Our colleagues Lukas Almhofer and Christian Paulik have published an article with the title `Kinetic and mechanistic aspects of furfural degradation in biorefineries´ in Progress in the Canadian Journal of Chemical Engineering (DOI: 10.1002/cjce.24593 Accepted: 14.04.2022)

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Abstract:

Furfural is one of the most promising platform chemicals for a future biobased industry and can already be produced from renewable raw materials. However, its production processes suffer from yield loss and fouling problems due to degradation reactions. To increase our understanding of furfural stability, we investigated the kinetics of its degradation (i) without acid catalyst and (ii) in 10 different acids that are frequently used in biomass processing or that are naturally present in biomass hydrolysates. The batch experiments were conducted in a parallel minireactor setup at temperatures ranging from 125 to 200
C. The results showed that acid-catalyzed furfural degradation reactions depend mainly on acid strength and give rise to a set of common degradation products (formic acid, glycolic acid, pyruvate, etc.). Sulphurous acid and lignosulphonic acid led to greater furfural degradation than expected, which appears to be driven by specific side reactions. Adding formic acid, in contrast, led to a lower degradation rate than expected. In general, we observed two distinct, competing degradation mechanisms. Selectivity for formic acid as a degradation product depends on temperature, furfural concentration, and the presence of an acid catalyst. A more detailed study of the formic acid yielding reaction showed it to be reversible, and we provide the first quantitative description of this reaction for any furan. The proposed kinetic model, together with the results presented, contributes to the development of more efficient furfural production processes.

Abstract:

The newly developed MALDI interpretation tool (“MALINTO”) allows for the accelerated characterization of complex synthetic polymers via MALDI mass spectrometry. While existing software provides solutions for simple polymers like poly(ethylene glycol), polystyrene, etc., they are limited in their application on polycondensates synthesized from two different kinds of monomers (e.g., diacid and diol in polyesters). In addition to such A₂ + B₂ polycondensates, MALINTO covers branched and even multicyclic polymer systems. Since the MALINTO software works based on input data of monomers/repeating units, end groups, and adducts, it can be applied on polymers whose components are previously known or elucidated. Using these input data, a list with theoretically possible polymer compositions and resulting m/z values is calculated, which is further compared to experimental mass spectrometry data. For optional semiquantitative studies, peak areas are allocated according to their assigned polymer composition to evaluate both comonomer and terminating group ratios. Several tools are implemented to avoid mistakes, for example, during peak assignment. In the present publication, the functions of MALINTO are described in detail and its broad applicability on different linear polymers as well as branched and multicyclic polycondensates is demonstrated. Fellow researchers will benefit from the accelerated peak assignment using the freely available MALINTO software and might be encouraged to explore the potential of MALDI mass spectrometry for (semi)quantitative applications.

Our colleagues Barbara Obereigner, Klaus Bretterbauer and Christian Paulik have published an article with the title `Key parameters and mechanism of blistering of coil-coatings in humid-hot laboratory environments´ in Progress in Organic Coatings (https://doi.org/10.1016/j.porgcoat.2022.107373, opens an external URL in a new window Accepted: 12.12.2022

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Abstract:

Blistering of organic coatings on hot dip galvanized (HDG) steel is of high practical relevance, especially in warm-humid environments. The aim of this work was to study the key parameters of blister formation and growth by accelerated laboratory testing at 60 and 70 ◦C. Following a statistical design of Taguchi, the components of a polyurethane (PU) primer formulation were varied and applied to hot-deep galvanized (HDG) steel. The presence of a topcoat was found to be a precondition for blistering. Degradation started at microcracks within the primer and was significantly influenced by the adhesion between primer and topcoat. A high content of anticorrosive pigments resulted in enhanced blister formation, while blister growth is mainly controlled by mass transport processes and shows a strong temperature dependence. This study focuses on one specific blistering mechanism, osmotic blistering, which is indicated by blister kinetics and leachate analysis, estimated pressure values inside the blister are in reasonable agreement by using two different calculation approaches.

Abstract:

Magnesium alkyls such as butyl octyl magnesium and butyl ethyl magnesium are used as precursors for highly active and water-free magnesium chloride support materials for Ziegler–Natta catalysts. These alkyls show a high viscosity in hydrocarbon solvents which negatively affect their industrial application. Density functional theory (DFT) calculations supported the hypothesis that magnesium alkyls can form oligomeric chain structures responsible for the high viscosity. Heterocumulenes such as isocyanates, isothiocyanates and carbodiimides were studied as additives reducing the viscosity, supported by DFT calculations. The modified alkyls have further been tested in catalyst synthesis and in the polymerization of ethylene. The polymerization results showed high activities and similar polymer properties compared with a catalyst prepared without modified magnesium alkyl.

Our colleagues Viktoria Kreuzer, Klaus Bretterbauer and Clemens Schwarzinger have published an article with the title `Spectroscopic studies on the formation of different diastereomers in polyesters based on nadic acid´  in the International Journal of Polymer Analysis and Characterization ( https://doi.org/10.1080/1023666X.2022.2112642 , opens an external URL in a new windowAccepted: 26 August 2022).

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Abstract:

Nadic acid-based polyesters were prepared by polycondensation with different diols and different stoichiometry of the monomers. Due to the four stereocenters of the acid component, four diastereomers can form in the polyester. The use of different alcohols and influence on the formation of diastereomers in the polyester was investigated. Identification of the stereoisomers has been done with 1D and 2D NMR spectroscopy, which revealed an influence of the diol component on their formation. Further structural elucidation was done by MALDI mass spectrometry and size exclusion chromatography. Another big influence of the diols was found on the glass transition temperatures, which ranged from −30 °C to 40 °C.

Our colleagues Daniel Pernusch, Gunnar Spiegel, and Christian Paulik have not only published one, but two papers with some other co-authors. The first paper with the title `Nitrogen Poisoning of HDPE and LLDPE based on Chemically Recycled Post-Consumer Plastic via a Kinetic and Microstructural Modeling Technique´ was published in the journal Macromolecular Reaction Engineering (https://doi.org/10.1002/mren.202200006, opens an external URL in a new window Accepted: 18 April 2022). In the same journal another article with the title `Assessing the Downstream Contamination of Chemically Recycled Ethylene Feed Streams on the Kinetic Behavior of Ziegler-Natta Catalysts and Microstructural Properties of HDPE and LLDPE´ was published (https://doi.org/10.1002/mren.202200042, opens an external URL in a new window Accepted: 1 September 2022).

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Abstract 1:
Chemical recycling of plastic waste has promise as a complementary technology to increase eco-efficiency of plastics life cycles. Accumulation of impurities in feed streams can affect sensitive compounds such as the Ziegler–Natta catalyst systems commonly used to produce polyolefins such as high density polyethylene (HDPE) and linear low density polyethylene (LLDPE). In a poison study, the influence of impurities—more specifically NO and N₂O—on the catalyst system are investigated comprehensively in terms of kinetic behavior and activity rates. A product composition analysis gives insights into product properties such as molecular weight distribution (MWD), comonomer composition distribution (CCD), melting point, and crystallinity. By applying known modeling techniques (kinetic modeling, MWD, and CCD deconvolution modeling), information beyond analytical data is obtained. The results of the study show that both poisons significantly affect catalyst kinetics and reduce catalyst activity. N₂O influences primarily the MWD, while NO poisoning strongly affects the CCD of LLDPE samples. Since the mechanical properties of the polymers produced depend on factors such as MWD and CCD, NO and N₂O poisoning may reduce their processability and applicability.

Abstract 2:

The sustainability of consumer materials, such as plastics, belongs to the most important aspect of eco-efficiency analyses. Besides mechanical recycling, chemical recycling represents an interesting waste management pathway. In theory, this technique does not rely on single-grade feedstock to maintain product quality. However, cross-contamination of feedstocks potentially leads to above-specification impurities in obtained pyrolysis oils. This study investigates the potential downstream poisoning of a fourth-generation Ziegler-Natta catalyst, using selected model poisons at high (worst-case) concentrations. With experimental and computational analysis, economic feasibility factors such as catalyst activity and microstructural properties are evaluated during the synthesis of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). Noticeable effects on the catalyst activity can be observed when the poison interacts with the co-catalyst, whereas a lower impact is observed for interactions with the activated catalyst-co-catalyst complex. Molecular weight distribution (MWD) and comonomer composition distribution (CCD) modeling highlighted marginal to no polymer property changes caused by contaminants. Combined with the applicability of pyrolysis post-treatments, these observations show that chemical recycling can be a promising technique for post-consumer plastic waste treatment.