载体焙烧温度对Rh-Mn-Li/SBA-15催化CO加氢性能的影响

SBA-15分别于550、700、800和900℃进行焙烧，然后以等体积共浸渍法将Rh、Mn和Li负载其上。催化剂的性能用CO加氢反应进行评价。催化剂分别用N₂物理吸附、X射线衍射、透射电子显微镜、H₂化学吸附和傅里叶变换红外光谱进行表征。即使在900℃下进行焙烧，SBA-15的结构仍得到保持。但是，当焙烧温度从550℃升高到900℃，SBA-15的比表面积、孔径和总孔容分别从842.6 m²·g^-1、9.57 nm和1.18 cm³·g^-1降到246.4 m²·g^-1、5.62 nm和0.34 cm³·g^-1。此外，Rh颗粒的尺寸都在1.5-4.0 nm范围内，并且随着载体的焙烧温度增加而增加。另外，Rh颗粒更倾向位于高温焙烧载体的介孔内，这可能是因为经过高温焙烧，载体微孔下降。所以，H₂和CO更易与负载在高温焙烧后的载体上的Rh颗粒接触。因此，当载体焙烧温度达到900℃时，Rh-Mn-Li/SBA-15催化剂有非常高的C₂₊含氧化合物的活性和选择性。

Effect of the Calcination Temperature of the Support on the Performance of Rh-Mn-Li/SBA-15 Catalysts for CO Hydrogenation

Rh, Mn and Li were supported on SBA-15 samples that had been calcined at 550, 700, 800, and 900℃, using an incipient co-impregnation technique. The catalytic performances of these materials were subsequently evaluated for the hydrogenation of carbon monoxide. The catalysts were characterized by means of N₂ adsorption-desorption, X-ray diffraction, transmission electron microscopy, H₂ chemisorption, and Fourier transform infrared spectroscopy. The structure of the SBA-15 support remained unchanged even after its calcination at 900℃. However, the specific surface area, pore size, and total pore volume of SBA-15 decreased from 842.6 m²·g^-1, 9.57 nm, and 1.18 cm³·g^-1 to 246.4 m²·g^-1, 5.62 nm, and 0.34 cm³·g^-1, respectively, when the calcination temperature increased from 550 to 900℃. In addition, the Rh particle size increased in the range of 1.5-4.0 nm with increasing calcination temperature. Furthermore, the Rh particles showed a greater tendency towards the mesopores of support when they were calcined at high temperatures, which could be attributed to the reduced number of micropores. These changes therefore made it easier for H₂ and CO to interact with the Rh particles immobilized on the supports calcined at high temperatures. High levels of activity and selectivity towards C₂₊ oxygenates were therefore obtained on the Rh-Mn-Li/SBA-15 prepared using the SBA-15 calcined at 900℃.