Alkaline Thermal Treatment of Cellulosic Biomass for H2 Production Using Ca-Based Bifunctional Materials

Hydrogen production from cellulosic biomass not only provides a sustainable approach to cope with the growing demand for energy but also facilitates the relief of environmental burden. In this study, we developed a series of Ca-based bifunctional materials (Ca(OH)(2) and Ni composites) for alkaline thermal treatment (ATT) of cellulose to produce high purity hydrogen at moderate temperatures (350-450 degrees C). Ca(OH)(2) served predominantly as a CO2 carrier and a H2O donor, and enlarged the surface area of the materials to improve H-2 production. However, excess Ca(OH)(2) tended to cover Ni particles and block pore structures resulting in a suppressed H-2 production. Ni promoted tar cracking and enhanced H-2 production, but the surface area of catalyst decreased with an increment in Ni, which suppressed H-2 generation. The yield of hydrogen was improved at elevated temperature. The maximum hydrogen yield, 34.5 mmol.g(-1) with 77% volume fraction, was obtained by adopting a molar ratio of cellulose:Ca(OH)(2):Ni as 1:6:2 at 450 degrees C for 10 min. GC-MS analysis results of tar products revealed that Ca(OH)(2) promoted primary pyrolysis of cellulose, and Ni promoted the decomposition of furan ring derivatives. The reaction temperature affected the distribution rather than the composition of the tar products.