Mobile and non-mobile catalysts for diesel-particulate combustion: A kinetic study

One of the potential ways to solve the problem of diesel particulate emission from both stationary and mobile sources is the use of traps carrying a suitable catalyst for promoting particulate combustion as soon as it is filtered. A Cu-K-V based catalyst, considered among the most promising in the literature, the KVO₃+CsCl and the K_0.7Cu_0.3VO₃+KCl catalysts were prepared and investigated. Their performance was compared to a reference V₂O₅ catalyst. The superior performance of the Cu-K-V catalyst is based on the grounds of both microreactor (temperature programmed combustion) and catalytic trap tests. Based on experimental data and modelling calculations, this paper elucidates how the mobility of catalyst components is the main reason for such an outcome performance and is a prerequisite to achieve an activity sufficient for trap self-regeneration.     

Influence of process parameters on ethylene-norbornene copolymers made by using [2,2′-methylenebis(1,3-dimethylcyclopentadienyl)]-zirconium dichloride and MAO

Ethylene-norbornene copolymerization was investigated by using metallocene catalysts, [2,2′-methylenebis( 1,3-dimethylcyclopentadienyl)]zirconium dichloride(2,2′-CH₂ (1,3-Me₂Cp)₂ZrCl₂, Catalyst A) and racemicethylenebis( indenly)zirconium dichloride (rac-Et(Ind)₂ ZrCl₂, Catalyst B), in the presence of methylaluminoxane as a cocatalyst. The influences of different process parameters such as polymerization temperature and ethylene pressure were studied by using a 56 wt% norbornene solution in toluene. The results show that Catalyst A has a higher activity in copolymerization than Catalyst B. Catalyst A also has a superior norbornene insertion performance to Catalyst B, resulting in polymers with higher glass transition temperatures, by approximately 70 ‡C, at similar polymerization conditions, indicative of a great commercial potential of Catalyst A.     

Compositional quantification of PtCo acid-leached fuel cell catalysts using EDX partial cross sections

The new generation of analytical electron microscopes with aberration correction and new EDX detectors provide improved possibilities for microanalysis. Here, we apply a new approach to quantitative EDX based on using partial cross sections. Our quantification method is applied to alloy PtCo nanoparticles, which have been acid leached to provide Pt enrichment or rather Co depletion at the particle surface. Such surface Co depletion is absent at the vertices of the more facetted nanoparticles. The leaching process demonstrates very little change in Co composition when investigating the whole particle but produces a localised surface depletion, which can only be determined by the high-resolution EDX elemental maps.     

利用炼化废弃物协同臭氧处理炼化废水的技术策略展望

环境管理的严格化对炼化行业的废弃物和废水治理水平提出了更高的要求。通过综述近几年的技术进展发现，炼化废弃物处理处置方面缺乏高附加值的全组分资源化技术，同时在炼化废水“提标”处理的工程化上缺乏低成本高性能催化氧化技术的支撑。本综述通过对比分析炼化废弃物和臭氧催化剂组成，提出了以炼化废弃物为原料制备催化剂，催化臭氧“提标”处理难降解炼化废水的“以废治废”技术策略。该策略可为炼化行业“废弃物处置”和“废水排放提标”难题的联合解决提供理论指导，深化炼化行业的节能减排、清洁生产与循环经济。     

Bulk preparation and characterization of mesoporous carbon nanotubes by catalytic decomposition of cyclohexane on sol–gel prepared Ni–Mo–Mg oxide catalyst

Multiwalled carbon nanotubes were synthesized using Ni–Mo–Mg oxide catalyst prepared by sol–gel technique. Carbon nanotubes were formed in situ by the reduction of nickel oxide (NiO) and molybdenum oxide (MoO₃) to Ni and Mo by a gas mixture of nitrogen, hydrogen and cyclohexane at 750 °C. Scanning Electron Microscopy (SEM) was used to confirm the formation of carbon nanotubes (CNTs). The pore size distribution of carbon nanotubes (CNTs) was investigated by N₂ adsorption and desorption. It was found that the pore size fell into the mesopore range: 2 < d < 50 nm. Interpretation was also made using Raman spectroscopy, Diffuse reflectance spectroscopy, X-ray diffraction and ESR spectra. This method is found to produce a very high yield weighing over 20 times of the catalyst. Based on the experimental conditions and results obtained a possible growth mechanism of the carbon nanotubes is proposed.     

Gas-phase growth of diameter-controlled carbon nanotubes

We demonstrate gas-phase (aerosol) generation of diameter-controlled carbon nanotubes (CNTs) by employing size-controlled monodisperse nickel nanoparticles produced by the combination of pulsed laser ablation and electrostatic classification. The electrostatic classifier sorted agglomerated mono-area nickel particles, and then a subsequent heating process at ∼ 1200 °C created sintered single primary particles with very narrow size distribution. These isolated single primary particles were then sent to an aerosol reactor where free-flight CNTs were grown with acetylene and hydrogen mix at temperature of ∼ 750 °C. The resulting CNTs formed in this continuous gas-phase process were found to have a uniform diameter, which is commensurate with the diameter of the size-controlled catalytic nickel particles.     

Preparation of mesoporous Co-B catalyst via self-assembled triblock copolymer templates

Mesoporous Co-B with worm-like morphology was firstly prepared via reduction of cobalt acetate by potassium borohydride in the presence of triblock copolymer templates. The as-prepared mesoporous Co-B was characterized by Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption-desorption. During the hydrolysis of KBH₄, the mesoporous Co-B exhibited much higher catalytic activity than the regular Co-B. It is attributed to the larger specific surface area (163.77 m²/g) and mesoporous channels. The average H₂ generation rate of the mesoporous Co-B was 3523 mL/min g catalyst in 1.3 wt% NaOH + 13 wt.% KBH₄ solution at 286 K, which may give a successive H₂ supply for a 571 W polymer electrolyte membrane fuel cell (PEMFC) at 100% H₂ utilization. Furthermore, the as-prepared mesoporous Co-B with high specific surface area is expected to find applications in many catalytic hydrogenation reactions.     

A new synthesis process and characterization of three-dimensionally ordered macroporous ZrO2

A three-dimensionally ordered macroporous (3DOM) material ZrO₂ has been successfully synthesized by using ZrOC1₂·8H₂O as precursor and polystyrene beads with diameters of 480 nm as template. The merit of this process is that ZrOC1₂·8H₂O is cheaper and has a high melting point. SEM images show that precursor concentration has an important effect in fabricating 3DOM ZrO₂. The sample prepared by using the precursor solution with a concentration of 1.6 M displays a well long-ranged ordered structure and uniform pore sizes. Precursor concentration between 1.3 M and 2.0 M is considered to be the most favorable to fabricate 3DOM ZrO₂. XRD analysis indicates that the crystallinity of 3DOM ZrO₂ is monoclinic phase. Nitrogen adsorption and desorption measurements at 77.4 K show detailed pore structures of 3DOM ZrO₂.     

Hybrid “Golden Fleece”: Synthesis and Catalytic Performance of Uniform Carbon Nanofibers and Silica Nanotubes Embedded with a High Population of Noble‐Metal Nanoparticles

Carbon nanofibers produced by hydrothermal carbonization display remarkable reactivity and the capability for in situ loading with very fine noble‐metal nanoparticles of metals such as Pd, Pt, and Au. Large quantities of uniform carbon nanofibers embedded/confined with various kinds of noble‐metal nanoparticles can be easily prepared, resulting in the formation of the so‐called uniform and well‐defined “hybrid fleece” structures. In addition, a general method has been developed to synthesize uniform silica nanotubes embedded/confined with noble‐metal nanoparticles by using the “hybrid fleece” consisting of carbon nanofibers loaded with noble‐metal nanoparticles as a template. To the best of our knowledge, the filling of silica nanotubes with a dense population of noble‐metal nanoparticles has not been demonstrated so far. These hybrid carbon structures embedded with noble‐metal nanoparticles in a heterogeneous “fleece” geometry serve as excellent catalysts for a model reaction involving the conversion of CO to CO₂ at low temperatures.