The Significance of Solid Chemical Catalysts in Global Decarbonization Efforts
Alexandra Velty
Instituto de Tecnología Química, Universitat Politècnica de València, Consejo Superior de Investigaciones Científicas, Spain
“Understanding solid catalyst molecular design and reaction aspects are crucial for chemical processes and sustainable planetary practices”
Climate change is one of the main challenges facing humanity today. The 2015 Paris agreements set "global average temperature increase well below 2°C above pre-industrial levels" by mid-century and continued efforts "to limit the temperature increase to 1.5°C above pre-industrial levels." Greenhouse gases are responsible for global warming and reaching net zero emissions and stabilizing climate change requires long-term planning. Carbon dioxide (CO2) is the most important greenhouse gas and human activities alter the carbon cycle by adding more CO2 to the atmosphere, and influence the ability of natural sinks, such as forests and soils, to remove and store CO2 from the atmosphere. Thus, decarbonization has become a global imperative and a priority for governments, businesses and society to avoid the catastrophic effects of climate change and to achieve net zero emissions targets. The transition to a world with zero net emissions requires a complete transformation of the way we produce, consume and move, and a crucial step is to replace fossil energy with renewable sources of energy (such as wind, solar, hydropower, geothermal and biomass). The U.S. energy information administration projects that world energy consumption should grow by nearly 50% between 2020 and 2050 as a result of population and economic growth (EIA projects increases in global energy consumption and emissions through 2050). Global chemical and petrochemical production amounted to USD 5.7 trillion in 2017 and is projected to quadruple by 2060 (Saving Costs in Chemicals Management). Fossil fuel and feedstock-based production leads to CO2 emissions during the production, use and end-of-life stages, making the chemical and petrochemical sectors the third largest contributor to industrial CO2 emissions, behind steel and cement production (Saygin, Deger, and Dolf Gielen, 2021).
In recent decades, the path to decarbonization has involved different strategies based directly on the carbon capture and storage in permanent geological CO2 reservoirs (deep geological formations such as depleted oil and gas reservoirs or saline aquifers) and on the carbon capture and conversion into valuable chemicals and fuels. Renewable energies such as wind, hydropower, sunlight and geothermal, will play a key role in the decarbonization. Other approach is the use of biomass derived from trees, plants, and agricultural and urban waste as renewable feedstock for the production of fuels, chemicals and functional materials that has received much attention by the scientific community to ensure the sustainable development of our society.
Unlike petroleum, biomass is renewable and "carbon neutral" because CO2 released is part of the natural carbon cycle and equal to the amount of CO2 absorbed during its growth. Trees and plants are grown, harvested and regrown in a relatively short period, turning biomass into a renewable source of energy and chemicals. In this way, biomass contributes to decarbonization at different stages, during its growth, biomass removes carbon dioxide from the atmosphere. Once sustainably managed and harvested, biomass can be converted, through sustainable processes, into chemicals and energy. Besides being a source of energy, biomass remains a valuable carbon source for producing a wide variety of chemicals.
Figure 1. The path to decarbonization involves different strategies based on carbon capture, storage and use, biomass conversion for the production of fuels, chemicals and functional materials, and the use of renewable energies.
Among various biomass feedstocks, including vegetable oils, chitin (a component of arthropod exoskeletons), and starch, lignocellulose, which is derived from plant dry matter, stands out as the most abundant form of biomass. With an annual production of approximately 170 billion metric tons, lignocellulose emerges as the most promising renewable candidate for the production of chemicals and fuels. Lignocellulose is composed of two primary carbohydrate (sugar) polymers, cellulose and hemicellulose, along with an aromatic-rich polymer known as lignin. The composition of lignocellulose varies depending on the wood/plant species, typically consisting of 30-50% cellulose, 20-35% hemicellulose, and 15-30% lignin. The decomposition of these natural polymers gives rise to a wide range of valuable substances, which provide a base for the production of chemicals4 and high-quality fuels by chemical transformation to meet global demand (Corma, Avelino, Sara Iborra, and Alexandra Velty, 2007).
Over the last twenty years, much effort has been devoted to developing efficient and eco-friendly methods to convert biomass into targeted chemicals and energy. The efficient and selective conversion of each lignocellulose component into the desired product or fuel is usually based on chemical catalysis, since catalysis allows the rate of a chemical reaction to be increased by the addition of a substance that is not consumed during the reaction. Biomass is usually first treated in the presence of a soluble or homogeneous catalyst to obtain simpler components easier to convert in subsequent steps in the presence of solid or heterogeneous catalysts into upgraded chemicals and fuels. Due to its diversity, in terms of composition and functional groups, biomass conversion requires catalysts that are selective in promoting specific chemical reactions and that actively facilitate the conversion process into the desired products. Consequently, heterogeneous catalysis, due to its recyclable and environmentally friendly nature as well as its applicability to continuous reactor operations, has received special attention for biomass conversion.
Over the last decades, heterogeneous catalysis has made great progress not only through the accumulation and rigorous interpretation of results based on knowledge and trial/error, but also through the development of fundamental knowledge. The systematic study and understanding of the reaction mechanism, kinetics, thermodynamics, determination of reaction intermediates and active species due to the benefits of computational chemistry, and the spectroscopic characterization of the catalytic material during reaction with the simultaneous measurement of catalytic activity/selectivity have allowed great insights in the preparation of materials and the development of new catalysts (Liu, Lichen, and Avelino Corma, 2021; Corma Canós, Avelino, 2016). More recently, a new design method of solid catalysts called the “ab initio design” allowing the positioning of active sites in the framework that selectively drive the reaction to the desired product has been a new breakthrough in the preparation of highly active and selective catalysts (Gallego, Eva María, et al., 2017). These advances demonstrate the importance of deep and fundamental understanding in driving the catalytic performance of chemical processes. Owing to high surface area, tunable composition, adjustable particle morphology and porous architecture, heterogeneous catalysts offer versatile physicochemical and adsorption/desorption properties for the design and development of efficient and green catalytic processes (Gallego, Eva María, et al., 2017).
Facing the era of sustainable development and to contribute to a healthy planetary development, over the last two decades we have worked on improving the efficiency and sustainability of chemical processes based on the design and preparation of new efficient and robust solid catalysts and on the use of sustainable raw materials such as lignocellulose, terpenes and vegetable oils (Liu, Lichen, and Avelino Corma, 2018). These studies concentrate on the redesign/re-engineering of current industrial processes or explore new avenues for the production of commodities and fine chemicals from renewable resources. We also found a route to convert CO2 into methane at lower temperatures than conventional processes, with excellent long-term catalyst stability. In this way, methane is produced from waste CO2 and green hydrogen, offering an alternative to fossil natural gas as a renewable fuel with a lower carbon footprint or as a H2 energy carrier. These endeavors play a vital role in enhancing the sustainability of chemical processes and therefore contributing to the much-needed global decarbonization.
Photo 1. Alexandra Velty and Avelino Corma, authors of the nominated work “Advanced zeolite and ordered mesoporous silica‐based catalysts for the conversion of CO2 to chemicals and fuels”.
Our subsequent paper published in Elementa: Science of the Anthropocene, hit on a solution linked to ecosystem and societal complexity and the consequences for time lags in the interaction of the two. This highlights the interactions involving both ecological and social connections. The ecological connections include the movement of pollutants from the land to the sea, or the migration of fish from the sea to the rivers and lakes. The social connections involve people’s values, management, and relationships among places and environments. Here our research points to an ignored, but critical feedback, where the impacts of humans on the land accumulate in the sea, but the land management strategy and consequent action are not informed by these far-field effects. The social-ecological connections we identify are not always straightforward to respond to because they can occur over large spatial and temporal scales. However, responding to them is critical for providing early warning of downstream changes and for preventing slow management responses to environmental issues.
Let me give a recent and painful real-world example from New Zealand. As a result of massive soil erosion on the east coast of the North Island during Cyclone Bola (1988), steep hillsides were retired from grazing and used for plantation forestry to help stabilise the land. Fast forward three decades and a large proportion of the forest reached harvest at the same time. The exposed soil associated with clear felling was left draped in woody debris to protect the soil from rain. However, another cyclone (Gabrielle, 2023) with extreme rainfall washed both soil and woody debris into the stream network, disturbing habitats, transporting vast amounts of silt and destroying low land farms and critical infrastructure. This debris also clogged the harbours and coastal beaches, smothered sea floor habitats destroying fisheries and impacted cultural and recreational values. This real-world example demonstrates the severe consequences of lags in information flow and management responses; if land use management decisions had been connected to cross-ecosystem domain impacts the outcomes could have been different. Our paper proposes a series of social-ecological properties related to cross-ecosystem domain connections that demand a reprioritisation of environmental management. These include properties related to the movement of stressors across ecosystem domains, and the role of people’s values and interests in one domain impacting people and ecological health in other domains. These properties inform actions that if implemented would reduce management response times across ecological domains and prevent tipping points. We can act on these social-ecological properties now, and the environmental gains from addressing the lags in decision-making will be substantial.
We are optimistic that sound science and knowledge generation, as well as cultural and societal partnerships, underpin the modifications and resource use changes that are necessary for improved environmental outcomes. Our work is at the forefront of such a vision with New Zealand providing a model ‘societal laboratory’, to highlight pathways to safe operating spaces. Guided by the wisdom of our indigenous people, we are focused on multiple ecological and societal timescales and the responsibility of being a good ancestor. We have had some early successes in engagement and uptake of our research and recommendations in the development of new <<<
environmental policy in New Zealand (see guidance document here). Over the past 18 months, our collective viewpoints have been a key component in written and oral submissions on new environmental bills before the New Zealand Parliament. The submissions emphasised the need to include cross-domain cumulative effects and were well received informing revisions to the bills.
Our vision is one where social and ecological connections across ecosystem domains are at the forefront of navigating to more sustainable futures where we live with nature, not off it. We believe that powerful, evidence-based, but simple messages can bring connections and interactions to the forefront of environmental management and policy. Living within the planetary boundaries requires a paradigm shift in behaviours, including the way we link science and management to on-ground action. While individual actions may be local, the behavioural shift underpins the way to a more integrated, broad-scale ability to act and affect planetary science and management. The Jena Declaration gives saliency to our research, especially cultural, social, and natural dimensions being inherently connected, locally embedded, and globally interrelated. Our research shows we can, with trust and open minds, transcend the disciplinary silos to support new forms of research organisation.
The challenge now is to extend holistic approaches into new “road unblocking” frameworks and practices. This means identifying opportunities where connected social-ecological research can alter behaviours, such as offering evidence needed to track value-focused, purposeful investments that facilitate sustainable social transitions. New research is needed to provide this evidence which will inevitably feedback to the development of new questions about fundamental ecological and earth-system processes. We believe that the new holistic approaches will create a dynamic where our science can be incorporated into decision making to ensure ‘environmental perspectives’ are rich and robust. Our research is the beginning of new connected research agendas and a new development of the next generation of research leadership searching for solutions to multiple planetary crises.
References
Saygin, Deger, and Dolf Gielen. Zero-emission pathway for the global chemical and petrochemical sector. Energies 14, no. 13, 2021. p.3772.
Corma, Avelino, Sara Iborra, and Alexandra Velty. Chemical routes for the transformation of biomass into chemicals. Chemical reviews 107, no. 6, 2007. pp.2411-2502.
Liu, Lichen, and Avelino Corma. Identification of the active sites in supported subnanometric metal catalysts. Nature Catalysis 4, no. 6, 2021. pp.453-456.
Corma Canós, Avelino. Heterogeneous catalysis: understanding for designing, and designing for applications. Angewandte Chemie International Edition 55, no. 21. 2016. pp.6112-6113.
Gallego, Eva María, M. Teresa Portilla, Cecilia Paris, Alejandro León-Escamilla, Mercedes Boronat, Manuel Moliner, and Avelino Corma. “Ab initio” synthesis of zeolites for preestablished catalytic reactions. Science 355, no. 6329. 2017. pp.1051-1054.
Liu, Lichen, and Avelino Corma. Metal catalysts for heterogeneous catalysis: from single atoms to nanoclusters and nanoparticles. Chemical reviews 118, no. 10. 2018. pp.4981-5079.
