Gallego-Villada Luis A, Cueto Jennifer, Alonso-Doncel María Del Mar, Mäki-Arvela Päivi, Alarcón Edwin A, Serrano David P, Murzin Dmitry Yu
Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University Henriksgatan 2 20500 Turku/Åbo Finland
Environmental Catalysis Research Group, Chemical Engineering Faculty, Universidad de Antioquia Medellín Colombia
Green Chem. 2024 Sep 16;26(20):10512-10528. doi: 10.1039/d4gc04003a. eCollection 2024 Oct 14.
Dendritic ZSM-5 zeolites were investigated in the isomerization of monoterpene epoxides, including limonene-1,2-epoxide (LE), α-pinene epoxide, and β-pinene epoxide, which yields high-value compounds used in fragrances, cosmetics, and pharmaceuticals. The fresh catalysts were thoroughly characterized using XRD, Ar physisorption, pyridine-FTIR, TEM, FTIR/DTBPyr, and Al MAS NMR. In comparison with conventional and hierarchical ZSM-5 materials, the dendritic zeolite with a crystallization time of 4 days (d-ZSM-5/4d) was the most active material, with a turnover frequency value of 4.4 min for LE isomerization. Likewise, remarkable yields of dihydrocarvone (DHC, 63%, 70 °C, 2 h), campholenic aldehyde (72.4%, 70 °C, 5 min), and myrtanal (47.7%, 50 °C, 5 min) were obtained with this material that exhibited the largest mesopore/external surface area (360 m g), showing also the narrowest mesopore size distribution. A direct relationship was observed between the TOF values and the concentration of external Brønsted acid sites, showing the presence of strong steric/diffusional limitations that are greatly overcome with the dendritic zeolites. The lower reactivity of -LE compared to -LE was attributed to the larger steric hindrance of the oxygen atom. Exploration of the solvent influence revealed that the reaction rate of LE was favored by non-polar solvents, while highly selective DHC formation occurred in the solvents of medium polarity. The d-ZSM-5/4d sample was shown to be robust because catalytic activity could be completely recovered by air calcination.
研究了树枝状ZSM-5沸石在单萜环氧化物异构化反应中的性能，这些单萜环氧化物包括柠檬烯-1,2-环氧化物（LE）、α-蒎烯环氧化物和β-蒎烯环氧化物，反应产物为用于香料、化妆品和药品的高价值化合物。采用XRD、Ar物理吸附、吡啶-FTIR、TEM、FTIR/DTBPyr和Al MAS NMR对新鲜催化剂进行了全面表征。与传统和分级ZSM-5材料相比，结晶时间为4天的树枝状沸石（d-ZSM-5/4d）是活性最高的材料，LE异构化的周转频率值为4.4 min⁻¹。同样，使用这种具有最大介孔/外比表面积（360 m²/g）且介孔尺寸分布最窄的材料，可获得高产率的二氢香芹酮（DHC，63%，70 °C，2 h）、龙脑醛（72.4%，70 °C，5 min）和桃金娘醛（47.7%，50 °C，5 min）。观察到TOF值与外表面布朗斯特酸位点浓度之间存在直接关系，表明存在强烈的空间/扩散限制，而树枝状沸石能大大克服这些限制。与（-）-LE相比，（+）-LE的反应活性较低，这归因于氧原子较大的空间位阻。对溶剂影响的研究表明，非极性溶剂有利于LE的反应速率，而在中等极性溶剂中会发生高选择性的DHC生成。d-ZSM-5/4d样品表现出良好的稳定性，因为通过空气煅烧可以完全恢复其催化活性。
