Co/海泡石催化剂赋存形态演变及其对乙醇蒸汽重整制氢性能影响

Speciation Evolution of Co/Sepiolite Catalyst and Its Effect on Hydrogen Production over Ethanol Steam Reforming

采用无定形海泡石(SEP)负载Co基催化剂进行乙醇蒸汽重整制氢,是一种绿色、可持续的制氢工艺。考虑乙醇蒸汽重整制氢具有结构敏感性,煅烧温度是调控催化剂关键物化性质的重要参数。多种表征分析表明,金属–载体相互作用受煅烧温度介导,以不同Co物种赋存形态具现。随着煅烧温度的升高,钴赋存形态由初始的钴氧化物到钴页硅酸盐,再到钴铝尖晶石的转变。乙醇蒸汽重整制氢实验表明,Co/SEP-600催化剂活性较优,并维持50 h稳定性,得益于其页硅酸盐多孔结构和Co0纳米颗粒精细尺寸。进一步提高煅烧温度将削弱Co/SEP-700的稳定性和Co/SEP-800的活性。因此,Co与海泡石骨架Si、Al原子之间的相互作用决定了催化剂的乙醇蒸汽重整制氢反应性,而煅烧温度则可调节催化剂活性和稳定性。此外,大尺寸Co0颗粒上沉积大量石墨碳,如Co/SEP-400,归因于其金属–载体相互作用较弱;而Co/SEP-800中具有难还原性的钴铝尖晶石相和强金属–载体相互作用,仅出现少量积碳。Hydrogen production over ethanol steam reforming proceeding on Co-based catalysts is a green and sustainable hydrogen production process. Considering the structure sensitivity of hydrogen production, the calcination temperature is an important parameter to regulate the key physico-chemical properties of catalysts. Characterization analysis shows that metal-support interaction is mediated by the calcination temperature. It is embodied in the form of different Co speciation. With the increase of calcination temperature, the cobalt occurrence form changes from the initial cobalt oxide to Co-phyllosilicate, and then to Co-Al spinel. The experiment results showed that Co/SEP-600 catalyst had a better activity and maintained a 50 h stability, which benefited from porous structure and fine Co0 nanoparticles of Co-phyllosilicate. A further increase of the calcination temperature would weaken the stability of Co/SEP-700 and the activity of Co/SEP-800. Therefore, the interaction between Co and the Si or Al framework atoms of sepiolite determines the reforming reactivity of catalysts, while the calcination temperature can adjust the activity and stability of catalysts. In addition, abundant graphite carbon deposited on large-size Co0 particles of Co/SEP-400 is attributed to the weak metal-support interaction, while Co/SEP-800 featured with irreducible Co-Al spinel and strong metal-support interaction and showed only a small carbon deposition.