Energy & Fuels, Vol.25, No.9, 4113-4121, 2011
Fast Pyrolysis of Rice Husk in a Fluidized Bed: Effects of the Gas Atmosphere and Catalyst on Bio-oil with a Relatively Low Content of Oxygen
The pyrolysis of rice husk is carried out in a fluidized-bed reactor at atmospheric pressure. The effects of pyrolysis parameters, i.e., gas atmosphere and catalyst, on the carbon conversion of rice husk and composition of bio-oils are studied. The experiments with catalysts under a hydrogen atmosphere to produce bio-oils with a much lower oxygen content compared to those under a nitrogen atmosphere are performed. The results show that the oxygen content of bio-oils is markedly reduced because the oxygenated hydrocarbons are hydrocracked, resulting in the formation of H2O, CO, and CO2, when catalysts are introduced under a nitrogen atmosphere and decreases even more under a hydrogen gas atmosphere (hydropyrolysis). The oxygen content of bio-oil under a hydrogen atmosphere decreases from over 31.1% without a catalyst to 25.91, 20.51, 26.51, and 10.1% with Ni/Al2O3, Ni/LY, dolomite, and CoMo/Al2O3, respectively. The use of CoMo/Al2O3 and Ni/LY catalysts under a hydrogen atmosphere shows high activity to decrease the oxygen content, which leads to a higher heating value and more aromatic hydrocarbons. These experiments indicate that catalytic hydropyrolysis is suitable for producing bio-oils with a lower molecular weight and high aromatic hydrocarbons, which are possible to use as a potential liquid fuel and chemical feedstock.