Impact of Coordination Features of Co(II)-Glycine Complex on the Surface Sites of Co/SiO2 for Fischer–Tropsch Synthesis

Qing-Qing Hao,Hua-Ping Ren,Wei Wang,Min Hu,Xiaoxun Ma,Zhi-Xia Xie

doi:10.3390/catal10111295

Abstract

To investigate the effect of coordination features of Co(II)-glycine complex on the performance of Co/SiO2 for Fischer–Tropsch (FT) synthesis, Co(II)-glycine complex precursors were prepared by the conventional method, i.e., simply adding glycine to the solution of Co nitrate and novel route, i.e., reaction of glycine with cobalt hydroxide. The SiO2-supported Co catalysts were prepared by using the different Co(II)-glycine complexes. It is found that glycine is an effective chelating agent for improving the dispersion of Co and the mass-specific activity in FT synthesis when the molar ratio of glycine/Co2+ = 3, which is independent to the preparation method in this study. Significantly, the surface Co properties were significantly influenced by the coordination features of the Co2+ and the molar ratio of glycine to Co2+ in the Co(II)-glycine complex. Specifically, the Co(3gly)/SiO2 catalyst prepared by the novel route exhibits smaller and homogenous Co nanoparticles, which result in improved stability compared to Co-3gly/SiO2 prepared by the conventional method. Thus, the newly developed method is more controllable and promising for the synthesis of Co-based catalysts for FT synthesis.

Highlights

Fischer–Tropsch (FT) synthesis is a promising process to convert syngas (CO + H2 ) derived from non-petroleum-based resources such as coal, biomass, and natural gas to super-clean fuels and high-value-added fine chemicals [1,2]
In the case of the novel route, the Co(II)-glycine complex was prepared by the reaction of glycine with Co(OH)2, which resulted in the formation of a homogenous
From the above discussion about the catalytic performance, we can conclude that glycine is an effective chelating agent to improve the dispersion of Co and the mass-specific activity of Co catalysts in Fischer–Tropsch synthesis independent of the preparation method used in this study, the reduction degree of Co is very low compared to the Co/SiO2 prepared in the absence of glycine

Summary

Introduction

Fischer–Tropsch (FT) synthesis is a promising process to convert syngas (CO + H2 ) derived from non-petroleum-based resources such as coal, biomass, and natural gas to super-clean fuels and high-value-added fine chemicals [1,2]. Cobalt nitrate precursor is often used owing to its high solubility allows for high metal loading in a single impregnation step. Poor dispersions and inhomogeneous size distributions of cobalt are frequently obtained, which result in the lower mass-specific activity and higher deactivation rate [9,10]. To achieve higher mass-specific activity of Co-based catalysts, different methods have been explored to increase the cobalt dispersion, such as changing the precursor [9,11], co-impregnation with chelating agents [12,13,14,15,16,17], or modifying the drying or calcination procedure [18,19,20]

Methods

Results

Conclusion