Selective Oxidative Dehydrogenation ODH of Dihydroanthracene to Anthracene

In this experiment the metal-free carbon nanotubes acted directly as a support and active phase for the liquid-phase ODH of dihydroanthracene to anthracene at low temperature. The results are compared with those obtained on other catalysts. Oxidative dehydrogenation of dihydroanthracene in the liquid-phase was carried out over different CNT-based materials. The results are presented in Table 7.3. The test was also performed on an exfoliated graphite material for comparison. The results clearly showed that the reaction was chemically selective whatever 

The catalytic activity on untreated or treated MWNTs could be due to a curvature effect, even if it is very weak because of the relatively large diameter of the tubes (30-50 nm). This is confirmed by the lower catalytic achvity observed on exfoliated carbon, which has not the same morphologic properhes (absence of curvature). Similar results have been obtained by Nakamichi et al. [84]. They observed a conversion reaching 93% over activated charcoal in the same reaction conditions. 

Experiments carried out on the same SiC nanofibers show similar catalytic results. The SEM observation of the sample after the desulfurization test shows the presence of inhomogeneous large soUd sulfur particles wrapping the SiC structure where a large part of the catalyst surface was still accessible (Fig. 7.19). The remaining free surface of the catalyst allows one to explain the high desulfurization activity despite the relatively high soUd sulfur deposition on the catalyst surface. 

In summary, the catalytic route provides an interesting way to prepare carbon nanotubes with high yield and selectivity at relatively low synthesis temperature. The easy scale-up of the catalytic method allows one to ensure the mass production of these ID materials with reasonable cost for large scale applications. The development of different methods to produce carbon nanotubes in a controlled macroscopic shape and size, i.e. constraint synthesis, patterned and aligned carbon nanotubes forest by pyrolysis of organic compounds, avoids the formation of fines 

Metal nanoparticles can be easily introduced into the carbon nanotubes tubule or onto the surface of carbon nanotubes and SiC nanotubes/nanofibers by a simple wetness impregnation followed by classical thermal treatments. It is thought that such new nanoscopic encapsulated materials will display unusual properties as compared to those of their unfilled counterparts and could open new opportunities in the catalysis field. 

---