Stirred Batch Reactor Research Articles

A Potentiometric Study of the Briggs‐Rauscher Oscillatory Reaction in a Solution of Ionic Surfactants and Tetrabutylammonium Hydrogensulphate

AbstractThe concentration effect of ionic surfactants (sodium dodecyl sulphate, N‐hexadecyl‐N,N,N‐trimethylammonium hydrogensulphate, 3‐(N,N‐dimethyl‐N‐myristylammonio)propanesulfonate) and tetrabutylammonium hydrogensulphate was investigated on the Briggs‐Rauscher (BR) oscillatory reaction in a stirred batch reactor at 25 ± 0.1 °C in both the absence and presence of an ionic surfactant. In the presence of the anionic surfactant, the induction period (IP) and the oscillation period (OP) increase markedly, and the amplitude of oscillations decreases with increasing concentration of sodium dodecyl sulphate. These effects have been observed when the concentration of surfactant is much higher than its critical micelle concentration. Another effect on IP and OP has been observed in the presence of cationic and zwitterionic surfactants. A decrease in IP leads to its extinction at a certain concentration and at the same time, chemical oscillations divide into two series of chemical oscillations. TBAH does not have a major influence on IP and OP of the BR oscillatory reaction. The observed effects are explained in terms of micellar catalysis or inhibition in different extents of individual reactants solubilisation respectively.

Kinetic Study of CaO-Catalyzed Transesterification of Cyclic Carbonates with Methanol

Simultaneous catalytic contributions of CaO in the liquid phase (homogeneous) and in the solid phase (heterogeneous) for transesterification are considered in the kinetic analysis, because sparingly soluble CaO has significant catalytic activity. Experimental concentration–time profiles were obtained at different catalyst loadings, propylene carbonate (PC) concentrations, and methanol concentrations in a temperature range of 20–60 °C in a stirred batch reactor for both the homogeneous and heterogeneous reactions. Kinetic models based on power-law rate forms were evaluated and discriminated to fit the experimental data. Reaction orders of 1 for PC, 2 for methanol, and 1 for both DMC and PG fit the experimental data best for the homogeneous reaction, whereas orders of 0.35 for PC, 1.9 for methanol, and 0 for both DMC and PG fit the experimental data best for the heterogeneous reaction. The heterogeneous CaO catalyst (Ea = 56.8 kJ/mol) was found to be more active than the homogeneous CaO catalyst (Ea = 82.4 ...

An empirical rate law for gypsum powder dissolution

The dissolution rates, normalized by surface area, of two different gypsum powders in aqueous solutions were measured by tracking changes in solution composition as a function of time in a continuously stirred batch reactor. The powders were classified into different size ranges to observe the influence of particle coarseness on dissolution kinetics. Changes in solid surface area during the experiment were modeled as a function of mass loss by measuring the specific surface areas of the powders before and after the experiments. Contrary to the implicit assumption in several previous studies, the total powder surface area increases, typically by a factor of two, prior to decreasing with ongoing dissolution. This phenomenon therefore has a significant influence, up to 50%, on the surface area-normalized rate. The initial solution composition was set to one of several prescribed saturation states so that an empirical rate law could be inferred over a wide range of saturations. The rate coefficient for both types of gypsum depended on size, being lower for coarser particles. Other than the difference in rate coefficients, the dissolution rate of both sources of gypsum can be described well by the same mathematical function of solution saturation, at least to within the uncertainty in the measurements. Data from previous studies of gypsum dissolution appear to follow approximately the same dependence on particle size as observed in this study.

Enzymatic Synthesis of Structured Monogalactosyldiacylglycerols Enriched in Pinolenic Acid.

We enzymatically prepared structured monogalactosydiacylglycerols (MGDGs) enriched in pinolenic acid (PLA). PLA-enriched free fatty acids (FFAs) containing ∼86 mol % PLA were produced from an FFA fraction obtained from pine nut oil (PLA content, ∼13 mol %) by urea crystallization. Commercial MGDGs (5 mg) were acidolyzed with PLA-enriched FFAs using four commercial immobilized lipases as biocatalysts. The reaction was performed in acetone (4 mL) in a stirred-batch reactor. Lipozyme RM IM (immobilized Rhizomucor miehei lipase) was the most effective biocatalyst for the reaction. Structured MGDGs containing 42.1 mol % PLA were obtained under optimal reaction conditions: temperature, 25 °C; substrate molar ratio, 1:30 (MGDGs/PLA-enriched FFAs); enzyme loading, 20 wt % of total substrates; and reaction time, 36 h. The structured MGDGs were separated from the reaction products at a purity of 96.6 wt % using silica column chromatography. The structured MGDGs could be possibly used as emulsifiers with appetite-suppression effects.

Kinetic modeling of catalytic esterification of non-edible macauba pulp oil using macroporous cation exchange resin

Conversion of non-edible oils through heterogeneous catalysis and their kinetic aspects are essential in order to produce economically viable biodiesel. Especially for oils containing high Free Fatty Acids (FFA) content since those cannot be viably converted through homogenous catalysis. Herein, the heterogeneous catalytic esterification kinetics of macauba pulp acid oil was exploited. The reaction tests were conducted in a stirred batch reactor with ethanol, and a cation exchange resin (Purolite® CT275)as a catalyst. The reaction kinetics was modeled based on a pseudo-homogeneous (PH) model of second order, showing good agreement with the experimental data acquired under different reaction conditions. The reaction progress was monitored by validated HPLC and GC methods. The internal and external mass transfer resistances were evaluated, and show that the rate limiting step is the surface reaction. To assess the catalyst stability, scanning electron microscopy was performed on both fresh and spent (after 10 reaction cycles) catalysts; reuse of catalyst was conducted without further treatment. The catalyst recycling demonstrates good performance where 85% of its performance was retained, and the SEM images show that the materials were structurally stable. Because the Pseudo-Homogeneous model properly described the kinetic aspects of the esterification process it was possible to estimate thermodynamic parameters by using the Arrhenius plot. The activation energy of the forward reaction was determined as 44.0 kJ/mol, while for the reverse reaction was 11.7 kJ/mol. Therefore, the kinetic and thermodynamic descriptions along with the catalyst stability upon several cycles without any further treatment reflect the viability of these resins for industrial application in the energy sector. Furthermore, combining these features with the low cost of macauba pulp acid oil, we conclude that the process is suitable for scaling up studies.

Biosurfactant Production from Used Vegetable Oil in the Anode Chamber of a Microbial Electrosynthesizing Fuel Cell

In this study, producing biosurfactant from used vegetable oil in the anode chamber of a microbial electrosynthesizing fuel cell (MEFC) with electrical energy production was investigated. Up to 10 mL/L used vegetable oil was used with an acclimated bacterial culture—Serratia sp. in the anode chamber. The biosurfactant production and bacterial growth in the anode chamber was compared to a continuously stirred batch reactor of comparable size. Up to 3.05 g/L of biosurfactant was produced in the anode solution and a reduction of surface tension to 25.2 mN/m was reached after 7 days of the MEFC operation. At the same time, a maximum power density of 1.13 mW/m2 was produced. The MEFC was further characterized using the electrochemical impedance spectroscopy. Mathematical expression was established to model the total impedance of the MEFC. The production of the biosurfactant from the used vegetable oil waste in the anode chamber and also producing electric power makes the MEFC multifunctional.

Adsorption and oxidation of 3-nitro-1,2,4-triazole-5-one (NTO) and its transformation product (3-amino-1,2,4-triazole-5-one, ATO) at ferrihydrite and birnessite surfaces

The emerging insensitive munitions compound (IMC) 3-nitro-1,2,4-triazole-5-one (NTO) is currently being used to replace conventional explosives such as 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), but the environmental fate of this increasingly widespread IMC remains poorly understood. Upon release from unexploded solid phase ordinances, NTO exhibits high aqueous solubility and, hence, potential mobilization to groundwater. Adsorption and abiotic transformation at metal oxide surfaces are possible mechanisms for natural attenuation. Here, the reactions at ferrihydrite and birnessite surfaces of NTO and its biotransformation product, 3-amino-1, 2, 4-triazol-5-one (ATO), were studied in stirred batch reactor systems at controlled pH (7.0). The study was carried out at metal oxide solid to solution ratios (SSR) of 0.15, 1.5 and 15 g kg−1. The samples were collected at various time intervals up to 3 h after reaction initiation, and analyzed using HPLC with photodiode array and mass spectrometric detection. We found no detectable adsorption or transformation of NTO upon reaction with birnessite, whereas ATO was highly susceptible to oxidation by the same mineral, showing nearly complete transformation within 5 min at 15 g kg−1 SSR to urea, CO2(g) and N2(g). The mean surface-area-normalized pseudo-first order rate constant (k) for ATO oxidation by birnessite across all SSRs was 0.05 ± 0.022 h−1 m−2, and oxidation kinetics were independent of dissolved O2 concentration. Both NTO and ATO were resistant to oxidation by ferrihydrite. However, NTO showed partial removal from solution upon reaction with ferrihydrite at 0.15 and 1.5 g kg−1 SSR and complete loss at 15 g kg−1 SSR due to strong adsorption. Conversely, ATO adsorption to ferrihydrite was much weaker than that measured for NTO.

Kinetic Studies of Lignin Solvolysis and Reduction by Reductive Catalytic Fractionation Decoupled in Flow-Through Reactors

Reductive catalytic fractionation (RCF) is an effective active-stabilization strategy to selectively extract and depolymerize lignin into aromatic monomers. Here, the kinetics of RCF were investigated by using flow-through reactors to decouple the two limiting mechanistic steps, namely lignin solvolysis and reduction. When operating in a solvolysis-limited regime, apparent energy barriers of 63 ± 1 and 64 ± 2 kJ mol–1 were measured for the solvent mediated lignin extraction of poplar using particle diameters of 0.5 < d < 1 mm and 0.075 < d < 0.25 mm, respectively. In contrast, when using mechanically stirred batch reactors, apparent barriers of 32 ± 1 and 39 ± 3 kJ mol–1 were measured for particle diameters of 0.5 < d < 1 mm and 0.075 < d < 0.25 mm, respectively. The difference of activation barriers between flow and batch reactors indicated that lignin extraction under typical RCF conditions in a 100 mL batch reactor stirred at 700 rpm was mass-transfer limited. In the reduction-limited regime, cleavage ...

A Potentiometric Study of the Briggs–Rauscher Oscillatory Reaction in a Solution of Nonionic Surfactants and tert‐Butanol

ABSTRACTThe concentration effect of nonionic surfactants (Triton X‐100, Brij 30, Brij 58, Tween 20, and Tween 80) and tert‐butanol was investigated on the Briggs–Rauscher oscillatory reaction in a stirred batch reactor at 25 ± 0.1°C in both the absence and presence of nonionic surfactant and tert‐butanol as well. The addition of Triton X‐100, Brij 58, and Tween 20 influenced the oscillatory parameters in a similar fashion: a decrease of the induction period until its disappearance, an increase of the oscillation period, an increase of the oscillation amplitude, an increase of the duration of the oscillation, and a gradual increase of the oscillation numbers. The addition of Brij 30 has no significant effect on the oscillation parameters of the Briggs‐Rauscher oscillatory reaction. The effect of tert‐butanol on the Briggs–Rauscher oscillatory reaction is very similar to the effect of Brij 58; however, we were unable to observe the disappearance of the induction period on the studied concentration range. The addition of Tween 80 to the reaction mixture has a similar effect as the addition of Triton X‐100, Brij 58, or Tween 20, except for the induction period, which in the case of Tween 80, it becomes larger. The observed effects are explained in terms of micellar catalysis or inhibition, that is, in a different extent of individual reactants of solubilization.

Oxidative desulfurization of 4,6-dimethyldibenzothiophene in a two impinging streams spray reactor

ABSTRACTOxidative desulfurization of 4,6-dimethyldibenzothiophene was performed in a two impinging streams spray reactor (TIS-SR) using H2O2 and phosphotungstic acid as oxidant and catalyst, respectively. The reaction was optimized using response surface methodology. The reaction constant of a pseudo first order rate based on the dynamic data obtained for the optimal operation conditions was calculated to be 9.45 × 10−4 s−1. It is about one order of magnitude larger than the one calculated for a conventional ideal stirred batch reactor at the same reaction conditions (1.03 × 10−4 s−1). Accordingly, ODS reaction rate may be substantially enhanced using TIS-SR.

Degradation of polyethylene microplastics in seawater: Insights into the environmental degradation of polymers

ABSTRACTMicroplastic contamination of aquatic environments has become an increasingly alarming problem. These, defined as particles <5 mm, are mostly formed due to the cracking and embrittlement of larger plastic particles. Recent reports show that the increasing presence of microplastics in the environment could have significant deleterious consequences over the health of marine organisms, but also across the food chain. Herein, we have studied the effects of artificial seawater on polyethylene (PE)-based beads by exposing them up to eight weeks to saltwater in stirred batch reactors in the dark and examined the structural and morphological changes these endured. Electron microscopy observations showed that artificial seawater induces severe microcracking of the pellets' surfaces. Additionally, Fourier transform infrared spectroscopy (FTIR) analyses evidenced the formation of oxidized groups whenever these particles were exposed to water and an increase in organic matter content of the waters in which the pellets were kept was evidenced by Raman spectroscopy. There were also noticeable consequences in the thermal stability of the polyethylene pellets, as determined by thermogravimetric studies (TGA). Furthermore, the parallel exposure of polyethylene pellets to UV radiation yielded less pronounced effects, thus underscoring its lower preponderance in the degradation of this material. These results highlight the importance of determining the mechanisms of degradation of microplastics in marine settings and what the implications may be for the environment. Overall, the herein presented results show that a relatively short period of time of accelerated exposure can yield quantifiable chemical and physical impacts on the structural and morphological characteristics of PE pellets.

Transient effectiveness factor. Simultaneous determination of kinetic, diffusion and adsorption equilibrium parameters in porous catalyst particles under diffusion control conditions

A method to determine kinetics, diffusion and adsorption equilibrium parameters simultaneously in porous catalyst particles, where a first order chemical reaction occurs under diffusion control conditions in batch reactor, was proposed. The method is based on the use of observable magnitudes from a few experiments in a well stirred batch reactor. By means of a model considering the accumulation of reactant in the catalyst particles, the transient effectiveness factor allows analyzing the time response of systems with different adsorption capacities. The analysis basis and consequent methodology are more general and precise that those resulting from the conventional assumption, which consider that the concentration profiles in the particles, fulfill the steady state condition. Once an initial period elapsed after the reactant injection, the transient effectiveness factor reaches a pseudo-equilibrium state, condition under which an analytical expression can be used to describe the evolution of the reactant concentration in the fluid phase as a function of time. The parameters characterizing that expression of the dynamic response of the reactor, i.e., the exponential decaying constant and the concentration extrapolated at time zero, allow using data from a few experiments to determine the corresponding system’s diffusion, adsorption and chemical reaction parameters under reaction conditions.

Optimization of Disperse Blue 3 mineralization by UV-LED/FeTiO3 activated persulfate using response surface methodology

Abstract Response surface methodology based on Box-Behnken design (BBD) was successfully applied for the optimization of the UV-LED/FeTiO3 activated persulfate (PS) process. Disperse Blue 3 (DB3) azo dye oxidation was carried out in a quartz jacketed stirred batch reactor using 405 nm UV at 10 W/m−2 as radiation source. The effects of temperature, catalyst concentration and persulfate dose upon the total organic carbon (TOC) removal were investigated. Optimum operating conditions were found to be: ilmenite: 320 mg/L−1, PS: 1.56 g/L−1 and 67 °C. Under these conditions, 96% mineralization was achieved. Ecotoxicity of the final effluent was evaluated using Aliivibrio fischeri bacteria, finding a negligible toxicity.

KINETICS OF ESTERIFICATION OF ACETIC ACID WITH 2-ETHYLHEXANOL IN THE PRESENCE OF AMBERLYST 36

The kinetics of esterification of acetic acid with 2-ethylhexanol catalyzed by Amberlyst 36 was studied in a stirred batch reactor. The equilibrium constant, K c , was found to be 81 and it is independent of temperature within the range of 333 to 363 K. The uncatalyzed reaction was proved to follow a second-order reversible reaction model. In the presence of Amberlyst 36, experimental data well fitted with a pseudo-homogeneous (PH) model.

Adsorption and catalytic oxidation of organic pollutants using Fe-zeolite.

In this work, a natural zeolite, modified and loaded with iron (NZ-A-Fe) as a heterogeneous catalyst, was characterized for its suitability as a permeable reactive barrier (PRB) material for treatment of aromatic hydrocarbons in groundwater. Adsorption and oxidation processes were analyzed. Batch adsorption tests for benzene, toluene and xylene (BTX) aqueous concentrated solutions were performed at neutral pH. Kinetic adsorption was described with the pseudo-second-order model. Experiments were performed using a stirred batch reactor with near 11 mM initial BTX concentration applying NZ-A-Fe as solid catalyst and H2O2 as an oxidant. BTX removal reached 80% in 600 min in these experimental conditions. Catalytic oxidation was described with a pseudo-first-order kinetic model. No significant iron leaching was detected during all the experiences. These investigations show that coupling adsorption with catalytic oxidation with this novel system is a promising procedure to simultaneously remove BTX from moderately concentrated aqueous solution at neutral pH in groundwater.

On the development of kinetic models for solvent-free benzyl alcohol oxidation over a gold-palladium catalyst

Bimetallic Au-Pd nanoparticles supported on TiO2 show excellent catalytic activity and selectivity to benzaldehyde in the solvent-free transformation of benzyl alcohol to benzaldehyde, where toluene is the main observed by-product, together with smaller amounts of benzoic acid, benzyl benzoate and dibenzyl ether. However, despite the industrial relevance of this reaction and importance of tuning the selectivity to the desired benzaldehyde, only a few attempts have been made in the literature on modeling the reaction kinetics for a quantitative description of this reaction system. A kinetic model for the oxidation of benzyl alcohol over Au-Pd is proposed in this paper. The model assumes that hydrogenolysis, disproportionation and dehydrogenation reactions may occur in parallel, and it has been found satisfactory after a model discrimination procedure was applied to a number of simplified candidate models developed from microkinetic studies. Despite its relative simplicity, the proposed model is capable of representing the reactant conversion and distribution of products observed in experiments carried out at different temperature, pressure and catalyst mass in a stirred batch reactor. Major findings include the quantitative evaluation of the impact of hydrogenolysis and disproportionation pathways on benzaldehyde production. At low temperature the disproportionation reaction is the dominant route to toluene formation, while hydrogenolysis dominates at high temperature.

Solvent free lipase catalyzed synthesis of butyl caprylate

The ester, butyl caprylate has wide applications in commercial market and it also possesses characteristic fruity flavor. The work exhibits the effect of various reaction parameters and the optimization study for the synthesis of butyl caprylate in presence of bio-catalyst. To achieve maximum conversion the optimum parameters thus established include; temperature 60 $$^{\circ }\hbox {C}$$ , mole ratio of caprylic acid and butanol as 1:2, lipase loading 2% (w/v), 250 rpm speed of agitation and 4g of molecular sieves. The immobilized enzyme was also recycled and reused for 7 cycles with only 30% loss from its initial activity. The thermodynamic parameters at different temperatures were also determined. The esterification was conducted successfully with 92% as maximum conversion in 5 h in a stirred batch reactor under solvent free system and in presence of molecular sieves that was used to adsorb water formed in reaction. Synopsis: Lipase catalysed synthesis of butyl caprylate is carried out in a stirred batch reactor. Novozym 435 was used as biocatalyst, butanol and caprylic acid are used as substrates. The esterification reaction was successfully performed in 5 h to yield 92% butyl caprylate.

Studi Kinetika Reaksi Metanolisis Pembuatan Metil Ester Sulfonat (MES) Menggunakan Reaktor Batch Berpengaduk

Surfactant is a surface active agent which is widely applied in chemical industry related to its ability to stabilize the emulsion between the oil phase and the water phase. Surfactant-based on vegetable oil is a technology developed in the field of surfactant which has been dominated by surfactants made from petroleum. Methyl ester sulfonate (MES) is an anionic surfactant produced by the reaction between fatty acid methyl ester with a sulfonating agent or called as sulfonation reaction. MES undergoes an advanced process called methanolysis and neutralization reactions. This study investigated the effect of reactant molar ratio, reaction time and reaction temperature on MES yield on methanolysis reaction. The highest MES yield of 49.71% was achieved at a reaction temperature of 120°C, the reaction time of 120 minutes and the molar ratio between MES and methanol of 1:3. The rate constants of methanolysis reactions are determined by reacting the reactants in the stirred batch reactor under those operating conditions.

Induction time, storage capacity, and rate of methane hydrate formation in the presence of SDS and silver nanoparticles

ABSTRACTIn this communication, the kinetic parameters of methane hydrate formation (induction time, quantity and rate of gas uptake, storage capacity (SC), and apparent rate constant) in the presence of sodium dodecyl sulfate (SDS), synthetized silver nanoparticles (SNPs), and mixture of SDS + SNPs have been studied. Experimental measurements were performed at temperature of 273.65 K and initial pressure of 7 MPa in a 460 cm3 stirred batch reactor. Our results show that adding SDS, SNPs and their mixture increases the quantity of gas uptake, water to hydrate conversion, and SC of methane hydrate formation, noticeably. Using 300 ppm SDS increases the SC and the quantity of methane uptake 615, and 770%, respectively, compared with pure water. Investigating the hydrate growth rate at the start of hydrate formation process shows that, using SNPs, SDS, and their mixture increases the initial apparent rate constant of hydrate rate, considerably. Our results show that the system of methane + water + SDS 500 ppm + SNPs 45 µM represents the maximum value of initial apparent rate constant, compared with other tested systems.

Morphologies of microparticles of partially neutralized sodium polyacrylate by inverse suspension polymerization

The morphologies of sodium polyacrylate super absorbent polymer microparticles synthesized by inverse suspension polymerization at 65°C are presented. The spherical polymer microparticles of 30–100 μm in diameter were prepared in a hydrocarbon medium with water soluble initiators in presence of a cross‐linking agent and suspension stabilizer in a stirred batch reactor. A variety of microparticles morphology has been observed for different reaction conditions such as monomer/water ratio, reaction time, cross‐linker type and concentration, hydrocarbon medium properties, and postreaction solvent washing. The observed polymer particle morphologies include highly deformed particles, spherical particles with smooth surfaces, spherical particles with wrinkled surfaces, particles with interior multihollows, highly porous particles, particles of empty core‐shell structures, etc. Some of these particles with complex morphologies such as multihollow or porous interior can improve the water absorption efficiency of the polymer particles because water can penetrate the particle more effectively. The polymer particles with wrinkled particle surface, which is formed during the postreaction treatment process, can also enhance the water absorption rate because of its increased external surface area. POLYM. ENG. SCI., 58:1564–1574, 2018. © 2017 Society of Plastics Engineers