Hydrogen-rich syngas from model biogas steam reforming over a Ni-Pr/hydrotalcite-derived catalyst: An RSM-central composite rotational design

A five-level Central Composite Rotational Design (CCRD 23, with 3 central (0) and six axial points) was performed to optimize hydrogen production via the continuous-flow-steam biogas reforming (SBR) reaction over a nickel-based catalyst, composed of Mg-Al oxides derived from hydrotalcite and containing 10 % of Ni and 1 % of praseodymium. The design included 17 long-term (24 h) runs, from which nonlinear regression models were fitted to the data. Five responses were measured under varying conditions: hydrogen selectivity (Y1), yield (Y2), and concentration at the reactor output (Y3). Also, the H2/CO molar ratio (Y4) and methane conversion (Y5). These conditions were altered by changing the temperature, methane content in the feed stream, and the amount of catalyst used. Hydrogen production was measured as hydrogen concentration (% v/v) at the reactor outlet and the hydrogen yield, a related variable. The highest hydrogen production was achieved at a temperature of 711 degrees C, with an input methane content of 70 %v/v and 87 mg of catalyst. Under these optimal conditions, a hydrogen yield of 74 % was obtained, with a selectivity of 77 % and 99 % methane conversion. The response surface methods demonstrated that the proposed model closely matched the experimental data, as confirmed by a careful statistical analysis showing correlation coefficients higher than 0.95.