National Science Review

PERSPECTIVE 10: nwad160, 2023

https://doi.org/10.1093/nsr/nwad160
Advance access publication 30 May 2023

CHEMISTRY

Special Topic: Green Carbon Science—A Scientific Basis for Carbon Neutrality
Transformation of CO2 and H2 to C2+ chemicals and fuels
Qingli Qian1 ,2 ,* and Buxing Han1 ,2 ,3 ,4 ,*

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CO2 is a greenhouse gas, and is also a spectively, which further formed the car-
cheap, easily available and renewable car- boxylic acids.
bon resource. Fixation of CO2 into chem- In 2016, a Pt/Co3 O4 catalyst was re-
icals has been extensively investigated ported to accelerate the synthesis of C2+
in the forms of thermocatalysis, electro- alcohols via CO2 hydrogenation, with a
catalysis and photocatalysis. CO2 is the space time yield (STY) of 0.509 mmol
highest oxidation state of carbon, and re- gcat −1 h−1 for alcohols and a C2+ OH se-
duction of CO2 is usually required in its Figure 1. Synthesis of C2+ chemicals from CO2 lectivity of 82.5% at 200o C [5]. Later, it
chemical utilization. Green hydrogen is and H2 . was reported that ethanol may be gener-
an ideal reductant to transform CO2 into ated via CO2 hydrogenation in water sol-
basic chemicals, because it can be ob- vent over CoAlOx catalyst with a selectiv-
tained by splitting water with renewable highlight the progress in this area by dis- ity of 92.1% and activity of 0.4 4 4 mmol
electricity from solar energy. CO2 hydro- cussing some typical related works. gcat −1 h−1 at 140°C [6].
genation is among the most important A route for acetic acid production via CO2 hydrogenation to liquid hy-
areas of CO2 conversion, and consider- methanol hydrocarboxylation with CO2 drocarbons is usually promoted by
able progress has been achieved in re- and H2 was developed in 2016, where heterogeneous catalysts, which may
cent decades, especially in the production Ru3 (CO)12 -Rh2 (OAc)4 was used as a simultaneously catalyze the RWGS reac-
of C1 molecules such as CO, methanol, catalyst [2]. The mechanistic study veri- tion and the subsequent Fischer–Tropsch
methane, and formic acid and its deriva- fied that CO2 directly took part in the re- synthesis (FTS). The RWGS reaction
tives. In many cases, multicarbon (C2+ ) action, which is different from the well- is endothermic and a higher tempera-
products are very useful in society. For known methanol carbonylation pathway. ture is needed to produce enough CO,
example, acetic acid is a bulk and ba- There were also several breakthroughs whereas the FTS reaction is exothermic
sic chemical, and its production capac- in synthesizing higher carboxylic acids and higher temperatures tend to inhibit
ity is ∼20 million tons/year. Ethanol and from CO2 and H2 . A pioneering work the formation of larger hydrocarbons. To
higher alcohols, as well as liquid (C5+ ) showing higher carboxylic acid synthe- overcome this thermodynamic limita-
hydrocarbons, are not only basic chem- sis from olefins, CO2 and H2 at 180o C tion, an additional zeolite catalyst may be
icals but also engine fuels and fuel ad- was reported in 2013. This was accel- appended to reform the smaller hydrocar-
ditives. Without doubt, the synthesis of erated by a catalytic system consisting bons into larger ones. A highly efficient
C2+ chemicals using CO2 and H2 is of of [RhCl(CO)2 ]2 catalyst, PPh3 ligand, Na–Fe3 O4 /HZSM-5 catalyst operating
great importance. However, this is a chal- CH3 I promoter and acidic additive (p- at 320o C was designed according to this
lenging task because it involves controlled TsOH·H2 O) [3]. In this work, CO was method, where gasoline fuel (C5 –C11 )
hydrogenation with simultaneous C–C generated in situ via a reverse water gas composed of aromatics, naphthenes,
bond formation. For a long time, there shift (RWGS) reaction, which reacted isoparaffins, olefins and n-paraffins was
were only sporadic reports of the produc- with the olefin via carbonylation to pro- produced [7]. Homogeneous catalysis is
tion of C2+ products from CO2 and H2 . duce carboxylic acids. In 2019, a strat- known for its high efficiency at a lower
With the ever-increasing attention of so- egy of carboxylic acid production from temperature. At 180°C, high efficiency
ciety on CO2 utilization, reports on this ethers, CO2 and H2 was put forward. was realized by coupling the homoge-
topic have increased remarkably in re- This was catalyzed by IrI4 catalyst with neous RuCl3 catalyzed RWGS reaction
cent years [1]. The progress can be briefly LiI promoter at 170°C [4]. The cat- and heterogeneous Ru0 catalyzed FTS
summarized according to product cate- alytic system simultaneously transformed reaction to generate C5 –C28 n-paraffins
gories (Fig. 1). In this perspective, we ether and CO2 into olefin and CO re- in a batch reactor [8]. Beyond CO2
© The Author(s) 2023. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original
work is properly cited.
 Natl Sci Rev, 2023, Vol. 10, nwad160

hydrogenation, this study opens up the to be designed and fabricated. The key to and Chemical Thermodynamics, CAS
possibility of combining homogeneous discovering new reactions is the develop- Research/Education Center for Excellence in
and heterogeneous catalysts to achieve ment of novel catalysts that may engen- Molecular Sciences, Center for Carbon Neutral
eminent cascade reactivity in a single der new reaction pathways. In many in- Chemistry, Institute of Chemistry, Chinese
reactor. The CO2 may also be firstly stances, noble metal catalysts are used, Academy of Sciences, China; 2 Physical Science
hydrogenated to methanol and subse- especially in homogeneously catalyzed Laboratory, Huairou National Comprehensive
quently reformed as liquid hydrocarbons CO2 hydrogenation to C2+ products. Science Center, China; 3 School of Chemistry and
in zeolite, and at 340o C the bifunctional Development of sustainable metal catal- Chemical Engineering, University of Chinese
In2 O3 /HZSM-5 catalyst demonstrated ysis or organocatalysis is of great impor- Academy of Sciences, China and 4 Shanghai Key
excellent performance when synthesizing tance, but is still a challenge. The reac- Laboratory of Green Chemistry and Chemical
gasoline (C5 –C11 ) consisting of isoparaf- tion courses of CO2 hydrogenation to Processes, School of Chemistry and Molecular

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fins, n-paraffins, olefins and aromatics C2+ chemicals are usually complex and Engineering, East China Normal University, China
[9]. Direct hydrogenation of CO2 into the conditions are relatively harsh, which ∗ Corresponding authors.

C5 –C26 n-paraffins and minor olefins was makes the mechanistic study more diffi- E-mails: qianql@iccas.ac.cn; hanbx@iccas.ac.cn
also realized over a simple Co6 /MnOx cult. Well-designed experiments and ad-
nanocatalyst at 200o C in a batch reactor vanced apparatus are needed to get more REFERENCES
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© The Author(s) 2023. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original
work is properly cited.

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