Transesterification of Triglycerides Using Nitrogen‐Functionalized Carbon Nanotubes

Abstract

Nitrogen-functionalized carbon nanotubes were synthesized by grafting amino groups to the surface of the nanotubes. The nanotubes exhibited promising results in the base-catalyzed liquid phase transesterification of glyceryl tributyrate with methanol, which is a model reaction for the production of biodiesel. The concentration of the active sites and the reaction parameters, such as temperature and glyceryl tributyrate to methanol ratio, were shown to significantly affect catalytic performance. The grafting technique employed allowed for design and control of the active sites. As a consequence, it was possible to design a nitrogen-functionalized carbon nanotube catalyst with a few strong, basic groups. This might be of interest for carbohydrate conversion reactions where strong basic sites are required but the pH of the solution should remain mild to avoid the degradation of the reactants and/or products.

Carbocatalysis in Liquid‐Phase Reactions

“…The intrinsic basicity of carbon materials is too weak to catalyze the transesterification reaction to any extent. Stronger basic sites can be introduced onto carbon materials by grafting with organic amine or imine groups . A 77 % conversion was obtained in the transesterification of C 4 triglycerides on amino‐functionalized CNTs (mass percentage 0.9 wt %) at 60 °C after 8 h; this conversion is even higher than that with the generally used commercial base catalyst hydrotalcite (Table ) .…”

“…In a systematic study, Villa et al. compared the performance of different amines (trimethylamine, ethylamine, and pyrrolidine) grafted on CNTs in the transesterification of glyceryl tributyrate with methanol . To achieve the same yield, a higher amount of catalyst with a lower density of basic or acidic sites is required.…”

A general post-synthetic modification approach of amino-tagged metal–organic frameworks to access efficient catalysts for the Knoevenagel condensation reaction

“…1 The Henry (nitro-aldol) reaction, the Claisen-Schmidt condensation and other condensation reactions can also be conducted in a similar fashion employing different nucleophiles. 3 To address the problems of recyclability and high loading common with homogeneous base catalysts, several efficient and recyclable solid base catalyst systems have been explored for the Knoevenagel condensation reaction, such as mesoporous titanosilicate, 4 modified MCM-41, 5 ionic liquids, 6 carbon nanotubes 7 and other aminefunctionalized solid supports. 3 To address the problems of recyclability and high loading common with homogeneous base catalysts, several efficient and recyclable solid base catalyst systems have been explored for the Knoevenagel condensation reaction, such as mesoporous titanosilicate, 4 modified MCM-41, 5 ionic liquids, 6 carbon nanotubes 7 and other aminefunctionalized solid supports.…”

Chapter 3. Novel carbon materials modified with heteroatoms as metal-free catalyst and metal catalyst support

“…In a recent work, CNTs functionalised with ammine groups have shown to be active for biomass conversion 91 and for the transesterificaton ot tryglicerides with methanol, 92,93 which is considered a test reaction for biodiesel production. This catalyst has the advantage that it does not contain high amounts of acidic oxygenated surface groups which are inevitably present in metal oxides.…”