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Applied Catalysis A, General (v.404, #1-2)
Alcohols as alternative fuels: An overview by Venkateswara Rao Surisetty; Ajay Kumar Dalai; Janusz Kozinski (pp. 1-11).
Display Omitted► Ethanol replaced other additives as octane boosters in automotive fuels. ► Syngas obtained from carbon resources can be catalytically converted to alcohols. ► Alkali-modified molybdenum-based catalysts are more attractive for alcohols synthesis.Due to the phase out of lead in all gasoline grades and the adverse health and environmental effects of MTBE, the synthesis of higher alcohols, particularly ethanol, from synthesis gas has drawn considerable interest. Low molecular weight alcohols such as ethanol have replaced other additives as octane boosters in automotive fuels. Adding alcohols to petroleum products allows the fuel to combust more completely due to the presence of oxygen, which increases the combustion efficiency and reduces air pollution. The presence of alcohols in fuel causes corrosion to metallic fuel system components. In order to make the best use of alcohols as alternative fuels; one can redesign the engine or the vehicle can be redesign or one can blend in one or more additives to the ethanol or methanol to improve its characteristics. Catalytic conversion of synthesis gas to alcohols is advantageous, as this uses various renewable and non-renewable carbon resources. Different catalytic systems can be used for synthesizing higher alcohols from synthesis gas. Depending on the process conditions and the catalyst used, the reaction mechanism varies and the products include primary and secondary alcohols of both normal and branched carbon chains. The present paper includes an overview of the processes and catalysts used depending on the production of specific alcohols, as well as, the reaction mechanisms currently accepted. Transition metal-promoted alkali-modified molybdenum sulphide catalysts are considered to be more attractive to improve CO hydrogenation and for the production of linear alcohols.
Keywords: Higher alcohols synthesis; Alternative fuels; Alcohol fuels; Modified methanol synthesis catalysts; Supported Rh-based catalysts; Alkali-modified MoS; 2; catalysts
Spatial and temporal mapping of coke formation during paraffin and olefin aromatization in individual H-ZSM-5 crystals by Young-Min Chung; Davide Mores; Bert M. Weckhuysen (pp. 12-20).
Display Omitted► Olefin reactants generate enhanced coke formation. ► Alkyl-branching causes confined carbonaceous deposits. ► Large coke compounds mainly form in the straight pores of H-ZSM-5. ► Paraffin reactants convert at the zeolite surface. ► Linear olefins produce graphitic-like external layer.The formation of carbonaceous deposits that occurs during the aromatization of C4–C7 paraffin and olefin hydrocarbons is visualized in a space- and time-resolved manner over individual micron-sized H-ZSM-5 zeolite crystals. In situ UV–vis and confocal fluorescence micro-spectroscopy techniques are applied in a comparative study for each individual light naphtha component. Optical microphotograph image analysis shows how crystal coloration depends on the reactant molecule. The corresponding absorption measurements confirm that olefinic hydrocarbons generate a pronounced coke deposition. Two main UV–vis bands, located at around 420 and 500nm, thereby shape the absorption spectrum profile and are assigned to aromatic and poly aromatic species. Increasing reactant chain length results in more extended coke deposits, while the introduction of methyl branching generates conjugated carbonaceous species of similar confined size. The larger coke deposits predominantly locate within the straight channels of the H-ZSM-5 zeolite catalyst, as demonstrated by polarization-dependent UV–vis micro-spectroscopy. In situ confocal fluorescence microscopy reveals spatial heterogeneities of photo-excited coke species between the olefin and paraffin reactants. Paraffinic reactants convert mainly at the crystal boundary region, while olefinic hydrocarbons cause the build-up of fluorescent coke compounds within the crystal core. Different fluorescence patterns are obtained when varying the laser excitation wavelengths, thereby detecting fluorescent emitting species having a different conjugation degree.
Keywords: In situ micro-spectroscopy; Coke deactivation; Light-naphtha-aromatization; H-ZSM-5
Effect of pore diameter of Ni–Mo/Al-SBA-15 catalysts on the hydrotreating of heavy gas oil by K. Chandra Mouli; Kapil Soni; Ajay Dalai; John Adjaye (pp. 21-29).
Display Omitted► High pore diameter (>10nm) Ni–Mo/Al-SBA-15 catalysts were synthesized. ► The pore structure of SBA-15 collapsed above 13nm pore diameter. ► The activity of HDS and HDN increased with increase in pore diameter till 13nm. ► Effect of pore diameter on catalytic activity is more on HDN than on HDS.SBA-15 with pore diameter greater than 10nm was synthesized by varying the synthesis parameters and adding swelling agent hexane and inorganic salt ammonium fluoride. Direct and post synthesis modification methods were employed to incorporate aluminum in the framework of SBA-15. In the direct synthesis approach, the highest pore diameter achieved was limited to 7nm, but post synthesis method was employed successfully to achieve high pore diameter catalysts. The pore structure of the synthesized SBA-15 did not collapse until 13nm of pore diameter as confirmed from the small angle XRD and TEM. The prepared Ni–Mo catalysts with different pore diameters were screened for hydrotreating of heavy gas oil (HGO) in a trickle bed continuous reactor. The catalyst with 13nm pore diameter gave highest conversion compared to other catalysts.
Keywords: Hydrotreating; TEM; NiMo/Al-SBA-15; Mesoporous materials; Hydrodesulfurization; Hydrodenitrogenation
Inhibition of the hydrogenation of tetralin by nitrogen and sulfur compounds over Ir/SBA-16 by Gerardo Simón Balangero Bottazzi; María Laura Martínez; Marcos Bruno Gómez Costa; Oscar Alfredo Anunziata; Andrea Raquel Beltramone (pp. 30-38).
Display Omitted► Ir/SBA-16 and Ir/Al-SBA-16 were synthesized with high dispersion and small clusters of iridium. ► High activity and resistant to inhibition by sulfur and nitrogen compounds at mild conditions. ► The inhibiting effect increased in the order: DBT
Keywords: Iridium containing SBA-16; Hydrogenation; Inhibition; Reaction kinetic; Sulfur; Nitrogen compounds
Kinetics of dimethyl carbonate synthesis from methanol and carbon dioxide over ZrO2–MgO catalyst in the presence of butylene oxide as additive by Valerie Eta; Päivi Mäki-Arvela; Johan Wärnå; Tapio Salmi; Jyri-Pekka Mikkola; Dmitry Yu. Murzin (pp. 39-46).
Display Omitted► Replacement of toxic chemicals such as phosgene with CO2. ► Shift of equilibrium towards DMC formation via water removal. ► Qualitative kinetics and kinetic modelling. ► Reaction mechanism and estimation of kinetic parameters.A kinetic investigation of dimethyl carbonate (DMC) synthesis from methanol and CO2 over ZrO2–MgO was performed by using butylene oxide as a chemical trap for the water formed during the reaction. The effect of the catalyst amount, the stirring speed, the temperature, as well as the amount of butylene oxide on the reaction rate and the selectivity to DMC was studied. The analysis of the reaction pathway suggests that DMC and butylene glycol are formed via the reaction of adsorbed mono-methoxycarbonate intermediate and methoxybutanol or methanol. A kinetic model was developed based on the reaction mechanism and it was in agreement with the experimental data. The apparent activation energy for the formation of DMC was 62kJ/mol.
Keywords: Dimethyl carbonate; Methanol; Carbon dioxide; Butylene oxide; Kinetics; ZrO; 2; –MgO
Influence of triisobutylaluminum on the polymerization of ethylene by SiO2-supported ansa-zirconocene catalysts by V.N. Panchenko; L.G. Echevkaya; V.A. Zakharov; M.A. Matsko (pp. 47-53).
Display Omitted► Treatment of SiO2/MAO/SBIZrCl2 catalysts with TIBA decreases their Al and Zr contents. ► TIBA interacts with surface-bound MAO to form modified, heptane-soluble MMAO. ► In solution, a catalyst gives PE with lower molar mass than that on the support surface.Catalysts for the polymerization of ethylene, which contain rac-Me2Si(Ind)2ZrCl2 (SBIZrCl2) bound to methylalumoxane-pretreated SiO2 supports (SiO2/MAO/SBIZrCl2), were studied with respect to leaching of zirconocene and MAO into heptane solutions caused by triisobutylaluminum (TIBA). The latter is found to solubilize surface-bound MAO and zirconocene components, such that the Al content in the solid catalysts is reduced by 15–40wt% and their Zr content by 50–60wt%. Consequently, ethylene polymerization with such TIBA-containing catalyst systems occurs both on the surface of the solid catalyst and in the solution phase. Polymerization in solution is favored by high MAO contents in the SiO2 carrier. Polymerization in solution leads to polyethylene (PE) products with lower molecular masses than polymerization on the support surface; this is the main cause of formation of PE with bimodal molecular mass distribution when ethylene is polymerized with SiO2/MAO/SBIZrCl2 catalysts co-activated by TIBA. It is proposed that the co-activator TIBA interacts with surface-bound MAO to modify MAO in such a manner that it becomes soluble in aliphatic hydrocarbons and capable of solubilizing some active zirconocene component.
Keywords: Ethylene polymerization; Supported metallocene catalyst; Polymer chain length; Triisobutylaluminum
Density functional theory (DFT) investigation on the structure and electronic properties of the cubic perovskite PbTiO3 by Huizhi Lv; Hongwei Gao; Yue Yang; Lekun Liu (pp. 54-58).
.Display Omitted► In this study we study the molecular structures and electronic properties of PbTiO3. ► We examine the performance of the different DFT and plane-wave pseudopotential methods. ► We conclude that GGA/PBE are good method for predicting the structure and properties of PbTiO3.This paper describes how to build models of PbTiO3 crystal in the material studio and how to do CASTEP calculation. This article focuses on discussing the best CASTEP calculation and pseudopotential, and analyzing the structure and properties of PbTiO3, namely the band structure and density of states (DOS). The calculated results are in good agreement with the experimental ones. The purpose of this paper is to prove the feasibility and accuracy of calculation.
Keywords: PbTiO; 3; Perovskite; DOS; DFT
Synthesis, characterization and photocatalytic activity of Bi-doped TiO2 photocatalysts under simulated solar irradiation by S. Murcia-López; M.C. Hidalgo; J.A. Navío (pp. 59-67).
Display Omitted► Bismuth doped TiO2 (BTO- x) was obtained by sol–gel and hydrothermal synthesis. ► Hydrothermal treatment has a clear positive influence on bismuth doping. ► Bi3+ content and calcination temperature are important parameters on photoactivity. ► BTOh-0.5 was very effective in phenol photocatalytic mineralization. ► Bi-doped TiO2 showed higher photoactivity than P25 under sunlike irradiation.A series of Bi3+-doped TiO2 catalysts with a doping concentration up to 2wt% were prepared by a sol–gel hydrothermal method. The prepared photocatalysts were characterized by different techniques to determine their structure, morphology and light absorption properties. The activities were evaluated in the photocatalytic oxidation of phenol in aqueous solution under UV–vis illumination. The experimental results indicate that the presence of Bi3+ in TiO2 catalysts enhances the photocatalytic reaction of phenol degradation, although the efficiency of the process markedly depends on the nominal content of the Bi3+ and on the calcination temperature. It was found that the optimal dosage of 0.5wt% Bi3+ in TiO2 and calcinations at 600°C 4h achieved the fastest reaction of phenol degradation under the experimental conditions. From the comparison of the initial rates of the photocatalytic degradation of phenol between home prepared undoped and Bi3+-doped TiO2 with commercial TiO2 Degussa P25, it can be inferred that home prepared TiO2 calcined at temperatures above 500°C clearly exceed the photocatalytic performance of P25. When bismuth is incorporated, the reaction rate values are even higher, especially at 600°C. Even when Bi3+-doped TiO2 (0.5wt% Bi3+) calcined at 600°C has almost the same BET surface than P25, its activity is better. In particular, the reaction rate for the sample with a 0.5% mass content of Bi3+ calcined at 600°C not only present higher value with respect to the other series but also a degree of mineralization close to 100%.
Keywords: Bismuth-doping; Titanium dioxide; Bi–TiO; 2; Phenol degradation; Photocatalysis
Wells–Dawson heteropolyacid as reusable catalyst for sustainable synthesis of flavones by Daniel O. Bennardi; Gustavo P. Romanelli; Ángel G. Sathicq; Juan C. Autino; Graciela T. Baronetti; Horacio J. Thomas (pp. 68-73).
Display Omitted► Wells–Dawson heteropolyacid as heterogeneous catalyst to obtain flavones. ► Supported catalyst was re-used three times without losing activity. ► Yields above 85% were obtained in 4–5h.The behavior of Wells–Dawson (H6P2W18O62·24H2O, WD) acid, both bulk and supported on silica, for the cyclodehydration reaction of 1-(2-hydroxyphenyl)-3-phenyl-1,3-propanedione to obtain flavone was studied in heterogeneous conditions, using toluene as solvent. Catalytic experiences with bulk and supported catalysts with different WD acid loadings and reuse of the catalysts were done. The catalytic activity of supported catalysts was higher than that of the bulk catalyst, and their activity was almost constant after three reaction cycles. The following reaction conditions: reflux toluene and 1%mmol of WD supported on silica (0.4g WD acid by gram of silica) were used for the preparation of five flavones. Yields above 85% were obtained in 4–5h.
Keywords: Acid catalysis; Heteropolyacids; Wells–Dawson; Flavones
Fischer–Tropsch synthesis on Co/ZnO catalyst—Effect of pretreatment procedure by Zhendong Pan; Dragomir B. Bukur (pp. 74-80).
Display Omitted► H2-activated Co/ZnO catalyst was more active than the CO-activated catalyst. ► H2-activated catalyst had higher olefin content and lower methane selectivity. ► Both cobalt carbide (Co xC; x=2 or 3) and metallic cobalt were found after CO pretreatments.The effect of catalyst pretreatment, using hydrogen or carbon monoxide, on the activity and selectivity of cobalt on ZnO catalyst (10wt% Co/ZnO) during Fischer–Tropsch synthesis was studied in a fixed bed reactor. Catalyst reduced with hydrogen had higher activity and higher olefin content, and produced less methane than the CO activated catalyst. Catalysts were characterized by means of Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR), and hydrogen chemisorption (H2-TPD) with pulse re-oxidation. Reduction of Co3O4 occurs in two stages during H2-TPR and CO-TPR. In the latter case CoO, metallic cobalt, cobalt carbides (Co xC; x=2 or 3) and carbon (from CO disproportionation) are formed during the reduction process. The existence of Co0 along with CoO and Co xC, indicates a possibility of two reaction paths for formation of Co xC from CoO: the direct path (CoO→Co xC) and a series reaction via Co0 (i.e. CoO→Co0→Co xC).
Keywords: Fischer–Tropsch synthesis; Co/ZnO catalyst; Hydrogen and carbon monoxide activation; Catalyst characterization
Methanol dehydration to dimethyl ether in a staged autothermal millisecond residence time reactor by Hui Sun; Lanny D. Schmidt (pp. 81-86).
Display Omitted► Methanol dehydrates to DME in auto thermal millisecond contact time reactor. ► Highest DME yield is ∼80% in the methanol side feed configuration. ► DME yield and methanol conversion for side feed methanol configuration is comparable to isothermal methanol dehydration.Methanol dehydration to dimethyl ether (DME) has been carried out in a two-stage autothermal millisecond residence time reactor using a noble metal coated catalyst in the upstream stage to generate heat and zeolite in the downstream stage to dehydrate methanol with a total residence time of less than 100ms. Two reactor configurations have been examined: (1) methanol fed from the top of the reactor with hydrogen as sacrificial fuel and (2) methanol fed between the two stages with methane as a sacrificial fuel. Methanol dehydration was also explored under isothermal conditions to compare with the results obtained under autothermal conditions. For autothermal experiments, reaction temperature and product distribution of the second stage was adjusted by varying the fuel to oxygen ratio and distance between two stages. The DME yield of the autothermal reactor with side-entering methanol was comparable to that of methanol dehydration reaction under isothermal conditions and was much better than the methanol top-feed configuration. The highest yield of DME obtained was ∼80% at C/O ratio of 1.0 which was comparable to the non-autothermal values reported in literature (∼80%) and close to equilibrium yield (84%). This demonstrates the ability to synthesize DME in staged autothermal reactors with short contact time, high yield and no external heating. This also shows that noble metal catalysts can be integrated with zeolite catalysts for upgrading oxygenated compounds to more energetically dense compounds in compact reactors having multiple feeds.
Keywords: Methanol dehydration; Dimethyl ether; Autothermal staged reactor; Noble metal catalyst; Zeolite H-ZSM-5
Ionic liquids as benign catalysts for the carbonylation of amines to formamides by Young-Seop Choi; Yu Na Shim; Jeesun Lee; Jung Hee Yoon; Chang Seop Hong; Minserk Cheong; Hoon Sik Kim; Ho Gyeom Jang; Je Seung Lee (pp. 87-92).
Display Omitted► Synthesis of imidazolium-based ionic liquids (ILs) bearing a bicarbonate anion. ► ILs as benign catalysts for the carbonylation of amines to produce formamides. ► Mechanistic investigation on the bi-functional roles of bicarbonate anion.1-Butyl-3-methylimidazolium hydrogen carbonate ([BMIm][HCO3]), prepared from the reaction of [BMIm]Cl with K2CO3 in methanol, exhibits high activity for the carbonylation of amines to produce formamides.Computational calculation results on the carbonylation reaction of methylamine implies that such high activity of [BMIm][HCO3] could be ascribed to the bi-functional actions of [HCO3]− as a hydrogen atom acceptor and a donor.
Keywords: Formamides; Carbonylation; Amines; Hydrogen carbonate; Ionic liquids
Alumina support-stabilized nanoscaled vanadium–phosphorous mixed oxides as new catalysts for propane ammoxidation by Ewelina Mikolajska; Elizabeth Rojas Garcia; Ricardo López Medina; Anna E. Lewandowska; Jose Luís G. Fierro; Miguel A. Bañares (pp. 93-102).
Display Omitted► P shifts V oxide activity from acetonitrile to acrylonitrile. ► The active phase for acrylonitrile formation appears related to V5+/V4+ redox cycle. ► Acrylonitrile yield is significantly higher per gram of supported than for bulk VPO. ► VPO catalysts exhibit higher performance than systems reported in the literature.Much attention has recently been devoted to the surface of bulk catalysts. It has been proved that the most critical phenomena occur at the surface, which differs significantly from the bulk. To evaluate the role of the bulk in VPO catalyst, vanadium and phosphorus were supported on γ-alumina by incipient wetness impregnation at a total V+P of two monolayers so that nanoscaled VPO phases (n-VPO) form on alumina, such size maximizes the surface-to-bulk ratio. Alumina support stabilizes V5+, which may be reduced, while V4+ predominates in bulk vanadyl pyrophosphate phase. In addition, the support modifies acid–base and textural properties. The presence of VPO nanocrystals supported on alumina (n-VPO) facilitates investigating the interaction between alumina-dispersed vanadia and VPO-lattice vanadium ions. Both, bulk and supported phases are active for propane ammoxidation affording acrylonitrile yields of 41% and 48%, respectively, at 500°C. The yield to acrylonitrile per mass unit of VPO increases by 150% at 500°C in the alumina-stabilized n-VPO system when compared to the bulk VPO.
Keywords: Support stabilized nanoscaled VPO; Vanadium phosphates; Propane; Ammoxidation; Acrylonitrile; Alumina; Surface vanadium oxide
Selective phenol hydrogenation in aqueous phase on Pd-based catalysts supported on hybrid TiO2-carbon materials by Juan Matos; Avelino Corma (pp. 103-112).
Phenol hydrogenation. (A) General reaction steps. (B) General pathway for selective hydrogenation of phenol to cyclohexanone.Display Omitted► Selective phenol hydrogenation under green chemistry conditions. ► Pd-based catalysts supported on hybrid TiO2-carbon materials. ► High selectivity to cyclohexanone with Pd on polar TiO2-C supports. ► High selectivity to cyclohexanol with Pd on non-polar TiO2-C supports. ► Control of the functionalization of the hybrid support.TiO2-C materials have been prepared by solvothermal and slurry synthesis and the influence of carbon properties upon the catalytic activity and selectivity of Pd-based catalysts on phenol hydrogenation in aqueous phase under mild reaction conditions has been studied. The nature of the catalysts can be modified to direct the reaction either to cyclohexanol (∼100% yield) or to cyclohexanone (∼96% yield). High selectivity to cyclohexanone is obtained with Pd on more polar TiO2-C supports, while when these are transformed into hydrophobic TiO2-C supports the resultant catalyst becomes selective to cyclohexanol. Thus, product distribution during the selective phenol hydrogenation in aqueous phase is easily controlled by controlling the functionalization of the hybrid support.
Keywords: Phenol hydrogenation; Selectivity; Pd-based catalysts; Hybrid TiO; 2; -C
Effects of acid leaching post-treatment on the catalytic performance of MoO3/mordenite-alumina catalysts for 1-butene metathesis reaction by Shengjun Huang; Huijuan Liu; Ling Zhang; Shenglin Liu; Wenjie Xin; Xiujie Li; Sujuan Xie; Longya Xu (pp. 113-119).
Molybdenum oxide catalysts supported on mordenite zeolite-alumina (HM-Al2O3) compositive support are post-treated by nitric acid leaching at 298K with different periods (12–48h). The most dominant effect by acid leaching post-treatment lies in the extraction of aluminum molybdate (Al2(MoO4)3). With this structural transformation, catalysts can sustain 1-butene metathesis reactions with significantly improved stability in propene formation.Display Omitted► Acid leaching post-treatment improves the metathesis stability of MoO3/HM-Al2O3. ► Acid leaching extracts aluminum molybdate. ► Aluminum molybdate is detrimental for metathesis stability. ► Removal of aluminum molybdate causes transition in coke species.Molybdenum oxide supported on mordenite zeolite-alumina composite is post-treated by nitric acid leaching with varying periods (12–48h). The post-treated molybdenum catalysts display much higher stability for propene formation in 1-butene metathesis reaction. The evolution of Mo species has been characterized by laser Raman,27Al MAS NMR and X-ray photoelectron spectroscopy. Characterization results have shown the extraction of aluminum molybdates (Al2(MoO4)3) after acid leaching post-treatment. This structural transformation relates to a transition in coke species on the spent molybdenum catalysts, and leads to the improvement in metathesis stability.
Keywords: 1-Butene metathesis; Mordenite-alumina; Acid leaching; Aluminum molybdate
Use of iron and manganese porphyrins in solution and immobilized on silica obtained by the sol–gel process as catalyst in the oxidation of organic substrates by Geani Maria Ucoski; Kelly Aparecida Dias de Freitas Castro; Kátia Jorge Ciuffi; Gustavo Pimenta Ricci; Jacqueline Aparecida Marques; Fábio Souza Nunes; Shirley Nakagaki (pp. 120-128).
Display Omitted► Preparation of metalloporphyrins [Fe(TAPP)]Cl and [Mn(TAPP)]Ac. ► Low-cost porphyrins with intermediate structure between 1st and 2nd generation. ► Heterogenization of metalloporphyrins in silica obtained by the sol–gel process. ► Efficiency and selectivity in oxidation reaction. ► Catalyst for heterogeneous catalysis with reuse capacity.The preparation and characterization of the metalloporphyrins [Fe(TAPP)]Cl, 5,10,15,20-tetrakis(acetalphenyl porphyrin) iron(III) chloride, and [Mn(TAPP)]Ac, 5,10,15,20-tetrakis (acetalphenyl porphyrin) manganese(III) acetate and of the solids obtained by their heterogenization in silica obtained by the sol–gel process in acidic and basic media are reported. The compounds were characterized by ultraviolet–visible absorption spectroscopy (UV–vis), X-ray diffraction (XRD), infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), and thermogravimetric analysis (TGA). The catalytic activity of the metalloporphyrins in solution and as heterogeneous catalysts concerning the oxidation of organic substrates like cyclooctene and cyclohexane was investigated. The catalysts employed here, which consist of reasonably low-cost metalloporphyrins with intermediate structure between first- and second-generation porphyrins, furnished promising results. These novel solid materials offered benefits such as higher product yields, compared to the first-generation catalysts, and inexpensive preparation routes, compared to the cost involved in the production of second-generation metalloporphyrins.
Keywords: Porphyrin; Silica; Sol–gel; Catalysis; Oxidation; Alkane activation
Modeling study of 5kWe-scale autothermal diesel fuel reformer by Derek Creaser; Xanthias Karatzas; Björn Lundberg; Lars J. Pettersson; Jazaer Dawody (pp. 129-140).
Display Omitted► Model developed for operation of autothermal diesel reformer with monolith catalyst. ► Total oxidation and steam reforming reactions occur simultaneously. ► Total oxidation reaction best describes heat effects in catalytic reactor. ► Transport effects important when coupling exothermic and endothermic processes.A model was developed that successfully describes key operating features of a 5kWe-scale autothermal diesel fuel reformer with an engineered monolith-supported Rh based catalyst. The model consisted of a kinetic model comprised of four overall reactions including total oxidation, fuel steam reforming, methane formation via fuel decomposition and the water–gas shift reaction. The model also accounted for heat and mass transport effects that were of importance when coupling the exothermic oxidation reactions with endothermic steam reforming reactions in a full-scale reformer. According to the model, the total oxidation and steam reforming reactions occurred simultaneously, however the heat effects of the oxidation reaction dominated near the reactor inlet resulting in a local hot spot. Transport resistances were found to hinder the rates of the main reactions, especially at higher temperature operating conditions. The model was primarily based on experimental data for a commercial low-sulphur diesel fuel (MK1), however it was found to also reasonably well describe the operation of the reactor with a diesel surrogate ( n-tetradecane).
Keywords: Autothermal reforming; Diesel reforming; Modeling; Fuel processor; Rh catalyst
Catalytic conversion of alcohols over alumina–zirconia mixed oxides: Reactivity and selectivity by Hossein A. Dabbagh; Mehdi Zamani (pp. 141-148).
Display Omitted► Mixed 25, 50 and 75wt.% Al2O3–ZrO2 composites were prepared by means of sol–gel method. ► Doping ZrO2 with alumina eliminates m-ZrO2 but stabilizes the tetragonal phase. ► Crystalline composite selectively dehydrates DPP over 2-octanol to give E-alkene. ► The amorphous composite produced the least stable kinetically controlled 1-alkene. ► BET surface area at 600 (amorphous) and 1000°C (crystalline) are 104.2 and 0.3m2/g.The amorphous and crystalline mixed 25, 50 and 75wt.% Al2O3–ZrO2 composites were prepared by means of sol–gel method using aluminum iso-propoxide and zirconyl nitrate precursors. Physicochemical properties were determined using XRD, BET, NH3-TPD, TGA, SEM, and FT-IR spectroscopy. Catalytic activity and selectivity were investigated for the dehydration of 2-octanol and 1,2-diphenyl-2-propanol (DPP). Al75Zr25 composite is more selective than other forms for the conversion of 2-octanol. The selectivity of DPP for 1-alkene formation was increased over Al25Zr75 catalyst. The crystalline 50wt.% catalyst dehydrated tertiary alcohol (DPP) selectively in the presence of 2-octanol. The amorphous 50wt.% catalyst dehydrated DPP predominately to 1-alkene isomer. The crystalline catalyst favored the formation of E-2-alkene.
Keywords: Amorphous; Crystalline; Mixed Al; 2; O; 3; –ZrO; 2; Catalyst reactivity-selectivity; Dehydration
Effect of reduction pretreatment and support materials on selective CO methanation over supported Ru catalysts by Shohei Tada; Ryuji Kikuchi; Kohei Urasaki; Shigeo Satokawa (pp. 149-154).
Display Omitted► The good correlation was found between CO2 methanation reaction rate and Ru/support interfacial length. ► CO2 methanation reaction rate decreased over Ru/TiO2 that has a small amount of CO2 adsorbed, leading to increase in CO methanation selectivity. ► CO methanation activity was improved over Ru/TiO2 due to the high surface area of Ru.Selective CO methanation over Ru/Al2O3 and Ru/TiO2 was investigated as a CO removal method from reforming gas, and the effect of reduction treatment and the support materials on the selectivity and activity was examined. CO methanation activity was degraded over both Ru catalysts by raising reduction treatment temperature, which brought about Ru particle growth except for Ru/TiO2 reduced at 600°C. Ru/TiO2 showed higher CO methanation activity than Ru/Al2O3 due to smaller Ru particle size. A close correlation was found between CO2 methanation rate and interfacial length of Ru particle and support, which indicates that the interface was identified as the reaction sites of CO2 methanation in CO and CO2 coexisting atmosphere. CO2 methanation over Ru/TiO2 was suppressed in spite of long length of the interface compared to Ru/Al2O3, stemming from the small amount of CO2 adsorbed onto Ru/TiO2. Ru/TiO2 catalyst exhibited wider temperature window for selective CO methanation than Ru/Al2O3 catalyst.
Keywords: CO methanation; Selectivity; Ruthenium; Alumina; Titania
Investigation of phenol degradation: True reaction kinetics on fixed film titanium dioxide photocatalyst by Massimiliano Vezzoli; Wayde N. Martens; John M. Bell (pp. 155-163).
.Display Omitted► Phenol photocatalytic oxidation true kinetic parameters were estimated. ► A generalised approach, modelling all reacting species as carbon content, was used. ► Good agreement between experimental and model was achieved. ► Novel fixed film reactors can be designed utilising this model.This study of photocatalytic oxidation of phenol over titanium dioxide films presents a method for the evaluation of true reaction kinetics. A flat plate reactor was designed for the specific purpose of investigating the influence of various reaction parameters, specifically photocatalytic film thickness, solution flow rate (1–8lmin−1), phenol concentration (20, 40 and 80ppm), and irradiation intensity (70.6, 57.9, 37.1and 20.4Wm−2), in order to further understand their impact on the reaction kinetics. Special attention was given to the mass transfer phenomena and the influence of film thickness.The kinetics of phenol degradation were investigated with different irradiation levels and initial pollutant concentration. Photocatalytic degradation experiments were performed to evaluate the influence of mass transfer on the reaction and, in addition, the benzoic acid method was applied for the evaluation of mass transfer coefficient.For this study the reactor was modelled as a batch-recycle reactor. A system of equations that accounts for irradiation, mass transfer and reaction rate was developed to describe the photocatalytic process, to fit the experimentaldataand to obtain kinetic parameters. The rate of phenol photocatalytic oxidation was described by a Langmuir–Hinshelwood type law that included competitive adsorption and degradation of phenol and its by-products. The by-products were modelledthrough their additive effect on the solution total organic carbon.
Keywords: Titanium dioxide photocatalysis; True reaction rate; Flat plate reactor; Phenol degradation; Langmuir–Hinshelwood; Mass transfer coefficient