Lattice Boltzmann Modeling-based Design of a Membrane-free Liquid-liquid Microseparator

The benefits of continuous processing and the challenges related to the integration with efficient downstream units for end-to-end manufacturing have spurred the development of efficient miniaturized continuously-operated separators. Membrane-free microseparators with specifically positioned internal structures subjecting fluids to a capillary pressure gradient have been previously shown to enable efficient gas-liquid separation. Here we present initial studies on the model-based design of a liquid-liquid microseparator with pillars of various diameters between two plates. For the optimization of in silico separator performance, mesoscopic lattice-Boltzmann modeling was used. Simulation results at various conditions revealed the possibility to improve the separation of two liquids by changing the geometrical characteristics of the microseparator. This work is licensed under a Creative Commons Attribution 4.0 International License

Theoretical Descriptions of Carbon Nanotubes Synthesis in a Chemical Vapor Deposition Reactor: A Review

The mechanisms by which carbon nanotubes nucleate and grow are still poorly understood. Understanding and mathematically describing the process is crucial for its optimization. This paper reviews different models which have been proposed to explain carbon nanotube growth in the chemical vapor deposition process. The review is divided into two sections, the first section describes some nucleation, growth and termination simulations based on molecular dynamics, and the second section describes some mathematical models based on transport and kinetics theories

Characterization of an enzymatic packed-bed microreactor: Experiments and modeling

A micro packed-bed reactor (µPBR) based on two-parallel-plates configuration with immobilized Candida antarctica lipase B in the form of porous particles (Novozym® 435) was theoretically and experimentally characterized. A residence time distribution (RTD) within µPBRs comprising various random distributions of particles placed in one layer was computationally predicted by a mesoscopic lattice Boltzmann (LB) method. Numerical simulations were compared with measurements of RTD, obtained by stimulus-response experiment with a pulse input using glucose as a tracer, monitored by an electrochemical glucose oxidase microbiosensor integrated with the reactor. The model was validated by a good agreement between the experimental data and predictions of LB model at different conditions. The developed µPBR was scaled-up in length and width comprising either a single or two layers of Novozym® 435 particles and compared regarding the selected enzyme-catalyzed transesterification. A linear increase in the productivity with the increase in all dimensions of the µPBR between two-plates demonstrated very efficient and simple approach for the capacity rise. Further characterization of µPBRs of various sizes using the piezoresistive pressure sensor revealed very low pressure drops as compared to their conventional counterparts and thereby great applicability for production systems based on numbering-up approach

Modelling of L-DOPA Oxidation Catalyzed by Laccase

Enzymatic oxidation of 3,4-dihydroxyphenyl-L-alanine (L-DOPA) with laccase from Trametes versicolor was investigated. The highest enzyme activity at pH 5.4 and at 25 ºC was found. The reaction kinetics and the effect of dissolved oxygen concentration on the reaction rate were evaluated. A mathematical model, comprised of double-substrate Michealis-Menten kinetics and mass balances for L-DOPA and dissolved oxygen concentrations, was developed in order to describe and predict the process of L-DOPA oxidation. Kinetic parameters, , and were estimated and experimentally verified by a set of experiments with constant additional aeration for different initial concentrations of L-DOPA and dissolved oxygen. A significant increase in reaction rate was established at a higher oxygen concentration in the inlet gas. The developed model was used to investigate the influence of dissolved oxygen concentration on L-DOPA conversion

Process Intensification through Microreactor Application

A substantial amount of publications each year demonstrate how through the application of microprocess engineering significant benefits can be obtained concerning product yield, purity and time needed for chemical transformations, compared to the equivalent bulk reactions. Microreactors clearly hold the potential to revolutionize chemical synthesis, but scarce articles demonstrate specific suggestions for possible replacement of existent industrial processes. The focus of this review is to assess whether significant advances have been made for the implementation of microstructured devices into existent industrial processes or their complete replacement. The papers are reviewed in light of particular beneficial microreactor characteristics with potential for process intensification

Hydrolysis of Micron Alkylketene Dimert Particles Under Alkaline Conditions

The hydrolysis of alkylketene dimer (AKD) in a diluted dispersion was studied under alkaline conditions. The dispersion consisted of particles with 1 #m in diameter with the reaction product forming a porous insoluble layer on the particle surface. The shrinking core model (SCM) for particles of unchanging size is proposed for describing the overall rate of hydrolysis reaction. The model assumes a process controlled by a surface reaction on the boundary between unreacted AKD core and outer ketone layer, with no significant transport phenomena due to the small particle dimensions and porous structure of the reaction product layer on the particle surface. Under conditions studied (at pH 10.3), where the concentration of OH– ions is in excess compared to the AKD concentration and in the temperature range between 40 and 60 C, the proposed model is in good agreement with experimental data. A temperature dependence of reaction rate was tested and the apparent activation energy was calculated as well. Compared to the activation energy for reaction between AKD and cellulose, AKD hydrolysis can represent an important competitive process that significantly influences the sizing efficiency