TiO2-modified nano-egg-shell Pd catalyst for selective hydrogenation of acetylene

Pd-based egg-shell nano-catalysts were prepared using porous hollow silica nanoparticles(PHSNs)as support,and the as-prepared catalysts were modified with TiO2 to promote their selectivity for hydrogenation of acetylene.Pd nanoparticles were loaded evenly on PHSNs and TiO2 was loaded on the active Pd particles.The effects of reduction time and temperature and the amount of TiO2 added on catalytic performances were investigated by using a fixed-bed micro-reactor.It was found that the catalysts showed better performance when reduced at 300 C than at 500 C,and if reduced for 1h than 3h.When the amount of Ti added was 6 times that of Pd,the catalyst showed the highest ethylene selectivity.     

Effect of Calcination Temperature on La-Modified Al2O3 Catalysts for Vapor Phase Hydrofluorination of Acetylene to Vinyl Fluoride

A La-modified Al₂O₃ catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH₃-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 oC exhibited the highest conversion of acetylene (94.6%) and highest selectivity to vinyl fluoride (83.4%) and lower coke deposition selectivity (0.72%). The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.     

乙炔与氢化锂单体和二聚体加成反应中的HOMO-HOMO相互作用

用前线分子轨道分析乙炔与氢化锂单体和二聚体加成反应的过渡态.结果表明,在其反应过渡态形成过程中,反应物间的HOMO-LUMO和HOMO-HOMO相互作用均起重要作用.较强烈的HOMO-HOMO相互作用与过渡态附近反应由亲电性加成向亲核性加成转变相关,该反应特性的转变又与LiH中的氢原子在反应中的电荷转移相关.     

NiP非晶态合金的负载方法及催化剂的结构与催化性能

采用ＮｉＢ作为引导剂,使ＮｉＰ完全定向沉积到载体上,用ＩＣＰ,ＸＲＤ,ＤＳＣ,ＢＥＴ,ＴＥＭ对制备的负载型ＮｉＰ（Ｂ）催化剂进行表征,研究了这类催化剂对乙烯中微量乙炔的选择加氢性能,结果表明,ＮｉＰ（Ｂ）以超细颗粒分散到载体上,由于少量Ｂ的存在,使其比相应的ＮｉＰ或ＮｉＢ具有更高的热稳定性。非晶态ＮｉＰ（Ｂ）合金催化剂具有比相应的晶态合金更好的催化性能。低温氢气处理可以除去表面镍的氧化物,从而提高     

A Fully Encapsulated Acetylenediide in Ag2C2⋅8 AgF

The reaction of Ag ₂ C ₂ with a concentrated aqueous solution of AgF leads to the title compound, in which the dianion C₂²⁻ is completely enclosed in the Ag₉ cage of a chandelierlike arrangement of ten silver atoms.     

Preparation,Characterization and Catalytic Performance of Carbon Nanotubes Promoted Ni‐B Amorphous Alloy

Ni‐B and Ni‐B/CNTs amorphous alloy catalysts were prepared by chemical reduction and impregnation‐chemical reduction methods, respectively, and characterized by TEM, ICP, XPS, XRD, BET and CO chemisorption techniques. Their catalytic activities were evaluated in acetylene selective hydrogenation reaction. Based on characterizations, the effects of carbon nanotubes on Ni‐B amorphous alloy were attributed to both its structure effect, dispersing Ni‐B particles, leading to bigger surface area of active nickel and enhancing the thermal stability, and the electronic effect, resulting in electron‐rich nickel centers. Therefore, the superior thermal stability and acetylene selective hydrogenation activities of Ni‐B/CNTs to Ni‐B amorphous catalyst were obtained in the present study.     

Acetylene as a ligand on clusters: An accurate determination of the crystal and molecular structure of (Cp)2Ni2Fe(CO)3(μ3−C2H2) and of (CP)2Ni2Fe2(CO)6(μ4−C2H2)

Abstarct The Cp)₂Ni₂Fe(CO)₃(µ₃-C₂H₂) and Cp)₂Ni₂Fe(CO)₃(µ₃-C₂H₂) (B) complexes have been synthesized and spectroscopically characterized. An accurate X-ray study and a comparison with related structures shows that the substituents of the alkyne ligands exert considerable effects on the bonding parameters.Crystal data for complex A, monoclinic space group P2₁/n,a = 8.418(1),b = 15.779(2),c = 14,493(1) Å, = 91.64(1)°,Z = 4, 2753 observed reflections,R = 0.022; crystal data for complex B, monoclinic space group C2/c,a = 16.2189(7),b = 7.445(3),c = 25.745(5) Å, = 103.74(3),Z=8, 1853 observed reflections,R = 0.051.     

Semiempirical valence-electron calculations of excited state geometries and vibrational frequencies

Summary The use of finite differences and finite second differences in order to approximate gradients and second derivatives of the energy for geometry optimization and determination of normal modes of vibration on the CI level of computation is discussed in connection with the semiempirical MNDOC-CI valence electron method. Results are given for ground and excited states of ethylene, acetylene, formaldehyde, acetaldehyde, acetone, formamide and acetamide and are compared with experimental andab initio data. Mean absolute errors for bond lengths, bond angles, excitation energies and vibrational frequencies indicate that the MNDOC-CI method is well suited to describe ground and excited states of organic molecules on the same level of approximation and with comparable accuracy.     

Diacetylene's weak bonding to acetylene clusters

An interaction potential previously developed for the acetylene–polyyne dimer was used to explore the interaction potential surfaces for clusters containing a diacetylene molecule and two or more acetylene molecules. Ab initio calculations were performed on the smallest clusters in order to assess the energetic and structural features predicted by the model potential. The preferred arrangements of the monomers in the clusters maximize the favorable quadrupole–quadrupole interactions between the monomers.