Catalytic heat exchanger for the CO2 methanation in the Power-to-Gas process

A prototype structured reactor was developed that resembles a plate heat exchanger where single plates with rectangular microchannels are coated with a commercial nickel-alumina catalyst ( d P < 10 μm) and stacked together. The commercial Ni/Al 2 O 3 catalyst was deposited on the channels via the frame coating procedure. A total of three measurement campaigns were conducted with an accumulated time of 390 h to evaluate the reactor performance using CO 2 and synthetic biogas methanation experiments with different H 2 /CO 2 ratios for various flow rates, temperatures, pressures and number of coated plates. During the first measurement campaign, CO 2 conversions of 88% were achieved at atmospheric pressure, which slightly decreased for the synthetic biogas methanation to 84%. With increasing pressure to 3 bar abs , the CO 2 conversion and CH 4 selectivity increased significantly to 94% and 99.5%. In the second campaign, maximum equilibrium conversion and selectivity respective values of 99.4% and 99.9% were reached at catalyst temperature of 397 °C, pressure of 3 bar abs , with H 2 /CO 2 = 5. The alternate reactive/non-reactive channel operation was verified during the third measuring campaign, proving that the reactor successfully works as a reactive heat exchanger. Autothermal operation was also achieved at GHSV CO2 = 6.5 L N g −1 h −1 , with a nonreactive channel flow rate and temperature of 5 L N min −1 and 260 °C, respectively. The stability of the reactor and catalyst activity was proven under CO 2 and synthetic biogas methanation for a total time of more than 270 h with operation pressure up to 3 bar abs .