Applied Catalysis A, General (v.371, #1-2)
Acknowledgement to Reviewers (I-VI).
Editorial Board (CO2).
Photocatalytic TiO2/adsorbent nanocomposites prepared via wet chemical impregnation for wastewater treatment: A review by Wei Zhang; Linda Zou; Lianzhou Wang (1-9).
Recent progress on preparation of TiO2/adsorbent nanocomposites (TNC) via wet chemical impregnation has been reviewed. The potential applications of TNC are growing continuously and very likely to find its place in future applications of wastewater treatment. In a TNC preparation via wet chemical impregnation, electronic properties (i.e. amount of charger carrier and its lifetime) and morphological properties (i.e. particle size, surface area and crystal phase) of TiO2 in as-prepared resultants are sensitively dependent on the experimental conditions during the synthesis. Currently, one major limitation in this promising area is that visible-light capacity has yet to be introduced into TNC system. It is envisaged that this could be realized via a single wet chemical procedure without significant increase of the process complexity. A schematic wet chemical assembly of TNC is shown here.Recent progress on preparation of TiO2/adsorbent nanocomposites (TNC) via wet chemical impregnation has been reviewed. The potential applications of TNC are growing continuously and the material is very likely to find its place in future applications of wastewater treatment. In a TNC preparation via wet chemical impregnation, electronic properties (i.e. amount of charger carrier and its lifetime) and morphological properties (i.e. particle size, surface area and crystal phase) of TiO2 in as-prepared resultants are sensitively dependent on the experimental conditions during the synthesis. Currently, one major limitation in this promising area is that visible-light capacity has yet to be introduced into TNC systems. It is envisaged that this could be realized via a single wet chemical procedure without significant increase of the process complexity.
Keywords: Wastewater treatment; TiO2 photocatalysts; Nanocomposite; Adsorbent; Dissolved organic compounds;
Nano TiO2 photo-catalyst and sodium hypophosphite for cross-linking cotton with poly carboxylic acids under UV and high temperature by A. Nazari; M. Montazer; A. Rashidi; M. Yazdanshenas; M. Anary-Abbasinejad (10-16).
Cross-linking of cotton fabrics with 1,2,3,4-butanetetracarboxylic acid (BTCA) and citric acid (CA) are effectively promoted by nano TiO2 and sodium hypophosphite under UV–High temp condition. It was found that dry crease recovery angle (DCRA) values are higher for samples treated under UV–High temp condition than samples treated under UV or High temp condition alone.The present research attempts to accomplish a cross-linking finish on the bleached cotton fabric by using a nano titanium dioxide photo-catalyst which can effectively operate under UV irradiation. In this study, the bleached cotton fabrics were treated with two cross-linking agents including 1,2,3,4-butane tetracarboxylic acid (BTCA) and citric acid (CA) in the presence of sodium hypophosphite (SHP) and nano TiO2 (NTO) and then, cured at three different conditions: UV irradiation (UV), High temperature (High temp) and a combination of UV and high temperature (UV–Temp). In addition, the bending length, yellowness index, wet and dry crease recovery angle, tensile strength retention (%) and water drop absorption time of treated samples were evaluated. Also, treated cotton fabrics and NTO were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) and X-ray Diffraction (XRD). The results show that samples treated with BTCA have higher values of dry crease recovery angle (DCRA) as compared with samples treated with CA. It was also found that DCRA values are higher for samples treated under UV–High temp condition than samples treated under UV or High temp condition alone. Nevertheless, yellowness indexes with BTCA were lower than CA and tensile strengths retention (%) with CA were higher than BTCA.
Keywords: BTCA; CA; Nano TiO2; Cotton fabric; UV irradiation;
Aerobic oxidation of benzylic alcohols with bis(3,5-di-tert-butylsalicylaldimine)copper(II) complexes by Jahir Uddin Ahmad; Pawel J. Figiel; Minna T. Räisänen; Markku Leskelä; Timo Repo (17-21).
A series of bis(3,5-di-tert-butylsalicylaldimine)copper(II) complexes were synthesized and employed in the catalytic oxidation of alcohols using molecular oxygen as a terminal oxidant. These complexes, when combined with TEMPO form a highly efficient catalytic system for the aerobic oxidation of primary benzylic and allylic alcohols under mild reaction conditions. For example at 60 °C and 1 bar of O2 pressure benzyl alcohol is quantitatively converted to benzyl aldehyde in 2 h with low catalyst loading. Attractive features of this catalytic system include the efficient use of molecular oxygen, high selectivity, low loading of both TEMPO (2 mol%) and copper catalyst (0.66 mol%) and mild reaction conditions (atmospheric oxygen and 60 °C temperature). In addition, the crystal structure of the complex was determined by X-ray diffraction analysis. The structure presents the Cu ion in a monomeric distorted square-planar geometry involving the unusual and sterically unfavorable cis-N2O2 coordination sphere.A catalytic procedure for aerobic oxidation of alcohols was developed by utilizing bis(3,5-di-tert-butylsalicylaldimine)copper(II) complexes. The use of molecular oxygen as an ultimate stoichiometric oxidant, low loading of both TEMPO and copper catalyst make the system attractive candidate for sustainable oxidation of benzylic alcohols. Under optimal conditions, various alcohols could be selectively transformed into their corresponding aldehydes in excellent conversions.
Keywords: Aerobic oxidation; Alcohols; TEMPO; Copper(II) complexes; Salicylaldimine;
Catalytic unzipping of carbon nanotubes to few-layer graphene sheets under microwaves irradiation by Izabela Janowska; Ovidiu Ersen; Timo Jacob; Philippe Vennégues; Dominique Bégin; Marc-Jacques Ledoux; Cuong Pham-Huu (22-30).
Catalytic unzipping of single-, double-, and multi-walled carbon nanotubes (SWNTs, DWNTs, and MWNTs) in the presence of Pd nanoparticles and an oxygen-containing liquid medium was performed under microwaves irradiation. In this unzipping process, the palladium particles act as a pair of scissors to cut nanotubes lengthways. This synthesis method makes a link between nanotubes and graphene sheets, yielding a significant amount of graphene.Catalytic unzipping of single-, double-, and multi-walled carbon nanotubes (SWNTs, DWNTs, and MWNTs), in the presence of Pd nanoparticles and an oxygen-containing liquid medium, to yield the few-layer graphene sheets, was performed under microwaves irradiation. In this unzipping process, the palladium particles act as a pair of scissors to cut the nanotube lengthways. Theoretical simulations with Reactive Forcefields confirm that the presence of Pd nanocatalysts and oxygen next to vacancies facilitate the unzipping process to form graphene from nanotube by significantly lowering the corresponding energy barrier. This synthesis method makes a link between nanotubes and graphene sheets, yielding a significant amount of graphene (between 4 and 8 wt.% with respect to the starting carbon material). Compared to previous methods, scaling-up can easily be achieved by increasing the number of synthesis reactors, leading to gram-amounts of graphene.
Keywords: Graphene; Carbon nanotubes; Catalysis; Microwaves; TEM;
Transient kinetic modeling of the oxidative dehydrogenation of propane over a vanadia-based catalyst in the absence of O2 by V. Balcaen; I. Sack; M. Olea; G.B. Marin (31-42).
The oxidative dehydrogenation of propane in the absence of O2 over the vanadia-based EL10V1 Eurocat catalyst is shown to occur through three reaction paths: αα (propane → propene), ββ (propane → CO2) and γγ (propene → CO2), in which four steps are found to be kinetically significant with parameters k 1, k 2, k 4 and k 13. The constructed kinetic model can quantitatively describe the interaction of propane with the catalyst at different reduction degrees and at different temperatures.The oxidative dehydrogenation of propane in the absence of O2 over the vanadia-based EL10V1 Eurocat catalyst is investigated in a Temporal Analysis of Products (TAP) reactor over a completely oxidized catalyst and at reduction degrees up to 0.47. Only CO2 and propene are detected as reaction products at temperatures from 723 to 823 K. The reduction of the catalyst with propane occurs through the formation of propene, the consecutive oxidation of propene to CO2 and the parallel total oxidation of propane. Four elementary reactions are considered as kinetically relevant: (1) the methyl C–H bond dissociation in propane during the formation of propene, (2) the methylene C–H bond breaking in propane to form surface isopropoxide, which finally transforms into CO2, (3) the C＝C double bond breaking in propene in the formation of surface formate species and (4) the oxidation of these surface formate species to CO2. The formation of propene via (1) is favored at the investigated conditions, while CO2 is largely produced by the sequential oxidation of propene (3–4), and to a lesser extent by the parallel route of the direct total oxidation of propane (2). Both the oxidative dehydrogenation and the direct total oxidation of propane reaction paths involve only one kinetically relevant step, (1) respectively (2), with an activation energy of 36 and 74 kJ mol−1 over a completely oxidized catalyst and of 15 and 40 kJ mol−1 over a partially reduced catalyst. The further oxidation of propene involves two kinetically relevant steps (3–4) of which only the double bond breaking (3) is slightly activated (5 kJ mol−1) over the completely oxidized catalyst, while both steps are non-activated when the catalyst is partially reduced.
Keywords: Vanadia-based catalyst; Reduction; Propane; TAP; Kinetic modeling;
Epoxidation catalysts derived from aluminium and gallium dawsonites by Georgiana Stoica; Marta Santiago; Pierre A. Jacobs; Javier Pérez-Ramírez; Paolo P. Pescarmona (43-53).
Aluminium and gallium dawsonites and the materials obtained by their thermal treatment in the range 373–873 K are active transition-metal-free catalysts for epoxidation reactions with hydrogen peroxide.As-synthesised and reconstructed NH4-Al-dawsonite and NH4-Ga-dawsonite, and the materials obtained by thermal treatment in the range 373–873 K, were studied as heterogeneous catalysts for the epoxidation of cyclooctene with hydrogen peroxide at 353 K and ambient pressure by means of High-Throughput Experimentation. The structural, morphological, and textural properties of the materials were investigated by elemental analysis, ICP-OES, XRD, FTIR, TEM, N2 adsorption, and TGA. The temperature at which the dawsonite precursors were treated proved to be crucial in determining the activity of the catalysts. The best catalyst identified in this work was obtained by calcination at 573 K of reconstructed Ga-dawsonite. This material provides an epoxide yield of 51% and 99% selectivity after 4 h at 353 K. Remarkably, many of the catalysts derived from Al-dawsonite displayed an enhanced epoxidation activity upon recycling, reaching up to 30% epoxide yield with 98% selectivity over Al-dawsonite treated at 473 K.
Keywords: Dawsonite; Aluminium; Gallium; Epoxidation; Alkenes; High-Throughput Experimentation;
Ni, Co and bimetallic Ni–Co catalysts for the dry reforming of methane by D. San-José-Alonso; J. Juan-Juan; M.J. Illán-Gómez; M.C. Román-Martínez (54-59).
Alumina supported Ni, Co and bimetallic Ni–Co catalysts (with 9 wt.% nominal metal content) have been prepared, characterized and tested for the dry reforming of methane. For catalysts characterization the following techniques have been used: Atomic Absorption Spectroscopy (ICP-AES), Transmission Electron Microscopy (TEM), Temperature Programmed Reduction (TPR-H2) and Temperature Programmed Oxidation (TPO). The dry reforming of methane was carried out at 973 K using a mixture CH4:CO2 (1:1). Among the catalysts studied, those with the highest cobalt content (Co(9) and NiCo(1–8)) are the most active and stable, but they produce a large amount of carbon. The higher activity exhibited by cobalt rich catalysts is related with the higher activity of this metal for methane decomposition, while their remarkable stability seems to be due to the presence of large particles involved in long-term conversion, because they produce non-deactivating carbon deposits.Alumina supported Ni, Co and bimetallic Ni–Co catalysts (with 9 wt.% nominal metal content) have been prepared, characterized and tested for the dry reforming of methane. For catalysts characterization the following techniques have been used: Atomic Absorption Spectroscopy (ICP-AES), Transmission Electron Microscopy (TEM), Temperature Programmed Reduction (TPR-H2) and Temperature Programmed Oxidation (TPO). The dry reforming of methane was carried out at 973 K using a mixture CH4:CO2 (1:1). Among the catalysts studied, those with the highest cobalt content (Co(9) and NiCo(1–8)) are the most active and stable, but they produce a large amount of carbon. The higher activity exhibited by cobalt rich catalysts is related with the higher activity of this metal for methane decomposition, while their remarkable stability seems to be due to the presence of large particles involved in long-term conversion, because they produce non-deactivating carbon deposits.
Keywords: Methane dry reforming; Ni catalysts; Co catalysts; Ni–Co bimetallic catalysts; Metal particle size; Biogas; Syngas production; Deposited carbon;
Dehydration–hydrogenation of glycerol into 1,2-propanediol at ambient hydrogen pressure by Masaki Akiyama; Satoshi Sato; Ryoji Takahashi; Kanichiro Inui; Masahiro Yokota (60-66).
We developed an efficient catalytic process in which glycerol was converted into 1,2-propanediol with yield higher than 96% over Cu catalyst at gradient temperatures and ambient hydrogen pressure. The developed process controls the equilibrium of the second-step hydrogenation to achieve high selectivity.The vapor-phase reaction of glycerol was performed over copper metal catalysts at ambient hydrogen pressure. Glycerol was converted into 1,2-propanediol (1,2-PDO) through the dehydration into hydroxyacetone, followed by the hydrogenation into 1,2-PDO. The yield of 1,2-PDO was limited up to 80% at a constant temperature of 190 °C because of a trade-off problem between the dehydration and the hydrogenation. The dehydration needs relatively high reaction temperatures, whereas the hydrogenation favors low temperatures and high hydrogen concentration. We developed an efficient process during which glycerol was converted into 1,2-PDO with yield higher than 96% in hydrogen flow at gradient temperatures; the dehydration into hydroxyacetone was catalyzed at ca. 200 °C, and the following hydrogenation into 1,2-PDO was completed at ca. 120 °C. The developed process controls the thermodynamic equilibrium of the second-step hydrogenation.
Keywords: Dehydration; Glycerol; 1,2-Propanediol; Hydroxyacetone; Hydrogenation; Copper;
Preferential oxidation of CO on copper-containing manganese oxides by You-Ichi Hasegawa; Ryo-Uta Maki; Makoto Sano; Takanori Miyake (67-72).
Copper-containing manganese oxides were studied for the preferential CO oxidation in H2-rich stream (1 vol% CO, 1 vol% O2, 60 vol% H2 and balance N2). Preferential and complete conversion of CO was attained at 75 °C with substantially 100% O2 selectivity. Preferential adsorption of CO on the highly reactive site and low H2-oxidation activity of the catalysts contributed to the excellent performance.Copper-containing manganese oxides (Cu/Mn (molar ratio) = 0–1/1) prepared by the sol–gel method were characterized by temperature-programmed desorption of CO (CO-TPD) and of H2 (H2-TPD), temperature-programmed reduction with H2 (H2-TPD), and competitive adsorption of CO and H2. Copper-containing manganese oxides (amorphous structure, mesopores of about 6 nm, and high surface areas of 170–230 m2 g−1) were used for preferential oxidation (PROX) of CO in a large excess of H2. It was observed that copper-containing manganese oxides could preferentially and totally oxidize 1 vol% CO at temperature lower than 100 °C. The reason for high O2 selectivity to CO oxidation was discussed. Preferential adsorption of CO to H2 on the highly active sites and low activity of the manganese oxide-based catalysts to oxidize H2 were the reasons for the favorable performance.
Keywords: Manganese oxide; Copper; Preferential oxidation of CO; PROX; Competitive adsorption;
Supported ruthenium catalysed selective hydrogenation of citral in presence of [NTf2]− based ionic liquids by Jürgen Arras; Dominik Ruppert; Peter Claus (73-77).
The influence of ionic liquids (ILs) based on the bis(trifluoromethanesulfonyl)amide anion ([BMIM][NTf2] and [HMIM][NTf2]) on the alumina supported ruthenium catalysed liquid-phase hydrogenation of citral was investigated applying these ILs as additive. For characterisation ICP-OES, hydrogen pulse chemisorption and nitrogen physisorption were applied, the latter was used after reaction to identify the presence of an ionic liquid layer on the catalyst. The catalytic results show that under the chosen reaction conditions (373 K, 7 MPa H2, 0.3 mol L−1 citral), additives like [NTf2]− based ionic liquids change the intramolecular selectivity (C＝O vs. C＝C hydrogenation) in a way that the desired unsaturated alcohols geraniol and nerol are the main products (S max = 46% at X = 50% compared to only 25% for neat Ru/Al2O3). Concerning the catalyst activity a decrease of the initial turnover frequency (0.048 s−1) in comparison to the IL-free catalyst (0.140 s−1) was observed. The results indicate that in presence of [BMIM][NTf2] and [HMIM][NTf2] the site-time yields towards citronellal were more decreased than for geraniol and nerol enhancing the selectivity of the latter ones.Ionic liquids ([BMIM][NTf2], [HMIM][NTf2]) were used as reaction modifiers in the supported ruthenium catalysed liquid-phase hydrogenation of citral enhancing the selectivity towards the preferred unsaturated alcohols geraniol and nerol. The IL inhibits primarily the C＝C hydrogenation and the decrease of the site-time-yield towards citronellal is more pronounced than for the unsaturated alcohols.
Keywords: Ionic liquid; Additive; Modifiers; Liquid-phase hydrogenation; Citral; α,β-Unsaturated aldehydes; Intramolecular selectivity;
Effect of additive Ag on the physicochemical and catalytic properties of LaMn0.9Co0.1O3.5 perovskite by G. Pecchi; C.M. Campos; M.G. Jiliberto; E.J. Delgado; J.L.G. Fierro (78-84).
The substitution degree of x Ag = 0.1 shows the cleanest surface composition, i.e. almost total insertion of silver in the LaMn0.9Co0.1O3.5. The highest reaction rate found for x Ag = 0.3 is explained considering that almost the same Ag insertion is obtained, but the larger surface of segregated Ag is responsible for the increased activity.Perovskite-type compounds La1−x Ag x Mn0.9Co0.1O3 (x Ag = 0.0, 0.1, 0.2, 0.3) were prepared by the amorphous citrate method, characterized by nitrogen adsorption, XRD, FTIR, SEM-EDAX, TPR, O2-TPD and XPS techniques, and tested in the catalytic removal of n-hexane in a flow reactor under an excess of oxygen. Partial substitution of La3+ by Ag+ was found to produce a large increase in the catalytic activity. Since all the samples exhibit almost the same specific area, the catalyst activity was found to depend mainly on the crystalline structure and on a new source of surface oxygen that comes from the interaction between O– and the low coordinated metal site. For the studied composition, characterization data revealed that the degree of substitution of x Ag = 0.1 shows the cleanest surface composition, i.e. almost total insertion of silver in the LaMn0.9Co0.1O3.5. The highest reaction rate found for x Ag = 0.3 is explained considering that almost the same Ag insertion is obtained, but the larger surface of segregated Ag particles contributes to enhancement in activity.
Keywords: Perovskite catalysts; Silver doped; n-Hexane combustion; Catalyst characterization;
Evidences of the in situ generation of highly active Lewis acid species on Zr-SBA-15 by Maria D. Gracia; Alina M. Balu; Juan M. Campelo; Rafael Luque; Jose M. Marinas; Antonio A. Romero (85-91).
The dramatic increase in activity of reused/treated Zr-SBA-15 in the alkylation of aromatics with benzyl chloride points to the formation of novel highly acidic Lewis Cl x Zr–O–Si species on the catalyst surface. Such materials provided quantitative conversions of starting material in less than 1 h compared to more than 12 h needed for the parent Zr-SBA-15.Zr-SBA-15 materials were synthesized and the activity of the catalysts was investigated in the alkylation of aromatics with benzyl chloride. While Zr-SBA-15 materials needed more than 12 h of reaction to achieve quantitative conversion, an unusually high catalytic activity was observed for reused materials that provided quantitative conversions of starting material in less than 1 h. This dramatic increase in activity observed for reused and/or treated Zr-SBA-15 in the alkylation of aromatics with benzyl chloride points to the formation of novel highly acidic Lewis Cl x Zr–O–Si species on the catalyst surface.
Keywords: Lewis acidity; In situ generation of acid sites; Zr-SBA-15; Alkylation of aromatics; Surface chemistry;
Preparation, characterisation and catalytic performance for soot oxidation of copper-containing ZnAl2O4 spinels by M. Zawadzki; W. Staszak; F.E. López-Suárez; M.J. Illán-Gómez; A. Bueno-López (92-98).
Copper-containing ZnAl2O4 spinel nanoparticles (5–12 nm) have been properly prepared by the glycothermal method and characterised by XRD, HRTEM, SEM-EDAX, N2 adsorption at −196 °C, FT-IR, and H2-TPR. Copper was loaded both within the mixed oxide structure (Zn0.95Cu0.05Al2O4) and impregnated (5%Cu/ZnAl2O4) in the previously prepared support (ZnAl2O4), the impregnated sample being the most active catalyst for soot combustion by NOx/O2.Copper-containing ZnAl2O4 catalysts have been properly prepared by the glycothermal method, with copper loaded within the mixed oxide structure (catalyst Zn0.95Cu0.05Al2O4) or impregnated in the previously prepared support ZnAl2O4 (catalyst 5%Cu/ZnAl2O4). The samples were characterised by XRD, HRTEM, SEM-EDAX, N2 adsorption at −196 °C, FT-IR, and H2-TPR, and the catalytic combustion of soot under NOx/O2 was tested. The mixed oxides, with confirmed spinel structure, consist of nanoparticles with around 5–12 nm. The impregnated catalyst is more active for soot combustion than both the bare support and the substituted catalyst, which is attributed to the proper reducibility of copper that catalyses the NO oxidation to NO2. This catalyst is also highly selective towards CO2 formation as soot combustion product.
Keywords: ZnAl2O4; Zinc aluminate; Spinel; Soot; NOx; Copper catalyst;
Quantitative analysis of infrared spectra of adsorbed species using transmission and diffuse reflectance modes by Julien Couble; Paul Gravejat; François Gaillard; Daniel Bianchi (99-107).
The heats of adsorption of linearly adsorbed CO species on TiO2 and CuO/Al2O3 are determined from the evolutions of their coverages with the adsorption temperature T a in isobar conditions using either diffuse reflectance or transmission FTIR spectra.IR spectroscopy in transmission and in diffuse reflectance modes is used to characterize the adsorbed CO species formed during the adsorption of CO on (a) a TiO2 solid and (b) a partially reduced CuO/Al2O3 solid. The experiments consist studying the evolution of the intensities of the characteristic IR bands with the adsorption temperature T a at a constant adsorption pressure P a. For the two IR analytical procedures, the spectra are used to measure the heats of adsorption of the adsorbed CO species on the two solids according to the AEIR procedure previously described using the IR transmission mode. This allows us to fix the experimental conditions allowing a quantitative analysis of the IR spectra recorded in diffuse reflectance. Mainly, it is shown that the relative reflectance at the position of the characteristic IR bands of the adsorbed CO species must be higher than a critical value during the measurements. According to the amount of adsorbed species, this can be achieved by the dilution of the catalyst with another material that does not contribute to the experimental data. In the present study, it is shown that TiO2 and CuO/Al2O3 can be used without and with dilution respectively. For the Cu/Al2O3 catalyst, the alumina support has been used for the dilution whereas KBr that exhibits acceptable optical properties leads to a significant modification of the heats of adsorption of the adsorbed CO species. This study suggests that heats of adsorption of adsorbed species formed on catalysts of low IR transmission can be determined by the AEIR method using the diffuse reflectance mode. This offers a way to extend the application of quantitative analysis of IR spectra of adsorbed species (i.e. AEIR method) to solid of low IR transmission in particular the industrial catalysts.
Keywords: Quantitative DRIFT; Transmission FTIR; Coverage; Heat of adsorption;
Co/MgO catalysts for hydrogenolysis of glycerol to 1, 2-propanediol by Xiaohui Guo; Yong Li; Ruijuan Shi; Qiying Liu; Ensheng Zhan; Wenjie Shen (108-113).
Enhanced interactions between Co and MgO effectively prevented aggregation of Co particles in the Co/MgO catalyst under the harsh reaction conditions of glycerol hydrogenolysis, showing a much higher activity and stability. Basic Mg(OH)2 particles formed by MgO hydration provided active sites for dehydrogenation of glycerol, while Co particles catalyzed hydrogenation of the reaction intermediates to 1, 2-propanediol.Hydrogenolysis of glycerol to 1, 2-propanediol was investigated on bi-functional Co/MgO catalysts where the interaction between cobalt species and MgO was adjusted by varying the temperature of calcination. Higher temperature treatment not only enhanced the interaction between Co3O4 and MgO, but also promoted the formation of MgCo2O4 spinel and Mg–Co–O solid solution. Although the reducibility of cobalt oxides was greatly decreased in the Co3O4/MgO precursor, this strong interaction prevented the aggregation of Co particles in the resulting Co/MgO catalyst under the harsh reaction conditions, giving a much higher activity and stability. Results revealed that MgO was hydrated to Mg(OH)2 during the course of reaction and that the sizes of Mg(OH)2 and Co particles increased considerably, especially during the initial stage of the reaction.
Keywords: Glycerol; Hydrogenolysis; 1, 2-Propanediol; Co/MgO;
Multiphase catalytic isomerisation of linoleic acid by transition metal complexes in ionic liquids by Crestina S. Consorti; Guilherme L.P. Aydos; Günter Ebeling; Jaïrton Dupont (114-120).
Methyl (ethyl) linoleate and soybean oil were efficiently transformed into their conjugated isomers by RuHCl(CO)(PPh3)3 or RhCl(PPh3)3 dissolved in ionic liquids (ILs). The transesterification side reactions were strongly dependent on the anion of the IL. The use of the Ru and Rh catalyst precursors in combination with ionophilic phosphines decreased metal leaching into the product phase.Methyl (ethyl) linoleate and soybean oil were efficiently transformed into their conjugated isomers (linoleic derivatives) by RuHCl(CO)(PPh3)3 or RhCl(PPh3)3 dissolved in ionic liquids (ILs), namely 1-n-butyl-3-methylimidazolium, N,N-methyl-n-butylpyrrolidinium and tetra-n-butylammonium cations associated with bromide (Br−), hexafluorophosphate (PF6 −) and bis(trifluoromethylsulfonyl)imidate (NTf2 −) anions. For example, methyl linoleate was converted to a mixture of conjugated products (E,Z, Z,Z and E,E linoleic methyl esters) in up to 80% yield when catalyzed by RuHClCO(PPh3)3 in BMI·NTf2 at 80 °C. In the case of RhCl(PPh3)3/SnCl2 associated with BMI·NTf2, complete conversion of methyl or ethyl linoleate was observed after 24 h at 60 °C, with an 85% selectivity for Z,E isomers. However, these reactions were accompanied by extensive transesterification side reactions between the methyl esters or triglycerides. The transesterification side reactions were strongly dependent on the anion of the ionic liquid. For example, extensive ethyl esters were formed in the reaction performed with RhCl(PPh3)3/SnCl2 associated with ethanol in 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imidate IL (65%). Conversely, the reaction performed using the simple salt NBu4·Br in combination with RhCl(PPh3)3/SnCl2 showed the most impressive results, rendering a more active catalytic system (97% of isomerised soybean oil after 24 h at 60 °C) while preventing transesterification. The use of the Ru and Rh catalyst precursors in combination with ionophilic phosphines decreased metal leaching into the product phase.
Keywords: Conjugated linoleic acid; Ionic liquids; Biphasic catalysis; Isomerisation;
Naphthenic acid removal from heavy oils on alkaline earth-metal oxides and ZnO catalysts by Lianhui Ding; Parviz Rahimi; Randall Hawkins; Sooraj Bhatt; Yu Shi (121-130).
Naphthenic acid removal from bitumen-derived HVGO by thermal cracking and catalytic decarboxylation was investigated. With MgO and ZnO, naphthenic acid removal proceeds mainly via catalytic decarboxylation. With CaO, multiple pathways were responsible for naphthenic acid conversion. With BaO, naphthenic acid conversion is mainly through neutralization. All BaO is converted to Ba(OH)2 during the reaction.Naphthenic acid removal from bitumen-derived HVGO by thermal cracking and catalytic decarboxylation was investigated over alkaline earth-metal oxides and ZnO catalysts in a batch reactor and a continuous fixed-bed reactor. The fresh and spent catalysts were characterized by XRD, TG-DTA, CO2-TPD, and SEM. With MgO and ZnO, naphthenic acid removal proceeds mainly via catalytic decarboxylation, and no crystalline phase changes are observed after reaction. With CaO, multiple pathways (catalytic decarboxylation, neutralization, and thermal cracking) were responsible for naphthenic acid conversion. Ca(OH)2 and CaCO3 were identified in the spent catalysts. With BaO, naphthenic acid conversion is mainly through neutralization. All BaO is converted to Ba(OH)2 during the reaction.
Keywords: Naphthenic acids; Catalytic decarboxylation; Catalysts; Removal;
Acidity control of ruthenium pillared clay and its application as a catalyst in hydrogenation reactions by F.C.A. Figueiredo; E. Jordão; R. Landers; W.A. Carvalho (131-141).
Aluminum pillared clay was used as a support for the preparation of catalysts containing ruthenium as active metal. The catalysts were characterized and tested for hydrogenation of dimethyl adipate reactions. The results showed a high conversion, typically above 95%. A barium treatment significantly reduced the Bronsted acidity of these catalysts, thus making more selective systems available.Aluminum pillared clay was used as a support for the preparation of catalysts containing ruthenium as active metal, in the presence or not of a promoter (tin) and an acid reducer (barium). The catalysts were characterized and tested for hydrogenation of dimethyl adipate reactions. The results showed a high conversion, typically above 95%, in all studied systems. This conversion occurs irrespectively of the presence of active metal; therefore, it may be due to the support's intrinsic activity. The acidity was identified as the main cause of this activity. A barium treatment of these catalysts significantly reduced this acidity, thus making more selective the available systems. The catalysts treated with barium reduced the formation of undesirable products up to 45%. Similarly, the presence of tin helped to obtain valuable products such as gamma-caprolactone and methyl caproate, which reached high selectivity values (18.6% and 16.9%, respectively).
Keywords: Pillared clay; Hydrogenation; Ruthenium; Acidity control; Adipate; Lactones;
Pt catalysts supported on β zeolite ion-exchanged with Cr(III) for hydroisomerization of n-heptane by Ping Liu; Xingguang Zhang; Yue Yao; Jun Wang (142-147).
For hydroisomerization of n-heptane, Hβ supported Cr catalyst shows very low conversion (☆) and isomerization selectivity (★). However, when Cr is introduced into Hβ supported Pt catalysts by Cr(III) ion-exchange, remarkable increases in conversion (□) and selectivity to isomerized products (▾) are obtained. The promotion effect of Cr arises from the increased number of strong acid sites, improved Pt dispersion, and enhanced reducibility of Pt.A series of Pt catalysts supported on Hβ zeolite ion-exchanged with Cr(III) were prepared, characterized by ICP, XRD, BET, NH3-TPD, H2-TPR and H2-chemisorption techniques, and evaluated in hydroisomerization of n-heptane with an atmospheric fixed-bed flow reactor. Pt catalyst supported on Hβ zeolite exhibits both lower selectivity to isomerized products and lower conversion of n-heptane than the counterparts supported on Cr(III)-exchanged Hβ zeolite. The optimal composition for Cr-bearing catalysts is 0.4 wt.% of Pt loading and 0.7 wt.% of Cr loading. This catalyst proves to be highly efficient in the hydroisomerization of n-heptane, giving a very high selectivity to isomerized products: 95.4% coupled with a high conversion of n-heptane: 72.1%. The substantial promotion effect of ion-exchanged Cr(III) species is discussed in relation to catalyst physicochemical properties.
Keywords: Hydroisomerization of n-heptane; β Zeolite; Bifunctional catalyst; Pt; Cr;
Cobalt(II) phthalocyanine catalyzed aerobic regeneration of carbonyl compounds from the corresponding oximes in 1-butyl-3-methylimidazolium bromide by Ahmad Shaabani; Elham Farhangi (148-152).
Cobalt(II) phthalocyanine catalyzed aerobic regenerations of aldehydes and ketones from aldoximes and ketoximes has been developed.Metallophthalocyanines (MPcs) catalyzed aerobic regenerations of aldehydes and ketones from aldoximes and ketoximes in various ionic liquids under neutral conditions have been studied. Among the various metallophthalocyanines (MPcs) and ionic liquids (ILs) examined, cobalt(II) phthalocyanine (Co-Pc) exhibited the best performances when used in 1-butyl-3-methylimidazolium bromide ([bmim]Br). Cobalt(II) phthalocyanine and [bmim]Br can be recycled and reused for several runs without any significant loss of catalytic activity.
Keywords: Oximes; Cobalt(II) phthalocyanine; Aerobic oxidation; 1-Butyl-3-methyl imidazolium bromide;
Partial oxidation of methane to syngas over the catalyst derived from double perovskite (La0.5Sr0.5)2FeNiO6−δ by Xiong Yin; Liang Hong (153-160).
The bulk double perovskite oxide containing dispersed SrCO3 micro-phases is an unique precursor of the catalyst, K2NiF4-supported Ni(0) clusters, for partial oxidation of methane (POM). The catalyst, generated from treating the precursor in the feed stream of POM at 850 °C, demonstrates unusually strong coking resistance besides almost quantitative conversion of methane and very high selectivity to syngas.Double perovskite-type oxide (La0.5Sr0.5)2FeNiO6−δ (LSFN) was invented as the precursor of a catalyst for the partial oxidation of methane (POM). The catalyst derived from LSFN is the K2NiF4-supported Ni(0) system, where K2NiF4 denotes the oxide (La0.5Sr0.5)2Ni1−x FeO4+δ , a chemically stable structure with mixed ionic and electronic conducting properties. Among the four catalysts derived from LSFN, the best catalyst showed a high CH4 conversion ( X C H 4 > 99 % ), high syngas selectivity (>98%) and, most importantly, nil coke formation at 900 °C. Detailed structural characterizations revealed that the presence of a small amount of SrCO3, left initially by incomplete formation of LSFN, and of nano-Ni(0) domains (or clusters <5 nm on average) on the K2NiF4 support is vital to this extraordinary catalytic performance. Furthermore, the decrease of H2/CO molar ratio with the increase in methane conversion happening in the course of activation was simulated using a group of the proposed key reaction steps of POM.
Keywords: Methane; Catalytic partial oxidation; Syngas; Double perovskite; Nickel catalyst;
A robust boehmite-supported cobalt tetraphenylporphyrin catalyst for aerobic oxidation of cyclohexane by Guan Huang; Tian-Ming Li; Shang-Yue Liu; Min-Guang Fan; Yue-Xiu Jiang; Yong-An Guo (161-165).
A new boehmite-supported cobalt tetraphenylporphyrin catalyst was used for the aerobic oxidation of cyclohexane. This nano-structured material showed robust stability after 10 consecutive uses for the oxidation with little change of original catalytic activity. On average, the catalyst exhibited 9.2% cyclohexane conversion, 92.1% selectivity for K/A oil and a catalyst turnover number of 1.14 × 105.Using a method of physically adsorbing and chemically coordinating cobalt porphyrin on to boehmite, a new boehmite-supported cobalt tetraphenylporphyrin [CoII TPP/BM] catalyst has been prepared and characterized by UV–Vis, FT-IR, XRD, TEM and TG techniques. The supported catalyst was used for aerobic oxidation of cyclohexane under mild conditions and in the absence of any solvent and additive. The experimental results indicate that, after 10 consecutive uses for the oxidation, a quantity of catalyst containing only 1 mg of cobalt porphyrin, can not only provide, on average, 9.2% cyclohexane conversion, 92.1% selectivity for K/A oil and a catalyst turnover number of 1.14 × 105, but also can maintain continuously the original catalytic activity with promotion by beomite (BM). A proposed reason for the good reusability and stability of the supported catalyst for aerobic oxidation of cyclohexane was that the anchored form of the single cobalt porphyrin molecules were highly dispersed and immobilized on the boehmite.
Keywords: Boehmite; Cobalt tetraphenylporphyrin; Cyclohexane oxidation; Air;
Ruthenium (II) phosphine/mesoporous silica catalysts: The impact of active phase loading and active site density on catalytic activity in hydrogenation of phenylacetylene by Dorota Duraczynska; Ewa M. Serwicka; Alicja Drelinkiewicz; Zbigniew Olejniczak (166-172).
All HMS supported catalysts proved active and selective in phenylacetylene semihydrogenation under mild conditions (temperature 40 °C and H2 pressure of 1 atm). The optimum catalytic performance requires high number of active sites within the catalytically active zone near the pore entrance, simultaneously avoiding blockage of the pore system and loss of the site isolation effect.Ruthenium (II) supported catalysts containing various amounts of [(η5-MeC5H4)Ru(η3-PPh2CHCH2)(η1-PPh2CHCH2)]+ deposited on aluminated mesoporous silica of HMS type (Si/Al = 20 or 40) were synthesized by ion exchange method. The solids were characterized by XRD, 27Al MAS NMR, FTIR and UV–vis spectroscopies. The textural properties were determined from nitrogen adsorption at 77 K. Textural analysis showed that increased loading of ruthenium complex onto support with high density of exchange sites (high Al content) eventually leads to overcrowding of active species in pore sections close to the pore mouth and hinders access to sites located deeper within the pore network. All HMS supported catalysts proved active and selective in phenylacetylene semihydrogenation under mild conditions (temperature 40 °C and H2 pressure of 1 atm), their performance showing a complex pattern depending on the catalyst loading with the active phase and the degree of support alumination. Results indicate that the optimum catalytic performance requires high number of active sites within the catalytically active zone near the pore entrance, simultaneously avoiding blockage of the pore system and loss of the site isolation effect (controlled by Si/Al ratio and active phase content). Best heterogenized catalysts are more active than unsupported ruthenium complex in the homogeneous system. The supported catalysts are stable under reaction conditions and can be easily recovered and reused, without any loss of catalytic activity and selectivity.
Keywords: Cationic hemilabile ruthenium (II) complex; Site density; Mesoporous silica; HMS; Hydrogenation of phenylacetylene; Immobilization; Ion exchange method;
Hydrogen production by autothermal reforming of kerosene over MgAlO x -supported Rh catalysts by Makoto Harada; Kazuhiro Takanabe; Jun Kubota; Kazunari Domen; Takashi Goto; Kazuya Akiyama; Yasunobu Inoue (173-178).
Autothermal reforming (ATR) of kerosene for hydrogen production was performed on the MgAlO x -supported Rh catalysts. Sphere-shaped supports with high compressive ultimate strength (0.90 MPa) were obtained from MG-30 hydrotalcite core (∼3 mm) by thorough heat treatment before impregnation of rhodium. The catalyst showed high tolerance to coking and high stability even at LHSV of 25 and daily start-up and shut-down (DSS) cycles, meeting practical requirements for the ATR catalysts.Autothermal reforming (ATR) of kerosene for hydrogen production was performed on the MgAlO x -supported Rh catalysts at LHSV of 15–25, S/C of 2.5, O/C of 0.5, at 101 kPa. Sphere-shaped supports with high compressive ultimate strength (0.90 MPa) were obtained from MG-30 hydrotalcite core (∼3 mm) by thorough heat treatment before impregnation of rhodium. Rhodium was loaded by pore-filling impregnation selectively to the surface of the sphere-shaped supports, confirmed by electron probe microanalysis. Stability tests on the prepared catalysts were performed, focusing on the small amount of C2–C3 hydrocarbons, concentrations of which reflect the catalytic activity and stability; i.e., low rates of C2–C3 olefin formation correspond to high activity of the catalysts. The reactor was designed to measure temperature profiles and gas distributions within the reactor (inner diameter ∼21.0 mm) and the catalyst bed (length 100 mm). The ATR reactions occur starting with an exothermic combustion of hydrocarbons, followed by an endothermic reforming. The maximum temperature reached ∼1200 K at the inlet of the catalyst bed and decreased to ∼1020 K towards the end of the catalyst bed. Among investigated catalysts, the catalysts treated in air at 1223 K gave the best performance for ATR of kerosene, giving H2 production reaching 60% of the exit gas. The concentration of the main byproduct, C2H4, over the optimized catalyst was lower than 0.03% at the exit of the reactor for 50 h of the study. The catalyst showed high tolerance to coking and high stability even at LHSV of 25 and daily start-up and shut-down (DSS) cycles, meeting practical requirements for the ATR catalysts.
Keywords: Kerosene; Autothermal reforming; Hydrogen; Rh catalyst; Hydrotalcite;
Effect of oxygen and nitrogen concentration of nitrogen doped TiOx film as photocatalyst prepared by reactive sputtering by Seon-Hong Lee; Eiji Yamasue; Hideyuki Okumura; Keiichi N. Ishihara (179-190).
The N-doping configuration in TiO2 is significantly affected by the oxygen concentration in sputtering, and the visible light photocatalysis of N-doped TiOx film requires the permissible range of oxygen and nitrogen concentrations in sputtering. The best range of the oxygen and nitrogen ratio in sputtering for the N-doped TiOx film as photocatalyst could be found. The interstitial N (NOx) doping states with the oxygen deficiency are more effective for photocatalysis than the substitutional N-doping states with the oxygen deficiency.The N-doped TiOx films were prepared by radio-frequency (RF) magnetron reactive sputtering of Ti target in a mixed gas of Ar, O2 and N2. The effects of varying oxygen and nitrogen flow ratios on the physical properties and photocatalytic properties with defect formation energies using DFT calculations were investigated, and the photocatalytic ability was evaluated by decomposition of NO gas. The photocatalytic properties as well as other film properties such as lattice parameters, grain sizes, surface atomic contents, surface doping configurations, and optical properties strongly depend on the gas flow ratios. The N-doping configuration in TiO2 is significantly affected by the oxygen concentration in sputtering, based on the XPS and the defect formation energy results. Also, the visible light photocatalysis of N-doped TiOx film requires a certain range of oxygen and nitrogen concentrations in the sputtering process. The substitutional N-doped TiO2 has weak photocatalysis compared with the interstitial N (or NOx)-doped TiO2, suggesting that the interstitial N (NOx)-doping states with the oxygen deficiency are more effective for photocatalysis than the substitutional N-doping states with the oxygen deficiency, probably due to the variation in the number and location of the impurity levels (active recombination sites) in the energy band gap.
Keywords: Photocatalyst; Nitrogen-doping; Oxygen deficiency; Titanium dioxide; Nitric oxidation decomposition;
K y Mg1−x Zn1+x O3 as a heterogeneous catalyst in the transesterification of palm oil to fatty acid methyl esters by M.A. Olutoye; B.H. Hameed (191-198).
An active heterogeneous catalyst has been developed. The catalytic efficiency was studied with the transesterification of palm oil into fatty acid methyl esters. Thermal treatment of the catalyst at 461 °C for 4 h was carried out. The results showed that a synergetic effect of active components was responsible for its high activity.An active heterogeneous catalyst of the type K y Mg1−x Zn1+x O3 that separates easily from an ester product mixture has been developed. The catalytic efficiency was studied with the transesterification of palm oil into fatty acid methyl esters. The catalyst was thermally treated at 461 °C for 4 h. A typical K2Mg0.34Zn1.66O3 oxide was characterized with powder X-ray diffraction and infrared Fourier transform, and its microstructure was studied by the use of scanning electron microscopy. The properties studied provided insight into the catalytic performance of the catalyst. The optimum conditions were obtained by varying parameters such as methanol to oil ratio, catalyst loading, temperature and time. The highest ester conversion of 87% was achieved under atmospheric pressure in 5 h at 188 °C using 64 g of refined palm oil, 38 g of methanol and 2.3 wt% catalyst dosage. The results showed that a synergetic effect of active components was responsible for its high activity.
Keywords: Methyl esters; KMgZnO oxide; Palm oil; Catalyst; Transesterification;
Reaction of thiophene with mono- and bimetallic Ni–Co particles supported on γ-Al2O3 and HDS activities of obtained sulfides by Igor Bezverkhyy; Sophie Schneefeld; Jonathan Skrzypski; Jean-Pierre Bellat (199-204).
It is found that the rate of reaction of reduced Ni/Al2O3 with thiophene is higher by a factor of 40 than that of Co/Al2O3. The reason of this difference is shown to be a lower rate of thiophene decomposition on metallic Co. In contrast, after sulfidation the activity in thiophene HDS is better for supported Co sulfide.Reaction between thiophene and M/γ-Al2O3 (20 wt.%, M = Ni, Co, 2Ni–Co and 2Co–Ni) was studied by thermal gravimetric analysis (TGA) and by sulfidation in a fixed bed microreactor. The samples were prepared by incipient wetness impregnation followed by drying and reduction in hydrogen flow at 450 °C. Formation of bimetallic particles in samples containing both Ni and Co was confirmed by HRTEM with EDX analysis. The reaction with thiophene (20 or 40 mbar) was done at 360 °C in hydrogen atmosphere. TGA of the reaction with thiophene revealed that the initial rate of sulfidation drops sharply when going from Ni/γ-Al2O3 to Co/γ-Al2O3 (by a factor of 40 under used conditions). It follows from the sulfidation in a fixed bed reactor that this difference can be attributed to a poor catalytic activity of metallic Co in thiophene hydrodesulfurization (HDS) and consequently much lower amount of produced H2S in comparison with Ni. Upon sulfidation the HDS activity of Ni-rich particles progressively decreases, while, surprisingly, that of Co-rich particles is enhanced so that after a complete sulfidation (confirmed by XRD and sulfur analysis) the catalytic activity of the obtained sulfides in thiophene HDS increases in the order: 2Ni–Co < Ni < 2Co–Ni < Co.
Keywords: Thiophene reactive adsorption; Thiophene hydrodesulfurization; Ni–Co mixed particles; Supported Ni; Supported Co;