Flying on carbon dioxide
Behaviour change is important to reduce global warming on our planet. But some habits, such as flying, are difficult to change. In such a case, a technical solution can play an important role.

For example, several ways of making synthetic paraffin are already known. At the RUG, Jingxiu Xie, assistant professor of Catalytic Processes for Gas Conversions, combines her knowledge of catalysis and chemical technology to make paraffin from carbon dioxide.

It is not really difficult for a chemist to make paraffin from carbon dioxide (CO2). This aviation fuel consists of hydrocarbons of eight to 16 carbon atoms. 'The first step is to convert carbon dioxide into the much more reactive carbon monoxide,' says Jingxiu Xie. 'We know how to do this, but it does take a lot of energy.' Then by combining carbon monoxide with hydrogen (H2), hydrocarbons can be formed. 'Carbon monoxide, hydrogen and oxygen is the classic syngas, which you can convert into liquid fuel via the classic Fischer-Tropsch synthesis reaction.' Oil company Shell recently used this method to demonstrate the potential of synthetic paraffin.

Waste gases 

But Xie does not want to start with a clean source of carbon monoxide (CO). Instead, she wants to use waste gases from large emitters of greenhouse gases, such as Tata Steel or the RWE power plant in Eemshaven. This waste gas contains all kinds of other molecules besides carbon monoxide and hydrogen. 'And the commercial catalysts used in the Fischer-Tropsch reaction do not work well in such a gas mixture,' says Xie. 'We know that it is possible to make jet fuel from carbon monoxide and hydrogen in the laboratory using a cobalt catalyst. But pollutants in the waste gas can produce shorter hydrocarbons. So we need to combine knowledge from catalysis with knowledge about chemical production technology to develop a process that does what we want: a completely green production of paraffin.'

Green paraffin

Moreover, the amount of energy needed to make carbon monoxide from carbon dioxide and to produce green hydrogen is a problem if you want to make truly green paraffin. Most hydrogen available now is made from natural gas (methane) - not a green source. Xie: "And there is not enough renewable energy to make unlimited green hydrogen by electrolysis of water. She therefore wants to make the whole process as energy-efficient as possible. This can be done, for example, by making the number of purification steps as small as possible. 'I worked in industry for two years, so I know how to tackle something like this.'

Small factories

Her ideas to make hydrocarbons from waste gas could change the whole chemical industry. 'Chemical factories are mostly very big now, so they can produce as cheaply as possible. But if we are going to use different types of carbon as feedstock in our processes, it is better to build small factories close to the source of that feedstock. That is, again, more expensive than the current large factories, another reason to make the production process as simple and thus cheap as possible.' The chemical industry mainly uses unsaturated hydrocarbons, so-called olefins, which require a different synthetic route than paraffin.

Good luck

Xie thinks her approach will be successful in not too long. More and more funding is also becoming available for her type of research. That research is a typical example of work that will benefit from FutureCarbonNL, a collaboration of Dutch universities, knowledge institutions, chemical and other industries, SMEs and green startups. FutureCarbonNL will soon submit a proposal worth some six hundred million euros to the Dutch Growth Fund. Some of that money will certainly go towards research of carbon capture and beneficial use. Xie: 'If FutureCarbonNL is successful, our group will definitely compete for research grants.' That will help her and her team develop processes to produce green paraffin for aviation and olefins, at the same time enabling a whole new set-up of the chemical industry.