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首页> 外文期刊>ACS catalysis >CO2 Reduction to Methanol on Au/CeO2 Catalysts: Mechanistic Insights from Activation/Deactivation and SSITKA Measurements
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CO2 Reduction to Methanol on Au/CeO2 Catalysts: Mechanistic Insights from Activation/Deactivation and SSITKA Measurements

机译：Au / CeO2催化剂上的CO 2还原到甲醇：激活/停用和Ssitka测量的机械洞察

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Aiming at a mechanistic understanding of the methanol (MeOH) synthesis from CO2/H-2 over Au/CeO2 catalysts and the activation/deactivation of these catalysts, we have investigated these processes by a combination of kinetic measurements, time-resolved in situ diffuse reflectance Fourier transform infrared (FTIR) spectroscopy (DRIFTS) measurements, and structural characterization by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). Kinetic measurements indicated a rapid activation phase, followed by a continuous slow deactivation. A faster deactivation of CO formation (reverse water-gas shift reaction) compared to that of methanol formation results in an increasing selectivity toward MeOH formation with time on stream. The activation of the catalyst is attributed to a rapid initial reduction of the support (formation of O vacancies). Since based on STEM imaging and XRD measurements sintering of Au nanoparticles is negligible, the subsequent deactivation is attributed to the slow buildup of site-blocking adsorbates, specifically surface carbonates, and/or over-reduction of the catalyst. This is supported also by the reversible nature of the deactivation upon recalcination in O-2/N-2. Steady-state isotopic transient kinetic analysis (SSITKA) measurements, following the buildup/decay of adsorbed formate and methoxy species by DRIFTS upon changing from a CO2/H-2 to a CO2/D-2 mixture and back under steady-state conditions, indicate that surface formate species are reaction intermediates in the dominant reaction pathway for CO2 hydrogenation to methanol, with the calculated rates of formation/decay comparable to the rate of methanol formation. The consequences of these results for the mechanistic understanding of this reaction are discussed.
机译：针对来自Au / CeO 2催化剂的CO 2 / H-2的甲醇（MeOH）合成的机械理解和这些催化剂的活化/去激活，我们通过动力学测量的组合研究了这些过程，以原位漫射时间分辨反射率傅里叶变换红外（FTIR）光谱（漂移）测量，X射线衍射（XRD）和扫描透射电子显微镜（茎）的结构表征。动力学测量表明了快速激活阶段，然后连续缓慢停用。与甲醇形成相比，CO形成（反向水 - 气体换体反应）的更快停用导致对MeOH形成的选择性增加，流量在流上。催化剂的激活归因于载体的快速初始降低（批次的形成）。由于基于茎成像和XRD测量Au纳米粒子的烧结可忽略不计，因此随后的去激活归因于位点阻断吸附物，特异性表面碳酸盐和/或催化剂过度还原的缓慢累积。在O-2 / N-2中重新振荡时，通过可逆性支持这一点。在从CO 2 / H-2改变为CO 2 / D-2混合物时，在吸附的甲酸盐和甲氧基物种的堆积/衰减后，稳态同位素瞬态动力学分析（Ssitka）测量。表明表面甲酸物种是用于CO 2氢化至甲醇的主要反应途径中的反应中间体，其计算速率与甲醇形成的速率相当。讨论了这些结果对该反应的机械理解的后果。

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