纯物质汽化热的人工神经网络算法

１前言纯物质汽化热是重要的基础化工数据，其测定、关联、预测和理论研究相当活跃。在诸多预测模型中最有代表性的当属基团贡献模型，但多采用基团的简单加和或加权组合，基团贡献值由实验数据回归，通用性差，难以区别同分异构体，预测结果不尽人意。人工神经网络具有基...     

Oxidative dehydrogenation of n-butane on V/MgO catalysts—kinetic study in anaerobic conditions

The kinetics of the oxidative dehydrogenation of butane on a V/MgO catalyst has been studied under anaerobic conditions. In these conditions the oxygen from the catalyst lattice is consumed by the reaction, and the oxidation degree of the catalyst changes during the experiment. A kinetic model is proposed in which each reaction rate is related with the oxidation degree of the catalyst. The whole kinetic model is useful for the modelling of reactors where the catalyst operates in non-steady state, i.e. where the oxidation degree of the catalyst changes with time. It has also been found that whereas the main contribution to the oxidative dehydrogenation reaction comes from the lattice oxygen, there is also a non-selective contribution from weakly adsorbed oxygen.     

CALCULATION OF THE VAPORIZATION ENTHALPY OF NONPOLAR FLUIDS AT THE STANDARD TEMPERATURE

Different analytical models were used to calculate the enthalpy of vaporization of nonpolar fluids at the standard temperature of 298.15 K. The models considered were some general classical expressions, three group contribution models that allow the property to be calculated at any temperature, another group contribution model specifically designed for calculations at the standard temperature, and finally a molecular model proposed by our research group. The results for 42 nonpolar fluids are compared with the value obtained in the correlation proposed in the DIPPR project.     

CALCULATION OF THE VAPORIZATION ENTHALPY OF NONPOLAR FLUIDS AT THE STANDARD TEMPERATURE

Different analytical models were used to calculate the enthalpy of vaporization of nonpolar fluids at the standard temperature of 298.15 K. The models considered were some general classical expressions, three group contribution models that allow the property to be calculated at any temperature, another group contribution model specifically designed for calculations at the standard temperature, and finally a molecular model proposed by our research group. The results for 42 nonpolar fluids are compared with the value obtained in the correlation proposed in the DIPPR project.     

Kinetics of the oxidative dehydrogenation (ODH) of methanol to formaldehyde by supported vanadium-based nanocatalysts

The aim of the present contribution was to develop a detailed kinetic analysis of the oxidative dehydrogenation (ODH) reaction of methanol to formaldehyde on a nano-structured supported vanadium oxide catalyst, selected in a preliminary screening. The chosen vanadium catalyst, supported on TiO₂/SiO₂, has been prepared by grafting vanadyl alkoxide, dissolved in dioxane, and characterized by BET, XRD, Raman, XPS and SEM. An exhaustive set of experimental runs has been conducted in an isothermal packed bed tubular reactor by investigating several operative conditions, such as: temperature, contact time, methanol/oxygen feed molar ratio and water feed concentration. Depending on the operative conditions adopted, the main products observed were formaldehyde and dimethoxymethane while lower amounts of methyl formate and CO₂ were also found. At low contact time, the main reaction product was dimethoxymethane which was then converted into formaldehyde through the reverse equilibrium reaction with water. As a confirmation of this observation, a peculiar behaviour was detected consisting in an increase of selectivity to formaldehyde by increasing methanol conversion. The obtained experimental data of methanol conversion and selectivity towards products were modelled by means of an integral reactor model and the related kinetic parameters were determined by non-linear regression analysis. The adopted reaction rate expressions were of the Mars van Krevelen–Langmuir Hinshelwood type and a good agreement was found between the model theoretical prediction and the experimental data. A reaction mechanism and a detailed reaction scheme (rake-type) were proposed for methanol ODH on a nano-structured catalyst that were able to interpret correctly the collected experimental observations.     

Rapid Estimation of NO Oxidation Kinetic Data from Experiments

Parameter estimation for Langmuir‐Hinshelwood/Hougen‐Watson type of kinetics in the field of automotive exhaust gas aftertreatment can be challenging as a great variety of parameter sets can result in a similar model quality as rate and inhibition parameters can interact during numerical optimization although they can be regarded independent from theory. This contribution introduces a method that enables the model‐based rapid estimation of NO oxidation kinetic information on a Pt‐only monolith catalyst from a straightforward set of synthesis gas test‐bench experiments.     

环氧乙烷合成银催化剂宏观动力学及失活分析

在工业生产的条件下用无梯度反应器研究了工业颗粒银催化剂上乙烯氧化合成环氧乙烷宏观动力学 ,得到了能反映该系统主副反应特性的双速率方程 .建立了二维非均相反应器模型 ,模拟并比较了工业生产操作数据 ,获得了该种催化剂的活性校正因子随使用时间变化的经验关联式和主副反应失活速率方程     

Synthetic resins: II: Preparation and characterization of resins prepared from aminoacetophenone

A number of resins were prepared by condensing m-aminoacetophenone with substituted aromatic compounds and formaldehyde in the presence of acids and bases as catalyst. The resins were characterized by infrared spectra. The solubility parameters were calculated from Small's group contribution which agreed well with the experimental value. The bacteriocidal properties of the resins have been studied.     

铬钒双金属催化剂乙烯聚合反应动力学模型化

双金属催化剂可催化乙烯聚合在单个反应器内制备双峰聚乙烯。考察了新型Cr-iV双金属催化剂及相应的单金属S-2和iV催化剂在不同实验条件下的乙烯均聚反应动力学。通过对Cr-iV催化剂聚合产物分子量分布曲线的解析发现铬钒活性中心之间存在相互作用,铬中心活性受到抑制,钒中心活性得到增强;聚合温度基本不改变铬钒活性中心生成的聚合物的质量分数。采用简化的单中心乙烯均聚动力学模型分别描述铬钒双活性中心的动力学行为,结合双金属催化剂的聚合实验结果确定了各个活性中心的动力学参数。相比单金属催化剂,Cr-iV催化剂中铬活性中心链增长速率常数降低,说明其聚合活性降低;而钒活性中心链失活速率常数减小,稳定性增强,活性提高。     

Platelet-like catalyst design for high yield production of multi-walled carbon nanotubes by catalytic chemical vapor deposition

We investigated the effect of catalyst design on the synthesis of multi-walled carbon nanotubes (MWCNTs) by chemical vapor deposition (CVD). A set of highly active supported sol–gel Co–Mo/MgO and Ni–Mo/MgO catalysts was prepared systematically modifying the calcination temperature. First, the evolution of catalysts’ crystallographic phases and their morphology were studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron (SEM) and transmission electron (TEM) microscopy. Second, the catalysts were used for the CVD growth of MWCNTs. The resulting materials were analysed by SEM and TEM, Raman and XRD to establish a relation between catalyst design and MWCNT yield. We show that our catalyst synthesis route leads to the formation of laminar non-porous catalyst systems, which at a calcination temperature of 800 °C stabilize in a crystallographic phase of Me_xMg_1−xMoO₄ (Me = Co or Ni). We give evidence that increased MWCNT yields of more than 3000 wt.% with respect to the catalysts are directly related to the aforementioned crystallographic phase. Finally, we propose a growth model based on the continuous exfoliation of platelet-like catalyst systems. This consistently explains the high catalytic activity towards MWCNT production using a non-porous catalyst. Our findings provide important insights for catalyst design strategies towards large-scale MWCNT production.     

Total Turnover Number – a Key Criterion for Process Evaluation

The dimensionless total turnover number TTN, the average number of turnovers per active site of a catalyst over the catalyst's lifetime, is a universal criterion for the operational stability of a catalyst. If the cost of the catalyst is known, the cost contribution per catalytic cycle can be determined. The present work honors the contributions by Prof. Christian Wandrey and his group on the topic of TTN and describes some recent developments on the subject.     

提高螺压高能改性双基推进剂性能的研究

研究了Ａｌ粉、ＲＤＸ及高氮量硝棉对螺压高能改性双基推进能量的贡献，配方选择了比较合适的Ａｌ粉、ＲＤＸ含量，解决了采用高氮量硝棉的推进剂的力学性能问题。另外对含能催化剂进行了开发研究，并成功地用在火药中，使得螺压高能改性双基推进剂的性能有了大幅度的提高。     

ETHYLENE OXIDATION ON SILVER CATALYSTS: EFFECT OF ETHYLENE OXIDE AND OF EXTERNAL TRANSFER LIMITATIONS

Ethylene oxidation to ethylene oxide and to carbon dioxide over silver catalysts was studied in a CSTR. The effects of two factors on the catalyst performance were examined. The first was the presence of excess ethylene oxide in the feed. A kinetic model was introduced which assumed that ethylene and ethylene oxide compete for the same sites on the catalyst surface. This model provided reasonable quantitative agreement with kinetic and potentiometric measurements. The second factor that was studied was the presence of external heat and mass transfer limitations. It was found that such limitations cause a significant decrease of the selectivity to ethylene oxide. This decrease is a result of the temperature difference between the catalyst surface and the bulk of the gas phase and of the fact that the activation energy of ethylene combustion is greater than that of ethylene epoxidation. The contribution of other factors such as inhibition by CO₂ or possible incomplete mixing in the reactor is shown to be insignificant.     

Kinetic and Technological Analysis of Dimethyl Toluene‐2,4‐Dicarbamate Synthesis

The synthesis of dimethyl toluene‐2,4‐dicarbamate from 2,4‐toluene diamine and dimethyl carbonate is a complex reaction system. First, the reaction enthalpies, the Gibbs function changes, and the equilibrium constants of the reactions were calculated by several methods of group contribution. Secondly, the kinetics of the synthesis reaction over a zinc acetate catalyst was investigated in a batch autoclave. The kinetic model equations were established by parameter estimation based on experimental data, and the model met the requirements of the statistical test. The calculated results based on the model agreed well with the experimental data. According to the results of both thermodynamic calculation and kinetic analysis, the influence of some technological parameters, such as content of methanol in the feed and reaction temperature, on the synthesis reaction was discussed.     

局部组成模型的研究（Ⅱ）：似化学局部组成的基团模型

本文在前文的分子模型基础上,提出了似化学局部组成的基团模型,可用于极性分子混合物申组分活度系数的预测。该模型划分基团的方法与UNIFAC不同,将极性分子划分为非极性基团。通过对90个二元体系的回归,得到了烷烃、芳烃、醇、酮、水五类物质9种基团间的相互作用参数;通过对三元体系活度系数和液液平衡结线的推算表明,本模型与UNIFAC模型相比,具有参数少、预测性能好等优点,而且从汽液平衡数据回归的参数可用于预测液液平衡。     

连四甲苯液相氧化过程热力学分析及动力学模拟

连四甲苯（PR）液相氧化制备苯偏四甲酸（MPA）是合成聚偏苯四甲酰亚胺单体的关键步骤。本文首先采用基团贡献法对MPA的热力学参数进行了估算,进一步分析了PR氧化过程热力学参数随温度的变化。结果表明,在研究温度范围内,该氧化过程为强放热反应,反应过程中需要及时移除反应热以控制温度的波动。通过间歇实验研究了不同催化剂浓度和温度对反应的影响,动力学实验结果表明,保持催化剂总浓度不变,改变催化剂配比对PR氧化速率影响不大,但是提高Mn浓度对MPA生成速率的提升效果最佳;升高温度能够明显提升目标产物MPA的选择性。基于自由基链式反应机理,建立了简化的PR氧化集总动力学模型,拟合回归得到苯环上首个甲基氧化的活化能为57.20 kJ·mol^-1;但是苯环上部分甲基被氧化为羧基后,其他甲基氧化的活化能增加为120.30 kJ·mol^-1,说明羧基的存在使甲基活性变弱,被进一步氧化的难度增加。论文相关研究成果可为MPA生产新工艺的开发和工业反应器设计提供参考依据。     

估算有机物正常沸点的基团贡献法的研究进展

有机物的正常沸点是重要的物性数据之一。尽管文献中有很多化合物正常沸点的实验值,但一些物质的正常沸点不能由实验获得,可以通过建立数学模型来估算缺少的有机物正常沸点,其中基团贡献法是人们获得正常沸点的最重要研究方法。本文对估算有机物正常沸点的基团贡献法进行了综述。主要介绍了Joback法、C—G法、许文法、定位分布贡献法、元素和化学键法等方法的原理、优缺点及应用范围;并对这些方法进行简单的比较;最后指出了有机物正常沸点的基团贡献法的发展趋势。     

SCR催化剂技术研究进展及专利技术分析

介绍了SCR催化剂的相关技术,SCR催化剂技术的国内外专利申请有3个申请高峰,目前已处于第三个申请高峰的上升阶段。SCR催化剂技术申请人国外主要为企业,我国主要是高校,申请专利量占我国申请人申请专利总量的50%以上。催化剂功效主要是提高催化剂的耐受性和活性,约占统计样本数量的22%和52%。通过配方技术提高功效的申请量达到906件,约占统计样本的78%。技术创新仍以SCR催化剂配方及提高催化剂活性稳定为研究热点,但不能忽略对催化剂材料、催化剂再生技术和降低催化剂成本等研究,开发出适合我国国情的具有自主知识产权的SCR催化剂成套技术。     

Particle loading in a catalyst-trap microreactor: Experiment vs. simulation

We present the results of a study of the catalyst loading behavior on the “catalyst-trap” microreactor, a novel microreactor recently reported by McGovern et al. (2008) [1]. The study focuses on the important issue of catalyst deployment inside microscale reactors which must be understood in order to further the implementation of emerging microtechnology for organic chemical synthesis. We initially set out to use the catalyst-trap microreactor to investigate the catalytic hydrogenation of 3-nitrotoluene. In that investigation a 100% yield was fortuitously achieved due to the activity of the reaction. However, the low trap occupancy ratio (20% of the traps had been loaded) could still be an impediment, especially for other more complex reactions. After extensively studying the loading procedure, 98% of the traps in the reactor were able to be successfully loaded. Simulations based on a random-walk model and the procedures of the loading experiments were conducted to better understand the filling mechanism. We found the physical catalyst loading procedure was consistent with the simple mechanism in our simulations. Through this work, catalytic area and catalytic efficiency have been significantly increased, and the synthetic capability enhanced as a result.     

一氧化二氮催化分解的研究与应用

为了建立小卫星新型多模式推进系统,英国Surrey公司从1990年开始研究一氧化二氮催化分解。研究重点是可多次肩动的一氧化二氮单元推进剂推力室,适用于小卫星的位置保持和相位保持。推力室催化剂床的尺寸取决于催化剂床装填系数和轴向温度分布。建议采用Ergun公式估算通过催化剂床的压力降。推进剂最大流量依赖于一氧化二氮供应系统自身增压能力。