Increasing Methanol Concentration Research Articles

Catalytic Compatibility of Methanol with Petroleum Naphtha in Mixed Feeds Used in the Thermal-Catalytic/Steam-Cracking (TCSC) Process for the Production of Propylene and Ethylene

In the thermal-catalytic steam-cracking (TCSC) of “naphtha–methanol” mixtures, the increasing presence of methanol in the feed significantly modified the kinetics of the catalytic cracking. The gradual and significant decrease of the apparent activation energy with increasing methanol concentration in the mixed feed was attributed to the effect of intensive interactions between the two types of molecules: hydrocarbons and methanol. The addition of methanol into petroleum naphtha feed, up to 25 wt%, did not significantly change the catalytic performance of the TCSC hybrid nano-catalyst, suggesting that this catalyst could create at such relatively low methanol concentrations, a certain compatibility between the feed components.

Regularities of retention of benzoic acids on microdispersed detonation nanodiamonds in water-methanol mobile phases

The dependences of the retention of benzoic acids on microdispersed sintered detonation nanodiamond (MSDN) on the concentration of the organic solvent in the eluent and the temperature of the chromatographic column under conditions of high-performance liquid chromatography (HPLC) are investigated. It is found that in the investigated range of methanol concentrations, the acids are retained by different mechanisms: at methanol contents of the eluent lower than 85%, retention decreases with increasing methanol concentration and increases at higher concentrations of the organic solvent. It is shown that retention of benzoic acids on MSDN under these conditions depends on the dissociation constant of the investigated substances. A comparison is made between the properties of MSDN and analogous properties of porous graphitic carbon.

Effects of Concentration, Temperature, and Solvent Composition on the Partial Molar Volumes of Sodium Lauryl Sulfate in Methanol (1) + Water (2) Mixed Solvent Media

Precise measurements on the density of sodium lauryl sulfate in pure water and in methanol (1) + water (2) mixed solvent media containing (0.10, 0.20, 0.30, and 0.40) volume fractions of methanol at (298.15, 308.15, 318.15, and 323.15) K are reported. The concentrations are varied from (0.3·10–1 to 1.3·10–1) mol·kg–1. The results were almost constant on the partial molar volumes with increasing surfactant concentration. Also, the partial molar volumes are found to increase with increasing temperature over the entire concentration range investigated in a given mixed solvent medium and are found to decrease with increasing methanol content in the solvent composition.

Rheological properties of physical gel formed by hydrophobically modified urethane ethoxylate (HEUR) associative polymers in methanol–water mixtures

We investigated the effects of methanol on the two rheological properties, dynamic modulus and flow behaviour, for an aqueous solution of hydrophobically ethoxylated urethane (HEUR). When the added methanol constitutes 0–10 mol% of the sample, the gel relaxation time shortens; when it constitutes 20 mol% of the sample, the distribution of relaxation times broadens. Relaxation of the physical gel formed by a transient network is directly related to the lifetime of the crosslink points, i.e. flower micelles. We speculate that methanol addition shortens the relaxation time by changing the hydrophobic interactions in the flower micelles. The changed hydrophobic interactions then affect not only the relaxation time but also the shape of the HEUR-chain molecular associating structures which in turn affects the mechanical spectrum. Under constant shear flow, shear thickening increases with increasing methanol concentration, and the increase in stress under constant shear flow shows unusual behaviour. A possible contributing factor to this behaviour may be the non-cosolvency of methanol with polyethyleneoxide (PEO). At some critical concentration, methanol in PEO aqueous solution becomes a poor solvent, which then affects the properties of the PEO chains in the transient networks of HEUR aqueous solution. The rheological properties of the transient networks clearly affect the properties of both the crosslink points and the chains. In short, methanol addition induces complicated changes in gel mechanical properties.

Self-assembly of thermo-responsive poly(oligo(ethylene glycol) methyl ether methacrylate)-C 60 in water-methanol mixtures

Well-defined statistical copolymer of poly (di(ethylene glycol) methyl ether methacrylate–stat-oligo(ethylene glycol) methyl ether methacrylate-C 60 ((PMEO 2MA-stat-POEGMA 300)-C 60) was synthesized via atom transfer radical polymerization (ATRP) reaction and atom transfer radical addition (ATRA) processes. The lower critical solution temperature (LCST) of PMEO 2MA-stat-POEGMA 300 increased from 42 to 95 °C when the amounts of methanol was increased from 0 to 30 vol%, beyond which the LCST could not be quantified. Similarly, the LCST of (PMEO 2MA-stat-POEGMA 300)-C 60 also increased with methanol content, however it was lower than PMEO 2MA- stat-POEGMA 300 for all methanol/water compositions. The CMC of (PMEO 2MA-stat-POEGMA 300)-C 60 increased with increasing methanol content, suggesting that methanol is a better solvent for PMEO 2MA-stat-POEGMA 300 segment. The amphiphilic (PMEO 2MA-stat-POEGMA 300)-C 60 structure formed spherical micelles in water/methanol mixture, and larger micelles were formed at higher methanol content. The hydrodynamic radius (R h) remained constant at temperature below the LCST. It increased dramatically at temperature greater than the LCST, and the (R g/R h) increased from ∼0.75 to ∼1.0. We believe that the (PMEO 2MA- stat-POEGMA 300) coronas dehydrate at higher temperature, and the micelles associate to form larger aggregates. In water/methanol mixtures, core-shell micelles and large compound micelles are produced below and above the LCST respectively.

Experimental and Theoretical Studies on the Enantioseparation and Chiral Recognition of Mandelate and Cyclohexylmandelate on Permethylated β-Cyclodextrin Chiral Stationary Phase

Enantioseparations of methyl mandelate (MMA) and methyl α-cyclohexylmandelate (MCHMA) on permethylated β-cyclodextrin (PM-β-CD) chiral stationary phase were explored in detail using high-performance liquid chromatography. The influence of the concentration of organic modifiers, along with the column temperature, was studied. In addition, the thermodynamics parameters of the enantioseparations were determined to discuss driven power in the process of enantioseparations. In addition, host−guest complexation of PM-β-CD with MMA enantiomers was simulated by quantum mechanics PM3 method for understanding the chiral recognition mechanism. The experimental results showed that the retention factor (k), separation factor (α), and resolution factor (Rs) for MMA and MCHMA resolved on the PM-β-CD column all generally decreased with the increase of methanol content, which indicated that the main chiral recognition mechanism is that the hydrophobic portions of MMA and MCHMA are included in the hydrophobic cavity of PM-β-CD to form inclusion complexes. In addition, there is an excellent linear relationship between the logarithms of retention factors (k) of MMA and MCHMA enantiomers and 1/T. It was demonstrated that the enantioseparations of MMA and MCHMA on PM-β-CD chiral column were enthalpy-driven processes. The modeling results can correctly predict the retention order and provide an atomistic account of how chiral discrimination takes place. It is found that the most stable structure of (R)-MMA/PM-β-CD complex is different with that of (S)-MMA/PM-β-CD complex. The main driving forces responsible for chiral recognition are hydrophobic forces and weak hydrogen bondings.

Poly(vinyl alcohol)‐based polymeric membrane: Preparation and tensile properties

AbstractA series of poly(vinyl alcohol) (PVA)‐based single‐layer organic polymeric membranes were prepared via the crosslinking of PVA with different amounts of formaldehyde. Meanwhile, for comparison, both a three‐layer organic polymeric membrane and a hybrid composite membrane were also prepared by the layer‐upon‐layer method. Their thermal stability and tensile properties were investigated to examine the effect of crosslinking on the membrane performances. Thermogravimetric analysis and differential scanning calorimetry thermal analyses showed that the thermal degradation temperature of the single‐layer crosslinked membrane C reached up to 325°C. Tensile testing indicated that the three‐layer organic polymeric membrane E had excellent tensile strength among these single‐layer and three‐layer membranes. The swelling properties revealed that the swelling degree value of these membranes decreased with an increase in methanol concentration; this suggests that they were not easily swollen by the methanol solution, which is meaningful for the separation of organic mixtures. Field emission scanning electron microscopy images exhibited that the crosslinking of functional groups impacted their structures and confirmed that their mechanical properties were related to their structures. These findings suggest that the crosslinking of functional groups is an effective method for adjusting the tensile strength of PVA‐based organic polymeric membranes and related hybrid composite membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Simultaneous Analysis of Multiple Endogenous Plant Hormones in Leaf Tissue of Oilseed Rape by Solid‐phase Extraction Coupled with High‐performance Liquid Chromatography–Electrospray Ionisation Tandem Mass Spectrometry

Plant hormones are important signalling molecules that act at lower concentrations to regulate numerous plant physiological and developmental processes. In order to study the functions of plant hormones, it is necessary to develop a high-throughput and highly selective and sensitive method for determination of plant hormones. Based on SPE-HPLC-ESI-MS/MS method, a highly selective and sensitive method for determination of six plant hormones in leaf tissue of oilseed rape was developed. The extraction was performed with C₁₈ solid-phase extraction cartridge and the sample was subsequently analysed by HPLC-ESI-MS/MS. Methanol and H₂O with 0.05% formic acid was selected as the mobile phase for HPLC, using a gradient of increasing methanol content. The plant hormones were quantified in MRM mode and identified in IDA mode by the hybrid triple quadrupole/linear ion trap mass spectrometer with high sensitivity and selectivity. Under the optimal conditions, good linearities were obtained for six plant hormones with the correlation coefficients above 0.9924. The detection limits of the target compounds were in the range of 0.005-0.2 ng/mL. Reproducibility of the method was obtained with intra-day and inter-day relative standard deviations. The extraction recovery yields of plant hormones under SPE conditions ranged from 67.03 to 119.83%. Compared with previous methods, sample preparation time and amount of sample required for analysis of plant hormones were reduced, and more classes of hormones were quantitatively measured.

Performance characteristics of a novel tubular-shaped passive direct methanol fuel cell

The present work consists of a tubular-shaped direct methanol fuel cell (DMFC) that is operated completely passively with methanol solution stored in a central fuel reservoir. The benefit of a tubular-shaped DMFC over a planar-shaped DMFC is the higher instantaneous volumetric power energy density (power/volume) associated with the larger active area provided by the tubular geometry. Membrane electrode assemblies (MEAs) with identical compositions were installed in both tubular and planar-shaped, passive DMFCs and tested with 1, 2, and 3M methanol solutions at room temperature. The peak power density for the tubular DMFC was 19.0mWcm−2 and 24.5mWcm−2 while the peak power density for the planar DMFC was 20.0mWcm−2 and 23.0mWcm−2 with Nafion® 212 and 115 MEAs, respectively. Even though the performance of the fuel cell improved with each increase in methanol concentration, the fuel and energy efficiencies decreased for both the tubular and planar geometries due to increased methanol crossover. The tubular DMFC experienced higher methanol crossover potentially due to a higher static fluid pressure in the anode fuel reservoir (AFR) caused by the vertical orientation of the tubular fuel reservoir. The performance of the tubular DMFC in this work represents an 870% improvement in power density from the previous best, passive, tubular DMFC found in the literature.

Preparation of α‐Calcium Sulfate Hemihydrate from Calcium Sulfate Dihydrate in Methanol–Water Solution under Mild Conditions

For the first time, α‐calcium sulfate hemihydrate (α‐HH) was successfully prepared from calcium sulfate dihydrate (DH) in methanol–water solution under atmospheric pressure. The effect of methanol concentrations (40–73 mol%) on the transition from DH to α‐HH were investigated at temperatures (60°–75°C) within a reaction time of 36 h. The results showed that an increase in methanol concentration could lower the transition temperature. The transition was speeded up by increasing methanol concentration from 47 to 57 mol% at 75°C. When the temperature dropped to 70°C, the transition rate firstly increased with the methanol concentration until it reached 69 mol% and then exhibited a reverse trend with increasing methanol concentration from 71 to 73 mol%. The accelerating effect, involved during the nucleation of α‐HH, attributes to the elevated supersaturation due to the fall in the water activity resulting from the increasing methanol concentration. The retarding effect, involved during the crystal growth of α‐HH, was likely derived from the specific adsorption of methanol molecules onto the surfaces of α‐HH crystals. Overall, the aqueous solution of methanol could act as a novel category of medium suitable for the α‐HH preparation from DH.

Effect of water–methanol content on the structure of Nafion in the sandwich model and solvent dynamics in nano-channels; a molecular dynamics study

Continuing an ongoing study, molecular dynamics (MD) simulations were performed to investigate the effects of methanol concentration on Nafion morphology, such as the size of solvent cluster, solvent location, and polymer structure via the sandwich model. Our survey shows that high methanol concentrations resulted in increment of solvent cluster size in Nafion membrane. The sulfonic acid clusters also befall much in order as subsequent layers of such ionic clusters are formed. The number of neighbouring hydronium ions around a sulfur atom is independent of methanol concentration, but the first shell of hydronium and water around sulfonic acid clusters is broader. Although methanol would prefer to interact with water molecules rather than sulfonic acid groups, gathering of methanol molecules via hydrophobic self-aggregation is preferred. Methanol is located closer to the hydrophobic part of the polymer than water, while water is located closer to the hydrophilic part of the polymer. It was found that methanol distributes specifically more than water in nano-channels. Investigation of solvent dynamics in nano-channels shows that diffusion coefficients (D) of water, methanol, and hydronium decrease with increasing methanol concentration and they may be ordered as follows: D Water > D Methanol > D Hydronium (D Water ≈ 1.6–2.0D Methanol and D Methanol ≈ 2.1–3.0D Hydronium).

Nonintrusive Monitoring and Control of Metallurgical Processes by Acoustic Measurements

The feasibility of developing a new online monitoring technique based on the characteristic acoustic response of gas bubbles in a liquid has been investigated. The method is intended to monitor the chemistry of the liquid through its relation to the bubble sound frequency. A low-temperature model consisting of water and alcohol mixtures was established, and the frequency of bubbles rising under varying concentrations of methanol was measured. It was shown that the frequency of the sound created by bubble pulsation varies with the percentage of alcohol in water. The frequency drops sharply with the increase in methanol content up to 20 wt pct, after which the decreases is gradual. Surface tension seems to be a critical liquid property affecting the sound frequency through its two-fold effects on the bubble size and the pulsation domain. The dependence between the frequency and the liquid composition suggests the feasibility of developing an acoustic-based technique for process control purposes.

PEMBUATAN BIODIESEL DARI KELAPA DENGAN METODE KERING

Producing biodiesel by dry method has been conducted in the Laboratory of Energy Conversion, Mechanical Engineering Department, Mataram University. In the conventional method, coconut flesh is scrabbed and then squizzed to separate the coconut milk then from this milk obtained oil. In dry method, the flesh is cut in to small pieces then cook in the sealed container.Its vapor is collected , condensated and eventually oil is produced.By transesterification process biodiesel is obtained. The combination of metanol : coconut oil is varied as follow :10 (K0), 1:10 (K10), 2:10 (K20), dan 3:10 (K30). Biodiesel produced is then tested to evaluate its specific gravity,kinematic viscosity,flash point and calorifiec value.The result show that increased methanol concentration reduced specific gravity,kinematic viscosity,flash point and calorifiec value. Specific gravity for K0, K10, K20, and K30 in the transesterification process are 0.864, 0.851, 0.849, and 0.843, respectively. Kinematic viscosity for K0, K10, K20, and K30 are 5.65 mm2/s, 4.80 mm2/s, 4.29 mm2/s, and 3.52 mm2/s, respectively. Flash point for K0, K10, K20, and K30 are 62.330C, 58.670C, 54.670C, and 520C. Calorifiec value for K0, K10, K20, and K30 are 19601.842 Btu/lb, 19105.375 Btu/lb, 17803.337 Btu/lb, and 16548.844 Btu/lb.

Solvent effects on structure, photoresponse and speed of gelation of a dicholesterol-linked azobenzene organogel

By introducing methanol as a co-solvent into cyclopentanone, solvent effects on structure, photoresponse and speed of gelation of a dicholesterol-linked azobenzene organogel DCAZO2 have been investigated. Optical microscopy (OM) and scanning electron microscopy (SEM) images reveal that the gel fibers form macroscopic aggregates by adding methanol. Minimum gelation concentration (MGC) of the gels decreases with increasing methanol content, while the gel-to-sol transition temperature (Tgel) decreases firstly and increases afterwards. For photoisomerization (corresponding to gel-sol transition), the first stage rate constant kg1 of the gels decreases with increasing methanol content. The photoisomerization process of the gel with 5% methanol is different from the other five samples, whose first stage rate constant kg1 is greater than its second stage rate constant kg2. By increasing methanol content from 0% to 30%, gelation time (corresponding to sol–gel transition) of both heated gel and UV-visible light irradiated gel decreases from 7 h to 5 min and 6 h to 0 min (before visible light irradiation is accomplished), respectively. Solubility parameters and Teas plots of the gelator and mixed solvents are systematically calculated to estimate the gelator-solvent interaction. It is found that gelation requires that the gelator-solvent interaction be neither too strong nor too weak, otherwise solution or precipitate are formed.

Electrochemical Impedance Spectroscopy of Direct Methanol Fuel Cell Having Ag/Ag2SO4 Reference Electrode

In this study, we succeeded in measuring the impedance spectra at the anode and cathode during the direct methanol fuel cell power generation using a single cell having a Ag/Ag2SO4 reference electrode. When the anode impedance is measured at 20 mA cm−2, two semicircles are observed in the high and middle frequency ranges, and the magnitude of the latter one increases with the increasing methanol concentration. At the cathode, the impedance spectra at 20 mA cm−2 show three semicircles, of which the magnitudes decrease with the increasing methanol concentration from 1 mol dm−3 to 5 mol dm−3, and increase again at 10 mol dm−3. These results demonstrate that the increased methanol concentration magnifies the methanol oxidation reaction resistance at the anode and affects the total resistance at the cathode.

Poly[2,7‐(9,9‐dihexylfluorene)]‐block‐Poly(2‐vinylpyridine) Rod–Coil Star‐block Copolymers: Synthesis, Micellar Structures, and Photophysical Properties

AbstractThe first successful synthesis of conjugated rod–coil star block copolymer, (PF‐b‐P2VP)n, containing conjugated poly[2,7‐(9,9‐dihexylfluorene)] (PF), and coil‐like poly(2‐vinylpyridine) (P2VP) by combining a Suzuki coupling reaction and living anionic polymerization is reported. With increasing methanol content in THF/methanol mixtures (PF‐b‐P2VP)n symmetric star‐block copolymers maintain spherical micelles, but PF‐b‐P2VP asymmetric diblock copolymers vary from spherical micelles to vesicles. Both the absorption and emission spectra of PF‐b‐P2VP blue shift with increasing methanol content, suggesting an “H‐type” aggregation. However, (PF‐b‐P2VP)n star‐block exhibits no shift in absorption but a red shift in the emission spectra, indicating a different type of aggregation. These results suggest the significance of polymer architectures on microphase‐separated morphologies and photophysical properties. magnified image

Photoelectrocatalytic activity for water treatment of TiO2/Ti electrodes prepared by anodization

TiO2 electrodes are made by anodization of Ti at various applied voltages. The increase of voltage facilitates the generation of anatase and rutile at high potential (superior to 140 V). Photoelectrochemical properties of prepared electrodes are investigated with and without methanol. TiO2/Ti electrode obtained at 140 V presents high photoelectrochemical properties. The electrode presents better separation of photogenerated electron-hole pairs, high photocurrent and easy charge transfer. The reaction of adsorbed methanol with generated holes increases the photocurrent. When the electrode is anodically biased (application of 1 to 2 V), the photocurrent increases with increased methanol concentration and at alkaline pH.

The Membrane–Electrode Interface in PEFCs: III. The Effect of Methanol Concentration in DMFCs

The effect of methanol feed concentration on the membrane–electrode interface was investigated in polymer electrolyte fuel cells (PEFCs). The membrane–electrode interfacial resistance in direct methanol fuel cellls (DMFCs) has a strong dependence on methanol concentration with increasing methanol concentration leading to higher interfacial resistances for methanol concentrations up to 5.0 M for two distinctly different polymer systems: Nafion (1100 equivalent weight) and a sulfonated poly(arylene ether)sulfone (BPSH-30). Initial interfacial resistances are correlated with resistance increases and performance losses during fuel cell life tests. The results from this study agree with our previous studies on the membrane–electrode interface and suggest that high methanol concentrations can be used to probe interfacial failure in an accelerated aging capacity. Conductivity of Nafion has a high dependence on methanol concentration, while conductivity of BPSH-30 is almost independent of methanol concentration.

Selectivity of calixarene-bonded silica phases in HPLC: Description of special characteristics with a multiple term linear equation at different methanol concentrations

Retention and selectivity characteristics of different calixarene-, resorcinarene- and alkyl-bonded stationary phases are examined by analyzing a set of test solutes covering the main interactions (hydrophobic, steric, ionic, polar) that apply in HPLC. Therefore Dolan and Snyder's multiple term linear equation has been adapted to fit the properties of calixarene-bonded columns. The obtained parameters are used to describe retention and selectivity of the novel Caltrex(®) phases and to elucidate underlying mechanisms of retention. Here, differences of stationary phase characteristics at different methanol concentrations in the mobile phases are examined. Both selectivity and retention were found to depend on the methanol content. Differences of these dependencies were found for different stationary phases and interactions. The differences between common alkyl-bonded and novel calixarene-bonded phases increase with increasing methanol content.

Anticooperative Effect Induced by Mixed Solvation in H+(CH3OH)m(H2O)n (m + n = 5 and 6): A Theoretical and Infrared Spectroscopic Study

When a solvent molecule is replaced by another molecule with larger proton affinity, the strength of all other hydrogen bonds decreases. This is the concept of anticooperativity by successive substitution in a mixed solvation system. In the present study, this concept is demonstrated in H(+)(CH(3)OH)(m)(H(2)O)(n) (m + n = 5 and 6) mixed clusters by a joint theoretical and infrared (IR) spectroscopic approach. The observed IR spectra of the mixed clusters exhibit two high-frequency shifts of hydrogen-bonded OH stretch bands with increasing methanol content. These trends are well reproduced by first-principle IR spectra simulated by thermal averaging over a set of configurational isomers under the quantum harmonic superposition approach. Theoretical analysis on the magnitude of charge transfer from the protonated site to the solvent molecules is found to be in agreement with the spectroscopic measurement that the individual hydrogen bond in the mixed clusters is weakened with an increase of the mixing ratio of methanol to water.