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Green Chemistry
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Journal Name
ARTICLE
On the basis of the experimental results above and the related
Acknowledgements
The work was supported financially by National Natural Science
Foundation of China (21871277 and 21703258), Beijing Municipal
Science & Technology Commission (Z1811000042180042).
DOI: 10.1039/D0GC00587H
knowledge in the literature,35 we proposed a possible reaction
mechanism of lignin transformation into 4-ethyltoluene, which is
shown schematically in Figure S8. In the process, there are mainly
five steps: (1) LiI firstly cleaved the ether linkage of the methoxy
groups in lignin to form CH3I and lithium phenolate of lignin with the
- 21
synergy of BF4 . (2) The water gas shift (WGS) reaction occurs
Notes and references
35, 38
promoted by the Rh catalyst.
(3) Lithium phenolate of lignin
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reacted with LiI to form LiOH and lignin contained iodine. (4) LiOH
further reacted with HI and generated LiI and H2O. (5) lignin
contained iodine was further hydrogenated with in-situ generated H2
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We further investigated the transformation of various lignin
samples and even lignocellulose using RhCl3-LiI-LiBF4 catalytic system
under optimized conditions and the corresponding results are
summarized in Table S6. It was clearly observed that 4-ethyltoluene
could be produced efficiently from various lignin promoted by the
RhCl3-LiI-LiBF4 catalytic system. The total yield of 4-ethyltoluene and
ethylbenzene from GVL-lignin could reach up to 13.07 wt%, and the
yield of 4-ethyltoluene was 9.50 wt%. More importantly, the
ethylbenzene and 4-ethyltoluene could be produced directly from
Poplar using RhCl3-LiI-LiBF4 catalytic system and 5.18 wt% yield of 4-
ethyltoluene was obtained based on the amount of lignin in Poplar.
Therefore, this catalytic system has potential to produce 4-
ethyltoluene from lignin or lignocellulose.
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Conclusions
In summary, we have proposed a one-pot catalytic process for the
direct production of 4-ethyltoluene from lignin or lignocellulose, and
found that using RhCl3-LiI-LiBF4 was efficient catalytic system in the
presence of CO. In the reaction process, LiI firstly cleaved the ether
linkage of the methoxy groups in lignin to form CH3I and lithium
phenolate of lignin. Then the lithium phenolate of lignin was further
hydrolysed, iodinated and hydrogenated with in-situ generated H2 to
form the methoxy-free lignin, which underwent depolymerization
and methylation to formed 4-ethyltoluene. The yield of 4-
ethyltoluene could reach 9.50 wt% when GVL-lignin was used as the
starting material. Moreover, yield of 4-ethyltoluene was 5.18 wt%
when raw poplar was directly used as the starting material. We
believe that the new strategy has promising potential of application
to produce 4-ethyltoluene utilizing lignin as the resource.
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Conflicts of interest
23. B. Ogunbadejo, A. Aitani, J. Čejka, M. Kubů and S. Al-Khattaf,
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The authors declare no competing financial interests.
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