Publication

Heading full speed towards the extensive use of H₂ for humanity's energy needs, blue hydrogen production from light hydrocarbons is one of the most promising alternatives. In this study the production of hydrogen through propane steam reforming (PSR) reaction is investigated over Rh nanoparticles dispersed on M_xO_y-Al₂O₃ supports of variable M_xO_y (M: La, Gd) content towards optimizing catalytic performance. The intrinsic activity and the formation of intermediate CH₄ are markedly affected by varying M_xO_y content passing through a maximum for 10 wt% La₂O₃ or Gd₂O₃. Up to 8- and 3.5-fold increases in turnover frequency (TOF) at 400 °C are achieved on these optimally loaded with La₂O₃ and Gd₂O₃ catalysts, respectively, accompanied by more than two-fold higher H₂ yields. The reducibility of both rhodium species and the M_xO_y-Al₂O₃ support strongly depends on the M_xO_y content, which then determines the catalytic activity. In situ diffuse reflectance infrared furrier transform spectroscopy (DRIFTS) experiments revealed that CH_x species generated by the dissociative adsorption of propane interact either with H₂ yielding CH₄ and/or with hydroxyl groups producing formate species and eventually CO_x and H₂ in a manner which depends on M_xO_y content. However, the latter path is over-favored for samples with 20 wt% M_xO_y possessing excessive reducibility, and in combination to an over-strengthening of formates adsorption, the conversion rate to CO_x and H₂ is strongly inhibited. Scaling-up the fabrication of the most active Rh/10%La₂O₃-Al₂O₃ catalyst at higher application readiness (structured as pellets) and testing under realistic conditions revealed its suitability for propane reformers.