Nitrogen-doped carbon xerogels as catalysts for advanced oxidation processes

Tuning CNT Properties for Metal-Free Environmental Catalytic Applications

“…The obtained results were very similar to those obtained in the absence of the radical scavenger, suggesting that hydroxyl radicals in solution were not the relevant species involved in the oxidation mechanism, and that oxalic acid oxidation should be mainly promoted by active oxygen species on the CNT surface produced from the decomposition of oxygen. When other N-doped carbon materials were tested in CWAO (carbon xerogels [85] and graphene based materials [51]) similar evidences were observed, suggesting again that hydroxyl radicals in solution are not in fact the main species involved in the oxidation mechanism, and that oxalic acid conversion by CWAO can occur by means of surface active species produced from the decomposition of oxygen. The enhanced catalytic activity observed in the presence of N-functionalities seems to result from the interaction of oxygen with the carbon surface [88].…”

“…A similar conclusion was defended in reference [26], ozonation of oxalic acid in the presence of CNTs occurring both on the surface and in solution. In the presence of N-doped carbons, the addition of tert-butanol into the reaction medium also leads to a slight decrease in oxalic acid removal, suggesting that the production of radicals in the liquid phase plays a secondary role in the catalytic ozonation [85].…”

“…The modification of metal-free carbon materials by tailoring textural and surface chemical properties can play an important role in their catalytic performance; in particular, N-doping was demonstrated to increase the activity of carbon catalysts in oxidation reactions [11,31,51,52,56,85,86]. Regarding the use of N-doped CNTs in oxalic acid oxidation by CWAO, CNTs modified with nitric acid, urea and gas-phase thermal treatment showed the highest basic character and also the highest catalytic activity, but the performance is similar to that observed with the original CNTs after cyclic runs [31].…”

Hydrodechlorination activity of catalysts based on nitrogen-doped carbons from low-density polyethylene

“…In catalysis, NDCs used as supports have enhanced the activity in several reactions such as hydrogenation, oxidation or photocatalysis, among others [11][12][13]. This has been related to several factors: the presence of nitrogen into the carbon network could favor a high dispersion of the metal on the support by driving the nucleation of the active phase to nitrogen-neighboring carbon atoms, thus controlling nanoparticles size [7,12]; the higher conductivity of the support caused by the excess of electrons introduced by nitrogen in the carbon network may improve the reactivity in electron-transfer processes [8,12]; the insertion of nitrogen into the carbon network produces changes in the acid-base properties of the surface, since the excess of electrons increases the basicity [12,14]. Different methods have been used to prepare NDCs, such as ammonia treatment of the carbon at high temperature [15], chemical vapor deposition on metal seeds [16] or solvothermal reduction of carbon and nitrogen precursors [7].…”

Catalytic wet oxidation of organic compounds over N-doped carbon nanotubes in batch and continuous operation

“…Carbon materials, such as activated carbons [17][18][19][20][21][22][23][24], carbon xerogels [18,25,26] and carbon nanotubes (CNTs) [1,3,[27][28][29][30][31] have already been successfully used as catalysts for the CWO of organic compounds. In particular, the application of CNTs as catalyst is interesting due to their thermal and mechanical properties, and non-porous nature (minimizing mass transfer resistances) [32,33].…”