► Selective epoxidation of methyl soyate over Al2O3-supported group VI metal oxides. ► High conversion (>90%) with 100% epoxide selectivity was obtained over MoO x /Al2O3. ► A new, 1H NMR method is reported to monitor the progress of epoxidation reaction. ► Active sites and structure–activity correlations are reported.Epoxidation of methyl soyate (biodiesel), soybean oil and oleic acid with tert.-butyl hydroperoxide (TBHP) was investigated over γ-alumina-supported group VI metal oxides (CrO x /Al2O3, MoO x /Al2O3 and WO x /Al2O3) prepared by impregnation method. The studies revealed that 15 wt% MoO x on γ-Al2O3 was the most active catalyst (conversion >90 mol% under optimized conditions). While MoO x /Al2O3 is selective mainly for epoxidation, the other catalysts are active for epoxidation as well as for decomposition of TBHP. The active species on the catalyst surface were investigated using in situ UV–visible spectroscopy. A linear correlation was observed between epoxidation activity and surface acidity of the catalyst. A new 1H NMR method was developed to monitor the progress of epoxidation reaction which was found to be superior to gas chromatographic method in estimating the conversion of double bonds of fatty compounds.
Keywords: Epoxidation; Alumina-supported group VI metal oxides; MoO x /Al2O3; Fatty acids; Vegetable oil; Biodiesel; 1H NMR spectroscopy;
Surface properties of Mg doped LaCoO3 particles with large surface areas and their enhanced catalytic activity for CO oxidation by Shangmei Sun; Li Yang; Guangsheng Pang; Shouhua Feng (199-203).
.Display Omitted► Mg-doped LaCoO3 particles were prepared in various particle sizes. ► The particle size had influence on the adsorbed oxygen species. ► The adsorbed oxygen took effect on the catalytic activity of Mg-doped LaCoO3. ► The desorption temperature of oxygen varied with changes in average particle size.Mg-doped LaCoO3 particles were prepared in various particle sizes via a modified sol–gel method using excess MgO as pinning particles. The adsorbed oxygen species of the products were studied by XPS, TPD-O2 and TPR-H2. The amount of adsorbed oxygen varied with changes in average particle size and had an important effect on the catalytic activity towards CO oxidation. XPS and TPD-O2 results indicated that there were two kinds of surface oxygen species and that the relative ratio of the surface adsorbed oxygen to lattice oxygen increased with an increasing BET surface area. The catalytic activities of Mg-doped LaCoO3 particles were clearly enhanced with the increase of surface area and the amount of adsorbed oxygen.
Keywords: Mg-doped LaCoO3; Sol–gel; CO oxidation; Perovskite;
Biotransformation of cyclohexene to value-added oxygenated derivative catalyzed by chloroperoxidase in the presence of small quantities of quaternary ammonium salts by Huizhen Zhang; Yucheng Jiang; Mancheng Hu; Shuni Li; Quanguo Zhai (204-209).
Display Omitted► Cyclohexene was turned to value-added derivative by CPO-catalyzed biotransformation. ► Small quantity of introduced quaternary ammonium salts played multiple functions. ► The strategy is environment-friendly, straightforward and applicable to large scale.Biotransformation of cyclohexene catalyzed by chloroperoxidase (CPO) from Caldariomyces fumago was employed to prepare value-added oxygenated derivative: trans-1,2-cyclohexanediol (CHD) using H2O2 as oxidants. The conversion of substrate was enhanced to 89.2% in the presence of small quantities of quaternary ammonium salts (QAS) compared to that of only 48.1% in aqueous phosphate buffer after 150 min. The enhancement was dependent on the concentration and alkyl group length of QAS. QAS were found playing multiple functions in reaction media: phase transfer catalysis and tuning the composition of product. UV–vis, fluorescence and circular dichroism (CD) spectral assay were employed to investigate the effect of QAS on micro-environment around active center and structure of protein. The strengthening of α-helix structure of CPO and more exposure heme for easily access of substrate was found responsible for the improvement of catalytic performance of CPO. Moreover, the determined kinetic parameters indicated the affinity and selectivity of CPO to substrate was improved according to the observation of a decrease of Michaelis constant K m while an increase of the second order rate constants k cat/K m.The strategy reported in this work is environment-friendly, straightforward and applicable to large scale preparation.
Keywords: Biotransformation; Chloroperoxidase; Cyclohexene; Quaternary ammonium salts;
Purines oxidation by immobilized xanthine oxidase on magnetic polysiloxane–polyvinyl alcohol composite by David F.M. Neri; Débora P.B. Bernardino; Eduardo I.C. Beltrão; Luiz B. Carvalho (210-214).
Display Omitted► High specific activity retention (half of the free enzyme). ► Optimal pH and temperature slightly higher than those of the free enzyme. ► No decrease of activity after five reuses and only 17% after ten reuses. ► Apparent Michaelis constant equal to that estimated for free enzyme. ► 6-Mercaptopurine oxidation following the same pathway described for the free enzyme.Bovine milk xanthine oxidase (XOD, E.C. 184.108.40.206) was covalently immobilized, via glutaraldehyde, on magnetic polysiloxane–polyvinyl alcohol (mPOS–PVA) particles yielding a preparation containing 9.5 ± 0.5 μg of protein per mg of support and specific activity of 36.3 ± 7.8 mU/mg of protein (55.0 ± 11.7% of the free enzyme). Optimal pH (8.8) and temperature (60 °C) were slightly higher than those established for the free enzyme (8.2 and 55 °C, respectively). No decrease of activity was observed after five reuses and only 17% was lost at the tenth reuse. The apparent Michaelis constant estimated for the mPOS–PVA–XOD (8.86 ± 0.88 μM) was not statistically different from the free enzyme (7.48 ± 1.01 μM). The 6-mercaptopurine oxidation catalyzed by the mPOS–PVA–XOD followed the same pathway described for the free enzyme, namely, 6-mercaptopurine → 6-mercapto-8-hydroxypurine → 6-thiouric acid, and no 6-thioxanthine was formed.
Keywords: Immobilization; Magnetic support; Xanthine oxidase; Catalyzed oxidation; 6-Mercaptopurine;
Bicomponent VO2-defects/MWCNT catalyst for hydroxylation of benzene to phenol: Promoter effect of defects on catalytic performance by Shaoqing Song; Shujuan Jiang; Richuan Rao; Hongxiao Yang; Aimin Zhang (215-219).
Display Omitted► VO2-defects/MWCNTs bicomponent catalysts. ► Defects of MWCNTs were firstly used as promoters. ► Defects could transfer electron and prevent phenol oxidation in the catalysis. ► Compared with other catalysts, VO2-defects/MWCNTs show excellent performance.A novel bicomponent catalyst, VO2 supported on multi-walled carbon nanotubes (MWCNTs) with defects as promoter (VO2-defects/MWCNTs) was synthesized for the hydroxylation of benzene to phenol. In the bicomponent system, VO2 nanoparticles with 2–10 nm were prepared by the spontaneous redox between V5+ and defects of MWCNTs. Moreover, defects of MWCNTs were firstly used as promoters for preventing the oxidation of phenol and transferring electrons in the catalysis. Thus, compared with other vanadium catalysts, VO2-defects/MWCNTs show excellent catalytic performance for the hydroxylation of benzene to phenol, which indicates defects as promoter are quite promising for catalyzing the hydroxylation of benzene.
Keywords: Bicomponent catalyst; VO2; Defects; Carbon nanotubes; Hydroxylation of benzene to phenol;
CaO-catalyzed synthesis of glycerol carbonate from glycerol and dimethyl carbonate: Isolation and characterization of an active Ca species by Fidelis Stefanus Hubertson Simanjuntak; Tae Kyung Kim; Sang Deuk Lee; Byoung Sung Ahn; Hoon Sik Kim; Hyunjoo Lee (220-225).
Display Omitted► CaO-catalyzed transesterification of DMC by glycerol was found to proceed in a homogeneous way when the molar ratio of DMC/glycerol less than 2. ► At the molar ratio of DMC/glycerol higher than 2, there is a considerable contribution of heterogenous catalyst. ► An active species was isolated from the reaction mixture and characterized as Ca(C3H7O3)(OCO2CH3).The transesterification of dimethyl carbonate (DMC) with glycerol to produce glycerol carbonate was investigated in the presence of CaO under various reaction conditions. CaO was completely dissolved in the reaction mixture of glycerol and DMC in 5 min at 75 °C and at the molar ratio of glycerol/DMC/CaO of 1/2/0.01.The isolation and the characterization of the dissolved Ca species by means of TOF-SIMS, elemental analysis, and FT-IR revealed that an active species, Ca(C3H7O3)(OCO2CH3) is generated from the interaction of CaO with glycerol and DMC.The mechanistic pathways to the formations of Ca(C3H7O3)(OCO2CH3) and glycerol carbonate are discussed on the basis of experimental and spectroscopic results.
Keywords: Glycerol; Glycerol carbonate; Dimethyl carbonate; CaO; Homogeneous catalyst;
Formation of platinum nanoflowers on 3-aminopropyltriethoxysilane monolayer: Growth mechanism and electrocatalysis by Yongxin Li; Hongying Xian; Yuan Zhou (226-232).
Display Omitted► Pt flowerlike nanostructures have been synthesized. ► The growth mechanism of the Pt nanoflowers attributes to the inhomogeneous diffusion of PtCl6 2− ions. ► The Pt nanoflowers exhibit excellent electrocatalytic activity.This work reports the fabrication of hierarchical flowerlike platinum nanostructures (Pt nanoflowers, PtNFs) on a 3-aminopropyltriethoxysilane (APTES) monolayer and their electrocatalytic applications. The obtained PtNFs were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and electrochemical methods. The growth mechanism of the PtNFs may be attributed to the inhomogeneous diffusion of PtCl6 2− ions on the surface of the electrode. Moreover, it has been found that the PtNFs modified electrodes exhibit excellent electrocatalytic activity for the oxidation of methanol and the reduction of oxygen when compared to conventional Pt nanoparticle modified electrodes. The increased catalytic activity may be a result of the unique morphology of the PtNFs.
Keywords: Pt nanoflower; Electrodeposition; Methanol; Oxygen; Electrocatalysis;
The effect of the composition of tri-elemental doping (K, Al, S) on the photocatalytic performance of synthesized TiO2 nanoparticles in oxidizing 2-chlorophenol over visible light illumination by Nolan C. Tolosa; Ming-Chun Lu; Herman D. Mendoza; Analiza P. Rollon (233-238).
Display Omitted► Ti(OBu)4 reacts with water forming titanium oxo-polymers. ► K, Al, and S doping increase TiO2 performance. ► K, Al, and S support TiO2 in oxidizing of chlorinated organic compounds.This study investigated the effect of tri-elemental doping specifically potasium (K), aluminum (Al) and sulfur (S) on the performance of the synthesized titanium dioxide (TiO2) nanoparticles under visible light illumination. The synthesized photocatalyst was prepared by sol–gel method using potash alum or potassium aluminun sulfate [KAl(SO4)2] as dopant. The process involves hydrolysis and condensation reactions of titanium alkoxides forming oxo-polymers. The process involved oxidation of 2-chlorophenol (2-CP) in aqueous conditions. The specific surface area, morphology, structure and surface charge of the synthesized photocatalyst were comparable to those of commercial Degussa P-25. Results show that the specific surface area of the catalysts decreased after calcination process. This effect corresponds with the XRD results, surface charge, EDS and photo-oxidation of the 2-CP using the TiO2/KAl(SO4)2 catalyst, wherein oxidation of 2-CP can be increased up to 96% in 4 h irradiation. However, complete mineralization of 2-CP needs longer irradiation time.
Keywords: 2-Chlorophenol; Alkoxides; Nanoparticles; Oxo-polymers; Tri-elemental;