Catalytic Combustion Of Air Diluted Methane By Monolithic Catalysts

Catalytic combustion of methane (CCM) in air is a high efficient and low pollutive technique for purpose of energy utilization and flue gas cleaning. Monolithic catalysts, featured by low pressure drop, high activity, good mechanical strength and high thermal stability, meet the needs of CCM which usually carried out at high temperature with high space velocity.There are four categories of monolithic catalysts applied in CCM, namely noble metals, perovskite, hexaaluminate and mixed metal oxides. The newest literature is first reviewed in this thesis, with the preparation methods of different categories of catalysts compared by merites and flaws. Based on which, powder catalysts as Pd/Al₂O₃, Pd-XO/Al₂O₃ (X=Mn, Ce, Zr, Co), LaXO3(X=Ni, Co, Mn) perovskite, LaMnAl11O19 hexaaluminate were prepared and characterized by XRD, SEM, BET and CO chemical adsorption. Also developed respectively for three categories of powder catalysts, i.e. Al₂O₃(Al₂O₃,Pd/Al₂O₃,Pd-XO/Al₂O₃),LaXO3 perovskite, LaMnAl11O19 hexaaluminate, the proper compositions of slurry with good fluency and stability, proper viscosity, and techniques for washcoating. By adjusting the slurry composition and times of washcoating, the thickness of the powder catalysts coated on surface of the triangular pore ceramic support can be manoeuvred. The well adherence of the washcoat was testified by ultrasonic vibration, and SEM observation proved a uniform coating on support, without the obvious accumulation of powder around the corner area.At last, the activities of the monolithic catalysts developed above were measured at GHSV 40000/h-1 for catalytic combustion of air diluted methane (0.5vol.%). Influences of catalyst composition and preparation methods to the physical-chemical properties and catalytic performance were tested and with their working mechanism discussed. The results can be applied for improving the low temperature activity and high temperature stability in CCM study.