基于镍基载氧剂的甲烷化学链燃烧机理与优化

基于吉布斯自由能最小化原理,在Aspen Plus软件上建立了Ni O-CH4化学链燃烧模型。通过计算反应器内的化学平衡,分析了反应物摩尔比、反应温度、反应压力和气体流量等对反应器出口气相产物组成的影响,明确了Ni O-CH4化学链燃烧的反应机理,进而对Ni O-CH4化学链燃烧的反应条件进行了优化。实验结果表明,当n（Ni O）∶n（CH4）≤1时,燃料的燃烧以甲烷重整反应为主;当14时,全部发生还原反应,生成CO2和H2O。当n（Ni O）∶n（CH4）=4、反应温度为1 000~1 100 K时,Ni O-CH4化学链燃烧效率的效率最高;适当提高反应压力有助于提高CH4化学链燃烧效率,抑制其他反应的发生,但反应压力不宜大于8 MPa;在满足燃烧器功率的要求下,应尽量降低气体流量。

静脉内注入全氟碳——一种人工载氧剂及其医学应用

个氟碳(PFC)经过乳化后可应用于脉管内,作为气体如氧气(O2)和空气的运载介质。1978年首次应用于静脉内,即上市的Fluosol-DATM 20％。美国于1989年准许Fluosol-DATM 20％用于冠状动脉成形术。经过改进这种乳化剂的化学构成,产生了新一代的全氟碳乳剂,其不良反应明显减少,携氧能力明显提高。

载体对镍基载氧剂化学链燃烧反应特性的作用

采用热重分析仪（TGA）研究了三种镍基载氧剂在化学链燃烧中的循环反应特性,考察了添加不同载体对载氧剂循环反应性能的影响,分析了影响载氧剂转化率的因素。实验结果表明,烧结使得NiO循环反应活性随着循环次数的增加而降低;添加铝酸镍（NiAl2O4）和铝酸钙（12CaO·7Al2O3）载体以后,镍基载氧剂比表面积和孔隙率得到提高,载体能有效抑制颗粒之间的烧结,使载氧剂的循环反应活性保持稳定。

化学链燃烧在二氧化碳减排中的应用及其研究进展

随着人们对二氧化碳减排的日益重视,化学链燃烧(Chemical Looping Combustion,CLC)技术因为其具有高效、二氧化碳内分离和低NOx等特点,已受到较多关注。介绍了化学链燃烧的基本概念和特点、目前国内外的研究情况以及未来的发展趋势。

化学链燃烧技术的研究现状及进展

介绍了化学链燃烧技术的基本概念,总结了现存的载氧剂及其制备方法,指出NiO/NiAl2O4、Fe2O3/Al2O3和CoO-NiO/YSZ是较为理想的金属载氧剂;介绍了4种化学链燃烧反应器模型,指出对能够长期稳定运行的反应器有待进一步研究;概括了化学链燃烧的耦合系统,通过模拟仿真得出其最高系统效率有望达到55.9%;最后,指出化学链燃烧技术可以向固体燃料燃烧、制氢方向发展。

化学链燃烧的研究现状及进展

化学链燃烧具有高效、二氧化碳内分离和低NOx等特点,已受到较多关注。介绍了化学链燃烧方式的基本概念,概括分析了它的主要特点,对化学链燃烧系统中具有重要作用的载氧剂的研究现状进行了详细的分析,并对有关化学链燃烧系统设计、试验以及与其它系统耦合方面的进展进行了描述,最后对化学链燃烧发展方向进行了展望。

Pt/Co_3O_4/3DOM Al_2O_3:Highly effective catalysts for toluene combustion

Three-dimensionally ordered macro-/mesoporous alumina（3DOM Al2O3）-supported cobalt oxide and platinum nanocatalysts（xPt/yCo3O4/3DOM Al2O3,Pt mass fraction（x%）= 0-1.4%,Co3O4 mass fraction（y%） = 0-9.2%） were prepared using poly（methyl methacrylate） templating,incipient wetness impregnation and polyvinyl alcohol-protected reduction.The resulting xPt/yCo3O4/3DOM Al2O3 samples displayed a high-quality 3DOM architecture with macropores（180-200 nm in diameter） and mesopores（4-6 nm in diameter） together with surface areas in the range of 94 to 102m^2/g.Using these techniques,Co3O4 nanoparticles（NPs,18.3 nm） were loaded on the 3DOM Al2O3 surface,after which Pt NPs（2.3-2.5 nm） were uniformly dispersed on theyCo3O4/3DOM Al2O3.The1.3Pt/8.9Co3O4/3DOM Al2O3 exhibited the best performance for toluene oxidation,with a T（90%） value（the temperature required to achieve 90%toluene conversion） of 160 ℃ at a space velocity of20000 mL g^（-1） h^（-1）.It is concluded that the excellent catalytic performance of the 1.3Pt/8.9Co3O4/3DOM Al2O3 is owing to well-dispersed Pt NPs,the high concentration of adsorbed oxygen species,good low-temperature reducibility,and strong interaction between the Pt and Co3O4 NPs,as well as the unique bimodal porous structure of the support.

Highly selective supported gold catalyst for CO-driven reduction of furfural in aqueous media

The reductive transformation of furfural （FAL） into furfuryl alcohol （FOL） is an attractive route for the use of renewable bio‐sources but it suffers from the heavy use of H2. We describe here a highly efficient reduction protocol for converting aqueous FAL to FOL. A single phase rutile TiO2 support with a gold catalyst （Au/TiO2‐R） that used CO/H2O as the hydrogen source catalyze this reduction efficiently under mild conditions. By eliminating the consumption of fossil fuel‐derived H2, our pro‐cess has the benefit afforded by using CO as a convenient and cost competitive reducing reagent.

Chemoselective Transfer Hydrogenation of Cinnamaldehyde over Activated Charcoal Supported Pt/Fe3O4 Catalyst

A variety of spherical and structured activated charcoal supported Pt/Fe3O4 composites with an average particle size of ~100 nm have been synthesized by a self-assembly method using the difference of reduction potential between Pt （Ⅳ） and Fe （Ⅱ） precursors as driving force. The formed Fe3O4 nanoparticles （NPs） effectively prevent the aggregation of Pt nanocrystallites and promote the dispersion of Pt NPs on the surface of catalyst, which will be favorable for the exposure of Pt active sites for high-efficient adsorption and contact of substrate and hydrogen donor. The electron-enrichment state of Pt NPs donated by Fe304 nanocrystallites is corroborated by XPS measurement, which is responsible for promoting and activating the terminal C=O bond of adsorbed substrate via a vertical configuration. The experimental results show that the activated charcoal supported Pt/Fe3O4 catalyst exhibits 94.8% selectivity towards cinnamyl alcohol by the transfer hydrogenation of einnamaldehyde with Pt loading of 2.46% under the optimum conditions of 120 ℃ for 6 h, and 2-propanol as a hydrogen donor. Additionally, the present study demonstrates that a high-efficient and recyclable catalyst can be rapidly separated from the mixture due to its natural magnetism upon the application of magnetic field.

Catalytic removal of volatile organic compounds using ordered porous transition metal oxide and supported noble metal catalysts

Most of volatile organic compounds （VOCs） are harmful to the atmosphere and human health. Cata‐lytic combustion is an effective way to eliminate VOCs. The key issue is the availability of high per‐formance catalysts. Many catalysts including transition metal oxides, mixed metal oxides, and sup‐ported noble metals have been developed. Among these catalysts, the porous ones attract much attention. In this review, we focus on recent advances in the synthesis of ordered mesoporous and macroporous transition metal oxides, perovskites, and supported noble metal catalysts and their catalytic oxidation of VOCs. The porous catalysts outperformed their bulk counterparts. This excel‐lent catalytic performance was due to their high surface areas, high concentration of adsorbed oxy‐gen species, low temperature reducibility, strong interaction between noble metal and support and highly dispersed noble metal nanoparticles and unique porous structures. Catalytic oxidation of carbon monoxide over typical catalysts was also discussed. We made conclusive remarks and pro‐posed future work for the removal of VOCs.

Gold stabilized on various oxide supports catalyzing formaldehyde oxidation at room temperature

Gold stabilized on reducible oxide （CeO2 and FeOx） and irreducible oxide （γ‐Al2O3, SiO2, and HZSM‐5） were prepared by deposition precipitation method and tested for catalytic oxidation of formaldehyde （HCHO） at room temperature under high GHSV of 600000 ml/（g＆#183;s）. Au/γ‐Al2O3 cata‐lyst showed distinctive catalytic performance, presenting the highest initial HCHO conversion and stability. Correlating the reaction rate with Au particle size, there is a linear relationship, suggesting that the smaller Au particle size with higher dispersion possesses high reactivity for HCHO oxida‐tion. All the catalysts deactivated at high GHSV （600000 ml/（g＆#183;s））, but in a quite different rate. Re‐ducible oxide （CeO2 and FeOx） could stabilize gold through O linkage and therefore exhibits a better stability for HCHO oxidation reaction. However, the aggregation of gold particles occurred over Au/SiO2 and Au/HZSM‐5 catalysts, which result in the fast deactivation. Therefore, our results sug‐gest that the reducibility of the supports for Au catalysis has no direct influence on the activity, but affects the catalytic stability.

Preparation, characterization and photocatalytic behavior of WO_3-TiO_2/Nb_2O_5 catalysts

TiO2/Nb2O5 photocatalyst loaded with WO3 （WO3-TiO2/Nb2O5） was prepared by a modified hydrolysis process, and characterized by X-ray diffractometry, transmission electron microscopy, Raman spectra and UV-Vis diffuse refraction spectroscopy. The photocatalytic activity of WO3-TiO2/Nb2O5 was investigated by employing splitting of water for O2 evolution. The results indicate that WO3 loading can pronouncedly improve the photocatalytic activity of TiOjNb2O5 by using Fe^3＋ as an electron acceptor under UV irradiation. The optimum molar fraction of the loaded WO3 is 2%, and the largest speed of O2 evolution for 2% WO3-TiO2/Nb2O5 catalyst is 151.8 μmol/（L·h）.

Morphology effect of zirconia support on the catalytic performance of supported Ni catalysts for dry reforming of methane

An immature pinecone shaped hierarchically structured zirconia （ZrO2-ipch） and a cobblestone-like zirconia nanoparticulate （ZrO2-cs）, both with the monoclinic phase （m-phase）, were synthesized by the facile hydrothermal method and used as the support for a Ni catalyst for the dry reforming of methane （DRM） with CO2. ZrO2-ipch is a much better support than ZrO2-cs and the traditional ZrO2 irregular particles made by a simple precipitation method （ZrO2-ip）. The supported Ni catalyst on ZrO2-ipch （Ni/ZrO2-ipch） exhibited outstanding catalytic activity and coke-resistant stability compared to the ones on ZrO2-cs （Ni/ZrO2-cs） and ZrO2-ip （Ni/ZrO2-ip）. Ni/ZrO2-ip exhibited the worst catalytic performance. The origin of the significantly enhanced catalytic performance was revealed by characterization including XRD, N2 adsorption measurement （BET）, TEM, H2-TPR, CO chemisorption, CO2-TPD, XPS and TGA. The superior catalytic activity of Ni/ZrO2-ipch to Ni/ZrO2-cs or Ni/ZrO2-ip was ascribed to a higher Ni dispersion, increased reducibility, enhanced oxygen mo- bility, and more basic sites with a higher strength, which were due to the unique hierarchically structural morphology of the ZrO2-ipch support. Ni/ZrO2-ipch exhibited better stability for the DRM reaction than Ni/ZrO2-ip, which was ascribed to its higher resistance to Ni sintering due to a strengthened metal-support interaction and the confinement effect of the mesopores and coke deposition resistance. The higher coking resistance of Ni/ZrO2-ipch for the DRM reaction in comparison with Ni/ZrOz-ip orignated from the coke-removalabitity of the higher amount of lattice oxygen and more basic sites, confirmed by XPS and CO2-TPD analysis, and the stabilized Ni on the Ni/ZrO2-ipch catalyst by the confinement effect of the mesopores of the hierarchical ZrO2-ipch sup- port. The superior catalytic performance and coking resistance of the Ni/ZrO2-ipch catalyst makes it a promising candidate for synthesis gas production from the DRM reaction.

High activity of a Pt decorated Ni/C nanocatalyst for hydrogen oxidation

The Pt decorated Ni/C nanocatalysts were prepared for hydrogen oxidation reaction（HOR） in fuel cell.By regulating the contents of Pt and Ni in the catalyst,both the composition and the structure affected the electrochemical catalytic characteristics of the Pt-Ni/C catalysts.When the Pt mass content was 3.1% percent and that of Ni was 13.9% percent,the Pt-Ni/C-3 catalyst exhibited a larger electrochemically active surface area and a higher exchange current density toward HOR than those of pure supported platinum sample.Our study demonstrates a feasible approach for designing the more efficient catalysts with lower content of noble metal for HOR in fuel cell.

Selective oxidation of methylamine over zirconia supported Pt-Ru, Pt and Ru catalysts

Pt-Ru, Pt and Ru catalysts supported on zirconia were prepared by impregnation method and were tested in selective oxidation of methylamine （MA） in aqueous media. Among three catalysts, Ru/ZrO2 was more active than Pt/ZrO2 while Pt-Ru/ZrO2 demonstrated the best catalytic activity due to the fact that Pt addition efficiently promoted the dispersion of active species in bimetallic catalyst. Therefore, the - 100% TOC conversion and N2 selectivity were achieved over Pt-Ru/ZrO2, Pt/ZrO2 and Ru/ZrO2 catalysts at 190, 220 and 250 ℃, respectively.

The relationship between the microstructures and catalytic behaviors of iron–oxygen precursors during direct coal liquefaction

A series of both unsupported and coal‐supported iron–oxygen compounds with gradual changes in microstructure were synthesized by a precipitation‐oxidation process at 20 to 70°C.The relationship between the microstructures and catalytic activities of these precursors during direct coal liquefaction was studied.The results show that the microstructure could be controlled through adjusting the synthesis temperature during the precipitation‐oxidation procedure,and that compounds synthesized at lower temperatures exhibit higher catalytic activity.As a result of their higher proportions ofγ‐FeOOH orα‐FeOOH crystalline phases,the unsupported iron–oxygen compounds synthesized at 20–30°C,which also had high specific surface areas and moisture levels,generate oil yields 4.5%–4.6%higher than those obtained with precursors synthesized at 70°C.It was also determined that higher oil yields were obtained when the catalytically‐active phase formed by the precursors during liquefaction(pyrrhotite,Fe1-xS)had smaller crystallites.Feed coal added as a carrier was found to efficiently disperse the active precursors,which in turn significantly improved the catalytic activity during coal liquefaction.

Catalytic ativities of single-atom catalysts for CO oxidation: Pt_1/FeO_x vs. Fe_1/FeO_x

An FeOx‐based Pt single‐atom catalyst(SAC),Pt1/FeOx,has stimulated significant recent interest owing to its extraordinary activity toward CO oxidation.The concept of SAC has also been successfully extended to other FeOx supported transition metal systems both experimentally and theoretically.However,the FeOx substrate itself(denoted by Fe1/FeOx following the same nomenclature of Pt1/FeOx)as a typical transition metal oxide possesses a very low catalytic activity toward CO oxidation,although it can be viewed as Fe1/FeOx SAC.Here,to understand the catalytic mechanism of FeOx‐based SACs for CO oxidation,we have performed density functional theory calculations on Pt1/FeOx and Fe1/FeOx for CO oxidation to address the differences between these two SACs in terms of the catalytic mechanism of CO oxidation and the chemical behavior of the catalysts.Our calculation results indicated that the catalytic cycle of Fe1/FeOx is much more difficult to accomplish than that of SAC Pt1/FeOx because of a high activation barrier(1.09eV)for regeneration of the oxygen vacancy formed when the second CO2molecule desorbs from the surface.Moreover,density of states and Bader charge analysis revealed differences in the catalytic performance for CO oxidation by the SACs Fe1/FeOx and Pt1/FeOx.This work provides insights into the fundamental interactions between the single‐atom Pt1and FeOx substrate,and the exceptional catalytic performance of this system for CO oxidation.

Synergism of Pt nanoparticles and iron oxide support for chemoselective hydrogenation of nitroarenes under mild conditions

An efficient and low-cost supported Pt catalyst for hydrogenation of niroarenes was prepared with colloid Pt precursors andα-Fe2O3 as a support.The catalyst with Pt content as low as 0.2 wt%exhibits high activities,chemoselectivities and stability in the hydrogenation of nitrobenzene and a variety of niroarenes.The conversion of nitrobenzene can reach 3170 molconv h^–1 molPt^–1 under mild conditions(30°C,5 bar),which is much higher than that of commercial Pt/C catalyst and many reported catalysts under similar reaction conditions.The spatial separation of the active sites for H2 dissociation and hydrogenation should be responsible for the high chemoselectivity,which decreases the contact possibility between the reducible groups of nitroarenes and Pt nanoparticles.The unique surface properties ofα-Fe2O3 play an important role in the reaction process.It provides active sites for hydrogen spillover and reactant adsorption,and ultimately completes the hydrogenation of the nitro group on the catalyst surface.

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.

Alumina Supported Vanadium Oxide Catalysts for Residue Hydrotreating

In order to evaluate the role of vanadium in the hydrogenation (HYD) reaction, a series of alumina supported vanadium catalysts were prepared and characterized by SEM, XRD, Raman spectrometry, 51V NMR, XPS, as well as TPR analyses. The catalytic performance of vanadium in HYD of model molecules (naphthalene) and real feedstock (Kuwait atmospheric residue) was studied after sulfidation of the catalysts. It can be concluded that the HYD capabilities of V/Al2O3 catalysts are lower than that of conventional NiMo/Al2O3 catalyst (RefNiMo). The V/Al2O3 catalysts can only facilitate hydrogenation of the first ring of naphthalene, but have little effect on the further hydrogenation of tetralin. Owing to the different forms of metals and sulfur compounds in residue, the weak HYD activity of V/Al2O3 catalysts is able to facilitate the HDM reaction of the residue, albeit with a slight effect on HDS activity.