Our colleagues Maria Wolfsgruber and Christian Paulik have published an article with the title `Potential Dependence of Gluconic Acid to Glucose Electroreduction on Silver´ in Catalysis Science & Technology (DOI: 10.1039/D3CY00897E)

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Abstract:

The electrocatalytic conversion of gluconic acid, an aldonic acid, as a model component of the spent sulfite liquor (SSL) represents a green approach for side-stream valorization. The biotechnological valorization of the SSL to more valuable products is inhibited by aldonic acids. Here, we discovered silver as electrocatalyst for the reduction of gluconic acid to glucose as a sustainable strategy to convert aldonic acids into fermentable carbohydrates. A potential screening in a twoelectrode compartment cell was investigated and showed the best conversion at −1.56 V vs. reversed hydrogen electrode (RHE) with 0.296 mmol∙L−1. The conversion rate decreased with higher and lower potentials than −1.56 V vs. RHE. SEM, EDS, and XPS analyses revealed no clear influence of the reaction on the electrocatalyst. LEIS measurements indicated only ion adsorption from the electrolyte and a slight surface oxidation. The electrocatalytic behavior of silver reveals a similar trend as for the electrocatalytic CO2 reduction reaction and nitrogen reduction reaction, where a maximum conversion is reached at one cathodic potential before the hydrogen reduction reaction becomes dominant. This highlights a key challenge in merging electrocatalysis and the biorefinery concept to create a bioelectrofinery for side-stream valorization, a crucial element of a bio-circular-green economy.

Our colleagues Valerie Rodin and Christian Paulik have published an article with the title `Techno-economic evaluation of the electrochemical production of renewable ethylene oxide from fluctuating power sources and CO₂´ in Journal of CO₂ Utilization (https://doi.org/10.1016/j.jcou.2023.102554, opens an external URL in a new window, Accepted: 31.07.2023)

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Abstract:

We present a techno-economic assessment of a novel ethylene oxide (EO) production process, which converts carbon dioxide (CO₂) and water electrocatalytically to ethylene (C₂H₄) and hydrogen peroxide (H₂O₂), which are further synthesized into EO. To ensure environmental sustainability, the primary focus was on available CO₂ from biogenic sources (biomethane and bioethanol plants) and renewable power sources (wind and photovoltaics) for decentralized applications. Accordingly, data on existing European CO₂ and renewable power sources were compiled for spatial analysis to develop technology roll-out and exploitation scenarios: 175 suitable locations were identified. Focusing on three locations, the production costs of EO and the product mix were calculated, considering various energy sources and plant configurations (as of 2030 and 2040). For a generic scenario, considering CO₂ to be available free of cost (existing biomethane upgrading) and electricity cost of 36€/MWh, the production cost of the product mix (EO, H₂O₂, methane, hydrogen) amount to 0.86 €/kg. This is at a similar order of magnitude as assessments on other Power-to-X value chains. Assuming that EO is the only utilizable product, the costs increase to 5.78 €/kg, which is significantly higher than for fossil alternatives. According to the sensitivity analysis, energy efficiency, electricity prices, and capital expenditure are the most relevant factors. Regarding the latter, an extended plant lifetime is a crucial factor.

Our colleagues Konstanze Kruta and Christian Paulik have published an article with the title `Effect of different washing conditions on the removal efficiency of selected compounds in biopolymers´ in Clean Technologies and Recycling (DOI: 10.3934/ctr.2023009, opens an external URL in a new window ,  Accepted: 05.07.2023)

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Abstract:

Recycling of plastic materials is a key sustainability topic. Hence, the scope of this study is to evaluate the potential of this purification step for achieving high-purity recyclates via mechanical recycling. In this study, the focus is set on the revalorization of poly(3-hydroxy butyrate) and poly(3-hydroxy butyrate-co-3-hydroxy valerate)—two biobased and biodegradable polymers that have properties similar to those of polyolefins and are therefore possible eco-friendly alternatives. Specifically, the washing process as an important part of polymer recycling processes is evaluated regarding different washing conditions on a laboratory scale. For this purpose, several virgin polymers were contaminated with volatile organic compounds that differed in functionality and molecular weight. Regarding contamination, concentration correlates with contamination time. Moreover, the contamination degree was found to be higher for polar contaminants since polar compounds show higher compatibility with the polymer. General beneficial effects of higher temperatures and longer washing times were observed. The choice of washing medium was relevant for different polarities of the contaminants. At higher process temperatures, material degradation occurred. Hence, recyclers have to pay attention to the difference in the interaction between impurities and the polymer and to the degradation of the polymer during recycling and the subsequent formation of degradation products. Since these biopolymers display comparable properties to polyolefins, great potential in packaging applications is apparent. Moreover, the method of analyzing the removal efficiency of volatile organic compounds via washing can be applied to all recyclable polymers.

Our colleagues Lukas Almhofer and Christian Paulik have published an article with the title `Simultaneous posthydrolysis and liquid–liquid extraction: a SIMPLLE process to detoxify eucalyptus prehydrolysis liquor´ in Biomass Conversion and Biorefinery (https://doi.org/10.1007/s13399-023-04570-6, opens an external URL in a new window,  Accepted: 29.06.2023)

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Abstract:

The prehydrolysis liquor from the prehydrolysis Kraft process is rich in sugars and could thus serve as a sustainable feedstock for the production of various chemicals. However, its industrial utilization is impeded by the presence of fermentation inhibitors and extensive lignin precipitation, the latter receiving only little attention in the literature.

In order to provide a feedstock suitable for biotechnological or chemical conversion, the prehydrolysis liquor from eucalyptus wood must be detoxified whilst preventing the precipitation of lignin. To increase the yield of monomeric sugars, acid posthydrolysis should be investigated.
Various solvents and solvent mixtures were screened for the high temperature liquid–liquid extraction of isothermally separated prehydrolysis liquor. Their capability to prevent lignin precipitation and to extract fermentation inhibitors was assessed using mass balances and size-exclusion chromatography. Based on the solvent screening, a process for simultaneous posthydrolysis and liquid–liquid extraction of eucalyptus prehydrolysis liquor was proposed and investigated using statistic experimental design.
Liquid–liquid extraction using aliphatic alcohols effectively prevents lignin precipitation, and the addition of 25% (w/w) tri-n-octylamine was found to increase the overall inhibitor extraction efficiency. The conditions for the simultaneous posthydrolysis were investigated using a Box-Behnken experimental design, allowing for a maximum monomeric sugar yield of 83.0% at a sugar purity of 91.6%.
The simultaneous posthydrolysis and liquid-liquid extraction (SIMPLLE) process thus avoids industrial-level problems associated with lignin precipitation. It provides a carbohydrate-rich stream with low levels of fermentation inhibitors, enabling further conversion to value added products.

Our chef, Christian Paulik has published an article with the title `Tethering cellulose fibers with disulphide linkages for rapid  and efficient adsorption of mercury ions and dye from wastewater: Adsorption mechanism and process optimization using RSM´ in Separation and Purification Technology (https://doi.org/10.1016/j.seppur.2023.124275, opens an external URL in a new window Accepted: 03.06.2023)

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Abstract:

Hemp stalks, readily available bio-waste in northern India, are good source of cellulose nanofibers (CNFs) with exceptional strength and stiffness. In this study, a facile route was envisaged to affix disulphide linkages on hemp derived CNFs (CNF-S-S-CNF) using 3,3-dithiopropionic acid. CNF-S-S-CNF with two sulphur groups on the cellulose backbone scored high selectivity for mercury ions (distribution coefficient of 5 × 105 mL.g􀀀 1) owing to soft–soft interactions, besides exhibiting affinity for safranin O (SO) due to strong electrostatic attractions. Thermal stability up to 700 ◦C advocated high temperature applications of CNF-S-S-CNF. Response surface methodology (RSM) with Box Behnken Design (BBD) was applied using Design Expert software 13 for tuning the process parameters. Statistical analysis of variance (ANOVA) established a maximum adsorption capacity, qe of 100% for Hg(II) ions achieved at optimum conditions of pH 5.5, Hg(II) concentration of 100 mg L-1 with adsorbent dosage of 100 mg and contact time of 9.50 min, while for SO, 100% adsorption was achieved at pH 6.5, SO concentration of 1 mg L-1 with adsorbent dosage of 60 mg and contact time of 9.50 min, in accord with the experimental results. Both, linear and non-linear kinetics and isotherm models were fitted to further understand the adsorption mechanism. The non-linear pseudo-second order demonstrated better adsorption kinetics for Hg(II), while SO fitted better to the linear pseudo-second order model. Ultra-rapid adsorption kinetics was achieved with pseudo second order rate constant, K2 of 0.197 g.mg􀀀 1.min􀀀 1 and 100% removal within 5 s (Co = 10 mg L-1) of Hg(II) ions. FTIR and XPS confirmed strong interactions of CNF-S-S-CNF with Hg(II) ions accomplishing a maximum adsorption capacity, qe exp of 828.5 mg/g. Regeneration of adsorbent for 8 cycles with retention of 96% and 80% efficacy for Hg(II) ions and SO, respectively endorse its outstanding potential in wastewater remediation.

Our colleagues Thomas Kisling, Christian Paulik and Klaus Bretterbauer have published an article with the title `Real-Time Monitoring of a Sol−Gel Reaction for Polysilane Production Using Inline NIR Spectroscopy´ in Langmuir (https://doi.org/10.1021/acs.langmuir.3c00601, opens an external URL in a new window Accepted: 28.05.2023)

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Abstract:

The sol−gel process is an effective method for the preparation of homogeneous structured nanomaterials whose physico-chemical properties strongly depend on the experimental conditions applied. The control of a three-component reaction with silanes showing multiple reaction sites revealed the need for an analytical tool that allows a rapid response to ongoing transformations in the reaction mixture. Herein, we describe the implementation of near-infrared (NIR) spectroscopy based on compact, mechanically robust, and cost-efficient micro-optomechanical system technology in the sol−gel process of three silanes with a total of nine reaction sites. The NIR-spectroscopically controlled reaction yields a long-time stable product with reproducible quality, fulfilling the demanding requirements for further use in coating processes. 1H nuclear magnetic resonance measurements are used as reference values for the calibration of a partial least squares (PLS) regression model. The precise prediction of the desired parameters from collected NIR spectroscopy data acquired during the sol−gel reaction proves the applicability of the calibrated PLS regression model. The determined shelf-life and further processing tests verify the high quality of the sol−gel and the produced highly cross-linked polysilane.

Our colleagues Manuel Pühringer, Christian Paulik and Klaus Bretterbauer have published an article with the title `Synthesis and characterization of polyacrylamide‑based biomimetic underwater adhesives´ in Monatshefte für Chemie (https://doi.org/10.1007/s00706-023-03057-4, opens an external URL in a new window Accepted: 21.03.2023)

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Abstract:

Adhesion in an aqueous environment is still a challenging topic. In recent years, the focus on biomimetic adhesives inspired by mussel proteins has greatly increased. The present paper focuses on a straightforward synthesis route for three biomimetic polymers with opportunity in a multi-gram scale and an overall yield of 83% over three steps. Two synthesized monomers combined with commercially available monomers are the basis for three different co-polymers with varying catechol content with nature inspired concentrations. Catechol-bearing monomers were protected prior to polymerization. Tensile tests in dry or wet conditions were performed with the deprotected polymers. The measured adhesion values determined via tensile tests increase with the amount of catechol introduced in the polymers and the highest adhesion values of 2.0 MPa for underwater adhesion were found for poly(phenethyl acrylamide co dopamine acrylamide) co-polymers.

Our colleagues Leitner Viktoria, Aufischer Gottfried, and Christian Paulik have published an article with the title `Agricultural residue lignin from novel low‑temperature pretreatment as potential raw material for LPF resins´ in Progress in Biomass Conversion and Biorefinery (https://doi.org/10.1007/s13399-023-04028-9, opens an external URL in a new window  Accepted: 02.03.2023)

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Abstract:

Appropriate digestate management is crucial for economic as well as ecologic optimization of biomethane production. Here, we present the production of a lignin-based phenol formaldehyde adhesive and its application to plywood from lignin separated after H3PO4 disintegration of digestate. Together with the work of Schroedter et al. (Microorganisms 9:1810, 2021), a full valorization of solid digestate is  demonstrated. The separated sulfur-free LXP-lignin had high purity of above 90% lignin with a carbohydrate content of < 3%, an ash content below 2%, and a molecular weight of 6163 Da. The depolymerizationof the LXP-lignin reduced the molecular weight to 3838 Da. The prepared lignin-based phenol formaldehyde resin has a viscosity of 350 mPa*s and a comparable tensile shear strength to the reference resin produced with the kraft lignin Indulin AT. Testing of nine-layer (500 × 500 mm) birch plywood panels showed promising results using standard resin recipes.

Our colleagues Lukas Göpperl, Daniel Pernusch, Julia Schwarz, and Christian Paulik have published an article with the title `Customizing the comonomer incorporation distribution in Ziegler–Natta-based LLDPE: Harnessing the influences of the titanation temperature during catalyst synthesis and of polymerization process parameters´ in Progress in the Canadian Journal of Chemical Engineering (DOI: 10.1002/cjce.24896 Accepted: 28.02.2023)

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Abstract:

The microstructure of linear low-density polyethylene (LLDPE) is strongly influenced by short-chain branches (SCBs) incorporated into the polymer backbone. Varying the number, distribution, and length of SCBs allows the properties of the resulting polymer to be tailored to meet specific requirements. Using Ziegler–Natta (ZN) catalysts for synthesis has disadvantages in terms of the comonomer
incorporation distribution (CID) compared to, for instance, metallocene and post–metallocene catalysts. Nevertheless, ZN catalysts continue to be widely used, as many of the new generations of catalysts are more difficult to handle and cannot match the cheap cost of ZN catalysts. To improve this aspect of ZN catalysts, we investigated the influence of catalyst titanation temperature and polymerization process parameters on the CID. Our results show that it is possible to manipulate the process parameters of the present ZN catalyst system to yield a desired comonomer amount and CID in the polymer. Varying the titanation temperature clearly influenced the titanium content of the catalyst. Molecular-weight distribution analysis and deconvolution results indicate that changes in the amounts of comonomer incorporated and in the CID are directly related to the catalyst’s active site that produces the lowest-molecular-weight fraction.

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.