Presence Of Methanol Vapor Research Articles

Reversible and Stepwise Single-Crystal-to-Single-Crystal Transformation of a Platinum(II) Complex with Vapochromic Luminescence.

The vapochromic single-crystal-to-single-crystal (SCSC) transformation of a highly luminescent PtII complex bearing an N-heterocyclic carbene [Pt(CN)2 (tBu-impy)] (tBu-impyH+ =1-tert-butyl-3-(2-pyridyl)-1H-imidazolium) is reported. The trihydrate form of the complex, which exhibits blue 3 MMLCT emission owing to weak Pt⋅⋅⋅Pt interactions, changed its luminescence color from blue to yellowish-green upon the desorption of water molecules while keeping the high emission quantum yield of more than 0.45. Variable-temperature and continuous in-situ tracking of single-crystal X-ray diffraction measurements revealed that the SCSC transformation proceeds reversibly by the release and reabsorption of water molecules, thereby changing the stacked structure slightly. As a result, the dynamics of vapor-induced SCSC transformation were elucidated: that the anhydrous form returned to the original trihydrate form in a two-step process under a water vapor atmosphere. In addition, the PtII complex exhibited a similar SCSC response accompanied by a luminescence color change in the presence of methanol vapor, while being inactive toward ethanol vapor.

Removal of toluene in a biotrickling filter in the presence of methanol vapors: Experimental study, mathematical modeling, and kinetic parameters optimization

The performance of biotrickling filters (BTFs) has been significantly affected during the co-treatment of volatile organic compounds (VOCs) with different hydrophilicities. Removal of toluene vapor as a hydrophobic compound in the absence and presence of methanol as a hydrophilic pollutant was studied in a BTF. The inlet loading ranges were 18−36 g.m−3.h−1 for toluene and 0−225 g.m−3.h−1 for methanol at constant empty bed residence time (EBRT) of 60 s. The removal efficiency of toluene (RET) varied from 30 to 80 %, while RE of methanol (REM) remained almost constant at > 90 % within different phases of experiments due to the unlimited solubility in water. A comprehensive dynamic mathematical model consisting of mass transfer through gas, liquid, and biofilm phases with the kinetic of biodegradation in the BTF and accumulation of methanol in liquid was developed. The interaction parameters were optimized by genetic algorithm and validated by experimental data. Sensitivity analysis on the optimized parameters showed that biofilm thickness and methanol interaction parameter had the most effects on RET as 45 % and 38 %, respectively. Model simulation showed that 43–90 % of biofilm depth was active for toluene degradation at different inlet gas-phase concentrations, indicating a diffusion-limited condition in the process. In contrast, all depth of biofilm was fully active for methanol degradation, showing a kinetic-limited regime dominant for methanol removal in the BTF under all operating conditions. Results showed that the developed model could effectively predict the dynamics of VOCs removals along with the determination of kinetic constants.

Fluidity enhancement of hard-to-fluidize nanoparticles by mixing with hydrophilic nanosilica and fluid catalytic cracking particles: Experimental and theoretical study

As a low-cost method, hydrophilic SiO2 nanoparticles (NPs) and fluid catalytic cracking (FCC) coarse particles were used as assistant materials to improve the fluidity of Al2O3 and TiO2 hard-to-fluidize nanopowders. To decrease the strong electrostatic forces between the hydrophilic nanopowders, prepared samples were fluidized in the presence of methanol vapor. Results revealed that the amount of SiO2 NPs, increased from 5 to 50 wt. %, has a beneficial effect on the fluidization quality of the binary (hard-to-fluidize NPs + SiO2) and ternary (hard-to-fluidize NPs + SiO2 + FCC) mixtures. However, the amount of FCC particles when it varied from 15 to 30 wt. % in the ternary mixtures should meet the optimal point, beyond which the fluidization quality was declined due to the segregation phenomenon. The laboratory results showed that the cost-effective ternary samples fluidized more homogeneously with higher bed expansions compared to the binary samples. In this regard, (Al2O3 + 20 wt. % SiO2) + 15 wt. % FCC and (TiO2 + 20 wt. % SiO2) + 15 wt. % FCC ternary samples were proposed as the alternatives of Al2O3 + 50 wt. % SiO2 and TiO2 + 50 wt. % SiO2 binary mixtures, respectively.

Structure of the Clean and Oxygen-Covered Cu(100) Surface at Room Temperature in the Presence of Methanol Vapor in the 10-200 mTorr Pressure Range.

Using ambient pressure X-ray photoelectron spectroscopy (APXPS) and high pressure scanning tunneling microscopy (HPSTM), we show that in equilibrium with 0.01-0.2 Torr of methanol vapor, at room temperature, the Cu(100) surface is covered with methoxy species forming a c(2 × 2) overlayer structure. In contrast, no methoxy is formed if the surface is saturated with an ordered oxygen layer, even when the methanol pressure is 0.2 Torr. At oxygen coverages below saturation, methanol dissociates and reacts with the atomic oxygen, producing methoxy and formate on the surface, and formaldehyde that desorbs to the gas phase. Unlike the case of pure carbon monoxide and carbon dioxide, methanol does not induce the restructuring of the Cu(100) surface. These results provide insight into catalytic anhydrous production of aldehydes.

Metallic 1T‐WS2 for Selective Impedimetric Vapor Sensing

Selective gas sensing is of immense importance for industrial as well as safety purposes. Here it is shown that metallic 1T phase transition metal dichalcogenides, such as tungsten sulfide (WS2), provide sensitive and selective platform for gas sensing. Using impedance spectroscopy distinguishable alterations can be detected on the impedance phase spectrum of interdigitated gold electrode modified with chemically exfoliated 1T‐WS2 caused by different vapors. In particular, it is found that the impedance phase spectra of 1T‐WS2 device present different resonant frequencies with maximum around 1 Hz in the presence of methanol vapor and around 1 kHz in the presence of water vapor. Such a well‐distinguished signal allows their selective detection also when they are present in a mixture. The impedance phase spectra allow the selective methanol and water vapor sensing with an impedimetric device based on 1T‐WS2. This system utilizing 1T phase of WS2 for selective gas sensing based on impedance spectroscopy opens new avenues for gas sensing and shall find wide spectra of applications.

In-situ catalytic upgrading of biomass pyrolysis vapor: Co-feeding with methanol in a multi-zone fixed bed reactor

The in-situ catalytic upgrading of the biomass pyrolysis vapor and its mixture with methanol were conducted in a fixed bed multi-zone reactor. The steps were comprised; thermally converting the biomass in the pyrolysis reactor, passing its vapor in contact with the HZSM-5 zeolite catalyst in the presence of methanol vapor, and transformation of the resulting upgraded pyrolysis vapor into the liquid product. The biomass pyrolysis and catalytic pyrolysis vapor upgrading were performed at 500°C. The highly valuable chemicals production was a function of the hydrogen to carbon effective ratio (H/Ceff) of the feed. This ratio was regulated by changing the relative amount of biomass and methanol. More aromatic hydrocarbons (50.02wt.%) and less coke deposition on the catalyst (1.3wt.%) were yielded from the biomass, when methanol was co-fed to the catalytic pyrolysis process (H/Ceff=1.35). In this contribution, the deposited coke on the catalyst was profoundly investigated. The coke, with high contents of oxo-aromatics and aromatic compounds, was generated by polymerization of biomass lignin derived components activated by catalyst acid sites.

Assembly and Interfacial Effects in Hybrid Nanostructures of Zinc Oxide and Gold

AbstractGold nanoparticles were linked to ZnO films and nanowires using phosphonic and carboxylic acid ligands. TEM and STEM-HAADF characterization showed that gold nanoparticles modified with both types of ligands anchored on ZnO nanowire surfaces as well as on ZnO films. After removing the ligands from the interface between ZnO nanowires and supported gold nanoparticles, the electric conductivity in the presence of methanol vapor increased by 100 times as compared to the bare ZnO nanowire, which suggested enhanced-catalytic effects due to the hybrid structure. In addition, ZnO/Au nanomaterials were synthesized by linking ZnO nanoparticles and carboxylate-functionalized gold nanoparticles in solution. UV-vis characterization showed both the bandgap absorption from ZnO and the plasmon absorption from gold nanoparticles. Formation of hybrid nanosystems like these using organic ligands as linkers not only can lead to materials with enhanced properties but also minimize the waste of precious elements because the assembly process is an additive, rather than subtractive, process.

Combustion and microexplosion of collision-merged methanol/alkane droplets

The combustion characteristics of freely falling droplets, individually generated by the merging of colliding methanol and alkane droplets, were investigated and compared with those for pure methanol and alkanes. The merging of the nominally immiscible methanol and alkanes was manifested in an apparently adhesive, but unmixed, manner in all test conditions. An air bubble was found to be trapped at the colliding interfaces where they were “adhered,” with the trapping favored for head-on or near head-on collision orientations. The trapped air bubble ostensibly induced heterogeneous nucleation of the methanol, being facilitated by the relatively low limit of superheat of methanol. Consequently, the droplet exploded almost immediately upon ignition, leading to an extremely short overall lifetime. For collision orientations that were more off-centered, bubble trapping and thereby heterogeneous nucleation were not favored. However, delayed, albeit strong, microexplosion occurred through homogeneous nucleation of methanol at the contacting interface. The global burning rate was therefore again augmented. In general, microexplosion was facilitated for high-boiling-point alkanes such as hexadecane and tetradecane. The co-vaporization of methanol and alkane from their respective hemispherical segments constituting the adhered droplet also led to flame colors that were more bluish than yellowish, indicating the reduction of soot from alkane burning in the presence of methanol vapor. In light of the difficulty of forming stable methanol/oil emulsions, the potential of separate injection of oil and methanol in opposed jet arrangement, in direct-injection engines to facilitate collision, is suggested.

Pore size distributions of silylated mesoporous silica MCM-48 membranes

Abstract Mesoporous silica MCM-48 membranes were synthesized on a porous alumina support using surfactant molecules which act as template for the polymerization of silica. Higher synthetic temperatures resulted in thicker silica wall. However, the average pore size of MCM-48 was independent of the synthetic temperature. The permeation of N2 through the calcined MCM-48 membrane was governed by the Knudsen diffusion. There was no contribution of viscous flow, which can be observed in large pinholes. The pore size distributions of silylated mesoporous silica MCM-48 membranes were evaluated by permporometry measurements in which N2 flux was monitored in the presence of methanol vapor. A sharp decrease in the N2 flux at a relative vapor pressure of methanol equal to 0.5 was observed, indicating a narrow pore size distribution of the MCM-48 membrane. The corresponding Kelvin diameter of the membranes was about 2.0 nm, which is consistent with the value for the silylated MCM-48 powder calculated with Barrett–Joyner–Halenda (BJH) method using N2 adsorption isotherm.

Photocatalytic Decomposition of N2O on Highly Dispersed Ag+ Ions on TiO2 Prepared by Photodeposition

Nitrous oxide (N2O) was photocatalytically decomposed on Ag-photodeposited TiO2 in the presence of methanol vapor. The N2O decomposition activity of Ag-photodeposited TiO2 was much higher than that of Ag-loaded TiO2 prepared by deposition–precipitation or impregnation methods. The difference in the N2O decomposition activity between the preparation methods was discussed in terms of the surface conditions observed by transmittance electron microscopy and X-ray photoelectron spectroscopy. The N2O decomposition activity depended on the amount of photodeposited Ag, and the TiO2 loaded with only 0.16 wt% Ag has revealed the highest level of activity. Highly dispersed Ag+ ions prepared by photodeposition were effective for the photocatalytic decomposition of N2O. In the deposition–precipitation or impregnation methods, Ag+ ions aggregated to form Ag particles and the N2O decomposition activity of these catalysts showed a low level of efficiency. Nitrogen of N2O was reduced into N2 gas, whereas oxygen was released as CO or CO2 by the reaction with methanol or its derivatives.

The behavior of surface formate ions as reaction intermediates in the decomposition of methanol over Cr 2O 3

The mechanism of the decomposition of methanol over Cr 2O 3 was studied by in situ infrared spectroscopy and by a tracer jump method. The stability of surface formate ions formed by the decomposition of methanol over Cr 2O 3 greatly depended on the reaction conditions. In the presence of methanol vapor, surface formate decomposes easily to H 2, CO, and CO 2, with an activation energy of 29 kcal mol −1, although it is quite stable under vacuum ( E a = 46 kcal mol −1). The infrared absorption bands of the formate ions are shifted in the presence of methanol vapor, suggesting some chemical interaction between formate ions and adsorbed methanol. By isotope-labeling experiments it was confirmed that the formate ion, observed by infrared spectroscopy, is the reaction intermediate of methanol decomposition in spite of its marked stability in the absence of methanol.