Showing papers in "Green and Sustainable Chemistry in 2020"

Bio-based and biodegradable polymers - State-of-the-art, challenges and emerging trends

Abstract: Frontiers of bio-based and biodegradable polymers are constantly expanding in a view to achieve sustainability. Hence, designing sustainable bioplastics made of either bio-based or biodegradable polymers opens up opportunities to overcome resource depletion and plastic pollution. This review presents a broad perspective on state-of-the-art technologies in bioplastics manufacturing along with the challenges underlying their production, application and post-consumer waste management. Recent scientific advances are catalysing the sustainable design of bioplastics to overcome the present challenges of plastic waste and emerging end-of-life options are contributing to circular economy. As research insights into developing sustainable bioplastics are rapidly evolving, their production and waste management approaches are not limited to those discussed in this review.

Deep eutectic solvents and their applications as green solvents

Abstract: Several examples illustrate the effectiveness of using Deep Eutectic Solvents (DESs) as environmentally responsible reaction media in polar organometallic chemistry and in metal-catalysed and biocatalysed processes in place of conventional, often hazardous volatile organic compounds (VOCs). Apart from the standpoint of ‘greenness’, applications of DESs in the aforementioned fields also reveal novel aspects of reactivity of practical significance, which are worthy of an in-depth mechanistic understanding: (a) metal-mediated organic transformations can be run in DESs competitively with protonolysis, often at room temperature and under air, (b) metal-catalysed reactions proceed efficiently and under milder conditions in DESs than in VOCs, with the catalyst and DES being easily and successfully recycled and (c) biocatalysts often exhibit higher stability, selectivity and performances in DES mixtures than in aqueous solutions, as well as a somewhat intriguing stereoselectivity.

Atmospheric CO2 mitigation technologies: carbon capture utilization and storage

Abstract: Recently, the utilization of carbon dioxide has gained in consideration as it may contribute to improve the economics of CO2 capture process by producing added value goods and is now considered a valid alternative to geological CO2 storage. Nowadays, the scientific community considers the integrated carbon capture, utilization and storage an important mitigation technology that involves the carbon dioxide sequestration from fuel combustion or industrial processes, its transport (via ship or pipeline) and conversion into valuable products or its permanent storage deep underground in geological formations. Noteworthy, CCS is functional to a linear economy, whereas utilization of carbon dioxide is at the hearth of a circular economy and its strategic role will grow in the future. In this mini review, the current state of the art in the field of capture, disposal, and reuse of CO2 as technologies for its overall reduction in the atmosphere will be discussed.

Pyrometallurgical recycling of Li-ion, Ni–Cd and Ni–MH batteries: A minireview

Abstract: This brief article review discusses the available pyrometallurgical methods for recycling of rechargeable batteries including Li-ion, Ni–Cd and Ni–MH batteries. Owing to the exponentially growing interest for using portable electronic devices and vehicles, rechargeable batteries have attracted significant attention in recent years, resulting in an increasing demand for critical metals such as Li, Co, Ni, rare earth elements. Because most of the published review articles have been investigated the hydrometallurgical methods, in this minireview, the current status of battery recycling, pretreatment, and especially pyrometallurgical methods of recycling of the rechargeable batteries are summarized.

The rise of lignin biorefinery

Abstract: Lignocellulosic biomass, ranging from softwood to agriculture and forestry wastes, represents the most abundant resource for modern biorefinery. In the course of the last years, we have witnessed the rise of ‘reductive catalytic fractionation’ processes of lignocellulosics in which priority attention is given to lignin that is ‘first’ converted into aromatic feedstocks. This opinion outlines recent advances in the reductive valorization of lignocellulosic biomass via lignin-first biorefinery approach, with particular emphasis on the fundamental catalytic reactions involved in the extraction and depolymerization of lignin and in the stabilization of the obtained phenolic units. Finally, a brief overview on the further transformations of lignin-derived monolignols and phenolics into value-added chemicals, fuels, polymeric materials, and active pharmaceutical ingredients is presented.

From waste to feed: A review of recent knowledge on insects as producers of protein and fat for animal feeds

Abstract: The use of insect-derived products in animal feed is a field of growing interest. Applying the circular economy principle, insects efficiently bioconvert organic waste into new products enabling advantages and value at different steps: reduction of waste management costs (landfilling, anaerobic digestion, incineration), lower resource use than other protein and fat productions, and value gain from the sale of insect-derived. After introducing the potential use of insects to upgrade food waste for animal feed purposes and briefly discussing the feed sector and the regulations that govern and limit the insect mass production and uses, this review presents the latest and most interesting research (from 2019) on the use of insect as feed.

New frontiers in biocatalysis for sustainable synthesis

Abstract: Today enzymatic catalysis is widely used in the pharmaceutical industry and is expanding fast into the fine and specialty chemicals sector, driven by the need for evermore sustainable chemistry. This review highlights the increasing emphasis now placed on achieving better process performance metrics to reflect the demand for cost-effective and scalable processes, ready for direct implementation into industry. The review also highlights other developments at the frontiers of this field including flow chemistry and multi-step enzymatic reactions, which benefit sustainability.

Materials Acceleration Platforms: On the way to autonomous experimentation

Abstract: Materials Acceleration Platforms are an emerging paradigm to accelerate materials discovery as an effort to develop technology solutions that can help address or mitigate climate change concerns. These platforms combine artificial intelligence, robotic systems, and high-performance computing to achieve autonomous experimentation. Nevertheless, their development faces challenges to achieve full autonomy. In this work, we present state-of-the-art robotic platforms and machine learning approaches for autonomous experimentation, their integration, and applications, particularly in the field of materials for clean energy technologies. Later, we discuss the challenges and suggest improvements to be considered in the endeavor to accomplish autonomous experimentation.

Lignocellulosic biomass for bioethanol: Recent advances, technology trends, and barriers to industrial development

Abstract: Among the major challenges of the century, reducing the world's dependence on fossil fuels is the most important. In this context, several approaches have been considered, including the production of lignocellulosic ethanol or second-generation bioethanol. After this preprocessing, second-generation bioethanol is produced using a process involving four primary steps. Different processes of hydrolysis and fermentation are highlighted and then technology trends and barriers to industrial development are commented.

Characterization and evaluation of immobilized enzymes for applications in flow reactors

Abstract: Flow biocatalysis mainly exploit immobilized enzymes for continuous chemical manufacturing. In the last decade, the use of immobilized biocatalysts in flow is growing rapidly, yet the immobilization protocols need to be optimized. In this review, we have discussed the most fundamental aspects to be considered when designing immobilized enzymes for productive and stable operations in flow. Furthermore, we analyze the protein loading, the activity recovery, the space-time yield (STY), the specific productivity and the turnover number, as complementary metrics to assess the efficiency and longevity of immobilized enzymes integrated into flow reactors. The science of the immobilization implies the engineering of the surface–protein interface, the material features and the reactor design to achieve highly active and robust heterogeneous biocatalysts under continuous operations. Hence, we encourage the flow biocatalysis community to accompany those engineering efforts with accurate assessments of both activity and stability.

New synthetic approaches to biofuels from lignocellulosic biomass

Abstract: Lignocellulose from terrestrial plant biomass is abundant and contains polymeric carbohydrates and lignin; both recognized as attractive renewable feedstocks for energy, chemicals and materials as alternatives to fossils to meet the targets for future sustainable development. Liquid biofuels are particularly important renewable commodities because of the vast infrastructure already in place to use them, especially for transportation, and efficient synthetic approaches and viable commercial manufacture processes are under development for both drop-in fuels and new fuel compounds. This work surveys the recent trends in lignocellulosic biomass conversion into fuels, and highlights innovative synthetic approaches based on novel chemo- and bio-catalyst systems and process strategies using biomass-derived carbohydrates and technical lignin.

Heterogeneous catalysts for cyclic carbonate synthesis from carbon dioxide and epoxides

Abstract: This review surveys six classes of heterogeneous catalysts that have been used in the conversion of epoxides and CO2 into cyclic carbonates; metal organic frameworks; silica-based catalysts; organic polymer supports; metal oxides; zeolites and carbon-based catalysts. Many of these catalysts are extremely active in the ring-opening of terminal epoxides, require fairly mild conditions and can be made in a sustainable manner. Some catalytic systems however require toxic and hazardous chemicals in their synthesis, and many struggle to ring-open the more sterically demanding and hindered internal epoxides. This review covers the most recent heterogeneous catalysts reported in the literature not only from a catalytic efficiency perspective but also from a green chemistry and sustainable viewpoint.

Recent advances toward sustainable flow photochemistry

Abstract: Although flow photochemistry has significant potential in advancing sustainable processing, there are substantial hurdles to attaining this. Development in three key areas over the past 3 years are discussed here: 1) light source technology; 2) reactor design; and 3) process understanding and intensification. A small number of illustrative examples provide an insight on the benefits that can be accessed through advances in these areas. More in-depth knowledge and experimentation around wavelength dependence can enhance efficiency and selectivity in transformations. Reactors capable of handling solid–liquid reactions can allow reliable processing of metal-free and recyclable catalyst systems. Concentrating and accelerating transition-metal/photoredox coupling methodologies make these processes increasingly attractive. Continuation of these trends will undoubtedly lead to future large-scale applications, carried out in a sustainable manner.

Recent progress on electrochemical reduction of CO2 to methanol

Abstract: Methanol is a future energy carrier because of its high volume-specific energy density and a significant intermediate for many bulk chemicals. Electrochemical reduction is a promising method to fabricate methanol (CH3OH) from carbon dioxide (CO2) where electrocatalyst, reactor configuration, and electrode play an essential role. In this review, seven types of electrocatalysts, that is, metal alloys, metal oxides, metal chalcogenides and carbides, metal–organic complexes, metal–free pyridine and metal–organic framework–based electrocatalysts, as well as the effect of reactor configuration and electrode were comprehensively summarized. Finally, challenges and perspectives on developing electrocatalysts were highlighted.

Green chemicals from used cooking oils: Trends, challenges, and opportunities

Abstract: Food waste reduction is fundamental for sustainable development and pursuing this goal, recycling and the valorization of used cooking oil (UCO) can play a major contribution. Although it has been traditionally used for biofuel production, the oleochemical potential of UCOs is vast. UCOs can be used as feedstock for a large variety of value-added green chemicals including plasticizers, binders, epoxides, surfactants, lubricants, polymers, biomaterials, and different building blocks. Thus, UCO transformation into functional chemicals can bring long-term stability to the supply chain, avoiding the current dependence on commodity products. In this regard, this work describes some of the potential benefits of using UCOs as feedstock in oleochemical biorefineries. In addition, some of the most recent investigations on the valorization of UCOs other than biofuel are presented. Finally, major challenges and future directions are discussed.

The importance of pH in controlling the selectivity of the electrochemical CO2 reduction

Abstract: The CO2 electrochemical reduction reaction (CO2RR) is seen as a promising technology for converting waste CO2 into carbon-based chemicals using renewable electricity to drive the reaction. The technological viability of this process is contingent on reducing CO2 selectively into one product with high current densities. With this purpose, several groups are studding different materials as electrocatalysts to establish relationships between catalyst structure and its performance. Although the catalyst is crucial for the reaction, the reaction conditions such as electrolyte, CO2 pressure, and working potential also play an important role on the catalytic performance which needs to be understood to optimize the process. This work focusses on the effect that the working pH has on the selectivity of the CO2RR and discuss how the process can be optimized by controlling the concentration of protons near the interphase.

Nanomaterials and catalysis for green chemistry

Abstract: Recently, green chemistry for the development of sustainable production systems requires tremendous research efforts on the design of catalysts through resource-efficient ways. The improvement of their catalytic performances is a key goal in modern society. Several approaches using environmentally friendly chemicals and materials for less hazardous synthesis and catalysis were analyzed. In this review, we focus on the synthesis of nanomaterials and catalytic applications to reduce the environmental impact, especially, by reducing waste, solvents, precursors, and derivatives. In addition, we highlight the special efforts toward the use of renewable feedstocks and their applications as well as the synthetic routes to develop nanocatalysts using a greener chemistry.

Green synthesis of polymeric membranes: Recent advances and future prospects

Abstract: Polymeric membranes are widely used in gas separations, liquid separations, and other processes such as fuel cells. However, methods and processes for manufacturing these membranes are usually harmful to the environment and/or human health. Although many new materials and synthesis methods are reported every year, green synthesis only makes up a small proportion. Therefore, more efforts are necessary to raise researchers’ awareness to green synthesis of membranes. One popular strategy to greenly synthesize membranes is to avoid toxic organic solvents or use water to replace organic solvents completely. However, many reported green methods could only realize green synthesis partly. The ultimate goal is to synthesize membranes in a completely eco-friendly way, where raw materials, membrane preparation, post-treatment, and other involved procedures are all ‘green’.

Potential benefits of using Hermetia illucens frass as a soil amendment on food production and for environmental impact reduction

Abstract: Nutrients, water, and light are the basic ingredients for crops. However, soil and water resources are under intense pressure, as the world's population increases and adopts lifestyles using environmentally intensive food products affecting air, soil, and water quality. Supply of nitrogen (N) and phosphorous (P) fertilizer has large socioeconomic benefits and has become essential to raise crops and animals to feed an ever-increasing world population, but only a small fraction of these nutrients end up in human mouths. A large fraction of nutrients is lost to the surrounding environment or in the form of food waste. Frass produced by the larvae of Hermetia illucens has the potential to recapture N and P from the food chain for reuse as a fertilizer, reducing the need for chemical fertilizers. Furthermore, research is beginning to identify additional benefits from this frass, such as beneficial modification of soil microbiota and plant behavior. In addition to reviewing the current research on the effects of H. illucens frass, environmental impact analyses are summarized, and regulatory and knowledge challenges to the wide-scale adoption of frass are discussed.

Furfural and 5-(hydroxymethyl)furfural: Two pivotal intermediates for bio-based chemistry

Abstract: Research on furfural and 5-(hydroxymethyl)furfural (HMF) concerns all fields of chemistry: catalysis, mechanistic studies, synthetic organic chemistry, materials sciences, chemical engineering. The purpose of this account is, by picking a selection of very recent literature, to show the vitality of the field and to illustrate how transdisciplinar approaches can help overcoming the strong overlap between catalysts, solvent and process issues. It highlights the necessity to encourage researches in two main directions, one being the optimization of the access to industrially relevant targets, and the second being the commitment of synthetic organic chemist to explorative studies on new reactions and new architectures.

Recycling of carbon fiber reinforced composite waste to close their life cycle in a cradle-to-cradle approach

Abstract: Carbon fiber reinforced polymers (CFRPs), with a demand expected to reach 194 ktons by 2022 and a global market increase to $48.7 billion are increasingly popular materials because of their ability to conjugate superior mechanical resistance and lightness, thus allowing their widespread application ranging from aerospace and wind turbines to automotive and sporting goods. A foreseeable consequence is the growth of production scraps and end-of-life composites. Considering the still high cost of the virgin carbon fiber (CF) and a CF demand expected to reach 117 ktons by 2022 (average of 30 €/kg and energetic cost of 183–286 MJ/kg), this review outlines recent advances of the existing methods to recycle cumulative composite wastes, still with many unresolved problems and issues, with emphasis on CF recovery and understanding their retained properties. Finally, a brief overview on the companies that offer carbon fiber reinforced polymer recovery services with the aim of addressing the issue of end of life is presented.

Food waste and social acceptance of a circular bioeconomy: the role of stakeholders

Abstract: To be socially accepted widely, the emerging circular bioeconomy needs to rely increasingly on residual bio-based feedstock and waste, hence reducing its dependency on crops which are in competition with agriculture/food markets. Food waste represents a valuable option as it allows for the production of a wide range of bio-based products ranging from biofuels to bioplastics. First successful experiences have shown that the involvement of stakeholders with different behaviours, values and backgrounds is a key enabler of the process. In particular, it acts as a key precondition for an increase in the social acceptability of the facilities by informing citizens and civil society organizations and, at the same time, it improves the feedstosck availability by increasing coordination between actors dealing with waste management.

Strategies for polymer to polymer recycling from waste: Current trends and opportunities for improving the circular economy of polymers in South America

Abstract: Polymers are one of the most versatile materials because oftheir excellent cost to performance ratio and durability Thesereasons have driven the extensive usage of polymers in manycommon applications, and often, their lifespan exceeds theneeds of the application This generates streams of polymerwastes which retain a substantial amount of their originalproperties and, therefore, could be recycled Mechanical,chemical, and thermal recycling can be used for polymerrecycling, although in the latter case, the polymeric componentis lost by thermal degradation (energy recovery) This articlereviews the recycling strategies which allow producing newpolymeric materials from waste and the current researchtrends that could enable new opportunities for creating high-value polymeric products from what is now considered as waste

Current trends on turning biomass wastes into carbon materials for electrochemical sensing and rechargeable battery applications

Abstract: The need to both avoid waste and develop sustainable technologies based on new renewable resources, has led to an encouraging research opportunity, focusing attention on the relative merits of applying different dedicated waste biomass as renewable, cheap, and abundant resources to minimize energy and material feedstock costs Carbonaceous materials obtained from waste biomass have received comprehensive interest over the past years due to their attractive electronic and structural properties, which allow them as advanced materials for a wide variety of applications Here, we highlight the range of waste biomass precursors available and current trends on bio-carbon production for its use in electrochemical devices for sensing systems and rechargeable batteries, which are expected to have a rapid scientific growing and industrial interest in the next years

Design of supported metal catalysts modified with metal oxides for hydrodeoxygenation of biomass-related molecules

Abstract: Hydrodeoxygenation is one of the important catalytic reactions for the conversion of biomass-related substrates to value-added fuels and chemicals because the value-added products tend to have much lower oxygen contents than the substrates. The combination of noble metals with cations and/or oxides of oxophilic metal species has been frequently reported to be very effective catalysts in hydrodeoxygenation and C–O hydrogenolysis. The interaction between two components can be strongly dependent on the combination, the molar ratio, the support materials, and so on, which can be connected to high catalytic performance. The comparison of various catalysts can contribute to the future catalyst design.

Recent developments in key biorefinery areas

Abstract: To meet decarbonisation goals and implement a more sustainable circular economy model, the chemical industry needs to transition from fossil to renewable sources of carbon. Current chemical production is dominated by petroleum, where this broadly uniform feedstock is separated using a single, simple process to give a small range of heteroatom-free molecules that are the platform to a myriad of products. In a biorefinery, however, many feedstocks of widely varying composition using markedly different technologies are processed to give one or two of a wide range of bioderived platform molecules. Here, recent publications are used to highlight selection of the most suitable second or third generation feedstocks, converted using integrated, complementary processes to generate multiple products. This approach generates a range of chemicals, more fully using the carbon source of choice in a sustainable manner, generating more value, which together makes the realisation of the biorefinery concept draw ever closer.

Single-atom catalysis for a sustainable and greener future

Abstract: The fact that supported single metal atoms can do catalysis provides unparalleled opportunities to develop innovative technologies for a sustainable and greener chemical industry. Single-atom catalysts not only maximize the utilization efficiency of expensive metals of rare resources but also have a great potential to significantly improve selectivity of the targeted catalytic reactions and lower the operation cost. This short review highlights the recent progress of understanding the nature of single-atom catalysts and their applications with a focus on major challenges encountered in heterogeneous catalysis such as carbon dioxide conversion, production of hydrogen, ammonia synthesis, and methane valorization.

Biochar for electrochemical applications

Abstract: Carbon-rich biochar can be produced by pyrolysis of biomass. Depending on the precise production pathway, the surface chemistry and porosity can be tuned and made compatible for a defined application. This shear benefit has persuaded researcher to explore its suitability in various electrochemical applications related to energy storage and conversion. In this article, we succinctly discuss the potentials of biochar in electrocatalysis, fuel cell, supercapacitors, and rechargeable batteries. We have concluded this article with recommendations for future research.

Ionic liquid–based green processes for ammonia separation and recovery

Abstract: The emergence of ionic liquids (ILs) has provided a highly effective and energy-saving way for separation and recovery of NH3 owing to their remarkable advantages, such as very low volatility and structure designability. This review presents a comprehensive summary on the latest progresses of pure ILs, IL hybrid solvents, and IL composite materials for NH3 separation from the perspective of material design to process simulation, involving the role of anions, cations, and functional sites of ILs in NH3 separation performance of IL-based systems, the interaction mechanisms between ILs and NH3, as well as the simulation of IL-based NH3 separation process. Finally, the research challenges and perspectives of IL-based NH3 separation and recovery in future are discussed.

Cost-effective routes for catalytic biomass upgrading

Abstract: Catalytic hydrodeoxygenation (HDO) is a fundamental and promising route for bio-oil upgrading to produce petroleum-like hydrocarbon fuels or chemical building blocks. One of the main challenges of this technology is the demand of high-pressure H2, which poses high costs and safety concerns. Accordingly, developing cost-effective routes for biomass or bio-oil upgrading without the supply of commercial H2 is essential to implement the HDO at commercial scale. This paper critically reviewed the very recent studies relating to the novel strategies for upgrading the bio-feedstocks with ‘green’ H2 generated from renewable sources. More precisely, catalytic transfer hydrogenation/hydrogenolysis (CTH), combined reforming and HDO, combined metal hydrolysis and HDO, water-assisted in-situ HDO and non-thermal plasma (NTP) technology and self-supported hydrogenolysis (SSH) are reviewed herein. Current challenges and research trends of each strategy are also proposed aiming to motivate further improvement of these novel routes to become competitive alternatives to conventional HDO technology.