Sustainable hydrogen production through catalytic pyrolysis of lignocellulosic biomass using carbon dioxide

Abstract

Although hydrogen is recognized a carbon-free fuel, its production face environmental challenges in carbon dioxide emissions due to energy-intensive processes. To pursue more sustainable hydrogen production, this study integrates carbon dioxide-cofed catalytic pyrolysis of lignocellulosic biomass, especially perilla straw, with the water-gas shift reaction. The introduction of carbon dioxide into the pyrolysis process enhances syngas production per unit mass of perilla straw, while mitigating process-related carbon dioxide emissions. At temperatures above 460 °C, carbon dioxide participated in partial oxidation of volatiles stemming from perilla straw, leading to its reduction into carbon monoxide. To investigate this genuine reaction feature associated with carbon dioxide, the pyrolysis system was modified with an additional heat supply in the presence of cobalt-, iron-, or nickel-based catalysts. Catalytic pyrolysis facilitated further thermal cracking of the volatiles into smaller molecules, thereby accelerating carbon dioxide reactivity under enhanced mass transfer. These mechanisms related to carbon dioxide selectively promoted the formation of carbon monoxide. The resulting carbon monoxide-rich syngas was subsequently fed into the water-gas shift reaction, where carbon monoxide reacted with steam to stoichiometrically produce hydrogen and carbon dioxide. Thus, this study suggests the potential of carbon dioxide-cofed catalytic pyrolysis of perilla straw as an effective approach for enhancing hydrogen production while achieving process-related carbon dioxide reduction.