Search

A continuous manufacturing platform was developed for the synthesis of aqueous colloidal 10–20 nm gold nanoparticles (Au NPs) in a flow reactor using chloroauric acid, sodium citrate and citric acid at 95 oC and 2.3 bar(a) pressure. The use of a two-phase flow system – using heptane as the continuous phase – prevented fouling on the reactor walls, while improving the residence time distribution. Continuous syntheses for up to 2 h demonstrated its potential application for continuous manufacturing, while live quality control was established using online UV-Vis photospectrometry that monitored the particle size and process yield. The synthesis was stable and reproducible over time for gold precursor concentration above 0.23 mM (after mixing), resulting in average particle size between 12 and 15 nm. A hydrophobic membrane separator provided successful separation of the aqueous and organic phases and collection of colloidal Au NPs in flow. Process yield increased at higher inlet flow rates (from 70 % to almost 100 %), due to lower residence time of the colloidal solution in the separator resulting in less fouling in the PTFE membrane. This study addresses the challenges for the translation of the synthesis from batch to flow and provides tools for the development of a continuous manufacturing platform for gold nanoparticles.Graphical abstract

Operando X-ray absorption spectroscopy (XAS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry (MS) provide complementary information on the catalyst structure, surface reaction mechanisms and activity relationships. The powerful combination of the techniques has been the driving force to design and engineer suitable spectroscopic operando reactors that can mitigate limitations inherent to conventional reaction cells and facilitate experiments under kinetic regimes. Microreactors have recently emerged as effective spectroscopic operando cells due to their plug-flow type operation with no dead volume and negligible mass and heat transfer resistances. Here we present a novel microfabricated reactor that can be used for both operando XAS and DRIFTS studies. The reactor has a glass-silicon-glass sandwich-like structure with a reaction channel (3000 μm × 600 μm; width × depth) packed with a catalyst bed (ca. 25 mg) and placed sideways to the X-ray beam, while the infrared beam illuminates the catalyst bed from the top. The outlet of the reactor is connected to MS for continuous monitoring of the reactor effluent. The feasibility of the microreactor is demonstrated by conducting two reactions: i) combustion of methane over 2 wt% Pd/Al2O3 studied by operando XAS at the Pd K-edge and ii) CO oxidation over 1 wt% Pt/Al2O3 catalyst studied by operando DRIFTS. The former shows that palladium is in an oxidised state at all studied temperatures, 250, 300, 350, 400 °C and the latter shows the presence of linearly adsorbed CO on the platinum surface. Furthermore, temperature-resolved reduction of palladium catalyst with methane and CO oxidation over platinum catalyst are also studied. Based on these results, the catalyst structure and surface reaction dynamics are discussed, which demonstrate not only the applicability and versatility of the microreactor for combined operando XAS and DRIFTS studies, but also illustrate the unique advantages of the microreactor for high space velocity and transient response experiments.

With recent advances in automated flow reactors and online analysis techniques, transient flow experiments are attracting significant interest as methods for rapidly gathering kinetic data. However, the design of these experiments is challenging and non-intuitive. This work addresses this challenge by using model-based design of experiments (MBDoE) to design optimum transient experiments for the purpose of identifying kinetic parameters with maximum precision. Using the case study of benzoic acid and ethanol esterification with sulfuric acid as the catalyst, the flowrate and temperature of a plug flow reactor were linearly ramped in time to create transient flow experiments. Two types of experiments were conducted, one where only flowrate was ramped while all other variables were held constant, and one where flowrate and temperature were ramped simultaneously. In both cases, model-based design of experiments (MBDoE) methods were used to design the transient experiments in order to choose the initial value and ramp rate of all ramped process variables, as well as choosing the fixed value of process variables that were not being ramped (feed concentration). The model-based designed experiments were compared against equivalent experiments designed by researcher intuition and standard design of experiments approaches, such as trying to cover a wide area of the design space. It is shown that MBDoE led to significantly more precise parameter estimates, and that the identified model was then able to predict with high accuracy the outlet concentration of other experiments.

An autonomous reactor platform was developed to rapidly identify a kinetic model for the esterification of benzoic acid with ethanol with the heterogeneous Amberlyst-15 catalyst. A five-step methodology for kinetic studies was employed to systematically reduce the number of experiments required to identify a practical kinetic model. This included (i) initial screening using traditional factorial designed steady-state experiments, (ii) proposing and testing candidate kinetic models, (iii) performing an identifiability analysis to reject models whose model parameters cannot be estimated for a given experimental budget, (iv) performing online Model-Based Design of Experiments (MBDoE) for model discrimination to identify the best model from a list of candidates, and (v) performing online MBDoE for improving parameter precision for the chosen model. This methodology combined with the reactor platform, which conducted all kinetic experiments unattended, reduces the number of experiments and time required to identify kinetic models, significantly increasing lab productivity.

The volumetric liquid-solid (L-S) mass transfer coefficient under gas-liquid (G-L) two-phase flow in a silicon-chip-based micropacked bed reactor (MPBR) was studied using the copper dissolution method and was related to the reactor hydrodynamic behavior. Using a high-speed camera and a robust computational image analysis method that selectively analyzed the bed voidage around the copper particles, the observed hydrodynamics were directly related to the L-S mass transfer rates in the MPBR. This hydrodynamic study revealed different pulsing structures inside the packed copper bed depending on the flow patterns established preceding the packed bed upon increasing gas velocity. A "liquid-dominated slug" flow regime was associated with an upstream slug flow feed. A "sparse slug" flow regime developed with an upstream slug-annular flow feed. At higher gas velocity, a "gas continuous with pulsing" regime developed with an annular flow feed, which had similar features to the pulsing flow in macroscale packed beds, but it was sensitive and easily destabilized by disturbances from upstream or downstream pressure fluctuations. The volumetric L-S mass transfer coefficient decreased with increasing gas velocity under the liquid-dominated slug flow regime and became rather less affected under the sparse slug flow regime. By resolving the transition from the liquid-dominated slug flow to the sparse slug flow and capturing the onset of the gas-continuous with pulsing regime, we gained new insights into the hydrodynamic effects of G-L flows on the L-S mass transfer rates in a MPBR.

Parameter estimation algorithms integrated in automated platforms for kinetic model identification are required to solve two optimization problems: i) a parameter estimation problem given the available samples; ii) a model-based design of experiments problem to select the conditions for collecting future samples. These problems may be ill-posed, leading to numerical failures when optimization routines are applied. In this work, an approach of online reparametrization is introduced to enhance the robustness of model identification algorithms towards ill-posed parameter estimation problems.

An autonomous flow microreactor platform was developed that was able to conduct reaction experiments and measure the outlet reactant and product concentrations using HPLC without user supervision. The platform performed unmanned kinetic experiments with the aim of precisely estimating the parameters of a kinetic model for the esterification between benzoic acid and ethanol catalysed by sulfuric acid. The capabilities of the autonomous platform were demonstrated on three different experimental scenarios: 1) performing steady-state experiments, where the experimental reaction conditions were pre-defined by the user; 2) performing steady-state experiments, where the conditions were optimised online by Model-Based Design of Experiments (MBDoE) algorithms, with the aim of improving parameter precision; 3) executing transient experiments, where the conditions were pre-selected by the user. For the steady-state experiments, the platform automatically performed online parameter estimation and MBDoE with a pre-selected kinetic model. It was demonstrated that a campaign of steady-state experiments designed using online MBDoE algorithms led to more precise parameter estimates than a campaign of experiments designed by the traditional factorial design. Transient experiments were shown to expedite kinetic parameter estimation and use less reagents than campaigns of steady-state experiments, as it was no longer necessary to wait for the system to reach steady-state. In general, the transient experiments offered less precise parameter estimates than the steady-state campaigns, however the experiments could be completed in just 2 h instead of the 8 h required for a campaign of steady-state experiments.

Online model-based redesign of experiments (OMBRE) techniques reduce the experimental effort substantially for achieving high model reliability along with the precise estimation of model parameters. In dynamic systems, OMBRE techniques allow redesigning an experiment while it is still running and information gathered from samples collected at multiple time points is used to update the experimental conditions before the completion of the experiment. For processes evolving through a sequence of steady state experiments, significant time delays may exist when collecting new information from each single run, because measurements can be available only after steady state conditions are reached. In this work an online model-based optimal redesign technique is employed in continuous flow reactors for improving the accuracy of estimation of kinetic parameters with great benefit in terms of time and analytical resources during the model identification task. The proposed approach is applied to a simulated case study and compared with the conventional sequential model-based design of experiments (MBDoE) techniques as well as the offline optimal redesign of experiments.

Parametric models derived from simplifying modelling assumptions give an approximated description of the physical system under study. The value of an approximated model depends on the consciousness of its descriptive limits and on the precise estimation of its parameters. In this manuscript, a framework for identifying the model domain of validity for the simplifying model hypotheses is presented. A model-based data mining method for parameter estimation is proposed as central block to classify the observed experimental conditions as compatible or incompatible with the approximated model. A nonlinear support vector classifier is then trained on the classified (observed) experimental conditions to identify a decision function for quantifying the expected model reliability in unexplored regions of the experimental design space. The proposed approach is employed for determining the domain of reliability for a simplified kinetic model of methanol oxidation on silver catalyst.

The development of energy efficient, reproducible, and high throughput approaches to gold nanoparticle (Au-NP) synthesis has gained increasing attention over the past decades due to applications in biomedicine, sensors, and catalysis. In this work, single mode microwave irradiation is for the first time combined with microflow chemistry to fabricate Au-NPs continuously and reproducibly with controllable size in an aqueous solution. The major experimental parameters including microwave power, citrate-to-gold molar ratio ([Cit]/[Au]), and reaction residence time have been investigated systematically. As indicated by TEM, the mean particle width of the synthesized Au-NPs is between 4 and 15 nm with mean aspect ratio between ∼1.4 and 2.2 after only 90 s of microwave irradiation. Furthermore, the Au particle morphology can be manipulated from nanowires to nanoparticles by adjusting the [Cit]/[Au] ratio. HRTEM analysis of the produced Au-NPs and UV–vis spectroscopy suggests a correlation between the red-shifted...

A flat Teflon AF-2400 membrane microchannel reactor was experimentally and theoretically investigated for aerobic oxidation of benzyl alcohol on a 5 wt% Ru/Al2O3 catalyst. The reactor consisted of gas and liquid channels (75 mm (L) × 3 mm (W) × 1 mm (D)), separated by a 0.07 mm thick semipermeable Teflon AF-2400 flat membrane, which allowed continuous supply of oxygen during the reaction and imultaneously avoided direct mixing of gaseous oxygen with organic reactants. A catalyst stability test was first carried out, and the experimental data obtained were used to estimate the kinetics of benzyl alcohol oxidation with a 2D reactor model. Using these kinetics, predictions from the 2D reactor model agreed well with the experimental data obtained at different liquid flow rates and oxygen pressures. The mass transfer and catalytic reaction in the membrane microchannel reactor were then theoretically studied by changing the membrane thickness, the liquid channel depth, and the reaction rate coefficient. Oxygen transverse mass transport in the catalyst bed was found to be the controlling process for the system investigated, and decreasing the liquid channel depth is suggested to improve the oxygen supply and enhance the benzyl alcohol conversion in the membrane reactor.

In this work, a microwave promoted flow (MWPF) system to reproducibly synthesize self-assembled hierarchical hematite superstructures (Hem-SSs) using the sole precursor (Fe(NO3)3·9H2O) and single mode microwave under aqueous conditions was developed. The functional characterisation by XRD, (HR)TEM, XPS, UV-vis and Raman spectroscopy proved that highly crystalline ellipsoid Hem-SSs (∼180 nm × 140 nm) were produced, built from primary hematite nanoparticles, 5–10 nm in size using 0.05 mol L−1 precursor concentration, 1 mL min−1 flow rate and short reaction time (about 6 min). Particles produced via conventional heating (CH) at 120 and 140 °C in the same flow reactor under similar experimental conditions were found to consist of mixtures of goethite and hematite. The effects of precursor concentration (0.1 and 0.2 mol L−1) and flow rate (2 and 5 mL min−1) were further investigated and the synthesis mechanism was also discussed. This novel method opens a window for continuous fabrication of metal or metal oxide nanoparticles/superstructures by a green approach.

Cao, E., Zuburtikudis, I., Al-Rifai, N., Roydhouse, M., & Gavriilidis, A. (2014). Enhanced Performance of Oxidation of Rosalva (9-decen-1-ol) to Costenal (9-decenal) on Porous Silicon-Supported Silver Catalyst in a Microstructured Reactor. Processes, 2(1), 141-157., The use of metal-assisted HF chemical etching as a convenient technique to produce a few microns thick porous layer in silicon microchannels was demonstrated. Gas phase selective oxidation of rosalva to its aldehyde (costenal) was performed in glass/silicon microstructured reactors at temperatures of 375–475 °C on silver catalyst which was deposited on both porous and flat silicon surface by sputter-coating. The effects of temperature (375–475 °C), rosalva concentration (1.17%–3.43%), O2 to rosalva ratio (0.5–20) and residence time on the reaction were investigated. The reactivity of rosalva on the porous silicon supported silver was 5.7–6.4 times higher than on the thin film silver catalyst at 450 °C. Furthermore, activation energy for the porous silicon supported silver was lower. Isothermal conditions in the microreactors allowed high conversion and selectivity to be achieved in a wide range of temperature and oxygen concentration. At typical reaction conditions (1.75% rosalva, O2/rosalva = 3, residence time 18 ms and 450 °C), conversion of 97% and selectivity of 95% to costenal was achieved, corresponding to a turnover frequency of 268 h−1.

Microreaction technology is an interdisciplinary field that has gained significant momentum in recent years due to the numerous advantages it offers compared to conventional systems in terms of enhanced heat and mass transfer and safer operation. The experimental efficiency achieved through the well-defined conditions offered by microchannel reactors has been utilised to elucidate intrinsic reaction kinetics, often in reaction spaces that were previously unexplored. In this review, we discuss prospects for advancing catalytic process development by combined application of microstructured flow reactors with techniques for in situ catalyst characterisation and mathematical optimisation.

Disproportionation of benzyl alcohol has been identified as the source of toluene formation in the solvent free oxidation of benzyl alcohol using supported gold palladium catalysts. There is a slight increase in the disproportionation reaction, and hence the toluene selectivity, when this reaction is performed in a continuous mode using a micro-packed bed reactor when compared to the same reaction performed in a conventional glass stirred batch reactor. Oxidation and disproportionation reactions respond slightly differently to the changes in reaction parameters, like oxygen concentration and pressure, when a micro packed bed reactor was used instead of a conventional glass stirred reactor. When MgO supported gold–palladium catalysts were used for this reaction, the toluene selectivity reduced substantially at the cost of conversion.

Oxidation of benzyl alcohol in the absence of solvent on 1% (Au–Pd)/TiO2 catalyst with pure oxygen was performed in silicon-glass micropacked-bed reactors (MPBRs). The overall size of the microreactor chip was 23 mm × 23 mm with a reaction channel dimension of 0.6 mm (W) × 0.3 mm (H) × 190 mm (L). A pillar structure (small rectangular posts of 60 μm (W) × 1 mm (L) 40 μm apart) was incorporated near the outlet of the reaction channel to retain the catalyst. The reaction was studied in the temperature range of 80–120 °C and at inlet pressures up to 5 bar(a). Benzyl alcohol conversion and benzaldehyde selectivity at 80 and 120 °C obtained in MPBRs were very close to those from conventional glass stirred reactors (GSRs) apart from the selectivity at 120 °C. Toluene was formed in the absence of oxygen, and its production was enhanced in the presence of oxygen. Increasing pressure improved both conversion and benzaldehyde selectivity. Mass transfer resistance in MPBRs was evaluated experimentally. The external mass transfer resistance could be ignored at a volumetric flow ratio of gas (STP) to liquid above 100, at a given liquid flow rate (0.003 mL/min). The effect of catalyst particle size on the reaction was examined with two ranges of particle size: 53–63 μm and 90–125 μm. Lower conversion was obtained with particle sizes of 90–125 μm, indicating the presence of internal mass transfer resistances. In situ Raman measurements in MPBRs were performed using a specially designed microreactor stage with a different microreactor configuration. Raman spectra obtained from liquid pockets at different points along the reaction channel could be used to obtain the benzaldehyde concentration profile along the catalyst bed. Bands due to formation of highly disordered graphitic carbon were observed on the catalyst surface.

Despite the great industrial importance of benzaldehyde as a reaction intermediate, only a few attempts have been made in the literature to develop kinetic models able of characterising the catalytic oxidation of benzyl alcohol to benzaldehyde quantitatively both in batch and flow systems. The purpose of this paper is to merge the information obtained from a laboratory scale batch glass stirred reactor (GSR) with the information obtained from a continuous-flow micro-packed bed reactor (MPBR) for an accurate and quantitative description of the products distribution in these reaction systems. A two-stage procedure is applied for this purpose where experimental design techniques are used for evaluating the most promising regions of the experimental space for the identification of kinetic models.

Operando Raman-GC studies of the catalytic oxidation of methanol to formaldehyde on silver using a microfabricated reactor as a reactor cell are presented. The microreactor is made of silicon and glass with a wide reaction channel of 8 mm and a channel depth of 120 mu m. The silver catalyst is incorporated into the microchannel by sputter coating. The reaction is performed at atmospheric pressure, temperature between 723 and 813 K with a feed containing 8.75% CH3OH, 3.5% O-2 and 6.63% H2O (He as balance) at residence time of 6-7 ms at reaction temperature. Raman spectra of the silver catalyst after exposure to 4.1% O-2 (He as balance) at 773 K show the presence of subsurface (at 640 cm(-1)) and surface (at 810 cm-1) atomic oxygen species. During an activation procedure consisting of repeated oxidation/reaction cycles at 773 K, the 810 cm-1 band disappears immediately after introducing a CH3OH/O-2/H2O/He mixture, indicating that this surface atomic oxygen species participates in the reaction. The 810 cm-1 band is not observed in the subsequent oxidation/reaction cycles; instead a broad feature between 400 and 800 cm-1 appears which may be associated with a severe restructuring of the catalyst by methanol oxidation. The catalyst stabilizes after three oxidation/ reaction cycles as shown by improved and approximately constant CH2O selectivities. This is accompanied by Raman spectra with sharp definition of the 400-800 cm(-1) band, indicating the importance of stabilization of subsurface oxygen species in obtaining high CH2O selectivity. Deactivation of the catalyst due to carbon deposition is observed when a feed without H2O is introduced into the reactor, as demonstrated by bands at 1350 and 1585 cm-1 in the Raman spectra and by decreased conversion of CH3OH with reaction time. The work presented demonstrates that microfabricated reactors can be easily integrated with Raman spectroscopy and GC for operando studies. (c) 2006 Elsevier B.V. All rights reserved.

© 2015 American Chemical Society. A Teflon AF-2400 tube-in-tube microreactor is investigated for the continuous, solvent-free, catalytic oxidation of benzyl alcohol with oxygen. The semipermeable Teflon AF-2400 tube acts as the interface between the gaseous oxidant and the liquid substrate. Because of the inherent safety of this contacting method, the use of pure oxygen is possible. The semipermeable tube was packed with 1 wt % Au-Pd/TiO2 catalyst particles and placed inside a PTFE tube to provide an annular region which was pressurized with pure oxygen. This design allowed continuous penetration of oxygen through the inner tube during the reaction, resulting in higher oxygen concentration in the catalyst bed and significantly improved conversion compared to a reactor operating with an oxygen presaturated feed. The amount of oxygen available for reaction in the tube-in-tube microreactor was 2 orders of magnitude higher than that in a nonpermeable reactor with oxygen presaturated feed. The semipermeable tube reactor performance in terms of both conversion and selectivity was enhanced by increasing the gas pressure, the catalyst contact time and by dilution of the catalyst. The highest conversion of benzyl alcohol obtained for the range of conditions investigated was 44.1%, with 73.0% selectivity to benzaldehyde, at 120 °C; catalyst contact time, 115 gcat·s/galcohol; and catalyst dilution factor, 4. ispartof: Industrial & Engineering Chemistry Research vol:54 issue:16 pages:4183-4189 status: published

A mobile microreactor system, with flow and temperature control for organic synthesis, is described. The system can be used anywhere a venting outlet is available. The microreactors can be operated in different flow patterns (continuous flow, stop-flow, or programmed-flow) providing reaction times from a few minutes to a few hours. The system was tested for the catalytic oxidation of benzyl alcohol to benzaldehyde by tetrapropylammonium perruthenate (TPAP) with N-methyl-morpholine-N-oxide in the liquid phase under stop-flow mode and on supported TPAP with oxygen under continuous flow mode. The conversion of benzyl alcohol in the microreactor was close to that of a small batch reactor for the liquid phase reaction. For the multiphase reaction, a conversion of 30–40 % was obtained with residence times below 1 min.

A mathematical model for natural gas reformer is established to draw up homogeneous phase one-dimensional reaction kinetics equation in the reforming tubes, and compute the tube external radiant heat transfer with zone method. Simulation result is compared with the operating data carried on Selas reformer used in Brown and Root Braun 1000 t NH3/day production system in Urumqi Second Ammonia Plant, and they match well. This model has laid the foundation for the design variable optimization research, for example, the relations among specific heat transfer area of furnace tube, tube outlet temperature, tube pressure drop and maximum tube-wall temperature, as well as the effect of tube pitch, furnace chamber width, burner arrangement, furnace wall blackness, production load, water carbon ratio and fuel distribution on operation behaviors.

Microstructured reactors were fabricated on silicon by deep reactive ion etching and were used to study the catalytic oxidative dehydrogenation of methanol to formaldehyde on silver catalyst at temperature up to 823 K. The reaction was carried out with higher oxygen concentration than that typically used in conventional lab-scale or larger reactors. Even when the reaction was performed with undiluted oxygen, conversion of methanol 60–75% with selectivity ∼90% was obtained. The reaction was carried out safely at conditions within the flammability limits. Effect of temperature, methanol concentration and residence time was also studied. The results show that the reaction was ca. 0.5 order with respect to methanol. Conversion increased with temperature almost linearly within the temperature range studied, with a slight decrease in selectivity to formaldehyde. The benefits of using microreactors for studying highly exothermic reactions were demonstrated, by comparing the silicon microreactor performance with that of a small quartz tube reactor.

Silicon-glass microfabricated reactors containing silver catalyst were used for oxidative dehydrogenation of 3-methyl-2-buten-1-ol to the corresponding aldehyde. The reactors were safely operated in a wide range of oxygen concentrations, in a temperature range of 310-464 degreesC and residence times of 15-50 ms. The effect of reactant concentrations was examined and it was found that high selectivities were obtained at high alcohol and low oxygen concentration. Conversion of 60-70% with high selectivity (similar to 95%) at alcohol concentrations of 4-7.2 vol% was achieved at oxygen/alcohol ratio of similar to 1 and reaction temperature of 400degrees C. Conversion increased smoothly with temperature and no ignition was observed. Selectivity deteriorated above 415 degreesC due to formation of carbon monoxide, carbon dioxide and higher molecular weight by-products. (C) 2004 Elsevier Ltd. All rights reserved.

The freeze denaturation of model proteins, LDH, ADH, and catalase, was investigated in absence of cryoprotectants using a microcryostage under well-controlled freezing and thawing rates. Most of the experimental data were obtained from a study using a dilute solution with an enzyme concentration of 0.025 g/l. The dependence of activity recovery of proteins on the freezing and thawing rates showed a reciprocal and independent effect, that is, slow freezing (at a freezing rate about 1 degrees C/min) and fast thawing (at a thawing rate >10 degrees C/min) produced higher activity recovery, whereas fast freezing with slow thawing resulted in more severe damage to proteins. With minimizing the freezing concentration and pH change of buffer solution by using a potassium phosphate buffer, this phenomenon could be ascribed to surface-induced denaturation during freezing and thawing process. Upon the fast freezing (e.g., when the freezing rate >20 degrees C/min), small ice crystals and a relatively large surface area of ice-liquid interface are formed, which increases the exposure of protein molecules to the ice-liquid interface and hence increases the damage to the proteins. During thawing, additional damage to proteins is caused by recrystallization process. Recrystallization exerts additional interfacial tension or shear on the entrapped proteins and hence causes additional damage to the latter. When buffer solutes participated during freezing, the activity recovery of proteins after freezing and thawing decreased due to the change of buffer solution pH during freezing. However, the patterns of the dependence on freezing and thawing rates of activity recovery did not change except for that at extreme low freezing rates (

Microreactor platforms represent advanced tools in reaction engineering for the quick development of reliable kinetic models. Experiments can be performed with a better reaction temperature control, enhanced heat and mass transfer and mixing of reactants. However, the effectiveness of the model identification procedure is strictly related to the execution of properly designed experiments, allowing elucidation of the reaction mechanisms and providing a precise estimation of the kinetic parameters. In this paper a model-based design of experiments (MBDoE) approach is proposed where experiments are designed for both discriminating among competing models and for improving the estimation of kinetic parameters. The procedure is tested on a real case study related to the identification of kinetic models of methanol oxidation on silver catalyst.

Microengineered reactors are a new type of reactor. Their novelty dictates a new approach in design, which requires familiarization with the various manufacturing techniques and materials, and with differences in fluid behaviour and dominant phenomena in the microscale. New approaches for energy management, catalyst incorporation and integration of functions and unit operations can be employed. Microengineered reactors have some unique characteristics which create the potential for high performance chemicals and information processing. These include efficient mass and heat transfer and precise control of the hydrodynamic environment. They can provide significant advantages in information generation in high throughput experimentation and process development, and from difficult to obtain operating regimes. In terms of chemicals manufacture, they allow distributed, mobile and intensified processing. This technology, still in its infancy has the potential to change the chemical engineering landscape.

Freezing is a very important operation in the biotechnological and biopharmaceutical industries. Biological materials, such as proteins, are insufficiently stable for distribution and storage in aqueous solutions. Therefore proteins are often frozen or freeze-dried to achieve the desired ‘shelf-life’. However, the freezing and freeze-drying process can cause loss of functional properties and conformational changes of proteins and affect the quality and yield of the protein products. Care must be taken to avoid any damaging effect on the proteins and other biological agents in solution. One of the identified factors affecting protein denaturation or cell survival is the solute redistribution due to freeze concentration. However, there are few data on freeze concentration due to difficulties with performing the experiments. In this work, solute redistribution during freezing in protein solutions is investigated using a purpose-built cylindrical test cell. Sodium permanganate is used as a substitute for NaCl in some experimental work as its concentration can be easily measured using a spectrophotometer. Freezing concentration was clearly demonstrated and it was found to be dependent on the freezing rate. The freezing of LDH protein solution was also studied. The concentration redistribution of LDH, together with NaCl in solution, was experimentally determined. It is concluded that the redistribution of protein concentration during freezing is not significant and can be neglected in practical analysis. The redistribution of NaCl in LDH solution during freezing is still significant, although the non-uniformity is greatly reduced compared to just salt aqueous solution case. This is due to macromolecules hindering diffusion and possible protein binding.

A scheme for the separation, purification and preparation of sub-micron, homoionic, Na-attapulgite from a natural mineral deposit is presented together with represen-tative analysis of the particle size distribution. Transmission electron microscopic examination indicated that particles were predominantly

Analytical surface charge (σ a ), electrophoretic, and physicochemical properties of an homoionic form of Na–attapulgite show some similarity with those exhibited by homoionic sodium forms of the platy clay minerals kaolinite and illite. Both electrophoretic mobility ( u e ) and analytic or titratable surface charge show dependency on pH and electrolyte concentration ( c ). Transmission electron microscopic examination indicated that particles were 1000 nm long, lath-like, and of aspect ratios (length:width:thickness) 100:3:1. Estimates of (hydrodynamic) equivalent spherical particle diameter ( d se ), made with photon correlation spectroscopy (PCS), were found to be ∼400 nm and reflect extreme nonisometric particle shape. Failure of PCS at pH u e and σ a was found to be approximately linear in the range 3 6.5. Apportionment of titratable charge to particle edges suggests a charge site density that is reasonable for the structure of this clay mineral.

Anodically bonded etched silicon microfluidic devices that allow infrared spectroscopic measurement of solutions are reported. These extend spatially well-resolved in situ infrared measurement to higher temperatures and pressures than previously reported, making them useful for effectively time-resolved measurement of realistic catalytic processes. A data processing technique necessary for the mitigation of interference fringes caused by multiple reflections of the probe beam is also described.

Although there has been a lot of work on the development of microchemical processing systems such as micro-reactors and micro-sensors, little attention has been paid to micro-separation units, and in particular, microscale distillation. In this paper, various silicon-glass microscale distillation chips with different channel configurations were fabricated and tested. A temperature gradient was setup across the chip by heating and cooling the two ends. The feed was located at the middle of the microchannel. Arrays of micropillars were incorporated in order to guide the liquid flow. It was found that the separation performance was promoted by increasing the length of the microchannel. However, this created an imbalance of the liquid flows at the two sides of the microchannel and caused flooding. This hydrodynamic limitation was addressed by incorporating micropillars on both sides of the channel. The most efficient microdistillation chip consisted of a microchannel with 600 microns width and 40 cm length. Experimental results showed high efficiency for the separation of a 50 mol% acetone-water mixture when the heating and cooling temperature were 95 °C and 42 °C respectively. The concentrations of acetone were 3 mol% in the bottom stream and 95 mol% in the distillate, which was equivalent to at least 4 equilibrium stages at total reflux conditions. Furthermore, a 50 mol% methanol-toluene mixture was separated into nearly pure toluene in the bottom stream and 75 mol% methanol in the distillate. The performance of the microdistillation unit was reproducible in repeated tests.

An experimental and theoretical study of capillary gas/liquid phase microseparators is presented. The device studied comprises a main microchannel with a set of capillaries fabricated to each side so that the liquid (wetting) phase can be separated from the gas (non-wetting) phase due to capillary effects. Different units are employed with different characteristics of capillaries (constant or tapered cross-sectional area and capillary size). We study how complete separation depends on the externally controlled pressure difference at the liquid and the gas outlet and how separation is affected by the imposed inlet flow rate. The results demonstrate that the operability pressure window becomes narrower as the fluid flow rates increase, and reveal discrepancies with theoretical predictions based on a simple Hagen–Poiseuille formulation. This is addressed by a new equation that takes into account interface curvature effects, and is found to be in qualitative agreement with the experimental results. In addition, we perform CFD simulations observing the emergence of interface breaking at high flow rates.