Polymer microspheres: synthesis, characterisation and post-functionalisation by olefin metathesis

Porous polymer particles are used in an extraordinarily wide range of advanced and everyday applications, from combinatorial chemistry, solid-phase organic synthesis and polymer-supported reagents, to environmental analyses and the purification of drinking water. The installation and exploitation of functional chemical handles on the particles is often a prerequisite for their successful exploitation, irrespective of the application and the porous nature of the particles. New methodology for the chemical modification of macroreticular polymers is the primary focus of the work presented in this thesis. Porous polymer microspheres decorated with a diverse range of functional groups were synthesised by the post-polymerisation chemical modification of beaded polymers via olefin cross metathesis. The polymer microspheres were prepared by the precipitation polymerisation of divinylbenzene in porogenic (pore-forming) solvents; the olefin cross-metathesis (CM) functionalisation reactions exploited the pendent (polymer-bound) vinyl groups that were not consumed by polymerisation. Olefin CM reactions involving the pendent vinyl groups were performed in dichloromethane using second-generation Grubbs catalyst (Grubbs II), and a wide range of coupling partners used. The results obtained indicate that high quality, porous polymer microspheres synthesised by precipitation polymerisation in near-θ solvents can be functionalised by olefin CM under very mild conditions to install a diverse range of chemical functionalities into a common polydivinylbenzene precursor. Gel-type polymer microspheres were prepared by the precipitation copolymerisation reaction of divinylbenzene and allyl methacrylate in neat acetonitrile. The unreacted pendent vinyl groups that were not consumed by polymerisation were subjected to internal and external olefin metathesis-based hypercrosslinking reactions. Internal hypercrosslinking was carried out by using ring-closing metathesis (RCM) reactions in toluene using Grubbs II catalyst. Under these conditions, hypercrosslinked (HXL) polymers with specific surface areas around 500 m2g-1 were synthesised. External hypercrosslinking was attempted by using CM/RCM in the presence of a multivinyl coupling partner in toluene using second-generation Hoveyda-Grubbs catalyst. The results obtained indicate that no HXL polymers were obtained. However, during the development of this methodology, a new type of polymerisation was discovered with tetraallylorthosilicate as monomer.

Niobium-based heterogeneous catalysts synthesised in supercritical carbon dioxide for selective olefin epoxidation

In this work, two different protocols for the synthesis of Nb2O5-SiO2 with a sol-gel route in which supercritical carbon dioxide was used as solvent have been developed. The tailored design of the reactor allowed the reactants to come into contact only when supercritical CO2 is present, and the high-throughput experimentation scCO2 unit allowed the screening of synthetic parameters, that led to a Nb2O5 incorporation into the silica matrix of 2.5 wt%. N2-physisorption revealed high surface areas and the presence of meso- and micropores. XRD allowed to demonstrate the amorphous character of these materials. SEM-EDX proved the excellent dispersion of Nb2O5 into the silica matrix. These materials were tested in the epoxidation of cyclooctene with hydrogen peroxide, which is considered an environmentally friendly oxidant. The catalysts were virtually inactive in an organic, polar, aprotic solvent (1,4-dioxane). However, the most active scCO2 Nb2O5-SiO2 catalyst achieved a cyclooctene conversion of 44% with a selectivity of 88% towards the epoxide when tested in ethanol. Catalytic tests on cyclohexene revealed the presence of the epoxide, which is remarkable, considering that this substrate is easily oxidised to the diol. The behaviour in protic and aprotic solvents is compared to that of TS-1.

Oxidizing species in the mechanism of cytochrome P450

This review discusses the mechanisms of oxygen activation by cytochrome P450 enzymes, the possible catalytic roles of the various iron-oxygen species formed in the catalytic cycle, and progress in understanding the mechanisms of hydrocarbon hydroxylation, heteroatom oxidation, and olefin epoxidation. The focus of the review is on recent results, but earlier work is discussed as appropriate. The literature through to February 2002 is surveyed, and 175 referenced are cited.

A strategy to extend reactive distillation column performance under catalyst deactivation

This work addresses the effects of catalyst deactivation and investigates methods to reduce their impact on the reactive distillation columns performance. The use of variable feed quality and reboil ratio are investigated using a rigorous dynamic model developed in gPROMS and applied to an illustrative example, i.e., the olefin metathesis system, wherein 2-pentene reacts to form 2-butene and 3-hexene. Three designs and different strategies on column energy supply to tackle catalyst deactivation are investigated and the results compared.

Synthesis, characterization and reactivity of new cobalt, palladium and nickel complexes bearing α-diimines and P, O ligands

This work describes the synthesis and characterization of a series of new α-diimine and P,O, β-keto and acetamide phosphines ligands, and their complexation to Ni(II), Co(II),Co(III) and Pd(II) to obtain a series of new compounds aiming to study their structural characteristics and to test their catalytic activity. All the compounds synthesized were characterized by the usual spectroscopic and spectrometric techniques: Elemental Analysis, MALDI-TOF-MS spectrometry, IR, UV-vis, 1H, 13C and 31P NMR spectroscopies. Some of the paramagnetic compounds were also characterized by EPR. For the majority of the compounds it was possible to solve their solid state structure by single crystal X-ray diffraction. Tests for olefin polymerization were performed in order to determine the catalytic activity of the Co(II) complexes. Chapter I presents a brief introduction to homogenous catalysis, highlighting the reactions catalyzed by the type of compounds described in this thesis, namely olefin polymerization and oligomerization and reactions catalyzed by the complexes bearing α-diimines and P,O type ligands. Chapter II is dedicated to the description of the synthesis of new α-diimines cobalt (II) complexes, of general formula [CoX2(α-diimine)], where X = Cl or I and the α-diimines are bis(aryl)acenaphthenequinonediimine) (Ar-BIAN) and 1,4-diaryl-2,3-dimethyl-1,4-diaza-1,3-butadiene (Ar-DAB). Structures solved by single crystal X-ray diffraction were obtained for all the described complexes. For some of the compounds, X-band EPR measurements were performed on polycrystalline samples, showing a high-spin Co(II) (S = 3/2) ion, in a distorted axial environment. EPR single crystal experiments on two of the compounds allowed us to determine the g tensor orientation in the molecular structure. In Chapter III we continue with the synthesis and characterization of more cobalt (II)complexes bearing α-diimines of general formula [CoX2(α-diimine)], with X = Cl or I and α-diimines are bis(aryl)acenaphthenequinonediimine) (Ar-BIAN) and 1,4-diaryl-2,3-dimethyl- 1,4-diaza-1,3-butadiene (Ar-DAB). The structures of three of the new compounds synthesized were determined by single crystal X-ray diffraction. A NMR paramagnetic characterization of all the compounds described is presented. Ethylene polymerization tests were done to determine the catalytic activity of several of the Co(II) complexes described in Chapter II and III and their results are shown. In Chapter IV a new rigid bidentate ligand, bis(1-naphthylimino)acenaphthene, and its complexes with Zn(II) and Pd(II), were synthesized. Both the ligand and its complexes show syn and anti isomers. Structures of the ligand and the anti isomer of the Pd(II) complex were solved by single crystal X-ray diffraction. All the compounds were characterized by elemental analysis, MALDI-TOF-MS spectrometry, and by IR, UV-vis, 1H, 13C, 1H-1H COSY, 1H-13C HSQC, 1H-13C HSQC-TOCSY and 1H-1H NOESY NMR when necessary. DFT studies showed that both conformers of [PdCl2(BIAN)] are isoenergetics and can be obtain experimentally. However, we can predict that the isomerization process is not available in square-planar complex, but is possible for the free ligand. The molecular geometry is very similar in both isomers, and only different orientations for naphthyl groups can be expected. Chapter V describes the synthesis of new P, O type ligands, β-keto phosphine, R2PCH2C(O)Ph, and acetamide phosphine R2PNHC(O)Me, as well as a series of new cobalt(III) complexes namely [(η5-C5H5)CoI2{Ph2PCH2C(O)Ph}], and [(η5- C5H5)CoI2{Ph2PNHC(O)Me}]. Treating these Co(III) compounds with an excess of Et3N, resulted in complexes η2-phosphinoenolate [(η5-C5H5)CoI{Ph2PCH…C(…O)Ph}] and η2- acetamide phosphine [(η5-C5H5)CoI{Ph2PN…C(…O)Me}]. Nickel (II) complexes were also obtained: cis-[Ni(Ph2PN…C(…O)Me)2] and cis-[Ni((i-Pr)2PN…C(…O)Me)2]. Their geometry and isomerism were discussed. Seven structures of the compounds described in this chapter were determined by single crystal X-ray diffraction. The general conclusions of this work can be found in Chapter VI.

Alternativas Processuais e Valorização de Correntes da Refinaria de Matosinhos.

Evolução, ato ou efeito de evoluir, sequência de transformações, desenvolvimento progressivo. Se tudo à nossa volta se transforma, a indústria tem de acompanhar esse sistema evolutivo, tornando assim imprescindível alterar ou melhorar processos de produção quando estes não se enquadram com a realidade, ou porque o mercado se altera, ou porque as necessidades mudam, ou por simplesmente ser mais rentável. Sendo a Galp Energia uma empresa que se encontra sempre na vanguarda da evolução tecnológica, encontra no Departamento de Engenharia Química do Instituto Superior de Engenharia do Porto um aliado na procura do melhor modo de valorizar os seus produtos. A Refinaria de Matosinhos tem atualmente duas correntes de gasolina leve e uma de refinado que apresentam grande potencialidade de valorização. Parte destas correntes incorporam atualmente a pool de nafta química da refinaria que é vendida à Repsol Polímeros. O desafio que é proposto baseia-se em valorizar essas correntes através da sua isomerização aumentando o seu RON podendo então ter como fim a pool de gasolinas. Tirando partido da tecnologia disponível para este efeito são apresentados quatro cenários de possíveis soluções. Sendo os dois primeiros excluídos por violarem restrições impostas, o terceiro e quarto cenários foram analisados de um ponto de vista económico. O terceiro cenário conduz a gasolina leve da Fábrica de Aromáticos para a pool de gasolinas sem qualquer tratamento e a gasolina leve da Fábrica de Combustíveis continua a integrar a pool de nafta química. O refinado da Fábrica de Aromáticos será enviado para um splitter, sendo a corrente de topo destinada à pool de nafta química e a corrente de fundo enviada a um reator de isomerização, Isomalk-4SM, passando previamente por uma torre de argila de forma a assegurar que a restrição em teor de olefinas no reator não é violada. O efluente, com RON maior, integrará igualmente a pool de gasolinas. No quarto cenário a corrente de refinado da Fábrica de Aromáticos não sofre qualquer tratamento, continuando a alimentar a unidade de solventes, a gasolina leve da Fábrica de Aromáticos irá diretamente para a pool de gasolinas e a gasolina leve da Fábrica de Combustíveis passará pelo Isomalk-2SM para aumentar o índice de octanos garantido assim ter condições de integrar a pool de gasolinas. Dissertação de Mestrado em Engenharia Química Isomerização de Gasolina Leve O terceiro cenário apresenta um aumento de 4 576 773 € anuais nas receitas e o quarto alcança 11 333 982 € anuais. O investimento inicial total do terceiro cenário é de 28 821 608 € quando o quarto cenário carece de um investimento inicial de apenas 18 028 349 €. Quanto aos custos associados à implementação da unidade estes demonstram-se elevados, o terceiro cenário apresenta um custo de 23 133 429 € enquanto o do quarto cenário é de 13 998 797 €. O quarto cenário apresenta-se assim como a solução mais rentável para o objetivo desta dissertação.

Cyclopentadienyl-functionalised N-heterocyclic carbenes: synthesis, coordination to Mo, Ru, Rh

Dissertation presented to obtain the Ph.D degree in Chemistry

Experimental Gravimetric Adsorption Equilibrium of n-Alkanes and Alkenes, Carbon Dioxide and Nitrogen in MIL-53(Al) and Zeolite 5A

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

Molecular simulation of gas adsorption equilibria in nanoporous materials

This work is divided into two distinct parts. The first part consists of the study of the metal organic framework UiO-66Zr, where the aim was to determine the force field that best describes the adsorption equilibrium properties of two different gases, methane and carbon dioxide. The other part of the work focuses on the study of the single wall carbon nanotube topology for ethane adsorption; the aim was to simplify as much as possible the solid-fluid force field model to increase the computational efficiency of the Monte Carlo simulations. The choice of both adsorbents relies on their potential use in adsorption processes, such as the capture and storage of carbon dioxide, natural gas storage, separation of components of biogas, and olefin/paraffin separations. The adsorption studies on the two porous materials were performed by molecular simulation using the grand canonical Monte Carlo (μ,V,T) method, over the temperature range of 298-343 K and pressure range 0.06-70 bar. The calibration curves of pressure and density as a function of chemical potential and temperature for the three adsorbates under study, were obtained Monte Carlo simulation in the canonical ensemble (N,V,T); polynomial fit and interpolation of the obtained data allowed to determine the pressure and gas density at any chemical potential. The adsorption equilibria of methane and carbon dioxide in UiO-66Zr were simulated and compared with the experimental data obtained by Jasmina H. Cavka et al. The results show that the best force field for both gases is a chargeless united-atom force field based on the TraPPE model. Using this validated force field it was possible to estimate the isosteric heats of adsorption and the Henry constants. In the Grand-Canonical Monte Carlo simulations of carbon nanotubes, we conclude that the fastest type of run is obtained with a force field that approximates the nanotube as a smooth cylinder; this approximation gives execution times that are 1.6 times faster than the typical atomistic runs.

Beiträge zur Totalsynthese von Epothilon A und Derivaten

Natural product, epothilone, total synthesis, olefin metathesis, aldol reaction

A reação de metátese de olefinas: reorganização e ciclização de compostos orgânicos

The olefin metathesis reaction allows the exchange of complex alkyl units between two olefins, with the formation of a new olefinic link and a sub-product olefin usually ethylene. This reaction has found extensive application in the last ten years with the development of the Grubbs and Schrock catalysts, in total synthesis of complex organic molecules, as opposed to the very important use in the petrochemical industry with relatively simple molecules. This review intends to trace a historical and mechanistic pathway from industry to academy, before illustrating the more recent advances.

Polimerização de estireno utilizando compostos organolantanídeos ativados por MAO

In an attempt to improve the performance of organolanthanide catalysts we investigated the use of the industrially important cocatalyst methylaluminoxane (MAO) to activate organolanthanide compounds in olefin polymerization. The catalytic systems LnBrCp2(THF)2/MAO (Cp=cyclopentadienyl) and LnBrCp*2THF/MAO (Cp*= pentamethylcyclopentadienyl), Ln=Pr and Yb, were active in styrene polymerization but inactive in ethylene and propylene polymerization. These systems produced atactic polystyrene with conversions of up to 8.2% (PrBrCp*2THF, Al/Ln=200, T=80ºC, t=4 h) in toluene. In the absence of solvent, the conversion is 26.0% (1.5 h) and the molar mass of the atactic polystyrene is almost ten times higher (43 kg/mol).

Metátese de olefinas no Brasil: "Brazil is romping it!"

Some aspects of the olefin metathesis reactions are summarized here (types of reactions, mechanism and catalysts). In particular, the research groups that have been working on this chemistry in Brazil are presented. The main goal of this paper is to make this type of reaction more widely known in the Brazilian chemical community.

Romp as a versatile method for the obtention of differentiated polymeric materials

Ring Opening Metathesis Polymerization (ROMP) of cyclic olefins is a powerful transition metal-catalyzed reaction for syntheses of polymers and copolymers. The key feature of this reaction is the [2+2]-cycloaddition mechanism, with retention of the olefinic unsaturation in the polymer chain and occurrence of living polymerization. With the development of metal-carbene type catalysts for this process, many addressed polymeric materials have been successfully prepared to be employed in several fields of the science and technology. This review summarizes recent examples of syntheses of polymers with amphiphilic features such as block, graft, brush or star copolymers; as well syntheses of biomaterials, dendronized architectures, photoactive polymers, cross-linked or self-healing materials, and polymers from renewed supplies.

Membrane emulsification in preparation of single site catalyst

In the theory part the membrane emulsification was studied. Emulsions are used in many industrial areas. Traditionally emulsions are prepared by using high shear in rotor-stator systems or in high pressure homogenizer systems. In membrane emulsification two immiscible liquids are mixed by pressuring one liquid through the membrane into the other liquid. With this technique energy could be saved, more homogeneous droplets could be formed and the amount of surfactant could be decreased. Ziegler-Natta and single-site catalysts are used in olefin polymerization processes. Nowadays, these catalysts are prepared according to traditional mixing emulsification. More homogeneous catalyst particles that have narrower particle size distribution might be prepared with membrane emulsification. The aim of the experimental part was to examine the possibility to prepare single site polypropylene catalyst using membrane emulsification technique. Different membrane materials and solidification techniques of the emulsion were examined. Also the toluene-PFC phase diagram was successfully measured during this thesis work. This phase diagram was used for process optimization. The polytetrafluoroethylene membranes had the largest contact angles with toluene and also the biggest difference between the contact angles measured with PFC and toluene. Despite of the contact angle measurement results no significant difference was noticed between particles prepared using PTFE membrane or metal sinter. The particle size distributions of catalyst prepared in these tests were quite wide. This would probably be fixed by using a membrane with a more homogeneous pore size distribution. It is also possible that the solidification rate has an effect on the particle sizes and particle morphology. When polymeric membranes are compared PTFE is probably still the best material for the process as it had the best chemical durability.