Enhong Cao

Enhong Cao
University College London | UCL

About

55
Publications
18,166
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1,527
Citations
Citations since 2017
21 Research Items
905 Citations
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
Introduction

Publications

Publications (55)
Article
Full-text available
An automated flow micropacked bed catalytic reactor platform was developed to conduct pre‐planned experiments for rapid screening of kinetic models. The microreactor was fabricated using photolithography and deep reactive ion etching of a silicon wafer, with a reaction channel width and depth of 2 mm and 420 μm respectively. It was packed with ca....
Article
Full-text available
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 o C 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,...
Article
Full-text available
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 ana...
Article
Full-text available
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 enginee...
Article
Full-text available
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 (...
Article
Full-text available
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)...
Article
Full-text available
Catalytic oxidation of methanol to formaldehyde is an important industrial process due to the value of formaldehyde either as a final product or as a precursor of numerous chemicals. The study of kinetics in this system is hindered by sources of uncertainty that are inherently associated to the nature and state of the catalyst (e.g. uncertain react...
Article
Full-text available
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...
Article
A flat Teflon AF-2400 membrane microchannel reactor was experimentally and theoretically investigated for aerobic oxidation of benzyl alcohol on a 5 wt% Ru/Al 2 O 3 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 cont...
Article
Full-text available
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, le...
Article
Automated model identification platforms were recently employed to identify parametric models online in the course of unmanned experimental campaigns. The algorithms controlling these platforms include two computational elements: i) a tool for parameter estimation; ii) a tool for model-based experimental design. Both tools require the solution of c...
Article
Full-text available
A flat membrane microchannel reactor was designed and demonstrated for the safe and scalable oxidation of solvent-free benzyl alcohol with molecular oxygen on Au-Pd/TiO2 catalyst. The microchannel reactor employed a mesh-supported Teflon AF-2400 membrane, with gas and liquid channels on each side. Catalyst particles were packed in the liquid flow c...
Article
Full-text available
The synthesis of benzylacetone from benzyl alcohol and of 4-(4-methoxyphenyl)butan-2-one from 4-methoxybenzyl alcohol, which were previously performed in a batch cascade, were successfully performed in a telescoped flow system consisting of three micropacked bed reactors and a tube-in-tube membrane to remove oxygen. The system consisted of approxim...
Conference Paper
Full-text available
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 multi...
Article
Full-text available
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 multi...
Preprint
Full-text available
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...
Article
Full-text available
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...
Article
Full-text available
Data on oxygen solubility in organic solvents are essential for catalyst evaluation, reactor design, and process safety of catalytic aerobic oxidations which is an emerging area in green chemistry. A novel approach using a Teflon AF-2400 tube-in-tube membrane contactor was developed for the measurement of gas solubility in organic solvents. The sem...
Article
Full-text available
Highly active, supported Au-Pd catalysts have been tested for catalysing benzyl alcohol oxidation in a silicon-glass micro-packed bed reactor. The effects of Au-Pd composition and anion content during catalyst preparation on catalyst deactivation were studied, and a relationship between the deactivation rate and the amount of Cl- and Au used in the...
Chapter
Full-text available
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 obtai...
Article
Developing energy efficient, reproducible and high throughput approaches to gold nanoparticles (Au-NPs) synthesis have gained increasing attention over the past decades due to their application in biomedicine, sensor and catalysis. In this work, single mode microwave irradiation is for the first time combined with microflow chemistry to fabricate A...
Article
Full-text available
A micropacked-bed multi-reactor platform with integrated portable Raman spectrometer is presented for fast evaluation of catalyst activity and stability for gas/liquid/solid reactions. The silicon-glass microreactor was designed and fabricated so that pockets containing the liquid reaction mixture were created after each packed bed, into which the...
Article
Full-text available
The stability of a bimetallic Au-Pd/TiO2 catalyst was examined in a packed bed microreactor for the oxidation of cinnamyl alcohol dissolved in toluene. The catalyst was prepared by co-impregnation with a Au-Pd weight ratio of 1:19. Experiments were performed at 80-120 °C, oxygen concentration 0-100% and total pressure 4 bara. Principal products obs...
Article
Full-text available
Continuous flow laboratory reactors are typically used for the development of kinetic models for catalytic reactions. Sequential model-based design of experiments (MBDoE) procedures have been proposed in literature where experiments are optimally designed for discriminating amongst candidate models or for improving the estimation of kinetic paramet...
Article
Full-text available
The hydrodynamics of a three-phase micro-packed bed reactor and its effect on catalysed benzyl alcohol oxidation with pure oxygen were studied in a silicon-glass microstructured reactor. The microreactor was operated at 120 °C and 1 barg and contained a channel with a 300 μm ×600 μm cross section, packed with 1 wt% Au-Pd/TiO2 catalyst 65 μm in aver...
Article
Synthesis of ordered superstructures, so-called mesocrystals, has gained increasing interest due to their unique properties including enhanced surface area, accessible pores and tunable electronic, optical and magnetic properties. A sustainable and energy-efficient process for mesocrystal synthesis in which no chemical additives are required is hig...
Article
Anodically bonded etched siliconmicrofluidic 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....
Book
Full-text available
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 ex...
Article
Full-text available
Partial oxidation of methanol to formaldehyde on silver catalyst represents an important industrial process due to the versatility of formaldehyde as an intermediate in chemical synthesis. The development of kinetic models is essential for a quantitative description of the changes in concentration of the chemical species involved in the process due...
Article
Full-text available
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...
Conference Paper
Full-text available
The various flow regimes prevalent during gold-palladium catalyzed benzyl alcohol oxidation in a micro-packed bed reactor and their influence on reaction performance are identified. The reaction is studied in a 300μm deep x 600μm wide silicon-glass micro-structured reactor packed with 65μm catalyst particles at a temperature of 120°C, pressure of 1...
Article
Full-text available
The synthesis of stable, supported, bimetallic nanoalloys with controlled size, morphology and composition is of great practical importance. Compared to their monometallic analogues, such materials exhibit remarkable enhancement in functional properties, which can be exploited in various fields including catalysis. Recently, we have reported a simp...
Article
Full-text available
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 differen...
Article
Full-text available
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 deposite...
Article
Full-text available
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-pac...
Article
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 23mm×23mm with a reaction channel dimension of 0.6mm (W)×0.3mm (H)×190mm (L). A pillar structure (small rectangular posts of 60μm (W)×1mm (L...
Article
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 fab...
Article
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 μm. The silver catalyst is incorporated into the microchannel by sputter coating. Th...
Article
In situ X-ray absorption spectroscopic studies have been performed at the silver K-edge, of a silver catalyst deposited in a microstructured reactor cell at operating conditions. Oxidative dehydrogenation of methanol to formaldehyde was performed at atmospheric pressure and 773K with a feed containing 9.7% CH3OH, 18.8% O2 (N2 as balance) at residen...
Article
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 t...
Article
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...
Article
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...
Article
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– and residence times of 15–50 ms. The effect of reactant concentrations was examin...
Article
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...
Article
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...
Article
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...
Article
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 <1μm long and “lath-like” with aspect ratio...
Article
Analytical surface charge (σa), 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 (ue) and analytic or titratable surface charge show dependency on pH and electrolyte...
Article
The effects of three flow patterns (plug, parabolic, and jet) on heat transfer and hydrocarbon steam reforming process in a top-firing tubular reformer have been studied based on the calculation of heat transfer by the zone method. For the flow patterns, though the temperature field and tube wall heat flux distribution in the reformer are different...

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