le Saché Estelle, Alvarez Moreno Andrea, Reina Tomas Ramirez
Department of Chemical and Process Engineering, University of Surrey, Guildford, United Kingdom.
Estado Sólido y Catálisis Ambiental, Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia, Bogotá, Colombia.
Front Chem. 2021 Apr 14;9:672419. doi: 10.3389/fchem.2021.672419. eCollection 2021.
Biogas is defined as the mixture of CH and CO produced by the anaerobic digestion of biomass. This particular mixture can be transformed in high valuable intermediates such as syngas through a process known as dry reforming (DRM). The reaction involved is highly endothermic, and catalysts capable to endure carbon deposition and metal particle sintering are required. Ni-pyrochlore catalysts have shown outstanding results in the DRM. However, most reported data deals with CH/CO stoichiometric ratios resulting is a very narrow picture of the overall biogas upgrading via DRM. Therefore, this study explores the performance of an optimized Ni-doped pyrochlore, and Ni-impregnated pyrochlore catalysts in the dry reforming of methane, under different CH/CO ratios, in order to simulate various representatives waste biomass feedstocks. Long-term stability tests showed that the ratio CH/CO in the feed gas stream has an important influence in the catalysts' deactivation. Ni doped pyrochlore catalyst, presents less deactivation than the Ni-impregnated pyrochlore. However, biogas mixtures with a CH content higher than 60%, lead to a stronger deactivation in both Ni-catalysts. These results were in agreement with the thermogravimetric analysis (TGA) of the post reacted samples that showed a very limited carbon formation when using biogas mixtures with CH content <60%, but CH/CO ratios higher than 1.25 lead to an evident carbon deposition. TGA analysis of the post reacted Ni impregnated pyrochlore, showed the highest amount of carbon deposited, even with lower stoichiometric CH/CO ratios. The later result indicates that stabilization of Ni in the pyrochlore structure is vital, in order to enhance the coke resistance of this type of catalysts.
沼气被定义为生物质厌氧消化产生的CH和CO的混合物。这种特殊的混合物可以通过一种称为干重整（DRM）的过程转化为高价值的中间体，如合成气。所涉及的反应是高度吸热的，需要能够耐受碳沉积和金属颗粒烧结的催化剂。镍基烧绿石催化剂在DRM中表现出优异的效果。然而，大多数报道的数据涉及CH/CO化学计量比，这导致通过DRM对整个沼气升级的描述非常有限。因此，本研究探索了一种优化的镍掺杂烧绿石和镍浸渍烧绿石催化剂在不同CH/CO比下甲烷干重整中的性能，以模拟各种代表性的废弃生物质原料。长期稳定性测试表明，进料气流中的CH/CO比在催化剂失活方面有重要影响。镍掺杂烧绿石催化剂的失活程度低于镍浸渍烧绿石催化剂。然而，CH含量高于60%的沼气混合物会导致两种镍催化剂的失活更强。这些结果与反应后样品的热重分析（TGA）一致，该分析表明，当使用CH含量<60%的沼气混合物时，碳形成非常有限，但CH/CO比高于1.25会导致明显的碳沉积。对反应后的镍浸渍烧绿石进行TGA分析，结果表明即使化学计量CH/CO比更低，碳沉积量也最高。后一个结果表明，镍在烧绿石结构中的稳定化对于提高这类催化剂的抗焦性至关重要。
