Isomerization of n-butane on dealuminated mordenite promoted with zirconium dioxide

Article abstract of DOI:10.1134/S107042720702019X

Zirconium dioxide promotes the catalytic activity of a dealuminated mordenite in n-butane isomerization. A method is suggested for preparing, without any solvents, a sulfated mordenite-zirconium catalyst active at relatively low temperatures.

Full text of DOI:10.1134/S107042720702019X

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 2, pp. 268 271.
Pleiades Publishing, Ltd., 2007.
Original Russian Text
pp. 269 272.
D.B. Tagiev, R.V. Starikov, A.A. Imanova, M.I. Rustamov, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 2,
CATALYSIS
Isomerization of n-Butane on Dealuminated Mordenite
Promoted with Zirconium Dioxide
D. B. Tagiev, R. V. Starikov, A. A. Imanova, and M. I. Rustamov
Mamedaliev Institute of Petrochemical Processes, National Academy of Sciences of Azerbaijan,
Baku, Azerbaijan
Received June 21, 2006
Abstract Zirconiun dioxide promotes the catalytic activity of a dealuminated mordenite in n-butane isomer-
ization. A method is suggested for preparing, without any solvents, a sulfated mordenite-zirconium catalyst
active at relatively low temperatures.
DOI: 10.1134/S107042720702019X
Isomerization of n-butane is one of the most im-
portant processes of petrochemical industry in produc-
tion of alkylates and other valuable products [1, 2].
To perform this reaction, different heterogeneous cat-
alysts have been suggested. Among them the chlori-
nated platinum-alumina catalysts, metallozeolites, and
sulfated zirconium dioxide are of particular interest
[1 8]. Each of these catalysts has advantages and dis-
advantages. For instance, chlorinated platinum-alumi-
na catalyst require a thorough pretreatment of the raw
material and are environmetally unfavorable. Iso-
merization with metallozeolites is performed at high
temperatures; they are favorable in isomerization of
C5 and C5 C6 paraffins. Sulfated zirconium dioxide
is active at relatively low temperatures. However,
additional studies are required to improve the stability
and reproducibility of its catalytic properties.
EXPERIMENTAL
The catalysts were prepared from dealuminated
H-mordenite with the SiO2/Al2O3 ratio of 17 (sample
HM17). To promote HM17 with zirconium dioxide, we
used impregnation and mechanical mixing of the zeo-
lite with ZrO(NO3)2 or ZrO(OH)2, with subsequent
decomposition of the mixture at 823 873 K [the sam-
ples were denoted as aZrO2/HM17 (impregnation) and
HM17 aZrO2 (mixing), where a is the ZrO2 content,
wt %]. The samples obtained were sulfated by their
treatment with 2 M solution of (NH4)2SO4. Catalysts
were molded with aluminum hydroxide as a binding
agent, dried at 383 393 K, and calcined at 823 873 K.
The conversion of n-butane was studied in a flow-
type apparatus at atmospheric pressure within the 433
523 K range. A 2 cm3 portion of cylindrical catalyst
granules 1 3 mm in size was charged into a quartz re-
actor and activated in an air flow at 773 K for 3 h.
After the experiments, the catalyst was regenerated
under the same conditions. After activation or regen-
eration, catalysts were cooled in an N2 flow to the re-
action temperature, and n-butane was started to be
Due to cellular structure and possibility of purpose-
ful modification of the physicochemical properties,
zeolites are promising catalysts for n-butane iso-
merization. It was shown in [9, 10] that dealumina-
tion of H-mordenite enchances its isomerization ac-
tivity. The activity of dealuminated H-mordenite can
be further raised by choosing appropriate promoters
[11, 12].
1
delivered at a flow rate of 300 ml h . No carrier gas
was used.
The induction period of the reaction was 20
30 min, depending on the experimental conditions.
During this time, the isobutane yield reached the max-
imum and then decreased to a constant value. The data
reported in this paper are related to 20th minute of
the reaction run. The reaction products were monitored
chromatographically, and catalysts, by powder X-ray
In this study, we examined the catalytic properties
of binary mordenite-zirconium and ternary sulfated
mordenite-zirconium catalysts to find the probable
synergism of such systems and to develop on their
base low-temperature catalysts of n-butane isomeriza-
tion.
268

ISOMERIZATION OF n-BUTANE
269
diffraction (DRON-3M X-ray diffractometer) and
thermal analysis (Q-1500D derivatograph).
Table 1. Isomerization of n-butane on mordenite-contain-
ing catalysts prepared by impregnation
Zirconium dioxide synthesized by decomposition of
ZrO(NO3)2 2H2O and calcination of ZrO(OH)2 hy-
drogel precipitated with NH4OH solution shows low
activity in n-butane isomerization. Sulfation of ZrO2
preliminarily calcined at 823 873 K does not raise
the isobutane yield. The active catalyst is formed after
treatment with an (NH4)2SO4 solution of ZrO(OH)2
dried at room temperature. In this case, the n-butane
conversion is 22.0% at 493 K; the yield of isobutane
reaches 16.9% (the residue consists of propane and n-
and isopentanes).
n-Butane Yield, wt %
T,
K
con-
ver-
sion, %
Catalyst
isobu- isopen-
tene
tane
HM17
523
523
493
493
28.0
28.2
22.0
30.0
34.5
16.1
15.4
16.9
18.5
21.3
2.5
3.7
2.4
3.0
4.0
4%SO24 /HM17
27%SO24 /ZrO2
5%ZrO2/HM17
4%SO24 /5%ZrO2/HM17 463
Table 2. Isomerization of n-butane on mordenite-zirconium
catalysts prepared by mechanical mixing of HM17 and
ZrO(NO3)2 2H2O
Impregnation of dealuminated mordenite HM17
with ZrO(NO3)2 aqueous solution, with further calci-
nations at 823 K, substantially improves the catalyst
activity, which appears in a rise in the isobutane and
isopentane yield and in a decrease in the optimal tem-
perature of the reaction. That is, ZrO2 has a promoting
effect on the activity of dealuminated mordenite.
n-Butane Yield, wt %
con-
ver-
Sam-
ple
no.
T,
Catalyst
K
isobu- isopen-
sion, %
tene
tane
It should be noted that, in contrast to HM17, whose
sulfation does not substantially affect its isomerization
activity, aZrO2/HM17 samples (a = 2.5 10.0 wt %)
show after sulfation a higher activity in n-butane iso-
merization at relatively low temperatures. These data
show that, in contrast to ZrO2, which directly pro-
motes HM17, sulfate ions raise the activity of dealumi-
nated mordenite only when the latter contains zirconi-
um dioxide. The data obtained are listed in Table 1.
1
2
3
HM17
493
24.5
48.2
12.7
54.5
3.0
52.7
33.5
5.8
12.0
25.9
9.1
28.5
2.6
25.5
19.9
4.5
0.6
3.1
1.6
5.3
HM17 5%ZrO2 493
HM17 10%ZrO2 463
493
4
HM17 15%ZrO2 463
493
3.4
4.6
0.6
2.9
5
6
HM17 20%ZrO2 493
HM17 ZrO(OH)2 463
(as calculated
for 10%ZrO2)
ZrO2
493
31.8
20.2
7
493
0.9
0.5
Depending on the ZrO2 content in mordenite-zir-
conium and sulfated mordenite-zirconium catalysts,
the n-butane conversion and the total yield of isopar-
affins (isobutane and isopentane) pass through max-
ima. As can be seen from the figure, the maximal ac-
tivity of the catalysts prepared by impregnation is ob-
served for samples containing 5.0 7.5 wt % ZrO2.
NH4OH. However, at the same ZrO2 content, the ac-
tivity of catalysts prepared using a zirconium salt
(Table 2, sample 3) is higher than the activity of
The same extremal dependences are observed for
catalysts prepared more simply by mechanical mixing
of HM17 and ZrO(NO3)2 2H2O without any solvent,
followed by molding with a binding agent, drying,
and calcination. A comparison of samples contain-
ing from 5 to 20 wt % ZrO2 showed that the HM17
10 wt % ZrO2 catalyst has the highest activity in n-bu-
tane isomerization. The corresponding data are listed
in Table 2.
It should be noted that such an extremal depen-
dence of the activity on the ZrO2 content is observed
for the catalysts prepared by mechanical mixing of
HM17 with a ZrO(OH)2 hydrogel synthesized by pre-
cipitation from ZrOCl2 8H2O solution with aqueous
(1, 3) conversion
isoparaffins A vs. the ZrO content in (1, 2) aZrO /HM
17
of n-butane and (2, 4) total yield of
2
2
2
and (3, 4) 4%SO /aZrO /HM catalysts.
4
2
17
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 2 2007

270
TAGIEV et al.
Table 3. n-Butane conversion in an apparatus with
two series-connected reactors (catalyst HM17 10% ZrO2
4% SO24 )
The high catalytic activity of sulfated ZrO2 pro-
moted with various metals (Mn, Fe, Ga, Pt, etc.) was
discussed in a number papers [6 8, 13 17]. In this
study, we showed that zirconium compounds promote
the activity of dealuminated mordenite, whereas sulfa-
tion does not affect isomerization activity of morden-
ite itself, but substantially improves that of the mor-
denite-zirconium catalysts. This fact suggests that
the promoting effect of sulfate ions is caused by
the presence of ZrO2 in the catalysts. At the same
time, it should be noted that dealuminated mordenite
is not only a support for ZrO2 and SO24 , but is the
dominating component of the mordenite-zirconium
catalysts, as indicated by the attainment of the maxi-
mal catalytic activity at small concentrations of ZrO2
and SO24 and by the preservation of the same features
of the reaction before and after promotion of HM17.
The parallel variation of the yields of propane, iso-
butane, and isopentane with time can be caused by
the bimolecular mechanism of the reaction. However,
this matter requires a further study.
Temperature, K
n-Butane
conver-
sion, %
Yiels, %
reactor1 reactor2
isobutene isopentane
448
463
493
448
463
8.9
36.3
51.6
37.2
43.9
7.4
19.2
26.0
25.3
28.9
0.2
2.3
4.9
3.4
4.1
463
463
the sample prepared from ZrO(OH) hydrogel (Table 2,
sample 6).
The difference in the properties of mordenite-zir-
conium catalysts prepared by impregnation or mech-
anical mixing is also manifested in that sulfation of
impregnated catalysts aZrO2/HM17 calcined at 823 K
raised their activity, while sulfation of the HM17
aZrO2 (mixed catalysts) samples calcined at the same
temperature does not substantially affect the activity.
The thermal analysis of the systems HM17,
5% ZrO2/HM17 and 4% SO24 /5% ZrO2/HM17 and of
samples prepared by mechanical mixing (HM17
10% ZrO2 and HM17 10% ZrO2 6% SO24 ) does not
show any substantial difference in their thermal be-
havior. Only one endothermic peak at 388 K, caused
by elimination of adsorbed water, exists in the DTA
curve of HM17. After impregnation of HM17 with
ZrO(NO3)2, this peak shifts to 398 K and a weak
endothermic peak appears at 628 K.
The three-component catalyst HM17 10% ZrO2
4% SO24 prepared by simultaneous mixing of HM17,
ZrO(NO3)2 2H2O, and (NH4)2SO4 followed by ther-
mal treatment under the above standard conditions has
a higher isomerization activity. At 463 493 K, the yield
of isobutane and isopentane on this catalyst was 19.2
26.0 and 2.3 4.9%, respectively, at an n-butane con-
version of 36.3 51.6%. The yield of the main by-pro-
duct of the reaction, propane, decreases substantially
faster as compared to the isobutane yield, and the se-
lectivity of the reaction correspondingly increases.
These facts are probably caused by dehydration and
decomposition of the zirconium salts. The high-tem-
perature peaks of sulfate decomposition were not
found, probably, because of the small amounts of sul-
fate groups in the samples examined.
Taking into account the data obtained, we studied
the conversion of n-butane on a catalytic apparatus
with two series-connected reactors. In this case, a high-
er yield of isoparaffins and selectivity can be reached
at lower temperatures. The data on n-butane conver-
sion and the yield of isoparaffins after the first and
second reactors at various temperatures are listed in
Table 3. As seen, the yield of isobutane in the two-re-
actor system at 448 463 K increases to 25.3 28.9%
at a small decrease in the isopentane yield. The reac-
tion selectivity with respect to isoparaffins increases
to 75% due to a substantial decrease in the propane
yield. These results are of certain interest because
the catalyst used contained no precious metals (Pt, Pd)
and was prepared by a simple and convenient method
at atmospheric pressure and without any carrier gas.
Such catalysts can be used as a basis for preparation
of more active catalysts for isomerization of n-par-
affins.
The X-ray diffraction patterns show that the crystal
structure of H-mordenite is preserved after dealumina-
tion and promotion with zirconium dioxide. In the dif-
fraction patterns of a powder with the composition
7.5% ZrO2/HM17 and ZrO2, prepared by decomposi-
tion of ZrO(NO3)2 2H2O at 873 K, reflections char-
acteristic of tetragonal ZrO2 at 2 = 30o were ob-
served [18]. Based on the data obtained, we can sug-
gest that impregnation of HM17 with a ZrO(NO3)2
aqueous solution, followed by thermal treatment at
823 873 K, yields a mixed mordenite-zirconium sys-
tem with a higher isomerization activity at relatively
low temperatures because of the interaction between
the decomposing zirconium salt and HM17. This pro-
cess affects the specific texture and acid base prop-
erties of the catalytic mixture.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 2 2007

ISOMERIZATION OF n-BUTANE
271
CONCLUSIONS
7. De Rossi, S., Ferraris, G., Valigi, M., and Gazroli, D.,
Appl. Catal. A, 2002, vol. 231, nos. 1 2, pp. 173 184.
(1) The promoting effect of ZrO2 on the catalytic
activity of dealuminated mordenite in isomerization
of n-butane was found.
8. Li, X., Nagoaka, N., Simon, L.J., et al., J. Catal.,
2005, vol. 232, no. 2, pp. 456 466.
9. Ganizares, P., de Lukas, A., and Dorado, F., Appl.
Catal. A, 200, vol. 196, no. 2, pp. 225 231.
10. Tagiev, D.B., Starikov, R.V., Imanova, A.A., et al.,
Protsessy Neftekhim. Neftepererab., 2004, no. 2,
pp. 103 107.
11. Tagiyev, D.B., Starikov, R.V., and Imanova, A.A.,
Abstracts of Papers. 3rd FEZA Conf., Prague, 2005,
p. 166.
(2) It was shown that the sulfated mordenite-zir-
conium catalyst prepared by a simple and convenient
method shows high activity in n-butane isomerization
at atmospheric pressure and relatively low temperatures.
REFERENCES
12. Tagiev, D.B., Starikov, R.V., Imanova, A.A., et al.,
Protsessy Neftekhim. Neftepererab., 2004, no. 3,
pp. 75 80.
1. Egizarov, Yu.G., Savchits, M.F., and Ustilovs-
kaya, E.Ya., Geterogenno-kataliticheskaya isomeriza-
tsiya uglevodorodov (Heterogeneous Catalytic Iso-
merization of Hydrocarbons), Moscow: Nauka i Tekh-
nika, 1989.
13. Keiich, N., Akihoro, O., and Kaoru, F., Appl. Catal. A,
2000, vol. 195, pp. 383 393.
14. Moreno, J.A.and Poncelet, D., Appl. Catal. A, 2001,
2. Yadav, G.D. and Nair, J.J., Microporous Mesi Mater.,
vol. 210, nos. 1 2, pp. 151 164.
1999, vol. 3, no. 1, pp. 1 11.
15. Hua, W. and Sommer, J., Appl. Catal. A, 2002,
3. Tran, M.-T., Gnep, N.S., Szabop, G., and Guisnet, M.,
vol. 227, nos. 1 2, pp. 279 286.
Appl. Catal. A., 1998, vol. 170, no. 1, pp. 49 58.
16. Wong, S.-T., Li, T., Cheng, S., et al., Appl. Catal. A,
4. Gembicki, S.A., Stud. Surf. Sci. Catal., 2000,
2005, vol. 296, no. 1, pp. 90 99.
vol. 130, pp. 147 154.
17. Li, X., Nagaoka, K., Simon, L.J., et al., J. Catal.,
5. Willegas, J.I., Kumar, N., Smeiskova, A., et al., Appl.
Catal. A., 2005, vol. 284, nos. 1 2, pp. 223 230.
2005, vol. 232, no. 2, pp. 456 466.
18. Morterra, C., Cerrato, G., Pinna, F., and Signoret-
6. Sony, X. and Sayari, A., Catal. Rev. Sci. Eng., 1996,
vol. 38, p. 239 412.
to, M., J. Catal., 1995, vol. 157, no. 1, pp. 109 123.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 2 2007