SYNTHESIS OF HIGH-PURITY CARBON NANOTUBES OVER ALUMINA AND SILICA SUPPORTED BIMETALLIC CATALYSTS

Carbon nanotubes (CNTs) were synthesized by a catalytic chemical vapor deposition method (CC VD) of ethylene over alumina and silica supported bimetallic catalysts based on Fe, Co and Ni The catalysts were prepared by a precipitation method calcined at 600 degrees C and in situ reduced in hydrogen flow at 700 degrees C The CNTs growth was carried out by a flow the mixture of C2H4 and nitrogen over the catalyst powder in a horizontal oven. The structure and morphology of as-synthesized CNTs were characterzed using SEM. The as-synthesized nanotubes were purified by acid and basic treatments In order to remove impurities such as amorphous carbon, graphite nanoparticles and metal catalysts. XRD and D TA/TG analyses showed that the amounts of by-products In the purified CNTs samples were reduced significantly According to the observed results, ethylene Is an active carbon source for growing high-density CNTs with high yield but more on alumina-supported catalysts than on their silica-supported counterparts. The last might be explained by SMSI formed in the case of alumina-supported catalysts, resulting in higher active phase dispersion