The selective hydrogenation of alkynes is a very important reaction in petrochemical industry. It is used to purify the alkene stream so that the alkynes will not poison the polymerization catalysts or degrade the polymer products. In the conventional process, the selective hydrogenation is commonly carried out in a fixed-bed reactor. However, the alkene selectivity is relatively low. When the conversion is high, the alkene selectivity is even negative because some alkene in the feed is hydrogenated into alkane.<br/>In the present work, a new process was proposed to carry out in a perfectly-mixed slurry reactor by coupling the selective absorption in the liquid phase with the selective hydrogenation on the catalyst surface. The catalysts were suspended in the liquid phase by intensive stirring. The selective hydrogenation of acetylene to ethylene was used as probe reaction. The hydrocarbon gas feed was 97% ethylene and 3% acetylene. Compared with the gas-phase hydrogenation, the ethylene selectivity was increased by ~30% at low acetylene conversions and by more than 40% at acetylene conversions near 100%, as shown in Fig. 1. The higher ethylene selectivity was resulted from the better suppression of both ethane and C4 species formation. Moreover, the catalyst stability in the liquid phase outperformed that in the gas phase, and the “hot spot” did not occur in the liquid phase.<br/>When using two reactors in a series, the acetylene conversion increased from 97.8% to 99.9%, while the ethylene selectivity did not change and the catalyst became more stable. By using more reactors in series, the acetylene conversion could achieve 99.99%, which was high enough to remove acetylene impurity below 10 ppm. In addition, elevated pressure also increased the acetylene conversion and enhanced the catalyst stability while maintaining the ethylene selectivity.

Selective hydrogenation in liquid phase: A new catalytic process for the purification of alkynes

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.