Maxim Stonor^1,3, Jingguang Chen¹, and Ah-Hyung Alissa Park^1,2,3

¹Department of Chemical Engineering,

²Department of Earth and Environmental Engineering,

³Lenfest Center for Sustainable Energy, The Earth Institute

Columbia University, New York, NY 10027

With fossil fuels becoming increasingly scarce and expensive to extract and process, a shift towards more sustainable energy generation is inevitable. Energy demand is predicted to increase 56% by 2040 with the majority share coming from non-OECD countries. While the use of biomass as renewable energy source is attractive, current biomass conversion technologies such as combustion and gasification face a number of challenges associated with low energy density and moisture content of biomass. A novel reaction involving a strong base (e.g., NaOH) and biomass (e.g., cellulose), the Alkaline Thermal Treatment (ATT) reaction, provides an innovative approach to produce CO_x-free H₂ by locking the carbon in a stable carbonate form while releasing pure H₂. In this study, various Ni-based catalysts with different surface structures are developed to enhance the overall H₂ conversion as well as selectivity. The efficiencies and mechanisms of Group I (e.g., NaOH and KOH) and II (e.g., Ca(OH)₂ and Mg(OH)₂) hydroxides are also investigated. While, the Group II hydroxides are weaker in their basicity, they have the benefit of being significantly lower in cost than NaOH and could potentially be obtained from waste sources. It has been found that a 10% Ni/ZrO₂ catalyst can increase H₂ formation by an order of magnitude in the case of Group II hydroxides and a factor of 2 for NaOH.  The use of Group I and II hydroxide also has led to interesting mechanistic studies since their reaction phases (i.e., pseudo-liquid vs solid) and reaction intermediates (e.g C₂ v.s. C₆ organic acids) are uniquely different. Furthermore, an investigation into the catalytic mechanisms has been conducted to determine whether the catalysts are involved in catalyzing liquid-solid-solid reactions between the water-cellulose/hydroxide/catalyst or whether the catalysts are primarily involved in subsequent gas reforming reactions such as the water-gas shift or steam reforming to produce additional H₂. Determining the catalytic mechanisms will help determine which parameters are the most crucial to H₂ formation and will aid in future reactor optimizations.