Nitrogen-containing carbon nanotubes as solid base catalysts

Abstract

Nitrogen-containing carbon nanotubes (NCNT) are effective re-usable solid base catalysts, their activity for a Knoevenagel condensation being related to the amount of pyridinic nitrogen incorporated in the NCNT structure, which could be tuned by the synthesis parameters of the catalyst.

Catalytic performance of carbon nanotubes in H2O2 decomposition: Experimental and quantum chemical study

“…Besides serving as a support, CNTs alone can be used as catalysts for some specific reactions, including methane and NO x decomposition [3,4], oxidative dehydrogenization of aromatic hydrocarbons and alkanes [5,6,7,8,9], oxidation of aniline [10], p-toluidine [11], and benzyl alcohol [12], catalytic wet air oxidation of phenol [13,14] and pcoumaric acid [15,16], aerobic oxidation of cyclohexane [17,18], ozonation of oxalic acid [19,20], selective oxidation of H 2 S [21], and heterogeneous hydroxylation of organics [22]. Nitrogen-doped CNTs were used as basic catalyst in Knoevenagel condensation [23] and CO oxidation [24] reactions. Based on these results, it is very reasonable to conclude that CNTs can serve as an excellent heterogeneous catalyst having (1) the potential to form a macrostructured catalyst of sufficient mechanical strength; (2) a tunable morphology and surface chemistry for enhanced catalytic activity and selectivity; (3) high surface area and specific porosity; (4) good thermal stability and resistance against acidic/basic environment.…”

Activity of Nitrogen Containing Carbon Nanotubes in Base Catalyzed Knoevenagel Condensation

“…Here we determined the total amount of surface sites by deconvolution of proton uptake curves which were derived from titration curves. This technique provides more detailed information about the pK a distribution of the accessible sites than can obtained from titration curves alone as was done before [27]. The site density of the NCNT is about an order of magnitude lower compared to the site density of AC-SAsuper samples and, although acidic, the site density of CNF OX .…”

“…As test reaction to analyse the NCNT's catalytic activity we chose the Knoevenagel condensation of benzaldehyde (BA) with ethylcyanoacetate (ECA) resulting in ethyl-a-cyanocinnamate (ECC) (Scheme 1.) In a preliminary study we showed that the pyridinic nitrogen atoms present in the NCNT were responsible for the catalytic activity [27]. Here we report a more detailed study on a kinetic analysis, including product inhibition and mass transfer limitation, of the above mentioned Knoevenagel condensation.…”

“…Nitrogen incorporation in carbon nanotubes (NCNT) is expected to result in base catalysts with the favourable properties of a nanostructured carbon. The basic character of the NCNT originates from the presence of pyridinic like nitrogen (N P ), located at the edges of the graphene layers [26,27]. Other nitrogen types present are quaternary N (N Q ), pyrrolic N (N PYR ) and oxidized pyridinic N (N OX ) [28][29][30] however their role in base-catalysis is expected to be limited.…”

Nitrogen and oxygen-doped metal-free carbon catalysts for chemoselective transfer hydrogenation of nitrobenzene, styrene, and 3-nitrostyrene with hydrazine

“…Carbon materials are known to act as an effective catalyst in several organic and pyridine on supported metal particles [5]. They showed that these nitrogen-doped carbon materials were active for Knoevenagel reactions.…”