Showing papers in "Reaction Kinetics and Catalysis Letters in 2002"
TL;DR: In this article, the effect of sulfur on diesel emission control is reviewed in two major characteristics: diesel exhaust contains a far higher amount of particulate matter, and diesel exhaust is far leaner, that is, far more oxidizing than a typical exhaust from petrol engines.
Abstract: The effect of sulfur on diesel emission control is reviewed in this paper. Diesel exhaust differs from that of petrol engine exhaust in two major characteristics. Firstly, diesel exhaust contains a far higher amount of particulate matter, and secondly, the exhaust is far leaner, that is, far more oxidizing than a typical exhaust from petrol engines. Under these conditions, the conventional three-way catalysts are not effective in reducing NOx . Emission from diesel engines is a complex phenomenon. The composition, the properties and the amount of these emissions depend on strictly technical parameters such as engine design and engine operation characteristics and on fuel and lube oil composition. Diesel fuel contains a small amount of sulfur which has an adverse effect even on the raw particulate emissions. The investigations on the effect of sulfur on hydrocarbons, CO and NOx abatement in diesel exhaust gas is reviewed together with the newest technologies to avoid catalyst deactivation by unwanted SO2 reactions.
72 citations
TL;DR: In this article, a very efficient way of cyclopentanone production via selective liquid phase oxidation with nitrous oxide is reported, which occurs without catalyst with nearly 100% selectivity.
Abstract: A very efficient way of cyclopentanone production via selective liquid phase oxidation of cyclopentene with nitrous oxide is reported. When contacting liquid cyclopentene at high temperature, nitrous oxide is able to interact directly with the C=C double bond of the hydrocarbon and transfer its oxygen to unsaturated carbon atom. The reaction occurs without catalyst with nearly 100% selectivity.
69 citations
TL;DR: The kinetic curves of levulinic acid accumulation in the process of saccharide dehydration at 80-98oC were compared in this paper. But the results showed that the results were not robust to moderate conditions, and that the yields of the sulfuric acid can reach 35 mol % for glucose and 50% for sucrose at 98oC.
Abstract: The kinetic curves of levulinic acid accumulation in the process of saccharide dehydration at 80-98oC are compared. The structural features of the substrates and 5-hydroxymethylfurfural, which is the intermediate of the process, explain the observed difference in the rates of fructose and glucose conversion. Sulfuric acid can be effectively used under moderate conditions to synthesize levulinic acid with yields exceeding 35 mol % for glucose and 50% for sucrose at 98oC.
61 citations
TL;DR: In this paper, the light alkenes formation capacity and the interaction of Mn with Fe and Fe-Co of Fischer-Tropsch catalysts have been studied, and it was found that Fe-co-Mn has a better catalytic stability than the Fe-mn catalyst.
Abstract: The light alkenes formation capacity and the interaction of Mn with Fe and Fe-Co of Fischer-Tropsch catalysts have been studied. The samples were characterized by X-ray diffraction and temperature-programmed reduction. It was found that Fe-Co-Mn has a better catalytic stability than the Fe-Mn catalyst. It is proposed that iron particle size and its interaction with oxide and carbide phases produced during the catalytic reaction are mainly responsible for the high activity and light alkene selectivity.
42 citations
TL;DR: In this article, a comparison of the results with those reported for CO hydrogenation on the same catalyst indicates that, although product distributions of CO2 and CO hydrogenations differ, the kinetics and mechanism are similar.
Abstract: CO2 fixation by hydrogenation over coprecipitated 36 wt.% Co/Al2O3 has been studied under a range of reaction conditions to clarify the effects of reaction variables and to determine the kinetics and mechanism of the reaction. A comparison of the results with those reported for CO hydrogenation on the same catalyst indicates that, although product distributions of CO2 and CO hydrogenation differ, the kinetics and mechanism are similar.
41 citations
36 citations
TL;DR: In this article, a series of silica-supported chromium oxide catalysts were used for the reaction and CO2 in the feed promoted the catalytic activity, achieving 30.7% conversion and 96.5% selectivity at 700oC.
Abstract: The oxidative dehydrogenation of ethane into ethylene by CO2 over a series of silica-supported chromium oxide catalysts was investigated. The results showed that the catalysts were effective for the reaction and CO2 in the feed promoted the catalytic activity. The 5%Cr/SiO2 catalyst exhibited the excellent performance with 30.7% ethane conversion and 96.5% ethylene selectivity at 700oC. ESR and UV-DRS were used to probe the active sites and the species with high valent states (Cr5+ and/or Cr6+) were found to be important for the reaction.
36 citations
TL;DR: In this article, the Fischer-Tropsch (F-T) element was used to modify the Cu/Mn/ZrO2 methanol synthesis catalyst.
Abstract: A Cu/Mn/ZrO2 methanol synthesis catalyst modified by Fischer-Tropsch (F-T) element (Ni,Co,Fe) was prepared by an coprecipatation method. The addition of F-T elements had a great effect on the catalyst performance. The higher alcohol selectivity increased greatly compared with that of the Cu/Mn/ZrO2 catalyst when nickel and cobalt were added, while the addition of iron improved the selectivity tohydrocarbon due to the interaction of the F-T element and the Cu/Mn/ZrO2 catalyst.
34 citations
TL;DR: In this article, the acid and coordination effect of the ligand played the same important role in the Na2WO4·2H2O catalyzed oxidation of cyclohexene to adipic acid with 30% hydrogen peroxide.
Abstract: In the absence of phase-transfer agents, the ligand effects are studied for the clean synthesis of adipic acid by direct oxidation of cyclohexene catalyzed by Na2WO4·2H2O with 30% hydrogen peroxide. In most cases, the isolated yield of the target product adipic acid is high if the ligand acidity is strong. Although the acidity of some phenolic ligands, L(+)ascorbic acid and 8-quinolinol is weak, the isolated yield of adipic acid is still high. It is demonstrated that the acid and coordination effect of the ligand play the same important role in the Na2WO4·2H2O catalyzed oxidation of cyclohexene to adipic acid with 30% hydrogen peroxide. Kinetic investigations show that the hydrolysis of cyclohexene oxide to 1,2-cyclohexandiol is the critical step and the acidity of reaction system is important.
34 citations
TL;DR: In this article, the authors studied the catalytic decomposition of ethanol in the presence of steam over Pd supported on a porous carbonaceous material and found that the catalyst exhibited high activity and long-term stability for the ethanol decomposition into a gas mixture containing carbon oxides, methane and hydrogen.
Abstract: Catalytic decomposition of ethanol in the presence of steam over Pd supported on a porous carbonaceous material was studied. XPS and TEM were used for the catalyst characterization. Experiments were performed under atmospheric pressure, temperature of 320-360°C and H2O/C2H5OH molar ratio 8.1. It was found that the catalyst exhibited a high activity and long-term stability for the ethanol decomposition into a gas mixture containing carbon oxides, methane and hydrogen.
33 citations
TL;DR: In this paper, the influence of the addition of CeO2 or Co3O4 to Ni-based catalysts on carbon deposition by CH4 and carbon elimination by CO2 was studied with a pulse reaction as well as BET, TGA, XPS and hydrogen chemisorption techniques.
Abstract: The influence of the addition of CeO2 or Co3O4 to Ni-based catalysts on carbon deposition by CH4 and carbon elimination by CO2 was studied with a pulse reaction as well as BET, TGA, XPS and hydrogen chemisorption techniques. It was found that addition of the CeO2 decreased the carbon deposition activity of CH4 and increased the carbon elimination ability of CO2, which could be explained by the interaction between the metal (Ni) and n-type semiconductor (CeO2). However, the addition of the Co3O4, which was transformed to Co0 during the reaction, accelerated carbon deposition by CH4 and resisted carbon elimination by CO2. A novel model of carbon deposition/carbon elimination over Ni-based catalysts has been proposed.
TL;DR: In this article, the stability and less coking on MgO-promoted catalysts are attributed to the lewis basicity of Mg O. The performance of the catalysts has been characterized by temperature-programmed reduction and XRD techniques.
Abstract: Simultaneous steam and CO2 reforming of methane to syngas (H2and CO) over NiO/MgO/a-Al2O3 catalyst have been investigated at different MgO wt.%. The catalyst has been characterized by temperature-programmed reduction and XRD techniques. Addition of MgO reduced the carbon deposition and energy consumption. The stability and less coking on MgO-promoted catalysts are attributed to the lewis basicity of MgO.
TL;DR: In this article, the effects of organic solvents on the ammoximation of cyclohexanone oxime with H2O2and NH3 over TS-1 were studied.
Abstract: The effects of organic solvents on the ammoximation of cyclohexanone to cyclohexanone oxime with H2O2and NH3 over TS-1 were studied. To investigate the effects of ammonia and organic solvents on the structure stability of the catalyst, TS-1 samples were pretreated under severe conditions in ammonia solution or ammonia solution plus methanol, toluene or t-butanol, respectively, and then characterized bySEM, XRD, FTIR, etc. The results revealed that t-butanol is the best solvent for the ammoximation reaction; ammonia tends to destroy the active sites, -Ti-O-Si- structure in TS-1, but the presence of organic solvents remarkably limits this damaging effect of ammonia.
TL;DR: In this paper, a comparative study of NiWO4, NiO, and WO3 catalysts for simultaneous conversion of NO and CO is presented. But, in the range (523 to 723) K NiO was more active than WO4 and NiO.
Abstract: We present a comparative study of NiWO4, NiO, and WO3 catalysts for simultaneous conversion of NO and CO. Samples were synthesized by reacting ammonium metatungstate and/or nickel nitrate at high temperature (773 K to 903 K) under an oxygen stream. Catalysts were characterized by X-ray diffraction, surface area measurements, energy dispersive spectroscopy and scanning electron microscopy. The catalytic reduction of NO by CO took place in the temperature range (523 to 973) K under highly reductive conditions (NO:CO= 1:5) over NiWO4NiO, and WO3, respectively. The 100 % NO conversion at GHSV of 11460 h-1 was achieved at 773 K over NiWO4 and at 848 K over NiO. The WO3 was deactivated at 898 K. However, in the range (523 to 723) K NiO was more active than NiWO4 and WO3 catalysts.
TL;DR: In this article, the specific reactivity of the surface oxygen, its amount, coefficients of bulk and near-surface diffusion, as dependent upon the sample composition and temperature, were estimated using sample reduction by CO in the pulse/flow mode.
Abstract: Ca and/or F-modified fluorite-like Ce-Zr-mixed oxides have been prepared by Pechinis method. The bulk structure of samples was characterized by XRD, EXAFS and FTIRS of the lattice modes. The surface properties were studied by SIMS and FTIRS of adsorbed CO and surface hydroxyls. The specific reactivity of the surface oxygen, its amount, coefficients of bulk and near-surface diffusion, as dependent upon the sample composition and temperature, were estimated using sample reduction by CO in the pulse/flow mode. Insertion of fluorine into the lattice results in decreasing the degree of oxygen polyhedra distortion, thus decreasing the amount of reactive oxygen and diffusion coefficients. Calcium and Pt addition counteracts this effect. At 500oC for Pt-supported Ce-Zr-O samples including those modified by Ca and F, the lattice oxygen is easily removed by methane generating CO and hydrogen with high selectivity. Reoxidation of reduced samples by water or carbon dioxide at the same temperature restores the oxygen capacity producing more hydrogen or carbon monoxide.
TL;DR: In this paper, the authors investigated the catalytic performance of Ni-V-O catalysts in a wide range of vanadium contents (5-40%), and found that the addition of a small amount vanadium significantly increased catalytic activity of NiO for oxidizing propane to propene, and that a synergetic effect exists between them in NiXV1-XOY (X = 0.95 to 0.85).
Abstract: The oxidative dehydrogenation (ODH) of propane was investigated on Ni-V-O catalysts in a wide range of vanadium contents (5-40%). The addition of a small amount of vanadium significantly increased the catalytic activity of NiO for oxidative dehydrogenation of propane to propene. The formation of propene has a good correlation with the coexistence of NiO and Ni3V2O8. This result strongly suggests that a synergetic effect exists between them in NiXV1-XOY (X = 0.95 to 0.6). The best results were obtained with a high Ni/V ratio (e.g. X = 0.95 to 0.85). The active sites and selective oxygen species are discussed. The influence of the catalyst preparation technique and the redox properties of the catalyst were also examined.
TL;DR: In this paper, Ni-supported USY-type zeolite (Si/Al2 = 14.0, 360) was found to have longer catalytic lifetime than Ni supported silica (Cab-O-Sil) catalyst.
Abstract: Hydrogen production by conversion of methane over Ni-supported zeolite catalysts was investigated, and Ni-supported USY-type zeolite (Si/Al2 = 14.0, 360) was found to have longer catalytic lifetime than Ni-supported silica (Cab-O-Sil) catalyst, which had been reported to have the longest catalytic lifetime for this reaction.
TL;DR: In this paper, Na-Mn-W/SiO2 catalysts were prepared and their catalytic performance for oxidative coupling of methane (OCM) was evaluated in a stainless-steel microreactor at elevated pressure.
Abstract: Na-Mn-W/SiO2 catalysts were prepared and their catalytic performance for oxidative coupling of methane (OCM) was evaluated in a stainless-steel microreactor at elevated pressure. The results show that a CH4 conversion of 15.1% with a C2+ selectivity of 71.8% was obtained under 750oC, 1.0×105h-1 GHSV, CH4/O2 ratio of 8 and 1.0 MPa. Moreover, 17.3% CH4 conversion with 51.6% C2 selectivity and 23.6% C3-C4 selectivity was obtained under 750oC, 2.0×105h-1 GHSV, CH4/O2 ratio of 8 and 1.0 MPa.
TL;DR: Carrascull, Alfredo Lazaro as discussed by the authors, et al. as discussed by the authors presented a model for the study of the relationship between Quimica and Bioquimica, and the Instituto de Investigaciones en Tecnologia Quimicas.
Abstract: Fil: Carrascull, Alfredo Lazaro. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - San Luis. Instituto de Investigaciones en Tecnologia Quimica. Universidad Nacional de San Luis. Facultad de Quimica, Bioquimica y Farmacia. Instituto de Investigaciones en Tecnologia Quimica; Argentina
TL;DR: A comparative study of the three catalysts for the selective cyclodehydration of 1,4-butanediol to tetrahydrofuran was carried out in this article to understand the effect of their composition and morphology on the catalytic activity.
Abstract: Metal(IV) phosphates of tin, zirconium and titanium in different morphological forms, viz. amorphous, calcined and crystalline, have been used as catalysts for selective cyclodehydration of 1,4-butanediol to tetrahydrofuran. A comparative study of the three catalysts for the above reaction has been carried out to understand the effect of their composition and morphology on the catalytic activity.
TL;DR: In this paper, three kinds of Ru/CeO2 catalysts were prepared and the mobility of the oxygen on Ru and their catalytic activity in the wet oxidation of acetic acid was investigated.
Abstract: Three kinds of Ru/CeO2 catalysts were prepared. The mobility of the oxygen on Ru and their catalytic activity in the wet oxidation of acetic acid was investigated. Ru was present in the form of RuO2, and TPR experiment showed that the reaction, RuO2 + 2H2 → Ru + 2H2O, took place in different temperature ranges depending upon the kind of the catalysts. The catalyst with easily reducible oxygen on Ru had high activity in wet oxidation, and the importance of the release of oxygen from Ru to the reactant was suggested.
TL;DR: In this paper, the activity of alumina-supported Cu-Cr and Co-Cr oxide catalysts in CO and C6H6 oxidation with both molecular and ozone-enriched oxygen was studied.
Abstract: The activity of alumina-supported Cu-Cr and Co-Cr oxide catalysts in CO and C6H6 oxidation with both molecular and ozone-enriched oxygen was studied. It was proved that the use of ozonized oxygen leads to a considerable decrease of the reaction temperatures.
TL;DR: In this article, the enthalpies of oxygen removal from the bulk of ceria and ceria-zirconia solid solutions were calculated using the semiempirical interacting bonds method.
Abstract: Semiempirical Interacting Bonds Method was used to calculate the enthalpies of oxygen removal from the bulk of ceria and ceria-zirconia solid solutions. The energy of the bulk reduction was obtained to agree reasonably with the experimental data when the complex defect comprised of the oxygen vacancy and interstitial oxygen atom surrounded by six cations was suggested to emerge due to an oxygen removal from the bulk. The zirconium cations dissolved in ceria affect the energies of the bulk reduction and bulk oxygen mobility due to a decrease in the local Me-O coordination number from 8 to 7.
TL;DR: In this paper, the surface energies and enthalpies of oxygen adsorption on the surface of ceria-based solid solutions were estimated using the semiempirical interacting bond method.
Abstract: Semiempirical Interacting Bonds Method (IBM) in the slab approximation with due regard to relaxation after the free surface formation was used to calculate the surface energies and enthalpies of oxygen adsorption on the surface of ceria-based solid solutions. The IBM-estimated surface energies agree well with the published values obtained using electrostatic models or the periodic ab initio Hartree-Fock code CRYSTAL. The most weakly bound forms of the surface oxygen appear to be located at the (111) face on the cerium cations which have complex defects of non-stoichiometry in the subsurface layer.
TL;DR: In this paper, it was shown that even after 6 h, ruthenium is not completely reduced and chlorine is still not completely eliminated in Ru/Al2O3 prepared from RuCl3.
Abstract: Increasing reduction time increases ruthenium reduction, but even after 6 h, ruthenium is not completely reduced and chlorine is not completely eliminated in Ru/Al2O3 prepared from RuCl3.
TL;DR: In this article, it has been established that carbon filaments consist of imperfect graphite layers and possess high adsorption capacity towards hydrogen, and it has also been shown that carbon can be deposited from chlorohydrocarbons on Ni(Co)/Al2O3.
Abstract: Morphology of carbons deposited from chlorohydrocarbons on Ni(Co)/Al2O3 has been investigated. It has been established that carbon filaments consist of imperfect graphite layers and possess high adsorption capacity towards hydrogen.
TL;DR: In this article, the enantioselective hydrogenation of ethyl pyruvate (EtPy) was studied in toluene and in acetic acid, under identical reaction conditions (H2pressure 1 bar, Pt-alumina catalyst E 4759, dihydrocinchonidine (DHCD) concentration 0.001-0.1 mmol/L).
Abstract: The enantioselective hydrogenation of ethyl pyruvate (EtPy) was studied in toluene and in acetic acid, under identical reaction conditions (H2pressure 1 bar, Pt-alumina catalyst E 4759, dihydrocinchonidine (DHCD) concentration 0.001- 0.1 mmol/L). The DHCD concentration necessary for achieving maximal enantioselectivity (i.e. 80% ee in toluene and 90% ee in acetic acid) is higher by one order of magnitude in toluene than in acetic acid. This relatively high difference suggests a difference in reaction mechanism. This study calls attention to the formation of new chiral surface sites via chemisorption of DHCD on platinum atoms and the possible role of such sites in enantioselection.
TL;DR: In this article, the effect of metal particle size on the selectivity to crotyl alcohol (SUOL) in the liquid phase hydrogenation of crotonaldehyde over SiO2 and a-Al2O3-supported Pt and Pt-Sn catalysts was investigated.
Abstract: The present work reports the effect of metal particle size on the selectivity to crotyl alcohol (SUOL) in the liquid phase hydrogenation of crotonaldehyde over SiO2 and a-Al2O3-supported Pt and Pt-Sn catalysts. It was demonstrated that, for the monometallic catalysts, a higher particle size led to a higher SUOL, while for the bimetallic catalysts, this effect was not so important.
TL;DR: In this paper, the effects of Cs+, H+ and Cu2+ counterions in vanadium containing heteropoly compounds CsxH1-xVO[PMo12O40] and CsyH0.5-yCu0.25VO [PMo 12 O40] on the catalytic oxidation of isobutane and characterization by TGA, IR and ESR spectroscopies are reported.
Abstract: Effects of Cs+, H+ and Cu2+ counterions in the vanadium containing heteropoly compounds CsxH1-xVO[PMo12O40] and CsyH0.5-yCu0.25VO[PMo12O40] on the catalytic oxidation of isobutane and characterization by TGA, IR and ESR spectroscopies are reported. A high selectivity of 76% for methacrylic acid and methacrolein together has been obtained with Cs0.75H0.25VO[PMo12O40] catalysts at a reactivity of 5.3x10-1 mmol/h cm3.
TL;DR: In this paper, a stoichiometric iron-molybdate has been prepared by coprecipitation and submitted to a long activity test to check the role of water in its deactivation behavior during methanol to formaldehyde oxidation.
Abstract: Stoichiometric iron-molybdate has been prepared by coprecipitation and submitted to a long activity test to check the role of water in its deactivation behavior during methanol to formaldehyde oxidation. Water retards the reoxidation of the catalyst which is responsible for the acceleration of its deactivation.