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In the aging male population, the occurrence of lower urinary tract symptoms (LUTS) caused by benign prostatic hyperplasia (BPH) is a common problem. Here, we introduce a new technique called 980 nm diode laser enucleation (DiLEP) to treat BPH1. Diode lasers can absorb both water and hemoglobin at the same time, so they are good for cutting and hemostasis2. The diode laser was approved by the FDA in 2007, and has been used in the treatment of BPH because of its effective cutting and hemostasis effect3. DiLEP presents several advantages over other techniques, such as TURP, HoLEP, and PVP. During the procedure, we define the boundary of a high-volume prostate and separate it into three lobes with a diode laser by burning two rings and one groove (like a Cupid's arrow). Compared to other procedures, mDiLEP has fewer intraoperative complications, a shorter learning curve, and achieves more tissue resection.

With increasing amount of unconventional natural gas, the production of ethane, propane and other low alkanes continues to increase. In our previous works, a partially decoupled process (PDP) was proposed for conversion of ethane based on numerical simulations, which showed higher acetylene and ethylene selectivities than the original partial oxidation process. In the current work, the PDP of ethane for producing acetylene and ethylene was studied experimentally to verify the PDP concept. In the PDP of ethane, coke-oven gas or other cheap gas combusts with stoichiometric oxygen as heat carrier, and ethane is mixed with the heat carrier and undergoes pyrolysis at high temperatures. The jet-in-cross-flow (JICF) reactor was designed and manufactured to realize the PDP. A positioning device of 0.1 mm accuracy and a mass spectrometer were used to measure the spatial profiles of the species concentrations. The maximum combined yield (52.7%) of acetylene and ethylene was obtained even at the condition of heat loss, confirming that the PDP of ethane was advantageous over the partial oxidation process and at least comparable to the steam cracking process.

The CFD-PBM coupled model was validated in a bubble column with organic liquids under industrial conditions. Experimental data of the gas holdup, bubble size distribution and mass transfer rate were collected from the literature. The liquid viscosity and surface tension were two important parameters affecting the hydrodynamics. Low liquid viscosity and surface tension enhanced the bubble breakup but hindered the bubble coalescence. Compared with water, organic liquids led to a higher gas holdup, smaller bubble size and larger mass transfer rate. The elevated temperature decreased the liquid viscosity and surface tension. The effects of temperature on the hydrodynamic and gas-liquid mass transfer behaviors were well predicted using the corresponding liquid properties. The CFD-PBM coupled model gave good predictions because it quantitatively described the effect of liquid properties on the bubble size, interphase forces, turbulence parameters, and bubble breakup and coalescence behaviors. The simulations with different bubble breakup models showed that the accuracy of the bubble breakup model was crucial for reliable predictions of the CFD-PBM coupled model.

In the water quenching process for partial oxidation (POX) of nature gas to acetylene, the temperature of the product gas mixture directly decreases from about 1800 K to 360 K, thus the heat cannot be recovered. To overcome this problem, a new gas quenching process of jet-in-cross-flow (JICF) was proposed for the partial oxidation (POX) process to enhance the energy efficiency. The computational fluid dynamics (CFD) coupled with detailed chemistry was employed to simulate the mixing and quenching performance in an industrial-scale JICF reactor. Both the Probability Distribution Function (PDF) and Eddy Dissipation Concept (EDC) models were used to compute the chemical source term, and the PDF model predicted a higher acetylene loss. The uniform index (UI), temperature, species concentrations and acetylene loss were investigated during the quenching process. Using the PDF, the optimum main/jets flow mass ratio was determined as 2.59, at which the loss percent of acetylene was about 3 wt%. The simulation results show that the gas quenching process is very attractive because the heat can be effectively recovered after the quenching at a cost of slight loss of acetylene.

Wet shale gas contains relatively high concentrations of heavier hydrocarbons. In industry, the cryogenic separation process is used to separate methane and heavier hydrocarbons for the downstream conversion. In this work, the feasibility of direct application of wet gas in the partial oxidation (POX) process was studied. Flat flame experiments of methane with addition of ethane and propane were conducted using a McKenna reactor. The results showed that the mole fractions of acetylene and CO increased by 15% and 25% when using wet gas as the feedstock. Four detailed chemical mechanisms were verified, and the Curran and modified GRI 3.0 mechanisms gave good predictions of the POX of wet gas. The modified GRI 3.0 was further used in the three-dimensional computational fluid dynamics (CFD) simulations of a 3-jet reactor at industrial conditions. The results showed that in the wet gas POX process a higher C2H2 yield was obtained, and the optimal equivalence ratio slightly increased from 4.0 to 4.07 and the op...

Recent advances in technologies of reactive distillation (RD) offer various design concepts for chemical processes. For separation of cracking C5 fraction, one of the main challenges is improving the conversion of cyclopentadiene (CPD) and the recovery of isoprene (IP). In the current work, a novel reactive distillation column with several liquid-holdup regions was designed, since it allows long residence time and provides flexibility for narrowing the efficiency gap between reaction and distillation. By use of Aspen Plus, a corresponding mathematic model was established and verified to be accurate. Following that, comprehensive studies were carried out for the design of liquid-holdup regions position. Details and principles about the separation performance with the liquid-holdup regions were revealed and optimized parameters were determined with 100 theoretical plates, feed position of 35th plate, and four liquid-holdup regions at 25th, 60th, 75th and 90th plate. The designed RD column could well meet the technical requirement, and influence of other important factors including residence time, operating pressure and reflux ratio was further investigated.

The bubble column reactor with phase change are used in some important chemical processes, but its hydrodynamics has not been well studied. In this work, the hydrodynamic behaviors of a bubble column with phase change were experimentally studied using a vapor-water system. The axial profiles of liquid temperature, total and local gas holdups, and bubbles size distribution were measured. The results showed that the hydrodynamics with phase change were very different from that without phase change. The temperature was lower than the liquid boiling point in the bottom region, and this difference decreased with increasing axial height. With phase change, the gas holdup showed a “U” shaped axial profile, while without phase change it showed a flat axial profile. In addition, phase change led to a much wider bubble size distribution. The results were analyzed based on the heat and mass transfer between the gas and liquid phases. These experimental data were valuable for further development of a mathematical model to describe the complex hydrodynamics in a bubble column with phase change.

The partial oxidation (POX) of natural gas is the main approach to produce acetylene. This process involves fuel-rich turbulent combustion, millisecond mixing and rapid quenching cooling, which are difficult to study by experiments and empirical macrokinetics. This work reported numerical simulations of the POX reactor by computational fluid dynamics (CFD) coupled with detailed chemistry. The GRI 3.0 and San Diego mechanisms were used. A modification was made to GRI 3.0 based on sensitive analysis and comparison with experimental data. With the modified GRI 3.0, the CFD simulation results agreed well with the industrial data. The influence of the reactant preheating temperature and equivalence ratio, which are most important operating parameters, was studied. The results showed that an optimum equivalence ratio exists for maximum acetylene yield. The increase of preheating temperature enhanced the acetylene yield and decreased the corresponding optimum equivalence ratio. The effect of adding C 2 H 6 was also studied to explore the feasibility of using wet shale gas as feedstock of POX.

Polyoxymethylene dimethyl ethers (CH3–O–(CH2O)n–CH3, PODEn) are potential environmentally benign coal-based diesel fuel blending compounds. They are synthesized from dimethoxymethane (DMM) and paraformaldehyde (PF). Among the PODEn homologues, PODE3–4 have a good match with diesel as a fuel, while the undersized PODE1–2 and oversized PODEn>4 have unsuitable properties. This work studied the molecular size reforming of undersized PODE1–2 and oversized PODEn>4 by two different methods, namely, self-reforming and reacting with DMM over an acidic ion exchange resin. The molecular size reforming of PODE1–2 and PODEn>4 by self-reforming gave a high concentration of formaldehyde, which shifted the distribution to longer chain PODEn and formed solid PF. In contrast, PODE1–2 and PODEn>4 were mainly converted to PODE3–4 by the reaction with DMM and the high concentration of formaldehyde was also diminished. The equilibrium reorganized molecular size distribution of PODE1–2 and PODEn>4 followed the Schulz–Flory distribution. A proposed kinetic model described well the molecular size reforming pathways of PODE1–2 and PODEn>4. A methanol-to-PODEn close-loop process was proposed to enhance atom-economy by recycling the PODE1–2 and PODEn>4 streams.

Polyoxymethylene dimethyl ethers (PODEn, CH3O(CH2O)nCH3, where n ⩾ 1) are ideal diesel fuel additives. Among the PODEn compounds, PODE3–5 have the best properties as diesel additives. A theoretical analysis of the molecular size distribution of PODEn synthesized from dimethoxymethane (DMM) and paraformaldehyde (PF) was performed based on a sequential reaction mechanism. The molecular size distribution model follows the Schulz–Flory distribution, and showed a good prediction ability at different reaction temperatures (T) and DMM/CH2O mole ratios (M), which verified the sequential reaction mechanism during the formation of PODEn. The product distribution was optimized using the molecular size distribution model and response surface methodology (RSM). At optimum operating conditions of T = 105 °C and M = 1.1, the conversion of formaldehyde X CH 2 O has a high value of 92.4%, and the fraction of PODE3–5 in the PODEn mixture is 33.2 wt%, while the fractions of PODEn>5 and PODE2 are 9.4 wt% and 24.3 wt%, respectively.

Polyoxymethylene dimethyl ethers (CH3–O–(CH2O)n–CH3, PODEn, n>1) are new concerned environmental benign alternative components for diesel fuels. This work aimed to investigate the kinetics of synthesis of PODEn from paraformaldehyde and dimethoxymethane catalyzed by ion-exchange resin NKC-9. Experiments were conducted in a designed space, namely reaction temperatures (60, 70, and 80 °C) vs. reaction times (2, 5, 10, 20, 30, 60, and 90 min), in a batch stirred autoclave. The transient molecular size distribution of PODEn compounds from paraformaldehyde and methylal followed Schulz–Flory distribution model. In this system, the concentration of formaldehyde in the homogenous solution (CF) was nearly constant. The sequential reversible reactions to produce PODEn were verified to follow a second-order kinetics for propagation and a first-order kinetics for depolymerization. The rate constants of propagation (kp) and depolymerization (kd) and the reaction equilibrium constant Kn were the same for the series of PODEn synthesis reactions. Respecting to 5 wt% dosage of NKC-9 resin catalyst, the pre-exponential factors Ap for propagation and Ad for depolymerization were 1.84×107 L mol–1 min–1 and 5.36×106 min–1, respectively. The activation energy Ep (39.52 kJ mol–1) for propagation was lower than Ed (52.01 kJ mol–1) for depolymerization, validating that the reversible reactions of producing PODEn compounds were exothermic.

Methylphenyldichlorosilane (MPDS, CH3C6H5SiCl2) is an important silicone monomer for the synthesis of high-performance polymethylphenylsiloxane polymers. In this work, the mechanism of the synthesis of MPDS from methyldichlorosilane and chlorobenzene by gas phase condensation was studied, and a kinetic model with 35 species and 58 elementary reactions was established. Experiments were carried out in a tubular reactor under a wide range of reaction conditions. The calculated mole fractions of the reactants and products were in a good agreement with the experimental results. A mechanism of the insertion of chloromethylsilylene into the C Cl bond of chlorobenzene was proposed, which was proved to be the main pathway of MPDS production. The established kinetic model can be used in design and optimization of the industrial reactor for MPDS synthesis.

Plant oil asphalt (POA) is an underutilized lipid-based biomass residue mainly generated in the biodiesel industry. This work presents application of the lumping strategy in kinetic modeling of vacuum pyrolysis of POA in a pilot-scale semi-batch reactor. Pyrolysis experiments were conducted under different reaction temperatures (410, 430, and 450 °C) and reaction times (10, 15, 20, 25, 40, 50, and 60 min). The reaction scheme was divided into five lumps, namely, feedstock lump (POA) and four pyrolytic product lumps (including biogas, biochar, hydrocarbon components in pyrolytic oil, and oxygenated components in pyrolytic oil). In the kinetic model, reactions from the feedstock lump to the four pyrolytic product lumps were assumed to be independent parallel, while the secondary reactions between four pyrolytic product lumps were neglected because of the short residence time of the pyrolytic vapor in the pyrolysis zone. Results showed that four independent parallel reactions all followed first-order kinetic...

Camellia seed shell was carbonized to obtain carbon carrier (C), then the carrier was sulfonated and incorporated with Ce 4+ to prepare a novel solid acid catalyst SO 4 2− /C/Ce 4+ by impregnation method. The structure and morphology of SO 4 2− /C/Ce 4+ was characterized by a variety of techniques. The catalytic activity of SO 4 2− /C/Ce 4+ was evaluated from the esterification reaction of model acidic oil with methanol, which was performed in a batch reactor. Results indicated that the highest conversion of model acidic oil was 95.45 wt% when the molar ratio of methanol to oleic acid was 12, reaction temperature was 66 °C and catalyst loading was 1 wt%. This catalyst also exhibited good catalytic stability. The high catalytic activity can be ascribed to the introduction of Ce 4+ reduced the ratio of graphitic carbon sheet effectively, which is favorable for the formation of high density of strong Bronsted acid sites. The high stability can be ascribed to the formation of stable coordination bonds among Ce and O, S atoms, which strengthens the electron withdrawing function that was provided by the sulfonated-polycyclic aromatic hydrocarbons.

To enhance the process of phenyltrichlorosilane synthesis using gas phase condensation, a series of chloralkanes were introduced. The influence of temperature and chloralkane amount on the synthesis was studied based on the product distribution from a tubular reactor. The promoting effect of chloralkane addition was mainly caused by the chloralkane radicals generated by the dissociation of C–Cl bond. The promoting effect of the chloromethane with more chlorine atoms was better than those with less chlorine atoms. Intermediates detected from the reactions with isoprene and bromobenzene demonstrated that both trichlorosilyl radical and dichlorosilylene existed in the reaction system in the presence of chloralkanes. A detailed reaction scheme was proposed.

Pressure has a significant effect on bubble breakup, and bubbles and droplets have very different breakup behaviors. This work aimed to propose a unified breakup model for both bubbles and droplets including the effect of pressure. A mechanism analysis was made on the internal flow through the bubble/droplet neck in the breakup process, and a mathematical model was obtained based on the Young–Laplace and Bernoulli equations. The internal flow behavior strongly depended on the pressure or gas density, and based on this mechanism, a unified breakup model was proposed for both bubbles and droplets. For the first time, this unified breakup model gave good predictions of both the effect of pressure or gas density on the bubble breakup rate and the different daughter size distributions of bubbles and droplets. The effect of the mother bubble/droplet diameter, turbulent energy dissipation rate and surface tension on the breakup rate, and daughter bubble/droplet size distribution was discussed. This bubble breakup model can be further used in a population balance model (PBM) to study the effect of pressure on the bubble size distribution and in a computational fluid dynamics-population balance model (CFD-PBM) coupled model to study the hydrodynamic behaviors of a bubble column at elevated pressures. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1391–1403, 2015

Plant oil asphalt (POA) is underutilized lipid-based biomass residue generated from the oleochemical industry. In this work, alkali metal compounds were used as catalysts for vacuum pyrolysis of POA. Their effects on the pyrolysis reaction rate, product yields and compositions were studied. The POA feed was characterized by proximate and ultimate analysis and inductively coupled plasma-mass spectrometry (ICP-MS). The pyrolytic oil was analyzed by gas chromatography–mass spectrometry (GC–MS), thermo-gravimetric analysis (TGA) and chromatography-simulated distillation analysis. The results showed that alkali metal compounds accelerated the pyrolysis reaction rate in the order of chlorides ≈ sulphates > hydroxides > carbonates > non-catalyst, and affected the yield of pyrolytic oil in the order of chlorides (80 wt.%) ≈ sulphates (77 wt.%) > non-catalyst (71 wt.%) > carbonates (68 wt.%) > hydroxides (55 wt.%). The quality of the pyrolytic oil was in the order of hydroxides > carbonates > non-catalyst ≈ chlorides ≈ sulphates.

Plant oil asphalt (POA) is a new concerned lipid-based residue biomass generated from the oleochemical industry. In this work, the pyrolysis kinetics of POA was studied by thermogravimetric analysis at heating rates of 7, 10, 20, and 30 K min–1 under a nitrogen atmosphere using the distributed activation energy model (DAEM). The kinetic parameters, including the activation energy E, distribution function of activation energy f(E), and pre-exponential factor k0, were obtained. The activation energy E ranged from 75 to 300 kJ mol–1, and the f(E) curve showed a broad peak around 155–200 kJ mol–1. The linear relationship between ln k0 and activation energy E indicated that there existed a kinetic compensation effect in pyrolysis of POA. A double-Gaussian DAEM was employed for simulation of POA pyrolysis by assuming POA as a mixture of two pseudo-components. In comparison to the single-Gaussian DAEM, the double-Gaussian DAEM was better to predict the pyrolysis behavior of POA. This work validated the applicabi...

A bi-component catalyst comprising CuCl and metallic copper was used in the direct synthesis of methylchlorosilane to study the catalytic synergy between the different copper sources. The catalyst exhibited high activity and high selectivity of dimethyldichlorosilane (M2) in the stirred bed reactor. The effect of the proportion of CuCl used was studied and 10%-30% CuCl gave the best yield of M2. The use of CuCl decreased the induction period of reaction, improved the selectivity in the induction stage, and gave a longer stable stage. These results suggest that bi-component catalyst has advantages in the direct synthesis reaction.

Ethane in unconventional natural gas was mainly used as the feedstock of the steam cracking process. In our previous work, a new ethane conversion process named partially decoupled process (PDP) was proposed and investigated by experiments and numerical simulations. In the ethane PDP, coke oven gas or other cheap gas combusts with stoichiometric oxygen as heat carrier, and ethane is mixed with the heat carrier and cracked at a high temperature. In this work, a new type of reactor named Forward-Impinging-Back (FIB) reactor was proposed for a better scale-up performance and investigated by CFD simulations coupled with a detailed reaction mechanism. The simulation results showed that a maximum C2 (C2H2 + C2H4) yield of 65.6% was obtained for the ethane PDP in a FIB reactor. The FIB reactor and Jet-In-Cross-Flow (JICF) reactor of small diameter had similar performance. When the reactor diameter increased from 30 mm to 390 mm, the C2 yield maintained at 64% in the FIB reactor, but decreased from 64.4% to 43.8% in JICF reactor.

Wastewater containing high concentrations of phenol and sodium sulfate is generated in sebacic acid (SA) industry. Castor oil acid, a raw material for producing SA, can be used to extract phenol from wastewater in order to reduce the amount of phenol used in the process and discharge of phenol. The results show that the extraction mechanism is that hydroxyl group of phenol is linked to carboxyl group of castor oil acid by hydrogen bond. The extraction process approaches equilibrium in 30 min. Extraction ratio increases with the increase of sodium sulfate and castor oil acid, and decreases as phenol increases. When the oil-water ratio is 1 : 3, the optimal distribution coefficient of 40 is obtained. Phenol saturation concentration in castor oil acid is 1.03 mol·L −1 after extraction for 4 times. The equilibrium constant ( K ex ) at 25 °C is 8.41 and the endothermic enthalpy (Δ H ) is 1.513 kJ·mol −1 . The Gibbs free energy (Δ G ) is −5.277 kJ·mol −1 and the value of Δ S is calculated to be 22.3 J·mol −1 ·K −1 .

The mechanism of the synthesis of phenyltrichlorosilane from trichlorosilane and chlorobenzene by gas phase condensation was studied. A kinetic model with 28 species and 56 elementary reactions was established, which was validated by experimental results from a tubular reactor under wide reaction conditions. The mole fraction profiles of the reactants and products from the kinetic model were in good agreement with the experimental results. This gas phase condensation reaction mainly followed an insertion mechanism of dichlorosilylene into the C Cl bond to form C 6 H 5 SiCl 3 . A reaction flux analysis showed that 99% of C 6 H 5 SiCl 3 was generated from the insertion reaction, 74% of SiCl 3 H was decomposed into SiCl 2 and 91% of SiCl 2 was inserted into C 6 H 5 Cl to form C 6 H 5 SiCl 3 . The proposed mechanism and kinetic model are useful for developing and designing commercial reactors to produce phenyltrichlorosilane.

The effect of liquid viscosity on the hydrodynamic behavior in a bubble column was investigated by experimental study and numerical simulation with a coupled CFD–PBM (population balance model) model. The total gas holdup and volume fractions of small and large bubbles were determined by the dynamic gas disengagement method. In the low viscosity range, the total gas holdup and the volume fractions of small and large bubbles were almost independent of the liquid viscosity. In the high viscosity range, an increased viscosity gave a decrease in the total gas holdup and volume fraction of small bubbles and an increase in the volume fraction of large bubbles. The simulation captured these features and showed that when the liquid viscosity was

The promoter effects of Zn and Sn in the direct synthesis of methylchlorosilanes were studied using a stirred bed. Zn and Sn were introduced not only before but also during the reaction. The activity and selectivity were characterized by online GC analysis and correlated with the Cu3Si content that was measured by the leaching method. It was found that Zn enhanced the formation of Cu3Si when it was added before the reaction. Zn improved the selectivity for dimethyldichlorosilane, but the excess Zn deactivated the reaction. Sn accelerated the consumption of Cu3Si. Added during the reaction, Sn led to a drastic reduction of Cu3Si coupled with a temporary rise in the formation of dimethyldichlorosilane. These results provided a new explanation for the role of promoters and suggested that the regulation on the direct synthesis process is probably due to the trade-off between the production and consumption of Cu3Si.

The effect of liquid viscosity on hydrodynamics and bubble behaviour of an external-loop airlift reactor within air–water system were studied by an electrical conductivity probe. Carboxyl methyl cellulose (CMC) was used to change liquid viscosity (1.00–51.25 cP). Gas holdup increased with superficial gas velocity increasing, as well as bubble Sauter diameter and bubble rise velocity. With liquid viscosity increasing, average gas holdup increased first then decreased, while bubble Sauter diameter was opposite, with critical viscosity µl ≈ 3.7 cP. The cross-sectional average bubble Sauter diameter increased obviously after µl > 3.7 cP, and its size distribution was wider within the higher viscosity. Bubble rise velocity increased significantly and nearly unchanged after µl > 10.3 cP. Gas holdup first increased then remained unchanged with the axial height increasing. The radial profile of local gas holdup presented a central peak distribution, and the value at inlet was smaller than that at the higher position. Average gas holdup was correlated greatly with superficial gas velocity and liquid viscosity.

Plant oil asphalt (POA) is a waste by-product in the biodiesel and fatty acid industry, especially in China. A novel vacuum pyrolysis method was developed obtaining diesel-like pyrolytic biodiesel from POA. This study was aimed at qualitatively analyzing components of POA and probing the influence of vacuum pressure on reaction selectivity, product composition and properties in POA vacuum pyrolysis. The POA was characterized by FT-IR, TGA, positive ion ESI FT-ICR MS, while the pyrolytic oil and pyrolytic biodiesel were analyzed by GC/MS. Pyrolytic biodiesel was tested for its properties such as density, viscosity, flash point, acid value, and cetane number according to the ASTM standard methods. At 400 °C, the pyrolytic biodiesel obtained at vacuum pressure range of 20–60 kPa achieved the ASTM standards of diesel fuel. An overall pathway of POA pyrolysis was proposed combining general pyrolysis changes and experimental data. The proposed POA components and their pyrolysis pathway reported are useful for the further study of POA utilization.

The kinetics of simultaneous transesterification and esterification with a carbon-based solid acid catalyst was studied. Two solid acid catalysts were prepared by the sulfonation of carbonized vegetable oil asphalt and petroleum asphalt. These catalysts were characterized on the basis of elemental analysis, acidity site concentration, the Brunauer-Emmett-Teller (BET) surface area and pore size. The kinetic parameters with the two catalysts were determined, and the reaction system can be described as a pseudo homogeneous catalyzed reaction. All the forward and reverse reactions follow second order kinetics. The calculated concentration values from the kinetic equations are in good agreement with experimental values.

CeO2-promoted Ni/Al2O3-ZrO2 (Ni/Al2O3-ZrO2-CeO2) catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy (IR), thermal gravimetric analysis (TGA), microscopic analysis, X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.

The pseudopotential in Shan and Chen-type multiphase models was investigated and modified based on a virial equation of state with newly proposed parameters. This modified pseudopotential was used in a lattice Boltzmann model and shown to be suitable for simulating sufficiently large gas–liquid density ratios with good numerical stability and only small spurious velocities. The spurious velocity was reduced by reducing the pseudo-sound speed by the use of suitable parameters. The multicomponent multiphase model based on this modified pseudopotential can be used in bubbly flow simulations. Bubble rise behavior was simulated using a 3D multicomponent and multiphase model with a high density ratio. The predicted terminal velocity and drag coefficient of a single bubble agreed well with those calculated from empirical correlations. The drag coefficient of bubbles in the homogenous regime decreased with increased gas holdup. A new relationship between the bubble drag coefficient and gas holdup in the homogenous regime was proposed.

UV/H2O2 was applied to deal with azo dye Reactive Red SBE (RR SBE) in aqueous and effects of hydrogen peroxide dosage, initial dye dosage, pH value, and different anions on color removal were investigated in detail. The online spectrophotometric method was used to detect the change dye absorbance at different reaction time. The results show that RR SBE can be completely decomposed in less than 40 min with 4.412 mM H2O2 dosage, initial dye 17 mg L−1 and neutral ambient. The RR SBE degradation performance follows pseudo first order kinetics and the reaction rate constant of ·OH and RR SBE is 2.32 × 109 M−1 s−1 that is estimated by UV/H2O2 kinetic model. The anions inhibiting effect on dye decolorization follows the order of PO43− > CO32− > Cl− > SO42− > HCO3− > HPO42−. The main intermediate product is phthalic acid dimethyl ester after UV/H2O2 degradation and possible decomposition mechanism of RR SBE is predicted by GC-MS analysis. © 2010 American Institute of Chemical Engineers Environ Prog, 2011

Oscillations in the gas holdup and liquid circulation velocity were found at low liquid levels in an airlift reactor with a designed gas–liquid separator. The hydrodynamic behavior and the frequency and amplitude of the oscillations were investigated. The gas holdup and liquid circulation velocity oscillated at the same frequency. The frequency increased from 0.07 to 0.18 Hz with an increase in the superficial gas velocity or liquid level. The gas holdup oscillation occurred mainly in the downcomer. The oscillation amplitude of the average gas holdup in the downcomer was 0.02 at superficial gas velocities of 0.03–0.06 m/s, and was close to zero at other superficial gas velocities. Using the superficial gas velocity and unaerated liquid level, the flow was classified into three regimes: non-circulating regime, self-oscillation regime and completely circulating regime. The self-oscillation regime, determined from the oscillation amplitude, became wider as the liquid level decreased.

A semi-empirical adsorption kinetic model was proposed with the time compensation method to describe the chemisorption of SO 2 in flue gas by carbon adsorbents for flue gas purification. The change in adsorption capacity and adsorption rate with time at different water vapor concentrations and different SO 2 concentrations was studied. The model was in good agreement with experimental data. The surface reaction was probably the rate controlling step in the early stage for SO 2 adsorption by ZL50 activated carbon. The parameters m and n in the n th order adsorption kinetic model were related to the magnitude of the time compensation and adsorption driving force, respectively. The change of parameter n with water vapor concentrations and sulfur dioxide concentrations was studied and some physical implications were given. The sum of square errors was less than 1.0 and the average absolute percentage deviations ranged from 0.5 to 3.2. The kinetic model was compared with other models in the literature.

A new process that coupled the reaction and separation in the production of biodiesel from feedstocks with Free Fatty Acids (FFAs) was studied. A novel solid acid catalyst, sulfonated-multiwalled carbon nanotubes (s-MWCNTs), was used in the synthesis of biodiesel from methanol and oleic acid in a 250 mL autoclave. s-MWCNTs with different concentrations of –SO 3 H were produced from the treatment of MWCNTs with concentrated H 2 SO 4 (96%) at 120–210 °C, and were characterized by SEM/EDS and FTIR analysis. Recycling of the methanol phase was used to separate the water produced from the reaction mixture, which increased the esterification conversion substantially and decreased the acidity of the product. A conversion of oleic acid of 95.46 wt.% was obtained with a catalyst/oleic acid mass ratio of 0.20%, methanol/oleic acid molar ratio of 5.8, temperature of 135 °C, and reaction time of 1.5 h. By removing water from the reaction mixture and adding the recycling of the methanol steam, the conversion of oleic acid was increased to 99.10 wt.% after 1 h.

The permeability of hydrogen through a Pd-Ag-Au-Ni membrane was determined at temperatures between (473 and 573) K at a hydrogen pressure of between (1.0 and 4.0) 10 5 Pa. Methoxymethane steam reforming (C 2 H 6 O + 3H 2 O(g) = 6H 2 + 2CO 2 ) with a Pd-Ag-Au-Ni membrane reactor is used to produce hydrogen in proton exchange membrane fuel cells (PEMFCs). This process uses a bifunctional catalyst of (CuO―ZnO―Al 2 O 3 ―ZrO 2 + ZSM-5) in mass fraction ratio of each component of 50 %. The determined methoxymethane conversion, hydrogen yield, and hydrogen recovery flow in a reactor were compared to those in a fixed bed reactor. The operating parameters were pressures of (1.0 to 4.0)•10 5 Pa, temperatures of (473 to 573) K, and input mass fraction ratios of H 2 O-to-C 2 H 6 O of (3 to 7) at velocities of between (1180 and 9000) cm 3 •g ―1 •h ―1 . The conversion of C 2 H 6 O was higher in the membrane reactor due to the countercurrent removal of hydrogen. In the membrane reactor, the thermal energy needed for the endothermic steam reforming can be provided by the combustion of the exit stream from the membrane reactor. The enthalpy for the reactions indicated coupling, and both reforming and oxidation reactions gave a energy recovery of about 85 %.

A carbon-based solid acid catalyst was prepared by the sulfonation of carbonized vegetable oil asphalt and used to catalyze the transesterification of methanol with cottonseed oil. This catalyst was characterized by scanning electron microscopy/energy dispersive spectroscopy, BET surface area and pore size measurement, thermogravimetry analysis and Fourier transform infrared spectroscopy. The sulfonated multi-walled carbon nanotubes (s-MWCNTs) was also prepared and used to catalyze the same transesterification as the asphalt catalyst. The asphalt-based catalyst shows higher activity than the s-MWCNTs for the production of biodiesel, which may be correlated to its high acid site density, its loose irregular network and large pores can provide more acid sites for the reactants. The conversion of cottonseed oil 89.93% was obtained (using the asphalt-based catalyst) when the methanol/cottonseed oil molar ratio was 18.2, reaction temperature at 260 °C, reaction time 3.0 h and catalyst/cottonseed oil mass ratio of 0.2%. Also, it can be re-used. The sulfonated polycyclic aromatic hydrocarbons provide an electron-withdrawing function to keep the acid site stable. The catalyst can substantially reduce energy consumption and waste generation in the production of biodiesel.

Experiments were carried out to characterize the kinetics of dimethyl ether (DME) steam reforming (SR) in a fixed bed reactor catalyzed by a bifunctional catalyst comprising a physical mixture of 50:50 wt.% CuO–ZnO–Al 2 O 3 –ZrO 2 + ZSM-5 at 200–300 °C and atmospheric pressure. The influences of the feed composition (steam/DME ratio), temperature and space velocity on DME conversion, hydrogen yield and CO 2 selectivity were obtained. A kinetic model for combined DME SR based on the reaction mechanisms for methanol to DME from Park and Froment and methanol SR from Peppley et al. was used. The kinetic parameters were determined by regression using the DME conversion, hydrogen yield and CO 2 selectivity at a given steam/DME feed ratio (steam/DME molar ratio of 3.5).

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.

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.

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

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.

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.