Upgrading Of Palmitic Acid Over Bi-functional Metal/Zeolite Catalysts In Presence Of H₂

Palmitic acid was chosen to be the model compound as the long-chain fatty acids of microalgae based bio-oil.Developing the bi-functional metal/zeolite catalysts to study the catalytic performances about the hydrodeoxygenation and hydroisomerozation of palmitic acid.Bi-functional Ni/H-ZSM-22 catalysts with melt infiltration,incipient wetness impregnation and wet impregnation methods,were used to catalyze palmitic acid,respectively.Compared to parent zeolite H-ZSM-22,there were decrease of relative crystallinity,some blockage effects of micropores and less strong acid sites after Ni loading.During upgrading the palmitic acid over bi-functional Ni/H-ZSM-22 catalysts in presence of H₂,the complete conversion of palmitic acid and 100 %alkanes selectivity were achieved at lower temperature?200 °C?.No deactivation was observed in five recycle reaction,indicating the excellent catalytic performance and stability of Ni/H-ZSM-22 catalysts.Higher reaction temperature?240-260 °C?,more iso-alkanes/n-alkanes formed,while hydrodecarbonylation route lost the carbon atom.Additionally,the catalysts prepared by melt infiltration were more inclined to hydrodeoxygenation routes and produced more iso-alkanes than their counterparts prepared by conventional impregnation methods.Metal Co was selected as the hydrogenation active component,incipient wetness impregnation and melt infiltration methods was used to prepare the bi-functional Co/H-ZSM-22 catalysts.The aim was to study the influences on product distribution by using different active metals upgrading the palmitic acid.The results showed that hydrodeoxygenation and hydroisomerization of palmitic acid were achieved over bi-functional Co/H-ZSM-22 catalysts,and the maximum of iso-products reached up to 73.4 % selectivity at 260 °C for 4 h in presence of 2 MPa.Compared to parent H-ZSM-22,the impregnation of Co for bi-functional catalysts could catalyze completely palmitic acid conversion into 100 % selectivity of alkanes in spite of low pressure?1MPa?.Low reaction pressure favored hydrodecarbonylation to produce more C15.Compared with Ni/H-ZSM-22 catalyst,Co/H-ZSM-22 catalyst yielded more C₁₆ and iso-alkanes.Microporous and mesoporous H-ZSM-5 zeolites were chosen as the support,melt infiltration methods was used to prepare the microporous and mesoporous bi-functional Ni/H-ZSM-5 and Co-H-ZSM-5catalysts,which were used to catalyze the palmitic acid.The catalytic deoxygenation of parent zeolitic supports H-ZSM-5without metal phase was observed the major route was hydrodecarbonylation and direct cracking.On one hand,the impregnation of Ni or Co species,tailored the deoxygenation route of parent zeolite H-ZSM-5,and enhanced hydrodeoxygenation route to produce more C₁₆.On the other hand,metal phase decreased the isomerization temperature,which is consistent with enhanced the acidic strength of whole bi-functional catalysts especially for Co/zeolite catalysts.Furthermore,the introduction of mesopores obviously enhanced iso-products and C₁₆ formation for Co-based catalysts.