Hydrogenation Of Model Compounds Of Bio-oil Over Nickle Phosphide Catalysts

Bio-oil obtained from rapid pyrolysis of biomass contains a large number of oxygen-containing compounds leading to its low heat value,poor stability and corrosive.These disadvantages make bio-oil cannot be directly used as vehicle transportation fuel.So it is necessary to upgrade bio-oil.Catalytic hydrogenation technology is the most promising bio-oil upgrading technology,and it can fundamentally reduce the oxygen content of bio-oil,hence,it can improve the physical and chemical properties of bio-oil.The key of catalytic hydrogenation technology is to develop the catalyst with high activity and stability.Non-noble metal phosphide catalysts,especially like nickel phosphide catalysts,with high activity and stability have been paid more and more attention.Therefore,this paper focuses on the preparation of nickel phosphide catalysts and their hydrogenation performance of biooil model compounds.The Ni₂P catalysts prepared by thermal decomposition in the past have some problems such as agglomeration serious,poor dispersibility and large particle size.In this paper,phenol,as bio-oil model compound was used to proceed hydrogenation reaction with o-Ni₂ P and i-Ni₂ P catalysts.Ni₂ P catalysts?o-Ni₂P?were prepared with nickel oleate as the nickel salt precursor,and it was compared with catalysts?i-Ni₂P?prepared with nickel chloride precursor.And the hydrogenation performance of the catalysts was investigated by hydrogenation of phenol.The X-ray diffraction?XRD?,transmission electron microscopy?TEM?and scanning electron microscopy?SEM?of the catalysts showed that the o-Ni₂ P catalysts have smaller particle size,better dispersibility and less agglomeration than i-Ni₂ P catalysts.The hydrogenation activity of two catalysts was investigated in the presence of decalin as the solvent.The catalytic activity was investigated at different temperatures and different times,respectively.The differences in catalyst stability were also investigated under the same conditions.The results showed that the two catalysts were active in the catalytic hydrodeoxygenation of phenol.Using i-Ni₂ P catalysts at the reaction temperature of 300 oC,the conversion of phenol was 74.3%,and the selectivity of cyclohexane was 59.2%.While with o-Ni₂ P catalysts at the same conditions,the conversion of phenol was 89.1% and the selectivity of cyclohexane was 81.6%.The results show that the activity of Ni₂ P was greatly improved due to the change of nickel precursor.The initial conversion rate of phenol catalyzed by o-Ni₂ P catalysts was 89.1%,which decreased slowly to 73.1% after four times cycles.While the conversion of phenol from 74.3% to 43.4% was obtained when i-Ni₂ P catalysts were used at the same conditions.The results show that the stability of Ni₂ P was enhanced by changing the precursor of nickel,in other words,the improvement of the stability of Ni₂ P can greatly improve its application value.In addition,the low temperature hydrogenation performance of Ni₁₂P₅ catalysts to the bio-oil model compound furfural was investigated.The furfural is prone to polymerization,leading to coking at high temperatures,which can lead to deactivation of the catalysts.We prepared high activity of low temperature Ni₁₂P₅ catalysts for the low temperature hydrogenation of furfural.The catalysts were characterized by XRD,TEM and SEM,and the effects of temperature,time and pressure on the catalytic hydrogenation performance were investigated.The results show that Ni₁₂P₅ catalysts had a high hydrogenation activity for furfural at low temperature.When the reaction temperature was 150 oC,the conversion of furfural could reach 100%.The selectivity of tetrahydrofurfuryl alcohol in the product was 97.2%.The selectivity of furfural hydrogenation products was affected by hydrogen pressure.At low hydrogen pressure,more cyclopentanol was formed.At high hydrogen pressure,tetrahydrofurfuryl alcohol was formed.From the investigation of the reaction time,we can speculate that the reaction path is that,in the hydrogenation condition,furfuralcohol is first formation,then formation of tetrahydrofurfuryl alcohol,or isomerization of furfuralcohol to cyclopentanone in the aqueous phase and then cyclopentanone to cyclopentanol.