scholarly journals A new perspective on vegetable oil epoxidation modeling: reaction and mass transfer in a liquid-liquid-solid system

2021 ◽  
Author(s):  
Tapio Salmi ◽  
Vincenzo Russo ◽  
Adriana Aguilera ◽  
Pasi Tolvanen ◽  
Johan Wärnå ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Molecular Diffusion ◽  
Batch Reactor ◽  
Reaction Diffusion ◽  
Catalyst System ◽  
Solid Catalyst ◽  
Multiphase Model ◽  
Rigid Spheres ◽  
Diffusion Phenomena ◽  
Solid System

A rigorous mathematical model was developed for a complex liquid-liquid-solid system in a batch reactor. The approach is general but particularly well applicable for the indirect epoxidation of vegetable oils according to the concept of N. Prileschajew. The model considers intra- and interfacial mass transfer effects coupled to the reaction kinetics. The liquid phases were described with chemical approach (aqueous phase) and a reaction-diffusion approach (oil phase). The oil droplets were treated as rigid spheres, in which the overall reaction rate is influenced by chemical reactions and molecular diffusion phenomena. The model was tested with a generic example, where two reactions proceeded simultaneously in the aqueous and oil phases. The example (i.e. fatty acid epoxidation à la Prileschajew) illustrated the power of the real multiphase model in epoxidation processes. The proposed modelling concept can be used for optimization purposes for many applications, which comprise a complex water-oil-solid catalyst system.

scholarly journals Solvent-Free Benzylation of Glycerol by Benzyl Alcohol Using Heteropoly Acid Impregnated on K-10 Clay as Catalyst

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 34
Author(s):  
Devendra P. Tekale ◽  
Ganapati D. Yadav ◽  
Ajay K. Dalai
Keyword(s):  
Heterogeneous Catalysis ◽  
Benzyl Alcohol ◽  
Batch Reactor ◽  
Value Added ◽  
Solvent Free ◽  
Biodiesel Production ◽  
Area Measurement ◽  
Solid Catalyst ◽  
Glycerol Ether ◽  
Insight Into

Value addition to glycerol, the sole co-product in biodiesel production, will lead to reform of the overall biodiesel economy. Different valuable chemicals can be produced from glycerol using heterogeneous catalysis and these valuable chemicals are useful in industries such as cosmetics, pharmaceuticals, fuels, soap, paints, and fine chemicals. Therefore, the conversion of glycerol to valuable chemicals using heterogeneous catalysis is a noteworthy area of research. Etherification of glycerol with alkenes or alcohols is an important reaction in converting glycerol to various value-added chemicals. This article describes reaction of glycerol with benzyl alcohol in solvent-free medium by using a clay supported modified heteropolyacid (HPA), Cs2.5H0.5PW12O40/K-10 (Cs-DTP/K-10) as solid catalyst and its comparison with other catalysts in a batch reactor. Mono-Benzyl glycerol ether (MBGE) was the major product formed in the reaction along with formation of di-benzyl glycerol ether (DBGE). The effects of different parameters were studied to optimize the reaction parameters. This work provides an insight into characterization of Cs2.5H0.5PW12O40/K-10 catalyst by advanced techniques such as surface area measurement, X-ray analysis, ICP-MS, FT-IR, and SEM. Reaction products were characterized and confirmed by using the GCMS method. The kinetic model was developed from an insight into the reaction mechanism. The apparent energy of activation was found to be 18.84 kcal/mol.

Effect of non-uniform passive advection on A+B->C radial reaction-diffusion fronts 

2021 ◽  
Author(s):  
Alessandro Comolli ◽  
Anne De Wit ◽  
Fabian Brau
Keyword(s):  
Molecular Diffusion ◽  
Early Time ◽  
Reaction Diffusion ◽  
Transport Processes ◽  
Calcium Carbonate Precipitation ◽  
Atmospheric Reactions ◽  
Passive Advection ◽  
Reaction Fronts ◽  
Time Regime ◽  
Long Time

<p>The interplay between chemical and transport processes can give rise to complex reaction fronts dynamics, whose understanding is crucial in a wide variety of environmental, hydrological and biological processes, among others. An important class of reactions is A+B->C processes, where A and B are two initially segregated miscible reactants that produce C upon contact. Depending on the nature of the reactants and on the transport processes that they undergo, this class of reaction describes a broad set of phenomena, including combustion, atmospheric reactions, calcium carbonate precipitation and more. Due to the complexity of the coupled chemical-hydrodynamic systems, theoretical studies generally deal with the particular case of reactants undergoing passive advection and molecular diffusion. A restricted number of different geometries have been studied, including uniform rectilinear [1], 2D radial [2] and 3D spherical [3] fronts. By symmetry considerations, these systems are effectively 1D.</p><p>Here, we consider a 3D axis-symmetric confined system in which a reactant A is injected radially into a sea of B and both species are transported by diffusion and passive non-uniform advection. The advective field <em>v<sub>r</sub>(r,z)</em> describes a radial Poiseuille flow. We find that the front dynamics is defined by three distinct temporal regimes, which we characterize analytically and numerically. These are i) an early-time regime where the amount of mixing is small and the dynamics is transport-dominated, ii) a strongly non-linear transient regime and iii) a long-time regime that exhibits Taylor-like dispersion, for which the system dynamics is similar to the 2D radial case.</p><p>                                  <img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.ff5ab530bdff57321640161/sdaolpUECMynit/12UGE&app=m&a=0&c=360a1556c809484116c55812c8c06624&ct=x&pn=gnp.elif&d=1" alt="" width="299" height="299">                                                     <img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.671a6980bdff51231640161/sdaolpUECMynit/12UGE&app=m&a=0&c=c5a857c3fab835057e3af84001a91d15&ct=x&pn=gnp.elif&d=1" alt="" width="302" height="302"></p><p>                                                   Fig. 1: Concentration profile of the product C in the transient (left) and asymptotic (right) regimes.</p><p> </p><p>References:</p><p>[1] L. Gálfi, Z. Rácz, Phys. Rev. A 38, 3151 (1988);</p><p>[2] F. Brau, G. Schuszter, A. De Wit, Phys. Rev. Lett. 118, 134101 (2017);</p><p>[3] A. Comolli, A. De Wit, F. Brau, Phys. Rev. E, 100 (5), 052213 (2019).</p>

Mass transfer impacts in flocculent and granular biomass from SBR systems

2004 ◽  
Vol 50 (10) ◽  
pp. 203-212 ◽  
Author(s):  
D. Gapes ◽  
B.-M. Wilén ◽  
J. Keller
Keyword(s):  
Mass Transfer ◽  
Particle Size ◽  
Oxygen Uptake ◽  
Activated Sludge ◽  
Uptake Rate ◽  
Oxygen Uptake Rate ◽  
Batch Reactor ◽  
Average Particle Size ◽  
Gas Analysis ◽  
Average Particle

An experimental study was conducted to describe mass transfer impacts within nitrifying aggregates sourced from sequencing batch reactor (SBR) activated sludge systems. Flocculent and granular sludge with high nitrification activity was obtained in two laboratory SBR systems, supplied with a synthetic, ammonium-based feed. The flocculent biomass was fractionated using a sieving procedure, in order to obtain biomass fractions with different particle size distributions. The oxygen uptake rate (OUR) response to changes in dissolved oxygen concentration was measured under highly controlled conditions in a titrimetric and off-gas analysis (TOGA) sensor, and the results used to assess mass transfer effects. As the average particle size of the biomass increased, mass transfer limitations were found to increase significantly. Empirically fitted, apparent KS,O2 values were demonstrated to be highly dependent on particle size, and reflect the mass transfer limitations occurring in the aggregates within a given system. Such parameters thus have little to do with the actual biokinetic parameter from which they are derived. The results obtained from the TOGA sensor study were consistent with those obtained from a microelectrode study on the same nitrifying granules. Together, these studies add considerable weight to the conclusion that consideration of external and internal mass transfer limitations is vital to the accurate description of activated sludge treatment processes, particularly those with a high oxygen uptake rate.

scholarly journals Production of lactic acid from cellulose using solid catalyst

2019 ◽  
Vol 268 ◽  
pp. 07006 ◽  
Author(s):  
Sujitra Doungsri ◽  
P. Rattanaphanee ◽  
Aatichat Wongkoblap
Keyword(s):  
Lactic Acid ◽  
Batch Reactor ◽  
Nitrogen Pressure ◽  
Reaction Pathways ◽  
Solid Catalyst ◽  
One Pot ◽  
Solid Catalysts ◽  
Platform Chemicals ◽  
Acid And Base ◽  
The One

Lactic acid (LA), one of the important biomass derived platform chemicals, has been used in food and chemical industries, especially in biodegradable polymer as polylactic acid (PLA). The aim of this work is to study the one-pot production of LA from cellulose by using different solid catalysts. The reaction was conducted in a high pressure batch reactor and the catalyst used in this study were ZrO2 and Al2O3. The reaction was carried out at temperature of 200oC for 6 hr. and under nitrogen pressure of 1 MP. It was found that the production yield of LA were 8.02% and 6.63%, when the ZrO2 and Al2O3 catalysts were used respectively. The result indicated that the ZrO2 may effect on the LA production because of the acid and base sites of the ZrO2. Therefore, the reaction pathways for conversion of cellulose into lactic acid have been investigated, and developed the new conditions to achieve the higher yield.

Parallel simulation of reaction–diffusion phenomena in percolation processes

2001 ◽  
Vol 17 (6) ◽  
pp. 679-688 ◽  
Author(s):  
Stefania Bandini ◽  
Giancarlo Mauri ◽  
Giulio Pavesi ◽  
Carla Simone
Keyword(s):  
Reaction Diffusion ◽  
Parallel Simulation ◽  
Diffusion Phenomena ◽  
Percolation Processes

Photocatalytic degradation of 2-propanol over TiO2-based thin films in a simulated pilot microreactor

2021 ◽  
Vol 02 ◽  
Author(s):  
Corrado Garlisi ◽  
Ahmed Yusuf ◽  
Giovanni Palmisano
Keyword(s):  
Thin Films ◽  
Gas Phase ◽  
Continuous Flow ◽  
Molecular Diffusion ◽  
Batch Reactor ◽  
High Surface ◽  
Operating Conditions ◽  
Flow Mode ◽  
Doped Tio2 ◽  
Kinetics Of

Background: Microreactor devices have attracted increasing attention over the last years due to their high surface-to-volume ratio which ensures a high heat and mass transfer, short molecular diffusion distance and greater spatial illumination homogeneity compared to traditional reactors. Objective: The aim of this study was to model the kinetics of photodegradation of 2-propanol over TiO2-based thin films in a gas-phase batch-reactor and simulate their performance in a microreactor device. Methods: The reaction was carried out in a gas-phase batch-reactor assessing the reactivity of a single-layer nitrogen (N)-doped TiO2 and a bilayer consisting of N-doped TiO2 as a bottom layer and copper (Cu)-doped TiO2 as a top layer. The kinetics of the photocatalytic process was modelled by Langmuir–Hinshelwood (LH) model. The constants obtained from LH model were used to simulate the performance of the photocatalysts in a microreactor operating in a continuous flow mode and investigating the effect of the volumetric flow rate (Q), initial concentration of pollutant (Co), number of microchannels (n) and microchannel length (l) on the photodegradation of 2-propanol. Results: N-Cu-TiO2 exhibited a higher reactivity but a lower to adsorption ability towards the target pollutant compared to N-TiO2. To maximize and leverage the advantages of microreactor, optimal operating conditions for a continuous flow mode, at steady state, should be moderately low Q and Co, long l and moderate n that minimizes flow maldistribution in parallel. Conclusion: The findings in this work could serve as a basis to design and fabricate efficient microreactors for the removal of VOC in air purification applications.

scholarly journals Mesoscale Reaction–Diffusion Phenomena Governing Lignin‐First Biomass Fractionation

ChemSusChem ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4495-4509 ◽  
Author(s):  
Nicholas E. Thornburg ◽  
M. Brennan Pecha ◽  
David G. Brandner ◽  
Michelle L. Reed ◽  
Josh V. Vermaas ◽  
...  
Keyword(s):  
Reaction Diffusion ◽  
Biomass Fractionation ◽  
Diffusion Phenomena

scholarly journals Diffusion in nanopores: correlating experimental findings with “first-principles” predictions

Adsorption ◽  
2020 ◽  
Vol 26 (7) ◽  
pp. 1001-1013 ◽  
Author(s):  
Seungtaik Hwang ◽  
Jörg Kärger
Keyword(s):  
First Principles ◽  
Molecular Diffusion ◽  
Diffusion Path ◽  
Observation Time ◽  
Present Communication ◽  
Diffusion Measurement ◽  
Guest Molecules ◽  
Host Materials ◽  
Diffusion Phenomena ◽  
Experimental Findings

Abstract Measurement of molecular diffusion in nanoporous host materials, which are typically inhomogeneous and anisotropic, often involves an intricate web of factors and relations to be taken into account since the associated diffusivities are a function of the diffusion path of the guest molecules during a given observation time. Depending on the observation time, therefore, the result of the experimental measurement can point to completely different conclusions about the underlying diffusion phenomena. The risk of misinterpretation of the experimental data, by correlating them with irrelevant phenomena, may be reduced if there is an option to compare the data with the results of totally independent measurements. The present communication addresses this issue with reference to the particular potentials of pulsed field gradient NMR and microimaging by infrared microscopy as techniques of microscopic diffusion measurement.

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