Abou-Elyazed Ahmed S, Sun Yinyong, El-Nahas Ahmed M, Yousif Ahmed M
MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology Harbin 150001 China
Chemistry Department, Faculty of Science, Menoufia University Shebin El-Kom Egypt
RSC Adv. 2020 Nov 12;10(68):41283-41295. doi: 10.1039/d0ra08217a. eCollection 2020 Nov 11.
Recently, the incorporation of hydrophobicity on the surface of UiO-66(Zr) has received much attention due to the deactivation of hydrophilic active sites of UiO-66(Zr) upon water adsorption. In this work, we report UiO-66(Zr) catalysts with an assortment of surface hydrophobicities fabricated by the solvent-free method to elucidate the impact of the environment framing Lewis acid sites on their catalytic activity in the production of fatty acid methyl ester (biodiesel) the esterification of fatty acids at room temperature with high selectivity (100%) and good recyclability. A detailed structural analysis of the materials by N sorption, FT-IR, SEM, XRD, water contact angle measurement, dynamic liquid scattering (DLS), NMR and TGA revealed the fabrication of stearic acid-grafted UiO-66(Zr) catalysts (10SA/UiO-66) with fine particle size and a highly hydrophobic network. 10SA/UiO-66(Zr) with enhanced hydrophobicity exhibited superior catalytic performance in the esterification of a fatty acid with a long alkyl chain compared with conventional solid acid catalysts and even liquid acid catalysts. Detailed kinetic studies corroborated that the adsorption of lipophilic acids at the Lewis acid sites besides the enhancement of wettability between the reactants was facilitated by the hydrophobic environment, thus significantly motivating the esterification reaction at room temperature. Furthermore, 10SA/UiO-66(Zr) showed good catalytic activity in the esterification of oleic acid in the presence of water (∼10% in the light of acid weight).
最近，由于UiO-66(Zr)的亲水性活性位点在水吸附后失活，UiO-66(Zr)表面疏水性的引入受到了广泛关注。在这项工作中，我们报道了通过无溶剂法制备的具有多种表面疏水性的UiO-66(Zr)催化剂，以阐明构建路易斯酸位点的环境对其在脂肪酸甲酯（生物柴油）生产中的催化活性的影响，即在室温下脂肪酸的酯化反应具有高选择性（100%）和良好的可回收性。通过N吸附、傅里叶变换红外光谱（FT-IR）、扫描电子显微镜（SEM）、X射线衍射（XRD）、水接触角测量、动态液体散射（DLS）、核磁共振（NMR）和热重分析（TGA）对材料进行的详细结构分析表明，制备出了粒径细小且具有高度疏水网络的硬脂酸接枝的UiO-66(Zr)催化剂（10SA/UiO-66）。与传统固体酸催化剂甚至液体酸催化剂相比，具有增强疏水性的10SA/UiO-66(Zr)在长烷基链脂肪酸的酯化反应中表现出优异的催化性能。详细的动力学研究证实，除了增强反应物之间的润湿性外，疏水环境还促进了亲脂性酸在路易斯酸位点的吸附，从而显著推动了室温下的酯化反应。此外，10SA/UiO-66(Zr)在有水存在（以酸重量计约10%）时油酸的酯化反应中表现出良好的催化活性。
