Investigation of High-Temperature and High-Pressure Gas Adsorption in Zeolite H-ZSM-5 via the Langatate Crystal Microbalance: CO2, H2O, Methanol, and Dimethyl Ether

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• 作者：Wenjin Ding ; Michael Klumpp ; Hui Li ; Ulrich Schygulla ; Peter Pfeifer ; Wilhelm Schwieger ; Katja Haas-Santo ; Roland Dittmeyer
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：October 15, 2015
• 年：2015
• 卷：119
• 期：41
• 页码：23478-23485
• 全文大小：432K
• ISSN：1932-7455

文摘

The adsorption of gases CO₂, H₂O, methanol, and dimethyl ether (DME) in zeolite H-ZSM-5 in the temperature range of 50鈥?50 掳C and pressure range of 0鈥?8 bar has been investigated using a high-temperature, high-frequency oscillating microbalance (langatate crystal microbalance, LCM). The determined adsorption data are needed to validate a detailed simulation model, which is meant to assist in the optimization of the preparation of bifunctional core鈥搒hell catalysts for one-stage DME synthesis from syngas. Compared to the conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 掳C, LCM can be used at higher temperatures, i.e., at or close to the reaction temperature of one-stage DME synthesis (200鈥?00 掳C), owing to the absence of crystalline-phase transitions up to its melting point (1470 掳C). Zeolite H-ZSM-5 crystallites have been synthesized on the langatate crystal by steam-assisted crystallization (SAC). The loaded H-ZSM-5 (Si/Al molar ratio 100) on the langatate crystal has been confirmed and characterized with X-ray diffraction (XRD), wavelength-dispersive X-ray spectroscopy (WDX), and scanning electron microscopy (SEM). The adsorption experiments showed that the adsorption of CO₂, methanol, and DME in H-ZSM-5 is fitted well by the single site Langmuir model, while the dual-site Langmuir model is needed for the adsorption of H₂O in H-ZSM-5. The determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data.