文摘
The detailed mechanisms of dimerization of propene to C6 species inside the main channel of zeolite SAPO-5 has been systematically studied using periodic density functional theory with dispersion correction (PBE-D2). Both the concerted and stepwise mechanisms were considered as well as the carbonium mechanisms. Both 2-methyl-2-pentene and 2,3-dimethyl-2-butene were found to be the most favorable products. However, the concerted and stepwise mechanisms can lead to the formation of 2-methyl-2-pentene but not 2,3-dimethyl-2-butene because of steric effect. The small difference of overall barriers indicates that both the concerted and stepwise mechanisms are competitive for the dimerization of propene, whereas the carbonium mechanisms are less competitive as the formation of carbonium C3H7+ is more difficult. This study provides detailed mechanisms for the dimerization of propene and useful information for carbon nanotube growth inside zeolite SAPO-5.