Solvent‐free Liquid‐phase Oxidation of 1‐Hexene using Supported Gold Catalysts

Abstract

We report the solvent‐free oxidation of 1‐hexene with air by using supported gold catalysts with a catalytic amount of tert‐butyl hydroperoxide (TBHP) as initiator. We confirm that gold supported on graphite is an effective catalyst for such oxidations and that graphite was the preferred support. Preparation of catalysts using modified sol‐immobilisation was found to be effective, particularly when the PVA stabiliser was removed by a solvent treatment prior to the reaction.

Solvent-free aerobic oxidation of 1-octene using graphite-supported gold–palladium nanoparticle catalysts

“…Previous studies on the oxidation of alkenes have shown several radical initiators and their effect on both the conversion and selectivity [13][14][15]. In this study, a series of concentrations of TBHP were used in the presence of 1 % Au/graphite at 80°C and were tested for the oxidation of 1-octene; the results are summarised in Table 1.…”

“…This observation suggests that a bimetallic catalyst may facilitate the reaction toward the allylic oxidation pathway. The solvent-free aerobic oxidation of alkenes with the chain length of C 6 [15], C 8 ( Table 2) and C 10 [1] using graphite supported gold nanoparticles showed increase in chain length is correlated with increase in % conversion (2, 3.7 and 12.3 %) and selectivity to epoxide (11.4, 26.7 and 30.9 %). Further catalytic studies on alkenes with different chain lengths are required to confirm the impact of chain length on catalysis.…”

“…Gold catalysts have been shown to be effective for several types of oxidation reactions, particularly the oxidation of alcohols, the direct synthesis of hydrogen peroxide, and the oxidation of alkenes [4][5][6][7][8][9]. The oxidation of cyclic alkenes [10][11][12][13][14] and terminal alkenes [1,8,15] has been studied using supported gold catalysts. Alshammari et al [16] discovered that most alkenes contain a stabilizer to prevent oxidation; upon their removal, the alkenes that they obtained under solvent-free conditions could be oxidized to cycloalkane oxides in the absence of radical initiators.…”

“…However, the conversion was increased up to 5 % in the presence of the radical initiator. The Hutchings group [15] investigated the effect of the removal of stabilizer from a catalyst that was prepared using the solimmobilization method (SI) regarding the oxidation of 1-hexene. The removal of the stabilizer from the catalyst led to enhanced activity when compared to material derived from a standard sol method.…”

“…This showed that ring size had an influence on the direct reaction either via the epoxidation or allylic oxidation pathway. Subsequently, the catalytic activity of supported gold nanoparticles in the solvent-free oxidation of dec-1-ene and 1-hexene was investigated with catalytic amounts of a radical initiator and air as the oxidant [1,15]. Gold/graphite catalyst showed different catalytic effects in the oxidation of 1-hexene and dec-1-ene, especially in the % conversion (2 and 12.3 %, respectively) and the selectivity to epoxide (11.4 and 30.9 %, respectively).…”