Catalytic Hydrotreatment of Fatty Acid Methyl Esters to Diesel‐like Alkanes Over Hβ Zeolite‐supported Nickel Catalysts

Abstract

AbstractA Ni/Hβ zeolite catalyst was prepared for the selective transformation of fatty acid methyl esters (FAMEs) into diesel‐like alkanes through hydrotreatment. Characterization of the physicochemical properties of a 10 wt % nickel‐loaded, Hβ zeolite support indicated that nickel(II) oxide aggregated into large particles approximately 23.9 nm in size, whereas nickel aggregated into particles 18.3 nm in size, significantly increasing the total acid sites of Hβ zeolite after hydrogen reduction. The reaction scheme of the whole FAME transformation was investigated by using a batch reactor. It was found that FAMEs were first hydrogenated mainly to saturated fatty acids, followed by hydrodeoxygenation without carbon loss, the main route toward alkanes. The hydrotreatment of FAMEs by decarboxylation or decarbonylation was favored at high temperatures and low hydrogen pressures on Hβ zeolite with higher nickel loadings. The metallic and acidic functionalities of nickel/Hβ zeolite catalysts exhibited a synergistic effect in hydrodeoxygenation without carbon loss, achieving high FAME conversion and yields of liquid C16 and C18 alkanes. Optimal catalytic performances were obtained with 10 wt % nickel loading over Hβ zeolite (Si/Al=25) at 270 °C with a pressure of 1.0 MPa H2 over 8 h. A maximum alkane product yield of 93.2 % was achieved for C15–C18 alkanes with complete FAME conversion. 80.3 % FAME conversion could was achieved after eight reaction cycles by using the nickel/Hβ zeolite catalyst with calcination after every use.