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Hindered Diffusion of Asphaltenes at Elevated Temperature and Pressure Progress Report

Description: During this time period work proceeded in two main areas, the performance and analysis of petroleum asphaltene diffusional uptake experiments at 325 C and the preparation and testing of some new carbon based catalysts. In the first area, we performed studies of the diffusion controlled uptake of petroleum asphaltenes into a porous carbon catalyst at 325 C. The experiments were performed under an inert He atmosphere using 1-methylnaphthalene as a solvent. These purpose of these experiments was to extend our previous data which was taken and reported in the prior semi-annual report. These previous experiments were performed only up to a temperature of 250 C. A comparison between the experimental data and model simulated data showed that the mathematical model satisfactorily fitted the adsorptive diffusion of the petroleum asphaltenes onto the porous carbon at 325 C. Comparing with previous results, the adsorption constant continued to decrease with an increase in temperature for the petroleum asphaltene/1-methylnaphthalene system. Also during this time period, some carbon catalyst supports were prepared in our laboratory and several sets of data were obtained in adsorption-diffusion uptake experiments using a petroleum asphaltene with toluene as solvent. These data are presented in this report, although, complete fitting of the data with the mathematical model has not yet been performed. These calculations will be performed during the next time period.
Date: September 29, 2000
Creator: Guin, James A.; Ramakrishnan, Ganesh; Asada, Keiji & Mosley, Brian

Hindered Diffusion of Asphaltenes at Elevated Temperature and Pressure Progress Report

Description: During this past six months we continued our ongoing studies of the diffusion controlled uptake of coal and petroleum asphaltenes into a porous carbon catalyst. Toluene was used as the solvent for experiments at 20 C and 75 C while 1-methylnaphthalene was the solvent for the higher temperature experiments at 100 C, 150 C and 250 C. All runs were made at a pressure of 250 psi (inert He gas). Experiments were performed at 20 C and 75 C, for the petroleum asphaltene/toluene system. For the coal asphaltene/toluene system, experiments were performed at 75 C. Experiments were performed at 100 C, 150 C and 250 C for the coal asphaltene/1-methylnaphthalene system. A comparison between the experimental data and model simulated data showed that the mathematical model satisfactorily fitted the adsorptive diffusion of both the coal and petroleum asphaltenes onto a porous activated carbon. The adsorption constant decreases with an increase in temperature for both, the coal asphaltene/1-methylnaphthalene system as well as the petroleum asphaltene/toluene system. It was found that the adsorption constant for the coal asphaltene/toluene system at 75 C was much higher than that of the petroleum asphaltene/toluene system at the same temperature providing evidence of the greater affinity of the coal asphaltenes for the carbon surface. This could be due to the presence of more functional heteroatomic groups in the coal asphaltenes compared to their petroleum counterparts. Also during this time period, a new carbon catalyst support was prepared in our laboratory which will be used in adsorption experiments during the next phase of work.
Date: April 7, 2000
Creator: Guin, James A.; Ramakrishnan, Ganesh & Asada, Keiji

Hindered Diffusion of Asphaltenes at Elevated Temperature and Pressure Progress Report

Description: The mathematical model which we have developed previously for diffusion controlled adsorption was extended to allow for the inclusion of the effects of extraparticle film mass transfer resistance as embodied in a finite Sherwood number. A Mathcad based program was used to simulate the experimental data using summation of a large number of terms in the infinite series solution. Parametric studies and accompanying plots revealed that the effects of film resistance on the uptake process were found to increase in significance as the adsorption capacity parameter in the model decreased. In addition, the two carbon catalyst supports prepared in our own laboratory were tested for their diffusional characteristics in uptake experiments using petroleum asphaltenes dissolved in toluene at three temperatures. The resulting experimental data were simulated with the mathematical model developed in the report.
Date: April 1, 2001
Creator: Guin, James A.; Ramakrishnan, Ganesh; Asada, Keiji & Mosley, Brian

Hindered Diffusion of Asphaltenes at Elevated Temperature and Pressure Progress Report

Description: During this time period, we performed experiments to examine the effects of solvent composition on the diffusion controlled uptake of quinoline into alumina catalyst pellets. Of particular interest was the effect of solvent aromaticity on the diffusive uptake process. The uptake experiments were performed at a temperature of 300 C for the adsorptive diffusion of quinoline in a solvent mixture of mineral oil and 1-methyl naphthalene onto alumina catalyst pellets. These experiments were conducted in a 40 cm{sup 3} microautoclave, the use of which is more economical from both a purchasing and waste disposal standpoint due to the small quantities of solvents and catalysts utilized, and is also significantly safer at the higher temperatures. In order to study the effect of aromaticity of the solvent on the hindered diffusion-adsorption process, the experiments were performed at different volume fractions of 1-methyl naphthalene. Detailed calculations were made to estimate the effects of aromaticity, i. e., as reflected by the percentage of 1-methyl naphthalene in the solvent, on the diffusive properties of the solute. Model simulation results were then performed which showed that the mathematical model incorporating diffusion and adsorption mechanisms satisfactorily fitted the adsorptive diffusion of quinoline onto the alumina catalyst at 300 C with various solvent aromaticities. The logarithm of the adsorption constant at a particular volume fraction of 1-methyl naphthalene, obtained by simulating the experimental data with the model solution, was found to be linearly dependent on an aromaticity factor.
Date: April 1, 1999
Creator: Guin, James A. & Vadlamani, Surya

Hindered Diffusion of Asphaltenes at Elevated Temperature and Pressure Progress Report

Description: During this time period, experiments were performed to study the diffusion controlled uptake of quinoline and a coal asphaltene into porous carbon catalyst pellets. Cyclohexane and toluene were used as solvents for quinoline and the coal asphaltene respectively. The experiments were performed at 27 C and 75 C, at a pressure of 250 psi (inert gas) for the quinoline/cyclohexane system. For the coal asphaltene/toluene system, experiments were performed at 27 C, also at a pressure of 250 psi. These experiments were performed in a 20 cm{sup 3} microautoclave, the use of which is advantageous since it is economical from both a chemical procurement and waste disposal standpoint due to the small quantities of solvents and catalysts used. A C++ program was written to simulate data using a mathematical model which incorporated both diffusional and adsorption mechanisms. The simulation results showed that the mathematical model satisfactorily fitted the adsorptive diffusion of quinoline and the coal asphaltene onto a porous activated carbon. For the quinoline/cyclohexane system, the adsorption constant decreased with an increase in temperature. The adsorption constant for the coal asphaltene/toluene system at 27 C was found to be much higher than that of the quinoline/cyclohexane system at the same temperature. Apparently the coal asphaltenes have a much greater affinity for the surface of the carbon catalyst than is evidenced by the quinoline molecule.
Date: October 7, 1999
Creator: Guin, James A. & Ramakrishnan, Ganesh

Hindered Diffusion of Asphaltenes at Elevated Temperature and Pressure Progress Report

Description: During this final time period of the project, work was carried out in two areas. A major amount of effort was devoted to preparation of the final technical report for the project. The data taken on the project were organized and the asphaltenes, solvents, and catalysts used in the diffusional uptake experiments were organized into various systems. Since a large portion of the time for this report was spent on the preparation of the final technical report itself, the executive summary of the final technical report has been included in this semi-annual report as indicative of the effort during this time period. In addition to work on the final technical report for the project, a limited experimental study of dye adsorption into active carbon particles was performed by an undergraduate student in chemical engineering, Mr. Zachery Emerson. The objective of this study was to compare the diffusional uptake performance in two different types of vessels, a stirred glass cell and the tubing microreactor, for a simple dye-water-carbon diffusional uptake system. Due to time limitations, only qualitative conclusions were drawn from this study.
Date: October 1, 2001
Creator: Guin, James A. & Emerson, Zachery