Role of supports in the tetrapropylammonium hydroxide treated titanium silicalite-1 extrudates

Titanium silicalite-1 (TS-1) was extruded with silica and alumina supports, and then the extrudates were treated with dilute tetrapropylammonium hydroxide (TPAOH) solution. The treated TS-1 extrudates were characterized and evaluated in the epoxidation of propene. The two supports exhibited different properties after the treatment. The dissolution of silicon, forming hollows in the TS-1 crystals, preferably occurred when alumina support was used. The inhibition of generation of hollows in the silica supported TS-1 arose from the dissolution and recrystallization of silica support. The crystallization of support also led to the unblocking of inherent micropores, which was beneficial for improving the catalytic performance. Alumina support showed a different result. A very small amount of aluminum was inserted into the framework of TS-1, but the small amount of framework Al caused a sharp increase of the acid amount, and thus a low selectivity of propene oxide and poor catalyst stability in propene epoxidation.