Applied Catalysis A, General (v.519, #C)

Contents (iii-vii).

Highly selective hydrodechlorination of 1,2-dichloroethane to ethylene over Ag-Pd/ZrO2 catalysts with trace Pd by Yuxiang Han; Jingya Sun; Heyun Fu; Xiaolei Qu; Haiqin Wan; Zhaoyi Xu; Shourong Zheng (1-6).
Display OmittedGas-phase catalytic hydrodechlorination is one of the most efficient and economic methods for the removal of volatile chlorinated alkanes. Novel Ag-based bimetallic catalysts with high ethylene selectivities were prepared using the co-impregnation method. The catalysts were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and IR spectroscopy of CO adsorption. The catalytic performance, in particular the selectivities of the catalysts was examined on hydrodechlorination of 1,2-dichloroethane. Two supported monometallic catalysts (Ag/ZrO2 and Pd/ZrO2) were included as comparative catalysts. Ag/ZrO2 exhibited a low 1,2-dichloroethane coversion and high chloroethylene selectivity for the gas-phase hydrodechlorination of 1,2-dichloroethane, while Pd/ZrO2 had a high conversion and ethane selectivity. In contrast to monometallic catalysts, Ag-Pd/ZrO2 with trace Pd had substantially enhanced ethylene selectivity, and the bimetallic catalyst with a Pd loading amount of 0.099 wt.% (denoted as Ag(1.99)-Pd(0.099)/ZrO2) exhibited nearly 100% ethylene selectivity. The excellent ethylene selectivity can be attributed to the highly dispersed metallic Pd in Ag particles of Ag(1.99)-Pd(0.099)/ZrO2 as evidenced by the IR spectra of CO adsorption. The findings in this study indicate that Ag-Pd/ZrO2 with trace Pd can be used as promising catalyts for highly effective and selective hydrodechlorination of volatile chlorinated alkanes.
Keywords: Ag-Pd/ZrO2 catalysts with trace Pd; Catalytic hydrodechlorination; 1,2-dichloroethane; Ethylene selectivity;

Tailoring the properties of BaTi0.8Cu0.2O3 catalyst selecting the synthesis method by Vicente Albaladejo-Fuentes; Franz Edwin López-Suárez; María Salvadora Sánchez-Adsuar; María José Illán-Gómez (7-15).
Display OmittedThe effect of the synthesis method (hydrothermal and sol-gel) on the properties of BaTi0.8Cu0.2O3 perovskites as catalysts for NOx and soot removal has been analyzed. X-ray powder diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), ICP-AES, N2 adsorption at −196 °C, Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and temperature programmed reduction with hydrogen (H2-TPR) have been used for catalysts characterization. To test their catalytic activity, NOx storage and soot combustion temperature programmed reaction tests have been carried out.The results allow to conclude that the synthesis method determines the position of copper on the perovskite structure and, therefore, the catalytic applications. When the hydrothermal method is used the copper is highly dispersed on the perovskite surface, obtaining a catalyst with a high activity for the NO to NO2 oxidation reaction, which can be used as oxidation catalyst for soot removal. Nevertheless, using the sol-gel method, copper is incorporated into the perovskite structure and, consequently, the catalyst presents a high NOx storage capacity
Keywords: BaTiO3 perovskite; Sol-gel method; Hydrothermal method; NOx storage; Diesel soot oxidation;

Nature of the active sites in CO oxidation on FeSiBEA zeolites by Ireneusz Kocemba; Jacek Rynkowski; Jacek Gurgul; Robert P. Socha; Kazimierz Łątka; Jean-Marc Krafft; Stanislaw Dzwigaj (16-26).
Display OmittedFeSiBEA zeolites containing 1 wt% of iron were prepared by a two-step postsynthesis method in acidic (pH = 2.6) (Fe1.0SiBEA(w)) and alkaline (pH = 10) (Fe1.0SiBEA(p)) conditions. The structure of the studied materials, their acidity as well as the nature and environment of iron present in the samples were studied by means of XRD, FTIR with CO as probe molecule, DR UV–vis, Mössbauer and XPS spectroscopies, respectively. Temperature-Programmed Surface Reaction (TPSR) was used to test the catalytic activity of FeSiBEA zeolites in CO oxidation in air in the temperature range of 298–773 K. It was shown that Fe1.0SiBEA(w) contains iron as framework pseudo-tetrahedral Fe(III), in contrast to Fe1.0SiBEA(p), in which additional octahedral FeOx oligomers were identified. Moreover, the presence of two kinds of pseudo-tetrahedral Fe(III) sites with different distortion was distinguished in Fe1.0SiBEA(w). The higher catalytic activity was showed by Fe1.0SiBEA(w) zeolite containing iron as a strongly distorted pseudo-tetrahedral Fe(III) well dispersed in the framework of SiBEA zeolite. The model of probable active iron centre in Fe1.0SiBEA(w) was presented.
Keywords: Fe; Zeolite; CO; Oxidation; Mössbauer;

A DFT+U study of the Mars Van Krevelen mechanism of CO oxidation on Au/TiO2 catalysts by Muhammad Adnan Saqlain; Akhtar Hussain; Muhammad Siddiq; Alexandre A. Leitão (27-33).
Display OmittedDensity Functional Theory calculations were carried out to study CO oxidation by lattice oxygen atoms of Au10/TiO2 (001) catalyst. The variation in ΔG° with temperature and the barriers associated with the elementary reactions were calculated. The Mars Van Krevelen (MvK) mechanism starts with the CO oxidation by lattice oxygen atoms located at the periphery of Au10 on Au10/TiO2 system. The variation in ΔG° indicates that the process is spontaneous at all the temperatures studied and requires 53 kJ/mol activation barrier. The CO2 desorption, as result of this oxidative process, leaves a surface oxygen vacancy at the perimeter of Au10/TiO2 which is refilled in the subsequent O2 adsorption step. The variation in ΔG° for adsorption of O2 showed that the adsorption process is spontaneous until 420 K. Dissociation of O2 into O + O is an exothermic process and activated by a small activation barrier (30 kJ/mol). The second cycle of CO oxidation is even more probable, having a lower activation barrier and high exothermicity. While the ΔG° for CO oxidation by lattice oxygen atoms is negative on Au10/TiO2, it is positive from 100 to 650 K on Au3/TiO2 and clean TiO2 (001) surfaces, respectively. Thus, CO oxidation by MvK mechanism on Au/TiO2 catalysts depends upon the size/dispersion of the Au cluster. Since, Au cluster facilitates CO oxidation by MvK mechanism, therefore, MvK mechanism is expected to take place together with the Langmuir-Hinshelwood mechanism on Au/TiO2 catalysts.
Keywords: Heterogeneous catalysis; Au/TiO2; CO oxidation; DFT; Mars-van Krevelan mechanism;

Display OmittedIn the present work, new visible light active bismuth molybdates of the general formula Bi2−xRExMo3O12 (where RE = Eu3+ and Pr3+ and x = 0.07–0.3) and α-Bi2Mo3O12 nanorods were synthesized by hydrothermal method. The activity of the photocatalysts was evaluated for Rhodamine B dye degradation under simulated sun light in the presence of H2O2. The substitution of Eu3+ and Pr3+ ions in place of Bi3+ ion enhanced the photocatalytic activity by inhibiting the charge carrier recombination. Among the new compounds, Bi1.9Eu0.1Mo3O12 and Bi1.8Pr0.2Mo3O12 exhibited two fold times excess photocatalytic activity when compared to the activity of α-Bi2Mo3O12. Various organic intermediates were identified by GC–MS analysis during photodegradation process of Rhodamine B. Among the competitive N-deethylation and chromophoric cleavage processes of Rhodamine B dye in solution, chromophoric cleavage was found to be a predominant process. Rhodamine B dye not only underwent photobleaching but also underwent degradation followed by mineralization to CO2 and H2O.
Keywords: Bismuth molybdates; Photocatalysts; UV–vis spectra; Electrochemical impedance;

Influence of the state of Zn species over Zn-ZSM-5/ZSM-11 on the coupling effects of cofeeding n-butane with methanol by Chao Song; Xiujie Li; Xiangxue Zhu; Shenglin Liu; Fucun Chen; Feng Liu; Longya Xu (48-55).
Display OmittedCombination of the exothermic methanol aromatization with the endothermic n-butane aromatization provides a good way to meet the increasing demand for aromatics. Here, a series of Zn-ZSM-5/ZSM-11 catalysts were prepared with different introduction methods. The influence of location and state of Zn species on the coupling effects of cofeeding n-butane with methanol were investigated in detail. UV–vis, H2-TPR and XPS spectra were applied to reveal the state of the Zn species on different catalysts. Quantitative results of NH3-TPD and Pyridine-FTIR were provided to compare the acidity changes of the catalyst after Zn loading. Physical mixing method led to high portion of bulk ZnO particles outside the channel which could promote the formation of C2 ―C4 light alkane in cofeeding reaction. Ion exchange and impregnation modes were beneficial for the formation of Zn―O―Zn bridging species in the micropore channel. Zn―O―Zn bridging species was found to increase the promoting effect of cofeeding n-butane with methanol on aromatics selectivity.
Keywords: Zn state; Cofeeding; Methanol; n-Butane; Aromatization;

Display OmittedTailoring the exposed crystal facet of a material is a very important strategy for improving the application performance. Herein, cubic phase Co3O4 with two different morphologies, nanoplates and nanologs, was synthesized, and CO oxidation, preferential oxidation of CO (CO-PROX) under H2-rich condition, water-gas shift (WGS) reaction, and supercapacitor properties were examined. The nanoplates with {112}-exposed facets showed better performance in all the test model systems. The {112} facets contained more active Co3+, which is responsible for the activation of CO oxidation (and H2 production) at a lower temperatures. A facial ion transport on the facet increased the specific capacitance of the plates. The wider application tests and the design of Co oxide nanostructures provide a better strategy for the development of Co-based materials.
Keywords: Co3O4; CO oxidation; Preferential oxidation of CO; Water-gas shift reaction; Supercapacitor;

Innovative photo-Fenton catalysis by PE-FeOx films leading to methylene blue (MB) degradation: Kinetics, surface properties and mechanism by Laura Suárez; Huiyu Dong; Cesar Pulgarin; Rosendo Sanjines; Zhimin Qiang; John Kiwi (68-77).
Schematic of the MB-degradation mechanism on PE-FeOx films under sunlight/visible irradiation.Display OmittedThis study reports an innovative preparation polyethylene-FeOx (PE-FeOx films) leading to the degradation of the methylene blue (MB) dye under low intensity sunlight/visible light (>400 nm). The intermediate highly oxidative radicals generated by PE-FeOx leading to MB discoloration/degradation in the presence of H2O2 were identified. The relative contribution to the MB discoloration by the Fe-ions leached from the PE-FeOx films into solution was determined quantitatively. This allows estimating the contribution of the heterogeneous and of the homogeneous leading to MB-degradation. The shift in the peak binding energy (BE) for Fe was detected by photoelectron spectroscopy (XPS) after the MB-degradation providing the evidence for redox catalysis occurring during MB-degradation at the PE-FeOx surface. The particle size and roughness of the PE-FeOx surfaces were determined by atomic force spectroscopy (AFM). The spectral properties of PE-FeOx films are reported and insight is provided for the mechanism of MB-degradation.
Keywords: PE-FeOx synthesis; MB-discoloration; Visible light; XPS; AFM; XRD; Repetitive MB degradation; H2O2; Heterogeneous catalysis; ROS diffusion distances;

Display OmittedWe discovered a general and comprehensive approach for the regioselective hydroboration of terminal and internal alkynes to synthesize vinylboronates using inexpensive and magnetically separable copper ferrite nanoparticles at low catalyst loading using Bis(pinacolato)diboron in the absence of ligand and additives, under mild and greener conditions. A diverse range of functional groups was tolerated in the reaction, including allene and enones, and the corresponding boronates were obtained in high yields under air. Moreover, the assynthesized alkenylboronates were used as precursors to prepare wide variety of vinylorgano chalcogenides regioselectively, in high yields. The present protocol enable the conversion of Csp ―H bonds to make Csp 2 ―B bonds via activation of B―B bond, followed by formation of Csp 2 ―Se (Te or S) bonds via activation of Se (Te or S)- Se (Te or S) bonds in a regioselective manner. Deuterium isotope labeling studies showed that the proton source of vinyl boronate stem from the solvent employed.
Keywords: Copper ferrite nanoparticles; Deuterium; Green synthesis; Hydroboration; Organochalcogenides;

Effect of Zn addition on the performance of Ni/Al2O3 catalyst for steam reforming of ethanol by Chatla Anjaneyulu; Lídia O.O.da Costa; Mauro C. Ribeiro; Raimundo C. Rabelo-Neto; Lisiane V. Mattos; A. Venugopal; Fábio B. Noronha (85-98).
Display OmittedA detailed investigation of the effect of Zn on the performance of supported Ni-based catalysts for steam reforming of ethanol is presented in this paper. A Ni/Al2O3 and two ZnO/Al2O3 supported Ni catalysts with different Zn/Al ratio were prepared. For the Ni/Al2O3 and Ni/ZnAl2O4 (Zn/Al = 0.5) catalysts, only metallic Ni particles were identified after reduction. Under ethanol steam reforming conditions, carbon filaments were formed during the reaction, which led to deactivation of the catalyst. It was shown that Zn present in excess (Ni/ZnO-Al2O3) may form an alloy with compositions ranging from Zn-rich tetragonal NiZn and Ni-rich cubic Ni4Zn. The formation of NiZn alloy with different compositions plays a key role in catalyst performance, improving resistance to coke formation and its stability.
Keywords: Hydrotalcite; Ni-Zn alloy; Hydrogen production; Steam reforming of ethanol; Catalyst deactivation; Carbon formation;

Display OmittedThe present work demonstrates a single-step preparation of sulfo carbon-based solid acid catalyst (CSO3H) obtained from cellulose by direct carbonization–sulfonation with conc. H2SO4. The variation of reaction conditions, such as, reaction temperature (50–180 °C), weight ratio of H2SO4 to cellulose (5/1–30/1) and reaction time (1–10 h) provided CSO3H with relatively abundant density of acid sites attached on catalyst surface. The CSO3H with the highest density of SO3H groups (0.81 mmol H+/g) was obtained at 100 °C using weight ratio of H2SO4 to cellulose (20/1) after 3 h of reaction. The catalyst was characterized by means of N2 sorption analysis (average pore diameter 12.8 nm, specific surface area 1.38 m2/g, pore volume 0.004 cm3/g), FT-IR, TG, XRD, FE-SEM and S elemental analysis. The conversion of rapeseed oil fatty acids (RFA) in esterification reactions with CSO3H as catalyst was quite similar to the commercial Amberlyst-15 and the biodiesel with ester content of ≥96.5% was successfully obtained under optimized reaction conditions.
Keywords: Cellulose; Carbon-based solid acid catalyst; Sulfonation; Esterification; Amberlyst-15; Biodiesel;

The sulfur-doped g-C3N4 (g-CNS) combined with zinc phthalocyanine (ZnTNPc) was prepared and the photocatalytic degradation of methylene blue (MB) was investigated under visible irradiation.Display OmittedA series of sulfur-doped graphitic carbon nitride (g-CNS) materials were prepared by thermal condensation of a high-quality thiourea and melamine under air atmosphere. When zinc phthalocyanine (ZnTNPc) was combined with g-CNS, the photocatalytic performance of ZnTNPc/g-CNS was 4.4 times higher than that of pure ZnTNPc under visible irradiation. More importantly, the ZnTNPc/g-CNS composites exhibited higher photocatalytic activity for the degradation of methylene blue than ZnTNPc/g-C3N4 under the same conditions. Some typical scavengers were added to identify the active species in the photocatalytic oxidation process. Mott-Schottky curve reveals that the introduction of sulfur atoms in the graphitic carbon nitride not only narrows the band gap but also results in a downshift of the conduction band. The mechanism of the enhanced photocatalytic activity of ZnTNPc/g-CNS is based on the synergetic effect between ZnTNPc and g-CNS, which causes a rapid photo induced charge separation and suppresses the possibility of recombination of electron-hole pairs. Our effects will provide a novel system to increase the number of active species participated in the photocatalytic process, and thus enhance the photocatalytic activity of carbon-based catalysts.
Keywords: Carbon nitride; Sulfur doping; Zinc phthalocyanine; Photocatalysis;

Bio-nanohybrid catalysts based on l-leucine immobilized in hydrotalcite and their activity in aldol reaction by Dana-Georgiana Crivoi; Ronald-Alexander Miranda; Elisabetta Finocchio; Jordi Llorca; Gianguido Ramis; Jesús E. Sueiras; Anna M. Segarra; Francisco Medina (116-129).
Display OmittedNanohybrid materials based on l-leucine (l-Leu) and hydrotalcites (HT) were prepared by the ion-exchange and reconstruction method, under mild synthesis conditions. The location, amount and the form of the immobilized l-Leu are affected not only by the time of synthesis, but also by temperature and ultrasound treatment. The XRD results demonstrate that the immobilization occurs in either a vertical or oblique orientation with respect to the HT layers. The catalytic activity of these materials was tested in the aldol addition reaction of cyclohexanone with different aromatic aldehydes, affording mainly the syn-diastereomer. Furthermore, the present study demonstrates that both diastereo- and enantioselectivity can be easily modulated by the appropriate combination of nanohybrid catalyst, solvent and reaction time.
Keywords: Asymmetric catalysis; Hydrotalcite; Immobilization; l-Leucine; Nanohybrid materials;

Increased conversion and selectivity of 4-nitrostyrene hydrogenation to 4-aminostyrene on Pt nanoparticles supported on titanium-tungsten mixed oxides by Marco Carrus; Marzia Fantauzzi; Francesca Riboni; Martin Makosch; Antonella Rossi; Elena Selli; Jeroen A. van Bokhoven (130-138).
Display OmittedA catalyst series consisting in platinum nanoparticles photodeposited on pure titania and on W/Ti mixed oxides, these latter prepared by the sol-gel method, were tested in the hydrogenation of 4-nitrostyrene. A remarkable increase in the reaction rate occurred when the catalyst support contained tungsten, with a parallel boosting in the selective reduction of the nitro group. With the selective W-containing catalysts, the reaction proceeded at constant rate (zero order rate law), while the tungsten-free catalyst showed a rate-dependence on the 4-nitrostyrene concentration (positive order reaction). The presence of tungsten in the support is beneficial not only because a higher surface area is obtained, thanks to the stabilization of anatase owing to the presence of tungsten, but also because it allows the photodeposition of smaller, better dispersed platinum particles, on which the adsorption of the aromatic part of 4-nitrostyrene is less favored. Tungsten not only substitutes titanium in the titania lattice, as revealed by HAAF-STEM analysis, but it is also present as WOx species partly covering the Pt nanoparticles photodeposited on the mixed oxide support, as revealed by an in depth distribution XPS analysis. This accounts for the progressively lower performance observed with increasing tungsten content in the catalysts, the highest conversion and selective hydrogenation of the 4-nitrostyrene nitro group having been achieved on the catalyst with a 1% W/Ti molar ratio.
Keywords: Selective hydrogenation; Reduction of nitro group; Supported Pt; W-Doped TiO2; X-ray photoelectron spectroscopy (XPS);

Cobalt ferrite nanoparticles for the preferential oxidation of CO by Carlos Alberto Chagas; Eugenio F. de Souza; Marta C.N.A. de Carvalho; Ruth L. Martins; Martin Schmal (139-145).
Display OmittedIn the present study cobalt ferrite (CoFe2O4) nanoparticles have been successfully prepared through the glucose-assisted hydrothermal method. We verified that the use of glucose is highly advantageous for the synthesis in order to prevent particle agglomerates as well as to obtain single-phase CoFe2O4 nanoparticles. The H2-TPR results showed that the CoFe2O4 indicates the reduction of CoO to Co° and of Fe2O3 to Fe3O4 followed by the reduction of Fe3O4 to metallic iron Fe°. XPS observations evidenced the presence of Fe3+ and Co2+ and practically exclude the existence of Fe2+ and Co3+ species at the surface. In situ DRIFTS-MS showed formate species at 100 °C which increased with increasing temperature due to the reaction between CO gas and hydroxyl groups of cobalt ferrite. The as-prepared material exhibited high CO conversion and good stability on stream at 250 °C during 30 h. In addition, it has been observed that the cobalt ferrite catalyst is inhibited by the presence of H2O and CO2, although a totally reversible process, but have no influence on the chemical structure of the surface active sites.
Keywords: Cobalt ferrite; Stability; CO-PROX; Hydrogen; Fuel cells;

Carboxymethyl cellulose supported ionic liquid as a heterogeneous catalyst for the cycloaddition of CO2 to cyclic carbonate by Xiaohui Wu; Mengpan Wang; Yinzheng Xie; Chen Chen; Kun Li; Mingming Yuan; Xiuge Zhao; Zhenshan Hou (146-154).
Display OmittedThe non-toxic biologic material carboxymethyl cellulose (CMC) supported imidazolium-based ionic liquids (ILs), coupling with a series of Lewis acids has been prepared and used as heterogeneous catalysts for the cycloaddition of CO2 to cyclic carbonate. The as-synthesized catalysts have been characterized by FT-IR, XRD, TGA, SEM etc. Especially, the protonated CMC (HCMC) supporting both the hydroxyl group functionalized IL (1-hydroxypropyl-3-n-butylimidazolium chloride, HBimCl) and NbCl5 (HBimCl-NbCl5/HCMC) exhibited the best catalytic performance. It was indicated that HBimCl on HBimCl-NbCl5/HCMC catalyst was highly leaching-resistant even if it was immobilized through non-covalent interaction. The IL and Lewis acid exhibited strong synergistic effects for the cycloaddition reaction. Additionally, the HBimCl-NbCl5/HCMC catalyst exhibited a high activity and excellent selectivity for a wide scope of substrates under optimum conditions and also it was further extended to application in the continuous fixed-bed flow reactor and showed an excellent catalytic stability. No loss of catalytic activity was observed even after 120 h on stream.
Keywords: Carboxymethyl cellulose; Ionic liquid; Heterogeneous catalysts; CO2; Cyclic carbonate;

Postsynthesis of FAU-type stannosilicate as efficient heterogeneous catalyst for Baeyer-Villiger oxidation by Zhiguo Zhu; Hao Xu; Jingang Jiang; Xue Liu; Jianghong Ding; Peng Wu (155-164).
FAU-type stannosilicate (Sn-Y) with hierarchical pore structure, postsynthesized by acid treatment and atom-planting method, shows excellent catalytic properties in the Baeyer-Villiger oxidation of ketones using hydrogen peroxide or tert-butyl hydroperoxide as an oxidant.Display OmittedSn-Y zeolite with hierarchical pore system was prepared using the atom-planting method from properly dealuminated USY zeolite and SnCl4 vapor. Sn ions were tetrahedrally incorporated into the zeolite framework by the reaction between the SnCl4 molecules and the “silanol nests” generated by steaming and acid treatment. The amount of incorporated Sn depended closely on the dealumination degree, in which the maximum Sn content of 2.6 wt.% was achieved when the parent USY zeolite was treated by precisely controlled acid treatment. Compared with Sn-MFI, Sn-MWW, Sn-MCM-41, hydrothermally synthesized or postsynthesized Sn-Beta, thus prepared Sn-Y zeolite showed excellent catalytic properties in the Baeyer-Villiger oxidation of 2-adamantanone using hydrogen peroxide or tert-butyl hydroperoxide as oxidant, which was mainly attributed to the open pore system contributed by 3-dimensional 12-membered ring channels and dealumination-derived intracrystal mesoporosity.
Keywords: USY zeolite; Dealumination; Stannosilicate; Postsynthesis; Baeyer-Villiger oxidation;