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  System and method for determining optimal reaction parameters using continuously running processUSPTO Application #: 20060234381Title: System and method for determining optimal reaction parameters using continuously running process Abstract: A reaction system enables a plurality of optimization experiments for a reaction to be performed continuously, to enable optimal reaction parameters to be determined. Dilution pumps are included to automatically vary the solvent mixed with reactants so a concentration of each reactant can be selectively varied. The reactants are introduced into a reaction module selectively coupled to residence time chambers or directly to an analytical unit. The analytical unit determines the yield and/or quality for each optimization experiment, enabling optimal parameters to be determined. Residence time chambers can be employed sequentially to enable total residence time to be varied. The controller performs as many experiments as required to enable each parameter to be varied according to a predefined testing program and can redefine a testing program based on the results from previous experiments. At least two reaction parameters can be varied according to periodic functions to further enhance analytical efficiency. (end of abstract)
Agent: Law Offices Of Ronald M Anderson - Bellevue, WA, US Inventors: Thomas Jochen Schwalbe, Volker Autze, Sebastian Oberbeck, Ansgar Kursawe, Kemal Hunkar Sahin USPTO Applicaton #: 20060234381 - Class: 436034000 (USPTO) Related Patent Categories: Chemistry: Analytical And Immunological Testing, Rate Of Reaction Determination The Patent Description & Claims data below is from USPTO Patent Application 20060234381. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application is a divisional of a prior co-pending U.S. patent application Ser. No. 10/824,186, filed on Apr. 14, 2004, which itself is based on a prior provisional patent application Ser. No. 60/462,860, filed on Apr. 14, 2003, the benefit of the filing dates of which is hereby claimed under 35 U.S.C. .sctn. 119(e) and 35 U.S.C. .sctn. 120. FIELD OF THE INVENTION [0002] This invention generally relates to a chemical processing apparatus, and more specifically, to a continuously operating system configured to vary reaction parameters over time in order to identify optimal reaction parameters. BACKGROUND OF THE INVENTION [0003] Apparatus for controlling and optimizing the production of chemical substances are well known in the prior art. Reaction parameters affecting the quantity and quality of the product generated include concentration levels of each reactant, temperature conditions, flow rates, and residence times. Varying one or more of the reaction parameters generally results in a change in product yield. It is therefore advantageous to optimize such reaction parameters to maximize production and quality. [0004] A basic prior art optimization procedure is as follows. Initial reaction conditions from an initial synthesis are used as a starting point. Using temperature, reaction time and concentrations at the values determined in the initial synthesis, three experiments with different equivalents (i.e. different stoichiometric ratios) are conducted. For example, where the initial synthesis was based on using a 1:1 ratio of a first reactant and a second reactant, ratios such as 1:1.1, 1:1.2, 1.1.3; or 1.1:1, 1.2:1, and 1.3:1 could be employed. In a second set of experiments, three different temperature conditions are applied. A third and fourth set of three experiments each are also performed, changing other variables in each set. After twelve such experiments have been performed (i.e., four sets of three experiments), the results are reviewed, and optimized reaction parameters are defined based on the data collected from the twelve experiments. An additional set of twelve experiments can then be performed, similarly varying the optimized parameters defined by the first series of experiments. In such an optimization procedure, typically twenty four experiments are required for a first optimization of reagent equivalents, temperature conditions, reaction time, and reagent concentration for a given reaction, as each experiment is repeated to check the reproducibility of the results. One disadvantage of this approach is that interactions between these parameters are difficult to quantify. [0005] Because of this difficulty, process optimization methods referred to as statistical design experiments have been developed. The goal of such methods is to model an equation in order to couple process variables with process results (i.e., the yield of a reaction). A well known two-value approach requires 2.sup.n+1 experiments, where n is the number of variables. Each variable is employed at two different values, and an additional experiment is performed using the mean of each variable (as a control to determine if the behavior is linear). Typically, every experiment is repeated to estimate the reproducibility. For the above-mentioned case, (2.sup.4+1)*2=34 experiments are needed. The disadvantage of such an empirical approach is the fact that the success of the optimization is largely based on how well each of the two values for each variable is selected. Selecting levels that are close together results in only small improvements in optimization being achieved; so that it is likely an additional 2.sup.n+1 sets of experiments will be required. Selecting values that are far apart results in a risk that one or more variables will exceed a critical parameter, which will significantly affect yields (such as exceeding a reaction temperature beyond which yield drops sharply or no reaction takes place). When this result occurs, the initial set of 2.sup.n+1 experiments are of little value, and the experiments must be repeated after different values have been selected. [0006] Furthermore, if the mean value experiment indicates that non linear behavior exists, then it is necessary to determine the impact of quadratic terms. This step can only be assessed by expanding the design of experiments to 3.sup.n experiments, where the three values are defined as the lower and upper bounds, as well as the mean values of these bounds. For the analysis of a four-parameter system, this approach implies a total of 3.sup.4=81 experiments will be required. Preferably, each set is repeated to validate reproducibility, so that a total of 162 experiments must be performed. In practice, some terms and factors in an equation model are often identical, and it is not unusual for the 81 experiments noted above to be reduced to about 40 experiments (without the duplication for validation of reproducibility). [0007] This analysis can be performed efficiently using software packages that determine the values for each experiment, the order in which these values should be changed, and evaluate the outcome to provide a mathematical relationship between the performance criteria being investigated and the variables to be adjusted to optimize the performance. Today, equipment for parallel batch experiments is also available, so that a number of experiments can be conducted at the same time. These parallel analysis systems are based on matrices of reaction modules in which the chemicals to be analyzed are input manually at variable concentrations. Some reaction conditions, such as temperature, are often identical for all the vessels being analyzed at any given time due to the physical dimensions and limitations of the system. The reaction duration is also generally identical for efficient analysis. Due to the discrete nature of experimentation, the evaluation at the end of the experiment has to be performed for all reaction modules separately, to determine the performance of each system. These results are analyzed off-line as one data set for a fixed temperature and reaction duration. Experimentation at different reaction temperatures requires the generation of another matrix with the same reactants, and repetition of the experiments at the new temperature, as well as a new analysis of the collected data. Once the analysis for concentrations and concentration ratios at different temperatures is completed, the same set of experiments can be performed to determine the effect of reaction time on yield. The repetitiveness of such experiments (i.e., the batch-like processing) is enforced due to the matrix-like structure of the parallel reaction vessels. [0008] While such methods can enable optimized reaction parameters to be achieved, it would be desirable to provide a method and apparatus based on optimizing reactions parameters using a continuously running system, as opposed to using the batch-based testing of the prior art. SUMMARY OF THE INVENTION [0009] The present invention employs a continuously operating system that enables reaction parameters to be varied over time, to optimize a chemical reaction. The time to achieve optimization is thus dramatically reduced compared to the prior art batch-based optimization techniques discussed above. [0010] The system employed includes a reaction module (preferably including a micro reactor, so that minimal reactant volumes are required), a plurality of residence time chambers, fluid lines coupling the micro reactor to the residence time chambers, fluid lines for introducing reactants into the reaction module, and fluid lines for directing a product exiting the reaction module into either residence time chambers or to an analytical unit. Pumps are employed to move fluid through the system, and temperature control is achieved using heat exchangers. The system is controlled by a processor, which in one preferred embodiment is implemented using a personal computer. The analytical unit is configured to analyze each product produced by the system. Based on the analysis, the controller identifies the process conditions that provide the highest yield of product. [0011] For optimization of reactions, the relative concentrations of reactants must be varied. Prior art optimization methods generally require batches of reactants at different concentrations levels to be prepared before a set of reactions are executed. In the present invention, dilution pumps are coupled to reactant feed lines and a solvent supply. The controller can vary the amount of solvent introduced into a reactant supply line, thereby automatically varying the concentrations of the reagents. Thus, the manual preparation of the reagent solutions at different concentrations of the prior art is eliminated. Not only does elimination of manually preparing reagent solutions of differing concentrations save time, but the fact that the reactant supply vessels need not be physically disconnected from the system eliminates problems associated with pausing the reaction operation to change reactant supply vessels. The controller can be configured to vary concentration randomly, or more preferably, according to a predefined protocol. The ability to manipulate flow rates of individual reactants, and the ability to add diluting solvents to manipulate the concentrations of each reactant enable an infinite number of combinations of flow rates and reactant concentrations to be achieved. The flexibility of the reactant pumps and dilution pumps enables concentration variations to be explored continuously, whereas in the prior art, after a first set of experiments were executed, new solutions having different concentrations had to be prepared before additional optimization experiments could be performed. [0012] Each reactant (generally at least two reactants are employed, although those of ordinary skill in the art will recognize that other types of reactions can be optimized, such as those using a single reactant and a catalyst, or three or more reactants) is introduced into the reaction module, where the reactants are mixed under the desired temperature conditions, and the reaction is initiated. The combined reactants are then directed into a first one of the plurality of residence time chambers. The mixed reactants are pumped through the residence time chambers for a period of time sufficient to enable the reaction to be completed. Adjustments in the residence time can be achieved by modifying the flow rates of both reactants. The residence time chambers are employed sequentially, such that mixed reactants/product exiting one residence time chamber are directed to a downstream residence time chamber for additional holding time. Residence time can also be varied by employing no residence time chambers for some reactions, some residence time chambers for other reactions, and all residence time chambers for still other reactions. Significantly, major changes in residence time can be analyzed efficiently by selectively changing the number of residence time chambers used for a particular reaction. Routing a product through one or more residence time chambers is achieved using appropriate valving. Through intelligent valve switching algorithms, information on multiple residence times can be obtained efficiently. In contrast, prior art optimization techniques either explored incremental changes in residence times, or explored larger changes by removing or installing residence time chambers, which generally required bringing the system to a temperature where an operator can install/remove a residence time chamber, purge both the heat transfer fluid and reactant/product liquids, reassemble the system, and heat up the system up to operating conditions before additional experimentation can be performed. [0013] The present invention encompasses methods for using such a continuously operating system for optimization of reaction parameters, or continuous kinetic parameter evaluations of chemical reactions. The primary goal of such methods is the efficient and rapid determination of optimal reaction performance criteria, such as yield, conversion, and selectivity. Operating conditions such as temperature, reactant concentrations, reactant concentration ratios, and residence times can be modified. Using these operating conditions and the resulting performance data, it is possible to calculate important chemical reaction parameters, such as activation energies, and reaction orders for the reactants being analyzed. Since these parameters are independent of the reactor used, the information can be used for numerically optimizing the performance of the reaction in any vessel. [0014] The optimization experiments can be performed according to several different protocols. In one embodiment, testing conditions are predefined, and the system is operated continuously until the predefined range of each variable is tested. The optimal reaction conditions providing the maximum performance can be evaluated after the entire range of parameters has been analyzed and all data has been collected. In another embodiment, the optimization can be performed in real-time. In this mode of operation, the performance information is reviewed as soon as it is obtained, to determine if new testing conditions can be defined based on the data obtained from previous experiments. In yet another embodiment, specific reaction parameters, such as temperature, concentration, and reactant equivalence are varied according to periodic functions, while data are continuously collected. These data can then be reviewed to identify optimal operating conditions. Reactant equivalence (stoichiometric ratio) can be varied based on changes to concentrations of individual reactants, as well as by manipulating flow rates. BRIEF DESCRIPTION OF THE DRAWING FIGURES [0015] The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: [0016] FIG. 1A schematically illustrates a continuous flow optimization system in accord with the present invention; [0017] FIG. 1B schematically illustrates the system of FIG. 1A with valves having been manipulated to direct a flow of fluid exiting a reaction module to an analytical unit, thus bypassing each residence time chamber; [0018] FIG. 1C schematically illustrates the system of FIG. 1A with valves having been manipulated to direct a flow of fluid exiting the reaction module to a first residence time chamber, and then to the analytical unit, thus bypassing the second and third residence time chambers; [0019] FIG. 1D schematically illustrates the system of FIG. 1A with valves having been manipulated to direct a flow of fluid exiting the reaction module to the first residence time chamber, then to the second residence time chamber, and then to the analytical unit, thus bypassing the third residence time chamber; Continue reading... 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