Green synthesis of carbon coated macrostructured catalysts: Optimized methodology and enhanced catalytic performance

Abstract

A novel green and efficient synthesis methodology for carbon-coated macrostructured catalysts was assessed. Sodium alginate was used as a dispersant to promote a suitable dispersion of the modified carbon nanotubes (CNT) to be incorporated on a structured support. The coating conditions were optimized to synthesize active and stable carbon-coated macrostructured catalysts. Achieving a total dispersant decomposition was one of the key steps to guarantee the coating stability, 550 °C being the optimal temperature. To assess the catalytic activity for these catalysts, the carbon-coated structures were tested as main catalysts for oxalic acid degradation through ozonation, and as support for bimetallic Pd-Cu catalysts, applied in NO3− conversion. The results achieved during ozonation allowed to outperform the ones obtained with macrostructured catalysts synthesized by more established techniques (such as chemical vapor deposition) with oxalic acid degradation, in a continuous system, of around 75%. As for the bimetallic samples, the species proved to be quite dispersed on the catalyst support, allowing a NO3− conversion of around 20% with a corresponding N2 selectivity of 55%, outperforming, again, the same type of catalyst synthesized with “less green” surfactants. This newly developed methodology is an important step for the sustainability of the structured catalyst design area.