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Sullivan, James A.
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Sullivan, James A.
Official Name
Sullivan, James A.
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Now showing 1 - 10 of 32
- PublicationThe combustion of carbon particulates using NO/O2 mixtures : The influence of SO42− and NOx trapping materialsThe activity of several catalysts are studied in the soot combustion reaction using air and NO/air as oxidising agents. Over Al2O3-supported catalysts NO(g) is a promoter for the combustion reaction with the extent of promotion depending on the Na loading. Over these catalysts SO42− poisons this promotion by preventing NO oxidation through a site blocking mechanism. SiO2 is unable to adsorb NO or catalyse its oxidation and over SiO2-supported Na catalysts NO(g) inhibits the combustion reaction. This is ascribed to a competition between NO and O2. Over Fe-ZSM-5 catalysts the presence of a NOx trapping component does not increase the combustion of soot in the presence of NO(g) and it is proposed that this previously reported effect is only seen under continuous NOx trap operation as NO2 is periodically released during regeneration and thus available for soot combustion. Experiments during which the [NO](g) is varied show that CO, rather than an adsorbed carbonyl-like intermediate, is formed upon reaction between NO2 (the proposed oxygen carrier) and soot.
336Scopus© Citations 9 - PublicationA combination of NOx trapping materials and Urea-SCR catalysts for use in the removal of NOx from mobile diesel enginesPreliminary studies on a series of nanocomposite BaO–Fe ZSM-5 materials have been carried out to determine the feasibility of combining NOx trapping and SCR-NH3 reactions to develop a system that might be applicable to reducing NOx emissions from diesel-powered vehicles. The materials are analysed for SCR-NH3 and SCR-urea reactivity, their NOx trapping and NH3 trapping capacities are probed using temperature programmed desorption (TPD) and the activities of the catalysts for promoting the NH3 ads + NO/O2 → N2 and NOx ads + NH3 → N2 reactions are studied using temperature programmed surface reaction (TPSR).
818Scopus© Citations 27 - PublicationSynthesis of a Sustainable Cellulose-Derived Biofuel Through a 1-Pot, 2-Catalyst Tandem ReactionThe preparation, characterisation and application of two catalysts active in selective hydrogenation (Pt/TiO2) and esterification (mesoporous SiO2 material modified with tethered sulfonic acid groups) reactions is described. The catalysts are characterised using a range of spectroscopic, microscopic and adsorption techniques. Pt/TiO2 catalysts promote valeric acid (a cellulose derived platform molecule) hydrogenation to pentanol, while –SO3H modified mesoporous SiO2 catalysts convert valeric acid/pentanol mixtures to pentyl valerate (a 10-C molecule which can be used as a diesel fuel substitute). Admixtures of the two catalysts catalyse the tandem conversion of valeric acid/hydrogen mixtures to form pentyl valerate in a single reaction. A rationale for the observed reactivity, selectivity and carbon balance is proposed.
183 - PublicationTowards an understanding of the beneficial effect of mesoporous materials on dehydrogenation characteristics of NH3BH3Ammonia borane (AB) was loaded onto a range of mesoporous materials (MCM-41, SBA-15 and MCF) by wet impregnation from THF solutions and its thermal dehydrogenation studied using TGA/MS. The interactions between the AB and the surfaces were characterised using difference FTIR spectroscopy. The presence of mesoporous materials promotes lower temperature H2 release, and greater selectivity towards the formation of H2, i.e. decreased formation of gaseous boroncontaining side products. D-FTIR results confirm interactions between isolated silanol groups or surface Si-O-Si species and AB and this supports the proposal that a H-bonding interaction between the surface and deposited AB is important in promoting decomposition at lower temperature. AB interacting with silanol groups decomposes more readily than that coordinated to Si-O-Si. The effect on the temperature of H2 release is greater for materials of larger pore size (rather than materials of larger surface area), i.e. MCF>SBA-15>MCM-41. This suggests that access to the internal surface of the mesoporous material (where the majority of surface silanols are located) is important, and this in turn suggests that polymeric species, which may have restricted access to the internal surface of the different materials, form when AB is dissolved in THF. Decomposition of B-N-containing gaseous materials (to AB(g)) following their formation, on the silanol groups of the SiO2, is suggested as the reason for the increased selectivity of the reaction to H2 (and decreased release of unwanted side products) in the presence of mesoporous material.
499Scopus© Citations 18 - PublicationThe reactivity of mesoporous silica modified with acidic sites in the production of biodieselThis work has studied a range of acidic catalysts which have been prepared through the modification of mesoporous silica materials. Specifically we have prepared –SO3H modified materials (in the presence and absence of a hydrophobic component) and–COOH and –CN materials. We have characterized these catalysts using TEM, TGA, TPD of probe molecules and IR and we have analysed their activity in the esterification of octanoic acid and the transesterification of triacetin. Activity in the esterification reaction (in which all catalysts are active) is not determined by the acid site concentration of the catalyst while the activity of active catalysts in the transesterification reaction (in which only –SO3H materials are active) appears related to acid site concentration.
668Scopus© Citations 23 - PublicationRoutes to visible light active C-doped TiO2 photocatalysts using carbon atoms from the Ti precursors(Elsevier, 2014-09)
; ; ; ; In this work, different thermal treatments of titanium isopropoxide-derived photo-catalyst precursors, designed with the purpose of generating C-doped TiO2 photo-catalysts using carbon atoms present in the TiOx gel precursors as dopants, are presented. Specifically, these look at varying the standard calcination techniques using heat treatments in He (rather than calcination in air) and lower temperature calcinations (200 °C rather than 500 °C). The formed materials are characterised using N2 physisorption, XRD, UV Visible spectroscopy and XPS and their activities in promoting the oxidation of 4-chlorophenol under visible-light-only conditions were analysed. The nature of carbon remaining on the (or in the) material is discussed found to be both surface graphitic carbon and carbon present in anionic dopant positions. The different contributions of each type of carbon to the catalytic photo-activity under visible light are discussed.514Scopus© Citations 25 - PublicationThe use of alkaline earth oxides as pH modifiers for selective glycerol oxidation over supported Au catalystsThe activity and selectivity of an Au/TiO2 catalyst in a reaction mixture which has had its pH adjusted by the addition of NaOH (aq) is compared to that of the same catalyst in reaction mixtures whose pH was adjusted using suspensions of BaO and CaO. It was found that the suspensions acted as effective bases and reactions in their presence showed similar conversions to those where NaOH(aq) was used. The selectivities of the reactions were different in each case. In all cases dihydroxyacetone, glyceric acid, glycolic acid and formic acid was produced but more glyceric acid was produced when alkaline earth oxide suspensions were used (at the expense of glycolic and formic acid) than when NaOH(aq) was used. Given glycolic and formic acids are produced from oxidation of glyceric acid, it seems that glyceric acid is somewhat stabilized against further oxidation in the presence of the group II oxides. One explanation for this is the formation of glyceric acid hemicalcium salts (and analogous Ba2+ species) in solution.
577Scopus© Citations 13 - PublicationCo-SBA-15 catalysts in the hydrolysis of NH3BH3 – Influences of Co precursors and catalyst pre-treatmentH2 was released from ammonia borane (AB) through a hydrolysis reaction over several Co-SBA-15 catalysts. Each catalyst had an induction time prior to becoming active. The activation time related to the in-situ reduction of Co species to an active nano-particulate form and the length of this this induction time varied as a function of the Co-precursor used. The rate of the hydrolysis reaction over the reduced and active catalysts depended on the precursor. While the induction time was not noted in subsequent reactions over the reduced catalysts, the reactivity differences remained. A rationale for the differences based on the preparation steps is suggested
303Scopus© Citations 7 - PublicationVisible light active C-doped titanate nanotubes prepared via alkaline hydrothermal treatment of C-doped nanoparticulate TiO2: Photo-electrochemical and photocatalytic properties(Elsevier, 2013-09-01)
; ; ; Carbon-doped titanate nanotubes (C-TNT) were formed via alkaline hydrothermal treatment of a TiO2 nanoparticulate material pre-doped with carbon. Attempts to form C and W co-doped titanate nanotubes using analogous C and W co-doped nanoparticulate materials were unsuccessful. Physical characterisations, such as X-ray diffraction, N2 physisorption and Transmission Electron Microscopy, confirmed the formation of titanate nanotubes ~7 nm in diameter and hundreds of nm in length with increased surface areas relative to the nanoparticulate precursors. X-ray Photoelectron Spectroscopy confirmed the retention of substitutional carbon dopant and the exclusion of tungsten dopant from the doped TNT materials. Converting doped (or undoped TiO2) into C-TNT (or TNT) slightly increases the material’s bandgap but the C-TNT material (in contrast to TNT and undoped TiO2) absorbs into the visible region of the spectrum. C-doped and un-doped titanate nanotube materials were more active in promoting the photo degradation of 4-chlorophenol under visible light than their analogous nanoparticulate precursors. C-TNT was the most photocatalytically active material tested. However, photocurrent response measurements showed C-TNT to be less effective at generating current following irradiation than both its nanoparticulate analogue and nanoparticulate P25 when screen printed onto electrode surfaces. We ascribe this to non-optimal alignment of the TNTs on the electrode surface.854Scopus© Citations 36 - PublicationBeneficial and problematic interactions between NOx trapping materials and carbonaceous particulate matterThe presence of a NOx trapping BaO component with a Pt active phase does not per-se promote carbon combustion. However when coupled with trap regeneration, promotion of soot combustion is seen. Operating NOx trapping materials promote combustion due to the periodic localised increases in [NO2](g) generated during the regeneration rather than due to a co-generated exotherm. However, it has been noted that the presence of soot prevents NOx traps from employing their full trapping capacity.
390Scopus© Citations 27