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Hydrodesulfurization of thiophene over noble metals supportedon ZSM-5 zeolites
H.K. Beyer, H.G. Karge, I. Kiricsi and J.B. Nagy (Eds.)
Catalysis by Microporous Materials
544
Studies in Surface Science and Catalysis, Vol. 94 9 1995 Elsevier Science B.V. All fights reserved.
Hydrodesulfurization of thiophene over noble metals supported on ZSM-5 zeolites M. Sugioka, C. Tochiyama, Y. Matsumoto and F. Sado Department of Applied Chemistry, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran 050, Japan
Pt/HZSM-5 showed high and stable catalytic activity for the hydrodesulfurization of thiophene at 400~ and its catalytic activity was higher than that of commercial CoMo/AI2Oa catalyst. It is concluded that the BrSnsted acid site and spillover hydrogen formed on Pt particle in Pt/HZS M-5 catalyst play an important role for the hydrodesulfurization of thiophene.
1. I N T R O D U C T I O N
Hydrodesulfurization of petroleum feedstocks is one of the important processes in the petroleum industry to produce clean fuels. The CoMo/AI2Oa catalyst is widely used. Recently, the need for fuels of lower sulfur content due to the serious problems of global-scale air pollution because of burning petroleum feedstocks initiated to develop hydrodesulfurization catalysts, which are of higher activity than commercial CoMo/AI203. It has been reported that metal-zeolite catalysts have high possibility as new hydrodesulfurization catalysts for petroleum [1-9]. The catalytic desulfurization of organic sulfur compounds over zeolites has been investigated systematically [10-12]. On the basis of fundamental catalytic studies, active zeolite-based hydrodesulfurization catalysts such as transition metal ion-exchanged Y zeolites(MeY)[13-16], MoS2/NiHY[17] and Rh/USY[18, 19] were developed. In the present work, the catalytic activity of noble metals (Pt, Rh, Pd, Ru) supported on NaZSM-5 and HZSM-5 zeolites were studied in the hydrodesulfurization of thiophene in order to develop more highly active
545 zeolite-based hydrodesulfurization catalysts. 2. E X P E R I M E N T A L
Hydrodesulfurization of thiophene was carried out at 400~ at 1 atm using conventional fixed-bed flow reactor. Thiophene was introduced into the reactor with flowing hydrogen saturated by thiophene at 0~ The reaction products were analyzed by gaschromatograph. ZSM-5(SiO2/AI203=22.1,TOSOH)-supported noble metal catalysts were prepared by the impregnation method using aqueous noble metal chloride solutions. The metal loading was 5 wt%. Catalysts were calcined at 500~ for 4 hr in air and reduced at 450~ for 1 hr prior to use. 3. RESULTS AND DISCUSSION 3.1 Activities of noble metal/zeolite catalysts The catalytic activity of various noble metals supported on
NaZSM-5 and HZS M-5 zeolites was examined in the hydrodesulfurization of thiophene at 400~ (Figure 1). The activity was markedly changed by the the kind of noble metal and the order of the catalytic activities of noble metal/NaZSM-5 catalysts was as follows: Pt/NaZSM-5 > Rh/NaZSM-5 > Pd/NaZSM-5 > Ru/NaZSM-5 Pt/NaZSM-5 showed the highest activity, however, it was lower than that of commercial CoMo/AI203 catalyst. Figure 2 shows the hydrodesulfurization of thiophene over various noble metal/HZSM-5 catalysts. It was found that the order of the catalytic activities of noble metal/HZSM-5 corresponded to that found with NaZSM-5 preparations. Pt/HZSM-5 catalyst showed stable activity. This activity was the highest, even higher than the activity of the CoMo/AI203 catalyst. The reaction products in the hydrodesulfurization of thiophene over noble metal/ZSM-5 catalysts were hydrogen sulfide and C1-C4 hydrocarbons. Noble metals supported on HZSM-5 zeolite show higher catalytic activity than on NaZSM-5, suggesting that the Br'0nsted acid sites of HZSM-5 in noble metal/HZSM-5 catalysts play important role in the hydrodesulfurization of thiophene.
546
100
80
g
" ""
" . , . . . ,,,, . . . . ,,., . . , . , . , . "4""----..,.....
,,,....,, . . , . ,., . , . .
. . . .
,,.,.,, . . . . . . .
Prcsulfidexi CoMolAl203
"-" 60 (:I o
ov-.l
40
5~% ,..__-Q'~"r
A
,,.
,,
_
_
Pv~zsM-5
5wt% 1~[~_.,SM-5
2O _
5wt% Pd/N~ZSM-5 5wt% Ru/NaZ~M-5
0
1
W/F Figure 1
,=
2, 37.9
3
4
"JL"m~e on Stream (t~') g.hr/mol I-L2/Thlophcne
5 ,=
30
Hydrodesulfurization of thiophene over noble m e t a l / N a Z S M - 5
catalysts at 4 0 0 ~
100 5wt% Pt/HZSM-5 80
vI:I
. o
60
o
o
8
20
5wt% Pd/HZ,SM-5
,,,,,,,
5wt96 R~.II=IZ.SM-5 ......
0
I
1
,,
I
2
......
I
3
"[Imo o- St~sm W/F ,= 37.9 g.hr/mol Figure 2. at 400=C.
,
I
.......
4
l
_
5
('m') H2/Thiophcnc =
30
Hydrodesulfurization of thiophene over noble metal/HZSM-5 catalysts
547 3.2 Catalytic properties of Pt/HZSM-5 It was found that Pt/HZSM-5 catalyst showed remarkable high and stable activity for the hydroclesulfurization of thiophene in comparison with other noble metal/HZS M-5 catalysts. The effect of sulfiding with H2S on the catalytic activity of noble metal/HZS M-5 in the hydrodesulfurization of thiophene and hydrocracking of benzene was examined in order to learn more about the origin of the high and stable catalytic activity of Pt/HZSM-5. Sulfiding was carried out by introduction of hydrogen sulfide (10 ml) into the reactor using glass syringe. Figure 3 shows the effect of sulfiding on the hydrodesulfurization of thiophene over various noble metal/HZSM-5 catalysts. It was revealed that the high and stable activity of the Pt/HZS M-5 catalyst was hardly affected by the introduction of hydrogen sulfide.
100
. ~
,ik
~lh
,dh
~.. !P'
A IF'_
A lp'
A 1~'
AIh Ip'
liI
~. 'lw
.L qP'
~
A IP'
~, IP'
,~
~ lw,
,aL
T 5wt% PtZHZSM-5 80
V
H2S Injeetion(10ml)
60
o
el,-4
H2S Injection(10ml) ,o
H2S Injection(10ml) 5wt% Pd/HZ.SM-5 .~5wt% R ~ M - 5
0 0
-=_. __-. ~ == =. = = _ - = _ .. = 1 2
,..,.
,.
I
3
Time on Stream (hr) W/F = 19.0 g.hr/mol H2/Thiophene = 30 Figure 3. Effect of introduction of hydrogen sulfide on the hydrodesulfurization of thiophene over noble metal/HZSM-5 catalysts at 400~
548
Figure 4 shows the effect of sulfiding for the hydrocracking of benzene over noble metal/HZSM-5 catalysts. It was found that the catalytic activity of noble metal/HZSM-5 was remarkably lowered by the introduction of hydrogen sulfide. The catalytic activity of Rh/HZSM-5, Pd/HZSM-5 and Ru/HZSM-5 did not recover with the time on stream, but, Pt/HZSM-5 regained almost its original activity.
100
5wt% Rh/HT__,SM.--5. 80
~" v
60
c~ r O
4o
_
H2S Injection(lOml) 5wt% Ru/ItZSM-5 r"
_
20
.H2S Injcction(lOml)
M-5
Pt/H~M-5
0
30
60
90
Time on Stream
120
/
150
180
(rain)
Figure 4. Effect of introduction of hydrogen sulfide on the hydrocracking of benzene over noble metal/HZSM-5 catalysts at 40(/'C.
Results suggest that interaction of the hydrogen sulfide and the platinum on the HZSM-5 is not very strong, therefore, the metallic nature of platinum is easily regenerated by the hydrogen during hydrodesulfurization. By this reason, Pt/HZSM-5 catalyst shows high and stable activity for the hydrodesulfurization of thiophene.
549
3.3 Mechanism of hydrodesulfurization of thiophene on Pt/HZSM-5 catalyst As mentioned above, Pt/HZS M-5 showed higher activity than Pt/NaZS M-5 in the hydrodesulfurization of thiophene. This indicates that the BrSnsted acid site of HZS M-5 in Pt/HZS M-5 catalyst plays an important role for the hydrodesulfurization of thiophene.lt can be assumed that the BrSnsted acid site in the Pt/I-IZSM-5 catalyst is one site active for the activation of thiophene, whereas Pt is an active site for the activation of hydrogen. In other words, Pt/HZSM-5 catalyst is a bifunctional catalyst for the hydrodesulfurization of thiophene, in which both Br0nsted acid and platinum metal sites are active sites. Participation of spillover hydrogen in the hydrodesulfurization of thiophene over Pt/I-IZS M-5 catalyst was assumed and examined. It was found that catalytic activity of Pt/SiO2(quarlz) mixed mechanically with HZSM-5 was higher than that obtained by simple addition of the data for the pure components(Figure 5). This implies that spillover hydrogen on Pt/HZSM-5 catalyst participates in the hydrodesulfurization of thiophene. The mechanism proposed is shown in Scheme 1. 100
80
~,
60
o
A
B
P t/Quartz+HZSM-5
40 ._
0.
0.1g
6
--3
{
q, 20
-
-
~
. . . . .~ . . . . . . . . .
~ "
HZSM-5 (B) 0.1g--1 0
20
40
~
~S-_ Calculated (A+B) ""O'"~'=" ~
/E-'Pt/Quartz (A) 0..lg 60
T i m e on S t r e a m
80
100
120
(min)
Figure 5. Hydrodesulfurization of thiophene over R/quartz(A) ,HZSM-5(B) and mechanically mixed (R/quartz(A) + HZSM-5(B)) catalysts at 40ffC.
550
H=S + C~~C. Hydrocarbon
H2
TI
H
Spillover Hydrogen H
P = , = = - = = ..-= = _ . = .._..~.~..=.-= = = = , : : : . . - .
H
t
s\O H
H+
[S=C=CH-CH=CH2 ] < = = = = = . = . - = = . : ~ .". ~ . = .. ~
...; : . ~ : =
.:.~.:=... ~ ~:..~
o!
~ . : . . ~ = - = : =. =.:.~.:: =: = = = =-:,:..:: . = . ......... ::..:., .... :: ...... . . . : : : . . . : . . =
H Z S M - 5 Scheme 1. The possible mechanism of thiophene hydrodesulfurization over Pt/HZSM-5 catalyst.
Accoding to this mechanism, thiophene is adsorbed on BrSnsted acid site of Pt/HZSM-5 and hydrogen is activated on Pt to form spillover hydrogen. The spillover hydrogen formed on Pt attacks the reaction intermediate, e.g., species such as S=C=CH-CH=CH2, formed by the decomposition of thiophene adsorbed on the strong BrOnsted acid site of the zeolites [16]. 4. CONCLUSION
It was observed that Pt/HZS M-5 was of higher catalytic activity than commercial CoMo/AI203 in the hydrodesulfurization of thiophene. Therefore, there is a possibility for using Pt/HZSM-5 as highly active, second generation hydrodesulfurization catalyst for petroleum feedstocks.
ACKNOWLEDGEMENTS
The authors express their gratitude to The Japan Petroleum Institute and Petroleum Energy Center for supporting these investigations.
551
REFERENCES
1. M.L. Vrinat, C. G. Gachet and L. de Mourgues, Stud. Surf. Sci. Catal., 5 2. 3. 4. 5. 6.
(1980) 219. C.S. Brooks, Surf. Technol., 10 (1980) 397. K.E. Givens and J. G. Dillard, J. Catal., 86 (1984) 108. T.G. Harvey and T. W. Matheson, J. Catal., 101 (1986) 253. R. Cid, F. Orellana and A. L6pez Agudo, Appl. Catal., 32 (1987) 327. Y. Okamoto, A. Maezawa, H. Kane and T. Imanaka, J. Mol. Catal., 52 (1989)
337. 7. S. Gobolos, M. Breysse, M. Cattenot, J. Decamp, M. Lacroix, J. L. Portefaix and M. Vrinat, Stud. Surf. Sci. Catal., 50 (1989) 243. 8. M. Laniecki and W. Zmierczak, Zeolites, 11 (1991) 18. 9. P. Kovacheva, N. Davidova and J. Novakova, Zeolites, 11 (1991)54. 10. M. Sugioka and K. Aomura, Intern. Chem. Eng., 13 (1973) 755. 11. M. Sugioka and K. Aomura, Bull. Japan Petrol. Inst., 17 (1975) 51. 12. M. Sugioka, T. Kamanaka and K. Aomura, Prepri. Am. Chem. Soc., Div. Petrol. Chem., 24 (1979) 740. 13. M. Sugioka and K.Aomura, Prepri. Am. Chem. Soc., Div. Petrol. Chem., 25 14. 15. 16. 17. 18. 19.
(1980) 245. M. Sugioka and K. Aomura, J. Japan Petrol. Inst., 26 (1983) 216. M. Sugioka, M. Sasaki and K. Aomura, J. Japan Petrol. Inst., 26 (1983) 362. M. Sugioka, J. Japan Petrol. Inst., 33 (1990) 280. M. Sugioka, Y. Takase and K. Takahashi, Proc. of JECAT'91, p.224 (1991). M. Sugioka, Zeoraito(Zeolite), 10 (1993) 121. M. Sugioka, ErdSI & Kohle, Erdgas, Petrochemie, (1995), in press.
Catalysis by Microporous Materials
544
Studies in Surface Science and Catalysis, Vol. 94 9 1995 Elsevier Science B.V. All fights reserved.
Hydrodesulfurization of thiophene over noble metals supported on ZSM-5 zeolites M. Sugioka, C. Tochiyama, Y. Matsumoto and F. Sado Department of Applied Chemistry, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran 050, Japan
Pt/HZSM-5 showed high and stable catalytic activity for the hydrodesulfurization of thiophene at 400~ and its catalytic activity was higher than that of commercial CoMo/AI2Oa catalyst. It is concluded that the BrSnsted acid site and spillover hydrogen formed on Pt particle in Pt/HZS M-5 catalyst play an important role for the hydrodesulfurization of thiophene.
1. I N T R O D U C T I O N
Hydrodesulfurization of petroleum feedstocks is one of the important processes in the petroleum industry to produce clean fuels. The CoMo/AI2Oa catalyst is widely used. Recently, the need for fuels of lower sulfur content due to the serious problems of global-scale air pollution because of burning petroleum feedstocks initiated to develop hydrodesulfurization catalysts, which are of higher activity than commercial CoMo/AI203. It has been reported that metal-zeolite catalysts have high possibility as new hydrodesulfurization catalysts for petroleum [1-9]. The catalytic desulfurization of organic sulfur compounds over zeolites has been investigated systematically [10-12]. On the basis of fundamental catalytic studies, active zeolite-based hydrodesulfurization catalysts such as transition metal ion-exchanged Y zeolites(MeY)[13-16], MoS2/NiHY[17] and Rh/USY[18, 19] were developed. In the present work, the catalytic activity of noble metals (Pt, Rh, Pd, Ru) supported on NaZSM-5 and HZSM-5 zeolites were studied in the hydrodesulfurization of thiophene in order to develop more highly active
545 zeolite-based hydrodesulfurization catalysts. 2. E X P E R I M E N T A L
Hydrodesulfurization of thiophene was carried out at 400~ at 1 atm using conventional fixed-bed flow reactor. Thiophene was introduced into the reactor with flowing hydrogen saturated by thiophene at 0~ The reaction products were analyzed by gaschromatograph. ZSM-5(SiO2/AI203=22.1,TOSOH)-supported noble metal catalysts were prepared by the impregnation method using aqueous noble metal chloride solutions. The metal loading was 5 wt%. Catalysts were calcined at 500~ for 4 hr in air and reduced at 450~ for 1 hr prior to use. 3. RESULTS AND DISCUSSION 3.1 Activities of noble metal/zeolite catalysts The catalytic activity of various noble metals supported on
NaZSM-5 and HZS M-5 zeolites was examined in the hydrodesulfurization of thiophene at 400~ (Figure 1). The activity was markedly changed by the the kind of noble metal and the order of the catalytic activities of noble metal/NaZSM-5 catalysts was as follows: Pt/NaZSM-5 > Rh/NaZSM-5 > Pd/NaZSM-5 > Ru/NaZSM-5 Pt/NaZSM-5 showed the highest activity, however, it was lower than that of commercial CoMo/AI203 catalyst. Figure 2 shows the hydrodesulfurization of thiophene over various noble metal/HZSM-5 catalysts. It was found that the order of the catalytic activities of noble metal/HZSM-5 corresponded to that found with NaZSM-5 preparations. Pt/HZSM-5 catalyst showed stable activity. This activity was the highest, even higher than the activity of the CoMo/AI203 catalyst. The reaction products in the hydrodesulfurization of thiophene over noble metal/ZSM-5 catalysts were hydrogen sulfide and C1-C4 hydrocarbons. Noble metals supported on HZSM-5 zeolite show higher catalytic activity than on NaZSM-5, suggesting that the Br'0nsted acid sites of HZSM-5 in noble metal/HZSM-5 catalysts play important role in the hydrodesulfurization of thiophene.
546
100
80
g
" ""
" . , . . . ,,,, . . . . ,,., . . , . , . , . "4""----..,.....
,,,....,, . . , . ,., . , . .
. . . .
,,.,.,, . . . . . . .
Prcsulfidexi CoMolAl203
"-" 60 (:I o
ov-.l
40
5~% ,..__-Q'~"r
A
,,.
,,
_
_
Pv~zsM-5
5wt% 1~[~_.,SM-5
2O _
5wt% Pd/N~ZSM-5 5wt% Ru/NaZ~M-5
0
1
W/F Figure 1
,=
2, 37.9
3
4
"JL"m~e on Stream (t~') g.hr/mol I-L2/Thlophcne
5 ,=
30
Hydrodesulfurization of thiophene over noble m e t a l / N a Z S M - 5
catalysts at 4 0 0 ~
100 5wt% Pt/HZSM-5 80
vI:I
. o
60
o
o
8
20
5wt% Pd/HZ,SM-5
,,,,,,,
5wt96 R~.II=IZ.SM-5 ......
0
I
1
,,
I
2
......
I
3
"[Imo o- St~sm W/F ,= 37.9 g.hr/mol Figure 2. at 400=C.
,
I
.......
4
l
_
5
('m') H2/Thiophcnc =
30
Hydrodesulfurization of thiophene over noble metal/HZSM-5 catalysts
547 3.2 Catalytic properties of Pt/HZSM-5 It was found that Pt/HZSM-5 catalyst showed remarkable high and stable activity for the hydroclesulfurization of thiophene in comparison with other noble metal/HZS M-5 catalysts. The effect of sulfiding with H2S on the catalytic activity of noble metal/HZS M-5 in the hydrodesulfurization of thiophene and hydrocracking of benzene was examined in order to learn more about the origin of the high and stable catalytic activity of Pt/HZSM-5. Sulfiding was carried out by introduction of hydrogen sulfide (10 ml) into the reactor using glass syringe. Figure 3 shows the effect of sulfiding on the hydrodesulfurization of thiophene over various noble metal/HZSM-5 catalysts. It was revealed that the high and stable activity of the Pt/HZS M-5 catalyst was hardly affected by the introduction of hydrogen sulfide.
100
. ~
,ik
~lh
,dh
~.. !P'
A IF'_
A lp'
A 1~'
AIh Ip'
liI
~. 'lw
.L qP'
~
A IP'
~, IP'
,~
~ lw,
,aL
T 5wt% PtZHZSM-5 80
V
H2S Injeetion(10ml)
60
o
el,-4
H2S Injection(10ml) ,o
H2S Injection(10ml) 5wt% Pd/HZ.SM-5 .~5wt% R ~ M - 5
0 0
-=_. __-. ~ == =. = = _ - = _ .. = 1 2
,..,.
,.
I
3
Time on Stream (hr) W/F = 19.0 g.hr/mol H2/Thiophene = 30 Figure 3. Effect of introduction of hydrogen sulfide on the hydrodesulfurization of thiophene over noble metal/HZSM-5 catalysts at 400~
548
Figure 4 shows the effect of sulfiding for the hydrocracking of benzene over noble metal/HZSM-5 catalysts. It was found that the catalytic activity of noble metal/HZSM-5 was remarkably lowered by the introduction of hydrogen sulfide. The catalytic activity of Rh/HZSM-5, Pd/HZSM-5 and Ru/HZSM-5 did not recover with the time on stream, but, Pt/HZSM-5 regained almost its original activity.
100
5wt% Rh/HT__,SM.--5. 80
~" v
60
c~ r O
4o
_
H2S Injection(lOml) 5wt% Ru/ItZSM-5 r"
_
20
.H2S Injcction(lOml)
M-5
Pt/H~M-5
0
30
60
90
Time on Stream
120
/
150
180
(rain)
Figure 4. Effect of introduction of hydrogen sulfide on the hydrocracking of benzene over noble metal/HZSM-5 catalysts at 40(/'C.
Results suggest that interaction of the hydrogen sulfide and the platinum on the HZSM-5 is not very strong, therefore, the metallic nature of platinum is easily regenerated by the hydrogen during hydrodesulfurization. By this reason, Pt/HZSM-5 catalyst shows high and stable activity for the hydrodesulfurization of thiophene.
549
3.3 Mechanism of hydrodesulfurization of thiophene on Pt/HZSM-5 catalyst As mentioned above, Pt/HZS M-5 showed higher activity than Pt/NaZS M-5 in the hydrodesulfurization of thiophene. This indicates that the BrSnsted acid site of HZS M-5 in Pt/HZS M-5 catalyst plays an important role for the hydrodesulfurization of thiophene.lt can be assumed that the BrSnsted acid site in the Pt/I-IZSM-5 catalyst is one site active for the activation of thiophene, whereas Pt is an active site for the activation of hydrogen. In other words, Pt/HZSM-5 catalyst is a bifunctional catalyst for the hydrodesulfurization of thiophene, in which both Br0nsted acid and platinum metal sites are active sites. Participation of spillover hydrogen in the hydrodesulfurization of thiophene over Pt/I-IZS M-5 catalyst was assumed and examined. It was found that catalytic activity of Pt/SiO2(quarlz) mixed mechanically with HZSM-5 was higher than that obtained by simple addition of the data for the pure components(Figure 5). This implies that spillover hydrogen on Pt/HZSM-5 catalyst participates in the hydrodesulfurization of thiophene. The mechanism proposed is shown in Scheme 1. 100
80
~,
60
o
A
B
P t/Quartz+HZSM-5
40 ._
0.
0.1g
6
--3
{
q, 20
-
-
~
. . . . .~ . . . . . . . . .
~ "
HZSM-5 (B) 0.1g--1 0
20
40
~
~S-_ Calculated (A+B) ""O'"~'=" ~
/E-'Pt/Quartz (A) 0..lg 60
T i m e on S t r e a m
80
100
120
(min)
Figure 5. Hydrodesulfurization of thiophene over R/quartz(A) ,HZSM-5(B) and mechanically mixed (R/quartz(A) + HZSM-5(B)) catalysts at 40ffC.
550
H=S + C~~C. Hydrocarbon
H2
TI
H
Spillover Hydrogen H
P = , = = - = = ..-= = _ . = .._..~.~..=.-= = = = , : : : . . - .
H
t
s\O H
H+
[S=C=CH-CH=CH2 ] < = = = = = . = . - = = . : ~ .". ~ . = .. ~
...; : . ~ : =
.:.~.:=... ~ ~:..~
o!
~ . : . . ~ = - = : =. =.:.~.:: =: = = = =-:,:..:: . = . ......... ::..:., .... :: ...... . . . : : : . . . : . . =
H Z S M - 5 Scheme 1. The possible mechanism of thiophene hydrodesulfurization over Pt/HZSM-5 catalyst.
Accoding to this mechanism, thiophene is adsorbed on BrSnsted acid site of Pt/HZSM-5 and hydrogen is activated on Pt to form spillover hydrogen. The spillover hydrogen formed on Pt attacks the reaction intermediate, e.g., species such as S=C=CH-CH=CH2, formed by the decomposition of thiophene adsorbed on the strong BrOnsted acid site of the zeolites [16]. 4. CONCLUSION
It was observed that Pt/HZS M-5 was of higher catalytic activity than commercial CoMo/AI203 in the hydrodesulfurization of thiophene. Therefore, there is a possibility for using Pt/HZSM-5 as highly active, second generation hydrodesulfurization catalyst for petroleum feedstocks.
ACKNOWLEDGEMENTS
The authors express their gratitude to The Japan Petroleum Institute and Petroleum Energy Center for supporting these investigations.
551
REFERENCES
1. M.L. Vrinat, C. G. Gachet and L. de Mourgues, Stud. Surf. Sci. Catal., 5 2. 3. 4. 5. 6.
(1980) 219. C.S. Brooks, Surf. Technol., 10 (1980) 397. K.E. Givens and J. G. Dillard, J. Catal., 86 (1984) 108. T.G. Harvey and T. W. Matheson, J. Catal., 101 (1986) 253. R. Cid, F. Orellana and A. L6pez Agudo, Appl. Catal., 32 (1987) 327. Y. Okamoto, A. Maezawa, H. Kane and T. Imanaka, J. Mol. Catal., 52 (1989)
337. 7. S. Gobolos, M. Breysse, M. Cattenot, J. Decamp, M. Lacroix, J. L. Portefaix and M. Vrinat, Stud. Surf. Sci. Catal., 50 (1989) 243. 8. M. Laniecki and W. Zmierczak, Zeolites, 11 (1991) 18. 9. P. Kovacheva, N. Davidova and J. Novakova, Zeolites, 11 (1991)54. 10. M. Sugioka and K. Aomura, Intern. Chem. Eng., 13 (1973) 755. 11. M. Sugioka and K. Aomura, Bull. Japan Petrol. Inst., 17 (1975) 51. 12. M. Sugioka, T. Kamanaka and K. Aomura, Prepri. Am. Chem. Soc., Div. Petrol. Chem., 24 (1979) 740. 13. M. Sugioka and K.Aomura, Prepri. Am. Chem. Soc., Div. Petrol. Chem., 25 14. 15. 16. 17. 18. 19.
(1980) 245. M. Sugioka and K. Aomura, J. Japan Petrol. Inst., 26 (1983) 216. M. Sugioka, M. Sasaki and K. Aomura, J. Japan Petrol. Inst., 26 (1983) 362. M. Sugioka, J. Japan Petrol. Inst., 33 (1990) 280. M. Sugioka, Y. Takase and K. Takahashi, Proc. of JECAT'91, p.224 (1991). M. Sugioka, Zeoraito(Zeolite), 10 (1993) 121. M. Sugioka, ErdSI & Kohle, Erdgas, Petrochemie, (1995), in press.