TPC方法研究催化剂热分解动力学

设计了ＴＰＣ方法研究催化剂前驱体的热分解；对ＴＰＣ方法求取催化剂的热分解动力学方程进行了理论推导；采用ＴＰＣ方法试验求得了Ｎｉ－Ｚｎ／Ｃ催化剂的热分解动力学参数。试验表明，ＴＰＣ方法能直观、灵敏、方便地反映催化剂活性组份前驱体的本征热分解。     

DSC study on simultaneous interpenetrating polymer network formation of epoxy resin and unsaturated polyester

A kinetic study on simultaneous interpenetrating polymer network formation of epoxy resin based on diglycidyl ether of Bisphenol A (DGEBA) and unsaturated polyester (UP) was performed by means of differential scanning calorimetry (DSC). Isothermal DSC characterizations of neat resins and their mixture (in a weight ratio of 50/50) were performed at different temperatures. Dynamic DSC characterization of the systems were performed at three different heating rates. A lower total heat of reaction developed during simultaneous polymerization in dynamic DSC tests was found, compared to the total heats developed during pure resins network formation. This phenomenon can be interpreted as an effect of network interlock that could not be compensated for completely by an increase in curing temperature. The kinetics of the reactions was described by empirical models. The DGEBA, in a 50/50 UP/DGEBA blend, indicated a higher rate constant than the pure DGEBA. The obtained results suggests that the hydroxyl end group of UP in the blend provided a favorably catalytic environment for the DGEBA cure. The results are in good agreement with the literature data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2689–2698, 2002     

Application of degradation kinetics to the rheology of poly(hydroxyalkanoates)

The time‐dependent rheological behavior of a series of 3‐hydroxybuytrate‐based semicrystalline copolymers is employed to determine the expected rheological curves that would be generated in the absence of any polymer degradation. Both dynamic frequency sweep and shear rate sweep experiments were analyzed. A model for the degradation kinetics, coupled with standard rheological relationships, was employed to extrapolate the measured sweeps to predicted curves at time zero, prior to degradation. The model is broadly applicable over a wide range of frequencies or shear rates, and generates a single degradation rate constant k for each polymer studied. A similar, although ad hoc, procedure was applied to the dynamic storage and loss moduli. The model provides a method for determining the rheological behavior of degrading polymers over a time interval, typically found in processing applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1794–1802, 2006     

Kinetics of phenol oxidation in a trickle bed reactor over active carbon catalyst

The wet air oxidation of phenol over a commercial active carbon catalyst was studied in a trickle bed reactor (TBR) in the temperature and oxygen partial pressure ranges of 120–160 °C and 0.1–0.2 MPa, respectively. The performance of the active carbon was compared in terms of phenol and COD destruction. The weight change of active carbon due to reaction was also measured. Finally, oxic phenol adsorption isotherms were assessed in batch conditions at 25, 125 and 160 °C. In order to use the conversion data obtained from the TBR for a kinetic study, special care was taken to check the kinetic control in the TBR experiments. Several kinetic models including power law or Langmuir–Hinshelwood expressions were considered to describe the catalytic oxidation of phenol over active carbon. The simple power law model with first order dependence on both phenol and oxygen concentration predicted satisfactorily the experimental data not only over the entire range of operating conditions studied, but also outside its validity range. Copyright © 2005 Society of Chemical Industry     

Expressing the equivalence of non‐isothermal and isothermal heat sterilization processes

Currently, the sterility of heat‐processed food and pharmaceuticals is assessed in terms of an F₀ value, based on the equivalence of the heat treatment to an isothermal process at a reference temperature. This F₀ value, however, has a meaning if, and only if, the inactivation kinetics of the targeted spores (or cells) follow a first‐order relationship and the temperature dependence of the D value, the reciprocal of the rate constant, is log‐linear. There is growing evidence that these conditions are not satisfied by many spores, including those of Clostridium botulinum and vegetative cells. Consequently, a replacement for the F₀ value is proposed in the form of a momentary equivalent time at the reference temperature based on the actual survival pattern of the spores, which need not be log‐linear. This equivalent time can be calculated together with the theoretical survival ratio in real time, thus enabling an operator to monitor the lethality of ongoing industrial heat processes. The concept is demonstrated with published survival data of C. botulinum, for which the Weibullian and log‐logistic models served as primary and secondary models, respectively. The safety factor according to the proposed method is in the number of added minutes of processing, beyond the theoretical time needed to reduce the survival ratio of the targeted spores or cells to a level that would produce practical (or commercial) sterility. Copyright © 2006 Society of Chemical Industry     

Interfacial activity and rate of palladium(II) extraction with decyl pyridine monocarboxylates

Decyl isonicotiniate and decyl nicotiniate permit a rapid extraction of palladium(II) from its hydrochloride solutions. Decyl picoliniate is not a suitable extractant. 4-Octylphenylamine can act as a phase transfer catalyst when its concentration in the organic phase is at least 2·5 × 10^?4 M . It seems that the interfacial adsorption of pyridine carboxylates and of 4-octylphenylamine is not the decisive phenomenon in palladium(II) extraction. The negligible protonation of the pyridine-type extractants and the phase transfer catalysis explains well the quick extraction of palladium(II) with the commercial and highly hydrophobic extractant ACORGA CLX-50.     

Mathematical modelling of the alcoholic fermentation of glucose by Zymomonas mobilis mobilis

The kinetics of alcoholic fermentation of a strain of Zymomonas mobilis, isolated from sugarcane juice, has been studied with the objective of determining the constansts of a non-structured mathematical model that represents the fermentation process. Assays in batch and in continuous culture have been carried out with different initial concentrations of glucose. The final concentrations of glucose, ethanol and biomass were determined. The following kinetic parameters were obtained: μ_max, 0·5 h^?1; K_s, 4·64 g dm^?3; P_max, 106 g dm^?3; Y_x/s, 0·0265 g g^?1; m, 1·4 g g^?1 h^?1; α, 17·38 g g^?1; β, 0·69 g g^?1 h^?1.     

Drying of Chestnuts (Castanea sativa Mill.) after Osmotic Dehydration with Sucrose and Glucose Solutions

Chestnuts were dehydrated by using a combined method of osmotic dehydration followed by air drying. Samples were osmotically pretreated with sucrose (60% w/w) and glucose (56% w/w) for 8 h, air-dried at temperatures of 45, 55, and 65°C, at a relative humidity of 30% and at a velocity of 2.7 m·s^-1 and the experimental data of the drying kinetics were obtained. Whole samples were dried with different peelings: (a) removal of endocarp and pericarp (peeled) and (b) additionally the internal rough surface (cut). In all cases, cut chestnuts show greater drying rates than peeled samples, indicating that a significant mass transfer resistance in the layer nearest to the surface takes place. Peeled samples pretreated with sucrose solutions behave in a similar way to untreated samples. For the rest of the samples, the cut samples osmotically treated with sucrose solutions and all the samples treated with the glucose solution, the drying rates decrease during drying. Drying kinetics are successfully modeled by employing a diffusional model that takes the shrinkage into account. The effective coefficient of water diffusion was evaluated and correlated with temperature. The quality of the final product was monitored by color change. In spite of the fact that the total color difference is not modified by the osmotic treatment, the L*, a*, and b* color coordinates of cut samples treated with sucrose and glucose solutions do undergo changes; the L* and a* coordinates change less than the b*.     

酶促合成生物柴油反应动力学

以Candidasp.99-125脂肪酶为催化剂,甘油三油酸酯和甲醇为底物,采用有序机制模型对酶促合成生物柴油的酯交换反应动力学进行了研究,并与经典乒乓机制模型进行了比较。研究结果表明,反应初速率的实验值与有序机制模型方程的计算值吻合很好。对于固定化Candidasp.99-125脂肪酶催化合成生物柴油的酯交换反应机理进行研究,采用有序机制模型比经典乒乓机制模型更为精确。反应过程中,醇抑制为竞争性抑制,在甘油三油酸酯浓度较小的范围内,醇抑制作用较为显著,醇浓度越低反应初速率越快。该有序机制模型可用来预测生物柴油的生产批次或连续反应器中酯交换反应的速率,确定最佳底物油脂和醇的浓度。