Synthesis, Structure, and Reactivity of a New Ti-Containing Microporous/Mesoporous Material

Abstract

A new class of porous, mixed phase titanosilicate materials containing a microporous TS-1 phase and a mesoporous Ti-MCM-48 phase has been successfully synthesized. A novel, one-pot synthesis method was used in which the organic templates for the mesoporous and microporous phases were added sequentially to the same reaction mixture, followed by crystallization at 150 degrees C. The gemini surfactant 18-12-18 was used to form the Ti-MCM-48 mesophase; subsequent addition of tetrapropylammonium cation (TPA+) led to the formation of TS-1. The relative amounts of the two phases within the final products were controlled by optimizing the crystallization time. Crystallization times between 12 and 50 h gave materials containing both phases, with an increasing amount of microphase formed at longer crystallization times. These materials, called "Ti-MMM-2" (microporous/mesoporous materials) were characterized using powder XRD, N2 physisorption, TEM, FTIR, DR-UV/Vis spectroscopy, and 29Si MAS NMR. In the epoxidation of cyclohexene with tert-butyl hydroperoxide (TBHP), Ti-MMM-2 samples exhibited higher catalytic activity (approximately 61%) than either TS-1 (16%) or Ti-MCM-48 (42%), with a very high selectivity (97%) for formation of cyclohexene oxide.

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

“…We found that the catalytic activity for the oxidation of cyclohexene to be in the order, Interestingly, all catalysts showed exclusive and 100% selectivity for the formation of cyclohexene oxide, contrary to a previous report in which other products have been identified [38]. The turnover number (moles of cyclohexene converted/mol Ti) after 12 h of reaction at room temperature was estimated to be 59, 32 activity.…”

“…Titania based MCM-48 materials have been utilized for selective oxidation of styrene [31], 2,6-di-tert-butylphenol [32,33], methyloleate [34], and cyclohexene [25,[35][36][37][38][39]. TiO2-MCM-48 prepared by a hydrothermal method was examined for the catalytic oxidation of cyclohexene.…”

“…In another study, TiO2-MCM-48 was prepared by a hydrothermal method at 150 °C for 20 h and using a gemini surfactant. The oxidation of cyclohexene was chosen as a test reaction and the turnover frequency was found to be 5.1 (h −1 ) [38]. The epoxidation of cyclohexene with aqueous hydrogen peroxide over mesostructured Ti(Cp)2Cl2-grafted TiO2-MCM-48 was examined in another study [39].…”

Modern Spectroscopic Methods Applied to Nanoscale Porous Materials

“…Hence, NMR is widely used for studying the structure of intermediate species in solidification processes of nanozeolites, 1-3 external and internal surface active sites of porous nanomaterials, 4,5 atomic coordination and guest-host interactions in aluminosilicate, aluminophosphate, and mixed tetrahedral-octahedral porous materials. [6][7][8][9][10][11][12][13] Electron spin resonance (ESR) spectroscopy is based on the response of electron spins to microwaves under an external magnetic field. Its application is restricted to materials containing transition elements of low concentration.…”

Preparation of Mesoporous Organically Modified Titanium Materials and their Activity in the Oxidation of Cyclohexene

“…The preparation of highly active and stable catalysts under various operating conditions using tbutylhydroperoxide (TBHP) as oxidant has been reported [20][21][22].…”