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Pt catalysts supported on the commonly used supports Al2O3, SiO2 and on mesostructured silicates SBA-15 and MCM-48 were examined in the dehydrogenation of decalin, that is the promising liquid organic hydrogen carrier (LOHC). Synthesized catalysts were studied by low-temperature nitrogen adsorption, temperature programmed reduction, high-resolution transmission electron microscopy. The catalysts are characterized by various dispersion of platinum. The activity of catalysts in decalin dehydrogenation decreases in the following order Pt/MCM-48 > Pt/SBA-15 > Pt/SiO2 > Pt/Al2O3. Pt/MCM-48 catalyst allows to release hydrogen in the decalin amount of 5.7 wt% and can be considered the promising LOHC hydrogen storage technology. [ABSTRACT FROM AUTHOR]

The performance of alumina supported unpromoted and cerium promoted nickel catalysts in CO2 methanation reaction was investigated. It was found that the activity of catalysts in CO2 methanation reaction at low reaction temperatures can be improved by the increase in nickel loading and introduction of cerium promoter. The catalysts showed high resistance for sintering and coking at high reaction temperatures. A few stages of catalysts deactivation by H2S in the methanation reaction carried out at 475 °C with the time on stream were identified. It was found that an introduction of H2S to the stream (8 ppm) did not induce rapid decrease of activity. Slight and then strong drop of CO2 conversion and simultaneously the loss of methane selectivity was observed after specific time, depending on the catalysts composition. Deactivation of catalysts was related to the nickel content and the presence of cerium. X-ray diffraction studies indicated small changes of crystallite size with the time on stream. Raman spectroscopy studies pointed out that deactivation of catalysts was not connected with formation of carbon deposits. An in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy studies showed that exposition of catalysts to the reaction mixture containing the traces of H2S led to the blocking of nickel active sites responsible for CO2 and H2 activation and successive transformation to carbonyl and formate species. [ABSTRACT FROM AUTHOR]

The adsorption of water, pyridine, CO and CO on a commercial γ-AlO and a commercial amorphous silica alumina (ASA) cracking catalyst are reinvestigated by means of FTIR spectroscopy. It is concluded that the real active hydroxyl groups on γ-AlO are those absorbing at 3790, 3770 and 3730 cm and that they are significantly acidic. The strongest Lewis acid sites are identified as Nuclear Magnetic Resonance (NMR)-silent (or still undetected) tricoordinated Al, becoming tetracoordinated when interacting with basic adsorbates. More than one pyridine molecule may adsorb over such highly coordinatively unsaturated sites at high pyridine vapour pressure. It has also been confirmed that the existence of Brønsted acid sites sufficiently strong to protonate pyridine on ASA is its intrinsic property, not due to coadsorbed water. A 'stuffed amorphous silica' model is proposed for low-alumina ASA, where part of Al ions compensate the charge in-balance due to the substitution of Al for Si in a silica-like tetrahedral framework. Interstitial Al occupy 4-, 5- or 6-coordination interstices in the amorphous silica-like framework as do alkali cations in 'stuffed silicas' aluminosilicates. Such 'interstitial' Al ions when located accidentally in opened interstices exposed at the surface play the role of strong Lewis sites. When these ions are located near a silanol group, they increase the Brønsted acidity of the terminal silanols by neutralizing the negative charge produced by their dissociation when interacting with bases. [ABSTRACT FROM AUTHOR]

γ-Alumina is widely used as an oxide support in catalysis, and palladium nanoparticles supported by alumina represent one of the most frequently used dispersed metals. The surface sites of the catalysts are often probed via FTIR spectroscopy upon CO adsorption, which may result in the formation of surface carbonate species. We have examined this process in detail utilizing FTIR to monitor carbonate formation on γ-alumina and zirconia upon exposure to isotopically labelled and unlabelled CO and CO. The same was carried out for well-defined Pd nanoparticles supported on AlO or ZrO. A water gas shift reaction of CO with surface hydroxyls was detected, which requires surface defect sites and adjacent OH groups. Furthermore, we have studied the effect of Cl synthesis residues, leading to strongly reduced carbonate formation and changes in the OH region (isolated OH groups were partly replaced or were even absent). To corroborate this finding, samples were deliberately poisoned with Cl to an extent comparable to that of synthesis residues, as confirmed by Auger electron spectroscopy. For catalysts prepared from Cl-containing precursors a new CO band at 2164 cm was observed in the carbonyl region, which was ascribed to Pd interacting with Cl. Finally, the FTIR measurements were complemented by quantification of the amount of carbonates formed via chemisorption, which provides a tool to determine the concentration of reactive defect sites on the alumina surface. [ABSTRACT FROM AUTHOR]

Catalyst deactivation is one of the major concerns in the production of substitute natural gas (SNG) via CO methanation. Catalysts in this application need to be active at low temperatures, resistant to polymeric carbon formation and stable at high temperatures and steam partial pressures. In the present work, a series of alumina-supported nickel catalysts promoted with Zr, Mg, Ba or Ca oxides were investigated. The catalysts were tested under low temperature CO methanation conditions in order to evaluate their resistance to carbon formation. The catalysts were also exposed to accelerated ageing conditions at high temperatures in order to study their thermal stability. The aged catalysts lost most of their activity mainly due to sintering of the support and the nickel crystallites. Apparently, none of these promoters had a satisfactory effect on the thermal resistance of the catalyst. Nevertheless, it was found that the presence of Zr can reduce the rate of polymeric carbon formation. [ABSTRACT FROM AUTHOR]

The aim of the work was to investigate the influence of support on the catalytic performance of Ni catalysts for the glycerol steam reforming reaction. Nickel catalysts (8 wt%) supported on AlO, ZrO, SiO were prepared by the wet impregnation technique. The catalysts' surface and bulk properties, at their calcined, reduced and used forms, were determined by ICP, BET, XRD, NH-TPD, CO-TPD, TPR, XPS, TEM, TPO, Raman, SEM techniques. The Ni/Si sample, even if it was less active for T <600 °C, produces more gaseous products and reveals higher H yield for the whole temperature range. Ni/Zr and Ni/Si catalysts facilitate the WGS reaction, producing a gas mixture with a high H/CO molar ratio. Ni/Si after stability tests exhibits highest values for total (70%) and gaseous products (45%) glycerol conversion, Y (2.5), S (80%), S (65%), H/CO molar ratio (6.0) and lowest values for S (31%), S (3.1%), CO/CO molar ratio (0.48) among all samples. The contribution of the graphitized carbon formed on the catalysts follows the trend Ni/Si ( I / I = 1.34) < Ni/Zr ( I / I = 1.08) < Ni/Al ( I / I = 0.88) and indicates that the fraction of different carbon types depends on the catalyst's support nature. It is suggested that the type of carbon is rather more important than the amount of carbon deposited in determining stability. It is confirmed that the nature of the support affects mainly the catalytic performance of the active phase and that Ni/SiO can be considered as a promising catalyst for the glycerol steam reforming reaction. [ABSTRACT FROM AUTHOR]

The abatement of dilute p-xylene (500 ppm) from a contaminated air stream (2 L min) by the non-thermal plasma in combination with an ozone decomposing catalyst (pelleted Mn/γ-AlO) was investigated. The reactor performance was evaluated in terms of p-xylene conversion, CO selectivity and ozone emission with and without external heating. Generally, the removal of p-xylene gradually increased with increasing the applied voltage from 16 to 22 kV (peak height). As the catalyst was used (i.e., packed inside the plasma active region), the reactor was able to remove ca. 82% of p-xylene at 22 kV, compared to 54% done by plasma alone. Under the same plasma-catalytic condition, the removal of p-xylene was successfully achieved ( ca. 96%) by heating up the reactor to 150 °C. Not only was the conversion improved, but also the mineralization of p-xylene was also enhanced considerably by the mild thermal heating, increasing the CO selectivity from ca. 41 to 59%. The ozone emission measurement showed that ozone formed in plasma was readily catalytically decomposed on Mn/γ-AlO at above 16 kV, even without external heating. As revealed by the reactor infrared thermographic images, the plasma-induced surface temperature of the catalyst was far higher than the external heating temperature (i.e., 150 °C), facilitating the catalytic degradation of ozone and reducing the formation of byproducts. Additionally, no organic compounds have been found on the spent catalyst, avoiding the possibility of catalyst deactivation during the course of experiment. [ABSTRACT FROM AUTHOR]

Methods of polystyrene beads producing with properties appropriate for catalyst and adsorbent synthesis have been investigated. Hierarchical silicalite-1 and Fe-silicalite-1 with zeolitic MFI structure, as well as three-dimensionally ordered titania, silica, alumina and zirconia have been prepared by hard-templating method using polystyrene beads. The materials were characterized by X-ray diffraction, scanning and transmission electron microscopies, low-temperature nitrogen adsorption technique and mercury porosimetry. Developed meso- and macroporous structure of the templated materials facilitated the supply of macromolecular reactants to the material surface and reduced the negative effect of byproduct deposition, resulting in favored advantages of the materials in a wide range of processes: hydroconversion of heavy oil, wet hydrogen peroxide oxidation of organic substrates in water, photocatalysis and gas chromatographic analysis. The obtained results of the material applications showed their potential attractiveness as catalysts and adsorbents. [ABSTRACT FROM AUTHOR]

Bimetallic Pd-Rh catalysts with precious metal loading of 0.2 wt% was prepared by incipient wetness impregnation of the support (γ-AlO or δ-AlO) with dual complex salt [Pd(NH)] [Rh(NO)]. Monometallic Pd and Rh catalysts as well as its mechanical mixture were used as the reference samples. All samples were exposed for in situ prompt thermal aging procedure, and characterized by EPR spectroscopy, UV-Vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. The nature of the support was found to have strong effect on high temperature stability of the samples. δ-AlO having non-uniform phase structure due to presence of θ-AlO and α-AlO traces causes the concentrating of rhodium near the interphase boundary, thus changing the mechanism of Rh bulk diffusion if compare with γ-AlO. No noticeable anchoring effects were observed for bimetallic Pd-Rh samples neither in terms of Rh bulk diffusion nor with regard to the Pd sintering. It has been found experimentally that phase transformation of γ-AlO at high temperatures does not play dramatic role for the deactivation of bimetallic Pd-Rh active species anchored to the electron-donor site of the support. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction of NO with NH was investigated over microstructured reactors based on Cu/AlO films deposited onto stainless steel microgrids. The catalytic activity results showed that these Cu/AlO films were more active and selective to produce N compared to the conventional catalysts in powder shape with the same copper loadings. The difference was explained by combined features provided by the microstructured catalysts such as the high acid character of the catalytic films, the high copper species dispersion, the nature of the metallic microreactor and its geometric configuration. [ABSTRACT FROM AUTHOR]

The promoting impact of potassium (0-1 wt% K) on nitrous oxide (NO) catalytic decomposition over Ir/AlO is investigated under both oxygen deficient and oxygen excess conditions. All samples were characterized by means of X-ray powder diffraction (XRD), temperature-programmed reduction (H-TPR), ammonia desorption (NH-TPD) and Fourier Transform Infrared Spectroscopy of pyridine adsorption (FTIR-Pyridine). The results reveal that the K-free Ir/AlO catalyst consists mainly of the IrO phase, exhibiting also significant Lewis acidity, which is gradually eliminated by the addition of K. Catalytic performance results showed that the deNO performance in the absence of O in the feed mixture is negatively affected upon increasing potassium loading. However, under oxygen excess conditions, a pronounced effect of K is observed. Although the catalytic performance of the un-doped catalyst is drastically hindered by the presence of O, the K-promotion notably prohibits the oxygen poisoning. The optimum deNO performance under oxygen excess conditions is obtained with potassium loading of 0.5 wt% K, which offers complete conversion of NO at 580 °C, instead of the corresponding 50 % NO conversion achieved with the un-modified sample. On the basis of characterization results, it was concluded that alkali-doping in combination with oxygen excess conditions are required towards the formation of active Ir entities. [ABSTRACT FROM AUTHOR]

Three HZSM-5 catalysts with different binders (alumina, silica, and clay) were evaluated for upgrading of pine pyrolysis vapors. All catalysts were based on the same HZSM-5 with silica to alumina molar ratio of 30. Experiments in micro-scale analytical Py-GCMS/FID showed that fresh catalysts with silica and clay produced predominantly aromatic hydrocarbons at similar carbon yields. The catalyst with alumina gave lower vapor yields and produced both hydrocarbons and partially deoxygenated products, in particular furans. The catalyst with alumina also gave higher coke yields and exhibited faster deactivation than the catalysts with clay and silica binders. The low hydrocarbon yields and coke formation were attributed to the acidic sites provided by alumina and blocking of the zeolite sites. The catalysts with silica and clay as binders were further tested in a 2-inch fluidized bed system for ex situ catalytic pyrolysis of pine. Similar oils were produced over both catalysts with carbon yields of approximately 23 % and oxygen contents of 20-21 %. [ABSTRACT FROM AUTHOR]

A number of supported cobalt catalysts for Fischer-Tropsch synthesis were considered. Catalysts were prepared by impregnation of the supports with a cobalt precursor resulting in cobalt concentrations of 15 or 20 wt%. The active metal was supported onto aluminum oxide, titanium dioxide and silicon carbide supports while rhenium or ruthenium metals were used as promoters, whose concentrations were 0, 0.2 or 1.0 wt%. The catalysts were characterized by a number of methods including BET, chemisorption, and XRD. Some of the catalysts were tested for catalytic activity and selectivity in the Fischer-Tropsch reaction using a fixed bed reactor. Based on the results, the addition of promoter metals increases the dispersion of the active metal cobalt and correspondingly a decrease in the cobalt metal particles, this effect was most evident for the alumina supported catalysts. Further, increased concentrations of the ruthenium promoter (1.0 wt%) slightly increased the selectivity to CH and decreased selectivity to C. [ABSTRACT FROM AUTHOR]

The objective of the study is to illustrate the advantages with using ceria-zirconia instead of promoted alumina as support for rhodium-based catalysts in oxidative steam reforming of biodiesel. The evaluation is based on long-term oxidative steam reforming experiments where the stability and durability of the catalysts are evaluated. The durability and fuel conversion of the two catalysts were comparable. However, the H yield of the ceria-zirconia supported catalyst was 10 % higher than for the catalyst supported on promoted alumina after 65 h on stream. Included are also measurements of the acidity of the catalysts, where it was concluded that the promoted alumina catalyst was significantly more acidic. The acidity of the materials could then be related to the amount of coke deposited, where the amount of coke on the alumina catalyst was almost five times higher after 50 h of operation compared to the ceria-zirconia catalyst. [ABSTRACT FROM AUTHOR]

Modification of supported Pt catalysts with thiols has recently been shown to improve the hydrogenation selectivity of α,β-unsaturated aldehydes to unsaturated alcohols. Here, we apply a variety of organic thiol coatings to Pd/AlO catalysts that typically have a much lower intrinsic selectivity for desired product formation. Thiol monolayers were found to increase hydrogenation selectivity to cinnamyl alcohol; however, unlike with Pt catalysts, the increase was independent of the identity of the organic tail. [ABSTRACT FROM AUTHOR]

CuCl/γ-AlO catalysts with and without promoter metal chlorides (Cu5.0, K3.1Cu5.0, La10.9Cu5.0, Li0.5Cu5.0, Cs10.4Cu5.0, Mg1.9Cu5.0, Ce5.5La5.45Cu5.0, and K1.55La5.45Cu5.0) were studied for the ethene oxychlorination reaction in a fixed-bed reactor at 503 and 573 K, with CH:HCl:O:He = 1.0:1.1:0.38:14.4 (mole ratio), P(tot) = 1 atm and weight hourly space velocity (WHSV) = 1.5 g g h (based on ethene). It was found that all promoter metals enhanced the activity of the catalyst, as well as its selectivity towards the target product 1,2-dichloroethane (1,2-EDC). Co-promoted catalysts (K1.55La5.45Cu5.0 and Ce5.5La5.45Cu5.0) gave even higher activity and product selectivity than the single metal promoted catalysts. The activity of the CuCl/γ-AlO catalyst, as well as the γ-AlO support, both with and without metal chloride promoter(s), were further tested for 1,2-EDC conversion to byproducts in a fixed-bed reactor at 503 K, under a feed stream of 1,2-EDC:Ar = 1:11.5 (mole ratio), at P(tot) = 1 atm and WHSV = 1.5 g g h (based on 1,2-EDC). Prior to testing, the catalysts were pretreated in flowing ethene, HCl and/or O. It was observed that Lewis and Brønsted acid sites on the alumina surface were main reaction sites for conversion of 1,2-EDC to chlorinated byproducts: vinyl chloride monomer (VCM), 1,1-EDC, 1,2-dichloroethene (1,2-DCE) and ethyl chloride (EC) as well as dimerisation (butadiene) and aromatisation reactions (toluene), both with and without the presence of the Cu phase. The Cu phase was shown to contribute mainly to CO and trichloroethane formation from 1,2-EDC via VCM. Co-promotion (K1.55La5.45Cu5.0) was found to enhance the activity of the Cu phase, and to mask acid sites on the alumina surface, thereby promoting ethene oxychlorination while at the same time hindering undesired conversion of the target product 1,2-EDC. [ABSTRACT FROM AUTHOR]

The contributions of Burtron H. Davis to the understanding and description of alcohol dehydration over metal oxide catalysts, is discussed and applied to process improvement and process synthesis. Some of the key findings from his work are that the dehydration mechanism over metal oxides involves a concerted removal of OH and adjacent H, that weakly basic metal oxides are sensitive to the acidity of the H abstracted during dehydration, and that anti-Saytzeff elimination is possible with >80 % selectivity over weakly basic metal oxides (InO, YO, ZrO, EuO and ThO). These findings were applied to show how the dehydration step of the industrial Fischer-Tropsch based process for 1-heptene to 1-octene conversion can be improved through the use of a weakly basic metal oxide catalyst with low hydration activity. New processes were also suggested for the production of 1-octene from more commonly available feed materials, such as the C fraction of natural gas condensate and petroleum naphtha. These processes employed weakly basic metal oxide catalysts with high hydration activity. [ABSTRACT FROM AUTHOR]

The preparation of Ag/AlO catalysts by nonhydrolytic sol-gel process leads to highly efficient HC-deNOx materials thanks to the silver ability to diffuse toward the surface. The presence of niobium as co-catalyst, with a Nb content comprised between 1 and 3 wt%, enhances the NO reduction efficiency at low temperatures (<250 °C). [ABSTRACT FROM AUTHOR]

The effect of void volume (apparent residence time variation) on oxidation of n-decane and on the n-decane-SCR of NO was studied on Ag/AlO with a silver loading of 2 wt% and on Cu exchanged Y zeolite. A positive effect on the reduction of NO was observed and the better result was observed occurring with a moderate autoignition of n-decane, which corresponds to an intermediate apparent residence time. [ABSTRACT FROM AUTHOR]

The influence of the addition of W to AlO, promoted or not by Ag, on the n-C SCR of NO was investigated. It was shown that the addition of W was detrimental to the n-C SCR reaction. Based on the NO-TPD, the XPS and the n-C SCR measurements, it was concluded that the loss of activity observed at temperatures lower than 400 °C on the Ag/W(5)-AlO catalyst compared with the Ag/AlO sample is likely due to the preferential deposition of Ag on the tungstate phase, making it inactive for the n-C SCR reaction which requires the active silver species to be in close contact with the AlO. At higher temperatures, the occupation, by the tungstates, of the AlO sites responsible for the n-C-SCR reaction is proposed to be an additional drawback accounting for the detrimental effect of W on AlO-supported catalysts promoted or not by Ag. [ABSTRACT FROM AUTHOR]

The oxidation state of palladium in a model Pd/ACZ three-way catalyst was monitored by synchronous XANES and mass spectrometry during two consecutive heating (to 850 °C) and cooling (to 100 °C) cycles under stoichiometric conditions simulating exhaust after treatment of a natural gas engine. During heating in the first cycle, PdO reduction occurred around 500 °C and the initial fully oxidized state of Pd was never recovered upon heating and cooling cycles. A mixed Pd/Pd oxidation state was at work in the second cycle. Hence, the operando XANES study reveals that the PdO/Pd pair exists in a working catalyst but is less active than the catalyst in its initial state of fully oxidized palladium. It is also evident from XANES spectra that ceria-zirconia promotes re-oxidation of metallic Pd, thus reasonably sustaining catalytic activity after exposure to high temperatures. [ABSTRACT FROM AUTHOR]

Two series of silica- and alumina-supported platinum catalysts were investigated in the hydrodechlorination (HdCl) of tetrachloromethane. During an initial period of reaction carried out at a lower H/CCl ratio the catalysts, especially those characterized by high metal dispersion, deactivated with time-on-stream. Two catalyst screening protocols were used. The first one concerned a gradually increased hydrogen partial pressure, whereas during the second one the H pressure was decreased. Although, in general, the hydrogen-rich reaction conditions resulted in improved catalyst performance (higher overall activity and selectivity to CHCl), the second protocol led to even better results. Reasons for such a behaviour are suggested. Because of very high activity of a few tested samples, changes in CCl conversion with the hydrogen partial pressure do not reflect real reaction orders in hydrogen. The same reason may lead to falsification of apparent activation energies. In certain cases the relation between conversion and hydrogen pressure showed a maximum, suggesting that HdCl undergoes via a Langmuir-Hinshelwood mechanism, when hydrogen and CCl compete for metal surface sites. Both carbon- and chlorine-containing deposits were found in the post-reaction catalyst samples. [ABSTRACT FROM AUTHOR]

Monodisperse γ-AlO beads with a diameter of 250 μm were prepared via a sol-gel method and the JetCutter. The bead-shaped support was used for the preparation of 0.23 % Au/γ-AlO catalyst beads which were applied in the oxidation of glucose to gluconic acid. Simplified calculations of the effectiveness factor revealed that especially at high glucose concentrations the use of hydrogen peroxide would lead to much a higher catalyst activity than the use of oxygen as oxidant which was confirmed by the experimental results. [ABSTRACT FROM AUTHOR]

Supported metal catalysts containing 5 wt% Pd on silica, alumina, and activated carbon were evaluated for liquid-phase deoxygenation of stearic (octadecanoic), lauric (dodecanoic), and capric (decanoic) acids under 5 % H at 300 °C and 15 atm. On-line quadrupole mass spectrometry (QMS) was used to measure CO + CO yield, CO selectivity, H consumption, and initial decarboxylation rate. Post-reaction analysis of liquid products by gas chromatography was used to determine n-alkane yields. The Pd/C catalyst was highly active and selective for stearic acid (SA) decarboxylation under these conditions. In contrast, SA deoxygenation over Pd/SiO occurred primarily via decarbonylation and at a much slower rate. Pd/AlO exhibited high initial SA decarboxylation activity but deactivated under the test conditions. Similar CO selectivity patterns among the catalysts were observed for deoxygenation of lauric and capric acids; however, the initial decarboxylation rates tended to be lower for these substrates. The influence of alkyl chain length on deoxygenation kinetics was investigated for a homologous series of C-C fatty acids using the Pd/C catalyst. As fatty acid carbon number decreases, reaction time and H consumption increase, and CO selectivity and initial decarboxylation rate decrease. The increase in initial decarboxylation rates for longer chain fatty acids is attributed to their greater propensity for adsorption on the activated carbon support. [ABSTRACT FROM AUTHOR]

High temperature aging of supported Pd/alumina causes a phase transformation of the transitional (γ, θ or δ) alumina support into alpha (α) alumina. This phase transformation is accompanied by a loss in surface area. This raises the question: how much is the drop in Pd dispersion caused by support sintering? We answer this question by a comparison of chemically similar Pd/alumina catalysts that differ only in one aspect, their physical treatment. The physical treatment is the milling of the support which is often used during wash coating of monolithic automotive catalysts. We show that milling of transitional alumina supports can accelerate their phase transformation into alpha alumina. By comparing catalysts that were milled with those that were not milled, we conclude that the sintering of the catalyst support does not contribute significantly to the sintering of the metal phase. Our results apply specifically to isothermal aging of the catalysts at 900 °C in 10% HO in N for periods of up to 200 h. [ABSTRACT FROM AUTHOR]

A series of different mechanical mixtures of a narrow-pore Co/γ-AlO catalyst and a Cu-based WGS-catalyst has been investigated in the low-temperature Fischer-Tropsch synthesis (483 K, 20 bar) with a model bio-syngas (H/CO = 1.0) in a fixed-bed reactor. The higher the fraction of WGS-catalyst in the mixture, the lower is the Co-catalyst-time yield to hydrocarbons. This is ascribed to a strong positive kinetic effect of water on the Fischer-Tropsch rate of the Co-catalyst, showing the importance of the indigenously produced water, especially in fixed-bed reactors where the partial pressure of water is zero at the reactor inlet. A preliminary kinetic modeling suggests that the reaction order in P $$ _{{{\text{H}}_{ 2} {\text{O}}}} $$ is 0.3 for the Co/γ-AlO catalyst in the range of the studied reactor-average partial pressures of water (i.e., 0.04-1.2 bar). [ABSTRACT FROM AUTHOR]

study of NiMo catalysts supported on MCM41 modified with alumina prepared by the sol-gel method is presented. Ni-Mo phases were impregnated on the supports using the solution method with the purpose to obtain a material whose hexagonal structure of the MCM41 would not be affected with the addition of these active phases. The impregnation of the metals method used in the present work was outstanding, the textural properties of the catalysts decreased from 42 to 67%. There was a diminution in the textural properties of the catalysts with respect to the supports, nevertheless the prepared materials had more significant textural properties that the conventional catalysts of HDS. The adsorption-desorption isotherms of the catalysts did not change considerably with the support source. By DRX was determined the structural properties of the metallic phases present in the material where phases such as NiMoO, MoO and NiO were observed. Support wall thickness was increased with the incorporation of Ni and Mo metals into the materials. By means of Raman spectroscopy, the presence of MoO and MoO species was corroborated. Through UV-vis where determined NiO of octahedral symmetry as well as Mo of tetrahedral and octahedral symmetry. The main reaction products were biphenyl (BP), cyclohexylbenzene (CHB) and bicyclohexyl (BCH) when the materials were tested in the HDS of DBT. [ABSTRACT FROM AUTHOR]

The reaction of alumina isopropoxide (AIP) in straight-chain primary alcohols at high temperatures yields the alkyl derivatives of boehmite. Crystallinity of the alkyl derivatives of boehmite can be controlled by the feed ratio of AIP/alcohol. The alumina samples derived from the products having poor crystallinity had large pore-volumes (1.16–3.24 cm3/g). [ABSTRACT FROM AUTHOR]

Nb2O5/Al2O3 catalysts calcined at high temperatures exhibited the Brønsted acid property. A monolayer of niobic acid-like compound, which has distorted octahedral symmetry, was stabilized over 16 wt% Nb2O5/Al2O3 catalyst calcined at 1,173 K. The two-dimensional Nb–O–Nb network of stabilized niobic acid-like compound probably accounts for the generation of Brønsted acid. [ABSTRACT FROM AUTHOR]

Alumina supported indium oxide, silver or bimetallic Ag–In catalysts with metal loading of ca. 2.5 wt% were prepared by excess solvent impregnation or incipient wetness impregnation. The influence of the impregnation was studied by testing the catalysts in DeNO x activity with ethanol in Lean Burn Conditions. [ABSTRACT FROM AUTHOR]

Alumina-supported indium and gallium oxide catalysts were prepared by excess solvent impregnation, characterized and tested for the reduction of NO x by ethanol in Lean Burn Conditions. The promotion of alumina by “poor” metals showed an interesting ability to selectively reduce NO x to N2. [ABSTRACT FROM AUTHOR]

Chromium oxide deposited on phosphorus-loaded alumina is used in the oxidative dehydrogenation (ODH) of propane to propylene. Operando Raman-GC studies allowed evaluating the molecular structure of surface Cr oxide species, their reactivity and their changes undergone during operation. The addition of phosphorous to the alumina substrate decreases propane conversion, mainly due to the decrease of CO x, there is a concomitant increase in the selectivity to propylene formation. The addition of phosphorous affects the nature of the Cr oxide species, which do not form of a new phase. The surface interaction between dispersed chromate species and phosphorous weakens the Cr=O bond and retards the aggregation of surface chromate species as Cr2O3 during reaction in ca. 170 °C. [ABSTRACT FROM AUTHOR]

The promotion of Fischer-Tropsch catalysts 10%Co/Al2O3, 10%Co/SiO2, 10%Co/TiO2 by 0.5% Ru and the modification of supports by 8.5 wt% ZrO2 have been studied. The following properties: catalyst specific surface area as well as reducibility and dispersion of metallic phase were studied by different techniques: BET, TPR, and H2 chemisorption. The modification of supports by non-reducible ZrO2, results in a decrease of cobalt oxide reduction on Al2O3 and TiO2 but not on SiO2 supports. Additionally the enhancement of cobalt dispersion was found for all catalysts with ZrO2 modified supports. The impact of Ru promotion is likely due to the stabilization of applied supports, prevention or blockage of interaction between surface Co species and support and an increase in cobalt oxide reducibility to the catalytically active metallic cobalt phase. [ABSTRACT FROM AUTHOR]

The solid base catalysts of MgO covered with SiO2, Al2O3, TiO2, and ZrO2 were prepared by decomposition of the corresponding alkoxide over an Mg(OH)2 surface in ethyl acetate solution followed by thermal decomposition. The acid-base properties of the prepared catalysts were estimated using 2-propanol decomposition activity and selectivity. The stability of catalysts for the aldol reaction of acetone against H2O was examined. The acid sites were generated on the MgO surface by covering with metal oxides. Base sites were formed when the MgO was covered with Al2O3. Catalysts made of MgO covered with more than 7 mol% Al2O3 showed sufficient stability against H2O as well as reusability. [ABSTRACT FROM AUTHOR]

Heterogeneous catalysts composed of Pd nanoparticles on zinc oxide (ZnO) and aluminum oxide (Al2O3, alumina) were synthesized and tested for catalytic activity. Palladium nanoparticles were synthesized via solution-precipitation methods and deposited on aluminum oxide and zinc oxide supports. The particles were synthesized by decomposing a palladium precursor (Pd(Mes)2) in a solution of trioctylphosphine [TOP route] or palladium acetate (Pd(OAc)2) in a solution of octylamine [amine route] at 300 °C. The particles were washed and suspended in hexane, whereupon they were deposited on an oxide powder. Supported nanoparticle powders were subjected to CO oxidation tests to determine catalytic activity. Particle sizes ranged from 2.4 ± 0.4 nm average diameter when prepared using trioctylphosphine to 4 ± 1 nm using the amine route. No significant size change was observed after removal of the surfactant and catalytic testing by CO oxidation. The highest conversion of CO to CO2 occurred with a calcined sample, indicating that the removal of surfactant increases activity. [ABSTRACT FROM AUTHOR]

The effect of calcination temperature and atmosphere on the properties of γ-Al2O3 supported cobalt Fischer-Tropsch catalysts has been investigated. One common precursor for all the catalysts was prepared by incipient wetness impregnation of γ-Al2O3 with an aqueous solution of cobalt nitrate hexahydrate. It was subjected to four different calcination atmospheres (air/50% steam: 30 mL/min, air: 30 mL/min, air: 50 mL/min, N2: 30 mL/min) and eight different calcination temperatures (range: 473–723 K), making the total number of samples 32. Both the post calcination nitrogen content and the cobalt dispersion were measured. The results demonstrated that in order to maximise the cobalt dispersion, it is necessary to use low calcination temperatures and remove the precursor decomposition products (NO, NO2, H2O) efficiently. The Fischer-Tropsch synthesis performance of two catalysts calcined at the same temperature, but at different air flow rates was evaluated. No significant effect of the air flow rate was found on the turnover frequency or C5+ selectivity, but a high flow rate resulted in 30% higher activity per gram catalyst. [ABSTRACT FROM AUTHOR]

Co/γ-Al2O3 and CoRe/γ-Al2O3 catalysts have been studied by the steady-state isotopic transient kinetic analysis (SSITKA) technique. It was found that neither the CO partial pressure, the temperature nor the space velocity influences the in situ CO adsorption. The space velocity, H2/CO ratio and temperature was found to affect the intrinsic activity ( $$(\tau\,_{{\rm{CH}}_{\left( 4 \right)}})$$ ) slightly, while the total pressure and syngas partial pressure had only a negligible effect. The surface concentrations and coverages were, however, unaffected by the space velocity, temperature, total pressure, syngas partial pressure and H2/CO ratio. All changes, however, affected the methane selectivity, indicating that the methane selectivity was not a function of the surface inventory of methane precursors. [ABSTRACT FROM AUTHOR]

The origin of CO oxidation performance variations between three different supported Au catalysts (Au/CeO2, Au/Al2O3, Au/TiO2) was examined by in situ XAFS and DRIFTS measurements. All samples were prepared identically, by deposition-precipitation of an aqueous Au(III) complex with urea, and contained the same gold loading (~1 wt %). The as-prepared supported Au(III) precursors exhibited different reduction behaviour during exposure to the CO/O2/He reaction mixture at 298 K. The reducibility of the Au(III) precursor was found to decrease as a function of the support material in the order: titania > ceria > alumina. The as-prepared samples were inactive catalysts, but Au/TiO2 and Au/CeO2 developed catalytic activity as the reduction of Au(III) to metallic Au proceeded. Au/Al2O3 remained inactive. The developed catalytic CO oxidation activity at 298 K varied as a function of the support as follows: titania > ceria > alumina ~ 0. The EXAFS of samples pretreated in air at 773 K and in H2 at 573 K reveals the presence of only metallic particles for Au/TiO2 and Au/Al2O3. Au(III) supported on CeO2 remains unreduced after calcination, but reduces during the treatment with H2. CO oxidation experiments performed at 298 K with the activated samples show that the presence of metallic gold is necessary to obtain active catalysts (Au/CeO2 is not active after calcination) and that the reducible supports facilitate the genesis of active catalysts, while metallic gold particles on alumina are not active. [ABSTRACT FROM AUTHOR]

In the present work the soot combustion activity of CeO2 doped with lanthanum hydroxide, as surface promoter, has been investigated. TGA experiments, run under different conditions, show that, in the presence of lanthana, the reaction of soot starts at low temperature (579 K) due to the possibility to form carbonate species. The emission of CO2 is delayed due to the strong interaction with lanthana. A mechanism of reaction involving a carbonate route is proposed. [ABSTRACT FROM AUTHOR]

In order to elucidate the effect of support in the catalytic performance, two selected potassium-promoted catalysts (K1Cu/beta and KCu2/Al2O3) were tested for the simultaneous NO x /soot removal from a simulated diesel exhaust. For comparative purpose, the behaviour of a platinum catalyst (Pt/beta) was also studied. Isothermal experiments revealed that the potassium-promoted catalysts show a high activity for NO x /soot removal in the 350–450 °C temperature range. In addition, the catalysts present the advantage that the main reaction products are N2 and CO2. Among the catalysts tested, KCu2/Al2O3 presents the best global performance at 450 °C: the highest soot consumption rate, even higher than the platinum catalysts, and a high NO x reduction. [ABSTRACT FROM AUTHOR]

The temperature window of NO x consumption lies between 140 and 500 °C. The 0.5 wt%Co/Al2O3 catalyst exhibits a total consumption of NO x between 300 and 350 °C at a space velocity of 50 000 h?1. The presence of acetonitrile and methylnitrite can explain the difference between N2 formation and NOx consumption at T< 400 °C. The Co2+, in octahedral site, has been shown to coordinate two NO molecules. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction (SCR) of NO X assisted by hydrocarbons was investigated on alumina in New European Driving Cycle (NEDC) conditions. The alumina efficiency towards the deNO X process was shown in the temperature range 200–400 °C involving a three-catalytic cycle mechanism. However, many parameters influence the catalytic activity: temperature, HC/NO X ratio and GHSV. [ABSTRACT FROM AUTHOR]

This contribution is devoted to study of the thermal stability and growth of gold nanoparticles supported on SiO2/Si(111) and Al2O3/SiO2/Si(111) as a function of initial cluster size, support material and level of surface coverage. Experimental evidence for “flipping” of two dimensional cluster structures from vertical orientation to horizontal on the support is presented. [ABSTRACT FROM AUTHOR]

The information obtained from the characterization of vanadium oxide single crystal surfaces is related to the study of vanadia nanoparticles supported on silica and alumina thin films, model systems for the so-called “supported monolayer vanadia catalysts”. It is found that these particles have properties similar to V2O3 surfaces, where the topmost V ions are involved in vanadyl groups and have a 5+ oxidation state. A vibrational spectroscopy investigation combined with DFT calculations show that the accepted interpretation of vibrational spectra from vanadia catalysts must be revised. [ABSTRACT FROM AUTHOR]

The formation of ammonia is inevitable during industrial-scale wet oxidation of wastewater if nitrogen-containing compounds are present. This undesired side-reaction requires additional measures for disposal. Common routes are either the use of noble metal-containing catalysts in the first oxidation step or end-of-pipe treatment. Problems rise for example from the insufficient stability of solid catalysts against hydrothermal impact. As most of the wet oxidation processes run at elevated pressure and temperature, running the heterogeneously catalysed oxidation of ammonia in the gas phase in a downstream reactor could protect the catalysts mainly from leaching and offers an economic alternative by avoiding loss of unused oxygen after depressurisation. This work reports on the oxidation of ammonia with air in steam atmosphere using Cu,Cr-containing supported and bulk catalysts at 235-305 °C and 30-60 bar. A copper chromite catalyst gave best performance (86% conversion at 305 °C, 45 bar, contact time 1 s). The spinel-type phase CuCr2O4 seems to be the active phase and shows superior stability. The results indicate that phase behaviour of water strongly influences activity and lifetime of catalysts. Characterisation of the solids (BET, XRD, XPS, ICP) proved that deactivation is mainly caused by leaching of Cr(VI) species from catalysts when the reaction runs near to dew point of water and by loss of BET surface area of supported catalysts due to hydrothermal impact. [ABSTRACT FROM AUTHOR]