جستجوی مقالات مرتبط با کلیدواژه "wet impregnation" در نشریات گروه "شیمی"

The Pd composite membranes were fabricated by an improved electroless plating procedure. The wetness-impregnation technique was applied for ceramic substrate activation. The adsorption Pd complex on the γ-AlOOH or γ-Al2O3 layer was studied in this work. The obtained results showed that the Pd complexes on the γ-AlOOH layer adsorbed more than the γ-Al2O3 layer. Additionally, the effect of Pd precursor concentration on substrate loading was investigated. The rate of palladium deposition increases at high Pd concentrations. The resulting membrane was characterized by XRD and SEM-EDX analysis. Furthermore, permeation fluxes of the as-synthesized membrane were evaluated for various gases at different H2 Pressure differences. The membrane permeance was determined to be 6.8×10−7 mol/m2.s.Pa at 798 K and 1 bar under pure hydrogen. The hydrogen permeance and selectivity of hydrogen relative to other gases (CH4, CO2, CO, and N2) were evaluated at 773 K. All gases exhibited dilution and inhibiting (especially CO) effects on hydrogen permeation. The prepared membrane does not seem damaged as the permeability recovered after treatment with pure hydrogen.

In this study, carbon nanotubes (CNTs) were deposited directly on impregnated Fe/carbon paper (CP) substrate (CNT/CP) utilizing chemical vapor deposition (CVD) process with the aim of using them as electrocatalytic electrode. The influence of wet impregnation conditions and CVD growth parameters on the characteristics of CNTs was investigated. Field emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDS), Transmission electron microscopy (TEM) and Raman spectroscopy were applied to characterize nucleation, growth and morphology of CNTs on CP. Measurement of Contact angle (CA) determined 125.9 and 145.0 ⁰C for CP and CNT/CP that displayed an increase in water repellence and degree hydrophobicity of CNT/CP to 15% than CP. Electrochemical impedance spectroscopy (EIS) analysis indicated the reduction of electrode charge transfer resistance from 5000 ohm value from CNT/CP to ohm value for CP that shows the increment in electrical conductivity of CNTCP. Half-cell test analysis represented that the improvement of performance and the increase of power density to ⁓8 % for Pt/CNT/CP compared to commercial catalyst Pt/C/CP (20 wt%) even with about 42% less Pt loading, can be attributed to strong adhesion of in-situ CNTs to the CP and lower agglomeration of CNTs along with outstanding electrical and thermal conductivity of CNTs. The obtained results indicated that the proposed nanostructure serves as a promising candidate for many technological applications specially carbon nanotube-supported catalyst.

Nowadays, due to the decline in oil supplies on the one hand and raising the price of petroleum, on the other hand, countries have led to other sources of fuel and energy. The use of methods such as the production of light hydrocarbons from synthesis gas is highly regarded by the Fischer-Tropsch process, in these countries. This process is performed by heterogeneous catalysts, which consist of two parts. The first part is a catalyst support (generally porous and made of silica) and the second is an active phase, which is generally made of metal. In fact, the catalyst is the heart of Fischer -Tropsch process. In this study, iron-cobalt-cerium tri-metallic nano-catalyst based on silica was prepared by the wet impregnation method. The catalyst was tested in a fixed bed micro-reactor and a wide range of products was analyzed by GC technique. By increasing temperature, the CO conversion was increased and the efficiency of products was improved. Finally, the structure of nano-catalyst was characterized using the technique of scanning electron microscopy (SEM) to realize the particle size and surface properties of the catalyst.

In this research carbon nanotubes were produced by chemical vapor deposition of acetylene over a mixture of iron and cobalt catalysts supported on nanometric TiO2 and the influences of two synthesis parameters: growth temperature and catalyst composition ratio on properties of end-product carbon nanotubes were investigated. The catalytic basis was prepared by wet impregnation method with different wt% mass ratio of Fe-Co/TiO2=20-0/80, 15-5/80, 10-10/80, 5-15/80 and 0-20/80 wt%. The nanomaterials (catalysts and carbon nanotubes) were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray map of elemental distribution (Xmap) and Raman spectroscopy. The results confirmed that by increasing the growth temperature from 650°C to 800°C; the growth rate, the average diameter and the amount of impurities of grown carbon nanotubes increase and their length and density decrease. Furthermore, it was observed that in comparison with monometallic Fe or Co, bimetallic compositions of these metals exhibit better catalytic activity in growth of carbon nanotubes. The highest yield of carbon nanotubes possessing minimum average diameter was obtained on Fe-Co/TiO2 catalyst with a mass ratio of 10-10/80 wt%.

Nanometric Carbid Silicon (SiC) supported monometallic and bimetallic catalysts containing Fe, Co, Ni transition metals were prepared by wet impregnation method. Multiwall carbon nanotubes (MWCNTs) were synthesized over the prepared catalysts from catalytic decomposition of acetylene at 850°C by thermal chemical vapor deposition (TCVD) technique. The synthesized nanomaterials (catalysts and CNTs) were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Raman spectroscopy. In this paper, using of nanometric SiC powder as catalyst support was examined and the effect of applied catalyst type on characteristics of grown CNTs was investigated. The results revealed that iron, cobalt and nickel are in oxide, cobalt ferrite (CoFe2O4) and nickel ferrite (NiFe2O4) forms and nanometric SiC powder can be applied as an appropriate catalyst support in CNT growth process. It was observed that the produced CNTs on bimetallic Fe-Co possess smaller average diameter, less amorphous carbon and denser morphology compared to other binary metallic combinations. It was found that the catalytic activity of bimetallic composition decreased in the order of Fe-Co> Fe-Ni> Co-Ni. Furthermore, the monometallic Fe catalyst has the most catalytic activity compared to monometallic Co and Ni catalysts.

Monometallic and bimetallic Ni and Co catalytic nanoparticles supported on Titanium dioxide (rutile phase) substrate were preparedby wet impregnation method. These nanoparicles were used as catalysts for synthesis of multiwalled carbon nanotubes (MWCNTs) from acetylene decomposition at 700°C by the catalytic chemical vapor deposition (CCVD) technique. The nanomaterials (catalyst and CNTs) were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Raman spectroscopy. In this paper, the usage of TiO2 powder as catalyst support was examined and the effect of applied catalyst type on characteristics of grown CNTs was investigated. The results showed that the rutile phase of TiO2 powder can be applied as a suitable catalyst support in CNT growth process. Furthermore, it was observed that the CNTs synthesized on Ni-Co bimetallic catalyst possess smaller average diameters, better quality and less amorphous carbon compared to Ni and Co monometallic catalyst types.