以凝胶时间表征环氧树脂6101固化反应动力学方程

由旋转黏度计测定了环氧树脂6101分别与3种固化剂所形成的体系在固化过程中剪切黏度随时间的变化曲线,用环形剪切法处理获得相应的凝胶时间。考察了凝胶时间与固化剂、溶剂含量及固化温度等的变化规律,并以凝胶时间作为固化速度的表征,分别建立了相应体系的固化动力学方程。所建立的固化动力学方程,能同时适用于有无溶剂场合,可根据体系的组成(环氧树脂、固化剂和溶剂)及固化温度预测其凝胶时间,为优化防腐涂料配方及固化工艺提供了理论指导。     

结晶法由硫辛酸厂含铝废水制备铵明矾

以硫辛酸厂含铝废水中的Al3+为原料,采用结晶法制备铵明矾,研究了时间、NH4+/Al3+摩尔比、SO42-/Al3+摩尔比、温度、搅拌速度对废水中铝去除率和铵明矾产量的影响,对所制铵明矾与商品铵明矾进行比较. 结果表明,两者具有几乎相同的晶体结构、形貌和化学组成,所得产品符合同类工业产品标准. 结晶法用硫辛酸厂含铝废水制备铵明矾的适宜条件为：反应时间8 h,NH4+/Al3+ 1.40,SO42-/Al3+ 2.90,温度5~15℃,搅拌速度35~55 r/min. 宏观反应动力学表明,在晶体生长期,Al3+在边界层扩散传质为反应控制步骤,液相主体Al3+浓度C随时间t的变化关系符合方程C=(C0-Ci)e-kt+Ci. 当搅拌速度较低时,铵明矾晶体平均粒径大,分布宽;搅拌速度增加,晶体平均粒径减小,粒径分布变窄.     

粉煤灰与硫酸氢铵焙烧反应动力学

提出了NH4HSO4法焙烧粉煤灰提取Al2O3的新方法,考察了焙烧温度、粉煤灰中Al2O3与NH4HSO4摩尔比对粉煤灰中Al反应率的影响,研究了粉煤灰与NH4HSO4焙烧反应动力学. 结果表明,粉煤灰与NH4HSO4焙烧反应受固体产物层扩散控制,300, 350, 400℃下的反应速率常数分别为1.25′10-3, 1.56′10-3, 1.89′10-3 min-1,反应活化能为17.19 kJ/mol,反应动力学方程为1-2/3a-(1-a)2/3=0.0422exp[-17190/(RT)]t,最佳工艺条件为：焙烧温度400℃,Al2O3与NH4HSO4摩尔比1:8,焙烧时间60 min;该条件下Al反应率达90%以上,主要产物为NH4Al(SO4)2和NH4Fe(SO4)2.     

冶金过程多组分体系同时反应的动力学模型及应用

将钢铁冶金中的多组分同时反应作为一个综合的反应体系进行研究,考虑其中各反应间的影响. 根据冶金热力学和动力学原理建立多组分渣-金-气反应体系同时反应动力学模型,编制计算程序,得出成分对时间的变化曲线,并用含Fe-Cr-Mn-C的渣-金反应体系的实验进行了验证. 结果表明,金属液中C和Mn组分的计算浓度与实测值基本吻合,Cr的计算浓度与实测值的相对误差在9.1%以内. 在直流电弧下熔炼存在大气通过渣层向金属液的传氧现象,其数值与大气向钢液直接传氧的数值相同. 采用模型方法能较好地解释过程中的反应现象,揭示过程的机理.     

果糖结晶过程优化

通过实验筛选得到适合果糖结晶的混合溶剂,利用中通量结晶仪器Crystalline测定了果糖在水-乙醇（水的摩尔分数为0.39）混合溶剂中的溶解度和介稳区,采用Apelblat方程拟合了溶解度数据。基于热力学数据设计了晶种引晶的果糖冷却结晶工艺,过程优化得到的产品收率可达78.2%以上,纯度可达99%以上,晶体形貌规则,表面光滑,粒度分布窄。当晶体粒径大于100 μm时,利用粒度无关生长的粒数衡算方程建立了果糖连续结晶过程的动力学模型,模型表明晶体生长级数大于成核级数。     

Low-temperature H2-SCR of NO on a novel Pt/MgO-CeO2 catalyst

The selective catalytic reduction of NO by H₂ under strongly oxidizing conditions (H₂-SCR) in the low-temperature range of 100–200 °C has been studied over Pt supported on a series of metal oxides (e.g., La₂O₃, MgO, Y₂O₃, CaO, CeO₂, TiO₂, SiO₂ and MgO-CeO₂). The Pt/MgO and Pt/CeO₂ solids showed the best catalytic behavior with respect to N₂ yield and the widest temperature window of operation compared with the other single metal oxide-supported Pt solids. An optimum 50 wt% MgO-50wt% CeO₂ support composition and 0.3 wt% Pt loading (in the 0.1–2.0 wt% range) were found in terms of specific reaction rate of N₂ production (mols N₂/g_cat s). High NO conversions (70–95%) and N₂ selectivities (80–85%) were also obtained in the 100–200 °C range at a GHSV of 80,000 h⁻¹ with the lowest 0.1 wt% Pt loading and using a feed stream of 0.25 vol% NO, 1 vol% H₂, 5 vol% O₂ and He as balance gas. Addition of 5 vol% H₂O in the latter feed stream had a positive influence on the catalytic performance and practically no effect on the stability of the 0.1 wt% Pt/MgO-CeO₂ during 24 h on reaction stream. Moreover, the latter catalytic system exhibited a high stability in the presence of 25–40 ppm SO₂ in the feed stream following a given support pretreatment. N₂ selectivity values in the 80–85% range were obtained over the 0.1 wt% Pt/MgO-CeO₂ catalyst in the 100–200 °C range in the presence of water and SO₂ in the feed stream. The above-mentioned results led to the obtainment of patents for the commercial exploitation of Pt/MgO-CeO₂ catalyst towards a new NO_x control technology in the low-temperature range of 100–200 °C using H₂ as reducing agent. Temperature-programmed desorption (TPD) of NO, and transient titration of the adsorbed surface intermediate NO_x species with H₂ experiments, following reaction, have revealed important information towards the understanding of basic mechanistic issues of the present catalytic system (e.g., surface coverage, number and location of active NO_x intermediate species, NO_x spillover).     

气动絮凝在CEPT工艺中的应用研究

针对气动絮凝做了比较详细的介绍,阐述了其压缩空气搅拌的机理、目前的应用现状和特点等,并对气动絮凝动力学公式的推导过程及其存在的问题进行了分析,提出了相应的建议.     

Oxidation of a coal particle in flow of a supercritical aqueous fluid

A study was made of the conversion of single spherical coal particles of diameter 1–5 mm in a supercritical H₂O/O₂ fluid with an oxygen mass fraction of 0–6.6% in a semibatch reactor at a pressure of 30 MPa and a temperature of 673–1023 K. A decrease in the particle mass was observed in two parallel processes: gasification of coal with water and oxidation of coal with oxygen. An activation energy 19 ± 7 kJ/mole and a pre-exponential factor 10^−2±0.4 sec⁻¹ were obtained under the assumption of zero order for the concentration H₂O and an Arrhenius dependence for the rate of gasification with water. The oxidation with oxygen at a temperature above 780 K was found to be limited by the rate of O₂ diffusion to the coal organic matter. Below 780 K, the rate of heterogeneous oxidation with oxygen is described by a first-order reaction for the concentration of O₂ and a zero-order reaction for the concentration of H₂O with an activation energy of 150 ± 27 kJ/mole and a pre-exponential factor of 10^7.6±1.9 cm³/(g · sec). __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 23–31, March–April, 2008.     

含磷阻燃共聚酯的热降解动力学及耐热性能研究

采用不同的升温速率,用Kissinger法研究了聚对苯二甲酸乙二酯(PET)和侧基含磷共聚酯(FR-PET)在氮气气氛中的热降解动力学;采用时-温等效原理对其耐热性能进行了深入研究,确定了动力学参数与材料寿命方程之间的关系,为直接估算材料的使用寿命提供了捷径。结果表明,阻燃剂的引入降低了PET整个热降解过程的平均活化能、指前因子及反应级数,并使PET的不同失重率所对应的时间延长,即FR-PET的耐热性能有所提高;在同一温度下,360℃以前FR-PET失重一半的时间要短于纯PET,在360℃以后则长于纯PET,说明在高温下相对于纯PET要难于点燃。利用Kissinger法确定的寿命与动力学关系式可较准确地预测材料的寿命。     

Kinetic analysis on spherulite growth rate of polypropylene catalloys

The kinetic analysis on melt-crystallization of polypropylene catalloys (PP-cats) was conducted through measuring their spherulite growth rates. A multiple melting behavior of PP-cats was found through differential scanning calorimetry (DSC) and the corresponding crystalline microstructures of PP-cats were studied by wide-angle X-ray diffraction (WAXD). The calculated T_m^o value of propylene homopolymer (PP) suggests an obvious melting point depression of PP-cats. Moreover, it is found that the existence of ethylene-propylene copolymer could result in the changes of crystalline microstructure of PP and the PP crystal is in favor of growing along (040) lattice plane of α-monoclinic crystal. The crystal growth rate of PP-cats decreases with the increase of ethylene-propylene copolymer content in PP-cats. A comparison of crystallization kinetics between PP-cats and virgin iPP through a modified Lauritzen-Hoffman model indicates that there appears a transition from regimes II to III in iPP and PP-cats containing low ethylene-propylene copolymer content. However, for the PP-cats containing high ethylene-propylene copolymer content, crystallization always processes in regime II. In addition, both calculated nucleation parameter (K_g) and the fold surface free energy (σ_e) for PP-cats increase with the increase of ethylene-propylene copolymer content, implying that the existence of ethylene-propylene copolymer is unfavorable for the surface nucleation of PP and regular folding of the molecule chain. It is believed that an increase in viscosity of the melts induced by different compositions could remarkably slow crystallization growth down, because under this condition surface nucleation dominates as compared with crystal growth.