Applied Catalysis A, General (v.378, #2)
Editorial Board (CO2).
Syngas production from CO2 reforming of methane using Ce-doped Ni-catalysts obtained from hydrotalcites by reconstruction method by C.E. Daza; C.R. Cabrera; S. Moreno; R. Molina (125-133).
Ce-doped Ni, Mg and Al hydrotalcites were synthesized through the reconstruction method in the presence of the [Ce(EDTA)]− complex. Surface CeO2-doped periclase oxides were obtained. Solids were used in the production of syngas through CO2 reforming of methane. H2/CO ratios between 0.8 and 1.2 were obtained. Ce had a positive effect in the elimination of coke.Ce-doped Ni, Mg and Al hydrotalcites were synthesized through the reconstruction method in the presence of the [Ce(EDTA)]− complex. The hydrotalcites and the mixed oxides derived after their thermal decomposition at 500 °C (16 h) were characterized by XRD, TGA-DTA, ICPS, IR, Raman, SEM-EDX, TEM, TPR-H2, TPD-CO2, XPS and N2 sorptometry. The reconstruction of the mixed oxide is not total in [Ce(EDTA)]− solutions with Ce between 1 and 10%wt. The hydrotalcite is reconstructed as hydroxyl-type phase; the reconstruction takes place in the external edges of the oxide granules. The complex is deposited, with high distribution, on the external surface of the reconstructed layered structure as species of Ce4+ and after the calcination generates surface CeO2-doped periclase oxides. Solids were used in the production of syngas through CO2 reforming of methane (CH4:CO2:Ar 5/5/40) using a total fixed flow of 50 mL min−1 and WHSV = 30 L g−1 h−1 between 500 and 800 °C with prior reduction. The increase in the Ce load had a promoter effect in catalytic conversions. H2/CO ratios between 0.8 and 1.2 were obtained. Ce had a positive effect in the elimination of coke, since a nominal optimal value of 3%wt. was obtained.
Keywords: Hydrotalcite; Cerium; Reconstruction; Syngas; Methane;
The synergistic effect of alcohol mixtures on transesterification of soybean oil using homogeneous and heterogeneous catalysts by M. Kim; C. DiMaggio; S. Yan; S.O. Salley; K.Y.S. Ng (134-143).
Methanolysis becomes linked with ethanolysis when a methanol/ethanol equimolar mixture is used as an alcohol source. Significant improvements in the transesterification activity were observed when mixed alcohol blends were employed. To explain this effect, a combined structure of methoxide–ethanol or ethoxide–methanol has been proposed and subsequently confirmed by reaction measurements and FTIR.In an effort to enhance the transesterification reaction of soybean oil and thereby the lubricity properties of the resulting biodiesel as well, the alcohol component of the reaction blend was altered to include several different combinations of methanol, ethanol, and propanol, rather than a single alcohol. For this work, various concentrations of a homogeneous catalyst, such as CH3ONa or C2H5ONa, or a heterogeneous catalyst, CaO–La2O3 or an anion exchanged resin, were used in the reaction. Ethanolysis was found to be faster than methanolysis with highly basic homogeneous catalysts due to the higher nucleophilicity of ethoxide relative to methoxide. The ethyl-ester yield approached a maximum earlier than the methyl-ester yield, even though the methyl-ester yield continuously increased with reaction. Also, methanolysis became linked with ethanolysis when a methanol–ethanol equimolar mixture was used as an alcohol source. In addition, significant improvement in the transesterification activity was observed at very earlier reaction times when a methanol–ethanol mixture was used and a high basicity condition existed where ethoxide can be formed. To explain this effect, a combined structure of methoxide–ethanol or ethoxide–methanol has been proposed and tentatively supported by reaction measurements and FTIR. In this model, the formed alkoxide generates two reactive sites resulting in an accelerated transesterification rate.
Keywords: Ethyl-esters; Lubricity; Transesterification; CaO–La2O3; Combined structure of methoxide–ethanol; Synergy effect; Methanol–ethanol mixture;
Effect of V in La2Ni x V1−x O4+δ on selective oxidative dehydrogenation of propane by Salvatore Crapanzano; Igor V. Babich; Leon Lefferts (144-150).
Non-stoichiometric redox compounds such as La2NiO4+δ and V-doped La2Ni1−x V x O4+1.5x+δ have been tested as oxidants in selective oxidation of propane in pulse mode for dense membrane reactor application. Doping La2NiO4+δ with vanadium widens the window of oxidation degree in which promising selectivity to propylene is achieved.In this study, non-stoichiometric redox compounds such as La2NiO4+δ , La2Ni0.95V0.05O4.07+δ and La2Ni0.9V0.1O4.15+δ have been tested as oxidants in selective oxidation of propane, in order to judge the suitability of these materials for a dense membrane reactor for selective propane oxidation. Reducibility of the samples has been investigated using temperature programmed reduction in H2/Ar flow. The catalysts’ activity and selectivity at 550 °C have been investigated employing sequential pulses of diluted propane over the oxides.Pulsing with propane induces step-by-step reduction of the oxide; consequently, the activity of remaining oxygen decreases with the number of pulses, affecting the products distribution. It is observed that at 550 °C on oxidized catalysts CO2 and H2O are the main products and the selectivity towards propylene is very low. At a certain reduction level, obtained after pulse 8 in our experiments, the production of CO2 stopped without changing the amount of C3H6 produced. At this stage, also CH4 and C2H4 are being formed. V-doped catalysts have shown a constant level of C3H6 production within a broad window of oxidation degree, while the performance of La2NiO4+δ , catalyst deteriorated drastically after just a few pulses. CO, CH4 and coke deposits are formed with La2NiO4+δ , caused by the formation of metallic Ni. Vanadium is able to prevent this phenomenon, thus drastically broadening the window of selective oxidation of propane.
Keywords: Selective oxidative dehydrogenation; Propane; La2NiO4; Over-stoichiometric oxygen; Pulse test;
Synthesis, structure and catalytic activity of nano-structured Sr–Ru–O type perovskite for hydrogen production by Ahmed Galal; Soher A. Darwish; Nada F. Atta; Shimaa M. Ali; Ahmed A. Abd El Fatah (151-159).
The present work deals with the synthesis of a novel type of perovskites that is used as electrode materials for the electrocatalytic production of hydrogen. The new catalyst prepared by microwave-assisted citrate methods showed excellent improvement in the production rate of hydrogen.SrRuO3 perovskite was synthesized by three different methods, namely microwave assistant-citrate, citrate-nitrate and coprecipitation. The resulting perovskite structure was characterized by XRD and SEM measurements. The electrocatalytic activity of the perovskites was examined toward hydrogen evolution reaction (HER) by Tafel linear polarization and impedance techniques. SrRuO3 prepared by the microwave method showed superior catalytic activity compared to those synthesized by other chemical methods. The values of the exchange current densities are −14.7 × 102, −52.2 and −13.1 μA cm−2 for SrRuO3 prepared by the microwave, citrate-nitrate and coprecipitation methods, respectively. The reaction order and the activation energy for each catalyst were determined. The calculated values of the activation energy are in good agreement with the trend for catalytic activity. Both Tafel and impedance data showed that the Volmer step is the rate-determining step. The particle size calculated from XRD measurements are 30.7, 41.5 and 42.2 nm for the perovskites prepared by microwave assistant-citrate, citrate-nitrate and coprecipitation methods, respectively.
Keywords: Perovskites; Microwave irradiation processing; Nano-particles; Electrocatalyst; Hydrogen evolution reaction; XRD; SEM; Tafel; Impedance;
Biodiesel production process by homogeneous/heterogeneous catalytic system using an acid–base catalyst by Anastasia Macario; Girolamo Giordano; Barbara Onida; Donato Cocina; Antonio Tagarelli; Angelo Maria Giuffrè (160-168).
The transesterification of triglycerides contained in waste oilseed fruits with methanol has been studied in heterogeneous/homogeneous systems using acid and base catalysts (strong acid catalysts: USY, BEA, FAU-X, weak acid catalysts: MCM-41 and ITQ-6, and acid–base catalysts: K-MCM-41, K-ITQ-6). The highest catalytic performances were achieved by K-ITQ-6 catalysts, after 24 h of reaction at 180 °C. A possible continuous biodiesel production process has been proposed. The figure shows triglycerides conversion, biodiesel yield and FFAs conversion, as function of time, obtained using K-ITQ-6 catalyst at 180 °C, at 5 wt% respect to the oil and 1:20 molar ratio between oil:methanol.The transesterification of triglycerides contained in waste oilseed fruits with methanol has been studied in heterogeneous/homogeneous systems using acid and base catalysts. The acid catalysts (strong acid catalysts: USY, BEA, FAU-X, and weak acid catalysts: MCM-41 and ITQ-6 with Si/Al = ∞) were prepared by hydrothermal synthesis procedures. In order to obtain acid–base catalysts, potassium was loaded on different materials by ionic exchange (obtaining K-MCM-41, K-ITQ-6,). XRD, ICP-MS, IR after CO and CO2 adsorption, thermal analyses and N2 adsorption/desorption techniques have been used for catalysts characterization. The highest triglycerides conversion and biodiesel yield values were achieved by K-ITQ-6 catalysts, after 24 h of reaction at 180 °C. Deactivation of this catalyst occurs for potassium leaching, but its regeneration and reuse are feasible and easy to perform. A possible continuous biodiesel production process has been proposed.
Keywords: Biodiesel; Transesterification; Esterification; Zeolites; Acid–base catalysis;
Visible light-driven iodine-doped titanium dioxide nanotubes prepared by hydrothermal process and post-calcination by Shuang Song; Jinjun Tu; Zhiqiao He; Fangyue Hong; Weiping Liu; Jianmeng Chen (169-174).
Iodine-doped TiO2 nanotubes (I-TNTs) were synthesized, characterized and evaluated in the photocatalytic degradation of phenol. The photocatalytic activity of these new I-TNTs is much greater than that of I-doped TiO2 nanoparticles, pure TNTs and P25 under visible light irradiation, and the I-TNTs hydrothermally synthesized at 150 °C are superior to those synthesized at 200 °C.A novel class of iodine-doped TiO2 nanotubes (I-TNTs) has been synthesized via a hydrothermal route using Degussa P25 as a precursor and subsequent calcination. The photocatalytic ability of the products was evaluated in terms of phenol degradation in an aqueous solution under visible light irradiation. The structural properties of the catalysts were characterized by X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) method, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra. According to the XRD data, I-TNTs are pure anatase, revealing a shift of crystallite phase for P25 from rutile to anatase. The surface area of I-TNTs is significantly larger than that of I-doped TiO2 (I-TiO2) nanoparticles, which is an important advantage of the photocatalysts formed with a hydrothermal procedure. XPS and UV–vis spectroscopy show that iodine was incorporated into the TiO2 lattice, and such incorporation extends the photoresponse of TiO2 from UV to the visible light region. As far as phenol degradation is concerned, the I-TNTs are clearly superior to I-TiO2 nanoparticles, pure TNTs and P25. The photocatalytic activity of I-TNTs hydrothermally synthesized at 150 °C had a significantly higher level than that synthesized at 200 °C. This is attributed to the increase of reactive sites and the enhancement of mass transfer that result from the large surface areas associated with the tubular morphology. Additionally, the increase of Ti3+ content also contributes to the improvement of photocatalytic activity of I-TNTs.
Keywords: Titanium dioxide; Iodine; Nanotube; Hydrothermal treatment; Photocatalysis;
Comparative study of Rh/MgO modified with Fe, Co or Ni for the catalytic partial oxidation of methane at short contact time. Part I: Characterization of catalysts by Hisanori Tanaka; Rie Kaino; Kazu Okumura; Tokushi Kizuka; Yoshinao Nakagawa; Keiichi Tomishige (175-186).
On Rh-Fe/MgO, added Fe is almost fully reduced to form large Rh–Fe alloy particles. On Rh-Ni/MgO, a part of the added Ni is reduced to form small Rh–Ni alloy particles. Added Co was reduced to some extent to form Rh–Co alloy particles, where the miscibility of Co with Rh can be lower than that of Fe and Ni.Rh/MgO catalysts modified with Fe, Co and Ni for the catalytic partial oxidation of methane were investigated by means of temperature-programmed reduction (TPR), H2 adsorption measurement, transmission electron microscopy (TEM) and extended X-ray absorption fine structure studies (EXAFS). The reduction of the additives (Fe, Co, Ni) on MgO was promoted by the presence of Rh, and the reducibility was Fe > Co > Ni. The Rh-Ni/MgO tends to give the metal particles with higher dispersion than Rh/MgO. In contrast, the addition of Fe to Rh/MgO aggregated the metal particles. The Co addition did not affect the size of metal particles so significantly. The Rh–M alloy formation (M = Fe, Co, Ni) was detected by the Rh K-edge and M K-edge EXAFS analyses. The miscibility of the additives with Rh is also discussed on the basis of the EXAFS analysis, and this property can be related to the surface concentration of the additives on the alloy particles.
Keywords: Catalytic partial oxidation; Methane; Rhodium; Base metal; Alloy;
Comparative study of Rh/MgO modified with Fe, Co or Ni for the catalytic partial oxidation of methane at short contact time. Part II: Catalytic performance and bed temperature profile by Hisanori Tanaka; Rie Kaino; Yoshinao Nakagawa; Keiichi Tomishige (187-194).
In catalytic partial oxidation of methane, modification of Rh/MgO with the optimized amount of Co or Ni gave high resistance to catalyst oxidation, which reduced the flat bed temperature by enabling overlapping exothermic and endothermic reaction zones.Modifying effects of Fe, Co or Ni over 1 wt% Rh/MgO on the catalytic performance in the catalytic partial oxidation (CPO) of methane were investigated. The optimization of the additive amount was determined by the results of the activity test in the CPO of methane with N2 dilution. The optimum amount of Co (Co/Rh = 1) or Ni (Ni/Rh = 1.5) addition to Rh/MgO enhanced the CH4 conversion and selectivities to H2 and CO, in contrast, the addition of Fe to Rh/MgO decreased the properties. The results of H2 titration and H2 adsorption on the catalysts quenched from the CPO reaction conditions indicate that the Rh-Co/MgO gave low oxidation degree during the CPO of methane and high resistance to the oxidation was demonstrated. In the CPO of methane without N2 dilution, Rh-Co/MgO (Co/Rh = 1) had much lower catalyst bed temperatures than other catalysts, and it can suppress the hot spot formation. This property is also related to the high resistance to the oxidation. The catalyst surface is maintained in a reduced state even in the presence of oxygen enables the overlap of the exothermic oxidation zone with endothermic reforming zone and can decrease the bed temperature remarkably.
Keywords: Catalytic partial oxidation; Methane; Thermography; Hot spot; Rhodium; Base metal: alloy;
Novel nanostructure electrochemical sensor for electrocatalytic determination of norepinephrine in the presence of high concentrations of acetaminophene and folic acid by Mohammad Mazloum-Ardakani; Hadi Beitollahi; Mohammad Ali Sheikh-Mohseni; Hossein Naeimi; Nima Taghavinia (195-201).
The results show that the NE oxidation was catalyzed at pH 8.0 and its peak potential was shifted by 270 mV, to a less positive potential at the surface of the BHTME.In the present paper, the use of a carbon paste electrode modified by 2,2′-[1,2 buthanediylbis (nitriloethylidyne)]-bis-hydroquinone (BH) and TiO2 nanoparticles prepared by a simple and rapid method was described. The modified electrode showed an excellent character for electrocatalytic oxidization of norepinephrine (NE), acetaminophene (AC) and folic acid (FA). Using differential pulse voltammetry (DPV), a highly selective and simultaneous determination of NE, AC and FA has been explored at the modified electrode. Differential pulse voltammetry (DPV) peak currents of NE, AC and FA increased linearly with their concentration at the ranges of 4.0–1100.0 μM, 12.5–500.0 μM and 200.0–3200.0 μM, respectively and the detection limits for NE, AC and FA were 0.5 μM, 2.6 μM and 25.0 μM, respectively.
Keywords: Norepinephrine; Acetaminophene; Folic acid; TiO2 Nanoparticles; Modified carbon paste electrode; Electrocatalysis;
A proposed photocatalytic reactor design for in situ groundwater applications by L.L.P. Lim; R.J. Lynch (202-210).
A parameter study showed that the reactor efficiency is significantly reduced when the hydraulic residence time (HRT) is less than 1 day. This corresponds to an average water velocity of 20 cm d−1 for the reactor studied. As groundwater velocities are typically slower than this, it indicates the potential of this reactor design for in situ groundwater remediation.Groundwater remediation is a challenging task as many existing technologies do not clean up contaminated groundwater in situ. Photocatalysis can decompose a wide range of organic compounds and in principle could be applied to in situ groundwater remediation. However, photocatalytic reactor designs are typically small in scale and generally focus on process intensification to maximise its efficiency, particularly for high flows in wastewater treatment. These compact reactor designs may not be technically and economically viable for in situ groundwater remediation. This paper aims to propose a reactor design suitable for in situ groundwater remediation and characterise it with respect to the surface area to volume ratio, aeration, flow and reliability. The surface area study showed that arranging additional immobilised catalyst radially around the UVA lamp can also enhance the reactor efficiency. The reactor efficiency remained consistent throughout 5 successive experiments with continuous aeration. Aeration is an essential component of photocatalytic oxidation and it has an immediate impact on the photocatalytic degradation. The study demonstrated that under the conditions tested, there was a critical hydraulic residence time (HRT) of 1 day (corresponding to an average water velocity of 0.21 m d−1) beyond which the reactor efficiency can be maintained. This paper shows the potential of this reactor configuration for in situ groundwater remediation.
Keywords: Aeration; Groundwater clean up; Honeycomb reactor; Single pass flow; Reliability; Scale up; Surface area to volume ratio;
Synthesis and characterization of novel oxovanadium(IV) complexes with 4-acyl-5-pyrazolone donor ligands: Evaluation of their catalytic activity for the oxidation of styrene derivatives by Fabio Marchetti; Claudio Pettinari; Corrado Di Nicola; Riccardo Pettinari; Alessandra Crispini; Marcello Crucianelli; Andrea Di Giuseppe (211-220).
Seven new oxovanadium(IV) acylpyrazolonate complexes have been synthesized and fully characterized. High conversion values and high selectivity toward benzaldehyde (acetophenone) formation have been observed when they have been used as catalysts, for the hydrogen peroxide promoted oxidation of styrene derivatives, in acetonitrile.Reaction of VOSO4·5H2O with a methanol solution of the HQ proligand (HQ = 1-R1-4-R2(C＝O)pyrazol-5-one in general, in detail: HQnPe, R1 = phenyl, R2 = neopentyl; HQMe,Me, R1 = R2 = methyl; HQMe,naph, R1 = methyl, R2 = naphthalen-1-yl; HQnaph, R1 = phenyl, R2 = naphthalen-1-yl; HQPh, R1 = R2 = phenyl; HQCF3, R1 = phenyl, R2 = trifluoromethyl; HQpy,CF3, R1 = pyridin-2-yl, R2 = trifluoromethyl) gave seven novel VO(Q)2(H2O) complexes which have been characterized by elemental analyses, IR, ESI-MS, electronic spectroscopy and magnetic susceptibility measurements and, in the case of derivative VO(QCF3)2, also by EPR spectroscopy. The X-ray diffraction study, carried out on derivative VO(QnPe)2(H2O), evidenced a distorted octahedral environment with the two pyrazolonates in anti configuration and the vanadium atom 0.2914(7) Å away from the least-squares plane defined by the four equatorial oxygen atoms. The catalytic activity of these new oxovanadium(IV) complexes has been exhaustively tested for the oxidation of styrene, α-methylstyrene and cis-β-methylstyrene, in the presence of H2O2 as primary oxidant. The effects of oxidant to substrate molar ratio, catalyst amount, solvent and temperature have been studied. Overall, the vanadium complexes showed high activity and high to moderate selectivity toward the benzaldehyde (acetophenone) formation, depending from both the type of starting substrate and experimental reaction times.
Keywords: Oxovanadium complexes; β-Diketonates; Catalytic oxidation; Hydrogen peroxide; Olefin;
Heteropoly acid supported modified Montmorillonite clay: An effective catalyst for the esterification of acetic acid with sec-butanol by Siddhartha Kumar Bhorodwaj; Dipak Kumar Dutta (221-226).
Dodecatungstophosphoric acid, H3PW12O40·6H2O (DTP), supported on acid modified Montmorillonite clay (AT-Mont) matrix, is an efficient solid acid catalyst for the esterification of acetic acid with sec-butanol. Among different catalysts, the 20% loading of DTP on AT-Mont (15 min) shows the highest efficacy with about 80% conversion, having nearly 100% selectivity towards sec-butyl acetate.Esterifications of acetic acid with sec-butanol catalysed by supported dodecatungstophosphoric acid, H3PW12O40 (DTP) on acid modified Montmorillonite clay (AT-Mont) matrix have been carried out. A series of catalysts having 5%, 10%, 20% and 30% loading of DTP on different AT-Mont (15 min to 4 h) were synthesized and evaluated as catalysts; 20% DTP loaded on acid activated (15 min) clay showed the highest catalytic activity with about 80% conversion, having nearly 100% selectivity towards sec-butyl acetate. The high catalytic activity may be due to a high dispersion of the DTP on AT-Mont, providing more surface area (120 m2/g) and active sites than pure HPA. The variation of different reaction parameters, such as reaction temperature, reaction time, mole ratio of acid and alcohol and catalyst amount, on the conversion of acetic acid were studied. The samples were characterized by surface area, cation exchange capacity (CEC) measurements, TGA-DTA and FTIR spectroscopy.
Keywords: Montmorillonite clay; Heteropoly acid; Dodecatungstophosphoric acid; Catalyst; Esterification; Cation exchange capacity;
Light-induced photocatalytic degradation of stearic acid by c-axis oriented ZnO nanowires by G. Kenanakis; N. Katsarakis (227-233).
The photocatalytic activity of highly c-axis oriented ZnO nanowires’ arrays grown on sol–gel seeded glass substrates from aqueous solutions (ASG) was investigated against the degradation of stearic acid under UV-A light illumination. It is demonstrated that ZnO nanowires’ arrays show superior photocatalytic activity compared with the stand-alone seed layers, probably due to their large surface-to-volume ratio.The photocatalytic activity of highly c-axis oriented ZnO nanowires’ arrays grown on seeded glass substrates from aqueous solutions was investigated against the degradation of stearic acid under UV-A light illumination (365 nm). All chemically grown ZnO samples show very good crystallinity and high transmittance in the visible region. The nanowires’ diameter ranges from 35 ± 5 nm to 160 ± 10 nm depending on the grain size of the seed layer applied, while their length (1–1.2 μm) is mainly affected from growth time. It is demonstrated that ZnO nanowires’ arrays show superior photocatalytic activity compared with the stand-alone seed layers, probably due to their enhanced crystallinity and larger surface-to-volume ratio.
Keywords: Nanowires; Photocatalysis; Aqueous solution growth; Seed layer; ZnO; Stearic acid;
Degradation and regeneration of copper-iron spinel and zeolite composite catalysts in steam reforming of dimethyl ether by N. Shimoda; K. Faungnawakij; R. Kikuchi; K. Eguchi (234-242).
The catalyst degradation was attributable mainly to the carbon deposition. The regeneration treatment in air at 500–700 °C could not only recover the catalytic performance of the degraded catalysts as compared with the fresh catalyst, but could also improve it.The degradation and regeneration behaviors of some composite catalysts of ZSM-5 zeolite and Cu-Fe spinel in steam reforming of dimethyl ether (DME) were systematically studied in various conditions. The degradation of the catalyst could be inhibited by increasing the steam-to-DME ratio and/or lowering the gas hourly space velocity and the reforming temperature. A higher mixing ratio of Cu-Fe spinel to ZSM-5 could also prolong the life of the composite catalysts. The catalyst deactivation was attributable mainly to the carbon deposition in the reaction temperature range of 250–310 °C. The regeneration treatment in air at 500–700 °C could not only recover the catalytic performance of the degraded catalysts as compared with the fresh catalyst, but could also improve it. We confirmed that the promoting effect of the heat treatment in air was due to the high redispersion of metallic Cu via the re-construction of Cu-Fe spinel as well to as the removal of carbon deposit by burning; the acid property changes over zeolite catalyst were suggested to contribute to the improvement as well.
Keywords: Copper-iron spinel; Steam reforming; Dimethyl ether; Zeolite; Degradation; Regeneration; Heat treatment;