The use of bimetallic MCM-41 mesoporous catalysts for the synthesis of MWCNTs by chemical vapor deposition

Mesoporous MCM-41 molecular sieves incorporating chromium with different Si/Cr ratios (Si/Cr: 50, 75, 100 and 125) were synthesized hydrothermally and Co, Fe, Mn, Ni, Ti, Ru, and Pd were loaded on them using wet impregnation method. The synthesized materials were characterized by various physico-chemical techniques, such as ICP-AES, XRD, TGA, N2 sorption isotherms, DRS-UV and TEM. The production of MWCNTs by CVD using metal-containing mesoporous MCM-41 was investigated using acetylene as the carbon source. Fe/Cr-MCM-41 and Pd/Cr-MCM-41 are the most active catalysts for the growth of MWCNTs when compared with the other mono and bimetallic mesoporous catalysts. The MWCNTs have been analyzed by XRD, SEM, TGA, TEM and Raman spectroscopy. The strongest peak of the graphite band and the weak disorder band in the Raman spectrum confirmed the high purity of the MWCNTs. The structure of MWCNTs was studied by TEM which suggests that they are highly ordered and well graphitized. The formation of MWCNTs with uniform inner diameter in the range of 4–5 nm and outer diameter in the range of 12–13 nm was observed over Fe/Cr-MCM-41. These studies suggest that the bimetallic MCM-41 could be a kind of promising supports for catalytically synthesizing MWCNTs by CVD method.

The synthesis of MWCNTs were catalytically synthesized by the decomposition of acetylene over the Fe/Cr-MCM-41 and Pd/Cr-MCM-41 catalyst at 800 °C was found to produce with high quality and large quantity when compared with other prepared mono and bimetallic catalyst. The formation of ordered MWCNTs over Fe/Cr-MCM-41 catalytic template with uniform inner diameter in the range of 4–5 nm and outer diameter in the range of 12–13 nm was observed from HR-TEM image.Figure optionsDownload high-quality image (223 K)Download as PowerPoint slideHighlights
► Synthesis and characterization of Cr-MCM-41 and metal loaded Cr-MCM-41.
► Synthesis of well-ordered MWCNTs using efficient Fe/Cr-MCM-41 by CVD method.
► The bimetallic MCM-41 is suitable supports for catalytically synthesizing MWCNTs.