噻吩类含硫模型化合物的降解机理研究

为了探究煤中噻吩类有机硫化合物降解规律,采用密度泛函理论搜索过渡态提出了两条反应路径.通过对反应路径中各物种的原子电荷、热力学、动力学参数和噻吩降解的势能剖面图分析得出:各路径发生的难易程度是不同的,噻吩降解的最有利的反应路径为Path1,即首先是H9转移到S5上,接着H8从C3转移到C4上伴随着C4-S5键的断裂,然后H6转移到S5上,最后随着H7从C2转移到C1上,H2S离开原来的结构,丁二炔形成.利用密度泛函理论对煤中噻吩类含硫模型化合物在不同降解路径中的变化规律进行研究,可以有助于理解煤中噻吩硫的脱除机理,为煤中噻吩类有机硫的脱除实验及工业处理过程提供理论指导.     

微波辐射炼焦煤中噻吩硫结构的非热效应研究

采用XANES和XPS解析山西炼焦煤中有机硫的赋存特征,选择与煤中结构匹配的噻吩硫模型化合物进行微波辐射和水浴加热,通过Raman光谱比较研究两者对模型化合物中含硫结构的作用机制,利用Materials Studio构建、优化模型化合物结构,用密度泛函理论计算模拟微波场中模型化合物分子构型参数,解析含硫结构对微波的响应机理。结果表明：噻吩硫是炼焦煤中有机硫最主要的赋存形式。微波辐射后,模型化合物碳硫键和硫硫键的Raman谱吸收峰发生红移,温升速度快的模型化合物红移较小;相同温升的水浴加热后,几乎没有红移现象。微波能量不足以使模型化合物中碳硫键和硫硫键断裂,但能够改变分子构型,模型化合物含硫键在微波场中可能存在某种过渡态。微波作用对煤中噻吩硫结构存在非热效应。     

并五噻吩分子光谱和激发态的密度泛函理论

首次采用密度泛函理论(DFT)中的B3LYP方法,在6-31G(d)水平上对并五噻吩进行了构型优化,并作振动分析,未出现虚频。频率分析得到分子红外光谱和拉曼光谱,同时也得到分子的HOMO-LUMO能隙为3.86eV,所得计算结果与实验值基本符合。利用含时密度泛函理论(TDDFT)计算其激发态,得到振荡强度最大的五个允许跃迁的单激发态,所有激发态光谱均在紫外波段,故在可见光区域分子相对稳定,不易光致分解。对前线分子轨道HOMO和LUMO分析得到,HOMO到LUMO的跃迁是电子从C原子转移到S原子上,C—C原子之间形成离域键,这正是并五噻吩区别于一般有机材料而具有导电性的根本原因。结果表明:相对于并五苯,并五噻吩具有更高的稳定性,同时具有很好的导电性能和发光性能,是新一类有机半导体材料。     

炼焦煤中有机硫赋存表征及微波对噻吩硫作用机理研究（英文）

掌握炼焦煤中有机硫的禀赋特征,认知微波对煤中有机硫结构的化学作用机制,对丰富煤炭脱硫理论体系,优化煤炭微波脱硫工艺,开发煤精细加工新技术具有重要意义。应用XPS和XANES表征炼焦煤中有机硫的主要赋存结构类型及其相对含量,基于煤密度特性的差异,探索有机硫类型及其含量的变化规律。选择苯并噻吩和3-噻吩甲酸两种模型化合物,分别进行915和2 450 MHz频率微波辐射实验,通过Raman光谱研究模型化合物中含硫结构的变化特征,利用Materials Studio进行量子化学模拟,计算不同方向外加能量场作用下模型化合物的构型参数,比较微波辐射前后,模型化合物构象变化,解析煤中含硫化学键对微波能量的响应机制。XPS和XANES表征结果显示,炼焦煤中硫以有机硫为主,噻吩是煤中最主要的有机硫赋存形式。随着炼焦煤密度级的增加,噻吩硫相对含量逐渐减小,硫醇(醚)和(亚)砜相对含量逐渐增大,三类有机硫赋存含量趋于平均。施加不同方向的外加能量场后,苯并噻吩和3-噻吩甲酸中含硫化学键键长和键级变化不明显,说明微波能量场对化学键的拉伸和扭转作用有限,但是,对模型化合物分子结构中的键角和偶极矩具有影响,并且,不同的能量场施加方向对键角和偶极矩的影响效果不一样。Raman谱图分析显示, 915和2 450 MHz频率微波辐射后,模型化合物中含硫化学键振动峰都出现了红移。因此,微波辐射影响了模型化合物微环境局部结构,改变了其分子构型和分子极性,减小了晶格的振动恢复力,削弱了原子间的相互作用力,促进了含硫化学键的断裂及硫的解离。同时,发现915 MHz频率微波辐射具有比2 450 MHz更加明显的作用效果。     

三种五元化合物的荧光光谱的量子化学研究

采用密度泛函理论(DFT)中的B3LYP方法,在6-31G^*水平上对三种五元杂环物质进行了构型优化,对优化后的构型做振动分析,均未出现虚频率。在此基础上通过轨道分析,探索了分子内部电子跃迁的机理。结果表明,这三种五元化合物HOMO到LUMO的跃迁是电子从C1、C2、C3和C4转移到杂原子(吡咯中的N原子,呋喃中的O原子和噻吩中的S原子)上,并在6-31G^*水平上用单激发组态相互作用(CIS)方法分别计算了三种物质的荧光光谱,所得计算结果与实验值基本符合。     

自由基聚合中二硫酯结构及其活性的研究

用密度泛函方法,在B3LYP/6-31G+(d)水平上对三种二硫酯化合物进行了几何构型全优化.计算了C-S键离解能以及对于自由基的原子自旋密度,并且探讨了它们与化合物活性之间的关系,分析的结论与实验结论完全一致.同时结论也表明密度泛函理论计算能为C—S键离解能,原子自旋密度变化趋势提供一个很好的预测.     

煅烧石油焦脱除烟气中Hg0密度泛函理论研究

石油焦作为碳基吸附剂脱除燃煤烟气中Hg~0的研究近年来得到发展,本文建立了表征煅烧石油焦表面的四碳环并噻吩饱和簇模型,运用量子化学密度泛函理论B3LYP-D3方法,基于6-31g(d)/lanl2dz混合基组水平,从微观层面研究了煅烧石油焦吸附Hg~0的机理,同时计算了Hg在煅烧石油焦上的吸附能及Mayer键级,并分析了石油焦中噻吩硫在脱汞中的作用。研究结果表明,Hg~0在煅烧石油焦上的吸附以物理吸附为主,噻吩硫对Hg~0的吸附有促进作用。量子化学理论计算是研究煅烧石油焦吸附剂脱除Hg~0机理的一种有效方法。     

2-（4，5-二硫甲基-1，3-二硫环戊烯基）-3，4-富勒吡咯烷的合成表征及电子光谱的INDO/ S研究

通过亚胺叶立德与C60 发生 1,3 偶极环加成反应的方法 ,合成了一种新的具有分子内给 受体系的C60吡咯烷衍生物 2 (4 ,5 二硫甲基 1,3 二硫环戊烯基 ) 3,4 富勒吡咯烷 (C66H9NS4) ,以红外、元素分析、核磁共振氢谱、紫外进行了表征 .运用Gaussian98量子化学程序包 ,利用密度泛函的方法对分子的几何构型进行了优化 ,在优化的基础上 ,应用INDO/S的方法计算了化合物的电子光谱 ,计算结果表明 ,C66H9NS4的光谱吸收在 4 38.9nm ,与实验值 4 31.4nm基本一致     

ClF3O和环氧丙烷反应的理论研究

应用密度泛函理论对 ClF3 O 和环氧丙烷的反应机理进行了研究。在 B3PW91/6-31++G(d ,p )水平上优化了各驻点(反应物、中间体、过渡态和产物)的几何构型,并计算了它们的振动频率和零点振动能。采用 CCSD(T)/6-31++G(d ,p )//B3PW91/6-3l++G(d ,p )单点能计算方法求得各物质的能量,并做零点能校正。计算结果表明,ClF3 O 与 C3 H 6 O 可经过不同的反应路径,引发 C3 H 5 O 自由基和 ClOF2自由基生成环氧丙醇和三氟化氯,其中,位于 ClF3 O 周向位置的 F 原子与 C3 H 6 O 的 C(7)上与 CH 3异侧的 H(9)原子结合的活化能最低,仅15.63 kJ/mo1;ClF3 O 与 C3 H 6 O 反应生成的 C3 H 5 O 自由基和 ClOF2自由基继续反应,经过不同反应路径生成 C3 H 4 O、ClOF 和 HF,其中,ClOF2中的 F 原子和 C3 H 5 O 中的 H(2)或 H(4)原子结合是无能垒的过程。整个反应的主要路径为 C3 H 6 O+ClF3→O→TS12 P4(C3 H 5 O+HF+ClOF2→) P12(CH 2 CHCHO+2 HF+ClOF)。     

一种新型四硫富瓦烯衍生物的合成与表征

以二硫化碳和金属钠为基础物质合成了四硫富瓦烯（TTF）锌的配合物（TTF）Zn（NBu4）2。利用该化合物与苯甲酰氯反应得到的稳定化合物C17H10O2S5在甲醇钠溶液中与2,3-二溴丙醇反应成功合成出目标化合物（一种新配体）,其化学组成为C6H6OS5。利用IR谱、^1HNMR谱及元素分析对此化合物进行了表征。     

Ultrasound assisted oxidative desulfurization of model diesel fuel

Very stringent environmental regulations have limited the level of sulfur in diesel, therefore deep desulfurization of fuels is required. For that purpose, the frequently used industrial process is hydrodesulfurization (HDS) which enables effective elimination of sulfur compounds such as mercaptanes, thiols, sulfides, disulfides from diesel oil, but removal of thiophene sulfur compounds (benzothiophene, dibenzothiophene, 4,6 dimethyldibenzothiophene) is insufficient. Ultrasound assisted oxidative desulfurization (UAOD) as one of several new technologies enables performance under mild conditions without use of explosive hydrogen. A higher reactivity of thiophene sulfur compounds during UAOD also provides conversion into highly polar sulfoxides and sulfones that are easily removed by adsorption or extraction. Nowadays, different catalyst/oxidants systems are being studied to improve oxidation reaction efficiency and enhance the mass transfer in the interfacial region. In this paper, the effect of reaction temperature (40–70 °C) and oxidation time (5–150 min) for UAOD of model diesel fuel with a catalyst/oxidants system (acetic acid/hydrogen peroxide) was investigated in a 70 ml batch reactor. Furthermore, the effects of different initial concentrations of dibenzothiophene (DBT) and of ultrasound amplitude were additionally examined to achieve efficient sulfur removal. The obtained results indicated that temperature and US amplitude of 70 °C and 80% respectively were efficient for conversion of DBT (sulfur concentration up to 3976.86 ppm). The results indicate a rise in the yield of sulfones at higher temperatures and subsequent extraction with N,N-dimethylformamide conducted after the process of oxidation at different solvent/oil ratio revealed sulfur removal efficiency of 98.35%.     

Cu纳米粒催化CO2还原反应机理的理论研究

此文采用密度泛函理论,研究了Cu₃₈纳米粒催化剂模型,分别研究了CO₂和H₂O分子在催化剂上不同吸附位,确了稳定的吸附构型,并进一步研究了CO₂催化还原反应机理,确定催化剂的活性.本文主要研究催化CO₂还原生成CO过程,研究了两条可行的反应路径,路径I为水分子的H原子直接转移到CO₂上,路径II为H原子先迁移到Cu₃₈纳米粒上再转移到CO₂上,研究结果发现此步反应机理路径I优先.从微观角度解释了实验研究结果.     

Experimental and DFT investigation of surface degradation of polyvinylidene fluoride membrane in alkaline solution

The degradation processes of polyvinylidene fluoride (PVDF) membranes in alkaline solutions were studied using FTIR, FT-Raman, XPS and density functional theory (DFT) simulations. The activation energies for the degradation paths were calculated by LST/QST search methods. The corresponding Gibbs free energies were calculated using a continuum solvation model. The analysis of the spectra indicates the presence of C=C bonds, hydroxyl and carbonyl groups on PVDF membranes. It can be inferred, from DFT calculations, that defluorination is the energetically favorable path, followed by the formation of C=C bonds. The subsequent hydroxylation and carbonyl formation experience higher activation barriers than the formation of C=C bonds. The results indicate that the theoretical calculations are in accordance with the experimental data.     

The hydrolysis mechanism and kinetic analysis for COS hydrolysis: A DFT study

Density Functional Theory (DFT) was utilized to study the hydrolysis mechanism and kinetic analysis of carbonyl sulfide (COS). The structures of reactants (R), transition states (TS), intermediates (IM) and products (P) were analyzed and a conclusion reached that hydrolysis mechanism of COS occurs in two paths with One path as a C=S path and the other as a C=O path and all featuring potential for forming H₂S and CO₂. Function change analysis of COS hydrolysis indicated the rate-determining step of COS hydrolysis was the first elementary reaction as OH and H in H₂O attacked C=O and S=O in COS, respectively, with the two paths parallel and competitive and the C=S path more reactionary than the C=O path. Influence on each elementary reaction was also not consistent with reaction temperature increase. The study also included further investigation of the COS catalytic hydrolysis.     

Encapsulation and convex-face thiozonolysis of triatomic sulfur (S(3)) with carbon nanotubes

Nanotubes are a class of host cavities increasingly used to encapsulate unstable molecules, yet none have been exploited to host reactive sulfur species, such as thiozone (S(3)). In this paper, density functional theory and (ONIOM) calculations were used to compute single-walled carbon nanotube (SWNT)-thiozone combinations for the inclusion of S(3) into the hollow nanotube space and to rationalize when 1,2,3-thiozonide formation can take place. Nanotube diameter selectivity for the isomerization of the C(2v) form of S(3) to the D(3h) form proved to be elusive. Acyclic C(2v) S(3) was ~6 kcal/mol more stable than cyclic D(3h) S(3) whether it was free or encapsulated within an SWNT. 1,2,3-Thiozonide formation took place on the convex side of nanotubes of low tube radii, such as the armchair (4,4) and (5,5) SWNTs. In terms of the reaction mode of C(2v) S(3), the 1,3-dipolar addition reaction was preferred compared with the [2 + 2] cycloaddition and chelotrope paths.     

Structural and spectroscopic study of adsorption of anthracene on silver

Adsorption of anthracene on silver is investigated based on the density functional theory and the surface-enhanced Raman spectroscopy (SERS). Variations in bond and dihedral angles of the optimised geometry of anthracene indicate distortions in the hexagonal structure of the ring nearer to the silver cluster and deviations in the co-planarity of carbon atoms. Natural bond orbital analysis confirms intramolecular charge transfers from π(C–C) to π*(C–C) and π(C–C) to σ*(Ag–Ag) orbitals. Higher polarisation resulting from charge transfers on adsorption accounts for Raman enhancements of selective vibrational modes and band shifts. Surface plasmon resonance peak of silver nanoparticles after the adsorption of anthracene observed around 399 nm compares well with the theoretically simulated UV–vis spectrum derived using the time-dependent density functional theory. Theoretical and experimental SERS correlate well, confirming the process of adsorption, the tilted orientation of anthracene on the silver surface and the adsorption mechanism reported. Localisation of the electron density together with a reduced band gap after the adsorption on silver suggests its utility in the design of electro-active organic molecular devices.     

H_2在Al_nCr(n=1-7)团簇上吸附和解离的密度泛函研究

采用密度泛函理论中的B3LYP方法研究了H2在AlnCr(n=1-7)团簇上的吸附和解离.结果表明:AlnCr团簇结构与Aln+1团簇结构相似;物理吸附是H2以侧向的形式吸附在Cr原子上,H-H键长略微增长,H2的振动频率发生了红移;除了n=5外,其它AlnCr H2团簇的最稳定结构均是AlnCr团簇的最稳定结构与两个氢原子成键而成;AlnCr团簇向H原子转移了电荷;AlnCr H2团簇的平均结合能,垂直电离势和能隙均大于AlnCr团簇的,即AlnCr H2团簇比AlnCr团簇更稳定;Al7Cr对H2的化学吸附表现出较强的惰性,而AlnCr H2(n=1,2,6)则表现出较强的化学活性;由化学反应路径跟踪可知,通过改变AlnCr团簇中Al原子的个数可以调节H2的物理化学吸附行为.     

H2在AlnCr(n=1-7)团簇上吸附和解离的密度泛函研究

采用用密度泛函理论中的B3LYP方法研究了H2在AlnCr(n=1-7)团簇上的吸附和解离。结果表明：AlnCr团簇结构与Aln+1团簇结构相似;物理吸附是H2是以侧向的形式吸附在Cr原子上,H-H键长略微增长,H2的振动频率发生了红移;除了n=5外,其它AlnCrH2团簇的最稳定结构均是AlnCr团簇的最稳定结构与两个氢原子成键而成;AlnCr团簇向H原子转移了电荷;AlnCrH2团簇的平均结合能,垂直电离势和能隙均大于AlnCr团簇的,即AlnCrH2团簇比AlnCr团簇更稳定;Al7Cr对H2的化学吸附表现出较强的惰性,而AlnCrH2(n=1,2,6)则表现出较强的化学活性;由化学反应路径跟踪可知,通过改变AlnCr团簇中Al原子的个数可以调节H2的物理化学吸附行为。     

煤基化学链燃烧过程中硫的演变

在双阶段流化床反应器内,基于溶胶凝胶法制备的Fe2O3/Al2O3氧载体研究了褐煤化学链燃烧过程中燃料硫的迁移路径及分布特性,并讨论了温度、过氧系数对燃料硫释放分布的影响.结果表明:所有工况下,氧载体均未出现被硫化的现象;在热解气化学链燃烧阶段,气相含硫物质以SO2和H2S为主,煤焦气化气化学链燃烧阶段绝大部分为SO2气体,部分来源于煤焦中CaSO4的分解。另外,部分燃料硫被碱金属固定于煤灰中。同时,提高温度和过氧系数都能导致SO2/H2S值和SO2释放量增大。