Conversion of isopropyl alcohol over Ru and Pd loaded N-doped carbon nanotubes

Abstract

Ru and Pd (2 wt%) loaded on pure and on N-doped carbon nanotubes (N-CNTs) were prepared and tested using the isopropyl alcohol decomposition reaction as probe reaction. The presence of nitrogen functionalities (pyridinic, pyrrolic, and quaternary nitrogen) on the nitrogen doped support induced a higher metal dispersion: Pd/N-CNT (1.8 nm) < Pd/CNT (4.9 nm), and Ru/N-CNT (2.4 nm) < Ru/CNT (3.0 nm). The catalytic activity of the supports was determined first. Isopropyl alcohol conversion produces acetone on CNTs while on N-CNTs it led to both dehydration and dehydrogenation products. At 210 °C and in the presence of air, the isopropyl alcohol conversion was higher on the N-CNTs (25%) than on the CNTs (11%). The Pd loaded catalysts were more active and more selective than the Ru ones. At 115 °C, the Pd catalysts were 100% selective towards acetone for a conversion of 100%, whereas the Ru catalysts led to dehydration and dehydrogenation products. The nitrogen doping induced the appearance of redox properties when oxygen is present in the reaction mixture. The introduction of nitrogen in the carbon framework changes the acido-basic properties of the material. The Pd catalysts on nitrogen-doped nanotubes allows reaching turnover frequencies of 600 s −1 with 100% selectivity towards acetone formation.