Addition Of Toluene Research Articles

Enhanced performance of non-thermal plasma coupled with TiO2/GAC for decomposition of chlorinated organic compounds: influence of a hydrogen-rich substance

BackgroundNo study was found in the literature on the combination of TiO2/GAC catalyst and non-thermal plasma for chlorinated volatile organic compounds abatement in air. This paper presents this hybrid process for the decomposition of chloroform (as a target compound) using a multi-pin to plate discharge reactor. The experiments were performed using a high frequency pulsed transformer as the power supply system to examine the effect of SIE, frequency, as well as initial concentration on the chloroform removal efficiency (RE). Toluene was added as a hydrogen-rich source to shift the reactions into the formation of environmentally desirable products.ResultsRE of around 60% was observed with the NTP-alone process at the highest possible SIE (3000 J L−1), while it rocketed up to 100% (total oxidation) in the presence of TiO2/GAC at SIE of 1000 J L−1. About 100% O3 destruction over TiO2/GAC and both adsorption and catalytic activities of GAC may be considered as the reasons for better performance of the hybrid process. Toluene feeding diminished the chlorinated by-products such as Cl2 and TCE significantly. The selectivity towards CO2 was noticed to enhance noticeably, when both catalyst and toluene were introduced, regardless of the input concentration.ConclusionsOur findings suggest that the hybrid of NTP with TiO2/GAC will highly be effective in the abatement of chloroform, and the addition of toluene will successfully decline harmful chlorinated by-products.

Electroplating of Aluminum with Nickel Particle Codeposition

Aluminum-nickel nanostructured thin films have many uses. The exothermic mixing of the phases may be implemented for localized heat generation wherever restricted welding, brazing or local energy release may be required. Current fabrication methods generally rely on vapor deposition processes that require high vacuum and are limited to low rates. New fabrication methods such as electroplating these films can result in significant improvement of energetic density and cost savings. To pursue this, we investigated aluminum deposition to determine the characteristics and mechanism of the complex reduction process, nickel particle incorporation into an aluminum matrix, and nickel deposition properties in a multicomponent bath.Because aluminum has a lower atomic density than nickel and the desired mixing ratio is 1:1, the aluminum volume must be 60% of the total. The codeposition process is limited in its capability for particle incorporation by particle diffusion and geometric hindrances and therefore the particulate species is almost always a significantly lower volume percentage than the matrix. For this reason the aluminum is the matrix material that is deposited out of the electrolyte and the nickel component is incorporated as imbedded particles. Aluminum deposition must be carried out in aprotic solvents because the reduction potential is lower than that of hydrogen, making aluminum deposits using aqueous solutions inefficient and low quality. Electrolytes were characterized based on transport properties and deposition kinetics.Some of the most promising aluminum deposition is done in Chloroaluminate RTILs (room temperature ionic liquids) 2. These solutions are high aluminum concentration and low vapor pressure but typically high viscosity. Additions of toluene have improved the dendritic morphology and at 30-50 volume% toluene, the bath produces a smooth uniform coating of aluminum 1. The dilutions reduce the viscosity, and participate in complexing with the reactants, modifying the reduction and transport properties. These electrolytes are investigated with RDE and EIS to determine the reaction properties of aluminum deposition. The reported reduction of aluminum metal occurs from the complex Al2Cl7-. This bulky anion has very poor diffusion properties, there are kinetic limitations due to the complex multi-step reduction process and our experiments aim to analyze the reaction mechanism to optimize the electrolyte composition, speciation and applied deposition current and potential.EIS conductivity measurements show that pure TMPAC:AlCl3 ionic liquids have low conductivity and the conductivity is greatly increased with dilution with toluene or dichlorobenzene, although a maximum is reached as the improved transport starts to be overcome by the reduced ionic concentrations. This maximum conductivity is reached at about 50-60 molar% of DCB to IL.Although these aluminum deposition electrolytes have been used before, little fundamental understanding of mechanism has been undertaken; a better understanding of the reaction properties will allow for design of a more effective codeposition process. Codeposition with particulates in aluminum enables production of heterogeneous films with improved mechanical properties; and cost effective bilayer or alloy deposition will increase aluminum’s already large applicability. Bi-phasic films may also be produced by alternatively depositing Al and Ni layer, and Nickel properties in the electrolyte were studied to develop this fabrication method also.Comparisons are made between the electrochemically produced film and the commercial PVD film. These are characterized by energy release, burn rate. The high interfacial area of these films is subject to atomic diffusion which can reduce the burn characteristics. TEM analysis of the interfacial layers seems to indicate that the lower temperature process associated with codeposition can reduce this pre-reaction mixing. Accelerated aging is being performed on film from both fabrication methods and increased temperature heavily influences interatomic mixing.

Structures of benzylsuccinate synthase elucidate roles of accessory subunits in glycyl radical enzyme activation and activity.

Anaerobic degradation of the environmental pollutant toluene is initiated by the glycyl radical enzyme benzylsuccinate synthase (BSS), which catalyzes the radical addition of toluene to fumarate, forming benzylsuccinate. We have determined crystal structures of the catalytic α-subunit of BSS with its accessory subunits β and γ, which both bind a [4Fe-4S] cluster and are essential for BSS activity in vivo. We find that BSSα has the common glycyl radical enzyme fold, a 10-stranded β/α-barrel that surrounds the glycyl radical cofactor and active site. Both accessory subunits β and γ display folds related to high potential iron-sulfur proteins but differ substantially from each other in how they interact with the α-subunit. BSSγ binds distally to the active site, burying a hydrophobic region of BSSα, whereas BSSβ binds to a hydrophilic surface of BSSα that is proximal to the active site. To further investigate the function of BSSβ, we determined the structure of a BSSαγ complex. Remarkably, we find that the barrel partially opens, allowing the C-terminal region of BSSα that houses the glycyl radical to shift within the barrel toward an exit pathway. The structural changes that we observe in the BSSαγ complex center around the crucial glycyl radical domain, thus suggesting a role for BSSβ in modulating the conformational dynamics required for enzyme activity. Accompanying proteolysis experiments support these structural observations.

Emission spectroscopy of Ar + H2 + C7H8 plasmas: C7H8 flow rate dependence and pressure dependence

We have studied toluene flow rate dependence and pressure dependence of Ar emission intensities at 425.9 nm, 750.4 nm and 811.5 nm for Ar + H2 + C7H8 plasmas. Electron density and the electron impact excitation rate coefficients are nearly the same for Ar(100%) and Ar+H2(33%) plasmas. Toluene addition leads to a decrease in the high energy electron density, whereas the effective electron temperature and low energy electron density remain almost the same. The effective electron temperature, and Ar metastable density and/or low energy electron density decrease significantly with increasing the total pressure from 0.1 to 5 Torr.

Solvent-controlled lithiation of P[dbnd]C–N-heterocycles: Synthesis of mono- and bis(trimethylsilyl)-tert-butyl-dihydrobenzazaphospholes – A new type of highly bulky and basic phosphine ligands

The influence of solvents on the lithiation of N-methyl-1,3-benzazaphospholes is reported; these are accessible via catalytic phosphonylation of 2-bromoanilines, subsequent reduction to 2-phosphinoanilines and acid-catalysed disproportionative ring closure with excess paraformaldehyde. Reactions with tBuLi in polar solvents (THF, Et2O), particularly in the presence of tBuOK, lead to 2-lithiobenzazaphospholes (CH-lithiation) whereas hydrocarbons favour “normal” (hexane) or “inverse” (toluene) addition at the PC bond. Reactive Li-species were trapped by ClSiMe3, present during the lithiation in hydrocarbons, and give rise to 2- and 3-trimethylsilyl-dihydro-1,3-benzazaphospholes, respectively. In hexane, via preferred lithiation of the primary adduct, the 2,2′-bis(trimethylsilyl)-dihydro-1,3-benzazaphosphole is the main product. 5-Methyl-1,3-benzazaphosphole, with NH function, reacts in toluene in the “normal” mode to 3-tert-butyl-1,2-bis(trimethylsilyl)-5-methyl-dihydrobenzazaphosphole. The sterically demanding tert-butyl and trimethylsilyl groups are arranged in anti-position as shown by crystal structure analyses, the second 2-SiMe3 group in gauche position. The P-tert-butyl-2,2′-bis(trimethylsilyl)-dihydrobenzazaphospholes represent a new type of sterically congested dialkylaryl phosphine ligands with increased basicity by the +I-effect of the silyl groups and +M-effect of the basic nitrogen in o-position.

Synthesis and Characterization of γ-Al2O3 Nano Powder by Disc Milling of Al and MnO2 Powder

Nano-sized alumina particles have been generated by milling mixture of aluminium and manganese dioxide powders mixed in ratio of 1:7 by weight in a vibratory disc mill for different milling time of 450, 600 and 750min. The mill was operated at 700rpm. High energy milling of manganese dioxide particles with excess of aluminium powder ensures that nanoparticles generated, either of MnO2 or alumina, are mostly separate and surrounded by aluminium particles. The structural changes of powder particles during mechanical alloying were studied by X-ray diffraction, scanning electron microscopy and TEM. In the mixture of milled powders with particle size in the range 10 to 200nm. The addition of toluene was used as the process control agent to avoid severe agglomeration appears to be efficient to enhance the milling effect.

Hydrocracking of Heavy Oil by Means of In Situ Prepared Ultradispersed Nickel Nanocatalyst

This work adopts a water-in-oil (w/o) microemulsion method for the in situ preparation of ultradispersed metallic nickel (Ni0) nanocatalyst in heavy oil and assesses its hydrocracking activity. Catalyst preparation involved reducing Ni2+ added to the water pools of the heavy oil matrix in the form of aqueous Ni(NO3)2 solution using hydrazine. The volume of the aqueous precursors was limited to values which corresponded to visually stable single heavy oil phase. The product particles were collected by addition of toluene and characterized using XRD, TEM, and EDX. These techniques confirmed the formation of nickel nanoparticles of 22 ± 5 nm mean diameter. The hydrocracking activity of the as-prepared ultradispersed catalyst was evaluated using a semibatch reactor setup under 110 bar of hydrogen and 370 °C. Although no presulfiding was performed, XRD of the spent catalyst confirmed the formation of Ni3S2 nanoparticles with a mean particle size of the same range as the Ni0 particles. Results showed 2-fold imp...

Toluene destruction in thermal stage of Claus reactor with oxygen enriched air

Results are presented on the toluene destruction using oxygen enriched air as the oxidant with addition of defined amounts of H2S and toluene into H2/air flames under fuel-rich mixture conditions at equivalence ratio of Φ=3 (Claus condition). The oxygen enrichment allowed variation of temperature in the reactor and reduced nitrogen and total volumetric gas flow while maintaining the same equivalence ratio. The formation and destruction of hydrocarbons and other gas phase species during the combustion of H2S and C7H8 mixture are presented with oxygen enrichments (0%, 19.5% and 69.3% O2) to air. Toluene is often present in acid gas consisting of mainly H2S and CO2 so that combustion of H2S/C7H8 is of practical value. The formation of SO2 increased with oxygen enrichment to air. Increased oxygen in air reduced oxidation rate of H2 and increased H2S oxidation rate which enhanced faster rate of SO2 production to result in reduced formation of elemental sulfur. Addition of toluene to H2S reduced the rate of H2 oxidation and increased that of H2S. In contrast to the case of 100% H2S combustion, toluene favored faster increase in mole fractions of SO2 to a peak value but the formed SO2 decomposed with increased distance along the reactor. The decay of SO2 is attributed to the reactions between SO2 and other sulfur containing radicals or hydrocarbons formed (such as methane and acetylene) to produce elemental sulfur and carbon disulfide. Oxygen enrichment to the combustion air enhanced the rate of hydrocarbons decomposition which helped to reduce the amounts of CS2 formed. Formation of CS2 and hydrocarbons adversely impact the performance and efficiency of sulfur capture in a Claus process. These results assist in identifying conditions on the role of oxygen enrichment in designing compact Claus reactors.

Microbial community and function of enrichment cultures with methane and toluene

The interaction effect of co-existence of toluene and CH4 on community and activity of methanotrophs and toluene-degrading bacteria was characterized in three consortia enriched with CH4 and toluene (MT), toluene (T), and CH4 (M), respectively, in this study. The CH4 oxidation activity in the enrichment culture of MT was significantly lower than that of M at the end of the experiment (P = 0.001). The toluene degradation rate could be enhanced by continuous addition of CH4 and toluene in the initial days, but it was inhibited in the later days. Phylogenetic analysis of 16S rRNA genes showed that Proteobacteria and Bacteroidetes were dominant in the three enriched consortia, but the community of methanotrophs and toluene-degrading bacteria was significantly affected by the co-existence of CH4 and toluene. Both Methylosinus (91.8 %) and Methylocystis (8.2 %) were detected in the enrichment culture of MT, while only Methylocystis species were detected in M. The toluene-degrading bacteria including Burkholderia, Flavobacteria, Microbacterium, and Azoarcus were all detected in the enrichment culture of T. However, only Azoarcus was found in the enrichment culture of MT. Significantly higher contents of extracellular polymeric substances polysaccharose and protein in the enrichment culture of MT than that of T and M suggested that a higher environmental stress occurred in the enrichment culture of MT.

Effects of Exogenetic Ferrite on Removal of Toluene in Sediments from a Typical Coastal Wetland

Ferrite material is a kind of special ferromagnetic mental oxide with Fe3+ as a main component. Based on the assumption that the reduction of Fe3+ and the magnetic variations could produce potential active impacts on degradation of organic pollutants under anaerobic conditions, we took water and sediment samples from Chongming east intertidal flat, a typical coastal wetland, to investigate the effects of exogenetic addition of ferrite on the removal of toluene in sediments during an 11-day incubation. Ferrite (Fe12O19·Sr, M.W. 1061.75, Nanosized spherical material 800 nm, the purity >98%) was added into sediment samples by proportions of 0.0, 5.0, 10.0, 20.0 g/kg with 0.0, 0.2, 0.5, 1.0 ml/kg toluene, respectively. It is found that the rate of toluene removal is the highest when the ferrite added is 10.0 g/kg with toluene recovery rates of 0.24%, 20.79%, 30.36% for treatments of 0.2, 0.5, 1.0 ml/kg toluene addition by the end of 11th day of incubation, respectively. In contrast, the recovery rates are 1.85%, 50.05%, 55.68%, respectively, when ferrite content rises to 20.0 g/kg. In addition, all toluene recovery rates are less than 2% after 11 day incubations under the condition of 0.2 ml/kg toluene, indicating that the removal rate of toluene depends on the contents of toluene in sediments. In summary, it confirm that application of exogenetic ferrite material can effectively enhance the removal of toluene from the sediment.

Insights into the Glycyl Radical Enzyme Active Site of Benzylsuccinate Synthase: A Computational Study

The fumarate addition reaction, catalyzed by the enzyme benzylsuccinate synthase (BSS), is considered to be one of the most intriguing and energetically challenging reactions in biology. BSS belongs to the glycyl radical enzyme family and catalyzes the fumarate addition reaction, which enables microorganisms to utilize hydrocarbons as an energy source under anaerobic conditions. Unfortunately, the extreme sensitivity of the glycyl radical to oxygen has hampered the structural and kinetic characterization of BSS, thereby limiting our knowledge on this enzyme. To enhance our molecular-level understanding of BSS, a computational approach involving homology modeling, docking studies, and molecular dynamics (MD) simulations has been used to deduce the structure of BSS's catalytic subunit (BSSα) and illuminate the molecular basis for the fumarate addition reaction. We have identified two conserved and distinct binding pockets at the BSSα active site: a hydrophobic pocket for toluene binding and a polar pocket for fumaric acid binding. Subsequent dynamical and energetic evaluations have identified Glu509, Ser827, Leu390, and Phe384 as active site residues critical for substrate binding. The orientation of substrates at the active site observed in MD simulations is consistent with experimental observations of the syn addition of toluene to fumaric acid. It is also found that substrate binding tightens the active site and restricts the conformational flexibility of the thiyl radical, leading to hydrogen transfer distances conducive to the proposed reaction mechanism. The stability of substrates at the active site and the occurrence of feasible radical transfer distances between the thiyl radical, substrates, and the active site glycine indicate a substrate-assisted radical transfer pathway governing fumarate addition.

Role of toluene in hydrogen sulfide combustion under Claus condition

Experimental investigations on the effect of different amounts of toluene addition to H2S combustion in oxygen under Claus condition (Φ=3) are presented. Three toluene concentrations of 0.5%, 1% and 5% in H2S are presented and compared with the baseline case of 100% H2S oxygen combustion. Temperature data showed that addition of toluene to H2S gas stream increases the flame temperature because of large heating value associated with toluene. Addition of toluene resulted in the production of H2, which increased with increase in the amounts of toluene addition. Furthermore, increased addition of toluene concentration increased the asymptotic minimum value of hydrogen sulfide due to oxidation competition between the formed H2 and H2S. The results also showed that the presence of CO triggers the formation of COS with toluene addition due to reaction of CO with SO2. The results showed that SO2 mole fraction increased to a maximum value then decayed with distance along the reactor. Addition of toluene increased the rate of SO2 decay. These results have direct impact on sulfur capture in the Claus reactor and its performance.

A semi-detailed chemical kinetic model of a gasoline surrogate fuel for internal combustion engine applications

A semidetailed chemical kinetic mechanism (473 species and 1267 reactions) to describe the oxidation of a gasoline surrogate fuel consisting of n-heptane, iso-octane, toluene and diisobutylene (DIB) is developed. The model shows generally good agreement with the experimental ignition delay times measured in shock tubes for not only individual components but also their various mixtures over a wide range of temperatures and pressures. Although both simulations and experiments indicate toluene has a promoting effect on the auto-ignition of iso-octane in a specific region, the effect of toluene addition to isooctane is still not fully resolved. Nonetheless, it is found that the reactions of benzyl radical with allene are not important for the kinetic interactions. The measured laminar burning velocities of a research gasoline fuel, CR-87, can be well reproduced by using a TRF+DIB mixture (C6H5CH3/iC8H18/nC7H16/JC8H16, 45/25/20/10% by liquid volume) as a surrogate. In a homogeneous charge compression ignition (HCCI) engine, the model can capture the shift in resistance to auto-ignition for such TRF+DIB fuel when the operating conditions change. A sensitivity analysis shows the chemical origin of such shift cannot be solely explained based on the extent to which NTC (negative temperature coefficient) behavior is absent. The effect of decreasing the inlet temperature and increasing the inlet pressure is a result of the concerted action of manifold factors.

Thermo-chemical extraction of fuel oil from waste lubricating grease

This study investigated the recovery of oil from waste grease through the process of thermal degradation in an aqueous solution of potassium hydroxide (KOH) followed by solvent extraction. Waste high temperature metal bearing grease was dissolved in a 15w/w% KOH solution at 80°C while being agitated at 2000rpm using a shear action agitator for a period of 15min. Two distinct layers were observed after 8min of settling time. The top layer being of dark brown oil and the bottom layer was a heterogeneous mixture. The two layers were separated by decantation. The bottom layer was cooled down to 45°C followed by slow addition of toluene (C7H8) while agitating at 1200rpm for 15min to prevent solids settling and minimise rapid volatilisation of the organic compounds in the mixture. Two distinct layers were also formed, the top homogeneous mixture of light brown oil–toluene mixture and the bottom sludge layer. The solvent was recovered from the oil for re-use by fractional distillation of the homogenous mixture. It was observed that 15w/w% potassium hydroxide solution can chemically degrade the soap matrix in the grease and extract up to 49w/w% of the fuel oil when subjected to high shear stress at a temperature of 80°C. The 26w/w% extraction of oil in the remaining sludge was obtained by solvent extraction process with mass ratios of sludge to solvent of 2:1. Solvent recovery of 88% by mass was obtained via fractional distillation method. The combined extraction processes brought an overall oil yield of 75w/w% from the waste grease. The fuel oil obtained from this process has similar properties to paraffin oil and can be blended with other oils as an alternative energy source.

Evaluation of the sooting properties of real fuels and their commonly used surrogates in a laminar co-flow diffusion flame

In an effort to help determine the fidelity of simple surrogate fuels to represent real fuel chemistry in computational fluid dynamic simulations of engines, quantitative two-dimensional soot volume fraction measurements were made in a laminar coflow methane–air diffusion flame seeded with approximately 2200ppm of real and surrogate fuels. A combined laser extinction and laser-induced incandescence (LII) method was used to measure soot volume fraction. Additionally, soot particles were thermophoretically sampled from the flame and soot morphology data were collected with a transmission electron microscope (TEM). Vaporized liquid fuels were seeded at low concentrations to maintain constant thermodynamic conditions for each experiment. In all, 14 different fuels were investigated, including: three real fuels (gasoline, diesel, and jet fuel), two alkanes, and a variety of simple surrogate fuels. A toluene reference fuel (TRF) (30% aromatics) and gasoline (28% aromatics) were found to have similar soot volume fractions and soot morphology. The addition of toluene to the long-straight chain of n-tetradecane in similar concentrations (30vol.%) as the aromatic concentration of diesel (31.1vol.%) resulted in soot volume fractions that were very similar, although the primary particle size and mass-weighted radius of gyration were both smaller for the surrogate than for the conventional diesel fuel. Finally, the jet-fuel surrogate tested was found to have a lower sooting tendency than the jet-A fuel despite the jet-A fuel having a lower concentration of aromatics than the surrogate. Soot morphology between jet-A and the jet-fuel surrogate were the same within experimental uncertainty. The current work provides an experimental dataset for validation of fuel-surrogate chemistry and soot models.

Extinction Studies of Flames of Heavy Neat Hydrocarbons and Practical Fuels

Extinction strain rates of premixed and non-premixed flames of , , a petroleum-derived JP-5 jet fuel, a camelina-derived hydrotreated renewable JP-5 jet fuel, a petroleum-derived F-76 diesel fuel, and an algae-derived hydrotreated renewable F-76 diesel fuel were measured in the counterflow configuration at atmospheric pressure and a fuel-containing stream temperature of 443 K. Recently developed kinetic models were used to simulate the experimental data for and flames. The computed results are in close agreement with the data for premixed flames, whereas the data are over-predicted for non-premixed flames. Furthermore, the extinction strain rates of premixed and flames are similar, while compared to , non-premixed flames exhibit greater extinction resistance. Regarding the practical fuels, the extinction propensity of flames of petroleum-derived fuels is higher compared to bio-derived fuels. The extinction strain rates of flames of 80% toluene mixtures were computed also to evaluate the effects of addition of aromatics on extinction. The results confirmed that the addition of toluene increases the extinction propensity compared to neat flames under both premixed and non-premixed conditions, which explains partially the experimental results for petroleum- and bio-derived practical fuels.

Recovery of acetic acid from dilute aqueous solutions using catalytic dehydrative esterification with ethanol

We have developed a direct esterification of aqueous acetic acid with ethanol (molar ratio=1:1) catalyzed by polystyrene-supported or homogeneous sulfonic acids toward the recovery of acetic acid from wastewater in chemical plants. The equilibrium yield was significantly increased by the addition of toluene, which had a high ability to extract ethyl acetate from the aqueous phase. It was shown that low-loading and alkylated polystyrene-supported sulfonic acid efficiently accelerated the reaction. These results suggest that the construction of hydrophobic reaction environments in water was critical in improving the chemical yield. Addition of inorganic salts was also effective for the reaction under not only biphasic conditions (toluene–water) but also toluene-free conditions, because the mutual solubility of ethyl acetate and water was suppressed by the salting-out effect. Among the tested salts, CaCl2 was found to be the most suitable for this reaction system.

Simultaneous Determination of Benzene and Toluene in Pesticide Emulsifiable Concentrate by Headspace GC-MS

The toxic inert ingredients in pesticide formulations are strictly regulated in many countries. In this paper, a simple and efficient headspace-gas chromatography-mass spectrometry (HSGC-MS) method using fluorobenzene as an internal standard (IS) for rapid simultaneous determination of benzene and toluene in pesticide emulsifiable concentrate (EC) was established. The headspace and GC-MS conditions were investigated and developed. A nonpolar fused silica Rtx-5 capillary column (30 m × 0.20 mm i.d. and 0.25 μm film thickness) with temperature programming was used. Under optimized headspace conditions, equilibration temperature of 120°C, equilibration time of 5 min, and sample size of 50 μL, the regression of the peak area ratios of benzene and toluene to IS on the concentrations of analytes fitted a linear relationship well at the concentration levels ranging from 3.2 g/L to 16.0 g/L. Standard additions of benzene and toluene to blank different matrix solutions 1ead to recoveries of 100.1%–109.5% with a relative standard deviation (RSD) of 0.3%–8.1%. The method presented here stands out as simple and easily applicable, which provides a way for the determination of toxic volatile adjuvant in liquid pesticide formulations.

319 平坦バーナー低温度炎におけるトルエン添加がアルデヒド類生成に及ぼす影響(OS5-4 燃焼技術の基礎と応用研究(4),OS5 燃焼技術の基礎と応用研究)

319 平坦バーナー低温度炎におけるトルエン添加がアルデヒド類生成に及ぼす影響(OS5-4 燃焼技術の基礎と応用研究(4),OS5 燃焼技術の基礎と応用研究)

Lipase-catalyzed interfacial polymerization of ω-pentadecalactone in aqueous biphasic medium: A mechanistic study

The synthetic activity of lipases in biphasic o/w systems was investigated with respect to their use in the synthesis of polyester chains via transesterification reactions. Lipase-catalyzed ring-opening polymerization (ROP) of pentadecalactone (ω-PDL) dispersed in water was used as a model reaction to understand the synthetic activity of lipases in biphasic o/w system. We conducted a systematic investigation of the influence of reaction conditions on the macromolecular characteristics of oligo(ω-PDL) encompassing chemical, thermophysical and colloidal properties of the reaction medium. A model was proposed assuming Michaelis–Menten interfacial kinetics followed by chain extension via lipase-catalyzed linear polycondensation. The solidification of oligo(ω-PDL) chains with a degree of polymerization of approximately three was identified as a major factor limiting the molecular weight of obtained oligomers to ∼870 g mol−1, despite the fast reaction rate and complete conversion of ω-PDL. The addition of toluene into the dispersed phase at a volumetric ratio of 0.3–0.5 of toluene to ω-PDL allowed us to circumvent this problem and increase the molecular weight of obtained oligomers up to 1460 g mol−1. The molecular weight of polymer product according to this model was thus inversely related to the weight ratio percentage of interfacial lipase PS to ω-PDL per droplet and correspondingly correlated with the activity of lipase. Taking into account all these parameters allowed increasing the molar mass of oligo(ω-PDL) from 870 g mol−1 to 3507 g mol−1.