Direct templating assembly route for the preparation of highly-dispersed vanadia species encapsulated in mesoporous MCM-41 channel

Abstract

The statues of active sites such as number and dispersion on the surface of support are essential to improve the catalytic activity. In this paper, highly-dispersed and controllable quantities of vanadia species within channel of mesoporous MCM-41 were directly prepared by a direct templating assembly method (S + L -M + I -). This method was based on the self-assembly of cationic surfactants (CTA + , S + ), chelating agents (citrate ions, L -), vanadyl ions (VO 2+ , M + ) and silicates oligomers (I -) by the electrostatic and chelating interaction. First, the citrate ions were absorbed on the CTA + micelles' surface by electrostatic interaction, the vanadyl ions subsequently were anchored on their surface by chelating with citrate ions to form metallomicelles. Finally, the silicates were deposited on the metallomicelles to obtain the targeted product. The structure of samples, especially the oxidation state and surface distribution of vanadium species on the mesoporous silica were efficiently characterized with different techniques including XRD, N 2 adsorption, SEM, TEM, UV-vis, XPS, FT-IR, ICP and H 2 -TPR.Furthermore, the obtained samples, using hydroxylation of benzene as a probe reaction, exhibited superior catalytic activities when compared with post-synthesized sample.

A Facile Method for the Direct Introduction of FeOxin Mesoporous AMS Through A Templating Route (S−[MN]+I−) and Its Catalytic Application

“…Also, along with the growth amount of iron species in the channel of FeO x ‐AMS samples, the average pore size (D p ) would be dropped and the wall thickness (W t ) would be thickened continually, which may be ascribed to a pore‐filling. The similar phenomena were noted in previous reports. This is strongly proved iron functionalized APATES as a co‐structure directing agent would be effectively correlated with silica wall in the channel of FeO x ‐AMS samples.…”

Oriented Decoration in Metal-Functionalized Ordered Mesoporous Silicas and Their Catalytic Applications in the Oxidation of Aromatic Compounds

“…In fact, during the self-assembly process, the transition metals (M + ) could be directly introduced by the effect of coulomb interactions in the position between cationic surfactant micelles (S + ) and silicate oligomers (I − ). To achieve this process, as the schematic mechanism shown in Figure 5, our group developed a direct templating assembly method (S + X − M + I − ) to obtain the V/MCM catalysts [67], which was based on the self-assembly of cationic surfactants (CTA + , S + ), chelating agents (citrate ions, X − ), vanadyl ions (VO 2+ , M + ) and silicate oligomers (I − ) via electrostatic and chelating interaction. Through this method, the citrate ions (X − ) were firstly absorbed on the surface of CTA + micelles (S + ) by electrostatic interaction, then the vanadyl ions (M + ) were subsequently anchored on their surface by chelating with citrate ions to form metallomicelles (S + X − M + ), and the electronegative silicates oligomers (I − ) were finally deposited on the metallomicelles.…”

“…We employed the high content of Cu doping mesoporous MCM-41 [119], wherein the Cu-doped mesoporous MCM-41 afforded the superior catalytic conversion (~30%) for the benzene oxidation, and with the addition of promoters of B, Al, Zr or Ti, the selectivity of phenol could be up to 100%. Owing to the limitation of doping tactic for the mesoporous silica materials, our group [67] also developed the cationic surfactant induced dispersion strategy for the synthesis of highly-dispersed VO x inside the mesopores of MCM-41; consequently, the catalytic active VO x species exhibited the appreciable exposure and corresponding catalytic performance (29.8% conversion and 90% selectivity). Apart from those, the O 2 oxidation of benzene was extended by Sun et al [120]; through V/C modified silica-based mesoporous material and the conversion of benzene, selectivity of phenol was 12% and 100%, respectively.…”

Synthesis of well-ordered MCM-41 containing highly-dispersed NiO nanoparticles and efficient catalytic epoxidation of styrene

“…That could be attributed to the fact that the nickel oxide nanoparticle incorporated in the silicate walls and interacted with the walls. 35 And the FT-IR bands at 457 cm −1 are related to the bending vibration of the rocking mode of Si-O-Si. 36 The presence of Ni=O stretching vibration was confirmed by the absorption band at 669 cm −1 , demonstrating the presence of NiO in MCM-41.…”