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首页> 外文期刊>Catalysis science & technology >Enhancement of p-xylene selectivity in the reaction between 2,5-dimethylfuran and ethanol over an ammonium fluoride-modified ZSM-5 zeolite
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Enhancement of p-xylene selectivity in the reaction between 2,5-dimethylfuran and ethanol over an ammonium fluoride-modified ZSM-5 zeolite

机译：在2,5-二甲基呋喃和乙醇之间的反应中，P-二甲苯选择性在氟化铵改性的ZSM-5沸石上的反应增强

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摘要

A renewable synthesis of p-xylene (PX) via the Diels–Alder cycloaddition of biomass-derived 2,5-dimethylfuran (2,5-DMF) and ethanol was realized over various catalysts. During the tandem reaction, multiple competitive reactions occur, among which the hydrolysis of 2,5-DMF to 2,5-hexanedione, further dehydrating to 3-methyl-2-cyclopenten-1-one is the most detrimental to the main reaction as concluded from DFT calculations and experimental results. Besides, the product distributions vary with different catalysts. In comparison with HBeta and WOx/ZrO2, the HZSM-5 zeolite showed better performance with higher PX selectivity and yield. To further improve the reaction performance, the HZSM-5 zeolite was modified using NH4F at different times. After the modification for 5 min, denoted as FZ5-5, an optimum catalyst with the 2,5-DMF conversion of 70% and PX selectivity of 79% was obtained. Furthermore, the physicochemical properties of catalysts were comprehensively characterized using XRD, N2 adsorption–desorption isotherms, ICP, NH3-TPD, pyridine-IR, SEM, TEM and MAS NMR. The results demonstrate that the high catalytic activity is attributed to the hierarchical pore structure and specific acidic features caused by simultaneous desilication and dealumination during NH4F etching. The hierarchical pore structure facilitates the diffusion of reactants, and the sufficient acid sites with moderate strength and B/L ratio of 1.17 can effectively reduce the 2,5-DMF hydrolysis reaction rate and promote the main reaction.
机译：通过多种催化剂（2,5-DMF）和乙醇实现了各种催化剂，可通过双层 - alder cyclotition（PX）进行可再生合成。在串联反应期间，发生了多种竞争反应，其中2,5-DMF至2,5-己二酮的水解进一步脱水至3-甲基-2-氯二甲基-1clopenten-1-1-最有害于主要反应，因为它是主要反应从DFT计算和实验结果得出结论。此外，产品分布因不同的催化剂而变化。与HBETA和WOX/ZRO2相比，HZSM-5沸石表现出更好的性能，具有更高的PX选择性和产量。为了进一步改善反应性能，在不同时间使用NH4F修改了HZSM-5沸石。修饰5分钟后，表示为FZ5-5，获得了2,5-DMF转换为70％的最佳催化剂，PX选择性为79％。此外，使用XRD，N2吸附 - 吸附等温线，ICP，NH3-TPD，NH3-TPD，吡啶-IR，SEM，SEM，TEM，TEM和MASNMR，对催化剂的物理化学特性进行了全面的特征。结果表明，高催化活性归因于层次孔结构和由NH4F蚀刻过程中同时脱脱水和交易引起的特定酸性特征。分层孔结构促进反应物的扩散，并且具有中等强度和B/L比1.17的足够的酸位点可以有效地降低2,5-DMF水解反应速率并促进主反应。

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