Singular Points of Reactive Distillation Systems

For the conceptual design of countercurrently operated reactive distillation columns, fast methods are needed to estimate potential top and bottom products. The possible column bottom product composition can be determined from the stable singular points of a batch reactive reboiler. In a similar manner the top product composition can be obtained from the stable singular points of a batch reactive condenser. Geometrically, the singular points of both batch processes are located on a common potential singular point surface (PSPS) whose trajectory depends on the reaction stoichiometry and the phase equilibria. At the singular points, the PSPS intersects a reaction kinetic surface that is dependent on the reaction rate expression and the phase equilibrium of a reference component. Based on the singularity analysis, a single-feed reactive distillation column can be designed. Several hypothetical and real reaction systems are analyzed to illustrate the singularity analysis and the design procedure. Copyright © 1999–2013 John Wiley & Sons, Inc. All Rights Reserved. [accessed 2013 August 15th

Carbon Dioxide Separation with Novel Microporous Metal Organic Frameworks

The goal of this program was to develop a low cost novel sorbent to remove carbon dioxide from flue gas and gasification streams in electric utilities. Porous materials named metal-organic frameworks (MOFs) were found to have good capacity and selectivity for the capture of carbon dioxide. Several materials from the initial set of reference MOFs showed extremely high CO{sub 2} adsorption capacities and very desirable linear isotherm shapes. Sample preparation occurred at a high level, with a new family of materials suitable for intellectual property protection prepared and characterized. Raman spectroscopy was shown to be useful for the facile characterization of MOF materials during adsorption and especially, desorption. Further, the development of a Raman spectroscopic-based method of determining binary adsorption isotherms was initiated. It was discovered that a stronger base functionality will need to be added to MOF linkers in order to enhance CO{sub 2} selectivity over other gases via a chemisorption mechanism. A concentrated effort was expended on being able to accurately predict CO{sub 2} selectivities and on the calculation of predicted MOF surface area values from first principles. A method of modeling hydrolysis on MOF materials that correlates with experimental data was developed and refined. Complimentary experimental data were recorded via utilization of a combinatorial chemistry heat treatment unit and high-throughput X-ray diffractometer. The three main Deliverables for the project, namely (a) a MOF for pre-combustion (e.g., IGCC) CO{sub 2} capture, (b) a MOF for post-combustion (flue gas) CO{sub 2} capture, and (c) an assessment of commercial potential for a MOF in the IGCC application, were completed. The key properties for MOFs to work in this application - high CO{sub 2} capacity, good adsorption/desorption rates, high adsorption selectivity for CO{sub 2} over other gases such as methane and nitrogen, high stability to contaminants, namely moisture, and easy regenerability, were all addressed during this program. As predicted at the start of the program, MOFs have high potential for CO{sub 2} capture in the IGCC and flue gas applications

Effects of kinetics on reactive distillation

In the last decade, there has been growing success at developing commercial processes which combine reaction and separation. This technology offers the potential of significantly improved economics, reduced emissions and direct energy integration between the reaction and separation processes in the system. In this dissertation, we develop tools to analyze and design reactive distillation systems with multiple kinetically controlled chemical reactions. Residue curve maps are a useful tool in the conceptual design of distillation systems. They are the trajectories on a phase plane of the composition in a still during a simple distillation or open evaporation experiment. We derive a system of equations to model kinetically controlled reactive simple distillation. From these equations we define a dimensionless parameter, the Damkohler number, which is a measure of the amount of reaction in the system. A Damkohler number of zero implies a non-reactive system while a Damkohler number approaching infinity implies a system in which there is simultaneous reaction and phase equilibrium. The structure of the residue curve map determines whether a reactive distillation is feasible, and the structure changes with the Damkohler number. A good knowledge of the reaction kinetics is important for the analysis and design of kinetically controlled reactive distillation systems. Closed batch isothermal kinetic experiments and binary non-reactive adsorption experiments were performed for the esterification of acetic acid with methanol on the heterogeneous Amberlyst 15W catalyst. The kinetic data were then fitted with a Langmuir-Hinshelwood/Hougen-Watson model and the model was used to predict the course of simple distillation experiments. The structure of a residue curve map is determined by the composition and temperature of the solutions of the simple distillation equations. We developed a systematic way of studying the effect of kinetics on the structure of the residue curve maps by performing a bifurcation analysis of the simple distillation equations as a function of the Damkohler number starting with the non-reactive case where the singular points are the pure components and the non-reactive azeotropes. Batch reactive distillation combines the advantages of reactive distillation and batch processes. We have developed a simplified model that can be used to quickly screen through design alternatives and operating strategies to develop estimates for the number of stages, distillate policies, the initial feed ratios in the still, etc. Once promising designs and policies have been identified, a more detailed simulation at a finite reflux and with a finite holdup in the column can be performed for the conditions of interest. This model was applied to the study of the esterification of acetic acid and butanol to produce butyl acetate. For this process, we have suggested a new operating policy which will increase the purity of the main product without introducing additional purification steps. The results were also compared to those from a more detailed model

Kinetics & Mechanism of Cerium(IV) Oxidation of Cinnamic & Substituted Cinnamic Acids

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