Research Of Hydrogen Production From Catalytic Steam Reforming Of Bio-oil Model Compounds Over Nickel-Attapulgite-based Catalysts

The efficient utilization of biomass energy is one of the effective means to alleviate the ecological and energy crisis and the research subject in the field of environmental engineering and renewable energy sources.Hydrogen production from catalytic steam reforming of bio-oil(CSRB)could not only improve the utilization factor of biomass energy,but also resolve the issue of non-renewability of traditional methods for hydrogen production.Ni-based catalysts have been widely applied into CSRB due to its low-cost and high-rupturing capacity for C-C bonds in bio-oil molecules as well as high selectivity for hydrogen.However,the nickel-based catalysts are easily inactivation attributed to sinter and coke.In this paper,attapulgite(ATP)which is a natural clay mineral has a hollow nanofiber structure and is selected as support to load nickel active component.In addition,modified factors(such as Mg and Ce)and metal promoters(such as Co,Cu,Zn,and Fe)are introduced into Ni/ATP catalyst by using chemical precipitation method and to adjust the microstructure of Ni-attapulgite-based catalysts.They could improve the stability and H2 selectivity of Ni/ATP catalyst during CSRB process.Combining the N2 adsorption-desorption,SEM,TEM,H2-TPR,NH3-TPD and FTIR characterizations to analysis the physicochemical properties,such as the crystal structure,the strength of metal-support interaction,surface acidic properties and the metal dispersion.Furthermore,the influents of catalyst microstructures on catalytic catalytic activation,stability and selectivity during CSRB process are also investigated.The main research contents and conclusions are shown in the following.(1)A series of Ni/ATP catalysts were prepared by different methods and their structures,crystallographic features,metal-support interactions and metal dispersions were investigated by different characterizations.Subsequently,the mechanism of sinter and coke and the reaction rule of hydrogen production for constructed Ni-attapulgite-based catalysts during steam reforming of bio-oil model compounds acetic acid to produce hydrogen.The results revealed Ni/ATP catalyst prepared by precipitation method had the smallest Ni particle size 13 nm and the highest active metal dispersion 7.5%.Then it had the higher conversion of acetic acid(-85%,which was slight lower than that of Ni/ATP prepared by impregnation method)and the highest H2 yield(-82%)under the following reaction conditions:T= 650?,S/C = 3 and time on steam for 4 h.(2)In allusion to the easily coke of catalyst,the method of adding Mg into Ni/ATP was proposed.This method could realize the adjustment of surface acidity,the improvement of active metal dispersion and the enhancement of metal-support interaction.So the Ni/lOMg-ATP catalyst with higher resistance to coke formation was prepared.As a consequence,under the following reaction condition:S/C= 1.5,T=700 ? and GHSV =19310 h-1,the Ni/lOMg-ATP revealed the highest ethanol conversion(100%),H2 yield(96.7%)and the longest service life,as well as shown the lowest rate of carbon deposition 6.1 mg·(gcat·h)-1.(3)In allusion to the character of sinter,the active metals(Fe,Co,Cu and Zn)modified Ni-attapulgite-based catalysts were fabricated.The addition of active metals increased the resistance to sinter and enhanced the yield of H2 product and stability for catalytic steam reforming bio-oil model compounds.Among them,Ni-Cu/ATP displayed the highest reductive degree,which leading to the highest glycerol conversion of 98.1%and H2 yield of 4.11(mol H2/mol glycerol)as well as the highest H2 selectivity of 64.0%under the following conditions:W/G=9,GHSV= 9619h-1 and T= 700?.While Ni-Zn/ATP shown the excellent stability under the same conditions,which was attributed to it had the most powerful metal-support interaction.In the end,the most suitable catalyst for hydrogen production from CSRB was Ni-Zn/ATP.