Dry reforming of methane (DRM) suffers catalysts deactivation due to severe coking. Ni/MgO-Al 2 O 3 is a promising system for DRM catalysts with high coking resistance, as the addition of MgO in Ni/Al 2 O 3 catalysts can improve the alkalinity of the support and enhance the metal-support interaction. However, so far the activity and stability of Ni/MgO-Al 2 O 3 is still unsatisfactory while the role of Mg addition remains unclear. In this paper, a series Ni 0.5 /xMgO-Al 2 O 3 catalysts with flower-like hollow sphere morphology and high surface area were synthesized via a facile hydrothermal method. Appropriate Mg addition promotes the formation of NiAl 2 O 4 while more Mg addition leads to the formation of Ni x Mg y O. Both cases can enhance the MSI of the catalysts without changing the morphology of the catalyst. More Mg addition also leads to stronger CO 2 adsorption via improving the alkalinity. Nevertheless, overdose of Mg results in weaker MSI and the blockage of Ni active sites. Ni 0.5 /0.5MgO-Al 2 O 3 with moderate Mg addition shows excellent activity (CH 4 ∼ 75 %, CO 2 ∼ 85 %) and stability (>100 h) at a high GHSV = 144000 ml/g cat ·h −1 and 800 °C with nearly no coking formation (<0.8 wt%). This work helps reveal the role of MgO addition in Ni/Al 2 O 3 systems and gives new insights into the design of DRM catalysts with high activity and stability.
To develop an efficient and feasible catalyst for converting inedible vegetable oil to green biodiesel via a one-step decarboxylation process, a series of Ni-based MgO-Al 2 O 3 catalysts with different active Ni species were fabricated by adjusting the various Ni loading amounts (2.5–20%) and applied to the catalytic deoxygenation of OA to generate green biodiesel. Additionally, the structure-property relationship, deactivation mechanism and regeneration performance were also evaluated via various characterization technologies (XRD, BET, NH 3 -TPD, H 2 -TPR, XPS, SEM-EDX, HRTEM, TGA, Raman as well as GC/MS and UV-fluorescence spectra). The experimental results indicated that Ni introduction obviously enhanced the conversion ratio. Ni (10%)/MgO-Al 2 O 3 catalysts exhibited excellent catalytic performance with the highest HCs (95.12%), olefin content (57.37%) and green biodiesel content (75.90%) due to mild Brønsted-rich acidity sites, lower reduction temperature, higher active metallic Ni species content, suitable oxygen vacancy content and favorable texture properties via the decarbonylation reaction pathway. Furthermore, lower Ni loading was beneficial to gasoline and bioaviation fuel generation due to higher Brønsted-rich acidity sites and total acid amount, which boosted C-C scission by cracking reaction, and higher Ni content facilitated biodiesel formation. Additionally, Ni (10%)/MgO-Al 2 O 3 catalysts showed excellent reusability and regeneration due to Ni active species, but these advantages were slightly decreased (HCs: from 95.12% to 61.63%; biodiesel: from 75.90% to 57.52%) due to coke deposition and metal active species leaching and oxidation .
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