New Approach to the Acidity Characterization of Pristine Zeolite Crystals by Ethylene Using Reversed-Flow Inverse Gas Chromatography (RF-IGC)

详细信息    查看全文

• 作者：M. Amine BenghalemAmir Astafan ; Ludovic Pinard ; T. Jean Daou ; Thomas Belin
• 刊名：Journal of Physical Chemistry C
• 出版年：2017
• 出版时间：February 9, 2017
• 年：2017
• 卷：121
• 期：5
• 页码：2738-2747
• 全文大小：595K
• ISSN：1932-7455

文摘

The adsorption and diffusion are key parameters for the catalytic conversions of ethylene to hydrocarbons. Using microcrystals of beta zeolites and the reversed-flow inverse gas chromatography technique, a new approach is developed for the catalytic characterization of pristine crystals. On the basis of the monitoring of the dynamic concentration in a time-resolved way, this method allows one to follow the surface coverage and adsorption energies among other physicochemical criteria. Pristine crystals were synthesized to rule out the effect of surface defects. The impact of porosity and acidity was studied by ethylene adsorption over porous, nonporous, and acid materials. The acidity of the mother zeolite (acid and porous) was decreased by retro-exchanges and partial cokage. The modification of the ethylene sorption due to the Brønsted acidity was then highlighted. The local surface coverage was not affected by the presence of porosity, while a second adsorption phase of the ethylene was induced by the modification of the acidity. Moreover, a relation between the amount of Brønsted acidity and the ethylene lateral interactions measured by RF-IGC was evidenced.