Sustainable Chemistry for Climate Action最新文献

Hydrogen (H₂) usage was 90 tnes (Mt) in 2020, almost entirely for industrial and refining uses and generated almost completely from fossil fuels, leading to nearly 900 Mt of carbon dioxide emissions. However, there has been significant growth of H₂ in recent years. Electrolysers' total capacity, which are required to generate H₂ from electricity, has multiplied in the past years, reaching more than 300 MW through 2021. Approximately 350 projects reportedly under construction could push total capacity to 54 GW by the year 2030. Some other 40 projects totalling output of more than 35 GW are in the planning phase. If each of these projects is completed, global H₂ production from electrolysers could exceed 8 Mt by 2030. It's an opportunity to take advantage of H₂S prospects to be a crucial component of a clean, safe, and cost-effective sustainable future. This paper assesses the situation regarding H₂ at the moment and provides recommendations for its potential future advancement. The study reveals that clean H₂ is experiencing significant, unparalleled commercial and political force, with the amount of laws and projects all over the globe growing quickly. The paper concludes that in order to make H₂ more widely employed, it is crucial to significantly increase innovations and reduce costs. The practical and implementable suggestions provided to industries and governments will allow them to fully capitalise on this growing momentum.

With increasing environmental concerns due to the anthropologic emissions of greenhouse gasses, especially carbon dioxide (CO₂), the development of new technologies to capture the latter is of great public value. While amino-containing materials excel in capturing CO₂, they generally suffer from a few limitations, namely, the high energy penalty for desorption and the obstacle to directly convert CO₂ into valuable resources. In this context, molecular or polymeric compounds based on N-heterocyclic carbenes (NHCs) have emerged as versatile alternatives to efficiently sequester CO₂. NHCs are among the most investigated reactive species in chemistry: not only have they been intensively used as ligands for transition metal catalysts but also they exhibit a rich chemistry, either as true reagents or as organic catalysts. However, their air- and moisture-sensitivity represents a limitation to their use in synthesis. As reviewed thereafter, NHCs can selectively react with CO₂ forming stable adducts, in the form of zwitterionic betaine-type species, providing CO₂ directly-on-site for further fixation. Advances in the use of NHCs in this field are illustrated in this paper with a special emphasis on integration of NHCs in materials enabling heterogeneous utilizations in capture and catalysis.

The controversy about meeting the expected capture demands from carbon dioxide removals such as Direct Air Capture (DAC) are debatable. In the past, the vast investment in renewable technology is allowing today's rapid deployment. Why is this not currently happening in the CO₂ capture area? This bibliometric analysis which focused on the use of solid sorbents in the CO₂ capture field between 2001 and 2021, aims to answer these questions. The study reviewed three capture methods: post-combustion, pre-combustion and DAC, with particular emphasis on the latter. To understand the evolution of DAC, this novel approach highlights which authors and countries have been investigating the use of solid sorbents. The outcomes of this research showed that, during the first decade, there was a minor interest in funding and investigating solid sorbents for DAC solutions. It was only at the end of the second period when the use of these materials in the topic emerged to the surface. Acting as an example, the United States, China and the United Kingdom spent more financial help to investigate the use of sorbents. However, all of today's CO₂ capture plants are working for enhanced oil recovery. In the Republic of Ireland, there are a few articles exploring the use of these materials to uptake CO₂. It is possible that certain articles were not considered by the software. Upcoming analysis will answer this question and include all the existing materials in the wide spectrum of solid sorbents at the CO₂ capture field.

The conceptual design of a portable autonomous catalytic hydrogen generator is introduced. The generator is based on the bioethanol steam reforming over the developed ferrite catalyst. The generator admits the utilization of thermal energy of the reaction mixture for vaporization and heating the input water-alcohol mixture. Moreover, the generator is characterized by a simple single-stage design without a stage for hydrogen purification. The generator is capable to produce 1 kW/h of electricity with 0.63 kg/h water/alcohol mixture (50% ethanol) consumption. The energy conversion efficiency of the developed generator is 44%. The proposed hydrogen generator is suitable for various applications related to on-site hydrogen production.

Under the influence of human activities and the rapid development of industry and agriculture, atmospheric nitrate (NO⁻₃) pollution is becoming increasingly serious and has become an environmental problem worldwide. The stable isotopic composition of atmospheric NO⁻₃ (δ¹⁵N, δ¹⁸O, and Δ¹⁷O) can provide a strong basis for understanding the atmospheric nitrogen cycle to effectively control atmospheric NO_x pollution. In this work, the δ¹⁵N values associated with different sources of atmospheric NO⁻₃, the seasonal variation characteristics of δ¹⁵N-NO⁻₃, and the main influencing factors are reviewed. The δ¹⁸O and Δ¹⁷O values of different oxidants in the atmosphere and the spatiotemporal distribution characteristics and possible influencing factors of the δ¹⁸O and Δ¹⁷O values ​​of atmospheric NO⁻₃ are summarised. In addition, key advances in NO⁻₃ isotopic analysis technique is reviewed. Based on previous work, it is suggested that more attention should be given to the oxidative formation mechanism of NO⁻₃ (spatio-temporal differences in the isotopic compositions of different types of oxidants), the δ¹⁵N composition of different NOx sources, and the processes of formation, transport, depositional/chemical loss ofatmospheric NO⁻₃ with the help of observation and chemical models.

Conversion of CO₂ to valuable chemicals such as polymers via the electrochemical reduction of CO₂ to formate followed by the formate to oxalate coupling reaction (FOCR) is an interesting concept to replace fossil feedstocks with renewable ones. Yet, the activation of CO₂ is challenging and energy-intensive and today the production of one oxalate molecule first requires the reduction of two CO₂ molecules. Recently we confirmed the crucial role of the reactive carbonite intermediate in the FOCR. Due to its high reactivity, this intermediate might also be a strong enough nucleophile to react with CO₂ directly. If this is the case, we can form oxalate directly from CO₂ and formate and avoid the need for double electrochemical CO₂ reduction in oxalate production. In this work, we successfully established the conversion of CO₂ (with a theoretical yield of 52%) to oxalate (via the reaction with carbonite), as well as to formate and carbonate. The direct reaction of the reactive carbonite intermediate with CO₂ was the dominant pathway for CO₂ incorporation in oxalate. For enhancing the CO₂ incorporation in oxalate, we found a reaction temperature of 200°C, stoichiometric amounts of the base, and the presence of CO₂ in the supercritical state most suitable. The residence time is strongly depending on the reactor type but should be kept to a minimum to avoid carbonate formation. The presence of high amounts of hydride and supercritical CO₂ appeared to also cause the formation of carbonates as a side-product. The carbonate formation increased with higher temperatures and longer reaction times, which suggests a consecutive decomposition of oxalate formed in the reaction.

This paper discusses the status of the global fertilizer industry with a primary focus on Australian market. The conventional energy- and carbon-intensive ammonia production industry is taking serious steps in transforming to more environmentally benign pathways via utilizing ‘green’ hydrogen (hydrogen production via water electrolysis powered by renewable energy) feedstock into their production process and utilizing more of the CO₂ by-product into downstream processes such as urea production. However, it is very challenging for ammonia and other fertilizer production routes to use ‘green’ pathway to completely decarbonize agriculture and food industry. Here, we argue that urea synthesis can only be considered as a ‘green’ technology if ammonia feedstock is produced via a ‘green’ pathway and the CO₂ feedstock comes from non-fossil-fuel and carbon-neutral sources. Three possible resources for carbon-neutral CO₂ are identified and discussed within Australia's context: from biomass, renewable methane, and from direct air carbon capture (DAC). Each of these carbon-neutral CO₂ routes has many opportunities and challenges that may affect the cost of production, but the trajectory urea prices and growing market demand if supported by an adequate government regulatory framework would be able to make the ‘green’ urea production cost affordable. Achieving this goal however would require proper energy management systems to synchronize and optimize such a multi-player orientation for a common objective of maximizing the penetration of renewable sources at competitive costs. In this review, it is emphasized that this challenge could be addressed more effectively via a rigours intelligent energy network (IEN) by managing the dynamics of the supply and demand, integrating reliable storage systems, reclaiming the waste heat, and improving process efficiencies. Local ‘green’ urea production at competitive costs would help Australia realizing ambitions to become a leading green fertilizer and renewable energy exporter in the region.

In this work we have analyzed the synthesis of microporous materials using sucrose as carbon source and porous clay heterostructures as template to promote a hierarchical organization of pores, which is a novelty in the synthesis of carbonaceous materials. The study comprises the evaluation of the synthesis conditions such as the addition of a base (KOH) or the variation of the pyrolysis temperature (600, 750 and 900 °C). The studied materials were characterized via X ray diffraction, Transmission Electron Microscopy, gas adsorption, Attenuated Total Reflectance, Raman spectroscopy and X-ray Photoelectron Spectroscopy. Additionally, the performance of the synthesized adsorbents in terms of CO₂ uptake at three temperatures (0, 25 and 45 °C) was assessed and compared with similar materials reported in the literature. The results suggested by and large that the use of the base and the highest pyrolysis temperature (900 °C) during the synthesis enhances the CO₂ adsorption at the different evaluated temperatures. Nonetheless, it is at the lowest pyrolysis temperature i.e., 600 °C, where one can observe a more accentuated superior performance of the material synthesized with base than that obtained without the addition of KOH.

Carbon nanoparticles have demonstrated their potential to develop materials with advanced applications in which their luminescence and biocompatibility are exploited. In the search for sustainable methods to produce these nanoparticles, natural carbon sources such as plant- and animal-based products and by-products have been used. However, the existing procedures are still performed with high temperature, high pressure, and long reaction times. This report proposes a method to synthesize carbon nanoparticles using a tomato extract as the carbon source, followed by precipitation and calcination at a maximum of 60 °C under atmospheric pressure. This calcination temperature is the lowest reported and contributes to establishing a greener synthesis route. The detected fluorescence of these particles covers the entire region of the visible spectrum. The emission intensity is sensitive to zinc cations, demonstrating that this green method produces useful particles in detecting heavy metals similar to those reported by traditional methods. Furthermore, the aqueous solutions of these particles are photothermic when they are irradiated with red light, also showing their usefulness in biomedical developments. Therefore, this green synthesis at a very low temperature contributes to improving the green methods and boosts the sustainable development of advanced functional materials.

Background

In order to counteract the economic and environmental issues presented by Ionic Liquids (ILs) for carbon capture in post-combustion processes, Deep eutectic solvents (DESs) are being researched as potential absorbents. These are an emerging class of ILs that have a strong contribution from hydrogen bonding and have shown promising trends in CO₂ absorption in recent times.

Methods

In this study, three hydrogen bond acceptors (HBA), along with 2-hydroxypropanoic acid (Lactic Acid (LA)) as the hydrogen bond donor (HBD), have been identified and analyzed as CO₂ absorbents. Considering their structural properties, thermodynamic behavior, and experimental conditions as input parameters, a backpropagation neural network (BPNN) has been implemented to analyze and predict the extent of CO₂ solubility within each of the DES mixtures.

Significant Findings

BPNN successfully predicted trends in the solubility as a function of the alkyl chain length, temperature, and pressure. It was observed that the solubility of CO₂ increased with increasing alkyl chain length and pressure but decreased with increasing values of temperature. DES is found to be more economical than other ionic liquid solvents used for CO₂ absorption.