Liquid-Phase Epoxidation of Propylene with H2O2 over TS-1 Zeolite: Impurity Formation and Inhibition Study

The liquid-phase epoxidation of propylene with H2O2 over titanium silicalite-1 (TS-1) zeolite was investigated in detail with a focus on the formation and inhibition of various trace impurities like acetaldehyde, propionaldehyde, acetone, hydroxyacetone, acetals, esters, etc. The results showed that the formation of trace impurities involved the transformation of propylene oxide (PO), its oxidation/isomerization/ring-opening (solvolysis and hydrolysis) byproducts, methanol solvent, and even propylene. Roughly speaking, the epoxidation conditions, viz, low temperature, short residence time, and slightly alkaline reaction medium, that are beneficial to suppress the ring-opening byproducts of PO, were seen facilitating the inhibition of trace impurities as well. To lower the trace impurities via modification of the TS-1 catalyst, the hydrothermal modification of TS-1 with organic amines such as amino-2-propanol (MIPA) was attempted and its effectiveness was demonstrated. The TS-1 zeolite suitably modified by MIPA exhibited abundant Ti-OH groups (3672 cm(-1)) together with remarkably decreased PO adsorption.