A new route for the synthesis of manganese incorporated SBA-15

Manganese incorporated SBA-15 was synthesized by pre-hydrolyzing tetraethyl orthosilicate and manganese acetate above the isoelectric point of silica (pH 2-4) employing triblock copolymer as the template. The synthesized material was characterized by AAS, XRD, N-2 adsorption, FT-IR, TGA, ESR, diffuse reflectance UV-Vis and SEM techniques. The XRD results showed well-ordered hexagonal array of the synthesized materials. The thermal stability of synthesized material was evaluated using TGA. The results of AAS, ESR and UV-Vis DRS revealed that almost all manganese added in the initial reaction is introduced into the product at higher pH. Thus, higher pH of the synthesis gel favoured better incorporation of manganese in the framework. The incorporation of Mn2+ in the product was confirmed by ESR studies, and the presence of Mn3+ ions was clearly evident from UV-Vis DRS studies. Thus manganese exists both as bivalent and trivalent states in all the synthesized materials. (C) 2007 Elsevier Inc. All rights reserved.