Pseudo-homogeneous Reaction Research Articles

Heterogeneous nitration of nitrobenzene in microreactors: Process optimization and modelling

Aromatic nitration with mixed acid is an important step in the industrial synthesis of basic industrial chemicals, while the highly exothermic and heterogeneous nature of the reaction renders difficulties in achieving high safety and efficiency. In this work, a continuous flow microreactor system was developed for the nitration of nitrobenzene. Under the premise of high conversion and selectivity, the reaction time and temperature were reduced from more than 2 h and 80 ℃ in industrial operation to 10 min and 65 ℃ in microreactors, respectively. The reaction mechanism was verified that the reaction took place not only in the bulk aqueous phase but also at the phase interface. The kinetic parameters were then determined based on the assumption of pseudo-homogeneous reaction mixture. These findings may shed important insights into the high degree of controllability of nitration for a better process design and reactor optimization.

Pectooligosaccharides rich in galacturonic acid produced from Orange Processing Waste by autohydrolysis: Process optimization and kinetic analysis

Pectooligosaccharides (POS) are notorious for their prebiotics and elicitor activities. In this work, we have optimized the autohydrolysis of Orange Processing Waste (OPW) to obtain POS fractions via a Taguchi approach, maximizing homogalacturonan oligosaccharides yield by considering several process variables: particle diameter, stirring speed, liquid-solid ratio and time, determining that only time had a significant effect in the studied range. 19.38 % w/w POS yield from OPW was obtained in optima conditions. After ensuring no limitation due to mass transfer, the kinetic analysis assumed that homogalacturonan was converted into high, medium and low molecular weight oligosaccharides, and galacturonic acid. Moreover, we considered that there is one pseudo-homogeneous reaction type combined with three irreversible, elemental, of pseudo first global order (first order with respect to the reagent which is hydrolysed) reactions in series. The model successfully reproduced experimental data at constant temperature (150 °C–180 °C) and pH (3.73).

Nickel recovery from precipitate of NCA lithium-ion battery leach liquor by using disodium ethylene diamine tetraacetate

The nickel cobalt aluminium oxides (NCA) type Li-ion battery is a type of battery currently used in electric vehicles. The UGM battery team has recycled this type of battery to obtain high purity lithium metal. Aside from lithium, the NCA battery contains high-value metals, nickel is one of them. This experiment aims to test the ease of nickel to chelate with disodium ethylene diamine tetraacetate (EDTA). The experiment was carried out by means of a triple neck flask for 4 hours. The samples were taken at certain minutes and then fitted using a pseudo homogeneous first-order reaction equation. The chelate formed was further processed through multilevel precipitation or electrodialysis to separate nickel. Based on the experiment, nickel formed chelates optimally at 60°C using 0.086 M EDTA with the reaction constant for nickel being 1.4819 min−1. The Arrhenius constant and activation energy for nickel were 3.48×1011min−1 and 76,907 J/mole, respectively.

Developing Brønsted–Lewis acids bifunctionalized ionic liquids based heteropolyacid hybrid as high-efficient solid acids in esterification and biomass conversion

A class of Brønsted–Lewis acid bifunctionalized ionic liquids based heteropolyacid hybrid (BLA-ILs-HPA) solid acids were developed by combining the double sulfonic groups grafted, ionic liquids based heteropolyacid hybrid with Lewis acidic centers (M = Zn, Co, Fe, Ni, Cu). The prepared BLA-ILs-HPA show both Brønsted and Lewis acidic sites with extremely-high acid strength and enhanced stabilities, as determined by FT-IR, Py-IR, TG, XPS and 31P solid state NMR results. BLA-ILs-HPA were successfully applied in esterification camphene with acetic acid to produce isobornyl acetate, and dehydration of glucose to produce 5-hydrozymethylfural. BLA-ILs-HPA show enhanced catalytic activities in comparison with various acid catalysts. The effects of reaction temperatures, initial reactant molar ratio, catalyst dosage, and reaction time were studied in detail. The optimal reaction conditions were obtained, and the experimental data was successfully correlated by a pseudohomogeneous (PH) reaction kinetic model in the temperature range of 313.15–333.15 K. The calculated values obtained by the reaction kinetic model were in good agreement with the experimental data. Moreover, as a heterogeneous reaction catalyst, BLA-ILs-HPA can be recovered by simple treatment. After six times cycling, the decreasing in the catalytic activity of BLA-ILs-HPA could not be observed significantly, suggesting their good reusability.

Utilisation of biomass wastes based activated carbon supported heterogeneous acid catalyst for biodiesel production

Abstract This study evaluated the utilisation of biomass wastes as catalyst supports by comparing the catalytic performance of papaya seed, empty fruit bunch (EFB) and corncob biomass waste derived carbon based acid catalysts applied for biodiesel production through esterification reaction of palm fatty acid distillate (PFAD) and methanol. Arylation of 4-benzenediazonium sulfonate synthesis method was able to sulfonate the catalyst support efficiently. The activated carbon (AC) synthesised possessed high porosity with surface area ranged between 639.68 and 972.66 m2/g. The effect of catalyst synthesising condition including carbonisation temperature (600–1000 °C), sulfonation time (0.5–2.5 h) and sulfanilic acid to AC weight ratio (3:1–13:1) towards the FAME yield and free fatty acid (FFA) conversion were evaluated. At the optimum catalyst synthesis conditions, corncob waste derived sulfonated AC catalyst exhibited the highest FAME yield and FFA conversion of 72.09% and 93.49%, respectively. Reusability study showed that corncob waste derived sulfonated AC catalyst was able to achieve relatively high FAME yield at the first two reaction cycles. The esterification reaction followed the irreversible pseudo-homogeneous reaction model. The high catalytic efficiency of the catalyst had shown its high potential to fit into the cost-effective and sustainable framework for biodiesel production.

Babassu activated carbon as catalyst for chalcone production by Claisen–Schmidt reaction: kinetic study, mechanism proposal and continuous flow bed reactor

Powdered and granulated activated carbons from babassu were submitted to alkaline treatment with 2 mol L–1 NaOH solution, washed with distilled water to pH 8 and dried. The prepared carbons were tested as catalysts in the Claisen–Schmidt reaction between acetophenone and 4-nitrobenzaldehyde using methanol as solvent at room temperature for 24 h. Babassu granular carbon (BGC) and basic babassu granular carbon (BBGC) exhibited the highest conversions, of 69.26% and 66.59%, respectively. The kinetic study was carried out with BBGC, which led to values of kinetic constant k of 5.26 L mol–1 h–1 at 35 °C and 7.35 L mol–1 h–1 at 50 °C. The activation energy of the reaction was 18.91 kJ mol–1. This study proposes a second-order pseudo-homogeneous reaction catalyzed by BBGC. A continuous fixed-bed reactor operation was carried out with BBGC catalyst and the best conversion was 60% in 120 min using of 0.05 mol L–1 reactants concentration.

The Conversion Kinetics of Tincal to Boric Acid in Nitric Acid Solutions

Pure borax and various boron compounds are produced from the solutions in which tincal is dissolved with various reagents. Economically important boron compounds such as boric acid, borax, boric oxide, and refined hydrated sodium borates and perborates are produced from boron-containing ores. The production of boric acid by using nitric acid from tincal is more advantageous because it evaluates by-product NaNO3 as fertilizer production. In this study, the conversion kinetics of tincal to boric acid in nitric acid solutions were investigated by such parameters as particle size, 300-1500 µm; acid concentration,0.5-4 mol/L; solid-to-liquid ratio 0.04-0.10 g/mL; stirring speed 20.93-62.8 s-1, and reaction temperature, 30-60 oC. The conversion was found to increase with decreasing particle size and solid-to-liquid ratio and while it increased with increasing reaction temperature, acid concentration, and stirring speed. The conversion kinetics was examined using the heterogeneous and pseudo-homogeneous reaction models. The experimental results were found to be in better agreement with the correlation given in the following equation and the activation energy being 37.5 kJ/mol.

Autocatalytic Fractionation of Wood Hemicelluloses: Modeling of Multistage Operation

Eucalyptus globulus wood samples were treated with hot, compressed water (autohydrolysis) in consecutive stages under non-isothermal conditions in order to convert the hemicellulose fraction into soluble compounds through reactions catalyzed by in situ generated acids. The first stage was a conventional autohydrolysis, and liquid phase obtained under conditions leading to an optimal recovery of soluble saccharides was employed in a new reaction (second crossflow stage) using a fresh wood lot, in order to increase the concentrations of soluble saccharides. In the third crossflow stage, the best liquid phase from the second stage was employed to solubilize the hemicelluloses from a fresh wood lot. The concentration profiles determined for the soluble saccharides, acids, and furans present in the liquid phases from the diverse crossflow stages were employed for kinetic modeling, based on pseudohomogeneous reactions and Arrhenius-type dependence of the kinetic coefficients on temperature. Additional characterization of the reaction products by High Pressure Size Exclusion Chromatography, High Performance Anion Exchange Chromatography with Pulsed Amperometric Detection, and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry provided further insight on the properties of the soluble saccharides present in the various reaction media.

Interface tuning of Cu+/Cu0 by zirconia for dimethyl oxalate hydrogenation to ethylene glycol over Cu/SiO2 catalyst

An efficient ZrO2–doped Cu/SiO2 catalyst was fabricated through hydrolysis precipitation method (HP) and used to produce ethylene glycol (EG) through dimethyl oxalate (DMO) hydrogenation. The states for zirconia on copper catalyst and roles in DMO hydrogenation were investigated through various characterization tools, including N2 physical adsorption, XRD, H2–TPR, Methyl glycolate–TPD–MS, XPS, XAES as well. Compared with common ammonia evaporation and co–precipitation methods used in catalyst preparation, this HP method is found to effectively suppress the agglomeration and further size growth of copper nanoparticles by enhancing the interactions between copper and zirconia species. More importantly, uniform distribution of ZrO2 dopant is achieved due to the pseudo-homogeneous reactions in the mixing step of catalyst preparation. A proper amount of zirconium dopant helps achieve the desirable proportion of Cu+/(Cu++Cu0) for surface copper species, especially promotes the production of Cu+ species originated from Cu–ZrO2 species at the interface of copper and zirconia particles. In comparison with Cu+ species formed from copper phyllosilicates reduction, the Cu+ sites derived from Cu–ZrO2 species show higher adsorption ability of MG, an important intermediate species in ethylene glycol production. These adsorbed MG molecules further react with atomic hydrogen shifted from adjacent metallic copper surface, leading to a higher catalytic behavior. For the EG production via DMO hydrogenation, the turnover frequency (TOF) normalized by Cu0 species on CuZr/SiO2 catalyst is 1.8 times than that of traditional Cu/SiO2 counterpart. Due to the enhanced synergy effect between Cu+ and Cu0 active sites, a lower activation energy of ester hydrogenation on this ZrO2–doped Cu/SiO2 catalyst is believed to be responsible for the significant improvement.

Dissolution of Tunisian phosphate ore by a mixture of sulfuric and phosphoric acid: Kinetics study by means of differential reaction calorimetry

A mixture of phosphoric and sulfuric acid was used to investigate the dissolution kinetics of phosphate ore by Differential Reaction Calorimetry (DRC). The effect of the solid-to-iquid ratio, concentration, stirring speed, particle size and temperature of the reaction is examined. It was established that the dissolution rate increased with stirring speed and particle size. However, rising the olid-to-iquid ratio, temperature and concentration decreased the dissolution rate. It was determined that the dissolution rate fits in the first order of the pseudo-homogeneous reaction model. Two negative values of apparent activation energies were found in the range of 25 to 60?C. The experimental data were tested by graphical and statistical methods and it was found that the following models were best fitted for the experimental data and an empirical equation for the process was developed. -ln (1 ? x) = [2,2 E-09((S/L)0.75C -0.461G0.447(SS) 0.471exp (2671/T)]t. T? 40?C -ln (1 ? x) = [2,2 E-09((S/L)0.75C -0.461G0.447(SS) 0.471exp (6959/T)]t. T > 45?C

Dissolution kinetics of borogypsum in di-ammonium hydrogen phosphate solutions

This work examines the dissolution kinetics of borogypsum in di-ammonium hydrogen phosphate solutions ((NH4)2PO4) in a batch reactor. The parameters selected were the reaction temperature (15–53 °C), di-ammonium hydrogen phosphate concentration (1–4 M), stirring speed (50–800 rpm), and solid/liquid ratio (1/50–1/5). The dissolution rate increased by increasing the temperature (from 0.32 to 0.82), di-ammonium hydrogen phosphate concentration (from 0.35 to 0.821), and by decreasing solid-to-liquid ratio (from 0.77 to 0.24). The dissolution rate increased up to stirring speed of 600 rpm (from 0.135 to 0.56), and then decreased with increasing stirring speed (from 0.56 to 0.351). The dissolution rate was described by first-order pseudo-homogeneous reaction model. The activation energy of this study was calculated as 42.103 kJ mol−1. A kinetics model including the used parameters in this study was suggested as follows:−ln(1−X)=223.63C0.911(S/L)−0.7689W0.6212e(−5064.2/T)t

An Effective CuZn–SiO2 Bimetallic Catalyst Prepared by Hydrolysis Precipitation Method for the Hydrogenation of Methyl Acetate to Ethanol

A highly active CuZn–SiO2 catalyst with excellent stability in hydrogenation of methyl acetate (MA) was fabricated by the hydrolysis precipitation (HP) method. The HP method caused notable high dispersion of both copper and zinc species due to the strong interaction between metal species and silica support caused by the pseudo-homogeneous reaction during the mixing process. According to the linear correlation between the TOF (Cu+) and Zn/Cu ratio, the Cu+ was considered the predominant active site, and the Cu+ site derived from the strong interaction between copper and zinc species has higher activity than those Cu+ species generated from copper phyllosilicate. Compared to the CuZnO/Al2O3 and Cu–SiO2 catalysts, the Cu9Zn1–SiO2 catalyst displayed the highest catalytic activity on account of the high dispersion of active species and the enhanced ability of Cu+ species on ester adsorption by stronger Cu-ZnO interaction.

Modeling and simulation of batch kinetics of non-edible karanja oil for biodiesel production: A mass transfer study

Alcoholysis reaction for non-edible karanja vegetable oil is investigated in the presence of potassium hydroxide catalyst. The mass transfer and chemical kinetics studies were conducted in a batch reactor together with the effect of temperature on overall reaction kinetics at optimized molar ratio of oil to methanol (1:6) and 1% catalyst weight at a mixing speed of 600rpm. The overall karanja alcoholysis reaction is modeled based on three control mechanisms, an initial mass transfer regime followed by irreversible pseudo second order and finally a reversible second order equilibrium reaction. A higher mass transfer resistance was observed as compared to that of edible oils (sunflower and rapeseed) which was attributed to the presence of impurities, especially gums that alter the fundamental physical properties of the oil. At high temperatures equilibrium reaction rate is more dominant than the irreversible pseudo homogeneous reaction, thereby making the alcoholysis reaction initially irreversible reaction controlled. The study establishes that time and temperature are the main parameters influencing the mass transfer and reaction rate, with the volumetric mass transfer coefficients as 51×10−3, 135×10−3 and 334×10−3min−1 at temperatures of 35°C, 45°C and 55°C respectively. The results are subsequently used to predict the mass transfer effect at lower temperatures and higher scale of operation as a function of mixing speed.

INVESTIGATION OF KINETICS AND MECHANISM OF PRICEITE LEACHING IN SULPHURIC ACID SOLUTIONS

The leaching kinetics and mechanism of priceite having the formula of 4CaO5B2O37H2O was investigated in sulphuric acid solutions. For the dissolution process, the effects of reaction temperature, sulphuric acid solution concentration, solid/liquid ratio, particle size, and stirring speed were investigated as effective parameters for the experiments. The experimental data indicated that the dissolution rate increased with the increasing reaction temperature, the decreasing particle size, and the solid/liquid ratio. The conversion rate increased up to 1.0 mol/dm 3 with the increasing acid concentration, and then decreased with the increasing acid concentration over concentrations of 1 mol/dm 3 . It was also determined that the stirring speed had no significant effect on the dissolution rate. The dissolution process of priceite in sulphuric acid solution was tested with regard to heterogeneous and homogeneous reaction models, and it was found that the dissolution rate was controlled by first order pseudo-homogeneous reaction model. The activation energy of the dissolution process was determined as 26.07 kJmol -1 . The results were evaluated graphically and statistically. The experimental data were found to fit well with the mathematical model.

Modeling of a membrane reactor system for crude palm oil transesterification. Part I: Chemical and phase equilibrium

Using a membrane reactor for reversible transesterification reaction involves reaction and product separation within a single unit. However, a pseudohomogeneous reaction and heterogeneous separation must be maintained for successful membrane reactor operation. Present research is aimed to develop an integrated model of chemical and phase equilibrium (CPE) and modified Maxwell–Stefan equation that describes the simultaneous CPE and mass transport phenomena of biodiesel production from crude palm oil (CPO) using a membrane reactor. In the first part of this work, a systematic approach describing simultaneous CPE of CPO transesterification in the membrane reactor was developed with the reconciliation of transesterification reaction and phase equilibrium that involves six‐component. The results revealed that regressed apparent equilibrium constant, value of 17.557 1.51% were higher than the literatures. This indicates that forward reaction of the reversible CPO transesterification is much favored in the membrane reactor than the conventional reactor. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1968–1980, 2015

Detection of rabbit IgG by using functional magnetic particles and an enzyme-conjugated antibody with a homemade magnetic microplate.

BackgroundThe enzyme-linked immunosorbent assay (ELISA) has been used for diagnosing medical and plant pathologies. In addition, it is used for quality-control evaluations in various industries. The ELISA is the simplest method for obtaining excellent results; however, it is time consuming because the immunoreagents interact only on the contact surfaces. Antibody-labeled magnetic particles can be dispersed in a solution to yield a pseudohomogeneous reaction with antigens which improved the efficiency of immunoreaction, and can be easily separated from the unreactive substances by applying a magnetic force. We used a homemade magnetic microplate, functional magnetic particles (MPs) and enzyme-labeled secondary antibody to perform the sandwich ELISA successfully.ResultsUsing antibody-labeled MPs enabled reducing the analysis time to one-third of that required in using a conventional ELISA. The secondary antibody conjugated with horseradish peroxidase (HRP) was affinity-bound to the analyte (IgG in this study). The calibration curve was established according to the measured absorbance of the 3, 3′, 5, 5′-tetramethybezidine–HRP reaction products versus the concentrations of standard IgG. The linear range of IgG detection was 114 ng/mL–3.5 ng/mL. The limit of detection (LOD) of IgG was 3.4 ng/mL. The recovery and coefficient of variation were 100% (±7%) and 116% (±4%) for the spiked concentrations of 56.8 ng/mL and 14.2 ng/mL, respectively.ConclusionPseudohomogeneous reactions can be performed using functional MPs and a magnetic microplate. Using antibody-labeled MPs, the analysis time can be reduced to one-third of that required in using a conventional ELISA. The substrate–enzyme reaction products can be easily transferred to another microplate, and their absorbance can be measured without interference by light scattering caused by magnetic microbeads. This method demonstrates great potential for detecting other biomarkers and in biochemical applications.Graphical A magnetic ELISA with convenient magnetic microplate.Electronic supplementary materialThe online version of this article (doi:10.1186/s13065-015-0088-1) contains supplementary material, which is available to authorized users.

Ultrasensitive detection of DNA and RNA based on enzyme-free click chemical ligation chain reaction on dispersed gold nanoparticles.

An ultrasensitive colorimetric DNA and RNA assay using a combination of enzyme-free click chemical ligation chain reaction (CCLCR) on dispersed gold nanoparticles (GNPs) and a magnetic separation process has been developed. The click chemical ligation between an azide-containing probe DNA-modified GNP and a dibenzocyclooctyne-containing probe biotinyl DNA occurred through hybridization with target DNA (RNA) to form the biotinyl-ligated GNPs (ligated products). Eventually, both the biotinyl-ligated GNPs and target DNA (RNA) were amplified exponentially using thermal cycling. After separation of the biotinyl-ligated GNPs using streptavidin-modified magnetic beads, the change in intensity of the surface plasmon band at 525 nm in the supernatants was observed by UV/vis measurement and was also evident visually. The CCLCR assay provides ultrasensitive detection (50 zM: several copies) of target DNA that is comparable to PCR-based approaches. Note that target RNA could also be detected with similar sensitivity without the need for reverse transcription to the corresponding cDNA. The amplification efficiency of the CCLCR assay was as high as 82% due to the pseudohomogeneous reaction behavior of CCLCR on dispersed GNPs. In addition, the CCLCR assay was able to discriminate differences in single-base mismatches and to specifically detect target DNA and target RNA from the cell lysate.

Kinetic Investigation of Reaction Between Colemanite Ore and Methanol

In the field of industry, it is very important that boron compounds are produced from boron ores. The aim of this study was to investigate the dissolution kinetics with carbon dioxide of colemanite in methanol medium in a pressure reactor and to derive an alternative process for producing boron compounds. Reaction temperature, stirring speed, solid/liquid ratio, pressure, and particle size were selected as parameters for the dissolution rate of colemanite. It was found that the dissolution rate increased with increase in pressure and reaction temperature, and with decrease in particle size and solid/liquid ratio. No effect of stirring speed was observed on conversion. The dissolution kinetics of colemanite were examined using both heterogeneous and homogeneous reaction models, and it was determined that the reaction rate can be described by a second-order pseudo-homogeneous reaction model. The activation energy was found to be 51.4 kJ/mol.

Kurnakovite deposits on the Qinghai-Tibet Plateau (II): an investigation from chemical kinetics of chloropinnoite dissolution

Lakes on the Qinghai-Tibet Plateau (QTP) are of particular interest to researchers because of their unusual high concentrations of lithium (Li), boron (B), and potassium (K). Kurnakovite, a member of the inderite group, is well-distributed on the QTP, however, the geochemical mechanisms of kurnakovite transformation requires further identification and clarification. This study aims to elucidate the geochemical mechanisms of kurnakovite deposits on the QTP from chloropinnoite dissolution using chemical kinetic and spectroscopic techniques. The new borate, chloropinnoite 2MgO · 2B2O3 · MgCl2 · 14H2O, was obtained from the natural concentrated salt lake brine on the QTP. The kinetics of chloropinnoite dissolved in 4.5 % (wt%) boric acid solution at 303, 313, and 323 K were investigated. The characterization of the phase transitions and the kinetics were carried out by chemical titration analysis, X-ray powder diffraction spectrometry, Fourier Transform Infrared (FT-IR), and Raman spectrometry. The results demonstrate that similar kinetic processes occur at all three temperatures and can be divided into dissolution, supersaturation, and precipitation, according to three distinct kinetic curves. Kurnakovite was the final phase transition (terminal secondary mineral) within the chloropinnoite-boric acid solution. The dissolution rate of chloropinnoite (the dissolution stage) could be described by second order pseudo-homogeneous reaction model. According to the spectroscopy data, geochemical mechanism of kurnakovite was identified. The new geochemical hypothesis well explains the geochemical mechanism of kurnakovite minerals on the QTP.

Chemical disinfection with H2O2 − The proposal of a reaction kinetic model

The inactivation (death) of Escherichia coli bacteria in water employing hydrogen peroxide has been studied and a five log decrease in CFUcm−3 was achieved. The reaction kinetics was modeled as a series of biochemical steps represented by pseudo-homogeneous reactions between hydroxyl radicals and the components of the cellular walls. Afterwards, the lysate was supposed to undergo a group of parallel reactions leading to the oxidation of the chemical components of the cell. It was assumed that the initiation step of hydrogen peroxide dissociation is promoted by the presence of iron or iron-superoxide compounds. In addition the model takes into account that the reaction forming the lysate as well as the ones that follow the destruction of the bacterium wall, compete for the available oxidizing radicals with the steps that involve the attack on active and injured bacteria. A four parameter representation shows good agreement for the whole range of employed hydrogen peroxide concentrations. The results are valid for any form and size of the employed reactor as long as the described operating conditions (pH and concentrations) are maintained. This development constitutes a very general model that is capable to describe inactivation processes whose graphical representation also shows the presence of shoulders at the beginning and tailings in the end of the operation.