Reusability Investigation of a Ruthenium Catalyst
during Ruthenium Ion-Catalyzed Oxidative Depolymerization of Lignite
for the Production of Valuable Organic Acids
posted on 2021-09-28, 12:03authored byXuefeng Yao, Xiaolu Wang, Yuxin Chen, Lu Zhang, Quansheng Liu, Runxia He, Huacong Zhou, Xingshun Cong
A clean and efficient
conversion process is essential for the utilization
of low-rank coals. Lignite, a typical representative of the low-rank
coal family, has huge potential for the production of valuable chemicals
via the oxidative depolymerization reaction. Ruthenium ion-catalyzed
oxidation (RICO) is an effective route for lignite depolymerization
under mild conditions, but the high cost of precious Ru limits the
potential large-scale application of RICO. How to recycle and reuse
Ru is critical to promote the application of RICO. In this work, a
novel and efficient approach for reusing Ru through recycling the
solvent mixture containing Ru was established for RICO. First, the
influence of different reaction parameters on the depolymerization
degree of lignite and benzene polycarboxylic acid (BPCA) yields was
investigated. Second, the distribution of Ru in the organic phase
(OP), aqueous phase (AP), and residual solid phase (RSP) was analyzed
after the RICO reaction. Finally, based on the distribution of Ru
in different phases, a novel route of recycling Ru by reusing the
Ru-containing solvents was proposed. The results showed that the dosage
of RuCl3 and NaIO4 had a significant influence
on both the depolymerization degree of lignite and BPCA yields. The
distribution of Ru had a close relationship with the depolymerization
degree of lignite and the dosage of NaIO4. After the depolymerization
reaction, the CCl4 phase containing Ru was reused directly
as the solvent for the next run, which could fulfill the reuse of
both CCl4 and Ru. The results proved that the Ru-containing
CCl4 phase could maintain catalytic performance for 5 runs.
This work provides an efficient route to reuse Ru for the RICO depolymerization
of lignite into valuable organic acids. As far as we know, this is
the first report concerning the recycling and reuse of Ru during the
RICO of lignite. This work is important for the application of RICO
in lignite depolymerization.