Lewis acidic Sn centers isolated within Beta zeolite frameworks catalyze bimolecular ethanol dehydration to diethyl ether, yet with kinetic behavior sensitive to the hydrophobic character of their confining microporous voids. Sn sites in open ((HO)-Sn-(OSi)₃) and closed (Sn-(OSi)₄) configurations, quantified from infrared spectra of adsorbed CD₃CN before and after reaction, convert to structurally similar intermediates during ethanol dehydration catalysis (404 K) and revert to their initial configurations after regenerative oxidation treatments (21% O₂, 803 K). Dehydration rate data (404 K, 0.5–35 kPa C₂H₅OH, 0.1–50 kPa H₂O) measured on ten low-defect (Sn-Beta-F) and high-defect (Sn-Beta-OH) zeolites were described by a rate equation that was derived from mechanisms identified previously by density functional theory calculations and simplified using microkinetic modeling to identify kinetically-relevant pathways and intermediates. Polar hydroxyl defect groups located in the microporous environments that confine Sn sites preferentially stabilize reactive (ethanol-ethanol) and inhibitory (ethanol-water) dimeric intermediates over monomeric ethanol intermediates. As a result, equilibrium constants (404 K) for ethanol-water and ethanol-ethanol dimer formation are 3–4× higher on Sn-Beta-OH than on Sn-Beta-F, consistent with insights from single-component (302 K) and two-component (303 K, 403 K) ethanol and water adsorption measurements. Intrinsic dehydration rate constants (404 K) were identical, within error, among Sn-Beta-OH and Sn-Beta-F zeolites; thus, measured differences in dehydration turnover rates solely reflect differences in prevalent surface coverages of inhibitory and reactive dimeric intermediates at active Sn sites. The confinement of Lewis acidic binding sites within secondary microporous environments of different defect density confers the ability to discriminate surface intermediates on the basis of polarity, providing a design strategy to accelerate turnover rates and suppress inhibition by water.

在Beta沸石骨架内分离的路易斯酸性Sn中心催化双分子乙醇脱水成乙醚，但动力学行为对其封闭微孔空隙的疏水特性敏感。从反应前后吸附的CD ₃ CN的红外光谱中定量得出开放（（HO）-Sn-（OSi ）₃）和封闭（Sn-（OSi ）₄）构型的Sn位点，在乙醇脱水过程中转化为结构相似的中间体催化（404 K），并恢复到它们的初始构型再生氧化处理（21％氧气后₂，803 K）。脱水速率数据（404 K，0.5–35 kPa C ₂ H ₅ OH，0.1–50 kPa H ₂O）是通过速率方程描述的，对十种低缺陷（Sn-Beta-F）和高缺陷（Sn-Beta-OH）沸石进行了测量，该速率方程是从先前通过密度泛函理论计算确定的机理中得出的，并使用微动力学模型进行了简化识别动力学相关的途径和中间体。位于微孔环境中并限制Sn位点的极性羟基缺陷基团比单体乙醇中间体优先稳定反应性（乙醇-乙醇）和抑制性（乙醇-水）二聚体中间体。结果，与Sn-Beta-F相比，Sn-Beta-OH上的乙醇-水和乙醇-乙醇二聚体形成的平衡常数（404 K）高3-4倍，这与单组分（302 K ）和两组分（303 K，403 K）乙醇和水的吸附测量值。Sn-Beta-OH和Sn-Beta-F沸石的固有脱水速率常数（404 K）相同，但有误差。因此，测得的脱水周转率差异仅反映了活性Sn位点上抑制性和反应性二聚中间体的普遍表面覆盖率的差异。在具有不同缺陷密度的次生微孔环境中，路易斯酸性结合位点的限制赋予了基于极性区分表面中间体的能力，从而提供了一种设计策略来加速周转速度并抑制水的抑制作用。