Presented at the Research Congress 2013 De La Salle University Manila March 7-9, 2013 SEE-II-012 1 EFFECT OF PROCESS PARAMETERS ON CNT DIAMETER THROUGH THE CATALYTIC THERMAL DECOMPOSITION OF METHANE Gian Paolo Obligacion Bernardo 1 and Leonila C. Abella 2 1 De La Salle University - Manila 2 Chemical Engineering, College of Engineering, De La Salle University - Manila Abstract: Carbon nanotubes (CNTs) bear physical and chemical properties which allow them to be used in a wide range of applications, such for structural support, adsorbents, batteries and hydrogen fuel cells. CNTs are most commonly synthesized through the catalytic thermal decomposition of methane (CTDM). Recent studies are being done on cleaner alternative sources of energy indicating a demand for both utilizing CNTs for hydrogen fuel cells and reducing the amount of greenhouse gases, such as methane. The capability of the CNTs to adsorb H 2 has been found to be mainly dependent on the diameter of the CNTs. As such, it was of interest to study the effect of the process parameters on the CNT diameters for the production of CNTs through CTDM. The process parameters investigated were the inlet CH 4 concentration, the reaction temperature and the catalyst metal loading. The determination of the significance of the process and catalyst parameters was done using ANOVA and general regression. Catalyst pre-characterization confirmed the presence of γ- Al 2 O 3 , NiO and NiCu catalyst components which have been found to be necessary in the production of CNTs. BET Analysis confirmed the proportional relationship of the surface area of the catalyst with the catalyst metal loading. Catalyst post-characterization measured the CNT diameters through SEM analysis. CNTs with the minimum average diameter of 48.5nm were synthesized with 5% ( vol / vol ) inlet CH 4 concentration, 30% Ni catalyst loading with 12:5 mol:mol Ni:Cu, and 950°C reaction temperature, while CNTs with the maximum average diameter of 135.0nm were synthesized with 20% ( vol / vol ) inlet CH 4 concentration, 30% Ni catalyst loading with 12:5 mol:mol Ni:Cu, and 750°C reaction temperature. Catalyst post-characterization quantified the effects of the process parameters on the diameters of the CNTs formed. Among the parameters, the reaction temperature from 750°C to 950°C had the strongest effect while the initial surface area of the catalyst with values from of 80m 2 /g to 90 m 2 /g had the least effect on the CNT diameter. Both the catalyst metal loading from 10% to 30% Ni (w/w) with 12:5 mol:mol Ni:Cu and the inlet CH 4 concentration from 5% to 20% (v/v) had weaker effects on the diameters of the CNTs. Key Words: carbon nanotubes, catalysis, methane decomposition, process parameters