Increasing olefins by H2 and CH4 addition to the catalytic partial oxidation of n-octane

The catalytic partial oxidation (CPO) of n-octane over Rh and Pt-coated α-Al2O3 catalysts at approximately 5 ms contact times is examined with H2 and CH4 addition to the reactor feed. The aim is to preferentially oxidize H2 or CH4 and allow more octane to react in the gas phase to form high value chemicals such as ethylene and other olefins. The addition of H2 increases olefin selectivities on both 80 and 45 ppi foams coated with Rh or Pt, and the highest increase in olefin selectivity occurs at H2/O2 = 3/1 on Pt-coated 45 ppi catalysts. In this case, the selectivity to ethylene increases from a maximum of 38 to 51%, and total olefin selectivity increases from 75 to 83% without a decrease in octane conversion. The effect of adding CH4 is heavily dependent on the catalyst metal and average pore size of the support structure. On Pt catalysts and 45 ppi Rh-coated catalysts, the addition of methane can increase olefin selectivities by several percent. However, on 80 ppi Rh-coated foams, adding methane actually suppresses the formation of olefins and increases selectivity to H2 and CO.