Absence Of Air Research Articles

Effects of heating, aerial exposure and illumination on stability of fucoxanthin in canola oil

The effects of heating, aerial exposure and illumination on the stability of fucoxanthin was investigated in canola oil. In the absence of air and light, the heating caused the degradation of total and all-trans fucoxanthin at all tested temperatures between 25 and 100°C. The increase of heating temperature promoted the formation of 13-cis and 13′-cis and the degradation of 9′-cis. The degradation and formation reactions were found to follow simple first-order kinetics and to be energetically unfavorable, non-spontaneous processes. Arrhenius-type temperature dependence was observed for the degradation of total and all-trans fucoxanthin but not for the reactions of cis isomers. The aerial exposure promoted the oxidative fucoxanthin degradation at 25°C, whilst illumination caused the initial formation of all-trans, with concurrent sudden degradation of 13-cis and 13′-cis, and the considerable formation of 9′-cis. The fucoxanthin degradation was synergistically promoted when exposed to both air and light.

Ash-Forming Matter in Torrefied Birch Wood: Changes in Chemical Association

Torrefaction is heat treatment of biomass at relatively low temperatures (∼240–300 °C) in the absence of air. The torrefied fuel offers advantages to traditional biomass, such as higher energy density, better grindability, and reduced biological decay. These factors could, for example, lead to increased use of biomass in pulverized coal boilers. Ash-forming elements are present in biomass as water-soluble salts, ion-exchangeable elements, included or excluded minerals, and covalently bound sulfur and chlorine. In this work, we have studied the change in the chemical association of ash-forming elements in birch wood as a function of the extent of torrefaction. The birch wood was torrefied at 240, 255, 270, or 280 °C at ECN, The Netherlands. The raw and torrefied birch wood samples were studied using three different techniques: chemical fractionation, potentiometric titration, and methylene blue sorption. Chemical fractionation was performed on the original wood sample, and the samples of wood were torrefied at either 240 or 280 °C. These results give a first understanding of the changes in the association of ash-forming elements during torrefaction. The most significant changes can be seen in the distribution of calcium, magnesium, and manganese, with some change in water solubility seen in potassium. These changes may, in part, be due to the destruction of carboxylic acid groups, which were measured by both potentiometric titration and methylene blue sorption. In addition to some changes in water and acid solubility of phosphorus, a clear decrease in the concentration of both chloride and sulfur was measured. The results provide new data about chemical changes with regards to the inorganic elements during torrefaction. The decrease in the chloride content should be investigated further with high-chloride-containing fuels. If a significant level of chloride is removed by torrefaction, this would be a significant additional benefit for the combustion of torrefied biomass.

Removal of Acid Blue 29 in aqueous solution by Fenton and Fenton-like processes

The decoloration and mineralization of the azo dye, Acid Blue 29 (AB 29) in aqueous solution was investigated in the presence and absence of air by Fenton and Fenton-like processes using hydrogen peroxide (HP) and sodium persulfate (SPS), respectively, as oxidants. The effect of various operational parameters and presence of Cl-, CO32-, HCO3-, and SO42- ions on the decoloration was examined. Higher decoloration was observed at pH 3 and 5 in both the cases. On the basis of mineralization efficiency (34.1 and 28.5%, respectively, with HP and SPS in 180 min), it was concluded that HP is a better oxidant than that of SPS. The decoloration in the absence of air is decreased until a certain time period, beyond which it increases and becomes same as that in the presence of air. This is explained on the basis of in situ generation of HP and peroxyl radicals. Although all ions under study inhibit decoloration significantly, the inhibition efficiency of SO42- is less than that of others.

The Production of Biogas Using Kitchen Waste

Kitchen waste is the best alternative for biogas production in a community level biogas plant. It is produced when bacteria degrade organic matter in the absence of air. Biogas contains around 55-65% of methane, 30-40% of carbon dioxide. The calorific value of biogas is appreciably high (around 4700 kcal or 20 MJ at around 55% methane content). The gas can effectively be utilized for generation of power through a biogas based power-generation system after dewatering and cleaning of the gas. In addition, the slurry produced in the process provides valuable organic manure for farming and sustaining the soil fertility. In this paper, an attempt has been made to test the performance of different ratio of kitchen waste in a metal made portable floating type biogas plant of volume capacity 0.018 m3 for outdoor climatic condition of New Delhi, India . Each of the biogas plant 30 Kg slurry capacity in batch system for all measurement. During these period, the temperature, solar radiation and relative humidity have been measured. We have also analysed the constituent of biogas, pH, volume and rate of biogas production at different level of temperature observation on daily basis. Here we also compare the rate of biogas production from kitchen waste with the other energy sources used for cooking purposes like LPG, Kerosene and Coal.

Fixed Bed Adsorption Column Studies for the Removal of Aqueous Phenol from Activated Carbon Prepared from Sugarcane Bagasse

Fixed bed adsorption has become a frequently used industrial application in wastewater treatment processes. Various low cost adsorbents have been studied for their applicability in treatment of different types of effluents. In this study, the potential of activated carbon derived from sugarcane bagasse was studied for the removal of aqueous phenol in a fixed column. Sugarcane bagasse was thermally activated under 600°C in absence of air. A series of batch experiments were performed in order to identify the appropriate adsorption isotherm. Both Langmuir and Freundlich equilibrium isotherms were analyzed according to the experiment data and related parameters were estimated. Results revealed that the Langmuir isotherm provides the best fit with experimental data. Fixed bed experiments were performed and, breakthrough curves were drawn by varying activated carbon bed height. Accordingly the ideal breakthrough curves (IBC) were prepared and bed capacity (BC), length of the unused bed (LUB), the time required for full bed exhaustion at infinite rapid adsorption TS and the breakthrough times Tb were calculated for each scenarios.

Amphiphatic thioxanthone-anthracene photoinitiator for free-radical polymerization

A novel thioxanthone-anthracene (TX-A) photoinitiator possessing an octyl group, TX-A-Oct, as amphipathic photoinitiator was synthesized by click chemistry. Its ability to initiate photopolymerization of various monomers, namely methyl methacrylate (MMA), acryl amide (Am), butyl acrylate (BA), styrene (St), and a multifunctional monomer trimethylolpropane triacrylate (TMPTA), was examined in both the presence and absence of air. TX-A-Oct was found to be effective in initiating polymerization also in the absence of a co-initiator. UV, FTIR, and fluorescence spectroscopic analysis and polymerization studies revealed that depending on the conditions photoinitiations occur through both anthracene and thioxanthone chromophoric groups by hydrogen abstraction and endoperoxide formation processes, respectively.

Combustion synthesis of some iron oxides used as adsorbents for phenol and p-chlorophenol removal from wastewater

The effect of the fuel nature and of the reaction atmosphere (in air/in the absence of air) on the synthesis of iron oxides by the combustion method was investigated. Working in air, using urea with ammonium chloride as fuel, the final product of reaction is α-Fe2O3. Working in the absence of air, using oxalic, tartaric, respectively, citric acid as fuel, the single phase resulted in combustion reaction was Fe3O4. From the synthesized iron oxides investigated as potential sorbents for the removal of phenol and p-chlorophenol (PCP) from wastewater, only the sorbents obtained using tartaric acid as fuel (S3) and those obtained using citric acid as fuel (S2) show adsorption capacity for the two pollutants. The sorbent S3 shows better adsorption capacity for both phenol and for PCP compared with sorbent S2.

Dioxygen binding and activation by a highly reactive Cr(II) compound containing S,N-donors derived from o-aminothiophenol

We report the synthesis, characterization, and reactivity of a Cr(II) complex, [Cr(H2O)(LISQ)2] (1) [(LISQ)1− is o-iminothionebenzosemiquinonate(1−) π-radical], that is highly stable in solid state in the presence of air but undergoes spontaneous change in solution, both in the presence and absence of air. Physicochemical studies in solution show that a superoxo-CrIII species, [Cr(O2)(OH)(LISQ)2]− is generated initially in DMF solution of 1 in the presence of air owing to its immediate deprotonation followed by O2 binding to the deprotonated species. The formation of this superoxo-CrIII species is prominent and gradual in the presence of CH3OH, a scavenger of CrO2+ species. This Cr(O2)2+ species in turn is converted to another highly reactive O=Cr(IV) intermediate [O=Cr(OH)(LISQ)2]− which undergoes disproportionation producing an unstable O=Cr(V) species, [O=Cr(OH)(LISQ)2] and a stable Cr(III) compound, [Cr(OH)(DMF)(LISQ)2] (2). The rate of this disproportionation is enhanced in the presence of MnCl2, [N(n-Bu)4]PF6 and KSCN. The generated O=Cr(IV) species interacts with DNA with complete cleavage. The O=Cr(V) species slowly disappears from solution as revealed from EPR studies.

Aqueous-phase ketonization of acetic acid over Ru/TiO2/carbon catalysts

The ketonization of acetic acid over Ru/TiO2 and Ru/TiO2/C catalysts has been accomplished in the liquid phase at temperatures significantly lower than those typically needed for this reaction. The catalysts were prepared by impregnating the activated carbon support with titanium(IV) isopropoxide, followed by slow hydrolysis and calcination in the absence of air. The resulting TiO2/C powder was further impregnated with Ru(III) chloride, dried, and calcined in air. After an in situ pre-reduction in H2, the resulting Ru/TiO2/C exhibited high activity and selectivity to acetone in both organic and aqueous phases at 180°C. By contrast, when the TiO2/C sample was pre-calcined in air before the addition of Ru, the resulting catalyst showed significantly lower activity, even when it was pre-reduced in situ, and was essentially inactive without pre-reduction. It is believed that surface Ti3+ species can be readily formed and favor the ketonization reaction in the presence of liquid water. A combination of techniques including TEM, BET, TPR, XRD, XPS, and EPR was used to characterize the reducibility of the catalysts as well as the formation of and stability of Ti3+ sites. It is proposed that the presence of Ru on TiO2 facilitates the formation of these reduced sites. Furthermore, the hydrophobicity of the carbon support is believed to slow down the typical inhibiting effect of water for reactions catalyzed by reduced Ti3+ sites.

Flow and yield stress behaviour of ultrafine Mallee biochar slurry fuels: The effect of particle size distribution and additives

The yield stress and flow behaviour of ultrafine Mallee biochar–water slurries were evaluated as a function of particle size distribution, solid concentration and additives including carboxymethylcellulose sodium salt (CMC) and poly(budadiene-maleic acid) sodium salt (BMA). The Mallee biochar was made from Oil Mallee chips carbonised in the absence of air at 750°C in an indirectly-fired kiln with a solid residence time of ca. 30min. The biochar–water slurries were prepared, with and without additives, by (1) dry-milling the biochar for different times and then mixing the resulting powders with water and (2) by wet-milling the biochar also for different times. The milling, dry or wet over different times resulted in different particle size distributions, the effect which on the rheological properties on the slurries was also investigated. The slurries displayed highly shear-thinning flow behaviour, typical of a flocculated dispersion. It was found that the yield stress decreased with increasing particle size and the relationship can be represented by a power law model. The yield stress showed a dependence on D50 (median diameter) or D4,3 (volume average diameter) to the power of −0.8. In the presence of 1 and 5dwb% BMA, the dependence on D4,3 was to the power of −2 and −3, respectively. A power law model was also shown to describe the relationship between the yield stress and the solid volume fraction. The power law index ranged from 11.3 to 12.3 for slurries prepared from wet-milled biochar powders and from 14 to 18 for slurries prepared from dry-milled biochar powders. The highly charged BMA additive did not completely disperse the Mallee biochar slurries however it did reduce the yield stress and viscosity of the slurries significantly. Zeta potential data also strongly indicate the occurrence of BMA and CMC adsorption on the char particles. However, the CMC additive did not produce the significant reduction in the yield stress as expected.

Rheological characterization of novel physically crosslinked terpolymeric hydrogels at different temperatures

The main objective of this research work is to reveal the detailed and extensive rheological characterization of terpolymeric hydrogel formulations using a variety of monomers having different concentrations of acrylic acid and applying a range of temperatures. The hydrogels with the different concentrations of acrylic acid were prepared in the absence of air using three different monomers, by free radical polymerization, gradually increasing the temperature up to polymerization point, using ethyl alcohol as solvent. Different shear measurements were performed to study rheological properties, temperature dependence, and yield strength of acrylic acid pharmaceutical hydrogels. Various models were applied to analyze the rheological behavior of the gels. The acrylic acid pharmaceutical gels having physical cross links in the gel networks, exhibit remarkable temperature dependence especially with relatively higher concentration of acrylic acid at greater shear rate. Flow curves plotted at various temperatures indicate that these gels exhibit a reasonable pseudoplastic behavior. All these hydrogels require appropriate yield strength to break their network structures. The gel samples exhibit the best fit to the Modified Bingham model, which can explain the overall flow behavior of these topical gels. The rheological analysis indicates that these gels may be used as topical gels for targeted and controlled drug delivery at a specific site.

Modelo de un proceso de cristalización continua de un sorbete por medio de la metodología de momentos

Freezing is an important step in the manufacturing process of ice-cream and sorbet, since the operating conditions have a strong influence on the micro-structure, and consequently on the sensorial attributes of the final product. This steep of freezing is carried out by a scraped surface heat exchanger (SSHE) where the product quality is conditioned by process conditions as the evaporation temperature of a refrigerant fluid, the mix flow rate, the dasher speed and the cylinder pressure due to the air introduction. In order to study the relevance of a control system based on the influence of process variables on product quality, this paper presents a model for a continuous crystallization of a sorbet using the method of moments, which is validated by experimental data.The model created by this methodology has been able to represent the influence of the process conditions during the crystallization of the sorbet on the final product characteristics such as crystal size and the draw temperature in the outlet of the SSHE in absence of air. The model based in moments is studied as a reduced model of the population balance equation and includes the phenomena of heterogeneous nucleation and growth. This model developed represents minimal computational requirements and is highly adapted for optimization and/or process control tasks.

Influence of Porosity on Performance of Freeze-granulated Fe2O3/Al2O3 Oxygen Carriers Used for Chemical Looping Combustion

Chemical looping combustion (CLC) is a promising solution for the next coal-fired power generation technology with inherent CO2 separation capability. One of the critical aspects for the development of the CLC process is to develop suitable oxygen carrier (OC) particles to transfer oxygen to the fuel in the absence of air. Relevant studies have focused on active material screening, thermodynamic analysis and operational tests. This investigation was conducted on the microstructural property of OCs, to be specific, the particle porosity effect on the performance of iron-based OCs. Fe2O3, supported on Al2O3 was used as the oxygen carrier. The effect of water content of the spray slurry used to produce the OC was varied to determine the influence of OC porosity on reactivity, oxygen transfer capacity and mechanical durability. A preliminary test was done to establish the minimum and maximum water percentage needed to make slurry. A process that included freeze granulation (FG), freeze drying, and calcination was used to prepare four samples of iron oxide/alumina with various water-to-solid phase ratios. A scanning electron microscope (SEM) was used to characterize the porosity of FG Fe2O3/Al2O3 particles. A direct relationship was observed. A Shimpo FGE-10X force gauge was used to measure the crushing strength of selected samples. A thermogravimetric analyzer (TGA) coupled with a mass spectrometer (MS) was used to study the change in reaction rates through multiple reduction-oxidation cycles of the samples. Crystallinity of the OCs in reduced and oxidized forms were confirmed by XRD analysis.

Bearing Thermal Conductance Measurement Test Method and Experimental Design

Abstract Bearings are used in a number of spacecraft applications, ranging from minimal motion devices, such as pointing mechanisms, to high-speed components, such as control moment gyroscopes and reaction and momentum wheels. Terrestrial applications include pumps, axles, and tooling. Heat-transfer modes for rotational systems in a vacuum environment differ from their terrestrial counterpart. In space, with the absence of air, heat transfer consists of radiation from the rotating system and conductance through the bearings themselves. Depending on the application, conductance could dominate the effects on bearing temperatures and thermal gradients. Accurate thermal predictions are important because they can drive life and performance requirements. To accurately predict bearing temperatures, basic bearing thermal conductance data was needed. However, bearing thermal conductance tends to be the most significant unknown in a rotational system in the space environment. To address this shortcoming, this paper explores a new vacuum test rig designed to measure bearing conductance under simulated operational conditions. Experimental variables include control of the bearing rotational speed, applied axial load, and average bearing temperature and temperature gradient via an applied heat source/heat sink mechanism. All tests are conducted in vacuum. The experimental variables studied herein allowed parametric studies to be conducted under controlled thermal and mechanical conditions, permitting the exploration of the influences of those operational variables on bearing thermal conductance. This paper will describe the test method, the use of uncertainty analysis to design the experiment, and a verification study.

Sensory Analysis of Pawpaw (Asimina triloba) Pulp Puree: Consumer Appraisal and Descriptive Lexicon

Consumer and descriptive sensory analysis was performed on pawpaw pulp. Consumer sensory analysis showed that mango was preferred compared to the pawpaw, but that only one-third of those who preferred the mango were correctly able to identify it. Consumers generated 25 flavor descriptors for pawpaw pulp, with banana and mango being the most identified. Descriptive sensory analysis was performed on pawpaw pulp that was stored frozen in the presence or absence of air and with and without heat treatment. Differences in color were detected, however no differences in any of the sensory attributes were detected during 12 months of frozen storage, suggesting that the flavor of pawpaw pulp is stable during frozen storage. The comprehensive analysis of the sensory and quality of pawpaw pulp described in this paper, including the development of a defined, standardized pawpaw sensory lexicon, is an important step in the evolution of pawpaw research.

UV Light Induced Transformation of 1-Methylnaphthalene in the Presence of Air and Its Implications for Contaminants Research

Understanding chemical transformations of contaminants and the resulting products is extremely important in devising proper monitoring methods for such contaminants and in assessing potential human exposure to the transformation products in the environment. Ultraviolet (UV) light from the sun can induce various photochemical transformations of contaminants in the environment. Alkylnaphthalenes are light-molecular-weight polycyclic aromatic hydrocarbons (PAHs) which are one of the most widespread organic pollutants present in ambient air as a result of a variety of incomplete combustion sources. In this study, 1-methylnapthalene,a typical example of an alkylnaphthalene, was subjected to UV irradiation to investigate its transformation in the presence and absence of air. Twenty-one products were detected in the reaction mixtures. Some photo-oxidation products were identified, including both ring-opened and ring-retained oxygenated compounds, such as 1-naphthaldehyde, 1-naphthoic acid, 1-naphthalenemethanol and phthalic anhydride. Although dimeric products were observed in the presence of air, more were found in the presence of helium or argon gas, indicating a different photo-oxidation pathway from those commonly observed in other media, such as water. Under just 48 hours of exposure to the UV light in the presence of air, three major products were formed with a production yield of about 10% each. Compared to 1-methylnapthalene, the UV induced transformation products observed in this study are more volatile, acidic, water soluble or toxic. The formation of these products may significantly change our understanding of the risks assessed solely from the parent compound in contaminants research and supports the inclusion of airborne transformations of the parent compound in risk assessment.

Heteronuclear NOE Spectroscopy of Ionic Liquids

(19)F,(1)H HOESY experiments with three ionic liquids ([bmim]BF(4), [bmim]PF(6) and [emim]BF(4)) were run in two different solvents and neat. The results give preferred probabilities of presence and enable us to systematically study interactions between the cations and the anions in the ionic liquid phase by NMR spectroscopy. The influence of different solvents and of the presence or absence of air (i.e. oxygen) is discussed. This enabled us to substantially speed up the NMR experiments and to develop a more precise method for the investigation of liquid-phase structures in ionic liquids.

Spectroscopic Studies on the Oxidation of Catechin in Aqueous Solution

The spectroscopic behavior of catechin (5,7,3',4'-tetrahydroxyflavan-3-ol), has been studied in the presence and the absence of air using UV-vis absorption spectrophotometry and fluorescence spectroscopy. The UV-vis absorption spectrum of catechin shows a very sharp and strong absorption maximum peak at 275 nm in deaerated water. New absorption maximum peaks appeared in aerated water, as well as in basic aqueous solution, caused by the oxidation of catechin. The absorbances in the UV-vis absorption spectrum of catechin decreased when the solution was left in the dark for a long time. The fluorescence emission spectrum of catechin after a long time period differs markedly from that in freshly prepared solution; the fluorescence maxia shifted as time passes after adding catechin to the solutions. When the deaerated basic catechin solutions were left in the dark for a long time, their fluorescence quantum yields were found to be nearly zero. This suggests that the oxidized catechin molecules were seen to have slowly undergone successive chemical reactions in basic buffer solution.

Hydrolytic Stability of l-(+)-Ascorbic Acid in Low Methoxyl Pectin Films with Potential Antioxidant Activity at Food Interfaces

l-(+)-Ascorbic acid (AA) was compartmentalized into a low methoxyl pectin (LMP) film in view of localized antioxidant activity at food interfaces. The AA hydrolysis was specifically studied in the present work in order to determine the ability of the formulated LMP film to stabilize AA. Hence, films were stored at controlled relative humidity (RH) in the absence of air. A commercial LMP characterized by a 40% degree of methylesterification (DM) was used. Since sucrose is normally added for its standardization, films were also made with the dialyzed LMP in order to determine the sucrose effect. Glycerol was used for plasticization. Kinetics of AA loss and subsequent browning development were determined, which are dependent on the RH. Considerable AA retention (t 1/2 = 744, 727, and 185 days) was achieved at 33.3%, 57.7%, or 75.2% RH, respectively, at 25 °C. Browning rate constants decreased in one order of magnitude with respect to kinetic constants determined from films previously developed with high methoxyl pectin (HMP; DM of 73%). Absence of sucrose in the LMP network only affected the browning kinetics at 75.2% RH. The glass transition temperature (T g) decreased with the increment of moisture content of the films and in a similar degree (T g ≈ −90 °C) to that observed for the HMP films, indicating the contribution of water to the network plasticization. However, water was more confined in the LMP network as inferred from the water availability determined by the 1H-NMR and DSC. This was attributed to the water interaction at the Ca2+ junction zones. Sucrose seemed to hinder the retention of water molecules by the polymeric network at 75.2% RH.

Thermal Stability of Cyclopentane as an Organic Rankine Cycle Working Fluid

Laboratory experiments were performed to determine the maximum operating temperature for cyclopentane as an organic Rankine cycle working fluid. The thermochemical decomposition of cyclopentane was measured in a recirculation loop at 240, 300, and 350 °C at 43 bar in a glass-lined heated tube. It was determined that, in the absence of air at the two lower temperatures, decomposition was minor after more than 12 days of continuous operation. At 240 °C, the total cyclopentane decomposition products were approximately 65 ppm, and at 300 °C, the total decomposition products were on the order of 270 ppm at the end of the experiment. At 350 °C, the decomposition products were significantly higher and reached 1500 ppm. When the feed was saturated with air under prevailing atmospheric conditions, the decomposition rate increased dramatically. Residues found in the reactor after the decomposition experiments were examined by a number of different techniques. The mass of the residues increased with experimental temperature but was lower at the same temperature when the feed was saturated with air. Analysis of the residues suggested that the residues were primarily heavy saturated hydrocarbons.