Application Of Metal-based Electrically Heated Monloithic Catalyst For Catalytic Combustion Of Lean Methane

Methane, as the main component of natural gas, has large reserves, and great potential of energy use. Its catalytic combustion can reduce the ignition temperature greatly than conventional flame burning, by deepening the degree of oxidation of methane to improve combustion efficiency. The monolithic catalyst has been widely used in catalytic combustion because of its unique structure and fast heat and mass transfer. But the active component is difficult to load on the carrier because of the different properties between active component and carrier. So the adhesion stability of the monolithic catalyst is not high, thus affecting its activity and application.In this paper, we use FeCrAl alloys as the carrier, change the carrier surface micro-environment though high temperature calcination, anodic oxidation and anodic oxidation-in situ synthesis of zeolite membrane pretreatment methods. Then we load perovskite La0.7Sr0.3MnO3 active component on the carrier through the dip-coating method, spray pyrolysis method, composite plating method respectively. At last, calcined at 800℃, 900℃respectively, the metal-based electrically heated monolithic catalysts were prepared. We studied the effects of carrier pretreatment methods to the fastness degree of active component by analyzing catalyst weight gain and weight loss. We analyed the phase and surface morphology of monolithic catalysts systematically, by XRD and SEM. We investigated the impact of different carrier pretreatment methods, calcination temperature and reaction space velocity on catalytic properties of the monolithic catalysts.We studied the properties of metal-based electrically heated monolithic catalysts prepared by dip-coating method in methane catalytic combustion reaction. The results showed that, anodized-zeolite membrane pretreatment carrier catalyst showed better ignition activity at low temperature and catalytic stability at high temperature than the other two pretreatment carrier catalysts, T10 (the temperature of methane conversion rate is 10%) was 315℃, T90 (the temperature of methane conversion rate is10%) was 679℃; different pretreatment carrier catalysts showed better catalytic activity in 12100,24200 mL/(cat-g)·h low, medium space velocity than 36400 mL/(cat-g)·h high space velocity; Catalysts calcined at 900℃generally show better catalytic activity than that of calcined at 800℃. We studied the properties of metal-based electrically heated monolithic catalysts prepared by spray pyrolysis method in methane catalytic combustion reaction. The results showed that, anodized oxidation, anodized-zeolite membrane carrier catalysts calcined at 900℃, showed a good ignition activity at low temperature, under low and medium space velocity, T1o were 302℃and 310℃.900℃4 h calcined carrier catalyst calcined at 900℃showed good high-temperature activity under low-speed, T90=658℃. Catalyst calcined at 900℃generally showed better catalytic activity than that of calcined at 800℃. This conclusion is same as dip-coating method's.We studied the properties of metal-based electrically heated monolithic catalysts prepared by composite plating method in methane catalytic combustion reaction. The results showed that, catalysts showed good catalytic activity under low and medium space velocity, T10 was about 308-350℃, the zeolite membrane catalyst showed the best ignition activity at low temperature, T10 decreased to 308℃. This conclusion contrasts with the previous two methods'.The activity of catalytic combustion of methane of the metal-based electrically heated monolithic catalysts prepared through three methods was evaluated on the electric heating reactor designed and builted our own. FeCrAl alloy was not only the carrier of monolithic catalyst but also electric heating elements of the electric heating reactor, it has the advantages of heating rapidly, to achieve the desired reaction temperature in a short time, good heat transfer effect, small temperature gradient of radial and axial of monolithic catalyst and heating evenly. It improves energy efficiency and saves energy.