共查询到20条相似文献,搜索用时 31 毫秒
1.
T. Yokochi M. T. Usita Y. Kamisaka T. Nakahara O. Suzuki 《Journal of the American Oil Chemists' Society》1990,67(11):846-851
The fungal oil extracted fromMortierella ramanniana var.angulispora (IFO 8187) was solvent winterized in order to raise the content of γ-linolenic acid (GLA). Effects of winterization conditions
(solvent, oil concentration in the solvent and temperature) and changes of glyceride compositions were discussed. The fungal
oil was separated into four diglycerides and 17 triglycerides (TG) with high performance liquid chromatography. The predominant
species were POO, POP and LOP, whose contents were 24.4, 22.9 and 9.4% of the total TG, respectively. Ethanol at 4°C gave
the highest GLA content of 10.5% in spite of lower yield than with acetone at −20°C. The highest separation efficiency for
GLA (ηGLA) was 0.27 with acetone at −20°C and 10% oil concentration, resulting in 8.3% of GLA from the fungal oil at 5.7% LGA. In case
of lower oil concentration at 5–20%, ηGLA showed higher in the following order: acetone (−20°C)>n-hexane (−20°C)>acetone (4°C)>petroleum ether (−20°C). The winterization process also proved to be effective for the separation
of TG type, Sa2U (Sa; saturated fatty acid; U, unsaturated fatty acid) into the crystallized fraction and SaU2 into the liquid fraction. Acetone at −20°C showed higher separation efficiency for triunsaturated TG than the other solvents. 相似文献
2.
Mertens W. G. Rubin L. J. Teasdale B. F. 《Journal of the American Oil Chemists' Society》1961,38(6):286-289
A fractional crystallization method for the winterization of cottonseed oil with solvents was developed in our laboratories
and pilot plant.
Small amounts of solvent (e.g., 10% by weight of acetone) were mixed with the oil. This mixture was rapidly chilled to 0°C. and kept at this temperature
for 3–4 hrs.; the liquid portion was separated from the solids.
After solvent evaporation a salad oil of good quality was obtained. The yield is equal to or better than that obtained with
conventional methods.
The method is suitable for a continuous operation since rapid chilling can be used, and only a short over-all time is necessary.
Great advantages of the process are the use of low amounts of solvent and of a refrigeration system not requiring temperatures
below 0°C. 相似文献
3.
Immersion experiments with Aflas (I), poly(tetrafluoroethylene‐co‐propylene), and Fluorel (II) [poly(vinylidene fluoride‐co‐perfluoropropylene)], showed greater swelling of I in nonpolar liquids and much higher swelling of II in polar liquids: over 100% (wt/wt) in two ketones and a phosphate ester. Sorption isotherms determined for toluene and acetone at 25 and 35°C were fitted with the Flory–Rehner relation, employing a concentration‐dependent solvent–polymer interaction parameter. The fitted K parameters indicated that the degree of crosslinking in II was lower than in I. However, the high swelling of II by polar solvents is attributed primarily to the polar nature of II resulting from the asymmetric CF(CF3) moiety. Diffusion coefficients determined from sorption kinetics, corrected for nonisothermal effects, and converted to solvent self‐diffusion coefficients were fitted with the Fujita free‐volume relation. The values were much higher for I than II with acetone and also slightly higher for I with toluene. The estimated zero‐concentration values were 1.5 E‐09 cm2/s for Aflas–acetone, 0.3 E‐09 cm2/s for Fluorel–acetone, and even lower for toluene. The low diffusion coefficients, which contribute to the superior barrier performance of these elastomers, is due, in part, to the high glass transition temperatures of I and II, −7 and −21°C, respectively. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1525–1535, 1999 相似文献
4.
Dae Eon Jung Ki Hyun Lee Eun Jeoung Lee Byoung Chul Kim 《Polymer International》2019,68(11):1856-1862
The temperature‐dependent transition of the crystal phases of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) was investigated in the electrospinning process. A solution of PVDF‐HFP in N,N‐dimethyl acetamide (DMAc) produced only the β‐phase‐dominant crystal up to 70 °C, irrespective of the spinneret temperature. In a mixed solvent of DMAc and acetone, however, the crystal phase of the electrospun fibers was dependent on temperature: β‐phase‐dominant at 30 and 50 °C and α‐phase‐dominant at 70 °C. The transition was related to a change of the coagulation rate during electrospinning, because the less perfect α phase is preferable to the β phase at a higher coagulation rate. The temperature‐dependent increase of the coagulation rate was more drastic in the presence of acetone, so the transition took place only in the mixed solvent. At elevated temperature, acetone not only raised the evaporation rate of the solvent but promoted the phase separation of the polymer resulting from the lower critical solution temperature behavior, which was rheologically traced. © 2019 Society of Chemical Industry 相似文献
5.
Some thermo‐viscosity parameters like Viscosity‐molecular weight constant (K), the short‐range parameter, (A) and long‐range parameter (B) have been evaluated for the polymer “Dextran” of three different molecular weights (M?w = 19,500, 75,000, and 250,000) in three different solvents like 6 (M) aqueous urea, 2 (M) aqueous glycine, and 50% aqueous glucose at temperatures ranging from 25 to 50°C. The study reveals that the viscosity‐molecular weight constant (K) decreases with increase in temperature for polar solvents like aqueous urea and aqueous glycine. The value of “K” increases with the rise in temperature within the range of 25 to 35°C in case of a nonpolar solvent aqueous glucose and then “K” decreases with the increase in temperature within the range of 40 to 50°C for the nonpolar solvent aqueous glucose. The short‐range parameter (A) shows the same trend as shown by “K” and the long‐range parameter “B” exhibits no definite trend with the variation of temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 440–452, 2001 相似文献
6.
The solubilities of SO2 are reported in the solvents N, N-dimethyl acetamide (DMA), N, N-dimethyl formamide (DMF), ethyl acetate, acetonitrile, chlorobenzene, methanol, (1,2-ethanediol) ethylene glycol and acetone for atmospheric pressure and for temperatures ranging from 268 K to 333 K (-5°C to 60°C). Solubilities of H2S are also reported for the first five of the above-mentioned solvents and for hexane for similar conditions. These gases and solvents exhibit extreme molecular interactions which are reflected in unusual solubility behavior. This paper is a continuing attempt in providing data and analyses for improving the understanding of gas solubilities in complex gas-solvent systems. Solubilities expressed as hydrogen-bonding factors have been found useful in systematically relating gas solubilities in one associating or reacting solvent to another chemically similar solvent. Thus, with a limited amount of data for gas solubilities, it is often possible to predict solubilities even in highly associated or reacting gas-solvent solutions. 相似文献
7.
Ginting Suka Irwan Yoichi Aoyama Shin‐ichi Kuroda Hitoshi Kubota Takashi Kondo 《应用聚合物科学杂志》2005,97(6):2469-2475
Photografting (λ > 300 nm) of N‐isopropylacrylamide (NIPAAm) and glycidyl methacrylate (GMA) binary monomers (NIPAAm/GMA) on low‐density polyethylene film (thickness = 30 μm) was investigated at 60°C using mixed solvent consisting of water and an organic solvent such as acetone. Xanthone was used as a photoinitiator by coating it on the film surfaces. A maximum percentage of grafting was observed at a certain concentration of acetone in the mixed solvent, which was commonly observed for both ratios of NIPAAm/GMA, 8/2 and 7/3. Based on the photografting of NIPAAm/GMA on xanthone‐coated film, monomer reactivity ratios of NIPAAm (r1) and GMA (r2) were calculated using the Fineman–Ross method. The values were 0.31 ± 0.1 and 4.8 ± 0.2 for the water solvent system, while they were 0.96 ± 0.1 and 4.9 ± 0.1 for the mixed solvent system. NIPAAm/GMA‐grafted films with a homogeneous distribution of grafted chains were formed by photografting using water and mixed solvents. The NIPAAm/GMA‐grafted films exhibited temperature‐responsive characters, whereas the grafted films showed a reversible change in the degree of swelling between 0 and 50°C, respectively. Epoxy groups in the grafted poly(NIPAAm/GMA) chains could be aminated with ethylenediamine in N,N′‐dimethylformamide at 70°C for 3 h. Complexes of the aminated NIPAAm/GMA‐grafted chains with cupric ion exhibited catalytic activity for the decomposition of hydrogen peroxide at 20 to 50°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2469–2475, 2005 相似文献
8.
Mesoporous aluninosilicate Al-MCM-41 molecular sieves with Si/Al ratios 25, 50, 75 and 100 have been synthesized under hydrothermal
condition and these materials were characterized by XRD, FTIR, BET and pyridine adsorption techniques. The catalytic performance
was examined in the vapor phase tert-butylation of anisole with tert-butanol at the temperatures between 150 and 250 °C under atmospheric pressure. The results indicate that Al-MCM-41 (25) was
found to be more active than its relatives. The major products are found to be 4-tert-butyl anisole (4-TBA), 2-tert-butyl anisole (2-TBA) and 2,4 di-tert-butyl-anisole (2,4-DTBA). Maximum conversion of anisole is observed at 175 °C and decreased thereafter with increasing temperature.
The influence of molar feed ratio, influence of temperature, WHSV and time on stream on the selectivity of products was investigated
and the results are discussed. 相似文献
9.
S. Bhattacharyya D. K. Bhattacharyya B. K. De 《European Journal of Lipid Science and Technology》2000,102(5):323-328
Investigation has been carried out with an intention to prepare shortening, margarine fat bases, and value-added edible fat products like cocobutter substitute from tallow. For this, tallow was fractionated at low (12 and 15 °C) and intermediate (25 °C) temperatures by solvent (acetone) fractionation process. The stearin fractions (yield: 23—40% (w/w) and slip melting point: 45—50.5 °C) thus obtained were blended and interesterified with liquid oils, such as sunflower, soybean, rice bran etc. by microbial lipase catalyzed route. The olein fractions (yield: 60—77% (w/w) and slip melting point: 21—32.5 °C) were also chemically interesterified (using NaOMe) and biochemically (using Rhizomucor miehei lipase, Lipozyme IM 20). The olein fractions were also blended with sal (Shorea robusta) fat, sal olein, and acidolysed karanja (Pongamia glabra) stearin. As revealed from their slip melting point and solid fat index, the products thus prepared were found to be suitable for shortening, margarine fat bases, and vanaspati substitute. 相似文献
10.
Stereocomplexes of isotactic and syndiotactic poly(methyl methacrylate) (i- and s-PMMA) were prepared by mixing dilute i- and s-PMMA solutions in acetone or DMF at different temperatures. At 50°C the rate of complex formation is larger than at 20° or 70°C. Differential scanning calorimetry and X-ray powder diffraction measurements were performed on the material crystallized from mixed solutions. The thermograms showed 3 endotherms at temperatures not depending on the i-/s-PMMA ratio of the sample. The endo therm at ~280°C is caused by degradation of PMMA, the maximum at ~210°C by melting of the stereocomplex and the endotherm at ~185°C by melting of solvent stabilized s-PMMA. By comparing X-ray powder diffraction patterns of s-PMMA crystallized from borderline solvents with those of stereocomplexes of i-/s-PMMA with different drying histories it is concluded that the reflection at 2 θ = 4°10′ belongs to a solvent stabilized s-PMMA structure. Partial association of i- and s-PMMA chains in an i-/s-PMMA ratio of about 1:1 and crystallization of solvent rich s-PMMA is proposed as a mechanism for the complex formation under the present conditions. 相似文献
11.
Byeong Sub Kwak Byung-Hyun Choi Mi-Jung Ji Sun-Min Park Misook Kang 《Journal of Industrial and Engineering Chemistry》2012,18(1):11-15
Nanometer-sized nickel oxide (NiO) particles were synthesized by thermal reactions with nickel (II) carbonate as a metal-containing precursor and four solvents: water, ethanol, butanol, and acetone. The optimal reaction conditions to obtain spherical NiO were determined to be the acetone solvent, nickel carbonate precursor, and a reaction temperature and time of 200 °C and 48 h, respectively. TEM images revealed perfectly spherical NiO nanoparticles of size ranging from 2.0 to 10.0 nm in the acetone solvent. The reaction mechanism for the formation of the NiO nanoparticles is proposed based on a pathway of chelated Ni complex during crystal growth. Although metallic Ni was also formed from reactions using the two alcoholic solvents, the Ni(OH)2 structure remained in the water solvent after thermal treatment. 相似文献
12.
M. K. Kundu 《European Journal of Lipid Science and Technology》1970,72(12):1029-1031
The crystallizations of the kusum oil and the mixed fatty acids thereof were studied from several solvents at various temperatures (+10° C to ?60° C). The results indicate in general that in the range of temperatures studied, petroleum ether as a single solvent is comparable in efficiency to methanol and superior to both acetone and ethanol in respect of separation of the saturated and unsaturated components of the fatty acid mixture. The saturated and unsaturated fractions of the oil also are better separated by petroleum ether than acetone. Further, oleic acid essentially free from linoleic acid is obtainable by a preliminary crystallization of the fatty acid mixture from petroleum ether at ca. ?12° C, followed by two additional crystallizations from acetone at ca. ?55° C. 相似文献
13.
Praewpanit Nuamcharoen Takaomi Kobayashi Pranut Potiyaraj Makoto Shiozaki 《Polymer International》2020,69(8):719-727
Poly(vinylidene fluoride) (PVDF) nanofibers were fabricated via electrospinning with an investigation of various ratios of binary solvents at different temperatures. The amount of acetone influenced the morphology. Scanning electron microscopy showed a PVDF membrane composed of smooth and unblemished fibers without beads and dark spots with small diameters of 201 ± 54 nm at a dimethylformamide‐to‐acetone ratio of 4:6. The temperature of pre‐thermal treatment from room temperature to 120 °C was investigated to promote the β crystalline phase in electrospun PVDF nanofibers. The result was characterized using Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD). PVDF solution prepared at 80 °C was used to increase the β crystalline phase of the electrospun PVDF nanofibers due to the transformation of α to β phase occurring during the spinning process and also bead‐free PVDF nanofibers were obtained. Differential scanning calorimetry revealed crystallization behavior corresponding with that determined using FTIR spectroscopy and XRD. Therefore, the solvent proportion and pretreatment temperature were observed to affect ultrafine nanofiber and crystalline structure of PVDF, respectively. © 2020 Society of Chemical Industry 相似文献
14.
Palm stearin with a melting point (m.p.) of 49.8°C was fractionated from acetone to produce a low-melting palm stearin (m.p.=35°C)
and a higher-melting palm stearin (HMPS, m.p.=58°C) fraction. HMPS was modified by interesterification with 60% (by weight)
of individual liquid oils from sunflower, soybean, and rice bran by means of Mucor miehei lipase. The interesterified products were evaluated for m.p., solid fat content, and carbon number glyceride composition.
When HMPS was interesterified individually with sunflower, soybean or rice bran at the 60% level, the m.p. of the interesterified
products were 37.5, 38.9, and 39.6°C, respectively. The solid fat content of the interesterified products were 30–35 at 10°C,
17–19 at 20°C, and 6–10 at 30°C, respectively. The carbon number glyceride compositions also changed significantly. C48 and C54 glycerides decreased remarkably with a corresponding increase of the C50 and C52 glycerides. All these interesterified products were suitable for use as trans acid-free and polyunsaturated fatty acid-rich shortening and margarine fat bases. 相似文献
15.
Zhaohui LIU Wei QI Weina WU Yue LIU Zhimin HE 《Frontiers of Chemical Engineering in China》2008,2(4):439-442
The effects of some sugars (glucose, mannose, fructose, sucrose and chitosan) and polyols (glycol, glycerol and sorbitol)
as protective additive on the thermostability of β-mannanase were studied. The optimal reaction temperatures of β-mannanase and the thermodynamics and the deactivation kinetics with or without additives were also investigated. The experimental
results show that sucrose, chitosan and sorbitol could apparently improve the thermal stability of β-mannanase when their concentration was kept at 2 g/L. The optimal combination additive proportion was sucrose: chitosan :
sorbitol = 1 : 2 : 2 (molar ratio) using the orthogonal experimental design. The sucrose, chitosan, glycerol, sorbitol and
the combination additive might increase the optimal reaction temperature from 50°C to about 60°C due to their good protection
effect. The thermal deactivationcurves of β-mannanase accorded with the kinetic rules of first order reaction, and the corresponding kinetic and thermodynamic parameters
were calculated. Meanwhile, the protective mechanism of the additives against deactivation of enzyme was also discussed.
__________
Translated from Journal of Tianjin University, 2007, 41(1): 114–118 [译自: 天津大学学报] 相似文献
16.
Iván Jachmanián Lucía Margenat Ana I. Torres Maria A. Grompone 《Journal of the American Oil Chemists' Society》2007,84(6):597-601
The solubility of different ethyl esters derivatized from hake liver oil in supercritical carbon dioxide was studied. A selectivity
factor was used to determine optimal conditions to fractionate the ethyl ester mixture. A strong influence of solvent pressure
and temperature was observed within 8.63–18.04 MPa and 40–70 °C. The lowest total solubility of the ethyl ester mixture was
obtained when using supercritical carbon dioxide at the lowest density (the lowest pressure and the highest temperatures value
tested). The highest discrimination against long-chain polyunsaturated fatty acids (e.g. EPA and DHA) was also obtained at
these above conditions. Conversely, higher solubility and lower selectivity were obtained when solvent density increased.
Considering this inverse correlation between selectivity and solubility, a single-step batch-fractionation process was designed
to increase the 22:6 ethyl ester content from an initial value of 17.5% in the starting material to 55% in the final extract. 相似文献
17.
A new high‐temperature resistance polyimide foam was synthesized from 2,3,3′,4′‐biphenyltetracarboxylic dianhydride (α‐BPDA) and p‐phenylenediamine (p‐PDA). The structures and foaming process of polyimide precursor powders were characterized by wide‐angle X‐ray diffractometer (WXRD) and the self‐made visualization device, respectively. The imidization degree, thermal mechanical properties and thermal stability of the polyimide foams with different post‐treatment temperatures were also measured by fourier transform infrared spectrometer spectrum (FTIR), dynamic thermal mechanical anaylsis (DMTA), and thermogravimetric analysis (TGA). Results showed that the inflation onset temperatures of polyimide precursor powders ranged from 122 to 135°C with varying the heating rate. And the increase in the imidization degree, glass transition temperatures (Tg) and temperatures for 5 wt% mass loss of high‐temperature resistance polyimide foams can be achieved with increasing post‐treatment temperature. It was quite surprising to find that Tg of high‐temperature resistance polyimide foam post‐treated at 420°C was up to above 450°C, and the char yield at 800°C was more than 60%. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers 相似文献
18.
Thuan-Hieu Tran Woo-Jin Chang Young-Bum Kim Joo-Young Yoon Yoon-Mo Koo Eun-Ki Kim Jin-Hwan Kim 《Korean Journal of Chemical Engineering》2007,24(6):1053-1057
A lyophilization method for long-term preservation of the initial bioluminescence of Photobacterium phosphoreum was investigated. The initial bioluminescence of lyophilized P. phosphoreum at different temperatures, −20 °C, 4 °C, room temperature (16–25 °C) and 45 °C, was monitored for 6 months with different
additives. Saccharose, skim milk, and a mixture of saccharose and skim milk were tested. Skim milk showed the best protection
for bioluminescence among the additives used. The initial bioluminescence remained high during 6 months at a wide range of
storage temperatures, i.e., −20 °C, 4 °C, and room temperature, with skim milk as an additive. The average bioluminescence
of lyophilized P. phosphoreum using skim milk as additive reached 33392 RLU within 30 min of regeneration. Bioluminescence increased slightly after 10
h of incubation. 相似文献
19.
《Ceramics International》2017,43(12):8932-8937
Aluminum oxide (AlOx) thin films were synthesized by mist-chemical vapor deposition (mist-CVD) using aluminum acetylacetonate (Al(acac)3) dissolved in an aqueous solvent mixture of acetone and water. Nitrogen gas was used to purge the precursor solution and growth rates between 7.5–13.3 nm/min were achieved at substrate temperatures of 250–350 °C. The AlOx layers deposited at temperatures below 350 °C exhibit 3–5 at% residual carbon levels, however those grown at 350 °C exhibit only 1–2 at% carbon impurity. Reasonable dielectric properties were obtained in the latter, with a dielectric constant (κ) of ~ 7.0, breakdown field of ~ 9 MV/cm and relatively low leakage current density of ~ 8.3×10−10 A/cm2. 相似文献
20.
Soluble asymmetric bismaleimide with low molten viscosity and its high glass transition temperature polymer
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Three novel bismaleimide monomers (MBA‐BMI, EBA‐BMI, and PBA‐BMI) with unsymmetrical backbone and different pendant groups were synthesized using asymmetric diamine and maleic anhydride as the precursors. The prepared bismaleimide monomers show good solubility in common organic solvents such as acetone and tetrahydrofuran. The EBA‐BMI melt treated at 180 °C also shows low viscosity about 190–934 mPa s at the temperature range of 160–139 °C below its melting point (166 °C). In addition to the good processability, all three cured bismaleimides show high storage moduli at high temperatures (2.0 GPa at 400 °C), high glass transition temperatures over 400 °C, and good thermal stability with the 5% weight loss temperatures around 470 °C under nitrogen atmosphere. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43491. 相似文献