In this article, we review the recent progress that has been made in the field of Lewis-acid catalysis of carbon carbon-bond-forming reactions in aqueous solution. Since water hampers the hard hard interactions between the catalyst and the reactant, it often complicates catalysis. However, once coordination has taken place, water can have beneficial effects on rates and selectivities of Lewis acid catalysed Diels Alder reactions, aldol reactions, allylation reactions, Barbier and Mannich type reactions as well as Michael additions.
In mijn vorige blog schreef ik dat ik "groene chemie" niet zo'n goede term vind. Dit bericht borduurt daar enigszins op voort en is mijn persoonlijke kritische noot bij de transitie naar een groene(re) economie die momenteel in volle gang is.
Many origin of life theories argue that molecular self-organization explains the spontaneous emergence of structural and dynamical constraints. However, the preservation of these constraints over time is not well-explained because ofthe self-undermining and self-limiting nature of these same processes. A process called autogenesis has been proposed in which a synergetic coupling between self-organized processes preserves the constraints thereby accumulated. Thispaper presents a computer simulation of this process (the AutogenicAutomaton) and compares its behavior to the same self-organizing processes when uncoupled. We demonstrate that this coupling produces a second-order constraint that can both resist dissipation and become replicated in new substrates over time.
MULTIFILE
Paper sludge contains papermaking mineral additives and fibers, which could be reused or recycled, thus enhancing the circularity. One of the promising technologies is the fast pyrolysis of paper sludge, which is capable of recovering > 99 wt.% of the fine minerals in the paper sludge and also affording a bio-liquid. The fine minerals (e.g., ‘circular’ CaCO3) can be reused as filler in consumer products thereby reducing the required primary resources. However, the bio-liquid has a lower quality compared to fossil fuels, and only a limited application, e.g., for heat generation, has been applied. This could be significantly improved by catalytic upgrading of the fast pyrolysis vapor, known as an ex-situ catalytic pyrolysis approach. We have recently found that a high-quality bio-oil (mainly ‘bio-based’ paraffins and low-molecular-weight aromatics, carbon yield of 21%, and HHV of 41.1 MJ kg-1) was produced (Chem. Eng. J., 420 (2021), 129714). Nevertheless, catalyst deactivation occurred after a few hours’ of reaction. As such, catalyst stability and regenerability are of research interest and also of high relevance for industrial implementation. This project aims to study the potential of the add-on catalytic upgrading step to the industrial fast pyrolysis of paper sludge process. One important performance metric for sustainable catalysis in the industry is the level of catalyst consumption (kgcat tprod-1) for catalytic pyrolysis of paper sludge. Another important research topic is to establish the correlation between yield and selectivity of the bio-chemicals and the catalyst characteristics. For this, different types of catalysts (e.g., FCC-type E-Cat) will be tested and several reaction-regeneration cycles will be performed. These studies will determine under which conditions catalytic fast pyrolysis of paper sludge is technically and economically viable.
In the context of sustainability, the use of biocatalysis in organic synthesis is increasingly observed as an essential tool towards a modern and ‘green’ chemical industry. However, the lack of a diverse set of commercially available enzymes with a broad selectivity toward industrially-relevant substrates keeps hampering the widespread implementation of biocatalysis. Aminoverse B.V. aims to contribute to this challenge by developing enzymatic screening kits and identifying novel enzyme families with significant potential for biocatalysis. One of the most important, yet notoriously challenging reaction in organic synthesis is site-selective functionalization (e.g. hydroxylation) of inert C-H bonds. Interestingly, Fe(II)/α-ketoglutarate-dependent oxygenases (KGOs) have been found to perform C-H hydroxylation, as well as other oxyfunctionalization, spontaneously in nature. However, as KGOs are not commercially available, or even extensively studied in this context, their potential is not readily accessible to the chemical industry. This project aims to demonstrate the potential of KGOs in biocatalysis. In order to achieve this, the following challenges will be addressed: i) establishing an enzymatic screening methodology to study the activity and selectivity of recombinant KGOs towards industrially relevant substrates, ii) establishing analytical methods to characterize KGO-catalyzed substrate conversion and product formation. Eventually, the proof-of-principle demonstrated during this project will allow Aminoverse B.V. to develop a commercial biocatalysis kit comprised of KGO enzymes with a diverse activity profile, allowing their application in the sustainable production of either commodity, fine or speciality chemicals. The project consortium is composed of: i) Aminoverse B.V, a start-up company dedicated to facilitate chemical partners towards implementing biocatalysis in their chemical processes, and ii) Zuyd University, which will link Aminoverse B.V. with students and (bio)chemical professionals in creating a novel collaboration which will not only stimulate the development of (bio)chemical students, but also the translation of academic knowledge on KGOs towards a feasible biocatalytic application.
About 35-40 kton used mattresses available yearly for the recycling only in the Netherlands. Mattresses that are offered at recycling companies, municipal yards and retailers often find their way to incinerators. However, several fraction components of used mattresses can be reused/resale in a useful manner. One of the mattress fractions is textile cover with residue of Polyurethane (PU) foam. Effective removal of PU foam would enable further reuse of textile materials. Use of harsh chemicals/ thermo-, photo-, oxidative, processes including hydrolysis, aminolysis, phosphorolysis, glycolysis etc [1,2] for PU foam degradation is not a good solution, since it will cause non-specific damage to textiles and other parts, making recycle/ reuse difficult. Therefore, Mattress Recycling Europe BV (MRE) is looking for an eco-friendly mild process for selective degradation of PU foam component. PU is a mixed polymer; therefore, it is important to establish the physio-chemical nature of PU before identifying suitable and sustainable degradation route. The proposed solution is selective degradation of PU polymer using biotechnology. Enzymatic bio-catalysis enables a targeted, specific reaction at mild process conditions (pH, temperature) without harming other components in the process. Primarily hydrolase class of enzymes is assumed to be among the most effective options for the proposed degradation of PU foam residue [3,4]. From previous research, adding mechanical shear provides a synergistic effect for enzyme catalysed reaction [5-7]. Therefore, within the scope of this exploratory practice-oriented project, technical feasibility of bio-catalyst and shear (including well established PU degradation techniques) towards the selective degradation of PU foam residue attached to textile part from used mattresses will be explored together with cost estimation of the overall process and re-usability of enzymes using suitable immobilisation technique, addressing an urgent industrial need in the field of green chemistry.
