A three-phase nonequilibrium model for catalytic distillation

Nonequilibrium model for steady state simulation of catalytic distillation is presented. Mathematical model takes into account both mass and heat transfers across the gas liquid interface and through the liquid-solid (catalyst) interface. Equations describing the mentioned phenomena are based on the effective diffusivity approach. The resulting system of nonlinear algebraic equations was implemented in the FORTRAN programming language and solved by the BUNLSI (Ferraris & Tronconi, 1986) solver. The described model was verified using the experimental data obtained from a continuous distillation column equipped with catalytic packing. As an experimental model system, synthesis of propyl propionate from propan-1-ol and propionic acid was chosen. Comparison of experimental and simulation data is presented, and appropriateness of the developed model for other types of catalytic distillation processes is discussed. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.     

Reactive Distillation: An Attractive Alternative for the Synthesis of Unsaturated Polyester

Summary: Unsaturated polyester is traditionally produced in a batch wise operating reaction vessel connected to a distillation unit. An attractive alternative for the synthesis of unsaturated polyester is a reactive distillation. To value such alternative synthesis route reliable process models need to be developed. In this paper, the strategy is described for the development of the reactive distillation model. Essential parts of the reactive distillation model are kinetic and thermodynamic which are subsequently validated with the experimental data of the traditional batch process such as acid value of the polyester, weight of the distillate and glycol concentration in the distillate. We find that the models predict these important variables reliably. Unsaturated polyester production time is around 12 hours in the traditional batch process. However, the simulation study of the reactive distillation process shows that the total production time of unsaturated polyester in a continuous reactive distillation system is between 1.5 hours to 2 hours for the same product quality as during batch production. The equilibrium conversion is raised by 7% compared to the traditional batch process. The model demonstrated that reactive distillation has the potential to intensify the process by factor of 6 to 8 in comparison to the batch reactor.     

基于模糊理论的汽轮机故障诊断

针对汽轮发电机组的单一故障诊断的局限性,对现有的故障进行分析和比较.根据振动信号的基本原理,应用了综合模糊诊断的方法对汽轮机的六种常见故障进行诊断.首先由不同故障在不同特征倍频的比例关系得到故障的模糊矩阵,分段对故障振动信号求隶属度,再与故障的模糊矩阵相乘即可求出各故障的隶属度,并用Minkowski距离公式计算隶属度距离大小,来判断诊断的准确性;最后提出模糊诊断的前景及存在的问题.     

共沸蒸馏法制备表面化学改性氢氧化镁纳米颗粒

首次将表面改性剂如硬脂酸、硬脂酸锌或稀土偶联剂加入到传统的共沸蒸馏体系中,使Mg(OH)2纳米颗粒的表面改性和干燥过程同时完成。 通过 XRD、TEM、FT-IR、TG和CAM（接触角测试）等技术手段对样品的结构、形貌和性质进行了表征。 结果表明,表面改性剂不但能够和Mg(OH)2纳米颗粒的表面的OH-离子发生化学反应形成表面修饰层, 减少硬团聚现象,而且还使纳米颗粒表面由亲水性变为疏水性。 另外,对共沸蒸馏法制备表面改性纳米颗粒的机理进行了讨论,为纳米颗粒表面改性提供了一种新思路。     

镁铝混合氧化物负载镍催化剂的制备及在液化石油气低温重整反应中的催化性能

采用共沉淀-浸渍法制备了不同Ni 含量的 Ni/Mg(Al)O 催化剂并用于液化石油气(LPG)的低温水蒸气重整反应. X 射线衍射和程序升温还原结果表明, 在 800 ℃焙烧的 Ni/Mg(Al)O 催化剂中, NiO 与 MgO 反应生成 Mg-Ni-O 固溶体, 还原后形成金属 Ni 纳米颗粒. 详细研究了 Ni 含量(质量分数)、反应温度和水/碳摩尔比(n_H2O/n_C) 等对催化剂性能的影响. 实验结果表明, 15%Ni/Mg(Al)O 催化剂对 LPG 低温重整反应具有最佳的催化性能. 提高反应温度能显著提高 Ni/Mg(Al)O 催化剂的催化性能. 当n_H2O/n_C=2时, 在400~500 ℃的温度范围使LPG完全转化的最大反应空速从 28900 mL·h^-1·g^-1Cat提高到 86800 mL·h^-1·g^-1Cat. 适当增大水/碳摩尔比有利于 LPG 转化为小分子气体, 但在 LPG 摩尔流量不变的情况下, 反应气中水含量过高会导致 LPG 转化率降低. 反应后催化剂的X射线衍射谱(XRD)和热重分析(TG)结果表明, Ni/Mg(Al)O催化剂优良的催化活性和反应稳定性可归因于催化剂表面Ni晶粒较高的稳定性和抗积炭性能.     

铈镧比对CexNi0.5La0.5-xO系催化剂甘油氧化蒸汽重整制氢性能的影响

利用共沉淀法制备了CeO₂和La₂O₃复合载体的Ce_xNi_0.5La_0.5-xOO(CeNiLaO)系催化剂,在固定床反应器中考察其甘油氧化蒸汽重整制氢(OSRG)性能,并采用X射线衍射(XRD)、程序升温还原(H₂-TPR)、激光拉曼光谱(Raman)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等手段对催化剂进行表征分析。结果表明：La₂O₃能够有效地分散Ni颗粒,减弱Ni颗粒在反应过程中的烧结,CeO₂提供的晶格氧能够消除催化剂表面的积碳,同时La会部分进入Ce的晶格取代部分Ce⁴⁺造成晶格畸变,提高表面的氧空穴数。La₂O₃和CeO₂的共同作用有利于减弱Ni因为烧结和积碳引起的失活。在不同Ce/La摩尔比的催化剂中,Ce_0.4Ni_0.5La_0.1O表现出最好的催化活性,并且该催化剂在长达210 h的稳定性测试中,甘油的转化率都在95%以上,气相产物中的氢气浓度达50%。     

Graphite dust resuspension in an HTR-10 steam generator

Graphite dust has an important effect on the safety of high-temperature gas-cooled reactors (HTR). The flow field in the steam generator was studied by the computational fluid dynamics (CFD) method, with the results indicating that the friction velocity in the windward and the leeward of the heat transfer tubes is relatively low and is higher at the sides. Further analysis of the resuspension of graphite dust indicates that the resuspension fraction reaches nearly zero for particles with a diameter less than 1 μm, whereas it will increases as the helium velocity in the steam generator increases for particle size larger than 1 μm. Moreover, the resuspension fraction increases as the particle size increases. The results also indicate that resuspension of the particles with sizes larger than 1 μm exhibited obvious differences in different parts of the steam generator.     

水蒸汽蒸馏条件下鱼腥草中癸酰乙醛的高效提取及质谱定性

根据质谱学规律,剖析了在电子轰击下中药材鱼腥草中最关键的抗菌成分鱼腥草素(癸酰乙醛)的离子形成机理:癸酰乙醛的分子中存在两个-C=O,处于端位上的-C=O活性远大于-CH3,易失去H2O(M+-18)、CO(M+-28)等基团,产生较强的m/z180、170等离子碎片,此外,还易失去H2O+H2O(M+-36)、H2O+CO(M+-46)、CO+CO(M+-56)等基团,产生m/z162、152、142等离子碎片,这同实验中得到的癸酰乙醛质谱图完全吻合,纠正了文献中对癸酰乙醛的错误定性。在此基础上采用常规、Ar气保护和减压三种水蒸汽蒸馏方式提取鱼腥草挥发油,发现在惰性气氛或较低温度下有利于癸酰乙醛的提取,与常规水蒸汽蒸馏条件相比,Ar气保护下癸酰乙醛的含量从0.03%提高至0.53%,而减压条件下癸酰乙醛的溶出效率进一步提高至3.37%。研究表明常规水蒸汽蒸馏条件下癸酰乙醛易氧化分解是得到较少癸酰乙醛的根本原因。     

Comparison of Liquid–Liquid Extraction,Simultaneous Distillation Extraction,Ultrasound-Assisted Solvent Extraction,and Headspace Solid-Phase Microextraction for the Determination of Volatile Compounds in Jujube Extract by Gas Chromatography/Mass Spectrometry

Jujube extract has a unique flavor that has been used as a common fragrance due to the volatile compounds. In this study, the volatiles of jujube extract were isolated by liquid–liquid extraction, simultaneous distillation extraction, ultrasound-assisted solvent extraction, and headspace solid-phase microextraction, and analyzed by gas chromatography–mass spectrometry. Altogether 92 compounds were identified by the four methods, of which 53 components were identified for the first time; however, only 21 compounds were identified by all these methods. The performance characteristics of the four pretreatment techniques were compared by principal component analysis which showed that the volatile compounds obtained by liquid–liquid extraction and ultrasound-assisted solvent extraction were similar both in categories and in content; whereas, the volatiles extracted by simultaneous distillation extraction, ultrasound-assisted solvent extraction, and headspace solid-phase microextraction greatly varied. The results indicated that a multi-pretreatment technique should be adopted in order to obtain the most complete information about the volatile compounds in jujube extract. The ultrasound-assisted solvent extraction method exhibited excellent repeatability and recoveries, and was very suitable for quantitative analysis. Although the recoveries and reproducibility of headspace solid-phase microextraction were inferior to the other methods, it was more sensitive than other methods.     

Synthesis and Characterization of New Polyetheramides

Polyetheramides (PEAs) are prepared by polycondensation of N,N′-diacetyl-o-tolidide with Bisphenol A, C, or F, phenolphthalein, resorcinol, catechol, hydroquinone, or 1,5- or 2,7-dihydroxynaphthalene or ethylene, butylene, propylene, diethylene, or triethylene glycol. The fusible and soluble oligomers are characterized. An attempt is made to bring out the relationship between various properties of PEAs and their structures.