Sustainable production of chemical intermediates for nylon manufacture: A techno-economic analysis for renewable production of caprolactone

Oxime chemistry in crop protection

An overview is given on the significance of the oxime moiety in crop protection chemistry. This review focuses on the two most important aspects of agrochemical oximes, which are the occurrence and role of oxime groups in compounds with herbicidal, fungicidal and insecticidal activity, as well as the application of oxime derivatives as intermediates in the synthesis of crop protection agents not bearing any oxime function. Especially noteworthy is the fact, that in the synthesis of agrochemicals, oximes can be cyclized to isooxazoline, isoxazole, oxadiazole, oxazine, pyrrole, isothiazole and imidazole rings. © 2024 Society of Chemical Industry.

Lignocellulosic biorefineries: A multiscale approach for resource exploitation

Biomass can become the source for chemicals towards a sustainable production system. However, the challenges it presents such as the variety of species, their widespread and sparse availability, and the expensive transportation claims for an integrated approach to design the novel production system. Multiscale approaches have not been properly extended to biorefineryes design and deployment, due to the comprehensive experimental and modelling work they require. A systems perspective provides the systematic framework to analyze the availability and composition of raw materials across regions, how that affects process design, the portfolio of products that can be obtained by evaluating the strong link between the biomass features and the process design. The use of lignocellulosic materials requires for a multidisciplinary work, that must lead to new process engineers with technical competences in biology, biotechnology but also process engineering, mathematics, computer science and social sciences towards a sustainable process/chemical industry.

Polymers without Petrochemicals: Sustainable Routes to Conventional Monomers

Access to a wide range of plastic materials has been rationalized by the increased demand from growing populations and the development of high-throughput production systems. Plastic materials at low costs with reliable properties have been utilized in many everyday products. Multibillion-dollar companies are established around these plastic materials, and each polymer takes years to optimize, secure intellectual property, comply with the regulatory bodies such as the Registration, Evaluation, Authorisation and Restriction of Chemicals and the Environmental Protection Agency and develop consumer confidence. Therefore, developing a fully sustainable new plastic material with even a slightly different chemical structure is a costly and long process. Hence, the production of the common plastic materials with exactly the same chemical structures that does not require any new registration processes better reflects the reality of how to address the critical future of sustainable plastics. In this review, we have highlighted the very recent examples on the synthesis of common monomers using chemicals from sustainable feedstocks that can be used as a like-for-like substitute to prepare conventional petrochemical-free thermoplastics.

Catalysts as Key Enablers for the Synthesis of Bioplastics with Sophisticated Architectures

Bioplastics are one of the answers to environmental pollution and linear material flows. The most promising bioplastic polylactide (PLA) is already replacing conventional plastics in a number of applications. The properties of PLA, however, do not fit for all potential application areas, but they can be altered by the introduction of comonomers. The copolymerization of lactide (LA) with other lactones like ϵ-caprolactone (CL) has been established for several years. Nevertheless, controlling copolymerizations remains a challenge due to the high complexity of the system. Copolymerization of LA with other monomer classes is much less investigated, but has the chance to overcome the limitations in material properties that occur when only lactones are used. The crucial factor for all copolymerizations is the catalyst. It dominates the reaction kinetics and determines the resulting microstructure. In this review, copolymerization catalysts for LA are presented divided into catalysts for the synthesis of lactone block copolymers, lactone random copolymers, and multimechanistically synthesized copolymers. The selected catalysts are highlighted either owing to their industrially applicable polymerization conditions or their non-standard mechanism.

Extraction of Novel Effective Nanocomposite Photocatalyst from Corn Stalk for Water Photo Splitting under Visible Light Radiation

Novel (Ca, Mg)CO₃&SiO₂ NPs-decorated multilayer graphene sheets could be successfully prepared from corn stalk pith using a simple alkaline hydrothermal treatment process followed by calcination in an inert atmosphere. The produced nanocomposite was characterized by SEM, EDX, TEM, FTIR, and XRD analytical techniques, which confirm the formation of multilayer graphene sheets decorated by inorganic nanoparticles. The nanocomposite shows efficient activity as a photocatalyst for water-splitting reactions under visible light. The influence of preparation parameter variations, including the alkaline solution concentration, hydrothermal temperature, reaction time, and calcination temperature, on the hydrogen evolution rate was investigated by preparing many samples at different conditions. The experimental work indicated that treatment of the corn stalk pith hydrothermally by 1.0 M KOH solution at 170 °C for 3 h and calcinating the obtained solid at 600 °C results in the maximum hydrogen production rate. A value of 43.35 mmol H₂/gcat.min has been obtained associated with the energy-to-hydrogen conversion efficiency of 9%. Overall, this study opens a new avenue for extracting valuable nanocatalysts from biomass wastes to be exploited in hot applications such as hydrogen generation from water photo-splitting under visible light radiation.

Novel Challenges on the Catalytic Synthesis of 5-Hydroxymethylfurfural (HMF) from Real Feedstocks

The depletion of fossil resources makes the transition towards renewable ones more urgent. For this purpose, the synthesis of strategic platform-chemicals, such as 5-hydroxymethylfurfural (HMF), represents a fundamental challenge for the development of a feasible bio-refinery. HMF perfectly deals with this necessity, because it can be obtained from the hexose fraction of biomass. Thanks to its high reactivity, it can be exploited for the synthesis of renewable monomers, solvents, and bio-fuels. Sustainable HMF synthesis requires the use of waste biomasses, rather than model compounds such as monosaccharides or polysaccharides, making its production more economically advantageous from an industrial perspective. However, the production of HMF from real feedstocks generally suffers from scarce selectivity, due to their complex chemical composition and HMF instability. On this basis, different strategies have been adopted to maximize the HMF yield. Under this perspective, the properties of the catalytic system, as well as the choice of a suitable solvent and the addition of an eventual pretreatment of the biomass, represent key aspects of the optimization of HMF synthesis. On this basis, the present review summarizes and critically discusses the most recent and attractive strategies for HMF production from real feedstocks, focusing on the smartest catalytic systems and the overall sustainability of the adopted reaction conditions.

Master of Chaos and Order: Opposite Microstructures of PCL‐ co ‐PGA‐ co ‐PLA Accessible by a Single Catalyst**

One catalyst, two reaction set‐ups, three monomers and unlimited macromolecular microstructural designs: The iron guanidine complex [FeCl₂(TMG5NMe₂asme)] (1) polymerizes lactide faster than the industrially used Sn(Oct)₂ and shows high activity towards glycolide and ϵ‐caprolactone. Its distinguished features enable the synthesis of both block and random‐like copolymers in the melt by a simple change of the polymerization set‐up. Sequential addition of monomers yields highly ordered block copolymers including the symmetrical PLA‐b‐PGA‐b‐PCL‐b‐PGA‐b‐PLA pentablock copolymers, while polymerizations of monomer mixtures feature enhanced transesterifications and pave the way to di‐ and terpolymers with highly dispersed repeating unit distributions. A robust catalyst active under industrially applicable conditions and producing copolymers with desired microstructures is a major step towards biocompatible polymers with tailor‐made properties as alternatives for traditional plastics on the way towards a sustainable, circular material flow.

Experimental insights into catalytic oxidation of 1,6-hexanediol to ε-caprolactone over (p-cymene)RuCl2(L) complexes in non-polar media

The activity-pocket site dimension (θc) dependence of (p-cymene)RuCl2(L) supports associative interchange mechanism for 1,6-hexandiol oxidation to ε-caprolactone. Methyl isobutyl carbinol, a H-accepting product, reacts with Ru, causing deactivation.

Fractionation, characterization, and economic evaluation of alkali lignin from saw industry waste

The present work was focused on the investigation of lignin isolation from saw industry biomass (sawdust (SD)) using alkali solution, and to perform economic analysis for 2000 kg/batch hypothetical plant using techno-economic analysis. The isolated lignin was fractionated using organic solvent to obtain purified lignin. FTIR and ¹H NMR analysis were performed to examine the structural characteristics of lignin. Lignin nanoparticles (LN) showed higher total phenolic content (TPC) (244.1 ± 2 µg of GAE per mg) and antioxidant activity (63.2 ± 1.7%) compared with crude lignin (CL), ethanol fractionated lignin (EL), and acetone fractionated lignin (AL). SuperPro designer was exposed to design and simulated 2000 kg/batch of sawdust fractionation process. The techno-economic analysis estimated that the lignin production cost is about $ 487,000 per year, and the annual revenue could be $ 1,850,000 per year. The techno-economic analysis and sensitivity analysis could be useful for the industrial level sawdust fractionation process.

Climbing Ropes—Environmental Hotspots in Their Life Cycle and Potentials for Optimization

This paper examines the environmental impacts of climbing ropes using life cycle assessment (LCA). An online survey was conducted to evaluate users’ behaviour and the potential of an open loop recycling project for old ropes. The results of the LCA study show that the production of the base material, polyamide 6, has, at 50%, the highest impact on the total global warming potential of 46.6 kg CO2-eq. per climbing rope and on most of the other environmental issues. At present, there is no practical alternative for a base material. However, the survey indicated a high willingness of climbers to return their ropes for the purpose of recycling. If all old ropes stored at home or being used for non-climbing purposes in Switzerland were to be recycled, 1170 t CO2-eq. could be saved by substituting primary material and avoiding waste incineration.

Optimizing the linker length for fusing an alcohol dehydrogenase with a cyclohexanone monooxygenase

The use of enzymes in organic synthesis is highly appealing due their remarkably high chemo-, regio- and enantioselectivity. Nevertheless, for biosynthetic routes to be industrially useful, the enzymes must fulfill several requirements. Particularly, in case of cofactor-dependent enzymes self-sufficient systems are highly valuable. This can be achieved by fusing enzymes with complementary cofactor dependency. Such bifunctional enzymes are also relatively easy to handle, may enhance stability, and promote product intermediate channeling. However, usually the characteristics of the linker, fusing the target enzymes, are not thoroughly evaluated. A poor linker design can lead to detrimental effects on expression levels, enzyme stability and/or enzyme performance. In this chapter, the effect of the length of a glycine-rich linker was explored for the case study of ɛ-caprolactone synthesis through an alcohol dehydrogenase-cyclohexanone monooxygenase fusion system. The procedure includes cloning of linker variants, expression analysis, determination of thermostability and effect on activity and conversion levels of 15 variants of different linker sizes. The protocols can also be used for the creation of other protein-protein fusions.

Next Generation of Zinc Bisguanidine Polymerization Catalysts towards Highly Crystalline, Biodegradable Polyesters

Polylactide and polycaprolactone are both biodegradable polymers produced through metal-catalyzed ring-opening polymerization. For a truly sustainable lifecycle of these polymers it is essential to replace the industrially used cytotoxic catalyst tin(II) bis(2-ethylhexanoate) [Sn(Oct)₂ ] with non-toxic alternatives. Here, we report the fastest known robust catalyst in the polymerization of lactide and ϵ-caprolactone. This zinc guanidine catalyst can polymerize non-purified technical rac-lactide and ϵ-caprolactone in the melt at different [M]/[I] ratios with fast rate constants, high molar masses, and high yields in a short time, leading to colorless, transparent polymer. Moreover, we report that polylactide and polycaprolactone produced by zinc-guanidine complexes have favorably high crystallinities. In fact, the obtained polylactide shows a more robust degradation profile than its Sn(Oct)₂ -catalysed equivalent due to a higher degree of crystallinity.