Colloidal Cu/ZnO catalysts for the hydrogenation of carbon dioxide to methanol: investigating catalyst preparation and ligand effects
Colloidal Cu/ZnO catalysts for the hydrogenation of carbon dioxide to methanol: investigating catalyst preparation and ligand effects
复制标题
DOI：
10.1039/c7cy01191a
复制
发表时间：
2017-08
影响因子：
5
通讯作者：
Sebastian D. Pike;Andrés García-Trenco;E. White;Alice H. M. Leung;J. Weiner;M. Shaffer;Charlotte K. Williams
中科院分区：
文献类型：
--
作者：
Sebastian D. Pike;Andrés García-Trenco;E. White;Alice H. M. Leung;J. Weiner;M. Shaffer;Charlotte K. Williams
从CO2加氢生产甲醇是一种有前途的潜在途径，可再生液体燃料和可再生能源载体。本文报道了基于Cu（0）和ZnO纳米颗粒（NPs）的混合物并使用低温有机金属程序制备胶体催化剂的三种不同路线。胶体表面由次膦酸盐配体：二辛基次膦酸盐（[DOPA]−）配位，在有机溶剂中具有高溶解度。此外，合成路线允许精细控制ZnO：Cu和配体负载。通过将Cu（0）或空气稳定的Cu 2 O NP的小NP（2nm）与ZnO NP（3 nm）混合，或通过在ZnO NP（ZnO：2nm，Cu：6 nm）存在下合成Cu（0）来制备催化剂。将所得胶体催化剂应用于CO2至甲醇的液相氢化（210 °C，50巴，CO2：H2的摩尔比为3：1）。当与非均相Cu-ZnO-Al 2 O3商业催化剂相比时，催化剂通常表现出3倍高的速率（21 vs.7mmolMeOHgCuZnO-1h-1）。后催化胶体的表征显示出在还原条件下形成的清晰的Cu/ZnO界面（HR-TEM），以及Cu（0）NP尺寸（3至7 nm）和催化剂的纳米级重构的差异。表征和催化结果的组合表明，活性主要由Cu（0）颗粒尺寸和配体负载决定。较小的Cu（0）NPs表现出较低的转换频率（TOF）值，而较高的配体负载（[DOPA]−：（Cu + Zn）为0.2-1.1）导致较小的Cu（0）NPs并减少Cu/ZnO界面的形成。紫外-可见光谱显示，Cu（0）NP在催化后比催化前在空气下对氧化更稳定，这可能是由于在催化条件下ZnO迁移到Cu表面上。
The production of methanol from CO2 hydrogenation is a promising potential route to a renewable liquid fuel and renewable energy vector. Herein, three distinct routes to make colloidal catalysts based on mixtures of Cu(0) and ZnO nanoparticles (NPs) and using low-temperature organometallic procedures are reported. The colloids are surface coordinated by a phosphinate ligand: dioctylphosphinate ([DOPA]−), which delivers a high solubility in organic solvents. Further, the synthetic routes allow fine control of the ZnO:Cu and ligand loadings. The catalysts are prepared by mixing small NPs (2 nm) of either Cu(0) or air-stable Cu2O NPs with ZnO NPs (3 nm), or by the synthesis of Cu(0) in presence of ZnO NPs (ZnO: 2 nm, Cu: 6 nm). The resulting colloidal catalysts are applied in the liquid phase hydrogenation of CO2 to methanol (210 °C, 50 bar, 3 : 1 molar ratio of CO2 : H2). The catalysts typically exhibit 3 times higher rates when compared to a heterogeneous Cu–ZnO–Al2O3 commercial catalyst (21 vs. 7 mmolMeOH gCuZnO−1 h−1). The characterisation of the post-catalysis colloids show clear Cu/ZnO interfaces (HR-TEM), which are formed under reducing conditions, as well as differences in the Cu(0) NP size (from 3 to 7 nm) and nanoscale restructuring of the catalysts. The combination of characterisation and catalytic results indicate that the activity is mostly dictated by the Cu(0) particle size and ligand loading. Smaller Cu(0) NPs exhibited lower turnover frequency (TOF) values, whereas higher ligand loadings ([DOPA]−:(Cu + Zn) of 0.2–1.1) lead to smaller Cu(0) NPs and reduce the formation of Cu/ZnO interfaces. UV-vis spectroscopy reveals that the Cu(0) NPs are more stable to oxidation under air after catalysis than beforehand, potentially due to migration of ZnO onto the Cu surface whilst under catalytic conditions.