CO2 Utilisation Chemicals from the Smokestack: New Developments Turn CO2 into Raw Material
CO2 to chemicals: What potential has the utilisation of carbon dioxide for chemicals production? — CO2 has a bad image. But can the undesired exhaust gas also be used as a raw material? Not an easy task, yet researchers from all over the world are working hard on turning the climate killer as a raw material. And those, who believe this will remain a thought game played in ivory towers or think that these minor experiments will remain confined to the cellar laboratory are making a big mistake: The first production scale plant is already on-stream....
This material does not show its secrets: An absolutely normal foam, flexible and light and versatile, as is used in the manufacture of cushions and mattresses. But this is also not the reason why Covestro, earlier Bayer Material Science, is making such a sensation out of the polymer.
If the Leverkusen-based company is to be believed, the plastic will usher in a new era of chemistry. Anyway, a material has come into the lime light which otherwise makes only negative headlines: CO2. Actually, the developers have succeeded in replacing approx. 20% of crude oil-based raw materials which are normally used to manufacture poly-oil, the most important preliminary product used in Polyurethane foam (PUR), with the climate killer gas.
The 'Holy Grail' of Chemistry
Not an easy task, because CO2 is extremely inactive. Use is hardly possible from the thermodynamic perspective, if one ignores urea and carbonate production. But CO2 as raw material for polymers?
he sector has been working on this vision for decades, ever since the concept was described by scientists of the University of Kyoto in 1969. For a long time, the process remained science fiction – Catch words like “Dream Reaction” or the “Holy Grail of chemistry” show the status the “Chemistry from the chimney” had.
Now it seems the Grail has been found: Covestro had started research on the use of CO2 ever since the Bayer days. After successful tests, it was decided in 2014 that 15 million Euro will be invested at the Dormagen site to establish a preliminary production plant with a capacity of 5000 tons per annum. Another 7.5 million Euro came from Federal subsidies.
The next step for CO2
With the new flagship project, the Leverkusen-based company started the poly-oil synthesis on an industrial scale, in June 2016. The molecule on a CO2 base is provided initially for the manufacture of PUR foam for mattresses and cushion furniture. People at Dormagen are convinced that from the point of view of quality, the foam is as good as any material made of petrochemical raw materials.
“One must perceive CO2 differently: Its use as an alternative hydrocarbon source is the answer to the massive challenges of our time – finding a replacement for our limited fossil resources like oil and gas and to close material cycles”, said Covestro Chairman of the Board of Directors Patrick Thomas at the opening ceremony.
The key to the Dream Reaction is a revolutionary catalyst which enables the integration of CO2 molecules along with Propylene oxide (PO) directly in the hydrocarbon chain. “To ensure that both substances react in the stirred boiler, extra high pressure and temperatures are necessary”, says Project Manager Dr. Carsten Malsch.
CO2 still exists in gaseous form at room temperature while PO boils at 34 °C. Once the reaction is in progress, the binding energy of the Propylene oxide is sufficient for a continuation, explained the developers – there is no need to feed additional heat. We have one CO2 molecule in the centre of three PO molecules – approx. 20% by weight. The poly-oil is finally used with Isocyanate for foam production.
In this context, the following rule is applicable: Long chain poly-oils yield softer polyurethanes. Good to know because the newly developed molecule is ideal for smooth PUR production, but yields stiffer forms of foam with petrochemical raw materials. As approximately two thirds of a PUR consists of poly-oils, the finished plastic contains approx. 10% CO2.
Developing A Catalysts for CO" Utilisation
“The search for a suitable catalyst lasted 40 years. That we have found it is attributable most of all to the collaboration with RWTH Aachen”, recollects Dr. Malsch. At the CAT Catalytic Center – a research institution run jointly with RWTH – the developers put their heads together. Rector Prof. Dr. Ernst Schmachtenberg also remembers the herculean task: “Using CO2 in an efficient way chemically, is a scientific challenge. We made a breakthrough in the interaction between application-oriented basic research and research-based industry.”
Catalysts on the basis of transition metals like Cobalt, Zinc, Chromium or Aluminium were tested for their suitability for polymerization with CO2. As the plastics industry requires long-chain hydrocarbons, it was necessary to avoid the occurrence of cyclical connections. ZnCl2 catalysts in particular were very convincing in the matter of selectivity and economy.
The Role of Research and Development
“Research must address global questions and be able to answer them”, Prof. Schmachtenberg is confident. The scientist sees in the Dream Production project the opportunity of detaching the CO2 economy from the vicious circle of fossil raw materials and climate-damaging emissions: “Not only does Germany have the opportunity to show how the energy threshold works, it can also illustrate how a carbon cycle economy is possible!”
Cradle-to-cradle means the “make new from old” concept of “sustaining” a raw material in a continuous cycle. 5000 tons per annum poly-oil are only the beginning, they say in Leverkusen. Covestro interprets the investment as an opportunity of experiencing the technology. Interested third parties will be given access to the process within the framework of a license (see box). A gigantic effort considering the global demand of 15 billion tons of PUR – a market with an average 5% growth rate per annum.
The hunt continues
Elsewhere too, the test tubes are glowing: In April 2016, the biotechnology company Brain and Südzucker disclosed that it is working on the microbiological synthesis of Carboxylic acid from CO2.
After the first trials with a two-phase process on a laboratory scale, the Strategic Alliance Zero Carb FP process is being tested at a bio-ethanol plant in Phase 2. In this context, the intermediate products occurring from CO2 like mono- or di Carboxylic acid will be used to manufacture polymers and plastics.
Even formic acid is being queried as target molecule, as it occurs under comparatively milder reaction conditions (approx. 30 bar and 25 °C). At present, scientists of the University of Stuttgart, of the German Centre for Air and Space Travel and of the Plinke Company are working on this project.
Researchers are relying on catalytic micro-reactors with which 1.5 kg of CO2 is being converted at present per sqm. of electrode area per hour. Formic acid is required in the textile industry, but it can also serve as energy storage, as it disintegrates into Hydrogen and CO2.
And the chemicals giant BASF too has cast an eye on the exhaust gas. After conducting research on CO2-based Sodium acrylate within the framework of the Acer project, the group is working on the manufacture of Polypropylene carbonate (PPC) from CO2 and Propylene oxide. To facilitate the market introduction of such products, the Ludwigshafen-based group has developed new plastic formulas from PPC and Polyhydroxyl butyrate (PHB) or Poly-milk acid with partners from industry and research.
How Green is the Process?
Is the industry now climate-neutral? Not wholly. Of course, the use of CO2 will help save crude oil, but fossil-based raw materials cannot be avoided. What remains of the green industry in view of the estimated 70 million tons of CO2, which the German chemicals industry blows into the atmosphere year after year through the chimney?
Initial calculations of the RWTH sound optimistic: Over the entire life cycle, the Dream Production would consume less energy than the petrochemical process, say the researchers. The attempted 5000 tonnes per annum are not enormous by itself – but they certainly announce another important step on a path that is very long.