Methyl Tert Research Articles

Threat and Risk Analysis-Based Neural Network for a Chemical Explosion (TRANCE) Model to Predict Hazards in Petroleum Refinery.

Risk analysis and prediction is a primary monitoring strategy to identify abnormal events occurring in chemical processes. The accidental release of toxic gases may result in severe problems for people and the environment. Risk analysis of hazardous chemicals using consequence modeling is essential to improve the process reliability and safety of the refineries. In petroleum refineries: toluene, hydrogen, isooctane, kerosene, methanol, and naphtha are key process plants with toxic and flammable chemicals. The major process plants considered for risk assessment in the refinery are the gasoline hydrotreatment unit, crude distillation, aromatic recovery, continuous catalytic reformer, methyl-tert-butyl-ether, and kerosene merox units. Additionally, we propose a threat and risk analysis neural network for the chemical explosion (TRANCE) model for refinery incident scenarios. Significantly, 160 attributes were collected for the modeling on the basis of the significance of failure and hazardous chemical leaks in the refinery. Hazard analysis shows that the leakages of hydrogen and gasoline at the gasoline hydrotreatment unit, kerosene at the kerosene merox plant, and crude oil at crude-distillation units were areas of profound concern. The developed TRANCE model predicted the chemical explosion distance with an R2 accuracy value of 0.9994 and MSE of 679.5343.

INFLUENCE OF NANO CERIUM OXIDE IN EMISSION REDUCTION WITH METHYL TERT-BUTYL ETHER - GASOLINE BLENDS AT HCCI ENGINE

This article is focused to analyse the HCCI engine operated with blends of nano CeO 2 , Methyl tert- butyl ether (MTBE)-gasoline blends. The blending proportions of MTBE are 5vol%, 10vol%, 15vol% and 20vol%. For CeO 2 , it is 30ppm, 60ppm and 90ppm. The mixing is carried out with high shearing ultrasonication process. The optimal air-fuel ratio and chamber pressure were identified as 2.52 and 2.5 bar. From the experimentations, The Brake thermal Efficiency was found to be improved up to 3% with CeO 2 + MTBE blends than pure gasoline, and the brake-specific fuel consumption was reduced up to 0.03 kg/kW hr compared with a conventional gasoline engine. The emission parameters such as NOx, CO and HC have been identified as relatively lower as 857ppm, 0.07vol% and 11ppm respectively with MTBE 15 + 90ppm than gasoline. The use of both MTBE and CeO 2 nanoparticles are found better to improve the performance and reduce the emission further.

Extraction mechanism analysis and energy saving enhancement of extraction separation of methyl tert-butyl ether and methanol by ionic liquid based on molecular dynamics simulation

• The ILs extractant is screened by quantum chemistry and MD simulation. • The process flow of applying ILs in the production of MTBE was designed. • The sequential iterative optimization integrating reaction conditions is proposed. • The TAC in MTBE production was reduced by 26.77% when applying ILs. Methyl tert-butyl ether as an excellent gasoline additive has been widely used. There are a lot of mixtures of Methyl tert-butyl ether and methanol in the process of Methyl tert-butyl ether production. In this work, the interaction between different ionic liquids and methyl tert butyl ether / methanol was studied by the combination of quantum chemistry and molecular dynamics. In addition, there is little difference between the experimental data and the MD simulation results, indicating that the extraction performance can be predicted by MD simulation even without the phase equilibrium data. The interaction energy, radial and spatial distribution functions, and self-diffusion coefficients are calculated based on the molecular dynamics simulation results. It is proved that anions play a key role in the extraction process. The process of synthesis of methyl tert-butyl ether with ionic liquid extraction as separation unit was studied and the optimum process parameters were determined. Methyl tert-butyl ether with mole fraction greater than 99.9% could be obtained by ionic liquid extraction, and the use of Ionic liquids liquid-liquid extraction can save 26.77% of total annual cost than extractive distillation using conventional solvents. It plays a guiding role in the selection of green solvent ionic liquids extractant and the energy saving of liquid-liquid extraction.

Mesoporous magnesia sorbent for removal of organic contaminant methyl tert -butyl ether (MTBE) from water

ABSTRACT Methyl tertiary butyl ether (MTBE) is used as a gasoline additive formed by the reaction of isobutylene and methanol. Due to its high water solubility and low soil adsorption coefficient, leakages from storage facilities cause immediate groundwater contamination. The aim is to use alternative adsorbent for the removal of MTBE that causes various environmental and health problems. Mesoporous magnesia (MgO) that was synthesized via template-free hydrothermal method and commercial adsorbent Sepabeads-207 (SP-207) were used in this study. MTBE adsorption experiments were carried out at room temperature with a fixed sorbent/liquid ratio (0.1 g sorbent/10 mL aqueous solution) and 100–500 mg/L MTBE initial concentrations. Batch adsorption experiments showed that MgO and SP-207 have high MTBE adsorption capacity with a maximum adsorption amount of 333 and 233 mg MTBE/g adsorbent. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models of adsorption isotherms were used to investigate the adsorption behavior and the Langmuir isotherm model showed a better fit. Adsorption kinetic studies were also performed, and the pseudo-second-order kinetics fitted well with experimental data. Gibbs free energy changes of adsorption were obtained as −48.4 and −60.3 kJ/mol for MgO and SP-207, respectively. Methanol was used to regenerate the used adsorbents, and the re-use of MgO demonstrated good performance.

Alkylation of resorcinol with tertiary butanol over zeolite catalysts: Shape selectivity vs acidity

The catalytic performance of various zeolites such as H-ZSM-5, H-Y, H-beta, H-Mordenite in resorcinol alkylation with tertiary butanol demonstrated that pore characteristics have major influence on product selectivity, whereas acid strength and number of acid sites influenced resorcinol conversion. The passivation of external surface of H-beta zeolite by silylation and amine poisoning produced shape selectively O-alkylated resorcinol methyl tert butyl ether (RMTBE) and 4-tert butyl resorcinol (4-TBR). We propose that 4-TBR formation goes over external acid sites through RMTBE isomerization, whereas formation of 4-TBR takes place inside the pores through direct C-alkylation mechanism.

Porous Carbon Spheres Derived from Waste Ion-Exchange Resins and Research on Adsorption of Methylene Blue

A kind of porous carbon spherical material with high specific surface (SBET=1,292 m2/g) was synthesized from deactivated methyl tert butyl ether (MTBE) resins with KOH as the activator (KAC). This synthesized material was characterized by Brunner Emmet Teller (BET) measurements, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TG), and X-ray fluorescence (XRF). Additionally, the mechanism of adsorbing methylene blue (MB) on this porous carbon sphere was studied and interpreted from kinetics, adsorption equilibrium and thermodynamic properties. Results showed that the kinetics data fitted the pseudo-second-order model well; the adsorption equilibrium data followed Langmuir model with a maximum adsorption capacity of 478.5 mg/g; and the thermodynamic parameters displayed an endothermic and spontaneous adsorption process of MB on carbon spheres.

Influence of contaminant exposure on the development of aerobic ETBE biodegradation potential in microbial communities from a gasoline-impacted aquifer

Aerobic biodegradation of ethyl tert butyl ether (ETBE) in a gasoline-impacted aquifer was investigated in laboratory microcosms containing groundwater and aquifer material from ETBE-impacted and non-impacted locations amended with either ETBE, or ETBE plus methyl tert butyl ether (MTBE). As sole substrate, ETBE was biodegraded (maximum rate of 0.54 day−1) without a lag in ETBE-impacted microcosms but with a lag of up to 66 days in non-impacted microcosms (maximum rate of 0.38 day−1). As co-substrate, ETBE was biodegraded preferentially (maximum rate of 0.25 and 0.99 day−1 in non-impacted and impacted microcosms, respectively) before MTBE (maximum rate of 0.24 and 0.36 day−1 in non-impacted and impacted microcosms, respectively). Further addition of ETBE and MTBE reduced lags and increased biodegradation rates. ethB gene copy numbers increased significantly (>100 fold) after exposure to ETBE, while overall cell numbers remained constant, suggesting that ethB-containing microorganisms come to dominate the microbial communities. Deep sequencing of 16S rRNA genes identified members of the Comamonadaceae family that increased in relative abundance upon exposure to ETBE. This study demonstrates the potential for ETBE biodegradation within the unsaturated and saturated zone, and that ETBE biodegrading capability is rapidly developed and maintained within the aquifer microbial community over extended timescales.

Shock tube investigation of methyl tert butyl ether and methyl tetrahydrofuran high‐temperature kinetics

AbstractThe autoignition and pyrolysis of two C5 ethers, methyl tert butyl ether (MTBE) and 2‐methyltetrahydrofuran (2‐MTHF), are investigated using the shock tube reactor. The experiments are carried out at pressures of 3.5 and 12 atm at temperatures above 1000 K with argon as a diluent gas. By means of direct laser absorption, carbon monoxide time histories and associated chemical kinetic timescales are also determined. It is observed that the competition between ignition and pyrolysis times depends on the temperature and equivalence ratio of the ignition mixture, such that there is a temperature above which pyrolysis predominates oxidative kinetics. This crossover temperature shifts toward higher temperatures for reactive systems with a fixed fuel concentration but higher oxygen content. The resulting experimental observations are also compared with predictions of existing chemical kinetic models from the literature. The results point to differences in chemical reactivity, such that in pyrolysis conditions, the reactivity of the cyclic ether, 2‐MTHF, is generally higher than that of the aliphatic ether, MTBE. While agreement between experimental observations and model predictions is observed under certain conditions, significant variance between observations and predictions is observed under other conditions. With respect to prediction of the pyrolysis time used to capture the global kinetics of pyrolysis, it is observed that the relation of this time to the time needed to attain 90% of the equilibrium CO concentration varies greatly with the result that the models used in this work generally predict a faster initial formation of CO but a much slower approach to the equilibrium concentration. This is thought to arise from the slow transformation of intermediate CH2O and CH2CO to CO. The chemical kinetic models considered in this work are therefore not capable of predicting the CO time histories during pyrolysis.

Thin film composite membranes with desirable support layer for MeOH/MTBE pervaporation

ABSTRACTA comprehensive study was performed on a new application of thin film composite membranes and selecting a stable sublayer for them as pervaporation membranes in organic solvent separation. For this purpose, four different polymeric sublayers of polyethersulfone (PES), cellulose acetate, polyacrylonitrile, and polyetherimide were prepared, and the interaction of methanol (MeOH) and methyl tert butyl ether (MTBE) with them was investigated. The contact angle results, scanning electron microscopy images, and swelling and mechanical strength measurements obviously displayed the effect of immersion in organic solvents on the sublayers. Finally, a polyamide active layer was subsequently deposited on the PES membrane surface as the stable sublayer via interfacial polymerization based on a multistep statistical optimization strategy involving fractional factorial design and a response surface method. The prepared TFC membranes were tested in the pervaporation of a MeOH/MTBE mixture and exhibited excellent performance compared with the current membranes in this context. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47519.

CHROMATOGRAPHIC DETERMINATION OF RESIDUAL ORGANIC SOLVENTS IN (2R,4R,4aR,7R,8aR)-4,7-DIMETHYL-2-(THIOPHEN-2-YL)OCTAHYDRO-2H- CHROMEN-4-OL WHICH EXHIBITS HIGH ANALGESIC ACTIVITY

Introduction of a substance into medical practice requires the indispensable evidence of the substance purity as early as the stage of preclinical testing. The content of residual organic solvents, which can affect the pharmacological activity of the drug, is one of the indicators of the substance quality control. Four solvents are used during synthesis and isolation of the substance: dichloromethane, ethyl acetate, methyl tert -butyl ether (MTBE), and n -hexane. Two methods of determining residual organic solvents in (2 R ,4 R ,4 aR ,7 R ,8 aR )-4,7-dimethyl-2-(thiophen-2-yl)octahydro-2 H -chromen-4-ol using gas chromatography are offered: i) introduction of a gas sample and separation of the components on a commercial HP-5ms capillary column (30 m × 0.35 mm × 0.25 im); ii) introduction of a liquid sample and separation on a capillary column (30 m × 0.32 mm × 0.30 im) filled with a modified poly(1-trimethylsilyl-1- propyne) (PTMS). Since the first method provides only determination of n -hexane and ethyl acetate, the procedure was developed and validated for determination of four residual solvents, i.e., dichloromethane, ethyl acetate, methyl n -butyl ether, and n -hexane in test substance using gas chromatography on the column with a modified PTMSP-based phase. We detected trace amounts of ethyl acetate and methyl n -butyl ether; the content of dichloromethane and n -hexane in the substance appeared below the detection limits. The average content of ethyl acetate and MTBE in the substance for 9 parallel determinations (0.10 and 0.20 ppm) appeared 5 and 2.5 × 104 times lower than maximum permissible content (5000 ppm), respectively. The developed technique was assessed for: specificity, linearity of the calibration curve, correctness, precision at the level of the repeatability and intralaboratory precision, and stability of the chromatographic system. Standard deviations in the determination of ethyl acetate and MTBE in the substance do not exceed 0.03 and 0.09, respectively. The procedure is specific, accurate and reliable for determination of the residual organic solvents in the substance.

APPLICATION OF PRIGOGINE-FLORY-PATTERSON THEORY TO EXCESS MOLAR VOLUMES OF BINARY LIQUID MIXTURES OF {METHYL TERT BUTYL ETHER (MTBE) + ALCOHOLS} AT DIFFERENT TEMPERATURES AND ATMOSPHERIC PRESSURE

No presente estudo, dados experimentais de volume molar excesso ( ) de soluções líquidas binárias de metil terc butl éter (MTBE) + metanol, ou + etanol, ou + 1-propanol, ou + 2-propanol, ou + 1-butanol, ou + 1-pentanol, ou + 1-hexanol foram usados para testar a aplicabilidade da Teoria Prigogine-Flory-Patterson (PFP Theory), como função da composição a diferentes temperaturas e pressão atmosférica. De acordo com o modelo, a contribuição interacional é a mais importante para descrever o comportamento do . Foi observado que a Teoria PFP reproduz os dados experimentais usando apenas um parâmetro ajustável. Para todos os sistemas estudados foi obtida uma boa concordância entre os resultados experimentais e a Teoria.

Development and validation of a confirmatory method for the determination of stilbene estrogens in ostrich serum

ABSTRACTA simple and accurate ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for the first time as a confirmatory method for the simultaneous determination of stilbenes – hexestrol and diethylstibestrol in serum. Extraction was based on a simple acid denaturation of protein followed by liquid–liquid extraction using methyl tert butyl ether. Extracts were directly injected into the UHPLC-MS/MS without further purification. Excellent recoveries in the range 82–99% and 91–128% were obtained for hexestrol and diethylstibestrol, respectively. Both within-day repeatability and between-day reproducibility were generally satisfactory with RSD <20%. The linearity of the internal standard based matrix-matched calibration curve measured as the coefficient of regression (r2) was generally >0.99 for both hexestrol and diethylstibestrol. Both matrix effect and uncertainties associated with sample preparation and instrumental analysis were significantly reduced with the use of a deuterated compound (hexestrol-d4) as internal standard. The LOD and LOQ were 0.09 and 0.08 ng/ml, and 0.28 and 0.25 ng/ml, respectively, for hexestrol and diethylstibestrol. The method was found to be suitable for the simultaneous determination of hexestrol and diethylstibestrol in serum.

Reutilization of waste scrap tyre as the immobilization matrix for the enhanced bioremoval of a monoaromatic hydrocarbons, methyl tert-butyl ether, and chlorinated ethenes mixture from water.

BTEX (benzene, toluene, ethylbenzene, ortho-, meta-, and para-xylenes), methyl tert-butyl ether (MTBE), cis-1,2-dichloroethylene (cis-DCE), and trichloroethylene (TCE) are among the major soil and groundwater contaminants frequently co-existing, as a result of their widespread uses. Pseudomonas plecoglossicida was immobilized on waste scrap tyre to remove these contaminants mixture from synthetic contaminated water. The microbial activity was enhanced in the immobilized system, shown by the higher colony forming units (CFUs) (40%), while BTEX were used as growth substrates. The adsorption capacity of tyres toward contaminants reached a maximum within one day, with BTEX (76.3%) and TCE (64.3%) showing the highest sorption removal capacities, followed by cis-DCE (30.0%) and MTBE (11.0%). The adsorption data fitted the Freundlich isotherm with a good linear correlation (0.989-0.999) for the initial contaminants concentration range applied (25-125mg/L). The monoaromatic hydrocarbons were almost completely removed in the immobilized system and the favourable removal efficiencies of 78% and 90% were obtained for cis-DCE and TCE, respectively. The hybrid (biological, immobilization/physical, sorption) system was further evaluated with the contaminants spiked intermittently for the stable performance. The addition of mineral salt medium further enhanced the bioremoval of contaminants by stimulating the microbial growth to some extent.

Source proximity and meteorological effects on residential outdoor VOCs in urban areas: Results from the Houston and Los Angeles RIOPA studies

Concentrations of volatile organic compounds (VOCs) measured outside homes in Houston, TX and Los Angeles, CA were characterized by the effects of source proximity and meteorological factors. Benzene, toluene, ethylbenzene, m,p-xylene, o-xylene (BTEX), methyl tert butyl ether (MTBE), tetrachloroethylene (perchloroethylene, PCE), and carbon tetrachloride (CCl4) were examined. Multiple stepwise regression analysis converged the best-fit models with predictors from meteorological conditions and the proximity to specific point, area, and mobile sources on the residential outdoor VOC concentrations. Negative associations of wind speed with concentrations demonstrated the effect of dilution by high wind speed. Atmospheric stability increase was associated with concentration increase. Petrochemical source proximity was a significant predictor for BTEX and MTBE concentrations in Houston. Ethylbenzene and xylene source proximity was a significant predictor in Los Angeles. Close proximity to area sources such as scrap metal recycling or dry cleaning facilities increased the MTBE, PCE, and CCl4 concentrations in Houston and Los Angeles. Models for ethylbenzene, m,p-xylene, and MTBE in Houston, and benzene in Los Angeles explained that for the median values of the meteorological factors, homes closest to influential highways would have concentrations that were 1.7–2.2 fold higher than those furthest from these mobile emission sources. If the median distance to sources were used in the models, the VOC concentrations varied 1.7 to 6.6 fold as the meteorological conditions varied over the observed range. These results highlight that each urban area is unique and localized sources need to be carefully evaluated to understand potential contributions to VOC air concentrations near residences, which influence baseline indoor air concentrations and personal exposures. Results of this study could assist in the appropriate design of monitoring networks for community-level sampling. They may also improve the accuracy of exposure models linking emission sources with estimated pollutant concentrations at the residential level.

Nanostructures in clear and homogeneous mixtures of rapeseed oil and ethanol in the presence of green additives

Ethanol and rapeseed oil are mixed in the presence of tributyl citrate, 2,5-dimethylfuran, 2-methylfuran, 2-methyl tetrahydrofuran, methyl tert butyl ether, ethyl tert butyl ether, FAME-rapeseed biodiesel, 1-heptanol, and 2-ethylhexyl nitrate, at 25 °C (298.15 K). All these additives come or can be obtained completely or partially from plants. The obtained ternary phase diagrams show a large domain of clear and homogeneous solutions and a liquid two-phase system due to the partial solubility of rapeseed oil and ethanol. All the tested additives have thus an evident cosolvent behavior for ethanol and rapeseed oil. In all the studied systems, the possible presence of nanostructures is checked with dynamic light scattering (DLS) and confirmed using static light scattering (SLS). In the system rapeseed oil/ethanol/1-heptanol, the presence of nanostructures is definitely established performing small-angle neutron scattering (SANS). The true geometry of these nanostructures could not be detected, but systematic conductivity measurements starting with the binary melt 1-heptanol/rapeseed oil in the presence of LiClO4 adding ethanol show clearly a continuous transition from ethanol-in-rapeseed oil to rapeseed oil-in-ethanol mixtures passing through a bicontinuous medium.

Preparative Isolation of Bioenhancer Loganetin from sf Alstonia scholaris by Fast Centrifugal Partition Chromatography

Fast centrifugal partition chromatography (FCPC) was successfully applied in the separation of close R f complex bioactive iridoid, loganetin directly from the ethyl acetate extract of Alstonia scholaris . The experiment was performed with a two-phase solvent system composed of methyl tert- butyl ether (MtBE)/ACN/Water (3:1.5:3 v/v/v) where the lower phase of the biphasic system, the aqueous layer containing 8 mM HCl, was the stationary phase, while the upper organic layer supplemented with 15 mM triethylamine TEA was designated as the mobile phase. From 1.5 g of EtOAc extract, 48 mg of loganetin (1) was obtained in 94.4% purity as determined by HPLC. The isolated compound (1) was characterized on the basis of its 1 H, 13 C–NMR, and ESI-MS spectroscopic data. Although loganetin does not possess antibacterial activity of its own, but in combination, it appreciably reduces the minimum inhibitory concentration (MIC) of nalidixic acid (NA) against nalidixic acid resistant (NAREC) and nalidixic acid sensitive (NASEC) strains of Escherichia coli . Loganetin, a very common, inexpensive, and non-toxic natural product may finds its application in the antibacterial drug development for treating multidrug-resistant Gram negative infections.

A Novel Vascular Homing Peptide Strategy to Selectively Enhance Pulmonary Drug Efficacy in Pulmonary Arterial Hypertension

A major limitation in the pharmacological treatment of pulmonary arterial hypertension (PAH) is the lack of pulmonary vascular selectivity. Recent studies have identified a tissue-penetrating homing peptide, CARSKNKDC (CAR), which specifically homes to hypertensive pulmonary arteries but not to normal pulmonary vessels or other tissues. Some tissue-penetrating vascular homing peptides have a unique ability to facilitate transport of co-administered drugs into the targeted cells/tissues without requiring physical conjugation of the drug to the peptide (bystander effect). We tested the hypothesis that co-administered CAR would selectively enhance the pulmonary vascular effects of i.v. vasodilators in Sugen5416/hypoxia/normoxia-exposed PAH rats. Systemically administered CAR was predominantly detected in cells of remodeled pulmonary arteries. Intravenously co-administered CAR enhanced pulmonary, but not systemic, effects of the vasodilators, fasudil and imatinib, in PAH rats. CAR increased lung tissue imatinib concentration in isolated PAH lungs without increasing pulmonary vascular permeability. Sublingual CAR was also effective in selectively enhancing the pulmonary vasodilation by imatinib and sildenafil. Our results suggest a new paradigm in the treatment of PAH, using an i.v./sublingual tissue-penetrating homing peptide to selectively augment pulmonary vascular effects of nonselective drugs without the potentially problematic conjugation process. CAR may be particularly useful as an add-on therapy to selectively enhance the pulmonary vascular efficacy of any ongoing drug treatment in patients with PAH.

Evaluation of non-conventional polar modifiers on immobilized chiral stationary phases for improved resolution of enantiomers by supercritical fluid chromatography

An evaluation of the use of non-conventional polar modifiers for the supercritical fluid chromatographic separation of enantiomers on immobilized chiral stationary phases is presented. The resolution of a group of nine commercially available racemates is studied on the Chiralpak IA, IB, IC, ID, IE, and IF chiral stationary phases using CO2-based eluents containing non-conventional polar modifiers such as dichloromethane, chloroform, tetrahydrofuran, 2-methyl tetrahydrofuran, methyl tert-butyl ether, cyclopentyl methyl ether, acetone, ethyl acetate, toluene, 2,2,2-trifluoroethanol, and N,N-dimethylformamide. Screening experiments and method development for the commercial racemates on the immobilized columns with the non-conventional solvents demonstrated an ability to adjust the retention and improve resolution. From these results we were able to assign a general eluotropic relationship between the non-conventional solvents and methanol. A general ability to selectively adjust chromatographic retention while improving analyte solubility can lead to improved preparative chromatographic performance.

Simulation of Reactive Distillation: Comparison of Equilibrium and Nonequilibrium Stage Models

In the present study, two distinctly different approaches are followed for modeling of reactive distillation column, the equilibrium stage model and the nonequilibrium stage model. These models are simulated with a computer code developed in the present study using MATLAB programming. In the equilibrium stage models, the vapor and liquid phases are assumed to be in equilibrium and allowance is made for finite reaction rates, where as in the nonequilibrium stage models simultaneous mass transfer and reaction rates are considered. These simulated model results are validated from the experimental data reported in the literature. The simulated results of equilibrium and nonequilibrium models are compared for concentration, temperature and reaction rate profiles in a reactive distillation column for Methyl Tert Butyle Ether (MTBE) production. Both the models show similar trend for the concentration, temperature and reaction rate profiles but the nonequilibrium model predictions are higher and closer to the experimental values reported in the literature. Keywords—Reactive Distillation, Equilibrium model, Nonequilibrium model, Methyl Tert-Butyl Ether

Centrifugal partition extraction in the pH-zone-refining displacement mode: An efficient strategy for the screening and isolation of biologically active phenolic compounds

Centrifugal partition extraction (CPE) was developed for the first time in the pH-zone-refining mode to fractionate a crude bark extract of the African tree Anogeissus leiocarpus Guill. & Perr. (Combretaceae). The fractionation process was performed at a flow rate of 20mL/min using a biphasic solvent system composed of methyl tert-butyl ether/acetonitrile/water (4:1:5, v/v/v) in the ascending mode. Sodium hydroxide (40mM) and trifluoroacetic acid (30mM) were used as retainer and displacer agents, respectively. In a single run of 67min, 3g of the initial crude extract were successfully separated into fractions selectively enriched in ionizable triterpenes, ellagic acid derivatives and flavonoids. The antioxidant potential of the initial crude extract, isolated compounds and fraction pools was also evaluated by using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) stable free radical scavenging assay, providing an interesting view about the effect of the degree of substitution of ellagic acid derivatives on their radical scavenging activity. This study will demonstrate that centrifugal partition extraction used in the pH-zone-refining mode can be proposed as an efficient strategy for the rapid screening of natural phenolic compounds.