Preparation And Performance Research Of Catalysts For Combustion Of Natural Gas Mediated By Inverse Micro-emulsion

Catalytic combustion is considered as a promising method for enhancing efficiency of the natural gas combustion with minimum emissions of NO_X. The performance of the catalysts is the key factor in industry application of the natural gas catalytic combustion technology. Hexaaluminate catalysts are considered as the most favorable catalysts for the natural gas combustion. The reaserch issue of the hexaaluminate catalysts is the to find advanced catalysts, which possess with high thermal ststability and high reaction activity.In this paper, the favorable system component of the inverse microemulsion and the components proportion was selected according to the study on the solubility of water phase in oil phase. And the phase transition process from cloud state to transparent for the water/TX-100+n-hexanol/ cyclohexane was researched by electrical conductivity methods. Then the hexa-aluminates catalysts and M-substituted barium hexa-aluminates were prepared by controlling several major parameters of the inverse microemulsion medium. For the sake of contrast, the conventional coprecipitation method was applied for catalyst samples preparation. The effluence of drying ways on the performance of catalysts was also investigated.The results show that components and the components proportion and the temperature have an important influence on the areas of the W/O region. And there was a best size dimension of water core in the inverse microemulsion when the components proportion was fixed. In contrast with the conventional coprecipitation method, catalyst sample prepared by the inverse microemulsion method possess with the advantage of smaller crystal particle size, larger specific surface area and higher catalytic reaction activity. BaAl₁₂O_19-d catalyst has high thermal stability and still have a surface area of 35.41 m²Â·g^-1 at 1200℃. TPD experiment indicated it has favorable performance of absorption and desorption, which can provide superficial absorption oxygen and crystal lattice oxygen for catalytic combustion of methane. Mn-substituted BaMn_xAl_12-xO_19-d catalysts were better than the other metal-substituted on the catalytic reaction activity and thermal stability. La-substituted can enhance the catalytic reaction activity largely. Precursor drying methods also have an important effect on the catalytic reaction activity, crystal phase structure and surface area. Supercritical drying can enhance the catalytic activity and the BET surface area. The catalyst BMAO-1 obtained by supercritical drying have higher specific surface area(up to 63.05 m²Â·g^-1) and more excellent catalytic reaction activity for methane combustion. The temperatures at 10%, 50% and 90% methane convertion were 434℃,547℃,620℃, respectively. And the 72h continuous lifetime experiment showed that the catalyst BMAO-1 has advanced thermal stability.