Regulation of sub-nanometric platinum on BaKL zeolite for boosting n-heptane aromatization

Abstract

Sub-nanometric Pt have attracted a great attention due to the advantageous to active CH bond of alkanes and trigger the cyclization at lower temperature. However, the regulation of sub-nanometric platinum on zeolite presents a significant challenge. Herein, by means of atomic layer deposition (ALD) technique, sub-nanometric Pt were fabricated on BaKL zeolite (Ba modified KL) and stabilized by the coordinated Ba atoms. The resultant catalyst (6Pt/BaKL) inhibited the hydrogenolysis and remarkably improve the aromatics selectivity (92 %) in n-heptane aromatization. The normalized turnover rate (TOR, ×10−2 moltoluene molPt−1 s−1) of 6Pt/BaKL catalyst is 3.6 times higher than that of 6Pt/KL catalyst. Density functional theory (DFT) calculation and kinetic experimental results revealed that sub-nanometric Pt decreased the energy barrier for the cleavage of primary CH bond of n-heptane, and the activation of terminal carbon atom of σC7= (2-C7=) promoted the formation of toluene via 2,7-ring closure of 2-C7= intermediate. These findings broaden the fundamental understanding the role of sub-nanometric Pt for the alkanes aromatization.