Zhang Tengfei, Liu Qing
Key Laboratory of Low Carbon Energy and Chemical Engineering, Shandong University of Science and Technology, Qingdao 266590, China.
ACS Appl Mater Interfaces. 2020 Apr 29;12(17):19587-19600. doi: 10.1021/acsami.0c03243. Epub 2020 Apr 19.
For the traditional preparation method, it is challenging to fabricate a supported nickel catalyst with fine size at high loading. In this work, a group of La-modified mesostructured cellular foam (MCF)-derived nickel phyllosilicates was designed and synthetized by a hydrothermal method followed by an impregnation-modification of LaO, whose Ni contents varied from 25.3 to 32.2 wt %. Both the special property of phyllosilicate and the addition of a LaO modifier played significant roles in achieving high Ni dispersion and excellent catalytic performance. The formed nickel phyllosilicate was beneficial to obtain small Ni nanoparticles (<5 nm) due to its strong metal-support interaction and high specific surface area; the addition of the LaO modifier could further reduce the Ni particle size and decrease the reduction difficulty of the fabricated samples. On the contrary, a large Ni particle size of 13.0 nm was observed on the impregnated Ni/MCF (N/M-Im) catalyst with a Ni content of 31.7 wt %. As a result, the nickel phyllosilicate catalyst showed higher catalytic activity than the impregnated one, and the La modifier could further improve the catalytic activity especially at low temperature (<400 °C). Among all catalysts, the modified phyllosilicate catalyst N/M-P-32-5L with 180 °C-32 h-hydrothermal treatment and LaO content of 5 wt % was the best owing to its small-sized Ni particles, high H and CO chemisorption capacity, large turnover frequency (TOF) value, and low activation energy of 69.83 kJ mol. In addition, the intermediates of formate and CO were detected through in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis. In a 100 h-lifetime test under harsh conditions and 600 °C-steam treatment, N/M-P-32-5L showed both high sintering resistance of Ni particles and high thermal stability without the collapse of pores as well as decrease of catalytic activity, which was attributed to the special physical and chemical properties of MCF-derived nickel phyllosilicate, strong metal-support interaction over the catalyst, and the promotion of the LaO modifier.
对于传统制备方法而言，在高负载量下制备具有精细尺寸的负载型镍催化剂具有挑战性。在本工作中，通过水热法随后进行LaO的浸渍改性，设计并合成了一组La改性的介孔蜂窝泡沫（MCF）衍生的镍层状硅酸盐，其Ni含量在25.3至32.2 wt%之间变化。层状硅酸盐的特殊性质以及LaO改性剂的添加在实现高Ni分散性和优异催化性能方面发挥了重要作用。形成的镍层状硅酸盐由于其强的金属-载体相互作用和高比表面积，有利于获得小的Ni纳米颗粒（<5 nm）；LaO改性剂的添加可以进一步减小Ni颗粒尺寸并降低所制备样品的还原难度。相反，在Ni含量为31.7 wt%的浸渍型Ni/MCF（N/M-Im）催化剂上观察到13.0 nm的大Ni颗粒尺寸。结果，镍层状硅酸盐催化剂显示出比浸渍型催化剂更高的催化活性，并且La改性剂可以进一步提高催化活性，特别是在低温（<400°C）下。在所有催化剂中，经过180°C - 32 h水热处理且LaO含量为5 wt%的改性层状硅酸盐催化剂N/M-P-32-5L是最好的，这归因于其小尺寸的Ni颗粒、高的H和CO化学吸附容量、大转化频率（TOF）值以及69.83 kJ mol的低活化能。此外，通过原位漫反射红外傅里叶变换光谱（DRIFTS）分析检测到了甲酸盐和CO中间体。在苛刻条件下600°C蒸汽处理的100 h寿命测试中，N/M-P-32-5L显示出Ni颗粒的高抗烧结性和高热稳定性，没有孔结构塌陷以及催化活性降低，这归因于MCF衍生的镍层状硅酸盐的特殊物理和化学性质、催化剂上强的金属-载体相互作用以及LaO改性剂的促进作用。
