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Title: Configurational diffusion of asphaltenes in fresh and aged catalyst extrudates. Quarterly progress report, 20 December 1993--20 March 1994

Abstract

The objective of this research is to determine the relationship between the size and shape of coal and petroleum macromolecules and their diffusion rates, i.e., effective diffusivities, in catalyst pore structures. That is, how do the effective intrapore diffusivities depend on molecule configuration and pore geometry. This quarter the authors developed a mathematical diffusion model for spent catalyst with a nonuniform pore structure due to nonuniform coke and metals deposition. Diffusion experiments with both spent extrudates and crushed catalysts were performed. Effective diffusivities were obtained by fitting the experimental data with a diffusion model. The results showed that a skin effect due to coke and metals deposition exists in the coal liquefaction catalysts. The uniform particle model did not satisfactorily represent the diffusion behavior in the spent catalyst extrudates, which gave rise to extremely high tortuosity values. On the other hand, the experimental results were well represented by the nonuniform particle model. Due to deposits in catalyst pores during the coal liquefaction process, the effective diffusivity decreased to a very low value.

Authors:
;
Publication Date:
Research Org.:
Auburn Univ., AL (United States). Dept. of Chemical Engineering
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10150725
Report Number(s):
DOE/PC/91311-T10
ON: DE94011780; BR: AA1525050; TRN: AHC29411%%35
DOE Contract Number:
FG22-91PC91311
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: [1994]
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; 02 PETROLEUM; ASPHALTENES; DIFFUSION; CATALYSTS; PERMEABILITY; PORE STRUCTURE; PROGRESS REPORT; MOLECULAR STRUCTURE; COAL LIQUIDS; PETROLEUM PRODUCTS; MATHEMATICAL MODELS; EXPERIMENTAL DATA; 010405; 020400; HYDROGENATION AND LIQUEFACTION; PROCESSING

Citation Formats

Guin, J.A., and Tarrer, A.R. Configurational diffusion of asphaltenes in fresh and aged catalyst extrudates. Quarterly progress report, 20 December 1993--20 March 1994. United States: N. p., 1994. Web. doi:10.2172/10150725.
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Guin, J.A., & Tarrer, A.R. Configurational diffusion of asphaltenes in fresh and aged catalyst extrudates. Quarterly progress report, 20 December 1993--20 March 1994. United States. doi:10.2172/10150725.
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Guin, J.A., and Tarrer, A.R. Sun . "Configurational diffusion of asphaltenes in fresh and aged catalyst extrudates. Quarterly progress report, 20 December 1993--20 March 1994". United States. doi:10.2172/10150725. https://www.osti.gov/servlets/purl/10150725.
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@article{osti_10150725,
title = {Configurational diffusion of asphaltenes in fresh and aged catalyst extrudates. Quarterly progress report, 20 December 1993--20 March 1994},
author = {Guin, J.A. and Tarrer, A.R.},
abstractNote = {The objective of this research is to determine the relationship between the size and shape of coal and petroleum macromolecules and their diffusion rates, i.e., effective diffusivities, in catalyst pore structures. That is, how do the effective intrapore diffusivities depend on molecule configuration and pore geometry. This quarter the authors developed a mathematical diffusion model for spent catalyst with a nonuniform pore structure due to nonuniform coke and metals deposition. Diffusion experiments with both spent extrudates and crushed catalysts were performed. Effective diffusivities were obtained by fitting the experimental data with a diffusion model. The results showed that a skin effect due to coke and metals deposition exists in the coal liquefaction catalysts. The uniform particle model did not satisfactorily represent the diffusion behavior in the spent catalyst extrudates, which gave rise to extremely high tortuosity values. On the other hand, the experimental results were well represented by the nonuniform particle model. Due to deposits in catalyst pores during the coal liquefaction process, the effective diffusivity decreased to a very low value.},
doi = {10.2172/10150725},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun May 01 00:00:00 EDT 1994},
month = {Sun May 01 00:00:00 EDT 1994}
}
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Technical Report:
View Technical Report (1.17 MB)
DOI:  10.2172/10150725
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  • This quarter, GPC column efficiency and resolution were tested. Better resolution and separation of petroleum asphaltenes were obtained in GPC by connecting four columns (1000{Angstrom}, 1000{Angstrom}, 500{Angstrom}, 500{Angstrom} pore sizes, respectively) in series. A good linear column calibration curve was obtained using several polystyrene standards with molecular weights ranging from 500 to 5 {times} 10{sup 4}. The molecular weight distribution of a petroleum asphaltenes was approximated by the polystyrene calibration curve.

  • ;
    The objective of this research is to determine the relationship between the size and shape of coal and petroleum macromolecules and their diffusion rates in catalyst pore structures. This quarter, the authors developed a mathematical diffusion model for catalysts with a nonuniform pore structure during the adsorptive diffusion process due to the adsorbed layer of solute molecules on the catalyst pore walls. Diffusion experiments with quinoline and polystyrene were performed. Effective diffusivities were obtained by fitting the experimental data with a diffusion model. Results showed that the uniform pore model did not satisfactorily represent the diffusion behavior of larger polystyrenemore » molecules, which gave rise to very high tortuosity values. The shrinking pore model better represented the adsorptive diffusion uptake behavior of a solute from the surrounding bath, especially for a diffusing solute with larger molecular size. Adsorption of solute molecules on the catalyst pore walls further restricts the diffusion rate due to increased steric and hydrodynamic hindrance factors. The tortuosity factor could also increase during adsorptive diffusion processes due to the increased constrictions caused by the adsorbed solute molecules.« less

  • The objective of this research is to determine the relationship between the size and shape of coal and petroleum macromolecules and their diffusion rates i.e., effective diffusivities, in catalyst pore structures. That is, how do the effective intrapore diffusivities depend on molecule configuration and pore geometry. Three tasks are planned to meet this objective: Task 1--relationship between effective intrapore diffusion coefficients, molecular size and pore geometry; Task 2--effects of solvent composition, solute concentration, and temperature on the molecular configuration and diffusion rate of coal and petroleum asphaltenes in catalyst pores; and Task 3--assessment of diffusional limitations in aged catalysts. Thismore » quarter, GPC (gel permeation chromatography) equipment was tested. In addition, asphaltenes were prepared by extracting a petroleum asphalt to obtain n-pentane insolubles. Two chemicals, THF and toluene, were chosen as solvents. Stock solutions of asphaltenes in solvents were prepared for the diffusion experiments. Some adsorptive uptake runs for asphaltenes on porous catalyst particles were performed. The results showed that uneven uptakes for asphaltene fractions with different molecular sizes occurred, with fractions of smaller molecules being more adsorbed. Knowledge of the transport properties of these materials into catalyst pores is necessary to allow rational design of catalysts and reaction operations associated with the upgrading of these asphaltenes.« less

  • ;
    Objective is to determine the relation between the size and shape of coal and petroleum macromolecules and their diffusion rates in catalyst pore structures. During this past quarter, experiments using narrow molecular weight polystyrenes and alumina extrudates made in the lab were carried out (cyclohexane was used as solvent). Freundlich and Langmuir constants for the adsorption equilibrium isotherms were determined for these materials. A Langmuir isotherm was a slightly better fit for the data. Results follow the expected trend and may be used to predict the adsorption isotherm for any polystyrene and alumina combination. 8 figs, 19 refs, 4 tabs.

  • ;
    The objective of this research is to determine the relationship between the size and shape of coal and petroleum macromolecules and their diffusion rates i.e., effective diffusivities, in catalyst pore structures. That is, how do the effective intrapore diffusivities depend on molecule configuration and pore geometry. This quarter, the investigators several approaches to check the effect of external mass transfer on the diffusion rate. Theoretical analyses and experimental results showed that the external mass transfer effect can be neglected for our experimental conditions.