首页|Graphitization of alumina as a way to stabilize its textural characteristics under hydrothermal conditions
Graphitization of alumina as a way to stabilize its textural characteristics under hydrothermal conditions
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NSTL
Gamma alumina is a widely used support for catalysts of various processes.However,in the case of aqueous-phase processes,hydrothermal conditions result in transformation of γ-Al2O3 to boehmite,which is accompanied by degradation of the porous structure and leads to rapid catalyst deactivation.Here,we demonstrate a simple approach to stabilize the textural characteristics of γ-AI2O3 under hydrothermal conditions,based on preliminary graphitization of its surface by chemical vapor deposition of ethylene.Different duration(5-240 min)revealed the optimal degree of alumina surface coverage with carbon,ensuring the preservation of its textural characteristics from collapse during hydrothermal treatment(HTT)at 200 ℃.Materials characterization was performed by X-ray diffraction,transmission electron microscopy,nitrogen physisorption,and Raman spectroscopy.It is shown that initial γ-Al2O3 during HTT transforms into boehmite with a dramatic decrease in the surface area from 217 to 42 m~2/g.Whereas the preliminary graphitization of its surface maintains high surface area of the material after HTT,which is achieved by forming a C@boehmite composite(294 m~2/g).The presented approach makes it possible to modify the surface of alumina supports with a layer of graphite-like carbon and can be used to improve or maintain the catalysts activity.
NSTL
