Development of a Joint Hydrogen and Syngas Combustion Mechanism Based on an Optimization Approach

A comprehensive and hierarchical optimization of a joint hydrogen and syngas combustion mechanism has been carried out. The Kéromnès et al. (Combust Flame, 2013, 160, 995–1011) mechanism for syngas combustion was updated with our recently optimized hydrogen combustion mechanism (Varga et al., Proc Combust Inst, 2015, 35, 589–596) and optimized using a comprehensive set of direct and indirect experimental data relevant to hydrogen and syngas combustion. The collection of experimental data consisted of ignition measurements in shock tubes and rapid compression machines, burning velocity measurements, and species profiles measured using shock tubes, flow reactors, and jet‐stirred reactors. The experimental conditions covered wide ranges of temperatures (800–2500 K), pressures (0.5–50 bar), equivalence ratios (? = 0.3–5.0), and C/H ratios (0–3). In total, 48 Arrhenius parameters and 5 third‐body collision efficiency parameters of 18 elementary reactions were optimized using these experimental data. A large number of directly measured rate coefficient values belonging to 15 of the reaction steps were also utilized. The optimization has resulted in a H₂/CO combustion mechanism, which is applicable to a wide range of conditions. Moreover, new recommended rate parameters with their covariance matrix and temperature‐dependent uncertainty ranges of the optimized rate coefficients are provided. The optimized mechanism was compared to 19 recent hydrogen and syngas combustion mechanisms and is shown to provide the best reproduction of the experimental data.     

燃烧反应机理构建的极小反应网络方法——氢氧燃烧

基于化学同时平衡原理,提出复杂反应体系的极小反应网络方法(MRN),在指定中间物种数目条件下,构建反应步数最小的详细燃烧反应机理.确定了8个物种的氢氧燃烧的6个独立反应,对缺乏动力学参数的独立反应进行组合替代,反应速率常数采用Arrhenius双参数形式.采用构建的9步反应氢氧燃烧机理(MRN-C0)进行了点火延迟时间和层流火焰速度的模拟.     

低浓度乙醇催化燃烧研究进展

近年来随着环境污染和能源危机的全球化,乙醇作为洁净燃料或燃料添加剂越来越受到人们的关注.美国每年加入汽油的乙醇大约15亿加仑[1],乙醇的加入能够提高燃料的辛烷值并减少污染物的产生.乙醇价廉,运输方便,便于贮存并且可由生物法制得[2],与传统燃料相比降低了NOx和SOx等污染     

A Hierarchical Optimization Approach to Optimal Production Scheduling in an Industrial Continuous Olefin Polymerization Reactor

The time‐optimal grade‐transition policies, as well as the selection of the optimal grade production sequence, are calculated for a gas‐phase ethylene/but‐1‐ene copolymerization FBR. The tuning parameters (i.e., proportional gain and integral time) of the feedback PI process controllers, as well as the time‐optimal trajectories of the feedforward controllers, are treated as decision variables. A two‐level decomposition approach is applied for solving the optimal‐grade transition‐scheduling problem, taking into account the impact of both transient operation and the sequence of grade transitions on the overall amount of off‐spec polymer and overall transition time.

     

粗略测量乙醇燃烧热的实验探究与反思

基于"粗略测定乙醇燃烧热"实验及其改进为案例, 针对实验结果和实验过程进行了探究分析;引导学生在简陋粗糙的实验条件下理解原理, 体验过程, 感悟控制实验条件对实验结论的重要性;从激发学生的学习效能感、"过程学习"的评价方式等角度对教学活动提出了建议。     

乙醇在钯电极上的电氧化机理

利用循环伏安与现场傅里叶变换红外(FTIR)光谱对乙醇在Pd电极上的电氧化机理进行了研究. 循环伏安测量表明, 乙醇在Pd上氧化的性能受pH值与乙醇浓度的影响. 当溶液pH>11.0时, Pd对乙醇才具有催化性能, 而且乙醇在Pd上氧化的性能随着pH值和乙醇浓度的增加而提高. 现场红外光谱电化学测量结果证明, 乙醇在不同pH 溶液中的氧化反应机理和产物不同. 当溶液pH>13.0 时, 产物只有乙酸盐, 说明乙醇仅发生部分氧化, 乙醇中的C—C键没有断裂. 当溶液pH≤13.0时, 尽管乙醇在Pd电极上的氧化活性受到抑制, 却发生完全氧化而产生二氧化碳, 说明乙醇的C—C键在低碱环境中容易断裂, 最后乙醇被完全氧化. 实验中没有检测到CO, 表明该反应途径是一个非毒化过程.     

Optimization of Combustion Efficiency Using a Fuel Composition Based on CH4 and/or H2

Russian Journal of Applied Chemistry - In this paper, we investigate the exergy analysis of the combustion chamber supplied by different fuel compositions based mainly on methane and/or hydrogen in...     

氧化锡基甲烷催化燃烧催化剂的硫中毒反应机理

测定了几种活性较高的氧化锡基甲烷燃烧催化剂在200×10－6（φ）SO2存在下的催化活性.结果发现,SnCrO样品具有很好的抗硫性能,而SnCuO及SnCoO样品在SO2存在时的活性大大降低.用XRD、BET、XPS、FT-IR及DTA-TG等技术对反应前后的样品进行了表征,结果表明,硫酸盐的热稳定性对催化剂在SO2处理过程中的变化起决定作用.在实验的温度下（500 ℃）,Co2(SO4)3和CuSO4均能稳定存在,而Cr2(SO4)3会分解.SnCrO样品在SO2存在下反应时只是表面吸附少量硫酸根,因此其催化活性基本保持不变.这是SnCrO样品具有良好抗硫性能的原因.     

Combustion of a Layered System Based on Sodium Chlorate

The velocity of combustion under atmospheric conditions in a constant-volume bomb of formulations based on sodium chlorate and polyethylene in the form of tubes (layered system) was subjected to a comparative study in relation to the type of additive, layer porosity, and fraction composition of sodium chlorate.     

Approach to Optimization of FRAP Methodology for Studies Based on Selected Monoterpenes

Terpenes, wide-spread secondary plant metabolites, constitute important parts of many natural compounds that hold various biological activities, including antioxidant, calming, antiviral, and analgesic activities. Due to their high volatility and low solubility in water, studies of compounds based on terpenes are difficult, and methodologies must be adjusted to their specific characteristics. Considering the significant influence of iron ions on dementia development, the activity of terpenes in reducing Fe³⁺ represents an important area to be determined. Previously obtained results were unreliable because ferric-reducing antioxidant power (FRAP) methodology was not adjusted regarding studying terpenes. Taking this fact into account, the aim of this study was to optimize the method for monoterpene assessment. The study included three modifications, namely, (1) slightly adjusting the entire FRAP procedure, (2) replacing methanol with other solvents (heptane, butanone, or ethyl acetate), and (3) adding Tween 20. Additionally, a thin layer chromatography (TLC) -FRAP assay was performed. The obtained results revealed significant improvement in the reduction activity of selected terpenes (linalool, α-phellandrene, and α-terpinene) in studies with Tween 20, whereas replacing methanol with other solvents did not show the expected effects.     

铁酸盐催化剂上乙醇的催化燃烧

用共沉淀法制备了N i,Co,Cu等的铁酸盐复合氧化物催化剂,并采用XRD、IR等手段对催化剂进行了表征,结果表明具有尖晶石结构的CuFe2O4复合氧化物催化剂对乙醇催化燃烧反应具有较高活性和选择性,Co部分掺杂的CuFe2O4其活性和选择性有所提高,乙醇可在约229℃达到完全转化,燃烧产物中没有发现乙醛副产物.     

基于氢键作用的杯芳烃超分子识别乙醇的传感机理及分析应用

采用4种杯芳烃衍生物为吸附涂膜材料, 考察了涂膜石英晶体微天平(QCM)传感器对环境大气中微量乙醇气体的识别性能, 发现C-乙基杯[4]连苯三酚芳烃(3)是识别乙醇气体最有效的活性涂膜材料. 制备了C-乙基杯[4]连苯三酚芳烃·2CH₃CH₂OH(5)单晶体并进行X射线衍射结构解析, 发现其识别机制是基于超分子主体3与客体乙醇分子之间形成的C-H…π, O-H…π及O-H…O氢键作用. 当涂膜质量为24.70 μg 时, 涂膜QCM传感器对乙醇的响应最灵敏, 达到10.53 Hz/(mg·L^-1). 分析了乙醇气体的吸附和解吸附动力学过程, 得到传感器对乙醇气体吸附和解吸附的初速度分别为-0.04600 Hz/s和0.03896 Hz/s. 该方法响应快, 具有选择性、 可逆性、 重现性和稳定性好的优点, 对乙醇样品测定的回收率为94.8% ~105.2%, 与气相色谱法的测定结果一致, 表明该方法可用于生活环境中乙醇气体的检测.     

Emergent Self-Assembly Pathways to Multidimensional Hierarchical Assemblies using a Hetero-Seeding Approach

The controlled formation of complex and functional 1-, 2-, and 3D hierarchical assemblies from molecular building blocks represents a key current challenge. Herein, we report the use of a seeded growth approach for a series of perylenediimide-based molecules (PDIs 1 – 4 ) to access otherwise inaccessible self-assembly pathways that yield complex hierarchical structures. The key to the new approach is to use hetero-seeds which possess a different composition and morphology from that of the molecular building block. For example, a nanotube seed (from PDI 3 ) and a microribbon seed (from PDI 4 ) were found to initiate different self-assembly pathways for PDI 1 , which normally assembles to yield nanocoils. This led to the formation of unprecedented 3D scroll-like and scarf-like hierarchical nanostructures, respectively. Also, the hetero-seeds from PDI 3 initiate hidden self-assembly pathways of PDI 2 to generate 1D tubular heterojunctions. Significantly, this new strategy offers new opportunities to create emergent and functional hierarchical and complex structures from small molecule precursors.     

碳氢燃料燃烧机理的自动简化

采用自行开发的碳氢燃料燃烧详细机理自动简化程序ReaxRed分别对包含257个物种和874步反应的RP-3航空煤油替代模型以及包含1389个物种和5935步反应的汽油混合替代模型进行机理自动简化.对RP-3替代模型,分别得到78个物种框架机理和61个物种全局简化机理,在较宽的参数范围内重现RP-3详细机理在点火延迟时间、熄火以及物种浓度分布等方面的模拟结果;通过强制敏感度及物种产率分析进一步说明了简化机理的合理性.对汽油混合替代模型,得到包含266个物种框架机理在较宽范围内重现单组分、两组分及多组分混合的点火延迟时间的模拟结果,并通过元素流动分析阐明了4种单组分燃料的燃烧路径.框架机理保留了详细机理的层级结构以及全局信息,更易于系统分析汽油的燃烧过程.     

Mechanism of Thermal Degradation of an Inorganic-Organic Hybrid Based on an Epoxy-POSS

A novel inorganic-organic hybrid material, belonging to the family of polyhedral oligomeric silsesquioxanes (POSS), was used to reduce the trend of a conventional epoxy-amine system to undergo combustion. The mixtures with different percentages in weight of POSS, and equal number of equivalents between of epoxy and amino groups were tested by thermogravimetic analysis (TGA) in both, argon and oxygen atmospheres. The results indicated that the char/ceramic yield values increase with the content of POSS and therefore, fire resistance is enhanced. Activation energies of degradation processes were obtained by Kissinger-Akahira-Sunose method. An empirical kinetic model satisfactorily explained the degradation mechanism of different blends.     

Solution Combustion Synthesis: Towards a Sustainable Approach for Metal Oxides

Solution combustion synthesis (SCS) has been widely used to produce simple and complex oxides with a desired morphology (size and shape). SCS is valuable due to low cost, simplicity and energy efficient synthesis. To guarantee the best molecular-level mixing of reactants in an aqueous or solvent-based solution some parameters need to be controlled, such as fuel type, metal cations precursors, stoichiometry ratio (φ), pH effect, atmosphere and initiation type. These determine the final properties of the oxide materials, providing the potential to reach different morphologies, which are essential for their final applications. This Review article focuses on the crucial parameters in SCS and how these affect the overall materials properties from nanostructures to thin films. To finalize, special attention is given to the application of SCS to form metal oxide thin films at low temperature and their application in thin film transistors (TFTs).     

Preparation of Hierarchical Mesoporous Silica Nanoparticles through a Single‐Templating Approach

Silicas with hierarchical porous architectures attracted much attention, due to their potential applications in catalysis and separation. Generally, they were prepared through dual‐ or triple‐templating approaches. Herein, mesoporous silica nanoparticles with rod‐like pore channels inside and lamellar mesopores on the surfaces were prepared using the self‐assemblies of a chiral low‐molecular‐weight amphiphile as templates through a single‐templating approach. The formation of the lamellar mesopores was studied by taking field‐emission scanning electron microscopy and transmission electron microscopy images after different reaction times. The lamellar pores were proposed to be formed by merging rod‐like micelles during the sol‐gel process. Moreover, helical nanofibers with rod‐like pore channels inside and lamellar mesopores on the surfaces were prepared with the addition of n‐octanol as a co‐structure‐directing agent.     

Development of an Electrochemical Sensor Nanoarray for Hydrazine Detection Using a Combinatorial Approach

The combinatorial screening of different metallic nanoparticles as electrocatalysts was investigated and efficiently applied for the detection of hydrazine. In a first step, glassy carbon microspheres decorated with metallic nanoparticles (Au, Pd, and Ag) were abrasively attached on the surface of a basal plane pyrolytic electrode giving a ‘multi–metal’ nanoarray. In a second step, electrodes modified with only one type of metallic nanoparticles allowed the identification of Pd as the unique catalytic material. In addition, a carbon‐epoxy composite electrode loaded with the Pd nanoparticles was then constructed for a practical use. The carbon‐epoxy composite nanoarray electrode was found to have excellent characteristics as for the sensing of hydrazine with a limit of detection of 2 μM.