聚氧乙烯链封端的聚酰胺-胺树状聚合物的性质与应用

研究了聚氧乙烯链封端的非离子型聚酰胺-胺树状聚合物的热稳定性以及在造纸助留和催化剂载体上的应用。结果表明,该类树状聚合物具有较好的热稳定性,温度低于300℃无明显热分解行为,最大的热分解温度均为400℃。助留性能测试表明,M4.0G与P44复配双元助留体系(摩尔比1∶23.22),造纸助留率为89.2%,比空白造纸助留率分别提高了18.3%。纸样的物理机械特性:撕裂指数、撕裂强度、耐破指数、耐破强度和抗张指数比空白纸样分别提高了8.6%、1.5%、35.5%、29.6%和4.3%。TEM测试表明:以聚氧乙烯大单体(PEO-A)链封端的聚酰胺-胺树状聚合物样品封装的钯金属纳米粒子单分散性较好,粒径分布在0.75～2.4nm。

Synthesis of Higher Alcohols from Syngas over Alkali Promoted K-Co-Mo Catalysts Supported on Multi-walled Carbon Nanotubes

A series of carbon nanotubes-supported K-Co-Mo catalysts were prepared by a sol-gel method combined with incipient wetness impregnation. The catalyst structures were characterized by X-ray diffraction, N2 adsorption-desorption, transmission electron microscopy and H2-TPD, and its catalytic performance toward the synthesis of higher alcohols from syngas was investigated. The as-prepared catalyst particles had a low crystallization degree and high dispersion on the outer and inner surface of CNTs. The uniform mesoporous structure of CNTs increased the diffusion rate of reactants and products, thus promoting the reaction conversion. Furthermore, the incorporation of CNTs support led to a high capability of hydrogen absorption and spillover and promoted the formation of alkyl group, which served as the key intermediate for the alcohol formation and carbon chain growth. Benefiting from these characteristics, the CNTs supported Mo-based catalyst showed the excellent catalytic performance for the higher alcohols synthesis as compared to the unsupported catalyst and activated carbon supported catalyst.

Correlation between catalytic activity of supported gold catalysts for carbon monoxide oxidation and metal–oxygen binding energy of the support metal oxides

The effect of a wide variety of metal oxide （MOx） supports has been discussed for CO oxidation on nanoparticulate gold catalysts. By using typical co‐precipitation and deposition–precipitation methods and under identical calcination conditions, supported gold catalysts were prepared on a wide variety of MOx supports, and the temperature for 50%conversion was measured to qualita‐tively evaluate the catalytic activities of these simple MOx and supported Au catalysts. Furthermore, the difference in these temperatures for the simple MOx compared to the supported Au catalysts is plotted against the metal–oxygen binding energies of the support MOx. A clear volcano‐like correla‐tion between the temperature difference and the metal–oxygen binding energies is observed. This correlation suggests that the use of MOx with appropriate metal–oxygen binding energies （300–500 kJ/atom O） greatly improves the catalytic activity of MOx by the deposition of Au NPs.

Three-dimensionally ordered macroporous CeO_2/Al_2O_3-supported Au nanoparticle catalysts: Effects of CeO_2 nanolayers on catalytic activity in soot oxidation

A series of catalysts consisting of three‐dimensionally ordered macroporous(3DOM)x‐CeO2/Al2O3‐supported Au nanoparticles(x=2,10,20,and40wt%)were successfully synthesized using a reduction‐deposition method.These catalysts were characterized using scanning electron microscopy,the Brunauer‐Emmett‐Teller method,X‐ray diffraction,transmission electron microscopy,ultraviolet‐visible spectroscopy,and temperature‐programmed reduction by H2.Au nanoparticles of mean particle size5nm were well dispersed and supported on the inner walls of uniform macropores.The3DOM structure improved the contact efficiency between soot and the catalyst.An Al‐Ce‐O solid solution was formed in the multilayer support,i.e.,x‐CeO2/Al2O3,by the incorporation of Al3+ions into the CeO2lattice,which resulted in the creation of extrinsic oxygen vacancies.Strong interactions between the metal(Au)and the support(Ce)increased the amount of active oxygen species,and this promoted soot oxidation.The catalytic performance in soot combustion was evaluated using a temperature‐programmed oxidation technique.The presence of CeO2nanolayers in the3DOM Au/x‐CeO2/Al2O3catalysts clearly improved the catalytic activities in soot oxidation.Among the prepared catalysts,3DOM Au/20%CeO2/Al2O3showed high catalytic activity and stability in diesel soot oxidation.

Understanding morphology-dependent Cu Ox-CeO2 interactions from the very beginning

Elucidation of the CuOx-CeO2 interactions is of great interest and importance in understanding complex CuOx-CeO2 interfacial catalysis in various reactions. In the present work, we have investigated structures and catalytic activity in CO oxidation of CuOx species on CeO2 rods, cubes and polyhedra predominantly exposing {110}+{100}, {100} and {111} facets by the incipient wetness impregnation method with the lowest Cu loading of 0.025%. The structural evolution of CuOx species was found to depend on both the Cu loading and the CeO2 morphology. As the Cu loading increases, CuOx species are deposited preferentially on the surface defect of CeO2 and then aggregate and grow, accompanied by the formation of isolated Cu ions, CuOx clusters strongly/weakly interacting with the CeO2, highly dispersed Cu O nanoparticles, and large Cu O nanoparticles. The isolated Cu^+ species and CuOx clusters weakly interacting with the CeO2 were observed mainly on the O-terminated CeO2{100} facets. Meanwhile, more Cu(I) species are stabilized during CO reduction processes in CuOx/c-CeO2 catalysts than in CuOx/r-CeO2 and CuOx/p-CeO2 catalysts. The catalytic activities of various CuOx/CeO2 catalysts in CO oxidation vary with both the CuOx species and the CeO2 morphology. These results comprehensively elucidate the CuOx-CeO2 interactions and exemplify their morphology-dependence.

Preparation of Carbon Nano-fiber Washcoat on Porous Silica Foam as Structured Catalyst Support

This paper reports how a hairy layer of carbon nano-fibers can be prepared on the macro-porous silica foam produced by the sphere templating method. Firstly, three-dimensional close-packed crystals of polystyrene spheres are assembled on porous disk substrate by vacuum filtration or evaporation. The polystyrene template is annealed slightly above the glass transition temperature in order to strengthen the colloidal crystal and ensure interconnection of the spheres so as to obtain porous materials with open structure. Following the treatment of hexdecyltrimethylammonium bromide, the polystyrene template is filled with silica colloidal solution, which solidifies in the cavities. Then the polystyrene particles are removed by calcination at 843K, leaving behind porous silica foam. Scanning electron microscopy images demonstrate that silica foam has uniform and open structured pores. Nickel particles were deposited on porous silica foam layer by the dipping method and porous carbon nano-fiber washcoat was prepared by catalytic decomposition of ethene over small nickel particles.

Catalytic performance enhancement by alloying Pd with Pt on ordered mesoporous manganese oxide for methane combustion

Ordered mesoporous Mn2O3 (meso‐Mn2O3) and meso‐Mn2O3‐supported Pd, Pt, and Pd‐Pt alloy x(PdyPt)/meso‐Mn2O3; x = (0.10?1.50) wt%; Pd/Pt molar ratio (y) = 4.9?5.1 nanocatalysts were prepared using KIT‐6‐templated and poly(vinyl alcohol)‐protected reduction methods, respectively.The meso‐Mn2O3 had a high surface area, i.e., 106 m2/g, and a cubic crystal structure. Noble‐metalnanoparticles (NPs) of size 2.1?2.8 nm were uniformly dispersed on the meso‐Mn2O3 surfaces. AlloyingPd with Pt enhanced the catalytic activity in methane combustion; 1.41(Pd5.1Pt)/meso‐Mn2O3gave the best performance; T10%, T50%, and T90% (the temperatures required for achieving methaneconversions of 10%, 50%, and 90%) were 265, 345, and 425 °C, respectively, at a space velocity of20000 mL/(g?h). The effects of SO2, CO2, H2O, and NO on methane combustion over1.41(Pd5.1Pt)/meso‐Mn2O3 were also examined. We conclude that the good catalytic performance of1.41(Pd5.1Pt)/meso‐Mn2O3 is associated with its high‐quality porous structure, high adsorbed oxygen species concentration, good low‐temperature reducibility, and strong interactions between Pd‐Pt alloy NPs and the meso‐Mn2O3 support.

TiO2 preparation by improved homogeneous precipitation and application in SCR catalyst

Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic reduction(SCR) catalyst. The influence rules of the two improved methods on characterization of TiO_2 samples, denitration activity and mechanical strength of honeycomb SCR catalyst samples were mainly focused on. The results indicate that the specific surface area, particle size and uniformity of TiO_2 samples are significantly improved by both of the ultrasonic and hydrothermal treatments compared with the traditional homogeneous precipitation. Also, the denitration activities of catalyst samples are enhanced by the two improved methods(the NO_x reduction ratio increases from 88.89% to 95.45% by ultrasonic homogeneous precipitation process, and to 94.12% by hydrothermal homogeneous precipitation process). On the other hand, because of good spherical shape and high particle distribution of TiO_2 sample from hydrothermal homogeneous precipitation process, the corresponding honeycomb catalyst samples get the best mechanical strength, which is even higher than that of the reference sample from commercial nano-TiO_2. So, it is concluded that the hydrothermal homogeneous precipitation can be a feasible and effective preparation method of TiO_2 carrier for the honeycomb SCR catalyst production.

Preparation and characterization of CuO-CoO-MnO/SiO_2 nanocomposite aerogels as catalyst carriers

CuO-CoO-MnO/SiO2 nanocomposite aerogels were prepared by using tetraethyl orthosilicate(TEOS) as Si source,and aqueous solution of Cu,Co and Mn acetates as the precursors via sol-gel process and ethanol supercritical drying technique.The gelatination mechanism was investigated by nuclear magnetic resonance(NMR) and X-ray photoelectron spectroscopy(XPS).The microstructure and composition of the CuO-CoO-MnO/SiO2 nanocomposite aerogels were characterized by field emission scanning electron microscopy(FE-SEM),transmission electron microscopy(TEM),electron dispersive spectroscopy(EDS) and XPS.The specific surface area,pore size and pore size distribution of the nanocomposite aerogels were determined by the Brunauer–Emmett–Teller(BET) method.The products were analyzed by gas chromatography(GC).The results show that the CuO-CoO-MnO/SiO2 nanocomposite aerogels are porous,with a particle size distribution of 10–150 nm,a pore size distribution of 2–16 nm,an average pore size of 7.68 nm,and a specific surface area of 664.4-695.8 m2/g.The molar fraction of transition metals in the nanocomposite aerogels is 0.71%-13.77%.This kind of structure is favorable not only to increase the loading of catalysts,but also to make full use of the effect of transition metal oxides as cocatalysts;CuO-CoO-MnO/SiO2 nanocomposite aerogels can be used as a novel catalyst carrier in the safer and environment-friendly synthesis of diphenyl carbonate and other fields of catalysis.