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1.	Ackelid, U, et al. (författare) Kinetics of ethylene oxidation on plane Pt/SiO2 catalysts in the viscous pressure regime: Evidence of support activity 1996 Ingår i: Catalysis Letters. - 1011-372X. ; 39:1-2, s. 129-139 Tidskriftsartikel (refereegranskat)abstract C2H4 oxidation on plane Pt/SiO2 model catalysts with various Pt loadings was studied at T = 373-473 K and in the pressure ranges 10-6-102 Torr C2H4 and 0.3-1500 Torr O2 (1 Torr = 133.3 Pa). Mass spectrometry combined with spatially resolved gas sampling enabled kinetic data to be collected far into the viscous pressure regime. Reaction orders and activation energies were similar to those of a macroscopic Pt surface. However, under fuel-lean conditions the global reaction rate decreases faster than the decrease in metal area. On the other hand, the global rate was independent of Pt loading and metal surface area in fuel-rich gas mixtures. This is interpreted in terms of a spillover effect.
2.	Andersson, Arne, et al. (författare) Ammoxidation of toluene over molybdenum oxides 1988 Ingår i: Catalysis Letters. - 1011-372X. ; 1:11, s. 377-383 Tidskriftsartikel (refereegranskat)abstract The ammoxidation of toluene was studied both in presence and absence of gaseous oxygen over MoO3 and in situ prepared Mo4O11 (orth.) and MoO2. Irrespective of the partial pressure of oxygen, total reaction rates decrease in the following order: MoO3 > Mo4O11 > MoO2. The corresponding sequence for the selectivity towards formation of benzonitrile was found to depend on the partial pressure of oxygen. In two phase samples, no synergistic effects were observed for the formations of nitrile and carbon oxides. A comparison of rates for selective and nonselective products obtained in presence of gaseous oxygen with those obtained in its absence yield information as to whether the various products are formed at identical or different crystal faces. In the case of MoO3, nitrile and carbon oxides were found to be competitively formed at the same faces, while over MoO2 they are formed at different faces. Both options seem to prevail on
3.	Arve, Kalle, et al. (författare) Did Chemisorption Become an Obsolete Method With Advent of Tem? Comparison of Mean Particle Size and Distribution of Silver on Alumina 2011 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 141:5, s. 665-669 Tidskriftsartikel (refereegranskat)abstract Silver particle size and dispersion on a Ag/Al2O3 for HC-SCR were examined by means of chemisorption and TEM. Experimental results showed that determination of the accurate mean particle size (mps) is challenging and that the both applied methods have specific characteristics increasing the inaccuracy in the results which has to be taken into account in evaluation of catalytic activity. The results from TEM imaging were found to depend highly on the mode in which the surface was scanned (bright field versus dark field). Generally the point resolution was higher in dark field but the obtained mps did not increased along with the increasing silver loading. The main limitation with the O-2-chemisorption was related to the choice of the stoichiometric factor between the adsorbent and silver atoms. However, together these techniques support each other and help to give a more realistic picture of the mean silver particle size, distribution and indications of the oxidation states on the alumina support.
4.	Auvray, Xavier, 1986, et al. (författare) Effect of enhanced support acidity on the sulfate storage and the activity of Pt/γ-Al2O3 for no oxidation and propylene oxidation 2014 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 144:1, s. 22-31 Tidskriftsartikel (refereegranskat)abstract NO oxidation and propylene oxidation were studied on standard and acidity-enhanced Pt/Al 2 O 3 catalyst. Deactivation by platinum oxide formation was suppressed by the presence of chlorine and sulfates. After a long SO 2 exposure, the activity of modified catalysts was higher than the standard catalyst. The aged chlorinated sample showed the best propylene oxidation activity while the sulfated one exhibited the best NO conversion. © 2013 Springer Science+Business Media New York.
5.	Berggrund, Malin, 1966, et al. (författare) Influence of Synthesis Conditions for ZSM-5 on the Hydrothermal Stability of Cu-ZSM-5 2009 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 130:1-2, s. 79-85 Tidskriftsartikel (refereegranskat)abstract The influence of syntheses parameters of zeolite ZSM-5 on the lean NO (x) reduction activity and hydrothermal stability of Cu-ZSM-5 has been investigated. The hydrothermal stability of Cu-ZSM-5 was found to depend on the aluminium source used and on the presence of Ca(OH)(2) in the synthesis mixture for ZSM-5.
6.	Brandin, Jan, 1958-, et al. (författare) Deactivation and Characterization of SCR Catalysts Used in Municipal Waste Incineration Applications 2018 Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 148:1, s. 312-327 Tidskriftsartikel (refereegranskat)abstract Catalysts used for selective catalytic reduction were deactivated for various times in a slipstream from a municipal solid waste incineration plant and then characterized. The activity for NO reduction with NH3 was measured. The Brunauer–Emmett–Teller surface areas were determined by N2 adsorption from which the pore size distributions in the mesopore region were obtained. Micropore areas and volumes were also obtained. The composition of fresh and deactivated catalysts as well as fly ash was determined by atomic absorption spectroscopy and scanning electron microscopy with energy dispersive X-ray analysis. The changes in surface area (8% decrease in BET surface area over 2311 h) and pore structure were small, while the change in activity was considerable. The apparent pre-exponential factor was 1.63 × 105 (1/min) in the most deactivated catalyst, compared to 2.65 × 106 (1/min) in the fresh catalyst, i.e. a reduction of 94%. The apparent activation energy for the fresh catalyst was 40 kJ/mol, decreasing to 27 kJ/mol with increasing deactivation. Characterization showed that catalytic poisoning is mainly due to decreased acidity of the catalyst caused due to increasing amounts of Na and K.
7.	Bratlie, Kaitlin M., et al. (författare) Compensation effect of benzene hydrogenation on Pt(111) and Pt(100) analyzed by the selective energy transfer model 2008 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 121:3-4, s. 173-178 Tidskriftsartikel (refereegranskat)abstract Kinetic measurements at low temperatures (310-360 K) using gas chromatography (GC) for benzene hydrogenation on Pt(100) and Pt(111) single crystal surfaces have been carried out at Torr pressures. These kinetic measurements demonstrated a linear compensation effect for the production of cyclohexane. A detailed application of the model of selective energy transfer to the experimentally obtained results yields the vibrational frequency of the adsorbate leading to reaction. This frequency is attributed to ring distortion modes. The vibrational frequency of the heat bath, or catalyst, is ascribed to a Pt-H mode. An approximate heat of adsorption of the reacting molecule is also calculated from the model.
8.	Carlsson, Per-Anders, 1972, et al. (författare) Methane oxidation over Pt/Al2O3 and Pd/Al2O3 catalysts under transient conditions 2007 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 115:1-2, s. 1-7 Tidskriftsartikel (refereegranskat)abstract We communicate experimental results for the oxidation of methane by oxygen over alumina supported Pd and Pt monolith catalysts under transient conditions. Temperature programmed reaction (TPReaction) and reactant pulse-response (PR) experiments have been performed, using a continuous gas-flow reactor equipped with a downstream mass spectrometer for gas phase analysis. Special attention was paid to the influence of gas composition changes, i.e., O 2 and H 2 pulsing, respectively, on the methane conversion. For Pt/Al 2 O 3 oxygen pulsing can significantly increase the methane conversion which can be even further improved by pulsing hydrogen instead. Such transient effects are not observed for the Pd/Al 2 O 3 catalyst for which instead constantly lean conditions is beneficial. Our results suggest that under lean conditions Pd and Pt crystallites may undergo bulk- and partial (surface oxide formation) oxidation, respectively, which for Pd results in more active surfaces, while for Pt the activity is reduced. The latter seems to connect to a lowering of the ability to dissociate methane. © 2007 Springer Science+Business Media, LLC.
9.	Dahl, Leif, et al. (författare) Catalytic behavior and characterization of (CuO)1-z(La2O3)z/2 based catalysts deposited on γ-Al2O3 and prepared in situ with 0.0≤z≤1.00 with and without addition of Pd 1996 Ingår i: Catalysis Letters. - 1572-879X .- 1011-372X. ; 37:1-2, s. 69-77 Tidskriftsartikel (refereegranskat)abstract (CuO)(1-z)(La2O3)(z/2) based catalysts with 0.0 less than or equal to z less than or equal to 1.0 supported on gamma-Al2O3 have been prepared in situ and the phases formed have been identified by XRD, SEM and TEM/EDS studies. The catalyst with z = 0.5 exhibited the best catalytic activity for oxidation of CO (T-50 = 295 and 390 degrees C with degrees of conversions of 93 and 92% at 450 degrees C under rich and lean conditions, respectively) and C3H6 (291 and 414 degrees C; 93 and 83%) and reduction of NO (405 degrees C; 60 and 0%). This catalyst contained appreciable amounts of the perovskite phase LaAl1-xCuxO3 and the enhanced catalytic properties are ascribed to the presence of this phase. Addition of Pd to this catalyst implied that the degree of conversion of NO increased and that the light-off temperatures for all involved gas species decreased. Ageing experiments revealed that LaAl1-xCuxO3 decomposed and that Cu containing Pd particles were formed during this procedure which in turn deteriorated the catalytic properties of the catalyst.
10.	Erkfeldt, Sara U, 1974, et al. (författare) Promoting Effect of Triglyme on Lean NOx Reduction Over Ag/Al2O3 2012 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 142:2, s. 183-189 Tidskriftsartikel (refereegranskat)abstract The highly oxygenated hydrocarbon triethylene glycol dimethyl ether or triglyme (CH3O-(C2H4O-)(3)CH3) was found to efficiently reduce NOx under lean conditions over Ag/Al2O3, but gave a low NOx conversion over Cu-ZSM-5. Furthermore, triglyme showed an extraordinary promoting effect when added together with propene as reducing agent for NOx over Ag/Al2O3 at low temperature. This is most likely due to that triglyme promotes the activation of propene.
11.	Eta, Valerie, et al. (författare) The Effect of Alkoxide Ionic Liquids on the Synthesis of Dimethyl Carbonate from CO2 and Methanol over ZrO2-MgO 2011 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 141:9, s. 1254-1261 Tidskriftsartikel (refereegranskat)abstract The use of carbon dioxide in the synthesis of chemicals, such as dimethyl carbonate (DMC), constitutes an environmentally attractive alternative to hazardous and toxic reagents. However, the direct synthesis of DMC from methanol and CO2 is characterized by low yields due to the reaction equilibrium and the thermodynamic limitations (Delta G(298K)(0) = + 26.3 kj/mol). Alkoxide ionic liquids possessing alkylimidazolium and benzalkonium cations were prepared, characterised and tested together with ZrO2-MgO catalyst for the synthesis of DMC from methanol and CO2. By using the novel ionic liquid as additives, ca. 12% conversion of methanol, and 90% selectivity to DMC was obtained at 120 A degrees C and 7.5 MPa. The water abstracting potential of the ionic liquids influenced the conversion of methanol and the selectivity to DMC. The alkoxide ionic liquids were recovered and reused in DMC synthesis without loss in activity and selectivity.
12.	Fornander, H., et al. (författare) Oxidation of carbon monoxide and deuterium on a Pd (100) film 1999 Ingår i: Catalysis Letters. - 1011-372X .- 1572-879X. ; 59, s. 107-113 Tidskriftsartikel (refereegranskat)abstract For Pd/MgO(100) pre-exposed to oxygen, the catalytic oxidation of CO and D2, respectively, has been studied in the temperature range 100–300 _C. At temperatures >200 _C, the CO2 desorption rate is independent of oxygen coverage, _O, and the reactive sticking coefficient for CO is close to unity. The D2O desorption rate is strongly dependent on _O. D2 adsorption is blocked by adsorbed oxygen and the maximum D2O desorption rate is reached when almost all oxygen has been consumed (_O < 0:03). The formation of an oxygen c(2 _ 2) structure, coexisting with the initial p(2 _ 2) phase, is reflected in the oxidation rates.
13.	Fridell, Erik, 1963, et al. (författare) The Mechanism for NOx Storage 2000 Ingår i: Catalysis Letters. - 1572-879X .- 1011-372X. ; 66:1-2, s. 71-74 Tidskriftsartikel (refereegranskat)abstract The mechanisms for storing of NOx in platinum-barium-alumina catalysts during lean-rich transients are investigated. Oxidation of NO to NO2 is found to be an important step. NO2 is found to be important for oxidation of the catalyst or of nitrites to form nitrates. NOx is then stored in the form of surface nitrates. FTIR studies show no formation of bulk nitrates in these experiments.
14.	Grasselli, R. K., et al. (författare) Inhibition of propylene oxidation to acrylic acid by amorphous overlayers on MoV(Nb)TeO based M2 catalysts 2008 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 126:3-4, s. 231-240 Tidskriftsartikel (refereegranskat)abstract One of the most effective catalysts for the selective oxidation of propane to acrylic acid (AA) and ammoxidation to acrylonitrile (AN) is the MoV(Nb,Ta)(Te,Sb)O system, comprised of two phases, with M1 the major catalyst and M2 the co-catalyst in symbiosis with M1, converting intermediately formed propylene to the respective desired end products. An improvement in either phase should enhance the overall desired yields of a combined M1/M2 conglomerate. The current study concentrates on the M2 phase (variously substituted and/or doped) where depending on composition and preparation technique crystalline materials or crystalline materials with amorphous overlayers are obtained. Crystalline M2 catalysts without amorphous overlayers are vastly superior to those encumbered with overlayers. In a comparative study the former give a maximum AN yield of 45% in propylene ammoxidation, the latter 24%. In the selective oxidation of propylene to acrylic acid, the difference in performance between the two types of catalysts becomes enormous: The crystalline M2 catalyst gives a maximum AA yield of 34% while the Te–molybdate overlayered M2 a meager 3%. Doping of crystalline M2 phase with P significantly enhances AA yields over the base and should be seriously considered in future attempts to improve M1/M2 propane/propylene catalyst systems.
15.	Guo, X. W., et al. (författare) Shape-selective methylation of 4-methylbiphenyl to 4,4 '-dimethylbiphenyl over zeolite HZSM-5 modified with metal oxides of MgO, CaO, SrO, BaO, and ZnO 2003 Ingår i: Catalysis Letters. - 1011-372X .- 1572-879X. ; 87:02-jan, s. 25-29 Tidskriftsartikel (refereegranskat)abstract A series of ZSM-5 samples modified with metal oxides MO(M = Mg, Ca, Sr, Ba and Zn) were employed for the alkylation of 4-methylbiphenyl (4-MBP) with methanol to 4,4'-dimethylbiphenyl (4,4'-DMBP) under fixed-bed down-flow conditions. The methylation results showed that the use of basic metal oxides can effectively enhance the selectivity to the target product 4,4'-DMBP. MgO is the most effective modifier among the metal oxides used and it can improve selectivity to 4,4'-DMBP up to 80% as compared to only 13% over the parent zeolite HZSM-5. The modi. cation effectiveness of metal oxides on 4,4'-DMBP selectivity can be arranged in the order MgO> SrO similar to ZnO similar to CaO> BaO. The optimization of MgO modi. cation through the content, salt types and loading methods revealed that proper MgO loading (5.6 wt%) can be more effective, and the impregnation method is much better than ion exchange. The correlation of physicochemical properties (TPD, TGA, chemical analysis and chemical adsorption, etc.) of the modified HZSM-5 with the catalytic data showed that the high selectivity over ZSM-5 modified with MgO largely results from the effective suppression of 4,4'-DMBP secondary reactions such as isomerization, dealkylation and alkylation.
16.	Hakimioun, Amir H., et al. (författare) Theoretical Investigation of the Size Effect on the Oxygen Adsorption Energy of Coinage Metal Nanoparticles 2021 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 151:11, s. 3165-3169 Tidskriftsartikel (refereegranskat)abstract This study evaluates the finite size effect on the oxygen adsorption energy of coinage metal (Cu, Ag and Au) cuboctahedral nanoparticles in the size range of 13 to 1415 atoms (0.7–3.5 nm in diameter). Trends in particle size effects are well described with single point calculations, in which the metal atoms are frozen in their bulk position and the oxygen atom is added in a location determined from periodic surface calculations. This is shown explicitly for Cu nanoparticles, for which full geometry optimization only leads to a constant offset between relaxed and unrelaxed adsorption energies that is independent of particle size. With increasing cluster size, the adsorption energy converges systematically to the limit of the (211) extended surface. The 55-atomic cluster is an outlier for all of the coinage metals and all three materials show similar behavior with respect to particle size.
17.	Hansen, Staffan, et al. (författare) Ammoxidation of Toluene over Y-Ba-Cu-Co-O Perovskites 1990 Ingår i: Catalysis Letters. - 1011-372X. ; 6:1, s. 33-42 Tidskriftsartikel (refereegranskat)abstract mmoxidation of toluene over the perovskites YBa2Cu3O6.1, YBa2Cu2CoO6.7 and YBaCuCoO4.9 was investigated at 400 °C. At low partial pressures of O2 benzonitrile was selectively formed, while CO2 was the main product at high pressures of O2. Systematic differences in activity were observed for the three phases and are related to the crystal contents of Cu and Co. At low O2 pressures, Cu-sites are active for nitrile formation, while Co-sites give CO2. At high O2 pressures, the activity for CO2 of Cu-sites increases more than that of Co-sites due to filling of near-surface oxygen vacancies.
18.	Hinz, A, et al. (författare) Influence of Pt loading on Al2O3 for the low temperature combustion of methanol with and without a trace amount of ammonia 2002 Ingår i: Catalysis Letters. - 1011-372X. ; 78:1-4, s. 177-183 Tidskriftsartikel (refereegranskat)abstract Pt/Al2O3 catalysts with platinum contents of 0.1, 1.0 and 3.0 wt% were used for the low temperature combustion of methanol in the absence and the respective presence of a trace amount of ammonia. It is observed that ammonia inhibits the combustion of methanol, which is due to competition between methanol and ammonia for the same sites. For a fixed space velocity and without ammonia in the gas, the performances of the catalysts increase up to a Pt loading of 1.0 wt%. In the presence of ammonia, however, no upper limit of performance is observed with increased Pt content. The results are discussed in terms of both Pt-support interface and the Pt surface being active.
19.	Huber, Florian, et al. (författare) Remarks on the passivation of reduced Cu-, Ni-, Fe-, Co-based catalysts 2006 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 110:3-4, s. 211-220 Tidskriftsartikel (refereegranskat)abstract Catalysts containing metals such as Cu, Ni, Fe, Co in their reduced state are often subjected to passivation procedures prior to characterization. Passivation with N2O or O-2 to create a protective oxide layer also results in a certain degree of sub-surface oxidation. The heat released during oxidation is a critical parameter. The extent of bulk oxidation depends on the type of oxidant as well as on the size of the metal particles, as shown for copper catalysts. The final, meta-stable passivation layer requires a certain thickness to sustain exposure to ambient atmosphere. The encapsulation of metal particles in carbon is an efficient method for preserving the metallic state, as demonstrated for metallic nickel and iron with carbon nanofibers. The use of passivated samples for characterization of the active, i.e., reduced, catalyst has limited value.
20.	Hultquist, Gunnar, et al. (författare) Reply to Lars O. Werme et al. : "Comments on 'Water Corrodes Copper'" 2010 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 135:3-4, s. 167-168 Tidskriftsartikel (refereegranskat)
21.	Hultquist, Gunnar, et al. (författare) Water Corrodes Copper 2009 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 132:3-4, s. 311-316 Tidskriftsartikel (refereegranskat)abstract According to a current concept, copper canisters of thickness 0.05 m will be safe for nuclear waste containment for 100,000 years. We show that more than 1 m copper thickness might be required for 100,000 years durability based on water exposures of copper for 20 h, 7 weeks, 15 years, and 333 years. An observed evolution of hydrogen which involves heterogeneous catalysis of molecular hydrogen, first principles simulations, thermodynamic considerations and corrosion product characterization provide further evidence that water corrodes copper resulting in the formation of a copper hydroxide. These findings cast additional doubt on copper for nuclear waste containment and other important applications.
22.	Härelind Ingelsten, Hanna, 1973, et al. (författare) Mechanistic Study of Lean NO2 Reduction by Propane Over HZSM-5 in the Presence of Water 2006 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 106:1-2, s. 15-19 Tidskriftsartikel (refereegranskat)abstract This study focuses on the mechanism of lean NO2 redn. by propane in the presence of water, over an acidic zeolite (HZSM-5). Fourier Transform IR spectroscopy measurements with NO2 and propane in excess oxygen show formation of surface bound NO+, isocyanate, unsatd. hydrocarbons and traces of amine species. Upon addn. of water the isocyanate species disappear and amine species are formed. Hence, it seems likely that the isocyanate species are hydrolyzed to amine species, which are possible reaction intermediates in the HC-SCR reaction over HZSM-5.
23.	Janson, Caroline, 1988, et al. (författare) Improved Oxygen Reduction Activity of Transition Metal-Chelating Ordered Mesoporous Carbon Fuel Cell Catalysts by Milder Template Removal 2019 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 149:5, s. 1297-1304 Tidskriftsartikel (refereegranskat)abstract In the synthesis of iron-chelating ordered mesoporous nitrogen-functionalized carbon (Fe–OMC) catalysts, the removal of the silica template is a crucial and critical step. The silica removal method used today for the Fe–OMCs is based on the very toxic hydrofluoric acid (HF), which usage should be limited where possible. Therefore, the aim of this study is to establish a mild (user-friendly), yet efficient, etch method based on dilute sodium hydroxide (NaOH), which does not impair the catalytic performance of the catalyst, to replace the currently used HF method. A comparison between catalysts etched with HF versus NaOH was performed in order to gain understanding how the two etch methods influence the final catalysts in terms of electrochemical, structural and catalytic properties. The NaOH etch was found to successfully remove the silica template, and interestingly, also improve the catalytic performance. The improved activity is explained by a carbon activation process occurring in the catalyst treated with the NaOH etch. With these findings, we show that it is possible to remove the silica in a more user-friendly way and simultaneously increase the catalysts’ performance by activation of the carbon. Graphical Abstract: [Figure not available: see fulltext.].
24.	Kamata, H, et al. (författare) Surface acid property and its relation to SCR activity of phosphorus added to commercial V2O5(WO3)/TiO2 catalyst 1998 Ingår i: Catalysis Letters. - 1011-372X. ; 53:1-2, s. 65-71 Tidskriftsartikel (refereegranskat)abstract To examine the influence of phosphorus on the commercial V2O5(WO3)/TiO2 SCR catalyst, measurements were carried out by means of infrared and Raman spectroscopy, XPS, and NO reduction measurement as a function of phosphorus loading. Phosphorus added to the catalyst was found to disperse well over the catalyst without a significant agglomeration up to 5 wt% P2O5 addition. The number of the hydroxyl groups bonded to the vanadium and titanium species decreased readily with increasing amount of phosphorus. Correspondingly the hydroxyl groups bonded to the phosphorus species were formed. NH3 adsorbed on both hydroxyl groups bonded to vanadium and phosphorus as ammonium ions, implying that the P-OH groups formed are also responsible for the Bronsted acidity. The NO reduction activity was found to be decreased with increasing amount of phosphorus; however, the influence of phosphorus was relatively small irrespective of the large amount of phosphorus addition. The deactivation might be caused by the change in the nature of the surface hydroxyl groups as Bronsted acid sites. Phosphorus species might partially wrap the surface V=O and W=O groups, which might also contribute to the deactivation.
25.	Keane, Mark A., et al. (författare) Application of the Selective Energy Transfer Model to Account for an Isokinetic Response in the Gas Phase Reductive Cleavage of Hydroxyl, Carbonyl and Carboxyl Groups from Benzene Over Nickel/Silica 2009 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 129:1-2, s. 93-103 Tidskriftsartikel (refereegranskat)abstract The gas phase hydrodeoxygenation of a series of aromatic alcohols, aldehydes and acids has been examined over Ni/SiO2. Compensation behaviour is established with an isokinetic temperature (518 +/- A 21 K) that is consistent with with the point of intersection of the Arrhenius lines. This is accounted for using the Selective Energy Transfer model that is based on resonance between the catalytic Ni-H vibration and out-of plane C-H vibrations of the aromatic reactants with a transferral of resonance energy from the catalyst to generate the "activated complex". The calculated wave number of this vibration mode is 720 +/- A 29 cm(-1) with an associated anhamonicity of -3.3 +/- A 0.9 cm(-1). Our analysis suggests that the oxygenated aromatic is weakly adsorbed on the catalyst and surface mobility facilitates reaction with adsorbed hydrogen atoms.
26.	Leistner, Kirsten, 1984, et al. (författare) Ammonia Desorption Peaks Can Be Assigned to Different Copper Sites in Cu/SSZ-13 2017 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 147:8, s. 1882-1890 Tidskriftsartikel (refereegranskat)abstract The purpose of this study is to attribute NH 3 -TPD peaks observed over Cu/SSZ-13 catalysts to different catalytic sites. This is done by comparing a large number of copper loadings, especially below 40% ion exchange, to be able to see effects relevant to sites in both 6-membered and 8-membered rings. We found that intermediate (200–300 °C) and high (400–500 °C) temperature NH 3 -TPD peaks followed similar trends to the copper species in 6-membered and 8-membered rings respectively, as seen by H 2 -TPR and NO-DRIFTS. Thus we propose that these two TPD peaks represent ammonia stored on H and Cu sites in 6 and 8-membered rings, respectively. This assignment is further supported by the finding that the intermediate and high temperature NH 3 -TPD peaks of samples with different Si/Al ratios also follow the same trend. Moreover, we observe that the activation energy for ammonia oxidation is significantly lower for Cu in 6MR compared to Cu in 8MR rings. Graphical Abstract: [Figure not available: see fulltext.].
27.	Lindström, B., et al. (författare) Deactivation of copper-based catalysts for fuel cell applications 2001 Ingår i: Catalysis Letters. - 1011-372X .- 1572-879X. ; 74:02-jan, s. 27-30 Tidskriftsartikel (refereegranskat)abstract The activity of copper catalysts for the steam reforming of methanol was investigated under deactivating conditions. The effects of adding poisonous substances which can occur in the fuel, such as sulphur and chlorine, were studied. Thermal ageing by sintering was observed while exposing the catalyst to high temperatures. The catalyst activity for steam reforming was greatly affected by the addition of low concentrations of sulphur and chlorine. Sulphur was more detrimental to the catalyst than chlorine.
28.	Martynova, Y., et al. (författare) CO Oxidation Over Monolayer Manganese Oxide Films on Pt(111) 2013 Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 143:11, s. 1108-1115 Tidskriftsartikel (refereegranskat)abstract Ultrathin manganese oxide films grown on Pt(111) were examined in the low temperature CO oxidation reaction at near atmospheric pressures. Structural characterization was performed by X-ray photoelectron spectroscopy, Auger electron spectroscopy, high-resolution electron energy loss spectroscopy, and temperature programmed desorption. The results show that the reactivity of MnOx ultrathin films is governed by a weakly bonded oxygen species, which may even be formed at low oxygen pressures (similar to 10(-6) mbar). For stable catalytic performance at realistic conditions the films required highly oxidizing conditions (CO:O-2 < 1:10), otherwise the films dewetted, ultimately resulting in the catalyst deactivation. Comparison with other thin films on Pt(111) shows, that the desorption temperature of weakly bonded oxygen species can be used as a benchmark for its activity in this reaction.
29.	Mihai, Oana, 1975, et al. (författare) The Effect of NO2/NOx Feed Ratio on the NH3-SCR System Over Cu–Zeolites with Varying Copper Loading 2014 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 144:1, s. 70-80 Tidskriftsartikel (refereegranskat)abstract In this study we examine the NO/NO2–NH3-SCR system over Cu–BEA with varying Cu loading. Significantly higher selective catalytic reduction (SCR) activity is observed at low temperature on highly loaded copper samples, whereas the reverse trend is noticed at high temperature. The N2O formation is substantially increased over “over-exchanged” Cu sites, where Cu co-ordinate to one Al and charge-balanced with one OH-group. This is also the case for NO2 reaction with NH3 to produce NO. Using transient experiments the formation/decomposition of ammonium nitrate species are examined. The decomposition depends on the temperature, the sequence of the feed as well as the type of copper species present.
30.	Nilsson, Marita, et al. (författare) Effect of Mn addition to CeO2-ZrO2-supported Rh and Ru catalysts on the activity for diesel reforming Ingår i: Catalysis Letters. - 1011-372X .- 1572-879X. Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
31.	Nilsson, Roland, et al. (författare) Ammoxidation of Propene over Antimony-Vanadium-Oxide Catalysts 1994 Ingår i: Catalysis Letters. - 1011-372X. ; 29, s. 409-420 Tidskriftsartikel (refereegranskat)abstract Antimony-vanadium-oxide catalysts were prepared with various Sb/V ratios and were used for propene ammoxidation. It was observed that antimony in excess of the amount required for forming SbVO4 was required to have a catalyst that is selective to acrylonitrile formation. Characterisation of catalysts with FTIR revealed partial reduction of the oxidised phase Sb0.92V0.92O4 upon use to form Sb0.95V1.05O4. XPS data showed the surfaces of most selective catalysts to be further enriched with antimony in course of the catalytic reaction, thereby creating a surface structure that is selective. For acrylonitrile formation a yield of 55% was obtained at 90% of conversion. In propene oxidation, on the other hand, the yield for acrolein formation was limited to 20% due to consecutive combustion of the aldehyde.
32.	Norberg, P, et al. (författare) Hydrogen-induced CO2 formation from ethylene deposits on Pt during consecutive O-2 and H-2 exposures 2000 Ingår i: Catalysis Letters. - 1011-372X .- 1572-879X. ; 65:1-3, s. 25-31 Tidskriftsartikel (refereegranskat)abstract The oxidation of C2H4 deposits on polycrystalline Pt when exposed to consecutive O-2 and H-2 pulses at room temperature has been investigated in a long (L=36 mm), shallow (d=600-700 nm) micromachined glass-SiO2-Pt channel. Hydrogen-induced CO2 formation from species accumulated on the Pt surface was observed. Frequent switching of the O-2/H-2 exposure pulses was found to increase the efficiency of the oxidation of the carbonaceous deposits markedly. The observations may be of general interest for the regeneration of contaminated catalysts.
33.	Nuri, Ayat, et al. (författare) Pd Nanoparticles Stabilized on the Cross-Linked Melamine-Based SBA-15 as a Catalyst for the Mizoroki–Heck Reaction 2022 Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 152, s. 991-1002 Tidskriftsartikel (refereegranskat)abstract Mesoporous SBA-15 silicate with a high surface area was prepared by a hydrothermal method, successively modified by organic melamine ligands and then used for deposition of Pd nanoparticles onto it. The synthesized materials were characterized with infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen physisorption, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP-OES). The catalyst was effectively used in the Mizoroki–Heck coupling reaction of various reactants in the presence of an organic base giving the desired products in a short reaction time and with small catalysts loadings. The reaction parameters such as the base type, amounts of catalyst, solvents, and the temperature were optimized. The catalyst was easily recovered and reused at least seven times without significant activity losses. Graphic Abstract: [Figure not available: see fulltext.]
34.	Nuri, Ayat, et al. (författare) Pd Supported IRMOF-3 : Heterogeneous, Efficient and Reusable Catalyst for Heck Reaction 2019 Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 149:7, s. 1941-1951 Tidskriftsartikel (refereegranskat)abstract IRMOF-3 with a high surface area prepared by a hydrothermal method was used for deposition of Pd(OAc)(2) on IRMOF-3 particles. The final catalyst was characterized with FT-IR, nitrogen physisorption, thermogravimetry, scanning electron microscopy, transmission electron microscopy combined with energy dispersive X-ray analysis, wide angle X-ray diffraction spectroscopy and X-ray photoelectron spectroscopy. The prepared porous catalyst was effectively used in the Heck coupling reaction in the presence of an organic base. The reaction parameters such as the type of base, amounts of catalyst and solvents, temperature were optimized. The catalyst was then easily separated, washed, and reused 4 times without significant losses of catalytic activity. [GRAPHICS] .
35.	Nuri, Ayat, et al. (författare) Synthesis and Characterization of Palladium Supported Amino Functionalized Magnetic-MOF-MIL-101 as an Efficient and Recoverable Catalyst for Mizoroki–Heck Cross-Coupling 2020 Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 150:9, s. 2617-2629 Tidskriftsartikel (refereegranskat)abstract Magnetic particles were prepared by a hydrothermal method and then successively covered by Metal–Organic-Frameworks MIL-101-NH2 with a high surface area. This was followed by deposition of Pd(OAc)2 on Fe3O4–NH2@MIL-101-NH2 particles. The final catalyst was characterized with FT-IR, nitrogen physisorption, thermogravimetry (TGA), scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), wide-angle X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS). The prepared magnetic catalyst was effectively used in the Heck coupling reaction in the presence of an inorganic base. The reaction parameters such as the base type, amounts of catalyst and solvents, temperature, and substrates ratios were optimized. The catalyst was then magnetically separated, washed, and reused 7 times without losing significantly catalytic activity.
36.	Odenbrand, C. U.Ingemar (författare) Penetration of Poisons Along the Monolith Length of a V2O5/TiO2 Diesel SCR Catalyst and Its Effect on Activity 2019 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 149:12, s. 3476-3490 Tidskriftsartikel (refereegranskat)abstract Abstract: Catalysts used for selective catalytic reduction of NOx on diesel engines were deactivated for 890 and 2299 h in the exhausts from a diesel engine running on Swedish diesel fuel mark 1. The deactivated catalytic monoliths (100 mm long) were cut in 10 mm pieces along their axis and were characterized by physicochemical methods as well as by determination of the activity in the reduction of NOx by NH3 and in the oxidation of NH3 by O2.
37.	Omojola, Oluwatoyin, 1988, et al. (författare) Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts 2018 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 148:1, s. 474-488 Tidskriftsartikel (refereegranskat)abstract The desorption of methanol and dimethyl ether has been studied over fresh and hydrocarbon-occluded ZSM-5 catalysts with Si/Al ratios of 25, 36 and 135 using a temporal analysis of products reactor. The catalysts were characterized by XRD, SEM, N2 physisorption and pyridine FT-IR. The crystal size increases with Si/Al ratio from 0.10 to 0.78 µm. The kinetic parameters were obtained using the Redhead method and a plug flow reactor model with coupled convection, adsorption and desorption steps. ZSM-5 catalysts with Si/Al ratios of 25 and 36 exhibit three adsorption sites (low, medium, and high temperature sites), while there is no difference between medium and high temperature sites at a Si/Al ratio of 135. Molecular adsorption on the low temperature site and dissociative adsorption on the medium and high temperature sites give a good match between experiment and the plug flow reactor model. The DME desorption activation energy was systematically higher than that of methanol. Adsorption stoichiometry shows that methanol and DME form clusters onto the binding sites. When non-activated re-adsorption is accounted for, a local equilibrium is reached only on the low and medium temperature binding sites. No differences were observed, other than in site densities, when extracting the kinetic parameters for fresh and activated ZSM-5 catalysts at full coverage.
38.	Parsland, Charlotte, et al. (författare) Ba-Ni-Hexaaluminate as a New Catalyst in the Steam Reforming of 1-Methyl Naphthalene and Methane Long-Term Studies on Sulphur Deactivation and Coke Formation 2020 Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 150, s. 1605-1617 Tidskriftsartikel (refereegranskat)abstract This work investigates the long-term performance of Ba-Ni-hexaaluminate, BaNixAl12-xO19 as a catalyst in reforming of 1-methyl naphthalene and/or methane in a model-gas simulating that from a circulating fluidized bed (CFB) gasifier during 23-29 h in a lab scale set-up, as well as the tendency for coke formation, sintering and sulphur poisoning. 1-Methyl naphthalene is used as a tar model substance. The Ba-Ni-hexaaluminate induces a high conversion of both compounds in the temperatures investigated (850 and 950 degrees C) under sulphur-free conditions. In sulphur-containing gas, the methane conversion stops at 20 ppm H2S and the reforming of 1-MNP at 850 degrees C is slightly reduced at 100 ppm.
39.	Paul, Jan, et al. (författare) Co2 conversion and oxalate stability on alkali promoted metal surfaces : sodium modified Al(100) 1988 Ingår i: Catalysis Letters. - 1011-372X .- 1572-879X. ; 1:12, s. 445-455 Tidskriftsartikel (refereegranskat)abstract CO2 conversion on alkali promoted metals in aprotic systems has been followed with surface sensitive spectroscopies. New results on sodium modified aluminum(100) are presented and compared with previous studies on magnesium [1], aluminum [2], and bulk alkali metals [3]. Electron energy loss spectra reveal two different states of CO2 adsorption at 100 K and monolayer sodium coverage. Vibrational bands at 650 cm-1 and 2325 cm-1 correspond to weakly bound molecular CO2 and a multitude of bands between 2300 cm-1 and 460 cm-1 to oxalate ions with low, possibly unidentate, coordination. Gentle annealing increases the coordination as apparent by vibrational shifts. This corresponds to oxalate to carbonate conversion, a process which is completed around room temperature. CO desorption was detected at 285 K and Auger measurements reveal a 1:3 C/O stoichiometry after high temperature annealing. We observe no release of CO2 above 110 K but an additional weak state of CO desorption around 470 K. High temperature annealing causes decomposition of all intermediates and leaves the aluminum surface covered with an irreducible carbide and oxide overlayer. We suggest that CO2 reduction and dimerization to C2O4 -2 is a common path to yield carbon deposition on all alkali promoted surfaces in hydrogen deficient systems. In contrast, oxalate decomposition is related to the specific chemistry of each substrate.
40.	Rownaghi, Ali, et al. (författare) Influence of rare-earth and bimetallic promoters on various VPO catalysts for partial oxidation of n-butane 2009 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 130:3-4 Tidskriftsartikel (refereegranskat)
41.	Rownaghi, Ali, et al. (författare) Influence of the ethylene glycol, water treatment and microwave irradiation on the characteristics and performance of VPO catalysts for n-butane oxidation to maleic anhydride 2009 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 130:3-4 Tidskriftsartikel (refereegranskat)
42.	Sa, Jacinto, et al. (författare) Heterogeneous Catalysis Experiments at XFELs. Are we Close to Producing a Catalysis Movie? 2014 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 144:2, s. 197-203 Tidskriftsartikel (refereegranskat)
43.	Sa, Jacinto, et al. (författare) Imaging of low temperature induced SMSI on Pd/TiO2 catalysts 2007 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 114:1-2, s. 91-95 Tidskriftsartikel (refereegranskat)
44.	Sadokhina, Nadezda, 1985, et al. (författare) An Experimental and Kinetic Modelling Study for Methane Oxidation over Pd-based Catalyst: Inhibition by Water 2017 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 147:9, s. 2360-2371 Tidskriftsartikel (refereegranskat)abstract The water inhibition of methane oxidation over a bimetallic Pt-Pd on CeO2-Al2O3 catalyst was investigated and the experimental data were used to develop a kinetic model, consisting of only three reaction steps. In the model, the water effect was assigned to the adsorption of H2O on surface sites, as well as to the formation and accumulation of surface hydroxyl groups. These two effects were accounted by the model, which could well describe the experimental data obtained under various conditions.
45.	Shwan, Soran, 1984, et al. (författare) Effect of thermal ageing on the nature of iron species in Fe-BEA 2013 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 143:1, s. 43-48 Tidskriftsartikel (refereegranskat)abstract The adsorption of NH3 and NO over fresh and thermally treated Fe-BEA catalysts were studied using in situ DRIFT spectroscopy to follow the evolution of different iron species before and after thermal treatment. Fe-BEA samples were prepared and thermally treated in air at 700 °C for 12, 24 and 48 h, and at 800 and 900 °C for 48 h. Compared to the fresh sample, the NH3 adsorption experiments indicate dealumination of the zeolite and iron oxide particle growth for the aged samples. Furthermore, the NO adsorption experiments show distinct absorption peaks which are assigned to isolated iron species, iron clusters and larger iron oxide particles. The thermally treated samples show migration of isolated iron species from the zeolite pores forming iron oxide particles. Further ageing results in a continuous migration and formation of larger iron oxide particles located on the external surface of the zeolite.
46.	Skoglundh, Magnus, 1965, et al. (författare) Characterization of a Pt-Pd combustion catalyst on an alumina washcoat, with and without prior hydrothermal treatment of the washcoat 1992 Ingår i: Catalysis Letters. - 1572-879X .- 1011-372X. ; 13:1-2, s. 27-38 Tidskriftsartikel (refereegranskat)abstract Two Pt/Pd catalysts on cordierite monoliths were prepared by impregnating two differently treated alumina washcoats with 10/micromol [Pt + Pd] per gram catalyst in the atomic ratio Pt/Pd = 4.0. Both washcoats were first thermally treated, calcined, for 2 h at 550C in air and one of them was additionally treated, hydrothermally, in 100% steam for 2 h at 814C. The hydrothermally treated catalyst was more active for complete oxidation of xylene in air:its light-off temperature was 232C compared to 259C for the sample calcined only. To explain this higher activity, both catalysts were characterized by BET surface area, pore-size distribution, hydrogen chemisorption, X-ray diffraction, TEM/STEM/EDS and low-energy ion scattering spectroscopy (LEIS). The catalyst with a hydrothermally treated washcoat had 30% lower surface area, larger alumina crystal size, higher degree of crystallization ofalumina and larger average catalyst pore size (11 nm vs. 6 nm), than the one with the washcoat, treated only thermally. The LEIS results indicated a surface enrichment of Pd on both catalysts. The Pt signal in LEIS was higher for the hydrothermally treated sample.
47.	Tamm, Stefanie, 1975, et al. (författare) DME as reductant for continuous Lean Reduction of NOx over ZSM-5 Catalysts 2008 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 123:3-4, s. 233-238 Tidskriftsartikel (refereegranskat)abstract Dimethyl ether (DME) is an interesting alternativefuel to diesel, but is not an efficient reductant inlean NOx conversion over typical diesel HC-SCR catalysts.Comparatively high deNOx activity was found overH-ZSM-5 in the presence of water, giving reduction of28% NO and 37% NO2 respectively with a DME/NOxratioof 4.
48.	Tamm, Stefanie, 1975, et al. (författare) Influence of Gas Phase Reactions on DME-SCR over gamma-alumina 2011 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 141:5, s. 656-664 Tidskriftsartikel (refereegranskat)abstract Above 300 A degrees C, gas phase reactions occur between dimethyl ether (DME), NO and O-2 generating NO2. The influence of these reactions on DME-SCR was studied in a setup that decoupled the occurrence of gas phase reactions from catalyst temperature. NOx conversion decreased at 350 A degrees C and increased at 250 A degrees C due to less DME available and higher NCO conversion with NO2, respectively.
49.	Tamm, Stefanie, 1975, et al. (författare) Silver as Storage Compound for NOx at Low Temperatures 2014 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 144:4, s. 674-684 Tidskriftsartikel (refereegranskat)abstract High loaded silver/alumina (16 wt%) was found to be suitable as a temporary NOx trap under cold start, so called passive NOx storage. High amounts of NOx can be stored in the presence of H-2 on this material below 200 degrees C and released below 400 degrees C under lean conditions or under rich conditions at adsorption temperature.
50.	Tamm, Stefanie, 1975, et al. (författare) The Effect of Hydrogen on the Storage of NOx Over Silver, Platinum and Barium Containing NSR Catalysts 2014 Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 144:7, s. 1101-1112 Tidskriftsartikel (refereegranskat)abstract Addition of hydrogen significantly increases the amount of stored nitrogen oxides (NOx) over Pt/Ba/Al2O3 at 100 A degrees C and Ag/Al2O3 between 100 and 200 A degrees C. This increase is unique for hydrogen as reductant. A higher apparent NOx storage capacity is also observed by simultaneous reduction of NO in a selective catalytic reduction (SCR) reaction, where, however, the conversion in H-2-SCR is

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