镁铝混合氧化物负载镍催化剂的制备及在液化石油气低温重整反应中的催化性能

采用共沉淀-浸渍法制备了不同Ni 含量的 Ni/Mg(Al)O 催化剂并用于液化石油气(LPG)的低温水蒸气重整反应. X 射线衍射和程序升温还原结果表明, 在 800 ℃焙烧的 Ni/Mg(Al)O 催化剂中, NiO 与 MgO 反应生成 Mg-Ni-O 固溶体, 还原后形成金属 Ni 纳米颗粒. 详细研究了 Ni 含量(质量分数)、反应温度和水/碳摩尔比(n_H2O/n_C) 等对催化剂性能的影响. 实验结果表明, 15%Ni/Mg(Al)O 催化剂对 LPG 低温重整反应具有最佳的催化性能. 提高反应温度能显著提高 Ni/Mg(Al)O 催化剂的催化性能. 当n_H2O/n_C=2时, 在400~500 ℃的温度范围使LPG完全转化的最大反应空速从 28900 mL·h^-1·g^-1Cat提高到 86800 mL·h^-1·g^-1Cat. 适当增大水/碳摩尔比有利于 LPG 转化为小分子气体, 但在 LPG 摩尔流量不变的情况下, 反应气中水含量过高会导致 LPG 转化率降低. 反应后催化剂的X射线衍射谱(XRD)和热重分析(TG)结果表明, Ni/Mg(Al)O催化剂优良的催化活性和反应稳定性可归因于催化剂表面Ni晶粒较高的稳定性和抗积炭性能.

Preparation of Mg-Al Mixed Oxide Supported Nickel Catalysts and Their Catalytic Activities in Low Temperature Reforming of Liquified Petroleum Gas

Ni/Mg(Al)O catalysts with different mass fractions of Ni were prepared by co-precipitation-impregnation method and used for low temperature steam reforming of liquified petroleum gas(LPG).X-ray diffraction and temperature-programmed reduction results showed that in the Ni/Mg(Al)O catalysts calcined at 800 ℃ Mg-Ni-O solid solution was formed,which could be reduced to produce metal Ni nanoparticles.The effects of Ni loading,reaction temperature and steam/carbon(nH2O/nC) ratio on the catalytic performance were discussed in detail.The experimental results revealed that the 15%Ni/Mg(Al)O catalyst showed the optimal catalytic performance.Elevating reaction temperature could remarkably enhance the catalytic activity of the Ni/Mg(Al)O catalysts.In the temperature range of 400—500 ℃ and at nH2O/nC=2,the highest space velo-city for completely converting LPG was enhanced from 28900 mL·h-1·g-1Cat to 86800 mL·h-1·g-1Cat.The proper increase in nH2O/nC favored reforming of LPG to small gas molecules.However,excessive amount of steam led to the decrease in LPG conversion when LPG molar flow rate was kept constant.The XRD and TG analyses showed that the excellent catalytic activity and stability of the used Ni/Mg(Al)O catalyst could likely be due to highly stable Ni crystallites on the catalyst surface and good resistance to carbon deposition.