Mechanistic Study of Carbon Oxidation with NO2 and O2 in the Presence of a Ru/Na‐Y Catalyst

The oxidation of model soot by NO₂ and O₂ in the presence of a Ru/Na‐Y catalyst under conditions close to automotive exhaust gas after‐treatment systems is investigated. Isothermal oxidation experiments of a physical mixture of carbon black and catalyst were performed in a temperature range of 300–400 °C. A remarkable increase of the oxidation rate by NO₂ and O₂ in the presence of the Ru/Na‐Y catalyst was observed. An overall mechanism involving oxygen transfer from the Ru catalyst to the carbon surface leading to an increase of C(O) complexes is proposed. These C(O) complexes are destabilized in the presence of NO₂ increasing the carbon oxidation rate.     

The Low‐Temperature High‐Pressure Phase Diagram of Energetic Materials: I. Hexahydro‐1,3,5‐Trinitro‐s‐Triazine

The reaction phase diagram of hexahydro‐1,3,5‐trinitro‐s‐triazine (RDX) has been studied as a function of temperature and pressure by Raman spectroscopy to 29 GPa and temperatures ranging from 4 to 298 K. Three stable phases (α, γ, and δ) have been found and their phase stabilities have been investigated. Phase boundaries were studied as a function of pressure and temperature, permitting a delineation of the various polymorph stability fields. A pressure–temperature reaction/phase diagram is constructed from the results of this study and compared to previous high temperature work.     

硝酸镁辅助直接硝解法合成RDX

以发烟硝酸（95%）为硝化剂,六水硝酸镁为助剂,对乌洛托品直接硝解法合成高能炸药黑索今（RDX）进行了工艺改进探索。在原直接法工艺基础上,考察六水硝酸镁的加入量、成熟期反应温度、成熟期反应时间三个主要因素对RDX收率的影响。得到优化的工艺条件为：以发烟硝酸（95%）为硝化剂,六水硝酸镁与乌洛托品的摩尔比为1︰2,成熟期反应温度为30 oC,成熟期反应时间为60 min。该优化后工艺能提高RDX产率到80.6%,比原工艺提高8.6%。     

Quantum Chemical Study on the Interactions of NO3 with RDX and Four Decomposition Intermediates

Recently, NO₃ (nitrate radical) was predicted to be formed during the decomposition of RDX. However, experimental studies of the gaseous products have never detected it. In order to verify the prediction, we studied the interactions of NO₃ with RDX and four RDX decomposition intermediates (RDR, C₃H₅N₅O₄, OST, and TAZ) by using density functional theory (DFT). It is found that NO₃ radical can be converted into NO₂ during the process of interactions with the above‐mentioned five molecules. In other words, NO₃ radical can be consumed in these processes, which gives an explanation for the disappearance of NO₃. Transition state theory (TST) calculations lead to the same results. The binding energies are calculated to estimate the strength of interactions. The energy of NO₃ with RDR is the largest, which indicates this process is most likely to occur. Our calculation provides a support to the prediction of the formation of NO₃.     

Innovative Carbon Dioxide‐Capturing Organic Solvent: Reaction Mechanism and Kinetics

The reaction rates of CO₂ with an innovative CO₂‐capturing organic solvent (CO₂COS), consisting of blends of 2‐tert‐butyl‐1,1,3,3‐tetramethylguanidine (BTMG) and 1‐propanol, were obtained as function of BTMG concentration and temperature. A stopped‐flow apparatus with conductivity detection was used. The reaction was modeled by means of a modified termolecular reaction mechanism which resulted in a second‐order rate constant, and activation energies were calculated for a defined temperature range. Quantum chemical calculations at the B3LYP/6‐31G(d) level also produced the activation energy of this reaction system which strongly supports the experimental findings.     

An Ab Initio Theoretical Study of 2,4,6‐Trinitro‐1,3,5‐Triazine, 3,6‐Dinitro‐1,2,4,5‐Tetrazine,and 2,5,8‐Trinitro‐Tri‐s‐Triazine

In order to evaluate 2,4,6‐trinitro‐1,3,5‐triazine (TNTAz), 3,6‐dinitro‐1,2,4,5‐tetrazine (DNTAz), and 2,5,8‐trinitro‐tri‐s‐triazine (TNTsTAz), the geometries of these compounds have been fully optimized employing the B3LYP density functional method and the AUG‐cc‐pVDZ basis set. The accurate gas phase enthalpies of formation have been obtained by using the atomization procedure and designing isodesmic reactions in which the parent rings are not destroyed. Based on B3LYP/AUG‐cc‐pVDZ calculated geometries and natural charges, the crystal structures have been predicted using the Karfunkel–Gdanitz method. Computed results show that there exists extended conjugation over the parent rings of these compounds. More energy content is reserved in DNTAz than in both TNTAz and TNTsTAz. The title compounds are much more sensitive than 1,3,5‐trinitrobenzene. The calculated detonation velocity of DNTAz reaches 9.73–9.88 km s⁻¹, being larger than those of CL‐20 and TNTAz. TNTsTAz has no advantage over the widely used energetic compounds such as RDX and HMX.     

制药工艺学中培养基于反应机理和动力学的学习思维方式

课程教学的意义本质上是该学科思维方式的培养,制药工艺学教学的主线应该是培养建立在药物合成反应机理与动力学基础之上的专业思维方式.我们通过一些过程化学研究的实例,科学地讲授以反应机理与动力学决定制药工艺配置的思维模式与研究方法学,从而合理地服务于教学、科学研究和药物制造.     

Ti2SC粉体的快速合成及其反应机理

以TiS2、Ti、石墨粉(C)为原料,在200～1100 ℃温度范围内,用微波混合加热法合成Ti2SC 陶瓷粉体。探讨了反应温度对Ti2SC制备的影响,并在1000～1400 ℃温度下用无压烧结进行对比研究。采用XRD、SEM、DSC和热力学对样品的物相、形貌和反应机理进行分析。研究结果表明：利用无压烧结到1400 ℃保温15 min,样品中主相是C,只合成了少量目标相Ti2SC。而用微波混合加热, 400 ℃时,样品中主相为Ti2SC,含有大量的C。升温到800 ℃,目标相衍射峰增强,C衍射峰减弱。在 1100 ℃保温3 min,合成了单相Ti2SC 粉体材料,其颗粒平均尺寸为2-5 mm。在TiS2-Ti-C体系中,400 ℃以下,TiS2和Ti反应生成Ti-S化合物;400 ℃及以上,Ti、C和Ti-S化合物反应生成Ti2SC。     

Amine Modifiers with an s‐Triazine Ring for Unsaturated Polyester Resins, 1

Summary: Synthesis and properties of amine modifiers for unsaturated polyester resins are presented. The modifiers were obtained by reacting 3‐azapentan‐1,5‐diol (diethanoloamine) with 2,4‐dichloro‐6‐methoxy‐1,3,5‐triazine, 2‐chloro‐4,6‐dimethoxy‐1,3,5‐triazine or with cyanuric chloride. They were incorporated into the structure of typical unsaturated polyester resins in the polycondensation stage, i.e. prior to dilution with styrene, in the amount of 0.25 through to 2.0 wt.‐%. The effect of the modifier presence on the curing behavior of the resulting resins is discussed.

Gelation times for unsaturated polyester resins modified with modifiers A , B , and C are shown with the curing system consisting of peroxide initiator and (?): 0.10 cm³, (?): 0.15 cm³, (?): 0.25 cm³, and (?): 0.50 cm³ of cobalt(II ) octenate solution per 25 g of resin.     

Reaction of NO and N2O gases with graphite in TGA

Thermal analyses were conducted in a thermogravimetric analyzer by isothermal techniques in order to characterize the carbon-nitrogen oxide reaction. The carbon samples employed in the present study were SP-1 graphite and Micro 450 graphite. Carbon-NO and carbon-N₂O reactions were carried out in a temperature range of 550–900 °C and 5–20 kPa of the partial pressure of reactant. In the NO reaction, reaction orders with respect to NO concentration and activation energy were 0.46-0.92 and 85–102 kJ/mol, respectively. The rate on the monolayer edge was higher than the rate on the multilayer edges. In the N₂O reaction, reaction orders with respect to N₂O concentration and activation energy were 0.55–1.35 and 167–190 kJ/mol, respectively.     

Mass Transfer Reaction Kinetics of β‐Isophorone Oxidation by Air in an Agitator Bubbling Reactor

The mass transfer reaction kinetics of β‐isophorone (β‐IP) oxidation reaction by air was investigated in a lab‐scale agitator bubbling reactor. This reaction can be regarded as instantaneous and there exists a critical concentration of β‐IP. When the catalyst concentration is kept unchanged, the reaction rate is only controlled by the gas film and the reaction kinetics is of zero order with respect to β‐IP when the β‐IP concentration lies over the critical concentration. The reaction rate is controlled by the dual film and the kinetics is of first order with respect to β‐IP when its concentration is below the critical concentration. Under the gas film‐controlling condition, the effect of temperature, agitator speed, and aeration on the reaction rate is evaluated. A correlation equation of gas phase volumetric mass transfer coefficients combining superficial gas velocity and agitator speed is defined.     

Simplified Free‐Radical Reaction Kinetics for p‐Xylene Oxidation to Terephthalic Acid

The kinetic models based on complex free‐radical mechanisms always involve lots of parameters, which result in model overparameterization. In this work, on the basis of free‐radical reaction mechanisms, a simplified kinetics for liquid‐phase catalytic oxidation of p‐xylene (PX) to terephthalic acid (TPA) was developed. By assuming that different peroxy radicals have equivalent reactivity, all the initiation rate constants are identical, and the differences in the rates of termination between various peroxy radicals are neglected, the kinetic model is simplified to include only six parameters that are to be determined by experiment. The kinetic model established in this paper was shown to have satisfactory precision in predicting the concentration profiles. The kinetic model proposed is even simpler than the first ‐ order kinetic model because the rate constants concerning chain propagation and termination are independent of temperature within the range investigated.     

MDI生成聚异氰脲酸酯的等温反应速度动力学研究

在催化剂的存在下，使ＭＤＩ进行等温聚合，采用ＦＴＩＲ快速红外光谱技术跟踪２２７０ｃｍ＾－１处峰的变化，以此来研究ＭＤＩ生成聚异氰脲酸酯的等温反应动力学，以及温度、催化剂浓度等对反应速度的影响。     

NO2 inhibits the catalytic reaction of NO and O2 over Pt

The rate equation for the overall reaction of NO and O₂ over Pt/Al₂O₃ was determined to be r=k_f[NO] ^1.05±0.08[O₂]^1.03±0.08[NO₂]^0.92±0.07(1-), with k_f as the forward rate constant, =([NO₂]/K[NO][O₂]^1/2), and K as the equilibrium constant for the overall reaction. An apparent activation energy of 82 kJ mol^–1 ± 9 kJ mol^–1 was observed. The inhibition by the product NO₂ makes it imperative to include the influence of NO₂ concentration in any analysis of the kinetics of this reaction. The reaction mechanism that fits our observed orders consists of the equilibrated dissociation of NO₂ to produce a surface mostly covered by oxygen, thereby inhibiting the equilibrium adsorption of NO, and the non-dissociative adsorption of O₂, which is the proposed rate determining step.     

壳聚糖及Zn2+模板壳聚糖膜与Zn2+螯合反应的动力学及机理探讨

分别用壳聚糖及Zn2 模板壳聚糖膜与Zn2 螯合反应,在30、40、50、60、70℃测定出锌离子浓度随时间变化的数据,由dc/dt=-kcn进行拟合,以线性相关系数为判据,得到该螯合反应的积分动力学模式函数:2c=-kt。表观活化能E壳(131.96 kJ/mol)>E膜(89.92 kJ/mol),表明Zn2 模板壳聚糖膜对Zn2 具有较强的“记忆”能力。并用红外光谱(IR)光电子能谱(XPS)对壳聚糖与Zn2 的螯合机理进行了探讨。结果表明Zn2 壳聚糖螯合物的配位原子是-NH2中的N,壳聚糖分子链上的-OH没有参与配位反应。     

Investigation on the Thermal Expansion and Theoretical Density of 1,3,5‐Trinitro‐1,3,5‐Triazacyclohexane

The CTE and the theoretical density are important properties for energetic materials. To obtain the CTE and the theoretical density of 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), XRD, and Rietveld refinement are employed to estimate the dimensional changes, within the temperature range from 30 to 170 °C. The CTE of a, b, c axis and volume are obtained as 3.07×10⁻⁵ K⁻¹, 8.28×10⁻⁵ K⁻¹, 9.19×10⁻⁵ K⁻¹, and 20.7×10⁻⁵ K⁻¹, respectively. Calculated from the refined cell parameters, the theoretical density at the given temperature can be obtained. The theoretical density at 20 °C (1.7994 g cm⁻³) is in close match with the RDX single‐crystal density (1.7990 g cm⁻³) measured by density gradient method. It is suggested that the CTE measured by XRD could perfectly meet with the thermal expansion of RDX.     

Kinetics of catalyzed and non‐catalyzed soot oxidation with nitrogen dioxide under regeneration particle trap conditions

BACKGROUND: For compliance with the regulations on diesel particulate matter, car manufacturers have developed diesel particulate filters (DPF). These technologies require a regeneration method which oxidizes soot deposits in the filter. In diesel exhaust emissions there are two suitable oxidizing gases: oxygen and nitrogen dioxide. Nitrogen dioxide is much more active than O₂ and can directly attack the carbon surface. This work describes the kinetics of the oxidation of soot by NO₂ over a wide range of conditions relevant for DPF. RESULTS: The catalyzed and the non‐catalyzed oxidation of soot have been performed in a fixed‐bed reactor. The experimental results show that the overall oxidation process can be described by two additive parallel reactions: a direct C ? NO₂ reaction catalyzed by H₂O and a cooperative C ? NO₂ ? O₂ reaction catalyzed by the Pt/Al₂O₃ catalyst. The results obtained allow to propose the following kinetic law for the specific rates of the catalyzed and the non‐catalyzed oxidation of soot in the regeneration filter conditions: CONCLUSION: The kinetic parameters describing the oxidation rate of soot by NO₂ over a range of temperature and gas composition have been obtained. The extracted kinetics data are relevant for modeling the removal of trapping soot in automotive gas exhaust technology. Copyright © 2009 Society of Chemical Industry     

甲烷化反应体系研究综述

对煤气甲烷化反应体系进行热力学分析,概述耐硫和非耐硫甲烷化的反应机理,剖析耐硫甲烷化催化剂失活的原因。