Two-stage steam reforming of bio-oil for hydrogen production: Influence of catalyst and temperature in the pre-reforming stage

In this study, the impact of pre-reforming procedure on the intermediate products and the production of hydrogen in the two-stage steam reforming of bio-oil generated from pine sawdust was explored. The evolution of the intermediate products in the liquid and gas phase affected by the pre-reforming catalyst (red mud, dolomite, biochar) and pre-reforming temperature was investigated, as is impact of intermediate products on the hydrogen production. The findings indicate that dolomite was identified as the most effective pre-reforming catalyst due to its high CaO/MgO content, which promoted the Boudouard reaction more effectively than the Fe 2 O 3 in in red mud. Low-temperature pre-reforming (≤450 °C) was more beneficial than high-temperature pre-reforming (≥550 °C) at which coke precursors, including aromatic hydrocarbons and phenols were easily produced, leading to rapid catalyst deactivation. Liquid-phase intermediates were primarily composed of furans, phenols, and ketones, with ketones accounting for up to 55.63 %, which may be related closely to the greatly promoted ketonization by the alkaline Ca(OH) 2 produced via the combination dolomite and water at low temperature. Ketones were actually more favorable to the second-stage reforming over Ni-based catalysts, and the ultimate hydrogen yield reached 66.52 %. Due to the low inclusion of phenol and aromatic hydrocarbon intermediates less susceptible to carbon deposition, the catalyst could be more stable. The two-stage steam reforming of pyrolysis bio-oil can avoid catalyst deactivation and enhance the hydrogen production to a higher degree, accomplished by changing the intermediates components with varied pre-reforming catalysts and temperatures.