Application of Inverse Gas Chromatography for Diffusion Measurements and Evaluation of Fluid Catalytic Cracking Catalysts

Wallenstein, D.; Fougret, Christoph; Brandt, Stefan; Hartmann, Ulrike

doi:10.1021/acs.iecr.6b00470

Cited by 12 publications

(16 citation statements)

References 23 publications

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“…Presented in Fig. 1 are electron micrographs of characteristic FCC particles after synthesis and as extracted from their respective units 36 . Particles of FCC1 measure on average 76 µm in diameter, FCC2 74 µm, and FCC3 91 µm.…”

Section: Resultsmentioning

confidence: 99%

“…Others already suggested that macroscopically measurable structural metrics do not accurately describe the diffusion limitations in or the catalytic performance of FCC particles and that diffusion coefficients, e.g., present a more accurate picture 41 , 42 . Wallenstein et al 36 reported diffusion coefficients in the range 10 −2 –10 −4 cm 2 s −1 , which suggest that intra-particle diffusion in FCC particles occurs predominantly within pores of ~1–80 nm in diameter, the so-called Knudsen regime 43 . Correspondingly, the tomograms presented here register numerous pore throats of the size of voxels within the interconnected pore networks.…”

Section: Discussionmentioning

confidence: 99%

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A three-dimensional view of structural changes caused by deactivation of fluid catalytic cracking catalysts

et al. 2017

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Since its commercial introduction three-quarters of a century ago, fluid catalytic cracking has been one of the most important conversion processes in the petroleum industry. In this process, porous composites composed of zeolite and clay crack the heavy fractions in crude oil into transportation fuel and petrochemical feedstocks. Yet, over time the catalytic activity of these composite particles decreases. Here, we report on ptychographic tomography, diffraction, and fluorescence tomography, as well as electron microscopy measurements, which elucidate the structural changes that lead to catalyst deactivation. In combination, these measurements reveal zeolite amorphization and distinct structural changes on the particle exterior as the driving forces behind catalyst deactivation. Amorphization of zeolites, in particular, close to the particle exterior, results in a reduction of catalytic capacity. A concretion of the outermost particle layer into a dense amorphous silica–alumina shell further reduces the mass transport to the active sites within the composite.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

A three-dimensional view of structural changes caused by deactivation of fluid catalytic cracking catalysts

et al. 2017

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“…The diffusion measured by IGC is called transport diffusion and is supported by flow and concentration gradients. 35 It is represented by the diffusion coefficient with units of area per time (e.g., cm 2 /s). The diffusion coefficient is calculated using the van Deemter equation (eq 5) 36 A In eq 5, HETP is the height equivalent to a theoretical plate, A is the eddy diffusion, B is the longitudinal diffusion, C is the mass-transfer resistance in the stationary phase (i.e., packed material), and μ is the average linear velocity of the column flow.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

“…The diffusion measured by IGC is called transport diffusion and is supported by flow and concentration gradients . It is represented by the diffusion coefficient with units of area per time (e.g., cm 2 /s).…”

Section: Materials and Methodsmentioning

confidence: 99%

“…The diffusion coefficient is calculated using the van Deemter equation (eq ) In eq , HETP is the height equivalent to a theoretical plate, A is the eddy diffusion, B is the longitudinal diffusion, C is the mass-transfer resistance in the stationary phase (i.e., packed material), and μ is the average linear velocity of the column flow. The detailed calculations followed those described by Wallenstein et al and are outlined in the Supporting Information. Ideally, a diffusion coefficient is determined at infinite dilution such that probe diffusion in a given material is not affected by probe intramolecular interactions.…”

Section: Materials and Methodsmentioning

confidence: 99%

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Physicochemical Gas–Solid Sorption Properties of Geologic Materials Using Inverse Gas Chromatography

et al. 2021

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The goal of this study was to determine the physicochemical properties of a variety of geologic materials using inverse gas chromatography (IGC) by varying probe gas selection, temperature, carrier gas flow rate, and humidity. This is accomplished by measuring the level of interaction between the materials of interest and known probe gases. Identifying a material’s physicochemical characteristics can help provide a better understanding of the transport of gaseous compounds in different geologic materials or between different geological layers under various conditions. Our research focused on measuring the enthalpy (heat) of adsorption, Henry’s constant, and diffusion coefficients of a suite of geologic materials, including two soil types (sandy clay-loam and loam), quartz sand, salt, and bentonite clay, with various particle sizes. The reproducibility of IGC measurements for geologic materials, which are inherently heterogeneous, was also assessed in comparison to the reproducibility for more homogeneous synthetic materials. This involved determining the variability of physicochemical measurements obtained from different IGC approaches, instruments, and researchers. For the investigated IGC-determined parameters, the need for standardization became apparent, including the need for application-relevant reference materials. The inherent physical and chemical heterogeneities of soil and many geologic materials can make the prediction of sorption properties difficult. Characterizing the properties of individual organic and inorganic components can help elucidate the primary factors influencing sorption interactions in more complex mixtures. This research examined the capabilities and potential challenges of characterizing the gas sorption properties of geologic materials using IGC.

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Using PFG‐NMR and iGC to Study Diffusion and Adsorption in Heterogeneous Catalysts

Thompson,

Graf,

Brendlé

et al. 2024

ChemCatChem

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Mass transport in porous systems is inherently complex, but also of utmost importance for industrial processes such as heterogeneous catalysis. For each of the different length scales of diffusive motion involved, specific characterization techniques have been developed – including, but not limited to PFG‐NMR, ZLC measurements and iGC. While each method can deliver detailed information on certain types of diffusion, none of them delivers a full picture of mass transport across multiple length scales. The goal of the present work was to evaluate the technical feasibility and characterization potential of the hyphenated combination of PFG‐NMR and iGC in a coupled experimental setup. Challenges, advantages, and limitations of this approach are discussed. It is shown that the simultaneous detection of self‐diffusion on short length scales (as probed by PFG‐NMR) and transport diffusion covering longer distances (detectable by iGC) cannot be realized under the used conditions, essentially due to the lack of kinetic control at higher reactant loadings. The key advantage of the developed coupled setup is the ability of the iGC instrument to provide defined and readily variable levels of catalyst loading, which enables advanced pore connectivity studies by PFG‐NMR and yields thermodynamic data on reactant adsorption at the same time.

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Application of Inverse Gas Chromatography for Diffusion Measurements and Evaluation of Fluid Catalytic Cracking Catalysts

Cited by 12 publications

References 23 publications

A three-dimensional view of structural changes caused by deactivation of fluid catalytic cracking catalysts

A three-dimensional view of structural changes caused by deactivation of fluid catalytic cracking catalysts

Physicochemical Gas–Solid Sorption Properties of Geologic Materials Using Inverse Gas Chromatography

Using PFG‐NMR and iGC to Study Diffusion and Adsorption in Heterogeneous Catalysts

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