Increasing Methanol Concentration Research Articles

Liquid–Liquid Equilibrium Behavior of Ternary Systems Comprising Biodiesel + Glycerol and Triglyceride + Methanol: Experimental Data and Modeling

Having a comprehensive knowledge of phase equilibrium is advantageous for industrial simulation and design of chemical processes. For further acquisition of primary data to facilitate the separation and purification of waste oil biodiesel systems, a liquid–liquid equilibrium (LLE) tank is deployed for the ternary system of waste oil biodiesel + methanol + glycerin, thereby enhancing the precision and efficiency of the process. The phase equilibrium system was constructed under the influence of atmospheric pressure at precise temperatures of 303.15 K, 313.15 K, and 323.15 K. The equilibrium components of each substance were analyzed by employing high-temperature gas chromatography, a sophisticated analytical method that enables the identification and quantification of individual components of a sample. Moreover, the ternary liquid–liquid equilibrium data were correlated by implementing the NRTL and UNIQUAC activity coefficient models. Subsequently, the binary interaction parameters of the ternary system were derived by conducting regression analysis. The experimental data demonstrated that the presence of lower methanol content in the system resulted in nearly immiscible biodiesel and glycerol phases, which ultimately facilitated the separation of biodiesel and glycerol. Conversely, with the increase in methanol content, the mutual solubility of biodiesel and glycerol was observed to increase gradually. The results showed that the calculated values of the NRTL and UNIQUAC models aligned well with the experimental values. The root-mean-square deviations of the NRTL and UNIQUAC models at 313.15 K were 2.76% and 3.56%, respectively.

Experimental Evaluation of Methanol/Jet-A Blends as Sustainable Aviation Fuels for Turbo-Engines: Performance and Environmental Impact Analysis

This study offers a comprehensive examination, both theoretically and experimentally, of the potential of methanol (M) as a sustainable aviation fuel (SAF) assessed in combination with kerosene (Ke—Jet-A aviation fuel + 5% Aeroshell oil). Different blends of methanol and kerosene (10%, 20%, and 30% vol. of (M) was added to Ke) were tested in an aviation micro turbo-engine under various operating regimes, such as idle, cruise, and maximum. Key engine parameters, including combustion temperature, fuel consumption, and thrust, were closely monitored during these trials. Essential performance indicators such as combustion efficiency, thermal efficiency, and specific consumption for all fuel blends under maximum operating conditions are also presented. Physical and chemical characteristics, such as viscosity, density, calorific value and flash point, were determined for each blend. Moreover, elemental analysis and FTIR spectroscopy were utilized to evaluate the chemical composition of the fuels. This study further investigated the air requirements for stoichiometric combustion and computed the resulting CO2 and H2O emissions. Experimental tests were conducted on the Jet Cat P80® micro turbo-engine, covering assessments of starting procedures, acceleration, deceleration, and pollutant emissions (CO and SO2) during various engine operating conditions. The results suggest that the examined fuel blends demonstrate stable engine performance at concentrations of 10% and 20% methanol. However, observations indicate that with an increase in methanol concentration, particularly at 30%, the stability of the engine at idle and, notably, at maximum speed decreases significantly. Specifically, at a 30% methanol concentration, the engine no longer operates stably, exhibiting significant rpm fluctuations, leading to the decision not to explore higher concentrations.

Enhanced Methanol Oxidation Using Polymer-Incorporated Ultra Rough Pt Electrodes

We report on the methanol oxidation reaction (MOR) on very rough Pt surfaces. Numerous previous studies show that the cyclic voltammetry of MOR on Pt exhibits hysteretic behavior due to Pt oxide poisoning during the anodic scan at higher potentials. Only after the Pt oxide is removed during the cathodic scan is the Pt surface reactivated and MOR activity resumed (Fig. 1). We developed an electrodeposition method yielding Pt electrodes with high roughness factors (Rf > 80) controlled by varying deposition time. These rough electrodes exhibit linear MOR without hysteresis (Fig. 1), indicating the rougher Pt surface is resistant to poisoning during MOR up to potentials of 1.4 V vs. RHE. The effect is found in either acidic or basic electrolyte. Further studies show the roughness effect is related effective increase in the surface concentration of methanol and effective decrease in the surface concentration of water. The lower water activity inhibits Pt surface oxidation and facilitates methanol oxidation. Treatments to artificially decrease surface water concentration have a similar effect. This study provides methods to increase the rate of organic molecule oxidation at electrode surfaces and is relevant to both electro synthesis and direct methanol fuel cell applications. Figure 1

One-pot synthesis of a poly(styrene-acrylic acid) copolymer-modified silica stationary phase and its applications in mixed-mode liquid chromatography

As modified ligands with a wide range of sources, abundant functional groups, and good biocompatibility, polymers have been widely used in the development of silica-based chromatographic stationary phases. In this study, a poly(styrene-acrylic acid) copolymer-modified silica stationary phase (SiO2@P(St-b-AA)) was prepared via one-pot free-radical polymerization. In this stationary phase, styrene and acrylic acid were used as functional repeating units for polymerization and vinyltrimethoxylsilane (VTMS) was used as a silane coupling agent to link the copolymer and silica. Various characterization methods, such as Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, and Zeta potential analysis, confirmed the successful preparation of the SiO2@P(St-b-AA) stationary phase, which had a well-maintained uniform spherical and mesoporous structure. The retention mechanisms and separation performance of the SiO2@P(St-b-AA) stationary phase in multiple separation modes were then evaluated. Hydrophobic and hydrophilic analytes as well as ionic compounds were selected as probes for different separation modes, and changes in the retention of the analytes under various chromatographic conditions, including different methanol or acetonitrile contents and buffer pH values, were investigated. In reversed-phase liquid chromatography (RPLC) mode, the retention factors of alkyl benzenes and polycyclic aromatic hydrocarbons (PAHs) on the stationary phase decreased with increasing methanol content in the mobile phase. This finding could be attributed to the hydrophobic and π-π interactions between the benzene ring and analytes. The retention changes of alkyl benzenes and PAHs revealed that the SiO2@P(St-b-AA) stationary phase, similar to the C18 stationary phase, exhibited a typical reversed-phase retention behavior. In hydrophilic interaction liquid chromatography (HILIC) mode, as the acetonitrile content increased, the retention factors of hydrophilic analytes gradually increased, and a typical hydrophilic interaction retention mechanism was inferred. In addition to hydrophilic interaction, the stationary phase also demonstrated hydrogen-bonding and electrostatic interactions with the analytes. Compared with the C18 and Amide stationary phases prepared by our groups, the SiO2@P(St-b-AA) stationary phase exhibited excellent separation performance for the model analytes in the RPLC and HILIC modes. Owing to the presence of charged carboxylic acid groups in the SiO2@P(St-b-AA) stationary phase, exploring its retention mechanism in ionic exchange chromatography (IEC) mode is of great importance. The effect of the mobile phase pH on the retention time of organic bases and acids was further studied to explore the electrostatic interaction between the stationary phase and charged analytes. The results revealed that the stationary phase has weak cation exchange ability toward organic bases and electrostatically repels organic acids. Moreover, the retention of organic bases and acids on the stationary phase was influenced by the analyte structure and mobile phase. Thus, the SiO2@P(St-b-AA) stationary phase could provide multiple interactions, as demonstrated by the separation modes described above. The SiO2@P(St-b-AA) stationary phase showed excellent performance and reproducibility in the separation of mixed samples with different polar components, indicating that it has promising application potential in mixed-mode liquid chromatography. Further investigation of the proposed method confirmed its repeatability and stability. In summary, this study not only described a novel stationary phase that could be used in RPLC, HILIC, and IEC modes but also presented a facile "one-pot" preparation approach that could provide a new route for the development of novel polymer-modified silica stationary phases.

Spontaneous multilayer formation of an amphiphilic alkylammonium cation with a long hydrocarbon chain at an air-clay dispersion interface

Langmuir film formation behavior of a trimethylammonium cation with a long hydrocarbon chain (CH3(CH2)29N+(CH3)3, C30TMA+) was investigated. To weaken the hydrophobic interactions between the hydrocarbon chains, methanol was added to the subphases. A solution of C30TMA+·I– was spread at air-water and air-clay dispersion interfaces. The surface pressure-molecular area curves of the floating C30TMA+ films showed that the surface pressure at the collapse point decreased with increasing methanol concentration in water and in the dispersion, indicating the weakening of the hydrophobic interaction. For the floating films on clay dispersions, the molecular area at the collapse point decreased with increasing methanol concentration. The decrease in the molecular area indicates multilayer formation of C30TMA+ at the air-dispersion interface at a low surface pressure, which was confirmed by the atomic force microscope images and X-ray diffraction (XRD) patterns of the deposited films. The out-of-plane and in-plane XRD results of the multilayers showed not only layer-by-layer ordering, but also lateral ordering of the closely packed C30TMA+ cations in each layer.

Influence of Operational Defects and Hotspot Temperature on Methanol Concentration in Transformer Oil

This paper investigated the variation law of methanol concentration in transformer oil caused by operational defects and hotspot temperature from 500 kV field transformers. The correlations between various operational defects and methanol in oil are explained in detail for the first time. It is observed that three types of operational defects such as bushing heating, fan failure and breather failure can lead to the increase of methanol concentration in oil. Furthermore, the associations of annual load factor and hotspot temperature with methanol are investigated. Besides, various hotspot temperatures of nine transformers are calculated by the temperature rise guide. The results show that the methanol concentration in oil at the bottom of the winding can indicate the hotspot temperature of the winding. To verify this view, the correlation between methanol concentration and hotspot temperature is also proved by the implementation of accelerated non-uniform thermal aging experiments. In addition, the methanol concentration is found to be unevenly distributed along the axial height of the winding. This work not only provides a novel direction for the maintenance of transformer components, but also gives a further support for the distribution mechanism of methanol in insulating oil.

Experimental and theoretical assessment of phenomena linked with separation and purification of biodiesel from Ricinus communis seed oil

This study investigated the phenomena associated with the separation and purification of biodiesel produced from Ricinus communis oil seeds using experimental and theoretical approaches. The alkaline transesterification technique was used to produce the biodiesel from the Ricinus communis oil seeds which were later compared with standards based on EN and ASTM. Experimental investigation of the components in the mixture for separation and purification was conducted using the standard turbidimetric method for binodal solubility and tie-line compositions. The gas chromatographic technique was used to determine the composition of the homogeneous mixture. Novel components separation and purification of the Ricinus communis seed oil biodiesel was achieved using ternary diagrams highlighting the constituent components of the biodiesel at different temperatures for enhanced separation and purification. At the coexisting extract and raffinate phases, the orientation angle of the component compositions increases as the methanol concentration increases and temperature increases. The analysis of seed oil in terms of its physicochemical properties showed density, refractive index, acid value, and free fatty acid values of 905 kg/m3, 1.486, 0.79 mg KOH/g, and 0.390 mg KOH/g respectively. The fatty acid composition of the seed oil and biodiesel revealed that the major characteristics of the oil and biodiesel were defined by the presence of linoleic acid (C18:2) and a ricinoleic acid hydroxyl group (C18:1, OH) with compositions of approximately 30% and 20% respectively. Fourier Transform Infra-Red (FTIR) spectrometry analysis of the oil and biodiesel showed that the absorption spectrum in terms of the wave number (cm−1) ranged from 1000 to 4000 cm−1 with esters as the main functional group providing the main structural backbone. The presence of different fatty acids leads to lateral homogeneity of the biodiesel molecules which can serve to organize the molecules into discrete domains with different properties for enhanced separation and purification at the investigated temperatures. Optimal separation and purification were achieved at the different temperatures showing the castor oil biodiesel, glycerol, and methanol components system at the prevailing composition, time, and temperatures from the tie-lines and binodal solubility compositions. This approach provides a means for the design of a more efficient separation process for optimal biodiesel purification after production with knowledge of how the components are distributed in the ternary mixture after the transesterification reaction. This, leads to greater efficiency of the process, reducing material and operational costs and eliminating environmental issues linked with the biodiesel production process as the volume of wastewater generated would be hugely eradicated. The findings of this study will be useful in the setting up of a small-to-medium-size biodiesel production facility with improvement in the efficiency of product separation and purification.

Electrochemical Properties and Perspectives of Nickel(II) and Cobalt(II) Coordination Polymers-Aspects and an Application in Electrocatalytic Oxidation of Methanol

The electrochemical sensing potential of two isostructural one-dimensional nickel(II) and cobalt(II) coordination polymers with 4,4′-bipyridine (4,4′-bpy) and 6-oxonicotinate (6-Onic), namely, {[Ni(4,4′-bpy)(H2O)4](6-Onic)2×2H2O}n and {[Co(4,4′-bpy)(H2O)4](6-Onic)2×2H2O}n, was investigated along with the polymers’ potential applications in the catalytic oxidation of methanol. The highly oxidative species from redox pairs Ni(II)/Ni(III) and Co(II)/Co(III) in these compounds represent catalytically active centres for oxidation of small molecules. A glassy carbon electrode (GCE) modified with a Ni polymer showed stability and reproducibility in 0.1 M NaOH, while the oxidation current inc 2reased with the increasing methanol concentration, suggesting that the Ni-polymer-modified electrode possess good sensing ability with respect to methanol. The GC electrode modified with the Co polymer is not reproducible and cannot be used for electroanalytical purposes under these experimental conditions. The GC electrode modified with the Ni polymer was successfully applied in the determination of methanol. This method showed favourable linear concentration dependence with a good sensitivity of 2.65 and 11.0 mA mM−1, a wide concentration range (0.001–4 mM), and a detection limit of 0.8 μM, which indicates its excellent application potential for methanol oxidation and thus its determination.

Assessment of innovative graphene oxide composite membranes for the improvement of direct methanol fuel cells performance

The main objective of the study was to verify potential of GO-PEM and its best effective usage in a Direct Methanol Fuel Cells (DMFC) application so investigating the effect of this filler on cell performance, varying several operating conditions, without affecting the mechanical and electric properties of the baseline PEM. In this work, GO was added to the Nafion polymer using a weight percentage varying from 0.5 to 1.5%. The present analysis showed that the GO-membranes have higher tensile strength, greater water, and methanol uptake. It was also demonstrated that the presence of carbon compounds slightly reduced the proton conductivity suggesting that an optimal GO-content must be determined. Comparing several physical and electrochemical properties, we concluded that the 1 wt. %GO-loading PEM represents the most effective solution. Later, the advantages of adopting GO-PEMs in DMFCs were also assessed. A comparative analysis of a GO-DMFC and a standard DMFC was carried out by changing the relevant control parameters, such as anode flow rate, temperature, and methanol concentration obtaining that: a) the GO-DMFC performance enhanced when increasing the temperature and the anode flow rate; b) an increase in methanol concentration had a beneficial effect on DMFC performance only up to a peak value after that a rapid reduction was noticed. Optimal conditions were obtained for an anode flow rate of 7 µl min−1, a temperature of 60 °C and a 1 M methanol concentration.

Novel CaLB-like Lipase Found Using ProspectBIO, a Software for Genome-Based Bioprospection

Enzymes have been highly demanded in diverse applications such as in the food, pharmaceutical, and industrial fuel sectors. Thus, in silico bioprospecting emerges as an efficient strategy for discovering new enzyme candidates. A new program called ProspectBIO was developed for this purpose as it can find non-annotated sequences by searching for homologs of a model enzyme directly in genomes. Here we describe the ProspectBIO software methodology and the experimental validation by prospecting for novel lipases by sequence homology to Candida antarctica lipase B (CaLB) and conserved motifs. As expected, we observed that the new bioprospecting software could find more sequences (1672) than a conventional similarity-based search in a protein database (733). Additionally, the absence of patent protection was introduced as a criterion resulting in the final selection of a putative lipase-encoding gene from Ustilago hordei (UhL). Expression of UhL in Pichia pastoris resulted in the production of an enzyme with activity towards a tributyrin substrate. The recombinant enzyme activity levels were 4-fold improved when lowering the temperature and increasing methanol concentrations during the induction phase in shake-flask cultures. Protein sequence alignment and structural modeling showed that the recombinant enzyme has high similarity and capability of adjustment to the structure of CaLB. However, amino acid substitutions identified in the active pocket entrance may be responsible for the differences in the substrate specificities of the two enzymes. Thus, the ProspectBIO software allowed the finding of a new promising lipase for biotechnological application without the need for laborious and expensive conventional bioprospecting experimental steps.

Multifunctional ternary ZnMgFe LDH as an efficient adsorbent for ceftriaxone sodium and antimicrobial agent: sustainability of adsorption waste as a catalyst for methanol electro-oxidation.

In order to achieve sustainable benefits for the adsorption of wastewater pollutants, spent adsorbents need to be recycled and/or valorized. This work studied a two-dimensional (2D) ZnMgFe layered double hydroxide (LDH) for ceftriaxone sodium (CTX) adsorption. This LDH showed a crystallite size of 9.8 nm, a BET surface area of 367.59 m2 g-1, and a micro-sphere-like morphology. The factors investigated in this study were the adsorbent dose, initial concentration, initial pH, and contact time. ZnMgFe LDH showed 99% removal of CTX with a maximum adsorption capacity of 241.75 mg g-1 at pH = 5. The Dubinin-Radushkevich model was found to be the most adequate isotherm model. The spent adsorbent (ZnMgFe LDH/CTX) was reused as an electro-oxidation catalyst for direct methanol fuel cells. ZnMgFe LDH/CTX showed almost a 10-fold increase in electrochemical activity for all scan rates compared to bare ZnMgFe LDH in 1 M KOH. As methanol concentration increases, the maximum current density generated by both the ZnMgFe LDH and ZnMgFe LDH/CTX samples increases. Moreover, the maximum current density for ZnMgFe LDH/CTX was 47 mA cm-2 at a methanol concentration of 3 M. Both samples possess reasonable stability over a 3600 S time window with no significant deterioration of electrochemical performance. Moreover, the antimicrobial studies showed that ZnMgFe LDH had a significant antifungal (especially Aspergillus, Mucor, and Penicillium species) and antibacterial (with greater action against Gram-positive than negative) impact on several severe infectious diseases, including Aspergillus. This study paves the way for the reuse and valorization of selected adsorbents toward circular economy requirements.

Experimental study and prediction model of combustion stability and combustion mode variation of burning methanol/biodiesel blends for diesel engines

The combustion stability is an essential metric for evaluating the stable operation of an engine. To analyze the underlying reasons affecting the combustion stability, tests of modified engines fueled by methanol/biodiesel blends were carried out. The influence of the potential ignition point (PIP), activation energy (Ea) field, flame diffusion, and other combustion characteristic parameters on the combustion stability is quantitatively analyzed through the CFD simulation model. The results show that under 2400 r/min and 100% load, a 10% volume concentration of methanol increases the peak pressure. The variation of the pressure and combustion characteristic parameters increased with the increase in methanol concentration. The increase in methanol concentration increases the number of PIP, expands the distribution range of low Ea, and reduces the flame diffusion rate. The PIP, Ea field, and flame diffusion have an echelon progressive, positive correlation with the combustion mode. The increase in methanol concentration is sufficient to cause the conversion of the mixed fuel combustion mode, and the corresponding methanol volume concentration threshold is 21–22%.

(Digital Presentation) Electrocatalytic Oxidation of Methanol over Silver Based Electrocatalysts Synthesized By Solution Combustion Technique

Herein, we report the electrocatalytic properties of Ag-M/C (M=Cu, Zn, Fe, Cr, Mn) catalysts produced using solution combustion synthesis (SCS) method for methanol oxidation reaction (MOR). The morphological properties of the synthesized catalysts were studied using SEM, EDX, TEM, XRD and XPS techniques. The characterization results indicated that out of all catalysts, AgCu/C had the most porous surface, small and well distributed particles with high surface area making it a good choice for electrocatalytic experiments. The XPS results showed a shift in peak in the AgCu/C sample due to the charge transfer between Ag and Cu indicating a strong interaction between Ag and Cu. The electrochemical properties of the catalysts were studied at 1 M methanol concentration and 1 M KOH (electrolyte) concentration by performing Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV) experiments. It was observed that AgCu/C exhibited a greater electrocatalytic activity and was therefore, found to be a more viable catalyst for MOR. Following this, further concentration studies were conducted on AgCu/C for methanol concentrations of 0.5M, 1M, 1.5M, 2.5M to evaluate the rate dependency of the catalyst on MeOH concentration. The CV and LSV curves depicted a linear increase in current density proportional to the increase in methanol concentration, indicating power-law dependency. The catalyst also displayed long-term stability when chronoamperometry test was performed for 20 hours.

Study of biomethanol as sustainable replacement of Autogas at variable ignition timing

Bio-methanol has recently interested researchers looking for a suitable alternative due to its low carbon/hydrogen (C/H) ratio. Adding methanol to Autogas could thereby improve combustion while lowering emissions. In the present investigation, testing is conducted at a compression ratio of 14:1 on various fuel ratios (55/45 to 75/25 with a 5% change) of methanol/Autogas with ignition timing ranging from 28°CA bTDC to 14°CA bTDC. The results indicate improvements due to the addition of 65% methanol. Improved brake thermal efficiency (BTE) by 6.27%, peak pressure (Pmax) by 0.36%, heat release rate (HRRmax), peak temperature (Tmax) by 0.89%, and rise in exhaust gas temperature (EGT). Simultaneously, combustion duration, HC & CO emissions, and the coefficient of variations in indicated mean effective pressure (CoVIMEP) are reduced. With methanol, the volumetric efficiency (ηvol) improves continuously. Optimal ignition timing is shown to advance with increasing methanol concentration. With ignition retard, the flame development phase (CA10) decreases by 1.7%/2°CA ignition retard, whereas the flame propagation phase (CA10–90) decreases to a minimum and then increases. Due to combustion instability, ignition retard increases the Cyclic variation and CoVIMEP, while Pmax, HRRmax, Tmax, and BTE increase to a maximum and then drop. Ignition retard is an effective way of reducing NOx emissions, although CO and HC emissions increase significantly. Due to reduced carbon supply, carbon emissions are extremely low even at higher methanol concentrations than Autogas-rich fuel. NOx emissions are also extremely low (62.5 % of the ignition angle at 24°CA), revealing that a higher methanol ratio could be used with minimal risk of power loss.

Sol-Gel Synthesized High Entropy Metal Oxides as High-Performance Catalysts for Electrochemical Water Oxidation.

Hexanary high-entropy oxides (HEOs) were synthesized through the mechanochemical sol-gel method for electrocatalytic water oxidation reaction (WOR). As-synthesized catalysts were subjected to characterization, including X-ray diffraction (XRD), Fourier transforms infrared (FTIR) analysis, and scanning electron microscopy (SEM). All the oxide systems exhibited sharp diffraction peaks in XRD patterns indicating the defined crystal structure. Strong absorption between 400–700 cm−1 in FTIR indicated the formation of metal-oxide bonds in all HEO systems. WOR was investigated via cyclic voltammetry using HEOs as electrode platforms, 1M KOH as the basic medium, and 1M methanol (CH3OH) as the facilitator. Voltammetric profiles for both equiatomic (EHEOs) and non-equiatomic (NEHEOs) were investigated, and NEHEOs exhibited the maximum current output for WOR. Moreover, methanol addition improved the current profiles, thus leading to the electrode utility in direct methanol fuel cells as a sequential increase in methanol concentration from 1M to 2M enhanced the OER current density from 61.4 to 94.3 mA cm−2 using NEHEO. The NEHEOs comprising a greater percentage of Al, ([Al0.35(Mg, Fe, Cu, Ni, Co)0.65]3O4) displayed high WOR catalytic performance with the maximum diffusion coefficient, D° (10.90 cm2 s−1) and heterogeneous rate constant, k° (7.98 cm s−1) values. These primary findings from the EC processes for WOR provide the foundation for their applications in high-energy devices. Conclusively, HEOs are proven as novel and efficient catalytic platforms for electrochemical water oxidation.

LED light-induced enhanced photocatalytic hydrogen evolution on Au@TiO2 core–shell modified by nitrogen doping and reduced graphene oxide

This study focused on the large band gap of TiO2 for its use as a photocatalyst under light emitting diode (LED) light irradiation. The photocatalytic activities of core–shell structured Au@TiO2 nanoparticles (NPs), nitrogen doped Au@TiO2 NPs, and Au@TiO2/rGO nanocomposites (NCs) were investigated under various light intensities and sacrificial reagents. All the materials showed better photocatalytic activity under white LED light irradiation than under blue LED light. The N-doped core–shell structured Au@TiO2 NPs (Au@N–TiO2) and Au@TiO2/rGO NCs showed enhanced photocatalytic activity with an average H2 evolution rate of 9205 μmol h−1g−1 and 9815 μmol h−1g−1, respectively. All these materials showed an increasing rate of hydrogen evolution with increasing light intensity and catalyst loading. In addition, methanol was more suitable as a sacrificial reagent than lactic acid. The rate of hydrogen evolution increased with increasing methanol concentration up to 25% in DI water and decreased at higher concentrations. Overall, Au@TiO2 core–shell-based nanocomposites can be used as an improved photocatalyst in photocatalytic hydrogen production.

Effect of Solvent Quality on Structure and Dynamics of Lignin in Solution.

Due to its significant aromatic content, lignin is an attractive source of valuable organic chemicals. As most of the proposed lignin depolymerization processes are expected to be liquid-phase, it is necessary to understand the effect of solvent quality on the structure and dynamics of lignin. Here we use all-atom molecular dynamics simulations to understand the evolution of lignin structure as a function of methanol concentration in methanol/water solution at different temperatures. We utilize two different lignin models: softwood consisting of guaiacyl (G) monomer and hardwood consisting of heteropolymer containing guaiacyl/syringyl (S) with a 1.35:1 ratio. The presence of additional methoxy groups in the hardwood lignin leads to a more extended configuration than softwood lignin with increasing methanol concentration. Structural features (radius of gyration and solvent accessible surface area) of lignin correlate with the strength of intermolecular forces quantified using cohesive energy density. We find that methanol preferentially solvates the nonpolar segments of the lignin polymer while water molecules solvate the polar functional groups. Thus, as the methanol concentration increases, methanol can better solvate lignin polymer, leading to a more extended configuration suitable for catalytic transformation to value-added chemicals.

Methanol Electro-Oxidation over Combustion Synthesized Silver Based Electrocatalysts

Herein, we report the electrocatalytic properties of Ag-M/C (M=Cu, Zn, Fe, Cr, Mn) catalysts produced using solution combustion synthesis (SCS) method for methanol oxidation reaction (MOR). The morphological properties of the synthesized catalysts were studied using SEM, EDX, TEM, XRD and XPS techniques. The characterization results indicated that out of all catalysts, AgCu/C had the most porous surface, small and well distributed particles with high surface area making it a good choice for electrocatalytic experiments. The XPS results showed a shift in peak in the AgCu/C sample due to the charge transfer between Ag and Cu indicating a strong interaction between Ag and Cu. The electrochemical properties of the catalysts were studied at 1 M methanol concentration and 1 M KOH (electrolyte) concentration by performing Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV) experiments. It was observed that AgCu/C exhibited a greater electrocatalytic activity and was therefore, found to be a more viable catalyst for MOR. Following this, further concentration studies were conducted on AgCu/C for methanol concentrations of 0.5M, 1M, 1.5M, 2.5M to evaluate the rate dependency of the catalyst on MeOH concentration. The CV and LSV curves depicted a linear increase in current density proportional to the increase in methanol concentration, indicating power-law dependency. The catalyst also displayed long-term stability when chronoamperometry test was performed for 20 hours.

Experimental investigation on characteristics of venturi cavitating flow and Rhodamine B degradation in methanol solution

Hydrodynamic cavitation (HC) commonly occurs within industrial pipelines and its unsteady flow characteristics are of great significance for energy conservation and efficiency improvement. This study investigates the effects of methanol concentration (0–20 wt%) on the cavitating flow characteristics and the degradation of Rhodamine B (RhB) under operating conditions of a 0.7 MPa pressure drop, temperature of 30 °C, 200 passes through a venturi reactor, and an initial RhB concentration of 40 μmol/L. The transient cavitation behavior was monitored using a high-speed camera. The cavitation images show that the presence of methanol generates more stable bubbles, which results in less violent bubble collapse. The pressure pulsation and vibration induced by cavitation flow were synchronously measured using high-frequency pressure and acceleration sensors. The spectral analyses of the pressure pulsation indicate that methanol has no effect on the dominant frequency (∼5.5 Hz) at different positions, and the amplitude initially increases with increasing methanol concentration and then stabilizes. The pressure pulsation intensity increases due to the increased vapor pressure of the solution. The vibration spectral analyses show that methanol has little effect on the peak frequencies, which occur near 4.0 kHz and 14.3 kHz of the low and high-frequency bands, respectively, whereas the peak amplitude decreases with increasing methanol concentration. The per-pass degradation model of RhB in methanol solution considering pyrolysis of methanol was verified for the first time and show to adequately describe the experimental data. The degradation percentage and per-pass degradation factor decrease with increasing methanol concentration. The reduced surface tension of the solution prolongs the bubble lifespan and prevents bubble coalescence, thus weakening the vibration and degradation performance. The results provide important insight for cavitation applications and degradation modeling of mixed solutions.

Theoretical calculation on excited state hydrogen bond kinetics of PRODAN derivative 2b molecule in methanol solution

To explore the mechanism of intermolecular hydrogen bond relating to PRODAN derivative 2b in methanol solvent on photoexcitation process, spectral behavior calculations of PRODAN-2b and its hydrogen bonding complex were studied by using density functional theory (DFT) and time-dependent density functional theory (TDDFT). After photo excitation, the hydrogen bond between PRODAN-2b and methanol become stronger. It was found that with the increase in the number of methanol molecules, the more hydrogen bonds between PRODAN-2b and methanol were formed and the hydrogen bondings were also enhanced. Further evidence for enhanced hydrogen bond due to intramolecular charge transfer excitation character of PRODAN-2b is presented. This effect leads to the red shift of absorption and fluorescence spectra of PRODAN-2b molecules in methanol solvent with increasing methanol concentration.