Autothermal Reforming from Chemistry to Engineering

The industrial processes for hydrogen production are well established [9, 30, 31], but may not be appropriate for small-scale stationary applications such as residential fuel cells or for unattended operation such as on-site hydrogen generation. These new applications allow for new process designs based on catalyst and engineering improvements [10, 32]. Hence a study of the ATR process has to involve both chemical and engineering aspects. 

Catalyst formulations for ATR fuel processors mainly depend on the fuel and the operating temperature. ATR catalysts are required to be active simultaneously for hydrocarbon oxidation and SR reactions, be robust at high temperatures for extended periods and be resistant to sulfur poisoning and carbon deposition, especially in the catalytic zone that runs oxygen limited [33]. Moreover, they must be resistant to intermittent operation and cycles, especially in start-up and shut-down steps. 

As ATR is a combination of POX and SR reactions, the active species to be employed for the preparation of a good ATR catalyst are the same as those for these two processes, especially Ni, Pt, Pd, Rh, Ru and Ir. 

Small amounts of other compounds can be added to Ni-based catalysts to improve the functional characteristics of the final catalyst. Typically, they are calcium aluminate to enhance the mechanical resistance of the catalyst pellets, potassium oxide to improve the resistance to coke formation and silica to form a stable silicate with potassium oxide [34]. Promotion with rare earth oxides such as La2C 3 also results in enhanced resistance to coking. 

A series of nickel/(rare earth phosphate) catalysts were investigated by Nagaoka et al. [35] for methane ATR. Among them, Ni/(Gd, Ce or Er phosphate) showed good activity, maintaining a stable CH4 conversion during time on-stream tests 

---