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.
Y Zeolite plays an irreplaceable role in many important applications due to its unique physicochemical properties, which has attracted extensive attention from researchers. Response surface methodology (RSM) was used to optimize the process parameters for the hydrothermal synthesis of Y zeolite using kaolin activated by microwave heating. The best relative crystallinity was 108.17% could be achieved at the condition: the aging temperature of guiding agent was 65 ℃, the crystallization temperature was 100 ℃, the crystallization time was 24 h. In addition, the aging temperature of guiding agent was the most important influence factor. Under the optimal condition, the SiO 2 /Al 2 O 3 ratio of synthesized Y zeolite was 4.54, 90% of the particle size was less than 60 μm, and the specific surface area of Y zeolite was 479 m 2 /g. The successful preparation of Y zeolite with high crystallinity is expected to provide reference for the application of wastewater treatment, CO 2 sequestration and fluid catalytic cracking for petroleum.
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