3.2. Effect of catalysts
To lower the specific energy (or improve energy conversion efficiency) of the reforming process, experiments are conducted in mode 2. The experimental conditions are the same as that in mode 1, except the 500 g commercial Z107
Ni/Al2O3 catalysts placed in tube reactor. In this case, without additional calefaction, the catalysts are heated up automatically by the caloric from the plasma jet and the temperature of catalyst bed can be maintained at about 760 C measured by thermal couple.
As shown in Fig. 3, with the help of catalysts, experiments in mode 2 show better conversions, better selectivities, as well as lower SE and higher ECE than that in mode 1. Besides, the optimum total feed flux is up to 5 m3/h.
The process in mode 2 is actually a “two-stage reaction”. The thermochemical conversions of feed gases take place
firstly in the plasma jet region, and then the unconverted feed gases are further converted on the catalyst bed. It is the
catalytic reaction that enhances the performance of this process. The notable enhancements in selectivities of H2 and
CO in mode 2 can be attributed to the Ni-based catalysts. This kind of catalyst also used in steam-methane reforming can
prohibit the side-reaction of H2 þ O ¼ H2O, and contribute to the reaction of C þ O ¼ CO in the process. Compared with the results of experiments in mode 1, the SE in mode 2 reduces by 20% and the ECE increases by 20% resulting from the increased conversions of CH4 and CO2 and selectivities of H2 and CO, when the total feed gases flux is 5 m3/h.