稠环芳烃直接加氢的分子模拟研究

为提高重质油轻质化效率,抑制生焦,需对其中稠环芳烃加氢的具体过程详细探讨。本论文构建了一系列不同芳环数组成的稠环芳烃,以分子模拟为手段从反应机理层面研究稠环芳烃(PAHs)加氢反应过程。采用基于密度泛函理论的DMol~3模块对反应过程进行模拟计算,得到不同稠环芳烃加氢过程的反应热和能垒,通过数据比较探索稠环芳烃按照自由基热反应机理加氢时反应的难易程度。数据分析的结果显示,在自由基足量存在且能与模型化合物有效接触的理想状态下,稠环芳烃分子芳环数、分子饱和度对加氢难易程度影响不大,芳环极易与氢自由基结合,重质油加氢困难并非是因为稠环芳烃与氢自由基直接反应困难造成。     

双芘环荧光体Pyrene-diIL-Pyrene荧光特性的分子动力学研究

采用分子动力学模拟方法研究双芘环荧光体Pyrene-diIL-Pyrene(PDP)在水和甲醇中荧光改变的机制.结果表明,平衡时(1)该荧光体当分子中的芘环中心间距小于6 A时,芘环在甲醇中比在水中的排列无序;(2)最近邻芘环中心间距从约4 1 A处移到了6.0 A处,降低了芘分子形成芘激子的概率,进而表明该荧光体的激...     

对硝基苯酚加氢试验及连续化工艺设计

针对间歇铁粉还原法生产对氨基苯酚劳动强度高,产品质量波动大,环境污染严重的缺点,研究了对硝基苯酚催化加氢连续化生产工艺。在给定温度、压力和进料组成的条件下,对低浓度下PNP加氢反应动力学进行了试验研究。结果表明,搅拌速率大于1000rpm时,外扩散影响可以消除。在低浓度下PNP反应速率和PNP浓度成线性关系。在此基础上,设计年产20000吨PAP规模的连续反应系统,包括搅拌釜加氢反应器和保护反应器。搅拌釜加氢反应器体积为32m3,直径为3.3m,高度5m。蛇管换热面积为142.7m2,蛇管传热系数为565W·m-2·K-1,搅拌形式为四叶折叶开式涡轮,直径1.1m,转速200rpm。保护反应器为直管,直径300mm,长度4m,出口PNP浓度200mg·L-1。     

芘功能化单分子层荧光薄膜荧光猝灭机理的分子动力学研究

实验证明,芘功能化单分子层荧光薄膜的荧光能被溶液中的硝基苯显著猝灭,为了找到猝灭的根本原因,本文采用分子动力学模拟方法来研究猝灭的机理.模拟结果表明,该薄膜在真空环境中,一对芘环中心的距离分布在(4～10)A之间,且主要是在5.3 A左右,该距离正适合于形成芘激子.当把硝基苯分子加入到该薄膜中时,我们发现芘分子在这一距...     

柴油馏分深度加氢脱硫过程中有色体形成机理的研究

为了生产含低硫、色度好的柴油产品，采用计算机分子模拟技术研究了柴油馏分深度加氢脱硫(HDS)过程中多环芳烃有色体的形成机理。研究结果显示，柴油馏分中难脱除硫化物4-MDBT、4，6-DMDBT的HDS中间产物生成多环芳烃的反应历程中每步反应的活化能较低，其中的缩合环化反应为吸热反应。模拟产物符合实验事实，表明模拟计算的多环芳烃有色体形成路径是可能的、合理的。     

计算机仿真应用于石油组分切割的方法与理论

石油的复杂性导致其组分的不确定性,而石油组分的切割是进行石油化工流程模拟的基础.结合在完成某化工厂柴油加氢动态仿真过程中进行的石油组分切割实例,介绍了组分切割的具体步骤,并针对现实工厂中提供的不同数据总结了石油组分确定的方案,最后提出了石油组分确定的理论-非线性的数据校正技术.     

硫化钼基加氢脱硫催化剂活性位的研究进展

硫化钼基催化剂是加氢脱硫过程的常用催化剂,其活性相结构与加氢脱硫性能的关系一直是催化加氢领域研究的热点问题,该问题对开发更高活性和选择性的催化剂具有十分重要的意义。本文综述了近年来加氢脱硫催化剂的表征和理论计算方面的研究进展,对MoS_2、CoMoS和NiMoS的具体微观结构进行了分析,并对可能的加氢脱硫活性位以及噻吩在活性位上加氢脱硫的反应路径进行了探讨。     

基于ASPEN PLUS的超临界汽油中低温煤焦油加氢裂解工艺模拟(英文)

为了尽快实现超临界汽油中低温煤焦油加氢裂解工艺的工业化,利用ASPEN PLUS模拟煤焦油在超临界溶剂中的加氢过程,以获得整个工艺运行的基本参数。本文基于超临界汽油中低温煤焦油加氢裂解的中试试验数据,对超临界汽油中低温煤焦油加氢裂解工艺进行模拟。首先,煤焦油代表组份选自煤焦油中含量较高的组分,汽油溶剂在模拟中根据其沸点曲线定义为虚拟组分;其次,根据碳离子反应机理,所有的煤焦油代表组分发生裂解反应,并将所有反应输入模型;加氢裂解过程主要选用RK-SOAVE和BK10物性方法,超临界汽油在模拟过程中定义为亨利组分:最后,根据煤焦油加氢裂解的反应特征,模型中主要包含3个基本模块,即RYIELD、Separtor和PetroFrac,分别模拟加氢裂解、气液分离和常压分馏。模拟时将超临界汽油中低温煤焦油加氢裂解中试实验条件数据输入模型,模拟结果表明:模型预测值与实验值基本一致,表明该模型能较好的反映超临界汽油中低温煤焦油加氢裂解工艺过程。并利用模型对年处理15万吨的超临界汽油中煤焦油加氢裂解工艺进行优化设计,获得了工艺的基本参数和能耗,为超临界汽油中低温煤焦油加氢裂解工艺工业化提供了理论依据和设计参考。     

稠环芳烃基态及激发态亲核反应活性的量化研究

采用量子化学限制性Hartree Fock方法(RHF)和多参考态组态相互作用方法(MRCI),对渺位缩合和迫位缩合稠环芳烃的基态和激发态的最高活性碳位进行了研究。前线轨道的能级研究表明,基态时随着环数的增加,渺位缩合稠环芳烃的前线轨道能级差从1065 kJ/mol逐渐减小到976.4 kJ/mol,说明随着环数的增加,渺位缩合稠环芳烃分子的稳定性逐渐降低,分子反应活性逐渐增强。而迫位缩合稠环芳烃由于分子内部芳香环的结合程度和碳原子的共用程度不一致导致处于基态时前线轨道能极差并没有随着芳环数的增加呈现出线性行为。进一步,通过比较C原子的Mulliken电荷,以及不同位置C-C键的键级和键长研究了稠环芳烃的亲核加氢反应的最高活性碳位。结果表明,处于基态时,渺位缩合稠环芳烃的最高活性碳位出现在内侧芳环的外侧碳位上,而迫位缩合稠环芳烃的最高活性的碳位出现在外侧芳环的外碳位置;处于激发态时,大多数渺位缩合、迫位缩合稠环芳烃的最高活性碳位与基态是重合的,部分稠环芳烃的最高活性碳位会发生转移。     

加氢装置能量优化浅议

未来我国各类加氢装置的投建数量将随着各类车用燃料和化工原料的品质要求越来越多、规模越来越大,加氢装置的能耗较高且各类加氢装置的流程非常相似,在认清加氢工艺流程的能量特点的基础上,打破传统的局部节能思维,采用将分离部分向反应部分回吐热量的方法进行全装置综合节能,并以一工程实例证明该节能思路的可行性。     

奈韦拉平闭环前体的量子化学研究与实验

采用密度泛函B3LYP/6-31G(d)方法对奈韦拉平闭环前体2-环丙胺基-N-(2-氯-4-甲基-3-吡啶基)-3-吡啶甲酰胺进行了量子化学研究,并通过闭环前体在强碱的作用下,在有机溶剂中加热回流合成奈韦拉平进行了实验验证。理论计算结果表明,闭环前体分子稳定性较差,具有较强的反应活性;偶极矩与奈韦拉平差别不是很大;与卤素原子相连的碳原子是亲核取代反应的活性中心,仲胺氮原子和羰基氧原子的亲核性存在着竟争。实验结果显示,强碱的用量是影响闭环反应的主要因素,根据理论计算推测的主要产物和副产物,与实验结果相一致。     

三相淤浆床甲醇合成反应器模型及过程模拟计算结果

应用三相淤浆床甲醇合成反应器流体力学数据和甲醇合成过程基础数据,采用Ｃ－３０２铜基催化剂,采用液体石蜡油作为热载体,以ＣＯ、ＣＯ２加氢合成甲醇为独立反应,以ＣＯ、Ｃ炎关键组分,建立三相淤浆床反应器的数学模型,利用序贯模块方法对整个回路进行模拟计算。     

Ni/AC 催化剂的制备、表征与 1,4- 丁炔二醇加氢性能

开发高效的 Ni 基加氢催化剂，实现 1,4-丁炔二醇加氢定向合成 1,4-丁二醇，是构建煤基初级化学品高值化延伸产业链的关键。针对目前广泛采用的 Raney Ni 催化剂，无载体支撑，存在活性比表面低、加氢选择性差等问题，该文制备了以发达孔隙结构的活性炭(active carbon，AC)为载体的 Ni/AC 催化剂，结合表征手段探讨了催化剂结构与性能的构效关系。研究结果表明，随着 Ni 负载量的升高，活性炭表面暴露的活性镍物种先增加后减少，加氢活性也呈火山形分布。25Ni/AC(Ni 的质量分数为 25%)催化剂对 1,4-丁二醇的选择性最高，达 86.2%，对半加氢产物 1,4-丁烯二醇与半缩醛 2-羟基四氢呋喃的选择性分别为 1.2% 与 6.8%。造成此现象的原因是该样品中高分散的活性 Ni 提供了大量活性氢，促进了加氢反应。低 Ni 负载量的催化剂因 Ni 活性中心间距较远，表面活性 H 密度低，而易于发生异构副反应生成半缩醛 2-羟基四氢呋喃。当 Ni 负载量较高时，Ni 聚集造成加氢活性下降。     

Experimental and modeling studies of acetylene detection in hydrogen/acetylene mixtures on PdM bimetallic metal-insulator-semiconductor devices

The effect of the composition of the metal gate on acetylene response in hydrogen/acetylene mixtures was tested for a number of metal-insulator-semiconductor (MIS) devices with bimetallic gates. The motivation for this study was that bimetallic catalysts are employed in the commercial acetylene hydrogenation process because of superior performance compared to the pure metals. A variety of metal compositions and operating temperatures were tested, with the largest reproducible acetylene response observed for a 15% Ag/Pd sensor at 398 K. Kinetic modeling of the relevant surface reactions on Pd and bimetallic PdAg provided insights into how temperature, feed concentration, and Ag content affected response. The model predicted that significant coverages of carbon species formed on the surface, mainly CH(s) and C(s) on Pd and CCH(s) on PdAg, and that these species strongly influenced sensor responses. The dynamic changes in the surface coverages of carbonaceous intermediates after acetylene introduction were correlated with a response overshoot seen experimentally. The model indicated that the superior performance of Ag/Pd sensors relative to Pd sensors could be explained in terms of a higher hydrogen consumption rate. These results indicate a strong connection between the high reaction rates observed for industrial Ag/Pd acetylene hydrogenation catalysts and acetylene response in Ag/Pd MIS sensors.     

煤焦油加氢裂化集总动力学模型的研究

基于对煤焦油加氢过程分析,建立了煤焦油加氢裂化五集总(煤焦油、汽油、柴油、气体、焦炭)动力学模型。利用煤焦油加氢裂化的实验室小试结果,对加氢反应过程的动力学参数利用MATLAB软件编程进行了回归。结果表明,该模型能很好的预测产品的分布,其计算结果和实验值一致。在此基础上重点讨论了在一定温度下空速、氢油比、氢气的初始压力等操作条件对产品分布的影响,为进一步工艺流程的优化提供了依据。     

DFT simulations and microkinetic modelling of 1-pentyne hydrogenation on Cu20 model catalysts

Adsorption and dissociation of H₂ and hydrogenation of 1-pentyne on neutral and anionic Cu₂₀ clusters have been investigated using the density functional theory and microkinetic modelling. Molecular adsorption of H₂ is found to occur strictly at atop sites. The H₂ dimer is activated upon adsorption, and the dissociation occurs with moderate energy barriers. The dissociated H atoms reside preferentially on 3-fold face and 2-fold edge sites. Based on these results, the reaction paths leading to the partial and total hydrogenation of 1-pentyne have been studied step-by-step. The results suggest that copper clusters can display selective activity on the hydrogenation of alkyne and alkene molecules. The hydrogenated products are more stable than the corresponding initial reactants following an energetic staircase with the number of added H atoms. Stable semi-hydrogenated intermediates are formed before the partial (1-pentene) and total (pentane) hydrogenation stages of 1-pentyne. The microkinetic model analysis shows that C₅H₁₀ is the dominant product. Increasing the reactants (C₅H₈/H₂) ratio enhances the formation of products (C₅H₁₀ and C₅H₁₂).     

Ab initio calculations on the five-membered alumino-silicate framework rings model: implications for dissolution in alkaline solutions

An ab initio restricted Hartree-Fock calculation utilising the standard 6-31G basis set was used to calculate total energies after PM3 calculations of energy-optimised geometries for the five-membered alumino-silicate framework rings cluster for a total of ten T sites. Calculations have shown that in the absence of protons or other ions, the most favourable sites for 1A1, 2A1 and 3A1 substitution of Si are the T6, T1 and T9 sites respectively. With more Al atoms replacing Si in a cluster, T-O bond lengths and T-O-T angles show lengthening and sharpening trends respectively, which indicates that the structure is distorted to a more relaxed symmetry with Obr atoms moving outwards. The calculated bond lengths and angles have been shown to match the values observed in previous studies, including those for a four-membered alumino-silicate single ring cluster. Based on the optimised five-membered alumino-silicate framework rings model, a further ab initio HF calculation has been conducted on ring breakage for releasing Al(Q3) and Si(Q3) centres to form T(OH)4 and HOT(OM)3 tetrahedra under local and highly alkaline environment. The obtained results suggest that Al(Q3) compared with Si(Q3) breaks more readily with the exothermal reaction enthalpy being in excess of -244.4 kJ/mol, while the most reactive Si(Q3) centre shows an exothermal reaction enthalpy of only -33.8 kJ/mol. This indicates that Al dissolves in preference to Si in local environment. The dissolution mechanism of the five-membered Al-Si framework rings model in highly alkaline solutions has been suggested to be composed of an ion-pairing reaction and an interaction between the remaining broken ring cluster triple bond TOH and MOH.     

并行矩阵乘的光化学反应模拟研究

在Linux环境下,为缩短激光诱导光化学反应模拟运行时间,针对光化学反应模拟中力矩阵的稀疏特征,将力矩阵进行分块划分,采用优化的行列分解算法对分块矩阵进行并行化,运用OpenMP实现光化学反应力计算并行化。实验结果表明,在500个C原子参与运算的情况下,单步计算时间缩短到优化前计算时间的10-2数量级,在十六核处理器上获得了十四倍的加速比和80%以上的效率,为高效模拟大分子体系光化学反应提供平台。     

Reaction analysis and visualization of ReaxFF molecular dynamics simulations

ReaxFF MD (Reactive Force Field Molecular Dynamics) is a promising method for investigating complex chemical reactions in relatively larger scale molecular systems. The existing analysis tools for ReaxFF MD lack the capability of capturing chemical reactions directly by analyzing the simulation trajectory, which is critical in exploring reaction mechanisms. This paper presents the algorithms, implementation strategies, features, and applications of VARxMD, a tool for Visualization and Analysis of Reactive Molecular Dynamics. VARxMD is dedicated to detailed chemical reaction analysis and visualization from the trajectories obtained in ReaxFF MD simulations. The interrelationships among the atoms, bonds, fragments, species and reactions are analyzed directly from the three-dimensional (3D) coordinates and bond orders of the atoms in a trajectory, which are accomplished by determination of atomic connectivity for recognizing connected molecular fragments, perception of bond types in the connected fragments for molecules or radicals, indexing of all these molecules or radicals (chemical species) based on their 3D coordinates and recognition of bond breaking or forming in the chemical species for reactions. Consequently, detailed chemical reactions taking place between two sampled frames can be generated automatically. VARxMD is the first tool specialized for reaction analysis and visualization in ReaxFF MD simulations. Applications of VARxMD in ReaxFF MD simulations of coal and HDPE (high-density polyethylene) pyrolysis show that VARxMD provides the capabilities in exploring the reaction mechanism in large systems with complex chemical reactions involved that are difficult to access manually.     

A conceptual basis to encode and detect organic functional groups in XML

A conceptual basis to define and detect organic functional groups is developed. The basic model of a functional group is termed as a primary functional group and is characterized by a group center composed of one or more group center atoms bonded to terminal atoms and skeletal carbon atoms. The generic group center patterns are identified from the structures of known functional groups. Accordingly, a chemical ontology ‘Font’ is developed to organize the existing functional groups as well as the new ones to be defined by the chemists. The basic model is extended to accommodate various combinations of primary functional groups as functional group assemblies. A concept of skeletal group is proposed to define the characteristic groups composed of only carbon atoms to be regarded as equivalent to functional groups. The combination of primary functional groups with skeletal groups is categorized as skeletal group assembly. In order to make the model suitable for reaction modeling purpose, a Graphical User Interface (GUI) is developed to define the functional groups and to encode in XML format appropriate to detect them in chemical structures. The system is capable of detecting multiple instances of primary functional groups as well as the overlapping poly-functional groups as the respective assemblies.