The effect of Zr modification on the catalytic activity of Co/SiO₂ was investigated for nonoxidative propane dehydrogenation. Isolated Zr on SiO₂ surface sites were prepared by organometallic synthesis using Zr(O^tBu)₄ as a precursor. The resulting Zr/SiO₂ support was functionalized with Co²⁺ ions via strong electrostatic adsorption. Spectroscopic (diffuse reflectance infrared Fourier transform spectroscopy, UV–vis, electron paramagnetic resonance) and microscopic characterization (transmission electron microscopy, scanning transition electron microscopy) results are consistent with single-site cobalt that preferentially associates with the mono-dispersed Zr at a variety of loadings and Co/Zr ratios. The oxidation state of Co in the as-prepared Co/SiO₂ and Co–Zr/SiO₂ was both +2 with tetrahedral and octahedral geometries, respectively. In situ X-ray absorption near edge structure and extended X-ray absorption fine structure results confirmed that the oxidation state of Co remained as +2 under reaction condition for both Co/SiO₂ and Co–Zr/SiO₂ samples and both catalysts have tetrahedral Co²⁺ as the active catalyst. Despite similar Co coordination environments, the catalytic activity and selectivity was significantly improved by the Zr modification of the silica support versus Co/SiO₂. This was attributed to the change in oxygen donor ability and Co–O bond strength of the ≡SiO–Zr–O sites of Co–Zr/SiO₂ compared with the ≡SiO– ligands in Co/SiO₂. These results show that tuning of the support SiO₂ oxygen donation ability by use of an anchoring site (e.g., ≡SiO–Zr–O^–) can be used to alter both rate and selectivity of propane dehydrogenation with single-site heterogeneous catalysts. These results also show some preference for Co²⁺ active sites to associate with ≡SiO–Zr–O^– sites over ≡SiO–.

中文翻译：

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锆改性可促进单点钴多相丙烷丙烷脱氢催化剂的催化活性。

研究了Zr改性对Co / SiO ₂催化活性进行非氧化丙烷脱氢的影响。通过有机金属合成，使用Zr（O ^t Bu）₄作为前体，在SiO ₂表面位点上分离出Zr 。将所得的Zr / SiO ₂载体用Co ²⁺官能化离子通过强静电吸附。光谱（漫反射红外傅里叶变换光谱，紫外可见光，电子顺磁共振）和显微表征（透射电子显微镜，扫描跃迁电子显微镜）的结果与单点钴相吻合，后者优先与多种形式的单分散Zr缔合负载和Co / Zr比率。所制备的Co / SiO ₂和Co–Zr / SiO ₂中，Co的氧化态均为四面体和八面体，均为+2。X射线边缘结构的原位吸收和扩展的X射线吸收的精细结构的结果证实，在Co / SiO ₂和Co-Zr / SiO的反应条件下，Co的氧化态均保持为+2_2个样品，并且两种催化剂均具有四面体Co ²⁺作为活性催化剂。尽管有相似的Co配位环境，但与Co / SiO ₂相比，二氧化硅载体的Zr改性显着提高了催化活性和选择性。这是由于在氧供体的能力和Co-锆/二氧化硅的≡SiO锆-O网站的CO-O粘结强度变化₂用钴/二氧化硅的≡SiO-配体相比，₂。这些结果表明的支持的SiO该调谐₂氧捐赠能力通过使用锚定位置（例如，≡SiO -锆-O的^-）可用于通过单中心非均相催化剂改变丙烷脱氢的速率和选择性。这些结果也表现出一定的偏爱有限公司²⁺活性位点，以联想与≡SiO锆-O ^-在≡SiO-网站。