Synthesis and Characterization of Carbon Nanotubes on Fe/Al Al2O3 Composite Catalyst by Chemical Vapour Deposition Method

Abstract

This study reports the preparation and characterization of mono-metallic iron (Fe) catalyst on aluminum oxide (Al2O3) support for the synthesis of carbon nanotubes (CNTs). The Fe catalyst supported on Al2O3 was prepared using wet impregnation method and the process was optimized using factorial design of experiment approach. The influence of process variables (mass of support, stirring speed, drying time and drying temperature) were investigated. The catalyst sample with the highest yield (91.20%) after calcination obtained at drying time of 7 hours, mass of support of 10.50 g, stirring speed of 700 rpm and drying temperature of 110oC was selected for subsequent CNTs synthesis, the sample was characterized using XRD, FTIR, SEM/EDS, BET and DLS techniques in order to determine the catalyst crystallinity, functional group(s), morphology, surface area/elemental composition and particle size respectively. The results obtained revealed that the catalyst has a specific surface area of 302.98 m2/g. The morphology study of the catalyst with SEM indicated that the metal particles are evenly dispersed on the support with the particle size in the ranges of 100-1000 nm as revealed by the DLS analysis. FTIR spectrum indicated that the catalyst developed has two major two functional groups which are nitrate and hydroxyl group. The catalyst developed was utilized for the synthesis of CNTs by chemical vapour deposition method (CVD) with acetylene as the carbon source and argon as the carrier gas. The influences of production time and temperature on the yield of the CNTs were investigated. The CNTs synthesized was characterized using XRD, FTIR, SEM/EDS, TGA, BET and DLS techniques. The results obtained indicated that CNTs highest yield of 98.30% was obtained at production temperature of 750oC. A nano-particle size within the range of 60.1 nm to 120 nm with highest abundance of 50 % was found to be presents in the CNTs with a surface area of 867.81 m2g. The results also showed that the CNTs produced are thermally stable and TEM results indicated that they are multiwall carbon nanotubes. It can be inferred from various analyses conducted that the monometallic (Fe) catalyst on Al2O3 is a suitable catalyst for the production of good quality multiwall carbon nanotubes in a CVD reactor.