Design of novel well-defined organorhenium heterogeneous catalyst for unsaturated fatty acid derivatives self-metathesis

La formation des liaisons C-C est parmi les cibles les plus élevés de la science et de la technologie de la catalyse. Dans ce cadre, la réaction de métathèse catalytique a gagné une importance considérable en raison de l'efficacité du processus de transformation. Par conséquent, un grand progrès a été réalisé dans ce domaine avec le développement de plusieurs catalyseurs homogènes et hétérogènes, ainsi que les différentes approches de métathèse. Cette formule a permis une conception plus facile et plus durable de diverses stratégies de synthèse dans différents domaines, y compris la synthèse organique, la science des polymères, etc. Cependant, le développement des catalyseurs de métathèse robustes pour les applications à grande échelle est encore une tâche difficile. Tenant compte de cela, les résultats de recherche présentés dans cette thèse de doctorat se concentrent sur la synthèse d'un nouveau catalyseur hétérogène de métathèse. Par conséquent, le méthyltrioxorhénium (MTO) a été supporté sur différents matériaux à base d'alumine. La performance des catalyseurs synthétisés a été étudié par l'auto-métathèse de l'oléate de méthyle, choisi comme substrat modèle; volumineux et fonctionnalisé, afin d'évaluer la tolérance des espèces actives aux groupements fonctionnels, ainsi que d'évaluer sa diffusion à l'intérieur des canaux mésoporeux. Tout d'abord, des supports très organisés à base alumine mésoporeux organisée modifiée avec le chlorure de zinc (ZnCl2-AMO) ont été préparés avec succès grâce à un procédé sol-gel puis une imprégnation post-synthèse. Le MTO supporté sur ces supports catalytiques est très actif pour l'auto-métathèse de l'oléate de méthyle, avec des vitesses de réaction plus élevées et une meilleure sélectivité par rapport aux catalyseurs à base d'alumine classiques. Cette amélioration est attribuée à des meilleurs phénomènes de transfert de masse à l'intérieur du réseau mésoporeux organisé. Ensuite, nous avons développé une voie de synthèse efficace en une seule étape pour la préparation des matériaux ZnCl2-AMO. Cette approche a permis l'accès à des supports ZnCl2-AMO très ordonnés avec de meilleurs rendements de synthèse ainsi que de meilleures propriétés physiques et de surface. En outre, ces fonctionnalités améliorées ont permis aux catalyseurs à base de MTO supportés sur ces matériaux préparés en une seule étape de manifester une meilleure performance catalytique par rapport à celle de ZnCl2-AMO préparé par le processus en plusieurs étapes. Toutefois, des études spectroscopiques ont révélé la formation d'espèces actives semblables sur la surface pour tous les supports catalytiques préparées. Ces caractérisations nous ont guidés pour étudier et proposer un mécanisme complet pour les voies de formation des produits de métathèse, ainsi que le cycle catalytique de métathèse, démontrant l'effet d'encombrement stérique sur l'interface de catalyseurs qui contrôle la sélectivité de la réaction. La synthèse des catalyseurs de métathèse MTO/ZnCl2-AMO nous a permis d'effectuer efficacement les transformations de métathèse utilisant des matières premières renouvelables (par exemple des acides gras estérifiés provenant des huiles végétales), offrant un accès à une variété de monomères fonctionnalisés, qui pourraient éventuellement être utilisés pour d'autres transformations telles que la synthèse des bio-polymères à valeur ajoutée à base (par exemple, les bioplastiques, biosurfactants).Sustainable C-C bond forming reactions have been among the highest target of catalysis science and technology. In this scope, metathesis reaction has been gaining enormous attention due to the efficiency of the transformation process. Therefore, a great progress has been made in this area by developing several homogeneous and heterogeneous catalysts as well as distinct metathesis reaction approaches. This allows an easier and more sustainable design for various synthesis strategies in different fields including organic synthesis, polymer science, etc. However, the development of robust metathesis catalysts for large scale applications is still a challenging task. Taking this into account, this research presented in this doctoral dissertation is focusing on the synthesis of new heterogeneous metathesis catalysts. Therefore, methyltrioxorhenium (MTO) was supported on various alumina-based materials. The synthesized catalysts' performance was studied though methyl oleate self-metathesis, chosen as a model bulky functionalized substrate, in order to evaluate the active species tolerance to functional groups as well as to evaluate its diffusion inside the mesoporous channels. First, highly organized ZnCl2-modified OMA supports were successfully prepared through a sol-gel method followed by a post-synthesis modification via wet-impregnation process. MTO supported on these catalytic supports were found o be highly active for methyl oleate self-metathesis, displaying higher reaction rate and products selectivity compared to the conventional wormhole-like alumina-based catalysts. This improvement is ascribed to enhanced mass transfer phenomena inside the organized mesoporous network. Afterwards, we have developed efficient one-pot synthesis route ZnCl2-modified OMA supports. Interestingly, this approaches allowed access to numerous highly ordered ZnCl2-modified OMA supports with better synthesis yields and improved textural and surface properties. Moreover, these enhanced features allowed the MTO-based catalyst supported on these one-step prepared materials to exhibit higher metathesis reaction performance compared to ZnCl2-modified OMA supports prepared via the two-steps processes. However, spectroscopic investigations revealed the formation of similar surface active species for all the prepared catalytic supports. These characterizations guided us to study and propose a comprehensive mechanism of metathesis products formation pathways as well as the metathesis catalytic cycle, demonstrating the steric hindrance effect on the catalysts interface that governed the reaction selectivity. The synthesis of the 3 wt.% MTO/ZnCl2-OMA catalysts allowed us to efficiently perform metathesis reaction using renewable feedstock (e.g. fatty acid esters derived from vegetable oils), offering access to a variety of functionalized monomers which could be used for further transformations such as the synthesis of value-added bio-based polymers (e.g. bioplastics, biosurfactants)

Synthesis and evaluation of novel porous materials for environmental remediation

Porous materials have been widely used as adsorbents for water treatment due to their unique properties such as high surface area, excellent mechanical properties and good chemical stability. The work in this thesis aimed to develop novel porous materials for pollution remediation, with the focus being on materials that can be produced economically and environmentally friendly. The first part of this thesis covers two types of mesoporous carbon materials including mesoporous and magnetic mesoporous carbon materials which were fabricated through a soft templating method (Chapter 3). It has been shown that these porous carbon materials with monolithic form have high surface area, which is envisaged excellent adsorbent capacity. But there are some drawback which limit their use for water treatment as the preparation of these materials is time consuming, there are high operation cost and difficulties in regeneration and operation. Cellulose was considered as an attractive alternative material for preparation of porous materials for pollution remediation because it is naturally abundant, renewable, non-toxic and a lowcost biopolymer.In the second part of this work a cellulose-based hydrogel was successfully synthesized using hydroxypropyl cellulose (HPC) with divinyl sulfone (DVS) as a chemical crosslinker via a modified temperature induced phase separation (TIPS) method (Chapter 4). The HPC hydrogel obtained was characterised and the results showed that the properties of this hydrogel depended on the gelation temperature. The FTIR results confirmed the chemical cross-linking between HPC and DVS. HPC hydrogel demonstrated a flexible behaviour without breakage under compression tests. In addition, there were good shape recovery properties upon adsorption of water. The morphology of the cross-linked HPC hydrogel showed an interconnected macroporous network structure, which allowed application for water purification.Further work was then carried to develop a new and simple method to prepare a novel thermoresponsive HPC hydrogel with a graded pore size (Chapter 5). This method combined two approaches, varying the temperature between the upper and lower part of the hydrogel utilising the lower critical solution temperature (LCST) via the temperature induced phase separation (TIPS) method, which achieved a gradual change in pore geometry and pore size. The added inclusion of cryogenic treatment of the sample ensured a gradient porous HPC hydrogel was obtained with high permeability. Double network (DN) hydrogels have a structure that can effectively improve the adsorption capacity as the second network can introduce more functional groups into hydrogel structures, which is of great importance in the adsorption process due to improve the adsorption capacities. The DN hydrogels can also improve the mechanical strength of hydrogel materials, which makes it easier to regenerate. To this purpose, novel hybriddouble networks hydrogel was prepared in this work via mixing two types of crosslinked polymers, these were covalently crosslinked HPC with DVS and ionically crosslinked alginate with calcium ions (Chapter 6). Alginate was selected to be the second network polymer as alginate has carboxylate functional groups that can be used to remove cationic pollutant by electrostatic interactions, thus improving the adsorption capacity of the HPC single network (HPC SN) hydrogel. SEM images of the double network produced s confirmed that the hydrogel was composed of two independently cross-linked networks with a homogeneous interconnecting porous structure. The mechanical tests on the DN hydrogel showed that it was much stronger compared with HPC SN hydrogel. The adsorption and filtration of organic pollutants by HPC hydrogel were investigated through dye adsorption experiments (Chapter 7). The results were showed a great ability of HPC hydrogel for selective adsorption towards MB dye. In order to evaluate the possibility of reuse of HPC hydrogel, the recyclability of these materials was examined. The obtained results indicated that the reusability of the HPC hydrogel was at some cycles without any loss in its sorption behaviour. Therefore, the HPC hydrogel can be a good reusable and economical adsorbent to remove the cationic species. It is important to note that HPC hydrogel column was further used for the first time for selective separation of dye mixtures by simple gravity filtration and the hydrogel can be re-used multiple times. Despite being one of the most promising types of porous materials for environmental applications, their low adsorption capacity is a significant disadvantage for their use inthese applications. Adsorption of methylene blue dye (MB) on HPC/CA DN hydrogel was investigated through batch and column adsorption experiments and compared with HPC SN hydrogel (Chapter 7). The adsorption isotherms for both HPC SN and HPC/CA DN hydrogels fitted well with the Langmuir adsorption model and the maximum adsorption capacity of HPC/CA DN hydrogel was found to be 169.49 mg g-1, which is larger than for the HPC SN hydrogel (112.35 mg g-1). The results showed a significant pH-dependent equilibrium for the adsorption capacity of MB dye for both hydrogels in this study, which decreased dramatically with decreasing the pH of the MB dye solution. This meant that the MB-loaded HPC hydrogel could be easily regenerated under acidic conditions. The thermodynamic analysis of MB dye adsorption onto both HPC SN andHPC/CA DN hydrogels were also studied and the process was shown to be an exothermic and spontaneous process. An adsorption kinetic study was also carried out and the results obtained showed that the adsorption of MB dye adsorption on both hydrogels was well described by the pseudo-second-order kinetic model. In the column study, the adsorbent reuse was investigated and the selective separation of a dye mixture was also studied through ten cycles. Both hydrogels columns showed efficient selective adsorbent for cationic dyes, with the removal of MB dye being very efficient, whilst extremely low removal of FL dye. However, the HPC/CA DN hydrogels column exhibited a higher adsorption capacity than HPC SN hydrogel due to the dual functional groups (hydroxyl and carboxyl groups) in HPC/CA DN hydrogel. Based on the selective adsorptiontowards cationic methylene blue over anionic sodium fluorescein dye, HPC SN and HPC/CA DN hydrogels columns could easily separate two dyes from aqueous solutions of dye mixtures by simple gravity filtration. Both HPC SN and HPC/CA DN hydrogel column showed high separation efficiency of more than 99%. It was also found that separation efficiency of the HPC SN decreased to 86% by the 10th cycle for this column, while no significant losses in the separation efficiency were detected even after ten cycles for the HPC/CA DN hydrogel column. These results show that the HPC/CA double network polymer hydrogels have great potential for improving the adsorption capacity with good reusability and would be a promising eco-friendly adsorbent for the treatment of dye wastewaters

APPLICATIONS OF INNOVATIVE BUILDING MATERIAL AND COMPUTER VISION METHODS IN GEOTECHNICAL ENGINEERING

Ph.D

7th International Conference for Young Chemists (ICYC 2019)

Along with the celebration of USM Golden Jubilee in 2019, we bring you the most anticipated event in commemorating the 50 years of USM excellence in higher education. The International Conference for Young Chemists (ICYC) is a biennial conference organised by the postgraduate students of the School of Chemical Sciences, Universiti Sains Malaysia with the aim to gather local and international postgraduate researchers to create interaction and networking in the field of Chemistry. The idea of this conference started back in the year 2001 where it was known as the Regional Conference for Young Chemists (RCYC) targeting postgraduate researchers from the Asia Pacific Region (Malaysia, Singapore, Indonesia, the Philippines, India and Japan). What used to be the Regional Conference for Young Chemists (RCYC), has been rebranded into the International Conference for Young Chemists as we know it today. We are targeting postgraduate researchers from all around the world rather than just in this region. In fact, in August 2019, it is going to be the seventh time this international conference is going to be hel

Bifunctional supported catalysts for fine chemical synthesis

The objective was to prepare and optimise solid acid and solid base catalysts for liquid phase reactions. The approach has been to functionalize porous silica support materials with acid and base catalytic groups. Solid acid, solid base and bifunctional solid acid/base catalysts were studied. Evidence for acid-base cooperative catalytic mechanisms was found, suggesting that these bifunctional catalysts could show significant advantages over singly functionalized materials of mixtures thereof. Silicas functionalized with tethered aminopropyl groups were prepared by both a grafting method and a sol–gel method. The solids were fully characterized and were tested in the nitroaldol condensation between nitromethane and benzaldehyde to afford nitrostyrene and the aldol reaction between 4-nitrobenzaldehyde and acetone to afford 4-(4-nitrophenyl)-4-hydroxy-2-butanone. The catalytic activities of these materials were found to be dependent on the dispersion and accessibilities of the active sites which, in turn, depend on the methods utilized for the catalyst preparation. Solid acid catalysts were prepared by grafting silica with mercaptopropyl-trimethoxysilane (MPTS) followed by oxidation. The influence of the oxidation procedure on the acidity of the catalyst is described. The use of concentrated HNO3 optimizes the oxidation process and increases the concentration of active sites in comparison to H2O2. The activities of these catalysts were tested in the deacetalization of benzaldehyde dimethyl acetal to benzaldehyde. The use of solid acid and solid base catalysts in the same system was examined, in a two-stage acid-catalyzed deacetalization and base-catalyzed Henry reaction. Solid bifunctional acid-base catalysts were prepared by grafting on amorphous silica in two ways: 1) by grafting propylsulfonic acid and aminopropyl groups to the silica surface (NH2-SiO2-SO3H) and 2) by grafting aminopropyl groups and then partially neutralizing with phosphotungstic acid, relying on the H2PW12O40- ion for surface acidity (NH2-SiO2-NH3+[H2PW12O40-]. These two bifunctional catalysts were compared with each other and with the singly functionalised catalysts described above. Surface acidities and basicities were characterized by adsorption calorimetry, using SO2 as a probe for surface basicity and NH3 for surface acidity. Catalytic activities were measured in the tandem deacetalization/Henry reaction described above, and in an aldol reaction in which a cooperative acid-base catalytic mechanism is thought to be effective. Overall NH2-SiO2-SO3H catalysts showed higher concentrations and strengths of both acid and base sites, and higher activities. Both catalysts showed evidence of cooperative acid-base catalytic sites. Even in the deacetalization/Henry reaction, the bifunctional catalysts exhibited a catalytic advantage over physical mixtures of singly functionalized catalysts. A further bifunctional acid-base catalyst was prepared and studied by tethering proline to silica. In this case, the catalyst was chiral and was tested in the asymmetric aldol reaction between acetone and 4-nitrobenzaldehyde. Grafting methods with and without protecting groups for the active sites on proline were investigated. Remarkably the optimised supported proline catalysts showed higher activities and higher enantioselectivities than proline in homogeneous solution, and showed minimal loss in activity with time. Both activity and enantioselectivity depended strongly on the nature of the reaction solvent