The discovery of heterogeneous catalysts capable of direct gas-phase production of propylene oxide (PO) from propylene and molecular oxygen remains a challenge in industrial catalysis. The SnO2-CuO-NaCl/SiO2 system has been shown to produce PO at 55-60% selectivity with propylene conversion of 1% at 250 degrees C and 1 bar. A product shift toward CO2, found to occur during continuous operation, was counteracted by cofeeding 10-50 ppm 1-chloropropane, maintaining peak PO selectivities for 12 h. Temperature-programmed-reduction (TPR) studies indicated that Na increases copper dispersion. Additional catalyst characterization studies performed by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed the presence of distinct phases of CuO, SnO2, and NaCl.