Sharif Digital Repository

A novel mesoporous silica-functionalized dual Brønsted acidic species has been introduced as an efficient catalyst for solvent-free esterification of fatty acids with ethanol. The structure of the catalyst has been characterized by FT-IR spectroscopy, thermal gravimetric analysis (TGA), TEM and N2 adsorption-desorption. TGA of catalyst 1 showed no weight loss before 200 °C, indicating a high degree of hydrophobicity of the surface of the mesoporous silica. TEM images and nitrogen adsorption-desorption showed no noticeable changes to the structure of the catalyst before and after acid treatment. pH metric analysis was performed for the catalyst to determine the loading of the acidic sites.... 

(ZnO)1-x(CdO)x nanofibers were fabricated via electrospinning of polymer precursor by subsequent annealing in air. Field emission scanning electron microscopy (FESEM) showed the smooth and beadless nanofibers and X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed the ZnO hexagonal and the CdO cubic structure. Diffuse reflectance spectroscopy (DRS) showed the band gap energy reduction by increasing the amount of CdO in (ZnO)1-x(CdO)x nanofibers that resulted in the photocatalytic activity under the visible light for dye degradation. Under the UV light CdO acted as both electron and hole sink in the (ZnO) 1-x(CdO)x nanofibers and a possible photocatalytic activity... 

MCM-41 nanoparticles were prepared by in situ assembly of inorganic precursors and CTAB. The structure of nanoparticles was characterized by XRD, TEM, particle size analysis, N2 adsorption techniques. The surface modification of particles in order to perfect dispersion in polysulfone (PSf) matrix was performed by dimethyldichlorosilane (DMDCS) and aminopropyltrimethoxysilane (APTMS) as new modification agents. Thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and SEM analysis were applied to investigate thermal stability, glass transition temperature and quality of distribution of particle in the nanocomposite membrane, respectively. The PDMS was used to coat the... 

The preparation, characterization and catalytic application of a novel copper-loaded ionic liquid-based periodic mesoporous organosilica (Cu@PMO-IL) are described. The mesoporous structure of the Cu@PMO-IL material is characterized by transmission electron microscopy (TEM) and nitrogen adsorption-desorption analysis. The thermal stability of the material is also determined by thermal gravimetric analysis (TGA). The presence of copper species in the material framework is confirmed by X-ray photoelectron spectroscopy (XPS) and elemental analysis (EA). The catalytic application of Cu@PMO-IL nanocatalyst is then investigated in the Biginelli condensation of different aldehydes with urea and... 

The MgO-supported Fe-Co-Mn catalysts, prepared using co-precipitation procedure, were tested for production of light olefins via CO hydrogenation reaction. The effect of a range of drying conditions including drying temperature and drying time on the structure and catalytic performance of Fe-Co-Mn/MgO catalyst for Fischer-Tropsch synthesis was investigated in a fixed bed micro-reactor under the same operational conditions of T = 350 °C, P = 1 bar, H2/CO = 2/1, and GHSV = 4500 h-1. It was found that the catalyst dried at 120 °C for 16 h has shown the best catalytic performance for CO hydrogenation. Furthermore, the effect of drying conditions on different surface reaction rates was also... 

In order to improve the catalytic activity and durability of proton-exchange-membrane-fuel-cells (PEMFCs), Nafion-free Pt-based catalyst using the superacid-doped polymer coated multiwall carbon nanotubes (MWCNTs) was investigated. The modification and nano polymerization of MWCNTs were developed by polyvinylpyrrolidone (PVP). The following observations were made in the presence of polymer: better dispersion of MWCNTs, higher thermal stability of MWCNT/PVP than that of pristine MWCNT up to 450 °C as tested by thermal gravimetric analysis (TGA), homogeneous distribution of Pt without agglomeration as observed by transmission electron microscope (TEM), and not too much difference in Pt loading...