Catalytic activity of Co-åkermanite and Co-pyroxene in oxidation reactions

2011 ◽  
Vol 89 (8) ◽  
pp. 939-947 ◽  
Author(s):  
Irena Mihailova ◽  
Dimitar Mehandjiev
Keyword(s):  
Catalytic Activity ◽  
Solid Phase ◽  
Sol Gel ◽  
Cobalt Content ◽  
Octahedral Coordination ◽  
Tetrahedral Coordination ◽  
Oxidation Reactions ◽  
Oxidation Of Co ◽  
Phase Synthesis ◽  
Catalytically Active

Two calcium–cobalt silicates were synthesized in which cobalt occupies different structural positions. The crystal phases belong to two main structural silicate types. In the Co-åkermanite structure (Ca2CoSi2O7), cobalt cations take tetrahedral coordination toward oxygen atoms. In the Co-pyroxene structure of CaCoSi2O6, cobalt displays octahedral coordination. Ca2CoSi2O7 was prepared by solid-phase synthesis and CaCoSi2O6 was prepared by sol–gel method. The synthesis of the phases was confirmed by XRD, FTIR, and EPR data. On the basis of the XPS analysis, it can be concluded that Co2+ cations exist in the studied silicates. Thus, it is possible to study the catalytic activity of two silicate phases containing Co2+ cations in different coordinations: tetrahedral and octahedral. It was found that cobalt silicates with crystal structures corresponding to pyroxene and åkermanite possess catalytic activity in the reactions of complete oxidation of CO and toluene. Co-pyroxene exhibits higher catalytic activity than Co-åkermanite, but the higher cobalt content on the surface of Co-pyroxene should also be taken into account. Then, it turns out that catalytically active complexes with Со2+ ions in tetrahedral coordination are more efficient than those with such ions in octahedral coordination when equal concentrations of cobalt were used on the surface of the catalysts.

Lignin-assisted solid-phase synthesis of nano-CuO for a photocatalyst with excellent catalytic activity and high performance supercapacitor electrodes

RSC Advances ◽  
2016 ◽  
Vol 6 (70) ◽  
pp. 65644-65653 ◽  
Author(s):  
Xiaohong Wang ◽  
Fangsheng Wu ◽  
Yawei Duan ◽  
Yingying Wang ◽  
Chen Hao ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
High Performance ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Phase Method ◽  
Phase Synthesis ◽  
Solid Phase Method

CuO nanostructures were successfully synthesized using NaOH and Cu(NO3)2 as starting materials by an aminated lignin (AL)-assisted solid-phase method.

Three-Dimensional Periodic Hematite Photocatalysts Fabricating by Direct Writing Method

2014 ◽  
Vol 1025-1026 ◽  
pp. 621-627
Author(s):  
Qin Mei Peng ◽  
Bo Li ◽  
Jin Wang ◽  
Ji Jiao Li ◽  
Ji Zhou
Keyword(s):  
Methylene Blue ◽  
Catalytic Activity ◽  
Organic Contaminants ◽  
Degradation Rate ◽  
Sol Gel ◽  
Three Dimensional ◽  
High Catalytic Activity ◽  
Direct Writing ◽  
Catalytically Active ◽  
Gel Technique

Three-dimensional (3-D) periodic hematite scaffold was successfully fabricated by direct writing method as a catalyst for degradation of organic contaminants. Photo-catalytically active α-Fe2O3 nanoparticles have been synthesized by sol-gel technique. Aqueous slurries of iron oxides were freeform fabricated to produce hematite scaffolds with a 3-D periodic architecture and multiscale porosity. The catalytic activity of the hematite scaffolds was evaluated in the degradation of Methylene Blue (MB). It was found that the degradation rate of MB dye was over 83%. The result strongly indicates that the hematite scaffolds exhibits a high catalytic activity. Moreover, this work provides an important step forward in the creation of suitable structures for photocatalyst.

scholarly journals Effect of Na2O Doping on the Surface and Catalytic Properties of the Mn2O3/Al2O3 System

1995 ◽  
Vol 12 (2) ◽  
pp. 119-128 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.M. Ghozza ◽  
S. Hammad
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Catalytic Properties ◽  
Xrd Analysis ◽  
Manganese Carbonate ◽  
Oxidation Of Co ◽  
Mechanical Mixing ◽  
Catalytic Activities ◽  
Specific Catalytic Activity ◽  
Catalytically Active

Manganese/aluminium mixed oxide solids having the formula 0.2MnCO3/Al2O3 were prepared by mechanical mixing of a known weight of finely powdered manganese carbonate and aluminium hydroxide. The solids obtained were treated with NaNO3 (0.75–6 mol%) solution and dried at 110°C, then calcined in air at 500°C and 800°C for 6 h. The phases produced were identified by XRD analysis. The surface properties (SBET, Vp and r̄) of the pure and doped solids were studied by using N2 adsorption at – 196°C and their catalytic activities were determined by studying the oxidation of CO by O2at 125–300°C. The results obtained reveal that pure and doped mixed solids preheated in air at 500°C and 800°C consist of Mn2O3 (partridgite) and a poorly crystalline γ-alumina. Doping with sodium oxide at 500°C and 800°C resulted in a small decrease (14–19%) in the SBET value of the treated solids. However, this treatment brought about a significant modification in the catalytic activity of the doped solids. Doping with 0.75% Na2O at 500°C led to an increase of about 30–50% in the specific catalytic activity which was found to decrease on increasing the percentage of Na2O above this limit, falling to values smaller than that measured for the undoped catalyst. Doping at 800°C led to a progressive decrease in the activity of the treated solid to an extent proportional to the amount of dopant present. The doping process at 500°C and 800°C did not modify the mechanism of the catalytic reaction but altered the number of catalytically-active sites contributing in the catalysis of CO oxidation by O2 without changing their energetic nature.

Fabrication of BST Films by Electrophoretic Deposition from Nano-Scaled (Ba,Sr)TiO3 Synthesized by Different Methods

2007 ◽  
Vol 280-283 ◽  
pp. 243-246 ◽  
Author(s):  
Jian Ling Zhao ◽  
Xiao Hui Wang ◽  
Long Tu Li
Keyword(s):  
Electrophoretic Deposition ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Sol Gel ◽  
Deposition Parameter ◽  
Phase Synthesis ◽  
Coprecipitation Process ◽  
Tio3 Film ◽  
Bst Films ◽  
Lower Temperature

(Ba,Sr)TiO3 films with thickness between 1 ~ 20 µm are fabricated by electrophoretic deposition using (Ba,Sr)TiO3 nanopowder synthesized by different methods including sol-gel, coprecipitation and conventional solid phase synthesis. Experiments show that conventional solid phase synthesis need higher crystallization temperature (>1000°C) and result in larger size of particle while in sol-gel and coprecipitation process (Ba,Sr)TiO3 crystallizes at lower temperature and results in smaller size of particle . Powders synthesized from various routes have different surface property. Deposition parameter must be adjusted accordingly to obtain dense and smooth (Ba,Sr)TiO3 film.

scholarly journals Tailoring of Magnesium Substitution on Structure and Magnetic Properties of Lithium Ferrites

2021 ◽  
Vol 22 (2) ◽  
pp. 217-223
Author(s):  
Julia Mazurenko
Keyword(s):  
Magnetic Properties ◽  
Solid Phase ◽  
Sol Gel ◽  
Combustion Method ◽  
Magnetic Characteristics ◽  
Phase Synthesis ◽  
Lithium Ferrites ◽  
Auto Combustion ◽  
Similar Materials ◽  
Shift Data

In this study is reported influence of Mg2+ doping on structure and magnetic properties of nano-sized Li0.5Fe2.5-XMgXO4 (0.0, 0.2, 0.4, 0.6, 0.8) synthesized using sol-gel auto-combustion method. The X-ray diffractometric and Mössbauer data analysis of samples confirmed the formation of pure Li0.5Fe2.5-XMgXO4 nanoparticles ranges crystallite size from 15 nm to 35 nm. Iron ions are redistributed on the A and B sites in a ratio of approximately 4:6, and magnesium ions 8:2, respectively. The advantages of the B position of the above ions are as follows: Li+>Fe3+>Mg2+. RT-Mössbauer indicated the presence of 57Fe in both sublattices. Position identification was performed based on the distribution of the over exchange fields and isomeric shift data. Magnetic characteristics were obtained for rings made of synthesized material. They showed a non-monotonic dependence on the composition and found significantly higher rates compared to similar materials obtained by solid-phase synthesis.

scholarly journals Surface and Catalytic Properties of NiO and Fe2O3 Solids

1997 ◽  
Vol 15 (8) ◽  
pp. 593-607 ◽  
Author(s):  
A. Abd. El-Aal ◽  
A.M. Ghozza ◽  
G.A. El-Shobaky
Keyword(s):  
Catalytic Activity ◽  
Calcination Temperature ◽  
Active Sites ◽  
Pore Radius ◽  
Total Pore Volume ◽  
Surface Characteristics ◽  
Oxidation Of Co ◽  
Catalytic Activities ◽  
Catalytically Active ◽  
The Mean

The surface characteristics, viz., the specific surface area SBET, the total pore volume Vp and the mean pore radius r̄, of NiO and Fe2O3 were determined from N2 adsorption isotherms conducted at −196°C for the different adsorbents preheated in air at temperatures in the range 300–800°C. The catalytic activities exhibited in CO oxidation by O2 on the various solids were investigated at temperatures varying between 150°C and 400°C. The effect of heating the NiO and Fe2O3 solids in CO and O2 atmospheres at 175–275°C on their catalytic activities was also studied. The results showed that increasing the calcination temperature in the range 300–800°C resulted in a progressive decrease in the SBET value of NiO and Fe2O3. The computed values of the apparent activation energy for the sintering of the oxides were 71 and 92 kJ/mol, respectively. The sintering of NiO and Fe2O3 took place mainly via a particle adhesion mechanism. The catalytic activity of NiO decreased progressively on increasing its calcination temperature from 300°C to 800°C, due to a decrease in its SBET value and the progressive removal of excess O2 which was present as non-stoichiometric NiO. This treatment also decreased the catalytic activity of Fe2O3. The decrease was, however, more pronounced when the temperature increased from 300°C to 400°C which was a result of the crystallization of the ferric oxide into the α-Fe2O3 phase. An increase in the calcination temperature for both oxides from 300°C to 800°C did not modify the mechanism of oxidation of CO by O2 over the various solids but rather changed the concentration of catalytically active sites. Heating NiO and Fe2O3 in CO and O2 atmospheres at 175–275°C modified their catalytic activities, with Fe2O3 being influenced to a greater extent than NiO.

scholarly journals Effect of Metal Loading in Unpromoted and Promoted CoMo/Al2O3–TiO2 Catalysts for the Hydrodeoxygenation of Phenol

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 550 ◽  
Author(s):  
J. Andrés Tavizón-Pozos ◽  
Carlos E. Santolalla-Vargas ◽  
Omar U. Valdés-Martínez ◽  
José Antonio de los Reyes Heredia
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Mixed Oxides ◽  
Batch Reactor ◽  
Sol Gel ◽  
Active Phase ◽  
Catalytic Performance ◽  
Octahedral Coordination ◽  
Optimum Amount ◽  
Co Concentration

This paper reports the effects of changes in the supported active phase concentration over titania containing mixed oxides catalysts for hydrodeoxygenation (HDO). Mo and CoMo supported on sol–gel Al2O3–TiO2 (Al/Ti = 2) were synthetized and tested for the HDO of phenol in a batch reactor at 5.5 MPa, 593 K, and 100 ppm S. Characterization results showed that the increase in Mo loading led to an increase in the amount of oxide Mo species with octahedral coordination (MoOh), which produced more active sites and augmented the catalytic activity. The study of the change of Co concentration allowed prototypes of the oxide species and their relationship with the CoMo/AT2 activity to be described. Catalysts were tested at four different Co/(Co + Mo) ratios. The results presented a correlation between the available fraction of CoOh and the catalytic performance. At low CoOh fractions (Co/(Co + Mo) = 0.1), Co could not promote all MoS2 slabs and metallic sites from this latter phase performed the reaction. Also, at high Co/(Co + Mo) ratios (0.3 and 0.4), there was a loss of Co species. The Co/(Co + Mo) = 0.2 ratio presented an optimum amount of available CoOh and catalytic activity since the XPS results indicated a higher concentration of the CoMoS phase than at a higher ratio.

scholarly journals Zirconia-supported 11-molybdovanadophosphoric acid catalysts: effect of the preparation method on their catalytic activity and selectivity

2018 ◽  
Vol 74 (11) ◽  
pp. 1334-1347 ◽  
Author(s):  
Bouchra El Bakkali ◽  
Guido Trautwein ◽  
Juan Alcañiz-Monge ◽  
Santiago Reinoso
Keyword(s):  
Catalytic Activity ◽  
Heterogeneous Catalysts ◽  
Catalyst Activity ◽  
Sol Gel ◽  
Relevant Parameter ◽  
Consecutive Reaction ◽  
Green Route ◽  
Catalytically Active ◽  
Molybdovanadophosphoric Acid ◽  
Derivatives Of

The oxidation of adamantane with hydrogen peroxide catalyzed by zirconia-supported 11-molybdovanadophosphoric acid is shown to be a suitable green route for the synthesis of adamantanol and adamantanone. This work evaluates how the catalyst activity and selectivity are affected by some of its preparative parameters, such as the method for supporting the catalytically active heteropoly acid over the zirconia matrix or the pretreatments applied to the resulting materials before being used as heterogeneous catalysts. Our results indicate that the most effective catalysts able to maintain their activity after several reaction runs are those prepared by following the sol-gel route, whereas the most selective catalysts are those obtained by impregnation methods. Moreover, the calcination temperature has also been identified as a relevant parameter influencing the performance of catalysts based on supported heteropoly acids. The increasing catalytic activity observed over several consecutive reaction runs has been attributed to the formation of peroxo derivatives of polyoxometalate clusters at the surface of the catalyst and their accumulation after each reaction cycle.

Catalytic Activity of Tetranitro-Copper Phthalocyanine Supported on Carbon Nanotubes towards Oxygen Reduction Reaction

2013 ◽  
Vol 706-708 ◽  
pp. 15-19 ◽  
Author(s):  
Feng Ying Chen ◽  
Ke Zhi Li ◽  
He Jun Li
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction ◽  
Copper Phthalocyanine ◽  
Solid Phase ◽  
Synthesis Method ◽  
Rotating Disk ◽  
Reduction Reaction ◽  
Rotating Disk Electrode ◽  
Multiwalled Carbon ◽  
Phase Synthesis

Acid-functionalized multiwalled carbon nanotube (AF-MWCNT)-supported tetranitro-copper phthalocyanine (TNCuPc) assemblies were prepared by solid phase synthesis method. The products were characterized by infrared spectroscopy, scanning electron microscopy and XRD. The electrocatalytic activity of the obtained AF-MWCNT-supported TNCuPc assemblies was measured by cyclic voltammetry (CV) and rotating disk electrode (RDE) techniques in an oxygen-saturated 0.1 M KOH. The results showed that the catalytic activity of TNCuPc/AF-MWCNTs towards oxygen reduction was a two-step, two-electron process for oxygen reduction.

Hard-Templating Synthesis of Mesopours La1-xSrxMnO3+σ Perovskite and Catalysis Activity in CO Oxidation

2011 ◽  
Vol 306-307 ◽  
pp. 1342-1349 ◽  
Author(s):  
Xue Hui Huang ◽  
Ming Li
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
Surface Area ◽  
Sol Gel ◽  
Oxidation Of Co ◽  
X Ray ◽  
Adsorption Desorption ◽  
Templating Synthesis ◽  
Scanning Electron ◽  
Hard Templating

La1-xSrxMnO3+σperovskite/ySBA-15(x=0, 0.1, 0.2, 0.3、y=0, 1, 2, 3) catalyzers were prepared by two different methods, which are the hard-templating and sol-gel methods. The catalysts were characterized by Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), X-ray fluorescence spectroscopy(XRD) and N2adsorption/desorption(BET). Their catalytic activity in the oxidation of CO was evaluated. BET and SEM results showed that the repeated template samples had higher surface area(143.7m2/g) and smaller particle size(18nm). The catalytic activity for CO reached the highest value when x=0.2 and y=2. The repeated template samples had higher activity than the sol-gel samples due to the higher surface area.

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