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Grand canonical ensemble Monte Carlo (GCMC) simulations were carried out to inve stigate the adsorption and separation of CO/H2 in carbon slit nanopores. Both H2 and CO are modeled as single site spherical LennardJones (LJ) molecules. The classical Steele 10-4-3 potential is used to describe the interaction betw een pore wall and fluid molecules. It was found that the adsorbed amount of H2 in the mixture is larger than that of pure H2 at the identical pressure, whil e that of CO is less for the mixture than for pure CO. By means of a series of s imulations, an optimal pore width of 0.74nm was obtained for adsorption separ ation. In this case, the adsorbed amounts of H2 and CO are 2.0 and 12.9mmol/g for an equimolar mixture at 300K and 1.0MPa, with an equilibrium separa tion factor of 6.5. The effects of varying the pressure, temperature and compos ition of gas mixture on adsorption were also investigated. It was found that the equilibrium separation factor increases with the decrease of pressure, with the increase becoming more significant at low pressure, and exceeds 9 at 0.03MPa . The equilibrium separation factor decreased almost linearly with the increase of temperature, while it is strongly affected by the concentration of H2 in th e bulk gas mixture.
An ultra-performance liquid chromatographic (UPLC) method has been developed for the determination of the six aromatic acids (o-phthalic acid, terephthalic acid, 3-carboxybenzaldehyde, m-phthalic acid, benzoic acid and m-toluic acid) in the wastewater discharged from a plant producing terephthalic acid. Analyses were performed using a Waters Acquity BEH C18 column (2.1mm×50mm, 1.7μm). A three-component mobile phase (methanol, water, formic acid) was used for gradient elution, and ultraviolet detection was performed at 254nm. The external standard method was employed. The linear range was 0.5-100μg/mL (with terephthalic acid in the range 0.25-50μg/mL).The correlation coefficients were all more than 0.9998. The inter-day relative standard deviations (RSD) of the six aromatic acids in three groups of samples were less than 1.5% (n=3). The mean standard recoveries of the six aromatic acids were between 80% and 110%, and RSD values were less than 6% (n=3), showing that the repeatability of the UPLC method is acceptable.
In order to avoid environmental pollution caused by by-products containing chromium(Ⅵ), which are produced by conventional chromium oxide technology, this paper presented a new production process for preparing chromium oxide by hydrothermal reduction of sodium chromate using starch as a reductive. On the basic of analyzing reaction mechanism, the kinetics of hydrothermal reduction of sodium chromate by starch(St) have been studied and the affecting factors for the rate of reduction of Cr(Ⅵ) have been investigated. The results show that reaction temperature, reaction time and reactant concentration are the main factors affecting the rate of reduction of Cr(Ⅵ). A constanttemperature, constantvolume and irreversible reaction kinetic model was selected to describe its reaction process and the kinetic equation can be expressed as:
r=-d［Cr(Ⅵ)］/dt=1.367×1013e-100.566×1000/RT［Cr(Ⅵ)］［St］, i.e., the pre-exponential constant, apparent activation energy and overall reaction order are 1.367×1013L/(mol·h), 100.566kJ/mol and second-order or pseudo-second-order, respectively. The reaction is of the chemical reaction controlled type and the reaction order is first-order or pseudo-first-order with respect to Cr(Ⅵ) and starch.
The structures of 2,7′-(ethylene)-bis-8-thioquinoline ［2,7′-Eth(tq)2］and its metal-organic compounds M［2,7′-Eth(tq)2］2 (M=Zn,Mg,Be) have been optimized at the B3LYP/6-31G level. The absorption spectra based on the above structures were obtained by the time-dependent density functional theory TD-B3LYP with the 6-31G basis set. At the same time, the hydrogen bonding in 2,7′-Eth(tq)2 and M［2,7′-Eth(tq)2］2 has been studied using natural bonding orbital (NBO) and atoms in molecules (AIM) analysis. All compounds are excellent electron transport materials, and the position of the absorption spectrum bands can be tuned by varying the nature of the metal cation coordinated to the anionic 2,7′-Eth(tq)2 ligand. The absorption bands of M［2,7′-Eth(tq)2］2 show a substantial red shift compared with that of 2,7′-Eth(tq)2. There are also hydrogen bonds present in the molecules, which increase the stability of the molecules.
Linear aliphatic/aromatic copolyesters have been synthesized. using dimethyl terephthalate, adipic acid and four diols (ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol) with different aliphatic/aromatic feed molar ratios. The thermal properties and biodegradabilities of poly(ethylene terephthalate-co-ethylene adipate) (PETA), poly(propylene terephthalate-co-propylene adipate) (PPTA), poly(butylene terephthalate-co-butylene adipate) (PBTA) and poly(hexylene terephthalate-co-hexylene adipate) (PHTA) were studied. For copolyesters prepared from the same diol but with different feed molar ratios, the glass transition temperature (Tg) decreased monotonically and both the melting temperature (Tm) and biodegradabilities increased with increasing content of aliphatic unit. As far as copolyesters with the same aliphatic/aromatic feed molar ratios but prepared from different diols are concerned, the biodegradabilities increased and Tg decreased with the increasing number of carbon atoms in the aliphatic diol. The value of Tm was found to decrease in the order Tm (PPTA)＞Tm(PBTA)＞Tm (PHTA)＞Tm(PETA), indicating that PPTA has the best thermal properties.
The copolymer (acrylamide-dimethyldiallylammonium chloride) (AM-DMDAAC) has been synthesized by inverse microemulsion polymerization by assist-initiation with ultrasonic waves. The effects of different initiatory systems, ultrasonic output power, amount and molar ratio of monomer and initiator on the intrinsic viscosity and cationic degree of the polymer were investigated. The results indicated that the synergy between initiator and ultrasonic waves led to copolymers with larger intrinsic viscosity and higher cationic degree. The influence of ultrasonic output power on polymer properties was significant: the maximum cationic degree was 17.70% (molar fraction) with an ultrasonic output power of 175W, while the maximum intrinsic viscosity was 3.9585dl/g with an ultrasonic output power of 125W. For an ultrasonic output power of 125W, monomer ratio n(AM)∶n(DMDAAC) of 6∶4, with the weight of monomer being 25% of that of the water phase, the molar concentration of initiator being 1.12% of that of the monomer and a molar ratio n(reducer)∶n(oxidizer) of 1∶1, the optimal combination of intrinsic viscosity and cationic degree, 3.2747dl/g and 17.35% respectively, were obtained.
Neodymium-doped yttrium aluminum garnet (Nd∶YAG) powders with different neodymium contents have been prepared by a precipitation method using urea and nitrate salts of aluminum, neodymium, and yttrium as raw materials. TG/DSC, FT-IR, XRD, SEM and fluorescence spectrophotometry were used to study the precursor composition and the influence of varying neodymium content on the phase composition, morphologies, and luminescence. The results showed that the precursor obtained by the urea method contained both hydroxide and carbonate phases. After sintering at 1000℃ for 2h, the phase composition of the powder changed with increasing Nd-doped content from a single phase YAG to the coexistence of YAG, yttrium aluminum monoclinic (YAM) and yttrium aluminum perovskite (YAP). The average particle diameter increased with increasing content of the neodymium dopant. The fluorescence intensity initially increased with increasing Nd content, and then decreased, with the maximum intensity appearing at a Nd content of 1.69%.
8-［4′-propoxy(1,1-biphenyl)-yloxy］-octanoic acid has been synthesized in two steps from 4,4′-dihydroxybiphenyl and the factors influencing the yield studied. The optimal reaction conditions were found to be as follows: in the first step, with a molar ratio n(4, 4′-dihydroxybiphenyl)∶ n(1-bromopropane)∶ n(alkali) of 1∶1.2∶1, and the weight of potassium iodide being 4.5% of that of 4,4′-dihydroxybiphenyl, under reflux for 8 hours, 4-propoxy-4′-hydroxybiphenyl was obtained; in the second step, with a molar ratio n-(potassium carbonate)∶ n(8-bromooctanoic acid ethyl ester)∶n (4-propoxy-4′-hydroxy)biphenyl of 2∶1.5∶1, and with the dosage of phase transfer agent (tetrabutylammonium bromide) being 10% of that of 4-propoxy-4′-hydroxybiphenyl, refluxing for 24 hours, followed by hydrolysis in methanol, afforded 8-［4′-propoxy (1,1-biphenyl)-yloxy］-octanoic acid in a yield of 40% with a purity of 94.9%. The chemical structure of 8-［4′-propoxy (1,1-biphenyl)-yloxy］-octanoic acid was confirmed by FTIR, and 1H and 13 C NMR spectroscopy. The phase transition and liquid crystalline behavior of 8-［4′-propoxy (1, 1-biphenyl)-yloxy］-octanoic acid were characterized by differential scanning calorimetry (DSC) and polarizing microscopy (POM). The experimental results indicated that 8-［4′-propoxy (1,1-biphenyl)-yloxy］-octanoic acid is a thermotropic liquid crystal.
The factors that directly affect ion exchange membrane electrolysis in alumina production by alkali-dissolution and carbonization-precipitation, such as the purification of the mother liquid, the design of the electrolysis cell, the electrode materials, the concentration of sodium carbonate, the electrolysis extent, the concentration of sodium hydroxide, the operating temperature and the current density, have been investigated. Aluminates in the mother liquid can be precipitated and filtered by adding sufficient sodium bicarbonate to regulate the pH value to under 10.2.The electrolysis technology used in the chlor-alkali industry can then be directly employed. Suitable operating conditions for preparation of NaOH and NaHCO3 by membrane electrolysis of Na2CO3 were found to be as follows: Na2CO3 anolyte with concentration of 1.5-1.8mol/L, NaOH catholyte with concentration of 5-7mol/L, temperature of 80℃, current density of 1000-2500A/m2, and electrolysis extent of 85％-90%. The cell voltage was decreased by 400mV when the Ru-Ti anode was replaced by Ru-Ni, which has lower overpotential of oxygen evolution, but the resistance of the latter to transpassive corrosion needs to be improved.
By analyzing the structure and properties of polyacrylonitrile (PAN)-based carbon fibers, it was found that the proportion of quaternary aromatic carbon atoms (i.e., those not bonded to hydrogen) in the low temperature treated structure is a key factor affecting the modulus of the final carbon fibers. The proportions of quaternary aromatic carbon atoms were determined by solid-state 13C nuclear magnetic resonance (NMR). The results showed that PAN fiber samples with smaller titer or which were treated for longer stabilization times had higher proportions of quaternary aromatic carbon atoms, and that the tensile moduli of the resulting carbon fibers were also higher.
Copolymers of styrene (St), ethyl acrylate (EA) and vinyltrimethoxylsilane (VTMS) have been synthesized by emulsion copolymerization using sodium dodecyl sulfate and polyoxyethylene octylphenol ether as emulsifiers in order to modify the thermal properties of the St-EA copolymers. The effects of varying the concentrations of emulsifier, initiator, and organosiloxane as well as the polymerization temperature on the polymerization conversion and rate were investigated in detail. The copolymer was characterized by infrared spectrometry (IR) and thermogravimetric analysis (TGA). Copolymerization of VTMS with St-EA was confirmed by the appearance of an absorption peak at 1096cm-1 (due to Si—O—Si bonds) in the IR spectrum. The siloxane moieties in the copolymer chain underwent hydrolysis and self-condensation, resulting in a change in the structure of the copolymers from linear into a cross-linked network. As a result, the thermal stability of the copolymers was enhanced. The polymerization rate increased with increasing polymerization temperature, molar concentration of emulsifier and molar concentration of initiator and decreased with increasing molar concentration of VTMS. The apparent activation energy and kinetic features of the polymerization system were also obtained.
A method for the determination of aconitine-type alkaloids, the main effective components in the compound prescription Fugui Gutong, has been developed. The alkaloid content was determined by acid dye colorimetry, based on the spectrometric features of the ion-pair compounds produced in the reaction between the aconitine-type alkaloids and bromcresol green in pH 3.5 citric acid-disodium hydrogen phosphate buffer solution, with the absorbance being measured at a wavelength of 412.5nm. The linearity range was 10.12-22.77μg/mL (r=0.9996, n=6). The average recovery of total alkaloids was 99.27%. The method is accurate, reliable, and easy to carry out and shows high selectivity for the determation of the content of aconitine-type alkaloids in Fugui Gutong.
Laccase has been immobilized on a ceramicchitosan composite support by using glutaraldehyde as crosslinking reagent. The effects of varying the immobilization conditions were investigated and the properties of the immobilized enzyme were characterized. The optimal immobilization conditions were found to be: 3.0mL of 1.25mg/mL of laccase in phosphate buffer (0.1mol/L,pH 4.0) reacted with 0.15g ceramic-chitosan composite support at 4℃ for 24h. Under these immobilization conditions, an immobilization efficiency of 51.0% was obtained. The maximum activity of the immobilized enzyme was 55.87U/g. The immobilized enzyme exhibited itsmaximum activity at pH 30 and the activities of the immobilized enzyme were highest at 25℃ and 50℃. The Km value of immobilized laccase with diammonium 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonate) was 66.64μmol/L in pH 3.0 buffer at 25℃. The thermal, operational, and storage stabilities of free laccase were all increased after immobilization.
Flue gas desulfurization using iron in Fenton's reagent, Fe/H2O2, to remove SO2 has been demonstrated. The effects of varying the mass concentration of H2O2, dosage of Fe, gas flow rate and inlet volume fraction on desulfurization efficiency were studied using a simple bubbler designed in our laboratory. High desulfurization levels were observed even when the mass concentration ofH2O2was only 6g/L. The optimum dosage of Fe was found to be 4.2g/L. The removal efficiency of SO2 was above 99% when the gas flow rate was 400L/h, and was unaffected by the inlet volume fraction. Similar results were demonstrated in a ring packed tower experiment.
Virtual simulation demands a design having a high programming level, which is difficult to realize in a simulation environment. By combining virtual technology and network technology, this paper puts forward a virtual simulation platform based on virtual reality, and makes use of 3ds Max and Virtools technology to devise a number of units with obstacle avoidance and synergistic movement functions. During the whole process, 3ds Max is used to create the virtual movement scenes and virtual movement units and Virtools is used to process the data and realize interactive control. Construction of this virtual platform does not involve expensive development costs and time, and can save a great deal of resources and can thus enable virtual reality technology to become more practical.
A new design of a multichannel rotary press filter is presented. The strength and deformation of the dewatering disk under complex loads have been determined by using finiteelement code. Optimization of the design of the dewatering disk is also presented. Numerical simulation shows that all the design demands can be satisfied. Compared with the initial design, the optimized design can save 28% of material, while both strength and deformation properties are satisfactory.
Through the training of time delays on the branches of a universal learning network (ULN) to the optimal values, the modeling precision for a continuous stirred tank reactor (CSTR)—a complicated nonlinear system with a large lag—was greatly improved. Furthermore, an improved ULN internal model control method (improved ULNIMC) based on fuzzy control theory has been proposed. In simulations of a CSTR using this new method, the tracking and fixed setpoint control when subjected to an external disturbance showed good performances.
A model of inositol 1,4,5-triphosphate-Ca2+ ( IP3-Ca2+) oscillations has been investigated. By applying the center manifold theorem and bifurcation theory, a theoretical analysis of bifurcation in the model was first performed. The results for the model not only exhibited saddlenode bifurcation and Hopf bifurcation but also showed that supercritical Hopf bifurcation and subcritical Hopf bifurcation play very important roles in the oscillations of Ca2+and IP3 concentrations. The numerical simulations, including the bifurcation diagram of fixed points, the bifurcation diagram of the system in twodimensional parameter space, and phase portraits, have been plotted in order to illustrate the theoretical analysis. By combining the existing numerical results with the theoretical analysis results in this paper, a complete description of the dynamics of IP3-Ca2+oscillations has been obtained.
Balanced biorthogonal multiscaling functions have been constructed using linear combinations of a pair of existing ones with compact support in order to solve problems in the application of unbalanced biorthogonal multiwavelets. Furthermore, by setting some realizable conditions on masks and designing nonlinear equations, we can obtain new scaling functions which have more desirable properties when the original scaling functions are of certain approximation order.
The orders for which the graphic arrangements determined by brokenwheel graphs are quadratic have been analyzed. With the aid of a computer, the orders for which the graphic arrangements with finite points are quadratic were found. Between these orders, there is regularity that can be extended to a graphic arrangement with n points. A sufficient and necessary condition for the brokenwheel graphic arrangements to be quadratic has been obtained.
