Sustainable Chemical Processes Research Articles

Multi-Stage Stochastic Programming Under Endogenous Uncertainty of Integrated Sustainable Chemical Process Design and Expansion Planning

Multi-Stage Stochastic Programming Under Endogenous Uncertainty of Integrated Sustainable Chemical Process Design and Expansion Planning

Photo-Induced Aerobic Oxidation of C–H Bonds

The photo-induced aerobic oxidation of C–H bonds has become an increasingly valuable strategy in organic synthesis, offering a green and efficient method for introducing oxygen into organic molecules. The utilization of molecular oxygen as an oxidant, coupled with visible-light photocatalysis, has gained significant attention due to its sustainability, atom economy, and environmentally benign nature. This review highlights the recent advancements in the field, focusing on the development of metal-free and transition-metal-based photocatalytic systems and novel photosensitizers capable of promoting selective C–H bond oxidation. The mechanistic pathways involved in various substrate oxidations, including benzylic, alkyl, alkene, and alkyne C–H bond transformations, are discussed. This review concludes with insights into the potential for integrating photocatalysis with renewable energy sources, positioning photo-induced aerobic oxidation as a cornerstone of sustainable chemical processes.

From waste to resource: Hydrogen generation and antimicrobial activity of Ag-based photocatalysts recovered from biomedical waste

Electrocardiogram (ECG) disposable electrodes contain a substantial amount of silver (Ag), which can be extracted and recycled. Most current methods for recovering Ag from waste are expensive and environmentally harmful. This study investigated a sustainable chemical process for extracting Ag from discarded medical electrodes using a simple Cu(II) solution under moderately acidic conditions. Using response surface methodology (RSM) based on a three-level, full-factorial design, the optimized extraction conditions were determined as pH = 4.78, T = 80°C, [Cu(II)]₀ = 8.0 × 10⁻³ M, and [NaCl]₀ = 3.72 M. Under these conditions, a process efficiency approaching 100 % was achieved. Moreover, the recovery of metallic silver exceeded 85 %, even when using real matrices. (i.e., discarded ECG electrodes). As a result, the Ag-containing leachate solutions were utilized to synthesize silver-based materials with varying Ag content. These materials demonstrated (i) excellent photocatalytic activity for hydrogen production in aqueous solutions containing organic compounds and (ii) significant antipathogenic properties. In summary, effective Ag/TiO₂ photocatalytic materials with high efficiency for hydrogen production and antimicrobial activity were successfully prepared through a novel, sustainable, and cost-effective chemical recovery process of silver from discarded ECG electrodes.

Based on magnetically recoverable catalysts: a green strategy to sulfonamides.

The synthesis of sulfonamides, a class of compounds with significant pharmaceutical and medicinal applications, has seen remarkable advancements with the advent of magnetic nanocatalysts. Magnetic nanocomposites are one of the most efficient and widely used catalysts, and they are in complete harmony with the principles of modern green chemistry from the point of view of catalysis. These catalysts, typically composed of metal complexes supported on magnetic nanoparticles, offer unique advantages such as ease of recovery and reusability, which are crucial for sustainable and eco-friendly chemical processes. This review comprehensively examines recent developments in applying magnetic nanocatalysts to prepare sulfonamides. Key focus areas include the design and synthesis of various magnetic nanocatalysts (MNC), their catalytic performance in different reaction conditions, and mechanistic insights into their catalytic activity. By summarizing the latest research and technological advancements, this article aims to provide a valuable resource for researchers and practitioners in catalysis and pharmaceutical chemistry.

Mechanistic Insights on Coverage-Dependent Selectivity Limitations in Vinyl Acetate Synthesis.

Developing improved catalysts for sustainable chemical processes often involves understanding atomistic origins of catalytic activity, selectivity, and stability. Using density functional theory and steady-state kinetic analyses, we probe the elementary steps that form decomposition products that limit selectivity in vinyl acetate (VA) synthesis on Pd surfaces covered with acetate species. Acetate formation and coupling with ethylene control the VA formation catalytic cycle and steady-state coverage, but acetate and ethylene can separately decompose to form CO2. Both decompositions involve initial C-H activations at acetate vacancies, followed by additional C-H activations and eventual C-O formations and C-C cleavages involving reactions with molecular oxygen. Acetate decomposition paths with non-oxidative kinetically-relevant steps exhibit similar free energy barriers to oxidative paths. In contrast, the non-oxidative ethylene path involving an ethylidyne intermediate exhibits a much lower barrier than paths with oxidative kinetically-relevant steps. Ethylene decomposition is very facile at low coverages but is more coverage-sensitive, leading to similar decomposition and VA formation barriers at coverages accessible at steady state, which is consistent with moderate VA selectivity in measurements and ethylene vs. acetate decomposition contributions assessed from regressed kinetic parameters. These insights provide a detailed framework for describing VA synthesis rates and selectivity on metallic catalyst surfaces.

Constructing Organic-Inorganic Woven Hybrid Membrane for Highly-Selective Catalytic Conversion of Lignin-based Phenolic Molecule to Value-added Products

Addressing the global need for sustainable chemical processes, this study introduces an innovative Woven Hybrid Membrane (WHM) specifically designed for the efficient oxidation of vanillyl alcohol (VAA) to vanillin (VLN). This transformation is crucial for converting lignocellulosic biomass into valuable chemical products, aligning with sustainable development goals. Utilizing a novel catalytic system that combines 2,2,6,6-tetramethylpiperidine 1-oxyl (TMP) and copper on a unique mesh-like structure, the WHM enhances both the economic and environmental viability of the process. This design not only overcomes the limitations of powdered catalysts, which are challenging to recover and reuse, but also promotes high catalytic efficiency and selectivity. By employing oxygen as the oxidant, our system maintains near 100% selectivity for VLN, demonstrating high conversion rates across multiple cycles without significant degradation in performance. Advanced analytical techniques, including electrochemical analysis and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), were used to explore the catalyst’s functionality and the reaction mechanism. The results confirm the stability and effectiveness of the WHM, showcasing its potential as a reusable, highly efficient, and environmentally friendly catalyst. This research represents a significant step forward in the field of sustainable industrial chemistry, offering a robust solution for the bio-refinery industry's push towards greener processes.

Selective Photocatalytic Benzene Oxidation Using Iron‐Carbon Nitride Fragments Functionalized with Cyamelurate‐Like Groups

Carbon nitrides have emerged as promising supports for catalytically active metals in various chemical reactions. Among these, the selective oxidation of benzene to phenol stands out as particularly challenging within the chemical industry due to its traditionally low yields and complex reaction pathways. In our current investigation, we have focused on the synthesis of ionic carbon nitride fragments via a straightforward alkaline hydrolysis method. These fragments demonstrate a remarkable ability to stabilize iron cations within the carbon nitride structure (Frag‐Fe), resulting in a highly efficient photocatalyst for benzene oxidation. Employing hydrogen peroxide as the oxidant in a single‐step reaction, we achieved an impressive 47% yield of phenol using Frag‐Fe at 12 hours, with negligible production of CO2 as a byproduct. This compelling outcome underscores the effectiveness of our alkaline synthesis approach in generating carbon nitride‐based photocatalysts with exceptional activity for C‐H oxidation reactions. Our findings not only contribute to the advancement of carbon nitride‐based catalysis, but also hold significant promise for the development of more sustainable and efficient chemical processes in the future.

3D Hierarchical Composites of Hydrotalcite-Coated Carbon Microspheres as Catalysts in Baeyer–Villiger Oxidation Reactions

The use of heterogeneous catalysts is fundamental in the search for sustainable chemical processes. Research on hierarchical materials is a growing field aimed at optimizing the synthesis of catalysts. In this work, layered materials with metals of different cationic ratios and three-dimensional hierarchical structures have been synthesized in a simple and easy way using carbon spheres as support. All materials were characterized with various techniques such as XRF, elemental analysis XRD, FT-IR, SEM, and TEM to study their composition and structure. Finally, these materials were used in the Baeyer–Villiger reaction, which was carried out under optimized conditions. The results showed that the metal ratio was an important factor in the coating process, affecting the catalytic capacity of the materials.

Advancements in Green Chemical Engineering: Developing Sustainable Catalysts for Carbon Capture and Utilization

The development of sustainable catalysts for carbon capture and utilization (CCU) represents a pivotal advancement in green chemical engineering, addressing both climate change and resource scarcity. This study utilizes a qualitative approach, specifically employing literature review and library research methods, to analyze recent advancements in catalyst development for CCU technologies. The analysis highlights the growing emphasis on designing catalysts that are not only efficient but also eco-friendly, with a focus on minimizing environmental impact. By examining various catalytic processes, including chemical absorption, photocatalysis, and electrochemical reduction, this research identifies key strategies for enhancing the effectiveness and sustainability of CCU systems. The findings reveal that while significant progress has been made in improving catalyst performance, challenges remain in scaling up these technologies for industrial applications. Moreover, this study underscores the role of green chemical engineering in fostering a circular economy by converting captured carbon dioxide into valuable products such as fuels and chemicals. Future research should focus on overcoming existing limitations, including catalyst stability and cost-effectiveness, to ensure broader adoption of sustainable CCU technologies. This review contributes to the growing body of knowledge on sustainable chemical processes and offers a roadmap for advancing green engineering practices.

Green Chemistry and Responsible Research and Innovation: Moving Beyond the 12 Principles

Green chemistry focuses on designing products and processes that minimize hazardous substances and address pollution, resource depletion, and climate change. Green chemistry products and processes could contribute to the transition to circular economy and reaching Sustainable Development Goals. However, green chemistry philosophy offers none or little guidance on social, ethical, economic, or political aspects that are inherent to complex transition processes. Such broad and future-oriented considerations are at the heart of ‘Responsible Research and Innovation’ (RRI) approach but to date the ideas of RRI and green chemistry remain largely unconnected. This study aims to shed light on how RRI and green chemistry approaches can be combined. A refined responsible roadmapping method is proposed to help researchers to go beyond the 12 principles of green chemistry and develop inter- and transdisciplinary research agendas that address technical, environmental as well as social, ethical, economic and political considerations. The method was piloted in three research projects aspiring to develop sustainable and safe chemical processes and their applications. The study demonstrates that at the early stage of research planning, the responsible roadmapping method can facilitate the integration of RRI and green chemistry practices and the development of interdisciplinary research plans, which address technical, environmental, socio-ethical, economic and political dimensions. The implications of our study for future research on roadmapping methods as well as for policy and innovation practice are discussed.

Tailoring of Zinc Oxide-based microstructures to efficiently promote piezocatalytic water oxidation and oxygen production

Two zinc oxide (ZnO) nanomaterials, exhibiting distinct morphologies, were synthesized in wurtzite phase through chemical precipitation. The elongated shape rod-like ZnO (R-ZnO) exhibited more pronounced piezoelectric characteristics compared to the more compact flower-like ZnO (F-ZnO). Detailed characterization including piezoforce microscopy, finite element simulation, revealed that the remarkable piezoelectric properties of R-ZnO are due to its strongly anisotropic structure, enabling significant mechanical deformation under ultrasound in aqueous suspension. The piezocatalytical degradation of these materials was assessed using methylene blue as a test organic dye across various ultrasound frequencies, with R-ZnO consistently outperforming F-ZnO. This highlighted the impact of structural deformability on piezocatalytic efficiency. Additionally, the capability of R-ZnO to facilitate oxygen evolution from water through ultrasound-induced stress was explored in an oxygen-free environment. Our findings demonstrate that R-ZnO can effectively catalyze water oxidation and produce oxygen directly, showcasing its potential as a standalone catalyst for environmental remediation and sustainable chemical processes.

The interface between research funding and environmental policies in an emergent economy using neural topic modeling: Proposals for a research agenda

AbstractResearchers have been calling for further analysis of the relationships between academia and policy making. Since several studies are conducted with resources from public funding agencies, it is essential to assess whether governments have been supporting research that can contribute to future environmental policies and whether research has been supporting the elaboration of public policies. To fill these gaps, the objective of this study was to evaluate the similarities and gaps between research and environmental policies. A bibliometric analysis of studies funded by Chilean agencies and text analytics techniques were employed to analyze research and environmental policies. We used BERTopic, a topic modeling technique that generates coherent topic representations. Then, topics obtained from the two sets of documents (research and policies) were compared. This study found that sustainability, life‐cycle assessment, climate change, and ecosystem services are central research themes in the country. The topic modeling analysis showed that research has been concentrated on the areas of “Sustainable Fisheries and Aquaculture Management” and “Sustainable Bioenergy Production and Chemical Processes.” The topics most frequently present in the environmental policies were “Environmental Education for Children: Awareness and Care,” “Bird Conservation and Habitat Importance in Chile,” and “National Biodiversity Conservation and Sustainable Use Strategy.” The greatest gaps are observed in the clusters of “Sustainable Bioenergy Production and Chemical Processes” and “Copper Mining and Mineral Processing Techniques” (prevalent in research) and in “Anatomy and Physiology of Aquatic and Terrestrial Organisms” and “Biogeography and Taxonomy of Southern Hemisphere Insects” (prevalent in policy).

H2-driven biocatalysis for flavin-dependent ene-reduction in a continuous closed-loop flow system utilizing H2 from water electrolysis

Despite the increasing demand for efficient and sustainable chemical processes, the development of scalable systems using biocatalysis for fine chemical production remains a significant challenge. We have developed a scalable flow system using immobilized enzymes to facilitate flavin-dependent biocatalysis, targeting as a proof-of-concept asymmetric alkene reduction. The system integrates a flavin-dependent Old Yellow Enzyme (OYE) and a soluble hydrogenase to enable H2-driven regeneration of the OYE cofactor FMNH2. Molecular hydrogen was produced by water electrolysis using a proton exchange membrane (PEM) electrolyzer and introduced into the flow system via a designed gas membrane addition module at a high diffusion rate. The flow system shows remarkable stability and reusability, consistently achieving >99% conversion of ketoisophorone to levodione. It also demonstrates versatility and selectivity in reducing various cyclic enones and can be extended to further flavin-based biocatalytic approaches and gas-dependent reactions. This electro-driven continuous flow system, therefore, has significant potential for advancing sustainable processes in fine chemical synthesis.

Experimental Verification of Low-Pressure Kinetics Model for Direct Synthesis of Dimethyl Carbonate Over CeO2 Catalyst

AbstractDimethyl carbonate (DMC) has emerged as a promising candidate for sustainable chemical processes due to its remarkable versatility and low toxicity. From a green chemistry perspective, the direct synthesis of DMC has been considered the most promising route, as water is the only byproduct generated in the reaction between CO2 and methanol. However, this synthetic route has faced significant thermodynamic limitations, even at elevated pressure conditions. Therefore, a two-part study explored low-pressure synthesis of DMC via the direct route, and a low-pressure kinetic model for the CeO2 catalyst was developed based on the results. Proposed Langmuir–Hinshelwood mechanisms were verified using experimental data generated in our labs. The investigation suggests that DMC formation in the direct synthetic route is a surface reaction of CO2 and methanol on the catalyst. The kinetic model predictions closely aligned with experimental data, demonstrating a 17% mean absolute percentage error and indicating a high level of predictability. Additionally, a rigorous assessment was conducted on CO2 fixations in DMC synthesis, quantifying CO2 capture and its conversion into stable or high-value products, formally designated as CO2 Fixation (CO2Fix). The CO2Fix analysis revealed that, at a conversion rate of 27%, the process can achieve a "net zero" state when operated at an approximate pressure of 30 bar, thereby supporting the viability of low-pressure synthesis. Increasing the conversion rate to levels exceeding 95% significantly enhances the CO2Fix metric, potentially surpassing 3.5 or higher.

Immobilized proline-based electro-organocatalyst for the synthesis of bis-β-diketone via Knoevenagel condensation reaction

In the quest for more sustainable chemical processes, we devised a technique using electro-organocatalysis to synthesize bis-β-diketone compounds via Knoevenagel condensation of benzaldehyde and dimedone. Our approach involves a modified electrode fabricated via anchoring L-proline onto a carbon fiber paper electrode supported by poly-3,4-diaminobenzoic acid (PDABA), which enhances efficiency in addition to the simple catalyst separation from the reaction mixture in heterogeneous catalysis. The electrochemical and surface topographical studies for the fabricated electrode were carried out, revealing high efficiency in comparison to the bare carbon fiber paper electrode. This electrochemical reaction operates under mild conditions utilizing lithium perchlorate and acetonitrile, yielding high amounts of the desired product. This study showcases a promising pathway for producing valuable organic compounds in an environmentally friendly manner, marking a significant stride forward in sustainable synthesis practices.

Efficient synthesis of lactic acid from cellulose through the synergistic effect of zinc chloride hydrate and metal salts

The chemocatalystic conversion of cellulose, the main component of lignocellulosic biomass, to building-block chemicals in water under mild conditions, is an ideal but highly challenging process due to the robust crystal structure of cellulose. It is also the key to establishing a sustainable biomass-based chemical process. Here, we present a highly efficient and selective chemocatalytic hydrolysis of cellulose using ZnCl2·3H2O hydrate as the pretreatment reagent and water-compatible metal salts - ErCl3 as the catalyst, into lactic acid (LA), which is an important chemical building-block widely utilized in the food industry and in the production of chemicals and biodegradable plastic. With 94.0 % conversion of cellulose, an impressive LA yield of 84.6 % was achieved at 170 °C after 4 h under ambient air pressure in water. High yields of LA were also obtained from other carbohydrates, such as fructose (68.3 %), glucose (52.7 %), starch (54.4 %), and inulin (67 %). A series of experiments demonstrated that Er(III) combination with water catalyzed cascading steps of soluble cellulose into LA after ZnCl2·3H2O hydrate disrupted the hydrogen bonds in the cellulose, Zn(II) played an indirect role by promoting LA formation through inhibition of side reactions. A plausible mechanism was proposed for the chemocatalytic conversion of cellulose to LA.

Introduction, Types, Properties, and Applications of Switchable Solvents: A Review

AbstractSwitchable solvents (SS) are a class of liquids with the unique ability to significantly alter their physical properties in response to external stimuli such as changes in temperature or the introduction or removal of CO2 gas. This reversible behaviour allows them to return to their original state with minimal changes, making them highly advantageous for various applications. A notable example of a switchable solvent is waste carbon dioxide gas, which is non‐toxic, non‐flammable, and cost‐effective. The versatility of switchable solvents extends to their polarity and physical states, which can be modified through molecular adjustments, opening new pathways for research and industrial applications. This review provides a comprehensive overview of switchable solvents, including their classification, history, properties, and applications, with a particular focus on their role in green chemistry. The types of switchable solvents discussed include Switchable‐Polarity Solvents (SPS), Switchable‐Hydrophilicity Solvents (SHS), and Switchable Water. Each type is examined in terms of synthesis, chemical properties, and development. The desirable properties of switchable solvents, such as their efficiency and recyclability, make them suitable alternatives to traditional solvents in various fields. Their applications range from water treatment and oil extraction to cleaning solid particles and recovering residual motor oil. Additionally, switchable solvents have proven effective as reaction media and in recovering polystyrene from foam. This paper also highlights the environmental benefits of switchable solvents, emphasizing their role in reducing the ecological impact of chemical processes. The potential for future developments in this field is significant, with ongoing research aimed at enhancing their performance and expanding their applications. By providing a detailed analysis of switchable solvents, this review aims to support researchers and industry professionals in developing more sustainable and efficient chemical processes.

Graphene-based Nanomaterials Ascatalysts for the Synthesis of Medicinally Privileged Heterocycles: Importance and Outlook

<p>Catalysis is an integral part of sustainable and green chemical processes. During the last two decades, the wonder 2D carbon material with honeycomb structure, graphene, and other functionalized graphenes have emerged as extremely versatile and robust nanomaterials in heterogeneous catalysis. The incredible catalytic efficacy of such carbon nanomaterials relies on their unique physicochemical properties, including large surface area, diverse catalytic active sites, multiple chemical functionalities, tunable electron density, synergistic effect, etc., making them noteworthy as metal-free catalysts and catalytic supports. </p><p> The article presents an overview of the catalytic applications of various graphene-based nanomaterials (GBNs), either metal-free or embedded with metal/metal oxide NPs, in synthesizing medicinally privileged heterocyclic compounds. It also summarizes the general methodologies for preparing graphene and various GBNs, their chemical structures, characterization techniques, and discussions on the potential active sites that are responsible for wider catalytic activity. Overall discussions unequivocally establish a promising paradigm for uncovering more innovative graphene-based materials and their subsequent applications in diverse fields, including heterogeneous catalysis.</p>

A Radical Revolution in the 21st Century

AbstractThis Special Collection on “Radical Chemistry in Homogeneous Catalysis and Organic Synthesis” organized in collaboration with the European Journal of Organic Chemistry and ChemCatChem showcases the maturity of field. Overall, this Special Collection encompasses 11 reviews and 27 research articles, covering a diverse range of topics. It presents the latest advancements in the controlled generation of radical species using transition metal catalysis, photoredox catalysis, or electrochemistry. It highlights the importance of moving towards more sustainable chemical processes, with particular focus on the development of novel organo(photo)catalysts, or efficient catalyst‐free reactions. It presents new transformations to access complex scaffolds as well as new building blocks and reagents, further simplifying single‐electron disconnection logic. In addition, it also highlights the key advancements in addressing some of the current challenges in radical chemistry, such the development of enantioselective reactions or how to scale‐up radical processes to meet the needs of the fine chemical industry.

Understanding the Effects of Forced and Bubble-Induced Convection in Transport-Limited Organic Electrosynthesis

Organic electrosynthesis offers a sustainable path to decarbonize the chemical industry by integrating renewable energy in chemical manufacturing. However, achieving the selectivity and energy efficiency required for industrial applications is challenging due to the inherent mass transport limitations of most electro-organic reactions. Electrochemical reactions rely on transport of reactants to the electrode surface and become mass transport-limited when the reactant diffusion rate is lower than the reaction rate at the electrode. In organic electrosynthesis with several possible products, mass transport limitations can result in decreased selectivity towards the desired product as the various reaction pathways compete. Convection can mitigate mass transport limitations, but fundamental engineering guidelines for selecting and scaling up convection methods in electrochemical systems do not exist. As a result, the impact of convection on industrial-scale complex organic electrochemical processes remain poorly understood. Here we show that the Sherwood number (Sh)—the ratio of convective mass transport to diffusive mass transport—is a crucial metric to characterize mass transport, determine reactor performance, and enable effective scale-up. We investigate the interplay between mass transport and electrochemical reaction rates under convective flows in the context of the electrosynthesis of adiponitrile, one of the largest organic electrochemical processes in the industry. We use experiments and data-driven predictive models to demonstrate that forced liquid convection and bubble-induced convection produce nearly equivalent mass transport conditions when the corresponding Sherwood numbers are equal. This conclusion shows that the Sherwood number characterizes the mass transport condition independent of the underlying convection mechanism. Additionally, we show that the reactor performance scales with the Sherwood number for a given current density and reactant concentration. This scaling enables accurate prediction of performance irrespective of the convection method, and demonstrates that adiponitrile Faradaic efficiencies of >80% can be achieved for current densities of up to 200 mA/cm2 when Sh > 100. Our results provide guidelines for the design and selection of convection methods, from lab to industrial scale, and contribute to the development of more sustainable chemical manufacturing processes.