John Breen
University of Limerick
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Featured researches published by John Breen.
Applied Catalysis B-environmental | 2002
Robbie Burch; John Breen; Frederic Meunier
Abstract Research on the selective reduction of NOx with hydrocarbons under lean-burn conditions using non-zeolitic oxides and platinum group metal (PGM) catalysts has been critically reviewed. Alumina and silver-promoted alumina catalysts have been described in detail with particular emphasis on an analysis of the various reaction mechanisms that have been put forward in the literature. The influence of the nature of the reducing agent, and the preparation and structure of the catalysts have also been discussed and rationalised for several other oxide systems. It is concluded for non-zeolitic oxides that species that are strongly adsorbed on the surface, such as nitrates/nitrites and acetates, could be key intermediates in the formation of various reduced and oxidised species of nitrogen, the further reaction of which leads eventually to the formation of molecular nitrogen. For the platinum group metal catalysts, the different mechanisms that have been proposed in the literature have been critically assessed. It is concluded that although there is indirect, mainly spectroscopic, evidence for various reaction intermediates on the catalyst surface, it is difficult to confirm that any of these are involved in a critical mechanistic step because of a lack of a direct quantitative correlation between infrared and kinetic measurements. A simple mechanism which involves the dissociation of NO on a reduced metal surface to give N(ads) and O(ads), with subsequent desorption of N2 and N2O and removal of O(ads) by the reductant can explain many of the results with the platinum group metal catalysts, although an additional contribution from organo-nitro-type species may contribute to the overall NOx reduction activity with these catalysts. It is concluded, after the investigation of hundreds of catalyst formulations, that many of the fundamental questions relating to lean deNOx reactions have been addressed and the main boundary conditions have been established. It seems clear that catalysts with sufficient activity, selectivity or stability to satisfy the demanding conditions that appertain in automotive applications are still far away. The rapidly growing interest in NOx storage systems reflects this situation, and it now seems to be the case that acceptable direct NOx reduction catalysts may be very difficult to find for lean-burn applications.
Catalysis Today | 1999
John Breen; J.R.H. Ross
Abstract The steam reforming of methanol to form mixtures of carbon dioxide and hydrogen, together with traces of carbon monoxide, is considered to be a potential source of hydrogen as the fuel for a fuel-cell to be used in mobile power sources. After outlining some of the constraints inherent in the use of the reaction and the types of catalysts which have been used by other investigators, this paper presents results on the preparation and testing of a series of copper-containing catalysts for this reaction. It is shown that the reaction sequence probably involves the formation of methyl formate which then decomposes to give CO 2 as the primary product; CO is formed by the reverse water–gas shift reaction and this only occurs to an appreciable extent when the methanol is almost completely converted. A number of different copper-containing catalysts are then described and it is shown that of these sequentially precipitated Cu/ZnO/ZrO 2 /Al 2 O 3 materials have the highest activities and stabilities for the steam reforming reaction.
Catalysis Today | 2000
Frederic Meunier; V. Zuzaniuk; John Breen; M. Olsson; J.R.H. Ross
The distribution of gaseous products and the nature of the surface species generated during the selective catalytic reduction of NO with C3H6 in the presence of excess O2 (i.e. C3H6-SCR) were studied over both a 0.4% Co/γ-Al2O3 catalyst and a sulphated 1.2% Ag/γ-Al2O3 catalyst. The results were compared with those previously reported for the C3H6-SCR over 1.2% Ag/γ-Al2O3 and γ-Al2O3. High concentrations of NO2 were observed in the product stream of the SCR reaction over the 0.4% Co/γ-Al2O3 and sulphated 1.2% Ag/γ-Al2O3 materials. The results show that (as in the case of the γ-Al2O3 and also probably that of the 1.2% Ag/γ-Al2O3) the NO2 was formed via an alternative route to the direct oxidation of NO with O2. The yields of NO2 were higher over the Co/γ-Al2O3 than over the other materials and in contrast to the other materials, no NH3 was produced over the Co/γ-Al2O3 catalyst. Based on these results and those of in situ DRIFTS experiments, a global reaction scheme incorporating organo-nitrogen species as key intermediates is proposed. In this scheme, NO, propene and oxygen react to form organo-nitro and/or organo-nitrito adsorbed species, the reaction products of which combine to yield N2. The results reported here suggest that Co preferentially promotes the formation of nitrito-compounds which can readily decompose to NO2, whereas Ag preferentially promotes the formation of nitro-compounds (from reaction of strongly bound ad-NOx species) which can decompose to isocyanates and ammonia. The sulphation of the 1.2% Ag/γ-Al2O3 reduced the surface concentration of strongly bound ad-NOx species which were thought to react with the reductant or derived species to yield the organo-nitrogen species.
Journal of Apicultural Research | 1997
Mary F Coffey; John Breen
SUMMARYThe floral sources of pollen and nectar used by honey bees in Ireland were studied during 1991–1994 by regular two-weekly sampling of pollen pellets from three colonies at a single site, and pollen and nectar samples from four individual colonies at different sites located in mid-western Ireland. Samples were analysed using dry weight and pollen analysis; relative abundance of pollen types was expressed as a percentage of the total number of pollen grains counted and presented as dominance-diversity curves. At the single site, 76 pollen types were identified and a seasonal variation in the dominance of species was apparent The diversity of species being foraged reached a maximum during June and July. Native nectariferous species were the most important pollen sources, while pollen was also gathered from introduced and entomophilous/anemophilous species especially during spring and early summer. Trees and shrubs were important pollen sources early in the year while herbs and shrubs increased in impo...
Chemical Communications | 1999
John Breen; Frederic Meunier; J.R.H. Ross
CO is not a primary but is a secondary product of the steam reforming of methanol over a CuO/ZnO/ZrO2/Al2O3 catalyst, CO is formed as a secondary product by the reverse WGS reaction only when the methanol has reacted.
Conservation Genetics | 2007
Hannaleena Mäki-Petäys; John Breen
Ants are ecologically important species in many environments forming a big proportion of the total animal biomass. However, their special features such as sociality and complementary sex-determination system have received little attention in conservation discussions. We examined the social and genetic structure of the hairy wood ant Formica lugubris in Ireland to evaluate factors relevant to the vulnerability of small, isolated wood ant populations. We also clarified the conservation status of the species in Ireland. Our results showed that the populations are mainly monogynous (one queen per nest). Consequently the effective population size is very low (<100 individuals) in Ireland. We found extremely little genetic variation, signs of inbreeding and inbreeding depression, which can be a consequence of the small effective population size and of the restricted gene flow due to strong isolation of populations. Putatively high genetic diversity at the sex-determining locus can reflect a larger population in the past. The study shows that even though the population may seem stable because of the long life span of queen ants, sociality can impact species conservation by keeping the effective population size small. According to our results, the hairy wood ant can be considered native to Ireland. Hence it needs urgent protection and the genetic issues need to be considered in the future management strategies.
Topics in Catalysis | 2001
G.A Konin; A.N. Il'ichev; Valerii A. Matyshak; T.I. Khomenko; V. N. Korchak; V. A. Sadykov; Vladimir Doronin; Rimma Bunina; G. M. Alikina; Tatiana Kuznetsova; E. A. Paukshtis; V. B. Fenelonov; V. I. Zaikovskii; A.S. Ivanova; S. A. Beloshapkin; A. Ya. Rozovskii; Valentin F. Tretyakov; J.R.H. Ross; John Breen
Thermally stable Al- and Zr-PILC loaded with copper and cobalt cations and silver nanoparticles were synthesized. The structural and surface features of these nanosystems were studied and compared with those of bulk analogs – partially stabilized ZrO2 loaded with the same active components. Specificity of the catalytic properties of nanocomposites in SCR of NOx by propane, propylene and decane in the excess of oxygen appears to be determined both by distribution of active components on the catalytic surface and degree of their interaction with supports. Formation of ads.-NOx, nitroxyl-hydrocarbon CxHyNO2⋅ and isocyanate NCO intermediates was observed by ESR and IR spectroscopy in situ.
International Journal of Mining, Reclamation and Environment | 2008
C. Garavan; John Breen; Richard Moles; Bernadette O'Regan
An environmental investigation was initiated following the deaths of cattle from lead poisoning in a former Irish lead and zinc mining area. A study was undertaken to determine blood lead levels (BLL) of children living in the area over a period of three years. Dust and soil samples were collected for environmental lead exposure assessment. The BLL of the children decreased by ∼10% in each of the three years of the screening programme. These levels are at, or below, findings from similar BLL studies undertaken in former mining areas worldwide. The study in this report suggests that the elevated environmental lead (Pb) levels are not currently being transferred to humans. Community awareness of environmental health issues has increased significantly in recent years, creating the need for more detailed scientific studies that can identify potential environmental health problems. The Silvermines project was one such study. The objective of this article is to report the study findings.
MRS Proceedings | 1999
V. A. Sadykov; Rimma Bunina; G. M. Alikina; Vladimir Doronin; T. P. Sorokina; D. I. Kochubei; B. N. Novgorodov; E. A. Paukshtis; V. B. Fenelonov; A. Yu. Derevyankin; A.S. Ivanova; V. I. Zaikovskii; Tatyana Kuznetsova; B. A. Beloshapkin; V. N. Kolomiichuk; L. M. Plasova; Valerii A. Matyshak; G.A Konin; A. Ya. Rozovskii; Valentin F. Tretyakov; T. N. Burdeynaya; M.N Davydova; J.R.H. Ross; John Breen; F. C. Meunier
Thermally stable alumina and zirconia pillared clays loaded with copper and cobalt cations and silver nanoparticles were synthesized. The structural and surface features of these nanosystems were studied and compared with those of bulk analogs -partially stabilized zirconias and γ-alumina loaded with the same active components. Specificity of the catalytic properties of nanocomposites in the reactions of nitrogen oxides reduction by propane, propylene and decane in the excess of oxygen appears to be determined both by the degree of interaction between pillars and active components and the type of reducing agent.
Journal of Apicultural Research | 2016
Mary F Coffey; John Breen
This two-year study aimed to assess the efficacy and tolerability of the oxalic acid product Api-Bioxal® as a winter treatment administered using the trickling and vaporizer methods at the dosage rate recommended by the manufacturers (Trial 1) and at the lower dosage recommended by The European Group for Integrated Varroa Control for cool temperate climates such as Ireland (Trial 2). Trial 1: In August 2011, 45 colonies were standardized based on brood area and blocked into 2 treatment groups (n = 15) and a control group using natural mite-fall pre-treatment. Three weeks post-treatment a control treatment (CheckMite+) was administered to the test colonies and the percent efficacy of Api-Bioxal® was calculated. Invasion pressure was monitored by treating the control colonies continuously with CheckMite+. Tolerability was assessed by monitoring adult bee mortality post-treatment and spring build-up was assessed on brood area. The mean (± s.e.) percent efficacy for the trickling method (81.5 ± 3.5%) was significantly lower than for the vaporizer (95.2 ± 1.6%) and control (97.7 ± 1.0%) groups. Bee mortality post-treatment was significantly higher in the trickling group but Api-Bioxal® treatment had no negative impact on spring build-up irrespective of the application method. This high bee mortality and relatively low efficacy led to Trial 2. Trial 2: In August 2012, 72 colonies were standardized using brood area and divided into 5 treatment groups (n = 12) plus a control group. The application methods and dosage rates recommended by the manufacturers (6.0% trickling method in a 1:1 sugar/water syrup and 2.3-g vaporizer method) were again assessed in addition to a lower dosage of 4.5% in 1:1 sugar/water using the trickling method and 1.3 g for vaporizer method. The control colonies were untreated. The mean percent efficacy calculated for the five treatment groups exceeded 90% and were all significantly higher than the 8.57% efficacy estimated for the control group. Bee mortality was again significantly higher in the colonies treated using the trickling method at the 6.0% concentration and significantly decreased when the dosage concentration was reduced to 4.5%. Api-Bioxal® applied using the vaporizer method, irrespective of the quantity administered, was well tolerated by the colonies and bee mortality was similar to the natural mortality observed in the control group. We conclude that in a cool temperate climate, Api-Bioxal® is an effective varroacide when administered as a single winter treatment under broodless conditions using both the trickling and vaporizer methods. Colonies tolerated the product better at the reduced dosage rate of 4.5% using trickling method or 1.3 g using the vaporizer method without compromising the efficacy of the treatment.