Aqueous-phase Reforming Of Low-boiling Fraction Of Bio-oil For Hydrogen Production

High water content in crude bio-oil has a negative effect on the combustion performance. More seriously in the low-boiling fraction (LBF) of bio-oil, which is got from vacuum distillation, the content of water is up to 70-80%. Obviously it is hard to make use of it directly. While aqueous-phase reforming (APR) for hydrogen production is a good choice to utilize LBF.In the work the possibility of APR for hydrogen production and the reaction conditions are discussed firstly. The catalysts of acid, neutral and alkaline carriers supported Pt are selected to investigate the activity and selectivity to APR. And the possible reaction mechanism of APR was discussed through the model reactions. The results are listed below.The optimum reaction condition for APR in the system of LBF is:10 mL LBF and 30 mL water on 0.5 g 2 wt.% Pt/Al2O3, the reaction temperature 533 K, the reaction time 4 h.554 mL gaseous products including hydrogen (66%), carbon dioxide(22.5%), methane etc hydrocarbons(7.6%), carbon oxide(0.2%) were collected.Different Si/Al ratio of HZSM-5, SiO2, Al2(Si03)3, active carbon, Al2O3, TiO2, ZrO2, and La2O3 are selected to support Pt as the catalysts of APR reaction. Comparing the results the activity of APR and selectivity of hydrogen production are discussed. XRD, CO2-TPD, NH3-TPD, TEM, TG, and BET are done in the catalyst characterization. It is observed that Pt/Al2O3 is of the highest activity and selectivity for APR reaction. It seems that the connection between activity of APR and the acidity of carriers is closely. And the size of Pt particles also has impacts on activity and selectivity of APR. The size of carriers is smaller with the suitable acidity, the activity is higher. The catalyst Pt/Al2O3 is deactivation after 4 hours due to the coke deposit.The results show that under reaction conditions the organics in LBF may happen reactions such as hydrolysis, hydrogenation, dehydration, decarboxylation, cracking, and so on. These reactions lead to the intermediate products producing with C-C and C-O bonds breaking. Also the intermediate products may react with each other. And then carbon and hydrogen are produced during the process of reforming. Carbon monoxide and water undergo water-gas shift (WGS) reaction to produce carbon dioxide and hydrogen. Carbon monoxide and carbon dioxide may also react with hydrogen to produce methane at the cost of consuming hydrogen. The cracking of furfural is probable the main reason of the carbon formation.