Applied Catalysis A, General (v.491, #C)
Editorial Board (IFC).
Microwave assisted heterogeneous vapor-phase oxidation of 3-picoline to nicotinic acid over vanadium–titanium oxide catalytic system by Yevgeniya Alkayeva; Ruslan Gibadullin; Maksim Merakhovich; Alexander Abdurakhmanov; Anastasiya Holubyeva; Alexei Shutilov; Galina Zenkovets (1-7).
Binary vanadium–titanium oxide catalysts as well as pure V2O5 and TiO2 (anatase) were studied in microwave assisted vapor-phase oxidation of 3-picoline by oxygen in the presence of nitrogen and water vapors. The main product of the reaction over all catalysts was nicotinic acid. 3-pyridinecarbaldehyde, 3-cyanopyridine, and CO2 were obtained at smaller amounts. The highest rate of the reaction calculated per square meter of the catalyst surface was observed over pure vanadium oxide. Decrease in vanadium oxide content in the binary catalysts led to decrease in the rate of 3-picoline conversion. Titanium dioxide (anatase) demonstrated the lowest activity. Much more energy was necessary to heat pure titanium oxide to the reaction temperature when compared to the pure vanadium oxide. The microwave heating effect can be located on the V2O5 catalyst active component. Due to specific temperature distribution, the lattice oxygen in the microwave effective dielectric vanadium oxide becomes more mobile inducing the rate of 3-picoline oxidation to nicotinic acid. The data obtained under microwave heating were compared to the results produced over the same catalysts by applying classical conventional energy.
Keywords: 3-picoline oxidation; Heterogeneous vapor-phase catalysis; Microwave heating; Vanadium–titanium oxide system;
Promoted RhPt bimetallic catalyst supported on δ-Al2O3 and CeO2–ZrO2 during full-scale autothermal reforming for automotive applications: Post-mortem characterization by A.V. González; J. Rostrup-Nielsen; K. Engvall; L.J. Pettersson (8-16).
Spent catalyst after 40 h on stream. Aged washcoat samples taken at the poited locations. F: front, M: middle, B: back.The influence of sulfur and coke formation on the steam reforming of diesel was evaluated for two promoted RhPt bimetallic catalysts, composed of 1:1 Rh:Pt/10:10 La2O3: CeO2/ δ-Al2O3 (CAT 1) and 1:1 Rh:Pt/4:5 MgO: Y2O3/CeO2 − ZrO2 (CAT 2). The intrinsic activity is related to the total Rh and Pt area observed after the exposure to sulfur. Therefore, the degree of deactivation is related to the amount of sulfur deposited on the active metal sites. Sulfur analysis on the aged catalyst washcoat showed a decreasing sulfur concentration in the axial direction of the reformer. The estimated sulfur coverage related to metal surface area after 40 h on stream reached values of 0.145 in CAT 2, below the equilibrated sulfur coverage of 0.19 after tests with DIN 590. Thus, showing a partial deactivation due to sulfur poisoning. Further catalyst characterization on carbon deposits and thermal aging was performed by TPO, TGA, BET, CO chemisorption, and TEM analysis.
Keywords: ATR; Infrastructure fuel; Sulfur; Deactivation; RhPt bimetallic catalysts;
Effect of imidazole on biomimetic cyclohexane oxidation by first-, second-, and third-generation manganese porphyrins using PhIO and PhI(OAc)2 as oxidants by Vinicius Santos da Silva; Alexandre Moreira Meireles; Dayse Carvalho da Silva Martins; Júlio Santos Rebouças; Gilson DeFreitas-Silva; Ynara Marina Idemori (17-27).
In this work, spectrophotometric titrations of first- (MnIIITPPCl), second- (MnIIIAPTPPCl and MnIIIT4CMPPCl), and third- (MnIIIBr9APTPPCl and MnIIIBr8T4CMPPCl) generation manganese(III) porphyrins ([MnIIIP]+) were carried out in order to investigate the axial coordination equilibrium between imidazole (Im) and these metalloporphyrin complexes. Cyclohexane oxidation by PhIO or PhI(OAc)2 catalyzed by the aforementioned [MnIIIP]+, in the presence of various [MnIIIP]+/Im molar ratios, was investigated as a means to study the contribution that the penta-, [MnIIIP(Im)]+, or hexacoordinate, [MnIIIP(Im)2]+, species at equilibrium may exert into catalyst efficiency and oxidative stability. The computational program SQUAD was used to analyze the spectrophotometric data and calculate the equilibrium constants used by program HySS to generate the species distribution curves for the various [MnIIIP]+/Im systems. In general, higher catalytic efficiency in the PhIO systems was achieved with the use of imidazole ranging from 1:0.5 to 1:5 [MnIIIP]+/Im ratio, depending on the nature of [MnIIIP]+. The catalytic systems with PhI(OAc)2 as oxidant were more sensitive to Im addition, and optimum yields were achieved with lower [MnIIIP]+/Im ratio (up to 1:1). It is noteworthy that the presence of imidazole reduced the usual instability of the third-generation catalyst MnIIIBr8T4CMPPCl toward oxidative destruction by PhI(OAc)2, but did not exert such a protective effect in the PhIO oxidations.
Keywords: Manganese porphyrins; Cyclohexane oxidation; Imidazole; Iodosylbenzene; Iodobenzene diacetate;
Cu nanostructures of various shapes and sizes as superior catalysts for nitro-aromatic reduction and co-catalyst for Cu/TiO2 photocatalysis by Rupinder Kaur; Bonamali Pal (28-36).
The lengthy Cu nanowires (CuNW) and CuNW/TiO2 exhibit superior catalytic effect and co-catalytic efficiency for m-chloronitrobenzene reduction and photooxidation of acetic acid as compared to nanorods (NR) and spherical (NS) shaped Cu nanoparticles, respectively.Cu nanostructures of various shapes and sizes have prepared to study their comparative optical, electrokinetic, catalysis for nitro-aromatic reduction and co-catalysis activity for photooxidation of acetic acid by Cu/TiO2 composites. As-prepared Cu nanospheres of three different sizes (3–20 nm), nanorods (length ≈ 600–700 nm and width ≈ 15–20 nm) and nanowires (length ≈ 4–6 μm and width ≈ 60–80 nm) displayed characteristic surface plasmon bands at 590–645 nm, 576 and 826 nm, and 559 and 905 nm, respectively. The zeta potential ζ = −35.9 mV for nanowires and −30.08 mV for nanorods is found to be higher than ζ = −12.28 mV for spherical nanoparticles. A significant enhancement in the reduction rate was observed with decreasing size (20–3 nm) and increasing surface to volume ratio (0.34–1.73 nm−1) of Cu nanospheres and lengthy Cu nanowires exhibit the highest catalytic activity (≈96%) relative to nanorods (≈80%) and nanospheres (≈72%) for the reduction of nitrobenzene, m-nitrotoluene, m-chloronitrobenzene to their respective amines. The co-catalytic activity of Cu nanostructures imparted to TiO2 for the photocatalytic oxidation of acetic acid is highly decreased as: Cu nanowires/TiO2 (k = 1.6 × 10−2 min−1) > Cu nanorods/TiO2 (k = 4.8 × 10−3 min−1) > Cu nanospheres/TiO2 (k = 3.8 × 10−4 min−1) > TiO2 (k = 1.08 × 10−5 min−1) because of the differences in photoexcited electron–hole pairs separation efficiency between Cu nanostructures of different shapes.
Keywords: Cu nanostructures; Cu nanocatalysts; Nitro-aromatic reduction; Cu catalysis; Cu/TiO2 photoactivity;
Catalytic gas-phase fluorination of 1,1,2,3-tetrachloropropene to 2-chloro-3,3,3-trifluoropropene over the fluorinated Cr2O3-based catalysts by Wei Mao; Liangang Kou; Bo Wang; YanBo Bai; Wei Wang; Jian Lu (37-44).
Gas-phase fluorination of 1,1,2,3-tetrachloropropene to 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) was investigated over the fluorinated Cr2O3 catalysts with and without promoters. The reaction conditions showed significantly effects on product distribution including temperature, molar ratio of reactants and contact time. The selectivity to HCFO-1233xf was favored under relative higher temperature, larger HF/1,1,2,3-tetrachloropropene ratio and shorter contact time. Based on the data of product distribution over the fluorinated Cr2O3 catalyst, a possible reaction path involving complicated consecutive steps was proposed including the addition/elimination and the direct Cl/F exchange. The XRD, XPS and Raman results indicated that introducing Mg, Ca and La onto Cr2O3 promoted the formation of highly dispersed CrO x F y species during the pre-fluorination process, whereas the presence of Y inhibited the formation of CrO x F y . The BET results showed that the addition of La and Y into Cr2O3 enhanced the surface area of fluorinated samples. The fluorinated Cr2O3 promoted by La (La/F-Cr2O3) catalyst displayed the best activity and lifetime among the prepared catalysts, which can be attributed to its rich CrO x F y species and high surface area.
Keywords: Fluorination; 1,1,2,3-tetrachloropropene; 2-chloro-3,3,3-trifluoropropene; HF; Fluorinated chromia;
Rapid reduction of GO by hydrogen spill-over mechanism by in situ generated nanoparticles at room temperature and their catalytic performance towards 4-nitrophenol reduction and ethanol oxidation by B.K. Barman; K.K. Nanda (45-51).
Here, we report the clean and facile synthesis of Pt and Pd nanoparticles decorated on reduced graphene oxide (rGO) by the simultaneous reduction of graphene oxide (GO) and the metal ions in Mg/acid medium. As-generated Pt and Pd nanoparticles serve as a heterogeneous catalyst for the further reduction of the rGO by the hydrogen spill-over process. The C/O ratio is much higher as compared to the rGO obtained by the reduction of GO by only Mg/acid. Overall, the process is rapid, facile and green that does not require any toxic chemical agent or any rigorous chemical reactions. We perform the catalytic reduction of 4-nitophenol (4-NP) to 4-aminophenol (4-AP) at room temperature by Pd@rGO and Pt@rGO. The reduction is complete within 35 s for Pd@rGO and 60 s for Pt@rGO when 50 μg of hybrid catalyst is used for 0.5 ml of 1 mM of 4-NP. In case of ethanol oxidation, the current density for Pd@rGO is comparable to commercial Pt/C but is doubled for Pt@rGO. Overall, both structures show highly stable catalytic activity compared to commercial Pt/C.
Keywords: Pt; Pd based graphene; Hydrogen spill-over mechanism; 4-Nitrophenol reduction and electrochemical ethanol oxidation;
RGO–TiO2–ZnO composites: Synthesis, characterization, and application to photocatalysis by Fatima Tuz Johra; Woo-Gwang Jung (52-57).
Chemical approaches to the reduction of graphene oxide (GO) for large-scale production of reduced graphene oxide (RGO) sheets have become a reality, speeding up the availability of graphene. In this work, an RGO–TiO2–ZnO composite was synthesized through the hydrothermal reduction of GO in a deionized (DI) water solution containing TiO2 and ZnO precursors at 180 °C. Morphological and structural characterizations using several techniques are reported. The photocatalytic activity of the synthesized RGO–TiO2–ZnO composite is approximately 63% at 120 min under 100 W UV irradiation, which is much higher than that of pure ZnO (11%). The enhanced properties are described in terms of increased light absorption intensity and the reduction of electron–hole pair recombination in the composite owing to the stepwise energy level structure in the composite.
Keywords: Reduced graphene oxide; Hydrothermal; UV irradiation; Photocatalytic; Electron–hole pair;
Highly efficient and magnetically recyclable graphene-supported Pd/Fe3O4 nanoparticle catalysts for Suzuki and Heck cross-coupling reactions by Hany A. Elazab; Ali R. Siamaki; Sherif Moussa; B. Frank Gupton; M. Samy El-Shall (58-69).
Herein, we report a facile and efficient one-step method for the synthesis of highly active, Pd/Fe3O4 nanoparticles supported on graphene nanosheets (Pd/Fe3O4/G) that exhibit excellent catalytic activity for Suzuki and Heck coupling reactions and that can be magnetically separated from the reaction mixture and recycled multiple times without loss of catalytic activity. The synthesis approach is based on the Microwave (MW)-assisted reduction of palladium and ferric nitrates in the presence of graphene oxide (GO) nanosheets using hydrazine hydrate as the reducing agent. The results provide a fundamental understanding of the system variables by comparing the catalytic activity and recyclability of four different catalysts with different properties. The most active and recyclable catalyst contains 7.6 wt% Pd nanoparticles with 4-6 nm diameters in Pd(0) oxidation state well-dispersed with 30 wt% Fe3O4 nanoparticles with 12–16 nm diameters on highly reduced GO containing a C/O ratio of 8.1. These combined properties produce remarkable catalytic activity for Suzuki cross coupling reactions under MW reaction conditions with an extremely high turnover number (TON) of 9250 and turn over frequency (TOF) of 111,000 h−1 at 80 °C. The magnetic properties imparted by the Fe3O4 component of the catalyst enables the catalyst to be easily isolated and recycled, thus greatly simplifying the ability to purify the reaction products and increasing the economic value of the catalyst. The utility of these magnetic catalysts towards Suzuki and Heck cross coupling reactions with a variety of functionalized substrates was also demonstrated.
Keywords: Magnetite nanoparticles; Palladium/magnetite/graphene catalyst; Suzuki coupling; Heck coupling; Magnetic separation of catalysts;
Chemoselective hydrogenation of aromatic ketones with Pt-based heterogeneous catalysts. Substituent effects by Virginia Vetere; Andrea B. Merlo; Mónica L. Casella (70-77).
Adsorption modes of aromatic ketones on Pt surface.Catalytic reduction of aromatic ketones is an interesting reaction that leads to the obtaining of alcohols. Some of these alcohols are employed as intermediaries to produce chemical fine compounds. The bimetallic catalysts are widely used in the chemoselective hydrogenation. The Surface Organometallic Chemistry on Metals (SOMC/M) is a methodology employed to obtain bimetallic systems.In the present work the hydrogenation of ketones derived from acetophenone has been studied. The aim was observe the effect on activity and selectivity to aromatic alcohols by the presence of substituents in the ring. The chemical characteristics of substituents groups could influence the way aromatic ketones are absorbed on the metallic surface. This fact can be explained by a combination of geometric and electronic effects.
Keywords: Aromatic ketones; Bimetallic catalysts; PtSn; Surface Organometallic Chemistry of Metals;
Ti-rich TS-1: A highly active catalyst for epoxidation of methallyl chloride to 2-methyl epichlorohydrin by Weiyong Jiao; Yue He; Junfen Li; Jianguo Wang; Takashi Tatsumi; Weibin Fan (78-85).
Ti-rich TS-1 showed high catalytic activity and H2O2 efficiency for epoxidation of methallyl chloride (MAC). Unexpectedly, it was much more active in tert-butyl alcohol (TBA) solvent than in methanol and acetonitrile partially because TBA increased the adsorption amount of MAC in the channel of Ti-rich TS-1, and consequently enhanced the MAC concentration around the Ti sites. By optimizing reaction conditions, the MAC conversion reached 85.4% with epoxide selectivity of 96.7%, which could be maintained by regenerating the catalyst by calcination. Addition of alkali or salt into the reaction system or impregnation of these materials on the Ti-rich TS-1 led to a drastic decrease in activity. In combination with NH3-TPD and diffuse reflectance UV–vis spectroscopy results, it was found that active Ti-OOH (η 2) intermediates were formed for framework tetrahedral Ti species with moderately strong Brönsted acidity. This indicates that an Eley–Rideal-type reaction mechanism probably dominated the MAC epoxidation over Ti-rich TS-1.
Keywords: TS-1; Methallyl chloride; Epoxidation; tert-butyl alcohol; Catalytic mechanism;
Insights into ethanol decomposition over Pt: A DFT energy decomposition analysis for the reaction mechanism leading to C2H6 and CH4 by Isabela Dancini-Pontes; Nádia R.C. Fernandes-Machado; Marcos de Souza; Rodrigo M. Pontes (86-93).
The search for environmentally correct processes is one of the greatest challenges in current energy research. Hydrogen production trough ethanol reforming emerges as a promising technology. In this work, the mechanism for ethanol decomposition over platinum was investigated by density functional theory (DFT). The various reaction intermediaries and transition states were optimized over a cluster of five Pt atoms at the B3LYP-D3/6-31+G(d,p) level of theory for ethanol with the SBKJC ECP basis set for the metal atoms. This approach showed to be fully consistent with experimental observations. Two routes were considered, one leading to the formation of CH4 and CO and the other leading to C2H6. In agreement with previous calculation and experimental studies, the route forming CH4 and CO is favored. The reaction barriers were investigated by the Localized Molecular Orbital Energy Decomposition Analysis (LMOEDA) method. In general, the reaction steps that involve solely the scission of a O―H or C―H bond present elevate reaction barriers. Some other steps, however, include a concomitant strengthening of the C―O bond as the C―H bond elongates. These reaction steps present relatively low reaction barriers. For some other cases, it is the distinct interaction with the metal experienced by the transition state and the ground state that determines the energy barrier. The LMOEDA method proved to be an invaluable tool for the understanding of reaction mechanisms and for the rational design of news catalysts.
Keywords: Ethanol reforming; Reaction mechanism; DFT; Platinum cluster; Theoretical calculations;
Facile fabrication of Ti supported CuO film composed of bamboo-leaf-like nanosheets and their high catalytic performance in the oxidative degradation of methylene blue with hydrogen peroxide by Jinyun Liao; Hao Li; Xibin Zhang; Dingshu Xiao; Na Qiang (94-99).
The design and preparation of heterogeneous Fenton-like catalysts with high catalytic activity and good reusability is a very important task in the field of environmental catalysis. In this work, nanostructured CuO film composed of bamboo-leaf-like CuO nanosheets supported on Ti substrate was synthesized by a facile solution-chemistry method. When the as-prepared CuO film acted as a catalyst, the oxidative degradation of methylene blue (MB) with H2O2 followed the pseudo-first order kinetics and the rate constant could reach 0.0906 min−1 at 30 °C, which was 6.6 times larger than the rate constant of MB degradation catalyzed by commercial CuO nanoparticles. The apparent activation energy of MB degradation was ca. 26.2 kJ mol−1. After 6 successive catalytic cycles, the as-prepared CuO film still remained its original catalytic activity, exhibiting much better reusability and durability than recently reported heterogeneous Fenton-like catalysts.
Keywords: Nanostructured film; CuO; Heterogeneous Fenton-like catalyst; Methylene blue; Degradation;
Factors affecting coke formation on H-ZSM-5 in naphtha cracking by Rahat Javaid; Kohei Urata; Shinya Furukawa; Takayuki Komatsu (100-105).
The coke formation on H-ZSM-5 zeolite during the catalytic cracking of alkanes constituting naphtha was investigated with a focus on the reaction route and the role of acid concentration and crystallite size of H-ZSM-5. To reveal the coke formation route, cracking of n-hexane, methylcyclopentane or methylcyclohexane was carried out on H-ZSM-5(Si/Al = 107). Cracking of n-hexane produced benzene, toluene and xylene (BTX) as secondary products from successive reaction routes through light alkenes. Only in the cracking of methylcyclopentane and methylcyclohexane, direct reaction routes partially contributed to the BTX formation. In any cases, most of the coke would be formed through BTX. The reaction of BTX into coke was analyzed from the catalytic results on Na+-exchanged and phosphorus embedded H-ZSM-5 with various crystallite sizes. The ratio of accumulated amounts of coke and BTX (coke/BTX ratio) was obtained as a measure of selectivity for coke formation. The coke/BTX ratio did not show a significant correlation with the acid concentration of catalysts, whereas the ratio gave a strong correlation with the crystallite size. H-ZSM-5 with smaller crystallite sizes would help BTX molecules escaping immediately out of micropores before being converted into coke precursor, which minimizes the coke formation.
Keywords: H-ZSM-5; Naphtha cracking; Coke; Deactivation;
Reusable chiral salen Mn(III) complexes with phase transfer capability efficiently catalyze the asymmetric epoxidation of unfunctionalized olefins with NaClO by Yaju Chen; Rong Tan; Yaoyao Zhang; Guangwu Zhao; Weiguo Zheng; Rongchang Luo; Donghong Yin (106-115).
Polymeric chiral salen Mn(III) complexes with built-in phase-transfer capability were first prepared and proved highly efficient and reusable in asymmetric epoxidation of unfunctionalized olefins with aqueous NaClO. Almost quantitative conversion (91%) with excellent enantioselectivity (93% ee value) was achieved in asymmetric epoxidation of chromene-based substrates with PICP-3.A series of chiral salen Mn(III) polymers with build-in phase transfer capability was prepared by bridging the chiral salen Mn(III) units with polyethylene glycol (PEG)-based di-imidazolium ionic liquid (IL) side by side. Technologies of characterization suggested the alternation of intact chiral salen Mn(III) unit with PEG-based dicationic imidazolium IL moiety in the rigid one-dimension polymers. Amphipathic nature of PEG-based di-imidazolium IL moiety allowed the obtained catalysts to undergo inherent phase transfer catalysis in asymmetric epoxidation of unfunctionalized olefins with NaClO, which in turn increased the reaction rate of epoxidation in water–dichloromethane biphasic system. Decreasing total length of polyether chain leads to an increase in built-in phase transfer capability of corresponding complex, which further enhances the catalytic performance. 91–97% of conversion was obtained in the enantioselective epoxidation of styrene, α-methylstyrene, indene, 1,2-dihydronaphthalene, 6-cyano-2,2-dimethylchromene, and 6-nitro-2,2-dimethylchromene catalyzed by the complex where number of ethylene oxide unit is 3 within 60 min, which is significant higher than that observed for the neat complex (56–74%) and the ICP (62–85%). High enantiomeric excess (ee) for the epoxides (in the range of 67–93%) was also achieved, except for styrene (ee, 34%) and α-methylstyrene (ee, 41%). Furthermore, the efficient phase transfer catalysts could be easily recovered by solvent precipitation and be recycled for seven times without significant loss of the activity and enantioselectivity.
Keywords: Chiral salen Mn(III) complex; Phase transfer catalysis; Enantioselective epoxidation; Unfunctionalized olefins; Aqueous/organic biphasic system;
Highly active and stable Ni-based bimodal pore catalyst for dry reforming of methane by Zhenghong Bao; Yongwu Lu; Jun Han; Yebo Li; Fei Yu (116-126).
Bimodal pore NiCeMgAl catalysts were synthesized via the refluxed co-precipitation method. Methane reforming using carbon dioxide over this bimodal pore NiCeMgAl catalyst for syngas production was systematically studied by optimizing the active component NiO-loading, calcination temperature, reduction temperature and gas hourly space velocity (GHSV). The Ni15CeMgAl sample with 15 wt% NiO loading, was found to be active enough at 750 °C with a high CH4 conversion of 96.5%. The proper reduction temperature for the NiCeMgAl catalyst is either 550–650 °C or 850 °C. Higher calcination temperature favors the formation of NiAl2O4 and MgAl2O4 spinel structures. The Ni active sites derived from the NiAl2O4 spinel structure had longer stability than those from the free NiO. Compared with non-bimodal pore NiCeMgAl catalyst, bimodal pore NiCeMgAl catalyst has a longer stability in the feed gas without dilution. The large pores in the bimodal pore Ni15CeMgAl catalyst were supposed to contribute to the quick molecule transfer during the dry reforming of methane (DRM) reaction when the GHSV was less than 96,000 h−1. The evolution of the Ni15CeMgAl catalyst before and after the DRM reaction was investigated by BET, XRD, TEM, and TGA techniques. A schema of the DRM reaction on the bimodal pore Ni15CeMgAl catalyst was proposed, and the correlation between the structure evolution and catalytic performance change was also discussed.
Keywords: Nickel catalyst; Bimodal pore; Reflux; Dry reforming of methane;
Nickel-promoted copper–silica nanocomposite catalysts for hydrogenation of levulinic acid to lactones using formic acid as a hydrogen feeder by Pravin P. Upare; Myung-Geun Jeong; Young Kyu Hwang; Dae Han Kim; Young Dok Kim; Dong Won Hwang; U.-Hwang Lee; Jong-San Chang (127-135).
Highly active, thermally stable nickel-promoted copper–silica nanocomposite catalysts were prepared via a deposition–precipitation method and used for hydrogenation of levulinic acid (LA) using formic acid (FA) as H2 feeder. Ni(20)Cu(60)-SiO2 (3:1 weight ratio of Cu to Ni, 80 wt% metal content) showed better activity for vapor-phase formation of γ-valerolactone (GVL) from LA with FA as a hydrogen source. The catalyst selectively converts 99% of LA into 96% of GVL; the remaining 4% is angelica-lactone (AL). The effect of different concentrations of Ni promoted on Cu-silica and different LA to FA molar ratios on the catalyst activity affecting the hydrogen-free hydrogenation of LA was studied. The catalyst Ni(20)Cu(60)-SiO2 exhibited long-term stability (200 h) without loss in activity. Characterization using TEM, XPS, TPR, XRD and N2O titration was performed to find the most active phase for LA hydrogenation to GVL and the reason for the long-term stability. It was found that Ni-promoted well-dispersed metallic Cu species were the most active phases in hydrogenation, and the nanocomposite nature of the catalyst helped in providing long-term stability to the active phase.
Keywords: γ-Valerolactone; Levulinic acid; Hydrogenation; Formic acid; Nickel-promoted copper on silica.;
Photocatalytic ozonation of phenazopyridine using TiO2 nanoparticles coated on ceramic plates: mechanistic studies, degradation intermediates and ecotoxicological assessments by Mehrangiz Fathinia; Alireza Khataee (136-154).
Removal of phenazopyridine (PhP), an analgesic drug, from water with different oxidation processes including photocatalysis, ozonation and photocatalytic ozonation was studied. The experiments were conducted using a semi-batch reactor where TiO2 nanoparticles were immobilized on ceramic plates irradiated by UV-A light in the proximity of oxygen and/or ozone. The surface morphology, topography and roughness of the bare and TiO2-coated ceramic plates were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Comparing the processes of photocatalysis, ozonation and photocatalytic ozonation revealed that using photocatalytic ozonation led to the highest efficiency (85% at 35 min) in PhP removal. The influence of pH, PhP initial concentration and ozone gas flow rate on the removal of PhP was investigated in both individual and combined processes. The presence of synergy was investigated under various operational parameters. The mechanism of photocatalytic ozonation process was investigated in the presence of various reactive oxygen species (ROS) scavengers. The main intermediate products of PhP produced in ozonation and photocatalytic ozonation processes were verified by the GC–MS technique. The chronic phytotoxicity of PhP and its intermediate compounds formed in ozonation and photocatalytic ozonation was evaluated using aquatic species Spirodela polyrrhiza (S. polyrrhiza). It was found that the photocatalytic ozonation process, in contrast to the single ozonation process, can efficiently reduce the phytotoxicity of the PhP from aqueous solutions.
Keywords: TiO2 nanoparticles; Pharmaceuticals; Photocatalysis; Ozonation; Phenazopyridine; Ecotoxicity.;
Understanding the role of Co in Co–ZnO mixed oxide catalysts for the selective hydrogenolysis of glycerol by V. Rekha; C. Sumana; S. Paul Douglas; N. Lingaiah (155-162).
A series of Co–ZnO catalysts with varying Co to Zn ratio were prepared by co-precipitation method and these were characterized by X-ray diffraction, temperature programmed reduction, H2 chemisorption, X-ray photoelectron spectroscopy and transmission electron microscopy. The developed catalysts were evaluated for selective hydrogenolysis of glycerol to 1,2-propanediol. Glycerol conversion was found to be dependent on the ratio of Co to ZnO and a weight ratio Co/Zn of 50:50 was shown about 70% glycerol conversion with 80% selectivity to 1,2-propanediol. Glycerol hydrogenolysis activity was found to be related to Co metal area as well as amount of ZnO in the catalyst. The proposed catalysts were stable under the reaction conditions and reusable with consistent activity. Different reaction parameters were studied and optimum reaction conditions were established. A kinetic model for the hydrogenolysis reaction was also derived.
Keywords: Glycerol; Cobalt oxide; Zinc oxide; Hydrogenolysis; 1,2-Propanediol;
Efficient production of 1,3-butadiene in the catalytic dehydration of 2,3-butanediol by Hailing Duan; Yasuhiro Yamada; Satoshi Sato (163-169).
Vapor-phase catalytic dehydration of 2,3-butanediol (2,3-BDO) was investigated over rare earth oxide catalysts and In2O3 at around 400 °C. In the dehydration of 2,3-BDO over Sc2O3, 1,3-butadiene was mainly produced together with butanone, 2-methyl-propanal, 2-methyl-propanol, 3-buten-2-ol, and butene isomers. Sc2O3 calcined at 800 °C showed the highest 1,3-butadiene yield of 88.3% at 411 °C in H2 carrier gas flow. Since 3-buten-2-ol is produced selectively from 2,3-BDO over Sc2O3 at a low temperature of 325 °C, 3-buten-2-ol rather than butanone is a probable intermediate from 2,3-BDO to 1,3-butadiene. 3-Buten-2-ol is readily converted into 1,3-butadiene at temperatures lower than 411 °C over Sc2O3 and Al2O3. In addition, double-bed catalysts composed of an upper catalyst bed of Sc2O3 and a lower of Al2O3 successfully converted 2,3-BDO directly into 1,3-butadiene with a stable selectivity higher than 94% at 318 °C and 100% conversion of 2,3-BDO.
Keywords: Dehydration; 2,3-Butanediol; 1,3-Butadiene; 3-Buten-2-ol; Rare earth oxide; Sc2O3;
Au/Pt/TiO2 catalysts prepared by redox method for the chemoselective 1,2-propanediol oxidation to lactic acid and an NMR spectroscopy approach for analyzing the product mixture by Elena Redina; Alexander Greish; Roman Novikov; Anastasiya Strelkova; Olga Kirichenko; Olga Tkachenko; Gennady Kapustin; Ilya Sinev; Leonid Kustov (170-183).
1,2-propanediol obtained from the waste glycerol is the most prominent substrate to produce lactic acid (LA) through the sustainable “green” catalytic oxidative route. We showed that bimetallic Au/Pt/TiO2 catalysts that could be easily prepared by the redox reaction with preadsorbed hydrogen possessed a high activity in the formation of lactic acid from 1,2-propanediol through selective primary hydroxyl group oxidation by an oxygen–air mixture or an air. The most efficient catalyst with the highest TON value was the sample with the lowest Au content. Even the addition of 0.025 wt.% of gold to the 1%Pt/TiO2 catalyst by the redox method resulted in the enhanced 1,2-propanediol conversion up to 96% with the 91% selectivity to LA. The high oxidation activity of the Au/Pt/TiO2 catalysts was ascribed to the strong interaction between the two metals in Au/Pt bimetallic particles and between the bimetallic particles and the support, which was proved by X-ray photoelectron spectroscopy (XPS) analysis, Fourier transform infrared spectroscopy of adsorbed CO (DRIFTS) technique, and temperature programmed reduction method (TPR-H2). The reaction products were identified and analyzed with the use of 1D and 2D nuclear magnetic resonance spectroscopy (NMR) methods, which also allowed suggesting a plausible up-to-date scheme of 1,2-propanediol catalytic oxidation.
Keywords: Gold–platinum catalyst; Redox method; Bimetallic catalyst preparation; Lactic acid; 1,2-propanediol oxidation; NMR; DRIFTS;
Catalysis of nickel nanoparticles with high thermal stability for ammonia decomposition by Hitoshi Inokawa; Takayuki Ichikawa; Hiroki Miyaoka (184-188).
Catalytic properties of nickel (Ni) nanoparticles for thermal ammonia decomposition were investigated. The nanoparticles were synthesized from Ni(C5H5)2 in/on pores of zeolite with an aim to prevent diffusion and sintering of the nanoparticles at high temperature. The Ni nanoparticles were smaller than 5 nm and maintained their nano-size after the NH3 decomposition reaction at 500 °C, whereas Ni particles synthesized by a conventional impregnation method formed large particles, such as 50 nm, after the reaction. The Ni nanoparticles showed much higher activity than Ni particles synthesized by the conventional impregnation method. By the investigation of kinetic properties, it was confirmed that the frequency factor was related to the high catalytic activity. Therefore, both high dispersion level and high thermal stability brought Ni nanoparticles the enhancement of their catalysis.
Keywords: Nanoparticle; Ammonia; Hydrogen; Nickel; Zeolite;
Quinoxaline synthesis via oxidative cyclization reaction using metal–organic framework Cu(BDC) as an efficient heterogeneous catalyst by Giao H. Dang; Yen T.H. Vu; Quoc A. Dong; Dung T. Le; Thanh Truong; Nam T.S. Phan (189-195).
A metal–organic framework Cu(BDC) was synthesized, and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. The Cu(BDC) was employed as an efficient heterogeneous catalyst for the oxidative cyclization reaction between α-hydroxyacetophenone and phenylenediamine to form 2-phenylquinoxaline as the principal product. The optimal conditions involved the use of air atmosphere oxidant in toluene solvent at 100 °C in 3 h. In addition, the Cu(BDC) exhibited higher catalytic activity in the quinoxaline synthesis reaction than that of others Cu–MOFs such as MOF-199, MOF-118, and Cu2(BDC)2(DABCO), and higher than that of Mn(BDC), and Ni2(BDC)2(DABCO). The Cu(BDC) catalyst could be recovered and reused several times without a significant degradation in catalytic activity.
Keywords: Metal–organic framework; Oxidative cyclization; Quinoxaline; Cu(BDC); Heterogeneous catalyst;