Shaped mesostructured Ni/CeO2 as active catalysts in hydrogen production from acetic acid oxidative steam reforming

Oxidative steam reforming (OSR) of acetic acid was carried out using shaped catalysts prepared by combining Ni supported on mesostructured ceria with various clays (kaolinite, sepiolite, attapulgite, and bentonite). Bentonite or attapulgite extrudates calcined with 1°C/min heating rate demonstrated better mechanical resistance. Higher acetic acid conversion and hydrogen yield were obtained using attapulgite. Conditions to avoid concentration gradients around or within the catalyst pellets were determined by analyzing both external mass transfer limitations and internal diffusion resistance (Weisz-Prater criterion<1).
Finally, the reusability of Ni/m-CeO2-A extrudates, prepared using attapulgite, was evaluated. Used Ni/m-CeO2-A completed five successive regeneration-reaction cycles at 550°C under high space velocity (WHSV=60 h-1) to provoke severe catalyst deactivation by coke deposition. The regeneration was performed in-situ under airflow to remove coke deposits, followed by hydrogen flow to reduce NiO and restore the active phase. Notably, initial conversion and hydrogen yield were almost recovered after each regeneration step.

采用将负载于介孔结构氧化铈（mesostructured ceria）的镍与各类黏土（高岭石、海泡石、凹凸棒石、膨润土）复配制备的成型催化剂，开展乙酸氧化蒸汽重整（Oxidative steam reforming, OSR）实验。以1℃/min升温速率焙烧得到的膨润土基或凹凸棒石基挤出成型催化剂颗粒，展现出更优异的机械强度。使用凹凸棒石基催化剂时，可获得更高的乙酸转化率与氢气产率。通过分析外扩散限制与内扩散阻力，结合魏斯-普拉特判据（Weisz-Prater criterion<1），确定了可避免催化剂颗粒内外出现浓度梯度的反应条件。
最后，对采用凹凸棒石制备的Ni/m-CeO2-A挤出成型催化剂的重复使用性能进行了评价。将使用过的Ni/m-CeO2-A催化剂在550℃、高空速（重量空速，Weight Hourly Space Velocity, WHSV=60 h⁻¹）条件下完成5次连续的再生-反应循环，以诱发积碳造成严重的催化剂失活。再生过程采用原位气流吹扫去除积碳，随后通入氢气还原氧化镍以恢复活性相。值得注意的是，每次再生步骤后，初始乙酸转化率与氢气产率几乎完全恢复。