表面活性剂辅助共沉淀法制备Ni-Mg-Al固体碱催化剂用于CH_4-CO_2重整反应

Ni-Mg-Al solid basic layered double oxide catalysts prepared using surfactant-assisted coprecipitation method for CO_2 reforming of CH_4

采用表面活性剂辅助共沉淀法制备了Ni-Mg-Al固体碱催化剂并用于CH4-CO2重整反应,探讨了表面活性剂对Ni(111),Ni(200)晶面的择优取向作用,在800℃下比较了不同表面活性剂制备的催化剂的催化性能,详细考察了CTAB制备的催化剂CB-LDO在不同反应温度下的催化活性和稳定性.采用红外光谱、X射线衍射、程序升温还原、X射线光电子能谱、高分辨透射电镜和程序升温氧化等表征手段分析了催化剂的活性、稳定性和失活原因.结果表明,四丙基氢氧化铵(TPAOH)促进Ni(200)的生长,而聚氧乙烯-聚氧丙烯-聚氧乙烯(P123)、聚乙烯吡咯烷酮(PVP)和十六烷基三甲基溴化铵(CTAB)抑制Ni(200)晶面的生长;Ni(200)的结晶程度对CH4的活化起到关键的作用,催化剂CB-LDO在高温下反应会发生晶型的转化,Ni(200)晶面由于反应过程中生成NiAl2O4尖晶石而得到缓慢释放,使催化剂的活性得以维持较高的水平.

Ni‐Mg‐Al solid basic catalysts for CO2 reforming of CH4 were prepared using a surfactant‐assisted coprecipitation method. The preferred orientations of the surfactants on the Ni（111） and Ni（200） crystal planes were investigated. The catalytic performance of the surfactant‐modified catalysts was tested at 800 °C. The cetyltrimethylammonium bromide （CTAB）‐modified catalyst （CB‐LDO;LDO=layered double oxide） was further studied at various reaction temperatures. All the catalysts were characterized using Fourier‐transform infrared spectroscopy, X‐ray diffraction, temperature‐pro‐grammed reduction, X‐ray photoelectron spectroscopy, high‐resolution transmission electron mi‐croscopy, and temperature‐programmed oxidation. The results show that growth of the Ni（200） plane is promoted by tetrapropylammonium hydroxide and restrained by P123, PVP, and CTAB. The crystallinity degree of Ni（200） plays a key role in the activation of CH4. The CB‐LDO catalysts retain high activities and stabilities, because of the crystal phase transformation at high tempera‐ture during the reaction;this leads to the formation of spinel NiAl2O4 and exposure of the Ni（200） crystal plane.