Prior Catalytic Methanation Of Co In Hydrogen-rich Gas By The Use Of A Metal Foam Microreactor

There is 0.5～2vol% of CO in hydrogen-rich gas producted by methanol reforming,it willpoison the Pt anode and dramatically depress the performance of proton exchange membrane fuelcells (PEMFC) while the hydrogen-rich gas is used to be raw material gas for PEMFC. It is veryessential to clean up CO to a degree <100×10-6 that can be acceptable for the anode.Prior methanation of CO is one of most possible effective methods to remove trace CO inhydrogen-rich gas . Due to the strong exothermic reaction of CO methanation, in traditionalreactors,it's easy to form local high-temperature because of the limitation of heat and masstransfer, resulting in partial CO2 methanation and consuming great amount of hydrogen. Metalfoam microreactor can effectivelly control CO2 methanation and decrease consumption ofhydrogen because of its good heat and mass transfer properties. This paper prepared porousnano-zirconia which was synthesized by a surfactant-assisted route in which surfactant acted astemplate under the hydrothermal method and 4Ni-2Ru/ZrO2 bimetallic catalysts byco-impregnation method.Coated the catalysts into the foam nickel as a structured support in amicroreactor designed by our lab to remove trace CO in hydrogen-rich gas with prior methanation.The dimensions of microreactor were 70×50×3 mm and the foam nickel were 30×27×1.8 mm.The results showed that:outlet concentration of CO can be reduced to 7×10-6 at 260℃whilethe calcination temperature is 350℃,the catalysts coated on foam nickel derectly.CO conversionkeeps at a very high level more than 99.6% ,outlet concentration can be reduced to below 50×10-6 ,CO2 conversion was less than 4%,H2 consumption was less than 9% even at a high reactiontemperature as 300℃at the condition of GHSV=5000 h-1.The effects of pre-treament and operation condition were studied over 4Ni-2Ru/ZrO2bimetallic catalysts. The results showed that,the Ru particle size will grow under higher reductiontemperature,this change result in a bad performance of catalysts.the best reduction temperature is300℃,outlet concentration of CO can be reduced to 13×10-6 at 260℃. we can find that:theoptimum reaction temperature of CO prior methanation decreased with decreasing inlet COconcentration ,therefore,contact microreactors can decrease optimum temperature in order todecrease CO2 methanation and H2 consumption.Add O2 to raw material gas with molar ratio of O2to CO is 2:1, the results showed that:the performance of catalysts was better than before adding O2 under a low temperature.The optimum space velocity is 2000 h-1 to 6000h-1,especially, at thespace velocity of 5000h-1,the outlet concentration of CO can be reduced to 7×10-6, CO2conversion is less than 1.5% .The stability experiment showed that, 4Ni-2Ru/ZrO2 bimetalliccatalysts had a good thermal stability.XRD, H2-TPR, and SEM measurements were adopted for the characterization of thecatalysts, the results showed that Ni-Ru catalysts formatted Ni-Ru clusters because of Ru metal indoping, which improved Ni metal dispersion,sintering capacity of catalysts and decreasedcatalysts reduction temperature.