Hao Liying, Sun Jikui, Wang Qingyin, Xie Haijiao, Yang Xiangui, Wei Qiang
State Key Laboratory of Oral Diseases, West China School of Stomatology, Sichuan University, No. 14, Section 3, Renmin South Road, Chengdu, Sichuan 610041, China.
National Engineering Laboratory for VOCs Pollution Control Material &Technology, University of Chinese Academy of Sciences, 19 A Yuquan Road, Shijingshan District, Beijing 100049, China.
ACS Appl Mater Interfaces. 2024 Aug 14;16(32):42080-42092. doi: 10.1021/acsami.4c05587. Epub 2024 Jul 30.
As an atom-economical reaction, the direct generation of dimethyl carbonate (DMC) and ethylene glycol (EG) via the transesterification of CHOH and ethylene carbonate (EC) has several promising applications, but the exploration of carriers with high specific surface areas and novel heterogeneous catalysts with more basic sites remains a long-standing research challenge. For this purpose, herein, a nitrogen-doped mesoporous carbon (NMC, 439 m/g) based K-O Lewis base catalyst (K-O/NMC) with well-dispersed strongly basic sites (2.23 mmol/g, 84.5%) was designed and synthesized. The compositions and structures of NMC and K-O/NMC were comprehensively investigated via Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, N adsorption-desorption, CO temperature-programmed desorption, and contact angle measurements. The optimal structural configuration and electron cloud distribution of the K-O/NMC catalyst were simulated using first-principles calculations. The electron transfer predominantly manifested as a flow from K-O to C-O/C-N, and the interatomic interactions between each atom were enhanced and exhibited a tendency for a more stable state after redistribution. Furthermore, the adsorption energies () of CHOH at K-O-O and K-O-N sites were -1.4185 eV and -1.3377 eV, respectively, and the O atom in CHOH exhibited a stronger adsorption tendency for the K atom at the K-O-O site. Under the optimal conditions, the EC conversion, DMC/EG selectivity, and turnover number/frequency were 80.9%, 98.6%/99.4%, and 40.5/60.8 h, respectively, with a reaction rate constant (k) of 0.1005 mol/(L·min). Results showed that the heterogeneous K-O/NMC catalyst prepared herein greatly reduced the reaction cost while guaranteeing the catalytic effect, and the whole system required a lower reaction temperature (65 °C), a shorter reaction time (40 min), and a lower catalyst amount (2.0 wt % of EC). Therefore, K-O/NMC can be used as a catalyst in different transesterification reactions.
作为一种原子经济反应，通过碳酸乙烯酯（EC）与甲醇（CHOH）的酯交换直接生成碳酸二甲酯（DMC）和乙二醇（EG）具有多种有前景的应用，但探索具有高比表面积的载体以及具有更多碱性位点的新型多相催化剂仍然是一个长期的研究挑战。为此，本文设计并合成了一种基于氮掺杂介孔碳（NMC，439 m/g）的K-O路易斯碱催化剂（K-O/NMC），其具有分散良好的强碱性位点（2.23 mmol/g，84.5%）。通过傅里叶变换红外光谱、X射线衍射、X射线光电子能谱、扫描电子显微镜、透射电子显微镜、N吸附-脱附、CO程序升温脱附以及接触角测量等方法对NMC和K-O/NMC的组成和结构进行了全面研究。利用第一性原理计算模拟了K-O/NMC催化剂的最佳结构构型和电子云分布。电子转移主要表现为从K-O流向C-O/C-N，各原子之间的原子间相互作用增强，重新分布后呈现出更稳定的状态趋势。此外，CHOH在K-O-O和K-O-N位点的吸附能（）分别为-1.4185 eV和-1.3377 eV，CHOH中的O原子在K-O-O位点对K原子表现出更强的吸附倾向。在最佳条件下，EC转化率、DMC/EG选择性以及周转数/频率分别为80.9%、98.6%/99.4%和40.5/60.8 h，反应速率常数（k）为0.1005 mol/(L·min)。结果表明，本文制备的多相K-O/NMC催化剂在保证催化效果的同时大大降低了反应成本，整个体系所需反应温度较低（65°C）、反应时间较短（40分钟）且催化剂量较低（EC的2.0 wt%）。因此，K-O/NMC可作为不同酯交换反应的催化剂。
