The Research Of Catalytic Steam Reforming Of Bio-oil For Hydrogen Production

Hydrogen is an ideal energy carrier that can be used as an essential clean fuel form. However, hydrogen production from fossil fuels will not only bring about environmental pollution, but also requires a complete consumption of the raw materials of the fossil fuel. As a consequence, the development of renewable clean energy-biomass energy will play a large role in China’s energy structure adjustment in order to reduce greenhouse gas emissions and protect the ecological environment. Because dispersion level and energy density would determine the transport cost and economic feasibility of one particular fuel form, bio-oil that is well-known for its fast pyrolysis has represented one type of promising new energy forms with easy dispersion and high energy density.This paper provided a brief introduction of bio-oil pyrolysis characteristics, carried out kinetics analysis with different reaction conditions considered explicitly based on the basic law of the catalytic steam reforming, and revealed catalytic mechanism in steam reforming of bio-oil for hydrogen production.When the Ni transition metal ingredients are divided according to the active group of inexpensive catalyst, the main body of the carrier is sepiolite, and the carrier assistant ingredient consists of MgO and MoO3.A series of Ni base catalyst Ni/Sepiolite was prepared with the impregnation method. Ni/MgO-Sepiolite, Ni/Mo-Sepiolite and Ni/Mo-MgO-Sepiolite are applied to obtain the optimum reaction conditions of catalyst preparation, with XRD, XPS, BET, SEM and TG/DTG attributed to the catalyst.The pyrolysis behaviors and kinetics of the water-soluble components of bio-oil were studied by thermogravimetric (TG) analysis. The curves of TG and corresponding DTA were analyzed in the oxygen atmosphere within a fixed bed reactor. Based on the experimental data, activation energies, reaction order and kinetic parameters were calculated using the Achar-Brindley-Sharp-Wendworth differential method and the Coats-Redfern integral method. Also, potential involving mechanisms were explored with thermal kinetic equations ultimately obtained. The results showed that the pyrolysis process of water-soluble components of bio-oil can be divided into three stages, including the evaporation stage of volatile fractions, the decomposition stage of heavy fractions and the char combustion stage. To activate energy forms, the volatilization dynamic is higher than bio-oil obtained directly from the decomposition stage. The first stage was expressed as first order reaction whereas the second stage was expressed as second order reaction. The kinetic reaction order was characterized as first order reaction of the first stage, followed by the second order reaction of the second stage. The correlation coefficient of these two stages showed that the reactions were of well conformity.The mixtures of acetic acid, acetone, glycerol urfural and phenol were selected and dubbed as bio-oil model compounds. Studies on the acetic acid, glycerol, phenol, furol and mixed model steam reforming for hydrogen production were carried out within a fixed bed reactor with modified Ni/Mo-MgO-Sepiolite catalyst to optimize reaction conditions and to compare catalytic properties of various catalysts.Hydrogen was produced during the catalytic steam reforming process of bio-oil within a fixed bed reactor. Sepiolite catalysts modified with nickel (Ni) and molybdenum (Mo) were prepared using the precipitation method. Influential parameters such as temperature, catalyst, steam to carbon ratio (H2O/C), the feeding space velocity (feeding rate) and reforming reaction length were quantified. The results of this experiment showed that the yield with the acidified sepiolite catalyst was67.5%. In contrast, the yield with the non-acidified sepiolite catalyst was only46.2%.The mixtures of acetic acid, glycerol, urfural and phenol were selected and dubbed as bio-oil model compounds. The thermodynamic analysis was carried out to understand the steam catalytic reforming hydrogen production process with the Gibbs energy reduced the least. The effect of reaction temperature, C/H2O and the feeding rate on gasous components of the molecular balance was investigated, with involving mathematical model successfully established.The catalytic activity of modified sepiolite, the effect of catalyst on the steam reforming and the associated catalytic mechanisms were analyzed based on the experimental results. Some impurities could be removed from sepiolite after a nickel-molybdenum-modification on sepiolite to improve the original sepiolite grade, to ensure a better storage and catalysis performance, and to have a stronger catalytic performance compared to the circumstances where only original sepiolite was applied. The main reason for catalyst deactivation was due to coke plugging. Both the channels of the carrier and the active metal surfaces were likely to be blocked by the coke.