A (5:1 by moles) CO2 (or Ar)-C3H8 mixture was passed, 30 mL/min, through a microreactor over 0.5 g of (I) unsupported metal oxide catalyst or (ii) supported 5% Ga2O3 catalyst (+ 1.5 g quartz glass) at 873 K. Over Ga2O3, in the first 10 min of the reaction, CO2 increased the yield of C3H6 by 6% over that with Ar, but in 1 h it was equivalent to Ar; the conversion and selectivity toward C3H6 were 35% and 88.7%, resp.; in 4 h, the C deposited on the catalyst was 3%. Slight amounts of CH4, C2H4 and C2H6 were formed. In a (4.5:0.5:1 by moles) CO2/O-2/C3H8 reaction mixture, O-2 enhanced the conversion but reduced the selectivity toward C3H6 and prolonged the catalyst life only slightly. Catalyst activity fell in the descending order: (i) Ga2O3 > V2O5 > Cr2O3 > CeO2 > Al2O3 > ZrO2 > SiO2 and (ii) Ga2O3/C (= Ga2O3) > Ga2O3/ZrO2 > Ga2O3/Al2O3 > Ga2O3/TiO2 > Ga2O3/SiO2. Support's acid-base properties affected the activity more than did the weakly acidic properties of Ga2O3. As a promoter, K suppressed the activity of Ga2O3 (K/Ga = 0.07 mol).