共查询到20条相似文献,搜索用时 31 毫秒
1.
Madeira laurel oil was fractionated by liquid extraction combined with TLC, and TAGs were analyzed by HPLC coupled with atmospheric
pressure chemical ionization-MS (APCI-MS). Eluted molecular species compositions of the eluted TAG in the complex natural
mixture were determined by GC identification of FAME and byLC-atmospheric pressure chemical ionization (APCI)-MS analysis
of the lipid. The APCI-MS spectra of most TAG exhibited [M+H]+ and [M−RCOO]+ ions, which defined the M.W. and the molecular association of fatty acyl residues, respectively. Despite the relatively high
degree of saturation, with a saturated/unsaturated ratio of 0.70, no totally saturated TAG nor mixed asymmetric TAG with two
saturated FA (SSM or SSU, where S is saturated, M is monounsaturated, and U is unsaturated) were found. This type of molecular
structure provides a possible explanation for the relatively low m.p. (12–15°C) and also the high oxidative resistance observed. 相似文献
2.
The fixed oil extracted from Laurus spp. fruit from Madeira Island, Portugal, is used in local traditional medicine for a wide variety of health complaints.
Physical properties, density and refractive index, as well as the TAG FA composition, sterols, and waxes were determined.
The oil was found to have an unusually high content of volatiles (ca. 10%), with trans-ocimene and germacrene D predominating. Oleic (30%) and linoleic (20%) acids were the main unsaturated FA, whereas lauric
(18%) and palmitic (up to 22.5%) acids were the main saturated FA in the neutral lipid fraction. The oil had a sterol content
on the same order as olive oil, with β-sitosterol (84%) predominating. Two sesquiterpene lactones, dehydrocostuslactone and
costunolide, accounted for 5% of the overall composition. Madeira laurel oil is not currently used as an edible oil because
of its very strong flavor. Its claimed medicinal properties have not yet been validated, and this is the first report on the
characterization of the commercial product. 相似文献
3.
Enzymatic glycerolysis of soybean oil 总被引:1,自引:0,他引:1
Enzymatic glycerolysis of soybean oil was studied. Of the nine lipases that were tested in the initial screening, Pseudomonas sp. resulted in the highest yield of monoglycerides. Lipase from Pseudomonas sp. was further studied for the influence of temperature, thermal stability, enzyme/oil ratio, and glycerol/oil ratio. A
full factorial optimization approach was performed. The following conditions were tested over the specified ranges: temperature
(30–70°C), thermal stability (30–70°C), enzyme/oil ratio (0.05–0.2 g enzyme/10 g oil), glycerol/oil ratio (1:1–3:1 glycerol/oil
molar ratio) and 1 h reaction time. The stability of the enzyme at the reaction temperature was also incorporated as a separate
variable. At temperatures above 40°C enzyme denaturation offset the higher activity. The optimal conditions were selected
to be the basis for a continuous process: 40°C, a glycerol/oil molar ratio of 2:1, and an enzyme/oil ratio of 0.1 g enzyme/10
g oil. A definition for glycerolysis activity was adopted. The glycerolysis activity (1 GU) was defined as the amount of enzyme
necessary to consume 1 μmol of substrate (glycerol and oil) per minute. This research is intended to explore the reaction
parameters that are important in a continuous enzymatic glycerolysis process. 相似文献
4.
Sebnem Selen Isbilir Hakki M. Ozcan Hulya Yagar 《Journal of the American Oil Chemists' Society》2008,85(3):227-233
Lipase was isolated from bay laurel (Laurus nobilis L.) seeds, some biochemical properties were determined. The bay laurel oil was used as the substrate in all experiments.
The pH optimum was found to be 8.0 in the presence of this substrate. The temperature optimum was 50 °C. The specific activity
of the lipase was found to be 296 U mg protein−1 in optimal conditions. The enzyme activity is quite stable in the range of pH 7.0–10. The enzyme was stable for 1 h at its
optimum temperature, and retained about 68% of activity at 60 °C during this time. K
m
and V
max values were determined as 0.975 g and 1.298 U mg protein−1, respectively. Also, storage stability and metal effect on lipolytic activity were investigated. Enzyme activity was maintained
for 9, 12, and 42 days at room temperature, 4 and −20 °C, respectively. Ca2+, Co2+, Cu2+, Fe2+, and Mg2+ lightly enhanced bay laurel lipase activity. 相似文献
5.
Kinetics of palm oil transesterification in a batch reactor 总被引:20,自引:15,他引:20
Methyl esters were produced by transesterification of palm oil with methanol in the presence of a catalyst (KOH). The rate
of transesterification in a batch reactor increased with temperature up to 60°C. Higher temperatures did not reduce the time
to reach maximal conversion. The conversion of triglycerides (TG), diglycerides (DG), and monoglycerides (MG) appeared to
be second order up to 30 min of reaction time. Reaction rate constants for TG, DG, and MG hydrolysis reactions were 0.018–0.191
(wt%·min)−1, and were higher at higher temperatures and higher for the MG reaction than for TG hydrolysis. Activation energies were 14.7,
14.2, and 6.4 kcal/mol for the TG, DG, and MG hydrolysis reactions, respectively. The optimal catalyst concentration was 1%
KOH. 相似文献
6.
The base-catalyzed transmethylation of soybean oil has been studied under conditions whereby the reaction starts as a single
phase, but later becomes two phases as glycerol separates. Methanol/oil molar ratios of 6∶1 were used at 23°C. The catalysts
were sodium hydroxide (0.5, 1.0, and 2.0 wt%), potassium hydroxide (1.0 and 1.4 wt%), and sodium methoxide (0.5, 1.0, and
1.35 wt%), all concentrations being with respect to the oil. Oxolane (tetrahydrofuran) was used to form a single reaction
phase. The reactions deviated from homogeneous kinetics as glycerol separated, taking with it most of the catalyst. When 1.0
wt% sodium hydroxide was used, the methyl ester content reached 97.5 wt% after 4 h, compared with 85–90 wt% in the two-phase
reaction. Sodium hydroxide (1.0 wt%), sodium methoxide (1.35 wt%), and potassium hydroxide (1.4 wt%) gave similar results,
presumably because the same number of moles was used. The ASTM biodiesel specification for chemically bound glycerol was achieved
after only 3 min when 2.0 wt% sodium hydroxide was used. However, the standard was not achieved after 4 h when 1.0 wt% sodium
hydroxide was used, the MG content being 1.1–1.6 wt%. The use of 2.0 wt% catalyst is commercially impractical. 相似文献
7.
Hongbin Ma Shufen Li Boyang Wang Ruihong Wang Songjiang Tian 《Journal of the American Oil Chemists' Society》2008,85(3):263-270
The heterogeneous base catalyst, γ-Al2O3 loaded with KOH and K (K/KOH/γ-Al2O3) was first prepared and used in the transesterification of rapeseed oil with methanol to produce biodiesel. The prepared
catalyst was characterized by X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller method, infrared spectroscopy
and X-ray photoelectron spectroscopy. It was found that when γ-Al2O3 is loaded with KOH and K, the Al–O–K species is produced, resulting in an increase in the catalytic activity. The impacts
of catalyst preparation conditions on the catalytic activities of K/KOH/γ-Al2O3 were investigated. The results demonstrate that the catalyst K/KOH/γ-Al2O3 has high catalytic activity when the added amounts of KOH and K are 20 and 7.5 wt% respectively. The transesterification
of rapeseed oil to biodiesel with the prepared heterogeneous base catalyst was optimized. It was found that the yield of biodiesel
can reach as high as 84.52% after 1 h reaction at 60°C, with a 9:1 molar ratio of methanol to oil, a catalyst amount of 4 wt%,
and a stirring rate of 270 g. 相似文献
8.
The transesterification of soybean oil to biodiesel using Ba–ZnO as a solid catalyst was investigated. The Ba–ZnO sample with
loading of 2.5 mmol/g Ba on ZnO and being calcined at 873 K for 5 h, was found to be the optimum catalyst, which could exhibit
the highest basicity and the best catalytic activity for the reaction. When the transesterification reaction was carried out
at reflux of methanol (338 K), with a 12:1 molar ratio of methanol to oil and a catalyst amount of 6 wt.%, the conversion
of soybean oil was 95.8%. Furthermore, XRD, XPS, DTA–TG and the Hammett indicator method were employed for the catalyst characterizations,
and the relation between the catalytic efficiency and the basicity of the catalysts was also discussed. 相似文献
9.
G. Lakshminarayana R. Subbarao Y. Sita Rama Sastry V. Kale T. Chandrasekhara Rao A. Gangadhar 《Journal of the American Oil Chemists' Society》1984,61(7):1204-1206
The effects of variations in pressure (20–40 kg/cm2), oil-to-water ratio (1:0.4–1:1, w/w) and time (0–8 hr) on the extent of hydrolysis of castor oil were studied. Higher pressure,
lower oil-to-water ratio and longer duration gave higher percentage splits. At 40 kg/cm2 pressure and an oil-to-water ratio of 1:1, ca. 92% split was obtained in 8 hr. When the oil was hydrolyzed in 2 stages at
20 kg/cm2 with an oil-to-water ratio of 1:0.4, ca. 96% split was obtained in a total period of 10 hr. Splitting at 20 kg/cm2 gave minimal amounts of dienoic acids because of the decomposition of estolides. 相似文献
10.
Amanda D’Cruz Mangesh G. Kulkarni Lekha Charan Meher Ajay K. Dalai 《Journal of the American Oil Chemists' Society》2007,84(10):937-943
A series of alkali metal (Li, Na, K) promoted alkali earth oxides (CaO, BaO, MgO), as well as K2CO3 supported on alumina (Al2O3), were prepared and used as catalysts for transesterification of canola oil with methanol. Four catalysts such as K2CO3/Al2O3 and alkali metal (Li, Na, K) promoted BaO were effective for transesterification with >85 wt% of methyl esters. ICP-MS analysis
revealed that leaching of barium in ester phase was too high (~1,000 ppm) when BaO based catalysts were used. As barium is
highly toxic, these catalysts were not used further for transesterification of canola oil. Optimization of reaction conditions
such as molar ratio of alcohol to oil (6:1–12:1), reaction temperature (40–60 °C) and catalyst loading (1–3 wt%) was performed
for most efficient and environmentally friendly K2CO3/Al2O3 catalyst to maximize ester yield using response surface methodology (RSM). The RSM suggested that a molar ratio of alcohol
to oil 11.48:1, a reaction temperature of 60 °C, and catalyst loading 3.16 wt% were optimum for the production of ester from
canola oil. The predicted value of ester yield was 96.3 wt% in 2 h, which was in agreement with the experimental results within
1.28%. 相似文献
11.
Continuous transmethylation of palm oil in an organic solvent 总被引:6,自引:0,他引:6
Kanit Krisnangkura Ratchadaporn Simamaharnnop 《Journal of the American Oil Chemists' Society》1992,69(2):166-169
Palm oil was transmethylated continuously at 70°C in an organic solvent with sodium methoxide as a catalyst. The optimum ratio
of toluene to palm oil is 1∶1 (v/v). When the methanol-to-oil molar ratio was 13∶1, transmethylation was 96% complete within
60 seconds. At higher molar ratio (17∶1), transmethylation was 99% complete in 15 seconds. For lower molar ratios of methanol-to-oil
(9∶1 and 5.8∶1), yields of palm oil methyl ester (POME) were 84 and 58%, respectively. Benzene was also a good solvent for
transmethylation, but the yield of POME was slightly lower than toluene. Tetrahydrofuran did not accelerate transmethylation. 相似文献
12.
The kinetic and equilibrium constants were determined for the hydrogenation of soybean oil on a commercial nickel catalyst
in a 300-ml Parr batch reactor. These constants were used to calculate the hydrogen gas absorption coefficients by coupling
mass transfer with reaction rate based on a Langmuir Hinshelwood model. The activation energy for the rate-determining step
was 23 kcal/g mol whereas the adsorption energy for hydrogen was −12.5 kcal/g mol. The gas absorption coefficients varied
between 0.3 to 0.7 min−1 as the temperature ranged between 140–180 C. 相似文献
13.
Biodiesel production by the transesterification of cottonseed oil by solid acid catalysts 总被引:2,自引:0,他引:2
Chen He Peng Baoxiang Wang Dezheng Wang Jinfu 《Frontiers of Chemical Engineering in China》2007,1(1):11-15
Methyl esters (biodiesel) were produced by the transesterification of cottonseed oil with methanol in the presence of solid
acids as heterogeneous catalysts. The solid acids were prepared by mounting H2SO4 on TiO2 · nH2O and Zr(OH)4, respectively, followed by calcining at 823K. TiO2-SO4
2− and ZrO2-SO4
2− showed high activity for the transesterification. The yield of methyl esters was over 90% under the conditions of 230°C,
methanol/oil mole ratio of 12:1, reaction time 8 h and catalyst amount (catalyst/oil) of 2% (w). The solid acid catalysts
showed more better adaptability than solid base catalysts when the oil has high acidity. IR spectral analysis of absorbed
pyridine on the samples showed that there were Lewis and Br?nsted acid sites on the catalysts.
Translated from The Chinese Journal of Process Engineering, 2006, 6(4): 571–575 [译自: 过程工程学报] 相似文献
14.
In this study, transesterification of soybean oil to biodiesel using CaO as a solid base catalyst was studied. The reaction mechanism was proposed and the separate effects of the molar ratio of methanol to oil, reaction temperature, mass ratio of catalyst to oil and water content were investigated. The experimental results showed that a 12:1 molar ratio of methanol to oil, addition of 8% CaO catalyst, 65 °C reaction temperature and 2.03% water content in methanol gave the best results, and the biodiesel yield exceeded 95% at 3 h. The catalyst lifetime was longer than that of calcined K2CO3/γ-Al2O3 and KF/γ-Al2O3 catalysts. CaO maintained sustained activity even after being repeatedly used for 20 cycles and the biodiesel yield at 1.5 h was not affected much in the repeated experiments. 相似文献
15.
Ping Jing Qingbiao Li Mei Han Daohua Sun Lishan Jia Weiping Fang 《Frontiers of Chemical Engineering in China》2008,2(2):186-190
SO42−/ZrO2 solid super-acid catalysts (SZ) doped with Ni2+ or Sn2+ (Ni2+/SZ, Sn2+/SZ) were prepared for catalytic visbreaking of heavy petroleum oil from Shengli oil field. The visbreaking reactions were
carried out at 240°C and 3–4 MPa for 24 h using a heavy petroleum oil to catalyst mass ratio of 100 : 0.05. The effect of
water content on viscosity of heavy petroleum oil was also investigated. Both catalysts can promote thermolysis of heavy petroleum
oil and the viscosity was reduced from 0.319 Pa·s to 0.135 Pa·s for Ni2+/SZ and 0.163 Pa·s for (Sn2+/SZ) with visbreaking rates of 57.7% and 48.9%, respectively. After visbreaking, the saturated hydrocarbon content increased
while aromatics, resin, asphaltene, sulfur and nitrogen content decreased. The presence of water was disadvantageous to visbreaking
of heavy petroleum oil.
__________
Translated from Petrochemical Technology, 2007, 36(3): 237–241 [译自: 石油化工] 相似文献
16.
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
17.
F. O. Ayorinde K. D. Carlson R. P. Pavlik J. McVety 《Journal of the American Oil Chemists' Society》1990,67(8):512-518
Vernonia galamensis seed containing 40–42% oil and 30–34% epoxy acid, (cis-12,13-epoxy-cis-9-octadecenoic) was processed to oil and meal. Seed conditioning, pressing and solvent extraction research were conducted
in pilot facilities at the French Oil Mill Machinery Co. (Piqua, OH). The robust lipase system was successfully inactivated
by treating 200 lb. batches ofV. galamensis seed in a cooker/conditioner at 195–200°F and >10% moisture. Conditioned seed was mechanically pressed and the press discharge
cone setting was varied during operation from 1/32″ to 3/32″ to demonstrate the feasibility of both full pressing and prepressing.
Prepressing successfully reduced oil level in the press cake to ca. 20%. Press cake was extracted with hexane in a 1.5-ft3 batch-type, four-stage percolation unit with a 6″ square extraction cross section. Solvent extraction reduced oil level in
the defatted meal to 1–2%. The defatted meal was desolventized and toasted. Excessive foaming of the vernonia oil extract
made complete solvent stripping in the oil stripping unit difficult. 相似文献
18.
Kinetics of transesterification of palm-based methyl esters (POME) with trimethylolpropane (TMP) to polyol esters was investigated.
A kinetic model of reaction was obtained by assuming a series of irreversible elementary reactions at various temperatures.
The reaction rate constants were determined under limited conditions. The optimal ratios for k
2/k
1 and k
3/k
1 were 0.70–0.80 and 0.21–0.25, respectively. Both palm oil methyl esters (PPOME) and palm-kernel oil methyl esters (PKOME)
were reacted with TMP by using sodium methoxide as catalyst. The POME-to-TMP molar ratio and catalyst weight percentage were
held constant at 10∶1 and 0.4%, respectively. The effects of temperature (70–110°C) and raw materials (PKOME and PPOME) were
investigated and found to have a significant impact on the reaction kinetics. When using a large excess of POME and continual
withdrawal of methanol via vacuum, the reaction reached completion in less than 20 min at 80°C. After removal of unreacted POME, the final product contained
apprximately 98 wt% triesters. 相似文献
19.
Oguzhan Ilgen 《Fuel Processing Technology》2011,92(3):452-455
In this study, the catalytic activity of dolomite was evaluated for the transesterification of canola oil with methanol to biodiesel in a heterogeneous system. The influence of the calcination temperature of the catalyst and the reaction variables such as the temperature, catalyst amount, methanol/canola oil molar ratio, and time in biodiesel production were investigated. The maximum activity was obtained with the catalyst calcined at 850 °C. When the reaction was carried out at reflux of methanol, with a 6:1 molar ratio of methanol to canola oil and a catalyst amount of 3 wt.% the highest FAME yield of 91.78% was obtained after 3 h of reaction time. 相似文献
20.
The hydrogenation of castor oil was investigated using a catalytic transfer hydrogenation system in which palladium on carbon
was the catalyst and limonene was the solvent and hydrogen donor. The highest percentage of castor oil modification occurred
at 178°C using 1% Pd/C and an oil/limonene ratio of 1∶3. The optimized system presented very good reproducibility and 100%
conversion of the ricinoleate. GC using a mass spectrometer as detector and 1H NMR spectra of the products indicated that hydrogenation was accompanied by dehydrogenation leading to a mixture of 12-hydroxy
and 12-keto stearic derivatives. 相似文献