Outstanding Performance of Highly-Dispersed Zinc Species on Zeolites for the Continuous and Selective Dehydrogenation of Ethane with CO2 as Soft Oxidant
We report herein the preparation, characterization, and outstanding catalytic performance of a series of heterogeneous catalysts featuring highly-dispersed zinc sites on zeolitic SSZ-13 and ZSM-5 frameworks. The materials were evaluated in the oxidative dehydrogenation of ethane with CO2 as a soft oxidant, a very important reaction for the synthesis of platform chemicals. In particular, we found that Zn2.92/NaS50 exhibits high ethane conversion ability, excellent CO2 transformation ability, and good selectivity. In line with the experimental results, we show that the highly-selective character is due to the characteristic compositional structure of the zeolite support and its topology that can effectively confine CO2. An in-depth molecular analysis via operando studies and DFT calculation showed that the rate-limiting step of reaction with CO2 was the second C-H bond dissociation to give ethene. The addition of CO2 effectively reduced the energy barrier of this step, favoring desorption and limiting byproduct formation. Overall, this work demonstrates the breakthrough potential of novel heterogeneous catalysts made of highly-dispersed zinc species on zeolites in relevant transformations.