Modeling of a membrane reactor system for crude palm oil transesterification. Part I: Chemical and phase equilibrium

Using a membrane reactor for reversible transesterification reaction involves reaction and product separation within a single unit. However, a pseudohomogeneous reaction and heterogeneous separation must be maintained for successful membrane reactor operation. Present research is aimed to develop an integrated model of chemical and phase equilibrium (CPE) and modified Maxwell–Stefan equation that describes the simultaneous CPE and mass transport phenomena of biodiesel production from crude palm oil (CPO) using a membrane reactor. In the first part of this work, a systematic approach describing simultaneous CPE of CPO transesterification in the membrane reactor was developed with the reconciliation of transesterification reaction and phase equilibrium that involves six‐component. The results revealed that regressed apparent equilibrium constant, value of 17.557 1.51% were higher than the literatures. This indicates that forward reaction of the reversible CPO transesterification is much favored in the membrane reactor than the conventional reactor. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1968–1980, 2015     

Modeling analysis of membrane reactor for biodiesel production

Recently, membrane reactor technology was used to produce high‐quality biodiesel because of its advantage of simultaneous transesterification and separation. As the transesterification reaction involves two immiscible phases of methanol (MeOH) and oil (TG), a thorough investigation on the membrane reactor for biodiesel production with the consideration of chemical phase equilibrium (CPE) via modeling analysis, was conducted in this study. A mathematical model was developed based on the modified Maxwell‐Stefan model with the incorporation of CPE. The formation of TG rich micelles dispersed in the continuous phase of MeOH was the most important hypothesis in the model development. The preliminary experiment results show that the permeate compositions from the membrane reactor were closely related to CPE of the system, which was highly depending on the MeOH to TG molar ratio. TG free permeate can only be obtained if the continuous phase of MeOH was free from TG and the TG rich micelles were retained by the membrane. The model verification further confirmed the formation of micelles dispersed in the continuous MeOH phase within the feed side of the membrane reactor and the model was able to predict the performance of the membrane reactor for biodiesel production at an acceptable accuracy. © 2012 American Institute of Chemical Engineers AIChE J, 59: 258–271, 2013     

Assessing the performance of an industrial SBCR for Fischer–Tropsch synthesis: Experimental and modeling

The main objective of this study is to predict the performance of an industrial‐scale (ID = 5.8 m) slurry bubble column reactor (SBCR) operating with iron‐based catalyst for Fischer–Tropsch (FT) synthesis, with emphasis on catalyst deactivation. To achieve this objective, a comprehensive reactor model, incorporating the hydrodynamic and mass‐transfer parameters (gas holdup, ε_G, Sauter‐mean diameter of gas bubbles, d₃₂, and volumetric liquid‐side mass‐transfer coefficients, k_La), and FT as well as water gas shift reaction kinetics, was developed. The hydrodynamic and mass‐transfer parameters for He/N₂ gaseous mixtures, as surrogates for H₂/CO, were obtained in an actual molten FT reactor wax produced from the same reactor. The data were measured in a pilot‐scale (0.29 m) SBCR under different pressures (4–31 bar), temperatures (380–500 K), superficial gas velocities (0.1–0.3 m/s), and iron‐based catalyst concentrations (0–45 wt %). The data were modeled and predictive correlations were incorporated into the reactor model. The reactor model was then used to study the effects of catalyst concentration and reactor length‐to‐diameter ratio (L/D) on the water partial pressure, which is mainly responsible for iron catalyst deactivation, the H₂ and CO conversions and the C₅₊ product yields. The modeling results of the industrial SBCR investigated in this study showed that (1) the water partial pressure should be maintained under 3 bars to minimize deactivation of the iron‐based catalyst used; (2) the catalyst concentration has much more impact on the gas holdup and reactor performance than the reactor height; and (3) the reactor should be operated in the kinetically controlled regime with an L/D of 4.48 and a catalyst concentration of 22 wt % to maximize C₅₊ products yield, while minimizing the iron catalyst deactivation. Under such conditions, the H₂ and CO conversions were 49.4% and 69.3%, respectively, and the C₅₊ products yield was 435.6 ton/day. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3838–3857, 2015     

Hydrodeoxygenation of HMF over Pt/C in a continuous flow reactor

The three‐phase hydrodeoxygenation reaction of 5‐hydroxymethylfurfural (HMF) with H₂ was studied over a 10 wt % Pt/C catalyst using both batch and flow reactors, with ethanol, 1‐propanol, and toluene solvents. The reaction is shown to be sequential, with HMF reacting first to furfuryl ethers and other partially hydrogenated products. These intermediate products then form dimethyl furan (DMF), which in turn reacts further to undesired products. Furfuryl ethers were found to react to DMF much faster than HMF, explaining the higher reactivity of HMF when alcohol solvents were used. With the optimal residence time, it was possible to achieve yields approaching 70% in the flow reactor with the Pt/C catalyst. Much higher selectivities and yields were obtained in the flow reactor than in the batch reactor because side products are formed sequentially, rather than in parallel, demonstrating the importance of choosing the correct type of reactor in catalyst screening. © 2014 American Institute of Chemical Engineers AIChE J, 61: 590–597, 2015     

Methylcyclohexane dehydrogenation for hydrogen production via a bimodal catalytic membrane reactor

The dehydrogenation of methylcyclohexane (MCH) to toluene (TOL) for hydrogen production was theoretically and experimentally investigated in a bimodal catalytic membrane reactor (CMR), that combined Pt/Al₂O₃ catalysts with a hydrogen‐selective organosilica membrane prepared via sol‐gel processing using bis(triethoxysilyl) ethane (BTESE). Effects of operating conditions on the membrane reactor performance were systematically investigated, and the experimental results were in good agreement with those calculated by a simulation model with a fitted catalyst loading. With H₂ extraction from the reaction stream to the permeate stream, MCH conversion at 250°C was significantly increased beyond the equilibrium conversion of 0.44–0.86. Because of the high H₂ selectivity and permeance of BTESE‐derived membranes, a H₂ flow with purity higher than 99.8% was obtained in the permeate stream, and the H₂ recovery ratio reached 0.99 in a pressurized reactor. A system that combined the CMR with a fixed‐bed prereactor was proposed for MCH dehydrogenation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1628–1638, 2015     

Preparation of dual‐layer acetylated methyl cellulose hollow fiber membranes via co‐extrusion using thermally induced phase separation and non‐solvent induced phase separation methods

Dual‐layer acetylated methyl cellulose (AMC) hollow fiber membranes were prepared by coupling the thermally induced phase separation (TIPS) and non‐solvent induced phase separation (NIPS) methods through a co‐extrusion process. The TIPS layer was optimized by investigating the effects of coagulant composition on morphology and tensile strength. The solvent in the aqueous coagulation bath caused both delayed liquid–liquid demixing and decreased polymer concentration at the membrane surface, leading to porous structure. The addition of an additive (triethylene glycol, (TEG)) to the NIPS solution resolved the adhesion instability problem of the TIPS and NIPS layers, which occurred due to the different phase separation rates. The dual‐layer AMC membrane showed good mechanical strength and performance. Comparison of the fouling resistance of the AMC membranes with dual‐layer polyvinylidene fluoride (PVDF) hollow fiber membranes fabricated with the same method revealed less fouling of the AMC than the PVDF hollow fiber membrane. This study demonstrated that a dual‐layer AMC membrane with good mechanical strength, performance, and fouling resistance can be successfully fabricated by a one‐step process of TIPS and NIPS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42715.     

低温液相甲醇合成鼓泡浆态反应器数学模拟

建立了经由甲酸甲酯的低温液相甲醇合成鼓泡浆态反应器的数学模型 ,模拟了实验室鼓泡浆态反应器的行为 ,并利用模型考察了工艺参数如表观气速、催化剂浓度对反应的影响 ,对改进和提高低温液相浆态床反应器甲醇合成提供了信息 ,以便对开发低温甲醇合成工艺提供参考和指导     

Modeling heterogeneous photocatalytic inactivation of E. coli using suspended and immobilized TiO2 reactors

A study was carried out to develop a kinetic model of the photocatalytic inactivation of Escherichia coli using different TiO₂ catalysts. The model developed is based on a reaction scheme that involves effectively coupling mass‐transfer fluxes between bacteria and catalyst surface on one hand and bacterial degradation reaction on the other. The photocatalytic results were derived from experiments led in a batch reactor under both dark and Ultra Violet (UV) irradiation conditions. Using a reference catalyst, the robustness of the developed model was tested under solar conditions. The experimental data validated the model as successfully able to reproduce evolutions in the viable bacteria concentration in the range of parameters studied without any further adjustment of the kinetic parameters. The model was used to simulate the bacterial degradation kinetics under different working conditions to describe the partitioning of both bacterial adhesion and photocatalytic reaction in the solution to be treated © 2015 American Institute of Chemical Engineers AIChE J, 61: 2532–2542, 2015     

Aldol condensation of n‐butyraldehyde in a biphasic stirred tank reactor: Experiments and models

To model a biphasic stirred tank reactor, intrinsic reaction kinetics and interfacial area are required. In this study, reactor modeling for n‐butyraldehyde aldol condensation was investigated under industrially relevent conditions. The interfacial area in the reactor was directly measured using a borescope system under appropriate temperature, NaOH concentration and rpm conditions. To estimate the interfacial area, a semiempirical correlation was developed, which provides good estimates within ±15% error. The reactor model based on two‐film theory was developed, combining the interfacial area and intrinsic reaction kinetics reported in our prior work. The model was verified by reaction experiments in the range 0.05–1.9 M NaOH, 80–130°C, and 600–1000 rpm. The prediction errors using the interfacial area from direct measurements and the correlation were ±8% and ±15%, respectively, suggesting that the model accuracy may be improved with better interfacial area estimation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2228–2239, 2015     

A robust mixed‐conducting multichannel hollow fiber membrane reactor

To accelerate the commercial application of mixed‐conducting membrane reactor for catalytic reaction processes, a robust mixed‐conducting multichannel hollow fiber (MCMHF) membrane reactor was constructed and characterized in this work. The MCMHF membrane based on reduction‐tolerant and CO₂‐stable SrFe_0.8Nb_0.2O_3‐δ (SFN) oxide not only possesses a good mechanical strength but also has a high oxygen permeation flux under air/He gradient, which is about four times that of SFN disk membrane. When partial oxidation of methane (POM) was performed in the MCMHF membrane reactor, excellent reaction performance (oxygen flux of 19.2 mL min^?1 cm^?2, hydrogen production rate of 54.7 mL min^?1 cm^?2, methane conversion of 94.6% and the CO selectivity of 99%) was achieved at 1173 K. And also, the MCMHF membrane reactor for POM reaction was operated stably for 120 h without obvious degradation of reaction performance. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2592–2599, 2015     

Synthesis of butyl acrylate in a fixed‐bed adsorptive reactor over Amberlyst 15

The butyl acrylate synthesis from the esterification reaction of acrylic acid with 1‐butanol in a fixed‐bed adsorptive reactor packed with Amberlyst 15 ion exchange resin was evaluated. Adsorption experiments were carried out with nonreactive pairs at two temperatures (323 and 363 K). The experimental results were used to obtain multicomponent adsorption equilibrium isotherms of Langmuir type. Reactive adsorption experiments using different feed molar ratios and flow rates were performed, at 363 K, and used to validate a mathematical model developed to describe the dynamic behavior of the fixed‐bed adsorptive reactor for the butyl acrylate synthesis. Due to the simultaneous reaction and separation steps, it was possible to obtain a butyl acrylate maximum concentration 38% higher than the equilibrium concentration (for an equimolar reactants ratio solution as feed at a flow rate of 0.9 mL min^?1 and 363 K) showing that sorption‐enhanced reaction technologies are very promising for butyl acrylate synthesis. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1263–1274, 2015     

Thermodynamic and kinetic studies on alkoxylation of camphene over cation exchange resin catalysts

The alkoxylation of camphene with 2‐methyl‐1,3‐propanediol was studied using anhydrous macroporous and strong acid cation exchange resins as catalysts. The effects of various parameters, such as catalyst type, solvent, molar ratio of reactants, reaction temperature, and reusability of catalysts, were investigated in a 250 mL stirred tank reactor to optimize the reaction conditions. The UNIFAC group contribution method was used to correct liquid nonideality, giving the thermodynamic equilibrium constant at 333–370 K. The enthalpy changes calculated by three different methods (Gaussian 03, constant, and a function of temperature) were compared. The value (?74.6 ± 3.3 kJ/mol) calculated by the last method was closer to the theoretical value (?75.73 kJ/mol) than that given by the second method (?30.2 ±1.2 kJ/mol). A Langmuir–Hinshelwood–Hougen–Watson model based on activity was used to fit experimental data and the activation energy was 29.14 kJ/mol. The optimized reaction conditions were also verified in a 5 L reaction kettle. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1925–1932, 2015     

Damping properties of chlorinated polyethylene‐based hybrids: Effect of organic additives

In this article, the damping properties of organic hybrids consisting of chlorinated polyethylene (CPE), N,N‐dicyclohexyl‐2‐benzothia‐zolylsufenamide (DZ), and 4,4′‐thio‐bis(3‐methyl‐6‐tert‐butylphenol) (BPSR) have been investigated by dynamic mechanical analysis (DMA). It is found that DZ and BPSR seem to have a synergistic effect on the damping improvement of CPE/DZ/BPSR hybrids. For CPE/DZ/BPSR three‐component hybrids, when BPSR content is below 20 wt %, the values of damping peak maximum are just the same, while the damping peak position shifts to a higher temperature at a higher BPSR concentration. When BPSR content is fixed at 10 wt %, the damping peak maximum increases with increasing DZ/CPE ratio, while there is little shift in the peak position within the ratio range of 0.75–1.25. The decrease in damping peak maximum against annealing can be attributed to the phase separation resulting from the crystallization of hybrids components. Such a crystalline phase, which has been formed during annealing, contains not only pure DZ crystallites but also some CPE–DZ or CPE–DZ–BPSR eutectic crystals. Furthermore, the damping stability of the hybrids can be improved excellently by adding a small amount of BPSR or changing hot‐pressing temperature. These may imply that a series of high‐performance damping materials possessing both high damping peak maximum and controllable damping peak position can be achieved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3307–3311, 2006     

Inherent porous structure modified by titanium dioxide nanoparticle incorporation and effect on the fouling behavior of hybrid poly(vinylidene fluoride) membranes

The incorporation of nanoparticles (NPs) into a casting solution is a widely used practice for controlling the membrane fouling tendency, but the specific role of NPs in fouling control from an internal porous structure optimization has seldom been investigated. In this study, we evaluated the specific role of titanium dioxide (TiO₂)–NPs (Degussa P25) in mitigating membrane organic fouling. We prepared the membranes by tailoring the concentrations of the NPs well; this resulted in an optimized membrane microstructure consisting of fingerlike voids (beneath the skin layer of the membrane) and spongy voids (adjacent to the fingerlike voids). The NP incorporation induced the formation of spongy voids beneath the skin layer, and the increase in the NP concentration increased the formation of spongy voids. Moreover, surface images obtained by scanning electron microscopy, X‐ray photoelectron spectroscopy results, and contact angles confirmed that TiO₂–NPs were almost absent on the skin layer. Antifouling experiments were performed with a model organic foulant in two flow orientations [fingerlike voids facing the retentate (FVR) and spongy voids facing the retentate (SVR)]. The results show that the membrane fluxes in FVR decreased more than those in SVR. The membrane with 1.5 wt % TiO₂ operated in SVR exhibited the lowest flux decline; this suggested that spongy voids with TiO₂ exposure could mitigate fouling to a greater extent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43265.     

Modeling and simulation of biodiesel production using a membrane reactor integrated with a prereactor

To enable the transesterification performed as quickly as possible, whereas the purification of product simultaneously carried out as completely as possible, the biodiesel production using a membrane reactor integrated with a prereactor is developed in this work. The set of mathematical model equations for the whole system includes the kinetics of the transesterification, the phase equilibrium, the mass balance of the prereactor, and the equations for the tubular ceramic membrane derived from mass balances of both the feed side and the permeate side coupled with the mass transfer across the membrane. The integrated reactor performances are then investigated in terms of the permeated biodiesel flux and selectivity over a range of methanol to oil ratio in the feed, the initial reaction time in the prereactor, the volume ratio of the prereactor to the tube membrane, and the length of the tube membrane module. The results show that the prereactor can be used for the purpose of carrying out a substantial part of the transesterification reaction in the early stage. The subsequent membrane reactor, when the operating conditions are controlled at methanol to oil molar ratio in the feed of 24:1, the catalyst concentration to the oil of 0.05 wt% at 65 ^oC, can serve to separate the unreacted emulsified oil from the product stream. The production of biodiesel with high purity using this proposed system is further validated experimentally and found in agreement considerably well with the simulated ones by adjusting the operating conditions, including the initial reaction time in the prereactor and the tube membrane length.     

Compact hollow fibre reactors for efficient methane conversion

In this study, a micro-structured catalytic hollow fiber membrane reactor (CHFMR) has been prepared, characterized and evaluated for performing steam methane reforming (SMR) reaction, using Rh/CeO₂ as the catalyst and a palladium membrane for separating hydrogen from the reaction. Preliminary studies on a catalytic hollow fiber (CHF), a porous membrane reactor configuration without the palladium membrane, revealed that stable methane conversions reaching equilibrium values can be achieved, using approximately 36 mg of 2 wt.%Rh/CeO₂ catalyst incorporated inside the micro-channels of alumina hollow fibre substrates (around 7 cm long in the reaction zone). This proves the advantages of efficiently utilizing catalysts in such a way, such as significantly reduced external mass transfer resistance when compared with conventional packed bed reactors. It is interesting to observe catalyst deactivation in CHF when the quantity of catalyst incorporated is less than 36 mg, although the Rh/CeO₂ catalyst supposes to be quite resistant against carbon formation. The “shift” phenomenon expected in CHFMR was not observed by using 100 mg of 2 wt.%Rh/CeO₂ catalyst, mainly due to the less desired catalyst packing at the presence of the dense Pd separating layer. Problems of this type were solved by using 100 mg of 4 wt.% Rh/CeO₂ as the catalyst in CHFMR, resulting in methane conversion surpassing the equilibrium conversions and no detectable deactivation of the catalyst. As a result, the improved methodology of incorporating catalyst into the micro-channels of CHFMR is the key to a more efficient membrane reactor design of this type, for both the SMR in this study and the other catalytic reforming reactions.     

Adhesion optimization for catalyst coating on silicon-based reformer

CMZ (ca. 30.0 wt.% Cu, 20 wt.% Mn, and 50 wt.% Zn) catalyst was chosen for the partial oxidation of methanol (POM) reaction. To enhance adhesion between a silicon-based reactor and catalysts, boehmite and bentonite were used as binders. Changes in conditions such as pH value, ratio of bentonite/boehmite, amount of solid contents per area of substrate, and aging time have crucial effects on adhesion and result in variable performance of catalyst in POM reaction. Regarding optimized adhesion conditions, 13 wt.% weight loss was observed and methanol conversion could be kept at ca. 80–90% of original catalyst performance in a packed-bed reactor. However, poor performance was observed in the micro-channel reactor. The methanol conversion (C_MeOH), H₂ selectivity (S_H2), and H₂ yield (Y_H2) achieved 58%, 67%, 5.7 × 10^?6 mol/min in micro-channel reformer at 250 °C, respectively.     

Liquid phase methanol and dimethyl ether synthesis from syngas

The Liquid Phase Methanol Synthesis (LPMeOH^TM) process has been investigated in our laboratories since 1982The reaction chemistry of liquid phase methanol synthesis over commercial Cu/ZnO/Al₂O₃ catalysts, established for diverse feed gas conditions including H₂-rich, CO-rich, CO₂-rich, and CO-free environments, is predominantly based on the CO₂ hydrogenation reaction and the forward water-gas shift reactionImportant aspects of the liquid phase methanol synthesis investigated in this in-depth study include global kinetic rate expressions, external mass transfer mechanisms and rates, correlation for the overall gas-to-liquid mass transfer rate coefficient, computation of the multicomponent phase equilibrium and prediction of the ultimate and isolated chemical equilibrium compositions, thermal stability analysis of the liquid phase methanol synthesis reactor, investigation of pore diffusion in the methanol catalyst, and elucidation of catalyst deactivation/regenerationThese studies were conducted in a mechanically agitated slurry reactor as well as in a liquid entrained reactorA novel liquid phase process for co-production of dimethyl ether (DME) and methanol has also been developedThe process is based on dual-catalytic synthesis in a single reactor stage, where the methanol synthesis and water gas shift reactions takes place over Cu/ZnO/Al₂O₃ catalysts and the in-situ methanol dehydration reaction takes place over -Al₂O₃ catalystCo-production of DME and methanol can increase the single-stage reactor productivity by as much as 80%. By varying the mass ratios of methanol synthesis catalyst to methanol dehydration catalyst, it is possible to co-produce DME and methanol in any fixed proportion, from 5% DME to 95% DMEAlso, dual catalysts exhibit higher activity, and more importantly these activities are sustained for a longer catalyst on-stream life by alleviating catalyst deactivation.     

Fabrication of cellulose acetate ultrafiltration membrane with diphenyl ketone via thermally induced phase separation

With diphenyl ketone as diluent, cellulose acetate (CA) ultrafiltration (UF) membrane with a bicontinuous structure was prepared via thermally induced phase separation (TIPS) method. The liquid–liquid phase separation region of CA/diphenyl ketone system was measured and the maximum corresponding polymer concentration was approximately 53 wt %. The effects of polymer concentration, coarsening time and coarsening temperature on the morphologies, and mechanical properties of CA membranes were investigated systematically. As the polymer concentration increased from 15 to 30 wt %, the bicontinuous structure could be obtained and the tensile strength of CA membranes increased from 3.92 to 30.17 MPa. With the increase of coarsening time, the thickness of dense skin layer and the asymmetry of cross‐section reduced. However, excess coarsening rendered the membrane morphology evolved from a bicontinuous structure to a cellular structure. When the coarsening time was 5 min, the bicontinuous structure in cross‐section showed good interconnectivity and the dense skin layer exhibited a thin thickness of 2 μm. The fabricated CA hollow fiber UF membrane exhibited a high tensile strength of 31.00 MPa and rejection of 96.10% for dextran 20 kDa. It is indicated that diphenyl ketone is a competitive diluent to prepare CA membranes with excellent performance via TIPS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42669.     

Methanol recycling in the production of biodiesel in a membrane reactor

Membrane reactor technology was used to overcome challenges in biodiesel production. The membrane reactor produces a permeate stream which readily phase separates at room temperature into a fatty acid methyl ester (FAME)-rich non-polar phase and a methanol- and glycerol-rich polar phase. To decrease the overall methanol:oil molar ratio in the reaction system, the polar phase was recycled. Three recycle ratios were tested: 100%, 75% and 50%, at the same residence time and operating conditions. The permeate consistently separated to yield a FAME-rich non-polar phase containing a minimum of 85 wt.% FAME (the remainder being methanol) as well as a methanol/glycerol polar phase. At the highest recycle ratio, the FAME concentration ranged from 85.7 to 92.4 wt.% in the FAME-rich non-polar phase. In addition, the overall molar ratio of methanol:oil in the reaction system was significantly decreased to 10:1 while maintaining a FAME production rate of 0.04 kg/min. As a result, a high purity FAME product was produced.