M. Yates

Honeycomb monoliths of activated carbons for effluent gas purification

Abstract During the incineration of urban waste incomplete mineralisation of some organic species can give rise to effluents contaminated with VOCs, furans and dioxins. These units produce large volumes of gas to be treated, but with low contents of these toxic species, for which the pressure drop caused by passing through a conventional pellet adsorption bed can be considerable. Another solution is to spray activated carbon powder into the contaminated effluent gas, although this is an expensive method. Thus, to avoid the problems associated with pressure drop or high operation costs, commercial activated carbons have been conformed as open-channel honeycomb monoliths. Their adsorption capacities towards an aromatic probe molecule, o-dichlorobenzene, chosen to simulate dioxins have been tested in a static regime. The results were analysed together with the textural and mechanical properties of the monolith composites in order to establish criteria by which the most suitable honeycomb monolith composite material for industrial use could be prepared.

Microwave decomposition of a chlorinated pesticide (Lindane) supported on modified sepiolites

Inorganic porous materials based on modified sepiolites have been studied as supports for controlled degradation of Lindane, a chlorinated pesticide. In dry media conditions under microwave (MW) irradiation, sepiolite can dehydrohalogenate Lindane to pentachlorocyclohexene (PCCH). Trichlorobenzene (TCB) and PCCH are obtained with NaOH-modified sepiolite and, when nickel oxide is present in the solid, CO2 is also found as a product of the reaction, in different proportions depending on the surface characteristics.

Pillared clay and zirconia-based monolithic catalysts for selective catalytic reduction of nitric oxide by methane

Abstract New monolithic catalysts based on zirconia and pillared clays (PILC) have been studied for NOx removal by CH4 in the presence of oxygen. A comparative study of the influence of ZrO2 from various commercial sources for the system Pd–ZrO2 and the effect of the noble metal chosen for the system NM–PILC was carried out, trying to correlate the catalytic activity with the physico-chemical properties of these catalysts. The obtained results indicate that structure and surface acidity of the support plays an important role on the selectivity to NOx reduction, although properties such as the surface area or pore volume could also determine the overall activity of the monolithic catalysts.

Zeolitic materials as catalysts for organic syntheses

The major applications of zeolitic materials are as cation exchangers, selective adsorbents, catalysts and catalyst supports (mainly in catalytic cracking, hydroisomerization and aromatics processing). Their use in the synthesis of hydrocarbon intermediates and fine chemicals is at an earlier stage of research, although several international reunions and reviews have already shown the improvement achieved by using these solids in conventional catalytic processes. This improvement is found mainly in activity, selectivity and environmental concerns, new more environmentally friendly routes having been found for processes which previously produced undesirable side reactions or high amounts of environmentally hazardous residues (with the subsequent economic considerations). More than a hundred references form the main body of the present piece of work, which has three major objectives, the first of which is to outline the main properties of zeolitic materials in relation to their use as catalysts in organic syntheses, the second to present an up to date bibliographic review of their use for such purposes and the third to show the main improvements that these materials present with respect to the more conventional catalysts.

Characterization of alumina:sepiolite monoliths for use as industrial catalyst supports

A series of honeycomb monolithic catalyst supports based on alumina, sepiolite and mixtures of the two were prepared. The textural characterization of these was carried out after heat treatments up to 1473 K, in order to assess the relative merits or drawbacks in the use of sepiolite as a possible admixture to improve the mechanical strengths of the monoliths, whilst preserving high specific surface areas and porosities.

The use of sepiolite in the preparation of titania monoliths for the manufacture of industrial catalysts

Abstract In this work the merits of the use of a natural fibrous mineral, sepiolite, as a binder to produce titania based monoliths of high mechanical strength and abrasion resistance is discussed. The monoliths of square channels were conformed with an initial 7.5 channels cm −2 and 1 mm wall thickness. The textural characterization was made by mercury intrusion porosimetry (MIP), nitrogen adsorption/desorption (BET), and X-ray diffraction (XRD). The mechanical resistance, dimensional changes and weight losses at each stage of heat treatment were also determined. The thermal expansion coefficients (TEC) of the monoliths were determined between 200° and 400°C, since in practice the usual working temperature of DENOX catalysts lies between 250°–350°C.

The dynamic adsorption behaviour of volatile organic compounds on activated carbon honeycomb monoliths

Adsorption offers an efficient technology for removing volatile organic compounds (VOCs) from air pollution sources. Often activated carbons (ACs) are employed owing to their large specific surface areas, high micropore volumes, rapid adsorption capabilities and selectivity towards organic molecules compared to water vapour or air. However, when large volumes of gas have to be treated pressure drop limitations may arise from the use of conventional adsorption beds. For these applications conformation of the adsorption bed as honeycomb monoliths take advantage of the negligible pressure drop of these structures. Commercially available ACs were conformed as honeycomb monoliths with a magnesium silicate clay as binder. The textural and mechanical properties of the raw materials and the monolith composites were determined. These results were analysed together with the dynamic adsorption capacities towards o -dichlorobenzene ( o -DCB) a chlorinated probe molecule used to simulate a dioxin. With this data, criteria by which the dynamic adsorption capacity could be related to the textural properties of the adsorption units were established.

Influence of the operation time on the performance of a new SCR monolithic catalyst

Abstract The effect of the time in operation on the performance of a novel monolithic catalyst was studied in a life test carried out with real effluent gases from a coal fired power plant. Although deposition of fly ash and ammonium sulphates were observed, the catalytic activity, physical and mechanical properties of the catalyst remained largely unchanged after 5000 h of operation.

Preparation, characterization and in vitro osteoblast growth of waste-derived biomaterials

Renewable raw biocompatible materials can be prepared from beer production waste, that due to their nature contain the main chemical components present in bone (phosphorous, silicon, magnesium and calcium). Their characteristics can be tailored for use as replacement candidates in osteoporotic treatments, coatings for prostheses, bone grafts and odontoestomatologi implants, for example, with greater cost effectiveness than conventional scaffolds and eliminating the use of non-renewable raw materials or toxic substances in their preparation.

Biomaterials from beer manufacture waste for bone growth scaffolds

Abstract Agricultural wastes are a source of renewable raw materials (RRM), with structures that can be tailored for the use envisaged. Here, they have proved to be good replacement candidates for use as biomaterials for the growth of osteoblasts in bone replacement therapies. Their preparation is more cost effective than that of materials presently in use with the added bonus of converting a low-cost waste into a value-added product. Due to their origin these solids are ecomaterials. In this study, several techniques, including X-ray diffraction (XRD), chemical analysis, mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and bioassays, were used to compare the biocompatibility and cell growth of scaffolds produced from beer bagasse, a waste material from beer production, with a control sample used in bone and dental regenerative processes.