An Analysis upon Different Characterization Techniques for the Catalysts Preparation: Impact of Acidalkali and Metal Impregnation on the Characterization of Fly Ash Catalysts

Abstract

Describes the physical properties of the catalysts obtained on the basis of the characterization techniques. The cation exchange capacity (CEC) of fly ash was enhanced after acidalkali treatment and metal impregnation and this has been attributed to creation of defect sites and broken bonds on the oxide surfaces. Overall the order of increasing CEC is as followsF2 > N2 > C2 > M2 > F1 >N1 > C1 > M1 > F3 > C3 > N1 > M3 >> OAAS measurements showed that the amount of Fe(III), Co(II), Ni(II) and Mn(II) entering into the fly ash material was different and follow the order of Fe(III) > Co(II) > Ni(II) > Mn(II). XRF results confirm that silica is the major oxide and all the fly ash catalysts belong to Class F type fly ash. The LOI value (ww ) also increased after metal impregnation.The XRD spectra could show the differences in crystallinity and other properties in terms of the changes in the diffraction bands of the fly ash catalysts before and after acidalkali or metal impregnation treatment. These results were supplemented with the FT–IR study. It was observed that the M–O stretching band shifted after acid and alkali treatment of the fly ash for all the eight catalysts. However, formation of new bonds was not observed in any of the cases, indicating little change in chemical properties of the metal oxides.Scanning electron micrographs showed that the surfaces became rough and more porous after treatment of the fly ash with acid and alkali. After metal impregnation, the grains of salts over the surface of fly ash are clearly visible. BET adsorption-desorption isotherms of raw fly ash and the metal impregnated catalysts yielded Type II nitrogen adsorption isotherm with H3 hysteresis loop. The measurements indicated that both surface area and pore volume are higher for the acid treated fly ash catalysts than the others (water washed and alkali treated fly ash based catalysts) and the maximum surface area was found in acid treated Fe(III)-catalyst (F2) (3.60 m2g).