Deep oxidation of VOC mixtures with platinum supported on Al2O3/Al monoliths

Pt impregnated metallic monoliths prepared from anodised aluminium foils were tested to study their catalytic activity in complete oxidation of volatile organic compound (VOC) mixtures. The VOCs oxidised were 2-propanol, toluene, methyl ethyl ketone (MEK), acetone and their mixtures. Complete oxidation was obtained in all cases except for the case of 2-propanol, where acetone was found as an oxidation intermediate. Even if the adsorption of the VOC on the Al₂O₃ is governed by its polarity, the reactivity is mainly affected by the competition of the oxygen atoms chemisorbed on the Pt particles.     

Filtration of liquid aerosols with a horizontal fibrous filter

The aim of this study was to determine the filtration efficiency and pressure drop in liquid aerosol capture mechanisms using a fibrous coalescent filter. The experimental set-up was designed to measure filtration efficiency and pressure drop through the filter. To avoid the gravimetric effect, the filter was placed horizontally. A series of experiments highlighted the importance of operating conditions such as filtration velocity and aerosol concentration. The results demonstrated the advantage of working at high velocities to minimise the resistance of the medium and to enhance the mass efficiency of the coalescent filter. In parallel, no effect of aerosol concentrations in the pressure drop increase was noted.     

莫来石纤维多孔陶瓷的制备与性能

对纤维多孔陶瓷的制备及性能进行了研究。在制备纤维多孔陶瓷时,采用酸性磷酸铝A23(P/Al原子比为2 3)作粘结剂,所制备的多孔陶瓷在各方面都具有优良的性能。如导热系数λ(22℃)为0.0529W/m.℃、热膨胀系数α为4.75×10-6/℃、孔隙率为96.22%、容重为0.1142 g/cm3等。在环保、节能领域具有广泛的应用前景和重要的社会及经济意义。     

Hydrotreating processes for catalytic abatement of water pollutants

Opportunities and problems in application of catalytic hydrotreating processes, which are presented a viable approach in the abatement of water pollutants, are discussed. Analysis of the hydrodechlorination (HDC) and hydrodenitrification (HDN) using Pd-based catalysts supported on various materials like granulated activated carbon (GAC), fibrous activated carbon cloths (ACCs) or glass fiber cloths (GFCs) studied recently in our laboratory suggests the following perspectives:

Exhaustive regeneration of Pd/GAC saturated with p-chlorophenol can be achieved in a two-step approach, incorporating gas-phase HDC by hydrogen followed by oxidation by air.

Pd/ACC catalysts are good candidates for the liquid-phase HDC showing activity higher than that of Pd/GAC or Pd/GFC; the high adsorption capacity of Pd/ACC lead suggesting its use in a technology with periodic adsorption and HDC, in similarity to adsorption with regeneration of GAC.

Pd/GFC and Pd–Cu/GFC are promising catalyst for removal of nitrites and nitrates, showing activity and selectivity that compares favorably with those of powdered catalysts.

NH3-SCR of NO at low temperatures over sulphated vanadia on carbon-coated monoliths: Effect of H2O and SO2 traces in the gas feed

The objective of this research is to asses the impact of the addition of H₂O, SO₂, and both in the SCR of NO at low temperatures over sulphated vanadia on carbon-coated monoliths. The sulphated catalyst keeps a 100% conversion and total selectivity to N₂ in the low temperature range, i.e. 473–500 K, when either H₂O or SO₂ is added to the gas feed. However, a decline of steady state conversion and selectivity occurs when both H₂O and SO₂ are added simultaneously because H₂O speeds up the deposition of ammonium sulphate salts. This decrease of catalyst performance is reversed when the reaction is carried out under dry conditions at temperatures higher than 473 K but not at lower temperature (453 K). Thus, the catalyst has demonstrated to be a good candidate for the SCR of NO at low temperatures even in stack gases containing traces of undesired components.     

Oxidative dehydrogenation of ethane on Pt–Sn impregnated monoliths

The oxidative dehydrogenation of ethane was studied over Pt–Sn impregnated monoliths at 1 bar, 600–900 °C and with different contents of oxygen, hydrogen and steam in the feed gas. As expected a decrease in oxygen in the feed led to a decrease in the conversion of ethane due to lower temperatures in the reactor. Adding steam to the feed showed no effect on the ethane conversion or the ethene selectivity. When the hydrogen/ethane ratio in the feed was varied from 0 to 0.5 at 700 and 850 °C, it resulted in a significant increase in the selectivity to ethene while the ethane conversion remained relatively unchanged. At 700 °C the selectivity increased from about 50% to 93% (carbon basis) with only a small decrease in the conversion of ethane. The results clearly show that both Pt and Sn have a catalytic effect. Pt caused the ethane conversion to rise and addition of Sn resulted in much better ethene selectivity. However, even though Sn alone showed some catalytic effect at lower temperatures, it cannot explain the great difference between the Pt and Pt–Sn catalysts. A reasonable assumption is therefore that there exist interactions between Pt and Sn that gives the Pt–Sn catalysts excellent properties for oxidative dehydrogenation of ethane, in particular upon addition of hydrogen.     

Ceramic fibrous monolithic structures

High-strength ceramic fibers and composite structures that contain them are generally expensive. In a lower-cost approach for fabricating fibrous composites, reinforcing fiber-like cells that are distinct from a continuous matrix phase called the cell boundary can be formed in situ from powders. Structures can be constructed by assembly and consolidation of filaments that consist of the cell phase and its surrounding cell boundary.

Fabrication of ceramic fibrous monoliths (FMs) is reviewed and mechanical properties of the most widely studied FMs are discussed. Those based on Si₃N₄ cells within a BN cell boundary have achieved the best overall properties and uniformity of manufacture, but degrade severely at high temperatures in oxidizing environments. Those based on oxides are more stable, but are substantially weaker. Assessment of the future of FMs is offered, including cost reduction, fabrication practice, property improvement, and formation of complex structures.     

Fibrous porous ceramics with devisable phenolic resin reinforcing layer

Fibrous porous ceramics with devisable phenolic resin reinforcing layer were fabricated using low cost atmospheric impregnation technology at room temperature. In combination with additional sealing method, phenolic resin reinforcing layer with controllable thickness could be obtained on the surface of fibrous porous ceramics. Typical gradient profile was observed along the thickness direction of impregnation. The effects of the phenolic resin reinforcing layer on mechanical properties and thermal insulation properties were studied. The results revealed that compressive strength increased from 1.70?MPa to 2.61?MPa, tensile strength increased from 0.78?MPa to 0.91?MPa, and flexural strength increased from 9.55?MPa to 10.89?MPa with the phenolic resin layer increasing from 0?mm to 9?mm. Simultaneously, room-temperature thermal conductivity increased from 0.051?W/(m·K) to 0.055?W/(m·K). In addition, the impact resistance of the surface of the material was obviously improved. The contact angel of the surface of the material exceeded 125°, which effectively improved the environmental adaptability.     

Thermal and Electrical Conductivity of Amorphous and Graphitized Carbide‐Derived Carbon Monoliths

The influence of graphitization and composition of carbide‐derived carbon (CDC) monoliths on the electrical and thermal conductivity was investigated. Carbon monoliths with varying porosities were synthesized employing biomorphous macroporous TiC and SiC as precursors. Graphitization was carried out in situ during high‐temperature chlorination with and without addition of nickel, iron, and cobalt chloride to the carbide. The graphitized monoliths showed improved properties. The results demonstrate that despite graphitic carbon also glass‐like carbon, stemming from the carbide synthesis, increases the thermal and electrical conductivity significantly.     

Effect of pulp rheology on flotation of nickel sulphide ore with fibrous gangue particles

Abstract

Tests are carried out with suspensions of fibrous chrysotile particles and nickel sulphide ore containing chrysotile as a gangue. They corroborate published results, and indicate a very strong effect of particle shape on slurry rheology. Such suspensions exhibit time dependent properties. The flotation tests revealed that the viscosity of this system strongly affects flotation performance. At a solids concentration of 15–20% (w/w), the concentrate yield increases and the concentrate grade dramatically declines. This deterioration is observed when the Casson yield stress exceeds 1·5–2 Pa. The tests imply that the rheological properties of the investigated system are mainly determined by fibrous components. However, because of the presence of anisotropic mineral particles, the effect of particle–particle interactions cannot be separated from the effect of particle shape in this system.

On effectue des essais avec des suspensions de particules fibreuses de serpentine et de minerai de sulfure de nickel contenant de la serpentine comme gangue. Ces essais confirment les résultats publiés et indiquent un effet très prononcé de la forme des particules sur la rhéologie de la boue. De telles suspensions exhibent des propriétés dépendantes du temps. Les essais de flottation ont révélé que la viscosité de ce système affecte grandement le rendement de la flottation. À une concentration en solides de 15 à 20% (poids/poids), la production de concentré augmente et la qualité du concentré décline dramatiquement. Cette détérioration est observée lorsque la contrainte de Casson excède 1·5 à 2 Pa. Les essais impliquent que les propriétés rhéologiques du système étudié sont déterminées principalement par les composantes fibreuses. Cependant, à cause de la présence de particules minérales anisotropes, on ne peut pas séparer l’effet des interactions particule-particule de l’effet de la forme des particules dans ce système.