Hydrogen is a clean energy source whose utilization leaves no carbon footprint. Methane pyrolysis is a hydrogen production process that can generate a pure product stream. The reaction is endothermic (Δ) hence requires high temperatures to achieve a high reaction rate. The activation energy for the reaction can be reduced by using transition metal catalysts like nickel (Ni). With this catalytic approach, sintering becomes a major challenge. Core-shell catalyst design can encapsulate the active metal and prevent sintering while allowing a steady flux of reactants to the active sites. Using graphite on the shell side ensures allows reactant flux to the active metal. In this study, Ni@graphite core-shell catalyst was synthesized using an incipient wetness technique. The composition was verified by XRD, and the size of the Ni crystallite was 22 nm as calculated by the Scherer equation. The reaction was conducted in a fixed bed at 700°C, 90,000 ml/gcat.hr GHSV, CH4/N2 ratio of 1:1, and atmospheric pressure. The catalyst bed was made up of 200 mg catalyst and 1.8 g SiC. Interestingly, no pre-reduction step was required for this catalyst. The CH4 reaction rate was 9 mmol/gcat.min and performance was stable for 6 h TOS. The Ni crystallite size was 24 nm after the reaction (an 8% increase). This size increase was not due to sintering but the transformation of the active metal to a carbide. The study observed an IG/ID ratio of 2.03 from the Raman spectrum suggesting the reaction produced a similar carbon type to the shell side. This study revealed that Ni@graphite core-shell catalyst can inhibit sintering in methane pyrolysis while maintaining stable activity.
