Stripping Crystallization Research Articles

Development of Methodology for molecular crystallization of Menthol

Menthol, terpene alcohol with a strong minty, cooling odor and taste is highly popular in food, flavor, cosmetic and pharmaceutical industries. Crystallization of menthol from mint oil is a tedious process involving high cost and a much longer period. The present study has been undertaken to devise a new method with low input and with higher production rates. The crystallization of menthol was performed by the methods including Temperature programmed cooling process (TPCP); Short-path molecular fractional distillation (SPMFD) and Stripping crystallization (SC). About 99 % menthol contained in the mint oil was recovered during the crystallization process. The characterization techniques such as scanning electron microscopy (SEM) for surface morphology, x-ray diffraction (XRD) for crystal structure and crystallite size evaluation, and FTIR and Raman spectroscopy for analyzing the chemical nature of the crystals.

Effect of Al2O3 content on microstructure and oxidation behavior of silicate enamel coatings on a Ni-based superalloy at 1000 °C

Enamel coating, which is of low thermal conductivity and high chemical stability, has been employed for the protection of many hot parts against oxidation. It is composed of multiple oxides, and each oxide component plays a certain role on thermophysical properties. In this paper, a type of silicate enamel coating with different contents of oxide component Al 2 O 3 was prepared on K444 superalloy. Its microstructural evolution and cyclic oxidation behavior at 1000 °C were investigated. Results indicated that the A0 enamel coating, which was free of Al 2 O 3 in composition, suffered from serious crystallization at high temperature. The formation of quartz, cristobalite and SrSiO 3 crystals resulted in significant mass loss during cyclic oxidation. However, precipitation of these crystals was almost completely prohibited in the A10 and A15 coatings with 10 and 15 wt% Al 2 O 3 , respectively. The A10 coating had no mass loss after cyclic oxidation. But much high content of Al 2 O 3 resulted in the formation of abundant long strip crystals of SrAl 2 Si 2 O 8 in the A15 coating, which led to minor spallation. Furthermore, enamel coatings with Al 2 O 3 (above 6 wt%) promoted the formation of a continuous alumina scale at the enamel/alloy interface, which improved oxidation resistance and increased bonding strength. The well grown alumina scale at interface as well as the mild crystallization ensured high spallation resistance of the enamel coating A10.

Chiral Purification of S-2-Phenylpropionic Acid from an Enantiomer Mixture by Stripping Crystallization

Chiral Purification of <i>S</i>-2-Phenylpropionic Acid from an Enantiomer Mixture by Stripping Crystallization

Recovery of nitrogen and phosphorus from livestock slurry with treatment technologies: A meta-analysis

The livestock industry has developed rapidly in recent decades, but the improper treatment of livestock manure, especially slurry, causes environmental pollution. Treatment technologies are considered to be effective in alleviating nitrogen (N) and phosphorus (P) losses from livestock slurry. Here, we used published research data to conduct a meta-analysis of the recovery efficiencies of N and P of five mainstream treatment technologies, including ammonia stripping, air scrubbing, membrane filtration, microalgae cultivation and struvite crystallization. Additionally, the agronomic effects of the recovered products of these treatment technologies were evaluated. The results showed that all technologies exhibited clear recovery effects on N and P. The N recovery efficiencies ranged from 57% to 86%, and those of P ranged from 64% to 87%. Struvite crystallization was the most efficient treatment technology for both N and P recovery; moreover, the ammonia stripping and microalgae cultivation technologies were less efficient. The pH levels and temperatures are the main factors that influence ammonia stripping, struvite crystallization and microalgae cultivation, while membrane filtration and air scrubbing are mainly affected by the membrane types and properties. When the equal amount of N or P input to fields, the recovered products (ammonium sulfate and struvite crystals) may achieve a similar crop yield, relative to commercial N or P fertilizers. Our findings can provide deep suggestions and parameters for designing proper treatment technologies to reduce nutrient discharge from livestock slurry in regions with high livestock density and also for identifying the research gaps that should be paid more attention in the future.

Purification of Chlorophenol Isomers by Stripping Crystallization Combining Melt Crystallization and Vaporization.

Stripping crystallization (SC) was introduced in this work to purify p-chlorophenol from the p-chlorophenol-rich liquid mixture and to purify m-chlorophenol from the m-chlorophenol-rich liquid mixture, respectively. Essentially, SC combines melt crystallization and vaporization to produce the solid product and the vapor from a liquid mixture via a series of three-phase transformations at reduced pressures during the cooling process. At the end of the SC, only the solid product remained while the liquid mixture was almost eliminated and the produced vapor was removed. A set of differential equations based on the mass and energy balances were proposed to determine the incremental variations of the amounts of remaining liquid, produced solid and produced vapor during the batch SC process. The experimental yield and product purity of the final product obtained from the batch SC experiments were compared with those predicted by the model.

Purification of durene from the mixture of durene and isodurene by stripping crystallization

Purification of durene from the mixture of durene and isodurene by stripping crystallization

Ring-Shaped Polyoxometalate Built by {Mn 4 PW 9 } and PO 4 Units for Efficient Visible-Light-Driven Hydrogen Evolution

A novel mixed-valence, ring-shaped multinuclear Mn-containing polyoxometalate, [H2N(CH3)2]15NaH8-[MnIII3MnIV(μ3-O)3(OAc)PO4(B-α-PW9O34)]4·36H2O (1) was made and systematically characterized using v...

Purification of m-xylene from the mixed xylenes by stripping crystallization

Stripping crystallization (SC) was applied in this work for purification of m-xylene (MX) from the mixed xylenes consisting of MX, p-xylene (PX), o-xylene (OX) and ethylbenzene (EB). As SC is operated in a series of three-phase transformations by decreasing temperature and reducing pressure, SC combines melt crystallization and vaporization to produce the MX crystalline product and mixture vapor from the liquid mixture. An apparatus was design to be operated from − 47.85 °C and 3.21Pa to -80°C and 0.04Pa. A model based on the thermodynamics coupled with the mass and energy balances was proposed to determine a series of three-phase transformation conditions, which were adopted to direct the SC experiments. The experimental purity and recovery ratio of MX in the final product were compared with the calculated results predicted by the model.

Product Yield, Purity, and Effective Distribution Coefficient in Stripping Crystallization of R-2-Amino-1-phenylethanol from the Enantiomer Mixture

Stripping crystallization (SC) was applied for chiral purification of R-2-amino-1-phenylethanol (R-APE) from an enantiomer mixture. As SC is operated in a series of three-phase transformations by decreasing temperature and pressure, SC combines melt crystallization and vaporization to produce the R-APE crystalline product, and liquid phase and vapor phase of mixtures.

Separation of V-bearing phase from the vanadium slag system utilizing supergravity

The crystallization and separation behaviors of the V-spinel phase in the FeO-SiO2-V2O3-TiO2 system as the main components of vanadium slag were investigated to effectively concentrate and separate vanadium from the vanadium slag. Fine V-spinel precipitates were transformed into large lumps and strip crystals by decreasing the temperature from 1773 K to 1723 K. Ti-spinel phases began to crystallize from the molten slag by further decreasing the temperature to 1673 K. In order to adequately precipitate a single V-spinel phase with suitable grain size in the crystals from the molten slag, the temperature was chosen as 1723 K. With introduction of supergravity technology, the Ti-containing slag melt went through the filter to form the Ti-containing slag, while V-spinel crystals were intercepted by the filter to form the V-enriched slag. Consequently, with G = 700 at 1723 K for 10 minutes, the mass fraction of V2O3 was increased from 17.00 wt% before separation to 32.98 wt% in the enriched slag; the recovery ratio of V2O3 reached about 86.50%. In addition, the mass fraction of TiO2 reached about 19.41 wt% in the Ti-containing slag, which could be recycled as a titanium-bearing material in the metallurgical industry.

Chiral Separation of the Phenylglycinol Enantiomers by Stripping Crystallization.

Stripping crystallization (SC) is introduced in this work for chiral purification of R-phenylglycinol from the enantiomer mixture with an initial concentration ranging from 0.90 to 0.97. As opposed to the solid–liquid transformation in melt crystallization, the three-phase transformation occurs in SC at low pressures during the cooling process. SC combines melt crystallization and vaporization to produce a crystalline product and mixture vapor from a mixture melt due to the three-phase transformation. Thermodynamic calculations were applied to determine the operating pressure for the three-phase transformation during the cooling process in the SC experiments. To consider the possible deviations between the calculated and the actual three-phase transformation conditions, the product purity and the recovery ratio of R-phenylglycinol were investigated within a range of operating pressures during the cooling process.

Purification of Styrene from a Styrene/Ethylbenzene Mixture by Stripping Crystallization

Stripping crystallization (SC) was used to purify styrene (ST) from a liquid mixture of ST and ethylbenzene (EB). This new separation technology combines vaporization and crystallization to yield a crystalline product and a vaporous mixture from a liquid feed via three-phase equilibrium transformations. The three-phase equilibrium conditions for a liquid mixture determined by the thermodynamic calculations were adopted to direct the SC experiments. A unique apparatus was designed for SC experiments at low temperatures and pressures for a series of three-phase equilibrium conditions (from −33 °C and 9.0 Pa to −80 °C and 0.03 Pa). The experiments indicate that SC can be applied to the purification of ST from a liquid mixture of ST and EB with an initial ST concentration of 0.80–0.95.

Study of effect of parameters on separation of cresol isomers

The separation of para-cresol (4-methylphenol) and meta-cresol (3-methylphenol) from their mixture have been an interesting challenge because of their close boiling points, where the boiling point difference of isomers is merely 0.29°C. Stripping Crystallization is an intensified technique, used for separation of close boiling mixtures. This technique is based on the triple point condition, where the liquid mixture is simultaneously vaporized and crystallized, owing to three-phase equilibrium. In the current work, a detailed experimental study has been carried out to establish the feasibility of stripping crystallization process for separating out para- and meta- cresols from their mixture. Gas Chromatography has been used to determine the purity of the distinct cresols obtained from the experiments. Feasibility revealed the dependence of the process on different operating and design parameters. Hence, additional experiments were done to study the effect of these parameters. Cooling rate, seeding, availability of surface area and application of vacuum are found to be effecting the quality of the separated product. Obtained results are found to be in coherence with the available data reported in the literature.

Bent silicon strip crystals for high-energy charged particle beam collimation

For applications in high energy particles accelerators, such as the crystal-assisted beam collimation, several strip crystals exploiting anticlastic curvature were produced in the last decade at the Sensor and Semiconductor Laboratory (SSL) of Ferrara by means of revisited techniques for silicon micromachining, such as photolitography and wet etching. Those techniques were recently enhanced by introducing a further treatment called Magnetorheological Finishing (MRF), which allowed to fabricate crystals with ultraflat surface and miscut very close to zero. The technology of the mechanical devices used to hold and bend crystals has been also improved by employing a titanium alloy to realize the holders. Characterization method were also improved: the usage of a high resolution X-rays diffractometer was introduced to directly measure crystal bending and torsion. Accuracy of the diffractometer was furtherly enhanced with an autocollimator, which found an important application in miscut characterization. A new infrared light interferometer was used to map the thickness of the starting swafers with sub-micrometric precision, as well as to measure the length along the beam of the strips. Crystals were characterized at the H8 external lines of CERN-SPS with various hundreds-GeV ion beams, which gave results in agreement with the precharacterization performed at SSL. One strip was selected among the crystals to be installed in the LHC beam pipe during the Long Shutdown 1 in 2014. These crystals were very recently tested in a crystal-assisted collimation experiment with a 6.5TeV proton beam, resulting in the first observation of channeling at this record energy, being also the first observation of channeling of the beam circulating in the LHC.

Chiral purification of S-ibuprofen from ibuprofen enantiomers by stripping crystallization

A new technology, stripping crystallization (SC), is introduced in this work for chiral purification of S-ibuprofen from ibuprofen enantiomers. Basically, SC combines distillation and crystallization operated at reduced temperature and pressure for the liquid mixture feed to produce pure S-ibuprofen crystals and mixture vapors by maintaining a series of the three-phase equilibrium conditions based on the variations of the liquid composition. SC is continued until liquid is nearly eliminated. The final product only consists of S-ibuprofen crystals as all the vapors produced are removed from the system. A thermodynamic model is developed to simulate the three-phase equilibrium during the SC operation and to direct the batch SC experiments. The experiments show that, when SC is operated from 50°C and 290Pa to 37°C and 148Pa, seeding with ultrasound mixing or magnetic stirring can be efficiently employed to purify S-ibuprofen from ibuprofen enantiomers. The experimental results, including the final enantiomeric purity and recovery ratio of S-ibuprofen, are consistent with the simulation results predicted by the model.

Theoretical Comparative Analysis of BER in Multi-Channel Systems With Strip and Photonic Crystal Silicon Waveguides

We present a comparative analysis of the performance of multi-channel photonic systems containing strip or photonic crystal (PhC) silicon (Si) waveguides in the presence of white Gaussian noise. Specifically, we consider a multi-wavelength optical signal propagating either in a strip single-mode Si photonic waveguide (Si-PhW) or in a Si PhC waveguide (Si-PhCW), each channel consisting of a CW nonreturn-to-zero ON–OFF keying modulated signal. The output signal is demultiplexed and the signal in each channel is analyzed using direct-detection optical receivers. We describe the propagation of the optical signal in the Si-PhW and Si-PhCW using a linearized model and validate our main results by employing a rigorous theoretical model that incorporates all relevant linear and nonlinear optical effects and the mutual interaction between free-carriers and the optical field. The bit error rate (BER) of the transmitted signal is calculated by using both a time- and frequency-domain Karhunen–Loeve expansion method. Our analysis suggests that due to enhanced nonlinear effects, for comparable optical power, a similar BER is achieved in a PhC waveguide about $100\times$ shorter than a strip one, with a particularly strong signal degradation being observed in the slow-light regime of the Si-PhCW.

On thermal and radiation damage to silicon crystals in the LHC proton beam

We investigate thermal and radiation effects in silicon crystals which can be used for extracting beam halo particles in high energy accelerators. Application of bent crystals for removing halo is considered as a promising technique to enhance the beam collimation efficiency. Feasibility studies of a crystal-based cleaning system at the LHC have been recently approved in the framework of the UA9 experiment at CERN. In view of these studies and considering the enormous energy density stored in LHC beams, one requires a reliable knowledge of potential crystal damage due to thermal and radiation effects. In this article, we present damage estimates for a silicon strip crystal based on FLUKA simulations and subsequent thermal analysis using ANSYS Workbench. Heating of the crystal is investigated for hypothetical beam impact scenarios. The degradation of deflection efficiency due to radiation effects is estimated for amorphous crystal orientation and is then extrapolated down to channeling mode by evaluating the fraction of incoherent recoils of silicon atoms.

Purification of hydrobenzoin enantiomers by stripping crystallization

Stripping crystallization (SC) is introduced in this work for the purification of hydrobenzoin enantiomers. In principle, SC is operated at a series of the three-phase equilibrium conditions, in which the liquid mixture is simultaneously vaporized and crystallized. Thus, SC combines distillation and crystallization to produce pure crystals. A thermodynamic model is developed to simulate the three-phase equilibrium during the SC operation and to direct the batch SC experiments. The experiments show that SC can be applied to purify (R,R)-hydrobenzoin from the chiral hydrobenzoin mixture. The experimental purity of the final product obtained by SC is consistent with the simulated purity predicted by the model although the experimental recovery ratio is lower than the simulated recovery ratio.

Investigations into the Effects of the Cooling Rate on Stripping Crystallization

This study investigates how the cooling rate affects the performance of stripping crystallization (SC) for purification of a p-xylene (PX)/o-xylene (OX) mixture to elucidate the rate process of three-phase equilibrium. A thermodynamic model is developed to simulate the three-phase equilibrium conditions during the batch SC operation. Experimental results indicate that SC can be used to purify both PX from the PX-rich mixture and OX from the OX-rich mixture. A slower cooling rate generally gives rise to a longer operating time, leading to a product with a higher purity and lower recovery ratio. We conclude that the three-phase equilibrium can be achieved quickly, even at a cooling rate of 0.50 °C/min. Importantly, the results of this study demonstrate that the proposed thermodynamic model can reliably determine the three-phase equilibrium conditions for the studied system.

Radiation emission phenomena in bent silicon crystals: Theoretical and experimental studies with 120 GeV/c positrons

The radiation emission phenomena in bent silicon crystals have been thoroughly investigated at the CERN SPS-H4 beamline. The incoming and outgoing trajectories of charged particles impinging on a silicon strip crystal have been reconstructed by high precision silicon microstrip detectors. A spectrometer method has been exploited to measure the radiation emission spectra both in volume reflection and in channeling. The theoretical method used to evaluate the photon spectra is presented and compared with the experimental results.