SiO2和Al2O3负载的Ni基催化剂在甲烷干重整中的催化性能差异

CH₄与CO₂干重整反应对于环境保护和天然气资源的合理利用具有重要意义。SiO₂和Al₂O₃是适用于甲烷干重整反应的两种典型的催化剂载体。为了阐明这两种载体对催化剂性能的影响，本研究采用等体积浸渍法制备了Ni/Al₂O₃和Ni/SiO₂催化剂，并利用BET、TEM、H₂-TPR、XRD、TG和Raman等技术对还原和反应后的催化剂进行了表征。结果表明，由于载体的性质不同，Ni基催化剂在甲烷干重整中的催化性能也不同。Ni/SiO₂催化剂的初始活性较高，但由于其金属-载体相互作用较弱，催化稳定性较差，在800℃下反应15h其催化活性急剧下降；较弱的金属-载体相互作用使得Ni/SiO₂催化剂上的Ni颗粒较大，有利于积炭前驱物种的生成，导致催化剂快速失活。而对于Ni/Al₂O₃催化剂，金属-载体相互作用较强，Ni颗粒较小，但由于Ni与Al₂O₃生成了NiAl_xO_y物种，有效活性位减少，其催化活性相对较低，但催化稳定性较好，干重整反应进行50h其活性保持稳定；Ni与Al₂O₃之间较强的相互作用有利于形成小且稳定的Ni粒子，能减少积炭，因而具有优异的催化稳定性。

A comparison of Al2O3 and SiO2 supported Ni-based catalysts in their performance for the dry reforming of methane

Dry reforming of methane (DRM) with CO₂ is of great significance in the environmental protection and the utilization of natural gas. SiO₂ and Al₂O₃ are two typical catalyst supports used in DRM. To elucidate the effect of these two supports on the catalytic performance, in this work, Ni/SiO₂ and Ni/Al₂O₃ catalysts are prepared by the incipient wetness method and characterized by BET, TEM, H₂-TPR, XRD, TG and Raman technologies. The results indicate that the performance of Ni-based catalyst is closely related to the properties of support and the Ni/SiO₂ and Ni/Al₂O₃ catalysts are rather different in their DRM performance. Ni/SiO₂ catalyst exhibits higher initial activity but poor stability; its catalytic activity decreases rapidly in 15 h for DRM at 800°C. Because of the weak metal-support interaction, Ni species on the Ni/SiO₂ catalyst is present as large Ni particles, which may promote the formation of coke precursors, viz., the multi-carbon C_n species, leading to the fast carbonaceous deposition and catalyst deactivation. In contrast, the Ni/Al₂O₃ catalyst displays a lower activity but a much higher stability; its activity in DRM keeps stable in 50 h. Although Ni particles in the Ni/Al₂O₃ catalyst is much smaller, the strong metal-support interaction promotes the formation of NiAl_xO_y species during the catalyst preparation process, which may lead to a decrease in the content of active Ni species and give the Ni/Al₂O₃ catalyst a relatively low catalytic activity in DRM; however, the strong metal-support interaction between Ni and Al₂O₃ is also of benefit to the formation and stabilization of small Ni particles, which can alleviate the carbanceous deposition and afford the Ni/Al₂O₃ catalyst a better stability.