Gaseous Nitric Acid Activated Graphite Felts as Hierarchical Metal-Free Catalyst for Selective Oxidation of H2S

Zhenxin Xu,Cuong Duong-Viet,Cuong Pham-Huu,Lam Nguyen-Dinh,Housseinou Ba,Tri Truong-Huu,Bing Li

doi:10.3390/catal8040145

Abstract

In this study, we reported on the influence of gaseous HNO3 treatment on the formation of defects decorated with oxygenated functional groups on commercial graphite felts (GFs). The gaseous acid treatment also leads to a remarkable increase of the specific as well as effective surface area through the formation of a highly porous graphite structure from dense graphite filamentous. The as-synthesized catalyst was further used as a metal-free catalyst in the selective oxidation of H2S in industrial waste effluents. According to the results, the defects decorated with oxygenated groups were highly active for performing selective oxidation of H2S into elemental sulfur. The desulfurization activity was relatively high and extremely stable as a function of time on stream which indicated the high efficiency of these oxidized un-doped GFs as metal-free catalysts for the selective oxidation process. The high catalytic performance was attributed to both the presence of structural defects on the filamentous carbon wall, which acting as a dissociative adsorption center for the oxygen, and the oxygenated functional groups, which could play the role of active sites for the selective oxidation process.

Highlights

Nanocarbon-based metal-free catalysts consisting of a nitrogen-doped carbon matrix have received an ever increasing scientific and industrial interest in the field of heterogeneous catalysis over the last decade for several potential processes [1,2,3,4,5,6]
We have shown that oxidation with gaseous HNO3 can be an efficient and elegant pre-activation step to generate active metal-free carbon-based catalysts decorated with surface defects containing oxygenated functional groups from available and low cost commercial filamentous graphite felts
The gaseous acid treatment leads to the formation of a high surface area carbon-based material which can find use in several catalytic processes as either metal-free catalyst or as catalyst support

Summary

Introduction

Nanocarbon-based metal-free catalysts consisting of a nitrogen-doped carbon matrix have received an ever increasing scientific and industrial interest in the field of heterogeneous catalysis over the last decade for several potential processes [1,2,3,4,5,6]. Work reported by Pham-Huu and Gambastiani [14,15] has shown that nitrogen-doped mesoporous carbon film, synthesized from food stuff raw materials, displays a high performance for different catalytic processes such as oxygen reduction reaction (ORR), direct dehydrogenation of ethylbenzene and selective oxidation of H2 S. Such nitrogen-doped metal-free catalysts display an extremely high stability as a function of time on stream or cycling tests which. The incorporation of these oxygenated functional groups has generally been carried out through oxidation treatments of the pristine carbon materials with different oxidants such as liquid

Methods

Results

Conclusion