Tailoring Properties of Metal-Free Catalysts for the Highly Efficient Desulfurization of Sour Gases under Harsh Conditions

Abstract

Carbon-based nanomaterials, particularly in the form of N-doped networks, are receiving the attention of the catalysis community as effective metal-free systems for a relatively wide range of industrially relevant transformations. Among them, they have drawn attention as highly valuable and durable catalysts for the selective hydrogen sulfide oxidation to elemental sulfur in the treatment of natural gas. In this contribution, we report the outstanding performance of N-C/SiC based composites obtained by the surface coating of a non-oxide ceramic with a mesoporous N-doped carbon phase, starting from commercially available and cheap food-grade components. Our study points out on the importance of controlling the chemical and morphological properties of the N-C phase to get more effective and robust catalysts suitable to operate H2S removal from sour (acid) gases under severe desulfurization conditions (high GHSVs and concentrations of aromatics as sour gas stream contaminants). We firstly discuss the optimization of the SiC impregnation/thermal treatment sequences for the N-C phase growth as well as on the role of aromatic contaminants in concentrations as high as 4 vol.% on the catalyst performance and its stability on run. A long-term desulfurization process (up to 720 h), in the presence of intermittent toluene rates (as aromatic contaminant) and variable operative temperatures, has been used to validate the excellent performance of our optimized N-C2/SiC catalyst as well as to rationalize its unique stability and coke-resistance on run.

Porous Silicon Carbide (SiC): A Chance for Improving Catalysts or Just Another Active-Phase Carrier?

“…Pham-Huu et al have widely demonstrated the importance of SiC structures as inert and thermally stable supports for a C–N active phase to be employed in the selective H 2 S oxidation to elemental sulfur in sour gas tails. − Although SiC matrices mainly hold the role of refractory carriers for porous carbon networks in the form of N-doped systems as the active phase, they play a fundamental role in the catalyst shaping according to its downstream application. In particular, these authors have demonstrated the advantages of SiCs for the preparation of robust and durable hybrid organic–inorganic composites obtained from growing C deposits at the SiC surface both in the form of N-doped carbon nanotubes (N-CNTs) − (Figure left) or porous N-doped C networks obtained from the CVD technique or the metal-free thermal treatment of selected C- and N-source building blocks, − respectively.…”

Catalysts and Processes for H2S Conversion to Sulfur

“…The desulfurization of sour gases was studied by Duong-Viet et al in carbon-based nanomaterials in the form of N-doped networks by the coating of a ceramic SiC. The chemical and morphological properties of the nano-doped carbon phase/SiC-based composite were controlled to get more effective and robust catalysts able to remove H 2 S from sour gases under severe desulfurization conditions such as high GHSVs and concentrations of aromatics as sour gas stream contaminants [7].…”

Inducing atomically dispersed Cl–FeN4 sites for ORRs in the SiO2-mediated synthesis of highly mesoporous N-enriched C-networks

“…We have recently described an effective and general strategy to the production of highly metal loaded and atomically dispersed Fe-based composites as performing electrocatalysts for the oxygen reduction reaction, starting from cheap and food-grade raw components in combination with key thermo-chemical etching/doping phases (NH 3 atmosphere). 27 The employed methodology took advantage from a proprietary synthetic procedure originally applied to the preparation of N-enriched mesoporous carbon-based 1D-3D networks [36][37][38] or organic-inorganic composites [39][40][41] to be employed as metal-free catalysts for a wide series of industrially relevant transformations. Accordingly, Fe-SAs were prepared from D-glucose (C 6 H 12 O 6 ) as the main C-source, ammonium carbonate [(NH 4 ) 2 CO 3 ] as N-source and citric acid (C 6 H 8 O 7 ) as a sacrificial carrier for Fe 3+ and NH 4 + ions.…”