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71.
Helen L. Ngo Alberto Nuñez Wenbin Lin Thomas A. Foglia 《European Journal of Lipid Science and Technology》2007,109(3):214-224
Branched‐chain (bc) saturated fatty acids (SFA) have potential as oleochemical intermediates since they have better oxidative stability than linear unsaturated fatty acids (UFA) and have better low‐temperature properties than linear SFA. Previous studies in converting UFA to bc‐FA using clay catalysts have resulted in only modest yields and conversions. Recent reports, however, have suggested that certain zeolites can be effective catalysts for converting UFA to bc‐FA in higher yields and conversions. In this work, we examined the scope and potential of the zeolite‐catalyzed synthesis of bc‐FA starting from readily available monounsaturated linear FA. Our results show that common UFA such as oleic acid can be converted to bc‐isomers using modified Ferrierite zeolite catalysts with high conversions (98%) and high selectivity (85%) and that the zeolite catalysts are reusable for at least three cycles. The positions of branching (methyl) on the FA chain were determined from the GC‐MS spectra of the picolinyl esters of the bc‐FA. 相似文献
72.
本文通过胶体化学基本原理和实验数据,对水剂型腐植酸类液体肥料的组分、性质、浓度、流动性、稳定性、抗絮凝性等若干技术和质量问题进行了探讨,并提出一些改进建议。 相似文献
73.
Sang?Sung?Lee Soo?Chool?Lee Jae?Chang?KimEmail author 《Korean Journal of Chemical Engineering》2002,19(3):406-410
O-alkylation reaction of hydroquinone with excess methanol was performed by using alkali metal ion-exchanged zeolite catalysts
in a slurry type reactor to substitute the solid zeolite catalysts for the homogeneous liquid phase catalysts. This was also
done to produce selectively mono-alkylated 4-methoxyphenol, a valuable intermediate for the perfume, flavor, food and photo
industries. The effects of the basicity of various zeolites and reaction conditions such as temperature, reaction time and
the amount of catalyst on the catalytic activity and selectivity were tested to maximize the yield of 4-methoxyphenol. Thus
far, 84% selectivity at 95% conversion of hydroquinone was obtained at the optimum reaction conditions (240 ‡C, reaction with
0.6 g catalyst for 16 h), which was thought to result from the strong basic property and shape selectivity of the Cs ion-exchanged
NaX zeolite. 相似文献
74.
The hydrodynamic and gas mixing characteristics have been determined in a FCC regenerator (0.48 m I.D.x3.4 m high) with FCC
particles. Solids holdup in the dense bed decreases with increasing gas velocity, but it increases in the freeboard region.
The bubble/void fraction increases with an increase along the bed height at a given gas velocity and increases with increasing
gas velocity at a constant bed height. Backmixed tracer gas at the wall region is higher than that at the center region of
the bed. The gas backmixing coefficient decreases with increasing gas velocity. 相似文献
75.
Stormer-numerov approximation for numerical solutions of ordinary and partial differential equations
Stormer-Numerov approximations of high accuracy were developed for solutions of non-linear boundary value problems and nonlinear
elliptic partial differential equations. The approximations can be easily adopted also for parabolic partial differential
equations in one and more space dimensions and feature fourth-order accuracy. For boundary value problems only three nodes
are necessary to obtain the desired fourth order accuracy. The finite difference formula for parabolic partial differential
equations can be readily generalized to a nonequidistant mesh so that automatic regridding in space may be used. The Stomer-Numerov
approximations are important for solution of problems where storage limitations and computer time expenditure preclude standard
second order methods. Because of the fourth order approximations a low number of mesh points can be used for a majority of
chemical engineering problems. The application of Stormer-Numerov approximations is illustrated on a number of examples. 相似文献
76.
The effects of reaction temperature, pressure and residence time were investigated with a flow apparatus. Cellobiose decomposition
kinetics and products in suband supercritical water were examined at temperatures from 320 to 420 °C at pressures from 25
to 40 MPa, and at residence times within 3 sec. Cellobiose was found to decompose via hydrolysis and pyrolysis. The yield
of desired hydrolysis product, glucose, was the maximum value of 36.8% at 320 °C, 35 MPa, but the amount of 5-(hydroxymethyl)furfural
(HMF), fermentation inhibitor increased too because residence time increased in the subcritical region owing to decrease of
reaction rate. Meanwhile, though the yield of glucose is low in the supercritical region, the yield of HMF decreased compared
with the subcritical region; and at the minimum yield of HMF (380 °C, 25 MPa), the yield of glucose was 21.4%. The decomposition
of cellobiose followed first-order kinetics and the activation energy for the decomposition of cellobiose was 51.05 kJ/mol
at 40MPa. 相似文献
77.
Electrochemical cell current requirements for toxic organic waste destruction in Ce(IV)-mediated electrochemical oxidation process 总被引:1,自引:0,他引:1
Vasily V. Kokovkin Sang Joon Chung Subramanian Balaji Manickam Matheswaran Il-Shik Moon 《Korean Journal of Chemical Engineering》2007,24(5):749-756
The electrochemical cell for cerium oxidation and reactor for organic destruction are the most important operation units for
the successful working mediated electrochemical oxidation (MEO) process. In this study, electrochemical cells with DSA electrodes
of two types, single stack and double stack connected in series, were used. The performances towards the electrochemical generation
of Ce(IV) in nitric acid media at 80 °C were studied. The current-voltage curves and cerium electrolysis kinetics showed the
dependence on number of cell stacks needed to be connected in series for the destruction of a given quantity of organic pollutant.
The presence of an optimum region for Ce(III) oxidation with a contribution of oxygen evolution, especially at low Ce(III)
concentration (high conversion ratios), was found. The cells were applied for the Ce(IV) regeneration during the organic destruction.
The cell and reactor processes were fitted in a simple model proposed and used to calculate the current needed in terms of
Ce(III) oxidation rate and the number of cell stacks required for maintaining Ce(IV)/Ce(III) ratio at the same level during
the organic destruction. This consideration was based on the kinetic model previously developed by us for the organic destruction
in the MEO process. 相似文献
78.
含氟有机化合物氟化反应研究进展 总被引:2,自引:0,他引:2
介绍了含氟有机化合物的优点,一些常用的含氟有机化合物的分类和适用性,并介绍了主要的合成方法,按照合成物质的种类分为含氟非成环烷烃类、含氟环烷烃类及其衍生物和各自不同的应用.叙述了引入F原子或引入含氟端基的方法:电化学反应法、聚合反应法和其它反应法. 相似文献
79.
Bo Hyun Ryu Sang Yup Lee Dong Hyun Lee Gui Young Han Tae-Jin Lee Ki June Yoon 《Catalysis Today》2007,123(1-4):303-309
Carbon black has recently been reported to act as an effective catalyst for methane decomposition and to exhibit stable catalytic behavior despite carbon deposition, and thus it can be used for CO2-free production of hydrogen from natural gas. In this work, various carbon blacks with different primary particle size were investigated with respect to methane decomposition under atmospheric pressure from 1123 to 1223 K. Catalytic characteristics, such as activity, activation energy and reaction order, were investigated and compared. It was observed that with decreasing primary particle size (or increasing specific surface area), the specific activity increased and the activation energy decreased. The reaction orders for various pelletized, rubber-reinforcing carbon blacks were 0.6–0.7, about the same regardless of the primary particle size, while they were near 1 for fluffy carbon blacks. Fluffy carbon black showed higher activity and activation energy than the pelletized carbon black of the same primary particle size. Changes of the surface morphology during carbon deposition were observed by TEM. Variations of the number of active sites were discussed in regard of the primary particle size, carbon deposition and binder. The presence of different types of active sites was also suggested. 相似文献
80.
Kee Man LeeTae Kwon Kim Won Jin KimSeung Gon Kim Jeong Park Sang In Keel 《Fuel》2002,81(17):2249-2255
A visualization study on the effect of forcing amplitude in tone-excited jet diffusion flames has been conducted. Visualization techniques are employed using optical schemes, which are a light scattering photography. Flame stability curve is attained according to Reynolds number and forcing amplitude at a fuel tube resonant frequency. Flame behavior is globally grouped into two from attached flame to blown-out flame according to forcing amplitude; one sticks the tradition flame behavior which has been observed in general jet diffusion flames and the other shows a variety of flame modes such as the flame of a feeble forcing amplitude where traditionally well-organized vortex motion evolves, a fat flame, an elongated flame, and an in-burning flame. Particular attention is focused on an elongation flame, which is associated with a turnabout phenomenon of vortex motion, and on a reversal of the direction of vortex roll-up. It is found that the flame length with forcing amplitude is the direct outcome of the evolution process of the formed inner flow structure. Especially the negative part of the acoustic cycle under the influence of a strong positive pressure gradient causes the shapes of the fuel stem and fuel branch part and even the direction of vortex roll-up to dramatically change. 相似文献