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本文研究了活化温度对Rh担于不同纯度MgO上的催化剂性质的影响。用H_2化学吸附和乙烷氢解、环已烷脱氢的活性来检测金属一担体的相互作用,以人为掺杂和原位傅利叶变换红外光谱来测知杂质的影响。当纯度为99.5％的MgO作为Rh的担体时,在高温还原(HTR,773K)后其化学吸附能力和乙烷氢解活性相对于低温还原(LTR,573K)处理均有显著降低,分别降低了20倍和5个数量级,而环已烷脱氢活性却仅有中等程度的降低。高温还原后的催化剂的活性能被在673K进行氧化和随后的低温还原处理所恢复。当金属分散度基本保持不变时,上述催化剂体系的活性降低效应与Rh的担载量有关,即担载量越低,该效应越显著。但当纯度为99.999％的MgO作Rh的担体时,还原温度(HTR相对于LTR)对H_2化学吸附和乙烷氢解活性则没有显著影响。人为掺杂对比实验和原位红外光谱结果表明这种差别可归因于担体中杂质的影响,特别是硫酸盐杂质可能是引起Rh/MgO(99.5％)体系表观金属一担体强相互作用的硫中毒的前身。
The effect of activation temperature on the properties of Rh supported on MgO with different purity was investigated. The interaction between metal and metal support was detected by H 2 chemisorption, ethane hydrogenolysis and cyclohexane dehydrogenation. The effect of impurities was detected by human doping and in-situ Fourier transform infrared spectroscopy. When the purity of MgO is 99.5%, the chemisorption capacity and ethane hydrogenolysis activity of the MgO as a carrier for Rh after high temperature reduction (HTR, 773K) are significantly reduced compared with the low temperature reduction (LTR, 573K), respectively, reducing 20 times and 5 orders of magnitude, while the cyclohexane dehydrogenation activity is only moderately reduced. The activity of the high temperature reduced catalyst was restored by oxidation at 673 K and subsequent low temperature reduction. When the metal dispersion remains basically unchanged, the activity reduction effect of the above catalyst system is related to the Rh loading, ie, the lower the loading, the more significant this effect. However, when the purity of 99.999% MgO was used as the carrier for Rh, the reduction temperature (HTR vs LTR) had no significant effect on H 2 chemisorption and ethane hydrogenolysis. Comparison of artificial doping and in-situ FTIR results show that the difference can be attributed to the influence of impurities in the support. In particular, the sulfate impurities may cause the apparent metal-metal interaction of Rh / MgO (99.5%) system Sulfur poisoning predecessor.