Conventional Stirred Tank Reactor Research Articles

The controllable and efficient synthesis of two-dimensional metal-organic framework nanosheets for heterogeneous catalysis.

Two-dimensional (2D) MOFs exhibit unique periodicity in surface structures and thus have attracted much interest in the fields of catalysis, energy, and sensors. However, the expanded production scale of 2D MOFs had remained a great challenge in most previous studies. Herein, a controllable and efficient crystallization method for synthesizing 2D MOF nanosheets using high-gravity reactive precipitation is proposed, significantly improving heterogeneous catalysis efficiency. The two-dimensional ZIF-L nanosheets prepared in a rotating packed bed (RPB) reactor show a smaller lateral and lamellar thickness and a higher BET surface area compared to ZIF-L nanosheets prepared in a conventional stirred tank reactor (STR), with a greatly shortened reaction time. Applying the ZIF-L-RPB nanosheets as a catalyst, the catalytic Knoevenagel condensation as a probe reaction displays a high conversion rate of benzaldehyde (99.3%) within 2 h at room temperature, greatly exceeding that displayed by ZIF-L-STR and other reported catalysts. Furthermore, ZIL-L-RPB nanosheets of only 0.2 wt% enhanced the catalytic activity for the glycolysis of poly(ethylene terephthalate) (PET) with a PET conversion and a monomer yield of 90% in a short period of 15 min at 195 °C and almost completely depolymerized PET with a monomer yield of 94% in 30 min, which was far above that achieved by ZIL-L-STR. These results indicate the promising prospects of a high-gravity reactive precipitation strategy with precise size control in an economical way to prepare high-activity 2D MOF nanosheets for a wide range of heterogeneous catalysis.

Enhancing biodiesel production in stirred tank reactors through the implementation of a baffle array: Creating a reactor with unique characteristics

This study focuses on enhancing biodiesel production from expired refined palm oil by implementing baffle arrays with a suitable dimension ratio into a conventional stirred tank reactor. This reactor functions as a deglycerolizing reactor at low agitation speeds (250 rpm), or an intensive mixing at high agitation speeds (500 rpm). With these unique characteristics, this reactor outperformed its traditional counterparts and could produce biodiesel via a simplified, single-step transesterification process. The optimal reaction condition was 1:6 oil to MeOH ratio, 1.0 wt% KOCH3, 30-minute reaction time and 60 °C reaction temperature. Ester content of 98.13 wt% was obtained in the deglycerolizing reactor and 98.54 wt% in the intensive mixing reactor with the number of baffles of 16. This achievement represents a 50 % reaction time reduction and 30 % reactor cost reduction compared to the conventional reactor with similar reaction condition and production capability.

Preparation of C-S-H-PCE composites using an impinging stream reactor

The C-S-H-PCE composites (CPCs) serve as an accelerator for cement hydration. This work presents a novel approach for synthesizing CPCs using an impinging stream reactor (ISR). The resulting CPCs exhibited an average particle size of approximately 21 nm and significantly enhanced the compressive strength of mortar when used as an additive. The compressive strength value of the mortar after curing for 6 h is 18.7 N/mm2, which is 503 % higher than the control group. Moreover, the ISR method was superior to the conventional stirred tank reactor method in terms of product particle size and acceleration efficiency.

Nitration of o-xylene in the microreactor: Reaction kinetics and process intensification

Nitration reactions are extensively studied in organic synthesis despite their notorious dangers, high reaction rates, and heterogeneous reaction systems. To date, most industrial nitration reactions rely on conventional batch reactors characterized by low mass transfer rates and limited reaction conditions. In contrast, microreactors represent a valuable technology for intensifying such nitration reactions. In this work, we established a continuous flow system of o-xylene nitration and determined the kinetics and mass transfer. The effects of mixing performance, nitric acid concentration, molar ratio, reaction temperature, and residence time on the process safety were investigated separately. The experimental data is supported by dimensionless number calculations, providing a more comprehensive understanding of the nitration reaction's transport and reaction performance in a heart-shaped microreactor. Remarkably, the residence time of the heart-shaped microreactor was reduced by an order of magnitude, while the volumetric mass transfer coefficient was improved by several orders of magnitude compared to conventional stirred tank reactors. Moreover, the spent nitric acid could be efficiently recovered and reused after concentration, further enhancing the sustainability and cost-effectiveness of the process. Our findings demonstrate the significant potential of microreactors for intensifying nitration reactions and paving the way for the design and optimization of more efficient and safer synthetic processes.

Surfactant-Free Synthesis of PNIPAM-Based Smart Microgels for Drug Delivery Using a High-Gravity Rotating Packed Bed

Poly(N-isopropylacrylamide) (PNIPAM) microgels have a number of potential biomedical applications, especially being considered as next-generation drug delivery systems. So far, nm-sized PNIPAM microgels have been commonly prepared in lab-scale experiments. In this work, nm-size controllable and monodisperse PNIPAM-based microgels were synthesized for the first time by surfactant-free precipitation polymerization using a high-gravity rotating packed bed reactor (RPB). The microgel size could be synergistically controlled by adjusting the amount of cross-linker and initiator in an RPB. Compared with the conventional stirred tank reactor, the RPB synthesis procedure could obtain a higher yield within 2 h of the reaction time. The higee level exhibited significant influence on the microgel size. Depending on the variation of the higee level, the particle size was tailored from 129 to 325 nm, and the hydrodynamic diameter was tailored from 217.7 to 805.4 nm without the usage of surfactants. In addition, different comonomers were introduced to regulate the lower critical solution temperature (LCST), achieve multiresponsiveness, and control microgel size. The in vitro DOX-loaded release demonstrated that PNIPAM-based microgels dramatically contributed to the sustained release of drugs.

Kinetics of Biodiesel Production from Microalgae Using Microbubble Interfacial Technology.

As an alternative to fossil fuels, biodiesel can be a source of clean and environmentally friendly energy source. However, its commercial application is limited by expensive feedstock and the slow nature of the pretreatment step-acid catalysis. The conventional approach to carry out this reaction uses stirred tank reactors. Recently, the lab-scale experiments using microbubble mediated mass transfer technology have demonstrated its potential use at commercial scale. However, all the studies conducted so far have been at a lab scale~100 mL of feedstock. To analyze the feasibility of microbubble technology, a larger pilot scale study is required. In this context, a kinetic study of microbubble technology at an intermediate scale is conducted (3 L of oil). Owing to the target for industrial application of the process, a commercial feedstock (Spirulina), microalgae oil (MO) and a commercial catalyst para-toluene sulfonic acid (PTSA) are used. Experiments to characterize the kinetics space (response surface, RSM) required for up-scaling are designed to develop a robust model. The model is compared with that developed by the gated recurrent unit (GRU) method. The maximum biodiesel conversion of 99.45 ± 1.3% is achieved by using these conditions: the molar ratio of MO to MeOH of 1:23.73 ratio, time of 60 min, and a catalyst loading of 3.3 wt% MO with an MO volume of 3 L. Furthermore, predicted models of RSM and GRU show proper fits to the experimental result. It was found that GRU produced a more accurate and robust model with correlation coefficient R2 = 0.9999 and root-mean-squared error (RSME) = 0.0515 in comparison with RSM model with R2 = 0.9844 and RMSE = 3.0832, respectively. Although RSM and GRU are fully empirical representations, they can be used for reactor up-scaling horizontally with microbubbles if the liquid layer height is held constant while the microbubble injection replicates along the floor of the reactor vessel-maintaining the tessellation pattern of the smaller vessel. This scaling approach maintains the local mixing profile, which is the major uncontrolled variable in conventional stirred tank reactor up-scaling.

Continuous-flow synthesis of the liquid crystal intermediate 1-(4-ethoxy-2,3-difluorobenzyl)-4-propylcyclohexan-1-ol in a microfluidic system: Experimental and numerical studies

• A tube-in-tube membrane-dispersion microreactor is designed for continuous synthesis. • The EDPO yield is increased by 10%, and the reaction time is shortened by 72.8%. • Coupling of DFT calculation and CFD simulation is proposed for predicting yield. A tube-in-tube membrane-dispersion microreactor is designed for the continuous synthesis of a liquid crystal intermediate without clogging. Under the optimal conditions, the intermediate exhibited a high yield of 78.1% at the residence time of 16.3 min. Compared with the conventional stirred-tank reactor, the reaction time is shortened by 72.8% and the yield is increased by 10% when the proposed microreactor is used. Moreover, the bath temperature can be increased from −60 °C to −40 °C, thereby significantly saving energy. Furthermore, a coupling method of density functional theory (DFT) calculation and computational fluid dynamics (CFD) simulation is proposed to analyze the flow field and predict the yields, which are found to be in good agreement with the experimental values. This study provides a practical approach for the efficient, high-yield, and continuous synthesis of liquid crystal intermediates and offers an in-depth understanding of these reactions and the establishment of process predictive models.

High-gravity technology intensified Knoevenagel condensation-Michael addition polymerization of poly (ethylene glycol)-poly (n-butyl cyanoacrylate) for blood-brain barrier delivery

Poly (ethylene glycol)-poly (n-butyl cyanoacrylate) (PEG-PBCA) is a remarkable drug delivery carrier for permeating blood-brain barrier. In this work, a novel high-gravity procedure was reported to intensify Knoevenagel condensation-Michael addition polymerization of PEG-PBCA. A series of PEG-PBCA containing different block ratios were synthesized with narrow molecular weight distribution of polydispersity indexes less than 1.1. Furthermore, the reaction time reduced 60% compared to conventional stirred tank reactor process. Chemical structures of as-prepared polymers were characterized. In vitro drug delivery performance was evaluated. The cytotoxicity of PEG-PBCA to brain microvessel endothelial cells (BMVEC) decreases with the extension of the PEG chain and the shortening of the PBCA chain. The polymer cellular uptake to BMVECs was better after improving hydrophilicity by PEG block. Results of blood-brain barrier permeability demonstrated that medium length of PBCA chain and short PEG chain are favorable for hydrophobic Nile red permeation, while long PEG chain and short PBCA chain are beneficial to delivery water-soluble doxorubicin hydrochloride (Dox). The average apparent permeability coefficient increased 1.7 and 0.25 times than that of raw Nile red and Dox, respectively. High-gravity intensified condensation polymerization should have great potential in brain drug delivery system.

The Hydrodynamics and Mixing Performance in a Moving Baffle Oscillatory Baffled Reactor through Computational Fluid Dynamics (CFD)

Oscillatory baffled reactors (OBRs) have attracted much attention from researchers and industries alike due to their proven advantages in mixing, scale-up, and cost-effectiveness over conventional stirred tank reactors (STRs). This study quantitatively investigated how different mixing indices describe the mixing performance of a moving baffle OBR using computational fluid dynamics (CFD). In addition, the hydrodynamic behavior of the reactor was studied, considering parameters such as the Q-criterion, shear strain rate, and velocity vector. A modification of the Q-criterion showed advantages over the original Q-criterion in determination of the vortices’ locations. The dynamic mesh tool was utilized to simulate the moving baffles through ANSYS/Fluent. The mixing indices studied were the velocity ratio, turbulent length scale, turbulent time scale, mixing time, and axial dispersion coefficient. We found that the oscillation amplitude had the most significant impact on these indices. In contrast, the oscillatory Reynolds number did not necessarily describe the mixing intensity of a system. Of the tested indices, the axial dispersion coefficient showed advantages over the other indices for quantifying the mixing performance of a moving baffle OBR.

The Concept of Chemical Generators: On-Site On-Demand Production of Hazardous Reagents in Continuous Flow.

ConspectusIn recent years, a steadily growing number of chemists, from both academia and industry, have dedicated their research to the development of continuous flow processes performed in milli- or microreactors. The common availability of continuous flow equipment at virtually all scales and affordable cost has additionally impacted this trend. Furthermore, regulatory agencies such as the United States Food and Drug Administration actively encourage continuous manufacturing of active pharmaceutical ingredients (APIs) with the vision of quality and productivity improvements. That is why the pharmaceutical industry is progressively implementing continuous flow technologies. As a result of the exceptional characteristics of continuous flow reactors such as small reactor volumes and remarkably fast heat and mass transfer, process conditions which need to be avoided in conventional batch syntheses can be safely employed. Thus, continuous operation is particularly advantageous for reactions at high temperatures/pressures (novel process windows) and for ultrafast, exothermic reactions (flash chemistry).In addition to conditions that are outside of the operation range of conventional stirred tank reactors, reagents possessing a high hazard potential and therefore not amenable to batch processing can be safely utilized (forbidden chemistry). Because of the small reactor volumes, risks in case of a failure are minimized. Such hazardous reagents often are low molecular weight compounds, leading generally to the most atom-, time-, and cost-efficient route toward the desired product. Ideally, they are generated from benign, readily available and cheap precursors within the closed environment of the flow reactor on-site on-demand. By doing so, the transport, storage, and handling of those compounds, which impose a certain safety risk especially on a large scale, are circumvented. This strategy also positively impacts the global supply chain dependency, which can be a severe issue, particularly in times of stricter safety regulations or an epidemic. The concept of the in situ production of a hazardous material is generally referred to as the “generator” of the material. Importantly, in an integrated flow process, multiple modules can be assembled consecutively, allowing not only an in-line purification/separation and quenching of the reagent, but also its downstream conversion to a nonhazardous product.For the past decade, research in our group has focused on the continuous generation of hazardous reagents using a range of reactor designs and experimental techniques, particularly toward the synthesis of APIs. In this Account, we therefore introduce chemical generator concepts that have been developed in our laboratories for the production of toxic, explosive, and short-lived reagents. We have defined three different classes of generators depending on the reactivity/stability of the reagents, featuring reagents such as Br2, HCN, peracids, diazomethane (CH2N2), or hydrazoic acid (HN3). The various reactor designs, including in-line membrane separation techniques and real-time process analytical technologies for the generation, purification, and monitoring of those hazardous reagents, and also their downstream transformations are presented. This Account should serve as food for thought to extend the scope of chemical generators for accomplishing more efficient and more economic processes.

Advances in acrylamide bioproduction catalyzed with Rhodococcus cells harboring nitrile hydratase.

Acrylamide is an important bulk chemical used for producing polyacrylamide, which is widely applied in diverse fields, such as enhanced oil recovery and water treatment. Acrylamide production with a superior biocatalyst, free-resting Rhodococcus cells containing nitrile hydratase (NHase), has been proven to be simple but effective, thereby becoming the main method adopted in industry to date. Under the harsh industrial conditions, however, NHase-containing Rhodococcus cells in a natural state are prone to deactivation. Thus, multiple genetic strategies able to evolve recombinant Rhodococcus biocatalysts at either the enzyme or cell level have been reported. While most of the methods on enzyme engineering concentrate on NHase stability enhancement by strengthening the flexible sites, Rhodococcus cell engineering with various methods can enhance both the NHase activity and stability as well. Developing some new types of reactors, especially the microreactor, is also an effective way to improve the hydration process efficiency. Compared with the conventional stirred tank reactor, the membrane dispersion microreactor can enhance the heat and mass transfer in the hydration process with Rhodococcus cells as biocatalysts, thereby significantly improving the productivity of the acrylamide bioproduction process.

High-gravity-assisted preparation of aqueous dispersions of monodisperse palladium nanocrystals as pseudohomogeneous catalyst for highly efficient nitrobenzene reduction

Nitrobenzene (NB) reduction is an important catalytic reaction, which is commonly performed in aqueous medium mainly with heterogeneous catalysts. In this work, highly stable aqueous nanodispersions of Pd nanocrystals with a tunable average size between 2 and 11 nm are conveniently prepared in a high-gravity rotating packed bed (RPB) reactor, and firstly serve as a pseudohomogeneous catalyst for NB reduction. As compared to a conventional stirred tank reactor (STR), the product prepared in the RPB reactor has a more uniform particle size. More importantly, the reaction time can be greatly shortened from 3 min (STR) to 1 s (RPB), thereby realizing a continuous preparation. This Pd pseudohomogeneous catalyst displays a significantly size-dependent catalytic activity and a good stability performance. Ultra-small 2.6 nm Pd nanocrystals have a reaction rate five times as fast as 10.1 nm counterpart. The obtained kinetics data confirm to the Langmuir-Hinshelwood model well, having a small error of <10%. Furthermore, the adsorption behavior of NB molecules on the surface of Pd nanocrystals was also studied with density functional theory (DFT) calculation. Since the processing capacity of the used lab-scale RPB reached 44.2 g/h, this route may offer a general platform for mass production of monodisperse nanocrystals as pseudohomogeneous catalyst for highly efficient catalysis.

Identification of methanogenesis and syntrophy as important microbial metabolic processes for optimal thermophilic anaerobic digestion of energy cane thin stillage

The aim of this research was to identify key microorganisms for thermophilic (55 °C) anaerobic digestion of thin stillage derived from hydrolysis and ethanol fermentation of energy cane in a conventional stirred tank reactor with a 10-day hydraulic retention time. Efficient thermophilic anaerobic digestion with a specific methane production of 0.43 Lmethane/gtCOD used/d and biogas containing around 56% methane was accomplished. Due to an overnight temperature perturbation the specific methane production decreased to 0.16 Lmethane/gtCOD used/d. Analysis of the microbial community showed the importance of methanogenic Archaea belonging to Methanosarcina and Methanothermobacter as well as syntrophic Bacteria related to Thermacetogenium, Tepidanaerobacter and Anaerobaculum. This indicates that retention of biomass maintaining syntrophy and methanogenesis more efficiently may be useful for thermophilic anaerobic digestion of thin stillage derived from the production of energy cane ethanol.

An experimental study on synthesis of glycolic acid via carbonylation of formaldehyde using PTFE membrane contactor

The batch and continuous synthesis of glycolic acid via carbonylation of formaldehyde using high-temperature and high-pressure poly(tetrafluoroethylene) (PTFE) membrane contactor was demonstrated in this paper. The experiments in conventional stirred tank reactor were also conducted for comparison. The results showed that the yield of glycolic acid was significantly improved in membrane contactor system compared to the stirred tank reactor. At reaction temperature of 120 °C and reaction pressure of 5.0 MPa, the yield of glycolic acid was higher than 90% when the reaction time was 1 h, while it was only about 45% in the conventional stirred tank reactor. The enhancement of yield was due to the improvement of mass transfer or dispersion of CO in membrane contactor system, which could provide larger gas-liquid contact area and shorter mass transfer distance. The stability of PTFE hollow fibre membranes was also investigated by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), liquid entry pressure (LEP), bubble point (BP) and contact angle (CA) measurements. The characterizations indicated that PTFE membranes exhibited good chemical and thermal stability in this reaction system. This study provided new idea and reference for the carbonylation of formaldehyde and similar gas-liquid reactions.

Average shear rate in airlift bioreactors: searching for the true value.

The shear rate is an important bioreactor parameter that needs to be evaluated due to its impact on microorganism morphology and viability, and consequently on bioproduct formation. Airlift bioreactors, classified as low-shear devices, are used as an alternative to conventional stirred-tank reactors. Considerable efforts have been made to characterize the shear environments in airlift bioreactors, using the average shear rate ([Formula: see text]) as a key parameter. However, there is no agreement among the values obtained in different studies, which can differ even in orders of magnitude. The methodologies used to obtain [Formula: see text] in the different studies could be the reason for the lack of agreement among them. In this work, [Formula: see text] in a concentric tube airlift bioreactor was evaluated using computational fluid dynamics (CFD), as well as based on universal velocity profiles for liquid flows in smooth pipes and annuli. Good agreement was obtained between the CFD-based average shear rates and the values obtained from universal velocity profiles, indicating that CFD simulation is a valuable tool for [Formula: see text] prediction.

High-gravity-assisted scalable synthesis of zirconia nanodispersion for light emitting diodes encapsulation with enhanced light extraction efficiency

Zirconia-based hybrid polymers has become one of the ideal encapsulation material for light emitting diodes (LEDs) with high extraction efficiency due to their proper refractive index to those of semiconductor chips. However, the controlling of the dispersion for zirconia nanoparticles in polymeric hosts to obtain optically transparent hybrid nanocomposites has been one of the major challenges. Herein, we reported the synthesis of zirconia nanodispersion via high-gravity-assisted homogeneous precipitation in an internal circulation rotating packed bed (RPB) reactor followed by two-step modification. An alternative to conventional precipitation in batch stirred tank reactors (STR), the process intensification by high-gravity RPB results in homogeneous micromixing during the nucleation and growth of zirconia particles, which are benefit for continuous and reproducible production of ultrasmall zirconia nanoparticles. The obtained zirconia nanoparticles are purely cubic phase with narrow size-distribution in the range of 3–5 nm according to the X-ray diffraction and transmission electron microscopy characterization, which were similarity to that by the conventional methods. Nevertheless, the average hydrodynamic diameters of zirconia nanoparticles in aqueous solutions obtained by RPB methods were much smaller than those prepared in conventional STR, which enabled easy control and surface modification for highly dispersed nanodispersion in organic solvents and/or polymeric hosts. After two-step surface modification, zirconia nanoparticles with goal-directed structures were obtained, with highly dispersity in various organic solvents (e.g. toluene, trichloromethane, tetrahydrofuran, etc.) and aliphatic epoxy resin, forming transparent hybrid films with tunable refractive indexes. The preliminary applications of these zirconia nanodispersions for LEDs encapsulation were demonstrated. The light extraction efficiency of the LEDs devices packaged with zirconia/epoxy hybrid material increased by 10 percent when the doping content of zirconia nanoparticles was 0.2, compared to the devices encapsulated by original epoxy.

Study on the Synthesis of 2,3,5-Trimethyl-1,4-Benzoquinone by an RSR+STR Tandem Process

This study presents a novel RSR+STR tandem process for the catalytic oxidation of 2,3,6-trimethylphenol (TMP) to synthesize 2,3,5-trimethyl-1,4-benzoquinone (TMQ) in a gas–liquid–liquid three-phase reaction system by combining a rotor-stator reactor (RSR) with a conventional stirred tank reactor (STR). The effects of various operating conditions including rotation speed of the RSR, gas volumetric flow rate, liquid volumetric flow rate, water volume fraction in the liquid phase and reaction temperature on the TMP conversion and TMQ yield were investigated. The TMP conversion and TMQ yield in the RSR+STR tandem process reached 86.9% and 20.0%, respectively, which were much higher than those in the STR process under the same conditions where the conversion and yield were only 46.8% and 6.8% respectively. It is suggested that the improvement of TMQ synthesis in the RSR+STR tandem process is ascribed to the intensification of liquid–liquid mixing, gas–liquid transfer and oxidation reaction in the RSR.

Enzymatic production of cellulose nanofibers and sugars in a stirred-tank reactor: determination of impeller speed, power consumption, and rheological behavior

An integrated biorefinery process is proposed here for the enzymatic production of cellulose nanofiber (CNF) and sugars in a stirred-tank reactor using eucalyptus cellulose pulp as feedstock. Process engineering variables required for scale-up such as impeller speed, power consumption, and rheological behavior were determined under different experimental conditions of solids loading (10 and 15% w/v) and enzyme dosage (5 and 10 mg/g). Based on the mixing time, an impeller speed rotation of 470 rpm was selected for provision of adequate homogenization of the medium. Total energy consumption ranged from 161 to 207 W h and showed that significantly lower power consumption could be achieved using 10 mg/g enzyme loading with 10% w/v solids. Evaluation of rheological behavior showed that transition to a turbulent flow regime during the enzymatic hydrolysis reaction resulted in a constant power number ranging from 2.06 to 2.51, which was also lower for 10 mg/g enzyme loading with 10% w/v solids. Integrated analysis of glucose released and CNF generated after enzymatic hydrolysis showed that glucose values varied from 42.0 to 90.6 g/L, corresponding to cellulose conversion ranging from 57.2 to 76.4%. These values are suitable for the microbial fermentation of sugars into biofuels, while leaving a useful amount of residual nanomaterial. The residual solids of the enzymatic reactions presented the characteristics of CNF, as shown by X-ray diffraction (XRD) analyses, with crystallinity index (CI) values of 72–81%, as well as by morphological analysis using field emission scanning electron microscopy (FEG-SEM), which revealed diameters in the range 18–31 nm, making this nanomaterial suitable for use in a wide range of industrial applications. The findings indicated the potential of using conventional stirred-tank reactors for enzymatic hydrolysis for the integrated production of CNF and glucose, hence contributing to the implementation of future large-scale biorefineries.

The effect of mixing on Co‐precipitation and evolution of microstructure of Cu‐ZnO catalyst

The influence of feeding point in conventional stirred tank reactor and flow characteristics in micro‐reactor on the microstructure of Cu‐ZnO catalyst was studied. Cu‐Zn distribution in co‐precipitate was characterized by EDS and Zn fraction in zincian malachite was estimated from the 20 peak shift in XRD pattern. The theory analysis and experimental results, combining with measurement of segregation index, show that the contact pattern and mixing of reactants in precipitation process determine the uniformity of Cu‐Zn distribution in initial co‐precipitates at the micro‐scale. The uniform Cu‐Zn distribution is favorable for the formation of zincian malachite with higher Zn fraction, whereas the uneven distribution could lead to either zincian malachite with lower Zn fraction or aurichalcite‐like nonmalachite. These differences in the precursor structure act on subsequent calcination and reduction, as well as their products. Along this path, mixing affects the evolution of the catalyst microstructure by means of Cu‐Zn distribution. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2647–2654, 2018

Evaluation of power density on the bioethanol production using mesoscale oscillatory baffled reactor and stirred tank reactor

A recent development in oscillatory baffled reactor technology is down-scaling the reactor, so that it can be used for production of small-scale bioproduct. In the present study, a mesoscale oscillatory baffled reactor (MOBR) with central baffle system was developed. The reactor performance of the MOBR was compared with conventional stirred tank reactor (STR) to evaluate the performance of bioethanol fermentation using Saccharomyces cerevisiae. Evaluation was made at similar power density of 24.21, 57.38, 112.35 and 193.67 Wm-3 by varying frequency (f), amplitude (xo) and agitation speed (rpm). It was found that the MOBR improved the mixing intensity resulted in lower glucose concentration (0.988 gL-1) and higher bioethanol concentration (38.98 gL-1) after 12 hours fermentation at power density of 193.67 Wm-3. Based on the results, the bioethanol yield obtained using MOBR was 39% higher than the maximum achieved in STR. Bioethanol production using MOBR proved to be feasible as it is not only able to compete with conventional STR but also offers advantages of straight-forward scale-up, whereas it is complicated and difficult in STR. Overall, MOBR offers great prospective over the conventional STR.