Uniform Ni particles on amino-functionalized SBA-16 with excellent activity and stability for syngas methanation

Article abstract of DOI:10.1016/j.molcata.2016.03.028

Via modification of mesoporous material SBA-16 with silane coupling agent, a new functionalized SBA-16 catalyst immobilized Ni has been prepared. The performance of the catalyst for CO methanation then were systemically investigated in a continuous flow fixed-bed reactor. The as-synthesized catalyst was characterized with N₂ absorption-desorption, X-ray diffraction, Transmission electron microscopy (TEM), FT-IR spectrum, ²⁹Si-nuclear magnetic resonance (NMR), H₂ - Temperature Programmed Reduction (TPR) and H₂ pulse chemisorption. After modification by aminopropyl-trimethoxysilane (APTMS), the internal surface silanol group of support SBA-16 was replaced by amino-groups. The replacement of hydroxyl groups by amino groups could prevent the agglomeration of metal ion in the solution. Also uniform nickel particle size was observed because the replaced organic groups on SBA-16 could form homogeneous interaction towards the metal. Comparing with the catalyst without functionalized, the catalyst Ni/SBA-16-NH₂ exhibited higher activity, excellent heat-resistant performance and better stability in CO methanation. The CO conversion and CH₄ selectivity could be 100% and 99.9% at the optimal temperature. Meanwhile, the catalyst showed no decrease of activity in the 100 h life test.

Full text of DOI:10.1016/j.molcata.2016.03.028

Accepted Manuscript
Title: Uniform Ni particles on amino-functionalized SBA-16
with excellent activity and stability for syngas methanation
Author: Zhicheng Bian Xin Meng Miao Tao YuHao Lv
Zhong Xin
PII:
S1381-1169(16)30095-4
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2016.03.028
MOLCAA 9827
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Journal of Molecular Catalysis A: Chemical
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Revised date:
Accepted date:
4-12-2015
23-2-2016
16-3-2016
Please cite this article as: Zhicheng Bian, Xin Meng, Miao Tao, YuHao Lv, Zhong
Xin, Uniform Ni particles on amino-functionalized SBA-16 with excellent activity
and stability for syngas methanation, Journal of Molecular Catalysis A: Chemical
http://dx.doi.org/10.1016/j.molcata.2016.03.028
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Uniform Ni particles on amino-functionalized SBA-16 with excellent activity and
stability for syngas methanation
1
1,2
1
1
1,2
Zhicheng Bian ，Xin Meng ，Miao Tao ，YuHao Lv and Zhong Xin *
1Shanghai Key Laboratory of Multiphase Materials Chemical Engineering,
2State Key Laboratory of Chemical Engineering, School of Chemical Engineering, East China
University of Science and Technology, Shanghai, People Republic of China
*
Information for Corresponding author
Name: Zhong Xin
E-mail address: xzh@ecust.edu.cn.
Tel: +86-021-64251005; Fax: +86-021-64240862
Address: No.130 Meilong Road, Xuhui District, Shanghai, China.
1

Graphic
abstract
Highlights：



Amino-functionalized mesoporous material SBA-16 was
prepared by silylation.
Uniform size of nickel particles were observed on the
modified material.
Better thermalstability and long-term stability was achieved
for Ni/SBA-16-NH catalyst.
2
Abstract:
Via modification of mesoporous material SBA-16 with silane coupling agent, a new
functionalized SBA-16 catalyst immobilized Ni has been prepared. The performance of the
2

catalyst for CO methanation then were systemically investigated in a continuous flow fixed-bed
reactor. The as-synthesised catalyst was characterized with N absorption-desorption, X-ray
diffraction, Transmission electron microscopy (TEM), FT-IR spectrum, 29Si-nuclear magnetic
resonance (NMR), H -Temperature Programmed Reduction (TPR) and H pulse chemisorption.
2
2
2
After modification by aminopropyl-trimethoxysilane (APTMS), the internal surface silanol group
of support SBA-16 was replaced by amino-groups. The replacement of hydroxyl groups by amino
groups could prevent the agglomeration of metal ion in the solution. Also uniform nickel particle
size was observed because the replaced organic groups on SBA-16 could form homogeneous
interaction towards the metal. Comparing with the catalyst without functionalized, the catalyst
2
Ni/SBA-16-NH exhibited higher activity, excellent heat-resistant performance and better stability
4
in CO methanation. The CO conversion and CH selectivity could be 100% and 99.9% at the
optimal temperature. Meanwhile, the catalyst showed no decrease of activity in the 100 h life test.
Keyword: amino-functionalized, SBA-16, uniform particle size, CO methanation
1
. Introduction
Natural gas, a clean and efficient energy, has received more attention due to its high caloric
value and environmental friendlessness[1]. In recent years, due to the rise of natural gas price, the
wish for less dependency on natural gas import, and replacement of oil products, synthetic or
substitute natural gas (SNG) production from renewable or syngas from coal is attracting attention
in some developing countries. Among different fossil fuels, natural gas that consists primarily of
methane is ideal, owing to its ready availability, high energy density and conversion efficiency.
3

Meanwhile, natural gas can be transported efficiently at low cost using existing natural pipelines.
Therefore, coal to natural gas(SNG) has been investigated deeply because of the " rich in coal,
poor in oil and natural gas" energy landscape in China[2]. And recently severe environmental
problems occurred in China due to the combusting of coal. In this situation, coal to synthetic
natural gas (SNG) has attracted more and more attention. CO methanation reaction is one of the
key reactions in the coal-to-SNG process and the catalyst design is the hard core of the reaction.
Therefore, it would be worthwhile to develop an efficient catalyst for the methanation reaction.
2 4 2
For the production of SNG, the CO methanation (CO+3H =CH +H O) is a key reaction which is
highly exothermic and thermodynamically feasible[3]. Due to the property of the reaction,
catalysts with high activity and stability in high temperature is of vital importance.
Generally, nickel-based catalyst has been widely employed in CO methanation because of its
low price and relatively high activity. However, poor stability caused by carbon deposition and
aggregation of active nickel in high temperature limited the industrial application [4; 5]. Therefore,
development of catalyst with high activity and excellent stability is the purpose of the research. In
previous work, it is found that SBA-16 was a good support to impregnation metal species because
it has large surface area, tunable cage size (4-10 nm) and interconnected nanocage[6]. However,
the catalyst prepared by SBA-16 revealed poor stability at high temperature. In order to solve the
problem, one solution is to select a promoter metal such as Mo, Ce, Mg and Pt to produce a
synergistic effect with Ni, which was investigated deeply in recent research [3; 7-10].However, the
introduction of the noble metal may cause an environmental problem, which was difficult for
recycle. Another popular method to improve the stability of catalyst is the modification of the
support [11-13]. Recently, induction of organo-functional groups to ordered mesoporous silica by
4

silylation have achieved more attention in many fields, such as catalysis, separation and
absorption [14-17]. After silylation by organosilanes such as aminopropyl-trimethoxysilane
(
APTMS), the hydrophobic and hydrophilic nature of mesoporous silica surface was drastically
changed, because the hydrophilic silanol group was replaced by hydrophobic chloroalkyl chains
through silylation. Jianwen Wei et al found that amino-functionalized SBA-16 showed high
hydrothermal stability and thermal stability comparing with SBA-16[18]. Via modification of
2
mesoporous material SBA-16 followed by absorption of Pd(OAC) , the catalysts exhibited
excellent activity and recyclability for the aerobic oxidation of alcohols in water[19]. Hengquan
Yang also prepared a novel catalyst by immobilizing Pd and guanidine on the mesoporous
materialSBA-16 via a one-pot silylation and found the catalysts showed better activity for Suzuki
coupling and the aerobic oxidation of alcohols[19]. It is concluded modification with support by
silylation may improve the property of catalyst and enhance the stability of as-prepared catalysts.
This work aims to prepare a more stable catalyst for CO methanation. By grafting the amino
group onto the surface of mesoporous material SBA-16 by silylation and followed the
2
impregnation of Ni, we have successfully synthesized the Ni/SBA-16-NH catalysts. The behavior
of the prepared catalysts for CO methanation was also investigated and discussed.
2
2
. Experimental Section
.1. Synthesis
SBA-16 was synthesized according to published methods[6; 20]. Typically, 2.5 g Pluronic
2
F127 (Aldrich) and 15g K SO4 was dissolved in 150mL of a 2.0M HCl aqueous solution. After
stirring at 38℃ for 2 h, 12g tetraethoxysilane (TEOS, Wako, 95%) was then added to this solution.
The molar ratio of TEOS/F127/HCl/ K
2
2
SO4/H O was controlled at 1/0.0035/1.5/6/166. The
5

obtained mixture was vigorously stirred at 38℃ for 24 h. The mixture is then aged at 100℃ for
4 h under static conditions. The solid product was filtered, washed with distilled water and dried
2
overnight at 70℃. Finally the template F127 was removed by calcination at 550℃ for 6 h.
In general, the functionalization of SBA-16 were obtained by post-synthesis grafting
methods[21].Typically,1 g of SBA-16(evacuated at 125 for 6 h) was dispersed in 50mL of dry
tolune. Then 2~4 g aminopropyl-trimethoxysilane(APTMS) was added into the solution. After
2
stirring for 12h at 110 under a N atmosphere. The resulting solid was isolated by a filtration,
2
washed by tolune and ethanol three times and dried under vacuum overnight to give SBA-16-NH .
2
Ni/SBA-16-NH catalysts were prepared by incipient wetness impregnation. In previous work,
2
it was found that 10wt% Ni content was optimally for the reaction. Typically, SBA-16-NH (1.0g)
3 2 2
was added into an aqueous mixture (1.35mL) of Ni (NO ) ·6H O (Wako, 99.9%). The prepared
2
catalysts were denoted as Ni/SBA-16-NH . In addition, a reference Ni/SBA-16 catalysts were
prepared by wet-impregnation method with the same nickel content of 10%wt.
2
.2Characterization
FT-IR spectra were recorded on a Nicolet NEXUS 670 FT-IR spectrometer with a DTGS
29
detector, and samples were measured with KBr pellets. Solid-state Si magic angle spinning
(
MAS) NMR spectra were collected on a Varian INOVA 600 MHz instrument. Samples were spun
29
in 3.2 mm zirconia rotors at 7 kHz. Typical Si MAS NMR parameters were 4000 scans, a 90°
pulse length of 5 μs, and a delay of 5 s between scans.
Powder X-ray diffraction (XRD) patterns were recorded on a Bruker advanced D8 powder
α
X-ray diffractometer (Cu K , λ=1.5418 Å, 40KV, 40mA). The small angle scan ranges were
0
.5-10°with steps of 0.02°and 0.1s for each step. Nitrogen adsorption isotherms were measured at
6

-
196℃ using a physisorption analyzer (ASAP 2020, Micromeritics). Samples were degassed at
00℃ for 2 h prior to adsorption measurements. Specific surface area (SBET) was tested from
nitrogen adsorption data in the relative pressure range from 0.05 to 0.20 using the
Brunauer−Emmett−Teller (BET) method. Total pore volume (V ) was estimated from the amount
2
t
of adsorbed nitrogen at a relative pressure of 0.99.The pore size distribution (PSD) was analyzed
by using the nonlocal density functional theory (NLDFT) method considering the adsorption
branch of the isotherm, which was performed using an Autosorb-1-C software (Quantachrome
2 2
Inc.). H temperature-programmed reduction (H -TPR) was carried out on a TP-5000 type
multifunction adsorption instrument (AutoChem II 2920) in a temperature range from room
−
1
2
temperature to 900°C with a heating rate of 10°C min in a binary gas flow (10 vol % H /Ar) of
−
1
3
0 mL min and GC-4000A chromatograph thermal conductivity detector recorded the signal. H
2
pulse chemisorption (Micromeritics AutoChem II 2920) was carried out at 40℃ to investigate the
dispersion and metallic surface area of nickel metal in the reduced catalyst. The catalyst sample
2
was pretreated in He for 1h at 200℃. After cooling to room temperature in Ar, 10%H /Ar pulse
adsorption was performed at 40℃ for 10 times. Thermo gravimetric and differential thermal
analysis (TG-DTA) of the catalysts after reaction was conducted on a Netzsch Model STA PC
thermo analyzer in a temperature range of room temperature to 900 °C at a heating rate of 10 °C
min −1 in air flow
2
.3 Catalytic Performance
The evaluation of Ni catalysts for CO methanation was carried out in a continuous flow
fixed-bed reactor with a stainless steel tube (length, 40 cm; inner diameter, 10 mm). The catalyst
(
0.4g) diluted with 2.5 g of quartz was filled into the reactor and reduced in situ at 500 for 2 h in
7

2
a continuous flow of pure H (50mL/min). Finally, it was tested over a temperature range of
2
50-500 . The mixed reactant gas consisted of CO/H
added as an internal standard gas for GC analysis. Gas hourly space velocity (GHSV, mL (gas)/g
catalyst) ·h) was selected to be15000 except for specific clarification. The outlet gas stream was
cooled by a cold water trap and analyzed online by gas chromatography (Techcomp, GC7890T).
2 2 2
/N with a molar of 3:1:1, in which N was
(
2 2 4
The amounts of H , N , CH , and CO in the outlet gas were analyzed by a thermal conductivity
2 2 4 2 6 3 6 3 8
detector (TCD), while CO , C H , C H , C H , and C H were analyzed by another TCD with a
Plot Q column. The calculation formulas were described as equations (1)-(2):
CO conversion:
ꢅꢆꢇ,ꢈꢉꢊꢅꢆꢇ,ꢋꢌꢍ
Xꢀꢁꢂ%ꢃ ꢄ
CH
Sꢀꢏꢐꢂ%ꢃ ꢄ
ꢎ 100
(1)
(2)
ꢅꢆꢇ,ꢈꢉ
4
selectivity:
ꢅꢆꢑꢐ,ꢋꢌꢍ
ꢎ 100
ꢅꢆꢇ,ꢈꢉꢊꢅꢆꢇ,ꢋꢌꢍ
3
3
. Results and discussion
.1 Characterization of the samples
For amino-functionalized materials, it was significant to confirm the success in grafting amino
groups the surface and detect the amount of silanol groups available. The FT-IR spectra in
Figure.1 can provide an evidence for amino functionalization on the SBA-16. For two samples,
typical Si-O-Si bands of inorganic framework were presented: symmetric vibration around 800
cm-1and asymmetric stretching vibration around 1089 cm-1. Comparing to SBA-16, SBA-16-NH
2
obviously exhibited two additional peaks at 2920 cm-1 attributed to the vibrations of C-H in
-
1
2
aminopropyl group and 1560 cm related to the asymmetric bending of NH [11; 14; 19; 22].
The Si MAS NMR spectra of the SBA-16 and amino-functionalized SBA-16 were shown in
8

Figure 2.For the support before and after amino-functionalized, two peaks at -101and -111ppm
3
4
3
were referred to Q and Q peaks, respectively, indicating the presence of HOSi(OSi) and
Si(OSi)
two new peaks at -60 and -65ppm, which were assigned to the T and T silicon environment [18;
1; 23]. These two peaks were corresponded to RSi(OSi) (OH) and RSi(OSi) , respectively,
4
species in the silicate framework. After modification by APTMS, the support exhibited
2
3
2
2
3
revealing the successful silylation of amino-groups onto the support. The -NH
evaluated to be 1.89 mmol by CHNS elemental analysis. TG analysis was used to investigate the
thermal stability of SBA-16-NH and the result was shown in Figure 3. A slight mass loss of 2%
2
loading was
2
was of observed under 120℃,which was attributed to the physically absorbed water. Besides, a
major weight loss of 5% between 300-400℃ occurred due to the decomposition of amino groups,
suggesting the successful silylation of amino-groups onto the support. The TGA analysis indicated
that the amino groups were chemically bonded to the surface of SBA-16 and exhibit a relatively
high stability.
Powder X-ray diffraction patterns of as-synthesized samples were shown in Figure 4a.The
small angle XRD patterns showed two samples both exhibited the characteristic diffraction peaks
of cubic Im3m phase. A strong intensity reflection in 2θ=0.8° and other low intensity reflection at
1
.2°, which was corresponded to(110) and (200) planes[24]. According to the results, it was
established that functionalization with amino groups of SBA-16 did not reduce the mesoscopic
order. Figure 3b showed the N absorption-desorption isotherms of SBA-16, SBA-16-NH and
2
2
2
Ni/SBA-16-NH . The calculated texture properties of the samples were listed in Table 1. It can be
seen in Figure 4b that SBA-16 exhibited a type-IV isotherm pattern with an H2 hysteresis loop in
the relative pressure of 0.4-0.7,which was confirmed as a mesoporous cage-like structure[25].
9

Comparing to the reference material SBA-16, SBA-16-NH
pattern with an H2 hysteresis loop, indicating that the material after modification still remain the
mesostructure. However, it was found that the N adsorption-desorption volume decrease a lot,
2
also showed the type-IV isotherm
2
2
which corresponded to the decrease of pore volume of SBA-16-NH revealed in Table 1. Also in
2
Figure 4c, the pore size of SBA-16-NH decreased from 6.9nm to 4.9nm. This may be due to the
stereo-hindrance effect after the amino group grafted on the internal surface of the support. It was
also proved that almost hydroxyl groups on the internal surface was replaced by amino-groups. It
0
was worth noting that adsorption and desorption curve didn't closed in the range of p/p =0-0.3 for
2
SBA-16-NH . Such phenomenon may be the results of the decomposition organic group in
3 2
aminopropyl group and pore blockage formed [22; 26]. After impregnation of Ni (NO ) and the
followed calcination, the catalyst maintained the mesoporous cage-like structure with a slight
decrease in surface and pore volume.
In order to investigate the influence of APTMS concentration on the support and the catalyst,
molar ratio of SBA-16: APTMS was controlled as 0.1, 0.2, 0.4, 0.8. Table 1 listed the texture
2
properties of SBA-16 and SBA-16-NH (x), which the x indicated the molar ratio of SBA-16:
APTMS. As seen in Table 1, the BET surface area, pore volume did not suffer significant changes
between different concentrations of APTMS. Also from the CHNS element analysis, the amount
of grafted amino groups has no obvious changes with the increase of APTMS concentration. The
wide XRD diffraction(Figure 4d) was used to investigate the average particle size of nickel. In
Table 1, the average nickel particle size were calculated by Scherrer’s equation and the same trend
was found. This suggested that no obvious changes occurred with the increase concentration of
2
APTMS. SBA-16-NH (0.2) was selected for further investigation for catalytic performance.
10

The structure of the support and the dispersion of the metal species could be obviously
speculated from Transmission electron microscopic images. Figure 5 showed the TEM images of
the samples. It was revealed in Figure 5a-b that support before and after silylation both exhibited
highly ordered arrangement of mesopores, indicating the support after silylation maintained a
high-quality body-centered cubic mesostructure. After introduction of nickel species, some
shrinkage was suggested to partly occur. The amino-functionalized support obviously improved
the nickel dispersion. Ni particles with a much narrow distribution(10nm) was shown in Fig 5f,
while the catalyst Ni/SBA-16 exhibited a much wider distribution of nickel particles(Fig 5e).H
2
pulse chemisorption results also indicated the dispersion of nickel increased from 1.54% for
Ni/SBA-16 to 1.95% for Ni/SBA-16-NH . The impregnation process can be explained like:(i)in
2
2
+
the early step, the surface of support has a lot absorbed water, which the ion(Ni ) was dissolved
in;(ii)in the dry step, the surface water evaporated and the ion concentration in the water film was
increased and crystal growth formed. For Ni/SBA-16 catalyst, the support surface has much
hydroxyl groups and the mutual attraction between hydroxyl groups and absorbed water would
take the ion accumulated on the surface, which led the large particle formed. In contrast, the
support modified by organic groups reduced or eliminate the hydroxyl groups and exhibited some
steric hindrance effect, which would prevent the ions aggregation on the surface. It was also
suggested that the surface of the support was modified by amino groups and the metal species
could be absorbed in the nanocage of the support and the nickel was not easily accumulated with
the evaporation of the solvent in the drying step[11].
2
Figure 6 showed the H -TPR profiles of the unreduced catalysts. It can be seen that catalysts
prepared without silylation showed a low temperature reduction peak at 300℃ with a shoulder at
11

about 500℃,which points out the coexistence in the catalyst of NiO species of different degrees of
agglomeration. After the support were functionalized by APTMS, only one well-defined peak with
2
a maximum at 300℃ was observed in the TPR profiles of Ni/SBA-16-NH ,which the position
was corresponded to the reduction of dispersed NiO species. It was interesting to notice that the
amino-functionalized support resulted in a more homogeneous distribution of NiO species, which
was consistent with TEM images [27].
3
3
.2 Catalytic performance for CO methanation
.2.1 Activity for CO methanation
In previous section, the activity of Ni/SBA-16 have been deeply investigated. Although the
catalyst reveled good performance in activity test, it showed poor performance in heat-resistant
and stability test. Thus, the better performance in heat-resistant and stability test with comparable
activity with the reference catalyst is the purpose. Figure 7 showed the CO methanation
performance of Ni/SBA-16 catalysts at 0.1MPa under 300-500℃. It could be conclude that
2
Ni/SBA-16-NH and Ni/SBA-16 catalyst showed 100% CO conversion in the lower temperature
4
of 300-400℃. Regarding with CH selectivity, it was found that in the whole temperature range
the catalyst Ni/SBA-16-NH
catalysts exhibited best activity at the temperature range from 300-400℃. It worth noting that at
50℃ catalyst Ni/SBA-16-NH brought out the best activity with ~100% CO conversion and
2
exhibited better performance than Ni/SBA-16. Also it was found that
3
2
~
99.9% CH
4
selectivity. From TEM images ， it was found that the support with
amino-functionalized could result in highly uniform metal particle size, which further given rise to
the better activity.
12

3
.2.2 Stability of the catalyst
In previous section, it was found that catalysts prepared with amino-functioned SBA-16
exhibited higher activity than Ni/SBA-16. For CO methanation, heat-resistant performance and
stability of catalysts is of vital importance. In order to take a deep insight into the influence of
support, the heat-resistant performance of catalysts was investigated. The heat-resistant
performance was investigated by comparing the activities of catalysts before and after calcination
2
at 700 in N atmosphere. Firstly, the activities of catalysts were evaluated at 350 under 0.1MPa,
calcined at 700 for 2h and cooled to 350 for activities test under the similar situations. The
activities of catalysts before and after calcination are shown in table 2.
From table 2, it was found that the activity of Ni/SBA-16 catalyst showed an obvious decline
4
after calcination at 700℃ for 2 h. The CO methanation and CH selectivity decreased from 100%
2 2
and 96% to 95.2% and 83.7 in N atmosphere. For Ni/SBA-16-NH catalyst, there was no
2
significant decline for the activity after calcination at 700℃ in N atmosphere. Above evaluations
revealed that Ni/SBA-16-NH
2
exhibited a better activities Ni/SBA-16 and excellent
high-temperature-resistant performance comparing with Ni/SBA-16. In order to understand
whether carbon deposition or catalyst sintering is the main reasons leading to the deactivation of
the catalysts. TG was carried out in air for the catalysts after calcination and the results was shown
in Fig 8. Form the Figure 8, it can be found that with the increasing of temperature, four weight
changes were identified over Ni catalysts: water loss(50-100℃), carbon loss(150-300℃),
oxidation of metal nickel(300-450℃) and carbon loss(500-800℃), respectively. Therefore, the
carbon deposition over the catalysts was the sum of the weight loss at 150-300℃ and 500-750℃.
2
And the amount of carbon deposition was calculated to be 1.2% for Ni/SBA-16-NH and 2.0% for
13

Ni/SBA-16. The carbon deposition of two catalysts were not in big gap, indicating that the carbon
was not the main reason for the deactivation. Meanwhile, a regeneration measurement is carried
on. Conventionally, the carbon deposition is removed by air treatment. Since the remove of
deposition carbon can be easily achieved at 700℃ and the regeneration of catalysts was carried
by treating with air at 700℃. First the catalysts after calcination was treated by air at 700℃ for 4
h. Since the air treatment lead to the formation of NiO and the catalysts is further reduced under
H
2
flow at 500℃ for 2 h. The regenerated catalysts were also tested for CO methanation and the
results were listed in Table 2. As shown in Table 2, Ni/SBA-16 after generation still exhibit a
significant decrease in CO conversion and CH yield, while Ni/SBA-16-NH retained the same
4
2
activity as before. Thus, combining the TG results and activity test after regeneration, coke
formation can be exclude for the reasons of deactivation.
The TEM images of the calcined support and the catalysts were shown in Fig 9a-d. From Fig
9
7
a-b, the well-ordered structure SBA-16 and SBA-16-NH
2
was maintained after calcination at
00 ℃, indicating the good thermal stability of the supports. For Ni/SBA-16 catalyst, a
significant agglomeration of nickel particles was found, while uniform nickel species still existed
on the surface in Ni/SBA-16-NH . When the catalysts calcined at 700℃in gases atmosphere, the
2
catalysts underwent a high temperature reduction and more NiO species reduced. Metallic nickel
is easier to sinter at high temperature, leading to form large particle size. Therefore,
amino-functionalized support could stabilize the metal particle and remain better activity in harsh
reaction conditions.
For CO methanantion, heat-resistant performance and stability of the catalyst is of vital
2
importance in industry. In previous section, it was found that Ni/SBA-16-NH exhibited excellent
14

heat-resistant performance. The catalytic stability test of Ni/SBA-16-NH
2
was also investigated at
3
50℃ under atmosphere pressure with a WHSV of 15000 mL/g/h. Figure 10 showed the results
4
of stability test, which CO conversion and CH selectivity are plotted as the function of time.
Figure 10a showed the CO conversion of the catalyst in the stability test and it can be seen that
CO conversion for two catalysts is maintained at100% without an obvious decline. However, CH
4
selectivity for Ni/SBA-16 decreased from 96% to 89% during a100 h test. In contrast, for
Ni/SBA-16-NH catalyst, no obvious decline in CH selectivity was observed.
2
4
4
. Conclusion
By modification support SBA-16 with silylation, a highly nickel dispersed catalyst was
prepared for CO methanation. This catalyst showed high activity for the SNG production with the
CO conversion was almost100% and the CH selectivity was 99.9%, respectively. Comparing with
4
the catalyst without modification, a highly dispersion of nickel was found with a much narrow
particle size distribution (10nm). The catalyst could retain the high activity without obvious
decline after calcination at 700℃ in N
heat-resistant performance. Further, the long-term stability of catalysts were also investigated and
catalyst Ni/SBA-16-NH revealed much more stable than Ni/SBA-16.The significantly enhanced
2
atmosphere, which showed excellent behavior in
2
2
stability of the catalyst Ni/SBA-16-NH was attributed to the uniform particle size on the modified
surface of the support.
Acknowledgments
This research was financially supported by National Natural Science Funds of China (Grant No.
U1203293 and 91434128), the program of Shanghai Subject Chief scientist (Grant
No.10Xd1401500) and the Program of Shanghai Leading Talents (2013).
15

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16

Figure captions：
Figure 1. FT-IR spectra of SBA-16 and SBA-16-NH
2
Figure 2. 29Si solid-state nuclear magnetic resonance of SBA-16(A) and SBA-16-NH
(B)
2
2
Figure 3. TG and DTA results of the SBA-16-NH .
Figure 4. (a) Small-angle XRD patterns of the support and the Ni-catalysts (b) N
2
adsorption-desorption isotherms of the catalysts (c) Pore size distribution of SBA-16
and SBA-16-NH
2
2
Figure 5. TEM images of samples: (a) SBA-16 (b) SBA-16-NH (c) Ni/SBA-16 (d)
Ni/SBA-16-NH
Ni/SBA-16-NH
2
2
with Ni particle size distribution for (e) Ni/SBA-16 (f)
Figure 6.
2
H -TPR patterns of prepared catalysts
4
Figure 7. CO methanation properties on Ni catalysts: (a) CO conversion (b) CH selectivity.
Figure 8. Thermogravimetric(TG) results of the catalysts after calcination at 700℃.
Figure 9. TEM images of spent catalysts after calciantion at 700℃:(a)SBA-16(b) SBA-16-NH
2
(
c)Ni/SBA-16(d) Ni/SBA-16-NH
2
4
Figure 10. Catalytic stability of catalysts: (a) CO conversion (b) CH selectivity.
17

Figure 1
Figure 1

Figure 2
Figure 2

Figure 3
Figure 3

Figure 4
Figure 4

Figure 5
Figure 5

Figure 6
Figure 6

Figure 7
Figure 7

Figure 8
Figure 8

Figure 9
Figure 9

Figure 10
Figure 10

Table 1. Physicochemical Property of the samples
Metal
a
b
c
Surface area
Pore
volume
Pore size
(nm)
Grafted amino
samples
crystallite
2
3
e
(
m /g)
(cm /g)
groups (mmol)
d
size (nm)
SBA-16
827.7
70.0
0.532
0.068
0.064
0.063
0.061
0.350
0.361
6.9
5.0
4.9
4.7
4.6
6.6
6.5
-
-
SBA-16-NH
SBA-16-NH
SBA-16-NH
SBA-16-NH
Ni/SBA-16
2
2
2
2
(0.1)
(0.2)
(0.4)
(0.8)
15.2
13.1
14.0
14.2
1.75
1.85
1.86
1.89
68.7
65.3
63.2
490.7
570.7
2
Ni/SBA-16-NH (0.2)
a
Calculated using BET equation.
b
c
d
e
Pore volume, obtained from the volume of nitrogen absorbed at P/Po = 0.95.
Calculated by means of the NLDFT method from the absorption branches of the isotherms.
Calculated from Ni(111) plane by Scherrer’s equation.
Calculated by CHNS element analysis.
Table 2. Heat-resistant performance of catalysts
Catalyst
Before Calcination
After Calcination
After regeneration
C
CO/%
SCH4/%
CCO/%
SCH4/%
CCO/%
SCH4/%
Ni/SBA-16
100.0
100.0
96.2
99.9
95.2
83.7
99.9
96.0
85.1
99.9
Ni/SBA16-NH
2
100.0
100.0
18