Regulating the dispersion of CuO over SiO2 surface for selective oxidation of isobutane to tert-butanol.

Abstract

Controlling the highly selective oxidation of CH bonds in alkanes was still a challenge in the oxidation process, especially in oxygen atmospheres. Herein, three CuO/SiO₂ catalysts were designed and prepared by regulating the introduction of copper species to achieve the selective oxidation of tertiary C-H of isobutane (i-C₄H₁₀) to tert-butanol (TBA). Under the condition of 130 °C and 1.5 h, CuO/SiO₂-DP catalyst could achieve 92.7 % O₂ conversion and 85.1 % TBA selectivity, and the cycle stability could be maintained. The improvement of catalytic performance could be attributed to the efficient utilization of Cu atoms, which was related to the regulating the formation of copper phyllosilicate and the full utilization of Si-OH on the surface of SiO₂ during the catalyst synthesis process. Copper phyllosilicate formed a rich Si-O-Cu unit, enhanced the metal oxide-support interaction, inhibited the growth of copper species, improved the anchoring and dispersion of CuO, and ultimately improved the accessibility of substrate molecules on active CuO (111). In addition, the adsorption configuration of i-C₄H₁₀ and O₂ on CuO (111) was determined by in-situ FT-IR and DFT, and the existence form of O₂ after charge transfer was discussed. The reaction mechanism of i-C₄H₁₀ oxidation to TBA was revealed, which provided theoretical guidance for the selective preparation of TBA from i-C₄H₁₀ over metal oxides.