Four methods were adopted to prepare samples 20%NiO/Al 2 O 3 with calcination fixed at 500 °C, which were then reduced into 20%Ni/Al 2 O 3 and used as catalysts for reaction of selective methanation of CO in H 2 -rich gas (CO-SMET). XRD and TPR measurements indicate that nickel aluminates were formed in the calcined samples and their formation was influenced by preparation methods. Higher temperatures were required to reduce the calcined samples more efficiently and to achieve a higher catalytic activity for CO-SMET. Among the four methods, the precipitation method using ammonium carbonate as precipitant produced the highest catalytic activity both for CO methanation and for CO 2 methanation after reduction at 800 °C for 2 h. The calcined sample 20%NiO/Al 2 O 3 prepared with the method was therefore used as support and impregnated with Ru 3+ solution. Ru addition promoted reduction of Ni 2+ ions in the calcined sample even at the low temperatures of 400 °C and 500 °C. The catalyst 1%Ru–20%Ni/Al 2 O 3 reduced at 500 °C thus had a superior performance, removing CO to ca. 30 ppm with a selectivity as high as 75% at reaction temperature of 220 °C.
Xia Zhang,Wenzhi Li,Yihang Jiang,Leyu Zhu,Liqun Wang
Efficient lignin depolymerization is crucial in the generation of valuable liquid fuels and mono-phenols for enhancing the utilization and sustainability of biomass resources. However, the complicated three-dimensional structure of lignin, the propensity for intermediate products to condense, and an overreliance on high-pressure hydrogen in depolymerization reactions pose major challenges. In this regard, we prepared a La and Ru modified Y zeolite (Ru 2 La 0.5 /HYo) and employed isopropanol (IPA) as an in situ hydrogen donor for the efficient conversion of lignin without requiring an external hydrogen source. Ru 2 La 0.5 /HYo selectively activates and decomposes IPA, constantly liberating H 2 for lignin degradation. The Ru-mediated synergy between the L-acid and hydrogenation active sites stabilizes the active intermediate and inhibits condensation, thereby balancing the depolymerization and condensation rates. La coordination with the alumina in the molecular sieve limits Al leaching, preventing zeolite deactivation during the reaction and enabling lignin depolymerization to proceed steadily. After four consecutive trials, no significant decline in activity is unobserved. After a 12 h reaction at 290°C, the oxygen content dropped from 29.69 % to 15.47 %, and the higher heating value (HHV) improved from 25.41 to 34.65 MJ/kg. Extending the period to 24 h resulted in a 93.80 % yield of liquid product and a 63.68 % yield of petroleum ether soluble (PES) product, allowing lignin to be upgraded for liquid fuels generation.
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