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Item type:Publication, Access status: with files , Structure-performance guided design of sustainable plasticizers from biorenewable feedstocksThe search for more sustainable solutions for plastics production, moving away from petrochemical feedstocks as today's major raw material basis, is a research area of increasing interest. This task goes far beyond the issue of designing greener polymers and their related monomers as tailor-made plastics require, besides the polymer itself, further components. These additives also need to be switched from typically fossil-based to bio-renewable raw materials. One of such necessary components for many applications are plasticizers, and a major application of them is related to polyvinyl chloride (PVC) as one of the leading polymers with a wide range of applications. Typically today‘s plasticizers are based on fossil feedstocks, and some of them such as specific ortho-phthalates as the most important product class of plasticizers are now subject to restrictions and authorization by the EU's REACH legislation due to their toxicological profile. In this contribution, we report the synthesis and technical evaluation of alternative, novel bicyclic plasticizer candidates, which are fully accessible from renewable feedstocks. In detail, these new plasticizer target molecules are based on the use of the furan-derivative 2-methylfuran, maleic anhydride and 2-ethylhexanol as bio-based starting materials. The synthetic concept consists of an initial Diels-Alder reaction with 2-methylfuran and a subsequent hydrogenation and optional esterification step. The applied reactions are well-known as economic and sustainable technologies. Thus, not only the starting materials (being of bio-based origin) but also the selected reaction technologies for the syntheses of the target molecules are sustainable. Furthermore, a range of performance tests enabled an insight into structure-performance relationships and revealed promising plasticizing properties of this new bio-based plasticizer generation with, e. g., an attractive solution temperature fulfilling the criterium for a “fast fuser” as well as good compatibility with PVC.Publicationtype: Journal ArticleScopus© Citations 4 71 277 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Enzyme Cascade Reaction Monitoring and Control(2021); ; Enzymatic reaction cascades often consist of various starting materials, intermediates, products, and possible side products. To establish a highly efficient cascade reaction it is necessary to monitor these components, which enables an optimization of the overall system. The scope of this chapter is to provide knowledge about the basic principles of inline analytical technologies. Different definitions about the position and the type of measurement technique are introduced. Additionally, information on the accuracy and the limit of detection are given. Since for most inline methods a chemometric model for the calculation of concentration data from inline determined measurements is needed, a short introduction on chemometrics is provided. Furthermore, inline analytical tools which are suitable for the application in enzymatic cascade reactions are discussed and examples are given to highlight the possibilities arising by the use of such technologies. The analytical devices are critically assessed in terms of their applicability and a general workflow is given on the procedure of setting up inline or online analytical methods. At the end of the chapter, the impact of inline analytics used for monitoring and controlling enzymatic reaction cascades on the design of (industrial) processes is discussed and shortly the concepts of “quality by design” and “quality by control” are introduced.Publicationtype: Journal Article49 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Inline analytical supported process development towards alternative bio-based plasticizers(2021); Polyvinyl chloride (PVC) is nowadays the third most applied polymer with approximately 41 million tons produced in 2017. Plasticizers are added to the PVC polymer to increase the flexibility. The most common class of plasticizers are ortho-phthalic acid esters (phthalates). In the last years, the application of some of the latter was restricted due to health concerns. Therefore, the need for non-harmful alternatives arises. Additionally, bio-based plasticizer are a promising approach, since these will decrease the overall carbon footprint of the plasticized polymer. In this thesis, a three-step process is developed to produce bio-based plasticizers in a multi-gram scale using renewable resources as basis. Starting from 2-methylfuran and maleic acid anhydride, in a Diels-Alder reaction, a cyclic 6-membered ring intermediate for the plasticizing building block (1st step) is synthesized. This instable intermediate tends to undergo a retro-Diels Alder reaction and need to be stabilized via hydrogenation prior to further reaction steps avoiding the backwards reaction (2nd step). In a 3rd step, the cyclic plasticizer building block was successfully esterified at its acid groups in ortho-position. Here, 2-ethylhexanol, a standard alcohol applied in the synthesis of various plasticizers, is used. Additionally, the applicability of more than 80 enzymes for a biocatalytic esterification step was investigated. Throughout this work, inline analytic was employed for the characterization of the respective reaction steps. In detail, Fourier-transformed Infrared spectroscopy (FTIR) equipped with Attenuated Total Reflection (ATR) probes was implemented. These probes enable a non-destructive analysis directly inside the reactor vessel. To derive the respective concentrations from the recorded vibrational spectra, chemometric models were developed. In this work, the Indirect Hard Modeling (IHM) as a physically motivated hard modeling approach was applied. Besides using these established inline analytical methods in terms of process characterization, the inline measured data were used to set up kinetic models describing the each single reaction step. For this reason, the inline data were fitted to inline measured concentration profiles yielding the respective reaction rate constants. Concluding, in this thesis a promising approach for inline analytical-supported process development towards bio-based plasticizer is presented. Moreover, this approach can be transferred to other potential plasticizer candidates helping to reduce the time needed for the process development.Publicationtype: Doctoral Thesis208 912 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Towards bio-based plasticizers with reduced toxicity: Synthesis and performance testing of a 3-methylphthalate(2020-12); ; ; ; As a very durable material, soft polyvinyl chloride (PVC) is used for many applications in the field of consumer products. To enable the desired properties, for example for medical devices, the addition of plasticizers is required. For this purpose, mostly dialkyl phthalates are used being produced on a multi-million tons scale annually. Since some of these are associated with human health effects, there is an increasing demand for the search of alternatives. Besides reduced toxicity while maintaining excellent performance features, an economic access as well as biorenewable starting materials are further criteria, which should be ideally fulfilled by such a new plasticizer generation. Targeting these demands and in contrast to most available substitutes being based on petrochemical feedstock, we developed a synthetic route starting from bio-renewable platform chemicals. In detail, a Diels-Alder reaction of 2-methylfuran and maleic anhydride and subsequent dehydration leads to three phthalate derivatives with different alcohol components bearing a methyl group at the aromatic ring. As a representative substance, di(2-ethylhexyl) 3-methylphthalate was chosen for performance tests, and this new bio-based alternative offers properties similar to known plasticizers in such initial studies.Publicationtype: Journal Article159 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , FTIR based kinetic characterisation of an acid-catalysed esterification of 3-methylphthalic anhydride and 2-ethylhexanol(2020-06-28); ; ; ; In this study, an inline analytical method was designed and applied in process characterisation and development. The model reaction is the two-step diesterification of 3-methylphthalic anhydride with 2-ethylhexanol consisting of alcoholysis as the first step, followed by an acid-catalysed, second esterification step leading to the corresponding diester. The final product is a potential, alternative plasticiser. For the inline measurements, attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR) was implemented. In order to evaluate the spectra recorded during the reaction, a chemometric model was established. In this work, Indirect Hard Modeling (IHM), a non-linear modeling approach was employed. The respective model was calibrated by using offline samples analysed with gas (GC) and liquid chromatography (HPLC). After successful validation of the chemometric model, the inline measurements were utilized for reaction characterisation. The acid-catalysed, second esterification step was identified as the limiting reaction step. From batch reactions conducted at different temperatures, the energy of activation of this step was determined to be 79.5 kJ mol-1. Additionally, kinetics were shown to follow a pseudo-first order with respect to the monoester formation and a kinetic model was established. The model was validated in simulations with changed reaction conditions.Publicationtype: Journal Article111 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Simultaneous local determination of mass transfer and residence time distributions in organic multiphase systems(Elsevier, 2017-04-01); ; ; ; A new method for simultaneous local determination of mass transfer coefficients and residence time distributions in continuously operated bubble columns has been developed. Since for organic liquids not many experimental data sets are available in respect to mass transfer, measurements were carried out with the organic gas/liquid multiphase system consisting of cumene (1-methylethylbenzene) and carbon dioxide. The concentration of carbon dioxide in the gas phase was adjusted by mixing with nitrogen. To measure concentrations of compounds in the liquid phase, attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR) was applied: five ATR probes integrating silver-halide optical fibers with a length of 1.5 m were integrated in a bubble column of 128.5 cm height and a diameter of 10 cm. The probes were distributed over the height of the reactor and could be shifted within the reactor to measure radial profiles of the mass transfer coefficients in steady state operation mode at different positions. The superficial liquid velocity of the system was adjusted in the range of 0.7–1.4 cm s−1. The used superficial gas velocities were between 1.5 cm s−1 and 2.1 cm s−1 to ensure a homogeneous flow regime. Furthermore, tracer experiments with benzaldehyde for the investigation of the residence time distributions were performed. From the FTIR spectral data, CO2 and benzaldehyde tracer concentration data were determined simultaneously by conducting multivariate chemometric models. The corresponding mass transfer coefficients were calculated using a compartmental method for stationary flow. The residence time distributions were calculated from the benzoic aldehyde concentration data. Both parameters could be determined successfully. For the mass transfer coefficient of carbon dioxide into cumene, an interesting profile could be observed, which arose from several influences like areas of different bubble densities, caused by bubble breakage and coalescence, superficial velocities of gas and liquid as well as the applied type of sparger.Publicationtype: Journal Article97 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Effect of high pressure on hydrocarbon-degrading bacteria(Springer, 2014-10-15); ; ; ; The blowout of the Deepwater Horizon in the Gulf of Mexico in 2010 occurred at a depth of 1500 m, corresponding to a hydrostatic pressure of 15 MPa. Up to now, knowledge about the impact of high pressure on oil-degrading bacteria has been scarce. To investigate how the biodegradation of crude oil and its components is influenced by high pressures, like those in deep-sea environments, hydrocarbon degradation and growth of two model strains were studied in high-pressure reactors. The alkane-degrading strain Rhodococcus qingshengii TUHH-12 grew well on n-hexadecane at 15 MPa at a rate of 0.16 h−1, although slightly slower than at ambient pressure (0.36 h−1). In contrast, the growth of the aromatic hydrocarbon degrading strain Sphingobium yanoikuyae B1 was highly affected by elevated pressures. Pressures of up to 8.8 MPa had little effect on growth of this strain. However, above this pressure growth decreased and at 12 MPa or more no more growth was observed. Nevertheless, S. yanoikuyae continued to convert naphthalene at pressure >12 MPa, although at a lower rate than at 0.1 MPa. This suggests that certain metabolic functions of this bacterium were inhibited by pressure to a greater extent than the enzymes responsible for naphthalene degradation. These results show that high pressure has a strong influence on the biodegradation of crude oil components and that, contrary to previous assumptions, the role of pressure cannot be discounted when estimating the biodegradation and ultimate fate of deep-sea oil releases such as the Deepwater Horizon eventPublicationtype: Journal ArticleScopus© Citations 47 480 354