Novel reverse microemulsion and its application to synthesis of nanostructured La0.95Ba0.05MnAl11O19-alpha catalyst for methane combustion

a novel type of reverse microemulsion system composed of water, i-propanol and n-butanol was developed as a reaction medium to prepare substituted-hexaaluminate la0.95ba0.05mnal11o19-alpha catalyst for methane combustion. the structure and properties of water in the novel reverse microemulsion system were investigated by means of h-1 nmr, ft-ir, electrical conductometry and laser light scattering apparatus. the electric conductivity of the novel reverse microemulsion system followed a nonlinear correlation when the volume fraction of water was low. there existed a critical point of phi(p) (0.15) along the k similar to phi curve. h-1 nmr revealed that the chemical shift of the water proton signal moved to upfield with decreasing water content. ftir showed that the nu(o-d) band was shifted to higher frequency with increasing water concent. the size distribution of the al(oh)(3) gel particles formed by hydrolysis of al(i-oc3h7)(3) in the novel reverse microemulsion ranged from 226 to 329 nm with the average diameter of 267 nm. substituted hexaaluminate la0.95ba0.05mnal11o19-alpha synthesized in the novel reverse microemulsion system possesses a surface area of 65 m(2)/g, comparable to 32 m(2)/g of similar samples prepared with pure water. xrd measurements revealed that beta-al2o3 was the only phase for this catalyst after calcination at 1200 degrees c for 10 h and its particle size measured by tem is about 30 nm. this nanostructured hexaaluminate, when used as a catalyst for ch4 combustion, allowed a light-off of a stream of 1% ch4 in air at 420 degrees c, as compared to 5 10 degrees c required for similar catalyst prepared with pure water. the excellent low-temperature catalytic activity of this catalyst arised from the formation of nanostrctured hexaaluminate that contained larger amount of manganese.