A study of Nusselt and Sherwood numbers in a monolith reactor

A two-dimensional model of a single channel of a monolith reactor is used to evaluate the values of the Nusselt and Sherwood numbers under reaction conditions. The circular channel is assumed to have axisymmetry with a first-order reaction occurring at the wall. The values of the Nusselt and Sherwood numbers do not correlate uniquely with the Graetz number but rather depend on the reaction rate at the wall. Hence they depend on such variables as gas velocity, inlet temperature and reactant concentration.     

Application of ionic liquids as mobile phase additives and surface-bonded stationary phase in liquid chromatography

Ionic liquids (ILs) have gained wide recognition as novel solvents in chemistry. Their application in analytical chemistry, especially in separating analytes, is warranted due to their unique properties such as negligible vapor pressure, good thermal stability, tunable viscosity and miscibility with water and organic solvents, as well as good extractability for various organic compounds and metal ions. Recently, some new chromatographic separation media, formed by combining ILs on silica and polymer surface using covalently or non-covalently interaction, have been developed and applied to biological separation and environment analysis. This review will focus on some of the properties of ILs and their potential application as mobile phase modifier and surface-bonded stationary phase in high-performance liquid chromatography (HPLC) separation.     

L-脯氨酸键合手性配体交换色谱固定相的制备及手性拆分

合成了L－脯氨酸键合手性配体交换固定相，用元素分析和红外光谱对固定相进行了表征。该固定相在反相条件下对DL－氨基酸对映异构体有良好的拆分能力。     

Kinetic and Mass Transfer Model for Separation of Protein Using Ceramic Monoliths as a Stationary Phase

Rigid adsorbents used as matrix skeleton have advantages over soft gel media for downstream processing of proteins. The adsorption of bovine serum albumin (BSA) has been investigated on a rigid ceramic monolith coated with cross-linked microporous agarose (D5). The physical properties of the adsorbent and the adsorption equilibria, adsorption kinetics, and mass transfer behavior have been studied for five different flow rates, with a pH value ranging from pH 4.5 to 7.0. The optimal working flow rate was 14.0?cm³/min, and using this flow rate, increasing the pH does not generate a significant improvement in the adsorption capacity. The rates of BSA adsorption have been measured and it was possible to describe a theoretical model, in which the mass transfer involves a dispersion coefficient (k_disp), which describes the mass transfer in the adsorbent surface, from the volume of the protein solution to the agarose surface. This parameter presents an exponential tendency by increasing the flow rate from 2.37?×?10^?6 to 87.40?×?10^?6?cm/s for n?=?1. Values obtained for the adsorption kinetic constant (k_ads) followed the trend of the mass transfer parameter, increasing with the flow rate from 1.94?×?10⁴ to 117.39?×?10⁴?cm²/mol?s. The theoretical model predicts the protein concentration in equilibrium for successive column reuses and it can be readily used to determine the optimal reuse of column. Likewise, for a maximum flow rate of 14?cm³/min, pressure drop was 0.04?MPa, being an advantage in front of packed columns that have higher pressure drop.     

Preparation and characterization of three dimensionally ordered macroporous Li4Ti5O12 anode for lithium batteries

Three dimensionally ordered macroporous (3DOM) Li₄Ti₅O₁₂ membrane (80 μm thick) was prepared by a colloidal crystal templating process. Colloidal crystal consisting of monodisperse polystyrene particles (1 μm diameter) was used as the template for the preparation of macroporous Li₄Ti₅O₁₂. A precursor sol consisting of titanium isopropoxide and lithium acetate was impregnated into the void space of template, and it was calcined at various temperatures. A macroporous membrane of Li₄Ti₅O₁₂ with inverse-opal structure was successfully prepared at 800 °C. The interconnected pores with uniform size (0.8 μm) were clearly observed on the entire part of membrane. The electrochemical properties of the three dimensionally ordered Li₄Ti₅O₁₂ were characterized with cyclic voltammetry and galvanostatic charge and discharge in an organic electrolyte containing a lithium salt. The 3DOM Li₄Ti₅O₁₂ exhibited a discharge capacity of 160 mA h g⁻¹ at the electrode potential of 1.55 V versus Li/Li⁺ due to the solid state redox of Ti^3+/4+ accompanying with Li⁺ ion insertion and extraction. The discharge capacity was close to the theoretical capacity (167 mA h g⁻¹), which suggested that the Li⁺ ion insertion and extraction took place at the entire part of 3DOM Li₄Ti₅O₁₂ membrane. The 3DOM Li₄Ti₅O₁₂ electrode showed good cycle stability.     

高稳定性硅基杂化纤维素衍生物手性固定相的制备及其色谱拆分性能

合成了含少量3-(三乙氧基硅)丙基氨基甲酸酯的纤维素3,5-二甲基苯基氨基甲酸酯衍生物(CDMPC),并采用1,2-二(三乙氧基硅基)乙烷(BTSE)为偶联剂,通过溶胶-凝胶法成功制备得到新型硅基杂化手性固定相。该固定相的CDMPC含量达60%,在含有10%氯仿的流动相中保持良好的手性识别性能和机械强度。使用其拆分了多种手性化合物,拆分效果优于商品柱Chiralpak IB,其中对2,2,2-三氟-1-(9-蒽基)乙醇和反式二苯乙烯氧化物对映体的分离选择性分别达到2.99和2.48,表明该类硅基杂化类手性固定相在制备色谱领域中有潜在应用前景。     

丙氧基—18—冠—6硅胶键合固定相的合成及色谱性能的研究

以多孔硅胶为基质,固相合成并制备了一种新型丙氧基-18-冠-6键合固定相(P18-C-6 SB),详细研究了其合成反应条件。P18-C-6 SB 是一种热稳定性好、耐溶剂,表面键合浓度高的色谱固定相。已应用于芳香族异构体及同系物的分离。     

Eupergit手性配体交换色谱固定相的制备及应用

介绍了以Eupergit C 250L为载体,L-羟脯氨酸盐为手性配体,通过两者间的"一步交联反应",制备出一种新型的Eupergit手性配体交换固定相。交联反应过程简单、高效、副反应少。尝试通过此大颗粒的Eupergit手性配体固定相对丝氨酸手性对映异构体进行拆分,得到了良好的拆分结果。为将来在工业领域内,通过使用制备型拆分柱来拆分手性氨基酸的设想提供了有利的技术支持。     

Evaluation of models and correlations for pressure drop estimation in dense phase pneumatic conveying and an experimental analysis

This study reviews the models and correlations for dense phase conveying in an effort to explore existing and new data on the subject and to provide guidance to the designer on the best pressure drop model. Using various data sets the Mi (Konrad)-based model was found to be best for predicting the pressure drop across dense phase plugs. A series of industrial scale tests also shows agreement with the Mi (Konrad)-based model.     

Study of Single Phase Flow Heat Transfer and Friction Pressure Drop in a Spiral Internally Ribbed Tube

The experimental results of single‐phase flow heat transfer and pressure drop experiments in the turbulent flow regime in a spirally ribbed tube and a smooth tube are presented in this paper. The ribbed tube has an outside diameter of 22 mm and an inside diameter of 11 mm (an equivalent inside diameter of 11.6 mm) and the smooth tube has an outside diameter of 19 mm and an inside diameter of 15 mm. Both tubes were uniformly heated by passing an electrical current along the tubes with a heated length of 2500 mm. The working fluids are water and kerosene, respectively. The experimental Reynolds number is in the range of 10⁴–5 · 10⁴ for water and is in the range of 10⁴–2.2 · 10⁴ for kerosene. The experimental results of the ribbed tube are compared with those of the smooth tube. The heat transfer coefficients of the ribbed tube are 1.2–1.6 fold greater than those in the smooth tube and the pressure drop in the ribbed tube is also increased by a factor of 1.4–1.7 as compared with those in the smooth tube for water. The corresponding values for kerosene are 2–2.7 and 1.5–2, respectively. The heat‐transfer enhancement characteristics of the ribbed tube are assessed. This tube is especially suitable for augmenting single‐phase flow heat transfer of kerosene. Correlations for the heat transfer and the pressure drop for the spirally ribbed tube are proposed, according to the experimental data.     

The role of comprehensive chromatography in the characterization of edible oils and fats

Chromatography has a very long history in the analysis of edible oils and fats. Hyphenations of two chromatographic methods, or couplings of a chromatographic separation technique with spectroscopic detection and identification devices, are used if the resolving power of the technique needs to be improved. More recently, the analytical benefits of comprehensive two‐dimensional (2D) chromatography, in its various operational modes, have been exploited by the oil and fat chromatographic community. In comprehensive 2D chromatography, the entire sample injected is subjected to two independent separation processes. In the present contribution, the principles of comprehensive 2D chromatography are briefly discussed. Next, the advantages of comprehensive separations for lipid analysis are illustrated using the concept of generic chromatographic applications. This concept distinguishes three generic reasons to apply chromatographic separations: target compound analysis, group‐type separation, and chromatographic fingerprinting. Examples of how comprehensive multi‐dimensional methods were successfully applied to solve problems in the edible oils and fats area are given. We believe that these multi‐dimensional techniques truly add new dimensions to oil and fat analysis, providing researchers in the area with novel tools for unraveling edible oil or fat samples with their complex compositions.     

Visual analysis of particle bouncing and its effect on pressure drop in dilute phase pneumatic conveying

During the pneumatic conveying of plastic pellets, it has been observed that materials with similar physical characteristics may develop substantial difference in pressure drop, whose cause is not fully understood. This experimental study focused on the dynamic behavior of the particles during conveying and its influence on pressure drop.The bouncing of the particles during pneumatic conveying in dilute phase was visually analyzed by means of a high speed video camera. The experiments included two different plastic pellets of similar size and density but different modulus of elasticity. The conveying trials were carried out in a 0.052 m I.D. aluminum pipe conveying system approximately 35 m long. The loading was controlled by an airflow control valve and a variable speed drive rotary valve. For each material, a series of tests were performed creating a matrix of six solids rates for five different air velocities. During the conveying trials a high speed video camera was used to record the actual particle motion in a horizontal section with fully accelerated flow. The videos showed significant difference in bouncing between the soft and the hard pellets. The soft pellets showed very random and intense bouncing with strong rotation, which affected the rebound considerably. In fact, some particles bounced even backwards. On the other side, the hard pellets showed significantly less bouncing and rotation.In addition to the high speed videos, in each test the pressure drop was measured in the horizontal and vertical directions. As expected, a significant difference in pressure drop was recorded for the same conveying settings when using the different materials. The pressure drop showed a close relation to the bouncing of the particles, being much higher for the soft pellets.It can be concluded that the increased pressure drop, developed by the soft polyethylene pellets, is in part due to the multiple times the particles must be reaccelerated during their transit through the conveying system. Additionally, the reduction in the average particle velocity increases the drag force. All of this resulted in up to 3-fold increase in pressure drop across the conveying line compared to the hard polyethylene pellets that showed significantly less bouncing.     

Preparation of a monolithic and macroporous superabsorbent polymer via a high internal phase Pickering emulsion template

A superabsorbent polymer (SAP) possesses an ability to absorb an aqueous solution up to several hundred times its own weight. To utilize a SAP effectively, a high absorption rate is also essential in addition to a high absorption capability. Herein, using a template based on a high internal phase Pickering emulsion (HIPPE) stabilized by aluminum oxide (Al₂O₃) nanoparticles, we synthesize a SAP with a high absorption rate by forming macropores. In particular, by adjusting three different parameters, the concentration of the crosslinker, the internal volume fraction of the emulsion, and the particle concentration, we successfully formed a HIPPE-templated SAP with a high absorption rate for a saline solution, which was 51.6 g g⁻¹ of the absorbency within 10 s. We confirm that the swelling kinetics is mainly determined by the interconnectivity between the internal macro-pores. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48133.     

Pressure drop and mixing in single phase microreactors: Simplified designs of micromixers

Continuous flow microreactors can greatly improve the safety and product yields of processes in the pharmaceutical and fine chemical industry by overcoming many of the drawbacks of traditional batch and semi-batch stirred reactors. This study compares on a common scale the pressure drop and mixing performance of different size commercial microreactor plates composed of a tangential, SZ-shaped or caterpillar mixer followed by a rectangular serpentine main channel. The pressure drop was fitted to a friction factor model, which suggests that the mixing zone had significant chaotic secondary flow patterns, whereas the main channel did not. Moreover, the mixing zone was the main contributor to the overall pressure drop. Mixing performance was then characterized using competitive parallel reactions. Upon the formation of chaotic secondary flows, typically due to the interactions of artificially induced vortices, the mixer performance was found to be independent of geometry for a given energy dissipation rate. However, the mixer geometry will affect the critical Reynolds number that induces chaotic advection and changes the mixing time scale.     

Poly(acrylamide‐allyl glycidyl ether) cryogel as a novel stationary phase in dye‐affinity chromatography

Poly(acrylamide‐allyl glycidyl ether) [poly(AAm‐AGE)] cryogel was prepared by bulk polymerization which proceeds in an aqueous solution of monomers frozen inside a glass column (cryo‐polymerization). After thawing, the monolithic cryogel contains a continuous polymeric matrix having interconnected pores of 10–100 μm size. Cibacron Blue F3GA was immobilized by covalent binding onto poly(AAm‐AGE) cryogel via epoxy groups. Poly(AAm‐AGE) cryogel was characterized by swelling studies, FTIR, scanning electron microscopy, and elemental analysis. The equilibrium swelling degree of the poly(AAm‐AGE) monolithic cryogel was 6.84 g H₂O/g cryogel. Poly(AAm‐AGE) cryogel containing 68.9 μmol Cibacron Blue F3GA/g was used in the adsorption/desorption of human serum albumin (HSA) from aqueous solutions and human plasma. The nonspecific adsorption of HSA was very low (0.2 mg/g). The maximum amount of HSA adsorption from aqueous solution in acetate buffer was 27 mg/g at pH 5.0. Higher HSA adsorption value was obtained from human plasma (up to 74.2 mg/g). Desorption of HSA with a purity of 92% from Cibacron Blue F3GA attached poly(AAm‐AGE) cryogel was achieved using 0.1M Tris/HCl buffer containing 0.5M NaCl. It was observed that HSA could be repeatedly adsorbed and desorbed with poly(AAm‐AGE) cryogel without significant loss in the adsorption capacity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

液晶作为GC固定液的发展及趋势

综述和评价了液晶用作气相色谱（ＧＣ）固定液的现状及发展前景。目前，向列相、近晶相、胆甾相液晶分别按其各自的保留机理用于位置异构体的分离，以其高效、高选择性而优于常规固定液。继续将液晶冠醚用作ＧＣ固定液的研究并探索手性液晶对于对映异构体的分离是今后液晶固定液研究工作的主要方向。     

一种新型纤维素衍生物固定相的制备及对硝基苯胺异构体的分离

利用自制的环十二烷基胺对纤维素进行了改性,考察了将其作为高效液相色谱固定相对硝基苯胺3种异构体的分离,结果表明分离效果良好。     

Preparation, characterization and photoactivity of TiO2 obtained by a reverse microemulsion route

TiO₂ was synthesized by a reverse microemulsion route. By using different water contents in the reverse microemulsion, we obtained three different materials named R = 10, R = 20 and R = 30. The reverse microemulsion synthesis has the advantage that the kind of the crystalline titania structure obtained may be changed by simply modifying the water content in the microemulsion.The synthesized materials were characterized by nitrogen adsorption, scanning and transmission electron microscopy, and X-ray diffraction. Methylene blue (MB) was used as testing dye; we studied the pH effect and catalyst dosage in the MB photodegradation. The degradation kinetics was also studied.     

Flow characteristics and pressure drop across the Laval nozzle in dense phase pneumatic conveying of the pulverized coal

Experimental studies were performed to describe the physical phenomena occurring in dense phase pneumatic conveying of the pulverize coal with a Laval nozzle installed in the pipeline. The maximal coal mass flow rate decreased from 0.87 kg/s to 0.35 kg/s and an obvious decrease in the solids loading ratio was revealed after the Laval nozzle was installed. In addition, the Laval nozzle showed a better capacity of resisting disturbance, which made it easier to control the coal mass flow rate precisely and promoted the stable conveying process. These specific physical phenomena were proved to result from the high pressure drop of the Laval nozzle. Thereby, a mathematic model was developed to predict the two-phase pressure drop across the Laval nozzle. The pressure drop model described the experimental data within the 15% deviation. The main influence factors contributing to the pressure drop of the Laval nozzle were discussed using the model. Then the effects of gas mass flow rate, solids loading ratio, convergence angle, throat diameter and throat length were revealed.