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Steam reforming (SR) of dimethyl ether (DME) was investigated for the production of hydrogen for fuel cells. The activity of a series of solid acids for DME hydrolysis was investigated. The solid acid catalysts were ZSM-5 [Si/A1 25, 38 and 50: denoted Z(Si/A1)] and acidic alumina (γ-A12O3) with an acid strength order that was Z(25) ＞Z(38)＞Z(50)＞γ-A12O3. Stronger acidity gave higher DME hydrolysis conversion. Physical mixtures containing a CuO-ZnO-A12O3-ZrO2 catalyst and solid acid catalyst to couple DME hydrolysis and methanol SR were used to examine the acidity effects on DME SR. DME SR activity strongly depended on the activity for DME hydrolysis. Z(25) was the best solid acid catalyst for DME SR and gave a DME conversion＞90% [T=240℃, n(H2O)/n(DME)=3.5, space velocity=1179 ml•(g cat)^(-1)•h^(-1), and P=0.1MPa]. The influences of the reaction temperature, space velocity and feed molar ratio were studied. Hydrogen production significantly depended on temperature and space velocity. A bifunctional catalyst of CuO-ZnO-A12O3-ZrO2 catalyst and ZSM-5 gave a high H2 production rate and CO2 selectivity.

This paper described a method to predict the surface tension of a biodiesel fuel from the molecular structure of its fatty acid methyl ester (FAME) components. A topological index was proposed that used a combination of the distance matrix and adjacency matrix of the molecular structure. The topological index contains information on the molecular structure for the FAMEs, such as the carbon number and unsaturated bonds. The mean topological index values of five FAME mixtures (peanut, canola, coconut, and palm, soybean oil) were calculated by an integration using a modified Dalton-type mass-average equation. The relationship between the mean topological index and mean surface tension of FAME mixtures of biodiesel of known composition at 313 K was linear, and its regression equation allowed the surface tension of biodiesel fuels to be calculated. The relative error between the predicted surface tensions of the above biodiesel fuels and their measured values was within 2.19%. The surface tensions of five biodiesel fuels (corn, safflower, sunflower, and cottonseed, lard oil) were further predicted.

Biodiesel is a non-toxic and biodegradable substitute for petroleum-based diesel. However, it is impractical to use refined edible oils to produce biodiesel due to its high cost and priority for food products, especially in China, while waste oils with high free fatty acids (FFAs) can be considered as the raw materials. In the present work, a solid acid catalyst comprising SO42−/TiO2–SiO2 was prepared, characterized and studied for its activity for the production of biodiesel from several low cost feedstocks with high FFAs. The solid acid catalyst can be recycled, easily removed and can simultaneously catalyze esterification and transesterification. The influence of reaction parameters was studied, and the optimized reaction parameters are reaction temperature 200 °C, molar ratio of methanol to oil 9:1 and catalyst concentration 3 wt.%. The catalyst showed good stability. A continuous process for biodiesel production from cheap raw feedstocks was proposed, and a 10,000-tonnes/year biodiesel production demonstration plant has been built.

The goal of this study was to determine the effects of hindlimb unloading (HU) on the ex vivo growth and the osteogenic potential of mesenchymal stem cells (MSCs) from the femurs of rats. Microgravity was simulated by 28-day HU in male Sprague-Dawley (SD) rats, and the bone marrow (BM) was collected from hindlimb femurs of HU or control (CTL) rats. MSCs were isolated from BM and cultured for eight passages. Then MSCs at passages 2, 4, and 8 were induced for osteogenesis or adipogenesis. The results revealed that HU decreased the osteogenic potential of MSCs and also decreased the expression of osteoblast gene marker mRNAs in cells induced by osteogenic conditions. Meanwhile, the expression of Runx2 mRNA and the phosphorylation of ERK were also decreased. There were no significant differences of osteoblast gene marker and Runx2 mRNA expression between cells induced from different passages of MSCs in UH rats. Under adipogenic conditions, HU increased both the adipogenic potential of MSCs and the expression of adipocytic gene marker mRNAs in induced cells. HU also increased the expression of PPAR gamma 2 mRNA, but with no effect on the phosphorylation of p38MAPK. The adipogenic potential of MSCs and the expression of adipocytic gene marker mRNAs in induced cells decreased along with cell cultures under normal gravity. This suggests that the normal gravity during in vitro MSC culture and the centrifugal force produced during cell harvest after each passage could decrease the adipogenic potential of MSCs, but could not reverse the effect of HU on the osteogenic potential of MSCs.

A CuO−ZnO−Al2O3−ZrO2 + HZSM-5 physical mixture bifunctional catalyst with a high activity for dimethy ether (DME) synthesis was used for CO2 hydrogenation. Various factors that affect catalyst activity, including the reaction temperature, pressure, and space velocity, were investigated. CO2 conversion reached 0.309, and DME and methanol yields were 0.212 and 0.059 with a stoichiometric ratio of H2 to CO2 of 3 at 523 K, 5 MPa, and a space velocity of 6000 mL/(g cat·h). Well-studied kinetic models for methanol synthesis and methanol dehydration, respectively, were used to fit the experimental data and the kinetic parameters in the rate equations for DME synthesis were obtained by regression. A simulated process for CO2 hydrogenation indicated that a higher DME yield can be obtained with CO recycle that will also give a CO-free product.

Liquid dispersion in an external-loop airlift slurry reactor was experimentally studied. The effects of the superficial gas velocity, concentration of fine particle, flowing resistance, and liquid level in the gas–liquid separator on the liquid dispersion coefficient were investigated. A liquid dispersion model was proposed based on Taylor dispersion equation to predict the liquid dispersion coefficient. According to this model, the dispersion coefficient and the combination factor u L 2 e L have a linear relationship. Validation of the liquid dispersion model together with the hydrodynamic model in our previous work was made by comparing the experimental and predicted results. The good agreement showed that the models could predict the liquid dispersion coefficient and the hydrodynamic behaviors of an airlift slurry reactor in a wide range of operating conditions with a satisfactory accuracy.

The hydrodynamic behavior of a three-phase spouted bed with large particles of diameter 10.5, 12 and 16 mm was studied. Liquid circulation was used to spout the large particles. Experiments were carried out to study the influence of the superficial gas velocity, liquid circulation velocity, particle diameter and settled particle bed height on the minimum liquid spouting velocity, pressure drop and gas holdup. In the spouted regime, liquid circulation and the movement of the large particles enhance bubble breakup and increase the gas holdup. The frequent collision of these large particles with the reactor wall and nozzles are helpful in preventing fouling. This indicates a potential application in gas-liquid systems in which fouling occurs due to deposition and adhesion.

The local hydrodynamic behaviours in an external loop airlift slurry reactor, including the gas holdup, bubble rise velocity, bubble size, were measured with a fibre optic probe. The liquid circulation velocity was measured with an ultrasound Doppler velocimetry. Two-dimensional simulations were carried out in the framework of Two-Fluid formulation coupled with a k-ϵ turbulence model. The lateral forces and interphase turbulence were taken into account and good agreement between the experimental and simulation results was obtained. The simulations show that the lateral forces and interphase turbulence have noticeable influence and should be included in the CFD model. On a mesure a l'aide d'une sonde a fibres optiques les comportements hydrodynamiques locaux dans un reacteur a suspensions a air ascendant et a boucle externe, incluant la retention de gaz, la vitesse de montee des bulles et la taille des bulles. La vitesse de circulation du liquide a ete mesuree avec un velocimetre Doppler a ultrasons. Des simulations bidimensionnelles ont ete effectuees dans le cadre d'une formulation a deux fluides couplee a un modele de turbulence k-ϵ. On a tenu compte des forces laterales et de la turbulence interphasique et de bons accords ont ete trouves entre les resultats experimentaux et des simulations. Les simulations montrent que les forces laterales et la turbulence interphasique ont une influence notable et devraient etre incluses dans le modele CFD.

Structure parameters and field-dependent magnetic properties of BaFe 12 O 19 nanoparticles synthesized from different Fe/Ba ratios by reverse micelle technique were investigated. Pure barium ferrite phase and best magnetic properties could be obtained for the sample prepared from Fe/Ba ratio of 11, with grain size in the range of 20–30 nm as shown by TEM. The existence of α-Fe 2 O 3 in other materials obviously decreases the magnetization properties, but coercivities of the materials from Fe/Ba ratio of 9.5 and 10 are abnormally even higher than the prepared pure BaFe 12 O 19 . The abnormal high coercivities of some prepared materials were explained from anisotropy mechanisms of nanoparticles.

Gas–liquid mass transfer in a bubble column in both the homogeneous and heterogeneous flow regimes was studied by numerical simulations with a CFD–PBM (computation fluid dynamics–population balance model) coupled model and a gas–liquid mass transfer model. In the CFD–PBM coupled model, the gas–liquid interfacial area a is calculated from the gas holdup and bubble size distribution. In this work, multiple mechanisms for bubble coalescence, including coalescence due to turbulent eddies, different bubble rise velocities and bubble wake entrainment, and for bubble breakup due to eddy collision and instability of large bubbles were considered. Previous studies show that these considerations are crucial for proper predictions of both the homogenous and the heterogeneous flow regimes. Many parameters may affect the mass transfer coefficient, including the bubble size distribution, bubble slip velocity, turbulent energy dissipation rate and bubble coalescence and breakup. These complex factors were quantitatively counted in the CFD–PBM coupled model. For the mass transfer coefficient kl, two typical models were compared, namely the eddy cell model in which kl depends on the turbulent energy dissipation rate, and the slip penetration model in which kl depends on the bubble size and bubble slip velocity. Reasonable predictions of kla were obtained with both models in a wide range of superficial gas velocity, with only a slight modification of the model constants. The simulation results show that CFD–PBM coupled model is an efficient method for predicting the hydrodynamics, bubble size distribution, interfacial area and gas–liquid mass transfer rate in a bubble column. 2007 Elsevier Ltd. All rights reserved.

The hydrodynamics of a slurry airlift reactor at high solid concentrations were experimentally studied. The influences of the average solid concentration, superficial gas velocity and particle size on the radial and axial profiles of the solid holdup, average gas holdup and liquid circulation velocity were investigated. The local solid holdup was measured with an electrical conductivity probe. At low solid concentrations or high superficial gas velocities, the radial profile of the solid holdup was uniform. At high solid concentrations, the radial profile of the solid holdup was nonuniform, with higher values near the wall. This radial nonuniformity increased with decreased superficial gas velocity or increased average solid concentration. The axial profile of the cross-sectional average solid holdup was uniform at all conditions in this work, even at high solid concentrations. The average gas holdup and liquid circulation velocity increased with the superficial gas velocity but decreased with the average solid concentration. A mathematical model based on the balance of the transverse lift force and turbulent dispersion force was proposed to predict the radial profile of the solid holdup. Reasonable predictions were obtained from this model with an adjustable model parameter.

Transesterification of cottonseed oil with methanol to biodiesel was investigated in various Bronsted acidic ionic liquids with an alkane sulfonic acid group. The properties, structures, and acidities of the ionic liquids were experimentally characterized and theoretically analyzed. The Bronsted acidity−activity correlation for the ionic liquids was studied. Among all these ionic liquids, 1-(4-sulfonic acid) butylpyridinium hydrogen sulfate exhibited the best catalytic performance, which is ascribed to its strong Bronsted acidity. The catalytic activity of ionic liquids was near that of concentrated sulfuric acid. The influences of ionic liquid dosage, molar ratio of methanol to cottonseed oil, and reaction temperature were explored using 1-(4-sulfonic acid) butylpyridinium hydrogen sulfate as the catalyst; the results were systematically explained. A high yield of fatty acid methyl esters of 92% was obtained under a mild reaction condition. The separation of the biodiesel can be performed by simple decan...

With the dramatic increase in the international oil price, gas-to-liquid processes of Fischer -Tropsch (FT) synthesis, methanol synthesis, and dimethyl ether (DME) synthesis have become increasingly important and received much attention from both academic and industrial interests. The slurry reactor has the advantages of simple construction, excellent heat transfer performance, online catalyst addition and withdrawal, and a reasonable interphase mass transfer rate with low energy input, which make it very suitable for gas-to-liquid processes. However, its multiphase flow behaviors are very complex and the multiphase reactor has some remarkable scale-up effects; therefore, extensive studies are still needed for the development and design of a high-performance slurry reactor. This article gives a state-of-the-art review of the recent studies on the slurry reactor for gas-to-liquid processes. The influences of the superficial gas velocity, operating pressure and temperature, solid concentration, column dimensions, and gas distributor are discussed. Some recent developments in the liquid-solid separation in a slurry reactor are also summarized. The concept of using internals to intensify the mass transfer and improve the hydrodynamics is discussed based on both experimental results and theoretical analysis. Modeling and simulations of the gas -liquid and gas-liquid-solid flows are briefly reviewed, with focus on the new trend of coupling the population balance model (PBM) into the computational fluid dynamics (CFD) framework to describe the complex bubble behaviors and gas-liquid interphase interactions. The results of a 3000 ton/year pilot plant for DME synthesis are given, showing that the slurry reactor has promising applications in gas-to-liquid processes. Fast development of the world economy and increase of the international oil price have made the global energy and environmental problems increasingly serious. The supply of coal is much more abundant than that of oil; therefore, the development of coal-based technologies for producing clean fuel is very important for the sustainable development of the economy and of the energy supply for the world. Gas-to-liquid processes of Fischer-Tropsch (FT) synthesis, methanol synthesis, and dimethyl ether (DME) synthesis have become increasingly important and received much attention from both academic and industrial interests. 1-9 Besides providing clean fuel, the products of gasto-liquid processes can be further produced to many other chemical products. 10

Human mesenchymal stem cells (MSCs) are multipotential and are detected in bone marrow (BM), adipose tissue, placenta, and umbilical cord blood (UCB). In this study, we examined the ability of UCB-derived MSCs (UCB-MSCs) to support ex vivo expansion of hematopoietic stem/progenitor cells (HSPCs) from UCB and the engraftment of expanded HSPCs in NOD/SCID mice. The result showed that UCB-MSCs supported the proliferation and differentiation of CD34+ cells in vitro. The number of expanded total nucleated cells (TNCs) in MSC-based culture was twofold higher than cultures without MSC (control cultures). UCB-MSCs increased the expansion capabilities of CD34+ cells, long-term culture-initiating cells (LTC-ICs), granulocyte-macrophage colony-forming cells (GM-CFCs), and high proliferative potential colony-forming cells (HPP-CFCs) compared to control cultures. The expanded HSPCs were transplanted into lethally irradiated NOD/SCID mice to assess the effects of expanded cells on hematopoietic recovery. The number of white blood cells (WBCs) in the peripheral blood of mice transplanted with expanded cells from both the MSC-based and control cultures returned to pretreatment levels at day 25 posttransplant and then decreased. The WBC levels returned to pretreatment levels again at days 45–55 posttransplant. The level of human CD45+ cell engraftment in primary recipients transplanted with expanded cells from the MSC-based cultures was significantly higher than recipients transplanted with cells from the control cultures. Serial transplantation demonstrated that the expanded cells could establish long-term engraftment of hematopoietic cells. UCB-MSCs similar to those derived from adult bone marrow may provide novel targets for cellular and gene therapy.

This study aimed to investigate the potentials of ex vivo expansion and pluridifferentiation of cryopreserved adult human bone marrow mesenchymal stem cells (hMSCs) into adipocytes and neurocytes. Cryopreserved hMSCs were resuscitated and cultured for 15 passages, and then induced to adipocytes and neurocytes with corresponding induction medium. The induced cells were observed for morphological properties and expression of triglyceride or neuron-specific enolase and nestin was detected. The result showed that the resuscitated cells cultured in induction medium consisting of dexamethasone, 3-isobutyl-1-methylxanthine, indomethacin and insulin-like growth factor I (IGF-I) showed adipogenesis, and lipid vacuole accumulation was detectable after 21days. The resuscitated hMSCs were also induced into neurocytes and expressed nestin and neuron-specific enolase (NSE), which are special surface markers associated with neural cells at different stages. This study suggested that resuscitated hMSCs should still be a population of pluripotential cells and should be accessible for establishing an abundant hMSC reservoir for further experiment and treatment of various clinical diseases.

This study was supported by grants of New Ideas Capability for Backbone Teachers in Universities of Heilongjiang and of Scientific Research foundation in Qiqihar Medical College.Ulcer recurrence and poor healing may be critically important to the development of serious gastrointestinal complications in patients with long-term non-steroid anti-inflammatory drugs (NSAIDs). The present study is to investigate the effects of aspirin on ulcer recurrence and healing quality and to explore the mechanism.Gastric ulcers were induced with acetic acid in rats; aspirin was administrated by gavage from day 25 to day 54 after ulcer induction. The gastric juice volume, pH, gastric mucus, gastric mucosal blood flow (GMBF) and prostaglandin E(2) (PGE(2)) were measured. The mRNA transcription of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) were analyzed with RT-PCR and protein expression with Western blot.The gastric juice volume was significantly increased in aspirin group compared with those of fasting or saline control groups (P0.01); while the pH, mucus, GMBF and PGE(2) were significantly decreased in aspirin treated rats compared with those of other two groups (P0.01). COX-2, evaluated with mRNA and protein expression, was significantly augmented in aspirin group compared with others. The quality of ulcer healing (QOUH) in Aspirin group was poorer than that of fasting or saline control groups.Aspirin enhance the recurrence of gastric ulcer. The inhibition of cycloxygenase, mucus secretion and mucosal blood flow may be involved. Aspirin also impair the quality of ulcer healing.

Most studies on residence time distribution (RTD) have focused on the tail of the RTD curve, and very little attention has been paid to the effect of white noise on the measured results. The aim of this work is to study the effect of white noise on the calculated parameters with different data processing methods. The anti-disturbance abilities of the moment method and the least squares method are compared. The results show that the anti-disturbance ability of the least squares method was better than that of the moment method. As a result of peak overlapping in the RTD curve of a loop reactor, the moment method cannot be used to calculate the fluid velocity and dispersion coefficient. Experiments show that the least squares method is still applicable in a loop reactor.

The genetic correction of induced pluripotent stem cells (iPSCs) induced from somatic cells of patients with sensorineural hearing loss (caused by hereditary factors) is a promising method for its treatment. The correction of gene mutations in iPSCs could restore the normal function of cells and provide a rich source of cells for transplantation. In the present study, iPSCs were generated from a deaf patient with compound heterozygous MYO7A mutations (c.1184G>A and c.4118C>T; P-iPSCs), the asymptomatic father of the patient (MYO7A c.1184G>A mutation; CF-iPSCs), and a normal donor (MYO7AWT/WT; C-iPSCs). One of MYO7A mutation sites (c.4118C>T) in the P-iPSCs was corrected using CRISPR/Cas9. The corrected iPSCs (CP-iPSCs) retained cell pluripotency and normal karyotypes. Hair cell-like cells induced from CP-iPSCs showed restored organization of stereocilia-like protrusions; moreover, the electrophysiological function of these cells was similar to that of cells induced from C-iPSCs and CF-iPSCs. These results might facilitate the development of iPSC-based gene therapy for genetic disorders. Significance Induced pluripotent stem cells (iPSCs) were generated from a deaf patient with compound heterozygous MYO7A mutations (c.1184G>A and c.4118C>T). One of the MYO7A mutation sites (c.4118C>T) in the iPSCs was corrected using CRISPR/Cas9. The genetic correction of MYO7A mutation resulted in morphologic and functional recovery of hair cell-like cells derived from iPSCs. These findings confirm the hypothesis that MYO7A plays an important role in the assembly of stereocilia into stereociliary bundles. Thus, the present study might provide further insight into the pathogenesis of sensorineural hearing loss and facilitate the development of therapeutic strategies against monogenic disease through the genetic repair of patient-specific iPSCs.

To further predict textile quality fluctuation from the perspective of uncertainty factors, first, the reasons and regularities of quality fluctuation in the industrial textile processing were analyzed, and knowledge representation of textile quality attributes was studied. Second, through man-machine-environment system engineering HMESE theory, the uncertainty factors that affect textile quality were extracted, and its generation mechanism, interaction relationship and behavioral characteristics was explored. Then, an improved man-machine-environment brittle model oriented to the textile processing was built. As verified by the experiment, the results have shown that the improved brittle model has achieved a full range analysis of quality uncertainty of the textile, which are from the reason and regularity of quality fluctuation to generation mechanism, mutual relations, and behavior identification of the uncertainty factors.

This paper describes a study on the shape control of potassium dihydrogen phosphate (KDP) in batch cooling suspension crystallization by selecting the supersaturation as a media control variable. The effects of different cooling modes on the supersaturation level and hence on the crystal shape were investigated. The results clearly show that different shapes of crystals were obtained at the various supersaturation courses. When a specific shape of crystal is desired from suspension batch cooling crystallization, a suitable cooling mode should be selected and furthermore the optimal one can be found.

Inter-phase mass transfer is important to the design and performance of airlift loop reactors for either chemical or biochemical applications, and a good measurement technique is crucial for studying mass transfer in multiphase systems. According to the model of macro-scale mass transfer in airlift loop reactors, it was proved that the airlift loop reactor can be regarded as a continuous stirred tank reactor for measuring mass transfer coefficient. The calculated mass transfer coefficient on such a basis is different from the volumetric mass transfer coefficient in the macro-scale model and the difference is discussed. To describe the time delay of the probe response to the change of oxygen concentration in the liquid phase, a model taking into account the time constant of response is established. Sensitivity analysis shows that this model can be used to measure the volumetric mass transfer coefficient. Applying this model to the measurement of volumetric mass transfer coefficient in the loop reactor, results that coincide with the turbulence theory in the literate were obtained.

The flow behavior and mass transfer in a three-phase external-loop airlift reactor can be improved by adding large particles. The mass transfer and liquid dispersion behavior for a three-phase external-loop reactor with large particles are studied in terms of the effect of the diameter and loading of the large particles on the liquid dispersion coefficient and mass transfer coefficient. The results showed that increasing the diameter or loading of the large particles tend to decrease dispersion and intensify mass transfer, and that an increase in the diameter of the large particles remarkably decreases the particle loop rate, while the effect of fine particles is much less notable.

An ovine bacterial artificial chromosome (BAC) library containing 190,000 BAC clones was constructed and subsequently screened to construct a BAC-based physical map for the ovine major histocompatibility complex (MHC). Two hundred thirty-three BAC clones were selected by 84 overgo probes designed on human, mouse, and swine MHC sequence homologies. Ninety-four clones were ordered by DNA fingerprinting to form contigs I, II, and III that correspond to ovine MHC class I–class III, class IIa, and class IIb. The minimum tiling paths of contigs I, II, and III are 15, 4, and 4 BAC clones, spanning approximately 1900, 400, and 300 kb, respectively. The order and orientation of most BAC clones in each contig were confirmed by BAC-end sequencing. An open gap exists between class IIa and class III. This work helps to provide a foundation for detailed study of ovine MHC genes and of evolution of MHCs in mammals.

Inter-phase mass transfer is an important issue for design and development of airlift loop reactors of high performance in either chemical or biochemical applications. In this work, the axial dispersion in both gas and liquid phases was taken into account for modeling the macro-scale mass transfer in airlift loop reactors. Finite difference method was used to numerically solve the differential equation system of the mass transfer model. For oxygen, the numerical results showed that the solute concentration of the gas phase can be treated as constant and the flow pattern of the liquid phase as a plug flow. Based on the conclusion obtained from numerical solution, the mass transfer model was simplified and the analytical solution of the simplified model was obtained. Comparison between the numerical and analytical solutions showed that the simplification of the model was reasonable and there was almost no influence on the calculated results. Experimental measurements on the mass transfer rate were carried out to verify the mathematical model. The comparison between the experimental and calculated results showed that the mass transfer model has satisfactory prediction ability and can be used to describe the mass transfer process in airlift loop reactors.

The contact mass in the Rochow reaction was analyzed to understand catalyst deactivation during the reaction. Changes in crystalline structure, particle surface morphology, and the elemental composition of the contact mass were measured by XRD, SEM, EDX, and XRF, respectively, at four different reaction conversions. The results indicate that the main reason for contact-mass deactivation is copper enrichment on the surface of silicon. Coke deposition may hamper Cu diffusion and result in the copper enrichment.

The effect of copper concentration on the performance of the catalytic reaction between silicon and methyl chloride was investigated using online gas chromatogram. The catalyst concentration greatly influences various aspects of the direct organosilane synthesis process, including the reaction rate, the selectivity, and the silicon conversion. The reaction activity and the silicon conversion increase as the catalyst concentration increases. However, the reaction selectivity decreases for the catalyst concentrations more than 9 wt.%. The cross-sections of deactivated contact mass particles were observed by optical microscopy and analyzed by scanning electron microscope combined with energy dispersive X-ray detector (SEM-EDX). The observations showed that a textured substance formed on the original flat surface of the silicon particles after deactivation with copper only in a shallow surface layer of the contact mass. This indicates that the copper diffusion is the rate limiting step which causes the reaction deactivation.

Theoretical prediction of flow regime transition in bubble columns was studied based on the bubble size distribution by the population balance model (PBM). Models for bubble coalescence and breakup due to different mechanisms, including coalescence due to turbulent eddies, coalescence due to different bubble rise velocities, coalescence due to bubble wake entrainment, breakup due to eddy collision and breakup due to large bubble instability, were proposed. Simulation results showed that at relatively low superficial gas velocities, bubble coalescence and breakup were relatively weak and the bubble size was small and had a narrow distribution; with an increase in the superficial gas velocity, large bubbles began to form due to bubble coalescence, resulting in a much wider bubble size distribution. The regime transition was predicted to occur when the volume fraction of small bubbles sharply decreased. The predicted transition superficial gas velocity was about 4 cm/s for the air–water system, in accordance with the values obtained from experimental approaches.

The axial dispersion model was applied to the riser and down-comer, respectively, of an airlift loop reactor and a mathematical model was developed to describe its residence time distribution (RTD). A numerical solution was first obtained for the case where there is no gas–liquid separator. A tracer impulse was considered to flow in an infinite tube comprising alternating riser, gas–liquid separator and down-comer. The tracer concentration at a point in the reactor is the sum of all the tracer concentrations at the corresponding points in the infinite tube. Based on this model, an analytical solution was obtained for the mathematical model. The comparison between the analytical solution and experimental data shows that the model can be used to simulate the RTD in airlift loop reactors. By using the analytical solution in a loop reactor with partial recirculation, the solution with a recycle factor is obtained. A comparison with data in the literature shows that the solution with the recycle factor can be used for the RTD in a loop reactor with partial recirculation.

A new marrow-derived mesenchymal stem cell (hMSC) line that could support expansion of hematopoietic stem/progenitor cells (HSPCs) was developed. Primary hMSCs were infected with retrovirus containing Flt-3 ligand and thrombopoietin genes. CD34+ cells from cord blood were expanded with primary hMSCs or transduced hMSCs. The expansion of total nucleated cells, CD34+ cells and mixed colonies containing erythroid and myeloid cells and megakaryocytes for 2 weeks coculture with transduced hMSCs was remarkably increased. The outputs of long-term culture-initiating cells for 2 and 4 weeks coculture with transduced hMSCs were also largely increased. The expansion rates of HSPCs with transduced hMSCs were unchanged for 6 weeks. In contrast, the expansion rates of HSPCs with primary hMSCs declined drastically through 6 weeks. SCID-repopulating cell expansion with transduced hMSCs for 4 weeks was significantly higher than that of uncultured CD34,+ cells and HSPCs expanded with primary hMSCs.

In dispersed gas−liquid flows, the bubble size distribution plays an important role in the phase structure and the interphase forces, which, in turn, determine the multiphase hydrodynamic behaviors, including the spatial profiles of the gas fraction, gas and liquid velocities, and mixing and mass-transfer behaviors. The population balance model (PBM) is an effective method to simulate the bubble size distribution. The bubble coalescence and breakup models have a distinct influence on the prediction ability of the PBM. This work compares several typical bubble coalescence and breakup models. The results show that the bubble size distributions predicted by the PBM are quite different when different bubble coalescence and breakup models are used. By using proper bubble coalescence and breakup models, the bubble size distribution and regime transition can be reasonably predicted. The results also show that it is necessary to take into account bubble coalescence and breakup due to different mechanisms.

One important challenge in chemical industry, especially for processes of synthesis fuels, is the development of effective three-phase reactors for high pressure and temperature. In the present study, a novel airlift internal-loop reactor (ALR) was proposed and its hydrodynamic behaviors were experimentally studied. The local bubble rise velocity and liquid velocity are measured under different operating conditions. The influence of operating conditions including the superficial gas velocity and solid holdup on the bubble rise velocity and liquid velocity in the riser was studied. A mathematical model was proposed based on the energy balance to describe the multiphase flow characteristics in the internal-loop airlift reactor. The comparison between the calculated and experimental values shows that the proposed model can predict the flow behavior reasonably.

Small bubbles and flow uniformity are important for gas–liquid and gas–liquid–solid multiphase reactors. A reactor internal was designed and installed in an external-loop airlift reactor (EL-ALR) to enhance bubble breakup and flow redistribution and improve reactor performance. Hydrodynamic parameters, including local gas holdup, bubble rise velocity, bubble Sauter diameter and liquid velocity were measured. A radial maldistribution index was introduced to describe radial non-uniformity in the hydrodynamic parameters. The influence of the internal on this index was studied. Experimental results show that The effect of the internal is to make the radial profiles of the gas holdup, bubble rise velocity and liquid velocity radially uniform. The bubble Sauter diameter decreases and the bubble size distribution is narrower. With increasing distance away from the internal, the radial profiles change back to be similar to those before contact with it. The internal improves the flow behavior up to a distance of 1.4 m.

A computational fluid dynamics-population balance model (CFD-PBM) coupled model was developed that combines the advantages of CFD to calculate the entire flow field and of the PBM to calculate the local bubble size distribution. Bubble coalescence and breakup were taken into account to determine the evolution of the bubble size. Different bubble breakup and coalescence models were compared. An algorithm was proposed for computing the parameters based on the bubble size distribution, including the drag force, transverse lift force, wall lubrication force, turbulent dispersion force, and bubble-induced turbulence. With the bubble breakup and coalescence models and the interphase force formulations in this work, the CFD-PBM coupled model can give a unified description for both the homogeneous and the heterogeneous regimes. Good agreement was obtained with the experimental results for the gas holdup, liquid velocity, and bubble size distribution.

Ni-based catalysts supported on Al 2 O 3 -ZrO 2 (Ni/Al 2 O 3 -ZrO 2 ) were prepared by a direct sol-gel process with citric acid as the gelling agent. The evaluation of the catalyst prepared for methane reforming with CO 2 was carried out with thermal gravimetric analysis (TGA), infrared spectroscopy (IR), X-ray diffraction (XRD), microscopy analyses (SEM and TEM), temperature-programmed reduction (TPR) and in a micro-reactor system. The catalytic performance for CO 2 reforming of methane to synthesis gas in a continuous-flow micro-reactor under atmospheric pressure was investigated. TGA, IR, XRD and microscopy analyses show that the Ni particles have a nanostructure of around 5 nm and are uniformly dispersed on the Al 2 O 3 -ZrO 2 support, which exists as an amorphous phase. Catalytic tests using CO 2 reforming of methane to synthesis gas show that the catalytic activity increases with increasing metal loading, and the 20Ni/Al 2 O 3 -ZrO 2 (0.2 Ni/Al molar ratio) catalyst has excellent activity and stability, compared with that of the Al 2 O 3 supported Ni catalyst, with 91.9% conversion of CO 2 and 82.9% conversion of CH 4 over 50 h at 1073 K, atmospheric pressure, hourly space velocity of 11, 200 ml gcat -1 h -1 and CH 4 :CO 2 :N 2 of 2:2:1. The excellent catalytic activity and stability is attributed to the very highly and uniformly dispersed small metallic Ni particles, the reducibility of the Ni oxides and an interaction between metallic Ni particles and the support Al 2 O 3 -ZrO 2 .

The hydrodynamic behavior of an external loop airlift slurry reactor (ALSR) with and without a resistance-regulating element was studied with a fiber optic probe and ultrasound Doppler velocimetry. The influences of the superficial gas velocity and solid holdup on the global gas holdup and radial profiles of the suspension circulation velocity in the downer and of gas holdup, bubble size, and bubble rise velocity in the riser were studied. Local measurements allow a better understanding of the flow behavior in the reactor and can be used for CFD modeling and validation. Experimental results show that the resistance-regulating element increases the gas holdup and decreases the suspension circulation velocity, indicating that an optimum design of the flow resistance is needed to obtain the maximum gas-liquid volumetric mass transfer coefficient for a specific superficial gas velocity. A high superficial gas velocity and low solid holdup are favorable for increased uniformity of the radial profile of the gas...

The local hydrodynamic behaviors, including the gas holdup, bubble size and bubble rise velocity were measured in an external loop airlift reactor (EL-ALR) with two types of distributor—porous sinter plate and perforated plate, using an optic fiber probe. The radial and axial evolutions of these parameters and the influence of the gas distributor on the flow hydrodynamics were studied. Core-peaking and wall-peaking radial profiles of the gas holdup were found in the experiments corresponding to different bubble sizes. A mechanism model based on the assumption of the equilibrium of lateral forces acting on a bubble was proposed to interpret the different radial profiles of the gas holdup.

For a reactive distillation column with a novel internal which is made of several structured porous passages, the models of pressure drop and liquid holdup are developed. The simulation from the models shows that the internal can make more than 70% gas contact liquid in cross-current instead of counter-current, so that excessive pressure drop is avoided. In addition, below the load point, only superficial liquid velocity and the volume fraction of the internals have evident effects on the liquid holdup; above the load point, both superficial gas and liquid velocities have great effects on the liquid holdup, and so do the parameters of the internal because they can affect gas flow behavior.

Detailed local three-phase hydrodynamic parameters, namely, the liquid velocity, bubble rise velocity, and gas holdup, were obtained for an external-loop airlift reactor using a fiber-optic probe and laser Doppler anemometry techniques. The radial and axial evolutions of these parameters and the effect of the solid fraction on the flow hydrodynamics were studied. The experiments showed that the bubble size has a large influence on the evolutions of these parameters because of radial forces acting on the bubbles. Bubble coalescence prevails near the distributor, while bubble breakup is more important in the fully developed flow. The liquid velocity and gas holdup decrease and the bubble rise velocity increases as the solid fraction increases.

Several models for the daughter bubble/droplet size distribution are reviewed and a detailed discussion is given to get a better understanding of the daughter size distribution. A novel theoretical breakup kernel function for bubbles/droplets in a turbulent flow, based on an eddy-bubble/droplet collision method, is developed. It takes into account the energy distribution of turbulent eddies, effect of capillary pressure and surface energy increase during bubble/droplet breakup. An increase in the mother bubble/droplet size and energy dissipation rate increases the probability of unequal breakup. The model prediction is in good agreement with experimental results and the underlying physical situation.

The gas–liquid–solid three-phase circulating fluidized bed (TPCFB) is a novel multiphase reactor with outstanding performance in hydrodynamics, heat transfer, mass transfer and catalyst treatment. The object of this work is to study the bubble behavior in TPCFBs for better understanding of the hydrodynamics of the reactor. The local gas holdup, bubble size distribution, and bubble rise velocity in different radial positions are measured using a fiber optic probe, and the effects of operating conditions on bubble rise velocity are also investigated. Moreover, the bubble rise velocity and its distribution are compared with the data from gas–liquid two-phase external loop airlift reactors and gas–liquid–solid three phase fluidized beds without external circulation of liquid and particles.

An integrated hydrodynamic mathematical model is established from experimental results and a more rigorous definition is proposed for the uniformity of the axial gas distribution in a radial flow moving-bed reactor (RFMBR). A new iteration strategy is provided for the solution of the model. Simulations show the influence of the flow structure, the reactor dimension, the design of the axial gas distributor and the operation conditions on the axial uniformity of the gas distribution. This work provides a theoretical basis and useful method for the optimum design and operation of RFMBRs.

This work aims to extend the application of a commercial Doppler ultrasound velocimetry DOP2000 (Model 2030, signal processing S.A.) to multiphase systems. We firstly make a correction to the determination of Doppler angle and measuring location taking into account the ultrasound refraction and the ultrasound velocity difference in different medias, and then investigate the measurement of the solid concentration in a liquid–solid system and the bubble behavior in a gas–liquid system with low gas holdup. The experimental results show that the attenuation coefficient increases monotonously. A model based on the ultrasound reflection and refraction law is proposed to predict the received echo energy in homogeneous liquid–solid system. Furthermore, the signal response of bubbles is also discussed. By placing the probe in the direction of the flow, the difficulty of determining Doppler angle is avoided and the liquid and bubble rise velocities are simultaneously obtained.

In this paper, experiments are carried out for three Geldart-D powders in the hopper–standpipe systems with a gas-splitting part. Based on these experimental data, the hopper–standpipe system with gas-splitting part, which can increase the maximum pressure drop of the system in a positive gas conveying system by a factor of about 1.7 greater than Particle Plug Valve (PPV), is called “Improved Particle Plug Valve (IPPV)”. Furthermore, the increased pressure drop produced by this technique can be adequately predicted using the calculation procedure developed.

The liquid-solid circulating moving bed reactor is a novel one, which consists of two or more reaction chambers and a particle transport system. Particles move down to the lower reaction chamber from the upper reaction chamber through an upper conduit and to the particle transport system through a lower conduit, and then are conveyed into the upper reaction chamber through a riser. The circulating rate of particles and the flow of liquid in the two conduits are key factors to the continuous steady operation of the reactor; they can be controlled by varying operating conditions: the outlet liquid flow rate in the regeneration chamber, the outlet liquid flow rate in the reaction chamber, the inlet liquid flow rate of the reactants, and the flow rate of driving flow. A flow model has been proposed to quantify the operation characteristics of the reactor. The results predicted by the model show satisfactory agreement with the experimental data.

A new catalytic process for cumene hydroperoxide (CHP) decomposition using sulfonic resins is developed. A macroporous sulfonic resin entitled TH-02 is selected as the catalyst. A novel three-phase circulating fluidized bed (TPCFB) reactor in which the geometry and the particular flow regime resolve the conflict between heat transfer and resin fragmentation is used for this process. RTD results show that this reactor approximates a CSTR, and solids and liquid are distributed uniformly in it. Under the optimal reaction conditions, which are a volumetric ratio of CHP to acetone 1:2–1:3, temperature 75–85 °C preferably 80 °C, solid holdup 1–1.5 wt.% and WHSV of CHP 30–40 h −1 , the conversion and product selectivity of CHP can be over 99 and 98%, respectively.

In the packed column with a novel internal, which is made of several structured porous passages, gas is divided into two branches which meet liquid in countercurrent and cross-current, respectively, so the excessive pressure drop and “flooding” of conventional gas−liquid countercurrent flow can be avoided. A model for predicting dynamic liquid holdup is presented, and it shows a satisfactory agreement with the experimental results. Below the load point, only the superficial liquid velocity and the volume fraction of the internals have evident effects on the liquid holdup. Above the load point, both superficial gas and liquid velocities have great effects on the liquid holdup and so do the parameters of the internal because they can affect gas-flow behavior.

Based on the characteristics of particle plug valve (PPV) [Powder Technol. 115 (1), (2001) 8], a series connection of PPVs, which is used in a positive dilute gas-conveying system for feeding Geldart-D powder periodically from a low-pressurized vessel into a high-pressurized vessel is presented, and four modes of operation have been discussed and tested by experiments.

A new type of catalytic distillation column has been developed for catalytic distillation processes. The catalysts are loaded loosely in the downcomer of the new column, so that they can be replaced easily. A new type of column plate structure has also been proposed to accommodate the new distillation column. Experimental results show that the new column and plate structure have much improved performance, with high plate efficiency, low pressure drops across the plate and very good operation flexibility. The novel catalytic distillation columns could be employed to many catalytic distillation processes.