SiO₂-supported tungsten catalysts (WO₃/SiO₂) are currently used in industry to make propene via metathesis of butene and ethylene. Reliable information on structure–activity relationships, aimed at improved catalyst design, continues to be an active area of investigation. On the basis of ex situ XPS and solid-state NMR spectroscopy of calcined W-incorporated mesoporous silicates (W-KIT-6), complemented by computational studies and activity evaluation in a fixed-bed reactor, we demonstrate that W–O–Si species are the active site precursors for 2-butene + ethylene metathesis to produce propene at 450 °C. This conclusion is supported by evidence that the population of W–O–Si species on the calcined W-KIT-6 catalysts is linearly correlated with 2-butene conversion, regardless of W loading. We further show that for a given W loading, the accessible W–O–Si species and thereby the propene yield, can be enhanced by delaying the tungsten source addition during catalyst synthesis. Our results are consistent with previously reported in situ mechanistic studies using complementary analytical tools.

中文翻译：

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W结合硅酸盐中活性位点前体与烯烃复分解活性的相关性

SiO ₂负载的钨催化剂（WO ₃ / SiO ₂）目前在工业上用于通过丁烯和乙烯的复分解反应制得丙烯。旨在改进催化剂设计的关于结构-活性关系的可靠信息仍然是研究的活跃领域。在煅烧掺W介孔硅酸盐（W-KIT-6）的异位XPS和固态NMR光谱的基础上，结合在固定床反应器中的计算研究和活性评估，我们证明了W–O–Si这些物种是2-丁烯+乙烯复分解以在450°C下生成丙烯的活性位点前体。该结论得到了证据的支持，即煅烧的W-KIT-6催化剂上W–O–Si物种的种群与2-丁烯转化率呈线性相关，而与W的负载无关。我们进一步表明，对于给定的W负载，可利用的W–O–Si物种以及由此产生的丙烯收率，可以通过在催化剂合成过程中延迟钨源的添加来增强硫。我们的结果与先前报道的使用互补分析工具进行的原位力学研究一致。