INTERPRETATION OF MICROMIXING EFFECTS ON FAST CONSECUTIVE-COMPETING REACTIONS IN SEMI-BATCH STIRRED TANKS BY A SIMPLE INTERACTION MODEL

A model is proposed for interpreting micromixing experiments in a semi-batch reactor. In these experiments, a fast consecutive-competing reaction system is used A + B → R, R + B → S, B being added either dropwise or as a pulse into an excess of A. A segregation index X_s = 2n_s/n_B0 is measured after completion of the reaction for various locations of the injection point. The macroscopic flow pattern is assumed to be known, essentially characterized by the recirculation time t_c. Micromixing then takes place within the cloud via a mechanism of interaction with the mean environment (IEM model, micromixing time t_m). Experimental results published by Barthole et al. (precipitation of barium sulphate) and Bourne et al. (diazo coupling) are successfully interpreted by this model. The influence of stirring speed, injection volume, concentration of species and mode of injection (pulse or dropwise) are especially well accounted for. This model provides a simple method for predicting the influence of mixing on selectivity in semi-batch reactors.     

Rheological Study on Tack of Pressure-Sensitive Adhesives

It is pointed out that the tack of pressure-sensitive adhesives should be expressed in terms of rolling friction coefficient f of the adhesives. Values of f were determined by both rolling ball and pulling cylinder experiments, and the dependence of f upon viscoelastic properties and thickness of the adhesives was studied. The experimental results were interpreted by the model theory previously proposed. It is also shown that the tack of pressure-sensitive adhesives by the conventional ball tack tests corresponds to f measured at the velocity ranging from v ∼ 10 to v ∼ 10² cm/sec.     

Comparison of evaluation procedures for the subcritical crack growth parameter n

The uncertainty in the determination of the exponent n in the equation of the subcritical crack velocity from four-point-bending experiments is investigated with respect to different evaluation methods. If the bending strength values are Weibull distributed, and the crack-extension parameter n is calculated by linear regression of the bending strength values of a number of experiments at different loading rates, an analytical solution can be given for the mean value and the standard deviation. It turns out that both the mean value and the standard deviation depend on the Weibull modulus m and the true value n₀. The analytical solution illustrates the essential features of this dependence on m and n₀. For other evaluation methods, e.g. the one proposed as the CEN standard, this dependence is investigated by a Monte-Carlo simulation for different crack-extension parameters n₀ and different Weibull moduli m. The standard deviation, which is calculated, is the theoretical lowest limit for certain evaluation procedures. By this, the estimation of the margin of error is put on a firm ground. Since the standard deviation increases with n₀, there is only a limited range in which n can be determined by four point-bending tests. A new evaluation method, which gives a better approximation than the method proposed as the CEN standard, is presented. The computational effort of this evaluation method is only slightly larger. It furthermore allows the number of experiments to be analytically calculated, which is necessary to obtain a certain accuracy.     

亚马逊莓（Euterpe oleracea）美白相关成分和作用研究现状

作为棕榈科植物Euterpe属中分布最为广泛、研究与商业化程度最高的品种，Euterpe oleracea（E. oleracea）的果实（为亚马逊莓的一种）因其卓越的抗氧化性能而跻身“超级水果”之列，同时也成为国际上新的研究热点。本文综述了E. oleracea的相关成分和作用研究现状，指出其富含不饱和脂肪酸、氨基酸、维生素等营养成分，并含有大量的以酚类化合物为主的生物活性物质，例如黄酮类化合物、酚酸、花青素与原花青素等。其中，总脂肪酸、亚油酸、阿魏酸、槲皮素、原儿茶酸、原儿茶酸甲酯等成分被证实具有皮肤美白作用。对E. oleracea进行的细胞实验和动物实验发现，其果肉提取物具有抑制酪氨酸酶活性以及使细胞免受紫外线引起的氧化应激伤害等潜在的皮肤美白功效。文章建议在未来的研究中，对E. oleracea的美白成分进行进一步挖掘，并通过动物实验与临床试验对其美白功效进行验证。     

多指标正交实验优化可发性三聚氰胺甲醛树脂的制备

用己内酰胺作改性剂,通过正交实验设计考察了甲醛和三聚氰胺摩尔比(F/M)、溶液pH值、反应温度(T)和反应时间(t)对可发性三聚氰胺甲醛(MF)树脂的储存期、固含量、黏度、MF泡沫密度及泡孔尺寸均匀性的影响,运用综合评分法和综合平衡法对正交实验结果进行了分析,得出最优水平组合:F/M=2.5,pH=8.0,T=90℃,t=60min。最优条件下合成的MF树脂可发泡性良好,制得的泡沫性能优良。     

Thermal effects in styrene-butadiene rubber at high hydrostatic pressures

The temperature changes as a result of rapid hydrostatic pressure applications are reported for unvulcanized styrene-butadiene rubber (SBR) in the reference temperature range from 292 to 405 K and in the pressure range from 13.8 to 200 MN m⁻². The thermal effects were found to be a function of pressure and temperature. A curve fitting analysis showed that the empirical curve (∂T/∂P)=ab(ΔP)^b−1, described the experimental thermoelastic coefficients obtained from the experiments. The data were analysed by determining the predicted thermoelastic coefficients derived from the Thomson equation (∂T/∂P)=T_o/C_p. The experimental and the predicted Grüneisen parameter γ_T were also estimated. Close agreement was found at low pressure but differences were observed at higher pressures between the experimental and expected values for the thermoelastic coefficients and the Grüneisen parameter.     

Experimental studies of power consumption for agitated vessels equipped with non-standard baffles and high-speed agitator

The influence of the geometrical parameters of non-standard baffles on power consumption has been investigated for agitated vessels equipped with a high speed agitator (Rushton disc turbine, pitched-blade turbine or propeller) The following geometrical parameters of the baffles have been tested: number J, width B, length L and distance p between the lower edge of the baffle and the bottom of the vessel. Measurements were carried out according to a second-order rotatable design of experiment, using the strain gauge technique. The results of the experiments have been approximated in the form of equations.     

Chain length dependence of termination rate constant: computer experiment of effects on the kinetics of radical polymerization of styrene

The kinetics of the radical polymerization of styrene, initiated by AIBN, have been studied by computer experiments. The models adopted assume a termination rate constant for polystyryl radicals with degrees of polymerization m and n, given by:

k_t,mn=km^-n^-

Deviations from simple kinetic rules have been found for 0.0. For example, the rate of polymerization is roughly proportional to the 0.45 power of initiator concentration for = 0.1. Conventional methods for the kinetic study of radical polymerizations are shown to come to erroneous conclusions if the effects of the chain length dependence of termination rate constant are not taken into account.     

ON THE ROLE OF CONCENTRATION LEVEL OF NONDIFFUSING SPECIES IN GAS PHASE MASS TRANSFER AT HIGH TRANSFER RATES

Re-evaluation of high mass flux literature data from evaporation and absorption experiments suggest the validity of y_BM as a good correlation variable for predicting gas phase mass transfer at high transfer rates. This was done by testing Greiner and Winter's engineering model where y_BM explicitly emerges after manipulating their model equations. The manipulated model agrees well with the literature data within the range of 0.961 ≥y_BM ≥ a 0.549 and 7.3333 ≥ B ≥ -0.4757 which covers the mostly commonly chemical engineering conditions and geometries. Thus, the y_BM serves not only as a good correlation variable as has been commonly used under low to moderate mass transfer rales, but also applies to the controversial case of high mass transfer rates.     

盐酸氟桂利嗪的合成工艺改进

以氟苯和肉桂醇为起始原料,氟苯经傅克烷基化、水解、羰基还原和溴代得到双(4-氟苯基)溴甲烷,肉桂醇经氯代,再和哌嗪反应制得肉桂基哌嗪,然后与双(4-氟苯基)溴甲烷反应,最终制得产品.并做了重复性实验验证了稳定性.通过工艺条件的优化,确定合成盐酸氟桂利嗪的最佳工艺条件为:n(氟苯):n(AlCl₃):n(PEG-400)=1:1.1:0.04,45℃反应2h,n(4,4'-二氟二苯甲酮):n(硼氢化钠)=1:0.6,乙醇作溶剂,50℃保温2h,选择NBS作为4,4'-二氟二苯甲醇的溴代试剂,AIBN做引发剂,物料比为n(4,4'-二氟二苯甲醇):n(NBS):n(AIBN)=1:1:0.03,80℃反应3h,n(肉桂基氯):n(哌嗪)=1:3.5,50℃保温1.5h,粗品肉桂基哌嗪通过水洗、萃取和成盐等步骤提纯,收率达56.2%.盐酸氟桂利嗪的总收率由18.5%提高到30.0%,产物纯度在99%以上.产物结构经红外和质谱进行了表征确定.     

Bioleaching of molybdenum from coal liquefaction catalyst residues

It has been shown that the bacterium Thiobacillus ferrooxidans can solubilize MoS₂ from coal liquefaction catalyst residues. The MoS₂ is formed during the liquefaction process from a molybdenum catalyst precursor. MoS₂ is insoluble; in order to be recovered and reused, it must be converted to a soluble form. T. ferrooxidans can oxidatively solubilize the molybdenum in MoS₂ to molybdate, in which form it can be recovered as a soluble or HCl extractable material. Bioleaching experiments show that with a starting cell concentration of 1.0 × 10⁷ cells ml⁻¹, or greater, a significant amount of the molybdenum in the residue was solubilized. These experiments indicate that the amount of molybdenum biologically solubilized from the liquefaction residues is dependent on inoculum size, with all strains of T. ferrooxidans tested having equal ability, and on the particle size of the residue. An important factor in the solubilization of MoS₂ by T. ferrooxidans is the inhibitory effect of molybdate. Literature reports that as little as 10 ppm molybdate is inhibitory to growth or ferrous iron oxidation. However, leachates containing in excess of 70 ppm molybdenum (equivalent to 116 ppm molybdate) were generated as a result of bioleaching of the liquefaction residue. When cells from previous leaching experiments were used to inoculate flasks containing fresh media and additional liquefaction residue, the bacteria were able to bioleach the fresh residue. Recent experiments have focused on the ability of T. ferrooxidans to produce protective agents in the leachate that minimize the inhibitory effects of molybdate. We found that production of the protective factor(s) did not depend on previous exposure of the cells to molybdenum or liquefaction residue.     

MnO x /ZrO2 催化剂制备及催化臭氧氧化降解甲基橙

以商品化ZrO₂为载体,采用等体积浸渍法制备MnO _x /ZrO₂催化剂,对目标污染物甲基橙溶液进行催化臭氧降解效果研究。比较不同焙烧温度（350、400、500和550℃）、不同MnO _x 负载量（5%、10%、15%和18%）等制备条件对催化剂活性的影响,结果表明：在400℃,MnO _x 负载量为15%时,催化剂对催化臭氧降解甲基橙溶液表现出最好的活性。反应进行60 min后,甲基橙溶液的脱色率达92.8%,较单独臭氧氧化提高了36.1%。催化剂15%MnO _x /ZrO₂（400℃）的酸碱使用范围（pH为2.7、6.5、8.7、10.8）实验表明：甲基橙溶液不同初始pH条件同样会影响催化剂的活性,且pH=2.7时表现出最好的催化效果,甲基橙脱色率可达95%。循环实验表明,15%MnO _x /ZrO₂（400℃）具有较好的稳定性,催化剂循环使用三次后,甲基橙溶液脱色率仍保持在85%以上,且活性组分的流失是降低催化剂活性的一个重要原因。     

运用粒子图像测速仪研究双层桨搅拌槽内流体流动

The flow fields in a dual Rushton impeller stirred tank with diameter of 0.48 m （T） were measured by using Particle Image Velocimetry （PIV）. Three different size impellers were used in the experiments with diameters of D = 0.33T, 0.40T and 0.50T, respectively. The multi-block and 360° ensemble-averaged approaches were used to measure the radial and axial angle-resolved velocity distributions. Three typical flow patterns, named, merging flow, parallel flow and diverging flow, were obtained by changing the clearance of the bottom impeller above the tank base （C1） and the spacing between the two impellers （C2）. The results show that while C1 is equal to D, the parallel flow occurs as C2≥0.40T, C2≥0.38T and C2≥0.32T and the merging flow occurs as C2≤0.38T, C2≤0.36T and C2≤0.27T for the impellers with diameter of D=0.33T, 0.40T and 0.50T, respectively. When C2 is equal to D, the diverging flow occurs in the value of C1≤0.15T for all three impellers. The flow numbers of these impellers were calculated for the parallel flow. Trailing vortices generated by the lower impeller for the diverging flow were shown by the 10° angle-resolved velocity measurements. The peak value of turbulence kinetic energy （ k/V^2tip = 0.12-0.15 or above） appears along the center of the impeller discharging stream.     

链格孢菌对库存喷气燃料性质的影响

研究链格孢菌在生长过程中对库存喷气燃料总酸值等性质的影响。以菌丝干重为指标,通过三因素三水平正交试验,筛选了链格孢菌最佳培养条件;构建喷气燃料、培养基、菌液培养体系,研究了链格孢菌生长繁殖对喷气燃料总酸值以及银片腐蚀试验、水反应试验、表面张力等的影响;构建以喷气燃料替代物十二烷为唯一碳源的培养体系,通过气相色谱检测十二烷残留率,研究了链格孢菌生长繁殖与十二烷的降解特征。链格孢菌最佳培养条件为30℃、初始pH为8、钠元素浓度为0;链格孢菌在生长繁殖过程中,能产生酸性物质,增加喷气燃料总酸值、降低水相pH,能产生表面活性物质,降低喷气燃料表面张力、水相表面张力,但培养周期内对银片腐蚀试验、水反应试验无显著影响;链格孢菌能以十二烷为唯一碳源进行生长繁殖。链格孢菌在生长繁殖过程中,能增加喷气燃料总酸值,降低喷气燃料、水相表面张力以及水相pH。     

潜热型功能热流体在微小管道内的换热特性

针对现代电子器件的散热需求,采用潜热型功能热流体为工作介质进行实验,并搭建流动换热实验台,研究5%、10%和15%质量分数下潜热型功能热流体与去离子水在微小圆形管道内的换热特性,结果表明,在雷诺数Re为300~1000范围内,潜热型功能热流体均表现出比水更好的冷却性能及更低的壁面温度,在实验测试范围内,相变引起的壁面温度降低率最大可达26.8%;潜热型功能热流体平均Nu随着流动Re数的增加而增加,并通过对实验数据分析,拟合了平均Nu数与流动Re数、质量浓度和流体Pr数的经验公式,最大偏差不超过7.5%,可以较好反应潜热型功能热流体的换热特性;潜热型功能热流体沿着管道长度方向的强化换热比与潜热型功能热流体浓度及流动Re数有关,存在强化换热的最佳长度。     

非等温液-液对置撞击面温度分布均匀性

对不同条件下非等温过程液-液对置撞击后形成的气液混合撞击面的温度分布均匀性进行了研究。以温度不均匀系数和撞击面温度分布作为评价标准,利用Mixture模型数值模拟撞击过程,并基于平面激光诱导荧光（PLIF）技术进行可视化测量实验验证计算模型。通过对不同的喷嘴出口速度（v）、喷嘴对置间距（L）以及湍动能等条件下撞击面温度分布进行研究。结果表明,喷嘴直径和喷嘴对置间距一定时,增加喷嘴的出口流速,则温度不均匀系数整体呈下降趋势;喷嘴直径和喷嘴出口流速一定时,非等温液-液对置撞击后形成区域温度场分布随喷嘴间距的增加,其温度分布区间呈减小趋势。L=3D时,温度的分布区间最小,温度场分布最均匀。湍动能的分布曲线越平稳,液-液对置撞击后形成的气液混合撞击面的温度分布越均匀。     

Ce1-xNixOy氧载体在化学链甲烷重整耦合CO2还原中的应用

化学链甲烷重整耦合CO₂还原技术既能生产合成气还可以还原CO₂生成CO。采用共沉淀法制备不同Ce/Ni摩尔比的系列Ce_1-xNi_xO_{y（x = 0,0.2,0.4,0.6,0.8,1）氧载体。通过XRD、BET、XPS及CH4-TPR等表征对氧载体的理化性质进行了研究。系统考察了Ce1-xNixOy氧载体在化学链甲烷重整耦合CO2还原反应中的反应性能。与单一金属氧化物NiO和CeO2相比,Ce1-xNixOy复合氧载体在该反应中具有更高的活性和热稳定性。在甲烷部分氧化阶段,Ce0.2Ni0.8Oy和Ce0.4Ni0.6Oy氧载体具有较高的CH4转化率。经历了20次redox循环实验,Ce0.2Ni0.8Oy氧载体的CO2转化率几乎保持不变,表明Ce0.2Ni0.8Oy氧载体具有较高的热稳定性。}     

“一步法”微流控制备大直径复合乳粒中几何尺寸调控规律研究

复合乳粒几何尺寸的精密调控对于实现特定规格参数要求的聚合物空心微球的可控制备具有重要意义。基于“一步法”微流控装置,通过大量的实验获得了以油相与内水相流量比R和连续相毛细管数Ca为变量的复合乳粒构建操作区域图,并在能稳定形成复合乳粒区域范围内探讨了Ca、R以及管道尺寸对大直径复合乳粒几何尺寸的影响规律。实验结果表明：随着连续相毛细管数增大,复合乳粒几何尺寸(内径、外径和壁厚)均减小;随着油相与内水相流量比增大,复合乳粒内径减小,壁厚增大,而外径则呈现先减小后增大的趋势。此外,复合乳粒几何尺寸随管道直径增大而增大,且存在极限尺寸。实验结果可为单分散大直径复合乳粒的定量可控制备提供实验设计依据。     

CO在成型催化剂上脱除NOx的反应动力学模型

采用实验和模拟相结合的方法研究了NO_x在固定床反应器中的吸附还原过程。选取商业常用的堇青石和TiO₂为主要的成型催化剂基体材料，以铜铁铈复合型金属氧化物为活性成分，制备了蜂窝成型催化剂，对蜂窝催化剂的吸附性能和脱硝还原活性进行测定。建立了固定床反应器中CO脱除NO_x的反应动力学模型，由于CO法脱硝反应的解耦分解，脱硝反应模型也由吸附模型和还原模型组成。吸附模型由固相和气相的微分质量平衡方程建立，还原模型由一组微分方程组成。通过固定床NO_x吸附曲线和不同温度下NO_x的转化率对模型中的关键参数进行了拟合，得到了CO在成型催化剂上脱除NO_x的反应动力学模型，该模型与实验数据吻合较好。在此基础上，模拟了其他条件下吸附过程的穿透曲线和还原反应的转化率。此模型能较好地揭示CO在蜂窝催化剂上还原NO_x的反应动力学，为CO法成型催化剂脱除NO_x的实验或者工程提供理论指导。     

Kinetics of adherence of a rigid truncated cone on an elastic half-space (unfilled natural rubber)

The equilibrium contact of a rigid flat-ended cone, applied against the flat and smooth surface of a soft elastomer sample (unfilled natural rubber), is studied with the help of fracture mechanics concepts, which can be easily introduced in this class of problems by using Sneddon's solution (Int. J. Eng. Sci. 3 (1965) 47) of Boussinesq's problem extended to all axisymmetric adhesive punches with a convex profile. The kinetics of adherence is measured when an imposed tensile force is applied in order to disturb the size of the contact area. Variations of the strain energy release rate G and of the associated dissipation function Φ=(G−w)/w, where w is the Dupré energy of adhesion, are studied as a function of the crack propagation speed V at the interface between a truncated cone made of PMMA and the rubber sample (the limit of the contact is considered as a crack tip). As expected, a master curve Φ(V) is found, confirming the variation of Φ as the 0.55 power function of V, as recently established by Barquins et al. in adherence of a perfect cone and flat-ended spheres in pull-off/push-on tests, adherence and rolling of cylinders experiments and rebound of balls tests, with the same elastic rubber-like material.