NiO-MgO Solid Solution For Selective Methanation Of CO In H₂-rich Gas

H2-rich gas with CO content below10ppm is required for proton exchange membranefuel cell (PEMFC) to power stably, but the H2-rich gas produced by steam reforming ofhydrocarbons and the following water-gas shift reaction is largely composed of1%CO and18%CO2. CO selective methanation is an effective method to remove CO in hydrogen-richgas. It has high energy efficiency, the process is simply controlled, the resultant methaneand water has no toxic effects on the electrodes and environment.As a result, it has gainedattention gradually in recent years.Supported nickel-based catalysts are effective for selective methanation of CO andcheaper than precious metals. In this work, according to the characteristics that NiO andMgO are easy to form solid solution, we prepared NiO-MgO solid solution to prepareNi/Mg1-xNixO catalysts after reduction treatment, and then studied the activity of COselective methanation. The main contents and results are summarized as follows:1. The calcined samples were reduced in hydrogen-nitrogen mixture gas (70%H2+30%N2) and the reaction mixture (70%H2+18%CO2+11%N2+1%CO), respectively. Theobtained catalysts Ni/Mg1-xNixO were used for CO-SMET. It was found that the catalyticactivity of the catalysts reduced by nitrogen-hydrogen gas mixture were much better thanthose reduced by reaction mixture.2. The calcined samples were reduced with temperature increasing from roomtemperature to a set temperature (500°C~800°C). The obtained catalysts Ni/Mg1-xNixOwere used for CO-SMET. It was found that the higher the reduction temperature was, thebetter the activity of CO selective methanation was. The catalysts reduced at800°C showedthe best catalytic activity.3. The calcined samples were reduced in hydrogen-nitrogen mixture gas with differentconcentrations of H2(50%～100%), The obtained catalysts Ni/Mg1-xNixO were used forCO-SMET. It was found that the catalyst reduced by85%H2showed the best catalyticactivity. However, the catalytic activity of catalyst became worse when it was reduced by50%H2.4. The calcined samples with different Ni/Mg feed ratio (10%～40%) were reduced.The obtained catalysts Ni/Mg1-xNixO were used for CO-SMET. It was found that whenNi/Mg feed ratio was20%～30%, the catalyst showed the best catalytic activity for CO selective methanation.5. The samples calcined at different temperatures (400°C~800°C) were reduced. Theobtained catalysts Ni/Mg1-xNixO were used for CO-SMET. It was found that the catalyticactivity became worse with the calcination temperature increasing, especially the activity ofthe sample calcined at800°C decreased seriously.