Selective hydrodeoxygenation is the central challenge in converting bio-derived fatty acids into fatty alcohols under mild conditions. Herein, an effective and highly selective carbon-supported NiMo catalyst (NiMo@C) was developed by the thermolysis Ni-based metal–organic frameworks (MOF) impregnated Mo species. At a low temperature of 160 °C, the stearic acid can be efficiently converted into corresponding stearic alcohols over the NiMo@C with about 97% selectivity at 100% reactant conversion, which is superior to the most reported catalysts containing noble catalysts. The excellent catalytic performance of NiMo@C catalyst was mainly attributed to the ordered arrangement of Ni in the MOF and the uniform loading of molybdenum salt, which leads to an ideal distribution of Ni and Mo after pyrolysis of the MOF. The carbon support also prevents the aggregation of metal particles, which promotes the dissociation of hydrogen and enhances the synergy between Ni and Mo sites. More importantly, the synthesized NiMo@C catalyst showed excellent reusability with no loss of activity after 15 consecutive runs due to the stability of the catalyst structure. This provides a useful and simple method for synthesizing highly efficiency and stable NiMo@C bimetallic catalysts, which can facilely and selectively hydrogenate the bio-derived fatty acids to corresponding alcohols under mild conditions.
Zhiheng Wang,Yanyan Liu,Xin Li,Ruiyao Gao,Jiong Sun,Jiankun Liu,Songdong Yao
This study utilized the swelling properties of superabsorbent polymers (SAP) to adsorb zeolite sols and slurries to construct C-HY composites. The synthesized C-HY composites proved to be effective supports for NiMo catalysts in the hydrodesulfurization (HDS) of dibenzothiophene ( DBT ) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT). XRD , BET, SEM, TG, NH 3 -TPD, FTIR, H 2 -TPR, TEM and XPS were used to characterization the texutural structure, acidity and metal distribution of prepared NiMo/C-HY catalysts. By combining zeolite slurries with SAPs, HY can be efficiently incorporated into carbon substrate structure in three dimensions (3D), thereby changing the structural characteristics, morphology, acidity, and metal distribution of HDS catalysts. The conversion of DBT decreases sequentially: NiMo/C-HY-s > NiMo/C-HY-h > NiMo/C-HY-p > NiMo/C-HY-c, and the conversion of 4,6-DMDBT decreased sequentially: NiMo/C-HY-s > NiMo/C-HY-p > NiMo/C-HY-h ≫ NiMo/C-HY-c. The introduction of HY into the carbon support can increase the HDS reaction rate of NiMo/C by more than 1.2–1.5 times. The intrinsic reaction activity of NiMo/C-HY-s can even exceed that of traditional NiMo/Al 2 O 3 catalysts. Based on the same Mo loading amount, the HDS activity of NiMo/C-HY-s is twice that of NiMo/Al 2 O 3 in DBT HDS and 1.1–1.5 times that of NiMo/Al 2 O 3 in 4,6-DMDBT HDS. It is thought that HY in carbon composites promotes C–S bond cleavage of sulfur-containing molecules in DBT HDS. The unique dispersion of Mo species induced by HY favors the formation of highly stacked NiMoS active phases, which may be the crucial in 4,6-DMDBT HDS.
Lignin is an abundant source of aromatics with low effective hydrogen-to-carbon ratio (H/Ceff), and the depolymerization of lignin provides significant potential for producing liquid products with an improved H/Ceff value. In this work, the catalytic conversion of lignin monomers, dimer, trimers, and realistic lignin over spherical MOF-derived NiMo@C catalysts was well established, to get liquid fuels with a higher H/Ceff. The optimal ratio of the Ni4Mo1@C catalyst exhibited good hydrodeoxygenation activity and stability for the hydrotreatment of lignin model compounds and lignin. The addition of Mo facilitated the decrease of the particle size of a spherical structure, strengthened the electron-transfer capability between metals Mo and Ni, and enhanced the acid strength. All of these factors contributed to higher hydrodeoxygenation activity in the hydrotreatment process. Up to 100% conversion and 90% yields of ethylcyclohexane and cyclohexanol with H/Ceff values of 2.0 and 1.667, respectively, were obtained. The Ni4Mo1@C catalyst achieved a decrease of the oxygen element and an increase of H/Ceff and HHV values. The physicochemical characterizations were performed by various means including X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), H2-temperature-programmed reduction (H2-TPR), NH3-temperature-programmed desorption (NH3-TPD), pyridine-infrared spectroscopy (Py-IR), inductively coupled plasma emission spectrometer (ICP), and Raman and X-ray photoelectron spectroscopy (XPS) analyses, which definitely elucidated the formation of a synergistic effect between metals Mo and Ni. Additionally, a control experiment also illustrated the synergistic effect that facilitated the occurrence of the hydrotreatment process under lower temperatures after the addition of metal Mo. Based on the optimal reaction condition (240 °C, 4 h, 2.0 MPa H2), both lignin and its monomers/dimers/trimers could be effectively hydrotreated to afford liquid products with improved H/Ceff value compared to raw lignin.
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