Catalytic combustion of alcohols for microburner applications

The combustion of energy dense liquid fuels in a catalytic micro-combustor, whose temperatures can be used in energy conversion devices, is an attractive alternative to cumbersome batteries. To miniaturize the reactor, an evaporation model was developed to calculate the minimum distance required for complete droplet vaporization. By increasing the ambient temperature from 298 to 350 K, the distance required for complete evaporation of a 6.5 μm droplet decreases from 3.5 to 0.15 cm. A platinum mesh acted as a preliminary measurement and demonstrated 75% conversion of ethanol. We then selected a more active rhodium-coated alumina foam with a larger surface area and attained 100% conversion of ethanol and 95% conversion of 1-butanol under fuel lean conditions. Effluent post-combustion gas analysis showed that varying the equivalence ratio results in three possible modes of operation. A regime of high carbon selectivity for CO₂ occurs at low equivalence ratios and corresponds to complete combustion with a typical temperature of 775 K that is ideal for PbTe thermoelectric energy conversion devices. Conversely for equivalence ratios greater than 1, carbon selectivity for CO₂ decreases as hydrogen, olefin and paraffin production increases. By tuning the equivalence ratio, we have shown that a single device can combust completely for thermoelectric applications, operate as a fuel reformer to produce hydrogen gas for fuel cells or perform as a bio-refinery for paraffin and olefin synthesis.     

A comparative experimental and computational study of methanol, ethanol, and n-butanol flames

Laminar flame speeds and extinction strain rates of premixed methanol, ethanol, and n-butanol flames were determined experimentally in the counterflow configuration at atmospheric pressure and elevated unburned mixture temperatures. Additional measurements were conducted also to determine the laminar flame speeds of their n-alkane/air counterparts, namely methane, ethane, and n-butane in order to compare the effect of alkane and alcohol molecular structures on high-temperature flame kinetics. For both propagation and extinction experiments the flow velocities were determined using the digital particle image velocimetry method. Laminar flame speeds were derived through a non-linear extrapolation approach based on direct numerical simulations of the experiments. Two recently developed detailed kinetics models of n-butanol oxidation were used to simulate the experiments. The experimental results revealed that laminar flame speeds of ethanol/air and n-butanol/air flames are similar to those of their n-alkane/air counterparts, and that methane/air flames have consistently lower laminar flame speeds than methanol/air flames. The laminar flame speeds of methanol/air flames are considerably higher compared to both ethanol/air and n-butanol/air flames under fuel-rich conditions. Numerical simulations of n-butanol/air freely propagating flames, revealed discrepancies between the two kinetic models regarding the consumption pathways of n-butanol and its intermediates.     

Influence of SO<Subscript>2</Subscript> on the evolution of volatile compounds through alcoholic fermentation of must stabilized by pulsed electric fields

The aim of this work was to study the influence of sulphur dioxide (SO₂) on the formation of volatile compounds by yeast through wine alcoholic fermentation. Thus Parellada must was microbiologically stabilized using a pulsed electric field (PEF) treatment and inoculated with Saccharomyces cerevisiae Na33 strain. Fermentation was carried out with or without SO₂ and the results showed that the evolution of the volatile compounds profile throughout the process was similar. The content of volatile acids in wine obtained by using sulphur dioxide was not significantly different from that fermented without adding the compound. However, the final content of total alcohols and esters was significantly different even thought the differences were small. Consequently, when grape must is treated by PEF the sulphur dioxide concentration usually used in winemaking could be reduced to safer levels or even eliminated without an important effect on the volatile compounds content of the final product. Therefore, the absence of sulphur dioxide should not have a negative impact on the sensory characteristics of wine.     

Effects of alcohol-based inhibitors on corrosion of mild steel in hydrochloric acid

The inhibition efficiencies of Octyl alcohol (OCAL) and propargyl alcohol (PRAL) on the corrosion of mild steel in 15% commercial hydrochloric acid have been evaluated by mass loss method, electrochemical techniques and surface analysis techniques with 0–1% inhibitor concentration at 30 °C and 105 °C. Both OCAL and PRAL are excellent inhibitors for the above-mentioned system. OCAL gives 87% and 82% inhibition efficiencies at 30 °C and 105 °C, respectively, for 1% inhibitor concentration whereas PRAL gives 100% and 99% efficiencies at 30 °C and 105 °C, respectively, for 0.6% inhibitor concentration. Polarization studies confirm that OCAL and PRAL are mixed type inhibitors. OCAL and PRAL obey Temkin's adsorption isotherm at both the temperatures. UV-reflectance, FT-IR and SEM studies confirm that the surface of mild steel is not affected at the maximum concentration of OCAL and PRAL.     

FTIR study of gas-phase alcohols photocatalytic degradation with TiO2 and AC-TiO2

In this paper the degradation of gaseous alcohols (methanol, ethanol, 1-propanol and 1-butanol) has been studied in a continuous reaction system. Methanol and ethanol, but not 1-propanol and 1-butanol, have caused the catalyst bare-TiO₂ to become deactivated. The catalyst containing activated carbon, AC-TiO₂, has not shown almost deactivation in any experiment.

To explain this behaviour variation, a thorough FTIR study concerning the interaction of gaseous alcohols with the catalyst surface and the effect of light on the process was performed. Thus, the interaction of the different catalysts with the selected alcohols, the formed species and the hydroxyl group evolution under irradiation was studied.     

An overview of some reactions of thianthrene cation radical. Products and mechanisms of their formation

A comprehensive review of recent chemistry of thianthrene cation radical is presented. Particularly, products and mechanisms of their formation from reactions with azo compounds, hydrazones, oximes, sulfonamides, alcohols, phenols, alkenes, alkynes and organometallics are discussed. Also, reactions of 5-(substituted)thianthrenium salts are reviewed.     

Preparation of sulfuric acid ([3-(3-silicapropyl)sulfanyl]propyl)ester: A new and recyclable catalyst for the formylation and acetylation of alcohols under heterogeneous conditions

We describe a simple and efficient procedure for the preparation of sulfuric acid ([3-(3-silicapropyl)sulfanyl]propyl)ester (3) by the reaction of 3-(thio(propy-3-yl)silica)-propanol (2) and chlorosulfonic acid in chloroform. 3-(Thio(propy-3-yl)silica)-propanol was prepared by the reaction of 3-mercaptopropylsilica (MPS) with 3-chloropropanol in refluxing toluene. This solid sulfuric acid ([3-(3-silicapropyl)sulfanyl]propyl)ester is employed as a new catalyst for the formylation of alcohols with ethyl formate under mild and heterogeneous conditions at room temperature with good to excellent yields. Also, 3 can catalyze the acetylation of various alcohols by the reaction of alcohols with ethyl acetate under reflux conditions or with acetic anhydride at room temperature.     

Sensing properties of two-component Langmuir-Blodgett layer and its porous derivative in SAW sensor for vapors of methanol and ethanol

Two-component Langmuir-Blodgett film has been fabricated from equimolar mixture of 5-[[1,3-dioxo-3-[4-(1-oxooctadecyl)phenyl]propyl]amino]-1,3-benzenedicarboxylic acid with cetylamine. Porous one-component derivative of this film has been obtained by removing of cetylamine. Both films have been investigated as sensing layers of the surface acoustic wave sensors for vapors of methanol and ethanol in air. These films react on the alcohol vapors. Time of the sensor reaction is less than 2 s and this reaction is reversible. The response parameters of the sensor depend on the kind of the alcohol and the structure of the layer. An explanation of the observed differences in the behavior of both layers in contact with vapors of the alcohols has been proposed.     

Ultrafine bimetallic alloy supported on nitrogen doped reduced graphene oxide toward liquid-fuel oxidation: Profile of improved performance and extended durability

Herein, the ultrafine bimetallic alloy supported on nitrogen doped reduced graphene oxide (PtCu/NrGO) has been developed via wet-reflux strategy and applied as potential catalyst for electro-oxidation of liquid fuels in direct alcohol fuel cells (DAFCs). Possible conversion to PtCu/NrGO from the precursor materials was established in detail using transmission electron microscope (TEM), field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photo electron spectroscopy (XPS). The coupled structure of PtCu along with NrGO endowed an efficient catalyst with excellent catalytic activity and stability toward electro-oxidation of various alcohols compared to commercial Pt/C in acidic electrolyte. PtCu/NrGO exhibits the mass activity of 0.917, 0.620 and 0.495 A/mg_Pt toward the electro-oxidation of methanol, ethylene glycol and glycerol, about 6.8, 6.3 and 8.6 fold increment compared to Pt/C catalyst, respectively. Besides, PtCu/NrGO shows excellent durability with less activity decay even after 500 cycles.     

Conversion of Carbon Monoxide‐Rich Synthesis Gas to Hydrocarbons and Alcohols over Cu/Co/ZnO/SiO2 Catalysts

Catalysts of the type Cu/Co/ZnO/SiO₂ were prepared by impregnation, subsequent calcination and reduction with hydrogen. Characterization of the catalysts was carried out by ICP‐AES, BET measurements and powder X‐ray diffraction analyses. Furthermore, temperature programmed reduction was employed to investigate their reduction behavior. The catalysts were tested in the conversion of synthesis gas to hydrocarbons and alcohols. High CO conversions could be reached in a single reactor pass. Selectivity was highest for methane, and short‐chain hydrocarbons, but alcohols were also formed.