Biphasic Medium Research Articles

Synergetic effect of multi-site phase transfer catalysis system mediated free radical polymerization of acrylonitrile – a kinetic study

In this work, the kinetics and mechanism of free radical polymerization of acrylonitrile (AN) using potassium peroxydisulphate (PDS-K2S2O8) as a water soluble initiator in the presence of synthesized 4,4'-dihexadecyl-1,1'-bipyridine diiumdichloride (DHBPDDC) as multi-site phase-transfer catalyst (MPTC) has been investigated. The polymerization reaction were carried out under nitrogen atmosphere and unstirred condition at constant temperature 60+1°C in ethyl acetate/water biphasic medium. The effects of variation of monomer(AN), initiator(PDS) and catalyst(MPTC) solvent polarity and temperature on the rate of polymerisation (Rp) were ascertained. The order with respect to monomer(acrylonitrile) was found to be unity. The order with respect to initiator and catalyst was found to be 0.51, 0.48 respectively. However, an increase in the polarity of the solvent has slightly increased the rate of polymerization value (Rp). Based on the results obtained, a suitable kinetic mechanism scheme has been proposed to account for the experimental observations and its significance was discussed. The other thermodynamic parameters such as entropy of activation ((∆S#), enthalpy of activation (∆H#) and free energy of activation (∆G#) have been calculated.

Stepwise dissolution and composition determination of samples of multiple crystals using a dissolution medium containing aqueous alcohol and fluorocarbon phases.

Crystallisations are widely used in pharmaceutical and fine chemical manufacturing to control impurity levels, however crystallisations do not always reduce impurities to acceptable levels. Information on the location and distribution of impurities in crystallised materials would be helpful in such cases. A two phase dissolution medium featuring a fluorocarbon non-solvent vehicle and a aqueous ethanol solvent phase has been used to determine the composition of multi-particle crystalline samples through a partial dissolution approach combined with particle sizing and HPLC analysis. 4-Chloro-2-nitroacetanilide (1) was chosen as the host compound for this study, with 4-methyl-2-nitroacetanilide (2) and 4-tert-butyl-2-nitroacetanilide (3) chosen as the guest impurities that were added to supersaturated toluene solutions of 1 at levels up to 5 mol%. The crystals that formed were subjected to a series of partial dissolution steps carried out using the biphasic dissolution medium composed of a 50% aqueous ethanol solvent phase and a perfluorohexane continuous phase. To inhibit particle agglomeration, the mixture also contained 13,13,14,14,15,15,16,16,17,17,18,18-dodecafluoro-2,5,8,11-tetraoxaoctadecane (4) as a non-ionic surfactant. The partial dissolution steps showed a relatively even dissolution with each sequential step as determined from particle sizing. Analysis of the solutions by HPLC from each partial dissolution step allowed the level of impurity to be determined, and when combined with the particle sizing data this allowed an impurity distribution to be generated. Impurity 2 was found to be relatively evenly distributed while impurity 3 was localised on or near the surfaces of crystals.

Modified coal fly ash waste as an efficient heterogeneous catalyst for dehydration of xylose to furfural in biphasic medium

For the first time, application of acid-treated coal fly ash as a catalyst for selective dehydration of d-xylose to furfural was investigated in this work. Coal fly ash had been treated with sulphuric acid to promote de-alumination and consequently enhance the silanol concentration in the modified catalyst. This Brønsted acidic catalyst had been effective to convert 85% d-xylose to yield 62% furfural at 170 °C. On addition of 35 ppt of NaCl to the system furfural yield was improved to 68%. This promising result in equivalent salinity of sea water might open up possibilities to investigate inexpensive sea water as a replacement of distilled water to improve the product yield. The catalyst was stable enough to sustain minimum of 6 cycles of run. Apart from the abundant availability and cheap price of fly ash, utilizing it for heterogeneous catalysis drives to mitigate disposal problems of fly ash to partial extent. The dual advantages make the system eco-friendly.

Homogeneous Catalysis and Mechanisms in Water and Biphasic Media

After its discovery in the early 1980s and successful application on an industrial scale (Ruhrchemie/Rhone-Poulenc process) [...]

Aqueous biphasic hydroformylation of olefins: From classical phosphine-containing systems to emerging strategies based on water-soluble nonphosphine ligands

ABSTRACTThis review provides an overview of recent developments in the area of aqueous biphasic hydroformylation of higher olefins using metal catalysts and surfactants, cosolvents, thermoregulated ligands, cyclodextrins, and most importantly emerging water-soluble nonphosphine ligands. Water-soluble phosphine ligands have been widely explored for aqueous biphasic hydroformylation; however, phosphines are generally expensive and are prone to oxidation hence the recent interest in exploring other ligands. Various approaches have been used to introduce hydrophilicity to the ligands. The catalytic activity of monometallic and heterobimetallic systems containing nonphosphine ligands in aqueous biphasic media is emphasized in this review.

Production of 5-Hydroxymethylfurfural from Starch Through an Environmentally-Friendly Synthesis Pathway

In this work, an environment-friendly and recyclable system was developed for converting waxy corn starch to HMF, with boric acid and choline chloride acting as co-catalysts, and a biphasic medium of water-MIBK or water-THF used as solvent. A central composite design based Response Surface Methodology was used to optimise the reaction parameters. The highest HMF yield obtained for water-MIBK was 35.9 mol%, while for water-THF, a maximum yield of 60.3 mol% was attained. However, the water-MIBK system was more recyclable, with minimal decrease in HMF yields observed even after ten rounds of reuse. Therefore, this system merits further investigation with other feedstock and on a larger scale.

Efficient aerobic photooxygenation of aldehydes to carboxylic acids using cobalt(II) phthalocyanine sulfonate as a photosensitizer in organic-water biphasic media

The aerobic oxidation of a variety of aromatic aldehydes to the corresponding carboxylic acids by molecular oxygen in the presence of 4-carboxyl tetraphenylporphyrin (H2TCPP), methylene blue (MB), cobalt(II) phthalocyanine sulfonate (CoPcS) and FeTCPPCl as water-soluble photosensitizers in organic-water biphasic media at room temperature under either visible light or sunlight is described. The products were obtained with 25–100% conversion and 100% selectivity. This method has a wide range of applicabilities, has a straightforward workup procedure, is chemoselective and proceeds under mild reaction conditions. The resulting products were obtained in good yields in reasonable times.

Ocular manifestations of leishmaniasis in a cat: first case report from Brazil

ABSTRACT An 8-year-old domestic short hair female cat initially presented with bilateral uveitis with pseudotumoral appearance. The patient tested negative for feline immunodeficiency virus (FIV), feline leukemia virus (FeLV) and Toxoplasma gondii. Histopathology of a granulomatous lesion on the upper left conjunctiva revealed amastigotes compatible with Leishmania spp. Aqueous humor was aspired and the diagnosis was confirmed after isolation of promastigotes cultivated in biphasic NNN medium and by positive polymerase chain reaction (PCR) for Leishmania infantum. Treatment with allopurinol (10mg/kg/ BID/PO) was commenced and a natural insect repellent was prescribed. Six months of treatment with allopurinol associated with the initial topical medications helped to improve ocular signs. Leishmaniasis should be considered as a differential diagnosis in cats presenting uveitis with pseudotumoral appearance. To our knowledge, this is the first report of feline leishmaniasis with ocular manifestation in Brazil, in which diagnosis was confirmed by aqueous humor analysis.

Multi-Scale Numerical Viscoelastic Simulation of Fatigue Behavior of Asphalt Mixtures Modified with Polyphosphoric Acid

Fatigue cracking is one of the main distresses affects the service life of asphalt mixture. Recently, polyphosphoric acid (PPA) widely used as a modifier to improve mechanical and rheological characteristics of asphalt binders and mixtures especially at high and low service temperatures. While there are several studies devoted to investigate high and low service temperature of PPA modified asphalt binder and mixture, its fatigue behaviour needs to be studied in more detail. The main objective of this paper is to develop a multiscale heterogeneous numerical finite element (FE) model as well as experimental program to investigate the effect of PPA modification on fatigue behaviour of different bituminous composites from neat asphalt binder to asphalt mixture. The experimental program includes frequency sweep test at test temperature of 25°C by implementing dynamic shear rheometer (DSR) for neat and PPA modified asphalt binder and also indirect tensile fatigue (ITF) at frequency of 1 Hz (0.1 s loading time and 0.9 s rest time) under constant stress of 300 kPa at test temperature of 25°C by using a UTM-25kN. Three different contents of PPA is used for modifying neat asphalt binder including 0.5, 1 and 1.5 wt.% of neat binder to consider the variation of modifier extent on fatigue behaviour of neat asphalt binder and mixture. The mixture specimens were prepared with granite aggregate and asphalt binder of 85/100 penetration grade. The asphalt mixture is modeled as a biphasic medium composed of granular inclusions with linear elastic properties and bituminous matrix exhibiting linear viscoelastic behavior at small strain values. The generalized Maxwell rheological model was used to simulate viscoelastic behavior of the asphalt binder and PPA modified asphalt binder. In order to create the aggregate skeleton of the bituminous composites, a custom software (called “MOA”, French acronym for Random Object Modeler) developed in University of Limoges, has been used to generate random inclusions of various sizes and shapes. The experimental results of asphalt binder and mixture indicated that modification with PPA has a significant effect on improving asphalt mixture’s fatigue life especially in dosage of 1%. On the other hand, results of numerical simulation have shown a good agreement with experimental results.

Selective Hydrogenation of Aldehydes Using a Well-Defined Fe(II) PNP Pincer Complex in Biphasic Medium.

A biphasic process for the hydrogenation of aldehydes was developed using a well‐defined iron (II) PNP pincer complex as model system to investigate the performance of various ionic liquids. A number of suitable hydrophobic ionic liquids based on the N(Tf)2 − anion were identified, allowing to immobilize the iron (II) catalyst in the ionic liquid layer and to facilitate the separation of the desired alcohols. Further studies showed that targeted Brønsted basic ionic liquids can eliminate the need of an external base to activate the catalyst.

Self-influenced growth through evolving material inhomogeneities

We reformulate a model of avascular tumour growth in which the tumour tissue is studied as a biphasic medium featuring an interstitial fluid and a solid phase. The description of growth relies on two fundamental features: one of those is given by the mass transfer among the constituents of the phases, which is taken into account through source and sink terms; the other one is the multiplicative decomposition of the deformation gradient tensor of the solid phase, with the introduction of a growth tensor, which represents the growth-induced structural changes of the tumour. In general, such tensor is non-integrable, and it may allow to define a Levi-Civita connection with non-trivial curvature. Moreover, its evolution is related to the source and sink of mass of the solid phase through an evolution equation. Our goal is to study how growth can be influenced by the inhomogeneity of the growth tensor. To this end, we study the evolution of the latter, as predicted by two different models. In the first one, the dependence of the growth tensor on the tumour’s material points is not explicitly considered in the evolution equation. In the second model, instead, the inhomogeneity of the growth tensor is resolved explicitly by introducing the curvature associated with it into the evolution equation. We perform numerical simulations to compare the results produced by these two models, and evaluate a possible role of the material inhomogeneities on growth.

One-pot co-catalysis of corncob with dilute hydrochloric acid and tin-based solid acid for the enhancement of furfural production

A newly synthesized solid acid catalyst SO42−/SnO2-diatomite was prepared for synthesizing furfural from corncob in the presence of homogeneous Brönsted acid. The relationship between pKa of Brönsted acid and turnover frequency (TOF) of co-catalysis with Brönsted acid plus SO42−/SnO2-diatomite was explored on the conversion of corncob to furfural. HCl (pKa = −7.0) (0.5 wt%) plus SO42−/SnO2-diatomite (3.6 wt%) gave the highest furfural yield (40.1%) with TOF value at 2.98 h−1 in the aqueous media. In the γ-valerolactone–water (6:4, v:v) biphasic media containing 15 g/L ZnCl2, one-pot conversion of corncob with co-catalysts gave a furfural yield of 68.9% at 170 °C for 30 min. Additionally, an efficient SO42−/SnO2-diatomite recycling was achieved with a productivity of 15.6 g furfural/(g solid acid·day) after 5 cycles of repeated use. Clearly, this one-pot co-catalysis process has high potential application for furfural production in future.

Ionic Liquids for Controlled Synthesis of Functional Materials for Energy-Related Applications

The conventional synthesis of functional materials relies heavily on water and organic solvents. Alternatively, the synthesis of functional materials using or in the presence of ionic liquids represents a burgeoning direction in materials chemistry.1-4 Ionic liquids are a family of non-conventional molten salts that can act as both templates and precursors to functional materials, as well as solvents. They offer many advantages, such as negligible vapor pressures, wide liquidus ranges, good thermal stability, tunable solubility of both organic and inorganic molecules, and much synthesis flexibility. The unique solvation environment of these ionic liquids provides new reaction media for controlling formation of porous materials, creating functional groups in biphasic media, and tailoring morphologies of advanced materials. Challenges and opportunities in using ionic liquids for synthesizing functional materials in energy-related applications will be discussed. Acknowledgment: This work was conducted at the Oak Ridge National Laboratory and supported by the Office of Basic Energy Sciences, U.S. Department of Energy, under contract No. DE-AC05-00OR22725 with UT-Battelle, LLC. References (1) Ma, Z.; Yu, J. H.; Dai, S. Preparation of Inorganic Materials Using Ionic Liquids. Adv. Mater. 2010, 22, 261-285. (2) Sun, X. Q.; Luo, H. M.; Dai, S. Ionic Liquids-Based Extraction: A Promising Strategy for the Advanced Nuclear Fuel Cycle. Chem. Rev. 2012, 112, 2100–2128. (3) Huang, K.; Chen, F. F.; Tao, D. J.; Dai, S. Ionic liquid-formulated hybrid solvents for CO2 capture. Curr. Opin. Green Sustain. Chem. 2017, 5, 67-73. (4) Yang, Q. W.; Zhang, Z. Q.; Sun, X. G.; Hu, Y. S.; Xing, H. B.; Sheng Dai, S. Ionic liquids and derived materials for lithium and sodium batteries. Chem. Soc. Rev. 2018, 47, 2020-2064.

Oxidation of Monoterpenes Catalysed by a Water‐Soluble MnIII PEG‐Porphyrin in a Biphasic Medium

AbstractIt is well established that the transformation of abundant and cheap natural products, such as terpenoids, can produce other more valuable compounds. Thymoquinone, which has a commercial value significantly higher than that of its precursors, can be obtained by oxidation of carvacrol and thymol. In this work, a new water‐soluble MnIII PEG‐porphyrin is reported as catalyst in a water/hexane (1:1) biphasic medium for the oxidation of carvacrol and thymol into thymoquinone. The reactions were performed using tert‐butyl hydroperoxide as oxidant in the presence of ammonium acetate as co‐catalyst, reaching 94 and 78 % of conversion after 5 h of reaction for thymol and carvacrol, respectively. Experiments with oregano essential oil as substrate revealed selective transformation of thymol and carvacrol into thymoquinone. The main advantage of this biphasic system based on a water‐soluble catalyst and on substrates and products soluble in hexane, is the straightforward isolation, recovery and recycling of the catalyst by simple phase separation. Recycling studies of the MnIII PEG‐porphyrin using thymol as substrate showed high conversion values throughout four catalytic cycles.

Directed Evolution of Artificial Metalloenzymes: Genetic Optimization of the Catalytic Activity.

Artificial metalloenzymes (ArMs) based on the incorporation of a biotinylated metal cofactor within a streptavidin (Sav) combine attractive features of both enzymatic and homogeneous catalysis. To speed up their optimization, we present a directed evolution of an artificial transfer hydrogenase (ATHase) based on a stream-lined and optimized protocol for the design, overexpression and screening of Sav isoforms. Ten positions have been subjected to mutagenesis to yield two variants with improved catalytic activity and selectivity for the reduction of cyclic imines, along with greater stability in a biphasic medium.

Enhanced bioreduction synthesis of ethyl (R)-4-chloro-3-hydroybutanoate by alkalic salt pretreatment

In this study, biomass-hydrolysate was used for enhancing the bioreduction of ethyl 4-chloro-3-oxobutanoate (COBE). Firstly, dilute alkalic salt pretreatment was attempted to pretreat bamboo shoot shell (BSS). It was found that enzymatic in situ hydrolysis of 20–50 g/L BSS pretreated with dilute alkalic salts (0.4% Na2CO3, 0.032% Na2S) at 7.5% sulfidity by autoclaving at 110 °C for 40 min gave sugar yields at 59.9%–73.5%. Moreover, linear relationships were corrected on solid recovery-total delignification-sugar yield. In BSS-hydrolysates, xylose and glucose could promote the reductase activity of recombinant E. coli CCZU-A13. Compared with glucose, hydrolysate could increase the reductase activity by 1.35-folds. Furthermore, the cyclohexane-hydrolysate (10:90, v/v) biphasic media containing ethylene diamine tetraacetic acid (EDTA, 40 mM) and l-glutamine (150 mM) was built for the effective biosynthesis of ethyl (R)-4-chloro-3-hydroxybutanoate [(R)-CHBE] (94.6% yield) from 500 mM COBE. In conclusion, this strategy has high potential for the effective biosynthesis of (R)-CHBE (>99% e.e.).

Evaluation of a single-pass with biphasic intravenous contrast medium injection CT protocol for the assessment of complications post-simultaneous pancreas–kidney transplant

To evaluate the use of a single-pass with biphasic intravenous contrast medium injection computed tomography (CT) protocol to provide diagnostic quality CT studies for the assessment of complications post-simultaneous pancreas-kidney transplant (SPK). This was an audit of practice and the need for informed consent was waived. The protocol was used in consecutive patients undergoing CT to exclude intra-abdominal sepsis post-SPK between June and December 2015. Single CT acquisition of the abdomen and pelvis was initiated 70 seconds after the start of biphasic contrast medium injection (66 ml at 1.2 ml/s, followed by 34 ml at 2.4 ml/s, 370 mg iodine/ml). The named transplant pancreas vessels were identified and the attenuation values of the blood within were measured. Diagnostic quality was confirmed if values were >211 HU and >80 HU in the arteries and veins, respectively. Thirteen CT studies were performed in 10 patients. CT studies were excluded due to complete pancreatic necrosis, and transplant superior mesenteric artery (SMA) thrombus with pancreatic head ischaemia causing effacement of the transplant superior mesenteric vein (SMV). Diagnostic quality of the analysed CT studies were confirmed with mean attenuation value of blood >211 HU in the transplant pancreatic arteries (SMA=259.0±51.4 HU, splenic artery=245.3±37.5 HU), and >80 HU in the pancreatic veins (SMV=195.4±36.2 HU, splenic vein=185.1±54.2 HU). Diagnostic quality CT studies were obtained using the single-pass CT protocol. Radiation exposure to patients may be reduced with this protocol, while permitting simultaneous assessment of parenchymal and vascular complications post-SPK.

Enzymatic synthesis of fructooligosaccharides from sucrose by endo-inulinase-catalyzed transfructosylation reaction in biphasic systems

Abstract The biocatalytic approach based on the endo-inulinase-catalyzed transfructosylation reaction of sucrose in organic solvent/buffer biphasic reaction systems was investigated for the synthesis of fructooligosaccharides (FOSs). Combining kinetics and end-product profiling contributed to the understanding of the reaction selectivity and to the identification of the best biphasic system. Indeed, the highest FOS bioconversion yield (60.2%) was obtained in butyl acetate/buffer system, with nystose being the main end-product. The effects of the reaction parameters were studied using response surface methodology. Enzyme unit exhibited the most significant linear effect in the kestose concentration model, whereas the reaction time was the most significant parameter in the nystose concentration model. However, in the fructosyl-nystose concentration model, all linear terms exerted significant effects. Among the interactive effects, the interaction between reaction time and solvent proportion had the most significant effect on the kestose and nystose concentrations and on the bioconversion yield of FOS. The developed models are expected to provide the capability to FOS with targeted composition. FOS production by endo-inulinase was investigated in maple syrup-based biphasic media. The highest production of kestose was obtained using maple syrup 15°Bx, whereas the 66°Bx maple syrup resulted in the highest productions of nystose and fructosyl-nystose.

Manufacture of Furfural from Xylan-containing Biomass by Acidic Processing of Hemicellulose-Derived Saccharides in Biphasic Media Using Microwave Heating

Furfural was produced in biphasic media using a microwave-heated reactor. Diverse substrates were considered: xylose (considered as a reference compound) or hemicellulosic saccharides from Eucalyptus globulus wood or corncobs. Operation was carried out at 170°C for the desired reaction time in the presence of an acidic catalyst (sulfuric acid or HCl). The best furfural yields (67.8% and 72.5% from E. globulus wood and corncobs, respectively) were obtained operating for 10 min or 20 min with 1% or 0.5% HCl, respectively. These results were slightly lower than the ones obtained using xylose (a model substrate) under comparable reaction conditions, a fact ascribed to differences in the complexity of substrates and to the presence of contaminants.

Pluronic‐Conjugated Enzyme Cascade for In Situ Oxidation in Biphasic Media

AbstractA Pluronic‐conjugated enzyme cascade was synthesized for catalyzing oxidation reactions using hydrogen peroxide (H2O2) as the oxidant. The synthesis started with encapsulating enzymes in the micelles of aldehyde‐functionalized Pluronic (PL) containing bovine serum albumin (BSA). Schiff‐base bonds formed between the amine groups of proteins and the aldehyde groups of the PL, which were reduced to a more stable form, resulting in enzyme–PL conjugates. The effects of operation parameters on the conjugate yield were examined using glucose oxidase (GOx) and horseradish peroxidase (HRP) as examples. The co‐localization of GOx and HRP was confirmed by Förster resonance energy transfer (FRET), from which the average distance between GOx and HRP was interpreted as 6.1 nm. The proximity effect was confirmed by adding a high concentration of catalase (CAT) to a solution of GOx–HRP–PL to catalyze the oxidation of ABTS. The GOx–HRP–PL conjugate was readily solubilized in organic solvents such as dimethyl sulfoxide, methanol or chloroform. Phenol oxidation with GOx–HRP–PL in dimethyl sulfoxide/water biphasic media was conducted using glucose as the substrate to generate H2O2 in situ. The multiple enzyme conjugate provided a 1.3‐fold higher removal rate compared to their native counterparts in free form. The GOx–HRP–PL conjugate could be readily recovered by centrifugation at 4 °C and 90 % of the initial activity remained after 10 cycles.