共查询到19条相似文献,搜索用时 171 毫秒
1.
采用密度泛函理论(DFT)计算了Pd(111)表面含有N(N=1-4)个Au原子数目时的表面形成能,选取最优构型进一步研究了噻吩在Au/Pd(111)双金属表面的吸附模式及加氢脱硫反应过程.结果表明:当Pd(111)表面含有1个Au原子时,其形成能最低.在Au/Pd(111)双金属表面噻吩初始吸附于Pd-Hcp-30°位时,其构型最稳定.在各加氢脱硫过程中,反应总体均放出热量.对于直接脱硫机理,其所需活化能较低,但脱硫产物较难控制;对于间接脱硫机理,反应最有可能按照顺式加氢方式进行,C―S键断裂开环时所需活化能最高,是反应的限速步骤.此外,与单一Au(111)面及Pd(111)面相比,Au/Pd(111)双金属表面限速步骤的反应能垒最低,表明AuPd双金属催化剂比Au、Pd单金属催化剂更有利于噻吩加氢脱硫反应的进行. 相似文献
2.
采用密度泛函理论(DFT)计算了Pd(111)表面含有N(N=1-4)个Au原子数目时的表面形成能,选取最优构型进一步研究了噻吩在Au/Pd(111)双金属表面的吸附模式及加氢脱硫反应过程. 结果表明:当Pd(111)表面含有1个Au原子时,其形成能最低. 在Au/Pd(111)双金属表面噻吩初始吸附于Pd-Hcp-30°位时,其构型最稳定. 在各加氢脱硫过程中,反应总体均放出热量. 对于直接脱硫机理,其所需活化能较低,但脱硫产物较难控制;对于间接脱硫机理,反应最有可能按照顺式加氢方式进行,C―S键断裂开环时所需活化能最高,是反应的限速步骤. 此外,与单一Au(111)面及Pd(111)面相比,Au/Pd(111)双金属表面限速步骤的反应能垒最低,表明AuPd双金属催化剂比Au、Pd单金属催化剂更有利于噻吩加氢脱硫反应的进行. 相似文献
3.
使用密度泛函理论(DFT)中的B3LYP方法, 采用6-31G**和6-31++G**基组, 对噻吩的光解反应进行了理论研究. 对照实验结果, 我们研究了五个光解通道, 包括生成C 4H 4+S, C 2H 2+C 2H 2S和CS+C 3H 4的三个闭壳层分子解离通道与生成HCS+C 3H 3和HS+C 4H 3的自由基解离通道. 各个可能的反应通道的产物碎片的具体形式得到了确认. 研究发现在基态生成C 2H 2+C 2H 2S和在最低三态生成C 4H 4+S的反应从能量上考虑最为有利, 而实验上观测到的主要产物C 2H 2+C 2H 2S主要是在基态上产生的. 通过对比实验结果与计算结果, 我们认为噻吩光解反应机理与所用激发光波长有关. 相似文献
4.
用INDO系列方法对C 2H 5C 60H的1,2-加成和1,4-加成两种产物异构体的结构进行了理论研究,结果表明1,2-C 2H 5C 60H具有Cs对称性,1,4-C 2H 5C 60H没有任何对称性,1,2-C 2H 5C 60H的总能量比1,4-C 2H 5C 60H的低。以此优化构型为基础,计算了两种产物异构体的电子吸收光谱,讨论了其光谱红移的原因,同时对产物的NMR谱进行了探讨。 相似文献
5.
合成了四种有机-无机型杂多酸催化剂,包括[π-C 5H 5NC 16H 33] 3[PW 4O 16],[π-C 5H 5NC 16H 33] 3[PMo 4O 16],[π-C 5H 5NC 12H 25] 3[PW 4O 16]和[π-C 5H 5NC 12H 25] 3[PMo 4O 16]. 以有机硫的正辛烷溶液为模拟油品,H 2O 2为氧化剂,乙腈为萃取剂,在两相体系中,考察了上述四种催化剂对模拟油品中二苯并噻吩(DBT)氧化脱硫的催化活性. 结果表明,[π-C 5H 5NC 16H 33] 3[PW 4O 16]具有最佳的催化活性. 采用[π-C 5H 5NC 16H 33] 3[PW 4O 16]进行后续研究发现,反应完毕,[π-C 5H 5NC 16H 33] 3[PW 4O 16]以沉淀的形式析出,可以重复利用且脱硫效果很好. 研究表明,上述有机-无机型杂多酸属于相转移催化剂,氧化脱硫反应体系属于反应控制相转移催化体系. 在相同实验条件下,由于电子云密度和空间位阻效应共同的作用,DBT、噻吩(TH)、苯并噻吩(BT)和4,6-二甲基二苯并噻吩(4,6-DMDBT)脱硫由易到难的顺序为DBT >4,6-DMDBT >BT >TH,并分别通过GC-MS分析确定它们的氧化产物. 将[π-C 5H 5NC 16H 33] 3[PW 4O 16]进一步应用于柴油氧化脱硫,其中硫含量由355 mg/kg (mg/kg等同于ppmw)降至26 mg/kg,去除率达92.7%. 利用上述四种有机-无机型杂多酸作催化剂,研究DBT氧化反应过程动力学,确定DBT的表观反应级数均为一级,表观活化能为47.9~55.4 kJ/mol. 相似文献
6.
以负载氧化铜的改性氧化铝为催化剂, 在H 2O 2/HCOOH体系中, 对噻吩(C 4H 4S)的正庚烷溶液进行了氧化脱硫研究. 考察了改性酸度、酸性氧化体系、温度、烯烃和芳烃的存在等因素对噻吩脱除的影响, 并对噻吩的氧化机理进行了初步的探讨. 实验结果表明, 醋酸改性负载氧化铜的氧化铝对噻吩氧化的催化活性高; H 2O 2/HCOOH体系中, 噻吩硫的脱除率较其他酸性氧化体系中高; 在H 2O 2/HCOOH体系中, 负载氧化铜的酸改性氧化铝的催化活性对噻吩的催化氧化效果随温度的升高而增大, 但烯烃和芳烃的加入降低了噻吩硫的脱除率. 相似文献
7.
本文利用CNDO/2法讨论了一类新型共轭烃--多环聚梯型共轭烃存在的可能性。结果表明,对三元-五元环烃和四元-四元环烃为重复单元的直链多聚梯型共轭烃H 2-(-C 3C 5H 2-)- nH 2和H 2-(-C 4HC 4H-)- nH 2,在n是偶数时体系稳定。 相似文献
8.
运用MP2/aug-cc-pVDZ方法对2,5-二氢呋喃, 2,5-二氢噻吩与XF (X=F, Cl, Br)之间的卤键作用进行了理论研究. 研究发现: C 4H 6O, C 4H 6S与XF之间不仅存在O(S)…XF n型卤键, C=C双键与XF分子亦可形成π型卤键|对于C 4H 6O与XF之间的n型和π型卤键以及C 4H 6S与XF之间的π型卤键, 卤键键能Δ E、键鞍点处的电子密度 ρ( rc)以及电子给体到受体之间的电子转移数Δ q(XF)均按B…F 2<B…ClF<B…BrF (B=C 4H 6O, C 4H 6S)的顺序依次增大|对于卤键键能较大的体系C 4H 6O…BrF(n), C 4H 6O…BrF(π), C 4H 6S…F 2(n), C 4H 6S…ClF(n), C 4H 6S…BrF(n), C 4H 6S…BrF(π), 卤键作用介于离子键和共价键之间|而对于其它的卤键键能较小的体系, 卤键作用为闭壳层静电作用. 相似文献
9.
利用激光烧蚀-分子束法对Al等离子体与乙醇团簇的反应进行了研究.飞行时间质谱测得的主要反应产物有Al +(C 2H 5OH) n (n=3~10)与H +(C 2H 5OH) n (n=1~14)团簇正离子和(C 2H 5OH) n(H 2O)OH - (n=0~8)团簇负离子.实验发现,烧蚀产生的Al等离子体与脉冲分子束的不同位置反应,对团簇离子的类别、大小及强度分布均产生很大影响.Al等离子体与脉冲分子束的前段反应,主要产生金属-复合物团簇离子Al +(C 2H 5OH) n,且信号较强;Al等离子体与脉冲分子束的中段及后段反应,主要产生质子化团簇离子H +(C 2H 5OH) n和团簇负离子(C 2H 5OH) n(H 2O)OH -,同时还出现强度较小的其他水合团簇离子,如H +(H 2O)m(C 2H 5OH) n (m=1~2)等. 相似文献
10.
有机硫化物是大气主要污染物之一,其在大气中的光解产物还将造成二次污染,除了存在于有机硫化物中, S―S键还存在于胱氨酸等蛋白质中, S―S键的形成和断裂决定该类蛋白质的活性.本工作中,我们研究了用实验室常见的Nd:YAG激光器的四倍频266 nm激光光解C 2H 5SSC 2H 5过程,通过激光诱导荧光(LIF)光谱方法检测乙硫自由基C 2H 5S等光解产物.实验表明266 nm激光主要光解C 2H 5SSC 2H 5的S―S键产生C 2H 5S自由基.本文应用密度泛函理论的Becke3-Lee-Yang-Parr泛函(B3LYP方法)得到C 2H 5SSC 2H 5的S―S键、C―S键和C―C键的解离势能曲线,可知在266 nm光解条件下, C 2H 5SSC 2H 5在基态能够发生S―S键、C―S键解离, C―C键不发生解离.本文采用全活化空间自洽场(CASSCF)方法优化得到态和态的C 2H 5S自由基结构及其跃迁的绝热激发能,以辅助解析实验检测的C 2H 5S自由基的LIF光谱.实验结合理论计算最终得出,本实验266 nm光解条件下, C 2H 5SSC 2H 5主要发生S―S键解离,不排除少量分子发生C―S键解离的可能性. 相似文献
11.
利用密度泛函理论研究了γ-Mo2N(100)表面上的噻吩加氢脱硫(HDS)过程.噻吩在γ-Mo2N(100)表面上不同作用形式的结构优化结果显示,η5-Mo2N吸附构型最稳定,具有最大的吸附能(-0.56 eV),此时噻吩通过S原子与Mo2原子相连平行表面吸附在四重空位(hcp位).H原子和噻吩在hcp位发生稳定共吸附,hcp位是噻吩HDS的活性位点.噻吩在γ-Mo2N(100)表面进行直接脱硫反应,HDS过程分为S原子脱除和C4产物加氢饱和两部分.过渡态搜索确定了HDS最可能的反应机理及中间产物,首个H原子的反应需要最大的活化能(1.69 eV),是噻吩加氢脱硫的控速步骤.伴随H原子的不断加入,噻吩在γ-Mo2N(100)表面上优先生成―SH和丁二烯,随后―SH加氢生成H2S,丁二烯加氢饱和生成2-丁烯和丁烷.由于较弱的吸附,H2S、2-丁烯和丁烷很容易在γ-Mo2N(100)表面脱附成为产物. 相似文献
12.
A coincidence technique is used to study the influence of the internal energy of the reactant ion on the cross section of the ion-molecule reactions in the C 2H 4+ + C 2H 4 system. The experiment is performed at thermal collision energies. In the ion-molecule reactions of C 2H 4+ + C 2H 4 our measurements indicate a barrier between the initially formed collision complex (C 2H 4) 2+* and a tight complex (C 4H 8+)*. Using an extension of our earlier developed statistical model, now including a potential barrier between the initially formed loose complex (C 2H 4) 2+* and the tight complex (C 4H 8+)*, our experimental data can be reproduced. For comparison also the internal energy dependence of the unimolecular decomposition of photoionised 1-C 4H 8+ is measured. Assuming that the photoionised 1-C 4H 8+ is identical with the tight (C 4H 8+)* complex, the model applied to the ion-molecule reactions describes also the unimolecular decay of 1-C 4H 8+ correctly, using the same set of parameters. 相似文献
13.
Meerwein芳基化反应是在烯键上导入芳基的一种重要方法:ArN 2Cl+RCH=CHZ→ArCR=CHZ+ArCHRCHClZ化合物RCH=CHZ中Z为电子取代基时,反应容易进行,Z为OAc、OR时,也可以起芳基化反应,但烯胺(Z=NR 2)与芳基重氮盐作用,只得到偶联产物。烯胺与N,N-二烷基苯胺为插烯物(Vinglogs),由于氮原子上的未共电子对与π键共轭,使烯键或苯环碳原子上电子密度增加,容易起偶联反应。 相似文献
14.
The substitution reactions of 2,3-, 2,4-, 3,4-, or 3,5-dichlorobenzoyl chloride (Cl 2C 6H 3COCl) and 2,3-, 2,4-, 3,4-, or 3,5-dichlorobenzoate ion (Cl 2C 6H 5COO −) or benzoate ion (C 6H 5COO −) in a two-phase H 2O/CH 2Cl 2 medium using pyridine 1-oxide (PNO) as an inverse phase transfer catalyst were investigated. The reaction of Cl 2C 6H 3COCl and PNO in CH 2Cl 2 to produce the ionic intermediate, 1-(dichlorobenzoyloxy)-pyridinium chloride (Cl 2C 6H 3COONP +Cl −) is the rate-determining step. In the PNO-catalyzed two-phase reaction of Cl 2C 6H 3COCl and C 6H 5COONa, the order of reactivities of Cl 2C 6H 3COCl toward reaction with PNO is (2,3-, 2,4-)>3,5->3,4-2,6-Cl 2C 6H 3COCl, whereas it is 3,5->(2,3-, 3,4-)>2,4-Cl 2C 6H 3COCl in the PNO-catalyzed two-phase reaction of Cl 2C 6H 3COCl and the corresponding Cl 2C 6H 3COONa. The order of reactivities of Cl 2C 6H 3COO − ions towards the reaction with 1-(benzoyloxy)-pyridinium (C 6H 5COONP +) ion is (3,4-, 3,5-)>(2,3-, 2,4-Cl 2C 6H 3COO −). 相似文献
15.
The reaction of oxidative addition of -iodothiophene and bromopentafluorobenzene to zero-valent lanthanides has been carried out. The formation of organolanthanide derivatives RLnX (R = -C 4H 3S, C 6F 5) has been confirmed by isolation of the corresponding RSnPh 3 resulting from the interaction of RLnX with Ph 3SnCl. The reaction of lanthanide with C 6F 5Br is sensitive to the nature of the metal. 相似文献
16.
The compounds (π-C 5H 5)(CO) 2LM-X (L = CO, PR 3; M = Mo, W; X = BF 4, PF 6, AsF 6, SbF 6) react with H 2S, p-MeC 6H 4SH, Ph 2S and Ph 2SO(L′) to give ionic complexes [(π-C 5H 5)(CO) 2LML′] + X −. Also sulfur-bridged complexes, [(π-C 5H 5)(CO) 3W---SH---W(CO) 3(π-C 5H 5)] + AsF 6− and [(π-C 5H 5)(CO) 3M-μ-S 2C=NCH 2Ph-M(CO) 3(π-C 5H 5)], have been obtained. Reactions with SO 2 and CS 2 have been examined. 相似文献
17.
Ab initio study of the reactions of n-heptyl radicals(1-C 7H 15, 2-C 7H 15, 3-C 7H 15, and 4-C 7H 15) with methanol was conducted over the temperature range of 300-1500 K. Transition states for the reaction channels producing C 7H 15OH, CH 3, C 7H 15OCH 3, H, C 7H 16, CH 2OH and CH 3O were identified and the geometries of all stationary points were calculated at BB1K/MG3S level of theory. The potential barrier heights of the corresponding transition states were predicted by the CBS-QB3//BB1K and G4//BB1K methods, indicating that the eight H-abstraction channels are more kinetically favorable than the channels where OH transfers from CH 3OH to C 7H 15 and where the C 7H 15OCH 3+H products are given. The rate constants of H-abstraction channels were calculated with TST and TST/Eck. Both the forward and reverse rate constants have positive temperature dependence and the tunneling effect is only important at the temperature lower than 700 K. For the reactions of H-atom abstraction from methyl in CH 3OH by n-heptyl, a reverse and the corresponding forward rate constant are roughly equal. For the reactions of H-atom abstraction from OH in CH 3OH by n-heptyl, a reverse rate constant is larger by several orders of magnitude than the corresponding forward one. 相似文献
18.
LnCl 3 (Ln=Nd, Gd) reacts with C 5H 9C 5H 4Na (or K 2C 8H 8) in THF (C 5H 9C 5H 4 = cyclopentylcyclopentadienyl) in the ratio of 1 : to give (C 5H 9C 5H 4)LnCl 2(THF) n (orC 8H 8)LnCl 2(THF) n], which further reacts with K 2C 8H 8 (or C 5H 9C 5H 4Na) in THF to form the litle complexes. If Ln=Nd the complex (C 8H 8)Nd(C 5H 9C 5H 4)(THF) 2 (a) was obtained: when Ln=Gd the 1 : 1 complex [(C 8H 8)Gd(C %H 9)(THF)][(C 8H 8)Gd(C 5H 9H 4)(THF) 2] (b) was obtained in crystalline form. The crystal structure analysis shows that in (C8H8)Ln(C5H9C5H4)(THF)2 (Ln=Nd or Gd), the Cyclopentylcyclopentadieny (η5), cyclooctatetraenyl (η8) and two oxygen atoms from THF are coordinated to Nd3+ (or Gd3+) with coordination number 10. The centroid of the cyclopentadienyl ring (Cp′) in C5H9C5H4 group, cyclooctatetraenyl centroid (COTL) and two oxygens (THF) form a twisted tetrahedron around Nd3+ (or Gd3+). In (C8H8)Gd(C5H9C5H4)(THF), the cyclopentyl-cyclopentadienyl (η5), cyclooctatetraenyl (η8) and one oxygen atom are coordinated to Gd3+ with the coordination number of 9 and Cp′, COT and oxygen atom form a triangular plane around Gd3+, which is almost in the plane (dev. -0.0144 Å). 相似文献
19.
Reaction of ansa-cyclopentadienyl pyrrolyl ligand (C 5H 5)CH 2(2-C 4H 3NH) (2) with Ti(NMe 2) 4 affords bis(dimethylamido)titanium complex [(η 5-C 5H 4)CH 2(2-C 4H 3N)]Ti(NMe 2) 2 (3) via amine elimination. A cyclopentadiene ligand with two pendant pyrrolyl arms, a mixture of 1,3- and 1,4-{CH 2(2-C 4H 3NH)} 2C 5H 4 (4), undergoes an analogous reaction with Ti(NMe 2) 4 to give [1,3-{CH 2(2-C 4H 3N)} 2(η 5-C 5H 3)]Ti(NMe 2) (5). Molecular structures of 3 and 5 have been determined by single crystal X-ray diffraction studies. 相似文献
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