Preparation Of Alkanes Biodiesel By Hydrodeoxygenation Of Soybean Methyl Esters

With the increasing demand for petroleum resources and the increasing demands for environmental protection,renewable and environmentally friendly biodiesel has high expectations.At present,the first-generation biodiesel technology represented by fatty acid monoesters is relatively mature.However,fatty acid monoesters have problems such as poor oxidation stability and incomplete compatibility with petrochemical diesel engines.This is mainly caused by the oxygen content in fatty acid monoesters.Therefore,it is still necessary to develop the second-generation biodiesel technology centered on the deoxygenation of fatty acid monoesters.The alkane biodiesel obtained after deoxygenation is fully compatible with petrochemical diesel engines,and has greatly improved in combustion performance.The research core of fatty acid monoester deoxygenation technology is the design and development of hydrodeoxygenation catalyst.In this paper,the acidity of?-Al₂O₃,which is relatively weak in acidity,was adjusted,and two catalysts with excellent hydrodeoxygenation performance were obtained.The hydrodeoxygenation performance of fatty acid methyl ester was studied,and high yield C15?C18 alkane was obtained,which effectively solved the problem of high oxygen content of fatty acid methyl ester and provided a new path for the development of hydrodeoxygenation catalyst.First,the Al-MCM-41/?-Al₂O₃ support was prepared by kneading and squeezing,and the precious metal Pt was loaded on the support by the equal volume impregnation method,and a series of Pt/Al with different Al-MCM-41 contents were prepared respectively Al-MCM-41/?-Al₂O₃ catalyst.The catalysts were characterized using XRD,N₂ adsorption-desorption,NH₃-TPD and other techniques.Using soybean oil methyl ester as raw material,the hydrodeoxygenation performance of the catalyst was investigated in a fixed bed reactor.The optimized process conditions after single factor optimization are:T=350?,P=1.5 MPa,WHSV=0.5 h^-1,and V?H₂?:V?esters?=1000.Under this condition,the methyl ester conversion rate was 96.4%,and the C15?C18 alkane yield was 96.4%.Secondly,the squeeze strip method was used to prepare the?-Al₂O₃ carrier,and the noble metal Pd,transition metal Mo and non-metallic element P were supported on the?-Al₂O₃ carrier by the equal volume impregnation method to prepare Pd Mo P/?-Al₂O₃ series catalysts.Catalytic performance tests were carried out using soybean oil methyl ester as raw material.The catalysts were characterized using N₂adsorption-desorption,XRD,NH₃-TPD,Py-IR,XPS,and STEM-EDS.The results show that the simultaneous loading of Pd,Mo and P elements on?-Al₂O₃ realizes the adjustment of the acidity,the acidity of?-Al₂O₃ with a large amount of mesoporous structure,so that the hydrodeoxygenation reaction can obtain more C15?C18long-chain alkane products,and most of the liquid products are even carbonnormal alkane with long carbon chain length.The optimized process conditions are:temperature 315?,hydrogen pressure 1.5 MPa,weight hourly space velocity 0.5 h^-1,and hydrogen ester volume ratio 1100.Under this condition,the methyl ester conversion rate and C15?C18 alkane yield were 98.4%and 91.5%,respectively.Finally,the loading ratio of the catalyst Pd Mo P/?-Al₂O₃ was further adjusted.The results showed that the better ratio was Pd:Mo:P=0.5:9:1.67?wt?.Stability testing of this catalyst showed that the hydrodeoxygenation stability of Pd Mo P/?-Al₂O₃ catalyst needs to be improved.At the same time,its choice of HDO deoxygenation path has an absolute advantage over HDCX/HDCN.