Effect of Calcination Temperature on Characteristics and Performance of Ni/MgO Catalyst for CO2 Reforming of Toluene

A Ni/MgO catalyst for CO2 reforming of toluene was prepared by impregnating MgO with Ni(NO3)2. During calcination, some of the NiO diffused into the MgO and formed a solid solution structure of NiO-MgO, which was analyzed by Raman spectroscopy. In the temperature-programmed reduction with hydrogen analysis, only a small part of the Ni species in the outermost layer was reduced to metallic Ni at 700 °C. The calcination temperature played a key role in determining the subsequent catalytic activity of Ni/MgO, consequently the catalyst calcined at 600 °C had the highest activity. This catalyst also had the highest surface concentration of reduced Ni, which probably accounted for its high activity. During the reforming tests, a small amount of coke was deposited on Ni/MgO catalyst. Polyaromatic compounds were observed by Raman spectroscopy. The coke was probably responsible for the activity loss of Ni/MgO.

摘要考察了焙烧温度对 Ni/MgO 催化剂结构及其在甲苯二氧化碳重整反应中催化性能的影响. 由于 NiO-MgO 固溶体的形成, 样品的 X 射线衍射谱中没有出现明显的 NiO 衍射峰, 而在拉曼光谱中出现明显的散射信号. X 射线光电子能谱、氢气程序升温还原和 H2 脉冲吸附结果表明, 高温焙烧过程中 Ni 向催化剂体相扩散, 与 MgO 发生强互相互作用, 使得 Ni 物种难以还原, 但部分位于催化剂表面的 Ni 物种能够还原; 高温焙烧后催化剂表面活性 Ni 物种明显减少, 致使催化剂重整活性降低. 重整反应后, 催化剂表面存在少量多核芳烃类积炭, 这很可能是高温焙烧催化剂稳定性差的原因.

Raman spectroscopy is sensitive to characterize the surface NiO on a Ni/MgO solid solution catalyst. The coke containing polyaromatic compounds might deactivate the catalysts.Figure optionsDownload as PowerPoint slide