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10.1002/chem.202101928
Chemistry - A European Journal
FULL PAPER
Humins with Efficient Electromagnetic Wave Absorption: a By-
Product of Furfural Conversion to Isopropyl Levulinate via a
Tandem Catalytic Reaction in One-Pot
Mingwei Ma,a, † Na Liang,a, † Pan Hou,a Peng Zhang,a Jingjie Cao,a Hui Liu,a Xingliang Xu,b Huijuan
Yue,a Ge Tian *, a and Shouhua Feng a
Abstract: Both one-pot catalytic conversion of furfural (FAL) to
isopropyl levulinate (PL) and carbonization of by-product (humins) for
electromagnetic wave absorption are discussed, which provides
inspiration that humins can be applied to electromagnetic wave
absorption. In the former, phosphotungstic acid (PW) is employed as
a homogeneous catalyst to convert FAL to PL via a tandem reaction
in one pot, with the formation of a vast amount of humins. With FAL
and various intermediates as substrates, it was found that humins was
a polymerization product of FAL, furfuryl alcohol (FOL) and furfuryl
ester (FE) with furan rings. In addition, the in-situ attenuated total
reflection infrared (ATR-IR) spectra also provided a basis for the
proposed reaction route. In the latter, with the humins as raw material,
P species and WO3 doped nano-porous carbon (Humins-700)
platform formed after high-temperature annealing is used for
electromagnetic wave absorption and manifests desirable absorption
performance. The minimum reflection loss (RLmin) value is -47.3 dB at
13.0 GHz with a thickness of 2.0 mm and the effective absorption
bandwidth reaches 4.5 GHz (11.2 – 5.7 GHz).
its ester by catalytic hydrolysis or alcoholysis with Bronsted acid
(B).[5] And the FOL can be obtained by hydrogenation reduction
of FAL with the assistance of Lewis acid (L) or metal catalyst
under H2 atmosphere or alcohol solution.[6] Therefore,
a
bifunctional catalyst comprising L and B acid was designed to
carry out a one-pot conversion of FAL to LA or its ester (Scheme
1).[7] Recently, Zhang et al. used ZrO2@SBA-15 catalyst to
efficiently and selectively convert FAL to FOL or levulinate ester
and conducted a kinetic study.[7d] Galletti et al. used CuFe2O4 and
a commercial solid acid catalyst for a stepwise reaction to convert
furfural to isopropyl levulinate step by step.[7e]
However, the conversion from C5-C6 sugar, FAL, 5-
hydroxymethylfurfural (HMF) and other biomass or biomass
compounds into high value-added chemicals under the action of
acid catalysts inevitably leads to the formation of solid by-product,
called humins (Figure S1). It is a heterogeneous, polydisperse
material with rich organic functional groups.[8] The formation of
humins is undesirable because it reduces the yield of the target
product and incurs operational problems such as contamination
and blockage of valves and pipes during the process.[9]Since it is
unavoidable, we might as well utilize it while preventing its
generation, which is the focus of this work.
Introduction
The efforts to exploit humins have been ongoing for several
years, including combustion, carbonization, resin, catalytic
gasification, pyrolysis, and hydrotreatment.[10] Guigo et al. used
the humin based resin derived by sugar (C6) to modify the wood
to make it have better hydrophobicity and fire resistance.[11]
Among them, carbonization is one of the simpler and appropriate
methods, which could be widely applied in the synthesis of carbon
materials in the fields of catalysis, adsorption, electrochemical
energy storage, etc. Hedin et al. found that porous carbon-rich
humins with high specific surface area can be prepared from HMF
and sugars in concentrated sulfuric acid.[12] Luque et al. adopted
a solvent-free method (ball milling and thermal degradation) to
prepare nano-humins-based iron oxide composites, which could
oxidize isoeugenol to vanillin as catalyst under electromagnetic
wave heating.[13]
Today, the search for a greener and more sustainable path has
become a problem that must be addressed by humanity. Based
on this premise, the conversion of biomass to platform
compounds is a promising process that can replace traditional
fossil-based products.[1] At present, many important chemicals,
such as tetrahydrofuran, lactic acid, furfural (FAL), levulinic acid
(LA), furfuryl alcohol (FOL), etc. have been produced by catalytic
conversion of biomass-derived carbohydrates.[2] LA, a chemical
extracted from biomass, has been identified by the US
Department of Energy as one of the ten most valuable platform
chemicals,[3] and it is developed as intermediates in the
production of coatings, resins, anticancer agents, pesticides, and
as a condiment and spice in the fine chemical industry.[4] Recently,
FOL has been applied as a precursor for the production of LA or
Electromagnetic wave absorbing materials have attracted
widespread attention in civil and military applications. Carbon-
based materials are a fine electromagnetic wave absorbing
material with the advantages of light weight, large specific surface
area, good thermal conductivity, and tunable dielectric
properties.[14] And many researches were explored by adjusting
the microstructure and macroscopic morphology of carbon-based
materials.[15] Recently, carbon-rich biomass (spinach, waxberry,
loofah sponge, etc.) has also exhibited preferable
electromagnetic wave absorption performance after further
processing.[16]
[a]
M. Ma, † N. Liang, † P. Hou, P.Zhang, J. Cao, H. Liu, Prof. H. Yue,
Prof. G. Tian and Prof. S. Feng
State Key Laboratory of Inorganic Synthesis and Preparative
Chemistry
College of Chemistry, Jilin University
2699 Qian†jin Road, Changchun 130012 (P.R. China)
E-mail: tiange@jlu.edu.cn
[b]
X. Xu
College of Chemistry and Material Science, Shandong Agricultural
University
Shandong 271018, Taian (P. R. China)
Email: xingliangxu@163.com
[†]
These authors contributed equally to this work.
Supporting information for this article is given via a link at the end of
the document.
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