Stability of PdO-Re2O7/SO42-/ZrO2-Al2O3 catalyst for direct synthesis of propylene from ethylene

During tests of palladium-rhenium catalysts based on sulfated zirconia in the process of direct synthesis of propylene from ethylene, it was found out that modifying the support with γ-Al2O3 increases significantly the stability of the system. Multi-cycle tests showed that systems with alumina content of 20 and 40 wt. % maintain its activity during a few tens of hours at the level of 50-80 %. The propylene yield from cycle to cycle remains practically unchanged (28-35 wt. %). According to UV spectroscopy and GLC with MSD, changes in the palladium and rhenium valence state don’t occur during the catalysts operation. The catalyst deactivation is caused by the C8+ oligomers deposit on its surface resulting from secondary processes of butenes oligomerization on the catalyst acid sites and C6+ hydrocarbons metathesis.