• Increasing focal length boosts H 2 production to 5.63 mol/m 3 but intensifies coke. • Medium bed porosity (0.299–0.369) optimizes H 2 production at 4.12 mol/m 3 . • High porosity (0.534–0.588) reduces H 2 production to 2.32 mol/m 3 , reducing coke. • First optimization scenario: H 2 rate 0.002 mol/s, coke deposition 463.8–473.4 g. • Second scenario: H 2 production drops to 0.001 mol/s, coke reduced to 195–201 g. Solar-powered methane pyrolysis presents a promising approach for sustainable hydrogen production by utilizing solar energy to decompose methane into hydrogen and solid carbon without direct CO 2 emissions. However, deposited carbon on catalyst and reactor surfaces, which differs critically from the total carbon produced (the stoichiometric solid carbon resulting from methane conversion), is the factor that blocks gas flow, reduces heat transfer efficiency, and deactivates the catalyst, ultimately diminishing reactor performance and shortening operational lifespan. This computational study addresses mentioned challenge by hypothesizing that careful optimization of key operating parameters can maximize hydrogen yield while simultaneously minimizing coke deposition through a strategic trade-off approach. A combination of computational fluid dynamics simulations and response surface methodology was employed to investigate the effects of four key parameters that govern the fundamental physics and chemistry of the system: focal length (2.5–3.5 m) and rim angle (30–50°), which control the solar heat flux distribution and thermal gradients driving the endothermic reaction; and catalyst porosity (0.3–0.6) and catalyst loading (275–325 g/m 3 ), which determine the available surface area and active site density for methane decomposition. The computational fluid dynamics results revealed that increasing focal length from 2.5 m to 3.5 m enhanced hydrogen production from 1.84 mol/m 3 to 5.63 mol/m 3 )total produced carbon of 0.92 to 2.82 mol/m 3 (but concurrently reduced bed porosity from 0.355 to 0.262 due to intensified coke deposition. Medium catalyst porosity (0.299–0.369) achieved the highest hydrogen yield (4.12 mol/m 3 ) with minimal coke accumulation, while higher porosity (0.534–0.588) reduced hydrogen production to 2.32 mol/m 3 . The response surface methodology analysis identified two optimization scenarios with high desirability. The first scenario maximized hydrogen production (0.002 mol/s) with coke deposition of 463.8–473.4 g at focal length 3.31–3.35 m, rim angle 50°, catalyst porosity 0.30, and catalyst loading 275 g/m 3 (desirability 0.58). The second scenario incorporated economic considerations, achieving reduced coke deposition (195–201 g) with hydrogen production of 0.001 mol/s at focal length 2.5 m, rim angle 36.6–37.1°, catalyst porosity 0.50, and catalyst loading 275 g/m 3 (desirability 0.637). Statistical validation confirmed model accuracy with R 2 values of 0.9989 for hydrogen production and 0.9892 for coke deposition. These findings demonstrate that integrating computational fluid dynamics with response surface methodology enables effective reactor optimization, balancing hydrogen yield against coke deposition to enhance performance, extend reactor lifespan, and reduce operating costs for industrial applications.
Li et al. (Mon,) studied this question.