Nzodom Djozing William's, Valange Sabine, Nikitenko Sergey I, Chave Tony
Univ Montpellier, UMR 5257, ICSM, CEA, CNRS, ENSCM, Marcoule, F-30207 Bagnols Sur Cèze, France.
Université de Poitiers, CNRS, Institut de Chimie des Milieux et Matériaux de Poitiers-IC2MP, ENSI Poitiers, B1, 1 rue Marcel Doré, F-86073 Poitiers Cedex 9, France.
Dalton Trans. 2024 Oct 8;53(39):16407-16421. doi: 10.1039/d4dt01943a.
The sonohydrothermal (SHT) treatment is an innovative technique allowing the simultaneous coupling of low frequency ultrasound and hydrothermal conditions for the synthesis of materials. The aim of the present work was to investigate, for the first time, the synthesis of zeolite A and its formation mechanism under SHT conditions. The zeolite synthesis was carried out under sonohydrothermal conditions using a specially designed reactor that allows the application of ultrasonic irradiation at 20 kHz in an autoclave-type reactor heated up to 200 °C under autogenous pressure. The conversion kinetics of the amorphous hydrogel to zeolite A and its further conversion to sodalite were studied. Syntheses were performed in the SHT reactor at 80 and 100 °C, varying the synthesis time from 15 minutes to several hours. The required time to obtain fully crystalline zeolite A under sonohydrothermal conditions was only 25 minutes, highlighting a significantly improved crystallization rate compared to silent conditions (a 9.6-fold kinetic gain). In addition, the resulting zeolite A has smaller particles and a more homogeneous particle size distribution than the zeolite synthesized by hydrothermal treatment. These results can be explained by the sonofragmentation of the amorphous gel and the concomitant enhanced mass transfer of the building units at the interface between the crystallite surface and the solution resulting from the acoustic cavitation activity under SHT conditions. Compared to classical hydrothermal heating, a drastic kinetic increase of the transformation of zeolite A into the more stable sodalite phase was also observed under sonohydrothermal conditions.
超声水热（SHT）处理是一种创新技术，可将低频超声与水热条件同时耦合用于材料合成。本工作的目的是首次研究在SHT条件下沸石A的合成及其形成机理。沸石合成在超声水热条件下进行，使用专门设计的反应器，该反应器可在高达200°C的自生压力下于高压釜式反应器中施加20 kHz的超声辐射。研究了无定形水凝胶向沸石A的转化动力学及其进一步向方钠石的转化。在SHT反应器中于80和100°C进行合成，合成时间从15分钟变化到数小时。在超声水热条件下获得完全结晶的沸石A所需的时间仅为25分钟，与静态条件相比，突出显示了显著提高的结晶速率（动力学增益9.6倍）。此外，与通过水热处理合成的沸石相比，所得的沸石A具有更小的颗粒和更均匀的粒度分布。这些结果可以通过无定形凝胶的声破碎以及在SHT条件下声空化活性导致的微晶表面与溶液之间界面处构建单元的传质增强来解释。与传统水热加热相比，在超声水热条件下还观察到沸石A向更稳定的方钠石相转化的动力学急剧增加。
