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

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 C[dbnd]C 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.