Preparation And Hydrodeoxygenation Performance Of Nickle Phosphide Catalysts By Hydrogen Plasma

Nickel phosphide catalysts,new catalytic materials used in hydrodeoxygenation?HDO?of phenolic compounds in bio-oil,have been widely studied in recent years.However,the catalytic phases and preparation processes have great influence on the performance.It is beneficial to improve the catalytic performance of nickel phosphide,to controll the catalytic phase,to simplify the preparation procedure and to save the cost by optimizing the preparation method.In this thesis,the unsupported and supported nickel phosphide catalysts were prepared by means of H₂ plasma reduction?PR?and characterized by XRD,N₂-physical adsorption,TEM and NH₃-TPD.Besides,the activity test of the prepared catalysts were carried out to study the influences of P sources,Ni/P molar ratio and carriers by using phenol in the water or oil?decline?phase as the model reactant for the HDO of bio-oil.The performances of the catalysts preparaed by conventional H₂-TPR were also investigated as references.In addition,to simplify the preparation,the calcination process was omitted to study the effect of calcination on HDO performance of Ni₃P phase.Using phosphate as the source of phosphorus,unsupported Ni₃P,Ni₃P/SiO₂ and Ni₃P/HZSM-5?with loadings of 5,10 and 20 wt%?could be prepared successfully with Ni/P molar ratio of 3.All the catalysts exhibited high catalytic activity,especially for the 20 wt%Ni₃P/HZSM-5 catalyst,over which the conversion of phenol was 99.5%in the aqueous phase at 150 ^oC.The main products of phenol HDO over all these catalysts were cyclohexanol and cyclohexane,indicating that the main reaction path of phenol was hydrogenation followed by deoxygenation.Besides,the deoxygenation efficiency of phenol in the oil phase was higher than that in the aqueous phase.Ni₃P/HZSM-5 catalysts presented better deoxygenation performance than Ni₃P/SiO₂ with the same loading,which was due to the stronger acidity of Ni₃P/HZSM-5.Compared with the supported catalysts prepared by TPR method,the catalytic activity of catalysts prepared by PR method was obviously higher in both aqueous and oil phase.The main reason might be that during TPR method,sinter of the catalyst might occur at high temperature,leading to decreased dispersion.However,in PR process,the lower temperature is more beneficial to the formation and dispersion of Ni₃P active phase.Additionally,the performance of calcined unsupported Ni₃P was better than that of non-calcined catalyst,which could be ascribed to the formation of Ni₁₂P₅ in non-calcination process.As for the supported Ni₃P catalysts,the catalytic performances of non-calcined catalysts were better than those of calcined catalysts,due to the exposure of more active sites,the smaller particle size and the more dispersion of the non-calcined catalysts.Therefore,we can prepare highly active catalysts using the PR method without calcination to simplify the preparation procedure and save the cost effectively.