Effect of Surfactant Concentration on the Physico-chemical Characteristics of Mesoporous Molecular Sieve

Abstract

A series of mesoporous molecular sieve samples have been synthesized hydrothermally by using cetyltrimethylammonium bromide (CTAB) as a template, tetraethyl orthosilicate (TEOS) as a silica source, tetramethyl ammonium hydroxide as a base source and water as a solvent. The samples were prepared by adding required amount of surfactant, TEOS, water and TMAOH to maintain pH, then the obtained mixture was stirred for 10 min. and then transferred into autoclave. pH of the gel was adjusted to 10. The molar ratio of surfactant (CTAB) and TEOS was kept at 0.11:0.48, 0.165:0.48, 0.22:0.48 and 0.274:0.48 for samples A-I, A-II, A-III and A-IV respectively, while the aging time was kept 4 days and temperature remained constant at 393 K. The as-synthesized samples were thoroughly washed with distilled water and then dried at 373 K for 24 h. The as-synthesized samples were calcined at 723 K for 6 h in air. The as-synthesized samples were characterized for its morphology using Field Emission Scanning Electron Microscopy (FESEM), elemental analysis by using Energy Dispersive X-Ray (EDX), thermal stability by using Thermogravimetric Analysis (TGA), the functional groups within the samples before and after calcination was analyzed using Fourier Transform InfraRed Spectroscopy (FTIR). Formation of the mesoporous material depends on the surfactant, which act as a structure directing agent. Micelles of the surfactant arrange themselves and interact with the silicate ions to form the mesoporous material. In this study, the effect of concentratiohn was studied on the synthesis and found that due to increase in concentration of surfactant, more silica polymerized and formation of material increases.