Investigation of Room Temperature Synthesis of Titanium Dioxide Nanoclusters Dispersed on Cubic MCM-48 Mesoporous Materials

Sridhar Budhi,Ranjit Koodali,Chia-Ming Wu,Dan Zhao

doi:10.3390/catal5031603

Abstract

Titania containing cubic MCM-48 mesoporous materials were synthesized successfully at room temperature by a modified Stöber method. The integrity of the cubic mesoporous phase was retained even at relatively high loadings of titania. The TiO2-MCM-48 materials were extensively characterized by a variety of physico-chemical techniques. The physico-chemical characterization indicate that Ti4+ ions can be substituted in framework tetrahedral positions. The relative amount of Ti4+ ions in tetrahedral position was dependent on the order of addition of the precursor. Even at relatively high loadings of titania, no distinct bulk phase of titania could be observed indicating that the titania nanoclusters are well dispersed on the high surface area mesoporous material and probably exist as amorphous nanoclusters. The TiO2-MCM-48 materials were found to exhibit 100% selectivity in the cyclohexene oxidation at room temperature in the presence of tert-butylhydroperoxide (t-BHP) as the oxidant. The results suggest that room temperature synthesis is an attractive option for the preparation of TiO2-MCM-48 materials with interesting catalytic properties.

Highlights

The report of M41S series of periodic mesoporous materials in 1992 spurred excitement and brought a dramatic transformation in the field of porous materials [1,2]
The cubic MCM-48 material is an interesting material [11,12]. This is because MCM-48 consists of two continuous intersecting network of pores that leads to effective molecular trafficking of reactant(s) and product(s), minimizing clogging of pores and leading to enhanced catalytic reactivities in comparison to the uni-dimensional set of pores that occur in TiO2-MCM-41 [13]
We had reported a facile method for the rapid and reproducible synthesis of MCM-48 [15]. The advantages of this method are that a readily available and common cationic surfactant, cetyltrimethylammonium bromide (CTAB) can be used as the surfactant, avoiding the need for the use of specialized gemini surfactants [16], the synthesis can be conducted at room temperature, and the cubic phase can be formed in thirty minutes

Summary

Introduction

The report of M41S series of periodic mesoporous materials in 1992 spurred excitement and brought a dramatic transformation in the field of porous materials [1,2]. The availability of these types of mesoporous materials, helped push new frontiers in several interdisciplinary fields, notably catalysis [3], adsorption towards remediation of aqueous pollutants [4], and drug delivery [5]. MCM-48 is a favorable support material, literature reports regarding its use is lower in comparison to MCM-41 This is because the synthesis of the cubic MCM-48 phase is challenging and is formed only in a narrow range of conditions and is very sensitive to small deviations in the experimental conditions. The advantages of this method are that a readily available and common cationic surfactant, cetyltrimethylammonium bromide (CTAB) can be used as the surfactant, avoiding the need for the use of specialized gemini surfactants [16], the synthesis can be conducted at room temperature, and the cubic phase can be formed in thirty minutes

Methods

Results

Conclusion