Hydrogen-Rich Gas Production by Upgrading of Biomass Pyrolysis Vapors over NiBEA Catalyst: Impact of Dealumination and Preparation Method

The main goal of this work was to develop a highly active catalyst in lignocellulosic biomass conversion to hydrogen-rich gas. The studies were focused on the evaluation of an impact of dealumination of BEA zeolites on the catalytic performance of nickel-containing BEA zeolite catalysts in the investigated process. In order to increase an efficiency of hydrogen production, the effect of the catalyst preparation method was investigated (XRD, TEM, TPR, TPD-NH3, TG-DTA-MS and BET). During catalytic activity tests, cellulose and pinewood were initially pyrolyzed at 500 degrees C. The formed vapors were subsequently upgraded by passing them through a catalyst bed at 700 degrees C. The composition of the mixture of gaseous products was analyzed using GC-MS. The obtained results showed that Ni on dealuminated SiBEA zeolite, characterized by high number of vacant T atom sites, large surface area, high contribution of micropores, and relatively small pore size, was the most active among studied catalysts. The performed research demonstrated that increased reducibility of an active phase was beneficial for the enhancement of hydrogen production. The role of acid-base and redox sites as well as the influence of the state of Ni centers on the activity of Ni-containing dealuminated and nondealuminated BEA systems was also discussed. It is worth noticing that synthesized NiBEA zeolite catalysts, contrary to reference NiZSM-5 (possessing lower surface area and pore volume, lower reducibility and larger Ni crystallites), did not lose their activity in the conversion of lignocellulosic biomass in comparison to decomposition of pure cellulose.