Effect of Mixed Solvents and Additives on the Habit Modification of 6-APA Crystals

6-aminopenicillanic acid (6-APA) crystals obtained under different physical and chemical conditions of the solutions may present different habits. The habits of diamond-shaped plates are desirable compared with other habits of 6-APA crystals. To obtain ideal 6-APA crystals, the effects of the mixed solvents and additives on 6-APA crystal habits were investigated. Ethanol or acetone was used as the organic solvent, and impurities existing in the 6-APA purification process were used as the additives. 6-APA growth habits were changed when the concentrations of ethanol, acetone or phenyl acetic acid were increased to exceed their critical concentration. The observed results show that the dominant face on 6-APA crystals was identified to be {020}, but the overall habit was controlled by the relative growth rates of the {101} and {002} faces. Crystal growth rates and habits can be appreciably changed by specific adsorption of additives on crystal faces.In some cases solvent molecules can act in a similar way and may be regarded as bulk additives. The effects of additives and organic solvents on 6-APA crystal habits were the results of adsorption effect, which fitted the experimental results quite well.

Ultrasound assisted crystallization of cephalexin monohydrate:Nucleation mechanism and crystal habit control

With the high-quality requirements for cephalexin monohydrate,developing a robust and practical crystallization process to produce cephalexin monohydrate with good crystal habit,appropriate aspect ratio and high bulk density as well as suitable flowability is urgently needed.This research has explored the influence of ultrasound on crystallization of cephalexin monohydrate in terms of nucleation mechanism and crystal habit control.The results of metastable zone width and induction time measurement showed the presence of ultrasound irradiation can narrow the metastable zone and shorten induction time.Cavitation phenomena generated by ultrasound were used to qualitatively explain the mechanism of ultrasound promoting nucleation of cephalexin monohydrate.Furthermore,on the basis of classical nucleation theory and induction time data,a series of nucleation-related parameters(such as crystalliquid interfacial tension,radius of the critical nucleus and etc.)were calculated and showed a decreasing trend under ultrasound irradiation.The diffusion coefficient of the studied system was also determined to increase by 72.73%under ultrasound.The changes in these parameters have quantitatively confirmed the mechanism of ultrasound influence on the nucleation process.In further,the calculated surface entropy factor has confirmed that the growth of cephalexin monohydrate follows continuous growth mechanism under the research conditions of this work.Through the exploration of crystallization conditions,it is found that suitable ultrasonic treatment,seeding,supersaturation control and removal of fine crystals are conducive to improving the quality of cephalexin monohydrate product.Optimizing the crystallization process coupled continuous ultrasound irradiation with fine-crystal dissolution policy has achieved the controllable production of monodisperse cephalexin monohydrate crystal with good performance.

Effects of Solvent and Impurity on Crystal Habit Modification of 11α-Hydroxy-16α,17α-epoxyprogesterone

The effects of solvent and impurity on the crystal habit of 11α-hydroxy-16α,17α-epoxyprogesterone (HEP)grown from solution were studied by scanning electron microscope.Long prismatic crystals were produced when HEP was crystallized from pure acetone and N,N-dimethylformamide,while blocky crystals were produced from pure chloroform by cooling crystallization.One kind of isomorphic impurity,16α,17α-epoxyprogesterone(EP) was selected to examine its effect on the HEP crystal habit.When the content of EP in the mother liquor is very high(55.45%,solvent free basis),the habit of produced HEP crystals was greatly modified from prismatic to octa-hedral.The differential scanning calorimetry and X-ray powder diffraction analyses showed that the change of crystal habit was originated from the crystal structure modification.

Hydrothermal preparation and crystal habit of X-zeolite powder

The preparation of X-zeolite powder was investigated in hydrothermal system, the crystal growth process of X-zeolite in hydrothermal condition was characterized by means of X-ray diffraction, scanning electron microscope and infrared ray. The results show that X-zeolite powder with uniform granularity and intact crystal shape can be obtained in hydrothermal system of acid-treated stellerite KG-*5CD*2KG-*9NaOHKG-*5CD*2KG-*9NaAl（OH）4KG-*5CD*2KG-*9H2O; the crystallite size is in the range of 2CD*23μm. The best reaction time of hydrothermal preparation is 6h. The formation phases of X-zeolite crystal are as follows: dissolution of feedstocks → formation of [SiO4] 4- and [AlO4] 5- tetrahedron, many-membered ring, β cage → formation of crystal nucleus and nano-particle → aggregation growth of nano-particle → coalescence growth of crystallite. The crystal habits of X-zeolite are intimately related with crystallization orientation of β cage in crystal and with its coupling stability on every crystal face family.

Growth Habit of the Basic Oxysulfate Magnesium Whisker

The growth habit of the basic magnesium oxysulfate whisker was investigated based on the theoreticalmodelof anion coordination polyhedron growth units.It is found that typicalbasic magnesium oxysulfate whisker growth is consistent with anion tetrahedralcoordination incorporation rules.The growth units of basic magnesium oxysulfate whiskers are [Mg-（OH）_4]^（2-） and HSO_4^-.[Mg-（OH）_4]^（2-） is the favorable growth unit and whisker growth is in the direction of the [Mg-（OH）_4]^（2-） combination.A plurality of [Mg-（OH）_4]^（2-） s combine and become a larger dimensionalgrowth unit in a one-dimensionaldirection.Then HSO_4^- and larger dimensionalgrowth units connect as basic magnesium sulfate whiskers,according to the structuralcharacteristics of the basic magnesium sulfate whisker,which can guide the synthesis of magnesium hydroxide whisker.

Crystal habit for upconversion laser crystal of BaY_2F_8

BaY2F8 crystals had a relatively low symmetry, and its XRD data showed that those strong diffractions occured in a narrow angle range, so it was difficult to orientate the single crystals of BaYEFs. In this paper, based on the structure characteristics and XRD data, the crystal habit of BaY2F8 was analyzed. The strong bond in crystal structure of BaYEF8 was Y-FE-Y, which stretched to the shape of chain along the direction of [001]. And this was an advantaged direction for the crystal growth. The steady shapes of BaY2F8 were composed of rhombic prism { 130} and {021 }. The crystal showed an axial habit in the direction of [001]. The analysis of the crystal slice obtained by temperature gradient technique verified the above conclusion. The BaY2F8 crystal was grown by compulsive methods such as Czochralski method.

Heterogeneous crystallization of Chlorzoxazone for modulating the physicochemical properties of crystals Author links open overlay panel

The polymer on modulating the crystal's habit is an evolving research in pharmaceutical crystallization.This study demonstrates the crystal habit modification of chlorzoxazone(CHZ)by heterogeneous crystallization(HC)in the binary solvent acetonitrile-ethanol(A-E(1:1))in the presence of polyvinylpyrrolidine(PVP)at concentrations of 0.50,0.75,and 1.00 wt%.The A-E(1:1)and PVP in HC experiments influenced to change the shape of crystals from needle to plate shape and reduced the crystal size producing a lower aspect ratio(in the range of 1.5-2.3).In the presence of PVP,the CHZ size distribution is 65-78μm which tends to enhance the powder flow-ability of CHZ crystals and as the PVP concentration increases,the nucleation rate decreases.The solubility of size-reduced CHZ crystals at different pH is found to be improved by 1.2-1.4 times.Hence,HC is deemed effective in modifying the physicochemical attributes of CHZ.

Controlling solid form and crystal habit of triphenylmethanol by antisolvent crystallization in a microfluidic device

Crystal habit and crystal form are critical elements in determining product properties and functions. In this work, we developed a microfluidic antisolvent crystallization technique to rapidly screen and accurately control the solid form and crystal habit of triphenylmethanol(Ph_(3)COH). This advanced technique separates the primary mixing of solutions from crystal formation(nucleation and growth) by introducing the microfluidic device, avoiding clogging in microchannels to obtain high-quality crystals. The results show that we can achieve controllable preparation of pure 2Ph_(3)COH·DMSO(DMSO solvate), pure Ph_(3)COH(form β), and mixed crystals with different mass ratios. Moreover, the microscale can prompt the DMSO solvate to grow into hexagonal sheet-like and bulk crystals. We can regulate the aspect ratio of hexagonal sheet-like crystals in binary solvents and control the crystal habit of the form β to transition between long needle-like shapes and short hexagonal prisms in DMF-H_(2)O. Meanwhile, we revealed that the solvent ratio, the antisolvent flow rate, and the initial concentration of Ph_(3)COH are the main factors affecting the solid form selectivity and morphology transition. Such a novel method would be considered as a promising technique to be extended to screen and control key crystallization parameters of other substances.

Influences of additives on the crystal habit of potassium chloride

By means of constant control speed cooling crystallization,the influences of four additives,including lead chloride,cadmium chloride,sodium salicylate,and quaternary ammonium salt,on the crystal habit of KCl were investigated.The results show that the crystal habit of KCl is cube without additives,the crystal habit of KCl is ellipsoid-like in the presence of Pb^(2+),the crystal habit of KCl is strip in the presence of Cd^(2+),and the crystal habit of KCl is cavate cube in the presence of sodium salicylate.Xray diffractometry analysis reveals that these additives can change the crystal habit of KCl but not its crystal structure.

Characteristics of the genetic mineralogy of pyrite and its significance for prospecting in the Denggezhuang gold deposit,Jiaodong Peninsula,China

This paper reports the variation rules for the typomorphic parameters of the pyrite and the gold enrichment rules of the Denggezhuang quartz vein gold deposit at a large-depth scale, providing the mineral signs for deep prospecting prediction through detailed study of the characteristics of crystal＇ habits, chemical composition, the thermoelectricity of pyrites, and min- eralogical mapping. This paper primarily discusses the correlation between the mineralization intensity and the space-time evolution of the mineralogical parameters, clarifies the physicochemical conditions during gold mineralization, and provides information useful for deep mineralization prediction. We demonstrate that the crystal habits of the pyrites are very complex, primarily occurring as （ 100）, （210）, and their combinate form. （210） and （ 100）＋（210） have positive correlations with gold mineralization, and （ 100）＋（210） therefore can be useful for locating rich ore segments. The composition of pyrites is charac- teristically poor in S and rich in As. Their typical trace elements are composed of Mo, As, Pb, Cu, Bi, Zn, Au, Co, Se, Sb, Ag, Ni, Cr, and Te. The average contents of trace elements in pyrites from various stages show that the crystallizing temperature gradually decreased from an early stage to the metallogenic episodes. The precipitation and accumulation of Au and Ag occur primarily in the quartz-pyrite stage （III） and the polymetal minerals stage （IV）. The occurrence rate of P-type pyrites （P（%）） is 83.52%. There is a larger dispersion of the thermoelectrical coefficient of pyrite （a） in the Denggezhuang gold deposit than in other deposits in the Jiaodong Peninsula. The electrical conductivity assemblage of pyrites from I to V is characterized by P〉N〉P〉N〉P〉〉N〉P〉〉N〉P〉N, which is usually considered beneficial for mineralization. The relative contents of As＋Sb＋Se＋Te and Co＋Ni are closely correlated to P-type and N-type average values and their occurrence rates. According to the crystallizing temperature of pyrite, the mineralization intensity, and the denudation degree, the mineralization temperature of the Denggezhuang gold deposit is in the range of 150-322~C and is of a medium-low temperature. The orebody has already become denuded to the top-middle of the orebody, and the size of the orebody is larger than 900 m. Based on the vertical zon- ing of the thermoelectrical coefficients of pyrites and P-type pyrite mapping, it is suggested that the segment between -425 and -800 m may have exploration potential to the northeast of line 94 of the No. I2.2 orebody.

FBRM and PVM investigations of the double feed semi-batch crystallization of 6-aminopenicillanic acid

6-Aminopenicillanic acid(6-APA)is a crucial pharmaceutical intermediate in the chemistry of semi-synthetic antibiotics.The focused beam reflectance measurement(FBRM)technology and particle vision measurement(PVM)technology were employed to the processes of online-monitoring of 6-APA crystallization behavior in a double-feeding semi-batch crystallizer.Experiments were carried out with four kinds of double-feeding policies and the results were compared with the traditional single-feeding.Records and analysis of FBRM indicated that the nucleation of double feeding policy was much higher than single policy,and chord length of 6-APA was almost determined and had little change after the nucleation peak.Ostwald ripening process had no significant effect on further growth of 6-APA crystal.PVM images showed that the crystal habit of 6-APA was continuously changed during the crystallization process.The development of(002)face in the final crystal for the five feeding policies were different.