MWW-Type Titanosilicate Synthesized by Simply Treating ERB-P Zeolite with Acidic H2TiF6 and Its Catalytic Performance in a Liquid Epoxidation of 1-Hexene with H2O2

Synthesis of a Ti-incorporated zeolite using a simple and economical method has recently become a focus of attention. The direct hydrothermal synthesis of Ti-MWW is most commonly applied; however, it is challenging to perform and exhibits low titanium utilization. An innovative strategy of synthesizing Ti-MWW is proposed in the present study by simply treating the ERB-1 precursor of an MWW-type boron silicate with a H₂TiF₆/HNO₃ solution. This significantly shortens the Ti grafting process from 5 days to only a few hours and reduces the use of the structure-directing agent hexamethyleneimine (HMI); furthermore, no extraframework Ti is observed in the precursor, indicating good atomic economy. Typically, a piperidine (PI)-treated sample Ti-MWW_2-1-PI exhibits a higher conversion (76.6%) than the original Ti-MWW (44.8%) in the epoxidation of 1-hexene. X-ray diffraction (XRD), inductively coupled plasma (ICP), and transmission electron microscopy (TEM) techniques are used to explain in detail the probable mechanism underlying the incorporation of Ti species into the MWW framework. X-ray photoelectron spectroscopy (XPS) is employed to study the coordinate state of the Ti and F species in the samples after treatment with a piperidine solution. This method can be applied to synthesize other kinds of lamellar-structured zeolites with heteroatoms.

Thermolabile Organotitanium Monoalkyl Phosphates: Synthesis, Structures, and Utility as Epoxidation Catalysts and Single-Source Precursors for TiP2O7

The reaction of [Cp*TiCl₃] (Cp* = C₅Me₅) with monoalkyl phosphates (RO)PO₃H₂ (R = Me, Et, and ⁱPr) in tetrahydrofuran (THF) at 25 °C leads to the formation of binuclear complexes [Cp*₂Ti₂(μ-O₂P(OH)OR)₂(μ-O₂P(O)OR)₂] [R = Me (1), Et (2), and ⁱPr (3)]. On the other hand, the reaction of ( ^tBuO)₂PO₂K with [Cp*TiCl₃] in acetonitrile or THF results in isolation of either the dinuclear [Cp*₂Ti₂(μ-O₂P(OH)O ^tBu)₂(μ-O₂P(O)O ^tBu)₂] (4) or the trinuclear titanophosphate [Cp*₃Ti₃(μ-O₃PO ^tBu)₂(μ-O)₂(μ-O₂P(O ^tBu)₂)] (5), respectively. The formation of compounds 4 and 5 is facilitated by partial hydrolysis of the tert-butoxy groups of ( ^tBuO)₂PO₂K. New titanophosphates 1-5 have been characterized by spectroscopic and analytical methods, and the molecular structures have further been confirmed by single-crystal X-ray diffraction studies. Thermal decomposition studies of 1-5 reveal the initial loss of thermally labile alkyl substituents of the organophosphate ligands, followed by the loss of C₅Me₅ groups to form an organic-free amorphous titanophosphate in the temperature range 300-500 °C. This material transforms to highly crystalline titanium pyrophosphate TiP₂O₇ at 800 °C. Compounds 1-5 and the TiP₂O₇ materials obtained at 300, 500, and 800 °C through the thermal decomposition of 3 have been employed as efficient homogeneous catalysts for the alkene epoxidation reaction. Using hydrogen peroxide as the oxidant in an acetonitrile medium, these catalysts exhibit >90% alkene conversion with >90% epoxide selectivity in 4 h at temperatures below 100 °C.

A facile organosilane-based strategy for direct synthesis of thin MWW-type titanosilicate with high catalytic oxidation performance

A facile organosilane-based synthetic strategy was successfully developed to prepare thin Ti-MWW zeolite with high catalytic oxidation performance.

Structure and catalytic activity of a newly proposed titanium species in a Ti-YNU-1 zeolite: a density functional theory study

Density functional theory was applied to investigate the structure of the framework titanium (Ti) species in the Ti-YNU-1 zeolite, and to evaluate its catalytic activity for 1-hexene epoxidation with H₂O₂ as the oxidant.

Theoretical insights into C–C bond formation through isonitrile insertion into a Cp*Ti complex

Reaction of Cp*(Cl)Ti(2,3-dimethylbutadiene) with isonitriles is studied using DFT, detailed elementary reaction steps and N-substitution effects of isonitrile are examined.