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A spatially resolved technique was used to investigate the impact of deactivation on the spatial distribution of the effective diffusion in an aged washcoated monolith catalyst. The technique was applied to the investigation of the reactants and products of CO oxidation inside a commercial Pd/Al2O3 monolith catalyst. The spatially distributed effective diffusivities of O2, CO and CO2 were resolved and calculated by a modified Bosanquet approach, which confirmed that the dominant diffusion regimes in the substrate and the washcoat were molecular and Knudsen respectively in the zone affected by deactivation. The technique illustrated the extent to which the deactivation, and its impact on diffusion, varied throughout the washcoat. The results presented are of relevance to the simulation of aged catalysts for automotive applications. In scenarios such as this it is common to model the reduction in catalyst activity by reducing the surface area of the precious metal, with the washcoat diffusion parameters set to their initial, non-aged values. This research quantifies the significant extent to which the diffusion parameters are affected which, when incorporated into catalyst models, will result in more accurate predictions of vehicle emissions.

While methane-powered vehicles produce fewer greenhouse gas emissions in comparison to conventional fuel vehicles, there is a significant amount of methane slip in their exhaust that needs to be treated. This study investigates non-thermal plasma (NTP) assisted catalytic methane oxidation as an alternative method for the low temperature methane slip abatement applicable to the exhaust of biogas methane-powered vehicles. It is concluded that high CH4 conversion and CO2 selectivity can be obtained using NTP-catalysis at low temperature with Pd/Al2O3 found to be the most promising candidate among all catalysts tested. In addition, it was found that CH4 conversion efficiency was dependent on the feed gas components and gas hourly space velocity as well as how the activation energy is introduced. For example, a combination of plasma and external heat supply provides advantages in terms of CH4 conversion along with lower plasma energy consumption. The presence of N2 and O2 in the feed gas during NTP-catalytic methane oxidation results in unfavourable NOX formation which linearly increases with CH4 conversion. These results conclude that the most suitable aftertreatment option involves the combination of an oxidation catalyst with plasma to target the hydrocarbon and CH4 oxidation, followed by an ammonia-SCR system to convert the NOX formed in plasma assisted zone.

Heterogeneous immobilized ionic liquid catalysts were prepared via grafting of 1,3-dimethyl-3-(3-triethoxysilylpropyl)-imidazolium tetrafluoroborate or bis{(trifluoromethyl)sulfonyl} imide ([NTf 2 ] − ) on silica supports with different surfaces and pore size. In addition to the adsorption–desorption isotherms of nitrogen at −196 °C, the catalysts were characterized by TG-DTA, XPS, DRIFTS, DR-UV–vis, NMR, and XRD techniques. The catalytic behavior was checked in the acylation of three different sulfonamines: benzenesulfonamine, p -nitrobenzenesulfonamine, and p -methoxybenzene-sulfonamine with acetic acid, acetic anhydride and maleic anhydride. These tests confirmed the acid Lewis properties of these catalysts.

New strong Lewis acid SnTf-MCM-41 and SnTf-UVM-7 catalysts with unimodal and bimodal pore systems were prepared in a two-step synthesis in which the triflic acid (Tf) was incorporated to previously synthesized mesoporous tin-containing silicas. The Sn incorporation inside the pore walls was carried out through the Atrane method. The SnTf-UVM-7 catalysts were prepared by aggregating nanometric mesoporous particles defining a hierarchic textural-type additional pore system. Following these procedures, catalysts with different Si/Sn ratios—21.8 to 50.8 for SnTf-MCM-41 and 18.4 for SnTf-UVM-7—were prepared. These new materials were tested in the acylation of aromatic sulfonamides using acetic acid as the acylating agent and in the synthesis of (dl)-[α]-tocopherol through the condensation of 2,3,6-trimethylhydroquinone (TMHQ) with isophytol (IP). The activity data indicate that these heterogeneous catalysts are very active, corresponding to high yields in acylated compounds as 65.5% and very high selectivity to (dl)-[α]-tocopherol (94%, for a conversion of 98%).

The polymerization of ϵ-caprolactone initiated by two catalyst systems was studied: (1) carbazole-potassium in the presence of 18-crown-6 ether and (2) NdCl3/TBP/TIBA (neodymiumtrichloride/tri-n-butyl-phosphate/triisobutylaluminium) at the molar ratio 1/3/1. For both initiator systems conversion/time plots were determined and the polymers were characterized by IR, GPC and by 1H- and 13C−NMR spectroscopy. Polyesters with the highest molecular weight (Mn≅44 000 g/mol) were obtained for the polymerizations initiated by the carbazole-potassium/18-crown-6 ether system. The features of the polymerization initiated by the carbazole-potassium/18-crown-6 ether system are discussed on the basis of a simple scheme. The nature of this polymerization is non-living. Copyright © 2000 John Wiley & Sons, Ltd.

General aspects of fractal geometry are treated, and a mathematic model for characterisation of chromatographic gel behaviour is presented. The fractal dimension of the porous gel within a Waters Styragel HT 5 chromatography column, df= 2.3, as well as the linear dimension of pores, L = 0.3 μm, have been determined.