Preparation And Prperties Of Co₃O₄ Catalyst For Low Concentration Methane Catalytic Combustion

In ventilation air methane?VAM?,??CH4?is generally less than 1%?vol?,although the concentration is very low but the emissions are huge.At present,the effective use of low concentration methane is catalytic combustion.As a low-emission and high-efficiency technology,the key is to develop high activity and stability of the catalyst.Precious metal catalyst has good catalytic activity,but its own limitations restrict its application.It is necessary to develop low cost and high activity catalysts.Due to its good catalytic activity and low cost,Spinel structure of the cobalt oxide?Co₃O₄?has attracted the interest of researchers.Based on this,the preparation of different morphology Co₃O₄ catalysts for catalytic combustion of methane in this paper.The precursor of nano-flower ?-Co?OH?2 was synthesized by controlling the p H value of the solution with F127 as the surfactant.After the calcination treatment at 450 ? for 5 h,Co₃O₄ catalyst has been still retain the nano-flower morphology,and the activity and stability of catalytic combustion under different space velocity were investigated.Since the resulting nano-flower Co₃O₄ catalyst exposes the {112} crystal orientation,and plenty of adsorbed oxygen species which has a very good methane catalytic activity.When the mass hourly space velocities?WHSVs?is 16000 mL/?g·h?,the light-off temperature T10 % is about 25 ?,complete transformation temperature T90 % is about 408 ?,nano-flower Co₃O₄ catalyst activity is much better than commercial Co₃O₄ catalyst.The mixture of ?-Co?OH?2 and CoC₂O₄ with smooth surface of the columnar was synthesized by simple condensing and refluxing.After calcination at 350 ? for 2 h,Co₃O₄ catalyst with the columnar morphology of small particle packing is obtained.The activity and stability of catalytic combustion under different space velocity were investigated.Because of the high specific surface area,rich Co3+ species,and the?220?crystal plane parallel to the?110?crystal plane is exposed,Therefore,it also shows a very good methane catalytic activity.When WHSV is 16000 mL/?g·h?,T10 % is about 236 ?,T90 % is about 428 ?.In addition,after 20 h of the test at 450 ?,the methane conversion rate only slightly decreased.A series of Co₃O₄-CeO2?x?was prepared by introducing Ce into the rod-like Co₃O₄ nanocrystals by solvothermal method using imidazole-4,5-dicarboxylic acid as organic ligand and hexamethylenetetramine as precipitant.The effect of different amount of Ce on the catalytic activity and stability of low concentration methane was investigated.The results show that when the doping amount of Ce is between 30.8 % and 44.4 %,WHSV is 16 000 mL /?g·h?,T10 % is about 264 ?,T90 % Is about 450 ?and exhibits very good stability;when the doping amount of Ce is less than 30.8 % or higher than 44.4 %,the catalytic activity increases relatively small;when the doping amount of Ce is 61.6 %,the catalytic activity is equivalent to that of rod-like Co₃O₄ nanocrystalline catalyst.It can be seen that the doping amount of Ce and the methane conversion show a volcanic curve,and the addition of Ce improves the activity and stability of Co₃O₄ nanocrystalline catalyst.