Ni/改性蒙脱土-海泡石催化生物油重整制氢

Ni/Modified Montmorillonite-Sepiolite as Catalyst for Hydrogen Production from Bio-oil Steam Reforming

以碱处理后的蒙脱土-海泡石(Mmt-Spt)为载体,金属Ni为活性组分,制备了Ni/Mmt-Spt催化剂,考察其对生物油重整制氢的影响。比表面积分析(BET)结果表明改性后的Ni/Mmt-Spt催化剂具有较大的比表面积;扫描电子显微镜(SEM)分析结果表明催化剂反应后仍保持纤维状结构;X射线衍射(XRD)和NH_3-程序升温脱附(NH_3-TPD)分析结果表明Ni/Mmt-Spt催化剂上NiO的颗粒更小、分散更均匀。改性后Ni/Mmt-Spt催化剂的酸中心减少,催化剂中存在的Mg、Ca能促进水煤气变换反应进行,有利于提高氢气产率,并有助于消除积炭,降低结焦率。当重整制氢的工艺条件为900℃、水碳质量比6、质量空速(WHSV)2 h^(-1)时,Ni/Mmt-Spt催化剂对应的氢气产率为81.5%,潜在氢气产率为90.4%,结焦率为3.8%,与以Ni/Al_2O_3为催化剂相比,氢气产率高7.1%,结焦率低1.8%。

In order to reduce the use of fossil fuels and to solve environmental problems,the utilization of the renewable energy source has great significance.As an energy carrier,hydrogen is considered to be one of the most promising substitutes of fossil fuel in the future.The two-stage process involving biomass pyrolysis and bio-oil catalytic steam reforming is an important and economical technology for hydrogen production.Ni catalysts have been used extensively for bio-oil steam reforming process because of their high catalytic activity,along with low prices.However,the limitation of nickel catalysts is the carbon formation on the catalyst surface.Hence,it is theoretical and practical significance to prepare an cheap catalyst with high hydrogen yield and low char yield.In this paper,the catalyst carriers were natural montmorillonite (Mmt) and sepiolite (Spt).The Ni/Mmt-Spt catalyst was prepared by alkali-treated montmorillonite-sepiolite (Mmt-Spt) as the support and nickel as the active ingredient.The impact of Ni/Mmt-Spt for hydrogen production from bio-oil steam reforming was inspected.The specific surface area analysis (BET) results showed that the Ni/Mmt-Spt catalyst had a large specific surface area and the scanning electron microscope (SEM) results showed that Ni/Mmt-Spt catalyst retained the fibrous structure after the reaction.The NH3-temperature programmed desorption (NH3-TPD) results showed that the acidic center of the alkali-treated Ni/Mmt-Spt catalyst reduced.The X-ray diffraction (XRD) results showed the particle size of NiO on Ni/Mmt-Spt catalyst was small.The presence of Mg and Ca in the carrier can promote the water gas shift reaction and can help to eliminate carbon deposition to reduce the char yield.The reaction conditions for the steam reforming of bio-oil with the Ni/Mmt-Spt catalyst were optimized as the follows: temperature of 900 ℃,water/carbon mass ratio of 6 and weight hourly space velocity (WHSV) of 2 h^-1.The hydrogen yield of 81.5%,potential hydrogen yield of 90.4%and char yield of 3.8%can be obtained at the optimum conditions.The hydrogen yield of Ni/Mmt-Spt catalyst was 7.1%higher than that of Ni/Al2O3 catalyst.While the char yield of Ni/Mmt-Spt catalyst was 1.8%lower than that of Ni/Al2O3 catalyst.