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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Effects of Diluent Addition and Metal Support Interactions in Heterogeneous Catalysis: SiC/VPO Catalysts for Maleic Anhydride Production and Co/Silica Supported Catalysts for FTS

Kababji, Ala'a Hamed 23 March 2009 (has links)
This work begins with an introduction to catalysis focusing on heterogeneous systems and surface science phenomena. A study on the partial oxidation reaction of n-butane to maleic anhydride (MA) is presented in the first part. MA supplies are barely adequate for market requirements due to continued strong demand. Only slight improvement in catalytic performance would be welcome in the industrial community. The vanadium phosphorus oxide (VPO) catalyst was used in this work. The reaction is highly exothermic and the need to properly support the catalyst, not only for good dispersion but adequate heat dissipation is of crucial importance. For this, alpha-SiC commercial powders were used in synthesizing the catalyst due to its high thermal conductivity. Up to 25% MA yields were obtained and the reaction temperature was lowered by up to 28% using SiC/VPO mixed catalysts. The second part of this work is focused on the Fischer-Tropsch synthesis (FTS) process using cobalt silica supported catalysts. The main objective is the production of synthetic ultra high purity jet fuel (JP5). This is a very timely topic given the energy issues our world is facing. Almost all aspects of the FTS process have been extensively studied, however the effects of calcination temperature and silica support structure on the catalyst performance are lacking in literature. The catalysts were prepared using various silica supports. The catalysts had different drying and calcination temperatures. It was found that lower support surface area and calcination temperature catalysts exhibited higher activity due to lower support cobalt phase interaction. Co/silica catalysts calcined at 573K showed the highest CO conversion and the lowest CH4 selectivity. Catalysts prepared with 300m²/g support surface area exhibited 79.5% C5+ selectivity due to higher reducibility and less metal support interaction. The properties and performance of various prepared catalysts in both VPO and Co/silica systems are characterized by FTIR, XRD, BET, GC and XPS techniques. Theoretical FTS deactivation by sintering calculations and SiC/VPO particle temperature gradient calculations are presented as well. Finally, conclusions and future work on improving the yield and selectivity and scaling up the bench top setups are also presented.
2

On-line dynamic optimization and control strategy for improving the performance of batch reactors

Mujtaba, Iqbal M., Arpornwichanop, A., Kittisupakorn, P. January 2005 (has links)
No / Since batch reactors are generally applied to produce a wide variety of specialty products, there is a great deal of interest to enhance batch operation to achieve high quality and purity product while minimizing the conversion of undesired by-product. The use of process optimization in the control of batch reactors presents a useful tool for operating batch reactors efficiently and optimally. In this work, we develop an approach, based on an on-line dynamic optimization strategy, to modify optimal temperature set point profile for batch reactors. Two different optimization problems concerning batch operation: maximization of product concentration and minimization of batch time, are formulated and solved using a sequential optimization approach. An Extended Kalman Filter (EKF) is incorporated into the proposed approach in order to update current states from their delayed measurement and to estimate unmeasurable state variables. A nonlinear model-based controller: generic model control algorithm (GMC) is applied to drive the temperature of the batch reactor to follow the desired profile. A batch reactor with complex exothermic reaction scheme is used to demonstrate the effectiveness of the proposed approach. The simulation results indicate that with the proposed strategy, large improvement in batch reactor performance, in term of the amount of a desired product and batch operation time, can be achieved compared to the method where the optimal temperature set point is pre-determined.

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