(600u) The Effect of Rare Earth On the Structure and Performance of Pd/Cordierite Monolithic Catalysts

Jingjing Huang,Zhigang Jia*,Qingyuan Li,Zhao Zhang,Shengfu Ji*

State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China9

Email: jisf@mail.buct.edu.cn

Keywords: Pd; Monolithic catalyst; Rare earth; Methane; Catalytic combustion

Methane not only considered as an effective and clean energy, but also had strong greenhouse effect. The greenhouse effect of methane is 22 times more than that of CO₂, and the destroy ability to ozonosphere is 6 times more than that of CO₂, so the release of methane is very harmful to environment. It is not economic to use low concentration methane directly (such as coal mine ventilated gas), but by methane catalytic combustion technology, the heat energy can be available from the low concentration of methane. Moreover, it can also reduce the greenhouse effect from the release of methane. Thus, this method is significant to solve the energy and environment problems because of the achieving of resource and reduing the release of greenhouse gas.

Pd-based monolithic catalyst on cordierite honeycomb ceramic support had a lot of advantages on methane catalytic combustion aspect. Such as the straight channel of cordierite can take fom the pressure of catalytic bed, this is propitious to the mass and heat transfer. Furthermore, low thermal expansion coefficient of cordierite can keep the stable structure and mechanical strength of catalysts during the sharply change of reation temperature. Due to the price of noble metal Pd increasingly run up, how to reduce the content of Pd, and that keep the catalytic performance seems important at present. Rare earth was usually considered as activity component to be applied widely in methane catalytic combustion reaction. The aim of this paper was based on the stable catalytic activity, using rare earth modified noble metal Pd-based monolithic catalyst to reduce the content of noble metal Pd and the cost of catalyst.

First, the commercial cordierite honeycomb ceramic with 300 mesh was made into cylinder (diameter: 10 mm, length: 50 to 100 mm). Then coating the aluminium sol from boehmite,and the monolithic catalytic support with γ-Al₂O₃ on the surface of cordierite was prepared after drying and calcining. After that, La and Ce rare earth was loaded on the monolithic catalyst support through impregnation method. After the above procedure, the rare earth modified Pd/cordierite monolithic catalyst was prepared by loading Pd activity component followed drying and calcining.

Methane catalytic combustion performance of the monolithic catalyst was evaluated by fix-bed reactor. We mainly focus on the preparation process of catalyst, the content of La and Ce, and the relationship between the reaction condition and the performance of catalyst. The structure of catalyst was measured by XRD, BET and XPS. The result showed that adding of La and Ce can improve the performance of Pd/cordierite monolithic catalyst and also reduce the content of Pd. Besides, the process of preparing catalyst had close relation with the structure of catalyst and reaction performance for the methane catalytic combustion.