Lingmei Yang

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

A 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.

Synthesis of biodiesel by Fe(II)-Zn double-metal cyanide complexes

Abstract A kind of Fe(II)-Zn double-metal cyanide (DMC) complexes solid catalyst was prepared through coreaction of potassium ferrocyanide, zinc chloride, and complexing agent of tert -BuOH. The catalyst has highly catalytic activity on the simultaneous transesterification of triglycerides and esterification of free fatty acids (FFA) reactions. The effect of various factors on the reaction was studied, including different cocomplexing agents, DMC catalyst amount, reaction temperature, methanol/oil molar ratio, reaction time, and water and fatty acid content in raw materials. High catalytic activity was observed for DMC under relatively higher content of water or FFA. Under the optimum condition, the methyl ester yield can reach 98%. The 93.45% catalyst can be recovered after 6 cycles.

Insight into forced hydrogen re-arrangement and altered reaction pathways in a protocol for CO2 catalytic processing of oleic acid into C8–C15 alkanes

A new vision of using carbon dioxide (CO2) catalytic processing of oleic acid into C8–C15 alkanes over a nano-nickel/zeolite catalyst is reported in this paper. The inherent and essential reasons which make this achievable are clearly resolved by using totally new catalytic reaction pathways of oleic acid transformation in a CO2 atmosphere. The yield of C8–C15 ingredients reaches 73.10 mol% in a CO2 atmosphere, which is much higher than the 49.67 mol% yield obtained in a hydrogen (H2) atmosphere. In the absence of an external H2 source, products which are similar to aviation fuel are generated where aromatization of propene (C3H6) oxidative dehydrogenation (ODH) involving CO2 and propane (C3H8) and hydrogen transfer reactions are found to account for hydrogen liberation in oleic acid and achieve its re-arrangement in the final alkane products. The reaction pathway in the CO2 atmosphere is significantly different from that in the H2 atmosphere, as shown by the presence of 8-heptadecene, γ-stearolactone, and 3-heptadecene as reaction intermediates, as well as a CO formation pathway. Because of the highly dispersed Ni metal center on the zeolite support, H2 spillover is observed in the H2 atmosphere, which inhibits the production of short-chain alkanes and reveals the inherent disadvantage of using H2. The CO2 processing of oleic acid described in this paper will significantly contribute to future CO2 utilization chemistry and provide an economical and promising approach for the production of sustainable alkane products which are similar to aviation fuel.

Promotional effect of transition metal doping on the properties of KF/CaO catalyst for biodiesel synthesis

ABSTRACT A series of heterogeneous KF/CaO catalysts modified with transition metals (lanthanum, cerium, and zirconium) were prepared via wet impregnation method and applied to the trsansesterification process of waste cooking oil (WCO) as feedstock with methanol to biodiesel production. The structure, performance of the solid catalysts was characterized by X-ray diffraction (XRD), temperature programmed desorption of CO2 (CO2-TPD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The effect of methanol/oil molar ratio, 1reaction time, reaction temperature, catalyst amount, and stability was investigated. The results showed that 10 wt% of lanthanum, cerium, and zirconium improved the catalytic activity of KF/CaO catalyst. The maximum catalytic activity using the lanthanum doping of 10wt% on KF/CaO catalyst was reached 98.7% under the optimal reaction condition of methanol/oil molar ratio of 12:1, reaction for 1 h at reaction temperature of 65°C, and 4% (wt/wt oil) catalyst amount. In addition, the FAME yield of KF/CaO/La catalyst remained higher than 95% after 10 cycles. The promotional effect of lanthanum doping could be attributed to the enhancement of the basicity strength of KF/CaO catalyst and block the leach of Ca2+ in the transesterification reaction.