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Separation of Fischer-Tropsch wax from catalyst by supercritical extraction. Quarterly progress report, October 1, 1996--December 31, 1996

Description: One of the major objectives of this research project is to predict the phase behavior of model wax compounds in dense supercritical fluids such as hexane. Because initial results with the SAFT equation have been less promising than expected, the group at North Carolina State University has focused their recent attention on cubic equations of state, in particular the Peng-Robinson and Soave-Redlich-Kwong versions. The focus of this work has been on developing correlations that can be used to predict binary interaction parameters (i.e., k{sub ij}s) for a given binary wax-solvent system. As a first step, k{sub ij}s were first calculated from experimental data on systems containing alkanes between nC{sub 4} and nC{sub 23} at temperatures between 25 and 357{degrees} C. Attempts were then made to correlate these parameters with specific pure component properties of the alkanes of interest. Reasonably good agreement between experimental and predicted k{sub ij}s was found using a correlation that incorporates both temperature and the molecular size of the alkanes. As phase equilibrium data becomes available for higher molecular weight model wax compounds, the ability of the correlation to handle such systems will need to be tested. The phase equilibrium apparatus is currently undergoing modifications that will allow the system to run components that are solids at ambient temperatures. Some problems are still being resolved, as the heavy component tends to precipitate in the sample lines. Modifications have been made that should allow the system to operate reliably.
Date: January 1, 1997
Creator: Joyce, P.C. & Thies, M.C.
Partner: UNT Libraries Government Documents Department

Separation of Fischer-Tropsch Wax from Catalyst by Supercritical Extraction

Description: The proposed process of using supercritical fluid extraction in conjunction with the Fischer-Tropsch slurry bubble column reactor has been examined using the ASPEN Plus simulator by the research group at North Carolina State University. Qualitative results have been obtained for varying the following process parameters: solvent-to-wax ratio, solvent type (pentane or hexane), extraction temperature and pressure, and recovery unit temperature and pressure. The region of retrograde behavior was determined for pentane and hexane. Initial results show hexane to be the superior solvent; compared to pentane, hexane requires lower quantities of solvent makeup (the amount of solvent which needs to be added to account for solvent that cannot be recycled), and also results in a lower average molecular weight of slurry in the reactor. Studies indicate that increasing the extraction temperature, extraction pressure, recovery temperature, or solvent to wax ratio decreases the amount solvent makeup required. Decreasing the recovery pressure was found to decrease the makeup flowrate.
Date: January 31, 1997
Creator: Joyce, P.C. & Thies, M.C.
Partner: UNT Libraries Government Documents Department

Microwave processing improvements for methane conversion to ethylene

Description: This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project`s objective was to investigate microwave enhanced catalysis. Published work by others had demonstrated improved selectivity in microwave-driven catalytic conversion of 2-methylpentane to its isomers. We reproduced their experiment, discovering that there is no improvement in selectivity using microwaves. The selectivity at a given conversion was the same for both microwave heated and conventionally heated catalyst beds. Meetings with the authors of the previously published work led to the conjecture that their catalyst was not being prepared properly, leading to anomalously low selectivity for their conventional heating runs. An optical temperature diagnostic suitable for use on a microwave applicator was developed and characterized in this project. This pyrometer can measure the temperature of small scale features on the catalyst bed, and it has a fast response that can follow the rapid heating often encountered in a microwave processing system. The behavior of the microwave applicator system was studied, and theoretical models were developed to yield insight about the stability and control of the system.
Date: August 1, 1997
Creator: Stringfield, R.; Ott, K.; Nelson, E.; Anderson, G.; Chen, Dye-Zone; Dyer, T. et al.
Partner: UNT Libraries Government Documents Department