Structure and reactivity of single site Ti catalysts for propylene epoxidation
Structure and reactivity of single site Ti catalysts for propylene epoxidation
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DOI：
10.1016/j.jcat.2019.07.051
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发表时间：
2019-09
影响因子：
7.3
通讯作者：
Zheng Lu;Xiaoyang Liu;Bin Zhang;Z. Gan;Siwen Tang;Lu Ma;Tianpin Wu;G. Nelson;Yong Qin;C. Turner;Y. Lei
中科院分区：
文献类型：
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作者：
Zheng Lu;Xiaoyang Liu;Bin Zhang;Z. Gan;Siwen Tang;Lu Ma;Tianpin Wu;G. Nelson;Yong Qin;C. Turner;Y. Lei
以Au基催化剂为催化剂，以分子氧和氢气混合气体为氧化剂的丙烯环氧化反应，由于具有较高的环氧丙烷选择性和廉价的环境友好氧化剂而受到人们的关注。金属氧化物载体上的单活性中心钛在丙烯环氧化反应中获得高反应性和选择性方面起着重要作用。本文采用原子层沉积法（ALD）制备了单中心钛嵌入SiO2骨架的丙烯环氧化催化剂。采用高温煅烧作为后处理，以控制二氧化钛的结构和Tisingle键O配位数。利用紫外-可见光谱和X-射线吸收光谱，我们成功地建立了类似的丙烯转化率下的环氧丙烷（PO）的选择性是强烈相关的Tisingle键O的配位数和键长。使用集群模型，密度泛函理论（DFT）计算表明，部分电荷的单一Tisingle键SiO2网站的规模线性作为配位数的函数。此外，预测的Tisingle bondO键长遵循相同的趋势，在实验中发现，所观察到的实验活性关系提供额外的支持。
Propylene epoxidation using molecular oxygen and hydrogen mixture on Au-based catalysts has attracted attention because of high propylene oxide selectivity and the use of an inexpensive and environmental friendly oxidant. Single-site titanium on metal oxide supports plays an important role in achieving high reactivity and selectivity in propylene epoxidation. Here we used TiO2atomic layer deposition (ALD) to synthesize single-site titanium imbedded in the SiO2framework for propylene epoxidation. High temperature calcination was used as post-treatment to control the titania structure and Tisingle bondO coordination number. Using UV–vis spectroscopy and X-ray absorption spectroscopy, we successfully established that under similar propylene conversion the selectivity to propylene oxide (PO) is strongly correlated to the Tisingle bondO coordination number and bond length. Using a cluster model, density functional theory (DFT) calculations indicate that the partial charges of single Tisingle bondSiO2sites scale linearly as a function of the coordination number. Also, the predicted Tisingle bondO bond lengths follow the same trend as found in the experiments, providing additional support for the observed experimental activity relationships.