Reversible Second-order Reaction Research Articles

Adsorptive abatement of Pb2+ and crystal violet using chitosan-modified coal nanocomposites: A down flow column study

Every moment huge amounts of industrial wastewater are contaminating our surface/groundwater sources by discharging into the environment directly. This crude wastewater is the most problematic subject because it is the matrix of hazardous toxicants, which can drastically damage public health-safety. So, it is urgent to purify before discharging/reusing. This study focused on the recent improvement and latent implication of Activated Chitosan-Modified Coal(ACMC) bionanocomposite filter. Here, we briefly described how ACMC was produced and its potential application in the removal of Pb2+ and Crystal Violet (CV) effectively from wastewater. However, the influence of different parameters like initial concentration (20–40 ppm), volumetric flow rate (4–6 mL/min) and bed height (0.4–1.0 cm) were investigated appropriately meanwhile the adsorbent amount was (1.0–2.0 g). The adsorption efficiency and removal percent were strongly correlated with inlet concentration, flow rate, and bed height. The highest removal capacity and percentage were found nearly (243.08 and 238.51)mg/g additionally (78.48 and 82.50)% for Pb2+ and CV. Finally, three well-known column adsorption models namely Thomas, Yoon-Nelson and Adam-Bohart model were applied for the fitting of experimental data which exhibited a decent agreement with all three models that are also suitable for the description of breakthrough curve (BTC) and supports the Langmuir isotherm by following second-order reversible reaction kinetics. Thus this new class of ACMC nanoadsorbents could be beneficially used for the real-time bulk scale industrial wastewater treatment as a suitable replacement of hazardous fossil-based synthetic ones for sustainable environmental protection.

Simultaneous abatement of Ni2+ and Cu2+ effectually from industrial wastewater by a low cost natural clay-chitosan nanocomposite filter: Synthesis, characterization and fixed bed column adsorption study

Untreated industrial wastewaters are so hazardous object for environment. It is straightforwardly contaminates ground/surface water fonts and extremely damage the ecology, and human health safety. This article elicits some neoteric upliftment and latent significance of fixed bed activated chitosan-clay bio nano-filter (ACCBNF) composite for remarkable adsorption of Ni2+ and Cu2+ from wastewater. However, chitosan was synthesized following demineralization, deproteinized and finally by 50 % NaOH treatment. On contrary, ACCBNF were contrived by solution casting method. The characterization of ACCBNF composites was done by FTIR, XRD, SEM and TGA techniques. The influence of different parameters such as initial concentration of wastewater (40–60 ppm), flow rate of wastewater (3–5 mL/min) and bed height of column (1.5–3.5 cm) were explored appropriately for this study, where the amount of adsorbents were inter between to 2.57–5.98 g. This study revealed that the fictitious ACCBNF composites were highly crystalline, thermally stable, and have worthy surface activity and exhibit a very astonishing adsorption capacity against Ni2+ and Cu2+. It might be happened due to the association of nucleophilic groups of the chitosan edifice and the porosity of activated clay (modified). The uppermost R% was found around 81.13 % for Ni2+ and 88.88 % for Cu2+ ions respectively additionally the maximum adsorption capacity were found particularly for Ni2+ around 101.24 mg/g and for Cu2+ around 94.14 mg/g. Finally, two eminent column adsorption models, namely Thomas and Yoon nelson model were applied to fit the experimental data. The obtained data are in blameless agreement with both of the models in which the value of R2 lies between 0.971 and 0.998 for Thomas model in addition between 0.982 and 0.998 for Yoon nelson model. Besides this, they are suitable for the explanation of breakthrough curve at all the experimental conditions and it supports the Langmuir isotherm, also obeys second-order reversible reaction kinetics.

Brønsted acidic Heteropolyanion-Based ionic Liquid:A highly efficient Reaction-induced Self-separation catalyst for Baeyer-Villiger reaction

A novel Brønsted acidic heteropolyanion-based ionic liquid (IL) ([MIMPS]3PW12O40) was synthesized and employed to catalyze the Baeyer-Villiger (BV) reaction to produce ε-Caprolactone (ε-CL). Noteblely, the prepared IL catalyst exhibited higher catalytic activity compared to solid acid catalysts duo to its behavior of reaction-induced self-separation. It meaned that the IL catalyst could switch from solid to liquid, then back to solid state during the reaction, which broke the limit of the constant heterogeneous state of the catalyst in the reaction system. The characterization results of FT-IR, 1H NMR, XRD, and XPS indicated that the phosphotungstic anion (PW12O403-) was successfully modified by the organic precursor MIMPS. And TG-DTA and Py-IR results illustrated that the catalyst possessed good thermal stability and Brønsted acidity. Furthermore, the activity evaluation experiment of the catalyst confirmed that the introduced SO3H group of the cation part and the active component tungsten of the anion part were the key to the activity of the IL catalyst. More importantly, the synergistic effect between SO3H group and the active component tungstencatalyst leading to a superior catalytic performance such as cyclohexanone conversion attained 93.51 % and the yield and selectivity of ε-CL that were up to 93.26 % and 99.73 % under the optimum conditions. Finally, the kinetic process of the BV reaction was appropriately described by the second-order reversible reaction kinetics model and the calculated results were also in good agreement with the experimental datas.

Noise-to-state exponentially stabilizing (state, input)-disturbed CSTRs with non-vanishing noise

In this paper, we have proposed a (state, input)-disturbed CSTR (sidCSTR) model that considers unknown but bounded fluctuations in kinetics, flow rates, and heat exchange. A feedback control law is developed that stabilizes the sidCSTR system to reach noise-to-state exponential stability (NSES). The lower bound of the distribution for the state of the NSES sidCSTR system is analyzed both from the probability domain and the time domain. The performance and the validity of the proposed method are demonstrated using a case study dealing with a second-order reversible reaction.

Kinetics and Transesterification of the Oil Obtained from Cussonia bateri (Jansa Seed) as a Step in Biodiesel Production Using Natural Heterogeneous Catalyst

The ongoing search for a more sustainable, renewable, and affordable fuel source has necessitated the quest and search for a better diesel. Biodiesel, an environmentally friendly diesel, has been able to solve many of the issues that have arisen as a result of the use of fossil fuels. They are mostly synthesized by transesterification of a FFA with an alcohol employing an appropriate catalyst. This study examines the use of jansa seed oil as a low-cost feedstock for biodiesel production. Transesterification of free fatty acids (FFA) with methanol and ethanol catalyzed by snail shell was used to process the biodiesel. In the biodiesel production, the alcohol to oil molar ratio was 12:1, the catalyst amount was 0.75 g, and the reaction temperature was 65°C. The reversible second-order reaction rate was used to characterize the kinetics of FFA transesterification. Kinetic modeling of the biodiesel production process was also carried out in order to determine the sequence of the reaction and estimate the reaction rate constant. The activation energy of the ethyl ester was higher than that of the methyl ester, implying that the ethyl ester would require more energy (slower reaction rate) to activate a molecule for chemical transformation. The reusability of the catalyst for continuous transesterfication runs was investigated under the same operating conditions, and the conversion of the catalyst declined from 99.6 percent to 86.4 percent after the fifth regeneration cycle. Jansa seed oil has the potential to be a valuable raw source for generating fatty oil for the use as an alternate feedstock in the production of biodiesel.

Intensification of Processes for the Production of Ethyl Levulinate Using AlCl3·6H2O

A process for obtaining ethyl levulinate through the direct esterification of levulinic acid and ethanol using AlCl3·6H2O as a catalyst was investigated. AlCl3·6H2O was very active in promoting the reaction and, the correspondent kinetic and thermodynamic data were determined. The reaction followed a homogeneous second-order reversible reaction model: in the temperature range of 318–348 K, Ea was 56.3 kJ·K−1·mol−1, whereas Keq was in the field 2.37–3.31. The activity of AlCl3·6H2O was comparable to that of conventional mineral acids. Besides, AlCl3·6H2O also induced a separation of phases in which ethyl levulinate resulted mainly (>98 wt%) dissolved into the organic upper layer, well separated by most of the co-formed water, which decanted in the bottom. The catalyst resulted wholly dissolved into the aqueous phase (>95 wt%), allowing at the end of a reaction cycle, complete recovery, and possible reuse for several runs. With the increase of the AlCl3·6H2O content (from 1 to 5 mol%), the reaction proceeded fast, and the phases’ separation improved. Such a behavior eventually results in an intensification of processes of reaction and separation of products and catalyst in a single step. The use of AlCl3·6H2O leads to a significant reduction of energy consumed for the final achievement of ethyl levulinate, and a simplification of line-processes can be achieved.

Kinetics and Transesterification of the Oil Obtained from <i>Cussonia bateri</i> (Jansa Seed) as a Step in Biodiesel Production Using Natural Heterogeneous Catalyst

The ongoing search for a more sustainable, renewable, and affordable fuel source has necessitated the quest and search for a better diesel. Biodiesel, an environmentally friendly diesel, has been able to solve many of the issues that have arisen as a result of the use of fossil fuels. They are mostly synthesized by transesterification of a FFA with an alcohol employing an appropriate catalyst. This study examines the use of jansa seed oil as a low-cost feedstock for biodiesel production. Transesterification of free fatty acids (FFA) with methanol and ethanol catalyzed by snail shell was used to process the biodiesel. In the biodiesel production, the alcohol to oil molar ratio was 12:1, the catalyst amount was 0.75 g, and the reaction temperature was 65°C. The reversible second-order reaction rate was used to characterize the kinetics of FFA transesterification. Kinetic modeling of the biodiesel production process was also carried out in order to determine the sequence of the reaction and estimate the reaction rate constant. The activation energy of the ethyl ester was higher than that of the methyl ester, implying that the ethyl ester would require more energy (slower reaction rate) to activate a molecule for chemical transformation. The reusability of the catalyst for continuous transesterfication runs was investigated under the same operating conditions, and the conversion of the catalyst declined from 99.6 percent to 86.4 percent after the fifth regeneration cycle. Jansa seed oil has the potential to be a valuable raw source for generating fatty oil for the use as an alternate feedstock in the production of biodiesel.

Glycerolysis of free fatty acid in vegetable oil deodorizer distillate catalyzed by phosphonium-based deep eutectic solvent

Abstract Esterification of free fatty acids in a low-grade oil with glycerol, the by-product of transesterification, has been proposed as one possible method to reduce the cost of raw materials for biodiesel production. The glycerolysis reaction recycles the byproduct glycerol to create a much more efficient and cost-effective process. However, the glycerolysis reaction involves challenges, including its requirement of high temperature. This study is the first to apply the deep eutectic solvent (DES) as a catalyst for glycerolysis reaction to convert free fatty acid (FFA) in vegetable oil deodorizer distillate (VODD) being a waste product from the oil refining process into glycerides. The effects of temperature, catalyst dosage, and time on the esterification efficiency of fatty acid conversion were explored. The reaction progress and product solubility were studied by FT-IR and GC. The results revealed that the reaction reached equilibrium at an approximate free fatty acid (FFA) conversion of 90%. The reaction was a second-order reversible reaction, using 8 wt% catalyst loading lowered activation energy to 58.80 J/mol. The optimum condition was determined as 160 °C, 5 wt% DES loading, and 10 min reaction time.

Kinetics and thermodynamics of synthesis of palm oil-based trimethylolpropane triester using microwave irradiation

Enhancement of reaction performance utilizing microwave irradiation has drawn so much interest due to its shorter reaction time and low catalyst loading. These advantages are particularly significant from kinetics and thermodynamics perspectives. This study aimed to investigate the kinetics and thermodynamics of microwave-assisted transesterification of palm oil-based methyl ester into biolubricant. The transesterification reaction of palm oil methyl ester (PME) and trimethylolpropane (TMP) was conducted at 110–130 °C for 90 min under vacuum condition. Sodium methoxide was employed as the catalyst at 0.6 wt% of reactants fixed at molar ratio of 4:1 (PME: TMP). The experimental data were fitted with the second-order reversible reaction kinetics mechanisms. The data were solved via Runge-Kutta 4,5 order using MATLAB software. Analysis on the data revealed that the reaction rate constants at temperatures of 110–140 ℃ were in the range of 0.01–0.63 [(w/w)(min)]−1, with standard errors of 0.0026–0.0228 within 99.99% prediction interval. Microwave-assisted reaction obtained 17.0 kcal/mol of activation energy. This method reduced activation energy by 49% as compared to the conventional heating. Activation energy and time-periodic energy assessment showed that the reaction was endothermic. The reaction at 130 °C is the easiest to activate. The positive Gibbs free energy (ΔG > 0) found using Eyring-Polanyi equation indicated that the transesterification was non-spontaneous and endergonic.

Channel Capacity Analysis of a Comprehensive Absorbing Receiver for Molecular Communication via Diffusion

As a promising communication paradigm, Molecular Communication (MC) has been developing for more than ten years. During this period, with the continually development and mature of molecular channel, more and more factors from the actual molecular environment are taken into account to model the molecular channel more precisely. Due to the fact that chemical reactions are common and crucial in molecular communication environment, this paper investigates the impacts of various reaction rates on the channel modeling and channel capacity of MC. First, a detailed molecular system model is presented with a first-order degradation reaction in the channel and a second-order reversible reaction at the receiver side. Because of the Inter-Symbol Interference (ISI) induced by the stochastic nature of molecule motions, we propose an approximation method with low complexity to describe the received molecule signal with an arbitrary length of ISI. Based on the noisy molecular signal, closed-form expressions for probabilities of detection and false alarm are derived. The performance of channel capacity is evaluated concentrating on different circumstances with decoupled reaction rates and two prevalent modulation techniques (BCSK and MoSK) are implemented to ensure the accuracy and scientific of the conclusion. Numerical results show that the channel capacity could be enhanced significantly by selecting proper messenger molecules with desirable reaction rates in specific molecular channel.

Modeling of Ligand-Receptor Protein Interaction in Biodegradable Spherical Bounded Biological Micro-Environments

In this paper, we propose a generalized model for the Ligand-Receptor protein interaction in 3-D spherically bounded, diffusive biological microenvironments using molecular communication paradigm. Modeling a targeted cell as a receiver nano-machine, we derive analytical expressions for the Green’s function as well as for the expected number of the activated receptors. The molecular degradation in the environment due to enzymatic effects and the changes in pH levels are included via the first-order degradation reaction mechanism. A second-order reversible reaction mechanism is employed to model the reception process that involve the reaction of ligands to activate the receptor proteins lying on the receiver surface to form ligand-receptor complexes. We also present a particle-based simulator that incorporates the reversible reaction of molecules with the receptors present on the surface of a receiver that is located inside a bounded, 3-D microfluidic environment. Our simulations also include molecular degradation and boundary absorption of the ligands due to collision. The simulation results show perfect agreement with the results obtained from the analytical, bounded, and 3-D spherical model of the medium. The proposed models can be used for accurate prediction of the drug concentration profiles and number of activated receptors at any targeted cell.

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.

A transformation theory of stochastic evolution in Red Moon methodology to time evolution of chemical reaction process in the full atomistic system.

Atomistic information of a whole chemical reaction system, e.g., instantaneous microscopic molecular structures and orientations, offers important and deeper insight into clearly understanding unknown chemical phenomena. In accordance with the progress of a number of simultaneous chemical reactions, the Red Moon method (a hybrid Monte Carlo/molecular dynamics reaction method) is capable of simulating atomistically the chemical reaction process from an initial state to the final one of complex chemical reaction systems. In the present study, we have proposed a transformation theory to interpret the chemical reaction process of the Red Moon methodology as the time evolution process in harmony with the chemical kinetics. For the demonstration of the theory, we have chosen the gas reaction system in which the reversible second-order reaction H2 + I2 ⇌ 2HI occurs. First, the chemical reaction process was simulated from the initial configurational arrangement containing a number of H2 and I2 molecules, each at 300 K, 500 K, and 700 K. To reproduce the chemical equilibrium for the system, the collision frequencies for the reactions were taken into consideration in the theoretical treatment. As a result, the calculated equilibrium concentrations [H2]eq and equilibrium constants Keq at all the temperatures were in good agreement with their corresponding experimental values. Further, we applied the theoretical treatment for the time transformation to the system and have shown that the calculated half-life τ's of [H2] reproduce very well the analytical ones at all the temperatures. It is, therefore, concluded that the application of the present theoretical treatment with the Red Moon method makes it possible to analyze reasonably the time evolution of complex chemical reaction systems to chemical equilibrium at the atomistic level.

Kinetic, thermodynamic, optimization and reusability studies for the enzymatic synthesis of a saturated wax ester

Cetyl decanoate was synthesized by esterification reaction catalyzed by immobilized lipase from Thermomyces lanuginosus (TLL) via physical adsorption on poly-(styrene-divinylbenzene) resin (PSty–DVB). The effect of relevant factors on the ester synthesis was evaluated. In this study, a second-order reversible reaction kinetic model was proposed in order to estimate apparent kinetic constants and good agreement with experimental data was observed (0.9430≤R2≤0.9938). The reaction was found to be a spontaneous and endothermic process. The biocatalyst prepared with initial protein loading of 115mg/g of support (immobilized protein concentration of 108.7±3.1mg/g) yielded the highest initial reaction rate (113.5mM/min of reaction), then selected for subsequent tests. The reaction in heptane medium required a slight excess of cetyl alcohol (molar ratio acid:alcohol of 1:1.25) and 7.5% m/m of biocatalyst to attain a maximum conversion of 92.5% for 30min of reaction. In a solvent-free system, maximum conversion of 85.4% was observed for 50min of reaction conducted in an equimolar ratio acid:alcohol and 10% m/m of biocatalyst. The productivity for the reaction performed in heptane medium was higher than in a solvent-free system – 68.5 and 56.4mM/ming of biocatalyst, respectively. The prepared biocatalyst was more active than commercial biocatalysts such as IMMTLL–T2–150 and Lipozyme TL–IM that exhibited maximum conversion around 92% for 45 and 75min of reaction, respectively. The biocatalyst could be reused at least eight times without significant decrease of its activity.

Characterization and kinetic study of Diels-Alder reaction: Detailed study on N-phenylmaleimide and furan based benzoxazine with potential self-healing application

The Diels-Alder reaction between N-phenylmaleimide and benzoxazine bearing furan group was investigated for the purpose of successful appliance of self-healing in benzoxazine polymer networks. The reaction as a function of temper- ature/time was performed in molten state and in a solution, where also the kinetic study was performed. The Diels-Alder reaction leads to a mixture of two diastereomers: endo presented at lower cyclo-reversion temperature and exo at higher. Therefore, the conversion rates and exo/endo ratio were studied in detail for both systems. For instance, in molten state the Diels-Alder reaction was triggered by the temperature of the melting point at 60 °C with exo/endo ratio preferable to the endo adduct. The study of the kinetics in a solution revealed that the Diels-Alder reaction followed typical bimolecular reversible second-order reaction. The activation energies were close to the previous literature data; 48.4 and 51.9 kJ·mol -1 for Diels-Alder reaction, and 91.0 and 102.3 kJ·mol -1 for retro-Diels-Alder reaction, in acetonitrile and chloroform, respec- tively. The reaction equilibrium in a solution is much more affected by the retro-Diels-Alder reaction than in a molten state. This study shows detailed investigation of DA reaction and provides beneficial knowledge for further use in self-healing polymer networks.

Transesterification of Castor Oil with Methanol – Kinetic Modelling

Abstract In this research work, transesterification of castor oil with methanol and sulphuric acid catalyst has been carried out in a lab reactor of capacity 500 mL at various operating conditions (reaction temperature=35–65°C, pressure=1 atm, methanol/oil ratio=6:1 and 600 rpm). The effect of reaction temperature is considered, followed by the determination of kinetics of the production of biodiesel. Experimental results have been analysed with respect to three types of reaction kinetics, namely first-order irreversible reaction, second-order irreversible reaction and reversible reaction. For each of the schemes, the activation energy and Arrhenius constants were determined. The experimental data fits very well to second-order reversible reaction kinetics. Properties of fatty acid methyl ester (biodiesel) produced from castor oil have been experimentally determined and compared with standard values as given in EN 14214 norms.

The effect of tetrahydrofuran on the base-catalyzed sunflower oil methanolysis in a continuous reciprocating plate reactor

The homogeneous base-catalyzed methanolysis of sunflower oil in the presence and absence of tetrahydrofuran (THF) as a co-solvent was studied in a continuous cocurrent upflow reciprocating plate reactor (RPR). The measurements of the dispersed phase drop size demonstrated the effects of the THF concentration on the Sauter-mean drop diameter and the drop size distribution in both non-reactive (methanol/oil) and reactive (methanol/KOH/oil) systems. The presence of THF shifted both heterogeneous systems to the stable homogeneous emulsion consisted of small dispersed phase drops. The triacylglycerol (TAG) conversion degree was measured in the reactive system. The sigmoidal kinetics was observed in the absence and presence of THF at lower THF concentrations (≤10% of the oil mass). This shape was explained by the existence of the initial TAG mass transfer controlled region followed by the irreversible second-order reaction controlled region. However, at the highest THF concentration (30% of the oil mass) the irreversible and reversible second-order reaction kinetics was used to describe the variation of TAG conversion degree with time. The proposed kinetic models satisfactorily fitted the experimental data.

Kinetics of esterification of acetic acid with 1-octanol in the presence of Amberlyst 36

Kinetic data on the esterification of acetic acid with 1-octanol were obtained from both uncatalyzed and heterogeneously catalyzed reactions using a stirred batch reactor in toluene. The equilibrium constant, Kc, which is independent of temperature ranging from 333 to 358K, was found to be 60.7. The uncatalyzed reaction was proved to be a second-order reversible reaction. In the presence of Amberlyst 36, the reaction was found to follow the Eley–Rideal mechanism, and the surface reaction is a rate-limiting step. From this model, the reaction rate can be given by the expression:−rA=k(m/V)(CACB−(CECW/KC))(1+KACA+KWCW).The temperature dependencies of the constants appearing in the rate expressions were also calculated to be:k (L2/g dry resin⋅mol⋅min)=exp1.07−2991T,KA(L/mol)=exp12954T−38.28, andKW(L/mol)=exp25427T−76.15,where T is the absolute temperature in Kelvin.

A Study on Transreactions of PET/PEN Reactive Blending in a Twin-Screw Extruder Using an Axial Dispersion Model

Transreactions of PET and PEN melt-mixed in a twin-screw extruder are investigated. The extruder is modeled and characterized in the frame of a tubular system of closed type. The kinetic modeling is based on a modified second-order reversible reaction equation, which allows the dispersion equation to be solved analytically. The analysis shows a good agreement between the model and experiment. The axial dispersion model is employed to predict the extent of transesterification reactions (X) and degree of randomness (RD). 1 H NMR measurements are performed to estimate X and RD. Theoretical and experimental data are in good agreement. The model can thus be exploited to describe the effects of processing parameters, mixing time, mixing temperature, and blend composition on X and RD.

Kinetics of Ethyl Acetate Synthesis Catalyzed by Acidic Resins

A low-cost experiment to carry out the second-order reversible reaction of acetic acid esterification with ethanol to produce ethyl acetate is presented to illustrate concepts of kinetics and reactor modeling. The reaction is performed in a batch reactor, and the acetic acid concentration is measured by acid–base titration versus time. The experimental data are used to optimize the specific rate constant of the direct reaction, which is the unique parameter of the model; the rate constant for the inverse reaction is expressed in terms of the equilibrium constant. Good representations are generally obtained: the absolute average relative deviation found in this work is only 2.86%. After the experiment, students may carry out simulations for distinct operating conditions. The experimental data for short times are also analyzed approximately by using the classical approach for irreversible second-order reactions.