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Understanding the dynamics of a methane bubble in a liquid metal bubble column reactor is important for optimizing the reactor design and improving efficiency. To better understand methane bubble dynamics and the reaction to produce hydrogen, we employ ANSYS Fluent to investigate the gas-liquid interface, to relate the surface area where reaction occurs to bubble size, and to determine coalescing behavior as a function of dimensionless numbers. Once the simulation is verified by comparing bubble velocity [1], shape [2], and coalescing distance [3] for a water-air system, a methane bubble in liquid bismuth at 1000 k is examined [4] [5]. Experimentally obtained kinetic parameters for the reaction are used in the computations. The bubble interfacial area to volume ratio is maximized at a diameter of 4mm and does not induce breakage of the bubble. The coalescing distance for two bubbles of methane in bismuth is a third of the distance for air in water bubbles. REFERENCES 1. S. Baz-Rodríguez, A. Aguilar-Corona, and A. Soria, Rev. Mex. Ing. Quím. 8, 213 (2009). 2. R. Clift, J. R. Grace, and M. E. Weber, Bubbles, Drops, and Particles (Academic Press, New York, 1978). 3. T. Otake, S. Tone, K. Nakao, and Y. Mitsuhashi, Chem. Eng. Sci. 32, 377 (1977). 4. M. J. Assael, K. Gialou, K. Kakosimos, and I. Metaxa, High Temp. High Press. 41, 101 (2012). 5. Engineering ToolBox (2004), https://www.engineeringtoolbox.com/methane-d_1420.html. Funding acknowledgement The support of the US National Science Foundation under grant number 2317726 is gratefully acknowledged. 

Aqueous-phase postsynthetic modifications of the industrially important Y-type zeolite are commonly used to change overall acid site concentrations, introduce stabilizing rare-earth cations, impart bifunctional character through metal cation exchange, and tailor the distribution of Brønsted and Lewis acid sites. Zeolite Y is known to undergo framework degradation in the presence of both vapor- and liquid-phase water at temperatures exceeding 100 °C, and rare-earth exchanged and stabilized HY catalysts are commonly used for fluidized catalytic cracking due to their increased hydrothermal resilience. Here, using detailed spectroscopy, crystallography, and flow-reactor experiments, we reveal unexpected decreases in Brønsted acid site (BAS) density for zeolite HY following exposure even to room-temperature liquid water. These data indicate that aqueous-phase ion-exchange procedures commonly used to modify zeolite Y are impacted by the liquid water and its removal, even when fractional heating rates and inert conditions much less severe than standard practice are used for catalyst dehydration. X-ray diffraction, thermogravimetric, and spectroscopic analyses reveal that the majority of framework degradation occurs during the removal of a strongly bound water fraction in HY, which does not form when NH4Y is immersed in liquid water and which leads to reduced acidity in HY even when dehydration conditions much milder than those typically practiced are employed. Na+-exchanged HY prepared via room-temperature aqueous dissolution demonstrates that Brønsted acid sites are lost in excess of the theoretical maximum that is possible from sodium titration. The structural impact of low-temperature aqueous-phase ion-exchange methods complicates the interpretation of subsequent data and likely explains the wide variation in reported acid site concentrations and catalytic activity of HY zeolites with high-Al content 

Water is ubiquitous in many thermal treatments and reaction conditions involving zeolite catalysts, but the potential impacts are complex. The different types of water interaction with zeolites have profound consequences in the stability, structure/ composition, and reactivity of these important catalysts. This review analyzes the current knowledge about the mechanistic aspects of water adsorption and nucleation on zeolites surfaces and the concomitant role of zeolite defects, cations and extra framework species. Examples of experimental and computational studies of water interaction with zeolites of varying Si/Al ratios, topologies, and level of silanol defects are reviewed and analyzed. The different steps associated with the process of steaming, including the Al-O-Si bond hydrolysis and subsequent structural modifications, such as dealumination, mesopore formation, and amorphization, are evaluated in light of recent DFT calculations, as well as SS NMR and other spectroscopic studies. Differences between the mechanisms of water attack of the zeolite in vapor or liquid phase are highlighted and explained, as well as the effect of hydrophobic/hydrophilic properties of the zeolite walls. In parallel, the various roles of water as modifier of reactivity are reviewed and discussed, both for plain zeolites as well as rare-earth or phosphorous-modified materials.