生物柴油替代混合物化学动力学模型构建及路径分析

以癸酸甲酯(C11H22O2)和正庚烷(nC7H16)作为生物柴油替代混合物,通过相对分子质量、低热值以及含氧量与实际生物柴油对比确定两种组分按摩尔比1:1混合,并在此基础上构建了一个由691种组分、3226个基元反应组成的生物柴油替代混合物的化学动力学机理.在激波管条件下该机理计算的着火延迟与实验数据吻合很好;在发动机条件下该机理计算的缸内压力与实验值吻合很好,CO、未燃碳氢和NOx与实验结果趋势一致.此外,本文还对替代混合物的低温反应动力学过程进行了分析,结果表明癸酸甲酯脱氢产物主要为MD2J和MDMJ.MD2J在低温阶段的主要消耗途径除了加氧之外,还有与正庚烷基(C7H15-1)第一次加氧产物(C7H15O2-3)进行交叉反应;发生分解反应生成MP2D及与氧发生脱氢反应生成MD2D.另一种主要脱氢产物MDMJ在低温阶段的主要消耗途径为通过同分异构转化为MD2J和MD3J.     

钒卤代过氧化物酶构象模型分子的设计、合成及仿生催化活性

基于钒卤代过氧化物酶(V-HPOs)活性中心的N、O配位环境及活性中心与氨基酸残基、水分子之间的氢键作用的模拟, 我们设计、合成了两种钒氧配合物: (C₃H₅N₂)₂[(VO)₂(μ₂-C₂O₄)(C₂O₄)₂(H₂O)₂] (1)和(VO₂)₂(μ₂- C₂O₄)(C₂H₄N₂)₂ (2), 并通过X射线单晶衍射方法确定了它们的结构. 晶体结构分析表明上述钒氧配合物的配位环境与(V-HPOs)活性中心十分相似, 且在配合物的三维堆积结构中具有类α-螺旋结构. 溴化反应活性研究发现这些钒氧配合物在仿生催化实验中表现出较高的催化活性.     

羟基羧酸钛(Ⅲ)配合物的合成和热性质研究

三氯化钛分别与苹果酸铵、酒石酸铵和柠檬酸铵反应，制得三种新的固态配合物：苹果酸羟基钛(Ⅲ)、酒石酸羟基钛(Ⅲ)和柠檬酸钛(Ⅲ)(化学式分别为Ti(OH)(C₄H₄O₅)·1.5H₂O、Ti(OH)(C₄H₄O₆)·1.5H₂O和Ti(C₆H₅O₇)·1.5H     

丁烯自由基和O2反应机理的理论研究

应用量子化学密度泛函理论(DFT)对丁烯自由基C₄H₇和O₂的反应机理进行了研究. 在B3LYP/6-31G(d,p)水平上优化了反应通道上的反应物、中间体、过渡态和产物的几何构型, 并计算出它们的振动频率和零点能(ZPVE), 并对能量进行了零点能校正. 计算结果表明, C₄H₇和O₂形成三种氧环中间体, 再分别分解, 这是主要的反应形式. 生成物主要为羰基化合物, 其次还有一定比例的CO.     

溶剂热/水热条件下空旷结构草酸锌的合成

应用水热法及溶剂热方法，选择两种模板剂1，2-丙二胺和4，5-二氮芴-9-酮连氮(L)设计合成了草酸锌空旷结构材料[Zn₂(C₂O₄)3][C₃H₁₂N₂]·H₂O (Ⅰ)和[Zn₂(C₂O₄)₃]·L·6[H₃O] (Ⅱ)，使用CHN元素分析、     

适用于HCCI燃烧研究的甲苯参比燃料化学动力学简化模型

提出了一个适用于均质压燃着火(HCCI)燃烧过程的甲苯参比燃料简化机理模型, 包含70种组分和196个反应. 低温简化机理选用Tanaka等人构建的基础燃料氧化机理中的部分反应, 加入本文构建的甲苯简化子机理中. 高温简化机理主要利用到Patel等人的研究成果, 同时加入关键反应[H+O₂+M=O+OH+M]. 简化机理分别对替代混合物中的单组分、双组分、三组分物质进行了着火延迟期的预测计算, 预测结果与实验结果较为吻合. 与HCCI发动机实验的验证表明, 对于各工况下甲苯参比燃料的缸内计算, 该机理的预测能力是令人满意的. 由此可知, 本文提出的TRF简化机理在HCCI燃烧方面的预测性能是可靠的. HCCI发动机工况下最大放热率时刻的敏感性分析表明, 随着压力的升高, C₆H₅与O₂的反应变得更加重要; 甲醛是非常重要的中间产物, 是不应当被忽略的.     

Dawson结构(NH4)6P2Mo18O62·12H2O纳米粉体的室温固相合成及形成机理

以H₆P₂Mo₁₈O₆₂·23H₂O和(NH₄)₂C₂O₄·H₂O为原料，首次采用室温固相反应合成出(NH₄)₆P₂Mo₁₈O₆₂·12H₂O纳米粉体，并运用元素分析、FTIR、XRD、TEM、TG-DTA和BET等技术对其组成、结构和性能进行了表征。发现(NH₄)₆P₂Mo₁₈O₆₂·12H₂O纳米粉体平均粒径为40 nm，保留着杂多阴离子的Dawson结构，具有Dawson结构的特征衍射峰，比表面积为143.9 m²·g^-1，在445 ℃以下杂多阴离子有良好的热稳定性。在该固相反应中，研磨和放热反应热能可加速反应物分子的扩散速率和生成物分子的成核速率，使产物粒径减小；反应物含有结晶水和生成物H₂C₂O₄·2H₂O对形成小粒径的(NH₄)₆P₂Mo₁₈O₆₂·12H₂O纳米粉体起关键作用。     

固定床反应器上挤条小晶粒TS-1催化丙烯环氧化反应

采用纳米TS-1母液作为晶种, 在四丙基溴化铵(TPABr)-乙胺廉价水热体系中, 合成出晶粒尺寸为600 nm×400 nm×250 nm的小晶粒钛硅分子筛(TS-1), 用挤条法将其成型, 得到的挤条小晶粒TS-1被用于催化固定床反应器中的丙烯环氧化反应. 采用X射线衍射(XRD)光谱, 傅里叶变换红外(FT-IR)光谱, 紫外-可见(UV-Vis)漫反射光谱及氮气物理吸附对挤条成型的小晶粒TS-1进行表征, 并对丙烯环氧化的最优反应条件进行考察. 其中所考察的条件包括: 反应温度, 压力, 丙烯/H₂O₂摩尔比(n(C₃H₆)/n(H₂O₂)), 丙烯、甲醇及H₂O₂的质量空速(WHSV), 以及NH₃·H₂O浓度. 在所考察的范围内, 温度对环氧丙烷(PO)收率的影响较小, 当反应压力为2.0 MPa, n(C₃H₆)/n(H₂O₂)为4时, 可以得到最高的PO收率. 当丙烯、甲醇及H₂O₂的空速分别为0.93、2.5及0.25 h^-1时, PO在产物中的含量最高. 较低的NH₃·H₂O浓度对高PO收率更有利. 在优化的反应条件下, 对比不同晶粒大小TS-1的催化性能, 并考察了挤条小晶粒TS-1的长期运转性能, 连续反应1000 h, H₂O₂转化率及PO选择性仍能维持在95%以上.     

十一烯酸邻菲咯啉铜(Ⅱ)配合物的合成、表征、晶体结构及与DNA作用

A copper(Ⅱ) complex Cu(C₁₁H₁₉O₂)₂(phen)(H₂O), (C11H19O₂=undecylenic acid, phen=1,10-phenanthroline), was synthesized and characterized by elemental analysis, IR and TG-DTG. Its crystal structure was determined by single crystal X-ray diffraction method. The complex, C₃₄H₄₈N₂O₅Cu, crystallizes in the triclinic system, space group P1. The interaction of complex with DNA was also studied by ethidium bromide (EB) fluorescence spectroscopy. CCDC: 729209.     

微乳液法制备纳米草酸钆的热解机理的研究

Gd₂O₃∶Tb³⁺ luminescent nanoparticles were prepared by the thermal decomposition of the nanosized oxlate prepared in the reverse microemulsions based on triton X-100 / n-hexyl alcohol, n-octane, and water. From TG-DTA, XRD and FTIR analyses, the mechanism of thermal decomposition of the nanosized oxalate precursor is suggested as follows: Gd₂(C₂O₄)₃·10H₂O → Gd₂(C₂O₄)₃ + 10H₂O, Gd₂(C₂O₄)₃ → Gd₂O₂(CO₃) + 3CO +2CO₂, Gd₂O₂(CO₃) → Gd₂O₃ + CO₂. The kinetic parameters of thermal decomposition reaction-activation energy E of stage 2 and 3 are 194.6 kJ·mol^-1, 110.9 kJ·mol^-1, respectively, using Ozawa method. And the reaction order n is 2.9 and 0.43, respectively, according to the TG curves.     

Oxidation of the 1-naphthyl radical C10H7• with oxygen: Thermochemistry,kinetics, and possible reaction pathways

The reaction of the 1-naphthyl radical C₁₀H₇• (A2•) with molecular (³O₂) and atomic oxygen, as part of the oxidation reactions of naphthalene, is examined using ab-initio and DFT quantum chemistry calculations. The study focuses on pathways that produce the intermediate final products CO, phenyl and C₂H₂, which may constitute a repetitive reaction sequence for the successive diminution of six-membered rings also in larger polycyclic aromatic hydrocarbons. The primary attack of ³O₂ on the 1-naphthyl radical leads to a peroxy radical C₁₀H₇OO• (A2OO•), which undergoes further propagation and/or chain branching reactions. The thermochemistry of intermediates and transition state structures is investigated as well as the identification of all plausible reaction pathways for the A2• + O₂ / A2• + O systems. Structures and enthalpies of formation for the involved species are reported along with transition state barriers and reaction pathways. Standard enthalpies of formation are calculated using ab initio (CBS-QB3) and DFT calculations (B3LYP, M06, APFD). The reaction of A2• with ³O₂ opens six main consecutive reaction channels with new ones not currently considered in oxidation mechanisms. The reaction paths comprise important exothermic chain branching reactions and the formation of unsaturated oxygenated hydrocarbon intermediates. The primary attack of ³O₂ at the A2• radical has a well depth of some 50 kcal mol⁻¹ while the six consecutive channels exhibit energy barriers below the energy of the A2• radical. The kinetic parameters of each path are determined using chemical activation analysis based on the canonical transition state theory calculations. The investigated reactions could serve as part of a comprehensive mechanism for the oxidation of naphthalene. The principal result from this study is that the consecutive reactions of the A2• radical, viz. the channels conducting to a phenyl radical C₆H₅•, CO₂, CO (which oxidized to CO₂) and C₂H₂ are by orders of magnitude faster than the activation of naphthalene by oxygen (A2 + O₂ → A2• + HO₂).     

The mechanism of selective NO<Subscript>x</Subscript> reduction by hydrocarbons in excess oxygen on oxide catalysts: VI. Spectroscopic and kinetic characteristics of surface complexes on a Ni-Cr oxide catalyst

The reaction mechanism of the selective catalytic reduction of NO_x by propane in the presence of O₂ on a commercial Ni-Cr oxide catalyst was studied using in situ IR spectroscopy. It was found that nitrite, nitrate, and acetate surface complexes occurred under reaction conditions. Considerable amounts of hydrogen were formed in the interaction of NO + C₃H₈ + O₂ or C₃H₈ + O₂ reaction mixtures with the catalyst surface. The rates of conversion of the surface complexes detected under reaction conditions were measured. The resulting values were compared to the rate of the process. It was found that, at temperatures lower than 200°C, nitrate complexes reacted with the hydrocarbon to form acetate complexes; in this case, the formation of reaction products was not observed. In the temperature region above 250°C, two reaction paths took place. One of them consisted in the interaction of acetate and nitrate complexes with the formation of reaction products. The decomposition of NO on the reduced surface occurred in the second reaction path. Nitrogen atoms underwent recombination, and oxygen atoms reoxidized the catalyst surface and reacted with the activated hydrocarbon to form CO₂ and H₂O in a gas phase.     

Experimental and Kinetic Modeling Study of C2H2 Oxidation at High Pressure

A detailed chemical kinetic model for oxidation of acetylene at intermediate temperatures and high pressure has been developed and evaluated experimentally. The rate coefficients for the reactions of C₂H₂ with HO₂ and O₂ were investigated, based on the recent analysis of the potential energy diagram for C₂H₃ + O₂ by Goldsmith et al. and on new ab initio calculations, respectively. The C₂H₂ + HO₂ reaction involves nine pressure‐ and temperature‐dependent product channels, with formation of triplet CHCHO being dominant under most conditions. The barrier to reaction for C₂H₂ + O₂ was found to be more than 50 kcal mol^?1 and predictions of the initiation temperature were not sensitive to this reaction. Experiments were conducted with C₂H₂/O₂ mixtures highly diluted in N₂ in a high‐pressure flow reactor at 600–900 K and 60 bar, varying the reaction stoichiometry from very lean to fuel‐rich conditions. Model predictions were generally in satisfactory agreement with the experimental data. Under the investigated conditions, the oxidation pathways for C₂H₂ are more complex than those prevailing at higher temperatures and lower pressures. Acetylene is mostly consumed by recombination with H to form vinyl (reducing conditions) or with OH to form a CHCHOH adduct (stoichiometric to lean conditions). Both C₂H₃ and CHCHOH then react primarily with O₂. The CHCHOH + O₂ reaction leads to formation of significant amounts of glyoxal (OCHCHO) and formic acid (HOCHO), and the oxidation chemistry of these intermediates is important for the overall reaction.     

Theoretical Thermodynamic Efficiency Limit of Isothermal Solar Fuel Generation from H2O/CO2 Splitting in Membrane Reactors

Solar fuel generation from thermochemical H₂O or CO₂ splitting is a promising and attractive approach for harvesting fuel without CO₂ emissions. Yet, low conversion and high reaction temperature restrict its application. One method of increasing conversion at a lower temperature is to implement oxygen permeable membranes (OPM) into a membrane reactor configuration. This allows for the selective separation of generated oxygen and causes a forward shift in the equilibrium of H₂O or CO₂ splitting reactions. In this research, solar-driven fuel production via H₂O or CO₂ splitting with an OPM reactor is modeled in isothermal operation, with an emphasis on the calculation of the theoretical thermodynamic efficiency of the system. In addition to the energy required for the high temperature of the reaction, the energy required for maintaining low oxygen permeate pressure for oxygen removal has a large influence on the overall thermodynamic efficiency. The theoretical first-law thermodynamic efficiency is calculated using separation exergy, an electrochemical O₂ pump, and a vacuum pump, which shows a maximum efficiency of 63.8%, 61.7%, and 8.00% for H₂O splitting, respectively, and 63.6%, 61.5%, and 16.7% for CO₂ splitting, respectively, in a temperature range of 800 °C to 2000 °C. The theoretical second-law thermodynamic efficiency is 55.7% and 65.7% for both H₂O splitting and CO₂ splitting at 2000 °C. An efficient O₂ separation method is extremely crucial to achieve high thermodynamic efficiency, especially in the separation efficiency range of 0–20% and in relatively low reaction temperatures. This research is also applicable in other isothermal H₂O or CO₂ splitting systems (e.g., chemical cycling) due to similar thermodynamics.     

Organic ions in the gas phase—XXI. Competitive primary loss of C2H4 and CO from 1-tetralone under electron impact

Competing primary reactions by which 1-tetralone loses C₂H₄ and CO give rise to a doublet at mass 118 in the high-resolution mass spectrum corresponding to 96·4% C₈H₆O⁺ and 3·6% C₉H₁₀⁺, respectively. Study of the remainder of the spectrum however, suggests that these intensities constitute a poor measure of the relative importance of the two reaction paths. The C₉H₁₀⁺ ion evidently degrades more readily than C₈H₆O⁺, since an estimated 26% of the ions arising in these paths involve primary loss of CO. This estimate is supported by voltage dependence of the intensity distribution between the members of the doublet. As ionizing voltage is decreased, the intensity distribution is constant to about 20 volts, but between 20 and 10 volts the value for C₉H₁₀⁺ rises smoothly from about 3.5% to about 25%.     

Oxygen storage capacity of substituted YBaCo4O7+δ oxygen carriers

Depletion of non-renewable energy sources are at elevated manner due to the rapid growth of industrialization and transportation sector in last few decades and leads to further energy demand. Biodiesels especially second-generation fuels from non-edible oil resources are alternate sources for replacement of diesel fuel in CI engines due to their considerable environmental benefits. In the present work, non-edible feedstock of Calophyllum inophyllum seed oil (tamanu oil) is used for biodiesel production. Transesterification method is used for preparation of biodiesel in the existence of methanol with NaOH as catalyst. The copper nanoparticles are synthesized by electrochemical method, and it is characterized by using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). XRD and SEM results confirm the presence of copper nanoparticle and size of around 30 nm. This paper aims to investigate the effects of the copper additive nanoparticles with biodiesel blends on the engine performance, combustion and emission characteristics of single-cylinder direct-injection diesel engine and compared that with diesel fuel. The results showed that the addition of nano-additives enhances brake thermal efficiency and reduces specific fuel consumption compared to biodiesel blends but slightly lower than diesel. Combustion characteristics also are enhanced by improved oxidation reaction inside the combustion chamber which resulted in higher heat release rate. The emissions of HC, NO_x and O₂ are significantly reduced for nano-additive blends compared to diesel but increased CO₂ emission was observed. It is noticed that higher CO₂ emission and substantial reduction of unused O₂ emissions from engine fueled with nano-additive are evident for enhanced oxidation and better combustion. Energy and exergy analysis of the diesel engine is carried out to estimate the effect of using nanoparticle additive with biodiesel.

     

Kinetics and modeling of the thermal reaction of propene at 800 K. Part iii. Propene in the presence of small amounts of oxygen

The thermal reaction of propene was examined around 800 K in the presence of less than 20% oxygen. At initial time, the production of H₂, CH₄, C₂H₄, C₂H₆, allene, C₃H₈, 1,3-butadiene, butenes, 3- and 4-methylcyclopentene, a mixture of 1,4- and 1,5-hexadienes, methylcyclopentane (or dimethylcyclobutane), 4-methylpent-1-ene, and hex-1-ene, was observed along with hydrogen peroxide, CO, and small quantities of ethanal and CO₂. Oxygen increases the initial production of hydrogen and of most hydrocarbons and, particularly, that of C₆ dienes and of cyclenes. However, the production of allene, methylcyclopentane (or dimethylcyclobutane), and 4-methylpent-1-ene is practically not affected. A kinetic study confirms the mechanism proposed for the thermal reaction of propene. Formation of allene, thus, involves a four-center-unimolecular dehydrogenation of propene, that of 4-methylpent-1-ene is explained by an ene bimolecular reaction while methylcyclopentane (or dimethylcyclobutane) probably arises from a bimolecular process involving a biradical intermediate. Other products arise from a conventional chain radical mechanism. A kinetic scheme is proposed in which chains are primarily initiated by the bimolecular step: C₃H₆+O₂→HO₂·+C₃H₅· which competes with the second-order initiation of propene pyrolysis. Since allene production is not affected by oxygen, it is concluded that allyl radicals are not dehydrogenated by oxygen; but they oxidize in a branching step involving allylperoxyl radicals; r. radicals other than methyl, and allyl are dehydrogenated according to the conventional process: r·+O₂→unsaturated+HO₂· and account for the production of a large excess of C₆ diolefins, methylcyclopentenes, and hydrogen peroxide, when r. stands for C₆H₁₁, the allyl adduct. Hydrogen peroxide gives rise to a degenerate branching of chains. Based on the proposed scheme, a modeling of the reaction is shown to account fairly well for the concentration-time profiles. Rate constants of many steps are evaluated and discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 503–522, 1998     

Deep oxidative desulfurization of dibenzothiophene with molybdovanadophosphoric heteropolyacid-based catalysts

Three hydrophobic Keggin-type heteropolyacid catalysts, [C₃H₃N₂(CH₃)(C₂H₄)]₅PMo₁₀V₂O₄₀ ([C₂mim]PMoV), [C₃H₃N₂(CH₃)(C₄H₈)]₅PMo₁₀V₂O₄₀ ([C₄mim]PMoV) and [C₃H₃N₂(CH₃)(C₆H₁₂)]₅PMo₁₀V₂O₄₀ ([C₆mim]PMoV), were synthesized by reacting molybdovanadophosphoric acid with imidazolium bromides, and characterized by spectroscopic methods. Their use as catalysts in the extractive catalytic oxidative desulfurization process using hydrogen peroxide as the oxidant and acetonitrile as phase transfer agent was studied. The catalytic properties decreased in the order: [C₆mim]PMoV > [C₄mim]PMoV > [C₂mim]PMoV. The main factors influencing the rate of removal of dibenzothiophene (DBT) were investigated, including reaction temperature, the amounts of catalyst, H₂O₂ and acetonitrile. Nearly 100 % sulfur removal rate was achieved under optimal conditions. The catalyst could be recycled six times with only a slight decrease in activity. A reaction mechanism for DBT oxidation is proposed, in which the Keggin anions first obtain active oxygen from H₂O₂, then the DBT is oxidized to dibenzothiophene sulfones.     

Reaction of atomic oxygen with cyclopentadiene

The reaction of 1,3-cyclopentadiene (CPD) with ground-state atomic oxygen O(³P), produced by mercury photosensitized decomposition of nitrous oxide, was studied. The identified products were carbon monoxide and the following C₄H₆ isomers: 3-methylcyclopropene, 1,3-butadiene, 1,2-butadiene, and 1-butyne. The yield of carbon monoxide over oxygen atoms produced (?_CO) was equal to the sum of the yields of C₄H₆ isomers in any experiment. ?_CO was 0.43 at the total pressure of 6.5 torr and 0.20 at 500 torr. We did not succeed in detecting any addition products such as C₅H₆O isomers. It was found that 3-methylcyclopropene was produced with excess energy and was partly isomerized to other C₄H₆ isomers, especially to 1-butyne. The excess energy was estimated to be about 50 kcal/mol. The rate coefficient of the reaction was obtained relative to those for the reactions of atomic oxygen with trans-2-butene and 1-butene. The ratios k_CPD+O/k_{trans-2-butene+O}= 2.34 and k_CPD+O/k_1-butene+O = 11.3 were obtained. Probable reaction mechanisms and intermediates are suggested.     

O + C<Subscript>2</Subscript>H<Subscript>4</Subscript> potential energy surface: excited states and biradicals at the multireference level

The focus of this study is to understand the multiconfigurational nature of the biradical species involved in the early reaction paths of the oxygen plus ethylene PES. In previous work (J Phys Chem A 113, 12663, 2009), the lowest-lying O(³P) + C₂H₄ PES was extensively explored at the MCSCF, MRMP2, and MR-AQCC levels of theory. In the current work, ground and excited, triplet- and singlet-state reaction paths for the initial addition of oxygen to ethylene were found at the MCSCF and MRMP2 levels along with five singlet pathways near the ^·CH₂CH₂O^· biradical at the MCSCF, MRMP2, and CR-CC(2,3) levels. One of these five paths can lead to the CH₂CO + H₂ products from CH₃CHO rather than from the ^·CH₂CH₂O^· biradical, and this pathway was investigated with a variety of CAS sizes. To provide further comparison between the MRMP2 and CR-CC(2,3) levels, MR-AQCC single-point energies and optimizations were performed for select geometries. After the initial exploration of this region of the surface, the lowest singlet–triplet surface crossings were explicitly determined at the MCSCF level. Additional MRMP2 calculations were performed to demonstrate the limitations of single-state perturbation theory in this biradical region of the PES, and SO-MCQDPT2 single-point energies using SA MCSCF were calculated on a grid of geometries around the primary surface crossing. In particular, these calculations were examined to determine a proper active space and a physically reasonable number of electronic states. The results of this examination show that at least four states must be considered to represent this very complex region of the PES.