C-doped boron nitride nanotubes for the catalysis of acetylene hydrochlorination: A density functional theory study

Abstract

The mechanism of a novel mercury-free catalyst, carbon-doped boron nitride nanotubes (BNNTs), for acetylene hydrochlorination reaction was investigated by density function theory (DFT) calculations. Two types of carbon-doped BNNTs with different diameters, boron substituted and nitride substituted with carbon, were studied in detail as the catalyst of the acetylene hydrochlorination reaction. Results show the adsorption of C2H2 on carbon-doped BNNTs is dominant in the adsorption process due to the stronger interaction of C2H2 with carbon-doped BNNTs. HCl can be dissociated on carbon-doped BNNTs with small diameter during the adsorption process. The C2H2 is chemically adsorbed on the doped impurity C atom where it is activated to continue the addition reaction with the gaseous HCl molecule. The rate-limiting step is the splitting of HCl molecule and the attack of H and Cl atoms on CC bond of the activated C2H2 to form the transition state. The reaction can take place easily on carbon-doped BNNTs and a low energy barrier of 28.47 kcal/mol is found. The doping site and curvature have a slight impact on the catalytic performance in the reaction based on the comparison of energy barrier. The study reveals that the doped impurity C atom can largely improve the activity of BNNTs, and carbon-doped BNNTs can be an effective non-metal catalyst in the acetylene hydrochlorination reaction.