H. Guo et al.
Molecular Catalysis 504 (2021) 111483
catalytic process, that the metal-catalyzed hydrogenation step and the
acid-catalyzed dehydration (or dealcoholization) and lactonization step
catalysts including an acid support is a promising candidate for the
cascade conversion reaction of LA and LE. In our previous work, in order
to reduce the catalyst usage and reaction time, a highly active, low-cost
and magnetic CuNiCoB amorphous alloy catalyst was applied for BL
[
26–28]. At present, five categories of acid supports have been reported,
including oxides (ZrO , TiO , Al , SiO etc.), molecular sieves
ZrMCM-41, SnO
/SBA-15, H-β, HZSM-5, H-MFI, etc.), Metal-Organic
Frameworks (MOFs) and their derivatives (UiO-66-SO H,
2
2
2
O
3
2
(
2
1 3
hydrogenation to GVL [15]. The best catalyst Cu0.5Ni Co B (3 wt%
3
relative to BL) showed the highest GVL yield of 89.5 % with BL con-
◦
zirconium-cyanuric acid coordination polymer (Zr-CA), MIL-101(Cr),
MOF derived carbon, etc.), Acid functionalized carbons (ordered mes-
oporous carbon (OMC), benzenesulfonic acid-functionalized reduced
grapheme oxide (rCO)) and Acidic resins (DOWEX 50WX2-100, sulfo-
nated polyethersulfone (SPES) resin, Amberlyst-70, etc.) [28–32]. The
acidity type (Lewis and Brønsted acidity) and intensity of these supports
have a large effect on the catalytic activity and GVL selectivity. In order
to reduce the catalyst cost and operability, metallic oxides are regarded
as much promising catalyst support for industrial application. However,
version of 99.7 % at 200 C under 3.0 MPa. Nevertheless, there still exist
some drawbacks of the previous catalyst such as harsh reaction condi-
tions, low catalyst stability and partial loss of B species due to the lower
1 3
surface area of Cu0.5Ni Co B amorphous alloy. The successful solution of
these disadvantages of CuNiCoB amorphous alloy catalyst will provide a
high-efficiency and environmental friendly catalyst for industrial
application in lignocellulosic biomass conversion. Therefore, the CuNi-
CoB amorphous alloy catalyst was strongly expected to be loaded on a
support with high surface area and suitable acidity to further improve
the reaction efficiency of BL hydrogenation to GVL.
compared to the SnO
2
/SBA-15 which has both Lewis (L) and Brønsted
B) acidity, the transition metal oxides, specifically, ZrO , Al and
, which only exhibited Lewis acidity was not suitable to improve
(
2
2
O
3
1 1
Herein, Cu modified Ni Co B amorphous alloy catalysts with
SnO
2
different Cu addition content were firstly prepared by chemical reduc-
tion method and evaluated through BL hydrogenation reaction to obtain
the GVL yield [29]. Therefore, the oxide support with lower cost, higher
accessibility and more importantly, suitable Lewis/Brønsted ratio is the
basics for developing bifunctional catalysts.
+
the optimal CuNiCoB hydrogenation active site. H -PAL was applied to
load CuNiCoB amorphous alloy catalyst to enhance the activity and
+
In recent years, Palygorskite (PAL, or Attapulgite as it often called),
stability. Moreover, several third metals promoted H -PAL supported
with a theoretical formula of Mg
5
Si
8
O
20(OH)
2
(OH
2
)
4
⋅4H
2
O and fibrous
CuNiCoB amorphous alloy catalyst were also prepared, characterized
and tested for the BL hydrogenation reaction. The influences of the re-
action conditions, the stability and recyclability of the catalysts were
investigated.
structure, has been widely applied in heterogeneous catalysis as a
catalyst or catalyst support [33–39]. PAL can be effectively modified to
own higher surface area and pore volume through acid activation. The
surface acidity can also be adjusted to obtain coexisting Brønsted and
Lewis acidity sites which are generated from the structural hydroxyl
groups in the layer structure of PAL and exposed Al3 , respectively [40].
Accordingly, the acid-activated PAL has been applied in different
acid-catalyzed fields [37,39,41,42]. Except for the specific textures and
2. Experimental
+
2.1. Materials
surface acidity of PAL, the intrinsic SiO
2
and Al
2
O
3
contribute to adjust
Butyl levulinate (BL, 98 %), 1,4-pentanediol (1,4-PDO, 98 %) and
the interactions between metals and support, thus improving the
dispersion of active metals and enhancing the catalytic activity. In our
4
NaBH (98 %) were purchased from Aladdin Reagent Co. Ltd. (Shanghai,
China); γ-valerolactone (GVL, 98 %) from Macklin biochemical Co. Ltd.
(Shanghai, China); Butyl valerate (BV, 98 %) from TCI Co. Ltd.
+
previous work, the acid-activated PAL (H -PAL) supported NiCoB
amorphous alloy catalysts showed excellent hydrogenation activity and
stability for furfural (FUR) conversion into furfuryl alcohol (FA) [43].
(Shanghai, China). Copper chloride (CuCl
(NiCl O), Cobalt chloride (CoCl ⋅6H O), Ammonium molybdate
⋅6H
tetrahydrate ((NH Mo O), n-Butyl alcohol (n-BuOH) and Ab-
2
⋅6H
2
O), Nickel chloride
2
2
2
2
+
The best catalyst (20%NiCoB/H -PAL) showed an increase of 3.9 % in
4
)
6
7
O
24⋅4H
2
FUR conversion and 8.2 % in FA selectivity after six cycles due to the
newly generated CoNi alloy active site. But as far as we know, the
acid-activated PAL has not been applied in BL hydrogenation.
solute ethyl alcohol (EtOH) were purchased from Sinopharm Chemical
Reagent Co., Ltd. (Shanghai, China). n-Propyl alcohol (n-PrOH),
Lanthanum nitrate (La(NO
3
)
3
⋅6H
⋅5H
2
O), Cerium nitrate (Ce(NO
3
)
3
⋅6H
2
O)
In addition to the acidity of catalyst support, the metal loads, particle
sizes as well as the dispersion of hydrogenation active metal are also
very important control parameters in order to obtain a higher GVL yield.
The precious metals, such as Ru, Rh, Pt, Ir, Au-Pd, etc. have displayed
superior catalytic activity in FUR and BL hydrogenation reaction
and zirconium nitrate (Zr(NO
3
)
4
2
O) were purchased from Tianjin
Kemiou Chemical Reagent Co., Ltd. (Tianjin, China). Methanol (MeOH),
n-Pentyl alcohol (n-PeOH), cyclohexane (CH), n-Hexane and 1, 4-
dioxane were purchased from Tianjin Fuyu Fine Chemical Co., Ltd.
(Tianjin, China). Zinc nitrate (Zn(NO
3 2 2
) .6H O) and Ferric nitrate (Fe
[
44–47]. As a popular substitute for precious metals, the Ni-based,
(NO .9H O) were purchased from Damao Chemical Reagent Factory
3
)
3
2
Cu-based or Ni-Cu-based catalysts have been extensively used due to
(Tianjin, China). Natural palygorskite was provided by ZHONGKE New
+
low cost and high availability [48–59]. A hydrotalcite-like compounds
Energy Technological Development Co., Ltd (Huai-An, China). The H -
(
HTlcs) derived Cu-based catalyst achieved high GVL yield of 91 % from
PAL was prepared according to the previous procedure with the acid
concentration of 21 wt% [63]. All reagents were used without any
further purification.
◦
LA at 200 C under 7.0 MPa H
2
after 10 h [60]. Another magnetic and
recyclable Ni4.59Cu
1
Mg1.58Al1.96Fe0.70 catalyst with HTlcs structure
could yield 98.1 % of GVL from LA through the catalytic transfer hy-
◦
drogenation (CTH) reaction using methanol as the H-donor at 142 C
2.2. Catalyst preparation
after 3 h [61]. Furthermore, some oxides were also applied to support
active metals to improve the catalyst activity and stability. The Al
2
O
3
The Ni Co B amorphous alloy catalyst with Ni/Co molar ratio of 1/1,
1
1
supported bimetallic Cu-Ni catalyst (10Cu-5Ni/Al ) had the highest
2
O
3
1 1
CuB catalyst and Cu modified Ni Co B catalyst with Cu/Ni molar ratio of
activity for CTH of EL to GVL, providing a 97 % yield of GVL in 12 h at
x 1 1
x/1 (denoted as Cu Ni Co B) were prepared by the chemical reduction
◦
1
2
50 C [10], and another 10Cu-10Ni/Al
2
O
3
catalyst showed a higher
1 1
method [64]. The following study results showed that Cu0.5Ni Co B is
+
-methylfuran yield of 92 % from the CTH reaction of FUR with formic
the optimized Cu0.5Ni Co B hydrogenation active site. The H -PAL
1 1
acid as a hydrogen donor [48]. The ZrO
2
-Al
2
O
3
composite supported Cu
1 1
supported Cu0.5Ni Co B catalyst with a loading content of 20 wt%
◦
+
catalyst, which possesses ternary active sites (metal active sites Cu ,
(named as Cu0.5Ni Co B/H -PAL) was prepared by the
1 1
+
oxygen deficiencies derived from ZrO
2
, and acidic Al
2
O
3
), displayed
impregnation-reduction method. Typically, 10 g H -PAL powder (>100
mesh) was equivalent-volume impregnated with an aqueous solution of
1.43 g CuCl ⋅2H O, 3.98 g NiCl ⋅6H O and 3.98 g CoCl ⋅6H O under
superior catalytic activity and excellent recycling stability for GVL
synthesis from LA at low temperature due to the intimate synergies of
these ternary active sites [62]. In a word, the bifunctional Ni-Cu-based
2
2
2
2
2
2
◦
vacuum for 24 h at room temperature. It was then dried at 120 C for 1 h,
2