Applied Catalysis A, General (v.365, #1)
Editorial Board (CO2).
Polymer supports for low-temperature fuel cell catalysts by E. Antolini; E.R. Gonzalez (1-19).
Due their high accessible surface area, low resistance and high stability, conducting polymers have been investigated as carbon-substitute supports for fuel cell catalysts. This paper provides a review of the state-of-the-art in the development of metal/polymer composites as electrode materials for low-temperature fuel cells.Display OmittedThe dependence of the peak current density on the thickness of PPy film for the oxidation peaks (a) at about 0.62 V in the positive-going sweep and (b) at about 0.43 V in the negative-going sweep in the CV of methanol at the Pt/PPy/GC electrode.Due to their high accessible surface area, low resistance and high stability, conducting polymers have been investigated as carbon-substitute supports for fuel cell catalysts. The main reason for incorporating metallic particles into porous polymeric matrixes is to increase the specific area of these materials and thereby improve the catalytic efficiency. Polymer-supported metal particles also present higher tolerance to poisoning due to the adsorption of CO species, in comparison to the serious problem of poisoning of bulk and carbon-supported metals. Moreover, conducting polymers are not only electron conducting, but also proton conducting materials, so they can replace Nafion in the catalyst layer of fuel cell electrodes and provide enhanced performance. This paper provides a review of the state-of-the-art in the development of metal/polymer composites as electrode materials for low-temperature fuel cells.
Keywords: Supported catalysts; Nanostructures; Metals; Polymers; Fuel cells;
Composition optimization of silica-supported copper (II) chloride substance for phosgene production by Tianzhu Zhang; Carsten Troll; Bernhard Rieger; Juergen Kintrup; Oliver F.-K. Schlüter; Rainer Weber (20-27).
The composition of silica-supported copper (II) chloride substances for the oxychlorination of carbon monoxide to phosgene was optimized systematically here. When the molar ratio of Cu:K = 5:1 and the surface area of SiO2 is 25 m2 g−1, the substance 30Cu:6K/SiO2-1 can be used eight times, and the cumulative yield of phosgene is up to 89.6%.In this work, we checked the influences of the silica-supported copper (II) chloride substance composition on the oxychlorination of CO to phosgene. The effects of the content of copper (II) chloride, the ratio of copper to potassium, the different kinds of promoters, like sodium chloride, potassium chloride and caesium chloride, and the surface area of silica gel were systematically investigated. The lower surface area of the support can contribute to the formation of phosgene while the higher surface area of the support can lead to a rather low yield of phosgene. The reaction activity of silica-supported copper (II) chloride substance increases with the content of copper chloride (within 30 wt.%). However, in order to avoid the agglomeration of the substance, the content of copper chloride should be less than 30 wt.%. The optimized molar ratio of CuCl2 to KCl is 5:1. Of all three promoters, NaCl, KCl and CsCl, CsCl or KCl can function better than NaCl due to the stronger Lewis basicity. The molten phase can remarkably improve the contact of CuCl2 and CO. On the whole, the lower-surface-area support, the higher content of CuCl2 and the promoter CsCl or KCl are prefered in the oxychlorination of CO.
Keywords: Oxychlorination; IR; Carbon monoxide; Phosgene; Hydrogen chloride; Silica gel;
Esterification of free fatty acids for biodiesel production over heteropoly tungstate supported on niobia catalysts by K. Srilatha; N. Lingaiah; B.L.A. Prabhavathi Devi; R.B.N. Prasad; S. Venkateswar; P.S. Sai Prasad (28-33).
Esterification of free fatty acids of sunflower oil was efficiently carried out over niobia supported heteropoly tungstate under mild conditions. The activity of the catalyst depends on the amount of tungstate and on the calcination temperature of the catalyst. The esterification activity of the catalysts is correlated with the characteristics of the catalysts. The catalyst is easily recyclable and exhibited consistent activity upon reuse.A series of catalysts containing 5–30 wt% of 12-tungstophosphoric acid (TPA) supported on niobia were prepared and their catalytic activity was evaluated for esterification of free fatty acids with methanol. The catalysts were characterized by FT-infrared spectroscopy, X-ray diffraction and temperature programmed desorption of ammonia. The esterification activity depends on the content of TPA on niobia; the catalyst with 25 wt% of TPA exhibited highest activity. The best catalyst was subjected to different calcination temperatures to study the structural changes. We observed that esterification activity depends upon the structural variations of the catalyst. The effects of reaction variables such as catalyst loading, methanol to acid ratio, reaction time and temperature on the conversion of fatty acid were studied. The esterification activity of the catalysts is correlated with the characteristics of the catalysts.
Keywords: Esterification; Sunflower oil free fatty acids; Palmitic acid; Methanol; Tungstophosphoric acid; Niobia;
Conversion of methane to aromatics over Mo2C/ZSM-5 catalyst in different reactor types by Bruce Cook; Dimitri Mousko; Wolfgang Hoelderich; Roberto Zennaro (34-41).
Dehydroaromatization of methane is an interesting field with a lot of investigations performed during recent years. In the present work Mo2C/ZSM-5 was investigated for methane dehydroaromatization (MDA) activity in fixed and fluidized bed reactors. Better yields can be achieved in the fluidized bed reactor compared to the fixed bed reactor, but a long-term deactivation of the catalyst occurs more quickly. Mechanical stability of the catalyst was not high enough to be applied in the fluidized bed for a long time period. The influence of VHSV (volume hourly space velocity) as well as the effect of different temperatures was investigated in the fixed bed reactor. The addition of CO2 as a co-feed gas in fixed and fluidized bed reactors was studied, too. Detrimental effect of carbon dioxide on MDA reaction was detected.The catalyst on the basis of Mo/ZSM-5 was investigated for its methane dehydroaromatization activity in fixed and fluidized bed reactors. A comparison of catalyst behavior in fluidized and fixed bed reactor is given. The VHSV effect, as well as the effect of different temperatures was studied in fixed bed reactor. The addition of CO2 as a co-feed gas in fixed and fluidized bed reactors was investigated.
Keywords: MDA; Methane; Aromatics; Dehydroaromatization; Fluidized bed; Mo2C–ZSM-5;
In situ Fourier transform infrared spectroscopic studies of limonene epoxidation over PW-Amberlite by Rolando Barrera Zapata; Aída Luz Villa; Consuelo Montes de Correa; Christopher T. Williams (42-47).
In situ attenuated total reflection infrared spectroscopy (ATR-IR) in the liquid phase and in situ transmission IR spectroscopy in the gas phase were used to validate a previously proposed mechanism for limonene epoxidation with aqueous hydrogen peroxide over PW-Amberlite. Catalyst activation by the oxidant and the presence of reaction intermediates was evidenced by ATR-IR. Acetonitrile and limonene adsorption was determined by gas phase experiments. In situ attenuated total reflection infrared spectroscopy (ATR-IR) in the liquid phase and in situ transmission IR spectroscopy in the gas phase were used to validate a previously proposed mechanism for limonene epoxidation with aqueous hydrogen peroxide on PW-Amberlite. Catalyst activation by the oxidant was evidenced by ATR-IR through the presence of multiple bands in the 1220–910 cm−1 range, which are attributed to metal-oxygen interactions on the catalytic surface. The presence of reaction intermediates is linked to bands in the 840–820 cm−1 region. Gas phase experiments indicate that acetonitrile is easily adsorbed and desorbed from the catalyst, while limonene is adsorbed on the solvent or oxidant saturated PW-Amberlite and not on the fresh catalyst, as proposed in the mechanistic pathway.
Keywords: In situ IR; ATR infrared spectroscopy; Limonene epoxidation; PW-Amberlite;
The influence of metal loading and activation on mesoporous materials supported nickel phosphide hydrotreating catalysts by Tamás I. Korányi; Alessandro E. Coumans; Emiel J.M. Hensen; Ryong Ryoo; Hei Seung Kim; Éva Pfeifer; Zsolt Kasztovszky (48-54).
Pseudo first-order reaction rate constants related to unit catalyst mass for hydrodesulfurization (HDS) of dibenzothiophene (DBT) (left) and hydrodenitrogenation (HDN) of o-methylaniline (OMA) (right) as a function of time-on-stream over commercial CoMo/Al2O3 (a), 20 wt.% nickel phosphide (NiP) containing reference SiO2- (b), mesoporous MFI- (c), SBA-15- (d), KIT-6- (e), and 30 wt.% NiP containing SBA-15- (f) and KIT-6- (g) supported catalysts during simultaneous HDS of DBT and HDN of OMA at 613 K and 30 bar.Ordered mesoporous materials (SBA-15 and KIT-6 silica and MFI zeolite) supported nickel phosphide (Ni x P y ) hydrotreating catalysts were prepared by reduction of oxidic precursors with an initial stoichiometric Ni/P ratio of 2 The metal loading (20 and 30 wt.% Ni x P y ) and pretreatment conditions (773 K or 873 K reduction temperature, in situ sulfidation at 723 K) of the precursors were varied. Temperature programmed reduction, in situ XRD, and 31P NMR indicate the formation of metallic nickel then different nickel phosphides (Ni3P, Ni12P5, then Ni2P) in this order upon reduction. The changes in the textural properties of the catalysts compared to their parent supports promote the conclusion that a significant part of the Ni x P y phases is located inside the mesopores. The catalytic activity (parallel dibenzothiophene hydrodesulfurization and o-methyl aniline hydrodenitrogenation) increases strongly with increasing Ni x P y loading. The KIT-6 and SBA-15 supported catalysts exhibit higher hydrotreating activities than reference CoMo/Al2O3 and Ni12P5/SiO2 catalysts. In contrast, the catalyst based on a mesoporous MFI support had the lowest hydrotreating activity. This activity trend is explained by the propensity of high-surface area mesoporous silica supports to well disperse metal phosphide particles. The active phase composition of the spent catalysts is in the range of Ni2.0–2.6P1.0S0.4–0.7. This suggests that bulk Ni2P with some sulfur in its surface forms the active phase in the mesopores of SBA-15 and KIT-6.
Keywords: Nickel phosphide; SBA-15; KIT-6; Mesoporous MFI; Hydrodesulfurization; Dibenzothiophene; Hydrodenitrogenation; o-Methyl aniline;
Redox property of tungstated-zirconia analyzed by time resolved in situ UV–vis spectroscopy by Qiang Lin; Ken-ichi Shimizu; Atsushi Satsuma (55-61).
Kinetic analysis of surface W species on tungstated-zirconia has been carried out using time resolved in situ UV–vis spectroscopy to clarify the reduction–oxidation process of surface W, which is the origin of protonic acid on tungstated-zirconia. The rate of reduction (k R) gradually increased with WO3-loading, while the rate of re-oxidation (k O) showed the maximum value at the theoretical monolayer coverage. The very small amount of Pt(0.02 wt.%)-loading drastically improved both the reduction and re-oxidation rates.Kinetic analysis of surface W species on a series of tungstated-zirconia catalysts has been carried out using time resolved in situ UV–vis spectroscopy. The effects of WO3- and Pt-loading on the reduction–oxidation process between surface W6+ and W(6−δ)+ species, which is correlated to the solid acid properties of tungstated-zirconia, are discussed. The rate of reduction of surface W6+ in 0.5% H2/He gradually increased with WO3-loading. The rate of re-oxidation process in pure He increased with WO3-loading and showed the maximum value at the theoretical monolayer coverage at around 25 wt.% of WO3; however, that value was decreased by the further addition of WO3. Based on Raman and UV–vis spectroscopy results, the increase in the redox rates was correlated to the growth of polytungstate domain size, and the lower re-oxidation rate at higher WO3-loading was related to the formation of crystalline WO3. The very small amount of Pt(0.02 wt.%)-loading drastically improved both the reduction and re-oxidation rates, and the activation energy significantly decreased from 43 to 9 kJ mol−1 for the reduction process, and from 62 to 11 kJ mol−1 for the re-oxidation. Further Pt-loading induced a deleterious effect on the rate and degree of reduction.
Keywords: Tungstated-zirconia; Solid acid; UV–vis; Kinetics analysis;
Density functional theory study on water–gas-shift reaction over molybdenum disulfide by Xue-Rong Shi; Sheng-Guang Wang; Jia Hu; Hui Wang; Yan-Yan Chen; Zhangfeng Qin; Jianguo Wang (62-70).
Density functional theory calculations have been carried out to investigate the adsorption of reaction intermediates appearing during water–gas-shift reaction at the sulfur covered MoS2 (1 0 0) surfaces, Mo-termination with 37.5% S coverage and S-termination with 50% S coverage using periodic slabs. The pathway for water–gas-shift reaction on both terminations has been carefully studied where the most favorable reaction path precedes the redox mechanism, namely the reaction takes place as follows: CO + H2O → CO + OH + H → CO + O + 2H → CO2 + H2. The most likely reaction candidates for the formate species HCOO formation is the surface CO2 reaction with H as a side reaction of CO2 desorption on S-termination with 50% S coverage. The formed HCOO species will react further with adsorbed hydrogen yielding H2COO followed by breaking its C–O bond to form the surface CH2O and O species.Density functional theory calculations have been employed to investigate the water–gas-shift reaction mechanisms at sulfur covered MoS2 (1 0 0) surfaces using periodic slabs. The most favorable reaction path on both terminations precedes the redox mechanism, namely the reaction takes place as follows: CO + H2O → CO + OH + H → CO + O + 2H → CO2 + H2.
Keywords: Water–gas-shift reaction; Molybdenum disulfide; DFT studies;
Catalytic performance enhancement by heat treatment of CuFe2O4 spinel and γ-alumina composite catalysts for steam reforming of dimethyl ether by N. Shimoda; K. Faungnawakij; R. Kikuchi; T. Fukunaga; K. Eguchi (71-78).
The influence of heat treatment on catalytic activity and durability for steam reforming of dimethyl ether (DME SR) over the composite catalysts of CuFe2O4 spinel and γ-Al2O3 was investigated. The heat treatment in air after mixing of CuFe2O4 and Al2O3 improved the activity and durability of the composite catalysts for DME SR. The treatment temperature range of 700–800 °C is most effective to enhance the catalytic performance. According to XRD and TPR analyses, the new phase of Cu–Fe–AlO4 was produced by solid-state reaction at the interface between CuFe2O4 and Al2O3 after heat treatment, leading to high catalytic performance. This new active phase also formed over the composites of pre-reduced CuFe2O4 and Al2O3, due to the re-construction of Cu–Fe spinel by the heat treatment.The heat treatment at 700–800 °C after mixing of CuFe2O4 and Al2O3 improved the activity of the composite catalysts for steam reforming of dimethyl ether. The new phase of Cu–Fe–AlO4 was produced by a solid-state reaction, leading to high catalytic performance. This phase was also formed over the pre-reduced composites by heat treatment, due to the re-construction of Cu–Fe spinel.
Keywords: Copper–iron spinel; Steam reforming; Dimethyl ether; Heat treatment; Alumina;
Performance of Pd-promoted Mo–V–Te–Nb–O catalysts in the partial oxidation of propane to acrylic acid by Sang Seop Kum; Bu Young Jo; Sang Heup Moon (79-87).
The activity of Pd-promoted Mo1.0V0.3Te0.23Nb0.23O x catalysts for the partial oxidation of propane was increased due to an increase in the number of sites for the adsorption of propane and for the oxidative dehydrogenation of propane to propylene. The selectivity for acrylic acid production was increased due to the enhancement of the oxidative dehydrogenation step (RDS) and the suppression of the side-reaction steps.The performance of a Mo1.0V0.3Te0.23Nb0.23O x catalyst in the partial oxidation of propane to obtain acrylic acid (AA) was improved when the catalyst was modified with an optimal amount of Pd oxide. The activity was increased due to an increase in the number of sites for the adsorption of propane and for the conversion of the adsorbed propane to propylene via oxidative dehydrogenation, which is the rate-determining step (RDS) in the process. An increase in the number of acidic sites was also responsible for the activity improvement. The selectivity for AA production was increased due to the enhancement of the RDS, accompanied by the suppression of the side-reaction steps. Added Pd oxide reduced the amount of propane, which was strongly adsorbed on the catalyst, such that propane was rapidly desorbed from the surface without being over-oxidized to CO x . The suppression of AA oxidation also contributed to the improved selectivity. Both activity and selectivity of the catalyst were eventually lowered when the Pd content was greater than 10−2 wt% because the catalyst surface was covered with an excess amount of Pd oxide.
Keywords: Propane; Oxidation; Acrylic acid; Pd oxide; Oxidative dehydrogenation;
Functionalization of organic ions on hybrid MCM-41 for cycloaddition reaction: The effective conversion of carbon dioxide by Seshachalam Udayakumar; Mi-Kyung Lee; Hye-Lim Shim; Dae-Won Park (88-95).
The surface activity of MS41 was modified through consecutive immobilization of imidazole, followed by alkylation with an alkyl halide, resulting in the imidazole substituent-immobilized MS41 (RIm+X−-MS41 or IIL). A wide variety of CP-MS41 and RIm+X−-MS41 were synthesized and characterized by various physico-chemical techniques.Activation of chloropropyl MCM-41 (CP-MS41) and its utilization in the synthesis of allyl glycidyl carbonate over functionalized mesoporous MS41 solids has been investigated. The surface activity of MS41 was modified through consecutive immobilization of imidazole, followed by alkylation with an alkyl halide, resulting in the imidazole substituent-immobilized MS41 (RIm+X−-MS41 or IIL). A wide variety of CP-MS41 and RIm+X−-MS41 were synthesized and characterized using XRD, BET, elemental analysis (EA), SEM, CP13C, 29Si MAS-NMR, and FT-IR. EA and FT-IR confirmed adduct formation of ionic liquids with the chloropropyl groups on the host system. The efficiency of immobilization of activated materials was investigated by FT-IR and EA. RIm+X−-MS41 reacted further with oxiranes adsorbed on solid ions, forming cyclic carbonates. The IIL with a lower alkyl chain length and high electron-donating tendencies showed a higher level of reusability and superior activity. The CP-MS41 functionalized with isopropyl imidazolium bromide (iso-PImBr-MS41) exhibited the highest turnover number (TON) and turnover frequency (TOF).
Keywords: CO2 utilization; Ionic liquid functionalization; Eco-friendly processes; Hybrid MS41;
Oxidation of alkanes and olefins with hydrogen peroxide in acetonitrile solution catalyzed by a mesoporous titanium-silicate Ti-MMM-2 by Anderson J. Bonon; Dalmo Mandelli; Oxana A. Kholdeeva; Marina V. Barmatova; Yuriy N. Kozlov; Georgiy B. Shul’pin (96-104).
Oxidation of alkanes (cyclooctane, n-heptane, n-octane, isooctane, methylcyclohexane, cis- and trans-1,2-dimethylcyclohexane) to alkyl hydroperoxides and olefins [cyclooctene, 1-decene, (S)-limonene] mainly to epoxides and diols with H2O2 in acetonitrile catalyzed by mesoporous titanium-silicate Ti-MMM-2 is described. The reaction of (S)-limonene affords one isomer (SRR) of diepoxide as the main product. This fact indicates that the epoxidation of the two double bonds occurs simultaneously on two adjacent ‘Ti–O–OH’ centers on the catalyst surface.Mesoporous titanium-silicate Ti-MMM-2 catalyzes oxidation of alkanes (cyclooctane, n-heptane, n-octane, isooctane, methylcyclohexane, cis- and trans-1,2-dimethylcyclohexane) and olefins (cyclooctene, 1-decene, (S)-limonene) by H2O2 in acetonitrile solution at 60 °C. The catalytic reaction is truly heterogeneous in nature. The oxidation occurs via the formation of a ‘Ti–OOH’ species on the catalyst surface which either epoxidizes a nucleophilic double bond or generates, after O–O bond splitting, hydroxyl radical. The HO• radical attacks an alkane or olefin C–H bond producing alkyl radical. The reaction R• + O2 → ROO• leads to the formation of alkyl hydroperoxide as the main product of the alkane oxidation. In the case of alkenes this reaction leads to allylic oxidation products. The composition of products of the olefin oxygenation (the epoxide/alkyl hydroperoxide or epoxide/diol ratios, etc.) strongly depends on the nature of the substrate. In the oxidation of (S)-limonene, isomeric diepoxides are formed along with monoepoxides even at the early stage of the reaction and (SRR)-diepoxide predominates among other products. This can be rationalized by suggesting the epoxidation of the two double bonds to occur simultaneously on two adjacent ‘Ti–O–OH’ centers on the catalyst surface.
Keywords: Alkanes; Alkyl hydroperoxides; Epoxidation; Heterogeneous catalysis; Limonene; Mesoporous materials; Terpenes; Titanium-silicates;
Transesterification of soybean oil in the presence of diverse alcoholysis agents and Sn(IV) organometallic complexes as catalysts, employing two different types of reactors by Daniel R. de Mendonça; Jhosianna P.V. da Silva; Rusiene M. de Almeida; Carlos R. Wolf; Mario R. Meneghetti; Simoni M.P. Meneghetti (105-109).
A study on alcoholysis of soybean oil in the presence of Sn(IV) complexes was carried out. The results point out that the use of the closed steel reactor is advantageous, since higher yields are obtained in shorter reaction times. Several alcohols have been used as alcoholysis agents and using only a slight excess of alcohol, high yields of reaction were obtained.A systematic study on alcoholysis of soybean oil in the presence of Sn(IV) complexes, to produce fatty acid alkyl esters, was carried out under different reaction conditions. Firstly, two different types of reactors have been employed and compared: an open glass reactor, equipped with a reflux condenser, and a closed steel reactor. Results point out that the use of the closed steel reactor is advantageous, since higher yields are obtained in shorter reaction times. In the sequence, five alcohols have been used as alcoholysis agents (methanol, ethanol, n-butanol, iso-propanol, and iso-butanol) in the presence of dibutyl tin dilaurate as catalyst. Under these conditions and using only a slight excess of alcohol, high yields of fatty acid alkyl esters were obtained.
Keywords: Biodiesel; Tin(IV) complexes; Transesterification; Alcoholysis;
Avoiding segregation during the loading of a catalyst–inert powder mixture in a packed micro-bed by Daniël van Herk; Pedro Castaño; Massimiliano Quaglia; Michiel T. Kreutzer; Michiel Makkee; Jacob A. Moulijn (110-121).
This paper describes for each handling step how to minimise segregation during the loading of a catalyst–diluent powder mixture in a microreactor. Segregation is observed in a glass mock-up reactor. The term ρ p d p 2 is shown to sufficiently predict segregation due to the velocity difference during gravity flow. Optimising all the handling steps to minimise segregation result in a visually homogeneous bed.The optimal loading protocol of a microreactor (catalyst and inert: 0.1 mm, column: 2 mm internal diameter) with a catalyst–inert mixture is fundamentally different from that of a conventional lab-scale reactor (typical values: catalyst, 2 mm; inert, 0.2 mm; column, 10 mm internal diameter). This is shown to be due to segregation, occurring during loading. The following loading procedure has been used: premix the powders, funnel the mixture down, drop it within the reactor, and densify the bed. The average time a particle takes, from the mixing vial to reach its final position, depends on its properties, which in general results in an axially segregated bed. Radial segregation is observed for particles smaller than 60 μ m, as a result of electrostatic forces.This paper describes for each handling step how to minimise segregation during the loading of a catalyst–diluent solid mixture. This includes using a funnel with a low-friction and steep wall, minimising difference in velocity of particle-gravity flow, and adding more inert after the mixture, prior to the densification step. The term ρ p d p 2 is shown to sufficiently predict segregation due to the velocity difference during gravity flow. Segregation can be observed relatively easily in a glass mock-up reactor. Optimising all the handling steps to minimise segregation results in a visually homogeneous bed.
Keywords: Gravity flow; Catalyst loading; Microreactor loading;
Doped Ni Thin Layer Catalysts for Catalytic Decomposition of Natural Gas to produce hydrogen by G. Italiano; C. Espro; F. Arena; A. Parmaliana; F. Frusteri (122-129).
Doped Ni-based Thin Layer Catalysts (Ni-TLCs) for Catalytic Decomposition of Natural Gas (CDNG) to produce CO free hydrogen were investigated using a new Multilayer Catalytic Reactor (MCR). The influence of K, La, Mg and Cl on activity–stability patterns of a Ni-TLC catalyst was evaluated. The influence of dopant on Ni sintering phenomena and coke formation mechanism was addressed.Doped Ni-based Thin Layer Catalysts (Ni-TLCs) for Catalytic Decomposition of Natural Gas (CDNG) were investigated using a new Multilayer Catalytic Reactor (MCR). The influence of K, La, Mg and Cl on activity–stability patterns of a Ni-TLC catalyst was evaluated. An inverse straight-line relationship between carbon capacity (C/Ni, number of CH4 molecules decomposed for Ni atom until complete deactivation) and reaction temperature was found independently of the dopant used. However, dopants significantly affect Ni specific activity (TOF, s−1), acting as either an electronic promoter or inhibiting Ni sintering phenomena. Reaction temperature is a key parameter in determining the evolution of coke. At low reaction temperature (<823 K), carbon whiskers form prevalently on “bare” and Mg, La, and Cl doped samples, whereas only the encapsulating carbon type formed on a K doped system. High hydrogen productivity was obtained on an Mg doped catalyst which, furthermore, proved to be the most stable system.
Keywords: Methane decomposition; Hydrogen “CO x free”; Ni Thin Layer Catalyst; Multilayer Reactor; Silica cloth; Coke; Ni dopant;
One-dimensional metal atom chain [Ru(CO)4] n as a catalyst precursor—Hydroformylation of 1-hexene using carbon dioxide as a reactant by Maija-Liisa Kontkanen; Larisa Oresmaa; M. Andreina Moreno; Janne Jänis; Elina Laurila; Matti Haukka (130-134).
Polymeric 1D metal atom chain [Ru(CO)4] n was studied as a catalyst for hydroformylation of 1-hexene utilizing CO2 as a source of CO. The linear chain [Ru(CO)4] n acts as a precursor for active oligonuclear and mononuclear ruthenium carbonyl species, which prefer direct formation of alcohols. Compared to the better known Ru3(CO)12 catalyst, the activity of the [Ru(CO)4] n -based catalyst was found to be at the same level.The catalytic activity of the polymeric 1D metal atom chain [Ru(CO)4] n was studied in the context of the hydroformylation of 1-hexene utilizing CO2 as a source of CO. In the multi-step process, CO2 is first reduced via a reversed water–gas shift reaction to CO, which is then used in situ in conventional hydroformylation. A promoter is needed to prevent the direct hydrogenation of alkenes that occurs as a side reaction. Thus, the effect of the promoter and the solvent was also studied. Linear chain compounds can act as catalysts or as precursors for active species. The results show that the ruthenium complexes derived from a [Ru(CO)4] n precursor can effectively catalyze both the reversed water–gas shift reaction and the hydroformylation. The polymeric [Ru(CO)4] n favors the direct hydrogenation of the aldehydes, permitting the selective production of alcohols. Compared to the better known Ru3(CO)12 catalyst, the activities of polymeric [Ru(CO)4] n were found to be at the same level. The best yields of hydroformylation products were achieved when DMF was used as a solvent with a LiCl promoter. The ESI-MS analysis of the reaction products indicated that the catalytically active species in the [Ru(CO)4] n catalyzed reactions were essentially the same as those found in [Ru3(CO)12] reactions. This indicates that the original linear framework of [Ru(CO)4] n is not retained during the reaction, but that [Ru(CO)4] n serves as an effective precursor for a catalytically active mononuclear and oligonuclear species.
Keywords: Ruthenium carbonyl; Metal atom chain; Carbon dioxide; Hydroformylation; Reverse water–gas shift reaction;
Various hexagonally ordered mesoporous silicas as supports for chromium species—The effect of support on surface properties by M. Trejda; A. Wojtaszek; M. Ziolek; J. Kujawa (135-140).
Hexagonally ordered mesoporous silicas were applied as supports for chromium species introduced via incipient wetness impregnation. Formation of active centres as a result of the post-synthesis modification with CrO3 was found to depend strongly on the preparation conditions used in the synthesis of the support.Hexagonally ordered mesoporous silicas of MCM-41 type, SBA-3 and SBA-15 were applied as supports for chromium species introduced via incipient wetness impregnation. The samples were characterised by XRD, N2 adsorption, UV–vis spectroscopy, H2-TPR, and a test reaction (acetonylacetone cyclisation). Their catalytic performance in sulphurisation of methanol was studied. Formation of active centres on mesoporous silica supports as a result of the post-synthesis modification with CrO3 was found to depend strongly on the preparation conditions used in the synthesis of the support. These conditions determined not only the textural/structural parameters but also surface properties of the support, important for the anchoring of metal species which is crucial for catalytic activity.
Keywords: MCM-41; SBA-3; SBA-15; Basicity; Acetonylacetone cyclisation; Methanol sulphurisation;
Reaction kinetics of the esterification of myristic acid with isopropanol and n-propanol using p-toluene sulphonic acid as catalyst by M.C. de Jong; R. Feijt; E. Zondervan; T.A. Nijhuis; A.B. de Haan (141-147).
The esterification of myristic acid with isopropanol using a homogeneous catalyst (pTSA) at a temperature range of 343–403 K is investigated, and compared with the reaction with n-propanol. The experimental kinetic data were analysed on the basis of a homogeneous model. The reaction parameters for both reactions were obtained and compared.The reaction kinetics of the esterification of myristic acid with isopropanol with n-propanol were determined, using p-toluene sulphonic acid (pTSA) as catalyst, for a temperature range of 343–403 K. The reactions follow first order kinetics in all components. The kinetic model corresponds with the results for the esterification of myristic acid with isopropanol reported in literature for 333–353 K. As expected, the reaction rate increases with increasing amount of catalyst and with increasing temperature. The reaction rate and equilibrium conversion increases with an increasing alcohol to myristic acid feed ratio. The reaction with n-propanol is considerably faster (at 373 K about 3.8 times) than the reaction with isopropanol.
Keywords: Esterification; Isopropanol; Myristic acid; n-Propanol; pTSA catalysis;