1,721,010 research outputs found
An investigation into coking on catalyst support materials & supported metal catalysts
Get PDFThe deposition of coke on oxidation catalysts leads to
deactivation. For oxide supports this phenomena of coking has previously been identified with acidic sites. Measurement of coke formation on silica gel, a-, r|- and y-Al2 0 3 showed that the greatest amount of coke was formed on y-A12 0 3 followed by r(-Al2 0 3 with no detectable coking occurring on either a-Al2 0 3 or silica gel. Titration results showed y-Al2 0 3 to contain the highest concentration of acidic and Bronsted basic sites per gram followed by ri-Al2 0 3, a-Al2 0 3 and silica gel.
The acidity of y-Al20 3 was altered by treatment with HC1, NH3 and NaOH. HC1 treatment gave a reduction in coke deposition while NaOH treatment increased coking and NH3 treatment had no effect on the level of coking.
The effect of doping y-Al2 0 3 and 0.5%Pt/y-Al20 3 with Sn, Ce and Zr on the amount of coke formed was investigated. It was found that the level and method of impregnation affected the amount of coke formed on each catalyst. Individual addition of Sn, Ce, or Zr to y-Al2 0 3 brought about a large reduction in the level of coking relative to y-Al20 3 with the greatest reduction being seen for addition of Zr. Doping Pt/y-Al2 0 3 with Ce, Sn or Zr resulted in the lowest level of coking occurring on Pt-Sn/y-Al2 0 3. No correlation between acidic and Bronsted basic sites was observed for the metal impregnated catalysts suggesting that these metals exert a much greater influence on coking than do acidic or Bronsted basic sites.
The effect of Sn, Ce or Zr addition on activity of Pt/y-Al2 0 3 for oxidation of isobutane was investigated. Addition of Sn or Zr reduced activity while 0.3% and 3.0% Ce resulted in greater activity than that observed for Pt/y-Al2 0 3
From curriculum to classroom in upper second level science
Get PDFEducation in Ireland has gone through a significant period of change since the 1980s. Upper second level education has been the subject of extensive consultation and review, and revised specifications for Leaving Certificate biology, chemistry and physics were developed by the National Council for Curriculum and Assessment during the period 2006- 2014. The revised specifications are written as learning outcomes in which the key skills of information processing, being personally effective, working with others, communicating and critical and creative thinking are embedded. Curriculum development in Ireland reflects international practice, where development of key competences/skills is a fundamental theme underpinning recently developed curricula. Whilst knowledge and understanding of science concepts and theories is as important as ever, what learners are able to do with that knowledge and understanding is equally, and increasingly, important. Although curriculum development in Ireland is in line with curriculum development internationally, this study focuses on the local issues associated with curricular change, in particular the translation and communication of learning outcomes.
The construction of learning outcomes is a complex, non-linear, interacting system which teachers will need to deconstruct in order to fully understand them. Building on key literature, this study develops two organising frameworks that facilitate analysis of learning outcomes and of assessment items. Understanding the kinds of learning experiences that develop skills in students will contribute to curricular coherence, without the need for curriculum control.
The study describes two design based research projects in which teachers and students actively contributed to the process of curriculum development. The teachers worked at the interface between policy and research, and brought their experience and knowledge to the curriculum design process. The first project was concerned with pedagogy, the second with assessment. The outcomes of both projects informed the development of the upper second level science curricula in Ireland, and have set the scene for further developmental work
An investigation of gauze supported platinum alumina and cobalt supported oxide oxidation catalysts
Get PDFThe aim of this research involved preparation and optimisation of Pt/Al203 gauze supported catalysts with high thermal stability and surface area with a well-dispersed layer of Pt. Preparation involved nucleation/whiskering of an FeAl metallic alloy substrate forming hair like crystal of AI2O3, followed by application of alumina washcoat support onto the crystals. The washcoated substrate support was then impregnated with an active phase material (i.e. Pt metal). Evaluation and characterisation of the metallic substrate support (i.e. gauze material) onto which the alumina support and Pt were impregnated were investigated with a view to developing, optimizing and scale up of the process to pilot plant for commercial scale. Catalysts characterisation was carried out using AAS, BET surface area (N2 physisorption) to determine metal loadings and surface area of the substrate and alumina washcoat supports. Metal surface area, Pt dispersion and metal particle size together with activity of the Pt supported catalysts were measured using Pulse chemisorption and combustion activity techniques. In addition particle size measurement of alumina (i.e. Puralox powders) employed in the washcoat support were investigated using Malvern Mastersize Analyser, in a view to discover if a correlation between surface area and thermal stability of the washcoat support existed. It was found a smaller particle size washcoat solution produce a more thermally stable support material. Finally the use of Scanning electron microscopy (SEM) and Energy dispersive X-ray analysis (EDX) was used in the surface and subsurface characterisation of both the whiskered gauze (including whiskering under different atmospheres and conditions) and final Pt/Al20 3 prepared catalysts.
The second area of research involved preparation and characterisation of various PP rted and unsupported single metal oxide combustion catalysts as alternatives to the more expensive noble metal catalysts. The investigation reports on the potential use of supported unsuPported coball oxides for the combustion of methane. Particular
emPhasis is placed on the role played by various thermal analysis techniques in the elucidation of factors which affect catalyst performance.
Two combined thermal analysis-mass spectroscopy techniques have been used to ascertain the effects of various support materials on the preparation and subsequent combustion activity of supported cobalt oxide catalysts. Both techniques used involved small sample masses in order to minimise temperature and pressure gradient throughout the sample during reaction as the sample temperature was increased at a linear heating rate. Temperature programmed reduction (TPR) techniques employed not only reveal reduction, but also distinguish it from the adsorption (or evolution) of the H2 and the loss of adsorbed water. The thermal induced decomposition of supported and unsupported cobalt nitrate hexahydrate was studied using solid insertion probe mass spectrometer (SIP-MS) system operating under high vacuum. The support material was found to affect the decomposition process significantly. In particular, the decomposition of cobalt nitrate dispersed on y-A^Os occurred via a markedly altered process in comparison with the unsupported nitrate. The ZrC>2 and CeC>2 supports both exhibited a less pronounced effects on the decomposition process. After calcinations of the dispersed cobalt nitrate species, methane combustion activity was found to be much lower for the aluminasupported samples relative to the other supports used. A combined temperatureprogrammed reduction-mass spectrometry (TPR-MS) technique was used to elucidate a correlation between the catalysts activity and reducibility. Constant thermal rate analysis (CRTA) was also used to investigate the reduction of Co304/Ce02.
The main conclusion from the research found the use of cobalt as a viable alternative to, noble metal combustion catalysts. Deactivation problems due to sintering of the active C03O4 phase and reaction with the alumina support forming inactive mixed oxides (i.e. C0AI2O4 spinel) were also establish. Cobalt oxide supported on ceria or zirconia as well as cerium support were shown to be a highly active catalyst for the combustion of CH4. However, in both cases deactivation was observed upon exposure to the reaction mixture which maybe associated with sintering or the conversion of C03O4 to a less active CoO phase. However, despite such problems with the existing formulation, research into the use of C03O4 may provide a greater understanding of the origins to low-temperature combustion activity and design of new automotive exhaust applications in the drive to develop new catalytic technologies
Physical-chemical properties and sorption characteristics of peat
Get PDFThe physicochemical properties of peat fibre, peat moss and two processed forms of peat moss were studied. The properties examined included thermal analysis (by T G A and DSC), IR spectroscopy and the zero point o f charge From D S C analysis it was found that the ignition point for the peat materials occurred at about 200°C. Above this temperature there were three exothermic peaks recorded, the first at c 333°C corresponded to the decomposition of cellulose, the second at c 438°C to the decomposition of bitumens and/or humic substance and the third at c 479°C to the decomposition of lignin.
The surface area of the peat fibre was measured by methylene blue dye adsorption, N 2 adsorption and the negative adsorption o f chloride 1 0 ns. The surface areas measured by the three methods were 307, 2 3 and 0 05 m2 g_l respectively. The variation m surface areas was in keeping with the large differences in surface areas which have been reported for SOM.
The sorption of a series of alcohols from vapour and aqueous phase by peat fibre was also studied. It was found that the sorption of alcohols from the vapour phase decreased in the order ethanol > 2 -propanol > 1 -butanol > 1 -pentanol while the sorption from the aqueous phase decreased in the order 1 -hexanol > 1 -pentanol > 1 - butanol > 2-propanol > ethanol. The results were inconclusive, but suggested that the sorption from the vapour phase was princ ipally by adsorption followed by absorption into the interior o f the peat, while the sorption from the aqueous phase was princ ipally by adsorption.
A lab-scale biofilter was set up to eliminate ethanol vapour from an artificial waste gas stream using peat fibre as the filter material. A fter about 80 days o f operation over 80 % o f the ethanol vapour (inlet concentration c 76 g dm '3) was being eliminated. The elimination capacity was calculated to be c 61 g dm- 3 t r 1 and the critical gas constant to be c 60 g dm-3
The preparation and characterisation of hydrophobic polymeric membranes for use in the separation of liquid mixtures using pervaporation separation processes
Get PDFPervaporation is a membrane separation process used to separate liquid mixtures Separation is achieved by establishing a concentration vapour-pressure gradient across the membrane.
Polyurethane (PU) and polydimethylsiloxane (PDMS) membranes were prepared from their prepolymers by solution casting Dilute aqueous solutions of ethyl acetate, methyl isobutyl ketone, methyl ethyl ketone and aniline were separated using these polyurethane and polydimethylsiloxane polymeric membranes at temperature ranging from 50 to 80°C The effects of the systems operating temperature was studied.
The separations were characterised and examined by the effect of temperature on the composition of the retentate and permeate samples taken during the separation process. Gas chromatography was used to analyse the resulting retentate and permeate samples.
Extensive physical characterisation of the membranes was carried out using a number of techniques including Scanning Electron Microscopy, gravimetric sorption experiments, Differential Scanning Calorimetry.
A combination of the physical examinations and the pervaporation data was used to evaluate the membranes performances in the separation of all four solutions within the temperature range examined.
Higher selectivity values were obtained for separations carried out using the polydimethylsiloxane membrane whereas higher flux values were achieved using the polyurethane membranes. The most successful separations, based on selectivity and flux values, was deemed to be the separation of methyl isobutyl ketone and water at 80°C using the polydimethylsiloxane membrane, PDMS1, with selectivity and flux values reaching 774 and 0 400kg/m2hr, respectively.
Some of the physical charateristics of the membranes which were examined, such as the activation energy of permeation and the glass transition temperature, were found to be unsuitable for use as prediction methods for the performance of a particular membrane/liquid mixture system. The most preferable membrane preparation conditions were also isolated during the course of this study with the aid of scanning electron microscopy images
Elementary science in Irish primary schools from the late 1800s to the present day:to what extent is elementary science a new subject in Irish primary education today?
Get PDFThis thesis examines science in Primary Education in Ireland since the late 1800's. Much research has been done on science in education. Quayne (2003) described the development of post-primary science education in Ireland and drew attention to some features in primary science but did not seek to answer any specific questions. Kelham (1965) described the provision of science in schools in Scotland and Ireland. In this thesis the life and work of Henry Edward Armstrong and of William Mayhowe Heller, their philosophies into the teaching of elementary science and Armstrong's heuristic methods and his influence with Heller is discussed. The teaching of Science in Primary schools will be examined from the late 1800's with Heller organising the implementation of elementary science into the Irish National School system from 1900-1922 using Armstrong's heuristic teaching approaches. The thesis continues to analyse the teaching of science right through the century with the First National School Programme of 1922 to the 1971 curriculum and finally the revised 1999 curriculum. The history of Elementary Science gathered from documentary evidence together with the results of interviews with currently teaching and retired teachers are used as sources to provide an insight into science in the primary classroom from the late 1800's to the present day. Inspectors' reports and sample lessons from 1900 and 1999 provide a further insight into science teaching in the last century. Finally the thesis draws conclusions as to why science in the 1999 curriculum is considered by many teachers a new subject in Irish Primary Education. Elementary science is not a new subject in Irish Primary Education today. In fact lessons from the attempted 1900 implementation of science might even be applicable to the science curriculum of today
Questioning for appropriate assessment and learning
Get PDFAssessment methods/formats have come to the forefront of issues concerning educationalists in the last few decades as they began to question established methods. These
questions were mainly concerned with the understanding that was being assessed of students and what results were telling educators about the way in which their students were
engaging with chemistry material. All assessment formats have been grouped essentially into two types: summative and formative assessment. Summative assessment is concerned
with an end of term/module assessment which examines students understanding of information/concepts covered during the course of a topic. This provides teachers/lecturers with a grade to award students based on a single examination. This study has investigated three forms of assessment: the summative assessment employed at Leaving Certificate level for Chemistry and the formative assessment methods used in two chemistry modules in Dublin City University. This study is divided into four separate chapters, dealing with the aforementioned studies conducted and a the first chapter dealing with comprehensive literature review on assessment formats, question styles and
technology employed in this study. For the second chapter analysis was performed on the current Leaving Certificate
Chemistry Curriculum (implemented in 2000, first examined in 2002) and the examinations completed by students at Higher Level since 2000. One method of analysis performed
utilised Blooms Taxonomy to identify the level of questioning used at Leaving Certificate Level. Results have shown that the majority percentage of questions employed at Higher Level are of the lower order identified by Bloom, with little or no questions of the higher orders, such as analysis, synthesis and evaluation questions being identified. Further analysis performed have shown that there is a lack of assessment of students understanding
of some core/sub topics, while others are over assessed, in comparison to the number of classes allocated to them in the Chemistry curriculum.
The third chapter has investigated the implementation of a continuous assessment element into a physical chemistry module for second year undergraduate chemistry students. This study employed the use of an electronic assessment tool to encourage student engagement with lecture material. Results have shown that the continuous assessment element has successfully identified problem areas in chemical kinetics and thermodynamics which requires more focus and explanation on the part of the lecturer. Results have shown that students displayed a lack of engagement with lecture material and also student surveys have supported these findings. Data has shown however that students enjoyed the use of these electronic assessment tools and began to take a more active role in their learning towards the end of the module as they used the CA elements in their revision for the end of module examination.
The fourth and final chapter deals with the formative
assessment introduced into a practical laboratory session through the use of pre and post laboratory tasks for first year undergraduate chemistry students. In this study a VLE was used to host a series of pre laboratory quizzes and post laboratory activities which aimed to help encourage
engagement with laboratory material out of the practical session. The pre laboratory quizzes were designed to help prepare students for their practical session. The post
laboratory questions were designed to assess students' understanding through the application and analysis of concepts covered within the practical session. Results have
shown that the use of pre and post laboratory sessions has engaged students outside of the practical session and that students feel readily prepared for their practical upon completion of the pre - laboratory quiz. However students displayed a lack of engagement with chemical concepts in the majority of the completed chemistry laboratories and have admitted to finding the post - laboratory questions employed particularly challenging.
Those laboratories which did show an increase in student engagement with chemical concepts, have displayed a large degree of linkage between the elements of the concept
questioned on both pre and post laboratory tasks.
This study has highlighted that regardless of the assessment method employed at either second or third level, the information that is provided by formative assessment can be appropriately utilised to ensure that students engage with chemical content. The most important conclusion which has been made in relation to all of the assessments analysed is the importance of appropriate question use. In order to assess student understanding of a chemical concept or completion of learning outcomes/objectives, educators must ensure that the questions employed are challenging but doable for all students, no matter what their chemical background and that the information provided by student attempts will help to identify problem areas for the entire cohort of students
The development, implementation and evaluation of alternative approaches to teaching and learning in the chemistry laboratory
Get PDFThe focus of the thesis is on the evaluation of the effect of the implementation of a three-hour per week problem-based learning (PBL) module for 1SI year undergraduate
students. The research questions are outlined below:
• What approaches to learning are undergraduate students adopting at the initial stage of tertiary education?
• Are student approaches to learning related to age/gender/ time in university/achievement in examinations?
• Can a PBL module in chemistry be developed that can provide an effective teaching and learning environment, which develops students’ understanding in chemistry and engages the students with the context and processes o f chemistry?
• Will the introduction of such a PBL module in chemistry have an effect on students’ approaches to learning?
The main evaluation tool for determining student approaches to learning was the
learning style inventory - Approaches and Study Skills Inventory for Students. Other evaluation tools employed were student surveys, interviews and assessment data.
Key findings were that students on entry to tertiary level report a preference for deep and strategic approaches to learning over a surface approach. However, with time in university, the profile shifts with students indicating increasing use o f a surface approach. Mature students tended to prefer a deep approach in comparison to their younger counterparts and female students were more strategic than males in their
approach.
An introductory year-long chemistry PBL laboratory module was developed, implemented and evaluated. Interestingly, students who took part in the PBL module showed a lower preference for a surface approach having successfully completed the PBL module compared to those who followed the traditional approach despite showing similar trends at the start of the study. The effect on a deep approach to learning, after taking the PBL module, one sixth of the 1st year course, was not evident however. Conversely, the PBL students did significantly better in a non-formal exam designed to assess students learning in the first year chemistry laboratory. The students also successfully engaged with the chemistry content, context and processes and reported the benefit of the pre-lab, group work and practical aspects of the PBL approach
Oxidation studies on supported metal catalysts
Get PDFThe aim of this work was to examine Pt/Al2 0 3 , Pt-Sn/Al2C>3 and Pt/Sn(>2 catalysts for the oxidation of l-butane. The main conclusion which can be drawn from this study is that, although less active initially compared with the Pt/SnC>2 and Pt/Al203 samples, the Pt-Sn/Al203 catalysts were more resistant to thermal aging, maintaining a higher catalytic activity than the former catalysts after aging at 1073K. For example for 5wt% Pt/Al2C>3, 5wt% Pt/Sn0 2 and 5wt% Pt, 3wt% S11/AI2O3 catalysts pnor to aging the light off temperatures (LOTs) were 43 3K, 428K and 468K respectively After aging the LOTs for the corresponding samples was 478K, 499K and 468K respectively. There was no correlation between Pt particle size and activity. For the majonty of catalysts examined there was an increase in catalytic activity at a distinct temperature compared with initial activity, which may have been due to a secondary reaction or to the presence of different catalytic sites on the surface of the catalysts.
The AI2O3 support material consisted mostly of rj-A^C^ and was stable up to 1070K, but at higher temperatures the surface area and pore volume decreased. Treatment of the AI2O3 with HNO3 or HC1 (to increase support acidity) led to an increase in surface area. High temperature exposure of acid treated samples caused a more rapid decrease in surface area initially and the formation of higher amounts of a- AI2O3 compared with the untreated AI2O3, possibly due to the formation of cation vacancies during acid pretreatment Addition of the cations La3"1", Si^+ and Ce^+ to the untreated AI2O3 had little effect on surface area loss at 1370K but prevented (X-AI2O3 formation. After 48h at 1370K the surface area of untreated AI2O3 and acid pre-treated AI2O3 was similar, and the major cause of surface area loss was not due to (X-AI2O3 formation, but possibly pore loss.
Preparation variables for Pt/Al2C>3 catalysts were examined Pre-treatment of the AI2O3 support with HNO3 led to an increase in Pt uptake, higher Pt dispersion and higher catalytic activity compared with untreated catalysts studied while pre-treatment with HC1 or H2O had the opposite effect. The method of impregnation also affected the catalysts, with spray impregnation being the most effective method Drying at 31 OK for 16h after impregnation led to a nonhomogeneous distribution of Pt. The HC1 and H2O pre-treated catalysts exhibited an increase in activity after reduction in H2, the opposite being the case for the other Pt/Al203 catalysts examined.
In Pt-Sn/Al203 catalysts Sn was present in the form of Sn(II) and/or Sn(IV) and also as a Sn-aluminate species From H2 chemisorption measurements, Sn loadings <lwt% led to higher uptakes of H2 compared to Pt/Al203 samples For Pt/Sn0 2 catalysts no detectable amounts of H2 chemisorption occurred and surface Pt was in the form of a substrate bonded species, Pt-O-Sn
Developing thinking with four and five year old pupils: the impact of a cognitive acceleration programme through early science skill development
Get PDFThis thesis examines the extent to which a specific learning intervention programme, based on specific early science skill development may increase development in thinking in a particular early childhood sample.
The background literature has focused on Piaget's and Vygotsky's theories of cognitive development as they relate to the intervention programme and the age group of the participants in this research study. The review discusses the need to teach thinking and the relevant literature on the intervention programme is critically reviewed.
This research study, undertaken in and adapted for an Irish primary school, involved a sample of forty four participants aged between four and six years old.
An intervention group of twenty pupils participated in the learning intervention Lets Think!-Early Years programme – based on the theory of cognitive acceleration. The learning intervention programme consisted of fifteen lessons based on the early science skills of classification, seriation and causality. The remainder of the group were the non-intervention group.
All participants underwent three pre and post intervention tests and completed a pupil questionnaire. Local teachers completed a teacher questionnaire on questions relating to the research question and this combined with the researcher's observations recorded in a reflective journal provided the data to be analysed. A comparative analysis of responses obtained from the above tests, questionnaires
and reflective journal, suggest that pupils from the intervention group displayed a greater improvement in their thinking ability in comparison to the nonintervention
group, with the factors of gender and age of the pupils having a significant effect.
This finding indicates that a cognitive intervention programme through science may have a significant immediate and positive effect on the rate of the early year's pupil's cognitive development
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