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1.
The complex additives which contain (ω) 4%~6% phosphoric acid, 4%~6% calcium triple superphosphate, 80%~90% calcium phosphate, 2%~3% calcium carbonate, 2%~4% sodium hydrosuphite, 2%~4% ferric sulfate and 2%~4% aluminum sulfate were used to produce furfural by straw hydrolysis with sulfuric acid. The effect of reaction conditions on residue acidity and furfural productivity were investigated. The experimental results showed that the suitable conditions are sulfuric acid concentration 16% (ω), the added sulfuric acid amounting to 6% of all raw materials, the weight ratio of liquid to solid 2:1, the content of additives in straw 6%, temperature 100~130℃ and reaction time of 2 h, under which the productivity of furfural was 9.6% of rice straw and 10.5% of wheat straw respectively(or 80%~85% of the theoretical value), meanwhile the residue became a compound fertilizer.  相似文献   

2.
Thermal dehydration of gypsum and borogypsum was investigated under nonisothermal conditions in air by using simultaneous thermogravimetric-differential thermal analyzer. Nonisothermal experiments were carried out at various linear heating rates. Kinetics of dehydration in the temperature range of 373-503 K were evaluated from the DTA (differential thermal analysis)-TGA (thermogravimetric analysis) data by means of Coats-Redfern,Kissinger and Doyle Equations. Values of the activation energy and the pre-exponential factor of the dehydration were calculated. The results of thermal experiments and kinetic parameters indicated that borogypsum is similar to gypsum from dehydration mechanism point of view although it consists of boron and small amount of alkali metal oxides.  相似文献   

3.
水溶液中硫酸钾晶体生长动力学   总被引:3,自引:0,他引:3       下载免费PDF全文
陈勇  邵曼君  陈慧萍 《化工学报》2003,54(12):1766-1769
The single crystal growth rates of potassium sulfate in pure aqueous solution under different conditions were determined by photomicrography in a flow system for crystal growth. The effects of themain controlling factors, such as supersaturation, crystal size, solution velocity and crystal growth temperature, on crystal growth rates of potassium sulfate were discussed in detail by using non-linear regression from the experimental data, and several empirical relationships were given. The results showed that the growth rates of crystals increased with supersaturation, crystal size, solution velocity and temperature. Moreover supersaturation was the most important controlling factor influencing growth rates of crystals, crystal size and solution velocity were the secondary and temperature was the least.Furthermore, It was found that the growth rate of crystals along the [100] crystallographic axis was higher than that along the [001] in the same condition. The effect of every factor on crystal growth rates along the [100] crystallographic axis was stronger than that along the [001].  相似文献   

4.
Plenty of flue gas desulfurization (FGD) gypsum generated from coal-fired power plants for sulfur dioxide se-questration caused many environmental issues. Preparing calcium sulfate whisker (CSW) from FGD gypsum by hydrothermal synthesis is considered to be a promising approach to solve this troublesome problem and uti-lize calcium sulfate in a high-value-added way. The effects of particle size of FGD gypsum, slurry concentration, and additives on CSW were investigated in this work. The results indicated that fine particle size of FGD gypsum and moderately high slurry concentration were beneficial for crystal nucleation and growth. Three additives of magnesium chloride, citric acid, and sodium dodecyl benzene sulfonate (SDBS) were employed in this study. It was found that mean length and aspect ratio of CSW were both decreased by the usage of magnesium chloride, while a small quantity of citric acid or SDBS could improve the CSW morphology. When multi-additives of citric acid-SDBS were employed, the mean length and aspect ratio increased more than 20%. Moreover, surface morphology of CSW went better, and the particle size and crystal shape became more uniform.  相似文献   

5.
In order to obtain the reasonable operating conditions and minimize the power consumption in the stirred bioreactor, the hydrodynamic experiments in the stirred bioreactor have been taken to obtain the basic data. Subsequently, an Eulerian model for the gas–liquid–solid three phase flow in the stirred bioreactor has been proposed and the CFD simulation has been conducted. By comparing the results of experiment and simulation, it can be concluded that the simulation results were consistent with the experimental data. The inner relationship between operating variables and indicators could be obtained by comparing the results of just suspension speed, gas holdup, power consumption and operational maps, further the reasonable operating conditions could be also determined under the minimum power consumption. The operational maps could provide the theoretical foundation for industrial application of the gas–liquid–solid stirred bioreactors under the low solid concentration(no more than 20 wt%).  相似文献   

6.
酸性废水体系中硫酸钙反应结晶过程研究(英文)   总被引:1,自引:0,他引:1  
The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater dis charged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from plateletlike and nee dlelike shape to rodlike shape when the temperature was increased from 25 to 70 ℃. An increase in the agglom.  相似文献   

7.
Ni Mo bimetallic catalysts were prepared by a solid reaction method. On the Ni Mo catalyst, the selective liquid phase hydrogenation of nitrobenzene to aniline was achieved in slurry bubble mode. And the high yields(98.9%) were obtained under the conditions of 80 °C, solvent-free and atmospheric pressure. The effect of Mo on the catalytic behavior of Ni based catalyst was investigated. The characterization displayed that the inclusion of Mo could improve the specific surface area and pore volume, and the solid reaction method made metal Mo enrichment on the surface of catalyst. These two aspects should be responsible for excellent catalytic performance of Ni Mo catalyst. In sum, we described a simple and efficient Ni Mo catalyst and provided a facile and green procedure for liquid phase hydrogenation of nitrobenzene to aniline.  相似文献   

8.
The development of a process that could recover biofuel from industrial cellulose waste can not only reduce the negative environmental impacts by using fossil fuels, but also bring a green idea for the waste's disposing. In this study, hydrothermal pretreatment was optimized for cassava anaerobic residue, a cellulosic waste from cassava ethanol industry, to co-utilize xylose and glucose for producing bioethanol. The effect of the main pretreatment conditions, namely, temperature, solid content and time, was explored for the highest recovery of xylose in prehydrolysate and glucose in enzymatic hydrolysate. The single factor experiment results showed that the conditions for maximum xylose recovery in prehydrolysate and glucose recovery in enzymatic hydrolysate were 60 °C, 75 min, 10% solids and 160 °C, 75 min, 10% solids, respectively. Whereafter, response surface methodology(RSM) was applied to further optimize the pretreatment conditions for the maximum theoretical ethanol production through utilizing both xylose and glucose. A treatment at 163 °C, for 59 min and with 9.5%solids was found optimal, with the highest ethanol production of 20.2 mg·g~(-1) raw material. Furthermore, in order to assess the impacts of the pretreatment on cassava anaerobic residue, the changes in crystallinity and morphology for untreated and pretreated solids were investigated.  相似文献   

9.
Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied,The effects of shake speed,hydrophobictiy of organic solvent ,volume ratio of water phase to organic phase,pH value of aqueous phase and reaction temperature on the initial reaction rate,maximum yield and enantiomeric excess(ee) of the product were systematically explored,All the above-mentioned factors had significant infuence on the reaction.n-Hexane was found to be the best organic solvent for the reaction.The optimum shake speed,volume ratio of water phase to organic phase,pH value and reaction temperature were 150 r.min^-1,1/2,8 and 30℃ respectively,under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%,which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase ,To our best knowledge,this is the most satisfactory result obtained.  相似文献   

10.
The separation method using chiral stationary phase (CSP) for the preparation of enantioselective compound was widely used. In this work, supercritical fluid chromatography(SFC) was proposed to resolve the chiral mixtures. To determine the optimum operating conditions for the chiral separation of the racemic ibuprofen, the retention factors and resolutions with the change in pressure, temperature and the content of IPA (%, by volume) in supercritical CO2 were investigated. Experiments showed that the retention factor decreased with the increase of pressure and decrease in temperature. The retention factor was also influenced by the content of IPA in mobile phase, as the content of IPA in the supercritical fluid increased, the retention factor decreased. The resolution of the enantiomers became worse with the increase of IPA in the supercritical fluid. Through optimizing the experimental conditions, a SFC procedure with 13MPa, 311.15K and 4% IPA in CO2 was obtained. The peak shape of the enantiomers was symmetric with supercritical fluid chromatography when compared to the asymmetric peak shape obtained by the conventional liquid chromatography. This work demonstrated that the developed supercritical fluid chromatography procedure was suitable for the chiral separation of ibuprofen enantiomers.  相似文献   

11.
The partition coefficients of baicalin were measured in ethylene oxide and propylene oxide(EOPO)/salt aqueous two-phase systems at 298.15K,It was found that most of baicalin partitioned into EOPO-rich phase.The partition coefficients of baicalin varied from 10 to 120.The effect of various factors,including tie-line lngth,salt composition,molecular weight of EOPO,and solution pH,on the partition behavior was investigated on EOPO/salt systems.Furthermore the partition coefficients of baicalin were correlated using the modified Diamond-Hsu model.Good agreement with experimental data is obtained.The average relative deviations are less than 5.0%.  相似文献   

12.
Hydrocyclones are mechanical devices used in classifying and separating many different types of materials. A classification function of the hydrocyclone has been continually developed for solid–liquid separation. In the classification process of solids from liquids, it is desirable to reduce the amount of misplaced material; therefore, the separation sharpness, α(alpha), is a parameter that helps in evaluating misplaced material and has been developed as a model to help the designer predict the performance of the classification. However, the problem with the separation sharpness model is that it cannot be used outside the range of conditions under which it was developed. Therefore, this research aimed to develop the separation sharpness model to predict more accurately and cover a wide range of conditions using the multiple linear regression method. The new regression model of separation sharpness was based on a wide range of both experimental and industrial data-sets of 431 tests collaborating with the additional experiments of 117 tests that were obtained from a total of 548 tests. The new model of separation sharpness can be used in the range of 30–762 mm hydrocyclone body diameters and feed solid concentrations in the range of 0.5 wt%–80 wt%. When compared with the experimental separation sharpness, the accuracy of the separation sharpness model prediction has an error of 4.53% and ~ of 0.973.  相似文献   

13.
The transport of La(III) through a dispersion supported liquid membrane with polyvinylidene fluoride membrane as the liquid membrane support and dispersion solution including HCl solution as the stripping solution and 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) in kerosene as the membrane solution, was studied. As a result, the optimum transport conditions of La(III) were obtained as that concentration of HCl solution was 4.0 mol/L, concentration of PC-88A 0.16 mol/L, and volume ratio of membrane to stripping solution 30:30 in the dispersion phase, and pH value 4.0 in the feed phase. Ionic strength had no obvious effect on the transport of La(III). Under the optimum conditions, when initial concentration of La(III) was 0.8′10-4 mol/L, the transport rate was up to 96.3% during the transport time of 125 min. The kinetic equation was developed based on the law of mass diffusion and theory of interface chemistry. The diffusion coefficient of La(III) in the membrane and the thickness of diffusion layer between feed and membrane phases were obtained as 3.20′10-7 m2/s and 3.22′10-5 m, respectively. The calculated results were in good agreement with experimental results.  相似文献   

14.
Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent, volume ratio of water phase to organic phase, pH value of aqueous phase and reaction temperature on the initial reaction rate, maximum yield and enantiomeric excess (ee) of the product were systematically explored. All the above-mentioned factors had significant influence on the reaction. n-Hexane was found to be the best organic solvent for the reaction. The optimum shake speed, volume ratio of water phase to organic phase, pH value and reaction temperature were 150 r.min-1, 1/2, 8 and 30 ℃ respectively, under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%, which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase. To our best knowledge, this is the most satisfactory result obtained.  相似文献   

15.
Double emulsions are commonly stabilized by monomeric and/or polymeric emulsifiers. Pickering stabilization by solid particles such as colloidal microcrystalline cellulose has been mentioned only once as a possible technique to stabilize the external interface of the water-in-oil-in-water emulsion. No further work was carried out exploring this option. The present study shows that solid microcrystalline fat particles of α-form are capable of adsorbing at the water-oil interface and, together with other hydrophobic emulsifiers, can stabilize water-in-oil (W/O) emulsions. The crystals must be submicron in size in order to effectively adsorb and arrange at the interface. Large crystals do not fit and were found to flocculate as free crystals in the continuous oil phase. The α-form crystals can be obtained by flash-cooling saturated triglycerides in vegetable oils in the presence of emulsifiers, such as polyglycerol polyricinoleate (PGPR), that stabilize the dispersion and serve as α-tending crystal structure modifiers. It was assumed that PGPR also serves as a cross-linker or bridge between the crystalline fat particles and the water, and facilitates the anchoring of the fat particles in the oil phase in one direction while dangling itself in the water phase. The double emulsion droplets prepared with these W/O emulsions are relatively large in size (6–18 μm), but stable to coalescence. The marker (NaCl) does not seem to release with time, suggesting that the fat particles form microcapsules on the water interface, totally sealing the water from releasing its addenda. The systems seem to have a significant potential for food emulsions.  相似文献   

16.
亲和反胶团选择性萃取分离酵母乙醇脱氢酶   总被引:4,自引:0,他引:4       下载免费PDF全文
The reversed micelles were formed with cationic cetyltrimethylammonium bromide (CTAB) as surfactant and n-hexanol as cosolvent in the CTAB (50mmol L-1)/hexanol (15% by volume)/hexane system. Cibacron Blue 3GA (CB) as an affinity ligand in the aqueous phase was directly introduced to the reversed micelles with electrostatic interaction between anionic CB and cationic surfactant. High molecular weight (Mr) protein, yeast alcohol dehydrogenase (YADH, Mr = 141000) from baker's yeast, has been purified using the affinity reversed micelles by the phase transfer method. Various parameters, such as CB concentration, pH and ionic strength, on YADH forward and backward transfer were studied. YADH can be transferred into and out from the reversed micelles under mild conditions (only by regulation of solution pH and salt concentration) with the successful recovery of most YADH activity. Both forward and backward extractions occurred when the aqueous phase pH>pI with electrostatic attraction between YADH and CTAB. Th  相似文献   

17.
Selective hydrogenation of benzene is an atom economic green route to produce cyclohexene. The control of Zn species is the key to the catalytic performance of Ru–Zn catalysts. The influences of ZnO crystals on selective hydrogenation of benzene were explored. A series of Ru–Zn catalysts with different Zn contents and ZnO morphologies were prepared by changing the amount of NaOH in the co-precipitation process. The catalysts were characterized by N_2 physisorption, X-ray powder diffraction(XRD), inductively coupled plasma optical emission spectrometer(ICP-OES), scanning electron microscope(SEM), temperature-programmed reduction(H_2-TPR)and Malvern laser particle size analyzer. It is found that with increasing the amount of NaOH, the Zn content first increased then decreased, and the ZnO crystals changed from relatively thicker pyramidal-shaped crystals to slimmer needle-shaped crystals. The catalyst had the highest Zn content(22.1%) and strongest interaction between ZnO crystals and Ru particles at pH 10.6 of the solution after reduction. As a result, it had the lowest activity. The activity of Ru–Zn catalysts is affected by both the Zn content and the interaction between ZnO crystals and Ru particles. The effect of reduction time was also investigated. Prolonging the reduction time caused no significant growth of ZnO crystals but the aggregation of catalyst particles and growth of Ru nanocrystals, thus resulting in the decrease of catalytic activity.  相似文献   

18.
The melting temperature of Z coal ash was reduced by adding calcium–magnesium compound flux(W_(CaO)/W_(MgO)=1). In the process of simulated coal gasification, the coal ash and slag were prepared. The transformation of minerals in coal ash and slag upon the change of temperature was studied by using X-ray diffraction(XRD). With the increase of temperatures, forsterite in the ash disappears, while the diffraction peak strength of magnesium spinel increases,and the content of the calcium feldspar increases, then the content of the amorphous phase in the ash increases obviously. The species and evolution process of oxygen, silicon, aluminum, calcium, magnesium at different temperatures were analyzed by X-ray photoelectron spectroscopy(XPS). The decrease of the ash melting point mainly affects the structural changes of silicon, aluminum and oxygen. The coordination of aluminum and oxygen in the aluminum element structure, e.g., tetracoordinated aluminum oxide, was changed. Tetrahedral [AlO_4] and hexacoordinated aluminoxy octahedral [AlO_6] change with the temperature changing. The addition of Ca~(2+) and Mg~(2+) destroys silica chain, making bridge oxide silicon change into non-bridge oxysilicon; and bridge oxygen bond was broken and non-bridge oxygen bond was produced in the oxygen element structure. The addition of calcium and magnesium compound flux reacts with aluminum oxide tetrahedron, aluminum oxide octahedron and silicon tetrahedron to promote the breakage of the bridge oxygen bond. Ca~(2+) and Mg~(2+) are easily combined with silicon oxide and aluminum oxide tetrahedron and aluminum. Oxygen octahedrons combine with non-oxygen bonds to generate low-melting temperature feldspars and magnesite minerals, thereby reducing the coal ash melting temperatures. The structure of kaolinite and mullite was simulated by quantum chemistry calculation, and kaolinite molecule has a stable structure.  相似文献   

19.
Effects of salt and temperature on the liquid phase equilibrium of the (water + propionic acid + cyclohexanol) system were investigated. The liquid-liquid equilibrium data in the presence of KCl for various salt ionic strength of 0.5, 1.0, 1.5, 2.0, and 2.5 mol•dm3 and in absence of the salt at T (298.2, 303.2, and 308.2) K were determined. The experimental results were correlated based on the Othmer-Tobias equation and Pitzer ion-interaction model. Thermodynamic properties such as distribution coefficients and activity coefficients of propionic acid in water + cyclohexanol were determined. In addition, the separation factor, S, of the chosen solvent was obtained for the investigated system.  相似文献   

20.
Various conditions were investigated in detail for the novel organic template-free static hydrothermal synthesis of SUZ-4 zeolite in the presence of seeds. The obtained samples were characterized by XRD (X-ray diffraction), SEM (scanning electron microscope), TG (thermal gravimetric analysis), ICP (inductively coupling plasma) elemental analysis, nitrogen sorption isotherm and surface area. The results show that pure SUZ-4 zeolites with high crystallinity are obtained in a broad window of synthesis conditions: seed mass concentration 0.2%-2%, SIO2/A1203 molar ratio 21 25, KOH/SiO2 molar ratio 0.33 0.43, H20/SiO2 molar ratio 7.14-38.1, aging time 24 h, crystallization temperature 160℃, and crystallization time 6-10 d. Also, crystallinity and size of the rod-like SUZ-4 zeolite crystals are found to alter with the conditions.  相似文献   

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