| AVS 54th International Symposium | |
| Surface Science | Tuesday Sessions |
| Session SS1-TuM |
| Session: | Catalytic Chemistry of Hydrocarbons |
| Presenter: | J.C. De Jesus, PDVSA-Intevep, Venezuela |
| Authors: | J.C. De Jesus, PDVSA-Intevep, Venezuela I. Gonzalez, PDVSA-Intevep, Venezuela M. Garcia, Universidad Central de Venezuela C. Urbina, Universidad Central de Venezuela |
| Correspondent: | Click to Email |
In this study, a facile method for the preparation of nickel nanoparticles is employed to investigate the catalytic decomposition of methane into carbon nanotubes. Nickel acetate tetrahydrate decomposes readily below 350°C to form metallic nanoparticles (average size 10-80 nm), and weight changes measured inside a thermogravimetric analyzer (TGA) in methane streams can be related quantitatively to the production of carbon nanotubes by catalytic cracking. C to Ni atomic ratios (C/Ni) estimated directly from TGA data provided a systematic approach to study in-situ the catalytic activity of the nickel nanoparticles. Methane cracking starts at temperatures as low as 400°C and continues efficiently until approximately 600°C. Between 600°C and 660°C, methane decomposition momentarily breaks off, while presumably the catalytic system undergoes a self-reorganization. Cracking resumes at 660°C and continues slowly up to 950°C. The amount of carbon deposited in the 600-660°C interval shows a lineal dependence with methane concentrations, with C/Ni ratios ranging from 6 to 31. Transmission electron microscopy (TEM) images of the different C/Ni residues collected at 660°C showed that during cracking narrower carbon nanotubes are produced at elevated methane concentrations, suggesting dispersion of nickel nanoparticles.