PROPANE CONVERSION IN THE PRESENCE OF IRON-PROMOTED AND MANGANESE-PROMOTED SULFATED ZIRCONIA - EVIDENCE OF OLAH CARBOCATION CHEMISTRY

Iron- and manganese-promoted sulfated zirconia was tested for conversi on of propane at 1 bar, 200, 250, and 300 degrees C, and propane parti al pressures of 0.01, 0.025, and 0.05 bar. Propane was converted to pe ntanes, butanes, propene, ethane, ethene, and methane at 250 degrees C , but the conversions were low, for example, being only a fraction of a percent at a space velocity of 9.1 x 10(-7) mol/(g s) and a propane partial pressure of 0.05 bar. Carbonaceous deposits formed rapidly. At 250 degrees C, the number of propane molecules converted to gas-phase products was only about 1 per sulfate group after 16 days of operatio n in a continuous flow reactor. The observation of butanes and pentane s as products is consistent with Olah superacid solution chemistry, wh ereby propane is first protonated by a very strong acid to form a carb onium ion. The carbonium ion then decomposes into methane and an ethyl cation, which undergoes secondary reactions with propane to form high er-molecular-weight alkanes.