Topic of the Month: July 2015

Plastic from greenhouse gases

Greenhouse gases

© istockphoto / Hans Laubel

The world is experiencing an unprecedented summer. There is talk of the hottest July since weather records began. Is this pure chance or is it a consequence of climate change instead? It is time to rethink, regardless of the causes. What is vital is to reduce greenhouse gas emissions or to make useful things from them – plastic, for example!

Carbon dioxide is a chemical compound that occurs naturally and is produced in the course of oxidation and/or combustion processes. We breathe in oxygen and breathe out carbon dioxide (CO2). Green plants – including algae – absorb carbon dioxide and use it to produce the oxygen that is so essential to us. An efficient recycling process. Everything would be wonderful if we were not so successful at meddling with Mother Nature.

Are we facing climatic catastrophes?

The effect of excessive combustion of fossil fuels is that the proportion of carbon dioxide in the air will be continuing to increase in the foreseeable future – in spite of all the political promises that have been made and the objectives that have been agreed about climate protection. This increase in greenhouse gas concentration has consequences:

The temperature in the atmosphere is increasing, the polar caps and glaciers are melting and the sea level is rising. Habitats are changing. There is a real danger that entire areas of land will be flooded. Oceans are acidifying and deserts are expanding. Dry periods are increasing, precipitation and storms are becoming more ferocious. Reductions in crop levels must be expected, people are experiencing severe problems and are losing the whole basis for their existence. The same is true of animals too; many species will probably die out.
Pollar bear and melting ice

© istockphoto / Josef Friedhuber

An irgendeinem Punkt muss sich ein jeder die Frage stellen, ob wir immer so weiter machen können wie bisher und wohin uns unser moderner Lebensstil führt.

Vielleicht in eine Katastrophe, wie sie uns Roland Emmerich in seinen Blockbustern „The Day After Tomorrow“ oder „2012“ vor Augen führt: Die Erde begraben unter meterdickem Eis oder geflutet von unendlichen Wassermassen infolge der geschmolzenen Polkappen? Alles ist nur Fiktion, oder vielleicht doch nicht?

Lasst Worten Taten folgen

Es ist an der Zeit, sich von Lippenbekenntnissen zu verabschieden, die Augenwischerei zu beenden. Es ist an der Zeit, zu handeln. Die Marschroute liegt fest: Der Ausstoß schädlicher Klimagase muss rasch und nachhaltig reduziert werden. Es gibt keine Alternative! Ein Schritt in die richtige Richtung, ist die Gewinnung von Energie aus regenerativen Quellen – und zwar im großen Stil. Ein anderer liegt darin, technische Möglichkeiten zu finden und anzuwenden, um schädliche Klimagase „zu ernten“ und nutzbringend einzusetzen.

Eines nämlich steht unzweifelhaft fest: CO2 ist nicht nur ein Treibhausgas, sondern auch eine interessante Kohlenstoffquelle, wie sie für die Herstellung hochwertiger Polymere benötigt wird.

Allerdings erweist es sich als Herausforderung, ein solches Vorhaben in praktikable, effiziente und großtechnisch interessante Verfahrenstechnik umzumünzen. Einen interessanten und praktikablen Ansatz scheint die Firma Bayer Material Science gefunden zu haben. Ab 2016 will das Unternehmen nach eigenen Angaben Kohlendioxid zur Herstellung von Kunststoff nutzen.

Zu diesem Zweck wird derzeit am Standort Dormagen eine Produktionsstraße errichtet. Kürzlich erst wurde das Herzstück, ein 25 Tonnen schwerer chemischer Reaktor, eingesetzt. „Wir liegen optimal im Zeitplan“, sagt Projektleiter Dr. Karsten Malsch. Im Herbst werde noch ein Kohlendioxidtank eingebaut, dann sei die rund 15 Millionen Euro teure Anlage nach gut einjähriger Bauphase nahezu fertiggesellt. Wenn alles weiterhin so glatt laufe, wie bisher, sei die Anlage Anfang 2016 betriebsbereit, prognostiziert Maloch.

Drying Earth

© istockphoto / gmutlu

Malsch reveals that there are already specific production plans: Bayer Material Science intends to use carbon dioxide as a raw material source for the first time on a commercial scale in the context of the “Dream Production” project and incorporate it in polyols – central base products that are needed to manufacture such materials as foam plastic. The line is said to be designed for a production volume of 5,000 tonnes per year. The innovative new polyol, which will be containing about 20 per cent CO2, is evidently formulated in such a way that it can be used initially to manufacture mattresses made of flexible polyurethane foam.

Carbon dioxide as a substitute for mineral oil

The tests are said to have demonstrated that the material containing CO2 has comparable properties to conventionally manufactured plastic. This means that the carbon dioxide is replacing some of the mineral oil that is generally the sole basis for polyols and polyurethanes. “For a long time now, the plastics industry has been looking for alternative raw materials, in order to eliminate fossil sources, which are in shorter supply in the meantime,” says Malsch. He adds that demand for sustainable products is increasing among consumers. “We think that we are in a position to provide a comprehensive solution with our new processes.”

A considerable amount of research and development work has been needed so that CO2 can be used in plastics production. Bayer Material Science has received assistance from Aachen University scientists in this context. The main challenge was to find a catalyst that incites carbon dioxide – which is very inert at the chemical level – to react efficiently with other substances. The partners co-operating on the project discovered such an appropriate catalyst.

Interesting combination for interesting applications

It is the objective of US scientists to make sure that power stations no longer discharge carbon dioxide (CO2) into the atmosphere from their chimneys but feed it directly into a production plant instead. In the magazine Angewandte Chemie, they recently presented a process with which carbon dioxide and epoxides can be used to manufacture polycarbonate block copolymers that combine water-soluble and water-repellent areas and can aggregate to form nanoparticles or micelles.

Carbon dioxide and epoxides – highly reactive compounds with a three-atom ring consisting of two carbon atoms and one oxygen atom – can be polymerised into polycarbonates with the help of specially developed catalysts. These processes are proving to be a more environmentally sound alternative to common manufacturing processes and have already been introduced by some companies. Since the carbon dioxide-based polycarbonates produced to date are water-repellent and do not have any functional groups, applications for them are limited, however. Biomedical applications in particular, an area in which biocompatible polycarbonates have already established themselves, have left out up to now.

Sustainable chemical process engineering

A team of scientists headed by Donald J. Darensbourg from Texas A&M University is now providing a solution. The research scientists have succeeded for the first time in producing amphiphilic polycarbonate block copolymers, i.e. compounds that combine both water-repellent and hydrophilic properties. Not only the water-repellent areas but also the water-soluble areas are based on carbon dioxide. Darensbourg and his colleagues have also managed to incorporate various functional and charged groups in the polymers, i.e. components that have a strong impact on the chemical properties of a molecule and/or a polymer. Acid and/or alkaline groups can, for example, be attached that have a positive or negative charge in the appropriate pH range. Some of the amphiphilic polycarbonates manufactured in this way are in a position to grow into particles or micelles by themselves. This characteristic combined with the ability to attach bioactive substances as well creates numerous interesting new prospects for biomedical applications.

And, by way of conclusion ...

The German government is planning to invest billions of euros in innovative technologies that concentrate on sustainable development. The implementation of carbon dioxide and other greenhouse gases like methane in polymer materials is proving to be both worthwhile and promising. Above and beyond this, the polymer industry is well-known for innovative and creative solutions. It is therefore the ideal partner to respond effectively to the tough challenges that society faces.

Source

[1] Bayer Material Science
[2] Yanyan Wang, Jingwei Fan andProf. Donald J. Darensbourg, Construction of Versatile and Functional Nanostructures Derived from CO2-based Polycarbonates, Angewandte Chemie 127 (2015) 1-6 (DOI: 10.1002/anie.201505076)

Guido Deußing