10.1002/cctc.202000408
ChemCatChem
COMMUNICATION
Pt/SiO2@Mg(OH)2 catalyst. The lower temperature make it
possible to combine Route 3 with Route 4 to together promoted
the 1,2-PG generation. However, the contribution of hexitol by-
product could not make a so different 1,2-PG yield between
Pt/SiO2 (19.9%) and Pt/SiO2@Mg(OH)2 (53.8%). Thus, the other
aspect of Mg(OH)2 effect on Route 4 was investigated. The
reactions of the possible intermediates over Pt/SiO2@Mg(OH)2
and Pt/SiO2 catalysts were performed and the results were
showed in Table S3. As listed in entries 1 and 3, fructose was
catalyzed into 1,2-PG with a yield of 43.7% over Pt/SiO2, while
glucose could only achieve 19.9% yield of 1,2-PG because of
the isomerization barrier between glucose and fructose. While,
Pt/SiO2@Mg(OH)2 (entries
2 and 4) broke through the
isomerization barrier, leading to the efficient conversion of
glucose into 1,2-PG. By synthesizing these data, the pseudo-
yield[19] of isomerization reaction over Pt/SiO2 and
Pt/SiO2@Mg(OH)2 were 45.5 and 95.7%, respectively, which
indicated the promotion effect of Mg(OH)2 on isomerization of
glucose into fructose (R1, Scheme 1). In previous studies, a
similar effect of Mg/NaY[20] on glucose isomerization in a single
glucose-fructose reaction system could support the effect of Mg
species. Moreover, the pseudo-yield of RAC reaction was
increased to 98.4% over Pt/SiO2@Mg(OH)2 from 50.9%, which
could be obtained by calculating the data in Entries 3, 4, 11 and
12. The increased pseudo-yield of RAC was higher than that in
existing literature[4a, 6a, 10, 21] (e.g., 90% over InCl2 and 49% over
SnCl2[19]). Hence, the promotion of R1 and R2 in Route 4
(Scheme 1) were simultaneously achieved by Pt/SiO2@Mg(OH)2.
In conclusion, the effect of Mg(OH)2 on 1,2-PG generation could
be attributed to the three reasons, including the promotion of
isomerization and RAC, as well as the re-conversion of by-
product hexitol.
Figure 4. Reusability and metal leaching of catalysts synthesized by different
methods. Reaction condition: catalyst (200 mg), glucose (11.25 mg/ml, 10 ml)
and H2 (initial 6 MPa) at 180 °C for 4 h.
In summary, we demonstrate
magnesium hydroxide assembly onto Pt/SiO2 to achieve a three-
pronged promotion of 1,2-PG production, including
a feasible strategy of
enhancement of isomerization of glucose into fructose and RAC
of fructose, as well as re-conversion of by-product hexitol into
1,2-PG. The Pt/SiO2@Mg(OH)2 possessed a core-shell structure
by in situ hydrothermal process and showed both excellent
performance and stability. This work could help facilitate studies
on development of high-valued chemicals from biomass
derivatives over base modified catalysts.
Acknowledgements
Besides the reaction performance of Pt/SiO2@Mg(OH)2,
catalytic stability in recycling is also an important property for the
practical application of catalysts. Therefore, the reusability of
Pt/SiO2@Mg(OH)2 and Mg-Pt/SiO2 synthesized by three
traditional methods were investigated. As Figure 4 shown, the
yield of 1,2-PG obtained by Pt/SiO2@Mg(OH)2 slightly
decreased from 53.8% to 49.8% and 44.5% by the second and
third runs, respectively. It showed more stable performance than
other catalysts. It could be attributed to slighter metal leaching,
which was verified by Figure 4 (right y). The Pt loading in
Pt/SiO2@Mg(OH)2 decreased from 5.12 to 4.65 and then to 4.45
wt% and the Mg(OH)2 loading was decreased from 5.03 to 4.78
and then to 4.45 during three times of reuse. In contrast, Pt/SiO2
showed a more significant Pt leaching. The difference indicated
the Mg(OH)2 shell might suppress the leaching of Pt on SiO2 and
rendered them stable under the reaction conditions. A similar
effect of solid base on catalytic stability was also reported by
Sun, et al.[5b] in Ni/C combined with Ca(OH)2 system. Compared
to a series of Mg-Pt/SiO2 catalysts with different structures, the
stability of Pt/SiO2@Mg(OH)2 might be attributed to the core-
shell structure, where Mg(OH)2 shell prevented the Pt particles
from leaching into the reaction media. However, Mg-Pt/SiO2
(PtF) prepared by impregnation method showed poor yields
although the Pt could be prevented from leaching by Mg species,
reasoning from the coverage of Pt active sites by Mg species.
While the core-shell structure of Pt/SiO2@Mg(OH)2 did not cover
the Pt active sites when protected the Pt particles. Thus,
Pt/SiO2@Mg(OH)2 prepared by in situ hydrothermal process
showed both excellent yield and stability.
This work was supported by National Key Research and
Development Plan (No. 2019YFC1906700), the National Natural
Science Foundation of China (No. 21978224 and 21676205)
and National Outstanding Youth Science Fund Project of
National Natural Science Foundation of China (No. 51625804).
Keywords: glucose • propylene glycol • hydrogenolysis •
magnesium hydroxide
[1]
a) R. Y. Sun, T. T. Wang, M. Y. Zheng, W. Q. Deng, J. F. Pang, A. Q.
Wang, X. D. Wang, T. Zhang, Acs Catal. 2015, 5, 874-883; b) M. Y. Gu,
Z. Shen, L. Yang, W. J. Dong, L. Kong, W. Zhang, B. Y. Peng, Y. L.
Zhang, Sci. Rep. 2019, 9, 11938; c) X. D. Wang, A. K. Beine, R.
Palkovits, Stud. Surf. Sci. Catal. 2019, 178, 173-193.
[2]
[3]
M. Y. Zheng, J. F. Pang, R. Y. Sun, A. Q. Wang, T. Zhang, Acs Catal.
2017, 7, 1939-1954.
a) M. Lucas, K. Fabičovicová, P. Claus, ChemCatChem 2017, 10, 612-
618; b) Z. H. Xiao, S. H. Jin, M. Pang, C. H. Liang, Green Chem. 2013,
15, 891-895; c) E. Girard, D. Delcroix, A. Cabiac, Catal. Sci. Technol.
2016, 6, 5534-5542; d) R. Y. Sun, M. Y. Zheng, J. F. Pang, X. Liu, J. H.
Wang, X. L. Pan, A. Q. Wang, X. D. Wang, T. Zhang, Acs Catal. 2016,
6, 191-201; e) Z. Q. Xiao, Q. Zhang, T. T. Chen, C. G. Cai, Q. Ge, Y.
Nie, J. B. Ji, J. W. Mao, Catal. Lett. 2018, 148, 3757-3770.
[4]
a) Z. C. Tan, L. Shi, Y. F. Zan, G. Miao, S. L. Li, L. Z. Kong, S. G. Li, Y.
H. Sun, Appl. Catal., A 2018, 560, 28-36; b) J. F. Pang, M. Y. Zheng, X.
S. Li, Y. Jiang, Y. Zhao, A. Q. Wang, J. H. Wang, X. D. Wang, T. Zhang,
Appl. Catal., B 2018, 239, 300-308; c) C. W. Liu, C. H. Zhang, S. K.
Sun, K. K. Liu, S. L. Hao, J. Xu, Y. L. Zhu, Y. G. Li, Acs Catal. 2015, 5,
5
This article is protected by copyright. All rights reserved.