MeOH System Research Articles

Structural modulation in colored polymer bands of methacrylic acid-based frontal polymerization

The periodic colored polymer bands have been investigated in frontal polymerization (FP) reaction containing methacrylic acid (MAA), hydroquinone, Benzoyl peroxide (BP), and N, N Dimethyl aniline (DMA) system. The MAA acts as a monomer, which was diluted adequately with methanol (MeOH), ethanol (EtOH), and butanol (BuOH) separately to observe the patterning characteristics in different reaction schemes. The structural modulations that include the periodicity of colored polymer bands, morphological changes, and spacings between two adjacent layers were studied. The colored variations of polymer bands and their dependency on the concentration of BP, hydroquinone and alcoholic compositions have been studied. The highly consistent pink-white colored polymer bands, loosely-packed band structures, and perfectly ordered band structures resulted in MeOH, EtOH, and BuOH systems, respectively, as discussed. The evolution of tiny bubbles and convection-type instability has been observed in different conditions of the FP reactions that significantly affect the planar movement of the polymer fronts. The hot spots, which usually represent the high-temperature regions of a typical frontal surface, have also been demonstrated in all reacting systems, which may cause spin mode propagation of the fronts and change the surface geometry, as described. The materials characterization was carried out using UV–visible spectrophotometer, NMR, FTIR, and FESEM techniques, providing information about the polymer phases involved in band structures, composition, and surface properties. The analytical data and results obtained during the study further emphasized that two different colored polymers, namely 1, 4-dihydroxy anthraquinone methacrylic acid and poly-methacrylic acid dihydroxy, anthraquinone produced simultaneously and crystallized periodically, results in the development of a colored polymer band structures. The possible reactions and associated chemical mechanisms concerning the observations, the nature of the monomer, and solvent characteristics have been proposed, which show a close agreement with the analytical data and results obtained during the study.

Renewable methanol production based on in situ synergistic utilization of excavated waste and landfill gas: life cycle techno-environmental-economic analysis

Excavated waste (EW) and landfill gas (LFG), as the two main landfill products, are essential objects of Enhanced landfill mining (ELFM). In this study, for the in situ synergistic utilization of LFG and the residue-derived fuel (RDF) from EW, an RDF-LFG to methanol (MeOH) unit with high exergy efficiency and low carbon emission is proposed. Then, to evaluate the environmental impacts and economic feasibility comprehensively, the life cycle assessment (LCA) and life cycle cost (LCC) are conducted on the EW-LFG to MeOH system based on the Aspen Plus simulation data of the RDF-LFG to MeOH unit. The system using EW landfilled in 2005 & 2015 as feedstocks are named Scheme A & B, respectively. The results show that both schemes have an exergy efficiency of more than 70 %. Regarding environmental impacts, RDF-LFG to MeOH, EW pretreatment, Storage and transport of products, and EW Mining are the main contributors. This study pays particular attention to global warming (GW) potential. The direct and indirect carbon emission of the RDF-LFG to MeOH unit are about 35 and 650 kg CO2 eq/ton MeOH, and the life-cycle GW of the EW-LFG to MeOH system is between 707 to 874 kg CO2 eq/ton MeOH. Levelized cost (LC) and levelized profit (LP) are about 452 $/ ton MeOH and 94 $/ton MeOH. With the transformation of the power grid, the decrease in carbon emission factor of power grids can improve both the environmental, and economic performance of the EW-LFG to MeOH system. Methanol selling price, carbon tax and electricity cost are the major sensible factors to the economic feasibility.

Variation of CI-2 Conformers upon Addition of Methanol to Water: An IMS-MS-Based Thermodynamic Analysis.

Chymotrypsin inhibitor 2 (CI-2) is a well-studied, textbook example of a cooperative, two-state, native ↔ denatured folding transition. A recent hybrid ion mobility spectrometry (IMS)/mass spectrometry (MS) thermal denaturation study of CI-2 (the well-studied truncated 64-residue model) in water reported evidence that this two-state transition involves numerous (∼41) unique native and non-native (denatured) solution conformations. The characterization of so many, often low-abundance, states is possible because of the very high dynamic range of IMS-MS measurements of ionic species that are produced upon electrospraying CI-2 solutions from a variable temperature electrospray ionization source. A thermodynamic analysis of these states revealed large changes in enthalpy (ΔH) and entropy (ΔS) at different temperatures, and it was suggested that such variation might arise because of temperature-dependent conformational changes of the protein in response to changes in the conformational entropy and the dielectric permeability of water, which drops from a value of ε ∼ 79 at 24 °C to ∼ 60 at 82 °C. Herein, we examine how adding methanol to water influences the distributions of CI-2 conformers and their ensuing stabilities. The dielectric constant of a 60:40 water:methanol (MeOH) drops from ε ∼ 60 at 24 °C to ∼ 51 at 64 °C. Although the same set of conformers observed in water appears to be present in 60:40 water:MeOH, the abundance of each is substantially altered by the presence of methanol. Relative free energy values (ΔG) and thermodynamic values [ΔH and ΔS and heat capacities (ΔCp)] are derived from a Gibbs-Helmholtz analysis. A comparison of these data from water and water:MeOH systems allows rare insight into how variations in solvation and temperature affect many-state protein equilibria. While these studies confirm that variations in solvent dielectric constant with temperature affect the distributions of conformers that are observed, our findings suggest that other solvent differences may also affect abundances.

Investigating hydrophobic environment in alkyl-group-functionalized silica particle with various chain lengths using absorption microspectroscopy.

A well-known solvatochromic dye, Reichardt's dye (R-dye), was used to evaluate the hydrophobicity of alkyl-group-functionalized silica particles (ASPs) with different chain lengths. The absorption spectra of R-dye were measured in a single ASP in a mixed solution of water and an organic solvent (methanol (MeOH), ethanol (EtOH), acetonitrile (ACN), tetrahydrofuran (THF), or N,N-dimethylformamide (DMF)) using absorption microspectroscopy. The polarity parameter in the ASPs (ET), determined by the absorption maximum, was observed to be smaller than those in bulk solutions, indicating that R-dye was present in a more hydrophobic environment. In EtOH, THF, and DMF, R-dye was distributed within the alkyl chain layer including the organic solvent. An increase in the organic solvent content of the bulk solution led to a higher organic solvent concentration in the alkyl chain layer, resulting in a decrease in ET. In MeOH and ACN, the R-dye was distributed within the alkyl chain layer and concentrated phase. Moreover, with the increase in the organic molecule content, the distribution of R-dye in the concentrated phase became dominant in MeOH and ACN system, leading to an increase in the ET value. The findings presented in this paper are expected to attract the attention of a wide range of researchers in chromatography.

Синтез и исследование свойств 5-R-2-пропаргилсульфанилбензимидазолов

Synthesis of new medicinal substances and biologically active compounds, in particular, heterocyclic ones, is an integral part of modern pharmacology development. This is one of the reasons for steady synthetic and biological interest in the chemistry of imidazoles and benzimi-dazoles. Synthesis of 2-propargylsulfanylbenzimidazole (2a) (yielding 85 %) and 5-methyl-2-propargylsulfanylbenzimidazole (2b) (yielding 56 %) has been carried out for the first time by alkylation of benzimidazole-2-thiol (1a) and 5-methylbenzimidazole-2-thiol (1b), respectively, with propargyl bromide in the KOH–DMF system. The structure of the synthesized compounds 2a,b has been studied by the ¹Н and ¹³С NMR spectroscopy, as well as GC–MS. It has been found that propargyl sulfides 2а,b undergo acetylene-allene rearrangement and subsequent chemical transformations during chromatography under the GC–MS analysis conditions due to the high temperature in the injector (> 200 °C). The literature data on the synthesis of halogen- and selenium derivatives of [1,3]thiazinobenzimidazole based on 2-propargylsulfanylbenzimidazoles exist. We synthesized tricyclic fused [1,3]thiazolo[3,2-a]benzimidazolium systems by heterocyclization of compounds 2a,b under conditions of acetylene-allene rearrangement (heating in the KOH–DMSO or MeONa–MeOH system). According to the 1H NMR data, the reactions of propargyl sulfides 2a,b with a twofold excess of iodine in chloroform proceeded to give 3-iodomethyleno-2,3-dihydro-9H-[1,3]thiazolo[2,3-b]benzimidazolium iodide (11) and 3-iodomethyleno-6-methyl-2,3-dihydro-9Н-[1,3]thiazolo[2,3-b]benzimidazolium polyiodide (10b), respectively. When the solvent was changed to a more polar one and the iodination of compound 2а in glacial acetic acid at the same ratio of starting reagents (1:2) was carried out, isomerization of the heterocyclization product having an exocyclic double bond into a heterocyclization product having an endocyclic double bond in the thiazolium ring was observed. As a result, an individual 3-iodomethyl-9H-[1,3]thiazolo[2,3-b]benzimidazolium polyiodide (12) was isolated, and its structure was studied by 1H NMR spectroscopy.

Proton donor effects on the reactivity of SmI2. Experimental and theoretical studies on methanol solvation vs. aqueous solvation

Proton donors are important components of many reactions mediated by samarium diiodide (SmI2). The addition of water to SmI2 creates a reagent system that enables the reduction of challenging substrates through proton-coupled electron-transfer (PCET). Simple alcohols such as methanol are often used successfully in reductions with SmI2 but often have reduced reactivity. The basis for the change in reactivity of SmI2-H2O and SmI2-MeOH is not apparent given the modest differences between water and methanol. A combination of Born-Oppenheimer molecular dynamics simulations and mechanistic experiments were performed to examine the differences between the reductants formed in situ for the SmI2-H2O and SmI2-MeOH systems. This work demonstrates that reduced coordination of MeOH to Sm(ii) results in a complex that reduces arenes through a sequential electron proton transfer at low concentrations and that this process is significantly slower than reduction by SmI2-H2O.

Density, excess molar volume, and COSMO-RS study of reactive aqueous solutions containing formaldehyde

In this study, the densities of formaldehyde (FA) + water (H2O) binary systems with formaldehyde fractions (xFA) of 0.05–0.27 at temperatures (T) of 293.15, 298.15, and 313.15 K were measured at 0.1 MPa, as well as those of a formaldehyde + water + methanol (MeOH) ternary system with xFA of 0.05–0.27 and xMeOH of 0.09–0.64. A thermodynamic model was combined with the conductor-like screening model for real solvents (COSMO-RS) coupled with a chemical reaction equilibrium and mass balance to describe the species distribution in the above solutions containing poly (oxymethylene) glycols ((HO(CH2O)nH, MGnn ≥ 1) and poly (oxymethylene) hemiformals (CH3O(CH2O)nH, HFn, n ≥ 1) produced by the reactions of FA with H2O and MeOH, respectively. The densities and volumes of these unknown oligomers, MGn and HFn, were computed by the COSMO-RS method and were correlated with the polymerization degree, n, and temperature, T. Furthermore, the densities of the FA + H2O and FA + H2O + MeOH solutions were calculated based on the species distribution and COSMO-RS simulations, which reproduced the experimental data well. Finally, the excess molar volumes of the FA + H2O and FA + H2O + MeOH systems were studied for the first time.

Solvent-Dependent Asymmetric Synthesis of Alkynyl and Monofluoroalkenyl Isoindolinones by CpRhIII -Catalyzed C-H Activation.

The asymmetric synthesis of alkynyl and monofluoroalkenyl isoindolinones from N-methoxy benzamides and α,α-difluoromethylene alkynes is enabled by C-H activation with a chiral CpRhIII catalyst. Remarkably, product formation is solvent-dependent; alkynyl isoindolinones are afforded in MeOH (up to 86 % yield, 99.6 % ee) whereas monofluoroalkenyl isoindolinones are generated in i PrCN (up to 98:2 Z/E, 93 % yield, 86 % ee). Mechanistic studies revealed chiral allene and E-configured alkenyl rhodium species as reaction intermediates. The latter is transformed into the corresponding Z-configured monofluoroalkene upon protonation in the i PrCN system and into an alkyne by an unusual anti β-F elimination in the MeOH system. Notably, kinetic resolution processes occur in this reaction. Despite the moderate enantiocontrol for the formation of the chiral allene, the Z-monofluoroalkenyl isoindolinones and alkynyl isoindolinones were obtained in good enantiopurities by one or two sequential kinetic resolution processes.

Solvent‐Dependent Asymmetric Synthesis of Alkynyl and Monofluoroalkenyl Isoindolinones by CpRhIII‐Catalyzed C−H Activation

AbstractThe asymmetric synthesis of alkynyl and monofluoroalkenyl isoindolinones from N‐methoxy benzamides and α,α‐difluoromethylene alkynes is enabled by C−H activation with a chiral CpRhIII catalyst. Remarkably, product formation is solvent‐dependent; alkynyl isoindolinones are afforded in MeOH (up to 86 % yield, 99.6 % ee) whereas monofluoroalkenyl isoindolinones are generated in iPrCN (up to 98:2 Z/E, 93 % yield, 86 % ee). Mechanistic studies revealed chiral allene and E‐configured alkenyl rhodium species as reaction intermediates. The latter is transformed into the corresponding Z‐configured monofluoroalkene upon protonation in the iPrCN system and into an alkyne by an unusual anti β‐F elimination in the MeOH system. Notably, kinetic resolution processes occur in this reaction. Despite the moderate enantiocontrol for the formation of the chiral allene, the Z‐monofluoroalkenyl isoindolinones and alkynyl isoindolinones were obtained in good enantiopurities by one or two sequential kinetic resolution processes.

Economic evaluation of MEG injection and regeneration process for oil FPSO

Injection and regeneration of MEG for an offshore oil field to prevent the risk of hydrate formation was compared to those of conventional hydrate inhibitor, MEOH (methanol). It was presumed that the injected MEG was regenerated in FPSO to 90 wt% concentration while the MeOH was simply treated without re-use. A multiphase simulation tool was employed to determine the temperature and pressure profile in subsea flowline, which provided the required concentration of hydrate inhibitors for hydrate prevention. While the required concentration of MeOH was around 18 to 30 wt% depending on the water depth, the concentration of MEG was varied from 28 to 46 wt%. NPC (net present cost) for MeOH and MEG injection was estimated as a function of injection count per year with economic assessment. The resulting NPC of MEG injection system for single injection event per year was expensive than that of MeOH injection system due to the higher total capital costs for MEG injection and regeneration system. However, the economic benefit of MeOH systems was decreased with increasing the injection event frequency because the injected MeOH cannot be recovered, and increasing storage tank and purchased MeOH cost were directly added to the total cost. When varying the water depth, i.e. ambient sea water temperature of the offshore oil field, the minimum number of injections per year was different for the MEG injection system to be economically favorable than the MeOH injection system. It became economically favorable when injected more than 2.2 times per year for the case of water depth 1250 m, while it required more than 3.3 times per year for the case of water depth of 600 m. The results showed that the MEG injection and regeneration system can be a feasible option for remote oil fields depending on the average number of hydrate inhibitor injection per year.

Dielectric relaxation studies of binary mixture of β-picoline and methanol using time domain reflectometry at different temperatures

Complex permittivity spectra of binary mixtures of varying concentrations of [Formula: see text]-picoline and Methanol (MeOH) have been obtained using time domain reflectometry (TDR) technique over frequency range 10 MHz to 25 GHz at 283.15, 288.15, 293.15 and 298.15 K temperatures. The dielectric relaxation parameters namely static permittivity ([Formula: see text]), high frequency limit permittivity ([Formula: see text]) and the relaxation time ([Formula: see text]) were determined by fitting complex permittivity data to the single Debye/Cole-Davidson model. Complex nonlinear least square (CNLS) fitting procedure was carried out using LEVMW software. The excess permittivity ([Formula: see text]) and the excess inverse relaxation time (1/[Formula: see text] which contain information regarding molecular structure and interaction between polar–polar liquids were also determined. From the experimental data, parameters such as effective Kirkwood correlation factor (geff), Bruggeman factor (fB) and some thermo dynamical parameters have been calculated. Excess parameters were fitted to the Redlich–Kister polynomial equation. The values of static permittivity and relaxation time increase nonlinearly with increase in the mol–fraction of MeOH at all temperatures. The values of excess static permittivity ([Formula: see text]E) and the excess inverse relaxation time (1/[Formula: see text] are negative for the studied [Formula: see text]-picoline — MeOH system at all temperatures.

Dielectric Relaxation Studies of Binary Mixture of α‐Picoline and Methanol Using Time Domain Reflectometry at Different Temperatures

AbstractComplex permittivity spectra of binary mixtures of varying concentrations of α‐picoline and methanol (MeOH) were obtained using time domain reflectometry (TDR) technique over frequency range 10 MHz to 25 GHz at 283.15 K, 288.15 K, 293.15 K and 298.15 K temperatures. The dielectric relaxation parame‐ ters namely static permittivity (σ0), high frequency limit permittivity (σoo1) and the relaxation time (ρ) were determined by fitting complex permittivity data to the single Debye/Cole‐Davidson model. Complex non linear least square (CNLS) fitting procedure was carried out using LEVMW software. The excess static permittivity (σ0E) and the excess inverse relaxation time (1/ρ)E which contains information regarding mo‐ lecular structure and interaction between polar — polar liquids, were also determined. From the experimental data, effective Kirkwood correlation factor (geff) and Bruggeman factor (fB) were calculated. Excess parameters were fitted to the Redlich‐Kister polynomial equation. The values of static permittivity and relaxation time increase non‐linearly with increase in the mol fraction of MeOH at all temperatures. The values of excess static permittivity (σ0E) and the excess inverse relaxation time (1/ρ)E are negative for the studied α‐picoline — MeOH system at all temperatures.

A ligand-free, powerful, and practical method for methoxylation of unactivated aryl bromides by use of the CuCl/HCOOMe/MeONa/MeOH system

A ligand-free, powerful, and practical method for mono and polymethoxylation of unactivated aryl bromides has been developed; CuCl was used as catalyst, HCOOMe as cocatalyst, and methanolic MeONa as both nucleophile and solvent. This eco-friendly procedure is characterized by operational simplicity, inexpensive substrates (unactivated mono to polybromoarenes), full conversion, and direct recovery of pure MeOH.

Protonation-deprotonation equilibria in tetrapyrroles Part 4: Mono- and diprotonations of deutero-, hemato-, meso-, and protoporphyrin IX dimethyl esters in methanolic hydrochloric acid

The N-protonations in the deutero, hemato, meso and protoporphyrin IX dimethyl esters (DME) were investigated by spectrophotometric titrations using HCl as the acid and methanol as the solvent. Two spectroscopically different protonated species were observed for each porphyrin DME in addition to the neutral form. These were assigned to the N-protonated monocation and dication. There were no difficulties encountered in observing the monocation formation in the HCl – MeOH system. Very sharp isosbestic points were characteristic of each protonation stage. The p K3 values for the porphyrins in the above order were 3.23, 4.70, 2.93 and 3.37; the p K4 values were 2.48, 2.62, 2.41 and 2.64, respectively. For all porphyrins studied, no further spectral changes were observed after the dication was completely formed. This was interpreted as indicating that the formation of more highly protonated species is not possible in fullydelocalized porphyrins possessing the 18 π-electron [18]diazaannulene delocalization pathway. When the titration was performed on the free dicarboxylic acid porphyrins, aggregation obscured the first protonation step and no clear monocation spectrum could be distinguished. However, also in that case the titration ended up to a UVvis spectrum typical of the dication and the effect of aggregation on the p K4 values was negligible. The UVvis spectrometric parameters are given for the neutral forms and for the protonated species of the porphyrin DMEs. The results are discussed in terms of the NH tautomerization connected to the π-electron delocalization pathway (aromaticity), which tends to hinder outofplane distortions in the porphyrin plane, and in terms of solvation and counterion stabilization of the protonated forms.

Chemical Constituents of the Leaves of Liriodendron chinense

Liriodendron is a genus of two species of characteristically large deciduous trees in the magnolia family (Magnoliaceae). Two species of Liriodendron are known to exist. Liriodendron tulipifera is native to eastern North America, while L. chinense is native to China and Vietnam. Both species often grow to great size, sometimes exceeding 32 m or 100 feet in height. In Hupeh, a province of China, L. chinense is called “Wo-Chang-Chiu,” which means goosefoot. This is referring to the shape of its leaves [1]. Earlier investigations on the chemical constituents of stems of L. chinense dealt with several alkaloids and sesquiterpenes [1, 2]. The chemical constituents of leaves of L. chinense have not yet been reported. This study deals with the isolation of chemical constituents from the leaves of L. chinense. To further understand the chemotaxonomy and to continue searching for biologically and chemically novel agents from Magnoliaceous plants [3], the leaves of L. chinense were chosen for further phytochemical investigation. The MeOH extract of its plants were subjected to solvent partitioning and chromatographic separation to afford 16 pure substances. The chemical constituents in the plants of L. chinense were separated by column chromatography. Investigation of the MeOH extract of the plants led to the isolation of 16 compounds, seven alkaloids: (–)-anonaine (1) [4], (+)-remerine (2) [5], (–)-asimilobine (3) [4], (–)-nornuciferine (4) [6], (–)-caaverine (5) [6], liriodenine (6) [4], and atherospermidine (7) [4]; two sesquiterpene lactones: epitulipinolide diepoxide (8) [7] and 11,13-dehydrolanuginolide (9) [8]; two lignans: (+)-syringaresinol (10) [9] and (+)-liriodendrin (11) [10]; three benzenoids: syringin (12) [1], syringaldehyde (13) [11], and syringic acid (14) [11]; one cyclitol: liriodendritol (15) [1]; and one steroid: -sitosterol (16) [4]. These compounds were obtained and characterized by comparison of their physical and spectral data (UV, IR, NMR, and MS) with values obtained in the literature. In addition to 7, 11, 15 and 16, all of these compounds were found for the first time from this species [1, 2]. The specimen of L. chinense was collected from Chiayi County, Taiwan in May, 2010. A voucher specimen was characterized by Dr. Jin-Cherng Huang of the Department of Forest Products Science and Furniture Engineering, National Chiayi University, Chiayi, Taiwan and deposited in the School of Medical and Health Sciences, Fooyin University, Kaohsiung County, Taiwan. The air-dried leaves of L. chinense (0.4 kg) were extracted with MeOH (50 L 5) at room temperature, and the MeOH extract (11.2 g) was obtained upon concentration under reduced pressure. The MeOH extract was chromatographed over silica gel using CH2Cl2–MeOH as eluent to produce six fractions. Part of fraction 2 (2.75 g) was subjected to silica gel column chromatography by eluting with n-hexane–acetone (60:1) to furnish five fractions (2-1–2-5). Fraction 2-3 (0.55 g) was further purified on another silica gel column using n-hexane–acetone (12:1) to obtain syringin (12) (6 mg). Part of fraction 3 (3.11 g) was subjected to silica gel column chromatography by eluting with n-hexane–acetone (50:1), then enriched with acetone to furnish three fractions (3-1–3-3). Fraction 3-1 (1.31 g) eluted with n-hexane–EtOAc (30:1) was further separated using silica gel column chromatography and preparative TLC (n-hexane–EtOAc, 10:1) to give -sitosterol (16) (37 mg). Fraction 3-2 (0.62 g) was further purified on a silica gel column using CH2Cl2–MeOH system to obtain syringaldehyde (13) (3 mg), syringic acid (14) (2 mg), and (+)-syringaresinol (10) (11 mg). Fraction 3-3 (0.33 g) eluted with n-hexane–acetone was further separated using silica gel column chromatography and preparative TLC (n-hexane–EtOAc, 6:1) to give liriodenine (6)

Cesium Carbonate Mediated Borylation of Aryl Iodides with Diboron in Methanol

AbstractHerein we describe the unexpected borylation of aryl iodides promoted by a Cs2CO3 and MeOH system. This formal nucleophilic boryl substitution could be applied to a wide range of functionalized aryl iodide compounds. The preliminary results indicate that this process is neither copper catalyzed nor radical mediated.

Zwitterionic Phosphine Ligand with a Lysine Tag and its Application for Hydroformylation of 1-Octene in Ionic Liquid/MeOH System

Here we report a highly active and selective hydroformylation of 1-octene in ionic liquid (IL)/MeOH system based on a zwitterionic phosphine ligand bearing a lysine moiety (L(NH2)COOH). The Rh-catalyst grafted lysine in the form of ammonium salt ([Rh-L(NH3 +)COOH]Tf2N) was successfully immobilized in the IL [bmim]Tf2N and recycled for seventeen times without significant loss of activity, selectivity and Rh catalysts. This study has provided a novel strategy for efficient separation and recycling of Rh catalysts.

Effect of the reducing agent on the hydrodechlorination of dioxins over 2 wt.% Pd/γ-Al2O3

2-Propanol and molecular H2 (in methanol (MeOH) and MeOH–water) were examined as reducing agents for the liquid phase hydrodechlorination (HDC) of dioxins over 2wt.% Pd/γ-Al2O3. Different amounts of NaOH were added to the reaction mixtures. The 2-propanol and H2(g)/MeOH systems presented similar HDC activity. Notwithstanding, Pd sintering and graphitic carbon directly bonded to Pd on catalyst surface was observed on samples used with H2(g)/MeOH. The addition of water to H2(g)/MeOH decreased Pd sintering and favored dissolution of sodium compounds. However, dioxin degradation efficiency diminished. By contrast, 2-propanol acting both as reducing agent and solvent provided hydrogen to the HDC reaction, avoided metal sintering and Pd–C formation. Besides, almost complete dioxin degradation under mild reaction conditions was obtained. Kinetic experiments of dioxin HDC with 2-propanol showed a maximum net reaction rate and turnover frequency (TOF) for a given initial concentration of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). After that value, both reaction rate and TOF decreased. On the other hand, reaction rates and TOFs of dioxin-like polychlorinated biphenyls (DL-PCBs) linearly increased with concentration.

Ultrafiltration of triglyceride from biodiesel using the phase diagram of oil–FAME–MeOH

To continuously obtain biodiesel of high purity, a membrane separator integrated with liquid–liquid extraction for the oil–FAME–MeOH system is studied. The liquid–liquid phase equilibrium data for the oil–FAME–MeOH are determined experimentally and compared with the general prediction of the modified UNIFAC. The tie line test demonstrates that composition of the methanol-rich phase is free of TG at 20 °C. Using the continuous cross-flow ultrafiltration, the oil-rich phase can be rejected by the ceramic membranes while the methanol-rich phase permeates through the membranes. When the feed bulk composition is controlled within the two-phase zone, such as the oil:FAME:MeOH of 20:30:50 wt.%, the permeate is found to be free of oil while the obtained permeate flux is higher than 300 kg/m 2 h under the transmembrane pressure of 600 mmHg and the inlet flow rate of 300 ml/min at 20 °C. By contrast, it shows almost no separation when the inlet concentration of oil–FAME–MeOH locates on its boundary line or within the single-phase zone. The quantitative filtration tests show that the compositions in the two liquid phases and the operating parameters are also considered simultaneously to screen the origin oil and get the FAME product of high purity.

Novel fluorene-based copolymer with pendant aza-crown ether: Highly sensitive and specific detection for CuSO4 and concurrent effect of anions

A novel fluorene-based copolymer with aza-15-crown-5 as pendant group was synthesized by Suzuki-coupling reaction, and characterized by 1H NMR, 13C NMR, EA, and GPC. The polymer was brightly blue emissive in common organic solvents, such as CHCl3, CH2Cl2, and THF. Fluorescent titration experiments carried out in THF–MeOH system indicate that the polymer has quite good selectivity and high sensitivity for CuSO4, which is contrasting to the weak responses for other copper salts such as Cu(ClO4)2, CuCl2, Cu(NO3)2, and Cu(OAc)2. Molecular simulation result suggests that this unique phenomenon may come from the synergistic effect of the bivalent counterion SO42−. This new system utilizing the strong luminescent property of polyfluorene as reporter and concurrent effect of the counterion SO42− may be developed as chemosensor for the special detection for CuSO4.