Behavior of Pd‐supported catalysts in phenylacetylene hydrogenation: Effect of combined use of polyvinylpyrrolidone and NaOH for magnetic support modification

Abstract

Recently, magnetic nanoparticles have attracted the attention as catalyst supports due to the possibility of magnetic separation, allowing for easy, fast, and clean recovery of the catalysts. A synthesis strategy of such supports plays an important role in improving the properties of the magnetic catalysts. Here, we proposed a simple and effective method to increase the activity and lifetime of the Pd magnetic catalyst. Polyvinylpyrrolidone‐maghemite nanoparticles were synthesized via one‐pot coprecipitation method using an excess of the NaOH. This was followed by adsorption of Pd2+ on the magnetic nanoparticles. The resulting catalyst showed activity (WCC = 4.0 × 10−6 mol s−1, WCC = 12.7 × 10−6 mol s−1) and selectivity (94%) in phenylacetylene hydrogenation. The catalyst was then magnetically recovered and reused 58 times. The activity of the catalyst increased significantly during the first three runs, changing the rate ratio of WCC to WCC from 1:3.2 to 1:1.6, and then decreased in the following runs. To understand the reason for this behavior, the catalyst was characterized, as well as catalytic studies were performed using similar catalysts for comparison. The results show that the NaOH adsorbed on magnetic support affects the size, stability, and catalytic properties of the Pd particles, and the effect of alkali is enhanced in the presence of the polymer.