Synthesis of 1,2-propanediamine via reductive amination of isopropanolamine over Raney Ni under the promotion of K2CO3

Article abstract of DOI:10.1007/s11696-019-00734-9

Catalytic amination of isopropanolamine and ammonia to 1,2-propanediamine over Raney Ni with potassium carbonate as the additive was reported. Characterization of N₂ adsorption–desorption and XRD were performed to reveal the textural and structural properties of the catalysts. With the additive of potassium carbonate, the selectivity of 1,2-propanediamine was improved, while the side generation of 2,5-dimethylpiperazine was suppressed. The catalytic reaction parameters were optimized and the yield of 1,2-propanediamine reached 80% under the optimized reaction condition.

Full text of DOI:10.1007/s11696-019-00734-9

Chemical Papers
https://doi.org/10.1007/s11696-019-00734-9
ORIGINAL PAPER
Synthesis of 1,2‑propanediamine via reductive amination
of isopropanolamine over Raney Ni under the promotion of K2CO3
Qin‑Wei Yu1 · Ya‑Ni Li1 · Qian Zhang1 · Wei‑Qiang Wang1 · Su‑Ning Mei1 · Feng Hui1 · Jian Shi1 · Feng‑Wei Zhao1 ·
Jian‑Ming Yang1 · Jian Lu1
Received: 18 December 2018 / Accepted: 4 March 2019
© Institute of Chemistry, Slovak Academy of Sciences 2019
Abstract
Catalytic amination of isopropanolamine and ammonia to 1,2-propanediamine over Raney Ni with potassium carbonate as
the additive was reported. Characterization of N2 adsorption–desorption and XRD were performed to reveal the textural
and structural properties of the catalysts. With the additive of potassium carbonate, the selectivity of 1,2-propanediamine
was improved, while the side generation of 2,5-dimethylpiperazine was suppressed. The catalytic reaction parameters were
optimized and the yield of 1,2-propanediamine reached 80% under the optimized reaction condition.
Keywords Isopropanolamine · 1,2-Propanediamine · Raney nickel · Potassium carbonate · Reductive amination
Introduction
More so, the selectivity of the diamine is low owing to the
generation of poly and cycle amine byproduct, which is
attributed to the high activity of amine for the strong nucleo-
philicity. Therefore, synthesis of diamine with high selec-
tivity by reductive amination of bifunctional alcohol is put
forward higher requirements.
Amines are basic and bulk chemical raw materials for pro-
duction of pharmaceuticals, agrochemicals, polymers and
dyes (Rossin and Peruzzini 2016; Choi et al. 2011; Suslov
et al. 2017). There are various methods for synthesizing
amines of which the most commonly used is through ami-
nation of alcohols and ammonia for the starting material
is inexpensive and readily available (Lawrence 2004; Leg-
nani et al. 2017; Subramanian et al. 2014; Bahadori et al.
2013; Crossley et al. 2016; Pera-Titus and Shi 2014; Liu
et al. 2017a, b; Pelckmans et al. 2017). Moreover, the only
by-product is water, and thus attracts much attention as green
and atom-economical chemistry.
To search high-performance catalytic system, many
attempts have been presented. It was reported (Imm et al.
2011; Pingen et al. 2013) that diamines can be synthesized
by amination of diols with Ru catalyst under the coopera-
tion of ligand and base in homogeneous process (Scheme 1,
reaction 1). The conversion and selectivity were both over
95% for specifc substrate alcohol. However, the amination
of linear alky diols was not involved. Although Ru catalyst
has high performance in the amination of cycle diols, the
recovery and reuse of noble metal and ligand from these
homogeneous catalytic systems were much more difcult.
Comparatively, the catalysts in the heterogeneous cata-
lytic reaction process are easily recovered and reused, in
spite of most of them hardly achieved satisfactory activity
and selectivity of primary diamines. Metal catalysts (Ru,
Ni, Co, etc.) were employed in heterogeneous amination
of bifunctional alcohol to diamine (Scheme 1, reaction 2).
With the supported Ru catalyst, poor conversion (lower
than 10%) was obtained for amination of propane-1,2- and
-1,3-diol and butane-2,3-diol, while the cyclic amines were
the main products for pentane-1,5-diol and hexane-1,6-diol
(Niemeier et al. 2017). Li et al. (2017) reported that the
Primary diamine is one of the most important amines
(Lawrence 2004; Zhao et al. 2015) which can be synthesized
via reductive amination of bifunctional alcohol (diol and
aminoalcohol). But amination of short-chain diol sufers low
conversion and is always accompanied by other side reac-
tions such as cracking, condensation, dehydration reaction.
* Jian-Ming Yang
yangjm204@163.com
* Jian Lu
lujian204@263.net
1
State Key Laboratory of Fluorine & Nitrogen Chemicals,
Xi’an Modern Chemistry Research Institute, Xi’an 710065,
Shaanxi, China
Vol.:(0123456789)
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Chemical Papers
Scheme 1 Synthesis method-
Previous work
ologies of diamine chemicals
M(L)n/base
solvent
homogeneous
H2N R NH2
HO R OH
(1)
(2)
M/support
NH3/H2
HO R OH(NH2)
H2N
R
NH2
heterogeneous
This work
(3)
hexane-1,6-diamine can be obtained with the Ru/Al2O3 cata-
lyst by the amination of 1,6-hexanediol, while the selectivity
of hexane-1,6-diamine was only 38%. Only aminoalcohols
were obtained by amination of propane-1,2-diol over Rh–In
catalyst (Takanashi et al. 2014). In this aspect, to reduce
the cost, noble metal-free catalysts have been developed.
For example, Co-modifed H-ZSM-5 catalyst was prepared
to investigate the reductive amination of ethanolamine to
ethylenediamine, but selectivity was lower than 20% (Zhang
et al. 2007). Co–Fe or Ni catalysts was studied for the ami-
nation of alky diols in supercritical ammonia (Fischer et al.
1999a, b, c, d; Jenzer et al. 1999). However, the selectivity
of diamines was below 40% for amination of linear alky
diols and selectivity was below 70% even for amination
of α-substituted or cycle diols. Recently, Ma et al. (2018)
reported reductive amination of monoethanolamine over
Ni–Re catalyst and the conversion was less than 45% when
the selectivity of ethylenediamine was about 80%. Therefore,
it is necessary to explore the new convenient heterogeneous
catalysts with high performance for preparation of diamines.
In previous work, we reported a direct reductive amina-
tion of 2-amino-2-methyl-1-propanol to produce 2-methyl-
1,2-propyldiamine over Raney Ni catalyst (Wang et al.
2017). Inspired by the promotion of base in homogeneous
catalytic system, herein, the direct amination of bifunctional
secondary alcohol with ammonia to diamine over Raney Ni
catalyst under the promoter of base was developed. The
introduction of base, especially for K2CO3, can improve the
selectivity of 1,2-propylenediamine by reductive amination
of isopropanolamine (Scheme 1, reaction 3) (Scheme 1).
Shaanxi, China. Raney Co catalyst (RTH-6110) used in
experiments was supplied by Dalian Tongyong Chemical
Co., Ltd., Liaoning, China. Above catalysts were used with-
out pre-treatment before experiments. The Ni–Al alloy pow-
ders (average particle size is 50 μm), containing about 50%
Ni and 50% Al (w/w), were produced by Dalian Tongyong
Chemical Co., Ltd., Liaoning, China.
Isopropanolamine (IPA,>99%) used in experiment was
purchased from Chengdu Kelong reagent Co., Ltd., Sichuan,
China. Ammonia was purchased from Xinghua Chemical
Industry Incorporated Co., Ltd, Shaanxi, China. The other
analytical reagents such as NaOCH3, Li2CO3, Na2CO3,
K2CO3, KOH and NaOH were supplied by Sinopharm
Chemical Reagent Co., Ltd., Shanghai, China. Deionized
water and high purity hydrogen were used in experiment.
Raney Ni catalyst was made by follow procedures: the
Ni–Al alloy powders (termed as Ni–Al) were added to 30
wt% aqueous sodium hydroxide in a beaker immersed in
thermostated water at 70 °C by batch carefully and kept at
80 °C for more than 5 h. The extracted catalysts were washed
with deionized water until neutralized. The samples were
fnally washed with absolute ethanol for three times, and
transferred to stoppered tubes for storage in absolute ethanol
at room temperature. The resultant Raney Ni was designated
as FR.
Catalyst characterization
The specifc surface areas of the samples were obtained with
a Micromeritics ASAP 2020 nitrogen adsorption instru-
ment at 77 K. The samples were degassed under vacuum at
250 °C for 8 h. BET surface areas were determined by the
Brunauer–Emmett–Teller (BET) method and total pore vol-
ume and average sizes were evaluated by the standard Bar-
rett–Joyner–Halenda (BJH) methodc of the isotherm. XRD
patterns of the samples were collected with an Empyrean,
PANalytical X-ray difractometer (Cu Kα, λ=0.15418 nm).
Experiment
Catalyst preparation
PdCl2(PPh3)2, Pd(OAc)2, RhCl(PPh3)3, IrCl3, Pt/C and 5%
Rh/C were from Kaida Chemical Engineering Co., Ltd.,
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Chemical Papers
Table 1 Amination of isopropanolamine with ammonia over various
The pattern for the structure refnement was taken in a 2θ
catalysts
range of 5–90° with a step width of 0.026°.
Entry Cat./loading
Conv.% Sel.%
PDA DMP
Yield%
(PDA)
Catalyst test
1a
2a
3a
4a,b
5a,c
6a,c
7
8
9
10
PdCl2(PPh3)2/3 mol% 41.9
17.7
–
20.9
–
–
–
42.4
34.6
83.8
86.3
3.0
–
16.6
–
–
–
4.9
14.6
6.6
4.9
7.4
–
17.4
–
–
–
2.2
5.9
58.1
49.1
The amination reactions were carried out in a 50-mL sealed
autoclave. The catalysts, isopropanolamine, and bases were
placed into the autoclave. Air in the autoclave was evacu-
ated by pressurization–depressurization cycles with nitrogen
and subsequently with hydrogen. Then, after vacuuming the
autoclave, liquid ammonia was placed into the reactor. After
that, the mixture was pressurized with hydrogen to specifc
pressure, and the stirring speed was set as 800 rpm. The
autoclave was heated to 170 °C and kept for specifc time
before it was cooled to room temperature and depressed to
atmospheric pressure. The mixture was fltrated and the
catalyst was washed with water and ethanol for three times,
respectively. The recycled Raney Ni collected from the
reaction without the additive of K2CO3 was denoted as AR;
recycled Raney Ni collected from the reaction with the addi-
tive of K2CO3 was denoted as KAR. The liquid mixture was
analyzed by GC–MS (Agilent 6890N/5975B). To separate
the reaction products, the temperature in the GC oven was
kept at 323 K for 5 min, and then heated to 523 K with the
ramp of 10 K/min. The liquid products were analyzed by a
gas chromatograph (Shimadzu GC-2014C) with a capillary
column (DB-35 30 m×0.32 mm×0.25 μm) equipped with a
fame ionization detector (FID). The conversion of IPA and
selectivity of 1,2-propylenediamine (PDA) for each experi-
ment was defned as follows:
Pd(OAc)2/3 mol%
RhCl(PPh3)3/3 mol%
IrCl3/3 mol%
Cu(NO3)2/3 mol%
Ni(NO3)2/3 mol%
Ru(5%)/C/10 wt%
Pd(5%)/C/10 wt%
Raney Ni/3 wt%
Raney Co/3 wt%
13.4
83.2
23.7
5.7
14.3
5.1
17.1
69.3
56.9
Reaction conditions: isopropanolamine (0.1 mol); ammonia
(0.16 mol); initial hydrogen pressure 4 MPa; 170 °C; 15 h
a0.04 mol IPA, 5 mL CH3Ph
b4 mol% PPh3
c6 mol%PPh3
of alcohols in previous study. Therefore, various catalysts for
the reductive amination of isopropanolamine with NH3 were
investigated to screen the catalyst, which is summarized in
Table 1.
Under the investigated reaction conditions, homogeneous
catalysts Pd(OAc)2, IrCl3, Cu(NO3)2 and Ni(NO3)2 showed
low activity and no target product was detected (Table 1,
entries 2, 4–6). PdCl2(PPh3)2 showed 7.4% yield of PDA
(Table 1, entries 1). RhCl(PPh3)3 turned out to be the most
active homogeneous catalyst (80% conversion of IPA) but
the yield of PDA was less than 20% as well as the low
selectivity (Table 1, entries 3). For heterogeneous catalysts,
Ru(5%)/C and Pd(5%)/C both gave very low yield of PDA
(Table 1, entries 7, 8). Raney-type Ni and Co catalysts pro-
vided higher activity and selectivity. For example, the Raney
Co gave PDA yield of 49.1% (Table 1, entries 10), while the
Raney Ni catalyst exhibited higher activity than Raney Co
catalyst, which gave 69.3% conversion and 58.1% yield of
PDA (Table 1, entry 9). Therefore, Raney Ni was employed
for further study.
mass amount of IPA reacted
X =
× 100 wt%
mass amount of IPA loaded
mass amount of PDA
S =
× 100 wt%
mass amount of all products
The yield of PDA was calculated as defned:
Y = X × S × 100%
Results and discussion
Catalyst screening
The efect of base on the catalytic performance
In the dehydrogenation and hydrogenation reaction, the
nature of the active center metal is the most important
parameter for the activity and the product distribution. Noble
metals (Ru, Ir, Pd, et.) (Yang et al. 2017; Imm et al. 2011;
Lafrance et al. 2012; Knoefel et al. 2017) and transition met-
als (Co, Ni, Cu) (Yue et al. 2017; Martinez-Asencio et al.
2011; Liu et al. 2017a, b; Takanashi et al. 2014) catalysts
are known to be efective catalysts for reductive amination
The catalytic performance can be effectively improved
when properly base was introduced into the homogene-
ous catalytic reaction of reductive amination of alcohol
(Roundhill 1992). Once Raney Ni was discovered as
the best catalyst in terms of activity and selectivity, the
effect of the base was investigated on the activity and
selectivity.
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Chemical Papers
Table 2 Amination of isopropanolamine over Raney Ni with various
be weakly absorbed on the Ni atoms which synergistically
combined with the efect of the oxygen atom from the base.
Consequently, the adsorption of substrates was changed and
the selectivity was adjusted. Additionally, the carbonate salts
may facilitate isolation of the surface primary amine species,
which diminishes the formation of secondary amines. For
the (NH4)2CO3, the catalyst almost lost the activity. Besides
the carbonate anion deactivated the catalyst, the ammonia
released by (NH4)2CO3 increased the chemisorption of
ammonia on the Ni, which decreased the adsorption of the
substrates (Du et al. 2006). Therefore, the activity decreased
dramatically when (NH4)2CO3 was added in the reaction
system. Then, Raney Ni/K2CO3 was found to be an efcient
catalytic system for reductive amination of isopropanola-
mine to produce PDA.
bases
Entry
Base
Con%
Sel%
PDA
Yield%
(PDA)
DMP
1
2
3
4
5
6
7
8
9
NaOCH3
t-BuOK
NaOH
38.2
28.5
22.4
11.6
42.9
36.6
55.5
3.7
25.7
7.9
18.1
7.9
19.1
8.5
5.7
7.7
1.5
–
9.8
2.3
4.0
17.9
18.6
86.5
81.3
93.7
17.1
79.1
KOH
2.2
Li2CO3
Na2CO3
K2CO3
(NH4)2CO3
KOAc
37.1
29.8
52.0
0.6
59.1
9.0
46.7
Reaction conditions: isopropanolamine (0.1 mol); ammo-
nia (0.2 mol); Raney Ni (3 wt%); base loading (10 mol%);
initial hydrogen pressure 4 MPa; 170 °C; 15 h.
Structural characteristics of catalysts
Table 3 listed the BET surface area, total pore volume and
average pore diameter of various catalysts determined by
the BET analysis.
When the bases were added into the reaction system,
all activities were decreased. When the strong base such
as sodium methoxide, potassium tert-butoxide was added,
the selectivity of PDA was also declined as well as the yield
(Table 2, entries 1 and 2). The activity decreased greatly
and gave the yield of PDA less than 4.0% when hydroxide
base was introduced (Table 2, entries 3 and 4). There was
no signifcant change of the selectivity when lithium car-
bonate or sodium carbonate was added (Table 2 entries 5,
6). When potassium carbonate was added, the selectivity
was enhanced, which reached up to 93.7% (Table 2, entry
7). Comparing with KOH, KOAc and (NH4)2CO3, it was
believed that the improvement of the selectivity was prob-
ably due to the synergistic efect of the potassium cation
and carbonated anion. The lone pair electrons of the oxygen
atom in the base of Table 2 can form the coordinate bond
with the unflled atomic d-orbital of Ni, which changed the
electronic properties of Ni and their close neighborhood
(Mink and Horváth 1998). Therefore, the activity was
declined. It can be induced that diferent bases poisoned
the catalyst with diferent levels due to the decrease of the
activity by addition of base. The diferent cations also can
The Ni–Al alloy powder had the lowest BET surface area,
total pore volume and the biggest average pore diameter,
which was consistent with its nonporous and alloy powered
property (Okamoto et al. 1980; Dellannay et al. 1982; Lei
et al. 2001). The surface area and pore volume of the spent
Raney Ni increased (Freel et al. 1969; Fouilloux et al. 1972),
while the pore diameter decreased (Table 3, entry 2 and 3).
When the K2CO3 was employed, the surface area and pore
volume of Raney Ni increased more than that of the pure Ni
catalyst, while the pore diameter became smaller (Table 3,
entries 3 vs. 4). Addition of K2CO3 increased the surface
area, pore volume and the amount of small pore of Raney Ni.
Figure 1 presents the XRD patterns of the samples. The
peaks of Ni2Al3 and NiAl3 were obviously visible for Ni–Al
alloy powered (Lei et al. 2001; Robertson and Anderson
1971) and the Ni peaks could be found in all of the Raney
Ni catalysts, which implied that all catalysts existed as crys-
talline phase completely. The XRD peaks at 2θ of 44.4°,
51.7° and 76.1° belonged to [1 1 1], [2 0 0] and [2 2 0] dif-
fraction peaks of Ni0 separately (Lu et al. 2015; Robertson
Table 3 Surface area, pore
volume, average pore diameter,
average crystallite size and
relative crystallinity of the
catalysts
Entry
Cat.
SBET (m2/g)
V (mL/g)
Average pore
diameter (Å)
Average crystal- Relative
lite size (Å)a
crystallinity
(%)b
1
2
3
4
Ni–Al
FR
AR
0.9
18.2
60.6
78.8
0.003
0.037
0.102
0.152
142.0
73.0
57.3
47.0
426
132
114
145
–
100.0
64.9
83.7
KAR
aCalculated from the peaks at 2θ=44.4°
bCalculated from the total areas of peaks at 2θ=44.4°, 51.7° and 76.1°
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Chemical Papers
Efect of K2CO3 on side reaction
Ni
Ni Al
NiAl
3
2
3
Ni(111)
Ni(200)
KAR
Ni(220)
It is widely accepted that reductive amination of alcohol
with ammonia involved two steps: dehydrogenation and
hydrogenation, as shown in Scheme 2.
AR
FR
The main reaction (solid line arrows) started with the
dehydrogenation of IPA on Raney Ni to generate carbonyl
compound 1 and one molecule of hydrogen (the dehydro-
genation process). Then, compound 1 participated in two
pathways. One was that compound 1 reacted with ammonia
to give an imine 2, which was then hydrogenated to PDA
catalyzed by Raney Ni. Meanwhile, the Raney Ni catalyst
was recycled (Scheme 2, left side). The other one was that
the compound 1 was self-coupled to compound 3, which was
further hydrogenated to 2,5-dimethylpiperazine (DMP). This
was the most important side reaction (Langdon et al. 1962).
To further investigate the efect of K2CO3, the reaction
was carried out without ammonia. Without ammonia, the
reaction only processed in route B. The results exhibited
high selectivities (> 80%) toward DMP with or without
K2CO3. The conversion of IPA was 81.0% in the absence
of K2CO3 (Table 4, entry 1), and decreased signifcantly to
33.6% using K2CO3 (Table 4, entries 1 vs. 2). Therefore,
introduction of K2CO3 inhibited the side reaction to DMP,
which contributed to the increase of the selectivity of PDA.
Ni-Al
10 20 30 40 50 60 70 80 90
2 theta
Fig. 1 XRD patterns of samples
and Anderson 1971). FR gave the high, narrow and intense
XRD peaks. Peaks of AR were broad and weak, which illus-
trated that the crystalline of the catalysts have been damaged
to some extent. XRD peak height of KAR was higher than
that of AR, while the peaks width of KAR was narrower.
Table 3 gave the average crystallite dimensions and rela-
tive crystallinity (assuming fresh Raney Ni was 100%) of
the catalysts which were calculated according to the classi-
cal Scherrer relation (Robertson and Anderson 1971). The
crystallite size of AR decreased from 132 to 114 Å after
reaction and the relative crystallinity went down to 64.9%
(Barnard et al. 2011). When K2CO3 was added into the reac-
tion, the crystallite size of KAR sample became larger than
that of FR and the relative crystallinity remained 83.7%,
which indicated that addition of K2CO3 had protected the
crystalline structure of Raney Ni in the reductive amination
of isopropanolamine. In other words, the K2CO3 adsorbed
on the surface of Ni particles and protected the crystallinity
of Ni. These were consistent with the deactivation of the
catalyst when K2CO3 was added.
Table 4 Condensation of IPA over Raney Ni without NH3 when
K2CO3 was introduced or not
Entry
Base
Loading
Con%
SDMP%
1
2
–
–
81.0
33.6
92.5
81.4
K2CO3
8 mol%
Reaction conditions: isopropanolamine (0.15 mol); Raney Ni
(3 wt%); initial hydrogen pressure 4 MPa; 170 °C; 10 h
Scheme 2 Catalytic reductive
amination of IPA to PDA and
the side reaction
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Chemical Papers
Efect of various reaction conditions
Con%
SelPDA
%
SelDMP%
Yield%
80
100
80
60
40
20
0
We further studied the efect of the amount of Raney Ni and
K2CO3 loading on the catalytic performance. With 10 mol%
K2CO3 added, the conversion of IPA increased along with
the increase of Raney Ni loading (Table 5, entries 1–3).
Moreover, the selectivity of PDA decreased with the increase
of the Raney Ni loading, while DMP increased. When the
amount of Raney Ni was 3 wt%, the activity decreased with
the increasing of the K2CO3 loading (Table 5, entries 4–6).
In addition, the selectivity of PDA increased, while DMP
declined. These indicated that the K2CO3 could reduce the
activity by poisoning the catalyst. However, the conversion
of route B reaction decreased more than route A with the
addition of K2CO3, the selectivity of PDA increased. There-
fore, it could be concluded that the selectivity of PDA was
improved with the sacrifce of the activity. When the Raney
Ni loading was increased to 5 wt% (Table 5, entries 7 and
8), the changes of activity and selectivity of PDA catered
to the above conclusion. The ratio of Raney Ni/K2CO3 has
accountable efect on the conversion and PDA selectivity.
The efect of hydrogen pressure was studied in the range
of 1–5 MPa. As shown in Fig. 2, IPA conversion decreased
with the increasing hydrogen pressure; the value decreased
from 80.0% at 2.0 MPa to 62.3% at 5.0 MPa. The selectiv-
ity of PDA slightly increased and then kept constant. These
results demonstrated that the hydrogen pressure was con-
sidered to give rise to the gradual decrease in the number of
working sites on the surface of catalyst. On the other hand,
the reaction pressure reached 10.2 MPa when initial hydro-
gen pressure was 3.0 MPa, while the pressure was 9.0 MPa
as initial hydrogen pressure was set to 2.0 MPa. The high
pressure may promote NH3 adsorption and accelerate the
condensation reaction of intermediate 1 with NH3 to some
extent, minimizing dimerization of the intermediate 1 to pro-
duce DMP (Fischer et al. 1999a, b, c, d).
60
40
20
0
2
3
4
5
PH2(MPa)
Fig. 2 Efect of initial hydrogen pressure. Reaction conditon: isopro-
panolamine (0.1 mol); ammonia (0.2 mol); Raney Ni (3 wt%); base
loading (10 mol%); 170 °C; 15 h
isopropanolamine from 1.2 to 4.0, the conversion passed
through maxima at 3.0, whereas the selectivity of PDA
kept increasing in the studied range (Fig. 3). When the
ratio is lower than 4.0, the increase of the concentration of
NH3 accelerated the selectivity of route A, as main reac-
tion, resulting in the increase of conversion. However, too
much NH3 would take more active sites by the chemisorp-
tions. Consequently, the surface adsorption of the organic
substrates was decreased, which led to decrease of conver-
sion when the ratio is greater than 3.0.
As illustrated in Fig. 4, the reaction time was optimized.
Obviously, the conversion increased with the extend-
ing reaction time. However, the selectivity of PDA was
slightly decreased, while the selectivity of DMP increased.
The yield of PDA could reach 80% when the reaction time
prolonged to 30 h.
The molar ratio of NH3 to isopropanolamine was also
investigated. With the increasing molar ratio of NH3 to
Table 5 Reductive amination
Entry
Raney Ni loading K2CO3 loading
Con%
Sel%
PDA
Yield%
(PDA)
of isopropanolamine on various
conditions
(wt%)
(mol%)
DMP
1
2
3
4
5
6
7
8
2
3
4
3
3
3
5
5
10
10
10
5
32.0
55.5
68.5
65.1
57.5
42.8
73.3
60.8
95.5
93.7
89.8
81.5
92.7
94.9
89.9
93.4
0.6
1.5
2.4
6.3
1.5
1.2
2.7
1.4
30.6
52.0
61.5
53.1
53.3
40.6
65.9
56.8
8
15
15
18
Reaction conditions: isopropanolamine (0.1 mol); ammonia (0.2 mol); initial hydrogen pressure 4 MPa;
170 °C; 15 h
1 3

Chemical Papers
Acknowledgements We are grateful to be supported by the Key
Research and Development Projects of Shanxi Province (Nos.
2017ZDXM-GY-070, 2017ZDXM-GY-042).
Con%
SelPDA
%
SelDMP
%
Yield%
100
80
60
40
20
80
60
40
20
0
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