Selective Hydrogenation of Acetylene on Pt<sub><i>n</i></sub>/TiO<sub>2</sub>(<i>n</i>= 1, 2, 4, 8) Surfaces: Structure Sensitivity Analysis
Hong-Yan Ma, Gui‐Chang Wang
Abstract
The selective hydrogenation of acetylene is of great importance in the chemical industry, especially for eliminating trace acetylene from the ethylene feed. The semihydrogenation of acetylene to ethylene on the oxygen-defected anatase TiO2 (110) (Ana-Ov) supported Ptn cluster (n = 1, 2, 4, 8) has been studied by density functional theory calculations corrected by Hubbard-U and aimed to explore the size dependence of both the catalytic activity and selectivity. The calculation results indicated that the adsorption strength of C2H2(C2H4) increases when Ptn cluster size is enlarged, implying the higher catalytic activity with the same trends is a possibility. According to the microkinetic model analysis, the reaction rate of the whole hydrogenation increases with Ptn size because of the lower hydrogenation barrier, but the selectivity for ethylene decreases because of the higher desorption barrier of ethylene on the contrary, namely a strong structure-sensitive reaction. Besides, as active sites increase along the Ptn cluster size, the probability of overhydrogenation of ethylene and green oil formation might be increased, which further reduces the selectivity toward ethylene. The relationship of the selectivity and activity with cluster size effect could supply a clue for designing Pt-based catalysts supported by TiO2 with high efficiency in semihydrogenation of acetylene.