A liquid–liquid phase transfer catalyzed (PTC) esterification reaction of 4-t-butylphenol in aqueous phase (1 M sodium hydroxide solution) and 4-methoxybenzoyl chloride in organic phase (dichloromethane) in a microchannel under parallel laminar flow conditions was studied in this work. Tetrabutylammonium bromide was used as the PTC. Stable liquid–liquid hydrodynamic flow and a defined specific interfacial area in a microreactor offer considerable benefits over conventional batch reactors and are crucial to study interactions between kinetics and mass transfer effects. Mentioned features were used to develop a 3D mathematical model considering convection in the flow direction, diffusion in all spatial directions, and reactions in organic and aqueous phases. Results have shown a much higher mass transfer rate of the PTC between both phases as the one predicted by the 3D mathematical model. It may be assumed that the instability of parallel flow, along with the mass transfer of catalyst between both phases, causes rippling and erratic pulsation at the interface which then leads to interfacial convection and increased mass transfer rates. With a proposed correlation for mass transfer enhancement due to interfacial convection, all the experimental data were successfully predicted by the model.
COBISS.SI-ID: 36262917
A process for providing intermediate compounds as building blocks for effectively producing statins is described. The presented process is based on acetoxyacetaldehyde and acetaldehyde as substrates, which are presented in an aldol reaction catalyzed by a crude deoxyribose-5-phosphate aldolase (DERA) expressing culture lysate. Different addition regimes of both reactants into a reaction mixture were applied. For the highest concentration of product ((2S,4R)-4,6-dihydroxytetrahydro-2H-pyran-2-yl)methyl acetate, in the presented crude DERA expressing culture lysate-catalyzed reaction used further in the production of statins, the best addition time of reactants is described. Improved process conditions and reactants’ feeding regime were achieved by converting a batch reaction to a fed-batch process, reaching the highest concentration of product ((2S,4R)-4,6-dihydroxytetrahydro-2H-pyran-2-yl)methyl acetate near 77 g/L. The complete process was designed in a practical and economical manner and could be used further on an industrial scale.
COBISS.SI-ID: 36649733
A mathematical model of the continuous fixed bed column adsorption process for isolation of antibiotic vancomycin from a fermentation broth filtrate on two different polymeric adsorbent resins (Amberlite XAD16N and 1600N) was developed and validated by laboratory-scale experiments. The model was utilized for the prediction of breakthrough curves and consequently dynamic adsorption capacities by the application of independently determined adsorption equilibrium and intra-particle kinetic data as well as hydrodynamic parameters in order to analyze the column performance. The application of structural adsorption/desorption kinetics improved agreement between the calculated and measured data much more than by varying the effect of external mass transfer. The study showed that the use of XAD1600N is advantageous in terms of process economics.
COBISS.SI-ID: 5252890
A mathematical model of enzyme-catalyzed reaction in a homogeneous system within a microreactor was developed and successfully validated by on-line dissolved oxygen measurements inside of the system.
COBISS.SI-ID: 36271621
Waste composite poly-methyl methacrylate filled with a fine dispersion aluminium trihydrate (PMMA/ATH) and Fischer-Tropsch wax were used as modifying agents for a 70/100 paving grade bitumen employed for road paving. The effect of modifying agent content, primary ageing and long-term oxidative ageing on rheological and mechanical properties of base and modified bitumen were studied. The rutting resistance at high service temperatures was analyzed with oscillatory shear tests and multiple stress creep recovery measurements. Waste PMMA/ATH powder proved suitable for bitumen modification, particularly in combination with wax. Moreover, aluminium trihydrate is a flame retardant material. PMMA/ATH is less susceptible to heat and oxygen, therefore modified bitumen samples show improved viscoelastic and physical characteristics compared to base bitumen at handling and in-service temperatures.
COBISS.SI-ID: 5069338