Catalytic Partial Oxidation of Iso-octane over Rh/α-Al2O3in an Adiabatic Reactor: An Experimental and Modeling Study

Catalytic partial oxidation (CPO) of hydrocarbons represents an interesting technology for hydrogen production on mobile systems. We investigated the CPO of 2,2,4-trimethyl pentane (iso-octane), chosen as surrogate for gasoline. CPO experiments were carried out in a laboratory scale autothermal reformer with honeycomb monolith catalysts (2% Rh/α-Al2O3), equipped with probes for spatially resolved measurements of temperature and concentration. The iso-octane CPO process follows a reaction pathway which mainly consists of the exothermic combustion reaction and the endothermic steam reforming. The chemical reaction is very fast, and sharp gradients of temperature and concentration establish at the catalyst inlet. Similarly to the CPO of light hydrocarbons, the consecutive reaction mechanism results in the formation of a hot spot of temperature at the catalyst inlet. However, compared to light hydrocarbons, this phenomenology is specifically emphasized in the case of iso-octane, because of the higher overall exothermicity and the lower diffusion rate, which limits the steam reforming reaction rate. The reactor design strategy previously suggested in the CPO of methane, based on the enlargement of the channel opening to selectively limit the rate of oxygen consumption, does not work for the CPO of iso-octane where the consumption of the fuel is also considerably limited by mass transfer. (Graph Presented).