Minimum Induction Time Research Articles

Collective Effect of Transformation of a Hydrogen Bond Network at the Initial State of Growth of Methane Hydrate

The molecular dynamics study of the rearrangement of the dynamic hydrogen bond network of liquid water to the crystal hydrogen bond network of methane hydrate in the process of their formation and growth is conducted. To reveal the nature of nucleation, the time dependences of the degree of “crystallinity” of the nearest environment of all water molecules, the rate of ordering of the hydrogen bond network, and the relation of these parameters to the rate of growth of methane hydrate are studied. The effect of the presence of sea salt ions and hydrate seed on these parameters is analyzed. Systems with a completely mixed gas, i.e., with the minimum induction time, are fabricated, and it is shown that gas hydrates can be nucleated simultaneously in the entire volume of the solution, which in turn indicates the collective formation of hydrates from liquid solution.

Accelerated methane storage in clathrate hydrates using surfactant-stabilized suspension with graphite nanoparticles

Abstract In this study, enhanced kinetics of methane hydrate formation in the sodium dodecyl sulfate (SDS) solution with different concentrations of suspended graphite nanoparticles (GNPs) were investigated at 6.1–9.0 MPa and 274.15 K. The GNPs with rough surfaces and excellent thermal conductivity not only provided a considerable number of microsites for hydrate nucleation but also facilitated the fast hydrate heat transfer in the suspension system. At a relatively low pressure of 6.1 MPa, the suspension with 0.4 wt% of GNPs exhibited the minimum induction time of 22 min and maximum methane uptake of 126.1 cm3·cm−3. However, the methane storage performances of the suspensions with higher and lower concentrations of GNPs were not satisfactory. At the applied pressure, the temperature increase arising from the hydrate heat in the suspension system with the optimized concentration (0.4 wt%) of GNPs was more significant than that in the traditional SDS solution. Furthermore, compared with those of the system without GNPs, enhanced hydration rate and storage capacity were achieved in the suspensions with GNPs, and the storage capacities were increased by 3.9%–17.0%. The promotion effect of GNPs on gas hydrate formation at low pressure is much more obvious than that at high pressure.

Energy saving in carbon dioxide hydrate formation process using Boehmite nanoparticles

This work reports on an attempt to save energy in the carbon dioxide hydrate formation process. The kinetics of carbon dioxide hydrate formation induced by synthesized Boehmite (AlOOH) nanoparticles was investigated at 274.15 K, different initial pressures (29, 32 and 35 bar), impeller speed (50, 100 and 200 rpm) and AlOOH concentrations (25, 50 75, 100, 200 ppm). It was also observed that there is a desirable concentration for AlOOH nanoparticles in which the maximum rate of gas consumption and minimum growth and induction time was obtained. According to the results at 29 bar and 100 rpm and in the presence of 50 ppm AlOOH, the gas consumption rate increased to 150%, while the induction time and growth time decreased about 82.8% and 46.1%, respectively. The maximum energy saving of 49.7% for 50 ppm AlOOH was observed, which is very important for industrial applications of carbon dioxide hydrate. The presented technique is useful for intensification of gas hydrate-based CO2 capture processes in the oil and gas industry with minimum energy consumption.

A new flow UV–Vis kinetics spectrophotometric method based on a photodegradative reaction for determining the oxidative stability of biodiesel

The biodiesel (BD) is an alternative fuel with some remarkable advantages compared to conventional diesel. However, the fatty acid methyl esters (FAMEs) which commonly compose BD are potentially oxidizable. This inherent characteristic of BD constitutes a problem for its storage and commercialization. In this sense, the evaluation of the oxidative stability (OS) of BD is still an important issue for being studied. According to EN 14112:2017, the minimum induction time limit is 6 h at 110 °C determined by Rancimat® reference method. The method developed in this work, proposes an alternative for determining the OS by means of a new flow UV Vis kinetics spectrophotometric method based on a photodegradative reaction and new term defined as Oximax at 4 min. This allowed the assessment of the OS of different BD samples at 4 min of photodegradation instead of the hours required by the reference method which uses thermal degradation. The studied BD samples were produced from different feedstock (i.e. sunflower, grapeseed, corn and soybean oils) at laboratory scale through a base-catalyst transesterification using methanol. Also, some BD samples were purchased from regional companies in order to apply the proposed method to commercial samples. Moreover, some parameters of quality of BD such as acid index, density and kinematic viscosity were determined in BD samples in accordance with the methods described in the Argentinian standard IRAM 6515-1:2006, and the obtained results were found satisfactory.

Thin liquid film drainage mechanism between air bubbles and low-rank coal particles in the presence of surfactant

Flotation strongly depends on bubble–particle attachment interactions. However, modelling of bubble–particle attachment interactions is challenging particularly due to the difficulties in quantifying the hydrophobic interactions between an air bubble and a non-spherical particle using a well-advanced technique such as atomic force microscopy; the reason is that these measurements are not reproducible when particles are non-spherical. This paper proposes a methodology to determine the hydrophobic interaction constants between air bubbles and coal particles in the presence of a surfactant. The bubble–particle hydrophobic constants were determined from first principles using the Navier-Stokes equation and the Glembotsky experimental technique. It was found that the higher the surfactant concentration, the higher the hydrophobic constants. The results showed that the calculated critical film rupture thickness is inversely related to the induction time measurements, and the maximum critical film rupture thickness matched the minimum induction time. The decrease in the electrostatic double layer repulsive energies resulted in the decrease in the induction times.

Antisolvent Sonocrystallisation of Sodium Chloride and the Evaluation of the Ultrasound Energy Using Modified Classical Nucleation Theory

The crystal nucleation rate of sodium chloride in ethanol was investigated by measuring the induction time at various supersaturation ratios under silent and ultrasound irradiation at frequencies between 22 and 500 kHz. Under silent conditions, the data follows the classical nucleation theory showing both the homogeneous and heterogeneous regions and giving an interfacial surface tension of 31.0 mN m−2. Sonication led to a non-linearity in the data and was fitted by a modified classical nucleation theory to account for the additional free energy being supplemented by sonication. For 98 kHz, this free energy increased from 1.33 × 108 to 1.90 × 108 J m−3 for sonication powers of 2 to 15 W, respectively. It is speculated that the energy was supplemented by the localised bubble collapses and collisions. Increasing the frequency from 22 to 500 kHz revealed that a minimum induction time was obtained at frequencies between 44 and 98 kHz, which has been attributed to the overall collapse intensity being the strongest at these frequencies.

Flow instability in laminar jet flames driven by alternating current electric fields

The effect of electric fields on the instability of laminar nonpremixed jet flames was investigated experimentally by applying the alternating current (AC) to a jet nozzle. We aimed to elucidate the origin of the occurrence of twin-lifted jet flames in laminar jet flow configurations, which occurred when AC electric fields were applied. The results indicated that a twin-lifted jet flame originated from cold jet instability, caused by interactions between negative ions in the jet flow via electron attachment as O2+e→O2– when AC electric fields were applied. This was confirmed by conducting systematic, parametric experiment, which included changing gaseous component in jets and applying different polarity of direct current (DC) to the nozzle. Using two deflection plates installed in parallel with the jet stream, we found that only negative DC on the nozzle could charge oxygen molecules negatively. Meanwhile, the cold jet instability occurred only for oxygen-containing jets. A shedding frequency of jet stream due to AC driven instability showed a good correlation with applied AC frequency exhibiting a frequency doubling. However, for the applied AC frequencies over 80Hz, the jet did not respond to the AC, indicating an existence of a minimum flow induction time in a dynamic response of negative ions to external AC fields. Detailed regime of the instability in terms of jet velocity, AC voltage and frequency was presented and discussed. Hypothesized mechanism to explain the instability was also proposed.

Kinetic study of ethylene hydrate formation in presence of graphene oxide and sodium dodecyl sulfate

The effects of synthesized graphene oxide suspension at concentrations of 50, 150 and 250ppm and aqueous solution of sodium dodecyl sulfate (SDS) at concentrations of 50, 100, 300 and 500ppm on kinetics of ethylene hydrate formation were studied. The induction time was measured at 4°C and initial pressures of 14 and 16bar, and the effective storage capacity was measured at 1.5°C and initial pressure of 30bar. The results indicated that although both graphene oxide suspension and SDS solution in the whole range of experimental concentrations reduced the induction time of ethylene hydrate formation, graphene oxide was more effective in decreasing the induction time. The minimum induction time was obtained when 150ppm graphene oxide suspension was used, which indicated an average decrease of 96% compared to pure water. In addition, the effective storage capacity measurements showed that additives at low concentrations did not promote the effective storage capacity noticeably, while graphene oxide suspension at 150 and 250ppm as well as SDS solution at 300 and 500ppm promoted the effective storage capacity of ethylene hydrate significantly. SDS showed better performance in increasing the effective storage capacity, as the highest effective storage capacity was attained by using 300ppm SDS solution, suggesting 259.8% improvement in comparison to pure water.

Effect of initial gas pressure on the reaction of Al with water

The effect of initial gas pressure on Al–water reaction was investigated systematically. It was found that there is a non-monotonic relationship between the initial pressure and the induction time for the beginning of Al–water reaction. The induction time decreases with decreasing the initial pressure at the first stage from atmospheric pressure, then reaches a minimum, and finally increases with further decreasing the initial pressure. The mechanism analyses revealed that the special vacuum pressure corresponding to the minimum induction time is close to the saturated vapor pressure, below which probably there are some vapor bubbles passing or adsorbing on Al particle surfaces due to boiling, retarding the hydration process of Al surface oxide film and increasing the reaction induction time. The present results imply that a suitable initial gas pressure should be chosen for Al–water reaction to generate hydrogen.

Oxidation Stability of Palm Methyl Ester: Effect of Metal Contaminants and Antioxidants

The European biodiesel standard EN-14214 calls for determining the oxidation stability (OS) at 110 °C with a minimum induction time of 6 h by the Rancimat method (EN-14112). The ASTM standard D-6751 has recently introduced a minimum induction period of 3 h. Palm methyl ester (PME) has been successfully evaluated as a diesel substitute in summer and with an additive in winter due to its poor cold-flow properties. Neat PME exhibited an OS of 9.24 h; thus, it was highly stable. Research was conducted to investigate the effect of the presence of transition metals, likely to be present in the metallurgy of storage tanks and barrels, on the highly stable PME. It was found that the influence of metal was detrimental and catalytic even for stable PME. Small concentrations of metal contaminants showed nearly the same influence on OS as large amounts. Copper showed the strongest detrimental and catalytic effect. Antioxidants, namely, tert-butylated hydroxytoluene (TBHT), tert-butylated phenol derivative (TBP), octylated butylated diphenyl amine (OBPA), and tert-butylhydroxquinone (TBHQ) were doped to improve the OS of metal-contaminated PME. It was found that the antioxidant TBHQ was most effective among all of the antioxidants used.

Synergistic effect of metal deactivator and antioxidant on oxidation stability of metal contaminated Jatropha biodiesel

Abstract Biodiesel is relatively unstable on storage and European biodiesel standard EN-14214 calls for determining oxidation stability at 110 °C with a minimum induction time of 6 h by the Rancimat method (EN-14112). According to proposed National Mission on biodiesel in India, we have undertaken studies on stability of biodiesel from tree borne non-edible oil seeds Jatropha. Neat Jatropha biodiesel exhibited oxidation stability of 3.95 h. It is found possible to meet the desired EN specification for neat Jatropha biodiesel and metal contaminated Jatropha biodiesel by using antioxidants; it will have a cost implication, as antioxidants are costly chemicals. Research was conducted to increase the oxidation stability of metal contaminated Jatropha biodiesel by doping metal deactivator with antioxidant, with varying concentrations in order to meet the aforementioned standard required for oxidation stability. It was found that usage of antioxidant can be reduced by 30–50%, therefore the cost, even if very small amount of metal deactivator is doped in Jatropha biodiesel to meet EN-14112 specification.

Influence of metal contaminants on oxidation stability of Jatropha biodiesel

Abstract According to proposed National Mission on biodiesel in India, we have undertaken studies on stability of biodiesel from tree borne non-edible oil seeds Jatropha. European biodiesel standard EN-14214 calls for determining oxidation stability at 110 °C with a minimum induction time of 6 h by the Rancimat method (EN-14112). Neat Jatropha biodiesel (JBD) exhibited oxidation stability of 3.95 h and research was conducted to investigate influence of presence of transition metals, likely to be present in the metallurgy of storage tanks and barrels, on oxidation stability of Jatropha methyl ester. It was found that influence of metal was detrimental to oxidation stability and catalytic. Even small concentrations of metal contaminants showed nearly same influence on oxidation stability as large amounts. Copper showed strongest detrimental and catalytic effect. The dependence of the oxidation stability on the type of metal showed that long-term storage tests in different types of metal containers for examining the influence of container material on oxidation stability of biodiesel may be replaced by significantly faster Rancimat test serving as an accelerated storage test.

Effect of agitation on the synthesis of zeolite beta and its synthesis mechanism in absence of alkali cations

Zeolite beta was hydrothermally synthesized in the TEAOH–SiO 2–Al(0)–H 2O system in the absence of alkali cations. The effects of agitation under various TEAOH/SiO 2 molar ratios on the crystallization kinetics, particle size, particle size distribution, and framework SiO 2/Al 2O 3 of synthesized zeolite beta were studied. The as-synthesis and calcinated zeolites were characterized by XRD, TEM, N 2 adsorption. The effect of the agitation on the induction time, the particle size, and the framework SiO 2/Al 2O 3 ratio of the synthesized zeolites was more pronounced at high TEAOH/SiO 2 molar ratio (0.6) than at a low TEAOH/SiO 2 molar ratio (0.21 and 0.4). Under agitation, the induction time, the particle size, and the framework SiO 2/Al 2O 3 molar ratio of the zeolite greatly decreased with the increase of the TEAOH/SiO 2 ratio. While under the static state, the minimum induction time and the crystal particle size existed at TEAOH/SiO 2 ratio = 0.4, and the framework SiO 2/Al 2O 3 molar ratio of the zeolite increased with the increase of TEAOH/SiO 2 ratio. The crystallization proceeded via solution phase nucleation mechanism.

Temperature modulated DSC and DSC studies on the origin of double melting peaks in poly(ether ether ketone)

Crystallization kinetics and melting behavior of poly(ether ether ketone) were studied by differential scanning calorimetry (DSC) and temperature-modulated DSC (TMDSC). The isothermal crystallization was performed between 290 and 320 °C. The Avrami exponents and the level off time were determined from the Avrami analysis. The minimum induction time required for the occurrence of double melting peaks was obtained by increasing the isothermal crystallization time in steps of one minute. It was found that the level off time did not represent the delimitation of single- or double-melting peak behavior. To elucidate the behavior of double melting peaks, the samples were crystallized isothermally between 280 and 320 °C for 10 min, and then they were heated to 380 °C at 2 °C/min. From the TMDSC results, the exothermic behavior in the non-reversing curves supports the mechanism of melting–recrystallization at T c ≤310 ° C. On the other hand, no exothermic flow for T c at 320 °C supports the mechanism of two different morphologies. As the isothermal crystallization temperature increased from 280 to 320 °C, the contribution of melting–recrystallization to the upper melting peak gradually decreased, and finally disappeared.

Lamellar Branching of Poly(bisphenol A-co-decane) Spherulites at Different Temperatures Studied by High-Temperature AFM

Thin films of poly(bisphenol A-co-decane) (BA-C10) were isothermally crystallized at different temperatures. The lamellar structures and branching during crystallization were observed in real time at different temperatures by an atomic force microscope equipped with a high-temperature heater accessory. Our observations indicated that induced nuclei developed into subsidiary lamellae, forming lamellar branches. Lamellar branches occurred randomly on the parent lamellae at high degrees of supercooling. However, lamellar branches were seldom observed at crystallization temperatures near the melting point. The minimum induction time for induced nucleation was found to occur at around 55 °C.

A comparison of induction time and crystallization rate for syndiotactic polystyrene

AbstractOne objective of this study was to measure the crystallization parameters for syndiotactic polystyrene (MW = 244,000) to support a computer simulation of this material in an injection molding application. A second objective was to introduce a new crystallization rate equation that adequately predicts crystallization rates over a broader temperature range than the Hoffman‐Lauritzen equation. A third objective was to establish a new clearly defined method for determining the true induction time of a semicrystalline polymer as a function of temperature. The new crystallization rate equation introduced in this study has been formulated to give appropriate crystallization rate constants for all the temperatures currently usable with the Hoffman‐Lauritzen equation. In addition, this new equation also predicts appropriate crystallization rate constants outside the range of the Hoffman‐Lauritzen equation from temperatures significantly below the glass transition temperature, Tg, to temperatures significantly above the melting point, Tm. Interestingly, the isolation of the true isothermal induction times from apparent induction times in this study nicely mirrored the isothermal crystallization rates at each specific temperature. Both the true induction time and the crystallization rate curves were found to be similarly unsymmetrical as a function of temperature. Also, the temperature at the minimum induction time and the temperature at the peak crystallization rate determined from nonisothermal crystallization rate measurements were found to be nearly identical. Consequently, the results from this study strongly suggest that there is a significant and potentially very useful relationship between induction time analysis and crystallization rate kinetics.

Adventitious Bud Formation from Mature Embryos of Picea chihuahuana Martı́nez, an Endangered Mexican Spruce Tree

Zygotic embryos of Picea chihuahuana Martı́nez were cultivated in vitro to determine the time of organogenic competence and to maximize adventitious bud induction. The induction medium consisted of modified B5 substrate supplemented with N6-benzyladenine (with or without naphthalene acetic acid) or kinetin (with or without 2-4, dichlorophenoxyacetic acid) at different concentrations and induction times. The minimum induction time required for bud formation was 14d with kinetin and 17d with N6-benzyladenine. After induction embryos were transferred to the proliferation medium (modified B5 substrate with 50% of its components and without growth regulators) for 30d. The subsequent buds were transferred every 15d to Schenk and Hildebrandt medium at half its concentration without growth regulators. The most effective treatments were 3 and 5mgl−1kinetin or N6-benzyladenine which produced five to seven buds per embryo. The largest shoots were subjected to rooting trials with pulses of different concentrations of indole butyric acid resulting in only one bud developing a root. Histological analysis revealed clusters of three to four cells that became more evident as induction time increased. Kinetin promoted the development of an organized structure prior to adventitious buds formation sooner than N6-benzyladenine.

Influence of temperature on crystallization of lactose in ice‐cream

SummarySandiness in ice‐cream due to lactose crystallization can still be a problem in many circumstances. Lactose crystallization occurs in ice‐cream as the unfrozen phase becomes supersaturated. However, the effects of storage temperature and temperature fluctuations on lactose crystallization have not been very well quantified. In this work, an accelerated storage apparatus was used to determine the effects of thermal fluctuations (from ±0.01°C to ±2.0°C), at several mean storage temperatures (from −5.0 to −20.0°C), on the onset of lactose nucleation and subsequent crystal growth in a standard vanilla ice‐cream. the induction time for nucleation initially decreased as temperature was lowered (for temperature oscillations of ±1.0°C), until a minimum induction time of 3 h was found between −10.0 and −12.0°C. Further decreases in storage temperature caused the induction time to increase. the induction time for nucleation increased as the extent of temperature fluctuations increased, from 0.01 to 2.0°C, while initial lactose crystal growth rate showed the opposite trend. the initial growth rate increased as temperature decreased between −5.0 and −10.0°C, but then decreased for temperatures below −10.0°C. At −20.0°C lactose crystals grew very slowly. At −10.0°C the rate of growth decreased with increasing amplitude of temperature oscillations.

Induced Oviposition of Precalcified Eggs Following Prostaglandin Administration

In order to obtain fertilized ova from White Leghorn chickens in the early cleavage stages, a nonsurgical procedure using prostaglandins (PG) was developed to induce premature oviposition of uncalcified eggs. The experimental design consisted of two 5 × 5 factorial arrangements of treatments using combinations of 0, .5, 1, 2, and 3 μg of PGF2α and PGE1 or PGF2α and PGE2. Frequency of PG-induced oviposition was highest (100%) with 1 μg of PGF2α and 3 μg of PGE1 or PGE2. Induced oviposition frequency decreased at the higher (2 and 3 μg of each PG) dosages. In general, induction time decreased as PG levels were increased; the minimum induction time was observed with injection of 3 μg of PGF2α with 2 or 3 μg of PGE1 (1.8 min). There was a significant interaction for frequency of induced oviposition between PGF2α and PGE1 (P<.05), but not between PGF2α and PGE2. There was also a significant interaction between PGF2α and PGE2 (P<.01) for induction time, which was not observed with PGF2α and PGE1. Oviposition could not be induced earlier than 5 to 5.5 h after the previous oviposition. Prostaglandin-induced oviposition provides an alternative to euthanasia, surgery, or manual expulsion for collection of precalcified eggs in the early cleavage stages.

Relationship between the duration of treatment and the incidence of renal cell tumors in male F344 rats administered potassium bromate.

In order to ascertain the minimum induction time, minimum treatment period and total dose required for development of renal cell tumors, KBrO3 at a concentration of 500 ppm was administered in the drinking water to a total of 232 male F344 rats divided into 14 experimental groups and the development of tumors was examined by two different approaches. In a continued-treatment study, administration of KBrO3 was stopped at week 13, 26, 39, 52 or 104 and rats were immediately sacrificed for comparison with controls given distilled water (DW) alone. Renal cell adenomas were found as early as after 26 weeks of treatment with KBrO3. The yields of dysplastic foci, adenomas and adenocarcinomas of the kidney, follicular cell tumors of the thyroid and mesotheliomas of the peritoneum increased with treatment, the final incidences all being statistically significant after administration of KBrO3 for 104 weeks. To examine the effect of discontinued treatment, on the other hand, the rats were given KBrO3 for the first 13, 26, 39 or 52 weeks and were subsequently maintained on DW alone until sacrifice at week 104. The incidences of tumors in these groups were compared with that of a group continuously administered KBrO3 for 104 weeks. The yields of renal dysplastic foci, adenomas and adenocarcinomas in all discontinued-treatment groups were approximately equal to or even higher than those in the group given KBrO3 continuously for 104 weeks. It is concluded that, under the conditions of this study: the minimum induction time for the development of renal adenomas was 26 weeks and the minimum treatment period and total dose for the induction of renal adenomas and adenocarcinomas were 13 weeks and 4 g/kg, respectively, when the rats were maintained thereafter on DW for 2 years.