High active Pd/MgO catalyst for CO oxidative coupling to dimethyl oxalate
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摘要: 利用溶液法结合高温煅烧处理合成MgO载体，通过浸渍法制备Pd/MgO催化剂并对其进行CO氧化偶联制草酸二甲酯催化性能研究。通过X射线粉末衍射、CO2程序升温脱附、比表面仪、热重分析、扫描电镜、透射电镜和微型催化评价装置对合成的样品进行结构和性能表征。结果表明，合成的MgO载体是一种Lewis碱性很强的纳米片结构，Pd纳米颗粒高度分散在MgO载体上，粒径小且分布均一。此MgO纳米片作为载体制备的Pd/MgO催化剂在较低的Pd负载量（0.5%）下表现出优异的CO氧化偶联催化性能，在反应温度130 ℃时CO单程转化率高达65%，草酸二甲酯选择性96%，稳定性超过100 h，明显越于工业催化剂（Pd/α-Al2O3），具有潜在的工业应用前景。Abstract: The MgO support was first synthesized by the solution method, with which the Pd/MgO nanocatalyst was then prepared by the impregnation method. The structure and performance of prepared catalyst were characterized by XRD, CO2-TPD, BET, TG, SEM, TEM and catalytic evaluation device. The research result shows that the synthesized MgO support consists of uniform nanosheets and strong Lewis basic sites. The active Pd nanoparticles of Pd/MgO catalyst are highly dispersed on the surface of MgO support with small and homogeneous size. Moreover, the Pd/MgO nanocatalyst with a low Pd loading (0.5%) exhibits an excellent catalytic performance with 65% CO conversion, 96% selectivity to DMO and more than 100 h on stream at 130 ℃. for CO oxidative coupling to dimethyl oxalate, much higher than industrial catalyst (Pd/α-Al2O3), which has a good prospect of industrial application.
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Key words:
- Pd/MgO /
- coal to ethylene glycol /
- CO oxidative coupling /
- dimethyl oxalate /
- catalytic performance
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图 2 MHC前驱体的XRD谱图和底部垂直线条表示碱式碳酸镁(MgCO3)4·Mg(OH)2·5H2O标准衍射峰(JCPDS标准卡片：23-1218)；MgO和Pd/MgO催化剂的XRD谱图
Figure 2 XRD patterns of MHC precursors (a), in which vertical bars at the bottom denote the standard data for zinc hydroxide carbonate (MgCO3)4·Mg(OH)2·5H2O (JCPDS, No.23-1218); XRD patterns of MgO and Pd/MgO catalyst (b)
图 4 Pd/MgO催化剂TEM照片、对应MgO载体上Pd纳米颗粒的粒径分布和Pd纳米颗粒的HRTEM照片
Figure 4 TEM image of Pd/MgO catalyst (a); the corresponding size distribution of Pd nanoparticles supported on MgO (b); HRTEM image of the individual Pd nanoparticle (c)
图 5 MgO和Pd/MgO催化剂的N2吸附-脱附曲线(插图为相应样品的孔径分布)
Figure 5 Nitrogen absorption-desorption isotherm of MgO (a) and Pd/MgO (b) catalyst, in which the insets correspond to the pore size distribution of the samples
—■—: adsorption; —●—: desorption
图 6 在0.5% Pd负载量时，反应温度对Pd/MgO催化剂性能的影响(a)；在反应温度130 ℃时，Pd负载量对Pd/MgO催化剂性能的影响(b)
Figure 6 Catalytic performances of Pd/MgO with 0.5% Pd loading at different reaction temperatures (a); catalytic performances of Pd/MgO catalysts with different Pd loadings at 130 ℃ (b)
—●—: CO conversion; —■—: DMO selectivity
图 7 Pd/MgO催化剂(0.5% Pd负载量)在130 ℃下反应100 h的稳定性评价
Figure 7 Space-time yield (STY) of DMO over Pd/MgO catalyst with 0.5% Pd loading at 130 ℃ for 100 h
表 1 Pd/MgO催化剂与工业催化剂的CO氧化偶联催化性能对比a
Table 1 CO oxidative coupling to dimethyl oxalate (DMO) on different catalystsa
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