Lei Shao

Beijing University of Chemical Technology, Peping, Beijing, China

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Publications (65)71.54 Total impact

  • Colloids and Surfaces A: Physicochemical and Engineering Aspects. 01/2014; 455:129–135.
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    ABSTRACT: The homogeneous catalytic oxidation of ammonium sulfite in a microporous tube-in-tube microchannel reactor (MTMCR) was studied in this paper. It was found that the oxidation rate of ammonium sulfite in the MTMCR is 360 times higher than that in a packing column and could be further boosted about 4–6 times by the Co2+ catalyst. The effects of different operating parameters on the oxidation of ammonium sulfite were investigated. Experimental results indicated that the oxidation ratio of ammonium sulfite increased with the increase of the oxygen volumetric flow rate, but decreased with the increase of the liquid volumetric flow rate and sulfite concentration, and a smaller micropore size and annular channel width resulted in a higher oxidation ratio of ammonium sulfite. The oxidation ratio reached 80% under the optimum operating conditions in the catalytic oxidation process. This study reveals that the MTMCR is a potential intensification device for the oxidation process of ammonium sulfite.
    Chemical Engineering Journal. 01/2014; 253:258–263.
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    ABSTRACT: Global warming due to greenhouse effects is on the rise, and many efforts to reduce emissions of CO2 which is a major greenhouse gas from combustion of carbonaceous materials are being made. In this study, chemical absorption of CO2 into N-methyldiethanolamine (MDEA) solution combined with effective activator piperazine (PZ), from a gas mixture containing N2 was carried out in a high-throughput microporous tube-in-tube microchannel reactor (MTMCR). As a novel microreactor, MTMCR greatly intensifies gas–liquid mass transfer due to its large gas–liquid interfacial area. The effects of different parameters on the overall volume mass transfer coefficient and CO2 removal efficiency were investigated. The results showed that both mass transfer coefficient and CO2 removal efficiency increased with an increase in the liquid flow rate, temperature and concentration of liquid solvent. Also, the gas–liquid mass transfer efficiency increased with a decrease in the size of the micropore and annular channel of MTMCR. The volume mass transfer coefficient and CO2 removal efficiency reached 1.70 s−1 and 97%, respectively, at flow rates of 100 L/h and 5.32 L/h for gas and liquid respectively, with alkanolamine solutions containing 10 wt.% MDEA and 4 wt.% PZ.
    Separation and Purification Technology 01/2014; 125:52–58. · 2.89 Impact Factor
  • Chemical Engineering and Processing: Process Intensification. 01/2014;
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    ABSTRACT: This article presents experimental investigation on the oxidative treatment of phenol in water by O3/H2O2 in a rotating packed bed (RPB). It was found that the phenol degradation ratio increased with increasing rotation speed, initial pH value of phenol solution, and temperature. The degradation ratio of phenol had a peak value with increasing H2O2 concentration. The optimum operating conditions in this study were determined as an H2O2 concentration of 6.5 mM and a rotation speed of 1200 rpm. Phenol degradation ratio reached 100% at an initial phenol concentration of 40 mg/L in the O3/H2O2 process.
    Ozone Science and Engineering 01/2013; 35(2). · 0.81 Impact Factor
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    ABSTRACT: More-accurate overall mass-transfer coefficients in a rotating packed bed (RPB) and local mass-transfer coefficients in different regions of the RPB were deduced by the material balance in order to obtain practical volumetric mass-transfer coefficients in the RPB. Experimental studies on the overall volumetric mass-transfer coefficients (KGa) of CO2 in NH3 and CO2 absorption into water in the RPB was carried out under different conditions. The experimental results indicated that there was a great difference between the value of KGa and KGa* attained by different boundary conditions. And it was concluded that an accurate design equation should be adopted to achieve a practical value of KGa in the RPB. It was also found that the KGa of CO2 increased with the increase of rotation speed, liquid volumetric flow rate, gas volumetric flow rate, NH3/CO2 molar ratio, and the decrease of temperature. The KGa of CO2 in the simultaneous absorption process of NH3 and CO2 was 2–6 times higher than that in the single CO2 absorption process.
    Industrial & Engineering Chemistry Research. 08/2012; 51(33):10949–10954.
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    ABSTRACT: A simple and efficient sonochemical method was developed for the degradation of organic matter and ammonia nitrogen in azodicarbonamide wastewater. The effects of initial pH, ultrasound format and peripheral water level on the sonolysis of hydrazine, urea, COD and ammonia nitrogen were investigated. It is found that the initial pH has a significant influence on the degradation of hydrazine and ammonia nitrogen, whereas this impact to urea is relatively small. It also shows that a noticeable enhancement of ammonia nitrogen removal could be achieved in a proper intermittent ultrasound operation mode, i.e., 1/1 min on/off mode. The height difference between the peripheral water level and the inner water level of the flask affects the efficiency of ultrasonic treatment as well.
    Chinese Journal of Chemical Engineering. 08/2012; 20(4):754–759.
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    ABSTRACT: The treatment of acidic phenolic wastewater by ferrous-catalyzed ozonation (O3/Fe(II)) process in a rotating packed bed (RPB) was studied, and the O3/Fe(II) process was compared with the O3 process. It was observed that the phenol degradation rate in the O3/Fe(II) process was roughly 10% higher than that of O3 process in acidic environment in the RPB. It is also found that the degradation efficiency of phenol was significantly affected by the rotation speed and inlet ozone concentration. Phenol degradation efficiency increased with increasing initial pH of the phenolic solution, rotation speed, and concentrations of the inlet ozone gas, as well as a decreasing liquid flow rate and initial concentrations of phenol. Phenol degradation efficiency reached maximum at a temperature of 25 °C and an initial Fe(II) concentration of 0.4 mM. The result of the contrast experiment showed that the biological oxygen demand/chemical oxygen demand (BOD/COD) of the phenol solution increased from 0.2 to 0.59 after the solution was treated by O3/Fe(II) process. The intermediates of the ferrous-catalyzed ozonation process were identified by gas chromatography/mass spectroscopy (GC/MS), and it is deduced that the pathway of phenol degradation in ferrous-catalyzed ozonation is different from that in ozonation. Hydroquinone and 1,4-benzoquinone were the main intermediates, and a small amount of polymeric intermediates was found in the O3/Fe(II) process.
    Industrial & Engineering Chemistry Research. 07/2012; 51(31):10509–10516.
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    ABSTRACT: In this work, gas–liquid mass transfer characteristics, such as effective interfacial area (ae) and liquid side mass transfer coefficient (kL), were investigated in a rotating packed bed (RPB) contactor with 5 novel rotors equipped with blades in the packing section and 1 conventional rotor without blades and fully filled with the same packing. The chemisorption of CO2 into a NaOH solution was used to evaluate ae and kL within each rotor of the RPB. The experimental results indicate that the rotors with blades can significantly intensify the mass transfer process at all rotational speeds, over a range of gas–liquid ratios. The mass transfer rate achieved within these novel rotors was between 8% and 68% higher in comparison with the conventional rotor. A model based on the Danckwerts surface renewal theory was developed to calculate the liquid side volumetric mass transfer coefficient (kLae) in the rotor. The experimentally obtained values of kLae are in agreement with model predictions within ±15%.
    Industrial & Engineering Chemistry Research. 06/2012; 51(26):9164–9172.
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    ABSTRACT: The ozonation of synthetic wastewater containing azo dye Acid Red 14 (AR 14) was investigated in a high-throughput microporous tube-in-tube microchannel reactor. The effects of design and operating parameters such as micropore size, annular channel width, liquid volumetric flow rate, ozone-containing gas volumetric flow rate, initial pH of the solution and initial AR 14 concentration on decolorization efficiency and ozone utilization efficiency were studied with the aim to optimize the operation conditions. An increase of the ozone-containing gas or liquid flow rate could greatly intensify the gas-liquid mass transfer. Reducing the micropore size and the annular channel width led to a higher mass transfer rate and was beneficial to decolorization. Decolorization efficiency increased with an increasing ozone-containing gas volumetric flow rate, as well as a decreasing liquid volumetric flow rate and initial AR 14 concentration. The optimum initial pH for AR 14 ozonation was determined as 9.0. The degradation kinetics was observed to be a pseudo-first-order reaction with respect to AR 14 concentration. The difference between the decolorization and COD removal efficiency indicated that many intermediates existed in AR 14 ozonation. The formation of six organic intermediates during ozonation was detected by GC/MS, while the concentration of nitrate and sulfate ions was determined by ion chromatography. The possible degradation mechanism of AR 14 in aqueous solution was proposed.
    Chemosphere 06/2012; 89(2):190-7. · 3.14 Impact Factor
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    ABSTRACT: The continuous production of Cu nanoparticles with a particle size of 2-5 nm was conducted by sodium borohydride reduction of copper sulfate in aqueous solution in a tube-in-tube microchannel reactor (TMR), which consists of an inner tube and an outer tube with the reaction performed in the annular microchannel between these two tubes. The as-prepared Cu nanoparticles were compared with those obtained by a conventional batch synthesis process by using transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis spectroscopy. Due to the highly intensified micromixing effects in the TMR, Cu nanoparticles prepared by this route exhibits a smaller particle size, narrower size distribution and better stability in air. The TMR shows an excellent ability of preparing high-quality Cu nanoparticles in mild conditions. In addition, with the unique microchannel structure, the throughput capability of the TMR for the production of Cu nanoparticles is up to several liters per minute.
    Journal of Nanoscience and Nanotechnology 06/2011; 11(6):5154-8. · 1.15 Impact Factor
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    ABSTRACT: In this article, preliminary experimental results are presented on the absorption of carbon dioxide (CO2) in a novel high-throughput microporous tube-in-tube microchannel reactor (MTMCR), with an aqueous solution of monoethanolamine (MEA) and a mixture of CO2/N2 as the working fluids. The effects of design and operating parameters on the CO2 removal efficiency were investigated. The absorbent concentration was given the priority as a key factor for consideration, with the result that the CO2 removal efficiency increased with increasing concentrationan and could reach 90% or even higher at a high throughput of 440 L/h for gas with an MEA concentration of 30 wt %. With a decrease of the superficial gas velocity or an increase of the superficial liquid velocity, the CO2 removal efficiency increased. Increasing the absorbent temperature yielded better absorption performance. Reducing the most important structural parameters of the MTMCR, such as the micropore size and the annular channel width, led to a higher mass-transfer rate and was beneficial for CO2 removal. This work also investigated the characteristics of the pressure drop of two-phase flows through the MTMCR. The results obtained imply a great potential for MTMCRs applied to the separation of the greenhouse gas CO2 from the exhausted gases.
    04/2011;
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    ABSTRACT: This article presents investigations on the synthesis of nano-CaCO3 by the simultaneous absorption of CO2 and NH3 into CaCl2 solution in a rotating packed bed (RPB). The influence of the experimental parameters including the high gravity level, gas volumetric flow rate, liquid volumetric flow rate, and initial CaCl2 concentration on the particle size of CaCO3 were studied. Transmission electron microscope image of the as-prepared CaCO3 shows that the mean size of the nano-CaCO3 particles was about 50 nm with a particle size distribution (PSD) of 10–80 nm. X-ray diffraction pattern demonstrates that the nano-CaCO3 has a calcite crystal structure.
    Chemical Engineering Journal. 04/2011; 168(2):731–736.
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    ABSTRACT: A sampling tube was installed closely to the rotor in a rotating packed bed (RPB) to collect the liquid immediately flowing out of the packing so as to measure the real effective gas–liquid interfacial area in the packing of the RPB (i.e. excluding the cavity zone). It was calculated that the contribution of the cavity zone to mass transfer accounted for about 13–25% of the overall mass transfer in the whole RPB. The existence of the end effect in the packing was confirmed by an investigation on the effective gas–liquid interfacial area in the packings with different radii. Effects of radial thickness of the packing, rotation speed, liquid and gas volumetric flow rate on the effective interfacial area were also studied.
    Chemical Engineering Journal - CHEM ENG J. 01/2011; 168(3):1377-1382.
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    ABSTRACT: High-throughput microporous tube-in-tube microchannel reactor (MTMCR) was first designed and developed as a novel gas–liquid contactor. Experimentally measured kLα in MTMCR is at least one or two orders of magnitude higher than those in the conventional gas–liquid contactors. A high throughput of 500 L/h for gas and 43.31 L/h for liquid is over 60 times higher than that of T-type microchannel. An increase of the gas or liquid flow rate, as well as a reduction of the micropore size and annular channel width of MTMCR, could greatly intensify the gas–liquid mass transfer. The interfacial area, α, in MTMCR was measured to be as high as 2.2 × 105 m2/m3, which is much higher than those of microchannels (3400–9000 m2/m3) and traditional contactors (50–2050 m2/m3). The artificial neural network model was proposed for predicting α, revealing only an average absolute relative error of <5%. © 2010 American Institute of Chemical Engineers AIChE J, 2011
    AIChE Journal 12/2010; 57(1):239 - 249. · 2.58 Impact Factor
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    ABSTRACT: This article presents the preparation of nanoparticles of amorphous cefuroxime axetil (CFA) in a microporous tube-in-tube microchannel reactor (MTMCR). The experimental results indicated that CFA particle with a tunable size of 400-1400 nm could be achieved under a high throughput in the range of 1.5-6L/min. The average particle size decreased with increasing overall volumetric flow rate and decreasing CFA concentration, micropore size, and annular channel width. The produced CFA nanoparticles were characterized by SEM, XRD, FT-IR, DSC and a dissolution test, which indicated that the nanosized CFA was amorphous and exhibited higher dissolution rate compared to the raw CFA. The MTMCR might offer a general and facile pathway for mass production of the nanoparticles of hydrophobic pharmaceuticals thanks to its high throughput capacity and excellent micromixing performance.
    International Journal of Pharmaceutics 08/2010; 395(1-2):260-5. · 3.99 Impact Factor
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    ABSTRACT: In this work, monodispersed pharmaceutical colloidal spheres of atorvastatin calcium (AC) with tunable sizes have been synthesized in a microfluidic system at continuous flow conditions. The influences of the key parameters, including the concentration of the AC methanol solution, the overall flow rate, the flow rate of isopropanol, and the flow rate of the AC methanol solution on particle size and size distribution were discussed. The results indicated that the drug concentration and the flow rate could efficiently control the particle size and improve the polydispersity of the resulting particles. The particle size decreased from 760 to 300 nm with an increase in the AC concentration from 30 to 60 mg/mL and significantly increased from 430 to 2500 nm with an increase in the flow rate of the AC methanol solution from 2.7 to 16 mL/min. However, with the increase of the overall flow rate at a fixed flow ratio of 10, the particle size slightly decreased from 240 (10/1 mL/min) to 210 nm (30/3 mL/min) and then dramatically increased to 680 nm (80/8 mL/min). Also, the particle size first decreased and then increased with an increase in the flow rate of isopropanol. The prepared AC colloidal spheres were amorphous and displayed enhanced dissolution rate compared with the commercial AC. This work shows that the continuous synthesis in a microfluidic reactor is a simple and economic way to prepare monodispersed pharmaceutical colloidal particles or nanoparticles with tunable sizes.
    Industrial & Engineering Chemistry Research - IND ENG CHEM RES. 03/2010; 49(9).
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    ABSTRACT: Process intensification has long been known to be a vital concept and is considered to be one of the fundamental pillars of the chemical engineering domain. This paper reviews the advances on the high-gravity (Higee) technology, including the theoretical studies on liquid flow, gas–liquid mass transfer, residence time distribution and micromixing, and the applications of Higee technology in absorption, stripping, nanoparticles preparation and other fields such as sulfonation, polymerization, synthesis of diphenyl-methane-diisocyanate and emulsification. The application of Higee in industry shows good adaptabilities of this technology and brings considerable profits.
    Chemical Engineering Journal. 01/2010;
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    ABSTRACT: A mass transfer model for devolatilization process of highly viscous media in rotating packed bed (RPB) was developed based on penetration theory and mass conservation. Before establishing the model, some mass transfer experiments of thin film were conducted in a designed diffusion cell including vacuum and feeding system. In this study, acetone was used as the volatile organic compound (VOC) and syrup as the highly viscous media. The thickness of thin film was changed by using different liquid distributor. It was found that bubbling played an important role in the devolatilization. The correlation of diffusion coefficient of acetone in highly viscous dilute solution was proposed. The relative error between predicted and experimental data was within the range of ±30% for diffusion coefficient of acetone in syrup. A comparison of experimental data of RPB with model indicated that the relative error was within ±30% for efficiency of acetone removal.
    Chinese Journal of Chemical Engineering - CHINESE J CHEM ENG. 01/2010; 18(2):194-201.
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    ABSTRACT: In this work, size-controllable nanoparticles of amorphous cefuroxime axetil (CFA), a poorly water-soluble drug, have been prepared in a Y-junction microchannel reactor (YMCR) by nanoprecipitation for enhancing dissolution rate of CFA. The effects of the operation parameters, such as flow rate of CFA acetone solution, antisolvent flow rate, overall flow rate, CFA concentration and precipitation temperature, on particle size and size distribution were experimentally investigated. The results indicated that the particle size obviously decreased from 1100 to 630nm with decreasing the CFA solution flow rate from 16 to 2mL/min, and decreased from 450 to 350nm with the decreased temperature from 50 to 5°C. However, with the increase of the antisolvent flow rate at a fixed CFA solution flow rate of 4mL/min, the particle size obviously decreased from 1229nm (20mL/min) to 581nm (60mL/min), and then increased to 698nm (80mL/min). Also, the particle size firstly decreased and then increased with the increase of the overall flow rate and CFA solution concentration. The as-prepared CFA nanoparticles displayed a size-dependent and significantly enhanced dissolution property when compared to raw CFA and commercial spray-dried CFA. This work suggests that the continuous synthesis in a microfluidic reactor is a simple and economic way to prepare pharmaceutical nanoparticles with tunable sizes.
    Chemical Engineering Journal - CHEM ENG J. 01/2010; 162(2):844-851.