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Applied Catalysis A, General (v.333, #1)
The effect of Rh addition on Pd/γ-Al2O3 catalysts deposited on FeCrAlloy fibers for total combustion of methane by Andrea Maione; Floriane André; Patricio Ruiz (pp. 1-10).
Bimetallic Pd–Rh/Al2O3 catalysts were deposited by dip coating on FeCrAlloy type fibers. The effect of different gaseous pretreatments (under O2/H2 or H2 flows) on the physico-chemical properties and the catalytic activity in the total combustion of methane was investigated. The gaseous pretreatments did not seem to exert any particular influence on the catalytic activity of these systems. When palladium is partially replaced by rhodium, the catalytic performances of the so-obtained bimetallic catalysts are lower than those of the monometallic Pd-based one. However it should be remarked that bimetallic catalysts with a Pd loading of 1% at least, show better methane conversion than the monometallic Rh-based samples. The long duration tests demonstrated that a bimetallic Pd–Rh catalyst has a better catalytic behaviour than a Pd-only catalyst. Such a behaviour could be due to the presence of Rh2O3, in the bimetallic catalyst, which avoids PdO reduction to Pd0 and consequent sintering. It is worth noticing that no direct interaction between Pd and Rh was observed. A cooperation between PdO and Rh2O3 seems to explain the higher catalytic performances of bimetallic Pd–Rh catalysts.Bimetallic Pd–Rh/Al2O3 catalysts are deposited by dip coating on FeCrAlloy type fibers. The influences of different gaseous pretreatments (under O2/H2 or H2 flows) on the physico-chemical properties and the catalytic activity in the total combustion of methane are investigated. It is shown that a bimetallic Pd(1%)–Rh(1%) catalyst has a better stability with time on stream than a Pd-only catalyst, since Rh2O3 avoids PdO sintering during reaction.▪
Keywords: Methane combustion; Palladium; Rhodium; FeCrAlloy fibers; Long duration tests
Catalytic partial oxidation of CH4 to H2 over cobalt catalysts at moderate temperatures by Rune Lødeng; Erlend Bjørgum; Bjørn Christian Enger; Jan Lasse Eilertsen; Anders Holmen; Bente Krogh; Morten Rønnekleiv; Erling Rytter (pp. 11-23).
Catalytic partial oxidation (CPO) of methane has been investigated over Co/Al2O3 catalysts with different metal (0.1wt.% of Ni, Pt, Rh, Ru or Pd) and oxide (<4wt.% Fe3O4/Cr2O3, La2O3, SnO2 or K2O) promoters. A comparison with Ni- and Fe-based catalysts was performed. Methane conversions and selectivities were determined in the temperature range 200–750°C at atmospheric pressure in a continuous fixed-bed quartz reactor.▪Catalytic partial oxidation (CPO) of methane has been investigated over Co/Al2O3 catalysts with different metal (0.1wt.% of Ni, Pt, Rh, Ru or Pd) and oxide (<4wt.% Fe3O4/Cr2O3, La2O3, SnO2 or K2O) promoters. A comparison with Ni- and Fe-based catalysts was performed. Methane conversions and selectivities were determined in the temperature range 200–750°C at atmospheric pressure in a continuous fixed-bed quartz reactor. The scope was to identify factors for control of product selectivity and investigate the potential of low temperature operation. The unpromoted 10wt.% Co/Al2O3 catalyst showed stable steady-state performance at 650°C in the gas hourly space velocity range 15–180NlCH4/gcath. Equilibrium behaviour was observed during ramping (−1°C/min) until a sudden extinction occurred around 450°C, seemingly coinciding with O2 breakthrough. Addition of 0.1wt.% metal promoter, particularly Pt and Rh, caused the activity to be maintained to lower temperatures. While Rh maintained H2 formation, Pt promoted combustion at low temperatures. Addition of 0.1wt.% Ni by co-impregnation promoted carbon formation and deactivation. Addition of surface oxides typically promoted instability, deactivation and combustion. While the performance of Ni catalysts was superior to Co catalysts at low temperatures, Fe-based catalysts showed combustion activity in the whole temperature range. A hydrogen yield according to equilibrium predictions seems to be the best possible achievement.
Keywords: Low temperature CPO; Methane; Hydrogen; Cobalt; Nickel
Batch and continuous nitration of toluene and chlorobenzene with acetyl nitrate over zeolite beta by M.G. Kuba; R. Prins; G.D. Pirngruber (pp. 24-29).
The nitration of toluene and chlorobenzene with acetyl nitrate is a very fast reaction that can be run in a continuous reaction setup with zeolite beta catalyst. Deactivation of the catalyst takes place due to dealumination and the adsorption of acetic acid and acetic acid anhydride. Active reaction centres for the nitration are protonated aluminium centres in the zeolite framework, but not free aluminium species inside the reaction mixture. Nitrate or counter ions like sodium are not involved in the reaction mechanism.▪Zeolite beta allows high yields and good selectivity in the batch nitration of toluene and chlorobenzene with acetyl nitrate. Deactivation of the HPB1 zeolite beta catalyst takes place due to dealumination and the adsorption of acetic acid and acetic acid anhydride, which causes a decrease of the selectivity to 4-nitrotoluene in the nitration of toluene. Active reaction centres for the nitration are protonated aluminium centres in the zeolite framework, but not free aluminium species inside the reaction mixture. Nitrate or counter ions like sodium are not involved in the reaction mechanism. In the continuous liquid-phase nitration with acetyl nitrate, the zeolite beta catalyst enhanced the conversion of toluene only slightly, compared to the non-catalysed homogeneous reaction. With the less reactive substrate chlorobenzene, however, zeolite beta acted as an efficient catalyst in the continuous nitration with acetyl nitrate.
Keywords: Nitration; Acetyl nitrate; Zeolite beta; Continuous; Batch; Toluene; Chlorobenzene
Isobutane dehydrogenation on zirconia-, alumina-, and zirconia/alumina-supported chromia catalysts by Satu T. Korhonen; Sanna M.K. Airaksinen; Miguel A. Bañares; A. Outi I. Krause (pp. 30-41).
The dehydrogenation activity of zirconia/alumina-, alumina-, and zirconia-supported chromia catalysts was compared. For the supports the deposition of zirconia decreased the acidity and the coke deposition, but had no effect on the cracking activity. Chromia/zirconia was the most active catalyst and chromia/zirconia/alumina the least. In contrast to the supports the coke deposition rate followed the activity for the chromia catalysts. ▪The performances of zirconia-, alumina-, and zirconia/alumina-supported chromia catalysts were investigated in the dehydrogenation of isobutane in order to elucidate the role of the support material in the dehydrogenation reaction. The dehydrogenation reaction was studied by activity measurements and by experiments using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and in situ Raman spectroscopy. Zirconia was deposited on alumina to clarify if it is possible to combine the beneficial properties of the industrially used chromia/alumina catalysts with those of the more active chromia/zirconia. Zirconia deposition on alumina decreased the Lewis acidity of the support and the coke formation rate during the dehydrogenation. The dehydrogenation activities of the supports were low. Deposition of chromium (1–2atCr/nm2) increased the activity for all catalysts. The chromia/zirconia catalyst had the highest activity, whereas the use of zirconia/alumina support decreased the activity. The coke deposition rate increased with increasing dehydrogenation activity. The results suggested that the Lewis acidity alone is not important for the activity of the chromia-containing catalysts, but the phase of zirconia might have an influence.
Keywords: Dehydrogenation; Infrared; Raman; Chromia; Zirconia; Alumina
GaCl x- or GaAlCl x-grafted Si-MCM-41: Highly active and moisture insensitive/stable catalyst for the acylation and benzylation of benzene, naphthalene and substituted benzenes by Vasant R. Choudhary; Rani Jha (pp. 42-48).
GaCl x- and GaAlCl x-grafted Si-MCM-41 catalysts were prepared by reacting anhydrous GaCl3 and mixed anhydrous GaCl3 and AlCl3, respectively, with the terminal hydroxyl groups of Si-MCM-41 (pore size: 2.5nm) in a dry non-aqueous reaction medium (CCl4) under reflux. The catalysts showed high activity for both the acylation and benzylation (with benzoyl chloride and benzyl chloride, respectively) of benzene, toluene, p-xylene, cumene, mesitylene, anisole and naphthalene. Both the catalysts are moisture insensitive or less moisture sensitive; the presence of moisture has a beneficial effect in the acylation over both the catalysts. The catalytically active sites of the GaCl x-grafted Si-MCM-41 are (–O–)2GaCl (i.e. partially chlorided Ga anchored to Si through –O– linkage) species and the equivalent sites of the GaAlCl x-grafted Si-MCM-41 are (–O–)2Ga(or Al)Cl and (–O–)3Ga(or Al) species. The high acylation/benzylation activities of both the catalysts even in the presence of moisture are attributed to their redox properties (Ga3+→Ga1+) rather than to their Lewis acid properties. After the grafting/chemical bonding, the grafted gallium chloride catalyst showed much higher acylation activity but lower benzylation activity than the physically deposited (on Si-MCM-41) or unsupported GaCl3. The GaAlCl x-grafted Si-MCM-41 showed higher acylation activity than the GaCl x-grafted Si-MCM-41, due to a synergetic effect of the Ga and Al species. However, the relative benzylation activity of the two catalysts showed strong dependence upon the presence or absence of electron donating group(s) and also upon the electron donating ability of the group(s) attached to the aromatic nucleus.Acylation (by benzoyl chloride) and benzylation (by benzyl chloride) of aromatic compounds, with or without containing electron donating groups, can be accomplished with high reaction rates, using the chemically anchored GaCl3 or mixed GaCl3 and AlCl3 on a mesoporous Si-MCM-41, as a catalyst, even in the presence of moisture.▪
Keywords: GaCl; x; -grafted Si-MCM-41; GaAlCl; x; -grafted Si-MCM-41; Acylation benzylation; Moisture insensitive
Characterization and catalytic behavior in the n-butane dehydrogenation of trimetallic InPtSn/MgAl2O4 catalysts by Sonia A. Bocanegra; Alberto A. Castro; Osvaldo A. Scelza; Sergio R. de Miguel (pp. 49-56).
This paper deals with the characterization and catalytic dehydrogenation behavior of trimetallic InPtSn catalysts with different Sn content (from 0.12wt% up to 1.08wt%) supported on MgAl2O4. It was observed that the different impregnation methods of Pt and Sn lead to trimetallic catalysts with similar catalytic behaviors between them. The characterization studies indicate the existence of geometric effects of In and Sn on Pt sites that produce a dilution of the Pt surface, and also a strong interaction between the three metals, which could lead to alloy formation. These facts positively influence the catalytic performance, thus increasing the activity, the selectivity to butenes and the stability of the metallic phase. ▪This paper deals with the characterization and catalytic dehydrogenation behavior of trimetallic InPtSn catalysts with different Sn content (from 0.12wt% up to 1.08wt%) supported on MgAl2O4. The support was initially impregnated with In, followed by a co-impregnation with Pt and Sn. The Pt and In contents in all catalysts were 0.30wt% and 0.28wt%, respectively. Besides, two catalysts with a Sn content of 0.37wt% were prepared by two different methods: (a) successive impregnation (first Pt, second Sn) and (b) impregnation with PtSn complex, [(CH3)4N]2[PtCl2(SnCl3)2]. Experiments of n-butane dehydrogenation reaction were carried out both in continuous flow equipment and in pulse equipment. The catalysts were characterized by TPR, XPS and test reactions of the metallic phase. Trimetallic catalysts display high activity and selectivity to butenes and low deactivation during the n-butane dehydrogenation reaction. In order to analyze the influence of the preparation method on the catalytic performance, the better trimetallic catalyst was selected. It was observed that the different impregnation methods of Pt and Sn lead to trimetallic catalysts with similar catalytic behaviors between them. The characterization studies indicate the existence of geometric effects of In and Sn on Pt sites that produce a dilution of the Pt surface, and also a strong interaction between the three metals, which could lead to alloy formation. These facts positively influence the catalytic performance, thus increasing the activity, the selectivity to butenes and the stability of the metallic phase.
Keywords: Trimetallic PtSnIn catalysts; MgAl; 2; O; 4; support; n; -Butane dehydrogenation; Catalyst characterization
Study of the deactivation process of HZSM5 zeolite during polyethylene pyrolysis by A. Marcilla; M.I. Beltrán; R. Navarro (pp. 57-66).
The deactivation process of HZSM5 zeolite during the catalytic cracking of LDPE and HDPE has been studied by repeated batch operation using the same sample of catalyst in consecutive cycles until almost a total loss in the activity of the catalyst was observed. The gaseous and condensed products generated in each cycle were analysed as well as the coked catalyst obtained. ▪The deactivation process of HZSM5 zeolite during the catalytic degradation of LDPE and HDPE has been studied by repeated batch operation using the same sample of catalyst in consecutive cycles until almost a total loss in the activity of the catalyst was observed. The gaseous and condensed products generated in each cycle were analysed as well as the coked catalyst obtained. They were characterized by nitrogen adsorption–desorption isotherms at 77K, temperature programmed desorption of ammonia and thermogravimetric analysis.The deactivation process of HZSM5 depends on the type of polyethylene used. With LDPE the zeolite showed a slow deactivation. In the first four consecutive cycles the coke deposit increased, significantly changing the properties of the catalyst although the yield of gaseous and condensed products remained nearly constant throughout. From the fifth cycle on no more coke was deposited on the catalyst but the composition of products changed progressively, tending to that obtained in a thermal process. This behaviour could be related to the change in coke composition because of the effect of the temperature and the time. On the other hand, with HDPE, a clear relationship of the coke content, acidity, activity and textural properties of the catalyst with the products generated was observed.
Keywords: Catalytic pyrolysis; Catalyst activity; Catalyst deactivation; HZSM5; LDPE; HDPE
A comparative study of zirconia and alumina supported Pt and Pt–Sn catalysts used for dehydrocyclization of n-octane by D.L. Hoang; S.A.-F. Farrage; J. Radnik; M.-M. Pohl; M. Schneider; H. Lieske; A. Martin (pp. 67-77).
Alumina and zirconia supported Pt and Pt–Sn catalysts have been tested in the dehydrocyclization of n-octane to alkylaromatics as desired products using pure hydrogen and water vapour containing hydrogen atmospheres (WVH2). The materials were characterized by TPR, XRD, XPS, TEM and EDX. ▪Alumina and zirconia supported Pt and Pt–Sn catalysts have been tested in the dehydrocyclization (DHC) of n-octane at 823K to alkylaromatics as desired products using pure hydrogen (H2) and water vapour containing hydrogen (WVH2) atmospheres. The materials were characterized by nitrogen adsorption, NH3-TPD, TPR, XRD, XPS, TEM and EDX. The characterization results reveal the formation of PtSn alloys on alumina support after a catalyst precursor reduction in H2 at 873K. This observation enables an interpretation of the higher on-stream stability of Pt–Sn/Al2O3 catalyst in H2 as well as in WVH2 compared to the monometallic sample, using the well-known concept of the ensemble effect of Sn by alloying to Pt. The alumina supported Pt and Pt–Sn catalysts act bifunctionally in H2 atmosphere, producing a mixture of benzene, mono- and dialkylaromatics, near the chemical equilibrium. In WVH2 atmosphere, however, o-xylene and ethylbenzene are predominant among the aromatic products, indicating a monofunctional action mode of the catalyst. Independent of the reaction atmosphere, the zirconia supported Pt and Pt–Sn catalysts act monofunctionally with o-xylene and ethylbenzene as predominating products among the aromatics produced. The zirconia supported samples are more stable in WVH2 than in H2 atmosphere. The addition of Sn significantly increases the activity of that catalyst but does not retard its deactivation in H2. The formation of PtSn alloys is not evidenced in the Pt–Sn/ZrO2 catalyst after hydrogen treatment. The behaviour of the zirconia supported catalysts can be interpreted considering the weak-acidic character of the support and its interactions with Pt as well as with SnO2.
Keywords: n; -Octane dehydrocyclization; Pt/Al; 2; O; 3; Pt–Sn/Al; 2; O; 3; Pt/ZrO; 2; Pt–Sn/ZrO; 2; TPR; XPS; TEM
Gas-phase nitration of toluene with zeolite beta by M.G. Kuba; R. Prins; G.D. Pirngruber (pp. 78-89).
The gas-phase nitration of toluene was studied with HNO3 and N2O4 in a setup for continuous nitration. The difference between these two nitrating agents, the mechanism of nitration, the reasons for catalyst deactivation and the optimum reaction conditions are discussed in the paper.▪The gas-phase nitration of toluene was studied over a solid-acid zeolite beta catalyst with two different nitrating agents, HNO3 and N2O4, in a setup for continuous nitration. The selectivity of the reactions to 4-nitrotoluene was good, but the catalysts deactivated within a few hours. HNO3 gave higher yields than N2O4, but both HNO3 and N2O4 required a temperature lower than 160°C to obtain acceptable yields and less oxidation products. At higher temperatures, catalyst deactivation was accelerated and the yield of nitrotoluene decreased. Lowering the feed rate of toluene led to a slower deactivation of catalyst. The deactivation of the catalyst was caused by pore blocking due to liquid reaction products as well as coke formation. Unlike in liquid-phase nitration, dealumination did not play a role in the deactivation of the catalyst, which could be regenerated by calcination in air.
Keywords: Nitration; Continuous gas-phase nitration; Zeolite beta; Solid-acid catalysts; Nitric acid; Nitrogen dioxide; HNO; 3; N; 2; O; 4; Toluene
Nickel catalysts promoted with cerium and lanthanum to reduce carbon formation in partial oxidation of methane reactions by Alessandra Fonseca Lucrédio; Gregory Jerkiewickz; Elisabete Moreira Assaf (pp. 90-95).
Mixed oxides of nickel, magnesium and aluminum prepared by precursors hydrotalcite type were substituted by lanthanum or cerium and were characterized by XPS; EDS; BET; XRD; TPR. The catalysts were tested in the POM and the results showed that the catalysts promoted led to a reduction in the velocity of the carbon formation. ▪Mixed oxides of nickel, magnesium and aluminum were prepared by precursors hydrotalcite type and were substituted by lanthanum or cerium using the method of anion exchange. The catalysts were characterized by X-Ray Photoelectronic Spectroscopy (XPS); Energy Dispersive X-Ray Spectroscopy (EDS); Surface Area Method BET; X-Ray Diffraction (XRD); Temperature Programmed Reduction (TPR) and Catalytic Tests. Analysis of the mixed oxides suggests that the hydrotalcite type precursor after thermal treatment lead a good dispersion of nickel forming the periclase (Ni, Mg)O replaced by cations of Al3+ and spinel structure (Ni,Mg)Al2O4. The catalysts were tested in the partial oxidation of methane and the results showed that the catalysts promoted with lanthanum and cerium led to a reduction in the velocity of the carbon formation.
Keywords: Catalysts; Nickel; Hydrotalcite; Cerium; Lanthanum
Supported metallocene on mesoporous materials by Fernando Silveira; Cristiane F. Petry; Dirce Pozebon; Sibele B. Pergher; Chaline Detoni; Fernanda C. Stedile; João H.Z. dos Santos (pp. 96-106).
A series of hybrid supported catalysts was prepared by sequentially grafting Cp2ZrCl2 and ( nBuCp)2ZrCl2 (1:3 ratio) onto alumino-silicates (MCM-41, SBA-15, MCM-22, ITQ-2), alumina and chrysotiles (native and leached). Supports and catalysts were characterized by Rutherford backscattering spectrometry, atomic force microscopy and nitrogen adsorption. Grafted metal content laid between 0.2 and 0.8wt.% Zr/SiO2 and 0.9wt.% Zr/Al2O3. All the systems were shown to be active in ethylene polymerization with methylaluminoxane as the cocatalyst. Catalyst activity and molecular weight were shown to depend on the textural characteristic of the silicas, namely grain size and pore diameter. The highest activity in ethylene polymerization (ca. 3200kgPEmolZr−1h−1) was obtained with the supported catalyst using SBA-15 with average particle size around 0.21μm. Resulting polymers were characterized by gel permeation chromatography and differential scanning calorimetry.A series of hybrid supported catalysts was prepared by sequentially grafting Cp2ZrCl2 and ( nBuCp)2ZrCl2 (1:3 ratio) onto alumino-silicates, alumina and chrysotile. The supported catalysts were characterized by Rutherford backscattering spectrometry, atomic force microscopy and nitrogen adsorption grafted metal content. Catalyst activity and polyethylene molecular weight were shown to be dependent on textural properties of the supports. ▪
Keywords: Supported metallocenes; MCM-22; SBA-15; Chrysotile; ITQ-2; AFM
Direct preparation of styrene carbonates from styrene using an ionic-liquid-based one-pot multistep synthetic process by Fumitaka Ono; Kun Qiao; Daisuke Tomida; Chiaki Yokoyama (pp. 107-113).
An ionic-liquid-based one-pot multistep process was investigated for direct synthesis of styrene carbonate from styrene. The whole method was consisted of Methyltrioxorhenium catalyzed epoxidation of styrene with urea hydrogen peroxide to styrene oxide using ionic liquid as solvent in the beginning, and then followed by coupling reaction of styrene oxide with CO2 by addition of ZnBr2/ionic liquid as catalyst, and ended with separation of styrene carbonate by m-xylene extraction and recycling of ionic liquid after retrieved by CH2Cl2 extraction. A 65% yield of styrene carbonate, the highest one reported so far for this reaction, was obtained, and some other advantages such as higher efficiency of oxidant utilization, easy separation of product and recyclability of ionic liquid were also achieved.▪One-pot synthesis of styrene carbonate from styrene is investigated using a multistep protocol in the presence of an ionic-liquid-based catalytic system that is consisted of MTO/UHP/Zn[EMIm]2Br4/[BMIm]BF4. Owing to the multistep operations and the compatibility of MTO and Zn[EMIm]2Br4 in ionic liquid, remarkable improvements of the reaction performance regarding the reaction of one-pot synthesis of styrene carbonate from styrene have been achieved. Compared to other methods reported previously concerning this reaction, the current approach can increase the yield of styrene carbonate to 83%. Other improvements such as better utilization percentage of oxidant, easy separation of product and reusability of ionic liquid can also be obtained.
Keywords: Ionic liquid; Styrene; Epoxidation; Carbonate; Carbon dioxide
A comparative study of solid acids in hydrolysis and steam reforming of dimethyl ether by Kajornsak Faungnawakij; Ryuji Kikuchi; Toshiaki Matsui; Tetsuya Fukunaga; Koichi Eguchi (pp. 114-121).
The catalytic performances of solid acids (Al2O3 derived from bayerite (PBT), γ-Al2O3 (ALO8), ZSM-5, H-mordenite, and TiO2) in hydrolysis of dimethyl ether (DME) to methanol have been investigated. The stronger and the larger acid sites give rise to higher conversion in hydrolysis; however, fast degradation due to coking and low quality of product are observed. The acid strength of the solid acids is as follows: H-mordenite>ZSM-5>PBT, ALO8>TiO2. The apparent activation energies of DME hydrolysis over H-mordenite, ZSM-5, PBT, ALO8, and TiO2 were determined as 73, 76, 101, 146, and 186kJmol−1, respectively. Next, steam reforming of dimethyl ether over composites of the solid acid and copper iron spinel was evaluated for hydrogen production. The composites of alumina and Cu spinel are active and durable to produce H2-rich reformate with CO2 as the major products along with trace amounts of CO. The Cu content of 13.3–17.7wt% in the composites was optimum in terms of reforming performance. Alumina–spinel composites are superior to zeolite–spinel ones with regard to stability. Increasing the steam-to-carbon ratio obviously suppresses the catalyst degradation.The performance of solid acids in hydrolysis of dimethyl ether (DME) strongly depends on the acid properties. The activation energies of DME hydrolysis over H-mordenite, ZSM-5, Al2O3 derived from bayerite (PBT), γ-Al2O3 (ALO8), and TiO2 were determined by Arrhenius plots. The composites of alumina and Cu spinel are superior to those of zeolite and Cu spinel with regard to stability in steam reforming of dimethyl ether.▪
Keywords: NH; 3; -TPD; Bayerite; ZSM-5; Coke; Hydrogen; Hydrolysis and steam reforming of dimethyl ether
Esterification of free fatty acids in sunflower oil over solid acid catalysts using batch and fixed bed-reactors by J. Ni; F.C. Meunier (pp. 122-130).
This work aimed at determining active and durable solid catalysts for the esterification of palmitic acid (C16H32O2) dissolved in commercial sunflower oil with methanol. Both a stirred batch reactor and, for the first time to our knowledge, a recirculating system using a fixed bed-reactor were used to investigate this system. A silica-supported Nafion® resin (SAC-13) appeared as the most promising catalyst, which could be reused many times without showing any significant deactivation.▪The esterification of free fatty acids (FFA) found in vegetable oils with CH3OH using a solid catalyst is a promising method to convert FFA into valuable fatty acid methyl ester (FAME, biodiesel) and obtain a FFA-free oil that can be further transesterified using alkali bases. The present work aimed at determining active and durable solid catalysts for the esterification of palmitic acid (PA, C16H32O2) dissolved in commercial sunflower oil with methanol. Contrary to the case of experiments realized at high dilution in solvents or in pure FFA medium, in which methanol is fully soluble, a lack of full miscibility occurred in the present case. Both a stirred batch reactor and, for the first time to our knowledge, a recirculating system using a fixed bed-reactor were used to investigate this system.A silica-supported Nafion® resin (SAC-13) appeared as the most promising catalyst, requiring no activation, contrary to sulfated zirconia (SZ) that must be activated above 400°C. The SZ material could not be fully regenerated after use because of sulfate group leaching and the fact that the adsorbed oil decomposed to form carbonaceous deposits at the higher temperatures needed to activate the sample by dehydration. The poisoning of SAC-13 by water was mild and simply reversed using a moisture-free feed or purging with a dry gas. The activity of SAC-13 measured with the batch reactor was essentially equal to that obtained using a fixed bed-reactor in a recirculating system and no rate difference was observed whether an extrudate or a powder form of the sample was used. No rate differences were also observed at various stirring rates. These observations stress that no mass transport limitations were taking place. The TOF (based on the number of sulfur atoms) obtained over the SAC-13 was about seven times lower than that obtained using concentrated sulfuric acid. The possibility to use a fixed bed reactor paves the way for simplified studies of similar systems in terms of (1) the separation of the catalyst and product and (2) the mechanical stability of the catalyst particles. The combination of SAC-13 and a fixed bed-reactor system could lead to a practical and cost-effective FFA removal unit in front of typical oil transesterification units.
Keywords: Esterification; Biodiesel; Acid catalysis; Sunflower oil; Palmitic acid; Sulfated zirconia; Acidic resin; Fixed bed; Recirculating reactor
Synthesis of arylaldehydes: Br2/DMSO catalytic system for the chemoselective oxidation of methylarenes by Mohammad Ghaffarzadeh; Mohammad Bolourtchian; Maral Gholamhosseni; Farshid Mohsenzadeh (pp. 131-135).
The oxidation of methylarenes to the corresponding arylaldehydes has been successfully achieved in the presence of a mild catalytic system (Br2/DMSO) under a simple operational and experimental procedure. The procedure is chemoselective on the toluene family of derivatives containing other alkyl groups and can be performed for a broad scope of methylarenes.
Keywords: Br; 2; /DMSO catalytic system; Arylaldehydes; Methylarenes; Chemoselectivity
Poly ( N-vinyl-2-pyrrolidone)-Cu(OAc)2: An efficient and reusable catalyst for sulfimidation by M. Lakshmi Kantam /; Rajashree Chakravarti; B. Neelima; R. Arundhati; B. Sreedhar (pp. 136-142).
A recoverable poly(vinylpyrrolidone) supported cupric acetate catalyst was prepared and characterized by FT-IR, XPS, ESR, UV-DRS and AAS techniques. The catalyst was used in the sulfimidation of sulfides in the presence of PhI=NTs [( N-( p-tolylsulfonyl)imino]phenyliodinane to obtain the corresponding sulfimides in good to excellent yields. The catalyst was used for four cycles with consistent activity. Chiral sulfimides were obtained with moderate enantioselectivities in the presence of chiral bis(oxazoline) ligands.▪A recoverable poly(vinylpyrrolidone)-supported cupric acetate catalyst was prepared and characterized by FT-IR, XPS, ESR, UV-DRS and AAS techniques. The catalyst was used in the sulfimidation of sulfides in the presence of PhI=NTs [( N-( p-tolylsulfonyl)imino]phenyliodinane to obtain the corresponding sulfimides in good to excellent yields. The catalyst was used for four cycles with consistent activity. Chiral sulfimides were obtained with moderate enantioselectivities in the presence of chiral bis(oxazoline) ligands.
Keywords: PVP-Cu(OAc); 2; PhI; =; NTs; Bis(oxazoline); Sulfides; Sulfimides
Oxyfunctionalisation of adamantane using inorganic–organic hybrid materials based on isopoly and heteropoly anions: Kinetics and mechanistic studies by Ankur Bordoloi; Ajayan Vinu; S.B. Halligudi (pp. 143-152).
Oxyfunctionalisation of adamantane with 30% aq.H2O2 in butyronitrile solvent was efficiently catalyzed by isopoly and heteropoly anions immobilized onto mesoporous silica (SBA-15) and 10-molybdo-2-vanadophosphoric acid (H5[PMo10V2O40]·32·5H2O)–SBA-15 gave highest activity to give mainly 1-adamantanol. Vanadium (V) superoxo intermediate species formed was responsible for the CH bond activation of adamantane to give 1-adamentanol. ▪Oxyfunctionalisation of adamantane with 30% aq.H2O2 in butyronitrile solvent was efficiently catalyzed by inorganic–organic hybrid materials synthesized by the immobilisation of isopoly (WOx=sodium tungstate, MoOx=sodium molybdate and VOx=sodium metavanadate) and heteropoly anions (V1=H4[PMo11VO40]·32·5H2O,and V3=H6[PMo9V3O40]·34H2O, STA=silicotungstic acid, TPA=tungstophosphoric acid and MPA=molybdophosphoric acid) onto mesoporous silica (SBA-15). These catalysts were well characterized by standard techniques and it was found that polyoxometalate has been retained all its bulk characteristics upon immobilisation onto mesoporous silica. Among the catalysts 10-molybdo-2-vanadophosphoric acid (H5[PMo10V2O40]·32·5H2O) immobilized onto amine-functionalized SBA-15 gave the highest activity under the conditions in the liquid phase oxidation of adamantane with 30% aq.H2O2 in butyronitrile solvent and gave mainly 1-adamantanol. Kinetic parameter measurements were performed by following initial rate approach for determining the rate dependence of the reaction. In situ UV-vis and electron paramagnetic resonance (EPR) spectroscopic studies carried out showed that the vanadium (V) superoxo intermediate species formed was responsible for the CH bond activation of adamantane to give 1-adamentanol. Based on this, a plausible mechanism for the oxidation of adamantane to 1-adamantanol has been proposed. The catalysts leaching studies carried out by following a standard procedure ruled out any contribution by the active vanadium species that could leach into the reaction medium and catalysts were truly functioned as heterogeneous catalysts.
Keywords: Inorganic–organic hybrid materials; Oxyfunctionalisation; Adamantane; Vanadium (V) superoxo intermediate