Isothermal vapour–liquid equilibria in the binary and ternary systems composed of 2-propanol, diisopropyl ether and 1-methoxy-2-propanol

Vapour pressures for 1-methoxy-2-propanol are reported as well as the vapour–liquid equilibrium data in the two binary 2-propanol + 1-methoxy-2-propanol, and diisopropyl ether + 1-methoxy-2-propanol systems, and in the ternary 2-propanol + diisopropyl ether + 1-methoxy-2-propanol system. The data were measured isothermally at 330.00 and 340.00 K covering the pressure range 5–98 kPa. The binary vapour–liquid equilibrium data were correlated using the Wilson, NRTL, and Redlich–Kister equations; resulting parameters were then used for calculation of phase behaviour in the ternary system and for subsequent comparison with experimental data.     

Comparative study of the separation of methanol–methyl acetate mixtures by pervaporation and vapor permeation using a commercial membrane

In the present study, the permeation behavior of methanol and methyl acetate in the pervaporation (PV) experiments are compared with those in vapor permeation (VP) experiments using a PVA-based composite membrane. Experiments have been carried out to study the selectivity and mass transport flux of the systems under varying operations conditions of feed temperature (40–60 °C) and feed methanol concentrations (2–34 wt%). The selected membrane was found to be methanol selective. Results show higher permeation flux but a similar separation factor for methanol in PV than in VP. For PV operation, the resulting separation factor at 60 °C shows a monotonous decrease (6.4–4.1) as the alcohol concentration in the feed mixture increases (2.3–34 wt%), whereas the total flux increases from 0.97 to 7.9 kg m⁻² h⁻¹. Based on the solution-diffusion theory, a mathematical model that describes satisfactorily the permeation fluxes of methanol and methyl acetate in both the PV and VP processes has been applied. The fluxes of both permeants can be explained by the solution-diffusion model with variable diffusion coefficients dependent on MeOH concentration in the membrane. Both PV and VP processes can be described with the same model but using different fitting parameters.     

Phosphomolybdic acid supported on silica gel and promoted with alkali metal ions as catalysts for the esterification of acetic acid by ethanol

Different ratios of phosphomolybdic acid PMA supported on silica gel (1–30 wt%) and promoted with alkali metal hydroxide have been prepared by an impregnation method and calcinated at 350 °C for 4 h. The catalysts were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction, FT-IR spectroscopy and N₂ adsorption measurements. The surface acidity and basicity of the catalysts were determined by adsorption of pyridine and the dehydration–dehydrogenation of 2-propanol. The gas-phase esterification of acetic acid by ethanol was carried out in a conventional flow bed reactor. The results clearly revealed that among the PMA loading, the use of 10 wt% catalyst showed maximum yield of ethyl acetate. This catalyst also improved on addition of Na or K-hydroxide. These results were correlated with the structure and the acid–base properties of the prepared catalysts.     

Excess molar volume measurements of ternary mixtures [2-propanol+ethyl acetate+n-hexane] and their binary constituents at 298.15, 308.15 and 313.15 K

The excess molar volume of the ternary mixture [2-propanol?+?ethyl acetate?+?n-hexane], and its binary constituents; [2-propanol?+?ethyl acetate], [2-propanol?+?n-hexane] and [ethyl acetate?+?n-hexane] were evaluated by the mixtures density measurements over the whole concentration range at three temperatures 298.15, 308.15 and 313.15?K. The excess molar volumes data were fitted to the Redlich–Kister (RK) type equation and the parameters of this equation have been calculated and presented for the studied mixtures.     

Densities and Viscosities of the Ternary Mixture (Benzene + 1-Propanol + Ethyl Acetate) at 298.15 K

Abstract

Densities and viscosities of the ternary mixture (benzene + 1-propanol + ethyl acetate) and the corresponding binary mixtures (benzene + 1-propanol, benzene + ethyl acetate and 1-propanol + ethyl acetate) have been measured at the temperature 298.15 K. From these measurements excess volumes, V^E , excess viscosities, η^E, and excess Gibbs energies of activation for viscous flow, G*^E , have been determined. The equation of Redlich-Kister has been used for fitting the excess properties of binary mixtures. The excess properties of the ternary system were fitted to Cibulka's equation.     

Synthesis of industrial scale NaY zeolite membranes and ethanol permeating performance in pervaporation and vapor permeation up to 130 °C and 570 kPa

NaY zeolite tubular membranes in an industrial scale of 80 cm long were synthesized on monolayer and asymmetric porous supports. The quality of synthesized membranes were evaluated by pervaporation (PV) experiments in 80 cm long at 75 °C in a mixture of water (10 wt.%)/ethanol (90 wt.%), resulting in higher permeation fluxes of 5.1 kg m⁻² h⁻¹ in the monolayer type membrane and of 9.1–10.1 kg m⁻² h⁻¹ in the asymmetric-type membranes, respectively. The uniformity with small performance fluctuation in longitudinal direction of the membranes were observed by PV for 10–12 cm long samples at 50 °C in a mixture of methanol (10 wt.%)/MTBE (90 wt.%). The ethanol single component permeation experiments in PV and vapor permeation (VP) up to 130 °C and 570 kPa were performed to determine the relations between the ethanol flux and the ethanol pressure difference across the membrane which is represented by permeance (Π, mol m⁻² s⁻¹ Pa⁻¹) for estimate of potential of ethanol extraction through the present NaY zeolite membranes applying feasible studies. Results indicate that (1) the permeation fluxes are linearly proportional to the driving force of vapor pressure for each sample in VP and PV. The permeances through an asymmetric support type membrane were rather constant of 0.6–1.2 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ in the wide temperature range of 90–130 °C in PV and VP, indicating that the ethanol permeances have weak temperature dependency with the feed at the saturated vapor pressure.

The results of superheating VP experiments showed that ethanol permeation fluxes are increased with increasing of the degree of superheating at a given constant feed vapor pressure. The ethanol permeances are increased with increasing of temperature at a given feed vapor pressure. The superheating VP could be a feasible process in industry.     

Studies on phenol permeation through supported liquid membranes containing functionalized polyorganosiloxanes

In this study, the functionalized, linear, hydrophobic fluid organosiloxane polymers, namely, methylhydrosiloxane–dimethylsiloxane copolymers supported on a polypropylene microporous flat sheet membrane (Celgard 2502 and 2402) have been tested as supported liquid membranes (SLMs) for phenol recovery from aqueous phases into a 0.1 M NaOH phase. The functionalized polymers include, Me₃SiO[MeSi(OR)O]_x[Me₂SiO]_ySiMe₃ (containing x = 15–18, 25–35 and 50–55 mol% of R, where R is –(CH₂)_nNMe₂ (n = 3 or 4 or 6) or –(CH₂)₂OEt pendent organofunctional groups. The functionalities, R, tested were derived from the commercially available 3-dimethylamino-1-propanol and 2-ethoxyethanol as well as newly synthesized 4-dimethylamino-1-butanol and 6-dimethylamino-1-hexanol which have been made for the purpose of this study.

The study showed that phenol permeation expressed as permeate flux through the membranes increases with the larger number of carbon spacers in the alkyl chain of the aminoalcohol pendent, larger porosity of the polypropylene support films, higher mol% of the methylhydrosiloxane portion functionalized and faster flow rates of both the feed and the receiving phases. Phenol permeation was enhanced significantly when the mol% of the methylhydrosiloxane portion was 50–55 or 25–35 with 6-dimethylamino-1-hexanol functionality supported on Celgard 2502.     

环氧丙烷和甲醇在MgO上合成1-甲氧基-2-丙醇反应机理

应用原位FT-IR详细研究了MgO上甲醇对环氧丙烷的加成反应. 结果表明在MgO催化剂上甲醇很易解离吸附形成甲氧基, 根据负碳离子机理, 吸附环氧丙烷可形成类丙烯物种. 甲氧基对类丙烯物种的加成反应遵循反-Markownikov法则, 高选择性地合成1-甲氧基-2-丙醇.     

A photocatalytic membrane reactor for VOC decomposition using Pt-modified titanium oxide porous membranes

Porous titanium oxide membranes with pore sizes in the range of 2.5–22 nm were prepared by a sol–gel procedure, and were applied for decomposition of methanol and ethanol as model volatile organic compounds (VOCs) in a photocatalytic membrane reactor, where oxidation reaction occurs both on the surface and inside the porous TiO₂ membrane while reactants are permeating via one-pass flow. Methanol was completely photo-oxidized by black-light irradiation to CO₂ when methanol at a concentration of 100 ppm was used at a feed flow rate of 500 × 10⁻⁶ m³/min, but the conversion decreased when the MeOH concentration in the feed was increased. Pt-modification was carried out by photo-deposition, and led to a decrease in pore diameter. Using Pt-modified membranes, a nearly complete oxidation of methanol up to 10,000 ppm at a feed flow rate of 500 × 10⁻⁶ m³/min was observed. Thus, such membranes would be effective for purifying a permeate stream after one-pass permeation through the TiO₂ membranes. The decomposition of ethanol is also discussed.     

Formation of cellulose acetate membranes using a supercritical fluid assisted process

Microporous cellulose acetate membranes have been prepared from polymer–acetone solutions using a supercritical fluid phase inversion process in which CO₂ acts as the non-solvent. Series of experiments were performed at various polymer concentrations, temperatures and pressures. The structure of the resulting membranes was analysed using scanning electron microscopy. We operated with polymer concentrations ranging between 5 and 40% (w/w) in acetone obtaining different pore dimensions and membrane structures. Increasing the percentage of polymer in the solution, the structure of the membranes changed from beads-like structure to cellular structure. Polymer concentration also influenced the mean diameter of the pores that ranged from 2 to 50 μm for polymer concentrations from 40 to 5% (w/w). We also tested membrane formation pressures between 100 and 200 bar and at temperature between 45 and 65 °C. Pressure influences the change in membrane structure from cellular to beads-like, whereas temperature has a minor influence on pore size: both the effects can be partially related to CO₂ density. Cellulose acetate membrane formation mechanisms have also been discussed.     

Temperature Dependence of Excess Molar Volumes of Ethanol + Water + Ethyl Acetate

In order to design and optimize equipment needed for production of distilled alcoholic beverages, an adequate knowledge of their physical properties and phase equilibria is necessary. The key thermodynamic information needed is for those chemicals that are the main components in terms of nonideal behavior. In this paper we present the temperature dependence of the excess molar volumes of the ternary system ethanol + water + ethyl acetate in the range 288.15–323.15 K at atmospheric pressure, due to the importance of ethyl acetate among the flavor compounds contained in this type of beverage. The observed excess molar volumes are usually negative over the whole homogeneous composition range, but take on positive values as the binary ethanol + ethyl acetate system is approached and the liquid phase separation region is observed. Because the current process designs are strongly computer oriented, the accuracy of theoretical model predictions was examined. The experimental data were used to test the capability of the Soave–Redlich–Kwong (SRK) equation of state to predict the ternary mixture behavior from binary mixture interaction parameters, which were obtained from previously published data. Derived properties, such as partial the excess molar volumes, excess isobaric expansibility, and the pressure derivative of excess molar enthalpy at constant temperature were calculated, due to their importance in the study of specific molecular interactions.     

The full evaporation technique: a promising alternative for residual solvents analysis in solid samples

The static headspace technique is the most common approach to residual solvent analysis in pharmaceutical and environmental matrices. This paper presents an alternative tool where the volatile impurities are released from the matrix by working directly on a small amount of sample at a high equilibration temperature: the so-called Full Evaporation Technique (FET). The capability of this method was evaluated on a mixture of nine solvents, which belong to Class 3 in the classification of the European Pharmacopoeia Agency for residual solvents, at various levels of concentration: ethanol, acetone, 2-propanol, methyl acetate, 2-butanone, ethyl acetate, tetrahydrofuran, 2-methyl-1-propanol, 1-butanol. Data on linearity, accuracy, precision and sensitivity are reported. Use of an internal standard proved to be necessary when using such a method. The method is then successfully applied to the analysis of solvent traces in permethylated beta-cyclodextrin.     

Liquid–liquid equilibria of water/1-propanol/methyl ethyl ketone/potassium chloride

The liquid–liquid equilibrium of water/1-propanol/methyl ethyl ketone (MEK) at 25°C was significantly modified by the presence of dissolved potassium chloride. Water is salted out of the organic phase while MEK is more preferentially salted out of the aqueous phase than 1-propanol. These results in considerable enlargement of the two-phase region and enhancement of the extractive efficiency of MEK for the separation of 1-propanol from its aqueous mixture. Good correlation of the liquid–liquid equilibria (LLE) of the system in the presence of potassium chloride up to saturation was obtained with Tan’s modified NRTL phase model for multicomponent solute–solvent mixtures with the solute–solvent interaction parameters expressed as a third-order polynomial function in salt concentration. Similar to the observation reported for vapour–liquid equilibrium (VLE) of solvent–solute mixtures, salting-in and salting-out of the solvent components from the respective phases can be predicted according to the relative solute–solvent interaction parameters of the solvent components in the two phases.     

Hydrothermally stable silica–alumina composite membranes for hydrogen separation

A thin layer (30–40 nm) of a dual-element silica–alumina composition was deposited on a porous alumina support by chemical vapor deposition (CVD) in an inert atmosphere at high temperature. Prior to CVD, an intermediate layer of γ-alumina was coated on the macroporous alumina support. The intermediate layer was prepared by the dip-coating and calcination of boehmite sols of different sizes to give a graded structure that was substantially free of defects. The resulting supported composite membrane had high permeance for hydrogen in the order of 2–3 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ at 873 K with selectivities of H₂ over CH₄, CO and CO₂ of 940, 700 and 590, respectively. The membrane operated by a hopping mechanism involving jumps of permeating molecules between solubility sites. The presence of aluminum improved the hydrothermal stability of the membranes for periods in excess of 500 h at 873 K in 16% steam, allowing the permeance to remain above 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹, although with decreased selectivities.     

Density fractionated hollow silica microspheres with high-yield by non-polymeric sol–gel/emulsion route

Hollow silica microspheres were synthesized by non-polymeric sol–gel/emulsion technique using tetra ethyl orthosilicate (TEOS) as a source of silica. A sol mixture of TEOS, water, ethanol and acid was emulsified in a solution of light paraffin oil and surfactant (Span-80). Calcined spheres were density fractionated between density ranges: <1.0, 1.0–1.594, 1.594–1.74 and >1.74 g cm⁻³. The samples were characterized by optical and scanning electron microscopy with energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and laser diffraction size analyzer. Spheres of densities lower than 1.74 g cm⁻³ were found to be hollow as observed from scanning electron microscopy (SEM) images and their yield was maximized to 100% by using a specific TEOS volume ratio with respect to volumes of surfactant and oil. Decreasing the calcination temperature from 700 to 500 °C enhances the yield of hollow spheres emphasizing importance of slower diffusion kinetics at lower calcination temperature. Outer diameters of spheres were between 5 and 60 μm with mean diameter expectedly increasing with increase in TEOS sol volume and with decrease in sphere density. It is proposed that silica shells form via hydrolysis and polycondensation at oil–water/ethanol interface in the water-in-oil emulsion, which subsequently form hollow spheres on removal of water–ethanol during calcination.     

Novel CO2 selectively permeating membranes containing PETEDA dendrimer

Pentaerythrityl tetraethylenediamine (PETEDA) dendrimer was synthesized from pentaerythrityl tetrabromide and ethylenediamine. Its molecular structure was characterized by elemental analysis, Fourier transform infrared resonance (FT-IR) and hydrogen nuclear magnetic resonance (¹H NMR) spectroscopy. The composite membranes for selectively permeating CO₂ were prepared by using PETEDA-PVA blend polymer as the active layer and polyethersulfone (PES) ultrafiltration membrane as the support layer and their permselectivity was tested by pure CO₂ and CH₄ gases and the gas mixture containing 10 vol.% CO₂ and 90 vol.% CH₄, respectively. For pure gases, the membrane containing 78.6 wt% PETEDA and 21.4 wt% PVA in the blend has a CO₂ permeance of 8.14 × 10⁻⁵ cm³ (STP) cm⁻² s⁻¹ cmHg⁻¹ and CO₂/CH₄ selectivity of 52 at 143.5 cmHg feed gas pressure. While feed gas pressure is 991.2 cmHg, CO₂ permeance reaches 3.56 × 10⁻⁵ cm³ (STP) cm⁻² s⁻¹ cmHg⁻¹ and CO₂/CH₄ selectivity is 19. For the gas mixture, the membrane has a CO₂ permeance of 6.94 × 10⁻⁵ cm³ (STP) cm⁻² s⁻¹ cmHg⁻¹ with a CO₂/CH₄ selectivity of 33 at 188.5 cmHg feed gas pressure, and a CO₂ permeance of 3.29 × 10⁻⁵ cm³ (STP) cm⁻² s⁻¹ cmHg⁻¹ with a CO₂/CH₄ selectivity of 7.5 at a higher feed gas pressure of 1164 cmHg. A possible gas transport mechanism in the composite membranes is proposed by investigating the permeating behavior of pure gases and the gas mixture and analyzing possible reactions between CO₂/CH₄ gases and the PETEDA-PVA blend polymer. The effect of PETEDA content in the blend polymer on permselectivity of the composite membranes was investigated, presenting that CO₂ permeance and CO₂/CH₄ selectivity increase and CH₄ permeance decreases, respectively with PETEDA content. This is explained by that with increasing PETEDA content, the carrier content increases, and the crystallinity and free volume of the PETEDA-PVA blend decrease that were confirmed by the experimental results of X-ray diffraction spectra (XRD) and positron annihilation lifetime spectroscopy (PALS).     

Chiral separation of (R,S)-2-phenyl-1-propanol through cellulose acetate butyrate membranes

As the cellulose acetate butyrate possessed multichiral carbon atoms in its molecular structure unit, enantioselective membrane was prepared using cellulose acetate butyrate as membrane material. The flux and permselective properties of membrane using aqueous solutions of (R,S)-2-phenyl-1-propanol as feed solution was studied. The top surface and cross-section morphology of the resulting membranes were examined by scanning electron microscopy. When the membrane was prepared with 15 wt.% cellulose acetate butyrate and 20 wt.% DMF in the casting solution, and the operating pressure and feed concentration of racemate were 2 kgf/cm² and 5 mmol/L, respectively, over 98% of enantiomeric excess (e.e.) was obtained. This is a report, for the first time, that the cellulose acetate butyrate is used as optical resolution membrane material for isolating the optical isomers of (R,S)-2-phenyl-1-propanol.     

1-Ethylthio-2-[2-thienyltelluro]ethane (L) a new (Te, S) ligand: Synthesis and complexation with Ag(I), Cu(I), Pd(II) and Pt(II) – Single crystal structures of [PdCl2(L)] and bis(thienyl) tellurium(IV) chloride

Lithium 2-thienyltellurolate, generated from 2-thienyl lithium, reacts at −78 °C in THF with chloroethyl ethyl sulfide to give a (Te, S) ligand 1-ethylthio-2-[2-thienyltelluro]ethane (L) as a red oil. The complexes [PdCl₂(L)] (1), [PtCl₂(L)] (2), [Ag(L)₂][ClO₄] (3) and [CuBr(L)]₂ (4) were synthesized. The complex [HgCl₂(L)] on crystallization decomposed giving Th₂TeCl₂ (5) [where Th = 2-thienyl], which was characterized by X-ray diffraction on its single crystals. The ligand L and complexes 1–4 exhibit proton and carbon-13 NMR spectra, which are characteristic. The coordination through Te in 1–4 is indicated by downfield coordination shifts in the position of the TeCH₂ signal of L. Complex 1 was characterized by X-ray diffraction on its single crystals. The geometry around Pd is square planar. The Pd–Te, Pd–S and Pd–Cl bond lengths are 2.5040(4), 2.273(1) and 2.322(1)/2.380(1) Å, respectively. There are intermolecular interactions between Te (coordinated to Pd) and Cl, and sulfur and Cl. The Te–Cl and S–Cl distances, 3.401 and 3.488 Å, respectively, are shorter than the sum of the van der Waal’s radii (3.81 and 3.55 Å, respectively). The Pd–Pd distance between the two molecules is 3.4156(6) Å, greater than the sum of van der Waal’s radii (3.26 Å). The structure of 5 is typical of that of a tellurium(IV) compound (saw-horse type). The two Te–Cl bond lengths are identical, 2.480(1) Å. The geometry around Te in 5 can be best described as pseudo tetrahedral (trigonal bipyramidal with a lone pair on one corner of the triangle).     

Phase equilibria of the ternary system vinyl acetate/(R,S)-1-phenylethanol/carbon dioxide at high pressure conditions

Phase equilibrium measurements, correlations and predictions are presented for the binary systems (R,S)-1-phenylethanol/CO₂ and vinyl acetate/CO₂ and for the ternary system vinyl acetate/(R,S)-1-phenylethanol/CO₂. Experiments for the ternary system were performed in the temperature range of 323–343 K and in the pressure range of 7–12 MPa, using a high pressure phase equilibrium apparatus with a high pressure visual variable volume cell. Phase compositions were determined by taking samples of each phase and analysing them by gas chromatography. Equilibrium data were correlated with the Peng–Robinson equation of state combined with the Mathias–Klotz–Prausnitz mixing rule. A good correlation of both phases behaviour was obtained with an average absolute deviation (AAD) of 6.80%. Predictions for the binary sub-systems and for the ternary system were performed using the Peng–Robinson and the Soave–Redlich–Kwong equation of state, with the predictive mixing rule MHV1.