The dimerization of isoprene on complex nickel catalysts

Summary Eight-membered dimers, 1,5(1,6)-dimethylcyclooctadiene-l,5, were obtained as the main products by dimerizing isoprene on a complex nickel catalysts.     

Hydrocarboxylation of polybutylene on palladium complex catalysts

Conclusions The introduction of carboxyl groups into up to 60% of the double bonds in a polybutadiene sample is possible at 90–170°C and 2.0–14.0 MPa in the presence of PdCl₂(PPh₃)₂ and added PPh₃.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1390–1392, June, 1989.The authors express their gratitude to S. D. Sominskii for assistance in carrying out the IR studies.     

Hydrodehalogenation of bromo- and chloropyridines over palladium complex and palladium metal catalysts

The hydrodehalogenation of 2-chloro-, 2-bromo-, 3-bromo, and 3,5-dibromopyridine has been studied in the presence of a palladium complex catalyst immobilized on silica gel, and a Pd/C catalyst. Cleavage of bromine from bromopyridines over the Pd complex is significantly faster than from the bromo-substituted furanes and thiophenes previously studied. Debromination over Pd/C is faster than over the complex catalyst. Over both catalysts 3-bromopyridine debrominates faster than the 2-isomer. When molecular deuterium is used, the respective deuterated pyridines can be obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1229–1232, September, 1985.     

负载型钯催化剂上生物质气化气催化燃烧

采用浸渍法制备了Pd/Al2O3、Pd/Ce/Al2O3、Pd/Mn/Al2O3、Pd/La/Al2O3四种催化剂。并借助XRD、BET对催化剂相结构、比表面积、孔结构进行了表征,在固定床反应器上考察了四种催化剂对CO、H2和CH4的催化燃烧性能。结果表明,随着La、Ce、Mn离子的引入使得催化剂的比表面积和孔容积不断降低;添加助剂Ce可以提高催化剂活性和热稳定性,助剂La可以提高催化剂的抗烧结能力,而助剂Mn在低温时可以提高催化剂活性,但并不能抑制催化剂的高温钝化。CO和H2的起燃顺序随催化剂的不同而不同,但四种催化剂对CO和H2的催化燃烧活性接近,均可以在低温条件下迅速燃烧,同时其燃烧特征温度明显低于CH4。     

苯胺衍生物式电位的QSAR研究

以AM1量子化学半经验分子轨道方法计算22个苯胺衍生物的分子结构参数,用多元线性回归的方法研究了13个式电位已知的苯胺衍生物的氧化式电位与其分子结构参数之间的关系.苯胺衍生物式电位与离子化电势(Ip),N原子上的净电荷(e(N),总的偶极矩(μt)和第四个碳上的净电荷(e(C4))有很好的相关性,回归方程为:E0′=-7.820 5 0.884 9(Ip-3.739(e(N)-0.093 56μt 0.925 1(e(C4)),(R=0.979,SD为0.023 6).依据回归方程合理地预测了其余9个苯胺衍生物的离子化电势和式电位,探讨了取代基性质和取代位置对离子化电势和式电位的影响.     

Suzuki-Miyaura coupling on heterogeneous palladium catalysts

Summary Five supported heterogeneous Pd catalysts have been prepared, characterized and found to be active and selective in the Suzuki-Miyaura coupling of boronic acids, and aromatic iodo and bromo compounds to form the corresponding biaryls in high selectivities. Reaction conditions, namely, the solvent, base (triethylamine, Na₂CO₃, Cs₂CO₃) and tetrabutylammonium chloride as an additive are shown to have profound effects on catalyst performance.</o:p>     

Exoemission accompanying electron interactions in complex copper-cerium oxide catalysts and synergism phenomena

The formation of the electronic structure of the surface of complex copper-cerium oxide catalysts with different copper concentrations was studied using the exoemission methods at different stages of preparation. The introduction of copper enhances the emissivity of CeO₂, and the number of charges emitted from the catalyst surface exceeds the emission activity of the starting CeO₂ and NuO components. The synergism phenomenon in exoemission is compared with synergism in the catalysis of CO oxidation by these systems. The problem of electron interactions between the components of the complex oxides is discussed. The electron interactions are caused by the electron transitions at the interface and result in an increase in both the emission of weakly bound electrons and catalytic activity in the oxidation of CO.     

Oxidation of alkylphenylacetylenes and dialkylacetylenes on palladium catalysts in DMSO

Alkylphenyl- and dialkylacetylenes are oxidized by the DMSO—PdCl₂ or DMSO—Pd/C system to give the corresponding 1,2-diketones. Oxidation of these compounds, unlike that of diarylacetylenes, is less selective and is accompanied by the partial cleavage of triple bonds and formation of ketones, 1,3-diketones, and aromatic compounds as secondary condensation products.     

Transformation of cyclohexene on palladium catalysts: activity and deactivation

The transformation of cyclohexene on palladium catalysts can take place via two competitive processes: disproportionation and dehydrogenation. A study conducted over a broad temperature range revealed that disproportionation prevails at low temperatures and dehydrogenation at high temperatures. When the reaction develops under continuous-flow conditions (viz. in a tubular reactor connected online to a mass spectrometer), a transition temperature exists for each catalyst above which hydrogen is formed in detectable amounts. Metal catalysts are strongly deactivated during the transformation of cyclohexene. This led us to examine the process by performing thermal programmed experiments, desorptions and thermal oxidations, which showed catalyst deactivation in this process to be the result of surface adsorption of benzene and carbon deposition. Finally, desorption and subsequent oxidation were found to effectively regenerate the catalysts, which thus regained their initial activity.     

New method for the synthesis of higher unsaturated sulfides and amines involving zirconium and palladium complex catalysts

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, p. 2645, November, 1988.     

Polymer-supported palladium and rhodium species as hydrogenation catalysts

The synthesis of new copolymers containing amino and heterocyclic ligands and their use for anchoring Pd and Rh species is described. The supported catalysts are effective for the hydrogenation of alkenes, dienes, alkynes, and nitrobenzene under very mild conditions. The catalysts have been characterized by chemical analysis, particle size measurement, IR, and x-ray photoelectron spectroscopy. Relative reactivities and the effects of substrate structure, solvents, catalyst loading, anchoring ligands, metal species, and particle size on the rates of hydrogenation have been determined using a wide variety of substrates. The kinetics of hydrogenation have been analyzed using concepts suitable under slurry reaction conditions. Comparisons between different oxidation states of the same metal and between different metal species have also been made. The recycling efficiencies of the catalysts have been determined and found to be very good. © 1997 John Wiley & Sons, Inc.     

Low-valence palladium complexes: Stoichiometric reactions and catalysis

New data on the structure and reactivity of palladium clusters are surveyed. The mechanisms of stoichiometric and catalytic reactions of the palladium cluster complexes with alkenes, alcohols, aldehydes, formic acid, CO, and phenol are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 807–815, March, 1998.     

Polymer-supported palladium and platinum species as hydrogenation catalysts

The synthesis of new hydrogel copolymers and their use for anchoring Pd and Pt species is described. The supported catalysts are effective for the reduction of alkenes, dienes, alkynes, and nitroaromatics under mild conditions. The catalysts have been characterized by chemical analysis, particle size measurement, IR, TGA, and x-ray photoelectron spectra. Relative reactivities and the effects of substrate structure, solvents, catalyst loading, particle size of the catalysts, and partial pressure of hydrogen have been determined. The kinetics of hydrogenation have been analyzed using concepts useful under slurry reaction conditions. The recycling efficiencies of the catalysts and product analysis to establish selectivities have been assessed. © 1992 John Wiley & Sons, Inc.     

Correlation between phase composition and activity of complex oxide catalysts

Correlation between the catalytic activity in oxidation of carbonaceous materials and a change in the phase composition of the La_1?x Cs _x VO_4±y and Ce_1?x Pr _x O_2?d catalysts was studied. The activity values obtained by iso- and polythermal methods are close.