Chemistry and the environment have not always seen eye to eye, but industrialists have really become aware of their responsibilities on environmental impacts and, coupled with the pressure exerted by public and political opinions, it has been a significant turning point in the 1990s. Environmental issues are now an integral part of process design, including the choice of reagents and the production, recycling and repurposing of waste.
Chimie ParisTech researchers are studying issues such as the recycling of waste from electrical and electronic equipment and the development of greener syntheses through the use of catalysis. This research is readily focused on industrial applications and is looking to optimize existing industrial processes or develop innovative systems, such as by using continuous chemistry.
Recycling: how can we reuse waste from our used electronics?
In order to be able to transform waste in such a way that it can then be reused, its properties and its dangerousness must be taken into account when reclaiming it as it is produced at the end of a lifecycle. This is a real technological headache, especially when processing nuclear waste to be reused in power plants, or when it comes to waste from electrical and electronic equipment (called WEEE).
According to the ADEME, created in 2006 in France, of 1.73 million tons of EEE placed on the market in 2016, the WEEE treatment and collection sector has collected over 725,000 tons of WEEE and processed approximately 721,000 tons. This waste contains many strategic metals:
- Cu and Sn in printed circuits,
- Li and Co in used batteries,
- Rare earths in used lightbulbs and lamps, with a mineral density that is greater than that of deposits we find today!
Reclaiming them is essential to save our available resources and break free from our dependence on global markets.
This is the objective of the work carried out in the Mines Urbaines Chair with the support of Eco-Systèmes and regrouping three establishments of the ParisTech network: Arts et Métiers ParisTech, Mines ParisTech and Chimie ParisTech, through three research teams.
The MIM2 (Materials, Interfaces and Soft Matter) team, led by Min-Hui Li, is interested in selective lithium recovery. Strong of its expertise in hydrometallurgy and its knowledge of leaching processes, it strives to develop an efficient and viable method to recover these metals. The MIM2 team is also exploring the selective recovery of tungsten and tantalum and is looking into the bioleaching of electronic boards in collaboration with the BRGM.
The use of thermal or cold plasmas is a promising avenue for the selective recovery of metals under certain conditions from D3E and is therefore the subject of research by the 2PM team led by Professor Michael Tatoulian.
The SEISAD (Synthesis, Electrochemistry, Imaging and Analytical Systems for Diagnosis) team, led by Anne Varenne, is developing miniaturized analytical systems based on microfluidics to improve the analysis of metals.
Chemistry is an integral part of current recycling issues. However, it also influences design processes much before recycling takes place.
The development of new synthetic strategies: how can we use chemistry for a more efficient and clean production?
The research currently being conducted at Chimie ParisTech in synthesis largely deal with the operation of catalytic systems to improve the yield, but also to better control the regioselectivity of the reaction or the microstructure in the case of polymers. The great diversity of the types of catalysts and the growing interest of the industry make this a real solution for more efficient and greener syntheses in the future (reduction in the amount of waste, number of steps, etc.)
The COCP (Chimie Organométallique et Catalyse de Polymérisation) team, led by Professor Christophe Thomas, is studying how to make eco-compatible syntheses with bioresources to make biodegradable polymers. To achieve this, the team is thinking about both the design of the polymer and its end of life (biodegradability, recycling, recovery, etc.), which happens to be dependent upon its use. On the design side, the team relies on the functionalization of bioresources by catalysis and on the development of tandem catalytic systems.
These tandem systems allow us to use the same catalytic system to perform several steps of the same synthesis. However, this requires many challenges, such as the stabilization of the catalyst in the medium, or the management of secondary and intermediate products, which must be compatible with the catalytic activity and not react with the main cycle. Tandem catalysis offers the possibility of synthesizing polymers from one-pot bioresources, which limits exposure to toxic products during production, energy consumption, waste production and energy barriers encountered in the cycle. Eventually, this would allow the formation of more complex macromolecules, which are currently inaccessible in synthesis with the methods we use now. New polymers produced from diacids from bioresources have already been made this way.
The team’s expertise in organometallic chemistry has also brought it to work on the modification of catalysts in situ, with a controlled transformation. The objective is to limit compatibility problems with certain functions and to reduce the impact of the structure of the reactive intermediates encountered. This suggests the possibility of producing from bioresources since they often prove to be highly functionalized and provided with numerous sensitive stereogenic centers.
This interest in bioresources and molecules is also shared by the CSB2D (Catalyse, Synthèse de Biomolécules et Développement Durable) team, led by Dr. Virginie Vidal. Specialized in the total synthesis of biomolecules, it uses metallo-organocatalytic methods to achieve coupling or functionalization in a more selective and controlled way. For example, obtaining different products by modifying operating conditions is a challenge in organic chemistry and is a powerful tool in divergent synthesis, which organic chemists have managed to achieve by studying the divergent catalytic activity of silver and gold on oxidative cycles. As for its work in organocatalysis, the team uses a Lewis acid to conduct alkyne-aldehyde couplings with good regioselectivity under mild conditions and without metal catalysts. Finally, it relies on already acquired synthetic methodologies to optimize reactions through the use of transitive metal compounds, such as ruthenium.
This particular focus demonstrates how chemistry integrates the environment in all of its fields of activity. At the request of manufacturers, the COCP team is improving existing catalytic systems by replacing toxic metals such as tin with more environmentally-friendly alternatives. This research should ultimately limit the exposure to pollutants and therefore their impact on public health, but should also help counteract this pollution and treat it.
Analyzing and treating pollutants: how can we detect, quantify and eliminate contaminants in order to limit the risks of exposure?
Chemistry has a key role to play in the fight against pollution, from understanding the phenomenon to dealing with it. The contribution of Chimie ParisTech’s researchers on this issue has to do with nuclear energy and the treatment of volatile organic compounds.
The MIM2(Materials, Interfaces and Soft Matter) team is studying the mechanisms for the formation of radioactive effluents within the primary and secondary circuits of the PWR (Pressurized Water Reactor) in partnership with EDF. PWRs are reactor types that are very widely used on the French nuclear fleet. Extreme temperature and pressure conditions prevail in these circuits that create significant corrosion phenomena that we must understand to be able to prevent them. The water becomes charged with radioactive pollution through these repeated passages in the circuits, which is deposited as soon as its temperature decreases, leading to the formation of hotspots that can be harmful. We must be able to control this source of pollution in the long term and know where the contaminated areas are located, especially when dismantling the power stations.
The 2PM (Processes, Plasma, Microsystems) team, led by Professor Michael Tatoulian, is working on treating the pollutant VOC (Volatile Organic Compound). These highly volatile compounds are harmful to our health, because they interact with the ozone and because they are toxic in nature. They are also harmful to the environment as they contribute to the greenhouse effect. To treat these compounds in the air, water and soil, the team is developing clean processes and microsystems using plasma chemistry. To achieve this, we must design and optimize chemical reactors in micro and macro systems and design them for a safer and cleaner industry.
What about tomorrow?
The link between chemistry and the environment is more important than ever.
Research on catalysis and the hopes raised by tandem systems will no doubt be part of upcoming industrial synthesis. The renewed interest in abundant metals like iron and all the efforts made on recycling rare earths point to a bright future for this science.
As for processes, continuous chemistry systems now carry the hopes of a more efficient, safer and more environmentally friendly chemistry. The goal would be to work with reagent and product flows continuously, thus achieving reactions without time interruption, unlike batch reactors commonly used in the industry. This would enable us to avoid downtime in production systems and to consider a miniaturization of reactors by prioritizing series reactions with weaker flows for greater control and safety. With the Start-Up Plas 4 Chem project, the 2PM team is working on this type of system to miniaturize a BASF process for converting cyclohexane to cyclohexanol/cyclohexanone. This new type of chemistry offers many possibilities and could constitute a real revolution in the design of processes as we know them.
Auteur : Quentin Bouteille
Engineering student at Chimie ParisTech - Class of 2019.
Reactivity in organic chemistry is primarily based on functional groups with known structure and properties which can globally predict the way in which the molecules that are equipped with them will behave. Consequently, in order to give a desired reactivity to a molecule, we can use functionalization by adding the group or by interconversion with a pre-existing group.
The simplest conception of an organic synthesis starts with a target molecule that is functionalized and modified throughout the synthesis until the final product is obtained, using relatively simple molecules. This synthesis method, called convergent synthesis, is not very efficient, a highly functionalized and fragile molecule is being used at the end of synthesis, and its is rarely possible to obtain complex products. Divergent synthesis offers an alternative approach by considering the molecule as a set of “sub-molecules”, called synthons, which will be synthesized independently and then assembled. The possibility of synthesizing several synthons from the same target molecule by modifying the operating conditions is therefore very interesting for this type of synthesis. This type of synthesis is preferred for its greater flexibility and higher efficiency.
In the nuclear industry, the term “hotspot” refers to an area in which radioactivity is very high and well above tolerated standards. It mainly happens when radioactive fluids leak and the pollution is specifically located where the fluid has accumulated and/or stagnated. The formation of hotspots is particularly well monitored after nuclear accidents in populated areas, as they can represent a real danger to the population. Understanding their formation and their evolution is therefore interesting when studying nuclear pollution phenomena.