Synthesis of titanium silicalite‐1 with high titanium content and its catalytic performance of propylene epoxidation

Abstract

Titanium silicalite-1 (TS-1) has unique catalytic properties for oxidation reactions due to the titanium atom in the framework. To increase the Ti content in the framework, polyvinylpyrrolidone (PVP) was added as a surfactant to modify TS-1 (PTS-1). The titanium content in PTS-1 as the active site in the catalytic reaction increased to 0.87 wt%, compared with the traditional TS-1 which has a titanium content of 0.64 wt%. Simultaneously, the average particle size of PTS-1 is reduced to 180 nm, compared with TS-1 (230 nm). The increase in Ti content makes the Au loading increase; thus, Au/PTS-1 shows higher catalytic performance for propylene epoxidation, and the propylene oxide (PO) formation rate increases from 95 g PO h −1 kg Cat −1 with Au/TS-1 to 190 g PO h −1 kg Cat −1 with Au/PTS-1. In addition, the mechanism for the modification of Ti content by PVP is proposed.

Design of Novel Photoactive Modified Titanium Silicalites and Their Application for Venlafaxine Degradation under Simulated Solar Irradiation

“…The synthesis method to prepare the titanium silicalites (TS) is based on the one described by W. Ma et al [ 38 ] Figure displays the scheme of the synthesis and the code list for the synthesised materials and the specifications of the reagents used. The detailed procedure of the modified TSs preparation can be found in Section S1, Supporting Information.…”

“…[ 49 ] The shape of the particles in this material derives from the presence of PVP in the synthesis media, which not only slows down the TBOT hydrolysis aiding the introduction of titanium in the matrix but also competes with the TPA + cation acting as a surfactant. This competition changes the crystal growth due to the PVP hydrogen bonding interactions within the TS skeleton, [ 38 ] yielding flat‐cylinder‐shaped particles with smaller sizes than titanium silicalites synthesized by similar procedures (0.5–3 μm). [ 18,50,51 ] The micrographs of the TSR materials show how the use of RTEOS has a big impact on their morphology, as they exhibit bigger, rougher, and more spherical‐shaped particles than those of TS0, suggesting that the organic moiety of RTEOS hinders the surface interaction of the colloids with the SDAs, which might be the reason why more the molar percentage of RTEOS, bigger the particles of the material (TS0 < TSPh5 < TSPh10).…”

“…Results in Table 2 show that most of the materials contain ≈0.9 wt% of titanium, consistent with the previously reported titanium silicalites synthesized under the same conditions. [ 38 ] The presence of carbon in the materials is due to the calcination residues from the organic templates, identified as dust in the micrographs. Surprisingly, TSP5 presents the highest titanium amount out of all the materials.…”

“…[49] The shape of the particles in this material derives from the presence of PVP in the synthesis media, which not only slows down the TBOT hydrolysis aiding the introduction of titanium in the matrix but also competes with the TPA þ cation acting as a surfactant. This competition changes the crystal growth due to the PVP hydrogen bonding interactions within the TS skeleton, [38] yielding flatcylinder-shaped particles with smaller sizes than titanium silicalites synthesized by similar procedures (0.5-3 μm). [18,50,51] The micrographs of the TSR materials show how the use of V micro a)…”

“…[ 37 ] In this context, Ma et al reported that polyvinylpyrrolidone (PVP) acts as a structure‐directing agent (SDA) in the synthesis of TSs, competing with commonly used surfactants, such as TPAOH, and regulating the nanostructuration of the silica skeleton. [ 38 ] In addition, PVP decreases the condensation rate once the titanium precursor is hydrolyzed, favoring its crosslinking with the hydrolyzed silica precursor.…”