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Product Crystals (product + crystal)
Selected AbstractsStructural transformations in organic crystals during photochemical reactionsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2004Ilona Turowska-Tyrk Abstract In the 1980s and 1990s, x-ray studies of the photochemical reaction course in crystals dealt with the analysis of changes in cell constants or movements of atom groups inside molecules. This review presents the results of crystallographic studies on the monitoring of the behaviour of whole molecules in organic crystals during photochemical reactions. Papers on this subject started to appear only a few years ago. The studies showed quantitatively that reactant and product molecules do not take a fixed position in a crystal during the reaction. The product molecules move smoothly to a position assumed in the pure product crystal and the reactant molecules move from a position occupied in the pure reactant crystal. Moreover, with the reaction progress the adjacent reactant molecules gradually come closer and change their mutual orientation to resemble the product. The analysis of the photoreaction kinetics in crystals is also presented. Copyright © 2004 John Wiley & Sons, Ltd. [source] Preparation of enantiomeric gossypol by crystallization,CHIRALITY, Issue 6 2003Michael K. Dowd Abstract Large enantiomorphic crystals of gossypol-acetone (1:3) were grown from acetone solutions of rac -gossypol-acetic acid (1:1) at 4°C. By controlling the initial gossypol concentration, crystallization time, and solution volume, single crystals were grown that weighed >50 mg, equivalent to >37 mg of enantiomeric gossypol. Even larger crystals were possible, but it was difficult to produce these reliably without contamination of the antipode. Essentially all of the acetone within the crystal form was removed by storing the crystals under vacuum for 3,4 days. By employing these techniques, gram quantities of enantiomeric gossypol were prepared in high chemical and optical purity. Based on measured and reported optical rotations, the optical purity of samples prepared by crystallization was greater than the optical purity of samples prepared by chromatographic separation of gossypol-amine diastereomers. The principal limitation of crystallization as a preparative method is the need to determine the chirality and purity of each product crystal. Nevertheless, the method competes favorably with preparative-scale chromatographic procedures. Chirality 15:486,493, 2003. Published 2003 Wiley-Liss, Inc. [source] Process control and monitoring of reactive crystallization of L -glutamic acidAICHE JOURNAL, Issue 8 2010Hannu Alatalo Abstract The aim of the present study was to investigate feedback control of a reactive crystallization process. The present study built up a control structure needed to control the driving force of reactive crystallization using the feed rate of added acid. The concentration of the crystallizing compound and pH was used to compute feedback in the closed-loop control of semi-batch precipitation. The concentration of L -glutamic acid was determined from measured MID-IR ATR-FTIR spectra based on a multivariate model. Dynamic change of set value was based on the mass of added sulfuric acid and pH. The studied properties of the product crystals were polymorphism and crystal size. The polymorphic composition was analyzed with a Raman spectrometer and was expressed by mass fraction of the ,-polymorph. The obtained results showed that the developed feedback process control system allows effective control of forming of polymorphs. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Workflow for managing impurities in an integrated crystallization processAICHE JOURNAL, Issue 3 2010Yuen S. Cheng Abstract A workflow consisting of experiments, modeling, and synthesis is presented for managing the impurity content in the product crystals of a crystallization process taking into consideration the entire train of crystallization and downstream processing steps. Experiments on solid,liquid equilibrium, impurity inclusion, washing, and deliquoring are designed in such a way that the experimental data or the model parameters derived from these data can be readily used for process design. Guidelines for experimental design and tradeoffs in process synthesis are discussed. The workflow is illustrated using the purification of Vitamin C (ascorbic acid) as a case study. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Multiobjective optimization of semibatch reactive crystallization processesAICHE JOURNAL, Issue 5 2007Debasis Sarkar Abstract The determination of the optimal feed profiles for a reactive crystallizer is an important dynamic optimization problem, as the feed profiles offer a significant control over the quality of the product crystals. Crystallization processes typically have multiple performance objectives and optimization using different objective functions leads to significantly different optimal operating conditions. Therefore, a multiobjective approach is more appropriate for optimization of these processes. The potential for multiobjective optimization approach is demonstrated for semibatch reactive crystallization processes. The multiobjective approach usually gives rise to a set of optimal solutions, largely known as Pareto-optimal solutions. The Pareto-optimal solutions can help the designer visualize the trade-offs between different objectives, and select an appropriate operating condition for the process. A well known multiobjective evolutionary algorithm, the elitist nondominated sorting genetic algorithm, has been adapted to illustrate the potential for the multiobjective optimization approach. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] | ||||||||||