Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences最新文献

The overarching purpose of carbon accounting is to reduce carbon emissions to meet net-zero targets and minimize the impact of climate change. However, the plethora of methods and approaches used means that products and systems sometimes cannot easily be compared. The mix of regional and life cycle-based systems can mean that we lack global oversight of our emissions and impact. In some situations where a regional approach is used, industry/business/regions are incentivized to reduce their own/territorial emissions, which can mean that an optimal global solution is not adopted. Countries where grid emissions are higher can be selected for production because it reduces regional (not global) carbon levels. Furthermore, these can be areas where the climate impact may be felt the most: not the just transition we aspire to. Our work provides an analysis of the current system together with its challenges and limitations, paving the way towards a more unified framework to create climate justice together with transparent and comparable accounting methodology for industry and regions alike. This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

Our industry today is predominantly based on linear value chains. Raw materials are extracted from primary sources, processed into products, used, and disposed of at the end of their life cycle. This linear economy causes a wide range of negative environmental impacts owing to the resulting greenhouse gas emissions and pollution of marine and terrestrial ecosystems. Closed carbon cycles and climate-neutral energy production are essential for the production not only of fuels but also of all chemicals, including plastics and fertilizers, to counteract climate change and further damage to the environment. In this regard, this article discusses the importance of heterogeneous catalysts for selected technologies associated with this transformation of the resource base and energy supply. It discusses the technological framework conditions of a net CO₂-neutral industry, with a focus on electrocatalytic water-splitting for hydrogen production, as well as the catalytic challenges of production of chemicals for the whole value chain using biomass, CO₂ and plastic waste as raw materials. This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

Replacing petrochemicals with refined waste biomass as a sustainable chemical source has become an attractive option to lower global carbon emissions. Popular methods of refining lignocellulosic waste biomass use thermochemical processes, which have significant environmental downsides. Using electrochemistry instead would overcome many of these downsides, directly driving chemical reactions with renewable electricity and revolutionizing the way many chemicals are produced today. This review mainly focuses on two furanic platform chemicals that are produced from the dehydration of cellulose, 5-hydroxymethylfurfural and furfural, which can be electrochemically reduced or oxidized to replace fuels and monomers that today are obtained from petrochemicals. Critical parameters such as electrode materials and electrolyte pH are discussed in relation to their influence on conversion efficiency and product distribution.This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

Hydrogen as energy vector from renewable sources and carbon dioxide as carbon source are central elements of a future sustainable interface between energy and chemistry. While often viewed merely as "substitutes" for fossil resources, the current article discusses opportunities to open new synthetic pathways and to generate novel molecular architectures for the delivery of the same or even improved functionalities expected from chemical products. Catalysis is the key science and technology in this endeavour and three general principles for the desing of catalytic systems are proposed as guidelines for fundamental research. This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

Sustainable methanol formation from CO₂/H₂ is potentially a key process in the post-fossil chemical industry. In this study, Hf- and Zr-based metal-organic framework (MOF) materials with UiO-67 topology, functionalized with Pt nanoparticles, have been tested for CO₂ hydrogenation at 30 bar and 170-240°C. The highest methanol formation rate, 14 mol_methanol mol_Pt^-1 h^-1, was obtained over a Hf-based catalyst, compared with the maximum of 6.2 mol_methanol mol_Pt^-1 h^-1 for the best Zr-based analogue. However, changing the node metal did not significantly affect product distribution or apparent activation energy for methanol formation (44-52 kJ mol^-1), strongly indicating that the higher activity of the Hf-based analogues is associated with a higher number of active sites. Both catalysts showed stable catalytic performance during testing under kinetic conditions, but the addition of 2 vol% water to the feed induced catalyst deactivation, in particular the Hf-MOFs. Interestingly, mainly methanol and methane formation rates decreased, while CO formation rates were less affected by deactivation. No direct correlation was found between catalytic stability and framework stability (crystallinity, specific surface area). Experimental and computational studies suggest that water adsorption strength to the MOF node may affect the relative catalytic stability of Hf-UiO-67-Pt versus Zr-UiO-67-Pt methanol catalysts.This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

In this article, we report the modification and photocatalytic evaluation of commercial TiO₂-P25 under visible light for methyl orange (MO) dye degradation under visible light. The activity of materials doped with N, Pd, Pt and Au on to the TiO₂-P25 was evaluated, with optimal photocatalytic performance achieved using Au nanoparticles doped on an N-functionalized titania surface. X-ray diffraction (XRD), physical nitrogen adsorption/desorption isotherm curves, transmission electron microscopy (TEM), diffuse reflectance spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to study the structural and textural properties of the samples. The chemical species present in the bulk and surface of the catalysts were identified using X-ray photoelectron spectroscopy (XPS) and microwave plasma-atomic emission spectroscopy. The results show that Au/N-TiO₂ photocatalyst presents a remarkable enhanced activity for MO dye degradation, under visible light illumination, reaching 100% after 4 h. The enhanced photocatalytic activity using this composite is attributable to the well-dispersed and small size of Au nanoparticles, large surface area, reduction of band-gap energy and the interaction between nitrogen and Au which promoted a synergistic effect. This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

The electrochemical reduction of CO₂ is a promising pathway for converting CO₂ into valuable fuels and chemicals. The local environment at the cathode of CO₂ electrolyzers plays a key role in determining activity and selectivity, but currently some mechanisms are still under debate. In particular, alkali metal cations have been shown to enhance the selectivity of metal catalysts, but their role remains less explored for molecular catalysts especially in high-current electrolyzers. Here, we investigated the enhancement effects of cations (Na⁺, K⁺, Cs⁺) on Co phthalocyanine (CoPc) in a state-of-the-art reverse-biased bipolar membrane electrolyzer. When added to the anolyte, these cations increased the Faradaic efficiency for CO, except in the case of Na⁺ in which the effect was transient, but the effects are convoluted with the transport process through the membrane. Alternatively, these cations can also be added directly to the cathode as chloride salts, allowing the use of a pure H₂O anolyte feed, leading to sustained improved CO selectivity (61% at 100 mA cm^-2 after 24 h). Our results show that cation addition is a simple yet effective strategy for improving the product selectivity of molecular electrocatalysts, opening up new avenues for tuning their local environment for CO₂ reduction.This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

The development of new technologies for the synthesis of green ammonia using exclusively hydrogen from water and nitrogen from air in processes driven exclusively by renewable energy is poised to decarbonize the production of this important molecule for the production of green fertilizers as well as offering a carbon-free vector for the long-term storage of renewable energy. In this article, we explore and quantify the CO₂ emission reduction potential of green ammonia, evaluating how it can facilitate the decarbonization of other hard-to-abate industrial processes such as steel, glass and cement industries. Green ammonia can be used as a direct replacement of fossil fuels used as energy sources in the different processes. In addition, green ammonia can facilitate the electrification of the processes (so-called Power-to-X) by storing renewable energy in the long term to balance a decarbonized grid against intermittent renewable energy supplies. This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

The pressing need to mitigate climate change and drastically reduce environmental pollution and loss of biodiversity has precipitated a so-called energy transition aimed at the decarbonization of energy and defossilization of the chemical industry. The goal is a carbon-neutral (net-zero) society driven by sustainable energy and a circular bio-based economy relying on renewable biomass as the raw material. It will involve the use of green carbon, defined as carbon derived from terrestrial or aquatic biomass or organic waste, including carbon dioxide and methane emissions. It will also necessitate the accompanying use of green hydrogen that is generated by electrolysis of water using a sustainable source of energy, e.g. solar, wind or nuclear. Ninety per cent of the industrial chemicals produced in oil refineries are industrial monomers that constitute the precursors of a large variety of polymers, many of which are plastics. Primary examples of the latter are polyolefins such as polyethylene, polypropylene, polyvinyl chloride and polystyrene. Polyolefins are extremely difficult to recycle back to the olefin monomers and discarded polyolefin plastics generally end up as the plastic waste that is responsible for the degradation of our natural habitat. By contrast, waste biomass, such as the lignocellulose contained in forestry residues and agricultural waste, constitutes a renewable feedstock for the sustainable production of industrial monomers and the corresponding polymers. The latter could be the same polyolefins that are currently produced in oil refineries but a more attractive long-term alternative is to produce polyesters and polyamides that can be recycled back to the original monomers: a paradigm shift to a truly bio-based circular economy on the road to a net-zero chemical industry. This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.