Bio-oil Steam Reforming For Hydrogen Production And Its Life Cycle Assessment

Biomass fast pyrolysis is an important technology for biomass energy conversion and utilization. The bio-oil produced from biomass fast pyrolysis system can be gathered and used for hydrogen production through a steam reforming process. Funded by related national program, we analyzed the production chemical process in thermodynamic calculation and investigated the bio-oil catalytic steam reforming experiment with self-developed catalysts in our research. We also make a life cycle analysis study for the process from biomass to bio-oil and bio-oil combustion and steam reforming for hydrogen production.We used acetic acid as a bio-oil model compound. Using thermodynamic calculation of hydrogen production via steam reforming of acetic acid was attempted to investigate the effects of temperature (200-1100℃), pressure (1-19atm)and steam to carbon ratio (1.5-10.5) on the concentration of equilibrium product gas and H2yield. The results show that temperature has a profound effect on the steam reforming of acetic acid. Lower pressure and higher steam to carbon ratio are in favor of higher hydrogen production.Acetic acid steam reforming process was investigated by self made catalysts. Pd/HZSM-5catalyst with5%wt Pd was prepared by wet impregnation method. The steam reforming experiment for hydrogen production was carried out on a fixed bed reactor. Acetic acid and ethanol were selected as the bio-oil model compound. The fresh and used HZSM-5and5%Pd/HZSM-5were characterized by N2physisorption, XRD, TEM, SEM, and NH3-TPD techniques. The carbon conversion, carbon selectivity of product gas and H2yield was calculated according to the experimental results. The results show that the addition of Pd to HZSM-5can improve the reforming performance and increase the hydrogen yield. It has been found that the best performance was obtained at T=600℃, S/C=9.2and GHSV=345h-1.Ethanol steam reforming process was investigated by Pd/HZSM-5catalyst and Ni catalysts supported on CeO2-ZrO2. The Ni/CeO2-ZrO2catalysts were prepared via coprecipitation and characterized by N2physisorption, XRD and SEM techniques. Effects of reaction temperature, gas hourly space velocity (Gc1HSV) and steam-to-carbon ration (S/C) on the performance of the catalysts for ethanol steam reforming (ESR) were investigated. It was found that the best catalytic performance was obtained by using Ni/Ce0.75Zr0.25catalyst at T=725℃, GclHSV=345h-1and S/C=9.2. Under this condition, H2yield reaches the highest of98.1%and carbon conversion reaches97.3%.Then a life cycle assessment of a industry-scale fast pyrolysis scenario for bio-oil production was conducted to evaluate whether the process would be environmentally friendly. The Net energy value (NEV), energy consumption, a global warming potential (GWP), acidification potential (AP) and some other environmental impact values in the life-cycle stages of biomass fast pyrolysis system were discussed in the paper. The normalization and weighting results of these environmental impacts were analyzed to investigate the impact distribution of different stages in the life cycle of biomass fast pyrolysis. The results show that the biomass fast pyrolysis technology is environmental friendly and hopefully could make positive contribution to climate change and environmental pollution problems.