The application of fractal porous media (FPM) theory in melt crystallization is a novel concept to be developed extensively, which has received wide attention in recent years. The primary advantage of FPM theory is the ability to describe the complex, random structure of porous crystal layers with fewer parameters. This review will introduce aspects of the property analysis of porous crystal layers grown in the heterogeneous thermal field. For the first time, the existing flow model of FPM theory will be outlined and an overview of the general issues, model modification, and validation of the separation process in melt crystallization will be discussed in detail. Kinetic and model research on separation evaluation and optimized operation will be mentioned to unfold the promising application field. Finally, the paper will conclude with perspectives on the future research directions, key challenges, and issues in this area.

Progress in the Application of Fractal Porous Media Theory to Property Analysis and Process Simulation in Melt Crystallization

Clindamycin phosphate (CP), an antibacterial agent, has been reported to form several solid-state forms. The crystal structures of two CP solvates, a dimethyl sulfoxide (DMSO) solvate and a methanol/water solvate (solvate V), have been determined by single crystal X-ray diffraction. The properties and transformations of these forms were characterized by powder X-ray diffraction, Single-crystal X-ray diffraction, differential scanning calorimetry, thermo gravimetric analysis, hot-stage microscopy, and dynamic vapor sorption. Very different hydrogen bonding networks exist among the host-host and host-solvent molecules in the two crystal structures, resulting in different moisture stabilities. The thermal stabilities of the two solvates upon heating and desolvation were also studied. When the temperature was above the boiling point of methanol, solvate V converted to a polymorphic phase after a one step desolvation process, whereas the desolvation temperature of the DMSO solvate was below the boiling point of DMSO. At the relative humidity above 43%, the DMSO solvate transformed to a hydrate at 25 °C. In contrast, solvate V did not transform at any of the humidities studied.

Solvates and polymorphs of clindamycin phosphate: Structural, thermal stability and moisture stability studies

Developing a green and sustainable technique seems necessary when facing an increase in the environmental burden. Layer melt crystallization (LMC) is recognized as an environmentally friendly separation technique because of its lower energy consumption and chemical waste emission. For the first time, this study applied LMC to prepare the high-purity isophthaloyl chloride (IPC), which is an important chemical intermediate in the synthesis of fibers. Under the optimal trajectory, the purity of IPC could improve from 97.811 to 99.381%, which reached the standard of subsequent production. Meanwhile, theoretical models were established and combined with the experimental results to visualize the crystallization and sweating processes. The fractal porosity model was used to describe the crystal layer structure, in which the pore structure could provide the adsorption sites for inclusion components and channels for the melt flow. Crystallization and sweating process kinetics models were established to explore the crystal layer growth and sweating melt flow characteristics. The distribution coefficient and the impurity removal rate were used to describe the separation efficiency. The interfacial solute distribution factor and the mass transfer coefficient were used to explore the solute and impurity distribution rules. The mechanisms of the mass flow were revealed. Finally, four different crystallizer structures were designed to intensify the heat and mass transfer, which significantly improved the separation efficiency. 

Highly Efficient and Solvent-Free Purification Technique and Model Study of Layer Melt Crystallization

Intensification design of green crystallization separation: process optimization and technology coupling

The invention discloses a refining method of a vitamin C. The method comprises the steps of dissolving a vitamin C crude product in water and discoloring by using activated carbon, sequentially filtering the discolored vitamin C solution through a plate filter, a winding filter, a first micropore filter and a second micropore filter to reduce the impurity content, introducing the filtered vitamin C solution into a crystallization tank for segmented cooling crystallization, carrying out airtight filtration, washing and drying on the crystallized vitamin C solution, and screening the dried vitamin C particles to obtain refined vitamin C. The method disclosed by the invention is convenient in operation, low in energy consumption and good in discoloring effect and has the advantages of reducing the light absorption value of the finished vitamin C, improving the purity of the finished product and shortening the refining time; the obtained refined vitamin C is stable in quality; the purity of the finished product can be up to 99.9%; the product yield can be up to 99.5%, the baking extinction value is less than or equal to 0.02; and the impurity degree is less than or equal to 8 in each 3g.

Refining method of vitamin C

In this paper a porous media seepage model was applied to analyze the permeability and study the seepage process of crystal pillar formed in the preparation of electronic grade phosphoric acid (EGPA). By inspecting the seeping process, the structure parameter of crystal pillar could be obtained. Two basic ideal models (perfectly separated model and perfectly connected model) were presented and a characterized factor φ was introduced to modify the model. A good simulation result was obtained which met the experiment result well. The relationship between φ and permeability were also discussed. The characterized factor φ showed potential application on optimizing process.

Permeability analysis and seepage process study on crystal layer in melt crystallization with fractal and porous media theory

The present invention relates to an equipment and its method for preparing vitamin C crystal by adopting fine crystal eliminating method. Said equipment nicludes crystallizer with jacket, fine crystal dissolving device, condensation device, vacuum system and distillate collecting device. Said invention also provides the concrete structure of the above-mentioned every device and their connection mode, also provides the concrete steps of said method.

Equipment and method for preparing crystal of vitamin C by fine crystal removing method

Penicillin sulfoxide is the intermediate for the synthesis of 7-amino-3-desacetoxycephalosporanic acid which is one of the most important nucleuses of cephalosporin antibiotic. In this contribution, two crystal structures of penicillin sulfoxide (forms I and II) were determined by X-ray diffraction, and their thermotropic properties were investigated by differential scanning calorimetry (DSC). Furthermore, the transformation of form II to form I was studied quantitatively by Raman spectroscopy, and its rates at different temperatures were determined. The results indicate that penicillin sulfoxide is more stable as form I, and the temperature plays an important role in the crystal transformation.

Polymorphism and crystal transformation of penicillin sulfoxide

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Permeability analysis and seepage process study on crystal layer in melt crystallization with fractal and porous media theory

Equipment and method for preparing crystal of vitamin C by fine crystal removing method

Polymorphism and crystal transformation of penicillin sulfoxide