Abstract
A series of Sn-modified SBA-15, was studied. On top of Sn-only modified materials, several materials were modified with Sn and then Ti or with Sn and then Al. The new materials were obtained by adsorption of vapors of metal chlorides on SBA-15 (at 30–110 °C), and hydrolysis of adsorbed chlorides by water vapor at 25 °C, and then evaporation of left-overs of volatile compounds at 140 °C. The Sn-modified SBA-15 had lower specific surface area, and a higher thermal stability than the original silica. Even in materials containing substantial amount of Sn, the presence of crystalline phases representing Sn compounds was not detected by XRD. In contrast, rutile and anatase were observed in Sn- and Ti-modified SBA-15 while crystalline phases representing Ti compounds were not detected when Ti was deposited directly on SBA-15 (not modified with Sn). The profiles of Sn concentration across the particles of Sn-modified SBA-15 indicate that Sn is located in the pores rather than on the external surface.
Highlights
Mesoporous silicas modified with metals have been extensively studied for many decades, and tin is among the metals, most frequently used to modify porous silicas
3.2 Preparation of Sn‐modified SBA‐15 The specimens of Sn-modified SBA-15 after hydrolysis of adsorbed SnCl4 were dried at various temperatures in order to establish the conditions necessary to completely remove the volatile compounds from silica
Tin is deposited on SBA-15 by evaporation and condensation of vapor of S nCl4 at temperatures of 30–50 °C in a closed reactor and by hydrolysis at room temperature
Summary
Mesoporous silicas modified with metals have been extensively studied for many decades, and tin is among the metals, most frequently used to modify porous silicas. Pang et al [5] obtained composites with Si/Sn molar ratios from 130 to 394 by impregnation of SBA-15 with ethanolic solution of S nCl4 pentahydrate. Their composites had slightly lower SSA and identical total pore volume as the original SBA-15. They studied a Sn-modified specimen obtained by incipient wetness impregnation, and their materials were used as catalysts for conversion of carbohydrates to methyl lactate
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