Greenhouse Gas CO2 to Gasoline
Carbon dioxide (CO2), a major greenhouse gas, is considered to be the main culprit in global warming. In recent years, countries have been striving to achieve CO2 reductions due to the impact of carbon emission policies. Petrol, one of the most used fuels in the world. With the development of modern society, petrol is not only a necessity for the production and living of a country, but has become a daily necessity that many ordinary people cannot live without every day. One is a greenhouse gas that contributes to climate warming, the other is a valuable energy source that people increasingly rely on, the two seemingly unrelated, but in the eyes of scientists have become inseparable.
2017, a team of researchers Sun Jian and Ge Qingjie from the Dalian Institute of Chemical Engineering, Chinese Academy of Sciences (DIC) discovered a new process for efficient conversion of CO2, and by designing a new multifunctional composite catalyst, they have achieved the first direct hydrogenation of CO2 to produce high-octane gasoline. The research results were published in the British journal Nature Communications on May 2, and the related process and catalytic materials have been patented, which has been hailed by peers as “a breakthrough in the field of CO2 catalytic conversion”.
In nature, plants absorb CO2 from the air and convert it into organic matter and oxygen through photosynthesis, a slow process that has led chemists to try to chemically recycle CO2. It would also reduce dependence on traditional fossil energy sources.
However, the activation and selective conversion of CO2 is still a major challenge. Compared to its more reactive twin, carbon monoxide, CO2 molecules are very stable and difficult to activate. Compared to the classical Fischer-Tropsch route, the catalytic reaction between CO2 and hydrogen molecules is more likely to produce small molecules such as methane, methanol and formic acid, while it is difficult to produce long-chain liquid hydrocarbon fuels.
In response to these problems, the team has creatively designed an efficient and stable multifunctional composite catalyst. Through the synergistic catalysis of multiple active sites, the catalyst achieved low selectivity for methane and carbon monoxide under near-industrial production conditions, and 78% selectivity for gasoline fraction hydrocarbons among the hydrocarbon products, far exceeding the results reported in the literature. Furthermore, the gasoline fractions were mainly high octane isoparaffins and aromatics, which basically met the composition requirements of the national V standard for benzene, aromatics and olefins.
The catalyst also has good stability and can operate continuously for more than 1000 hours, showing potential application prospects. Unlike conventional catalysts, this catalyst contains three compatible and complementary active sites (Fe3O4, Fe5C2 and acidic sites).
The CO2 molecule is converted in a ‘three-step’ tandem by means of a carefully constructed three-component active site, where the CO2 is first reduced to CO by an inverse water-gas conversion reaction on the Fe3O4 active site; the resulting CO is converted to an alpha olefin by a Fischer-Tropsch reaction on the Fe5C2 active site; the olefin intermediate then migrates to the acidic site on the The olefin intermediate then migrates to the acidic site on the molecular sieve and undergoes zwitterionisation, isomerisation and aromatisation to selectively produce gasoline distillate hydrocarbons.
The precise regulation of the structure and spatial arrangement of the three active sites is the key to achieving CO2 hydrogenation to gasoline. This technology not only opens up new ideas for the study of CO2 hydrogenation to liquid fuels, but also opens up new avenues for the use of intermittent renewable energy sources (wind, solar, water, etc.). In addition to reducing CO2 emissions, this new process also has significant economic benefits.
Papers : Directly converting CO2 into a gasoline fuel
Industrial mass production
According to a report in 《China News》 on March 4, the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences (DICP) released news that the world’s first pilot plant for hydrogenation of carbon dioxide to gasoline of 1,000 tons per year, jointly developed by the institute and Zhuhai Fusheng Energy Technology Co.
They have been experimenting with industrialisation since 2017 and completed the construction of a 1,000-tonne pilot plant in Zoucheng Industrial Park, Shandong Province, in 2020. They have also successively achieved tests such as commissioning, formal operation and industrial sideline data optimisation.
The China Petroleum and Chemical Industry Federation also organised a site assessment in October 2021. The unit was found to have significantly reduced the unit consumption of raw hydrogen and carbon dioxide, the overall process energy consumption was low, the gasoline products generated were environmentally friendly and clean, and the unit performance and output targets were successfully passed. A third party test found its octane number to be over 90 and its distillation range and composition to be in line with National VI standards.
On 4 March 2022, the technology passed another evaluation of the organisation’s scientific and technological achievements in Shanghai, where experts from the evaluation panel unanimously concluded that the CO2 hydrogenation gasoline technology achievement was the first of its kind in the world, with fully independent intellectual property rights and at an overall leading international level.
The experts of the evaluation team unanimously agreed that the CO2 hydrogenation technology is the first of its kind in the world and has completely independent intellectual property rights.
Surprising Highlights
The catalyst used is not difficult to prepare and the raw materials are cheap: FeCl3 + FeCl2 + NAOH + common molecular sieve, which is much cheaper than the fancy catalysts usually found in articles.They have also proposed mechanisms by which all three reaction steps can be tuned by adjusting the catalyst composition. In the future, better selectivity can be achieved with the help of suitable molecular sieves, which can also go on to synthesise some other useful products.
However, the performance of this material is not as good as the shocking reports, and the conversion figures are not very good for H2/CO2=3, but the value in the application does exist. It is also a highlight that the selective performance of the C5-C11 product is maintained between 70 and 80%, the fractionated product composition is stable, and the system has a long run time and is designed to meet the basic requirements for industrial applications.
The greatest significance of this research is on an applied level. Much of the research in the field of CO2 reduction is still in the laboratory using precious metals to brush up on ultimate efficiencies. This paper, however, does not follow the trend of brushing up the ultimate efficiency, but uses a relatively inexpensive catalyst. This paper is a return to the essence of CO2 reduction technology by achieving a reasonable conversion and selectivity under industrial conditions.
What is the significance of CO2 hydrogenation to gasoline
Many people may wonder, CO2 makes gasoline, gasoline burns and turns into CO2, you spend a lot of effort converting things back and forth, but in the end CO2 is still CO2 and it looks like a lot of energy wasted for nothing.
To be honest, that’s what I thought when I first approached the subject in question. But as my research progressed, I decided that the response still made a lot of sense.
1. Energy Storage.
There are many parts of the world where wind and solar power are suitable for development. Wind and solar energy are intermittent and unstable sources of energy, which are not good for direct input into the grid for use. And the energy consumption of CO2 to make petrol can come from this. From this point of view, wind, solar and industrial waste electricity, which are not easily used directly, can then be used to supply energy for this reaction (this point has also been mentioned in the paper).
The process of CO2 plus hydrogen to make oil is itself very inefficient, but if it is linked to this context and can absorb excess electricity, then after industrialisation the efficiency increases to a certain extent, this energy conversion route is feasible. It is a bit like a peaking power source in the grid, such as a pumped storage power station, where 4 degrees of electricity in the low season is exchanged for 3 degrees of electricity in the high season, if but from the power station itself it is of course not cost effective, but when linked to the peak-to-valley difference in the overall grid load, it is again cost effective.
So on a large scale the industrial chain of wind power + carbon capture + CO2 hydrogenation for oil is valid. If this technology, which can be used if water is available but can be converted into gasoline by adding co2, can be realised, then every solar power station and wind power station can be turned into an oil field.
2. Reduce the exploitation of fossil energy.
The CO2->gasoline->CO2 route, which involves CO2 in the carbon cycle, will reduce the exploitation of existing fossil energy sources and at the same time satisfy a part (albeit a small part) of the energy demand.
3. Application is in certain situations where the conversion of CO2 is particularly necessary.
For example, in confined spaces such as nuclear submarines, where the CO2 produced must be disposed of, it is possible to convert CO2 with peroxides to produce oxygen for oxygen; but with the emerging technology of converting CO2 into methanol and even now gasoline, it would make perfect sense to convert CO2 into fuel. For such occasions, where it must be converted away, the cost becomes slightly less important.
