Study On Modified Ni-based Catalyst For Hydrogen Production From Bio-oil Simulacrum Steam Reforming

Bio-oil steam reforming is an economical way to produce hydrogen.It is of theoretical and practical significance to prepare an inexpensive catalyst which has a high hydrogen yield and a low char yield.In this paper,Ni-based catalysts were prepared for catalytic reforming of bio-oil for hydrogen production.And the catalyst supports were inexpensive natural montmorillonite and sepiolite.The two Ni-based catalysts Ni/Spt and Ni/Mmt were prepared using sepiolite(Spt)and montmorillonite(Mmt)as supports respectively.And their effects for hydrogen production from acetic acid steam reforming were compared with Ni/Al2O3 catalyst.Both sepiolite and montmorillonite contained basic metal oxides such as MgO and CaO which can promote the reforming reaction and water gas shift reaction.The hydrogen yields of the three catalysts were:Ni/Al2O3<Ni/Mmt<Ni/Spt.Due to the different molecular structure and carbon content of acetic acid and phenol,Ni/Spt catalyst required lower temperature and lower water/oil ratio for hydrogen production from acetic acid than that of phenol.The Ni/Mmt-Spt catalyst was prepared by alkali-treated montmorillonite-sepiolite(Mmt-Spt)as support and nickel as the active ingredient.And the impact of Ni/Mmt-Spt for hydrogen production from bio-oil was inspected.The BET results showed that the Ni/Mmt-Spt catalyst had a large specific surface area.The XRD results showed that re retained the fibrous structure after the reaction.The NH3-TPD results showed the presence of Mg and Ca in the carrier and alkaline treatment can reduce the acidity of the carrier and help to reduce char yield.The hydrogen yield of 81.5%,the potential hydrogen yield of 90.4%and the char yield of 3.8%were obtained under the temperature of 900?,the water/oil ratio of 6 g/g and the weight hourly space velocity(WHSV)of 2 h-1 with Ni/Mmt-Spt catalyst.The hydrogen yield of Ni/Mmt-Spt was 7.1%higher than that of Ni/Al2O3 catalyst.And char yield of Ni/Mmt-Spt was 1.8%lower than that of Ni/Al2O3 catalyst.Based on the Ni/Mmt-Spt catalyst,four kinds of bimetallic catalysts were prepared.The catalytic effects of four bimetallic catalysts from high to low were:Ni-Co/Mmt-Spt,Ni-K/Mmt-Spt,Ni-Zn/Mmt-Spt,Ni-Fe/Mmt-Spt.The hydrogen yield of Ni-Co/Mmt-Spt catalyst was the highest.And the contents of CO and CH4 in the gas product were very low,indicating that the added Co metal can promote the water gas shift reaction.The product gas mainly composed of H2 and CO2 and changed little with the increase of the water/oil ratio.The selectivity of the raw bio-oil to generate hydrogen was relatively high.Under the optimal conditions(900?,S/B 9 g/g,WHSV 2 h-1),the hydrogen yield and carbon selectivity of the Ni-Co/Mmt-Spt catalyst were 92.0%and 95.0%,respectively.And the carbon selectivity of Ni-Co/Mmt-Spt catalyst was about 10%higher than that of the Ni/Mmt-Spt catalyst.