【摘要】 提出一种由水,异丙醇,正丁醇组成的新型微乳液,并以其为反应介质制备了甲烷高温燃烧La0.95Ba0.05MnAl11O19-α催化剂.采用1HNMR,FT-IR,电导法及激光粒度散射法研究了新型微乳液中水的结构及相特性.新型微乳液中水的体积分数小于一定值时,电导率与水含量成非线性关系,k～φ曲线上存在一临界值(φP=0.15).水质子的化学位移随水含量的降低移向高场.加入4%D2O测定的O—D键的伸缩振动随水含量增加而向高波数方向移动.异丙醇铝在新型微乳液中水解形成的Al(OH)3胶体粒子的粒径范围为226～329nm.采用新型微乳液作为反应介质制备的Ba0.05La0.95MnAl11O19-α催化剂的粒径在30nm,明显小于纯水制备的样品(100nm).BET比表面积为65m2/g,比纯水制备样品高出约一倍.XRD结果显示,1200℃焙烧10h即可获得含单一β-Al2O3相的催化剂.Ba0.05La0.95MnAl11O19-α催化剂甲烷催化燃烧的T10为420℃,比纯水制备样品下降了90℃.甲烷催化燃烧活性提高是由于含有较多Mnn+纳米结构六铝酸盐的形成.更多还原

【Abstract】 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-α catalyst for methane combustion. The structure and properties of water in the novel reverse microemulsion system were investigated by means of 1H 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 φP (0.15) along the k～φ curve. 1H NMR revealed that the chemical shift of the water proton signal moved to upfield with decreasing water content.FTIR showed that the νO-D band was shifted to higher frequency with increasing water concent. The size dis-tribution of the Al(OH)3 gel particles formed by hydrolysis of Al(i-OC3H7)3 in the novel reverse microemul-sion ranged from 226 to 329 nm with the average diameter of 267 nm. Substituted hexaaluminate La0.95Ba0.05MnAl11O19-α synthesized in the novel reverse microemulsion system possesses a surface area of 65 m2/g, comparable to 32 m2/g of similar samples prepared with pure water. XRD measurements revealed that β-Al2O3 was the only phase for this catalyst after calcination at 1200 ℃ 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 ℃, as compared to 510 ℃ 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.更多还原