The selective hydrogenation of acetylene on palladium–carbon nanostructured catalysts

A novel carbon nanostructured material was produced using the electric arc ablation method. The product was purified using a combination of extraction, acid reflux and selective oxidation. The purified carbon nanostructured material (CNS) consisted of single-walled carbon nanotubes (SWNTs) with an average tube diameter of 1.3 nm, and interconnected, nanostructured and multiwalled globules. Catalysts containing 1 and 5% (m/m) Pd supported on the CNS were synthesized involving an activation step, followed by electroless plating of the Pd on the CNS. The Pd/CNS catalysts consisted of Pd particles with an average diameter of 6 nm highly dispersed on the CNS. The activity and selectivity of the 1 and 5% Pd/CNS catalysts towards the hydrogenation of acetylene were determined under different conditions of temperature and pressure. The results were compared to that obtained for reference catalysts, namely 1 and 5% Pd/Al2O3, and 1 and 5% Pd/activated carbon, under the same conditions. The Pd/CNS catalysts proved to have superior selectivity and activity, and formed less green oil and no detectable coke formation compared to the commercial catalysts under the experimental conditions. It is postulated that this was due to reduced hydrogen spillover and sintering effects and the different surface morphology of the Pd/CNS catalysts compared to the commercial products.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (83 K)Download as PowerPoint slideResearch highlights▶ The Pd/CNS catalysts showed better and sustained ethylene selectivity and activity compared to the reference catalysts. ▶ The Pd/CNS catalysts showed less green oil formation and no detectable coke formation compared to the reference catalysts. ▶ The absence of coke on the CNS supported catalysts is a major improvement in acetylene hydrogenation. ▶The Pd particle morphology and changes in the morphology play important roles in the catalytic properties of the catalysts.