Methanol-ethanol Mixtures Research Articles

A Fast and Cost-Effective Electronic Nose Model for Methanol Detection Using Ensemble Learning

Methanol, commonly used to cut costs in the production of counterfeit alcohol, is extremely harmful to human health, potentially leading to severe outcomes, including death. In this study, an electronic nose system was designed using 11 inexpensive gas sensors to detect the proportion of methanol in an alcohol mixture. A total of 168 odor samples were taken and analyzed from eight types of ethanol–methanol mixtures prepared at different concentrations. Only 4 features out of 264 were selected using the feature selection method based on feature importance. These four features were extracted from the data of MQ-3, MQ-4, and MQ-137 sensors, and the classification process was carried out using the data of these sensors. A Voting Classifier, an ensemble model, was used with Linear Discriminant Analysis, Support Vector Machines, and Extra Trees algorithms. The Voting Classifier achieved 85.88% classification accuracy before and 81.85% after feature selection. With its cost effectiveness, fast processing time, and practicality, the recommended system shows great potential for detecting methanol, which threatens human health in counterfeit drink production.

Memristive gas sensor (gasistor) based on Ag/ordered TiO2 nanorods/FTO sandwich structure for evaluation of ethanol concentration in mixed ambient

Herein, we designed a memoristor-type gas sensor (gasistor) with Ag/ordered TiO2 nanorods/FTO sandwich structure for recognizing ethanol concentration in ethanol-methanol mixtures. The gas adsorption characteristics of different TiO2 substrates were first investigated by first-principle calculations. The results showed that the TiO2 surface in the low resistance state exhibited better immunity to other interfering gas molecules. However, similar adsorption energies and charge transfers calculated for adsorption of methanol and ethanol mean that the interference of methanol to the response of ethanol cannot be completely ignored. In next experiments, the Ag/TiO2/FTO gasistor with well-aligned TiO2 nanorods as the resistive layer was constructed successfully and demonstrated the stable resistive switching function and excellent retention characteristic. Further device tests confirm the ability of the gasistor in the low resistance state to discriminate between ethanol and methanol, as well as better anti-interference for other organic vapors. Also, an ultra-short recovery time (∼1.8 s) was observed by applying a direct current scanning voltage to the gasistor. Finally, to improve the recognition rate of ethanol in ethanol-methanol mixed atmosphere, a neural network algorithm based on back-propagation was incorporated and good prediction accuracy was obtained at ethanol concentrations ≥ 5 ppm.

Highly sensitive RF sensor based on microstrip meander line for measuring microfluidics dielectric properties of alcohol–alcohol mixtures

Abstract In this paper, a radio frequency sensor for measuring microfluidics dielectric properties is designed based on microstrip meander line. The meander sensor replaces the straight transmission lines with meander transmission lines in the part of the half-wavelength path difference to improve the sensitivity of the sensor and reduce its size. According to the experimental results, the meander sensor based on the meander line has higher accuracy and a lower relative error than the straight sensor in measuring methanol–ethanol mixtures with different molar fractions. The relative error measured by the meander sensor after calibration with an adjustable cavity is less than 1%. It is easier to detect the very slight variation in dielectric properties brought about by microfluidics. The detection technique can be further applied for the accurate detection of dielectric properties of valuable biological samples, providing a more concise and convenient way.

Investigation of solid–liquid equilibrium and thermodynamic models of D-Tagatose in mono-solvents and binary solvents

As a rare sugar, D-Tagatose is regarded as an excellent low-energy food sweetener. It is especially beneficial for physical health, such as inhibiting hyperglycemia, improving intestinal flora, and avoiding caries. It is broadly employed in food, medicine, cosmetics, and other fields. Acquiring D-Tagatose solubility is vital to develop D-Tagatose crystallization process to obtain high-quality D-Tagatose production. In this study, the solubility of D-Tagatose in seven pure solvents (methanol, ethanol, n-propanol, water, N, N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone), three binary solvents (ethanol-water mixtures, ethanol-methanol mixtures, and n-propanol-water mixtures) was determined by HPLC method at temperatures from 293.15 K to 323.15 K. Then, the Van't Hoff equation, Apelblat equation, λh equation, NRTL equation, CNIBS/Redlich-Kister model and modified Jouyban-Acree-van't Hoff model were used to correlate the solubility. The correlated solubility accounted for suitable compatibility with the experimental results (ARD <10%). Furthermore, we investigated the intermolecular interactions in the crystal structure through Hirshfeld surface analysis and estimated the overall charge distribution of molecules by molecular electrostatic potential surface (MEPs). Then, we analyzed the solvent effects and solvation free energy to explain the solubility behaviors. The results indicated that hydrogen bonds play a decisive role in determining the solubility of D-Tagatose.

Excess Molar Volumes, Apparent Molar Volumes, Partial Molar Volumes of Methionine, An Amino Acid, in Water + Ethanol And Water + Methanol Solutions at 298.15 K

Methionine is an amino acid that is extremely important for human health. To better understand the biochemical events occurring in the human body, the excess molar properties of methionine and aqueous ethanol and aqueous methanol mixtures were determined at 298.15 K. Interactions between components in solutions are explained. Negative deviations from the ideal state have been observed in methionine solutions due to hydrogen bonds, dipole interactions, charge-transfer interactions.

Dual-band measurement of complex permittivity in a microwave waveguide with a flexible, thin and sensitive metamaterial-based sensor

A dual-band metamaterial-based sensor is proposed to determine the complex dielectric constant of ethanol-methanol mixtures. The original sensor structure incorporates one connected dual H-shaped slot resonators at the center and one H-shaped slot resonator at the left and right sides of a rectangular copper patch to provide two distinct resonance frequencies. Polycarbonate is chosen as the substrate material due to its lightness, flexibility, robustness and transparency. Full-wave simulations of electric field distributions reveal that the dual resonances at 3.7 GHz and 4.6 GHz stem from different parts of the metamaterial. Measurements are carried out with a WR-229 microwave waveguide and the electromagnetic simulation results are confirmed with good agreement. A first-order equation that relates the complex dielectric constant to the shift of resonance frequency and peak attenuation is used to determine the complex dielectric constant of ethanol-methanol mixtures in the vicinity of 3.3 GHz and 4.4 GHz frequencies. A good agreement with the literature values is obtained validating the accuracy of the used model. Experimental results revealed that the frequency detection resolution and sensitivity parameter values of the proposed sensor are 25.3 MHz and 0.73% for the lower-frequency band and 9.6 MHz and 0.22% for the higher-frequency band, respectively. In addition to being able to operate at dual frequencies, the proposed metamaterial-based sensor has high sensitivities for the two resonance frequencies. Moreover, the advantages of the proposed sensor, as being electrically-small, flexible, noncontact and reusable, provide a good option for discrimination of binary liquid mixtures at multiple frequencies.

Correlation between Spectroscopic and Mechanical Properties of Gold Nanocrystals under Pressure

The effects of nonhydrostatic pressure on the morphology and stability of gold nanorods (AuNRs) and nanospheres (AuNSs) in 4:1 methanol–ethanol mixtures were studied by optical absorption spectroscopy and transmission electron microscopy at pressures of up to 23 and 30 GPa, respectively. Solvent solidification and associated nonhydrostatic stresses were found to have a negligible effect on the shape and size of AuNSs. On the contrary, while AuNRs maintained their initial morphology in the hydrostatic range, the uniaxial stress component induced under nonhydrostatic conditions had a shearing effect on the AuNRs, breaking them into smaller particles. Interestingly, colloidal stability was maintained in all cases, and the particles showed no sign of aggregation, despite the severe nonhydrostatic conditions to which both AuNR and AuNS colloids were subjected.

Monometallic platinum and palladium–based catalysts in the competitive oxidation of methanol over the liquid–phase methanol–ethanol mixtures

This work explored the catalytic performances of monometallic platinum and palladium–based catalysts applied in the competitive oxidation reaction of methanol in presence of ethanol as a possible quality control in counterfeit alcohol production. Pt and Pd over different supports like alumina, SBA–15, as well as faujasite type Y (FAU–Y) and ZSM–5 zeolites were applied in the competitive oxidation reaction of methanol and ethanol (equimolar amounts in 20 mL aqueous solution) with the addition of two kinds of oxidants (hydrogen peroxide (H2O2) and pure O2 gas) for sake of evaluating the alcohols oxidation effect. The results showed that Pt/FAU–Y catalyst had the best performance, due to the molecular size difference between methanol and ethanol and the negligible diffusivity of ethanol through the small pore faujasite, the optimized Pt active sites can be fully accessed by the methanol molecule.

Minkowski-like fractal resonator-based dielectric sensor for estimating the complex permittivity of binary mixtures of ethanol, methanol and water

A microwave dielectric sensor with defected ground structure including a Minkowski-like fractal resonator is proposed for estimating the complex permittivity of ethanol-water, methanol-water and ethanol-methanol mixtures. Positioned glass capillary tubes at the center of the metamaterial normal to the sensor surface, it is possible to see the fast impact of the shift of the transmission response for different liquid mixtures. The dimension of the proposed sensor is as small as 0.17λ0 × 0.17λ0 × 0.010λ0, where λ0 indicates the resonance wavelength in free-space. Complex permittivity of the liquid mixtures are estimated based on the shift of the resonance frequency and the magnitude of the S21 values by using a first-order model incorporating in characteristic matrix formulation. Estimated values indicated a very good agreement with the values in the reported studies. The sensitivity of the proposed sensor related to 0.07 μL effective sample volume is obtained to be 0.52 MHz/εr. The attractive features of the sensor, such as being label-free, reusable, easy to fabricate, practical, non-invasive and real-time, assure accurate determination of the complex permittivity of unknown liquid mixtures for applications in chemistry and medicine.

Experimental Measurement and Correlation of Solubilities of R-2[4-(6-Chloro-2-Benzoxazolyloxy)phenoxy]propanoic Acid in Methanol, Ethanol, and Methanol–Ethanol Mixed Solvents

The solubility of R-2[4-(6-chloro-2-benzoxazolyloxy)phenoxy]propanoic acid (abbreviated as Fenoxaprop-P) in methanol, ethanol and various methanol-ethanol mixed solvents have been experimentally measured in the temperature range from 273.15 to 323.15 K at atmospheric pressure using a laser monitoring observation technique. The experimental solubility of Fenoxaprop-P increases with increasing mole fraction of ethanol in the methanol–ethanol mixtures, which were analyzed by the solubility parameter. Experimental data were correlated with Buchowski–Ksiazczak λh equation and modified Apelblat equation. Computational results showed the Buchowski–Ksiazczak λh equation can fit the solubility data well. The dissolution enthalpy, entropy and Gibbs free energy of Fenoxaprop-P in methanol, ethanol and methanol-ethanol mixtures were also predicted by the Van’t Hoff and the Gibbs equation.

Clustering of alkanols confined in chabazite zeolites: Kinetic implications for dehydration of methanol-ethanol mixtures

Methanol-ethanol mixtures enable simultaneous quantification of bimolecular dehydration turnover rates (373 K, per H+) to dimethyl ether (DME) and methyl ethyl ether (MEE) on chabazite zeolites. Coverage terms for protonated alkanol clusters rigorously cancel in DME and MEE formation rate expressions, and enables isolating the kinetic relevance of trimer-mediated pathways to form DME, but not MEE, at high coverage (373 K, 2–50 kPa CH3OH). The kinetics of parallel product formation provide experimental evidence that DME formation rates are inhibited when larger protonated CH3OH clusters form (>3 CH3OH/H+) because they must desorb CH3OH to form kinetically-preferred trimer-mediated transition states.

Exploring pressure effects on metallic nanoparticles and surrounding media through plasmonic sensing

The sensing capabilities of gold nanorods under high-pressure conditions were investigated in methanol-ethanol mixtures (up to 13 GPa) and in water (up to 9 GPa) through their optical extinction. The longitudinal SPR band of AuNR exhibits a redshift with pressure which is the result of two main competing effects: compression of the conduction electrons which increases the bulk plasma frequency (blueshift) and increase in the solvent density (redshift). The variation in de SPR peak wavelength allows us to estimate the bulk modulus of the gold nanoparticles with a precision of 10 % and to obtain analytical functions providing the pressure dependence of the refractive index of water in three phases: liquid, ice VI and ice VII. Furthermore, the SPR band shows abrupt jumps at the liquid to ice phase VI and ice phase VII transitions, which are in accordance with the first-order character of these transitions.

Plasmonic Sensing of Refractive Index and Density in Methanol–Ethanol Mixtures at High Pressure

The localized surface plasmon resonance (LSPR) of gold nanospheres dispersed in methanol–ethanol 4:1 was measured as a function of pressure up to 60 GPa. The LSPR exhibits an intense red-shift with...

Scotch Tape Optical Vapor Sensor for Ethanol-Methanol Mixtures.

A simple optical vapor sensor based on conventional Scotch adhesive tape, for analyzing ethanol–methanol mixtures, is proposed and demonstrated. The sensing signal relies on the variation of optical power transmitted through the tape, resulting from the response of the adhesive material to vapor sorption. The optical sensor exhibits high selectivity for ethanol vapor over methanol vapor. When exposed to vapors from ethanol–methanol liquid mixtures, the sensor shows a linear detection range of 0–100 vol%, and detection limits of 8.8 vol% ethanol and 17.6 vol% methanol. Repeatability, reproducibility, reversibility, and sensitivity to other volatile organic compounds are also studied.

Methanol-ethanol “ideal” mixtures as a test ground for the computation of Kirkwood-Buff integrals

Mixtures of 1-alkanols are a textbook example of the concept of ideal mixtures. Yet, such mixtures have a very strong local order due to the hydrogen bonding interactions, with a strong tendency for chain formation. Despite this apparent non-ideality, the Kirkwood-Buff integrals of such system exhibit near ideal behavior. This dual property can be used to test the calculations of the Kirkwood-Buff integrals in a controlled mixing situation, and clarify many points, in particular the statistical problems that can be encountered. By studying the methanol-ethanol mixtures, we uncover an interesting physical asymmetry between low methanol and low ethanol concentrations, which can produce statistical artifacts in the calculation of Kirkwood-Buff integrals, illustrating and exemplifying some of the difficulties encountered in such calculations. Finally, liquid state integral equations results for these mixtures are reported. They help demonstrate that thermodynamic ideality hides complex correlations and microscopic non-ideality.

A Fully Integrated Low-Power 30 GHz Complex Dielectric Sensor in a 0.25-$\mu$m BiCMOS Technology

This paper presents an integrated low-power dielectric sensor in K-band frequencies implemented in a $0.25 \mu \mathrm{m}$ SiGe BiCMOS process, including the sensing front-end and readout circuits. The sensor enables the measurement of both real and imaginary part of permittivity of the material under test (MUT). The MUT is exposed on the resonator component in a sensing oscillator, and the oscillator results in permittivity- and conductivity-dependent change in the output frequency and output power, respectively. The frequency information is translated into dc voltage using a frequency discriminator, and the output power is detected using a power detector. The sensor has been calibrated using iso-propanol, ethanediol, and acetone solutions. Methanol–ethanol mixture solutions, in steps of 25% of concentration change, have been used to demonstrate the functionality of the sensor. The selectivity is showed using methanol–ethanol mixtures with concentration differences of 5% around a mixture ratio of 50:50. The chip is $2.3 \text{mm}^{2}$ in size and consumes 60 mW power. The sensor measures complex permittivity within 3.7% accuracy for the real part and 4.3% for the imaginary part. As a compact and low-power solution, the sensor is a potential candidate for minimal invasive investigations of chemicals and bio-materials at mm-wave frequencies.

High pressure Raman study of type-I collagen.

The high pressure response of type-I collagen from bovine Achilles tendon is investigated with micro-Raman spectroscopy. Fluorinert™ and methanol-ethanol mixtures were used as pressure transmitting media (PTM) in a diamond anvil cell. The Raman spectrum of collagen is dominated by three bands centred at approximately 1450, 1660 and 2930cm-1 , attributed to C-H deformation, C=O stretching of the peptide bond (amide-I band) and C-H stretching modes respectively. Upon pressure increase, using Fluorinert™ as PTM, a shift towards higher frequencies of the C-H stretching and deformation peaks is observed. Contrary, the amide-I band peaks are shifted to lower frequencies with moderate pressure slopes. On the other hand, when using the alcohol mixture as PTM, the amide-I band exhibits more pronounced C=O bond softening, deduced from the shift to lower frequencies, suggesting a strengthening of the hydrogen bonds between glycine and proline residues of different collagen chains due to the presence of the polar alcohol molecules. Furthermore, some of the peaks exhibit abrupt changes in their pressure slopes at approximately 2 GPa, implying a variation in the compressibility of the collagen fibres. This could be attributed to a pitch change from 10/3 to 7/2, sliding of the tropocollagen molecules, twisting variation at the molecular level and/or elimination of the D-gaps induced by kink compression. All spectral changes are reversible upon pressure release, which indicates that denaturation has not taken place. Finally, a minor lipid phase contamination was detected in some sample spots. Its pressure response is also monitored.

Comparison between the catalytic and photocatalytic activities of Cu/Al2O3 and TiO2 in the liquid–phase oxidation of methanol–ethanol mixtures: Development of a kinetic model for the preparation of catalyst

This work presents the preparation and characterization of copper supported on gamma alumina (γ–Al2O3) as a catalyst and compared with the photocatalytic activity of titania (TiO2) in the oxidation of methanol and ethanol mixtures; the ratio of both alcohols in the mixture was according to the commercial alcoholic beverages. In order to understand the thermal transformations of Cu/Al2O3 catalyst, a kinetic model of its synthesis has been developed and analyzed in terms of the oxidation of the precursor CuCl2∙2H2O impregnated onto Al2O3 to form CuO/Al2O3, and also its reduction to form the metallic copper supported on alumina (Cu/Al2O3) catalyst. The sequence of reactions was considered according to the X–ray diffraction (XRD) at different temperatures and thermal characterizations. The kinetic parameters revealed how the alumina support intervened in some steps to form the catalyst through chemical metal–support interactions. It was also verified that during the chemical changes that the active phase undergoes, its good dispersion is maintained on the support and the activation energy values of the model can predict that these metal–support chemical interactions were also preserved from the salt added to the formation of elementary copper. These kinetic model’s predictions were accurately demonstrated by High–resolution transmission electron microscopy (HRTEM) micrographs and X–ray photoelectron spectra (XPS) techniques, where the appearance of the copper aluminate phase (CuAl2O4) is an evidence of the metal–support interaction, which could have contributed to the elementary copper nanoparticles formation and the catalytic activity as an active phase in the oxidation of alcohols. Cu/Al2O3 catalyst showed a higher yield of acetic acid from ethanol than formic acid from methanol. In comparison, the TiO2 in the photocatalytic oxidation presented a higher yield of formic acid from methanol than acetic acid from ethanol. A similar behavior was observed in the oxidation tests of each alcohol separately, since, the photocatalytic oxidation of methanol, using TiO2, showed nearly the 100% of selectivity in the formation of formic acid from methanol, and the Cu/Al2O3 catalyst exhibited similar results but, in this case, the selectivity towards to acetic acid from ethanol. Stable acetate intermediates detected by FTIR in ethanol oxidation to acetic acid on Cu/Al2O3 showed that this oxidation proceeds via acetaldehyde intermediates.

Thermodynamics of R-(+)-2-(4-Hydroxyphenoxy)propanoic Acid Dissolution in Methanol, Ethanol, and Methanol-Ethanol Mixture

The solubilities of R-(+)-2-(4-hydroxyphenoxy)propanoic acid (D-HPPA) in methanol, ethanol and various methanol-ethanol mixtures are determined in the temperature range from 273.15 to 323.15 K at atmospheric pressure using a laser detecting system. The solubilities of D-HPPA increase with increasing mole fraction of ethanol in the methanol–ethanol mixtures. Experimental data were correlated with Buchowski-Ksiazczak λh equation and modified Apelblat equation; the first one gives better approximation for the experimental results. The enthalpy, entropy and Gibbs free energy of D-HPPA dissolution in methanol, ethanol and methanol-ethanol mixtures were also calculated from the solubility data.

Experimental study and thermodynamic modeling of xylitol and sorbitol solubility in mixtures of methanol and ethanol at different temperatures

The development of techniques related to biomass conversion into chemical products needs additional study and advances. It is necessary to perform experimental investigations and modeling in order to produce information about mixtures that could be used as reaction media or in separation processes. Research on phase equilibrium is fundamental for the achievement of valuable knowledge. Therefore, this research aims to perform a study of xylitol and sorbitol solubility in methanol-ethanol mixtures throughout the molar composition range and at temperatures ranging from 293.15K to 323.15K, under atmospheric conditions. The Jouyban-Acree, NRTL and UNIQUAC models were fitted to experimental data. The parameters of the models were explicitly obtained as temperature dependents.