The Steric Effect in Green Benzylation of Arenes with Benzyl Alcohol Catalyzed by Hierarchical H-beta Zeolite
The Steric Effect in Green Benzylation of Arenes with Benzyl Alcohol Catalyzed by Hierarchical H-beta Zeolite
复制标题
多级H-β沸石催化芳烃与苯甲醇绿色苯甲基化的空间效应
DOI：
10.3390/catal9100869
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发表时间：
2019-10-01
期刊：
影响因子：
3.9
通讯作者：
Yang, Jianxin
中科院分区：
文献类型：
--
作者：
Liu, Xinyu;Lu, Meihuan;Yang, Jianxin
芳烃与苯甲醇催化苄基化反应中的空间位阻效应一直没有得到很好的理解，这限制了苯甲烷衍生物的绿色合成。本研究应用一系列硅铝β沸石系统地评估催化剂孔隙率、反应物分子大小和反应温度等因素对催化苄基化的影响。首先，通过X射线粉末衍射、N-2吸附-脱附和对二甲苯探针苄基化反应筛选出合适的分级结构β沸石催化剂。在随后的底物扩展研究中，对于一个典型的苯苄基化反应，在文献报道的反应中，仅在353 K下10 min后，转化率就达到98%，选择性达到90%。观察到不同分子大小的芳烃对苄基化反应的空间效应。四种不同芳烃的反应活性顺序为：苯>甲苯>对二甲苯>均三甲苯。结合宏观动力学分析，首次指出了这种空间位阻效应的本质是由不同客体分子在主体分子筛表面的相对吸附效率决定的。
For decades the steric effect was still ambiguously understood in catalytic benzylation reactions of arenes with benzyl alcohol, which limited the green synthesis of phenylmethane derivates in industrial scale. This research applies a series of silica-alumina beta zeolites to systematically evaluate factors like catalyst porosity, reactants molecule size, and reaction temperature on catalytic benzylation. First, a suitable hierarchical beta zeolite catalyst was screened out by X-ray powder diffraction, N-2 adsorption-desorption, and probe benzylation with p-xylene. In the following substrates expanding study, for a typical benzylation of benzene, it showed extraordinary performance among literature reported ones that the conversion was 98% while selectivity was 90% at 353 K only after 10 min. The steric effect of aromatics with different molecular sizes on benzylation was observed. The reaction activities of four different aromatics followed the order: benzene > toluene > p-xylene > mesitylene. Combined with macroscopic kinetic analysis, this comprehensive study points out for the first time that the nature of this steric effect was dominated by the relative adsorption efficiency of different guest aromatic molecules on the host zeolite surface.