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采用以尿素水解为基础的水热合成法制备了La和Mn取代的六铝酸盐催化剂(Ba1-xLaxMn3A l9O19-α).在Mn含量达到阈值时,研究了不同量的La取代Ba对Ba1-xLaxMn3A l9O19-α的相组成、结构、热稳定性及甲烷催化燃烧活性的影响.当x≥0.4时,水热合成过程中生成的La2(CO3)3在530~580℃分解,800~900℃时与-γA l2O3反应生成LaA lO3钙钛矿相,可抑制由BaCO3分解而生成的Ba2+的固相扩散,从而阻止了BaA l2O4尖晶石相的生成,使Ba2+在固相中保持较高的分散性,促进了六铝酸盐(-βA l2O3)相的形成.当x<0.4时,BaA l2O4尖晶石相的存在引起催化剂比表面积和催化燃烧活性的降低.La3+取代Ba2+后,六铝酸盐结构发生一定程度的扭变.这种扭变越大,所形成的六铝酸盐催化剂的热稳定性越差.Ba1-xLaxMn3A l9O19-α催化剂的甲烷催化燃烧活性随x的增大而增加,x=0.8时催化剂的活性最佳.
La and Mn-substituted hexaaluminate catalysts (Ba1-xLaxMn3Al9o19-α) were prepared by hydrothermal synthesis based on urea hydrolysis. When the content of Mn reached the threshold, xLaxMn3Al9O19-αhad the phase composition, structure, thermal stability and catalytic activity of methane combustion.When x≥0.4, La2 (CO3) 3 generated during hydrothermal synthesis decomposed at 530 ~ 580 ℃, When LaAlO3 perovskite phase is formed by the reaction with -γAl2O3, the solid phase diffusion of Ba2 + generated by the decomposition of BaCO3 can be inhibited, thereby preventing the formation of BaAl2O4 spinel phase and keeping the Ba2 + Dispersibility, promoted the formation of hexaaluminate (-βA l2O3) phase.When x <0.4, the presence of BaAl2O4 spinel phase caused the reduction of specific surface area and catalytic combustion activity of the catalyst.La3 + replaced Ba2 + The salt structure of a certain degree of distortion.This distortion is greater, the thermal stability of the formed hexaaluminate catalyst worse.Ba1-xLaxMn3A19O19-α catalytic activity of methane combustion with the increase of x Increase, when x = 0.8 the catalyst activity is the best.