Preparation of Au/β-Mo2C catalyst with high thermal stability and its performance in the reverse water-gas shift
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摘要: 以程序升温碳化法合成β-Mo2C载体,采用原位沉淀法制备负载量不同的Au/β-Mo2C催化剂,利用XRD、STEM和氮气吸附-脱附等手段对Au在载体表面的分散性、微观形貌及孔结构等进行表征,并在逆水煤气变换(RWGS)反应中对其高温热稳定性进行了研究。XRD表征结果表明,在34.44°、38.02°、39.44°、52.12°、61.53°、69.62°和74.65°处出现了β-Mo2C对应的(100)、(002)、(101)、(102)、(110)、(103)和(200)晶面的X射线特征衍射峰;同时,未出现Au物种的特征吸收峰,说明Au负载量较低的0.1%和0.5%的催化剂上Au纳米粒子的分散性较好。STEM表征结果也显示,当负载量较低(0.5%、1.0%和2.0%)时,金纳米粒子以2 nm左右的原子簇形式均匀分散并锚定在β-Mo2C载体上。氮气吸附-脱附表征结果表明,催化剂具有良好的介孔结构。反应评价结果表明,0.2% Au/β-Mo2C催化剂在RWGS反应中具有较好的催化活性和较高的CO选择性,且反应后孔结构良好,Au纳米粒子仍然均匀分散,说明Au/β-Mo2C催化剂在此反应中具有较高的催化性能和高温热稳定性。Abstract: β-Mo2C support was first prepared by the temperature-programmed carbonization and the Au/β-Mo2C catalysts with different Au loadings were then obtained by using the in -situ precipitation method. The Au/β-Mo2C catalysts were characterized by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and nitrogen physisorption; their performance, the thermal stability at the high temperature in particular was then investigated in the reverse water-gas shift (RWGS). The XRD results reveal that the diffraction peaks appeared at 34.44°, 38.02°, 39.44°, 52.12°, 61.53°, 69.62° and 74.65° correspond to the (100), (002), (101), (102), (110), (103) and (200) planes of β-Mo2C, respectively, whereas no characteristic peak of Au species is detected, suggesting the high dispersion of Au nanoparticles on the Au/β-Mo2C catalysts with a low Au loading (0.1%-0.5%). The STEM results illustrate that for the Au/β-Mo2C catalysts with an Au loading of 0.5%-2.0%, gold nanoparticles in the form of atom clusters (about 2 nm) are anchored and uniformly dispersed on the β-Mo2C surface. The nitrogen physisorption results demonstrate that the Au/β-Mo2C catalysts have plenty of mesopores. The catalytic evaluation results indicate that the 0.2%Au/β-Mo2C catalyst exhibits high activity and high selectivity to CO for the RWGS reaction; moreover, after the reaction, the Au nanoparticles are still evenly dispersed and the pore structure remain intact, suggesting that the Au/β-Mo2C catalyst owns excellent performance and high thermal stability in the he reverse water-gas shift at high temperature.
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Key words:
- in-situ precipitation /
- lattice orientation /
- RWGS reaction /
- thermal stability /
- catalyst
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表 1 不同负载量催化剂Au/Mo2C反应前后的孔性质
Table 1 Textural properties of the Au/Mo2C catalysts with different Au loadings, fresh and spent ones after reaction
Catalyst ABET/(m2·g-1) vpore/(m3·g-1) dmean /nm fresh used fresh used fresh used Mo2C 29.00 - 0.051 - 6.81 - 0.2%Au/Mo2C 37.44 32.27 0.079 0.088 8.28 10.33 2.0%Au/Mo2C 40.80 33.21 0.090 0.100 8.80 12.35 -
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