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1.
The aim of this work was to find drag-reducing surfactants for both district heating and cooling that are environmentally
more acceptable than the organic salts of quaternary ammonium compounds that so far have dominated this application. Vortex
inhibition of test solutions in glass beakers has been used to screen a large number of surfactant mixtures, various electrolytes,
and temperatures. For the most interesting products, the pressure drop in a test loop was measured at various flow rates and
temperatures.N-cetyl sarcosinate andN-stearyl betaine, the latter together with Na-dodecylbenzene sulfonate, give good drag reduction (DR) properties at 65–100
and 45–85°C, respectively. The sarcosinate is sensitive to pH changes, whereas the betaine-sulfonate complex is more robust.
Ethoxylates of oleic acid monoethanolamide show good DR properties at 0–25°C. At an increased salt concentration, a mixture
of this surfactant with an ethoxylated oleyl alcohol worked well. At a still higher salt concentration, e.g., sea water, a
combination ofN-cetyl betaine and alkylbenzene sulfonate showed DR. 相似文献
2.
The kinetics of the transeterification of vegetable oil is known to follow a three-step reaction mechanism. The third step
involves the transesterification of MG. In this study, the transesterification of MG obtained from crude Pongamia oil was achieved with methanol in the presence of KOH as the catalyst. A MG/methanol ratio of 1∶10 was used at different
temperatures (30, 45, 55, and 60°C). 1H NMR was used to monitor the progress of transesterification. The study revealed that the kinetics of this reaction followed
a reversible second-order model, with a good fit obtained for all temperatures except 30°C. This result is explained as arising
out of the importance of transport effects at low temperatures. The forward rate constant increased with an increase in temperature,
whereas the reverse rate constant showed a decreasing trend, suggesting that the proposed reverse reaction was not an elementary
step. 相似文献
3.
It is well established that variation of the rate of cooling (r) of a lipid sample is an effective tool to influence the crystallization process and effect changes in network structure and
physical functionality. However, the extent of the physical changes does not always justify the extent to which the cooling
rate must be altered. It is therefore important to understand the rates at which marginal changes in physical functionality
begin to diminish, and to understand the mechanisms which introduce such limitations. A commercially available cocoa butter
alternative, Temcote (Bunge Oils, Bradley, IL), was crystallized under cooling rates varying from 0.1 to 20 °C min−1. The growth mode and polymorphism of each sample was studied using DSC and X-ray diffraction (XRD). The hardness of the sample
was monitored using cone penetrometry and its solid fat content (SFC) evolution was monitored using a temperature controlled
pulse-NMR. The data demonstrates that the melting profile of the sample could be greatly manipulated over a relatively narrow
range of cooling rates. Large increases in cooling rate increase the final SFC of the sample by approximately 6%. Doubling
the cooling rate increases the hardness of the sample 50%. Variation of the cooling rate as a tool to modify physical functionality
of the network was found to be effective only for cooling rates lower than 5 °C min−1. 相似文献
4.
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
5.
This study was undertaken to determine the quenching rates necessary to supercool polydimethylsiloxane. A technique was developed that allowed controlled quenching rates up to 52°C/see and a modified DTA apparatus was used to obtain thermograms during the warm-up cycle. No supercooling was observed for a cooling rate of 1.6°C/sec; 56% supercooling was found for a 9.6°C/sec cooling rate; 65% for 10.6°C/sec and 85% for a 52°C/sec cooling rate. Evidence was also presented showing that the crystals in polydimethylsiloxane consist of two forms. 相似文献
6.
Dynamic compressive behavior of basalt fiber reinforced concrete after exposure to elevated temperatures
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This paper investigated the dynamic behavior of basalt fiber reinforced concrete (BFRC) after elevated temperatures by using a 100‐mm‐diameter split Hopkinson pressure bar apparatus. Changes in weight and ultrasonic pulse velocity (UPV) were also studied. The results indicate that the weight losses of BFRC before cooling increase with temperature, while a reduction in weight loss value is observed after water cooling. The UPV values of BFRC decrease constantly as temperature increases, and the measured velocities under the same temperature increase with fiber content as temperature exceeds 200 °C. For a given temperature, the strain rate, dynamic strength, critical strain, and impact toughness of BFRC increase with impact velocity. For a given impact velocity, the increasing temperature generally leads to an increase in strain rate and critical strain and results in a decrease in dynamic strength and impact toughness except in the case of 200 °C. At 200 °C, however, a marginal reduction, even an improvement in dynamic strength is observed, and the impact toughness initially decreases, then increases with loading rate when compared with that at room temperature. Basalt fiber is effective in improving the strength performance, deformation capacity, and energy absorption property of concrete after high temperature. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
Wei Bai Dongliang Chen Qing Li Hechun Chen Shenglan Zhang Xiaochuan Huang Cheng-Dong Xiong 《Journal of Polymer Research》2009,16(5):471-480
The in vitro hydrolytic degradation of high molecular weight poly (para-dioxanone) was studied by examining the changes of weight retention, water absorption, pH value, tensile strength, break elongation,
thermal properties, and morphology of high molecular weight PPDO in phosphate buffered saline (PBS) (pH 7.44) at 37°C for
8 weeks. During the degradation, all samples’ weight retention decreased and water absorption increased significantly, whereas
hydrolysis rate of PPDO bars varied with molecular weight. Compared with lower molecular weight samples, higher molecular
weight PPDO samples exhibited higher hydrolysis rate. The samples’ glass transition temperature (Tg) decreased notably, while the degrees of crystallinity (Dc) increased. The samples almost totally lost their tensile strengths and breaking elongation after 4 weeks of degradation.
The results suggested that the stability of PPDO in vitro hydrolytic degradation increased with the increase of molecular weight. 相似文献
8.
Mangesh G. Kulkarni Sudhirprakash B. Sawant 《Journal of the American Oil Chemists' Society》2001,78(7):719-723
The primary aliphatic alcohols n-octanol, n-decanol, and n-dodecanol have been converted to their corresponding symmetrical esters by using HBr and H2O2 in the absence of a solvent. The reaction was carried out at 30, 40, and 50°C and at mole ratios of alcohol to HBr of 1∶0.1,
1∶0.2, 1∶0.3, and 1∶0.5. The rate of the reaction was found to increase with increase in the reaction temperature and concentration
of HBr. The maximal conversion of n-octanol was 72% at 40°C and a mole ratio of n-octanol to HBr of 1∶0.5. The kinetics of the reaction have been established, and the reaction was found to be first-order
with respect to alcohol and bromine concentration in the organic phase, and second-order with respect to both. The second-order
rate constants for n-octanol, n-decanol, and n-dodecanol are 27.08, 32.58, and 37.42 mL mol−1 min−1, respectively, at 40°C. The activation energy for the esterification reaction of n-octanol was found to be 16.32 kcal mol−1. 相似文献
9.
Nansuk You Songhun Yoon Wonkyu Lee Heung Yeoun Lee Sang-Yeop Park Jae Heon Shim Jong Soo Kim Chul Wee Lee 《Korean Journal of Chemical Engineering》2010,27(6):1718-1724
Based on a theoretical background [1,2], a lab scale cylindrical SAGD (steam assisted gravity drainage) model was designed,
constructed and operated. There are six different parts in the apparatus: (1) water supplier, (2) steam generator, (3) SAGD
cylindrical model, (4) cooling system, (5) constant pressure maintaining system and (6) production system. Temperature, pressure
and steam injection rate were controlled by computer, and product (mixture of oil and water) was collected/separated manually.
Extra heavy oil (<10 cp at 200 °C) and glass bead (diameter 1.5 mm) were mixed homogeneously for making porosity of 0.3 and
applied for simulating oil sand. For obtaining optimum operation conditions of SAGD apparatus, several attempts were made.
When the steam at high temperature (160–180 °C), high pressure (8–9 atm) was injected with 20–25 cc/min, cSOR (cumulative
steam to oil ratio) of about 5 was obtained with oil recovery of 78.8%. 相似文献
10.
An extracellular esterase (EC 3.1.1.1) from a thermophilicBacillus A30-1 (ATCC 53841) was purified 139-fold to homogeneity by sodium chloride (6 M) treatment, ammonium sulfate fractionation
(30–80%) and phenyl-Sepharose CL-6B column chromatography. The native enzyme was a single polypeptide chain with a molecular
weight of about 65,000 and an isoelectric point at pH 4.8. The optimum pH for esterase activity was 9.0, and its pH stability
range was 5.0–10.5. The optimum temperature for its activity was 60°C. The esterase had a half-life of 28 h at 50°C, 20 h
at 60°C and 16 h at 65°C. It showed the highest activity on tributyrin, with little or no activity toward long-chain (12–20
carbon) fatty acid esters. The enzyme displayed Km and Kcat values of 0.357 mM and 8365/min, respectively, for tributyrin hydrolysis at pH 9.0 and 60°C. Cyclodextrin (α, β, and γ),
Ca2+, Co2+, Mg2+ and Mn2+ enhanced the esterase activity, and Zn2+ and Fe2+ acted as inhibitors of the enzyme activity. The enzyme activity was not affected by ethylenediaminetetraacetic acid, p-chloromercuribenzoate
andN-bromosuccinimide.
This paper was presented in part at the 82nd Annual Meeting and Exposition of the American Oil Chemists’ Society, held May
12–15, 1991, in Chicago, Illinois. 相似文献
11.
The recent discovery of the binary metallic magnesium diboride (MgB2) superconductor having a remarkably high transition temperature (Tc) of 39 K has generated excitement among the scientist worldwide and gained great scientific interest. Various methods (viz.
PLD, solid state reaction etc.) are reported for the preparation of this material in different forms (bulk, wire, thin film)
which require a high processing temperature (750 to 950 °C). In this paper, we report a new method of processing MgB2 superconductor that meets all the properties when compared with other processes. In this work, polycrystalline MgB2 was prepared by using melting process at low temperature (660 °C). The stoichiometric mixture of Mg-rich and B-rich was pressed
into pellets and piled to form Mg-rich/B-rich/Mg-rich system. The piled specimen was then heated up to 800 °C for four hrs
with a heating rate of 5 °C/min. The sample was then kept at 660 °C for 12 hrs after cooling from 800 to 660 °C in 30 min.
For comparison, the sample was also sintered at 660 °C for 24 hrs. The samples were characterized by using XRD, EDX, SEM,
four probe AC methods and magnetization measurements using SQUID magnetometer. The critical temperature was found to be 39
K which shifts towards lower temperature with increasing applied field (0 to 9T). The critical current density, according
to Bean’s critical state model was estimated and found to be ∼105 A/cm2, which is comparable to the reported data. 相似文献
12.
Delphine Briand Eric Dubreucq Pierre Galzy 《Journal of the American Oil Chemists' Society》1995,72(11):1367-1373
This study describes the influence of various factors on the hydrolysis and alcoholysis activities of the lipase fromCandida parapsilosis (Ashford), Langeron and Talice in aqueous media. Optimal activities were obtained at 45°C and pH 6–6.5. The influence of
the nature of the substrate on the temperature activity profiles was observed. Total or partial recovery of the activities
was obtained when methanol was added to the enzyme extract after thermal denaturation. A tyrosin residue appeared to be necessary
for lipase function. Magnesium was a required metal cofactor. These activities were optimal in the presence of high amounts
of water (water activity >0.9). 相似文献
13.
In this study, a novel semi-interpenetrating network (semi-IPN’s) hydrogel, composed of acrylamide (AAm) with N-vinylimidazole (NVI) as comonomer, with poly (ethylene glycol)(PEG) and a multifunctional crosslinker such as trimethylolpropane
triacrylate (TMPTA) was prepared. Highly swollen poly (AAm/NVI) hydrogels and semi-IPN’s were synthesized by free radical
solution polymerization. Swelling experiments were performed in water at 25°C, gravimetrically. The influence of NVI and PEG
content in hydrogels were examined. Poly (AAm/NVI) and poly (AAm/NVI/PEG) hydrogels showed large extents of swelling in aqueous
media the swelling being highly dependent on the chemical composition of the hydrogels. Swelling ratio of poly (AAm/NVI) hydrogels
and poly (AAm/NVI/PEG) hydrogels was shown 7.16–39.85. Diffusion behavior was investigated. Water diffusion into hydrogels
was found to be non-Fickian in character. This study has given the quantitative information on the swelling characteristic of poly (AAm/NVI) hydrogel
and semi-IPN’s as water absorbent in many potential applications. 相似文献
14.
The temperature window of NO
x
consumption lies between 140 and 500 °C. The 0.5 wt%Co/Al2O3 catalyst exhibits a total consumption of NO
x
between 300 and 350 °C at a space velocity of 50 000 h−1. The presence of acetonitrile and methylnitrite can explain the difference between N2 formation and NOx consumption at T< 400 °C. The Co2+, in octahedral site, has been shown to coordinate two NO molecules. 相似文献
15.
Structured lipids: Lipase-catalyzed interesterification of tricaproin and trilinolein 总被引:2,自引:0,他引:2
Structured lipids were synthesized by interesterification of trilinolein and tricaproin with sn-1,3-specific (IM 60) and nonspecific (SP 435) lipases. The interesterification reaction was performed by incubating a 1:2
mole ratio of trilinolein and tricaproin in 3 mL hexane at 45°C for the IM 60 lipase from Rhizomucor miehei, and at 55°C for the SP 435 lipase from Candida antarctica. Reaction products were analyzed by reverse-phase high-performance liquid chromatography with an evaporative light-scattering
detector. The fatty acids at the sn-2 position were identified after pancreatic lipase hydrolysis and analysis with a gas chromatograph. IM 60 lipase produced
53,5 mol% dicaproyllinolein (total carbon number = C33) and 22.2% monocaproyldilinolein (C45). SP 435 lipase produced 41%
C33 and 18% C45. When caproic acid was used in place of tricaproin as the acyl donor, the IM 60 lipase produced 62.9% C33.
The effects of variation in mole ratio, temperature, added water, solvent polarity, and time course on the interesterification
reaction were also investigated. In the absence of organic solvent, IM 60 lipase produced 52.3% C33. 相似文献
16.
Kinetics of the lipolysis ofNigella sativa oil catalyzed by native lipase in crushed seed were studied between 20 and 90°C. Data fitted the pseudo first-order rate
equation at 20, 30 and 40°C; and the pseudo second-order equation at 50, 60 and 70°C, but neither equation fit at 80 and 90°C.
Lipolysis approximated first-order with respect to water. 相似文献
17.
Ngoc Trung Trinh Jong Hyeok Park Byung-Woo Kim 《Korean Journal of Chemical Engineering》2009,26(3):748-753
The microbial fuel cell (MFC) has attracted research attention as a biotechnology capable of converting hydrocarbon into electricity
production by using metal reducing bacteria as a biocatalyst. Electricity generation using a microbial fuel cell (MFC) was
investigated with acetate as the fuel and Geobacter sulfurreducens as the biocatalyst on the anode electrode. Stable current production of 0.20–0.24 mA was obtained at 30–32 °C. The maximum
power density of 418–470 mW/m2, obtained at an external resistor of 1,000 Ω, was increased over 2-fold (from 418 to 866 mW/m2) as the Pt loading on the cathode electrode was increased from 0.5 to 3.0 mg Pt/cm2. The optimal batch mode temperature was between 30 and 32 °C with a maximum power density of 418–470 mW/m2. The optimal temperature and Pt loading for MFC were determined in this study. Our results demonstrate that the cathode reaction
related through the Pt loading on the cathode electrode is a bottleneck for the MFC’s performance. 相似文献
18.
Yuji Shimada Norihito Sakai Akio Sugihara Hiroyuki Fujita Yo Honda Yoshio Tominaga 《Journal of the American Oil Chemists' Society》1998,75(11):1539-1544
γ-Linolenic acid (GLA) is a physiologically valuable fatty acid, and is desired as a medicine, but a useful method available
for industrial purification has not been established. Thus, large-scale purification was attempted by a combination of enzymatic
reactions and distillation. An oil containing 45% GLA (GLA45 oil) produced by selective hydrolysis of borage oil was used
as a starting material. GLA45 oil was hydrolyzed at 35°C in a mixture containing 33% water and 250 U/g-reaction mixture of
Pseudomonas sp. lipase; 91.5% hydrolysis was attained after 24 h. Film distillation of the dehydrated reaction mixture separated free
fatty acids (FFA; acid value 199) with a recovery of 94.5%. The FFA were selectively esterified at 30°C for 16 h with two
molar equivalents of lauryl alcohol and 50 U/g of Rhizopus delemar lipase in a mixture containing 20% water. The esterification extent was 52%, and the GLA content in the FFA fraction was
raised to 89.5%. FFA and lauryl esters were not separated by film distillation, but the FFA-rich fraction contaminated with
18% lauryl esters was recovered by simple distillation. To further increase the GLA content, the FFA-rich fraction was selectively
esterified again under similar conditions. As a result, the GLA content in the FFA fraction was raised to 97.3% at 15.2% esterification.
After simple distillation of the reaction mixture, lauryl esters contaminating the FFA-rich fraction were completely eliminated
by urea adduct fractionation. When 10 kg of GLA45 oil was used as a starting material, 2.07 kg of FFA with 98.6% GLA was obtained
with a recovery of 49.4% of the initial content. 相似文献
19.
Enzymatic synthesis of symmetrical 1,3-diacylglycerols by direct esterification of glycerol in solvent-free system 总被引:9,自引:1,他引:8
Roxana Rosu Mamoru Yasui Yugo Iwasaki Tsuneo Yamane 《Journal of the American Oil Chemists' Society》1999,76(7):839-843
1,3-Diacylglycerols were synthesized by direct esterification of glycerol with free fatty acids in a solvent-free system.
Free fatty acids with relatively low melting points (<45°C) such as unsaturated and medium-chain saturated fatty acids were
used. With stoichiometric ratios of the reactants and water removal by evaporation at 3 mm Hg vacuum applied at 1 h and thereafter,
the maximal 1,3-diacylglycerol content in the reaction mixture was: 84.6% for 1,3-dicaprylin, 84.4% for 1,3-dicaprin, 74.3%
for 1,3-dilinolein, 71.7% for 1,3-dieicosapentaenoin, 67.4% for 1,3-dilaurin, and 61.1% for 1,3-diolein. Some of the system’s
parameters (temperature, water removal, and molar ratio of the reactants) were optimized for the production of 1,3-dicaprylin,
and the maximal yield reached 98%. The product was used for the chemical synthesis of 1,3-dicapryloyl-2-eicosapentaenoylglycerol.
The yield after purification was 42%, and the purity of the triacylglycerol was 98% (both 1,3-dicapryloyl-2-eicosapentaenoylglycerol
and 1,2-dicapryloyl-3-eicosapentaenoylglycerol included) by gas chromatographic analysis, of which 90% was the desired structured
triacylglycerol (1,3-dicapryloyl-2-eicosapentaenoylglycerol) as determined by silver ion high-performance liquid chromatographic
analysis. 相似文献
20.
Sean F. O’Keefe V. A. Wiley D. Wright 《Journal of the American Oil Chemists' Society》1993,70(9):915-917
Oil was extracted from soybeans, degummed, alkalirefined and bleached. The oil was heated at 160, 180, 200, 220 and 240°C
for up to 156 h. Fatty acid methyl esters were prepared by boron trifluoride-catalyzed transesterification. Gas-liquid chromatography
with a cyanopropyl CPSil88 column was used to separate and quantitate fatty acid methyl esters. Fatty acids were identified
by comparison of retention times with standards and were calculated as area % and mg/g oil based on 17:0 internal standard.
The rates of 18:3ω3 loss and 18:3 Δ9-cis, Δ12-cis, Δ15-trans (18:3c,c,t) formation were determined, and the activation energies were calculated from Arrhenius plots. Freshly prepared soy oil had
10.1% 18:3ω3 and no detectable 18:3c,c,t. Loss of 18:3ω3 followed apparent first-order kinetics. The first-order rate constants ranged from .0018±.00014 min−1 at 160°C to .083±.0033 min−1 at 240°C. The formation of 18:3c,c,t did not follow simple kinetics, and initial rates were estimated. The initial rates (mg per g oil per h) of 18:3c,c,t formation ranged from 0.0031±0.0006 at 160°C to 2.4±.24 at 240°C. The Arrhenius activation energy for 18:3ω3 loss was 82.1±7.2
kJ mol−1. The apparent Arrhenius activation energy for 18:3c,c,t formation was 146.0±13.0 kJ mol−1. The results indicate that small differences in heating temperature can have a profound affect on 18:3c,c,t formation. Selection of appropriate deodorization conditions could limit the amount of 18:3c,c,t produced. 相似文献