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Life History Evolution : A Biological Meta-Theory for the Social Sciences
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ISBN: 9783319901251 Year: 2018 Publisher: Cham Springer International Publishing :Imprint: Palgrave Macmillan


Dissertation
The potential of steam distillation for the purification of valuable phenolic monomers in lignin-oil

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As a vast and renewable source of aromatics, lignin in lignocellulosic biomass holds a tremendous potential as a sustainable feedstock. The Centre for Surface Chemistry and Catalysis (COK) of the University of Leuven developed a lignin-first approach, in which the lignin is valorised through a reductive catalytic fractionation as a lignin-oil rich in phenolic monomers. The purification of these valuable monomers previously made use of an energy-intensive hexane extraction. This master thesis looks to improve the previous set-up. Both the technical and economic feasibility of a lignin-first biorefinery with a steam distillation set-up are studied, for the purification of phenolic monomers (mostly 4-n-propylsyringol (PS) and 4-n-propylguaiacol (PG)) in a hardwood and softwood lignin-oil. First, a proof of concept was delivered in two ways. An assessment of the relative volatility of PG and PS made clear that distillation was a feasible separation method. Additionally, a batch steam distillation experiment was undertaken. The experiment confirmed that steam distillation is capable of retrieving the monomers, while retaining the di- and oligomers in the lignin-oil. Furthermore, the onset of a phase separation between the water and monomeric phase could be observed in the product samples. Once the feasibility of steam distillation was established, an attempt was made to scale up these results to an industrial-size process unit. Three distinct units (two for hardwood, one for softwood) were modelled with Aspen Plus®, which could treat 16 kmol/hr of lignin-oil with 300 kmol/hr of steam. Each set-up contained a steam distillation (to isolate the monomers) and regular distillation (to purify the monomers) column. After a preliminary design, the set-ups were optimised with various sensitivity analyses. The columns in the set-ups contained between 25 and 35 stages and operated under distillate-to-feed ratios of 0.60 to 0.98 and reflux ratios of 0.7 to 5.0. The resulting set-ups respectively managed to recover PS (hardwood) or PG (softwood) with efficiencies of 99.73%, 98.09% and 96.93%. Purities of 99.85 wt%, 98.87% and 98.73 wt% were reached. Furthermore, approximately 3.85 times as much PS-product was produced as in the previous set-up, since the lignin-oil contained significantly more monomers due to the omission of the hexane extraction. Finally, the economic feasibility of the set-up was assessed. The three set-ups represented similar capital expenditures (CAPEX) between $14.66M and $14.71M, since they were of similar size and used the same types of equipment. The operational expenditures (OPEX) were high due to the large energy duties (between 24.51 and 26.69 MWh). Therefore, the OPEX per unit of feedstock were significantly higher than in the previous set-up, but due to the increased output the OPEX per unit of product were similar or even cheaper. This master thesis succeeded in its goal to investigate the feasibility of a steam distillation set-up for the purification of lignin-oil.

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Dissertation
Selective synthesis, oestrogenic activity, copolymerisation, and catalytic isomerisation of bisguaiacol F (BGF) regioisomers

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The non-renewable and endocrine disrupting nature of conventional petro-based bisphenols, like bisphenol A (BPA) and F (BPF), has sparked the quest for bio-based and oestrogen inactive bisphenol replacements, used for the production of aromatic polycarbonate (PC) and epoxy resins. A promising BPA/bisphenol replacement, is para,para’-bisguaiacol F (p,p’-BGF), a condensation product of lignin-derivable vanillyl alcohol (VA) and guaiacol. In this master thesis, the potential of p,p’-BGF as a green and safe(r) building block for PCs is examined. Special attention is given to the integrated and simultaneous valorisation of meta,para’-bisguaiacol F (m,p’-BGF), a significant side product inherently linked to p,p’-BGF synthesis. In a new and successful approach, both BGF regioisomers are selectively synthesised by acid-catalysed condensation of guaiacol with commercially available VA regioisomers. For p,p’-BGF (from VA), optimisation leads to a chemo- and regioselectivity of 56 wt% and 73%, respectively. Similar values (58 wt% and 72%) are obtained for m,p’-BGF (from isovanillyl alcohol). Preliminary results indicate the existence of acid-catalysed isomerisation for p,p’-BGF (to o,p’-BGF), but it seems to lacks for m,p’- and o,p’-isomers. Subsequent purification by column chromatography and successive (re)crystallisation yields isomerically pure (p,p’- and m,p’-)BGF (>99.5%). Before polymerisation, to ensure safer chemical design, their estrogenic activity (EA) is tested in an in vitro luciferase assay, and found to be significantly lower compared to BPA and BPF. p,p’- and m,p’-BGF display reduced potencies (84 and 89 times lower affinity than BPA) and lowered efficacies (52% and 38% of BPA’s maximum effect), respectively. One-on-one comparison of p,p’-BPF and p,p’-BGF demonstrates the direct link between lower EA and the presence of ortho-methoxy groups. Next, homo- and copolymers (25:75, 50:50 and 75:25) of p,p’- and m,p’-BGF are successfully prepared by interfacial polymerisation (in >80% yield) with in situ generated phosgene (from triphosgene), as unambiguously proven by (1H and 13C) NMR, FTIR and GPC. All BGF-based PCs (BGF-PCs) display nearly identical thermal and physicochemical properties, having Mw = 20.0-26.2 kDa, Mn = 5.5-6.2 kDa, Tg = 102-111 °C and Td;max = 417-419 °C, of which the latter two properties are almost similar to petro-based BPF-PC (Tg = 119 °C, Td;max= 447 °C), regardless of their different Mw.

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Dissertation
Reductive catalytic fractionation of lignocellulosic biomass: Evaluation of non-noble metal catalysts

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Environmental problems and the dependency on fossil resources urge the search for sustainable feedstocks for fuels and chemicals. Second generation biorefineries convert lignocellulose to platform chemicals, but currently fail to efficiently valorise lignin. As lignin is an abundant and renewable source of bio-based aromatics, the downstream processing of lignin is important to create a sustainable and economically viable biorefinery. This master’s thesis handles the reductive catalytic fractionation (RCF) of biomass, in which the processing of lignin occurs prior to the valorisation of the carbohydrate pulp. During the process lignin is extracted and depolymerised in the presence of a solvent and a hydrogenation catalyst, under pressurised hydrogen and at elevated temperatures. The aim is to yield a depolymerised lignin-oil, rich in monomeric compounds while maintaining a solid carbohydrate pulp. However, current processes use expensive noble metals, such as Pd and Ru, which increases the operational cost. The implementation of non-noble metal catalysts has been investigated in order to find cost-competitive alternatives for the selective noble metal catalysts. Initially, a variety of commercially available Ni- and Co-based powder catalysts were screened in standard reaction conditions (30 bar H2 and 250 ̊C), which pointed out that the Ni-based catalysts show an overall higher performance than the Co-catalysts. Two Ni-catalysts, the Ni 5249P and Ni 6458, achieved monomer yields close to the theoretical maximum but showed a lower selectivity than the noble metals. Experiments with Ni-catalyst pellets in a basket were also performed to test the catalytic stability. A reactor basket was used for an easy recuperation of the catalyst afterwards. The results demonstrated that even in the presence of acid and water Ni-leaching was limited (<1% leaching). Moreover, the addition of water significantly decreased monomer yields. The conversion of lignocellulosic wastes to platform chemicals is very appealing due to the recycling of waste streams and the low cost of the raw material. Therefore, the implementation of waste wood fines (WWF) in the RCF was tested. Moreover, catalyst recycling experiments with WWF resulted in a gradual decrease of the monomer yield over the different runs from 6.1 C% to 1.6 C% for the raw WWF and from 4.2 C% to 2.3 C% for the extracted WWF. Finally, to modify the catalytic selectivity, the Ni catalysts were doped with an inexpensive promotor metal (Fe, Mo and W). Despite a lower the monomer yield, the selectivity of the catalyst was clearly affected by the dopants.

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Book
Life History Evolution : A Biological Meta-Theory for the Social Sciences
Authors: --- --- --- --- --- et al.
ISBN: 3319901249 3319901257 Year: 2018 Publisher: Cham : Springer International Publishing : Imprint: Palgrave Macmillan,

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The social sciences share a mission to shed light on human nature and society. However, there is no widely accepted meta-theory; no foundation from which variables can be linked, causally sequenced, or ultimately explained. This book advances “life history evolution” as the missing meta-theory for the social sciences. Originally a biological theory for the variation between species, research on life history evolution now encompasses psychological and sociological variation within the human species that has long been the stock and trade of social scientific study. The eighteen chapters of this book review six disciplines, eighteen authors, and eighty-two volumes published between 1734 and 2015—re-reading the texts in the light of life history evolution. .


Dissertation
Exploration towards more performant polyester bioplastics via catalysis and stereospecific co-polymerisation

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Modern plastics have become an inseparable part of our everyday lives. The vast majority of today’s plastics are produced from non-renewable fossil fuels. These petroleum-based plastics, however, cause environmental issues due to their lack of sustainability and degradability. As a consequence, bio-based and biodegradable polymers, such as poly(lactic acid) (PLA) are promising, sustainable alternatives. Despite its potential, certain restraining factors and deficient properties cut down the growth of the PLA market. PLA is brittle and sensitive to thermal and hydrolytic degradation. Furthermore, this bioplastic has a poor melt strength and low melt viscosity and elasticity, which limits its processability. This master thesis focusses on stereospecific co-polymerisation to create modified PLA with enhanced properties. The co-polymers were characterized to provide a stronger insight in their structure-property relationship. This can provide the possibility of tuning PLA towards desirable properties for specific applications and processing methods. Commercial grade PLA is synthesized via ring opening polymerisation (ROP) of the cyclic di-ester of lactic acid (LA), lactide (LD). LD is made by backbiting depolymerisation of a PLA prepolymer. This process is inefficient, provides low LD yields and is confronted with racemisation. A recently developed procedure enables a direct LD synthesis with the help of zeolite catalysis in absence of racemisation. Moreover, other renewable di-ester monomers, such as symmetric ethylglycolide (EG) and asymmetric methylethylglycolide (MEG), can be synthesized in high yields by the same process. In a first approach these monomers were synthesized in different stereo-configurations and purified to use them in ROP with L- or D-LD. Incorporation of symmetric or asymmetric cyclic esters in polylactide (PLD) allowed the synthesis of high molecular weight polymers with a different iteration of side groups, a specific stereo-configuration and a different LD:co-monomer ratio. In a second approach, the co-polymers were examined in terms of their thermal and rheological properties. Incorporation of EG and MEG in PLD induced a decrease in the glass transition temperature, melt temperature and degree of crystallinity with increasing amount of co-monomer. Moreover, differences were seen between isotactic and heterotactic co-polymers. Melt rheology provided insight in the viscoelastic properties and melt strength of the polyesters under shear and stretch deformation. Unexpectedly high shear viscosities and melt elasticity were observed for co-polymers of LD and EG with a reverse stereo-configuration. These effects could not be achieved by co-polymerisation of L-LD and D-LD, nor with L-EG and L-LD. Despite this very high shear viscosity, no pronounced strain hardening behaviour was observed under stretch deformation. A possible explanation for this behaviour was proposed, but not investigated. Nevertheless, a clear improvement in the PLD melt strength and elasticity were observed, which could open the way to more performant bioplastics.

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Dissertation
Koppeling van vetzuren via ketonisatie met metaaloxide katalysatoren: op weg naar hernieuwbare bio-waxen

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In het kader van duurzame ontwikkeling van onze samenleving, dringt de nood aan hernieuwbare alternatieven voor fossiele olie zich almaar meer op. Biomassa lijkt hiervoor de beste perspectieven te bieden als alternatieve basisgrondstof voor koolwaterstoffen. Plantaardige en dierlijke oliën en vetten (of meer specifiek vetzuren) vormen door hun chemische structuur geschikte substraten voor de productie van de zwaardere fractie koolwaterstoffen, waaronder ook waxen. Koppeling van deze vetzuren met behulp van ketonisatie zorgt voor deoxygenatie en doet de ketenlengte toenemen, om de gewenste eigenschappen van de beoogde toepassing te bekomen. Dit volgt de visie van deze masterproef om chemicaliën te produceren uit biomassa, eerder dan brandstoffen. Het hoofddoel van deze studie bestaat specifiek uit het verwerven van chemische inzichten en kinetische informatie omtrent de amper beschreven ketonisatie van vetzuren (in solvent). In een eerste luik wordt nagegaan of dodecaan voldoet aan de eigenschappen die vereist zijn voor een solvent. Vervolgens wordt de ketonisatie van laurinezuur in solvent met een anatase type TiO2 katalysator uitgebreid onderzocht. Variatie van de reactiecondities laat hierbij toe een beeld te schetsen van diens invloed op ketonisatie en kinetische parameters zoals de snelheidsconstante, activatie energie en orde te bepalen. Hierbij wordt vastgesteld dat de globale omzettingssnelheid toeneemt bij hogere temperatuur, hogere substraatconcentratie en lagere druk. Bovendien lijkt de aanwezigheid van het solvent de globale reactiesnelheid positief te beïnvloeden. Ter benadering van een potentieel industrieel productieproces wordt vervolgens de ketonisatie van vetzuren met verschillende ketenlengtes alsook van hun mengsels getest. Bij toename van de ketenlengte wordt zo een hogere activatie energie geobserveerd, wat effect lijkt te hebben op de reactiviteit van de vetzuren in mengsels. Voor een willekeurig substraat lijkt een reactie met een korter vetzuur steeds preferentieel op te treden, wat wordt waargenomen door een hogere conversie en een hogere selectiviteit voor de producten uit kruisketonisatie. Na het ter beschikking komen van andere commerciële TiO2 katalysatoren, kan aan de hand van een vergelijkende test getracht worden de eigenschappen van een goede TiO2 katalysator voor ketonisatie te definiëren. Het specifiek oppervlak lijkt hierbij amper te correleren met de activiteit, terwijl toename in porievolume dan weer wel samen lijkt te gaan met een hogere omzetting. Eén materiaal met de rutiel kristalvorm lijkt, tegen de verwachtingen van de literatuur in, opvallend goed te presteren. Verdere testen wijzen bovendien uit dat op deze katalysator het effect van ketenlengte geen rol speelt voor de reactiviteit van de vetzuren.

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Multi
Design of Wideband CMOS Building Block Circuits for Receivers from 0.5 up to 4 GHz

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This thesis has been focused on the design of wideband circuits for multi-band/multi-standard receivers. Three projects have been developed during this Ph.D. and are presented in this thesis: the required specifications of a wideband spectrum-sensing receiver, two versions of a 130nm CMOS wideband low-noise variable gain amplifier, and a 40nm CMOS wideband high-IF receiver. The specifications of the spectrum-sensing receiver aim for the detection of three wideband signals WRAN, WiMax, and LTE. These are the principal wideband signals within the band from 50MHz to 4GHz, which has been selected because it was very crowded but with plenty of underused spaces. After the definition of the receiver specifications, the block-level specifications have also been calculated and verified through behavioral model simulations. The specifications have shown that a multi-standard receiver must cope with a large range of signal power, which motivated the design the low-noise variable gain amplifier (LNVGA). The purpose of the LNVGA is to allow for the reception of both strong and weak signals by either reducing their signal power to values that do not compress the following blocks, like the mixer, or increasing it so that the noise figure is reduced, which increases the receiver sensitivity. The two fabricated LNVGAs achieve a gain tuning range up to 45dB within a bandwidth of 3~GHz in addition to a NF as low as 3.4dB. In contrast to other published VGAs, the proposed LNVGAs are the only ones that achieve a large gain tuning range in combination with a reasonably low NF. The large gain tuning range has been obtained thanks to the proposed low imbalance active balun. Both LNVGAs have been designed in 130nm CMOS for a 1.2V supply. The final design is a 40nm CMOS wideband high-IF receiver. Due to the evolution of CMOS technology, receivers with a higher IF and without external components are feasible in CMOS nodes below 65nm. The main advantage of those high-IF receivers is their robustness to DC offsets, flicker noise, and even-order distortion. The two main contributions of this design are the LTNA and the modified bandpass switched-capacitor filter (SC-BPF). The LNTA uses a dual noise cancellation, which ensures a low noise figure. Since both the mixer and the SC-BPF are passive, the LTNA needs an output impedance higher than the input impedance of the following blocks. Hence, a folded-cascode has been merged into the LNTA to increase its output impedance. The original SC-BPF has been modified by adding cross-connected transconductors at the in-phase (I) and quadrature (Q) inputs. These cross-connected transconductors not only boost but also allow for a variation of the Q-factor of the SC-BPF with a minimum increase of power consumption and design complexity. The highest voltage gain achieved by the receiver is 30dB. While operating at the maximum gain, the receiver noise figure is 3.3dB. The highest IIP3 is -2.5dBm, and the IIP2 is as high as 35dBm. The receiver and clock generation circuitry drain together 25mA from a 0.9V power supply. In comparison to the state-of-the-art, our receiver has the smallest area in addition to the reduced power consumption, and it targets the largest RF band.


Dissertation
Reductive catalytic fractionation : A lignin-first biorefinery concept

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Instigated by environmental concerns and resource scarcity, a shift towards a circular, bio-based economy is on the horizon. This inevitable transition will hinge on the deployment of alternative technologies that are able to fulfil the needs of our society in a sustainable way. Within this context, plant biomass in the form of lignocellulose represents a promising renewable resource. Lignocellulose is a heterogeneous substance, mainly composed of carbohydrates (cellulose and hemicellulose) and a phenolic biopolymer, named lignin. These constituents form a recalcitrant composite material, engineered by Nature to withstand (bio)chemical conversion. In analogy to the petrorefinery, a biorefinery aims to transform biomass into a range of useful products, including chemicals, materials, and fuels.Historically, lignocellulosic biorefineries have been geared towards optimal carbohydrate valorisation (e.g. paper, cellulosic ethanol), whereas lignin has been considered as an inferior and inconvenient biopolymer. Lignin though embodies the largest source of bio-aromatics, and the utilisation of this feedstock for the production of chemicals is gaining increasing interest. However, primarily focusing on carbohydrate valorisation often evokes irreversible lignin condensation, impeding the selective conversion of lignin into bio-aromatics. To cope with the problem of lignin degradation, this dissertation promotes a shift towards an alternative mind-set, stating that lignin valorisation should already be taken into account in the early stages of the biorefinery, while dealing with (hemi)cellulose later (i.e. lignin-first concept). By doing so, next generation biorefineries will be able to obtain more value from lignin, and in extension, from the entire biomass.One of the few biorefinery schemes that elegantly circumvents lignin condensation, is named Reductive Catalytic Fractionation (RCF). RCF targets solvolytic extraction of lignin from raw biomass, combined with instantaneous tandem depolymerisation-stabilisation. The latter step is facilitated by a heterogeneous redox catalyst (e.g. Ru/C, Pd/C) under hydrogen atmosphere, and yields a low molecular weight lignin oil containing phenolic monomers, dimers and small oligomers. The carbohydrate fraction (cellulose and hemicellulose) on the other hand is retrieved as a delignified pulp, ready for further valorisation. Despite its promising potential, the RCF technology is still in its infancy. The relationship between process conditions and their effect on the main biomass constituents has not yet been profoundly investigated. A better understanding would allow to modify and steer the RCF biorefinery towards a desired (alternative) outcome, which is the ultimate goal of this PhD dissertation.One of the hurdles that obstructs industrial implementation is the requirement for relatively high temperatures to achieve effective biomass delignification. RCF is typically performed with pure low boiling alcohols at 250 °C, resulting in an unfavourably high operating pressure (e.g. 110 bar in case of methanol). To facilitate RCF at milder conditions, two strategies were investigated, being (i) the implementation of acidic or alkaline additives and (ii) the utilisation of alcohol/water mixtures instead of pure alcohols. Mildly acidic media were found to effectuate lignin extraction at lower temperature and pressure (200 °C, 58 bar), and are furthermore compatible with reductive depolymerisation-stabilisation. Alkaline media on the other hand cause substantial lignin repolymerisation, rendering low lignin monomer yields and a larger fraction of oligomers. Besides applying additives, tuning the composition of the solvent mixture forms another strategy since alcohol/water mixtures (e.g. methanol/water, ethanol/water) were found to extract more lignin than either the pure alcohol or pure water. The degree of delignification correlates with the polarity of the solvent mixture.The utilisation of acids and alcohol/water mixtures not only enhances biomass delignification, it also impacts the hemicellulose fraction. Mildly acidic and/or relatively polar media promote extraction of hemicellulose and lignin from the biomass, while the cellulose fraction remains intact. This phenomenon provides a tool to tune the composition of the carbohydrate pulp (holocellulose vs. cellulose) and thus increases the versatility of RCF. In case hemicellulose solubilisation is anticipated, conversion to stable carbohydrate products should be targeted in order to mitigate degradation. Two strategies were put forward that are compatible with RCF. The first one targets hemicellulose conversion by means of acid-catalysed alcoholysis into alkyl pyranosides (e.g. methyl xyloside). The presence of water should be avoided to prevent hydrolysis towards xylose or other sugars, which are relatively unstable. Secondly, the hydrolytic hydrogenation of hemicellulose towards C5 and C6 polyols was demonstrated. This approach uses the same redox catalyst for carbohydrate hydrogenation as for lignin stabilisation. Fine-tuning the various reaction parameters is key to enable effective conversion of both biopolymers.Simultaneous depolymerisation of lignin and hemicellulose obligates down-stream separation of the obtained products. Therefore, RCF was demonstrated using a solvent mixture comprising n‑butanol and water. This solvent system enables conversion of lignin and hemicellulose during RCF, and provides an integrated separation approach for the solubilised products (i.e. phenolics and polyols, respectively) once the reaction is completed. The limited miscibility of n‑butanol and water can be used to separate lignin-derived phenolics (preferentially in n‑butanol phase) from the more polar carbohydrate products (preferentially in aqueous phase) via liquid-liquid extraction. Noteworthy, the n‑butanol/water mixture is biphasic below the upper-critical solution temperature (circa 125 °C), but monophasic at typical RCF temperatures (≥160 °C). Because of this dual behaviour, the intrinsic complexity of a truly biphasic catalytic system is omitted, while still exploiting the benefits of an integrated product separation after reaction. A proof-of-concept on 2 L scale demonstrates the scalability potential of this biorefinery concept.


Dissertation
Catalysis in active oxygen barrier technologies for PET packaging

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Over the past decades, PET has grown to be one of the most widely used engineering polymers. Glass and metal containers have been slowly overrun by the cheaper, lighter and more resilient PET-bottles. Additionally, the much lower energy input that goes into the production of these bottles has proven them to be a much more environment-friendly alternative to the traditional containers. As a disadvantage, some properties of PET, such as the permeability of gases, might render it unqualified for certain products. However, there is a wide range of technologies to improve these properties by altering the composition or the production process.One of these technologies is the active oxygen barrier. Sauces, juices, beer and wine are all examples of oxygen sensitive products that are packaged in PET. The ingress of oxygen would not only deteriorate the nutritional value, but will create off-tastes and discoloration. For all these applications, it is imperative that the expiration date would be prolonged as much as possible by disabling the ingress of oxygen, a feat that is unattainable so far by any passive barrier. While a passive barrier just lowers the diffusion of the gas through the bottle wall, an active barrier will incite chemical interactions to scavenge oxygen that attempts to enter the bottle’s interior. The most widely used active oxygen barrier consists of a cobalt salt and a sacrificial polymer. Cobalt herein acts as an oxidation catalyst, providing oxygen activation at room temperature and making it sufficiently reactive to oxidize the sacrificial. However, recently the toxicity of cobalt has been put under review. The new studies have showed that the health of the plant workers may be in danger by the cobalt handling and prospects are that the metal would be banished in packaging soon. This project investigates the catalytic behavior of the metal salt and starting from the mechanism, crucial properties such as safety, recyclability and visual appeal, will be improved.The project is a cooperation between the SMaRT- and COK-departments at KU Leuven and the company Plastipak, currently the world’s largest PET-bottle producer with its European R&D-center being based in Brecht, Belgium.

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