Research paper presented on Catalyst Society Conference 2007

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ISSN : 0216 - 4183
DEVELOPMENT OF MESOPOROUS MATERIALS AND NOBLE METAL
BASED
HYDRODESULFURIZATION CATALYSTS
Lebong Andalaluna
Deputy for Information, Energy and Material Technology,
Agency for the Assesment and Application of Technology (BPPT),
Jl. M. H. Thamrin 8, Building II. Fl. 4, Jakarta 10340, Indonesia. E-mail:
andalaluna@yahoo.com
Yasuharu Kanda and Masatoshi Sugioka
Department of Applied Chemistry, Muroran Institute of Technology,
27 - 1 Mizumoto-cho, Muroran-shi, 050-8585, Japan. E-mail:
msugioka@mmm.muroran-it.ac.jp
Abstract
The paper describing progress on a series studies conducted by the authors in developing new type of
highly active hydrodesulfurization catalysts by employing mesoporous materials and noble metal. It
was found that Pt supported on acidic mesoporous materials MCM-41 (as-syntheses SiAlMCM-41,
post-syntheses modified (Al)SiMCM-41) catalysts showed high and stable catalytic activity for the
hydrodesulfurization of thiophene at 350ºC and the activities were observed higher than that of
commercial catalyst CoMo/Al2O3. Pt supported on moderately acidic MCM-41, Pt/SiAlMCM-41
(Si/Al=15) and Pt/Al(1)SiMCM-41 (1 wt% Al loading) were observed showing particular high
activities for the hydrodesulfurization of thiophene. It was concluded that the acidic property of
support material MCM-41 and the spillover hydrogen formed on Pt particle in Pt/MCM-41 catalysts
play important role for the hydrodesulfurization of thiophene.
Keywords:Noble metal, mesoporous material MCM-41, acidity, thiophene hydrodesulfurization
Introduction
Enormous growth of fossil fuel consumption in the past decades has brought detrimental consequences to
both of environmental and human life quality. In order to cope with these serious matters, various countries has
applied new regulation which is considered much more environmentally benign and provide significant impact to
improve our living environment quality. Various organic sulfur compounds present invariably in petroleum
feedstocks and the combustion of relevant fuels, such as diesel oil, would result in sulfur dioxide (SOx) emission to
the atmosphere. The SOx emission to the atmosphere then would lead to the acid rain, ozone depletion or smog. It is
stated by various countries that sulfur content for diesel oil would be lessen to 10 ppm level by 2008 as a goal. This
goal would limit the emission of SOx and subsequently, reduce significantly resulted pollution effects. Furthermore,
low-sulfur fuels would also enable the automobile manufacturers to implement their advanced low-sulfur sensitive
technology that can reduce further the emission of oxide and nitrogen particulate generated in fuel combustion.
Hydrodesulfurization process is an important process in the petroleum refining processes which aim at
excluding sulfur component in the petroleum feedstocks and producing clean fuel products. The development of
highly active hydrodesulfurization catalysts is a crucial issue in the petroleum industries by which petroleum
feedstocks with much lower sulfur content or sulfur-free fuel can be produced. The authors have been investigating
the development of highly active new generation zeolites based hydrodesulfurization catalysts [1-3]. On the other
hand, the emerging of new class of mesoporous materials recently, such as MCM-41 [4], FSM-16 [5], SBA-15 [6]
with large pore diameter in recent years attracted wide attention of utilization such as materials as solid acid catalyst
and catalyst support. Such as materials are expected to be effective materials for treating or synthesize large
molecule chemicals.
We reported that noble metals supported on mesoporous silicate FSM-16, especially Pt/FSM-16, showed high
and stable activity in the hydrodesulfurization of thiophene [7]. It was proposed that weak acid sites of support
material mesoporous silicates playing important role for high activity of thiophene hydrodesulfurization. Therefore,
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it is important to study the effect of acidity of support material to the hydrodesulfurization catalytic performance of
the catalyst, in order to improve further the catalytic performance of the catalyst system.
In present work, acidic mesoporous aluminosilicate (SiAlMCM-41, Si/Al=5, 15, 30) was synthesized and the
effect of the application of the materials as support material of noble metal catalysts for thiophene
hydrodesulfurization was studied. On the other hand, the effect of application of mesoporous silicate (SiMCM-41)
modified with impregnation of Al2O3, Ti(SO4)2 and ZrO2 ((MeSiMCM-41, Me=Al, Ti, Zr) as support material of Pt
(Pt/MeSiMCM-41) for thiophene hydrodesulfurization, was studied. The effect of application of SiMCM-41
modified with different Al modifier agent, Al2O3 and Al-sec-butoxide, as support material of Pt for thiophene
hydrodesulfurization, was also compared with Pt/SiMCM-41 and Pt/SiAlMCM-41 catalytic performances, as well.
Figure 1 showed an illustration of Pt/MeSiMCM-41 preparation path employed in this study. Infrared study on the
pyridine adsorption was performed over SiAlMCM-41 and surface modified SiMCM-41 (MeSiMCM-41) to study
the surface character of the materials.
Me (Al, Ti, Zr) NM chloride
solution solution
impregnation impregnation
Calcination Calcination
and reduction
Mesoporous silica Me-modified MCM-41 Highly dispersed Pt
SiMCM-41 (MeSiMCM-41) on MeSiMCM-41
Figure 1 – Mesoporous silica MCM-41 supported Pt hydrodesulfurization preparation path.
Experimental
Mesoporous silicate MCM-41 (SiMCM-41) was synthesized using dodecyltrimethyl ammonium bromide
(DTABr), tetrapropyl ammonium bromide (TPABr), hexadecyltrimethylammonium chloride (CTAC) surfactants
(Aldrich) with SiO2.Na2O as silica source. Acidic SiAlMCM-41 was synthesized by adding sodium aluminate
(NaAl2O4) during synthesis with Si/Al 5, 15, 30 into the gels mixture. Obtained hexagonal structure of mesoporous
silicate SiMCM-41 was further impregnated using Al, Ti and Zr aqueous solutions and Al-sec-butoxide with 1 wt%
and 4 wt% metal loading to obtain surface modified mesoporous silicate MCM-41 (MeSiMCM-41). Mesoporous
material supported noble metal (Pt, Pd, Rh, Ru) catalysts were prepared by impregnation method using metal
chloride aqueous solutions with 5 wt% metal loading. All catalysts were calcined at 500°C for 4 hours in air and
reduced at 450°C for 1 hour prior to the reaction. Presulfiding treatment of the catalysts was performed using 5%
H2S-H2 gas mixture at 400°C for 1 hour.
Hydrodesulfurization of thiophene was carried out at 350°C under atmospheric pressure, employing 0.1 gram
amount of catalyst, by use of a conventional fixed bed flow reactor. Thiophene was introduced into the reactor by
passing hydrogen (30 ml/min) through thiophene trap cooled at 0°C. The reaction products were analyzed by
Shimadzu gas-cromatograph equipped with SD-550 column. 2-propanol dehydration and cumene cracking of
support materials was carried out by use of pulse reactor system at 200°C and 400°C.
Characterization of SiAlMCM-41 and surface modified SiMCM-41 was performed by employing infrared
spectroscopic measurement of pyridine adsorption using Jasco FT-IR spectrometer. Pyridine adsorption was
performed by introducing 10 Torr of pyridine vapour into the cell at 100°C for 0.5 hour followed with 0.5 hour
evacuation at the same temperature.
Results and Discussions
Catalytic activities of MCM-41 supported noble metal catalysts in thiophene hydrodesulfurization
The hydrodesulfurization of thiophene over various noble metals (NM=Pt, Pd, Rh, Ru) supported on
mesoporous silicate MCM-41 (SiMCM-41) and aluminosilicate MCM-41 (SiAlMCM-41, Si/Al=15) catalysts at
350°C is shown in Figure 2. The catalytic activities of NM/SiMCM-41 were observed vary remarkably for differend
kind of noble metal supported on SiMCM-41 and the catalytic activities after 2 hours reaction were revealed in the
order as follow; Pt/SiMCM-41 > Pd/SiMCM-41 > Rh/SiMCM-41 >> Ru/SiMCM-41. Pt/SiMCM-41 and
Pd/SiMCM-41 catalysts were observed showing higher activities than that of commercial catalyst CoMo/Al2O3. The
high activities for both catalysts were maintained after 5 hours reaction.
The effect of application of acidic support to the catalytic activities of noble metals/MCM-41 were observed
vary remarkably for differend kind of noble metals and the catalytic activities after 2 hours reaction were revealed in
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the order as follow; Pt/SiAlMCM-41 > Pd/SiAlMCM-41 > Rh/SiAlMCM-41 >> Ru/SiAlMCM-41. Moreover,
Pt/SiAlMCM-41 catalyst was revealed showing much higher activity than that of commercial catalyst CoMo/Al2O3
at steady after 5 hours reaction. It was revealed that the application of acidic mesoporous material MCM-41 as
support material was very effective to improve the hydrodesulfurization performance of Pt based catalyst system.
Ru SiAlMCM-41
SiMCM-41
Rh
Pd
Pt
CoMo/ALO
0 10 20 30 40 50 60 70 80
Conversion (% )
Figure 2 - Thiophene hydrosulfurization over noble metals (NM=Pt, Pd, Rh, Ru) supported on mesoporous silicate
MCM-41 (SiMCM-41) and aluminosilicate MCM-41 (SiAlMCM-41).
W/F = 37.9 g.h/mol, reaction temperature 350°C.
Catalytic activities of Pt supported on acidic SiAlMCM-41 in thiophene hydrodesulfurization
In order to study further the effect of support acidity to Pt/MCM-41 catalysts system we employing several
SiAlMCM-41 (Si/Al = 30, 15, 5) with different acidic properties in order to examine the effect of support acidity
properties toward the hydrodesulfurization performance of Pt/SiAlMCM-41 catalysts. It is assumed that the acidic
properties of support material is in the order of Si/Al as follow: Si/Al=30<15<5 as studied using 2-propanol
dehydration and cumene cracking and infrared spectroscopic measurement of pyridine adsorption as well.
Table 1 – Thiophene hydrodesulfurization over Pt supported on acidic SiAlMCM-41.
Composition (%)
Catalysts Conversion (%) C1-C3 n-C4 C4=
CoMo/ALO 46.4 0.6 17.5 81.9
5 wt% Pt/SiMCM-41 51.5 1.9 71.5 26.2
5 wt% Pt/SiAlMCM-41 (Si/Al=30) 62.8 0.5 78.8 20.7
5 wt% Pt/SiAlMCM-41 (Si/Al=15) 74.1 1.4 90.6 7.9
5 wt% Pt/SiAlMCM-41 (Si/Al = 5) 36.0 0.6 71.8 27.6
Catalytic activities of Pt supported on various mesoporous aluminosilicate MCM-41 in the
hydrodesulfurization of thiophene is shown in Table 1. As shown in the table, Pt/SiAlMCM-41 with Si/Al=15
showed the most optimum thiophene hydrodesulfurization activity which lead to the conclusion that moderate
acidity (Si/Al=15) of support material would be most suitable for synthesizing highly active Pt/SiAlMCM-41
catalyst system for thiophene hydrodesulfurization. Less (Si/Al=30) or more (Si/Al=5) acidic support material
would lead to the decrease of catalytic performance. It is assumed that proper acidic properties of support material
would improve the hydrogenation capability of the catalyst system that lead to higher thiophene
hydrodesulfurization catalytic performance, as higher saturated product of n-C4 observed as shown in Table 1.
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Catalytic activities of Pt supported on surface modified SiMCM-41 (MeSiMCM-41, Me=Al, Ti, Zr) in
thiophene hydrodesulfurization
It was revealed in the previous section that moderate acidic property of support mesoporous material play an
important role in developing highly active Pt based hydrodesulfurization catalyst. Therefore, it is important to study
methodology in controlling surface acidity of support mesoporous material that would possibly improve further the
catalytic performance of the catalyst system. In this section, we studied the effect of the application of mesoporous
silicate SiMCM-41 modified with impregnation of Al2O3, Ti(SO4)2 and ZrO2 ((MeSiMCM-41, Me=Al, Ti, Zr) as
support material of Pt (Pt/MeSiMCM-41) for thiophene hydrodesulfurization, in order to develop highly active Pt
based hydrodesulfurization catalyst.
The catalytic activities of Pt supported on SiMCM-41 modified with Al, Ti and Zr in the hydrodesulfurization
of thiophene are shown in Figure 3, Figure 4 and Figure 5, respectively. It was revealed that Pt supported on surface
modified SiMCM-41 (Pt/MeSiMCM-41) with Me=Al, Zr showed better catalytic performance for the
hydrodesulfurization of thiophene than Pt/SiMCM-41 catalyst. Moreover, It was observed that Pt/AlSiMCM-41
showed better catalytic performance than Pt/ZrSiMCM-41 for thiophene hydrodesulfurization. On the other hand,
the application of TiSiMCM-41 as support material resulted in decreasing of catalytic activity of thiophene
hydrodesulfurization.
As shown in Figure 3, Pt/AlSiMCM-41 showed higher catalytic performance of thiophene hydrodesulfuri- zation
than that of Pt/SiMCM-41 for both of 1 wt% and 4 wt% Al loading. The catalytic performance was improved better
for lower Al loading (1 wt%) and decreased at higher Al loading (4 wt%).
5 wt% Pt/Al(4)SiMCM-41
5 wt% Pt/Al(1)SiMCM-41
5 wt% Pt/SiMCM-41
CoMo/ALO
0 10 20 30 40 50 60 70
Conversion (%)
Figure 3 - Thiophene hydrodesulfurization over Pt supported on SiMCM-41 modified with Al.
5 wt% Pt/Ti(4)SiMCM-41
5 wt% Pt/Ti(1)SiMCM-41
5 wt% Pt/SiMCM-41
CoMo/ALO
0 10 20 30 40 50 60 70
Conversion (%)
Figure 4 - Thiophene hydrodesulfurization over Pt supported on SiMCM-41 modified with Ti.
In the case of Pt/TiSiMCM-41, the catalytic activity was oberved almost the same with that of Pt/SiMCM-41
for lower Ti loading (1 wt%) while the activity was decreased, lower than that of Pt/SiMCM-41, for higher Ti
loading (4 wt%), as shown in Figure 4. Furthermore, Pt/ZrSiMCM-41 showed better catalytic performance for
thiophene hydrodesulfurization than that of Pt/SiMCM-41 for 4, 8 and 16 wt% Zr loading, as shown in Figure 5.
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The main reaction products in the hydrodesulfurization over Pt/SiMCM-41 were C4 hydrocarbons (butane
71%, butenes 27%) with trace amount of C1-C3 hydrocarbons. These results indicate that Pt/SiMCM-41 catalyst has
high hydrogenation ability for unsaturated C4 hydrocarbons and low hydrocracking activity for hydrocarbons in the
presence of hydrogen sulfide. It was observed for Pt/MeSiMCM-41 that butane composition in the reaction products
was higher than that of Pt/SiMCM-41 while the composition of cracking products was almost unchanged. Therefore,
it can be assumed that Pt/MeSiMCM-41 has higher hydrogenation ability than Pt/SiMCM-41.
5 wt% Pt/Zr(16)SiMCM-41
5 wt% Pt/Zr(8)SiMCM-41
5 wt% Pt/Zr(4)SiMCM-41
5 wt% Pt/SiMCM-41
CoMo/ALO
0 10 20 30 40 50 60 70
Conversion (%)
Figure 5 - Thiophene hydrodesulfurization over Pt supported on SiMCM-41 modified with Zr.
Catalytic activities of Pt supported on SiAlMCM-41 modified with different Al modifier agent in thiophene
hydrodesulfurization
It was revealed that the application of SiMCM-41 modified with aqueous solution Al2O3 as support material
for Pt improved the catalytic performance of Pt/mesoporous silicate in the hydrodesulfurization of thiophene. The
improvement is concluded having related with the increase of surface acidity of support material in the catalyst
system. In this section, we examine further the modification of siliceous SiMCM-41 in order to improve the
catalytic activity in thiophene hydrodesulfurization. In the study, siliceous SiMCM-41 was modified with aqueous
solution Al2O3 and organic Al-sec-butoxide with Al metal loading 1 wt% and 4 wt% and the hydrodesulfurization
performance with Pt as supported metal was evaluated.
Table 2 – Thiophene hydrodesulfurization over Pt supported on SiMCM-41 modified with different modifier agent.
Composition (%)
Catalysts Conversion (%) C1-C3 n-C4 C4=
CoMo/ALO 46.4 0.6 17.5 81.9
5 wt% Pt/SiMCM-41 51.5 1.9 71.5 26.2
5 wt% Pt/Al(1)SiMCM-41 64.4 0.6 86.9 12.4
5 wt% Pt/Al(4)SiMCM-41 62.8 1.0 82.9 16.2
5 wt% Pt/Al-OR(1)SiMCM-41 60.7 0.4 90.7 8.8
5 wt% Pt/Al-OR(4)SiMCM-41 65.0 0.8 84.4 14.8
Catalytic activities of Pt supported on surface modified mesoporous silicate SiMCM-41 ((Al)SiMCM-41,
(Al-OR)SiMCM-41) in the hydrodesulfurization of thiophene is shown in Table 2. The activities were based on
conversion after 2 hours reaction. As shown in the table, the application of SiMCM-41 modified with both of Al2O3
and Al-sec-butoxide improved the catalytic performance in thiophene hydrodesulfurization. It is assumed that acidic
properties of modified support material plays an important role for the catalytic activity improvement.
It was observed that for modification with aqueous solution Al2O3, the performance improvement is better for
lower Al metal loading. It was also observed, that higher saturated product n-C4 obtained at lower Al metal loading,
indicating better hydrogenation capability have some contribution for high catalytic activity of Pt/ Al(1)SiMCM-41.
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On the other hand, in the modification with organic Al-sec-butoxide the catalytic activity improvement was
observed better for higher metal loading. It is interesting to note that lower saturated product n-C4 obtained for
higher Al metal loading.
Catalytic activities of MCM-41 in 2-propanol dehydration and cumene cracking
Dehydration of 2-propanol and cumene cracking were employed as model reactions in this study, in order to
evaluate surface character and property of aluminosilicate MCM-41 and mesoporous silica MCM-41 modified with
metal impregnation (MeSiMCM-41, Me=Al, Ti, Zr). Dehydration of 2-propanol produces acetone as product over
basic and metallic catalyst. On the other hand, it produces propylene over acidic (Lewis and Broensted) catalyst.
Cumene cracking is known required relatively strong Broensted acid sites to proceed and producing benzene and
propylene as products.
Figure 6 shows the catalytic activities of SiAlMCM-41 with various Si/Al ratio in the dehydration of 2-
propanol and cumene cracking. It was observed that the surface acidity of SiAlMCM-41 increased for smaller Si/Al
ratio. The trend is attributed to the increase of surface acid sites along with the increase of Al numbers.
100 2-PA Dehydration
Cumene cracking
80
Conversion (%)
60
40
20
0
SiMCM SiAlMCM SiAlMCM SiAlMCM
(Si/Al=30) (Si/Al=15) (Si/Al=5)
Figure 6 – Catalytic activities of SiAlMCM-41 with various Si/Al ratio in 2-PA dehydration and cumene cracking.
The catalytic activities of SiMCM-41 and surface modified SiMCM-41 in the dehydration of 2-propanol and
cumene cracking is shown in Figure 7. Mesoporous silicate SiMCM-41 showed some catatlytic activity for the
dehydration of 2-propanol and the product was mainly propylene. However, SiMCM-41 was observed inactive for
cumene cracking in employed condition which indicated the absence of Broensted acid sites. Based on these results,
it can be assumed that SiMCM-41 has low surface acidity and mainly is Lewis acid. The activity of SiMCM-41 was
improved after modification with Al and Ti impregnation. TiSiMCM-41 showed higher activity of 2-propanol
dehydration than that of original SiMCM-41. However, no activity of cumene cracking was observed over
TiSiMCM-41. On the other hand, AlSiMCM-41 showed remarkable high activity of 2-propanol and some activity
of cumene cracking. These results showed that modification of SiMCM-41 with Al improved the surface acidity of
SiMCM-41 and generated both of Broensted and Lewis acid sites. Therefore, it can be concluded that Al is effective
as modifier metal in order to enhance surface acidity of SiMCM-41.
100 2-PA Dehydration
Cumene cracking
80
Conversion (%)
60
40
20
0
SiMCM-41 Al(4) Ti(4) Zr(4)
SiMCM-41 SiMCM-41 SiMCM-41
Figure 7 – Catalytic activities of surface modified SiMCM-41 in 2-PA and cumene cracking.
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Infrared study of support materials mesoporous MCM-41
We proposed in previous study that surface acidity of support material plays an important role for high
activity of Pt/mesoporous material catalyst system for thiophene hydrodesulfurization [1,2,7]. In order to clarify the
acidic properties of synthesized mesoporous aluminosilicate MCM-41 and the effect of modification of mesoporous
silicate MCM-41 with Al2O3, we observed the infrared spectras of SiMCM-41, SiAlMCM-41, surface modified
SiMCM-41 in the pyridine adsorption. Figure 8 shows infrared spectras of pyridine adsorbed on SiAlMCM-41
(Si/Al=30, 15, 5). Pyridine was adsorbed at 100°C followed with subsequent evacuation at the same temperature. It
was observed that SiMCM-41 showed weak absorption band of coordinated pyridine on Lewis acid site indicating
the present of small amount of Lewis acid sites. In the case of SiAlMCM-41, absorption bands of coordinated
pyridine on Lewis acid site was observed along with small absorption bands based on Bronsted acid sites around
1550 cm-1. It was observed that surface acidity of SiAlMCM-41 is in good relationship with Si/Al ratio, which
acidic property of SiAlMCM-41 is greater for lower Si/Al ratio.
Figure 9 shows infrared spectras of MeSiMCM-41 in the hydroxyl group region. The spectras were recorded
after evacuation at 500°C for 2 hours. For SiMCM-41 the silanol group (Si-OH) was observed at 3743 cm-1. After
impregnation with Al the SiOH absorption band was almost unchanged, indicating weak interaction of surface SiOH
with Al2O3 particle. The SiOH absorption band was decreased for modification of SiMCM-41 with Ti and Zr and
shoulder absorption band was also observed. The appearance of this shoulder might indicate that surface Ti(SO4)2
and ZrO2 particle interact strongly with surface SiOH.
L Pyr
0 .1
B Pyr
d)
Abs
c)
b)
a)
1570 1500 1400
W a v e N u m b e r [c m -1 ]
Figure 8 – Infrared spectras of SiMCM-41 and SiAlMCM-41 (Si/Al = 30, 15, 5) in the pyridine adsorption region.
a) SiMCM-41, b) SiAlMCM-41 (Si/Al=30), c) SiAlMCM-41 (Si/Al=15), d) SiAlMCM-41 (Si/Al=5).
3744
a)
Abs
b)
3680
c)
d)
4000 3200
Wave number [cm-1]
Figure 9 - Infrared spectras of MeSiMCM-41 in the –OH region. a) SiMCM-41, b) Al(4)SiMCM-41, c)
Ti(4)SiMCM-41, d) Zr(4)SiMCM-41.
Figure 10 shows the spectra of adsorbed pyridine on SiMCM-41 and MeSiMCM-41 support materials after
pyridine adsorption at 100°C. It was observed that SiMCM-41 show weak absorption band of coordinated pyridine
on Lewis acid site indicating the presence of small amount of Lewis acid site. The modification of SiMCM-41 by
impregnation of Al2O3, Ti(SO4)2 and ZrO2 increased the intencity of absorption band of coordinated pyridine. In
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the case of Al as modifier, small absorption band based on Bronsted acid site was also observed around 1550 cm-1.
The absorption band of Bronsted acid site was not observed for other MeSiMCM-41 at this measurement condition.
Based on these results, it is concluded that modification of SiMCM-41 with Al is more effective for generation of
Bronsted acid site over SiMCM-41 than using Ti or Zr.
L Pyr
1492 d)
B Pyr
A bs c)
1456
b)
1547
a)
1447
1580 1400
Wave number [cm-1]
Figure 10 - Infrared spectras of MeSiMCM-41 in the pyridine absorption region. a) SiMCM-41, b) Al(4)SiMCM-41,
c) Ti(4)SiMCM-41, d) Zr(4)SiMCM-41.
Conclussions
It was revealed in current study that the application of moderate acidic mesoporous materials as support
material for Pt catalysts (Pt/SiAlMCM-41) improved significantly the catalytic performance of thiophene
hydrodesulfurization. Some methods of siliceous MCM-41 modification, such as using Al2O3 or Al-sec-butoxide
was demonstrated as effective ways to control surface acidity of support material MCM-41 in order to synthesize
highly active hydrodesulfurization catalysts. Based on the results, we propose a possible mechanism for thiophene
hydrodesulfurization over Pt/mesoporous materials as shown in scheme-1. In the proposed mechanism, thiophene is
activated on the acid site of mesoporous silicates and hydrogen is activated on Pt to form spillover hydrogen. The
spillover hydrogen formed on Pt particle attacks the activated thiophene formed on the acid site of mesoporous
silicates.
Scheme-1. Model of hydrodesulfurization mechanism over Pt/Mesoporous catalysts.
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