Methanol Gas Research Articles

Sinergistic effect of titanium dioxide and iron oxide aerosols in adsorption and photocatalytic oxidation of dimethyl methylphosphonate

Kinetics of adsorption, dark and photocatalytic destruction of dimethyl methylphosphonate (DMMP) vapors was investigated on the surface of nanosized FeOOH (3 nm) and mixture of FeOOH with TiO2 (5 nm) (1 : 1) in aerosol state in a closed chamber. FeOOH aerosol adsorbs DMMP (100 ppm) with characteristic time 32 s and does not show photocatalytic activity. Adsorbed DMMP undergoes hydrolysis with formation of gaseous methanol with characteristic time 11 min, while mixed FeOOH-TiO2 aerosol adsorbs DMMP and converts it into CO and CO2 under the action of UV light.

The catalytic effect of H2 in the dehydrogenation coupling production of ethylene glycol from methanol using a dielectric barrier discharge

The catalytic effect of H2 in the one-step synthesis of ethylene glycol (EG) from methanol dehydrogenation coupling reaction using dielectric barrier discharge (DBD) was studied by in-situ optical emission spectroscopy and online chromatographic analysis. The influence of discharge frequency, methanol and H2 flow rates as well as reaction pressure was investigated systematically. Results show that, in the non-equilibrium plasma produced by DBD, H2 dramatically improved not only the conversion of methanol but also the selectivity for EG. Using the reaction conditions of 300 °C, 0.1 MPa, input power 11 W, discharge frequency 12.0 kHz, methanol gas flow rate 11.0 mL/min, and H2 flow rate 80–180 mL/min, the reaction of the CH3OH/H2 DBD plasma gave a methanol conversion close to 30% and a selectivity for EG of more than 75%. The change of the EG yield correlated with the intensity of the Hα spectral line. H atoms appear to be the catalytically active species in the reaction. In the DBD plasma, the stable ground state H2 molecule undergoes cumulative collision excitation with electrons before transitioning from higher energy excited states to the first excited state. The spontaneous dissociation of the first excited state H2 molecules generates the catalytically active H atom. The discharge reaction condition affects the catalytic performance of H2 by influencing the dissociation of H2 molecules into H atoms. The catalytic effect of H2 exhibited in the non-equilibrium plasma may be a new opportunity for the synthesis of chemicals.

245 GHz SiGe sensor system for gas spectroscopy

A 245 GHz sensor system for gas spectroscopy is presented, which includes a SiGe receiver (RX), a SiGe transmitter (TX), and a 0.6 m long gas absorption cell between the TX and RX. The integrated local oscillators of the RX and the TX are controlled by two external phase locked loops (PLLs), whose reference frequencies are swept with constant frequency offset for a low IF of the RX. The RX consists of a differential low noise amplifier (LNA), an integrated 122 GHz local oscillator (LO) with 1/64 divider, a 90° differential hybrid, and active subharmonic mixer. The TX consists of an integrated 122 GHz LO with 1/64 divider, and a frequency doubler. The RX and TX are fabricated in 0.13 µm SiGe BiCMOS with ft/fmax of 300/500 GHz. Using external dielectric lenses for the TX and RX, the absorption spectrum of gaseous methanol has been measured. The reference frequency of the TX-PLL is modulated for frequency-modulation spectroscopy. The performance of the sensor system is demonstrated by measuring the 2f absorption spectrum (second harmonic detection) of gaseous methanol.

Simplified preparation of SnO2 inverse opal for Methanol gas sensing performance

As a novel structure, inverse opal, with three dimensional periodic macropore and mesopore, huge specific surface area, is promising in highly sensitive gas sensing. In this paper, SnO2 inverse opal was prepared with a simplified polystyrene (PS) opal template cooperating with sol–gel method. The simplified method could spare much work and avoid the operation of the SnO2 inverse opal scraped from microslide. The performance of the SnO2 inverse opal sensor to methanol gas was systemically investigated. The results indicate that the sensing performance of the SnO2 inverse opal sensor to methanol gas is highly improved than traditional sensors. The response of the SnO2 inverse opal sensor is as high as 95 for 500 ppm methanol gas detection. In the range from 1 to 1000 ppm, the SnO2 inverse opal sensor shows fine linear relationship with the growth of the methanol gas concentrations.

Synthesis of three-dimensionally ordered macroporous LaFeO3 with enhanced methanol gas sensing properties

Three-dimensionally ordered macroporous (3DOM) LaFeO3 was synthesized by a simple PMMA template method. The structure morphology and composition of as-prepared products have been characterized by SEM, XRD, and TEM. The products show long-range ordered hexagonal arrangement forming an inverse opal nanostructure. The surface area of 3DOM LaFeO3 is almost twice larger than that of bulk LaFeO3. The methanol gas sensing performance of 3DOM LaFeO3 was systemically studied. The as-performed samples show p-type semi-conducting properties for all the tested gases within the temperature range of 150–300°C. The 3DOM LaFeO3 shows the highest gas response (as high as 96) and the fastest response–recovery times at 190°C. In addition, it shows superior selectivity to methanol. This enhancement in gas-sensing properties is attributed to its ordered macro-mesoporous structure, large surface area, numerous surface active sites and oxygen vacancies.

High Response and Selectivity Methanol Gas Sensor Using Molecular Imprinting Technique

A new gas sensor with high response and selectivity was fabricated by using molecularly imprinted powders (MIPs) which provide special recognition sites to methanol. The MIPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and fourier transform infrared spectrometer (FT-IR), respectively. The gas sensing properties of MIPs to methanol were investigated. The experimental results indicate that the sensors based on the MIPs show excellent gas sensing properties to methanol vapor, and the properties of the sensor with x=6:10 (x= methyl acrylic acid: LaFeO3, molar ratio) are the best. At the optimal operating temperature of 130°C, the response of the sensor (x=6:10) to 1 ppm methanol is 21, and the response and recovery times are 57 s and 67 s, respectively.

Research on the Ultra High Strength Steel Thermoforming Protective Atmosphere Heating Furnace

This paper studied protective atmosphere furnace used in the thermoforming production line of ultra high strength steel plate, simulation and analysis for the key technologies and structure of furnace have been made, and two patents formed (ZL201320006066.2, ZL201320007455.7). 1, Research and develop the structure of roller and its ends for heating furnace; 2, the heating process of furnace has analyzed and calculated, the protective atmosphere furnace developed fully meet the requirements of high-strength steel thermo-forming production line; 3, the mixture of high-purity nitrogen and dissociated methanol gas was used as the protect atmosphere, It has been verified the effect of protective atmosphere system is good. The high-strength steel plate protective atmosphere furnaces and production lines, we developed, has independent intellectual property rights, the properties and surface quality of thermoformed steel plate are good.

Enhancement of ethanol gas sensing response based on ordered V2O5 nanowire microyarns

In this paper, a prototype V2O5 nanowire microyarns-based gas sensor with high response and selectivity for ethanol was developed. The V2O5 nanowire yarns were directly spun from ultralong V2O5 nanowires viscous solution. This process is very similar to drawing a thread from a silk cocoon. The microyarns wound around alumina tubes like a spiral were tested for gas sensing toward ethanol, methanol, ammonia and toluene gases. It was found that the microyarns exhibit good response and selectivity to ethanol. The response of the yarns reaches the maximum value of 9.09 to 1000ppm ethanol at 330°C, which is around 3.5 times higher than that of the randomly ultralong nanowires. In contrast, only very little response was observed for methanol, ammonia and toluene, which indicated that V2O5 nanowire microyarns would be a potential candidate for practical gas detector.

Bi‐channel Surface Acoustic Wave Gas Sensor for Carbon Disulfide and Methanol Vapors in Polymer Plants

AbstractA C60‐polyphenylacetylene (C60‐PPA) and polyvinylpyrrolidone (PVP) coated two‐channel surface acoustic wave (SAW) crystal gas sensor with a homemade computer interface for data acquisition and data processing was developed and employed to detect carbon disulfide (CS2) and methanol (CH3OH) vapors in polymer plants. The frequency of surface acoustic wave oscillator decreases due to the adsorption of gas molecules on the coated materials of the SAW sensor. Six coating materials (C60‐PPA, nafion, PPA, crytand [2,2], polyethene glycol and PVP) were used to adsorb and detect carbon disulfide and methanol gases. Adsorption of all the six coating materials to CS2 and CH3OH was found to be physical adsorption. The C60‐PPA coated SAW detector exhibited more sensitive to CS2 than the other coating materials. In contrast, the PVP coated SAW detector was more sensitive to CH3OH than the other coating materials. With the two‐channel SAW sensor, the C60‐PPA coated SAW showed a good detection limit of 0.4 ppm and good reproducibility with RSD of 3.37 % (n=10) for CS2. Similarly, the PVP coated SAW also showed a good detection limit of 0.05 ppm and good reproducibility, with RSD of 0.86 % (n=10) for CH3OH. The interference effect of other organic molecules on the SAW detection system was negligible, except for the irreversible adsorption of C60‐PPA to propylamine. The frequency signals from the two‐channel SAW sensor array C60‐PPA and PVP coatings were processed by a back‐propagation artificial neural network (BPN) and multiple regression analysis (MRA). Thus a two‐channel SAW sensor array with BPN and MRA has been successfully applied for the qualitative and quantitative analyses of CS2 and CH3OH in mixtures.

Process-induced damage and its recovery for a CoFeB–MgO magnetic tunnel junction with perpendicular magnetic easy axis

We investigate the effect of process-induced damage (PID) caused by reactive ion etching using methanol (Me–OH) gas on the magnetic properties of the CoFeB free layer in a magnetic tunnel junction with a perpendicular easy axis (p-MTJ), and on the tunnel magnetoresistance (TMR) ratio of CoFeB–MgO p-MTJs. The dot pattern of the MTJ stack with size varied from 65 to 430 nm etched by the Me–OH plasma showed a smaller coercivity (Hc) than that fabricated by Ar ion milling. The increase in Hc was observed in the dot pattern of large size (430 nm) upon increasing He/H2 plasma treatment temperature after the Me–OH etching. A possible origin of the increase in Hc is the increase in nucleation field after He/H2 treatment. This suggests that Hc of the large dot pattern has the potential to be an index for detecting PID during the MTJ fabrication process. The TMR ratio of CoFeB–MgO p-MTJ deteriorated after the Me–OH plasma etching. This PID was considered to be due to oxidation from the pattern edge of the CoFeB free layer of the MTJ. The recovery process by the He/H2 plasma treatment was examined just after the Me–OH etching to reduce the oxidized part. The median TMR ratio of 102%, which is 5% higher than that of the sample without the He/H2 treatment, was observed after applying this reductive treatment at 180 °C. In addition, the recovery process had scalability with MTJ size, as the effect was observed more clearly in the MTJ smaller than 97 nm.

Antifreezes Act as Catalysts for Methane Hydrate Formation from Ice

AbstractContrary to the thermodynamic inhibiting effect of methanol on methane hydrate formation from aqueous phases, hydrate forms quickly at high yield by exposing frozen water–methanol mixtures with methanol concentrations ranging from 0.6–10 wt % to methane gas at pressures from 125 bars at 253 K. Formation rates are some two orders of magnitude greater than those obtained for samples without methanol and conversion of ice is essentially complete. Ammonia has a similar catalytic effect when used in concentrations of 0.3–2.7 wt %. The structure I methane hydrate formed in this manner was characterized by powder X‐ray diffraction and Raman spectroscopy. Steps in the possible mechanism of action of methanol were studied with molecular dynamics simulations of the Ih (0001) basal plane exposed to methanol and methane gas. Simulations show that methanol from a surface aqueous layer slowly migrates into the ice lattice. Methane gas is preferentially adsorbed into the aqueous methanol surface layer. Possible consequences of the catalytic methane hydrate formation on hydrate plug formation in gas pipelines, on large scale energy‐efficient gas hydrate formation, and in planetary science are discussed.

Brønsted Instead of Lewis Acidity in Functionalized MIL-101Cr MOFs for Efficient Heterogeneous (nano-MOF) Catalysis in the Condensation Reaction of Aldehydes with Alcohols

Porous chromium(III) 2-nitro-, 2-amino-, and nonfunctionalized terephthalate (MIL-101Cr) metal organic frameworks are heterogeneous catalysts for diacetal formation from benzaldehyde and methanol (B-M reaction) as well as other aldehydes and alcohols. MIL-101Cr-NO2 obtained by direct reaction between CrO3 and 2-nitro-terephthalate showed the highest activity with 99% conversion in the B-M reaction in 90 min and turnover numbers of 114. The activity decreased in the order MIL-101Cr-NO2 > MIL-101Cr > MIL-101Cr-NH2. Within different samples of nonfunctionalized MIL-101Cr the activity increased with surface area. Methanol gas sorption of the different MIL materials correlates with the BET surface area and pore volume but not with the diacetalization activity. Benzaldehyde adsorption from heptane showed no significant difference for the different MILs. Gas sorption studies of CD3CN to probe for a higher Lewis acidity in MIL-101Cr-NO2 remained inconclusive. A high B-M catalytic activity of wet MIL-101Cr-NO2 excluded significant contributions from coordinatively unsaturated Lewis-acid sites. pH measurements of methanol dispersions of the MIL materials gave the most acidic pH (as low as 1.9) for MIL-101Cr-NO2, which significantly increased over MIL-101Cr (3.0) to MIL-101Cr-NH2 (3.3). The increase in acidity is of short range or a surface effect to the heterogeneous MIL particles as protons dissociating from the polarized aqua ligands (Cr-OH2) have to stay near the insoluble counteranionic framework. The variation in Brønsted acidity of MIL-101Cr-NO2 > MIL-101Cr ≈ MIL-101Cr-NH2 correlates with the withdrawing effect of NO2 and the diacetalization activity. The catalytic B-M activity of soluble, substitution-inert, and acidic Cr(NO3)3·9H2O supports the Brønsted-acid effect of the MIL materials. Filtration and centrifugation experiments with MIL-101Cr-NO2 revealed that about 2/3 of the catalytic activity comes from nano-MOF particles with a diameter below 200 nm. The MIL-101Cr-NO2 catalysts can be recycled five times with very little loss in activity. The diacetalization activity of MIL-101Cr-NO2 decreases with the alcohol chain length from methanol over ethanol, n-propanol, n-butanol, to almost inactive n-pentanol, while conversions for benzaldehyde, paratolylaldehyde, 4-chlorobenzaldehyde, and cyclohexanone all reach 90% or more after 90 min.

COLD WATER VAPOR IN THE BARNARD 5 MOLECULAR CLOUD

After more than 30 years of investigations, the nature of gas-grain interactions at low temperatures remains an unresolved issue in astrochemistry. Water ice is the dominant ice found in cold molecular clouds, however, there is only one region where cold (~10 K) water vapor has been detected - L1544. This study aims to shed light on ice desorption mechanisms under cold cloud conditions by expanding the sample. The clumpy distribution of methanol in dark clouds testifies to transient desorption processes at work -- likely to also disrupt water ice mantles. Therefore, the Herschel HIFI instrument was used to search for cold water in a small sample of prominent methanol emission peaks. We report detections of the ground-state transition of o-H2O (J = 1_10 - 1_01) at 556.9360 GHz toward two positions in the cold molecular cloud Barnard 5. The relative abundances of methanol and water gas support a desorption mechanism which disrupts the outer ice mantle layers, rather than causing complete mantle removal.

Si doping influence on the catalytic performance of Pt/TiO2 mesoporous film catalyst for low-temperature methanol combustion

A series of Si-doped mesoporous TiO2 thin films with anatase phase were synthesized and used as the supporters of Pt catalyst for low-temperature catalytic combustion of gaseous methanol. The introduced Pt ions were processed by a simple photo-reduction method. The catalytic performance of thin film catalysts with different Si doping content were measured by gas chromatography method. It was found that the catalytic performance of Pt/TiO2 can be improved a lot by Si doping and the optimized value of Si/Ti ratio is 0.1. At this point, Pt/TiO2 exhibited the best catalytic activity towards methanol combustion reaching up to 92.8% at 100 °C. This conversion rate was 13.2% higher than that of the catalyst without doping. Moreover, the mechanism for Si affecting on the catalytic performance was proposed based on the XRD, FT-IR, SEM, TEM, N2 adsorption–desorption and XPS characterizations.

Effect of Alcohol-Assisted Annealing on the Quality of Silicon Oxide Thin Film

Silicon oxide thin films have been formed by use of the reaction between spin-coated silicone oil and ozone gas at atmospheric pressure and low temperature (250°C). Films formed at this temperature contained Si–OH bonds, owing to inadequate dehydration. To remove the Si–OH bonds at low temperature, the sample was dipped in ethanol at room temperature for 15 min then annealed on a hot plate at 250°C in methanol gas for 30 min. This treatment effectively dissociated the Si–OH bonds. It is believed the Si–OH bonds are replaced by Si-OCH3 bonds during the alcohol-assisted annealing. The leakage current of the metal-oxide-semiconductor after alcohol-assisted annealing was improved and the hysteresis width was reduced. This indicated that the number of trap sites owing to Si–OH bonds was reduced.

Effect of anode MPL on water and methanol transport in DMFC: Experimental and modeling analyses

The regulation of mass transport through anode diffusion layer is one of the major issue of direct methanol fuel cell. In fact it is critical to maintain an adequate methanol concentration in the anode electrode such that both the rate of methanol crossover and the mass transport loss can be minimized. In the present work the effect of anode micro-porous layer on system operation is investigated both experimentally and theoretically. The developed 2D two-phase isothermal model is validated with respect to three different typologies of measure at the same time, increasing results reliability. Model simulations highlight that anode micro-porous layer can cause an inversion of water diffusion flux through the membrane and enhances methanol gas diffusion mechanism, reducing methanol crossover. Finally the developed model is used as a tool to design an optimized anode diffusion layer.

Nanocrystalline samarium oxide coated fiber optic gas sensor

Nanocrystalline Sm2O3 coated fiber optic sensor is proposed for detecting toxic gases such as ammonia, methanol and ethanol vapors. Sm2O3 in the as prepared form as well as annealed form have been used as gas sensing materials, by making them as cladding of a PMMA fiber. The spectral characteristics of the Sm2O3 gas sensor are presented for ammonia, methanol and ethanol gases with different concentrations ranging from 0 to 500 ppm. The sensor exhibits a linear variation in the output light intensity with the concentration. The enhanced gas sensitivity and selectivity of the sensor for ethanol is discussed briefly.

Nanocrystalline cerium oxide coated fiber optic gas sensor

A clad-modified fiber optic sensor with nanocrystalline CeO2 is proposed for gas detection. As-prepared and annealed CeO2 (500 °C) samples have been used as gas sensing media. The spectral characteristics of the fiber optic gas sensor are studied for various concentrations of ammonia, ethanol and methanol gases (0–500 ppm). The sensor exhibits linear variation in the spectral peak intensity with the gas concentration. The characteristics of the sensor are also studied for gas selectivity. The time response characteristics of the sensor are reported.

Utilization of Conducting Polymers in Fabricating Polymer Electrolyte Membranes for Application in Direct Methanol Fuel Cells

Search for suitable materials for fabricating polymer electrolyte membranes (PEMs) for application in polymer electrolyte membrane fuel cells, and particularly in direct methanol fuel cells (DMFCs), has been an important field of research for the last several decades. Notable candidates that have emerged from this extensive and seemingly exhaustive research are Nafion®, poly(vinylidenefluoride), sulfonated poly(etheretherketone), poly(benzimidazole), Dow XUS®, Flemion® R, 3P-energy, Aciplex-S®, Gore-Tex®, Gore-Select®, and their different blends, copolymers and interpenetrating networks with compounds, such as poly(hexafluoropropylene), poly(acrylonitrile), poly(styrenesulfonate), and poly(methylmethacrylate). Nevertheless, the objective of achieving a much reduced methanol crossover, while maintaining a substantial level of proton conductivity, has remained by and large elusive. However, a ray of hope has been provided by conducting polymers (CPs), and this has led to a considerable number of researchers to plunge into the exploitation of this possibility. This review focuses on the application of CPs, mainly polyaniline and polypyrrole, as PEM constituents. Detailed comparisons between their functioning, and their respective utility in terms of achieving this objective have been provided. We have also discussed the following critical points: first, the effect of CPs on methanol crossover, proton conductivity, and gas diffusion, and second, thermal stability of CPs in the temperature range within which DMFC operates.

Oxidation of methanol to methyl formate over supported Pd nanoparticles: insights into the reaction mechanism at low temperature

The mechanism of methyl formate formation at low temperature was studied using DRIFT-operando. The first reaction step would be the formation of methoxy groups by dissociative adsorption of methanol and then transformation into formaldehyde. The final step would be the condensation of the formaldehyde species with gaseous methanol.