Spatial Profiles in RuO2-CuO-NaCl/SiO2 Packed-Bed Propylene Epoxidation Reactors

The spatially resolved species concentration and temperature profiles in a catalytic fixed-bed propylene epoxidation reactor were determined for RuO2-CuO-NaCl/SiO2 catalysts, using microprobe sampling and online gas chromatography. Experiments were performed at furnace temperatures of 250 and 270 C and feed gas compositions of 1 mol % C3H6, 4 mol % O-2, and 12/3 mol % C3H6, 31/3 mol % O-2, both with 95 mol % He dilution. The pressure was atmospheric, and the gas hourly space velocity (GHSV) was similar to 30 000 h(-1). The spatial profiles indicated that propylene oxide (PO) and acetone production exhibited well-defined induction periods. In contrast, acrolein (AC) formation was prompt and occurred early in the catalyst bed. These findings point to two different mechanisms associated with the formation of PO/AT and AC, respectively. The absence of any measurable propanal in the product mix suggests that C2 oxametallacycle propylene (C2OMMP) may be the preferred route for PO formation in this catalytic system. The spatial profiles reported represent information-rich data that are of significant utility for the development and validation of detailed chemical kinetic mechanisms for propylene partial oxidation in general and epoxidation in particular.