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 conversion of propane at 1 bar, 200, 250, and 300 degrees C, and propane partial pressures of 0.01, 0.025, and 0.05 bar. Propane was converted to pentanes, 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 operation in a continuous flow reactor. The observation of butanes and pentanes as products is consistent with Olah superacid solution chemistry, whereby propane is first protonated by a very strong acid to form a carbonium ion. The carbonium ion then decomposes into methane and an ethyl cation, which undergoes secondary reactions with propane to form higher-molecular-weight alkanes.