Vol. 25, No. 13 (2013)
Catalytic Performance of 3-Hydroxypropionaldehyde to 1,3-Propanediol over Ni/Hydrogen Mordenite 7191
this was for the Ni particles inside the channels with exchange
sites in the carrier and on the other hand, the Ni particles may
be smaller particles and highly dispersion and the amount was
limited.
In the TPR experiments, the sample peak area presented
the amount of hydrogen consumption in the reduction process,
which was related with the amount of oxygen species in the
samples. It can be seen that the high temperature reduction
peak area of Ni-4 was significantly larger than the other two,
it indicated that good dispersion of Ni-4 sample, may be more
small particles into the channels of zeolite. The high tempera-
ture reduction peak of Ni-2 and Ni-3 was roughly equal size.
Catalytic experiments: Effect of Ni/hydrogen mordenite
catalysts by different method on XHPA for hydroxypropion-
aldehyde to 1,3-propanediol was shown in Fig. 3. The XHPA
order for hydroxypropionaldehyde to 1,3-propanediol with the
reaction time of 2 h was as follows: Ni-4 > Ni-3 > Ni-2 >
Ni-1> Ni-5. From the characterization by the TEM and TPR,
the XHPA was proportional with the dispersion of Ni on the
catalyst. For the theory of several Ni catalyst loading the same
terms as the base to NiO were 5 % (wt), Ni dispersion of
particles larger exposed surface of the catalyst the greater the
number of active sites and the XHPA was high. The catalytic
performance of Ni-5 was very poor for the limited number of
active sites and the exchange bit of NiO was difficult to be
reduced to active site of Ni.
Fig. 1(f) shows the SAED picture of Ni-3 by wet mixing.
It can be seen that the structure of the sample was integrity
and the SAED pictures of other samples was the same as the
one of Ni-3. It illustrated that the carrier of hydrogen mordenite
does not undermine its structure with introduction of Ni
particles, the skeleton remains of its original features.
Temperature programmed reduction (TPR): Tempe-
rature programmed reduction spectrum of Ni/hydrogen
mordenite catalysts by different method was shown in Fig. 2.
It can be seen that the TPR patterns of Ni-1 and Ni-5 were
significantly different from the other samples. For the Ni-1
catalyst, there was only a large reduction peak with low
temperature of 356 ºC, combination with the above TEM
characterization, the peak should be attributed to the accumu-
lation of large particles NiO reduction peak4. For the weak
intermolecular forces between the big particles of NiO with
the carrier, so it was reduced more easily. In other words, the
reduction temperature was low. For the Ni-5 catalyst, there
was only a reduction peak with high temperature of 651 ºC,
the corresponding exchange sites in the zeolite on the Ni
species. Because this part of Ni and strong interaction between
carriers and their zeolite played a stabilizing role, it is difficult
to be reduced, so the reduction temperature is higher. For
Ni-2, Ni-3 and Ni-4 catalysts, there are two reduction peaks,
in addition to low temperature reduction peak of 360 ºC, also
a high temperature reduction peak of 560 ºC. It means that the
surface of these three catalysts have two different states of
NiO. That means low temperature reduction peak correspon-
ding to the reunion of the large particles of NiO. High tempe-
rature reduction peak, corresponding to the highly dispersed,
small particle size NiO, NiO are expected to enter this part of
the pores of the zeolite, in the highly dispersed. And because
of smaller particle size, so the above TEM characterization
was not detected in the presence of these particles.
100
Ni-1
Ni-2
Ni-3
80
Ni-4
Ni-5
60
Ni-3
Ni-2
40
Ni-4
Ni-1
20
Ni-5
0
0
2
4
6
8
10
12
14
Reaction time (h)
Fig. 3. Effect of Ni/hydrogen mordenite catalysts by different method on
XHPA for hydroxypropionaldehyde to 1,3-propanediol
The catalyst deactivation of Ni-1 was very fast, the XHPA
has declined almost 40 % in the first reaction time of 1 h. The
Ni particles in Ni-1 was relative larger than the other one and
easily reunite with each other, for the force between Ni species
with the support was weak (It can be seen from TPR charac-
terization). The Ni was easy loss during the reaction, which
may be caused by a sharp decline for Ni-1 in its main activity.
For the impregnation of Ni-4 catalyst activity also decreased
rapidly 4 h response, the activity of XHPA decreased from 98.9
to 53.5 %. Probably because more Ni particles dispersed within
the carrier channel, this part of the Ni particles in the reaction
process because of the loss of catalytic activity of pore blockage.
The XHPA of Ni-2 and Ni-3 catalyst is relatively stable.
Effect of Ni/hydrogen mordenite catalysts by different
method on SPDO for hydroxypropionaldehyde to 1,3-propanediol
was shown in Fig. 4. The SPDO order for hydroxypropionaldehyde
to 1,3-propanediol was as follows: Ni-1 > Ni-2 > Ni-3 > Ni-4
200
300
400
500
600
700
800
Temperature (ºC)
Fig. 2. TPR spectrum of Ni/hydrogen mordenite catalysts by different method