A series of solid base catalysts, KF/Ca−Mg−Al hydrotalcite (KF mass ratio of 100%) with different cation ratios, were prepared and studied in this research. Effects of the cation ratio of the Ca−Mg−Al hydrotalcite and the methanol/oil molar ratios on the fatty acid methanol ester (FAME) yield of the transesterification of palm oil with methanol were investigated. The results of the transesterification reactions showed that all of these kinds of catalysts had a very high activity for the biodiesel yields, obtaining 90% or more with 10 min of reaction under the conditions of 338 K, 12:1 methanol/oil molar ratio, and 5% (wt/wt oil) catalyst amount. In addition, the FAME yield could reach 99.6% in 10 min catalyzed by the optimal catalyst KF/Ca−Mg−Al hydrotalcite (2.2:0.8:1 Ca/Mg/Al; KF mass ratio of 100%), under the same reaction conditions as above.
The KF/hydrotalcite (HT) solid base catalysts were prepared by impregnation and characterized by X-ray diffraction. Biodiesel can be obtained from transesterification of palm oil with methanol over the KF/HT catalysts. The effect factors, such as KF/HT load ratio, methanol/oil molar ratio, catalyst amount, reaction time, and reaction temperature, were investigated. When the reaction was carried out at 338 K, with palm oil/methanol molar ratio of 12:1, reaction time of 3 h, and catalyst amount of 3 wt %, the yield of fatty acid methyl esters can reach 85%, and when the reaction time prolonged to 5 h, the yield can become 92%.
The dissociation constants (pK a ) of daidzein and genistein were determined at 298.2 K by ultraviolet (UV) spectroscopy method. The pK a1 and pK a2 values of daidzein are 7.51 ± 0.07 and 9.47 ± 0.14 and ones of genistein are 7.25 ± 0.84 and 9.53 ± 0.15, respectively. The solubilities of daidzein and genistein in water, methanol, ethyl ethanoate, propanone, trichloromethane, and hexane have been measured using UV spectrophotometric method from (288.2 to 328.2) K at atmospheric pressure. The solubilities of daidzein and genistein in all solvents increase with an increase in temperature. The solubility of daidzein in the six solvents was in the order propanone > methanol > ethyl ethanoate > hexane > trichloromethane > water, whereas the solubility order of genistein was propanone > ethyl ethanoate > methanol > hexane > trichloromethane > water. In comparing the solubility of genistein with that of daidzein, the 5-hydroxyl group of genistein causes a significantly higher solubility in methanol and ethyl ethanoate, a little higher solubility in trichloromethane (exception 328.2 K), an approximately equivalent solubility in water, and a slightly lower solubility in propanone. The measured solubility data were correlated with a modified Apelblat equation, λh model, and ideal model. From solubility of daidzein and genistein in these six solvents, the dissolution enthalpy, entropy, and change of the free Gibbs energy were evaluated using the van't Hoff equation.
Kinetics of the transesterification reaction catalyzed by solid base in a fixed-bed reactor was studied in this paper. The transesterification reaction between palm oil and methanol was catalyzed by KF/Ca−Mg−Al hydrotalcite solid base, which made it a complicated liquid−liquid−solid heterogeneous reaction. Isopropyl ether was used to obtain a homogeneous reactant system, and then liquid−liquid mass-transfer limitations were eliminated. Experimental results showed that, when the feed rate was faster than 0.3 mL/min, liquid−solid external diffusion mass-transfer limitations were negligible and, when the diameter of the catalyst particle was not larger than 0.18 mm, liquid−solid internal diffusion mass-transfer limitations could be neglected as well. Then, intrinsic reaction rates of this transesterification under different space velocities, temperatures, and concentrations were measured in a fixed-bed integral reactor. An intrinsic kinetic model was developed on the basis of the Eley−Rideal mechanism according to the experimental data, which indicated a new mechanism of the transesterification reaction catalyzed by solid base. The transesterification reaction occurred between methanol adsorbed on solid base active sites and glyceride from the liquid phase. The surface reaction of triglyceride with adsorbed methanol was assumed to be rate-determining. The model calculation agreed well with experimental data. Regression of experimental data indicated that the transesterification reaction was an endothermic reaction and the activation energy was 111.6 kJ/mol.
Mg–Al
oxides were prepared by facile solvent-free grinding
of Mg–Al layered double hydroxide and were used as catalysts
for continuous-flow transesterification of dimethyl carbonate and
ethanol. The surface and structure properties of the prepared Mg–Al
oxides were characterized by X-ray powder diffraction, scanning electron
microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared
spectra, and N2 adsorption–desorption. Moreover,
the acid–base properties of the prepared catalysts were characterized
using NH3-TPD, CO2-TPD, and pyridine-IR. The
Mg–Al oxides prepared using the solvent-free method with a
molar ratio of 2.0 (CHT-2-SF) exhibit good catalytic performance,
which has medium basic sites, weak acidic sites, and high Brunauer–Emmett–Teller
surface areas. A correlation between basicity–acidity and catalytic
activity demonstrates that the conversion of ethanol increases with
increasing medium basicity and weak acidity of the catalyst. The activity
of CHT-2-SF remained almost unchanged after 1800 h on stream.
Hemocompatibility and antibacterial property are essential for blood contact devices and medical intervention materials. In this study, positively charged quaternary ammonium (QAC) and hydrophobic benzyl group (OBzl) were introduced onto hydrophilic lysine methacrylamide (LysAAm) to obtain two monomers LysAAm−QAC and LysAAm−OBzl, respectively. The structure characterizations of LysAAm−QAC and LysAAm− OBzl were determined by proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, and time-of-flight secondary ion mass spectrometry. LysAAm−QAC and LysAAm−OBzl were cografted onto a silicon wafer with different feeding ratios to construct antifouling and antibacterial properties. The results of fibrinogen adsorption and platelet adhesion proved that the modified sample with the feeding ratio of 3:7 had superior antifouling property. Furthermore, an antimicrobial test with both 2 and 24 h indicated that the modified sample with the feeding ratio of 3:7 had antibacterial ability. The antifouling property was provided by the high surface coverage of LysAAm−QAC and LysAAm−OBzl (91.49%) and the hydrophilic main structure LysAAm on LysAAm−QAC and LysAAm−OBzl (water contact angle was 43.6°). The antibacterial property was improved with the proportion of LysAAm− OBzl (43.6−58.5%) because the increasing hydrophobic OBzl enhanced the ability to insert into the membrane of bacteria and raise the bactericidal efficiency. In application, LysAAm−QAC and LysAAm−OBzl with the feeding ratio of 3:7 were grafted onto the surface of poly(styrene-b-(ethylene-co-butylene)-b-styrene), and a bifunctional surface with antifouling and antibacterial properties was fabricated, which had promising applications in blood contact devices and medical intervention materials.
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