镍基气凝胶催化CH4-CO2重整制取合成气反应的研究 Ⅲ.影响催化剂积碳性能因素的探讨

考察了823K焙烧的干凝胶xNCA550、气凝胶aNCA550及浸渍型催化剂iNCA550在923K、1073K、1173K反应温度下的积碳行为，对催化剂表面碳的活性及类型进行了分析，并探讨了影响催化剂积碳的因素。实验结果表明，随反应温度的提高，催化剂的积碳能力减弱，尤以气凝胶催化剂aNCA550明显。催化剂的积碳主要发生在反应的初期，反应温度越高，到达积碳量相对稳定期所需要的时间越短；随着反应时间的延续，催化剂积碳量缓慢增长，并且表面碳的活性降低。催化剂的酸性和镍晶粒大小是影响其积碳性能的主要内在因素，而它们对积碳的影响程度受反应温度的影响，反应温度越高，催化剂表达酸性中心利于积碳的作用越小，小晶粒镍抑制催化剂积碳的能力越强。

STUDY OF CATALYZED BY NICKEL-BASED AEROGEL CO2 REFORMING OF CH4 TO SYNTHESIS GAS Ⅲ. ANALYSIS OF THE REASONS FOR CARBON DEPOSITION ON CATALYSTS

Using the techniques of incipient impregnation,sol gel method and the combination of sol gel with supercritical drying, the catalysts of NiO CeO 2 Al 2O 3, which calcinated at 823?K, have been prepared, and in sequence they are impregnation sample(iNCA550)?xerogel sample(xNCA550)?aerogel sample(aNCA550) Carbon deposition on these catalysts has been investigated, activities and kinds of carbon deposition have been analyzed, and the factors that influence carbon deposition have also been studied As reaction temperature increases, the amount of carbon deposition decreases, and the property of aNCA550 is more obvious than those of xNCA550 and iNCA550 Carbon deposition happens mainly at the beginning of reaction, and with the increase of temperature, the time to reach the equilibrium of carbon deposition becomes shorter Apart from reaction conditions, the acidity of catalysts and the size of nickel crystallite are important factors influencing carbon deposition on catalysts, and the extent of the influences is affected by reaction temperature The higher reaction temperature, the less promoting effect of acidity on carbon deposition, and the more predominant contribution of smaller nickel crystallite to inhibit catalysts from carbon deposition