SILCO – IL PROGETTO

Cemento poroso a base di silice derivato da rifiuti per la cattura, lo stoccaggio e il riutilizzo dell'anidride carbonica (SILCO).

CO₂ is one of the responsible for climate change, and efforts are paid to develop efficient and cost-effective capture, storage and re-use systems.

SILCO project has been designed and planned to address three targets of EU and Italian PNRR: climate change, by proposing new materials for CO₂ capture and use (SDG13 – climate action); affordable energy, by proposing CO₂ transformation into hydrocarbon (SDG7 - Affordable and clean energy), and responsible resources consumption, by proposing the development and application of waste-derived silica matrixes (SDG12 - Sustainable consumption and production), and particular attention is paid to the circularity of the proposed approach.

It is expected the development of Waste-derived Sorbent Matrixes (WSM) based on silica and/or modified silica having specific functionalization and porosity, suitable for highly efficient CO₂ capture and storage and to be used as catalysts support for high yield and selective fuel production.

Other important aspects of SILCO relate to the study and set up of methodologies for the characterization and the evaluation of the sorbents and catalysts structure-performances relationship. The innovative concept of SILCO stands on set up of methodologies able to allow efficient waste management, including CO₂, for waste reintroduction in the production cycle giving them new life and value.

Among others, SILCO applicative outputs can be:

1. the application of new WSMs, not currently available on the market, in current technologies, and
2. the possibility of implementing new technologies, dealing with recycling processes, yet not applied at industrial level.

SILCO ambitious long-term vision may be seminal for new technologies able to generate important work opportunities. Environmental implications of the reuse and recycling of silica residues are beneficial regarding raw material, resources, cost, and reduction in landfills. Even more impacting positive effects will be reached by considering CO₂ recovery and valorization. Global warming is considered one of the significant challenges of the twenty-first century, and CO₂ capture as well; thus, storage technologies are attracting large interest in reducing the ever-increasing amount of CO₂ released into the atmosphere and its impact on global climate change. Developing a robust catalyst for the selective reduction of CO₂ directly into hydrocarbon fuels is very challenging from both energy and environmental perspectives as it offers a renewable and green route to produce fuels. The production of synthetic natural gas from CO₂ employing a methanation reaction is thus a promising carbon capture and utilization technology that results in carbon recycling.

 

Waste-based Mesoporous Silicas (MS)

Mesoporous Silicas (MS) have attracted great attention as sorbent materials due to their exceptional features, i.e. ordered pore structures, high surface area and a broad selection of morphologies (powders, discs, rods, and spheres, etc.). Compared to conventional porous silica, MS show extremely well-ordered pores, due to the nano templating method applied in their synthesis. MS surfaces, containing silanol groups, are the key factors for their performances, which can be further improved via functionalization with different molecules.

Recently, industrial waste hexafluorosilicic acid H₂SiF₆ (FSA) has been proven to be a low-cost alternative for the synthesis of siliceous materials, currently undergoing pilot-plant production tests and mesoporous silica obtained from FSA have confirmed its suitability as sorbent support through surface modification showing performance comparable to that of similar material prepared from conventional precursors.

The CO₂-materials surface interactions vary from materials to materials, due to the nature of the functionalizing molecules. Moreover, surface functionalization with suitable functional groups may enhance the affinity of CO₂ and silica interactions. The captured CO₂ can be then stored or further converted to generate value added products (e.g. chemical and fuels), accordingly to the Carbon Capture and utilization (CCU) concept. This technology, that involves the conversion of waste CO₂ into added-value products by using renewable energy, is expected to have a strong impact in mitigating climate change.

Graphical representation of SILCO's basic idea is sketched in following Figure:

SILCO proposed the production of silica with well-defined morphological and structural characteristics and porosity, as secondary raw materials from the recovery and reuse of hexafluorosilicic acid (FSA), suitable for the gas recovering and catalytic applications, objectives of the project. FSA is a hazardous by-product of the aluminium fluoride and hydrofluoric acid production and of the fertilizer industries in the Mediterranean area (North Africa and Near Middle East) with limited applications, including the production of low-density aluminium fluoride and the fluoridation of drinking water and where this practice is legal (not in the EU), is mainly disposed into the sea upon neutralization. SILCO project aims to integrate a zero-waste, innovative and sustainable technology solution to use FSA to produce solid, non-hazardous critical raw material fluorspar (CaF2) for fluorine industry and precipitated silica (HD-SiO2), in full compliance with the green chemistry and the circular economy principles. It is based on the FSA amination process patented by Fluorsid for the fluorspar recovery. The integration deals with the modification of the silica recovering process to produce morphologically controlled SiO2 nanoparticles with defined sizes and surface area and porosity for applications such as CO₂ recovering and catalysts for methanol production from CO₂.

This could give much more attractive prospect for the reuse of silica counterpart of FSA, valorizing the recovery process of fluorspar, further improving the eco-sustainability of the process. The transition to more circular systems of production and consumption will inevitably impact both the numbers of people employed in the sector, and their skill.

SILCO experimental activities are designed to demonstrate the possibility to develop and use waste-derived silica and/or modified silica oxide having specific functionalization and porosity, suitable for highly efficient CO₂ capture and storage and, after functionalization, as catalyst for high yield and selective methane production. Moreover, the study and set up of methodologies for the characterization and the evaluation of the relationship structure-performances is planned as well.

The communication and information exchange plan within the project and between the fourth research units involved in it will be carried out according to the flow diagram reported in the project's Pert diagram: