Zeolite-seed-directed Ru nanoparticles highly resistant against sintering for efficient nitrogen activation to ammonia

Lingling Li; Jihui Cai; Yi Liu; Jun Ni; Bingyu Lin; Xiuyun Wang; Chak-Tong Au; Lilong Jiang

doi:10.1016/j.scib.2020.02.010

Zeolite-seed-directed Ru nanoparticles highly resistant against sintering for efficient nitrogen activation to ammonia

Sci Bull (Beijing). 2020 Jul 15;65(13):1085-1093. doi: 10.1016/j.scib.2020.02.010. Epub 2020 Feb 14.

Authors

Lingling Li¹, Jihui Cai¹, Yi Liu¹, Jun Ni¹, Bingyu Lin¹, Xiuyun Wang², Chak-Tong Au¹, Lilong Jiang³

Affiliations

¹ National Engineering Research Center of Chemical Fertilizer Catalyst, Fuzhou University, Fuzhou 350002, China.
² National Engineering Research Center of Chemical Fertilizer Catalyst, Fuzhou University, Fuzhou 350002, China. Electronic address: xywang2017@fzu.edu.cn.
³ National Engineering Research Center of Chemical Fertilizer Catalyst, Fuzhou University, Fuzhou 350002, China. Electronic address: jll@fzu.edu.cn.

PMID: 36659160
DOI: 10.1016/j.scib.2020.02.010

Abstract

To stabilize Ru nanoparticles against sintering is an urgent problem in the utilization of Ru-based catalysts for NH₃ synthesis. In the present study, we used Ru-containing ZSM-5 as seeds to crystallize ZSM-5, and the resulted Ru@ZSM-5 catalyst is highly resistant against Ru sintering. According to the results of diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) and transmission electron microscopy (TEM) analyses, the average size of Ru nanoparticles is around 3.6 nm, which is smaller than that of Ru/ZSM-5-IWI prepared by incipient wetness impregnation. In NH₃ synthesis (N₂:H₂ = 1:3) at 400 °C and 1 MPa, Ru@ZSM-5 displays a formation rate of 5.84 mmol_NH₃ g_cat^-1 h^-1, which is much higher than that of Ru/ZSM-5-IWI (2.13 mmol_NH₃ g_cat^-1 h^-1). According to the results of TEM, N₂-temperature-programmed desorption (N₂-TPD), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) studies, it is deduced that the superior performance of Ru@ZSM-5 is attributable to the small particle size and the ample existence of metallic Ru⁰ sites. This method of zeolite encapsulation is a feasible way to stabilize Ru nanoparticles for NH₃ synthesis.

Keywords: Ammonia synthesis; Ru particle size; Ru-containing ZSM-5 seed; Seed-directed synthesis; Sinter-resistant Ru nanoparticles.