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本研究利用动态热重法,对Ni系催化荆和RE—Ni系催化剂在烃类水蒸汽转化反应中的积碳性能进行对比实验。研究发现,在Ni系催化剂中加入稀土氧化物,可有效地改善催化剂的抗积碳性能,但必须在有水蒸汽存在下,与Ni密切接触才能发挥其效能。实验还发现,在Ni系和RE—Ni系催化荆上所积之碳均属“管须”状,但积碳速率的变化规律有显著不同。前者积碳曲线呈“S”型,停止积碳时,活性丧失;后者呈递减型,积碳速率为零时,活性保持不变。我们认为,在RE—Ni体系中,在水蒸汽存在下,利用稀土氧化物的氧化还原性,可以加速建立水的吸附解离平衡,释放出足够的氧,以提高稀土氧化物中晶格氧向Ni表面的迁移速率和Ni表面的氧化能力,从而加速在Ni表面上含碳物种的氧化,起到抑制碳积累的作用。
In this study, the dynamic thermogravimetric method was used to compare the carbon deposition performance of Ni-based catalysts and RE-Ni catalysts in hydrocarbon steam reforming. It has been found that addition of rare earth oxides to Ni-based catalysts can effectively improve the anti-carbon performance of the catalyst, but it must be closely contacted with Ni in the presence of water vapor to achieve its performance. The experiment also found that the carbon deposited on the Ni-based and RE-Ni-based catalytic Jing are “tube-like” shape, but the variation of carbon deposition rate are significantly different. The former carbon deposition curve was “S” type, stop the carbon deposition, the loss of activity; the latter showed a decreasing type, carbon deposition rate of zero, the activity remains unchanged. We believe that in the RE-Ni system, using the redox properties of rare earth oxides in the presence of water vapor, the equilibrium of adsorption and dissociation of water can be accelerated to release sufficient oxygen to increase the lattice oxygen in the rare earth oxides The migration rate to the Ni surface and the oxidation ability on the Ni surface, thereby accelerating the oxidation of the carbonaceous species on the Ni surface and acting as an inhibitor of carbon accumulation.