Hybrid Nanoreactors: Coupling Enzymes and Small-Molecule Catalysts within Virus-Like Particles

Virus-like particles (VLPs) provide unique scaffolds for the construction of coupled catalytic systems by attachment and encapsulation of catalysts within their hollow interiors. The interior of VLPs provides an environment where catalysts of biological or synthetic origins can be confined, protected, and colocalized in close proximity with catalysts of different types. Herein, we utilize the P22VLP as a scaffold to construct a synthetic hybrid catalyst by attachment of a small organometallic catalyst to the interior colocalized with an encapsulated enzyme. This produces a complex and active coupled biomimetic catalyst system. By combining both enzymatic and synthetic catalysts together, new biological synthetic hybrid materials can be produced that incorporate the best of both catalytic systems.     

一步法合成二甲醚双功能催化剂的研究进展

从一步法制二甲醚双功能催化剂的结构出发,综述了传统复合型和新型双层结构、核壳结构催化剂的制备、结构和性能的研究进展,并展望了双功能催化剂的发展趋势。     

From Zr-Rich to Ce-Rich: Thermal Stability of OSC Materials on the Whole Range of Composition

Car manufacturers use close coupled three way catalysts to reduce cold start emissions. These close coupled catalysts must show long term durability and thermal stability at temperatures higher than 1000 °C. Thus, during the past 10 years, a significant amount of attention has been paid to the design of CeO₂-ZrO₂ OSC materials with improved surface area, phase and OSC stability. Solid solutions of Ce/Zr mixed oxides are now commonly available on industrial scale. Recent studies have demonstrated that the introduction of rare earth oxides promoters such as La, Pr, Nd, Y, Sm [ENGELHARD WO patent o2 30546; OMG-DMC² EP Patent 1 181 970; DAIHATSU EP Patent 1 174 174; DELPHI US Patent 6 387 338; ENGELHARD WO Patent 02 22242] or aluminium oxide [TOYOTA EP Patent 1 172 139; Kanzawa et al. SAE Technical Paper 2003-01-0811] in the Ce/Zr matrix is a very good way to improve the thermal stability and the redox properties of these materials. Positive interactions between PGM and these 'promoters' are also claimed. Nevertheless, not only the composition but the optimization of the manufacturing processes is a key factor to obtain both high thermal stability (expressed as surface area and XRD phase purity) and OSC. To meet the increasingly stringent emission limits, Rhodia has developed a new generation of CeZr based mixed oxides. These materials show phase stability and thermal stability at temperatures higher than 1100 °C in a wide composition range: from Zr-rich to Ce-rich mixed oxides. These characteristics have been obtained with a new manufacturing process which leads to highly porous materials. The controlled morphology at microscopic and macroscopic scale prevents particle sintering under severe ageing conditions. Such materials are preferred PGM supports for cost effective catalysts with low PGM loading     

High-temperature close coupled catalysts Pd/Ce-Zr-M/Al2O3 (M = Y, Ca or Ba) used for the total oxidation of propane

A series of high-temperature close coupled catalysts Pd/Ce-Zr-M/Al₂O₃ (M = Y, Ca or Ba) were prepared by ultrasonic-assisted successive impregnation. The catalysts were subjected to a series of characterization measurements. The results of activity evaluation show that Y is the best promoter for propane total oxidation, especially at the calcination temperature of 1100 °C. It is interesting that although the BET specific surface areas and the dispersion of Pd species decrease, the Y-promoted catalyst calcined at 1100 °C shows higher catalytic activity than the corresponding one calcined at 900 °C and better sulfur-resisting performance. The results of TEM, TPHD and CO chemisorption indicate that Y can remarkably increase the dispersion of Pd species. However, the dispersion is hard to be connected with the activity increase as the calcination temperature is elevated from 900 to 1100 °C. The change of active phases and the interaction between Pd species and the supports may account for the activity enhancement. Combined with XRD, H₂-TPR and O₂-TPD results, it is deduced that the coexistence of metallic Pd and PdO species in the catalysts calcined at 1100 °C may be also favorable to C₃H₈ oxidation. In a word, Pd/Ce-Zr-Y/Al₂O₃ is indeed a promising high-temperature close coupled catalyst applicable to high temperature.     

基于Fe2V4O13的MHF反应器的构建及其特性研究

近年来,在难降解有机废水的处理技术中,Fenton催化氧化法因具有设备简单、操作容易、条件温和、反应速度快和氧化彻底等特点受到了环境工作者的广泛关注。为了解决悬浮态超细粉体Fenton-like催化剂降解污染物的高效率与其分离、连续重复使用的矛盾,将膜分离和多相Fenton-like催化氧化技术进行耦合,通过液相法制备了一种新的多元多相Fenton-like催化剂Fe2V4O13,构建了一种基于这种催化剂的陶瓷膜MHF反应器。研究结果表明：基于Fe2V4O13的MHF反应器为近似全混流反应器,污染较小。该反应器在连续运行过程中膜通量和降解效率都较稳定,处理量远高于普通Fenton-like反应器。     

用正交配置法求算双重孔催化剂的有效因子

本文讨论了基于正交配置法的双重孔催化剂有效因子计算法;成功地求解了具有耦合边界条件的二阶微分方程组:考察了用Legendre多项式与Jacobi多项式作为配置法的试验函数,以及在催化剂颗粒和微粒内配置点组合格式对计算的收敛速度和精确度的影响.文中给出了不可逆反应、可逆反应条件下双重孔催化剂的有效因子值.一级不可逆反应的计算值与精确解吻合;二级不可逆反应的计算值与Jayaraman的试差解相当接近.文中还给出了Langmuir-Hinshelwood动力学模型有效因子曲线组.     

Characterization of bimetallic rhodium-germanium catalysts prepared by surface redox reaction

The preparation of bimetallic rhodium-germanium/silica and rhodium-germanium/alumina catalysts was investigated by controlled surface reaction. Their catalytic performances were measured for two gas phase reactions (toluene hydrogenation at 323 K and cyclohexane dehydrogenation at 543 K) and for a liquid phase reaction (citral hydrogenation at 343 K).

Elemental analysis of bimetallic catalysts showed that germanium can be deposited by redox reaction between hydrogen activated on a parent monometallic rhodium catalyst and germanium tetrachloride dissolved in water (catalytic reduction method). EDX microanalysis of rhodium-germanium/silica catalysts indicated that rhodium and germanium were deposited in close contact on the silica support. However, on alumina-supported catalysts, germanium deposition occurred also separately on the support. For the different test reactions, the catalytic properties of rhodium were strongly altered by the addition of germanium. On alumina-supported catalysts, interesting catalytic effects were observed in citral hydrogenation when not only close contact exists between both metals but when, in addition, the second metal was deposited on the support in the close vicinity of rhodium.     

PET缩聚催化剂的发展及展望

介绍了PET催化剂的发展及现状,简要比较和评价了各种锑系催化剂及应用,对目前国内外较为关注的各种钛系催化剂及应用概况、合成技术等进行了分析和总结,对新型催化剂的发展趋势进行了展望。     

Studies of deactivation of metals by carbon deposition

Studies of carbon deposition from aliphatic and aromatic hydrocarbons over metal catalysts were carried out over the temperature range 700–1025 K using a microbalance coupled with a tubular reactor. The influence of the nature of the reactor wall on the rate of carbon formation, as well as the effect of hydrogen in preventing deactivation of the catalysts, was investigated. A general reaction scheme is proposed to explain the relationships between the different types of carbon formed on the catalysts.     

A comparative study of the water gas shift reaction over platinum catalysts supported on CeO2, TiO2 and Ce-modified TiO2

WGS reaction has been investigated on catalysts based on platinum supported over CeO₂, TiO₂ and Ce-modified TiO₂. XPS and XANES analyses performed on calcined catalysts revealed a close contact between Pt precursors and cerium species on CeO₂ and Ce-modified TiO₂ supports. TPR results corroborate the intimate contact between Pt and cerium entities in the Pt/Ce–TiO₂ catalyst that facilitates the reducibility of the support at low temperatures while the Ce–O–Ti surface interactions established in the Ce-modified TiO₂ support decreases the reduction of TiO₂ at high temperature. The changes in the support reducibility leads to significant differences in the WGS activity of the studied catalysts. Pt supported on Ce-modified TiO₂ support exhibits better activity than those corresponding to individual CeO₂ and TiO₂-supported catalysts. Additionally, the Ce–TiO₂-supported catalyst displays better stability at reaction temperatures higher than 573 K that observed on pure TiO₂-supported counterpart. Activity measurements, when coupled with the physicochemical characterization of catalysts suggest that the modifications in the surface reducibility of the support play an essential role in the enhancement of activity and stability observed when Pt is supported on the Ce-modified TiO₂ substrate.     

Catalytic denitrification of water with palladium-based catalysts supported on activated carbons

The performance of carbon-supported, Pd bimetallic catalysts for nitrate reduction has been investigated. Pd–In and Pd–Sn catalysts have been tested for a range of nitrate concentration up to 1000 ppm in acidic and close to neutral pH. Pd–Cu was also studied at pH 5 for reference. Nitrate reduction was inhibited strongly by nitrite and moderately by sulphate. Activated carbon catalysts are shown to display an activity similar to metal oxide supported catalysts.     

Performance and durability of PtCo alloy catalysts for oxygen electroreduction in acidic environments

The performance and durability of PtCo alloy catalysts for oxygen electroreduction in acidic environments were investigated by the electrochemical rotating disk electrode (RDE) technique, in situ electrochemical scanning tunneling microscopy (STM), and inductively coupled plasma-optical emission spectroscopy (ICP-OES). In comparison with benchmark Pt catalysts, PtCo alloy catalysts offer both enhanced catalytic activity towards molecular oxygen electroreduction and improved durability under electrochemical forces in acidic environments for short-term operation; however, PtCo alloy catalysts do not provide long-term improvement in catalytic activity and electrochemical durability due to the leaching of elemental cobalt from the alloys under intensive potential cycling. Therefore, similar to Pt, PtCo alloys are not viable cathode catalysts for low temperature fuel cells for transportation applications.     

非均相法催化制备生物柴油的最新研究进展

非均相连续化工艺是生物柴油规模化工业生产的发展方向。多相催化剂的研制和新型工艺过程的开发一直是生物柴油领域的研究热点,也是实现生物柴油绿色、经济、高效生产的关键。分析了酯交换反应可能的反应机理,综述了国内外生物柴油非均相酸碱催化剂的最新研究进展,评述了多种固体酸碱催化剂在生物柴油的制备中优异的催化性能和存在的问题,介绍了多种新型多相生物柴油反应器及反应分离耦合工艺在生物柴油连续化制备中的应用,最后展望了生物柴油未来的发展前景,指出新型固体酸碱双功能催化剂与先进多相连续反应分离耦合工艺的开发将推动生物柴油领域不断发展。     

车用催化剂与汽车污染治理

汽车用催化剂是当代最受人关注的催化剂之一,是当前控制汽车污染的最有效手段。本文从催化的角度,总结了二十余年来国外几代车用催化剂的发展和演变过程。同时,对发展中国家所特有的在用车排气的催化净化,进行了探讨与展望 。     

Trimerization of Butene over Ni-doped Zeolite Catalyst: Effect of Textural and Acidic Properties

The amount of acid sites on external surface and L/B ratio of the zeolite catalysts are close relative to the catalytic performance of the catalysts in butene trimerization. The doping of Ni into the zeolite modifies the textural and acidic properties of the catalyst. NiHβ(32) exhibits the highest catalytic performance and the lowest apparent activity energy in butene trimerization among the investigated catalysts, due to the reason that it has the proper amount of acid sites on external surface and the proper L/B ratio.     

Selective reduction of NOx by hydrocarbons in excess oxygen by alumina- and silica-supported catalysts

A range of alumina- and silica-supported metal catalysts have been investigated for the selective reduction of NO_x by propene in excess oxygen. Platinum, in particular, has been found to have a high activity and selectivity. There is a close correlation between the activity for NO_x reduction and propene combustion. For platinum group metals, it is found that silica-supported catalysts are more active than alumina-based materials. For Pt/SiO₂ catalysts, it is found that the specific activity for NO_x reduction decreases with decreasing metal dispersion. NO is found to inhibit the oxidation of propene on Pt-based catalysts     

甲醇与C4烯烃共裂解效应和催化剂稳定性

以改性ZSM-5分子筛为催化剂,在固定床反应器上,以甲醇与C<,4>烯烃共裂解制备乙烯和丙烯.结果表明,共裂解有利于促进乙烯和丙烯的生成,对副产物甲烷和碳氧化合物的生成有明显抑制作用,C<,4>烯烃的转化得到促进,C<,5>以上烃类的含量相对增加.同时,甲醇与C<,4>烯烃共裂解时,由于吸热和放热反应能量上的互补以及C...     

Preparation and characterization of chloroacetylated polystyrene‐supported zinc complexes and evaluation of their catalytic activities for the synthesis of 1,1‐diacetates

Zinc chloride was immobilized onto chloroacetylated polystyrene via different linkages to afford polymer‐supported Lewis acid catalysts. The functionalized beads and the immobilized catalysts were characterized by elemental analysis, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and inductively coupled plasma and thermal analysis. The reaction of aldehydes with anhydride in the presence of the supported catalysts was investigated. The effects of various parameters, including the solvent, amount of catalyst, and temperature, on the reaction were also studied. We found that the reaction proceeded smoothly under solvent‐free conditions at room temperature and afforded the corresponding acylals in good yields. Moreover, the catalysts could be recovered easily and reused several times without a significant loss in activity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

H2-O2气氛中丙烯环氧化反应研究进展

对H2-O2气氛中丙烯环氧化反应所采用的催化剂、反应器及操作方式进行了评述.综合分析了所使用的钯(金或银)/钛硅分子筛(或氧化钛)双功能催化剂的各项性能指标以及所采用的反应器型式.结合H2-O2直接合成H2O2所用催化剂,对原位氧化丙烯反应过程进行了系统描述.指出进一步的研究方向是借助反应或分离耦合技术,创造有利于原位生成的H2O2及时进行环氧化而避免分解的操作环境,包括催化剂表面状态、反应器型式、溶剂体系和操作方式,并提出以丙烷路线经脱氢、环氧化是制取环氧丙烷的最佳组合.     

Catalytic activity of Ga-containing zeolite catalysts in the coupled reforming of methanol and C<Subscript>3</Subscript>-C<Subscript>4</Subscript> alkanes

The catalytic activity of Ca-containing ZSM-5 type zeolite catalysts in the coupled reforming of methanol and the propane-butane fraction is reported. Modification of the high-silica catalyst with Ga or Ga + Pt causes, as the process temperature is raised, an increase in the propane-butane fraction conversion and in the arene yield. This behavior of the modified catalysts is due to the changes in their porous structure and acid properties and to the increase in their methanol and propane adsorption capacities.