Boosting kinetic separation of ethylene and ethane on microporous materials via crystal size control

The adsorptive separation of C_(2)H_(4)and C_(2)H_(6),as an alternative to distillation units consuming high energy,is a promising yet challenging research.The great similarity in the molecular size of C_(2)H_(4)and C_(2)H_(6)brings challenges to the regulation of adsorbents to realize efficient dynamic separation.Herein,we reported the enhancement of the kinetic separation of C_(2)H_(4)/C_(2)H_(6)by controlling the crystal size of ZnAtzPO_(4)(Atz=3-amino-1,2,4-triazole)to amplify the diffusion difference of C_(2)H_(4)and C_(2)H_(6).Through adjusting the synthesis temperature,reactant concentration,and ligands/metal ions molar ratio,ZnAtzPO4 crystals with different sizes were obtained.Both single-component kinetic adsorption tests and binary-component dynamic breakthrough experiments confirmed the enhancement of the dynamic separation of C_(2)H_(4)/C_(2)H_(6)with the increase in the crystal size of ZnAtzPO_(4).The separation selectivity of C_(2)H_(4)/C_(2)H_(6)increased from 1.3 to 98.5 with the increase in the crystal size of ZnAtzPO_(4).This work demonstrated the role of morphology and size control of adsorbent crystals in the improvement of the C_(2)H_(4)/C_(2)H_(6)kinetic separation performance.

Petrology,geochemistry,and crystal size distribution of the basaltic andesite-dacite association at Mt.Sumbing,Central Java,Indonesia:Insights to magma reservoir dynamics and petrogenesis

Ten rock samples consisting of one pyroclastic density current(PDC1)deposit,seven lava flows(LF1–7),and two summit lava domes(LD1,2)were studied to understand the petrogenesis and magma dynamics at Mt.Sumbing.The stratigraphy is arranged as LF1,PDC1,LF2,LF3,LF4,LF5,LF6,LF7,LD1,and LD2;furthermore,these rocks were divided into two types.TypeⅠ,observed in the oldest(LF1)sample,has poor MgO and high Ba/Nb,Th/Yb and Sr.The remaining samples(PDC1–LD2)represent typeⅡ,characterized by high MgO and low Ba/Nb,Th/Yb and Sr values.We suggest that type I is derived from AOC(altered oceanic crust)-rich melts that underwent significant crustal assimilation,while typeⅡoriginates from mantle-rich melts with less significant crustal assimilation.The early stage of typeⅡmagma(PDC1–LF3)was considered a closed system,evolving basaltic andesite into andesite(55.0–60.2 wt%SiO_(2))with a progressively increasing phenocryst(0.30–0.48φ_(PC))and decreasing crystal size distribution(CSD)slope(from-3.9 to-2.9).The evidence of fluctuating silica and phenocryst contents(between 55.9–59.7 wt%and 0.25–0.41φ_(PC),respectively),coupled with the kinked and steep(from-5.0 to-3.3)CSD curves imply the interchanging condition between open(i.e.,magma mixing)and closed magmatic systems during the middle stage(LF4–LF6).Finally,it underwent to closed system again during the final stage(LF7–LD2)because the magma reached dacitic composition(at most 68.9 wt%SiO_(2))with abundant phenocryst(0.38–0.45φ_(PC))and gentle CSD slope(from-4.1 to-1.2).

Correlation between H-ZSM-5 crystal size and catalytic performance in the methanol-to-aromatics reaction

The porosity of H‐ZSM‐5zeolite is known to facilitate the diffusion of molecules in the methanol‐to‐aromatics(MTA)reaction.The activity and selectivity of the H‐ZSM‐5catalyst in the MTAreaction has been studied as a function of crystal size.ZSM‐5zeolites with different crystal sizeswere successfully synthesized by conventional hydrothermal methods.Tailoring ZSM‐5particle sizewas easily controlled by changes to the sol‐gel composition,and in particular,the deionized waterto tetrapropylammonium hydroxide ratio,and crystallization time.The structure of the H‐ZSM‐5zeolites were characterized by X‐ray diffraction and the morphology of the zeolite particles wasdetermined by scanning electron microscopy.N2adsorption‐desorption measurements establishedchanges to the textural properties,and compositional properties were characterized by X‐ray fluorescencespectroscopy.Acidity measurements of the catalysts were measured by pyridine‐adsorbedFourier transform infrared spectroscopy and the temperature‐programmed desorption of ammonia.After subjecting the catalysts to the MTA reaction,the total amount of coke formed on the spentdeactivated catalysts was determined by thermal gravimetric analysis.The results show that theSiO2/Al2O3molar ratios and acidic properties of the H‐ZSM‐5samples are similar,however,thenano‐sized hierarchical ZSM‐5zeolite with an additional level of auxiliary pores possesses a higher

Recent Developments in the Crystallization Process： Toward the Pharmaceutical Industry

Crystallization is one of the oldest separation and purification unit operations, and has recently contributed to significant improvements in producing higher-value products with specific properties and in building efficient manufacturing processes. In this paper, we review recent developments in crystal engineering and crystallization process design and control in the pharmaceutical industry. We systematically summarize recent methods for understanding and developing new types of crystals such as co-crystals, polymorphs, and solvates, and include several milestones such as the launch of the first co-crystal drug, Entresto （No- vartis）, and the continuous manufacture of Orkambi （Vertex）. Conventional batch and continuous processes, which are becoming increasingly mature, are being coupled with various control strategies and the recently developed crystallizers are thus adapting to the needs of the pharmaceutical industry. The development of crystallization process design and control has led to the appearance of several new and innovative crystal- lizer geometries for continuous operation and improved performance. This paper also reviews major recent orogress in the area of process analytical technology.

Fabrication of a nano-sized ZSM-5 zeolite with intercrystalline mesopores for conversion of methanol to gasoline

Carbon deposition during methanol to hydrocarbons leads to the quick deactivation of ZSM-5 catalyst and it is one of the major problems for this technology. Decreasing the crystal size or introducing mesopores into ZSM-5 zeolites can improve its diffusion property and decrease the coke formation. In this paper, nano-sized ZSM-5 zeolite with intercrystalline mesopores combining the mesoporous and nano sized structure was fabricated. For comparison, the mesoporous ZSM-5 and nano-sized ZSM-5 were also prepared. These catalyst samples were characterized by XRD, BET, NH3-TPD, TEM, Py-IR and TG techniques and used on the conversion of methanol to gasoline in a fixed-bed reactor at T=405 degrees C, WHSV =4.74 h(-1) and P=1.0 MPa. It was found that the external surface area of the nano-sized ZSM-5 zeolite with intercrystalline mesopores reached 104 m(2)/g, larger than that of mesoporous ZSM-5 (66 m(2)/g) and nano sized ZSM-5 (76 m(2)/g). Catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores was 93 h, which was only longer than that of mesoporous ZSM-5 (86 h), but shorter than that of nano sized ZSM-5 (104 h). Strong acidity promoted the coke formation and thus decreased the catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores though it presented large external surface that could improve the diffusion property. The special zeolite catalyst was further dealuminated to decrease the strong acidity. After this, its coke formation rate was slowed and catalytic lifetime was prolonged to 106 h because of the large external surface area and decreased weak acidity. This special structural zeolite is a potential catalyst for methanol to gasoline reaction. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Selective conversion of methanol to propylene over highly dealuminated mordenite:Al location and crystal morphology effects

The growing consumption of light olefins has stimulated intensive researches on methanol to olefin(MTO)process which possesses great advantages for coal conversion to value‐added chemicals in an environmentally benign way.The catalysts commonly used for MTO process faces several challenges such as poor selectivity control,low hydrothermal stability and short lifetime.In the present study,we prepared a series of mordenite zeolites with variable Al contents(Si/Al molar ratios of 51−436)by a sequential dealumination treatment of air‐calcination and acid leaching.The textural properties,acidity and Al location before and after the dealumination treatment have been systematically studied and their effect on MTO especially the methanol to propylene(MTP)performance was thoroughly investigated.The mordenite zeolites with the Si/Al ratios over 150 selectively catalyzed methanol conversion in the MTP pathway,providing a high propylene selectivity of 63%and propylene/ethylene ratio of>10.Compared to the low‐silica MOR catalysts,highly dealuminated MOR showed much higher stability and longer lifetime,which can be further enhanced via harsh hydrothermal pretreatment.Furthermore,the lifetime was highly related to the crystal size along c‐axis.The excellent performance of highly dealuminated MOR is likely ascribed to the mesopores formed upon dealumination and the scarce Al sites located in the T sites shared by the 8‐member ring(MR)side pockets and 12‐MR pore channels.

Crystal Growth Models of Dexamethasone Sodium Phosphate in a MSMPR Reactive Crystallizer

The reactive crystallization process of dexamethasone sodium phosphate was investigated in a continuous mixed-suspension, mixed-product-removal(MSMPR) crystallizer. Analyzing experimental data, it was found that the growth of product crystal was size-dependent. The Bransom, CR, ASL, M J2 and M J3 size-dependent growth models were discussed in details. Using experimental steady state population density data of dexamethasone sodium phosphate, parameters of five size-dependent growth models were determined by the method of non-linear least-squares. By comparison of experimental population density and linear growth rate data with those obtained from the five size-dependent growth models, it was found that the MJ3 model predicts the growth more accurately than do the other four models. Based on the theory of population balance, the crystal nucleation and growth rate equations of dexamethasone sodium phosphate were determined by non-linear regression method. The effects of different operation parameters such as supersaturation, magma density and temperature on the quality of product crystal were also discussed, and the optimal operation conditions were derived.

Particle Size and Crystal Phase Effects in Fischer-Tropsch Catalysts

Fischer-Tropsch synthesis （FTS） is an increasingly important approach for producing liquid fuels and chemicals via syngas-that is, synthesis gas, a mixture of carbon monoxide and hydrogen-generated from coal, natural gas, or biomass. In FTS, dispersed transition metal nanoparticles are used to catalyze the reactions underlying the formation of carbon-carbon bonds. Catalytic activity and selectivity are strongly correlated with the electronic and geometric structure of the nanoparticles, which depend on the particle size, morphology, and crystallographic phase of the nanoparticles. In this article, we review recent works dealing with the aspects of bulk and surface sensitivity of the FTS reaction. Understanding the different catalytic behavior in more detail as a function of these parameters may guide the design of more active, selective, and stable FTS catalysts.

The Structure and Size-effect of Calcium Modified Lead Titanate Nanocrystal,Pb_(0.85)Ca_(0.15)TiO_3

Calcium modified lead titanate nanocrystal material Pb0.85Ca0.15TiO3 was synthesized by means of a solgel method.The changes of crystal structure and grainsize of the samples were investigated under different conditions of heat treatment.the results show that the tetragonal symmetry is reduced and the ferroelectricparaelectric phase transformation temperature is decreased with the reduce of the grainsize of the sample.the critical grainsize for the ferroelectricparaelectric phase transformation at room temperature was calculated.The change regularities of the lattice constant and tetragonality with the grainsize are discussed.

A Pioneering Experimental Study on the Batch Crystallization of the Citric Acid Monohydrate

Citric acid is an important organic substance whose marketing concerns various fields. Nevertheless, until 1997 the scientific literature reported little information about the process of crystallization by cooling through which the commercial product is obtained. In particular, the available studies were aimed to investigate only the kinetics of nucleation and crystal growth neglecting some effective aspects of the industrial crystallization in mechanically stirred apparatus. In order to fill that sci-tech gap, the Department of Chemical Engineering at the University ＂La Sapienza＂ of Rome decided to lead a long and meticulous experimental research on the crystallization in discontinuous （batch） of CAM （citric acid monohydrate） in the allotropic form that is stable at room temperature. Due to the number of people involved in that pioneering work, carried out in the historic laboratories of＂La Sapienza＂ （Faculty of Engineering）, and motivated by the publication of related M.Sc. dissertations and research papers, such collective effort was called ＂School of Industrial Crystallization＂. Among the graduate students in Chemical Engineering that 17 years ago participated in that fruitful experience there was also the author who, under the supervision of Prof. Barbara Mazzarotta, had the specific task of assessing the effects on CAM of changing the crystallization operating conditions until their optimization; the achievements are briefly illustrated in this paper.

Crystallization Conditions and Mineral Chemistry in the East of Tafresh, Central Iran, with Insights into Magmatic Processes

The Tafresh granitoids are located at the central part of the Urumieh-Dokhtar Magmatic Arc(UDMA)in Iran.These rocks,mainly consisting of diorite and granodiorite,were emplaced during the Early Miocene.They are composed of varying proportions of plagioclase+K-feldspar+hornblende±quartz±biotite.Discrimination diagrams and chemical indices of amphibole phases reveal a calc-alkaline affinity and fall clearly in the crust-mantle mixed source field.The estimated pressure,derived from Al in amphibole barometry,is approximately 3 Kb.The granitoids are I-type,metaluminous and belong to the calc-alkaline series.They are all enriched in light rare earth elements and large ion lithophile elements,depleted in high field strength elements and display geochemical features typical of subduction-related calc-alkaline arc magmas.Most crystal size distribution(CSD)line patterns from the granitoids show a non-straight trend which points to the effect of physical processes during petrogenesis.The presence of numerous mafic enclaves,sieve texture and oscillatory zoning along with the CSD results show that magma mixing in the magma chamber had an important role in the petrogenesis of Tafresh granitoids.Moreover,the CSD analysis suggests that the plagioclase crystals were crystallized in a time span of less than 1000 years,which is indicative of shallow depth magma crystallization.

Inhibition effect of phosphate on the crystal grain growth of nanosized titania

The inhibitory effect of phosphate on the crystal grain growth of nanosized titania during high temperature calcination was investigated. Nanosized titanium dioxide powders prepared by hydrolysis of titanium tetrachloride were soaked in phosphate solutions with different concentrations. The obtained powders calcined at various temperatures were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, and X-ray photoelectronic spectroscopy （XPS）. The grain size of the samples without phosphate treatment increased quickly when calcined at high temperatures, while the grain size of the samples with phosphate modification increased slowly when calcined at the same temperature. This phenomenon implies that phosphate treatment plays an important role in inhibiting the crystal grain growth of titania. The possible mechanism of the inhibition effect of phosphate on titania is discussed.

Crystal Growth and Crystallization Time Scales of the Panzhihua Layered Intrusion:Constraint from Crystal Size Distribution

The Panzhihua layered intrusions is generated closely related to the Emeishan LIPs.This paper analyzes the spatial distribution of plagioclase and pyroxene.The quantitative texture analysis of 2209 plagioclase shows that the characteristic length of plagioclase is 0.54 to 0.96 mm,the intercept variation range is large,from-0.67 to 0.96,and the slope is-1.85 to-1.04,the Aspect Ratio shows from 1.84 to 2.59 and fractal dimension D is 1.908–1.933.The quantitative texture analysis of 2342 pyroxene shows that the characteristic length of pyroxene is 0.38–0.64 mm,the intercept shows from 0.46 to 2.26,The slope ranges from-2.6 to-1.47,the Aspect Ratio value varies from 1.53 to 1.71,the fractal dimension D is 0.93 to 1.13.All the CSDs results of the Panzhihua intrusions indicate that plagioclase and pyroxene form in an open magma system and undergo four replenishment of magma injection.The plagioclase crystals do not grow as the lathlike shape,and the fractal growth leads to complex crystal surface.The plagioclase undergoes deformation compaction during the crystal process,and then is oriented.The pyroxene crystals grow along an approximately triaxial ratio and undergo texture adjustment and small crystal dissolution reabsorption.When all crystals in magma system grows up to 2 mm,the pyroxene undergoes cumulation in the Panzhihua layered intrusions.The plagioclase crystallization time scale is 171.23–304.41 years,representing that the crystallization is the more uniform in central part of the melt.The nucleation density continuously increases during the crystallization process of the magma system.The time scale to reach the final maximum crystal nucleation density is 15.28–58.98 years.

Crystallographic Characterization and Themal Decomposition Behavior of High-Purity Microcrystalline Magnesite

The intergranular cracking face is smooth and Iransgranular cracking fracture shows trace of cleavage. It is hard to .tirol characteristic rhombus in the dense small crystals. As measured by SEM, the particle size of microcrystalline magnesite originating in Sichuan - Tibet is uniform, most grains range in 2 -4 μm. Three-dimensional （ 3D ） crystal morphology assumes cubic or column.

Influence of Crystal Size of USY Zeolite on Performance of Hydro-upgrading Catalysts

The effect of crystal size of USY zeolite on the performance of hydro-upgrading catalysts for treating catalytically cracked(FCC) LCO(light cycle oil) was studied.Three W-Ni catalysts supported on USY zeolites with different crystal sizes and Al2O3 were prepared by impregnation method.The catalysts were characterized by XRD and BET methods,and evaluated in a micro-reactor using tetralin as the model compound and in an 100-mL hydrogenation test unit using FCC LCO as the feedstock.By contrast,catalyst made from smaller crystal-size USY zeolite had higher external surface area and shorter pore length,having more hydrogenation activity sites and short contact time of reactant molecules with acidity sites.The evaluation results showed that the catalyst prepared on the basis of small crystal-size USY zeolite had higher tetralin conversion and better hydro-upgrading performance for treating FCC LCO.

The Effect of Additives on Crystal Size of Sodium Sulphate

1 Introduction Anhydrous sodium,mainly produced in the United States,Canada,Japan,is indispensable commodities and raw materials in daily life and industry.In recent years,anhydrous sodium sulfate of general size was much oversupplied[1].However particles anhydrous sodium sulphate of large size is not adequate to the demand for its

Pyrene Nanocrystals Crystallized by a Continuous Flow Microreactor

Pyrene solution and distilled water were flowed through a microreactor at a predetermined flow rate to generate pyrene crystals. Pyrene nanocrystals were crystallized by a Continuous Flow Microreactor. The particle size and luminescence properties of pyrene nanocrystals produced were evaluated. The crystal mean size between 60 nm and 400 nm could be controlled by the operating conditions. The crystal mean size decreased with increasing flow rate and solution concentration. In addition, the crystal morphology also changed. In the case of slow flow conditions, a needle-like crystal morphology was obtained. The crystal morphology became spherical on increasing the flow rate. Pyrene crystals with size about 400 nm exhibited luminescence at about 470 nm. As the crystal size decreased, the intensity of the luminescence also declined. The luminescence wavelength was in the range of about 370 to 400 nm.

Size and Weight Fraction of Solvent Crystals in Poly (Vinyl Alcohol) Gel Prepared from Dimethylsulfoxide/Water Solution

The size and weight fraction of crystals of pure ice or dimethylsulfoxide (DMSO) in poly(vinyl alcohol) (PVA) gel prepared from a mixed solvent of DMSO/water were determined from melting peaks observed by differential scanning calorimetry (DSC). The depression of the melting point with respect to the equilibrium melting point and the melting enthalpy gave the crystal size and weight fraction, respectively. The sizes were in the range of a few nm to tens of nm, depending on the composition ratio of the mixed solvent (DMSO/water) and the polymer concentration. Based on the weight fraction, the critical condition at which the whole solvent became non-freezable was estimated, and it was found to depend on both the PVA concentration and the DMSO/water ratio. When the solvent was pure water, the critical PVA concentration was as high as 86.4 wt%, while for pure DMSO solvent it was 50.1 wt%.

Recent advances in naphtha catalytic cracking by nano ZSM-5:A review

This review discussed the use of nano ZSM‐5 in naphtha catalytic cracking. The impact of nano ZSM‐5 on product selectivity, reaction conversion and catalyst lifetime were compared with micro‐sized ZSM‐5. The application of nano ZSM‐5 not only increased the catalyst lifetime, but also gave more stability for light olefins selectivity. The effects of the reaction parameters of temperature and feedstock on the performance of nano ZSM‐5 were investigated, and showed that high temperature and linear alkanes as feedstock improved light olefin selectivity and conversion.

Ice Slurry Formation in a Cocurrent Liquid-Liquid Flow

A new technique for ice slurry production was explored. Multiple small water-drops were formed in another immiscible chilled liquid by a single-nozzled atomizer and frozen in the fluidized bed by direct contact heat transfer. Experiments were conducted to investigate the dynamic behaviors of the ice crystal making system. The results demonstrate that the ice crystals could be produced continuously and stably in the vertical bed with the circulating coolant of initial temperature below -5℃. The size distribution of the ice crystals appears non-uniform, but is more similar and more uniform at lower oil flow rate. The mean ice crystal size rests seriously with the jet velocity and the oil flow rate. It decreases with decreasing the oil flow rate, and reaches the maximum at an intermediate jet velocity at about 16.5 m.s y. The ice crystal size is also closely related to the phenomenon of drop-coalescing, which can be alleviated considerably by reducing the flow rate or lowering the temperature of the carrier oil. However, optimization of liquid-liquid atomization is a more effective approach to produce fine ice crystals of desired size.