Pd/γ-Al_2O_3复合催化膜的热稳定性

Improvement of thermal stability of Pd/γ -Al_2O_3 membranes by the dopant of Lanthana

由溶胶凝胶法制备出Ｐｄ/γ－Ａｌ２Ｏ３催化膜及镧掺杂改性的Ｌａ/Ｐｄ/γ－Ａｌ２Ｏ３膜,研究了镧的掺杂对Ｐｄ/γ－Ａｌ２Ｏ３膜热稳定性的影响．用ＤＴＡ、ＸＲＤ、ＢＥＴ分别对膜的晶相和微孔结构(包括比表面积、孔径和孔容)进行了研究,结果发现:镧的掺杂明显提高了α－Ａｌ２Ｏ３的相变温度和高温下Ｐｄ/γ－Ａｌ２Ｏ３催化膜的热稳定性．Ｐｄ/γ－Ａｌ２Ｏ３经１１００℃处理５ｈ后,其比表面积、孔径和孔容分别为４．４６ｍ２/ｇ、３５．１ｎｍ和０．０５１ｃｍ３/ｇ,而经镧掺杂改性的Ｌａ/Ｐｄ/γ－Ａｌ２Ｏ３膜的比表面积、孔径和孔容分别为５１．６ｍ２/ｇ、７．２ｎｍ和０．１３８ｃｍ３/ｇ．

The thermal stability of unsupported Pd/γ - Al2O3 membranes was studied by determining the changes of the pore structure (including average pore size,pore volume and BET surface area) of alumina gels, prepared by sol - gel method, after sintered at different temperatures ranging from 400 ℃ to 1 200 ℃ . The average pore size of the pure alumina membrane increased sharply after sintering at temperatures higher than 1 000℃. Addition of 3 % Lanthana can considerably stabilize the pore structure of the unsupported alumina membrane. The pore diameter for the La - doped membrane was stabilized within 7. 2 nm after sintering at 1 100℃ for 5 h. The substantial increase in the pore size for the Pd/γ - Al2O3 membrane at the sintering temperature of 1 000 ℃ to 1 200 ℃ was accompanied by the phase transformation from γ - Al2O3 to a - Al2O3. The addition of Lanthana can raise this phase transformation by more than 100 ℃ .