Effect Of Preparation Procedure Research Articles

CO2 methanation on Ni/Y2O3 Catalysts: The effects of preparation procedure and cerium oxide promotion

Present paper reports on the CO2 methanation (CME) performance of novel Ni catalysts supported on yttria, ceria, and ceria-doped yttria carriers. Catalysts were synthesized using incipient wetness impregnation and precursor nitrate co-decomposition. These systems outperformed on a mass-specific basis an industrial Ni/alumina benchmark catalyst. In addition, this work examines in details the impact of both the preparation procedure and the Ni-content on the CME activity both in terms of the reaction rate and the apparent activation energy. Our research demonstrates that Y2O3 is an effective catalytic support promoting stability and activity of the catalysts. CeO2–doping further improves activity, remarkably with little to no penalty to the thermal stability of the catalysts. Comparison of the performance of a conventional IWI-synthesized Ni-catalyst with a counterpart obtained via a co-decomposition route, demonstrated an advantage of the latter. Our findings suggest Ni-CeO2/Y2O3 prepared via co-decomposition may be advised as the active and stable catalysts for CME applications.

Mixed oxides of cerium and manganese as catalysts for total oxidation of ethyl acetate: effect of preparation procedure

Mixed oxides of cerium and manganese as catalysts for total oxidation of ethyl acetate: effect of preparation procedure

Effects of Preparation Procedures and Porosity on Thermoelectric Bulk Samples of Cu2SnS3 (CTS).

The thermoelectric behavior and stability of Cu2SnS3 (CTS) has been investigated in relation to different preparations and sintering conditions, leading to different microstructures and porosities. The studied system is CTS in its cubic polymorph, produced in powder form via a bottom-up approach based on high-energy reactive milling. The as-milled powder was sintered in two batches with different synthesis conditions to produce bulk CTS samples: manual cold pressing followed by traditional sintering (TS), or open die pressing (ODP). Despite the significant differences in densities, ~75% and ~90% of the theoretical density for TS and ODP, respectively, we observed no significant difference in electrical transport. The stable, best performing TS samples reached zT ~0.45, above 700 K, whereas zT reached ~0.34 for the best performing ODP in the same conditions. The higher zT of the TS sintered sample is due to the ultra-low thermal conductivity (κ ~0.3–0.2 W/mK), three-fold lower than ODP in the entire measured temperature range. The effect of porosity and production conditions on the transport properties is highlighted, which could pave the way to produce high-performing TE materials.

Effect of preparation procedure on properties of egg white protein and the fibrous microparticle stabilized complex emulsions.

This study, three different procedures were used for preparation of egg white protein (E) and egg white protein fibrous microparticle (EM) complex emulsions, to modify the interfacial and aqueous composition. According to the adding order of EM and E during emulsification, the emulsions were named as type I (EM and E mixed firstly, followed by emulsification), type II (emulsified with EM firstly, followed by the addition of E) and type III (emulsified with EM firstly, followed by the addition of E). The particle size, creaming stability at various salt concentration, elastic module (G'), and lipid oxidation degree were investigated. The results showed that, EM at interface is beneficial for improving salt resistance of the complex emulsions, while E was more effective in terms of preventing oxidation of oil, attributed to the possibility to form continuous elastic interface film. The type III complex emulsion at EM:E ratio of 2:1 showed both improved creaming and oxidation stability, behaving the potential to be used as carrier of lipo-nutrients.

Effect of preparation procedure and composition of catalysts based on Mn and Ce oxides in the simultaneous removal of NOX and o-DCB

Two series of catalysts based on Mn and Ce oxides were prepared by co-precipitation and impregnation, in order to study their physicochemical properties and catalytic performance in the simultaneous reduction of NO and oxidation of o-DCB. Co-precipitation catalysts showed better activity than those prepared by impregnation because of the formation of a MnOX-CeO2 solid solution, which improves redox and acid properties. Moreover, the catalysts with MnOX content between 80 and 90 mol.%, in which a coexistence between solid solution phase and Mn2O3 crystal was found, presented NO conversion above 90 % at temperatures below 250 °C and o-DCB conversion above 80 % at temperatures above 200 °C. The main by-products of SCR were N2O, produced in the whole range of temperature, and NO2, formed at temperatures above 300 °C. Selectivity to CO2 above 80 % was obtained using co-precipitation catalysts in all temperature range. Deactivation experiments showed that oxidation reaction strongly contributes to deactivate impregnation catalysts, whereas the effect of deactivation is lower in co-precipitation catalysts at high Mn contents.

Palladium Based-Polysaccharide Hydrogels as Catalysts in the Suzuki Cross-Coupling Reaction

A simple PdCl2(TPPTS)2 complex was successfully heterogenized in polysaccharide hydrogel beads by using two different methods: (1) dropping the complex and polysaccharide solution into aqueous or ethanol solution of 0.5 M calcium chloride, and (2) dropping the complex and polysaccharide solution into an aqueous solution of chitosan (C). FTIR analyses of the different beads revealed that the complex was heterogenized via interactions between the sulfonate group on the TPPTS and the hydroxyl groups on the polysaccharides. Additionally, the effects of preparation procedure and polysaccharide type on catalytic performance of the formed heterogeneous catalysts in Suzuki cross-coupling was also tested. It was found that the palladium-based hydrogels, which were prepared by the interactions of two polysaccharides, iota carageenan (I) and C, were more active and stable than those that precipitated in the CaCl2 solution. In addition, the I-C-PdCl2(TPPTS)2 heterogeneous catalyst could be easily recycled with minor loss of activity. Moreover, the conversion rates of all heterogeneous systems employed with iodobenzene and phenylboronic acid were higher than those of their homogeneous analogues, a finding that is probably due to the presence of water, which accelerates the reaction, in the hydrogels. At last, SEM–EDS analysis of the hydrogels showed that the complex was immobilized in the hydrogels and that the I-C-PdCl2(TPPTS)2 beads were less condense than the beads that were produced with I-PdCl2(TPPTS)2 in CaCl2 solution, which can explain the higher performance of the former.

Effect of Preparation Methods on the Physicochemical and Functional Properties of Ni/CeO2 Catalysts

The effect of preparation procedures (a polymer ester precursor method and incipient wetness impregnation) on the physicochemical and functional properties of Ni/CeO2 catalysts with different nickel contents (0–15 wt %) was studied in order to develop highly active and carbonization-resistant catalysts for hydrocarbon reforming. Based on the results of studying the samples by low-temperature nitrogen adsorption, X-ray phase analysis, Raman spectroscopy, transmission electron microscopy and temperature-programmed reduction with hydrogen, it was found that the textural, structural, and redox properties of the materials depend on the method of their synthesis. As compared with the samples prepared by impregnation, the Ni/CeO2 catalysts obtained by the polymer ester precursor method were characterized by different active component stabilization forms (a Ce1 –xNixOy solid solution phase and NiO particles <5 nm in size vs. a NiO phase with a particle size of 5–50 nm), a smaller average size of CeO2 crystallites (5.5 vs. 11 nm), a high specific surface area (105 vs. 75 m2/g), a defect structure, and a decreased reducibility. It was found that the samples of both series provided comparable yields of hydrogen (to 50% at 600°C) in an autothermal ethanol reforming reaction, but the Ni/CeO2 catalysts synthesized by the polymer ester precursor method were more resistant to the formation of carbonaceous deposits.

Effect of preparation procedures on catalytic activity and selectivity of copper-based mixed oxides in selective catalytic oxidation of ammonia into nitrogen and water vapour

The selective oxidation of ammonia into nitrogen and water vapour (NH3-SCO) was studied over Cu-Mg(Zn)-Al-(Zr) mixed metal oxides, obtained by coprecipitation and their subsequent calcination. The effect of acid-base properties of Cu-Mg-Al-Ox on catalytic activity was investigated by changing the Mg/Al molar ratio. Other Cu-containing oxides were prepared by rehydration of calcined Mg-Al hydrotalcite-like compounds or thermal decomposition of metal nitrate precursors. XRD, BET, NH3-TPD, H2-TPR, XPS, FTIR with adsorption of pyridine and CO as well as TEM techniques were used for catalysts characterization. The results of catalytic tests revealed a crucial role of easily reducible highly dispersed copper oxide species to obtain enhanced activity and N2 selectivity in NH3-SCO. The selective catalytic reduction of NO by NH3 (NH3-SCR) and in situ DRIFT of NH3 sorption indicated that NH3-SCO proceeds according to the internal selective catalytic reduction mechanism (i-SCR).

Effect of preparation procedure and nanostructuring on the thermoelectric properties of the lead telluride-based material system AgPbmBiTe2+m (BLST-m)

We report on the preparation and thermoelectric properties of the quaternary system AgPbmBiTe2+m (Bismuth-Lead-Silver-Tellurium, BLST-m) that were nanostructured by mechanical alloying. Nanopowders of various compositions were compacted by three different methods: cold pressing/annealing, hot pressing, and short term sintering. The products are compared with respect to microstructure and sample density. The thermoelectric properties were measured: thermal conductivity in the temperature range from 300 K to 800 K and electrical conductivity and Seebeck coefficient between 100 K and 800 K. The compacting method and the composition had a substantial impact on carrier concentration and mobility as well as on the thermoelectric parameters. Room temperature Hall measurements yielded carrier concentrations in the order of 1019 cm−3, slightly increasing with increasing content of the additive silver bismuth telluride to the lead telluride base. ZT values close to the ones of bulk samples were achieved. X-ray diffraction and transmission electron microscopy (TEM) showed macroscopically homogeneous distributions of the constituting elements inside the nanopowders ensembles, indicating a solid solution. However, high resolution transmission electron microscopy (HRTEM) revealed disorder on the nanoscale inside individual nanopowders grains.

Decomposition of methane over alumina supported Fe and Ni–Fe bimetallic catalyst: Effect of preparation procedure and calcination temperature

Catalytic decomposition of methane has been studied extensively as the production of hydrogen and formation of carbon nanotube is proven crucial from the scientific and technological point of view. In that context, variation of catalyst preparation procedure, calcination temperature and use of promoters could significantly alter the methane conversion, hydrogen yield and morphology of carbon nanotubes formed after the reaction. In this work, Ni promoted and unpromoted Fe/Al2O3 catalysts have been prepared by impregnation, sol–gel and co-precipitation method with calcination at two different temperatures. The catalysts were characterized by X-ray diffraction (XRD), N2 physisorption, temperature programmed reduction (TPR) and thermogravimetric analysis (TGA) techniques. The catalytic activity was tested for methane decomposition reaction. The catalytic activity was high when calcined at 500°C temperature irrespective of the preparation method. However while calcined at high temperature the catalyst prepared by impregnation method showed a high activity. It is found from XRD and TPR characterization that disordered iron oxides supported on alumina play an important role for dissociative chemisorptions of methane generating molecular hydrogen. The transmission electron microscope technique results of the spent catalysts showed the formation of carbon nanotube which is having length of 32–34nm. The Fe nanoparticles are present on the tip of the carbon nanotube and nanotube grows by contraction–elongation mechanism. Among three different methodologies impregnation method was more effective to generate adequate active sites in the catalyst surface. The Ni promotion enhances the reducibility of Fe/Al2O3 oxides showing a higher catalytic activity. The catalyst is stable up to six hours on stream as observed in the activity results.

Cobalt- and iron-based nanoparticles hosted in SBA-15 mesoporous silica and activated carbon from biomass: Effect of modification procedure

Ordered mesoporous silica of SBA-15 type and activated carbon, prepared from waste biomass (peach stones), are used as host matrix of nanosized iron and cobalt particles. The effect of preparation procedure on the state of loaded nanoparticles is in the focus of investigation. The obtained materials are characterized by Boehm method, low temperature physisorption of nitrogen, XRD, UV–Vis, FTIR, Mossbauer spectroscopy and temperature programmed reduction with hydrogen. The catalytic behaviour of the samples is tested in methanol decomposition. The dispersion, oxidative state and catalytic behaviour of loaded cobalt and iron nanoparticles are successfully tuned both by the nature of porous support and the metal precursor used during the samples preparation. Facile effect of active phase deposition from aqueous solution of nitrate precursors is assumed for activated carbon support. For the silica based materials the catalytic activity could be significantly improved when cobalt acetylacetonate is used during the modification. The complex effect of pore topology and surface functionality of different supports on the active phase formation is discussed.

Effect of preparation procedure on the formation of nanostructured ceria–zirconia mixed oxide catalysts for ethyl acetate oxidation: Homogeneous precipitation with urea vs template-assisted hydrothermal synthesis

Two series of ceria–zirconia mixed oxide samples with wide variation in the composition were synthesized using homogeneous precipitation with urea and template-assisted hydrothermal procedures. The samples were characterized by nitrogen physisorption, XRD, SEM, Raman, XPS, UV–vis, FTIR, pyridine-FTIR and TPR techniques. The catalytic activity in ethyl acetate total oxidation as a representative of VOCs was tested. The effect of preparation procedure on the texture, structure, morphology, acidic and redox properties was discussed in details in close relation with mixed oxides composition and possibilities for fine tuning of their catalytic activity. As compared to urea procedure, the hydrothermal treatment provides more homogeneous insertion of Zr ions within cubic ceria lattice even at high Zr content. As a result higher degree of distortion of the cubic lattice, creation of Ce3+ and oxygen vacancies and an increase in both Lewis acidity and redox ability is observed and these properties are not affected by the presence of template during the synthesis. The differences in the redox and surface acidic properties of both series of materials probably promote the realization of the catalytic process by various reaction pathways and thus influence in a complex way the catalytic activity and selectivity.

Investigation of washing and storage strategy on aging of Mg-aminoclay (MgAC) coated nanoscale zero-valent iron (nZVI) particles

The tendency towards agglomeration and oxidation of nanoscale zero-valent iron (nZVI) particles limits its application for in situ groundwater and soil remediation. Although the effect of surface coatings on nanoparticle stabilization has been commonly practiced, the effect of preparation procedures on aging of stabilized nZVI needs to be investigated. The effect of washing and storage, up to seven days, on aging of Mg-aminoclay (MgAC) coated nZVI is evaluated, following three procedures: pre- and post-storage washing with a 1mM NaHCO3 solution, and pre-storage washing with a stabilizer (MgAC) solution. Even though the initial particle size is identical, the observed size of pre-washed nZVI increases up to six times. This high aggregation tendency appears to be due to the desorption of MgAC during washing and storage, as verified by a decrease in the zeta potential, indicating a decrease of repulsion between nZVI particles. On the other hand, pre-storage washing is essential, in order to retain nZVI reactivity, by removal of residual reactants in the synthesis mixture. The reactivity of nZVI is examined with three parameters: optical density at 508nm as a measure of particle concentration, reactive iron content measured by H2 generation with acid digestion, and nitrate reduction capacity. All three parameters decrease significantly for post-storage washed nZVI, which corresponds to XRD results that exhibit transformation of Fe(0) to iron oxides. The reactivity tests display high linear correlations (r2>0.95, p<0.05) with respect to one another. Pre-storage washing, followed by addition of MgAC, exhibits high stability as pre-storage washing, as well as high reactivity as post-storage washing. Here, it is found that the proper washing procedure is crucial in coated nZVI preparation, to provide long lasting stability and to maintain reaction capacity during its preparation and transport.

Block and random copolyamides of poly(m‐xylylene adipamide) and poly(hexamethylene isophthalamide‐co‐terephthalamide): Methods of preparation and relationships between molecular structure and phase behavior

Copolymerization of poly(m‐xylylene adipamide) (MXD6) and poly(hexamethylene isophthalamide‐co‐terephthalamide) (PA6I‐6T) was used as an efficient strategy to prepare amorphous homogeneous systems with improved properties mainly for packaging applications. The preparation of block copolymers was first of all tried by co‐extrusion of the two polymers and then by thermal treatments at high temperatures in DSC or mixing in Brabender, also in the presence of a catalyst. The occurrence of transamidation reactions led to macromolecular structures with different randomness degrees. Further, random copolymers, with the full range of compositions, were synthetized from monomers, by a fast and simple two‐stage melt polycondensation. For all the copolymers, the sequence distribution was studied by using a 1H NMR method developed by the Authors. The effects of preparation procedures, of mixing temperature and time, of the presence of a catalyst on the chemical structure, and, then, on final properties were studied. Interesting correlations among block length, monomer distribution and phase behavior were discussed. POLYM. ENG. SCI., SCI., 55:1475–1484, 2015. © 2014 Society of Plastics Engineers

Effect of Preparation Procedure on the Catalytic Properties of Fe-ZSM-5 as SCR Catalyst

Fe-ZSM-5 catalysts, prepared by different methods, have been characterized by BET, ICP-AES, XRD, XPS, NH3-TPD and NO-TPD and evaluated for NOx reduction according to standard NH3-SCR, NH3 oxidation and NO oxidation, in absence and presence of water. The presence of water has a significant influence on both the SCR and oxidation reactions. The most active catalyst for NH3-SCR is prepared by ion exchange using FeCl2 as iron precursor. The XPS results indicate that Fe2+ ions are the main active sites for the SCR reactions, while Fe3+ ions are the primarily active sites for oxidation of ammonia.

Nanosized Cu0.5Co0.5Fe2O4 ferrite as catalyst for methanol decomposition: Effect of preparation procedure

Abstract Two series of Cu0.5Co0.5Fe2O4 ferrites were obtained by thermal or mechanochemical treatment of hydroxide carbonate precursor. The effect of the annealing temperature and the milling time, respectively, on the formation of the mixed ferrite phase was studied by DSC, XRD, Mossbauer spectroscopy and TPR with hydrogen. The catalytic behavior of the samples was tested in methanol decomposition to CO and H2. The initial phase composition of the obtained ferrites and the formation of the catalytic active phase under the reaction medium could be controlled by the preparation procedure used.

Effect of the composition and structure of the precursor compound on the catalytic properties of cobalt-aluminum catalysts in the Fischer-Tropsch synthesis

The effect of preparation procedure on the anionic composition and structure of hydroxo compounds as precursors of Co-Al catalysts and on their catalytic properties in the Fischer-Tropsch synthesis was studied. The dynamics of changes in the composition and structure of the hydroxide precursors of Co-Al catalysts during thermal treatment and subsequent activation was studied by thermal analysis, IR spectroscopy, XRD analysis, and in situ XRD analysis with the use of synchrotron radiation. It was found that the precursor compounds prepared by deposition-precipitation of cobalt cations on γ- and δ-Al2O3 under urea hydrolysis conditions, which had a hydrotalcite-type structure and contained nitrate, carbonate, and hydroxyl groups, turtned into the oxide compounds Co3 − xAlxO4 (0 < x < 2) with the spinel structure in the course of thermal treatment in an inert atmosphere. The hydrogen activation of an oxide precursor led to the formation of cobalt metal particles through the intermediate formation of a cobalt(II)-aluminum oxide phase. The catalyst was characterized by high activity and selectivity for C5+ hydrocarbons in the Fischer-Tropsch synthesis.

Structure and catalytic activity of hosted in mesoporous silicas copper species: Effect of preparation procedure and support pore topology

Copper modifications of ordered mesoporous materials with different pore topology (SBA-15 and KIT-6) were prepared by incipient wetness impregnation and “chemisorption–hydrolysis” methods and further oxidative or consecutive oxidative/reductive treatment. The samples were characterized by nitrogen physisorption, XRD, XPS, FTIR, UV–vis and TPR–TG techniques. The ordered structures and the “chemisorption–hydrolysis” post synthetic method provide the formation of homogeneously dispersed in the mesopores copper species. The “chemisorption–hydrolysis” modification of the silicas with more opened 3D ordered structure (KIT-6) provides the formation of highly active catalysts, but their activity could be easily suppressed after the treatment under the reduction medium.

Ba,K,Co/CeO 2 catalysts for NO x traps: Effect of preparation procedure

Ba,K,Co/CeO 2 catalysts for diesel soot and NO x abatement were studied. Different preparation procedures were analyzed, varying the cobalt precursor and the order of their impregnation. The catalyst interaction with NO + O 2 was studied using a microbalance and testing in both NO + O 2 and He atmospheres. Fourier Transformed Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD) were used to characterize the catalysts. The behavior of these catalysts as NO x traps was different. It was found that when cobalt nitrate was added to the Ba,K/CeO 2 catalyst, a high NO x adsorption capacity was obtained and, what is even more interesting, that the decomposition of the nitrated species occurred at lower temperature. The identification by XRD of a perovskite BaCoO 3 formed upon this preparation procedure was considered to be responsible for the different behavior observed in this particular catalyst.

Effect of preparation method on the structure and catalytic property of activated carbon supported nickel oxide catalysts

A series of activated carbon (AC) supported nickel oxide (NiO) catalysts were prepared by aqueous reduction preparation methods with nickel nitrate as a precursor. The effects of preparation procedure and reducing agent on catalyst structure and catalytic property were investigated. Based on the information obtained from physico-chemical characterizations and sorbitol dehydration performances, preparation methods were found to have a significant influence on NiO distribution and surface acidity. The catalysts prepared through the simultaneous loading-reduction procedure had stronger acidity and higher NiO dispersion on the outer surface of AC, which contributed jointly to high sorbitol conversion (turn-over frequency of 190–240 h −1) and slightly low selectivity to anhydro sugar alcohols ( ca. 66%). Correspondingly, with the procedure of reduction of supported nickel catalyst precursors, the selectivity to anhydro sugar alcohols was improved by ca. 10%, while sorbitol conversion was quite low ( ca. 20%). Reducing agent exerted less influence on the structure compared with preparation procedure. However, when the simultaneous loading-reduction procedure was used, sodium borohydride influenced the acidity remarkably by formation of a new strong acid site, resulting in better dehydration performances.