Pt supported by three-dimensional mesoporous MCM-48 with large specific surface area for toluene catalytic oxidation

Abstract

Supported catalyst Pt/MCM-48 was prepared by using MCM-48 with large specific surface area of ≈1400 m2/g as a support and applied for catalytic combustion of toluene. Compared with using microporous Silicalite-2, mesoporous molecular sieves SBA-15 and MCM-41 as well as commercial SiO2 as a support, the catalyst with MCM-48 as a support exhibits the best catalytic performance for toluene oxidation, demonstrating the highest catalytic performance for toluene oxidation. Then, the effect of various Pt loading amount on toluene oxidation was investigated and it was found that Pt/MCM-48 with 1%(mass fraction) Pt exhibits the best catalytic performance. Various introduction ways of Pt into support materials were compared among incipient-wetness impregnation method, in-situ synthesis method, methanol method and ethylene glycol method. The results indicate that the actual amount of Pt introduced in MCM-48 is similar to the theoretical amount via impregnation method and in-situ synthesis method, while is much less than the theoretical amount by using the solvent method. Nevertheless, both highest toluene conversion efficiency of Pt and the utilization rate of Pt atom are obtained over the Pt/MCM-48 by using methanol method. However, how to improve the actual Pt loading amount despite of keeping the high utility of single Pt atom is what we should focus on in the near future. Several characterizations, i.e., BET, XPS, STEM and H2-TPR etc., provide solid proofs that the MCM-48 with large specific surface area provide favorable condition for the high dispersion and good distribution of Pt in the support, which is beneficial for obtaining high proportion of Pt0. Meanwhile, the ordered three-dimensional mesoporous structure greatly improves the accessibility of the active sites and decreases the diffusion resistance of toluene, hence, greatly contributes to the superior toluene oxidation ability. In addition, GC-MS results show that toluene is firstly converted to the intermediates of aldehydes/phenols/acids, etc. on Pt/MCM-48, and finally converted to CO2 and fully deep oxidation could be achieved.

Keywords

• large specific surface area
• mcm-48
• pt
• toluene
• catalytic oxidation