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Applied Catalysis A, General (v.339, #1)
Structuration of LaMnO3 perovskite catalysts on ceramic and metallic monoliths: Physico-chemical characterisation and catalytic activity in methane combustion by E. Arendt; A. Maione; A. Klisinska; O. Sanz; M. Montes; S. Suarez; J. Blanco; P. Ruiz (pp. 1-14).
LaMnO3 perovskite was prepared by the citrate method and deposited on ceramic and metallic monoliths according to a dip coating or an orbital stirring procedure. Both types of structured catalysts were characterised by specific surface area measurements (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The parameters influencing the amount of deposited catalyst, such as the nature of the monolith and the coating technique, were investigated. Comparisons between structured and powdered catalysts showed a higher catalytic activity of the former. A better behaviour of structured LaMnO3 on metallic monoliths was observed at a lower temperature, and higher catalytic activities were observed for structured LaMnO3 on ceramic monoliths at a higher temperature. The influence of a diffusion limitation of the reaction rate in structured catalysts was observed.LaMnO3 perovskites were deposited on ceramic and metallic monoliths according to a dip coating or an orbital stirring procedure and characterised by different physico-chemical techniques (BET, SEM, XPS and XRD). Comparisons between structured and powdered catalysts showed a higher catalytic activity of the former. Metallic monoliths display better catalytic performances at low temperatures and the ceramic ones are more active at higher temperatures. ▪
Keywords: Perovskite; Metallic monolith; Ceramic monolith; Methane combustion
Interrelationship of process parameters in vapor phase pyridine synthesis by Kuppi Reddy Suresh Kumar Reddy; Inkollu Sreedhar; Kondapuram Vijaya Raghavan (pp. 15-20).
The synthesis of pyridine bases from acetaldehyde, formaldehyde and ammonia continues to provide the best prospect for meeting their growing demand. The catalytic aminocyclization has enough flexibility to tailor the catalyst and process parameters to achieve a market-friendly product distribution. An attempt has been made in the present work to investigate the vapor phase aminocyclization to achieve high pyridine yield and selectivity and minimal coke formation under a favorable interrelationship of critical catalyst and process parameters: temperature, catalyst, ammonia and aldehyde ratios, space velocity and physicochemical characteristics of catalyst. The role of internal and external diffusion resistance and effectiveness factor of catalyst at various conversion levels received attention. A deactivation model is proposed to simulate time-on-stream behavior of the catalyst.The synthesis of pyridine bases from acetaldehyde, formaldehyde and ammonia continues to provide the best prospect for meeting their growing demand. This work aimed to analyse and optimize the vapor phase aminocyclization to achieve high pyridine selectivity and minimal coke formation under a favorable interrelationship of critical process parameters.▪
Keywords: Pyridine synthesis; Zeolite catalysis; Diffusion studies; Catalyst deactivation
Isomerization ofd-glucose tod-fructose over metallosilicate solid bases by Sérgio Lima; Ana S. Dias; Zhi Lin; Paula Brandão; Paula Ferreira; Martyn Pillinger; João Rocha; Vanesa Calvino-Casilda; Anabela A. Valente (pp. 21-27).
The isomerization of glucose was studied in water at 100°C in the presence of various metallosilicates as solid base catalysts, namely the titanosilicates ETS-10, ETS-4 and AM-4, a sodium yttrium silicate analogue of the mineral montregianite (AV-1), an alkali calcium silicate analogue of the mineral rhodesite (AV-2), and a calcium silicate analogue of the mineral tobermorite (TOB). Fructose yields in the range of 20–40% were obtained within 2-h reaction. These results are either similar to or better than those achievable with the commercial zeolite Na–X or aqueous NaOH. Depending on the nature of the catalyst, different factors account for deactivation, such as loss of crystallinity, sodium/potassium leaching and surface passivation. Two of the more promising materials, AV-1 and TOB, were quite stable under the reaction conditions, as evidenced by powder X-ray diffraction analyses for the fresh and used catalysts. The used TOB catalyst exhibited a steady performance when recycled and for AV-1 fructose yields increased in recycling runs. The activity of the solid bases, with the exception of AV-1, could be correlated with the basicity characterized by Knoevenagel condensation tests.The isomerization of glucose in the presence of metallosilicates as solid base catalysts, namely titanosilicates ETS-10, ETS-4 and AM-4, a sodium yttrium silicate analogue of the mineral montregianite (AV-1), an alkali calcium silicate analogue of the mineral rhodesite (AV-2), and a calcium silicate analogue of the mineral tobermorite, gives 20–40% fructose yield within 2-h reaction, at 100°C.▪
Keywords: Glucose; Fructose; Isomerization; Solid bases; Metallosilicates; Alkali metals; Titanium; Yttrium
Reaction kinetics of liquid phase air oxidation of p-cresol to p-hydroxybenzaldehyde by V.S. Kshirsagar; J.M. Nadgeri; P.R. Tayade; C.V. Rode (pp. 28-35).
Kinetics of liquid phase oxidation of p-cresol to p-hydroxybenzaldehyde was studied using insoluble cobalt oxide (Co3O4) catalyst. XRD and XPS characterizations were done to confirm the phases and the chemical composition of the catalyst. On the basis of initial rate data, a rate expression was proposed considering a Langmuir–Hinshelwood (LH) type mechanism. The concentration time profile predicted by the reactor model was in good agreement with the experimental data. ▪The kinetics of liquid phase oxidation of p-cresol to p-hydroxybenzaldehyde has been investigated using insoluble cobalt oxide (Co3O4) catalyst at oxygen partial pressures in the range 0.1–1.5MPa, reaction temperatures 333–393K, p-cresol concentrations 0.49–1.53kmol/m3 and catalyst loadings 0.38–3.03kg/m3. The effects of oxygen partial pressure, reaction temperature, p-cresol concentration and catalyst loading on the initial rate of reaction have been studied. The initial rate varied linearly with catalyst loading up to 1.5kg/m3 beyond which it was independent of the catalyst loading while first-order dependence was observed with variation in oxygen partial pressure. A rate expression has been proposed considering Langmuir–Hinshelwood (LH) type mechanism, based on the initial rate data. A batch reactor model was also developed based on the kinetics studied and the concentration time profile predicted by the model was in good agreement with the experimental data. The activation energy for the liquid phase oxidation of p-cresol was found to be 39.6kJ/mol.
Keywords: p; -Cresol oxidation; Kinetics; XRD; XPS; Co; 3; O; 4
Effects of cage shape and size of 8-membered ring molecular sieves on their deactivation in methanol-to-olefin (MTO) reactions by Ji Won Park; Jae Youl Lee; Kwang Soo Kim; Suk Bong Hong; Gon Seo (pp. 36-44).
Small-port molecular sieves with CHA, ERI, LTA, and UFI topologies were prepared to investigate the effects of the cage shape and the cage size on their catalytic activities and on their deactivation behaviors in MTO reactions. The materials occluded in their cages are different according to their topologies as shown in their UV–VIS spectra, indicating the effects of cage shape and size on their deactivation behaviors.▪Four kinds of 8-membered ring (8-MR) small-port molecular sieves with CHA (SAPO-34), ERI (UZM-12), LTA (UZM-9), and UFI (UZM-5) topologies were prepared to investigate the effects of the cage shape and the cage size on their catalytic activities and on deactivation behaviors in methanol-to-olefin (MTO) reactions. UZM-5, -9, and -12 zeolites with Si/Al molar ratios of 5–6 showed high initial activities in the MTO reaction owing to their sufficient acidities, and they were highly selective to lower olefins such as SAPO-34 molecular sieve. However, they were rapidly deactivated in the order of CHA
Keywords: Methanol to olefin; 8-MR molecular sieve; CHA; ERI; LTA; UFI; Deactivation; Cage shape and size
Comparative study of triglyceride transesterification in the presence of catalytic amounts of sodium, magnesium, and calcium methoxides by Igor N. Martyanov; Abdelhamid Sayari (pp. 45-52).
An array of metal methoxides, homogeneous Mg(OCH3)2, solid MgO x(OCH3)2−2 x, Ca(OCH3)2, has been studied in a model reaction for biodiesel production. Peculiarities of each catalyst are elucidated.▪A solution of Mg(OCH3)2 in methanol, in-house prepared solid MgO x(OCH3)2−2 x, and commercial Ca(OCH3)2 were tested at 60°C in transesterification of tributyrin with methanol—a model reaction for biodiesel production. The homogeneous magnesium methoxide acts fast at the beginning of the reaction but quickly forms a suspension/precipitate mixture of much lower catalytic activity. The precipitate was found to be a complex composition including glycerol and butyric acid derivatives. The reaction over solid MgO x(OCH3)2−2 x is catalytic but sluggish with deactivation taking place in ca. 4h. Analysis of the used catalyst revealed surface butyric acid as the most likely species responsible for the catalyst deactivation. In the presence of Ca(OCH3)2, the yields of the products reach final values in about 4h. The reaction starts as a heterogeneous process, however, interaction of Ca(OCH3)2 with reaction products such as glycerol gives rise to catalytically active homogeneous species. Formed in a side reaction calcium butyric acid derivatives contribute to Ca(OCH3)2 dissolution but do not deactivate the surface of the catalyst.
Keywords: Biodiesel; Magnesium methoxide; Calcium methoxide; Transesterification; Heterogeneous catalyst
Catalytic activity of Keggin heteropolycompounds in the Pechmann reaction by R. Torviso; D. Mansilla; A. Belizán; E. Alesso; G. Moltrasio; P. Vázquez; L. Pizzio; M. Blanco; C. Cáceres (pp. 53-60).
Different heteropolycompounds were used as catalysts in the synthesis of coumarins from phenols and ethyl acetoacetate. Keggin heteropolyacids were supported on silica and the aluminium salts of these heteropolyacids were prepared. The catalytic activity using several phenols were determined and high yield of product was obtained in the case of 4-methyl-7-hydroxycoumarin, 4-methyl-5,7-dimethoxycoumarin and 4-methyl-7,8-benzocoumarin. The use of microwave radiation increases the reaction yield and mainly decreases the reaction time.▪Different heteropolycompounds were used as catalysts in the synthesis of coumarins from phenols and ethyl acetoacetate. The H3PMo12O40 and H3PW12O40 Keggin heteropolyacids were supported on different types of silica. On the other hand, the aluminium salts of these heteropolyacids and that of the H4SiW12O40 acid were prepared. The specific surface area ( SBET), and the mean pore diameter of the obtained catalysts were estimated from the adsorption isotherms of nitrogen at 77K. Their Fourier transform infrared spectra were recorded and their acidity was determined by potentiometric titration with a solution of n-butylamine in acetonitrile. The catalytic activity using several phenols such as resorcinol, 3,5-dimethoxyphenol, α-naphtol and β-naphtol were determined. High yield of product was obtained in the case of 4-methyl-7-hydroxycoumarin (80–95%), 4-methyl-5,7-dimethoxycoumarin (60–92%) and 4-methyl-7,8-benzocoumarin (90%). However, the 4-methyl-5,6-benzocoumarin yield was low. The use of microwave radiation as power source increases the reaction yield and mainly decreases the reaction time.
Keywords: Catalysts; Keggin heteropolycompounds; Pechmann reaction
Effect of iron and calcium over USY coke formation by Alyne S. Escobar; Marcelo M. Pereira; Henrique S. Cerqueira (pp. 61-67).
Different bifunctional catalysts were used in three model reactions: cyclohexane transformation, n-hexane cracking and ethane hydrogenolysis. Bimetallic catalyst NiVUSY forms relatively low amounts of coke when compared to monometallic catalysts, and exhibits a higher olefin to paraffin ratio. The addition of Fe or Ca to the bimetallic catalyst largely reduces coke formation and increases the olefin to paraffin ratio.▪Although several studies discuss the effect of metals on the FCC process, very few focus on those caused specifically by Fe and Ca. Within this work, different zeolite samples were prepared by impregnating nickel and vanadium on an ultra stable Y zeolite (USY), previously exchanged with iron and calcium. The samples were used in three model reactions: cyclohexane transformation at 300°C, n-hexane cracking (500°C) and ethane hydrogenolysis. The first reaction aimed at studying coke formation tendencies. The second reaction allowed an indirect measure of catalyst acidities and ethane hydrogenolysis (which was used to discuss nickel particle formation). Bifunctional catalysts presented a higher tendency to form coke compared to pure USY. This effect was much more pronounced in the presence of Ni and V. Bimetallic catalyst NiVUSY forms relatively low amounts of coke when compared to monometallic catalysts, and exhibits a higher olefin to paraffin ratio. The addition of Fe or Ca to the bimetallic catalyst largely reduces coke formation and increases the olefin to paraffin ratio. When compared to the NiVUSY catalyst, the reduction temperature decreases 20 and 50°C for FeNiVUSY and CaNiVUSY catalyst, respectively. In addition ethane hydrogenolysis reveals nickel activity only for FeNiVUSY catalyst. These results support that Fe and Ca affect nickel and vanadium chemical environment and probably their distribution on the catalyst surface.
Keywords: Nickel; Vanadium; Iron; Calcium; USY; Coke; FCC
Influence of the support during homocoupling of phenylboronic acid catalyzed by supported gold by Nicholas G. Willis; Javier Guzman (pp. 68-75).
The influence of the support properties in CeO2-, TiO2-, ZrO2-, and SiO2-supported gold and palladium catalysts on the conversion and selectivity during the Suzuki homocoupling of phenylboronic acid were investigated. Supported gold gives a selectivity of 100% towards biphenyl except when SiO2 is used as support. Palladium catalysts are less active than the supported gold catalysts and show a selectivity of about 75% with formation of benzene and phenol as byproducts. ▪Gold or palladium nanoparticles with an average diameter of 10 and 15nm, respectively, were deposited on the surface of CeO2, TiO2, ZrO2, and SiO2 powder supports by deposition–precipitation using a solution of HAuCl4 or Pd(NO3)2. The supports and catalysts were characterized by N2 adsorption, XRD, TEM, and FTIR spectroscopy. The influence of the crystallite size, degree of hydroxylation, and crystallinity of the supports on the conversion and selectivity during the Suzuki homocoupling of phenylboronic acid were investigated. Under the same reaction condition, the supported palladium catalysts are less active than the supported gold catalysts. The palladium catalysts show a selectivity of about 75% towards biphenyl with formation of benzene and phenol as byproducts. However, when supported gold is used for the reaction, a selectivity of 100% towards biphenyl is obtained in all cases except when SiO2 is used as support. The activity of the supported gold catalysts increases as the size of the crystallite support particles decreases and as the initial surface coverage of OH groups in the supports increases. The results confirm a previous model suggesting the participation of hydroxyl groups in the catalytic reaction through the dissociation of molecular water on the surface of the support to restore the surface hydroxyl groups.
Keywords: Gold; Metal oxides; Suzuki coupling; Support effects
Esterification and transesterification using modified-zirconia catalysts by Dora E. López; James G. Goodwin Jr.; David A. Bruce; Satoshi Furuta (pp. 76-83).
In this paper, modified zirconias (WZ, SZ, and TiZ) have been extensively compared under the same reaction conditions as catalysts for both the transesterification of triglycerides (TGs) and the esterification of carboxylic acids (free fatty acids, FFAs) with ethanol. In addition, for the first time, the catalyzed rate of hydrolysis/esterification+transesterification of triglycerides has been quantified and compared to that of the rate of simultaneous esterification of FFAs present in the same reaction mixture. Tricaprylin and caprylic acid were used as representative compounds for the comparison of the catalyst for transesterification and esterification since they give reaction rates related to those of larger TGs and FFAs typically present in vegetable oils and animal fats. For the measurement of the kinetics for the simultaneous reaction of a TG-FFA mixture, the reaction of tricaprylin and oleic acid with ethanol was studied using the most promising of the Zr-based catalysts, WZ. Reaction was carried out in a well-mixed batch reactor under mild conditions (75–120°C). TiZ, while more active than WZ for transesterification, had by far the lowest activity for esterification. SZ, while the most active catalyst (on a weight basis) for both transesterification and esterification reactions, exhibited significant sulfur loss, which greatly reduced its long term activity. As expected, esterification occurred at a much faster rate than transesterification. However, under simultaneous reaction conditions, by virtue of the water being produced in esterification and hydrolysis of the TG taking place, the conversion of the triglycerides to ester products was greatly increased. The resulting caprylic acid from hydrolysis did not accumulate in the reaction mixture due to its rapid esterification to ethyl caprylate. The activity results for WZ indicate how biodiesel can be efficiently produced from free-fatty-acid-containing feedstocks using a solid-acid-catalyzed pre-esterification step, and how a significant fraction of the triglycerides can also be converted at the same time assisted by initial hydrolysis with byproduct water from esterification.In this work, the activities of titania zirconia (TiZ), sulfated zirconia (SZ), and tungstated zirconia (WZ) were investigated for the transesterification of triglycerides (TGs) and the esterification of carboxylic acids (free fatty acids, FFAs) with ethanol. In addition, for the first time, the rate of hydrolysis/esterification+transesterification of triglycerides was quantified and compared to that of the rate of esterification of FFAs present in the same reaction mixture. Simultaneous reaction on tungstated zirconia of a mixture of oleic acid and of tricaprylin with ethanol at different reaction temperatures: (a) ethyl oleate yield, (b) ethyl caprylate yield.▪
Keywords: Biodiesel; Esterification; Transesterification; Solid acid catalyst; Sulfated zirconia; Tungstated zirconia; Titania zirconia
Supported rhodium nanoparticles obtained by Metal Vapour Synthesis as catalysts in the preparation of valuable organic compounds by Claudio Evangelisti; Nicoletta Panziera; Maria Vitulli; Paolo Pertici; Federica Balzano; Gloria Uccello-Barretta; Piero Salvadori (pp. 84-92).
The low metal loading Rh on γ-Al2O3 catalyst, containing trioctylamine, TOA, derived from mesitylene-solvated rhodium atoms, Rh(TOA)/γ-Al2O3, 0.1wt.% Rh, showed a high catalytic activity and selectivity in the hydrogenation of 4-(6-methoxy-2-naphthyl)-3-buten-2-one and of 2-acetyl-5,8-dimethoxy-3,4-dihydronaphthalene to 4-(6-methoxy-2-naphthyl)-butan-2-one, Nabumetone™, and to 2-acetyl-5,8-dimethoxy-1,2,3,4-tetrahydronaphthalene, an anti-inflammatory drug, precursor of antitumor anthracyclinic compounds, respectively, at room temperature and atmospheric pressure of hydrogen. No leaching of rhodium was observed. The catalyst was completely recovered and, if reused, it works without loss of activity.1H NMR DOSY analysis of the Rh(TOA)/mesitylene solution evidenced the presence of nanoparticles with a diameter of about 1.1nm.▪Rhodium nanoparticles, derived from mesitylene-solvated rhodium atoms, deposited on γ-Al2O3, are excellent catalysts for the selective hydrogenation of the double bond in α,β-unsaturated carbonyl compounds. The low metal loading Rh on γ-Al2O3 catalyst, containing trioctylamine, TOA, as stabilizing agent of the metal nanoparticles, Rh(TOA)/γ-Al2O3, 0.1wt.% Rh, showed the highest catalytic activity. Using this catalyst 4-(6,-methoxy-2,-naphthyl)-3-buten-2-one was reduced to the anti-inflammatory drug 4-(6,-methoxy-2,-naphthyl)-butan-2-one, Nabumetone™, with complete selectivity and under mild reaction conditions (room temperature, atmospheric pressure of hydrogen). Similarly, 2-acetyl-5,8-dimethoxy-3,4-dihydronaphthalene was hydrogenated with high selectivity (85%) to 2-acetyl-5,8-dimethoxy-1,2,3,4-tetrahydronaphthalene, precursor of antitumor anthracyclinic compounds, which was obtained chemically pure by crystallization. No leaching of rhodium was observed. The catalyst was completely recovered and, if reused, it works without loss of activity.1H NMR DOSY analysis of the Rh(TOA)/mesitylene solution evidenced the presence of nanoparticles with a diameter of about 1.1nm.
Keywords: Supported rhodium nanoparticles; Metal Vapour Synthesis; Selective hydrogenation; α,β-Unsaturated ketones; 1; H NMR DOSY analysis
Selective hydrogenation of trans-4-phenyl-3-butene-2-one to unsaturated alcohol over Ru/γ-Al2O3 modified by PPh3 and diamines by Derong Liu; Wei Xiong; Guangyin Fan; Hua Chen; Ruixiang Li; Xianjun Li (pp. 93-98).
Catalyst Ru/γ-Al2O3, which modified by triphenylphosphine and aliphatic and cycloaliphatic diamines, showed a highly catalytic activity and selectivity for the hydrogenation of CO double bond of trans-4-phenyl-3-butene-2-one. The conversion and selectivity of trans-4-phenyl-3-butene-2-one was up to 99% under the optimum reaction conditions.▪The selective hydrogenation of trans-4-phenyl-3-butene-2-one over Ru/γ-Al2O3 stabilized with triphenylphosphine was investigated in the presence of diamine and base. It was found that 1,2-diphenylethylene-1,2-diamine (DPEN) was the best modifier among the investigated diamines. Both DPEN and KOH not only promoted the selectivity of the CO bond hydrogenation, but also accelerated the rate of the hydrogenation. Under the optimum conditions: the reaction temperature of 35°C, H2 pressure of 4.0MPa, KOH concentration of 0.04mol/l, and reaction time of 3h, the conversion of trans-4-phenyl-3-butene-2-one was close to 100% and the selectivity to unsaturated alcohol was more than 99%. In combining with the effect of reaction factors on the hydrogenation, a possible hydrogenation mechanism is proposed.
Keywords: Ruthenium; Diamine; Selective hydrogenation; Trans; -4-phenyl-3-butene-2-one