Continuous Cooling Crystallization in a Coiled Flow Inverter Crystallizer Technology—Design, Characterization, and Hurdles

Continuous small-scale production is currently of utmost interest for fine chemicals and pharmaceuticals. For this purpose, equipment and process concepts in consideration of the hurdles for solids handling are required to transfer conventional batch processing to continuous operation. Based on empirical equations, pressure loss constraints, and an expandable modular system, a coiled flow inverter (CFI) crystallizer with an inner diameter of 1.6 mm was designed. It was characterized concerning its residence time behavior, tested for operation with seed crystals or an ultrasonic seed crystal unit, and evaluated for different purging mechanisms for stable operation. The residence time behavior in the CFI corresponds to ideal plug flow behavior. Crystal growth using seed crystals was demonstrated in the CFI for two amino acids. For fewer seed crystals, higher crystal growth rates were determined, while at the same time, secondary nucleation was observed. Feasibility for the interconnection of a sonicated seeding crystal unit could be shown. However, the hurdles are also identified and discussed. Prophylactic flushing combined with a photosensor for distinguishing between solvent and suspension phase can lead to stable and resource-efficient operation. The small-scale CFI technology was investigated in detail, and the limits and opportunities of the technology are presented here.

INFLUENCE OF CRYSTAL SEED TECHNIQUE ON RHEOLOGICAL PROPERTIES OF SUCROSE-FREE CHOCOLATE MASSES

Темперирование шоколадных масс – это процесс, обеспечивающий кристаллизацию какао масла в устойчивой β-модификации во избежание жирового поседения готового изделия. Приведены результаты исследований по применению затравочных кристаллов βV-формы при темперировании шоколадной массы с сахарозаменителями инулином и комплексом инулин–стевиозид взамен сахарозы. Установлено, что кристаллы βV-формы обеспечивают получение шоколадной массы с устойчивой β-модификацией какао масла вне зависимости от типа подсластителя. Определены оптимальные режимы процесса затравки кристаллов βV-формы в технологии получения шоколадной массы. Изучено влияние синергизма способа внесения затравки и типа подсластителя на структурно-механические свойства шоколадной массы. Показано, что твердость и реологические параметры шоколадной массы с сахарозаменителями по технологии с затравкой кристаллами βV-формы соответствовали аналогичным параметрам шоколадных масс, изготовленным со стадией традиционного темперирования, при значительном снижении длительности технологического процесса. Tempering chocolate masses is a process that ensures the crystallization of cocoa butter in a stable β-modification in order to avoid fatty bloom of the finished product. Presents the results of studies on the use of βV-form seed crystals in tempering chocolate mass with sweeteners inulin and inulin-stevioside complex instead of sucrose. It was found that crystals of the βV-form provide a chocolate mass with a stable β-modification of cocoa butter, regardless of the type of sweetener. The optimal modes of the process of seed crystals of βV-form in the technology of obtaining chocolate mass have been determined. The influence of the synergy of the method of introducing seeding and the type of sweetener on the structural and mechanical properties of the chocolate mass was studied. It is shown that the hardness and rheological parameters of the chocolate mass with sweeteners using technology with seeding of the βV-form crystals correspond to the same parameters chocolate mass technology with a traditional tempering stage with a significant reduction in the duration of the process.

Stabilization of Metastable Indomethacin α in Cellulose Nanocrystal Aerogel Scaffolds

Indomethacin (IM) is a small molecule active pharmaceutical ingredient (API) that exhibits polymorphism with the γ-form being the most thermodynamically stable form of the drug. The α-form is metastable, but it exhibits higher solubility, making it a more attractive form for drug delivery. As with other metastable polymorphs, α-IM undergoes interconversion to the stable form when subjected to certain stimuli, such as solvent, heat, pH, or exposure to seed crystals of the stable form. In this study, IM was crystallized into cellulose nanocrystal aerogel scaffolds as a mixture of the two polymorphic forms, α-IM and γ-IM. Differential scanning calorimetry (DSC) and Raman spectroscopy were used to quantitatively determine the amount of each form. Our investigation found that the metastable α-IM could be stabilized within the aerogel without phase transformation, even in the presence of external stimuli, including heat and γ-IM seed crystals. Because interconversion is often a concern during production of metastable forms of APIs, this approach has important implications in being able to produce and stabilize metastable drug forms. While IM was used as a model drug in this study, this approach could be expanded to additional drugs and provide access to other metastable API forms.

Al-ZSM-5 Nanocrystal Catalysts Grown from Silicalite-1 Seeds for Methane Conversion

This study evaluated Al-ZSM-5 nanocrystals grown from silicalite-1 seed crystals as catalysts for the methane dehydroaromatization (MDA) reaction. Silicalite-1 seed crystals sized between 30 and 40 nm were used to grow Al-ZSM-5 under various synthesis conditions. The size of Al-ZSM-5 was significantly affected by the Si/Al ratio (SAR), synthesis time, and silica nutrients/seed crystal ratio (NSR). Larger crystals were obtained with an increased SAR in the synthesis sols. Gradual growth of Al-ZSM-5 occurred with synthesis time, although the growth in crystal size ceased at 5 h of synthesis at 120 °C, indicating the rapid growth of Al-ZSM-5 aided by the silicalite-1 seeds. Precise tuning of Al-ZSM-5 size was possible by changing the nutrient/silicalite-1 seed ratio; a higher NSR led to larger crystals. Two representative Al-ZSM-5 crystals with SARs of 35 and 140 were prepared for catalyst testing, and the crystal sizes were tailored to <100 nm by controlling NSR. The MDA reaction was conducted in the presence of the prepared Al-ZSM-5. The catalyst size exhibited distinct differences in catalyst stability, while the SAR of catalysts did not produce noticeable changes in the catalyst stability of the Al-ZSM-5 crystals and commercial zeolites in this reaction system.

Growth Diamond on an Impact Lonsdaleite-bearing Diamond from the Popigai Astrobleme

The Popigai astrobleme contains huge reserves of diamonds with unusual properties. In impact diamonds from the Popigai astrobleme, the cubic phase and lonsdaleite are intergrown. In order to study the relationship of lonsdaleite-bearing impact diamonds with diamond, an experimental study of the features of diamond growth on lonsdaleite-bearing fragments was carried out. The experiments were carried out on a high-pressure apparatus of the “BARS” type at 5.5 GPa and 1450 ° C in the Fe-Ni-C system (nickel 36 wt.%). Impact Popigai diamonds were used as seed crystals. As a result of the study, it was found that the newly formed crystals are represented by a cubic phase, while the lonsdaleite in the seed crystals was preserved and the lonsdaleite / diamond ratio did not change. The newly formed cubic diamond in its main properties (Raman spectra, morphology, color, etc.) corresponds to synthetic diamonds grown in the iron-nickel system. The difference between the growth of crystals on seeds of impact diamonds and growth on a single-crystal seed of diamond was that the nucleation of crystals began from different points of the seed of the impact diamond. Multi-headed growth was observed and, as a result, an intergrowth of diamond crystals was formed. Probably, the initial misorientation of the points of nucleation of subindividuals leads to multi-headed growth of crystals in an intergrowth, in contrast to single-crystal growth of diamond on a single- crystal seed.

Principles to use reverse osmosis for drinking water supply and reduce concentrate disposal

Possibilities to reduce reverse osmosis concentrate flow and operational costs were investigated. The existing solutions are described using chemical softening and evaporation techniques. The presented article is devoted to investigation of possibilities to remove calcium carbonate from concentrate due to calcium deposition on “seed” crystals. A new technique to reduce concentrate flow is presented that consists of operation of membrane unit in circulation mode whereby concentrate is circulated through a “seed” reactor. In reactor calcium and carbonate ions deposit on the “seed” crystals thus reducing scaling hazard and concentrate TDS value. Water treatment flow diagram is presented and technical parameters of membrane facilities are determined that enables us to design the whole membrane process. Product flow on each membrane stage is determined to calculate the required amounts of membrane modules on each stage; scaling rates and calcium carbonate deposition rates are evaluated; caustic consumption is determined. Experimental technique is proposed and described to determine scaling rates in membrane modules and the amount of hardness removed from concentrate after treatment by the “seed” and the minimal volume of concentrate that could be reached. Relationships are presented to determine operational costs (energy and chemicals consumption), scaling rates in membrane modules on the first and second stages and total hardness removal during concentrate recirculation through the “seed” reactor on the third stage.