Preparation And Catalytic Performance Of Granular NiMo/?-Al₂O₃ Catalysts For Hydrodeoxygenation Of Fatty Acid Methyl Ester

Faced with the increasingly serious energy and environmental crisis,the development of renewable energy has become one of the main methods to solve this problem.As a kind of clean and renewable energy,biodiesel has been widely concerned,among them,the second generation biodiesel prepared by hydrodeoxygenation has the most development prospect.At present,study on the second generation biodiesel prepared by hydrodeoxygenation method in our country is still in the stage of laboratory research,the raw material of second generation biodiesel is high molecular weight oils,which requires the catalyst support with large pore diameter.Therefore,this paper aims to develop a support and catalyst with a high specific surface area,large pore volume and pore size.In this paper,a series of ?-Al₂O₃ supports were prepared by changing the amount of forming additives and the species of peptizetor in the process of extrusion forming method.and NiMo/?-Al₂O₃ supported catalysts were prepared by excess wetness impregnation method.Those supports and catalysts were characterized by N2 adsoptin and desorption,XRD,XRF,H2-TPR and NH3-TPD;The hydrogenation performance of the catalysts was evaluated by means of a high pressure fixed bed reactor with a mixture of fatty acid methyl ester as raw material.The effects of forming additives on the textural properties and physical structure of the supports and its influence on the active component loading,redox properties,surface acidity and catalytic hydrodeoxygenation catalytic performance were investigated.The main contents and results are as follows:?1?The ?-Al₂O₃ support prepared by extrusion method,and discussed the effects of the amount of forming additives?composite binder sesbania powder and citric acid,HNO3?and the species of peptizetor?HNO3 and acetic acid?on the physicochemical properties of supports and catalysts.The result showed that when the amount of the peptizetor HNO3 was 7.5 wt%,the pore distribution of ?-Al₂O₃ and the corresponding catalysts in 4-10 nm was more than other supports catalysts;And when the amount of citric acid and was sesbania powder 5.0 wt%and 2.5 wt%,the amount of HNO3 was 7.5 wt%,the ?-Al₂O₃ support?2#?had large specific surface area and pore volume,347 m2/g and 1.088 cm3/g respectively;Compared with the organic acid acetic acid,the?-Al₂O₃ support prepared by using inorganic acid HNO3 as peptizetor has a large specific surface area,pore volume,crushing strength.The forming additives has little effect on the physical structure,the loading of the active component,the reducibility and the surface acidity of catalyst.?2?A high pressure fixed bed reactor was established to study the catalytic hydrogenation of fatty acid methyl ester.The result showed that when the amount of the peptizetor HNO3 was 7.5 wt%,due to the supports and the corresponding catalysts had more pore distribution in 4-10nm,the catalytic performance of the catalyst was better,and the selectivity of C15-C18 in the liquid product was relatively higher;When the amount of citric acid and sesbania powder was 5.0 wt%and 2.5 wt%,the amount of HNO3 was 7.5 wt%,the catalytic performance of the catalyst?2#?was better than others,the conversion of fatty acid methyl ester was 90.53%,and the selectivity of C15-C18 was 71.66%.?3?Single factor experiment was carried out by using NiMo/?-Al₂O₃ catalyst?2#?,it was found that with the increase of reaction temperature and pressure,the conversion of fatty acid methyl ester and the selectivity of C15-C18 showed a trend of increasing firstly and then decreasing,the appropriate reaction temperature and reaction pressure were 325? and 2.9MPa.The stability of 2#catalyst was also investigated under the conditions of pressure 2.9 MPa,temperature 325?,weight hourly space velocity 2.0 h-1,and ratio of hydrogen to oil 1000 mL/mL.After 48h,the loss of the active component of the catalyst resulted in the reduction of the conversion of raw material to 74.25%,and the selectivity of C15-C18 was reduced to 51.26%.