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posao/doktorske studije na Texas A&M University u Qataru
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Author:  LazoZubic [ 26 Jan 2011, 09:52 ]
Post subject:  posao/doktorske studije na Texas A&M University u Qataru

ponuda za posao/doktorske studije na Texas A&M University u Qataru,
blize informacije mogu se dobiti kod Prof. Boskovica


“Kinetics of Fischer-Tropsch Synthesis on a Cobalt Catalyst” (Sep1, 2009- Aug 31, 2012)
1. Specific Aims
The specific goal of the project will be to determine kinetic parameters of Fischer-Tropsch synthesis (FTS) from experimental data in a stirred tank slurry reactor (STSR) under well defined conditions and over a wide range of process conditions. The STSR is an ideal choice of bench-scale reactor for catalyst testing, as it essentially mimics the slurry phase performance characteristics of the commercial-scale slurry bubble column reactor, and provides uniformity of temperature and concentrations in the reactor.
Kinetic models will be based on mechanistic studies from the literature and will take into account adsorption-desorption rates of reactants and product species. Concepts of the rate determining step and pseudo-steady state hypothesis will be used for reactive surface intermediates. Rigorous data reduction procedures and statistical methods will be employed to discriminate between various rival kinetic models and determine optimal values of kinetic parameters for each promoted catalyst investigated. The kinetic model developed in this study, coupled with the appropriate conservation equations and transport properties for a given reactor configuration (fixed bed or slurry bubble column reactor), would be useful for optimizing product yield, simulating the plant design, and evaluating the economic cost benefits.
Alumina supported cobalt (Co) catalysts, promoted with reduction promoters (Pt, Pd, Re, and Ru), will be used in this study, as these catalysts are often employed in slurry bubble column reactors for gas-to-liquids (GTL) processing. The impact of the reduction promoters on cobalt Fischer-Tropsch (FT) kinetics (reaction rates and product distribution) remains largely unknown. Catalyst characterization studies will provide insight on interactions between cobalt and promoters as well as between cobalt and the alumina support. Interactions between reduction promoter and cobalt will be studied using synchrotron methods (e.g., EXAFS, XANES), temperature programmed methods, and adsorption techniques, such as hydrogen chemisorption with pulse reoxidation. Particular effort will be made to determine which, if any, of the reduction promoters form alloys with cobalt, and whether such alloying benefits catalytic performance.
Task 1. Literature Review and Development of Kinetic Models
Kinetic models will be formulated utilizing the current state-of-the-art understanding of reaction mechanisms for the formation of reaction intermediates and hydrocarbon products. Models will be based on adsorption/desorption phenomena for reactants and product species. These models will be continually updated on the basis of experimental data obtained in Task 3, and subsequent data analysis conducted in Task 5. (TAMUQ, ongoing task, Years 1-3).
Task 2. Catalyst Synthesis and Characterization
Alumina supported cobalt (Co) catalysts promoted with noble metals (Re, Pt, Pd or Ru) will be synthesized utilizing equipment and procedures developed at CAER. Catalyst characterization by BET surface area, chemisorption, TPD, TPO, TPR and XRD will be conducted at CAER, whereas EXAFS and XANES experiments will be performed at Brookhaven National Laboratory by CAER personnel, depending on beamtime availability (CAER, ongoing task, Years 1-3).
Task 3. Experiments in a Stirred Tank Slurry Reactor
Experiments will be conducted in a 1 dm3 STSR with at least four catalysts over a wide range of process conditions of industrial significance. Baseline conditions will be repeated periodically to assess the extent of catalyst deactivation. Some replicate experiments at the same process conditions will be made to estimate experimental errors. (CAER, ongoing task, Years 1-3).
Task 4. Quantum Mechanics Calculations
THIS WILL NOT BE DONE.
Task 5. Model Discrimination and Parameter Estimation
The Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach and the concept of rate limiting step results in a large number of competing kinetic models. Discrimination between the rival models will be based upon the quality of fit, supplemented with statistical tests on parameter values and the physico-chemical meaningfulness of the estimated parameter values. (TAMUQ, ongoing task, Years 1 – 3).
Research Team
We have an excellent team of experienced experts to conduct and direct the proposed research. Professors Bukur (TAMUQ) and Davis (CAER) have actively carried out FT research over the last three decades.
Professor Bukur has been engaged in various aspects of slurry phase FTS process development (slurry bubble column reactor design, two- and three-phase hydrodynamic studies, slurry reactor modeling, kinetics of FTS, synthesis and testing of improved iron FT catalysts) since 1980. He has been among the pioneers in the development of comprehensive mechanistic based kinetic models for FTS and continues to make contributions in this area.
Professor Davis (PI at CAER) has made significant contributions in the field of FT catalysis including mechanistic and kinetic studies over iron and cobalt catalysts. Dr. Gary Jacobs (Co-PI at CAER) has considerable experience in characterization and testing of FT catalysts. CAER personnel have much experience in the operation of FT reactors and the characterization of the reaction products. Currently the CAER personnel operate 20 stirred tank slurry reactors and analyze the products produced during their operation. Most of these reactors are currently operated for companies and generate data that are provided to the companies for their use. Also, the CAER personnel have developed analytical procedures for accurate quantification of FT products. The FT reaction produces a broad spectrum of product, and its quantification is a non-trivial task.
Also we will benefit from the expertise and experience of two collaborators on this project. Dr. Froment (Research Professor at TAMU) has applied methodology for kinetic model discrimination and parameter estimation to a large number of complex reaction systems, including the FTS reaction. He will provide advice on kinetic model development and parameter estimation.

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