Doped activated carbons obtained from nitrogen and sulfur-containing polymers as metal-free catalysts for application in nitroarenes hydrogenation

• Published in: International journal of hydrogen energy 2024-01, Vol.53, p.490-502
• Main Authors: Villora-Picó, Juan-José, Gil-Muñoz, Gema, Sepúlveda-Escribano, Antonio, Pastor-Blas, M. Mercedes
• Format: Article
• Language: English
• Subjects: Hydrogenation of nitroarenes; N-doped activated carbon; Polyaniline; Polypyrrole; Polytiophene; S-doped activated carbon; S/N-Co-doped activated carbon
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2023.12.005

Activated carbons doped with nitrogen and/or sulfur have been obtained by pyrolysis followed of steam activation of a sulfur containing polymer (polythiophene) and two nitrogen-containing polymers (polyaniline and polypyrrole). These polymers were synthesized by oxidative chemical polymerization in aqueous media of their corresponding monomers. The influence of the steam activation on the textural properties and surface chemistry of the carbons has been evaluated and their catalytic activity has been determined in the hydrogenation reaction of 1-chloro-4-nitrobenzene. The degree of conversion in the reaction depends on the development of adequate porosity in the activated carbon (which is determined by the activation conditions) together with the presence of heteroatoms that act as active catalytic sites, with S showing considerably greater effectiveness than N. A compromise between an acceptable level of doping with sulfur and an adequate porosity is necessary, which has been achieved in a carbon obtained from polythiophene pyrolyzed at 900 °C and steam activated at 800 °C for 4 h, with a specific surface area of 742 m2/g and S content of 1.71 at%. [Display omitted] •N and S containing polymers used as precursors of metal-free doped activated carbons.•S-doped carbons are more active than N-doped carbons in the catalytic hydrogenation of 1-chloro-4-nitrobenzene.•Steam activation at high temperature develops carbon porosity but removes heteroatoms.•Compromise between S-doping and developed porosity is necessary to maximize catalytic performance.•100 % selectivity in the hydrogenation of the nitro group towards aniline in all cases.