Papers by Keyword: Alcohols

Abstract: To extinguish flammable polar liquids, it is proposed to use a multicomponent fire extinguishing system consisting of one or two layers of wetted lightweight bulk materials. It has been established that wetting bulk materials leads to a significant increase in the following components of fire extinguishing action: cooling, insulation, and dilution. In addition, the introduction of water into the fire extinguishing system leads to a decrease in the concentration of vapors of polar flammable liquids above the fire extinguishing layer of bulk materials due to their absorption by water. Crushed foam glass with a granule size of 10-15 mm was selected as a bulk material for the formation of the base layer of the fire extinguishing system. To improve the insulating properties of the base layer, it is proposed to apply swollen perlite with a granule size of 1.0-1.4 mm or swollen lamellar vermiculite with a scale size of 1 × 2.5 mm to its surface. Such sizes of perlite and vermiculite particles enable them to fill the cavities between the granules of the foam glass base layer, which leads to an increase in the insulating properties of the fire extinguishing system. The following were experimentally determined: bulk density, buoyancy in methanol, ethanol, propanol-2, and acetone, moisture retention of bulk materials, and the fraction of material that spilled through the foam glass layer. The fire extinguishing capacity of the proposed fire extinguishing systems based on bulk materials in the case of extinguishing polar flammable liquids was experimentally determined. The systems based on bulk materials have a combined fire extinguishing effect by the following mechanisms of combustion termination: cooling, insulation, and dilution. It is concluded that the advantages of the proposed system in comparison with existing fire extinguishing agents for polar flammable liquids are substantiated.

Abstract: A method of composite membrane obtaining effects on its transport properties. In the present work, for the first time, the influence of the method of applying a selective layer of polyheptylmethylsiloxane on the composite membrane pervaporation properties in the process of alcohol separation from water was studied. The comparison of two casting methods (kiss-coating and spin-coating) was conducted. Morphology of the obtained membranes and their separation properties during the pervaporation of the mixture of C₂-C₄ alcohols and water. It was shown that kiss-coating allows completely prevent leakage of the selective layer into the substrate pores. And, such a way, it allows to improve permeability of composite membrane (BuOH - 3.5 mol/(kPa·h·m2)). Besides, spin-coating method leads to higher selectivity (BuOH/H₂O - 2.3). It is caused by blocking the swelling of that part of the selective layer that is locked in the pores of the substrate. Thus, the choice of the casting method can determine the compatibility of the composite membrane with a specific separation task.

Abstract: . New developments in green catalytic oxidations of alcohols with H₂O₂ as oxidant in last decade are reviewed. Emphasis is placed on introducing the heterogeneous catalysts supported on different material in various of reactions, mechanism features are discussed as well.

Abstract: Adsorption behaviour of ZnSe, a popular material used in the manufacture of crystals for total internal reflectance techniques was studied for the adsorption of alcohols from dichloromethane solutions using infrared spectrometry. A series of n-alcohols were used in this study. The results show that the integrated area for the hydrogen bonded OH stretchings decrease and suggests that there is a continuous adsorption of alcohol molecules onto the ZnSe crystal by breaking the hydrogen bonds between alcohol molecules in solution.

Abstract: The surface polishing of Ti₃SiC₂ disk in fluids (water, ethanol, propanol, glycol, and glycerol) is conducted on a Buehler grinder/polisher and evaluated using surface roughness. Using Buehler automatic grinder/polisher, the Ti₃SiC₂ disks are grinded and polished in the as-mentioned lubricants by grinding disk of diamond with sizes of 45 μm to 3 μm. The surface roughnesses of Ti₃SiC₂ disks at each stage are measured by 3D surface profiler. The results show that the lowest surface roughness (Ra) of Ti₃SiC₂ disk obtained by mechanical polishing is 0.04 μm. The optimum polishing process of Ti₃SiC₂ disk is as follows: using water as lubricant, at a load of 5 N, for steps 1 to 4, the Ti₃SiC₂ and grinding disk rotates comparatively and the sizes of diamond particles on the abrasive disk are 45, 15, 9, and 3 μm, respectively. For step 5, the abrasive disk is woven cloth with no diamond particles. The duration of each step is 5 min. Using the same polishing process, the surface roughness of Ti₃SiC₂ disk by direct hot pressing is lower than that by in situ reactive hot pressing. Using the same polishing process but different lubricants, the surface roughness of the Ti₃SiC₂ disks increases in the order of water, ethanol, propanol, glycol, and glycerol. In water, the surface roughness of Ti₃SiC₂ disk decreases with the increasing quantity of water and polishing duration.

Abstract: A green oxidation of benzylic alcohols to the corresponding aldehydes or ketones was achieved in aqueous media using ionic liquid/H₂O₂/HCl catalytic oxidation system. The procedure is mild, environment-friendly and simple. Ionic liquids can be successfully recovered and reused for the oxidation of the same (different) substance. The directing effect of the ionic liquid is supported by the good selectivities and yields. These reactions demonstrate the catalytic oxidation and phase transfer function of the ionic liquid is stronger than that without ionic liquid.

Abstract: The terminal part of the e₊ track (the positron blob) is formed during ionization slowing down and subsequent ion-electron recombinations produced by a positron. It releases up to 1 keV of energy, which is converted into heat within few picoseconds. If a bulk temperature of a medium is below, but close enough to its melting point, some region of a substance may melt, yielding a peculiar temperature dependence of the lifetime (LT) spectra. We have estimated properties of the molten region with a help of macroscopic heat con- duction equation and suggested a model describing temperature dependence of the ortho- positronium lifetime in frozen methanol, ethanol, butanol and water close to their melting points.

Abstract: Magnesium aluminate (MgAl₂O₄) spinel nanoparticles were prepared by non-hydrolytic sol-gel method using anhydrous alcohols as oxygen donor. XRD and FTIR were used to characterise the effect of anhydrous alcohols on synthesis of MgAl₂O₄ spinel nanoparticles.The results showed that when the oxygen donor used in stoichiometric ratio for synthesizing MgAl₂O₄, anhydrous ethanol was the more effective oxygen donor than anhydrous isopropanol. But there was no remarkable effect on synthesis of MgAl₂O₄ spinel when the amount of anhydrous ethanol exceeded the stoichiometric ratio. The mean particle size MgAl₂O₄ spinel nanoparticles was in the range of 40 to 50 nm.

Abstract: The polycrystalline zinc oxide (ZnO) film was deposited on p-Si substrate by radio-frequency (RF) magnetron sputtering. The structure and morphology of the ZnO thin films are characterized by X-ray diffraction (XRD), the energy dispersive analysis of X-ray (EDX) and scanning electron microscope (SEM). The gas sensing properties of the ZnO/Si heterojunctions for alcohols with different chain lengths were investigated at room temperature. It is found that the current-voltage (I-V) characteristics of the ZnO/Si heterojunctions are sensitive to isopropanol, ethanol and methanol gas. We discussed a possible gas sensing mechanism of ZnO/Si heterojunction. The sensitivity of the ZnO/Si heterojunctions to the gases decreases from isopropanol to methanol and to ethanol at the same concentration. It can be explained by the volume effect and electron donating effect.

Abstract: Some typical multi-valent metal salt hydrates, such as chloride, nitrate, sulfate, and acetate of Fe3+, Al3+, Ga3+, In3+, ZrO2+, HfO2+, Zn2+, Co2+, Ni2+, Mn3+, Cr3+, and Cu2+ have catalytic activities for the esterification of saturated and unsaturated fatty acids and alcohols. Supporting these metal salt hydrates on ordered mesoporous silica such as MCM-41 enhanced the catalytic activity of the esterification. The esters of C10-C18 normal acid and alcohol were obtained in high yield by some of supported metal salt hydrates on MCM-41; however, the yield of the esters decreased with their chain length of acids and alcohols although the activities depended on type of metal salt hydrates. The catalyst is recyclable although some loss of activity was observed.