196 research outputs found
Synthesis and characterization of sulphated AIMCM-41 and its catalytic activity in dibenzoylation of biphenyl with benzoyl chloride
No full textBenzoylation of biphenyl with benzoyl chloride is an important acylation reaction, producing monosubstituted product, 4-phenyl benzophenone (4-PBP) and disubstituted product, 4, 4’- dibenzoylbiphenyl (4, 4’-DBBP). 4, 4’-DBBP is a monomer used as a component in emitting layer in polymer light emitting (PLED) devices. The objective of this study is to synthesize and characterize a highly active sulphated AlMCM-41 acid catalyst by enhancing its acidity through sulphation. Firstly, the AlMCM-41 with various SiO2/Al2O3 ratios was prepared by direct synthesis, followed by conversion to H-AlMCM-41 via ion exchange of NaAlMCM-41 with ammonium nitrate. Finally, sulphated AlMCM-41 was prepared by impregnation of sulphuric acid in toluene. The sulphated MCM-41 materials possess high surface area (>500 m2/g) and large quantities of Brönsted acid sites after characterizing with surface analyzer and pyridine infrared spectroscopy. 27Al MAS NMR indicates the presence of octahedrally coordinated extra-framework sulphated aluminiums (EFAL) and aluminium sulphate. The Hammett indicators show that the acid strength of the sulphated AlMCM-41 materials was stronger than sulphuric acid and H-AlMCM-41 because of sulphate groups attached to aluminium atom in sulphated AlMCM-41. The results of comparative study on the dibenzoylation of biphenyl reaction indicate that only sulphated AlMCM-41 gives both monosubstituted 4-PBP and disubstituted 4, 4’-DBBP with the highest activity compared to sulphuric acid, H-AlMCM-41 and sulphated amorphous silica
Exploratory study of heterocyclic nitrogen-based ionic liquids as supramolecular structure-directing agents in zeolite synthesis.
No full textThis project reported the synthesis of novel heterocyclic nitrogen-based ionic liquid molecules as novel structure-directing agents (SDAs) in the synthesis uf zeulite microporous materials. The first part of this project discussed about the synthesis of several types of
heterocyclic nitrogen-based SDAs. The prepared SDAs were then characterized using IR, IH NMR, TG/DTG and CHN analyses. The experiment was then followed by the formation study of iron-containing AIPO-5 crystals in the presence of phosphorous acid (H3P03) by using
imidazolium-based SDA ([bdmim ]el) under ionothermal condition. The formation process of FeAPO-5 during the ionothermal synthesis was monitored by microscopic and spectroscopic methods. The roles of Fe3+ and H3POJ in the formation of the FeAPO-5 framework were investigated. Possible mechanism for the growth of FeAPO-5 crystals was proposed based on the experimental results
Design and application of hyfrophilie nanoporous materials for selective capturing of water to increase lubricant lifetime
No full textL’eau sous forme dissoute, émulsifiée ou libre est l’une des contaminants les plus nocifs pour les huiles lubrifiantes. Sa concentration élevée dans les lubrifiants conduit à la dégradation et à la corrosion des ces derniers ainsi qu’à une usure excessive et un endommagement des surfaces métalliques lubrifiées. Vu les effets destructifs de la présence de l’eau dans les huiles lubrifiantes, le contrôle de leur teneur en eau semble indispensable afin de prolonger simultanément la durée de vie des lubrifiants et celle des machines. L’objectif de cette étude est de contrôler et réduire le contenu en eau des huiles lubrifiantes via des techniques d’adsorption ; techniques assez efficaces et écologiques pour remplacer la méthode traditionnelle de distillation. Afin de réaliser ce but, des matériaux microporeux et hydrophiles ont été choisis et préparés dans les buts de i) piéger l’eau au cours de la purification des huiles et ii) contrôler la quantité d’eau et le degré de dégradation durant le processus d’oxydation des huiles, ceci en utilisant les matériaux microporeux en tant qu’additifs. L’étude consiste premièrement en une sélection, une synthèse et une caractérisation des capacités de sorption d’eau de plusieurs matériaux microporeux, hydrophiles et de tailles nanométriques. D’abord, une synthèse écologique de tamis moléculaires de tailles nanométriques par chauffage aux micro-ondes a été développée. Cette méthode permet la réutilisation des réactifs non réagis réduisant ainsi, voire éliminant, les déchets résultant de la synthèse. Par conséquent, des rendements raisonnables de matériaux microporeux nanocristallins sont produits avec un coût et une toxicité remarquablement réduits. De plus, l’utilisation des irradiations micro-ondes permet la préparation de nanocristaux de matériaux microporeux en quelques minutes lorsque la synthèse par voie hydrothermale nécessite quelques jours. Ceci rend la synthèse fiable de point de vue économique et environnemental. Ensuite, une préparation de nanocristaux d’aluminophosphates en présence d’un liquide ionique a été reportée. Le liquide ionique joue un rôle double : en tant qu’agent permettant le remplissage des pores des matériaux synthétisés et en tant que solvant. Egalement, le liquide ionique n’ayant pas réagi est récupéré à la fin de la synthèse pour être réutilisé avec d’autres lots. Pour la vi préparation de cristaux nanométriques d’aluminosilicates, ayant une teneur importante en aluminium, des synthèses ont eu lieu à partir de systèmes ne contenant pas de structurants organiques, à basse températures (30-50 °C) et à faibles durées de synthèse (1-3 jours). La totalité des matériaux obtenus présentent de volumes poreux importants et une grande capacité d’eau répondant aux exigences de bons adsorbants hydrophiles. Dans le but d’augmenter la durée de vie des lubrifiants, un éco-recyclage de différentes huiles minérales et végétales a été mis en évidence par une adsorption sélective d’eau sur les nanocristaux de matériaux microporeux. [...]Water in solution, emulsion and separate form is one of the most harmful contaminants in lubricant oils. The high concentration of water in lubricants leads to oil degradation, corrosion, excessive wear and premature failure of lubricated metal surfaces. As water has such destructive effects on lubricants, a special attention to the control of the water level has to be paid in order to prolong the lifetime of both lubricants and machinery. The aim of this work is to control and reduce the water content in lubricant oils using adsorption technique as an effective and green alternative to replace the traditional distillation method. In order to achieve this goal, microporous materials with hydrophilic properties were selected and prepared to (i) capture the water during static oil purification and (ii) apply as additives to control the water level and degradation during the oxidation process of lubricating oils. The study starts with the selection, synthesis and characterization of water sorption behavior of several hydrophilic microporous materials with nanosized dimensions. Additionally, an environmentally benign synthesis of the nanosized molecular sieves by microwave heating involving an efficient re-utilization of nonreacted materials has been developed, resulting in decrease and almost no related wastes. Thus the quantity of expensive and toxic chemicals is reduced. This approach results in a reasonable crystalline yield of the nanomaterials, while the production cost is remarkably lowered. In addition, the use of microwave irradiation leads to a preparation of nanocrystalline material within several minutes instead of days compared to conventional heating, which makes the process economically viable and environmentally benign. Additionally, the preparation of discrete nanosized aluminophosphate crystals by an ionic liquid mediated approach is reported. The ionic liquid has a dual function, as pore filling agent and solvent. In addition, the non-reacted ionic liquid after the syntheses are recovered and reused for several batches. For the preparation of aluminosilicates, template-free syntheses of nanosized aluminosilicate crystals with high Al content have been carried out. They were synthesized at low temperature (30-50 °C) for short time (1- ix 3 days). All resulting materials have high pore volume and high water capacity, which meet the expected requirements for highly hydrophilic sorbents. Eco-recycling of mineral and vegetable oils for an increase of lubricant lifetime by selective adsorption of water using the microporous nanocrystals was carried out. The oils were oxidized and purified with the molecular sieves. The processes of oxidation and purification of the two types of oil is followed by Fourier transform infrared spectroscopy (FT-IR), atomic absorption spectroscopy (AAS), Karl Fischer (KF) titration, thermogravimetry analysis (TGA) and gas chromatography-mass spectrometry (GC-MS). In addition, FT-IR combined with a solvent (dimethyl sulfoxide, DMSO) extraction method is used to quantify the water content in lubricant oils, which rivals the accuracy of the classical KF titration; it is deemed to be an alternative analytical method for water content determination. The influence of treatment parameters including zeolite type, crystal size, temperature, sorbent loading and treatment time on the purification process of oxidized oil was studied. In addition, the hydrophilic microporous materials were applied as additives for controlling the water content and inhibiting the oxidation of oil. It is found that aluminosilicates control the water content and inhibit the oil degradation better at elevated temperatures, while aluminophosphates have an improved performance at mild conditions (< 90?C). Moreover, the oxidative stabilities of vegetable oils in the presence of the microporous additives are related to their poly-unsaturation contents. [...
Effectiveness of resiliency training and its impact on life quality and academic performance
No full textVarious studies have found resilient individuals to be people with optimistic, zestful, and energetic approaches to life. These individuals have the capability to recover from adversities, and adapt well to changing demands of stressful experiences. As the interest to improve resilience grows, training programmes that endeavour to enhance participants’ resiliency levels are starting to gain popularity. One such programme is the Adaptiv Resiliency Training (ART) programme delivered in Singapore by the Centre for Cognitive Technologies Pte Ltd. The purposes of the current study are to address the concern about effectiveness of the ART programme in the Singapore context, and how useful this programme is at enhancing students’ life quality and academic performance.There are four aims to the current study. The first aim is to assess whether a student who is not performing well academically could still be a happy and resilient student, while the second aim is to evaluate whether there is a correlation between locus of control and resilience level. The third aim is to evaluate whether the ART programme delivered in Singapore is effective in enhancing participants’ resiliency levels, and the fourth aim is to assess whether the US-based norms established for instruments used in the current study are applicable to the Singapore context.Participants in the current study comprised of 139 Diploma in Accountancy students from a local Singaporean polytechnic, and 59 teachers from a local secondary school. Through self-report questionnaires, resilience levels of the students were correlated with their academic results and life quality indices, and changes in resiliency and life quality indices of the teachers were tracked as they went through the ART programme. As such, a mixed design is used for this study, with a between-subject design adopted for the students group, and a within-subject repeated-measure design adopted for the teachers group. Based on responses from the students group, a factor analysis was performed and a revised resiliency measuring scale was proposed.Findings from the current study showed that although resiliency may not be a good gauge for academic performance, and that academically stronger students may not be more satisfied with life than academically weaker students, high-resilient students were found to be more satisfied and hopeful about life. Assessment of the locus of control showed that although Asians are high in internal locus of control, an indication of low-ego protection and a “vulnerable factor” for the development of depression, they are not plagued with depression but are, on the contrary, able to be resilient when faced with adversities. Subject to the limiting factors identified, results from evaluating the ART programme revealed increases in hopefulness and life satisfaction indices, reductions in burnout level, and enhancement in resiliency level of participants after attending the training session. Finally, analysis of the norms of instruments used in the current study showed that the US-based norms are not culturally biased, and could be adopted for local usage.In conclusion, based on findings from the current study after due consideration of the limitations identified, it was suggested that schools keen on enhancing life quality of students could consider adopting a formal resiliency training programme
Catalytic esterification of pyruvic acid with ethanol via amphiphile-templated SAPO-5 hierarchical molecular sieves
No full textSoft-templating synthesis of hierarchical SAPO-5 zeolites using dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TP), cetyltrimethylammonium bromide (CTA) and cetylpyridinium chloride (CP) is reported where the effects of these amphiphilic molecules on crystallization, morphological and structural characteristics of SAPO-5 are investigated. The results reveal that these compounds have shown their exceptional ability in molecular confinement and packing during the crystallization process which alter the morphological (crystal size and shape) and structural (porosity and acidity) properties of SAPO-5. The resulting SAPO-5 solids exhibit distinct morphologies having hierarchical porosity, and they enhance the catalytic esterification of pyruvic acid to produce ethyl pyruvate. TP-SAPO-5 with the highest hierarchical factor (HF = 0.065) and second highest in acidity (0.73 mmol/g) is the best catalyst (in terms of conversion and selectivity) compared to its hierarchical counterparts. Its performance (92.0 ± 1.2 % conversion, 85.9 ± 0.3 % selectivity) after parametric optimization is comparable as homogenous HCl and H2SO4 catalysts (88−92 % conversion, 84−92 % selectivity), and is much superior than H-Y, H-MOR, SAPO-34 zeolites (56−100 % conversion, 67−76 % selectivity). The hierarchical TP-SAPO-5 is also reusable up to five reaction cycles which offer it as an ideal green and selective acid catalyst for upgrading of biomass products.The authors would like to thank Ministry of Higher Education Malaysia (FRGS/1/2022/STG05/USM/02/12) for financially supporting this project.Peer reviewe
Goodwill - to be or not to be
No full textAccounting treatments for goodwill have always been shrouded in controversy. Diversity
in standards and practices among countries in this area has further complicated the
goodwill issue: Hence, the purpose of this report is to critically analyse the differing views
offered by the various accounting bodies on goodwill accounting.
Besides the evaluation of established literature to compare the vanous accounting
standards established by the different accounting bodies and to analyse the various
accounting treatments allowed by these standards, an empirical study was also carried out
on the companies listed in the Stock Exchange of Singapore (SES) to identify the current
accounting treatments for goodwill in Singapore.ACCOUNTANC
Quantitative moisture measurements in lubricating oils by FTIR spectroscopy combined with solvent extraction approach
No full textNanoporous materials as high selective water sorbents in lubricants
No full textCongrès du 06 au 09 septembre 2007International audienc
Quantitative moisture measurements in lubricating oils by FTIR spectroscopy combined with solvent extraction approach
No full textInternational audienceQuantitative measurements of moisture in mineral and synthetic polyol ester based lubricating oils using FTIR spectroscopy combined with solvent extraction approach are described. The samples are prepared by mixing dry dimethyl sulfoxide (DMSO) and lubricating oils, and after phase separation, the extracted bottom DMSO layers are analyzed with FTIR. The results from the solvent extraction show that the DMSO is an excellent aprotic solvent for water removal from lubricating oils. The spectroscopic data reveal that near IR region (5400-4800 cm(-1), molecular water) gives the best results for water determination in both mineral and synthetic lubricants, followed by mid-IR region (3800-3200 cm(-1), O-H stretching). However, the water content estimated from the IR region (1800-1550 cm(-1), O-H bending) has the lowest accuracy due to the interference from aminic, phenolic additives and other oxidation products present in the lubricants. The accuracy of the FIR spectroscopy combined with solvent extraction approach is exemplified by monitoring the water content in mineral oil during oxidation process at 150 degrees C for 30 days. The quantitative determination of the moisture in the fresh and oxidized oils by the developed approach is shown to be an alternative technique to Karl Fischer titration. (C) 2011 Elsevier B.V. All rights reserved
Nanoporous materials with enhanced hydrophilicity and high water sorption capacity
No full textInternational audienc
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