Wang Youju, Bai Yongyue, Chen Pohua, Chen Qiang, Wang Yongrui, Shu Xingtian
State Key Laboratory of Catalytic Materials and Reaction Engineering, Research Institute of Petroleum Processing, SINOPEC, Beijing 100083, China.
Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
Molecules. 2022 Aug 31;27(17):5625. doi: 10.3390/molecules27175625.
EWT zeolite belongs to ultra-large pore zeolite with the 10MR and 21MR channels, which has good thermal stability, certain acid strength and good application prospects in petroleum refining and petrochemical reactions. However, EWT zeolite has fewer medium/strong acid sites, especially Brönsted acid sites, which makes it difficult to apply to acid-catalyzed reactions. The regulation of acid amount and distribution was achieved by boron and aluminum substitution into the siliceous framework of EWT. The physico-chemical properties of the samples were characterized by XRD, SEM, N adsorption-desorption, XRF, ICP, Py-IR, NH-TPD and B & Al & Si MAS NMR. The results show that quantities of boron and aluminum elements can occupy the framework of [B,Al]-EWT to increase the density of medium and strong acid centers, with more acidity and Brönsted acid centers than EWT zeolite. In the reaction of glycerol with cyclohexanone, the conversion of the sample (U-90-08-10/U-90-H-HCl) is significantly higher than that of the EWT sample, approaching or exceeding the Beta zeolite. A catalytic activity study revealed a direct correlation between the Brönsted acidic site concentration and the activity of the catalyst. The U-90-08-10-H catalyst was also considerably stable in the catalytic process. This work shows, for the first time, that extra-large pore zeolites can be used in industrial acid-catalytic conversion processes with excellent catalytic performance.
EWT沸石属于具有10元环和21元环孔道的超大孔沸石，具有良好的热稳定性、一定的酸强度，在石油炼制和石化反应中具有良好的应用前景。然而，EWT沸石的中/强酸位点较少，尤其是布朗斯台德酸位点，这使得它难以应用于酸催化反应。通过将硼和铝取代到EWT的硅质骨架中实现了酸量和分布的调控。采用XRD、SEM、N吸附-脱附、XRF、ICP、Py-IR、NH-TPD以及B&Al&Si MAS NMR对样品的物理化学性质进行了表征。结果表明，大量的硼和铝元素能够占据[B,Al]-EWT的骨架，增加中强酸中心的密度，其酸度和布朗斯台德酸中心比EWT沸石更多。在甘油与环己酮的反应中，样品（U-90-08-10/U-90-H-HCl）的转化率显著高于EWT样品，接近或超过β沸石。催化活性研究表明布朗斯台德酸性位点浓度与催化剂活性之间存在直接关联。U-90-08-10-H催化剂在催化过程中也相当稳定。这项工作首次表明，超大孔沸石可用于具有优异催化性能的工业酸催化转化过程。
