State Environmental Protection Key Laboratory of Food Chain Pollution Control, School of Ecology and Environment, Beijing Technology and Business University, Beijing, 100048, China.
Key Laboratory of Cleaner Production and Integrated Resource Utilization of China National Light Industry, Beijing Technology and Business University, Beijing, 100048, China.
Environ Sci Pollut Res Int. 2022 Feb;29(7):10605-10616. doi: 10.1007/s11356-021-16204-3. Epub 2021 Sep 15.
In order to make clear the role of intercalated anions in layered double hydroxides (LDHs) for catalytic hydrolysis of carbonyl sulfide (COS), the adsorption and reaction characteristics of COS over the simple MgAl-Cl-LDH model catalyst were studied by both theoretical and experimental methods. Density functional theory (DFT) calculations by CASTEP found that the chloride ions in LDH function as the key Brønsted base sites to activate the adsorbed HO with enlarged bond length and angle, facilitate the dissociative adsorption of intermediates including mono-thiocarbonic acid (MTA) and hydrogen thiocarbonic acid (HTA), and participate in the formation of transient states and subsequent hydrogen transfer process with decreased energy barriers during COS hydrolysis. COS hydrolysis will preferentially go through the dissociated intermediates of mono-thiocarbonates (MT) and hydrogen thiocarbonates (HT) with dramatically decreased energy barriers, and the rate-determining step of COS hydrolysis over MgAl-Cl-LDH will be the nucleophilic addition of C=O in COS by HO (Ea = 1.10 eV). The experimental results further revealed that the apparent activation energy (0.89 eV) of COS hydrolysis over MgAl-Cl-LDH is close to theoretical value (1.10 eV), and the accumulated intermediates of MT, HT, or carbonate were also observed by FT-IR around 1363 cm on the used MgAl-Cl-LDH, which are well in accordance with the theoretical prediction. The demonstrated participation of intercalated chlorine anions in the evolution of intermediates and transient states as Brønsted base sites during COS hydrolysis will give new insight into the basic sites in LDH materials.
为了阐明层状双氢氧化物（LDHs）中插层阴离子在催化羰基硫（COS）水解反应中的作用，采用理论和实验相结合的方法研究了 COS 在简单的 MgAl-Cl-LDH 模型催化剂上的吸附和反应特性。CASTEP 密度泛函理论（DFT）计算发现，LDH 中的氯离子作为关键的布朗斯台德碱性位，可活化吸附的 HO，使其键长和键角增大，促进包括单硫代碳酸（MTA）和氢硫代碳酸（HTA）在内的中间体的离解吸附，并参与瞬态中间物的形成以及随后的氢转移过程，从而降低 COS 水解过程中的能量势垒。COS 水解将优先经历单硫代碳酸盐（MT）和氢硫代碳酸盐（HT）的离解中间体，其能量势垒显著降低，而在 MgAl-Cl-LDH 上 COS 水解的速率决定步骤将是 HO 对 COS 中 C=O 的亲核加成（Ea=1.10eV）。实验结果进一步表明，MgAl-Cl-LDH 上 COS 水解的表观活化能（0.89eV）接近理论值（1.10eV），并且在使用后的 MgAl-Cl-LDH 上通过 FT-IR 在 1363cm 左右还观察到 MT、HT 或碳酸盐的累积中间体，这与理论预测非常吻合。插层氯阴离子作为布朗斯台德碱性位参与 COS 水解过程中中间体和瞬态物的演化的这一发现，将为 LDH 材料中的碱性位提供新的认识。
