苯加氢反应中助剂K对Ni2Mo3N催化剂耐硫性能的影响

为提高Ni₂Mo₃N在芳烃加氢过程中的耐硫性,采用络合物分解法制备以碱金属K为助剂的K-Ni₂Mo₃N催化剂,并应用于0.01%(质量分数)噻吩存在下的苯加氢反应体系。研究表明,电子型助剂K的添加对于Ni₂Mo₃N晶体结构无影响,但可以提高催化剂噻吩初始耐硫性至85%(苯转化率)。分析原因发现,碱金属助剂K改变了催化剂表面Ni物种电子状态,增加Ni原子表面电子密度,使得表面Ni呈富电子状态,削弱噻吩与Ni间相互作用。     

Transformation of n-hexane on Al2O3and SiO2supported Pt, Pt+Ga and Ir+Pt+Ga catalysts prepared by anchoring methods

Summary Transformation of n-hexane over Al₂O₃and SiO₂supported Pt, Pt+Ga and Ir+Pt+Ga catalysts was studied in a continuous-flow reactor operated under slug-pulse mode at 520°C. Bimetallic catalysts were prepared by introducing first Ga(OEt)₃and then diallylplatinum as precursor compounds. Iridium was then introduced viadecomposition of Ir₄(CO)₁₂adsorbed onto Pt+Ga catalysts. The addition of Ga to Pt/SiO₂catalyst decreased hydrogenation, aromatization and hydrogenolysis selectivity. Over Pt/Al₂O₃catalyst Ga increased hydrogenolysis selectivity and decreased isomerization and C₅-cyclization. The main effect of Ir was to increase hydrogenolysis selectivity and the stability of catalysts.</o:p>     

Characterization of CoMo/TiO2 catalysts for thiophene hydrodesulfurization

The formation of polymolybdates with octahedrally and tetrahedrally coordinated molybdenum, a cobalt-molybdenum phase and structures analogous to CoTiO₂ in CoMo/TiO₂ catalysts using DR and IR spectroscopy have been investigated. Incorporation of cobalt leads to an increased hydrogenolysis of thiophene and diminishes the hydrogenation function of molybdenum.     

Thiophene Hydrogenation to Tetrahydrothiophene over Tungsten Sulfide Catalysts

Independent reactions of thiophene reduction to tetrahydrothiophene and thiophene hydrogenolysis to form hydrogen sulfide and C₄ hydrocarbons are shown to occur over supported tungsten sulfide catalysts and unsupported tungsten sulfide at an elevated temperature and a high pressure. The highest rate of tetrahydrothiophene formation over the supported catalysts is observed when alumina was used as a support, and the lowest reaction rate is found when silica gel was used as a support. Both catalysts are less active than unsupported tungsten disulfide. The rate of thiophene hydrogenation over tungsten disulfide increases with increasing thiophene concentration and hydrogen pressure and is inhibited by tetrahydrothiophene. The selectivity to tetrahydrothiophene is constant (70–90%) in the whole range up to high thiophene conversions. The high selectivity over tungsten sulfide catalysts is suggested to be due to the reaction pathway through thiophene protonation mediated with the surface SH groups and to the inhibition of hydrogenolysis.     

Mo_2C/γ-Al_2O_3催化剂上苯加氢反应的原位红外光谱研究

采用程序升温反应法制备了钝化态、还原钝化态和新鲜态Mo2C/γ-Al2O3催化剂,结合原位红外光谱表征技术和反应性能评价,考察、比较了三种催化剂苯加氢反应活性.原位红外光谱结果表明,新鲜态Mo2C/γ-Al2O3催化剂在室温就显示了较好的苯加氢反应活性,表现了类贵金属的催化活性.CO吸附在反应前后新鲜态Mo2C/γ-Al2O3催化剂上的对比结果表明,低价态的Mo位(Moδ+(0δ2))是苯加氢反应活性中心.三种催化剂的反应活性结果表明,新鲜态Mo2C/γ-Al2O3催化剂反应活性最好,催化剂寿命最长,失活之后在500°C下H2处理即可恢复原有活性.     

Benzene hydrogenation on sulfide catalyst under unsteady-state conditions

A kinetic model of benzene hydrogenation on a sulfide hydropurification catalyst (Ni,Mo)/Al₂O₃ has been developed. The model describes well the experimental data obtained under unsteady-state conditions and relies on the assumption that the catalyst surface contains only one type of active sites, i.e., Ni atoms in the sulfide bimetallic complex, and makes allowance for the transition of active sites into inactive sites. This revised version was published online in August 2006 with corrections to the Cover Date.     

ZnSO4和La2O3作共修饰剂单金属Ru催化剂上苯选择加氢制环己烯

用沉淀法制备了单金属纳米Ru（0）催化剂,考察了ZnSO₄和La₂O₃作共修饰剂对该催化剂催化苯选择加氢制环己烯性能的影响,并用X射线衍射（XRD）、X射线荧光（XRF）光谱、X射线光电子能谱（XPS）、俄歇电子能谱（AES）、透射电镜（TEM）和N₂物理吸附等手段对加氢前后催化剂进行了表征. 结果表明,在ZnSO₄存在下,随着添加碱性La₂O₃量的增加,ZnSO₄水解生成的（Zn（OH）₂）₃（ZnSO₄）（H₂O）_x（x=1,3）盐量增加,催化剂活性单调降低,环己烯选择性单调升高. 当La₂O₃/Ru 物质的量比为0.075 时,Ru催化剂上苯转化率为77.6%,环己烯选择性和收率分别为75.2%和58.4%. 且该催化体系具有良好的重复使用性能. 传质计算结果表明,苯、环己烯和氢气的液-固扩散限制和孔内扩散限制都可忽略. 因此,高环己烯选择性和收率的获得不能简单归结为物理效应,而与催化剂的结构和催化体系密切相关. 根据实验结果,我们推测在化学吸附有（Zn（OH）₂）₃（ZnSO₄）（H₂O）_x（x=1,3）盐的Ru（0）催化剂有两种活化苯的活性位：Ru⁰和Zn²⁺. 因为Zn²⁺将部分电子转移给了Ru,Zn²⁺活化苯的能力比Ru⁰弱. 同时由于Ru和Zn²⁺的原子半径接近,Zn²⁺可以覆盖一部分Ru⁰活性位,导致解离H₂的Ru⁰活性位减少. 这导致了Zn²⁺上活化的苯只能加氢生成环己烯和Ru（0）催化剂活性的降低. 本文利用双活性位模型来解释Ru基催化剂上的苯加氢反应,并用Hückel分子轨道理论说明了该模型的合理性.     

Catalytic properties of PdCu/Al2O3 system obtained via anchored metal complexes

The TON of PdCu/Al₂O₃ is two orders of magnitude lower in ethane hydrogenolysis and several times lower in vinylacetylene and CO hydrogenation as compared to that of a Pd/Al₂O₃ catalyst. Nonadditivity of the catalytic properties indicates the formation of bimetallic particles, whose thermal stability is lower than that of the monometallic one.     

Activity of palladium sulfide catalysts in the reaction of gas-phase hydrogenation of 2-methylthiophene

In the interaction of hydrogen with 2-methylthiophene in the gas phase over palladium sulfide catalysts at 180–260?C and 0.1–0.8 MPa, the saturation of the thiophene ring resulting in 2-methylthiolane and the hydrogenolysis of 2-methylthiophene occurs. When the conversion is lower than 60%, these reactions occur independently; at higher conversions, methylthiolane also undergoes hydrogenolysis. The specific catalytic activity of PdS supported on γ-Al₂O₃, TiO₂, and carbon and without support is much lower in the hydrogenation of 2-methylthiophene than the activity of PdS supported on SiO₂, aluminosilicate, and zeolite HNaY having strong Brönsted acid surface sites.     

Catalytic Hydrogenation of Thiophene to Thiolane in the Gas Phase

The hydrogenation of thiophene in the gas phase in the presence of palladium-sulfide catalyst leads to the production of thiolane and hydrogenolysis products (butane and hydrogen sulfide), which are formed during the decomposition of the thiophene and thiolane. The hydrogenation rate of thiophene increases with increase of its content in the reaction mixture and also with increase of the hydrogen pressure and is reduced by thiolane. The yield of thiolane calculated on the reacted thiophene is 70-90% with 30-60% conversion of the thiophene.     

Alkyl Polysulfides as Presulfiding Agents of a CoMo/Al2O3 Catalyst: Effect on Catalytic Properties

Abstract

Presulfiding a CoMo/Al₂O₃ catalyst with t-nonyl or t-dodecyl pentasulfides improved both activities for thiophene hydrodesulfurization and cyclohexene hydrogenation.     

Comparing the hydrodesulfurization reaction of thiophene on γ-Al2O3 supported CoMo, NiMo and NiW sulfide catalysts

The thiophene hydrodesulfurization (HDS) reaction on γ-Al₂O₃ supported CoMo, NiMo and NiW sulfide catalysts was compared in order to gain insight into the promoter effect on direct desulfurization (DDS) and hydrogenation (HYD) pathways. Ni-promoted Mo (or W) sulfide catalysts favor the hydrogen transfer reactions relative to CoMo sulfide catalyst, which facilitates the direct route instead. This different performance and also the dependence of the apparent Arrhenius parameters with the catalyst formulation were attributed to the major participation of Mo (or W) edge for the Ni-containing catalysts and S edge for CoMo sulfide catalyst upon the thiophene-HDS reaction.     

Activity of MoSe2/Al2O3 catalysts in decomposition of thiophene and selenophene

The rate of thiophene decomposition was shown to be independent of the type of chalcogens used in catalysts MoX₂/Al₂O₃, where X = S, Se. On the contrary, the rate of selenophene decomposition was shown to be higher on catalysts MoSe₂ than that on MoS₂. This observation suggests that the decomposition proceeds on anion vacancies. The decomposition of either thiophene over MoSe₂ or selenophene over MoS₂ results in the formation of partially substituted chalcogenides. At that, the molar ratios of the substituted chalcogen to Mo were shown to coincide in both cases. The fact that the rate of the thiophene decomposition does not depend on the degree of anion exchange indicates that the decomposition is not associated with hydrogenolysis.     

手性二胺修饰的负载型钌催化剂催化芳香酮不对称加氢

研究了用手性修饰剂(1S,2S)-(－)-1,2-二苯基乙二胺修饰的负载型钌催化剂(Ru/γ-Al₂O₃)催化芳香酮的不对称加氢反应, 在KOH的异丙醇溶液中, 10～20 ℃, p_H2＝5 MPa条件下, 芳香酮及其衍生物加氢产物的ee值达79.5%～85.0%, 2-乙酰基噻吩加氢产物的ee值可达86.2%. 此催化剂制备简单, 容易与产物分离, 重复使用4次, 对映选择性基本保持不变.     

The insertion and extrusion of heterosulfur bridges. XV. S-bridging of 2,2′-binaphthyl and 1-(2-naphthyl)cyclohexene. Studies on hydrodehalogenation during the reaction

Regioselectivity occurs in the sulfur-bridging reactions of 2,2′-binaphthyl (1) and 1-(2-naphthyl)cyclohexene (7) by means of hydrogen sulfide and a chromia-alumina-magnesia catalyst (designated I) in a flow apparatus at 550°. Thus, 1 gives a higher yield (6.1%) of dinaphtho[1,2–6:2′,l'-d]thiophene from 1,1′-bridging than of dinaphtho[1,2-b:2′,3′-d]thiophene (3.4%) from l,3′-bridging. No product expected from 3,3′-bridging was identified. Substrate 7 undergoes both dehydrogenation and bridging to yield 2-phenylnaphthalene (8%), benzo[b]naphtho[2,1-d]thiophene (9%) from alpha bridging, and benzo[b]naphtho[2,3-d]thiophene (3%) from beta bridging into the naphthalene ring. Exploratory studies showed that either sulfided catalyst I or a sulfided molybdenum( VI ) oxide-alumina-cobalt( II ) oxide catalyst ( II ) effects hydrodehalogenation of various monohalo- and polyhaloarenes (where halo, X, is chloro or bromo) at 450–550°. In the biphenyl, phenanthrene, naphthalene, and pyrene systems, halogen was lost either under sulfur-bridging conditions or under hydrogenolysis conditions, i.e. with methanol as a reactant. For every substrate the parent arene was isolated or identified as a reaction product. In selected experiments, acid HX was also identified in the effluent. Use of hydrogen sulfide as a reactant led to formation of dibenzothiophene and phenanthro[4,5-bcd]thiophene as main products in the biphenyl and phenanthrene systems, respectively; while use of methanol as a reactant gave small amounts of methyl bromide (for X = Br) and methylarenes.     

Hydrogenolysis of dimethyl disulfide in the presence of bimetallic sulfide catalysts

The hydrogenolysis of dimethyl disulfide in the presence of Ni,Mo and Co,Mo bimetallic sulfide catalysts was studied at atmospheric pressure and T = 160–400°C. At T ≤ 200°C, dimethyl disulfide undergoes hydrogenolysis at the S-S bond, yielding methanethiol in 95–100% yield. The selectivity of the reaction decreases with increasing residence time and temperature due to methanethiol undergoing condensation to dimethyl disulfide and hydrogenolysis at the C-S bond to yield methane and hydrogen sulfide. The specific activity of the Co,Mo/Al₂O₃ catalyst in hydrogenolysis at the S-S and C-S bonds is equal to or lower than the total activity of the monometallic catalysts. The Ni,Mo/Al₂O₃ catalyst is twice as active as the Ni/Al₂O₃ + Mo/Al₂O₃ or the cobalt-molybdenum bimetallic catalyst.     

串联双釜连续反应装置中Ru-Co-B/ZrO2上苯选择加氢制环己烯

采用化学还原法制备了苯选择加氢制环己烯催化剂Ru-B/ZrO₂,考察了Cr,Mn,Fe,Co,Ni,Cu和Zn等过渡金属的添加对Ru-B/ZrO₂催化剂性能的影响.结果表明,这些过渡金属的添加均可提高Ru-B/ZrO₂催化剂中的B含量.B的修饰及第二种金属或金属氧化物的集团效应和配位效应导致Ru-B/ZrO₂催化剂活性降低和环己烯选择性升高.当Co/Ru原子比为0.06时,Ru-Co-B/ZrO₂催化剂上反应25min苯转化率为75.8%时,环己烯选择性和收率分别为82.8%和62.8%.在双釜串联连续反应器中和优化反应条件下,Ru-Co-B/ZrO₂催化剂使用419h内苯转化率稳定在40%左右,环己烯选择性和收率分别稳定在73%和30%左右.     

Catalytic hydrogenation of 1,3-trans-pentadiene over Rh4(CO)12 supported on γ-Al2O3

Rh₄(CO)₁₂ anchored on γ-Al₂O₃ (Rh₄(CO)₁₂/Al₂O₃) has been studied as a catalyst for the hydrogenation of 1,3-trans-pentadiene. Under mild conditions (1 atm H₂ and temperatures between 60°C and 80°C) hydrogenation occurs at only one of the double bonds of the diene, and analysis of the products shows that the terminal double bond is preferentially hydrogenated. Hydrogenation of the second double bond of the conjugated diene occurring only after all the 1,3-trans-pentadiene has been consumed. In this respect Rh₄(CO)₁₂/Al₂O₃ behaves like toluene solutions of Rh₄(CO)₁₂. Anchoring of Rh₄(CO)₁₂ on the solid support gives a catalyst which is less active but more stable than toluene solutions of Rh₄(CO)₁₂. The effects of CO and of triphenylphosphine on catalytic activity and on specificity of Rh₄(CO)₁₂/Al₂O₃ have also been investigated and both shown to cause a reduction of the rate of hydrogenation of 1,3-trans-pentadiene.     

The insertion and extrusion of heterosulfur bridges. IX: Sulfur bridging in 2-phenylnaphthalene

Sulfur bridging of 2-phenylnaphlhalene ( 3 ) to form benzo[b ]naphtho[2,1-d]thiophene ( 5 ) (main product) and the isomeric benzo[b]naphtho[2,3-d]thiophene ( 4 ) is effected by means of hydrogen sulfide, benzene (solvent), and a sulfided cobaltous oxide-molybdic oxide-alumina (CMA-1) catalyst at 450–630° in a flow system (maximum yield 33% at 500°). The low yield is ascribed to decompositions of both 4 and 5 under reaction conditions.     

噻吩在γ-Mo2N(100)表面上加氢脱硫反应的密度泛函理论研究

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.