Preparation of Carbon Nanotubes with Supported Metal Oxide Nanoparticles: Effect of Metal Precursor on Thermal Decomposition Behavior of the Materials

Abstract

To develop new catalysts based on carbon nanomaterials with supported metal oxide nanoparticles for oxidative transformations of sulfur compounds, a series of metal oxide nanoparticle-decorated carbon nanotubes (MOx/CNTs) were prepared by incipient wetness impregnation at a variation of the active metal type (M = Ce, Mo, Cu). The thermal decomposition of bulk and CNT supported metal precursors used in the preparation of MOx/CNTs was analyzed under inert atmosphere employing several thermoanalytical techniques (thermogravimetry, differential thermogravimetry and differential scanning calorimetry) coupled with mass spectrometry. The thermolysis parameters of the bulk and supported metal precursors were compared and the effect of CNT support on the decomposition pattern of compounds was elucidated. It was established that the decomposition of metal precursors supported on CNTs was started and completed at temperatures of 15‒25 and 25‒70 °C lower, respectively, compared with the bulk active metal precursor. The enhancement of CNT support stability against thermal degradation is observed in the following row of metal cations: Ce < Cu < Мо < pristine and metal anions of precursor: nitrate < chloride < sulfate. The optimal mode of thermal treatment of catalyst and appropriate active metal precursors were selected for advanced synthesis of nanosized MOx/CNT catalyst.

Study of the structure of graphene oxide obtained by oxidation of intercalated graphite compound by Raman light scattering method

“…Along with the predicted changes (increase in defect content), more complete oxidation processes are observed, apparently related to the difference in the contact of the initial IGC surface with acids. Similar effects have been observed with carbon nanotubes [34][35][36]. The intensity and semi-width of the D1-band increase dramatically, while the intensity of the Gband decreases and its semi-width increases.…”

Synthesis and Characterization of Supported Mixed MoW Carbide Catalysts

“…From previous studies, it is known that after the formation of the MoO 3 , the oxide can be reduced to its MoO 2 form before carburization. 27,28,38,45,46,52 We observed a CO 2 peak at ∼450 °C and a significant mass change of 2.0% for the Mo carbide (and for the physical mixture), which we attribute to the reduction of MoO 3 to MoO 2 . This mass change is in reasonable agreement with the calculated values of 1.8% for Mo.…”

“…For the synthesis of carbide catalyst temperature-programmed desorption coupled with mass spectrometry (TPD-MS), thermal gravimetric analysis (TGA), and X-ray diffraction (XRD) are indispensable tools. TPD-MS gives information on the evolved gases, such as the temperature at which CO evolves and the carburization temperature. , Since TGA measures mass changes as a function of temperature, it is a suitable technique to follow the carburization process, especially for the CR method, while XRD gives information on the crystal structure during the formation of the oxides and carbides. In addition, scanning transmission electron microscopy coupled with electron diffraction (STEM-EDX) provides information on the particle sizes and elemental distribution in the final material.…”

The Development of Metal-Carbon Catalysts for Oxidative Desulfurization of Diesel Fractions

“…Thermal analysis revealed [30] that heating of the dried samples in an inert atmosphere leads to decomposition of salts -precursors of metals and to a partial degradation of the carbon matrix. The temperature at which M/CNT starts to degrade (T d ) depends on the nature of a metal precursor compound and increases in the series Ce < Сu ≈ Мо (see Table).…”