Study Of Catalytic Improvement Of CeO₂ Doped In Ni-Cu/HZSM-5 Catalyst In Bio-oil Hydrodeoxygenation Proceeding

Bio-oil is a renewable energy promising alternative to the traditional fossil energy,but its composition is complex,its chemical nature is instability,therefore,it is needed for further modification of quality to become high-quality liquid fuel.At present,the most effective means of the upgrading of bio-oil is the catalytic hydrogenation,in which the selection of catalyst plays a key role in the catalytic hydrogenation of bio-oil.In recent years,Ni-based catalyst is used in the bio-oil catalytic hydrogenation processing because of its high activity,low price.And the modified Ni-Cu-based catalyst has greatly increased the catalytic activity,but there still existed the problem of carbonization which leads to inactivation.It is reported that rare earth oxides?such as CeO₂,La₂O₃,etc.?adding to the nickel-based catalyst can significantly improve its activity,stability and resistance to carbon deposit.CeO₂,as an effective redoxagent,shows a good oxygen storage capacity by the gap between oxygen and oxygen conversion due to the transition between Ce4 + and Ce3 +.The release of lattice oxygen is beneficial to the transference of activated carbon,hence,leads to eliminating coke,in other words,an addition of CeO₂ to the nickel-based catalyst can play a very good anti-coke effect.In this paper,the effect of CeO₂ addition to the catalytic hydrogenation of Ni-Cu / HZSM-5 catalyst was studied.The results with analyses of TEM?XRD and H₂-TPR show that the addition of auxiliaries of CeO₂ can affect the dispersion,particle size and reducing ability of Ni.The oil phase yield was increased with increasing the amount of CeO₂ at the initial hydrogen pressure of 2MPa,T = 270 ?,n = 650 r / min for 1h.The oil phase yield was the highest value of 49.3% at the CeO₂ of 15%.It is also found with the measurements of TG,Raman and XPS that the addition of CeO₂ can effectively reduce the degree of graphitization of carbon deposit.The amount of carbon deposit shows a "V"-type feature with the increase of CeO₂ amount,the degree of graphitization is the lowest at the CeO₂ of 15%.In addition,the effect of the technological conditions such as reaction temperature?250 ?-330 ??and reaction time?1h-7h?on the activity and coke type of Ni-Cu/15% CeO₂-HZSM-5 catalyst was investigated.The results show that the reaction temperature is the main factor affecting the oil phase yield and carbon deposition type.With the gradual increase of the reaction temperature,the oil phase yield was gradually decreased,while the oil quality?including water content,oxygen content,calorific value?was increased;but the carbon deposit on the catalyst was increased,gradually tending to graphite-like carbon.It is found that the optimum reaction temperature is 270 ? based on energy view.The amount of carbon deposit increases then decreases and finally increases again with the increase of reaction time at 270 ?.This may be due to the catalytic hydrogenation of bio-oil is a reversible reaction process,the reactant concentration will be decreased with the reaction time leading to appearance of the reverse reaction.