American Journal of Oil and Chemical Technologies: Volume 2. Issue 5. May 2014
Petrotex Library Archive
American Journal of Oil and Chemical Technologies
Journal Website: http://www.petrotex.us/2013/02/17/317/
Desulfurization of a Petroleum efinery Cut Using Y- Zeolite
abdolkhani, a1,*, changalvaii, a.a1
1
Department of Chemical Engineering, Omidiyeh Islamic Azad University, Omidiyeh, Iran
Abstract:
In recent years, a great deal of research works has been done in an attempt to reduce the sulfur content of refinery products as much
as possible, as a minute amounts of sulfur compounds could poison the catalysts of the refinery units. Alternative ways of reducing
sulfur compounds of petroleum products to the conventional method of hydrodesulfurization (HDS) process, have attracted a
number of research works, lately. In this work, reduction of sulfur compounds to acceptable levels was studied experimentally,
through adsorption process at room temperature. Y-zeolite, ionically exchanged with phase ions, was prepared and studied in order
to evaluate its performance in removing the sulfur components of a refinery intermediate product. Ni-Y zeolitewas prepared by HY zeolite and nickel(II)nitrate hexahydrate, using the solid-state ion exchange(SSIE) method. Experimental results show that Ni-Y
zeolite exhibits a higher selectivity than other types of zeolite, in removing the sulfur compounds of petroleum products. Another
result, concluded from this study, indicates the importance of introducing the ion exchange metals into the zeolite structures to
fortify the adsorption of aromatic and sulfur of the organic liquid mixtures. This, may lead to production of promising transport
fuels in which environmental standards are better observed.
Keyword: Desulfrization, Petroleum cut, Improved ions, Adsorption, Y-zeolite
1.
Introduction
World In recent decades, increasing demands for fossil fuels, has turned the supply of sulfur-free fuels to an important challenge for
the refinery productions. [1,2]. Sulfur compounds of fossil fuels are the major element of producing SOx in the atmosphere [3],
which in turn is the main cause of acid rains in recent years [4,5]. For this reason, a number of countries are enacting laws to curb
and lessen the sulfur content of fossil fuels to safer levels.
Tables 1 and 2 show the USA laws ( US EPA) on the permitted amount of sulfur content of gasoline (petrol) and gasoil, both for
road and off road conditions [4]. According to these standards, the sulfur content of gasoline and gasoil have been reduced to 30
ppm and 15 ppm, up to 2006, respectively. Another challenge for refining industries is the availability of heavier crude oil, with
increasing consumption demands, which contain higher sulfur compounds. On the other hand, limiting laws concerning the
permitted amount of sulfur content of fuels are getting harder every day. The issue shows the importance, as well as the necessity
for further research works to reduce the sulfur components of fossil fuels, more than before [4].
Tables 1. the USA laws ( US EPA) on the permitted amount of sulfur content of gasoline (petrol)
Category
1998
Refinery average (ppmw)
1000 (maximum)
1995
2004
2005
2006
—
30
30
(<330S ppm(
Authors /American Journal of Oil and Chemical Technologies 5 (2014) 45-47
Corporate average
(ppmw)
120
90
—
Per-gallon cap (ppmw)
300
300
80
Tables 2. the USA laws ( US EPA) on the permitted amount of sulfur content of gasoil
1.1.
Category
1989
1993
2006
2010
Highway diesel (ppmw)
5000 (maximum)
500
15
15
Non-road diesel (ppmw)
20000
5000
500
15
Sulfur compounds
Sulfur compounds in fossil fuels, are generally, divided into the following groups:
Gasoline (petrol): thiophenes (T) and its derivatives, thiophenes (T) and its derivatives, benzothiophene (BT)
Jet fuel: benzothiophene (BT) and its alkylation derivatives
Gasoil: dibenzothiophene (DBT) and its alkylation derivatives
1.2.
A short literature survey:
In the past decade, research works were concentrated on metal oxides, reduced metals, activated carbon, activated alumina and
zeolites to find the absorbents with high absorption power, as well as selectivity [6,7,8]. Among these works, carbon and zeolite
materials showed better performance than the others [8].
King and Lee [9] used ZSM-5to absorb selected thiophenic compound. ZSM-5 with small size holes(5.2-5.6A), is not able to absorb
compounds with more than one ring, so absorbent with bigger holes like faujasites are being considered [10,11]. Yang et al used,
Na-Y zeolite, ionically exchanged Ag+ and Cu+, to remove sulfur components. In this work, for the first time, the selectivity of
zeolite for sulfur components removal was justified on the basis of π-complexation formation [12]. After that, they tried other
metals such as Ni and Zn to improve the faujasite zeolite for removing the sulfur components from liquid fuels. They succeeded to
reduce the sulfur contents of various petroleum cuts to less than 1 ppm, using Cu(I) -Y zeolite [8,13]. They also used zeolites,
improved with the ion exchange metals to study the removal of sulfur components from light petroleum cuts.
1.3.
A brief history of zeolites:
Zeolites were discovered for the first time by Cronsted, a Swedish mineralogist. After that, and specially by improvement of x-ray
diffraction (XRD) technique, a great deal of research work has been done on the issue. Today, about 40 types of natural zeolites
have been discovered, in which most of them have low silica-alumina ratio. Heulandite (HEU) and Mordenite (MOR), are two types
of natural zeolite which are widely used in agriculture and also as absorbents. Natural zeolite activities are low due to impurities and
small special surface. Some other natural zeolites, like Orionite (ERI) are poisonous and are not of practical use.
2
Authors /American Journal of Oil and Chemical Technologies 5 (2014) 45-47
2.
Materials and Methods
2.1.
Feed:
In this study, samples of heavy straight run gasoline, from atmospheric column of an Iranian refinery, was prepared and used for
desulfurization tests. The components of this sample, measured by gas chromatography (GC) technique, are presented in table3.
This is a very stable intermediate product of the refinery, and its compositional deviation is about 0.1% throughout the year, and its
total sulfur content of is about 140 ppmw.
Table 3. HSRG Specifications
2.2.
Synthesis of Na-Y zeolite
Synthesis of Na-Y zeolite with molar ratio of 2.43 for S2O/Al2O3, was adapted from
were used for the synthetic zeolite:
method [9]. The following molar ratios
H2O 180 SiO2 : 10 Na2O : Al2O3 : 10.67
The synthesis consisted of 3 parts:
2.2.1.
Preparation of seed gel
The seed gel was prepared with the following molar ratios:
H2O 180 SiO2 : 10 Na2O : Al2O3 : 10.67
The gel was prepared by dissolving weighed amounts of sodium hydroxide and sodium aluminate in water and stirred until a
colorless solution was reached. Then, the solution was then mixed with the sodium silicate solution.
2.2.2.
Preparation of feed gel
The following molar ratios were used in preparation of feed gel:
H2O 180 SiO2 : 10 Na2O : Al2O3 : 4.30
3
Authors /American Journal of Oil and Chemical Technologies 5 (2014) 45-47
A similar method for preparation of seed gel was followed (Section 2.2.1). After adding the solution with sodium silicate, the
mixture turns to gel immediately.
The mixture was left in a closed container for 24 hours at room temperature, until crystallization began, around the seeds. The
container was then placed in an oven, so that the crystallization process reached completion. If the temperature or residence time
changes, amorphous molecules are generated, which cause impurities in the zeolite. The process was then complete and the
resulting zeolite precipitated at the bottom of the container, which was separated from the aqueous phase in the top, by centrifuge,
which left the aqueous phase quite transparent. The aqueous phase was descanted, while the precipitated portion filtered and washed
with distilled water, until the pH of the filtered solution reached 9. The resulting zeolite was then heated in an oven, until it was
completely dried.
3.
Results and discussion:
3.1.
Identification of the synthesized zeolite:
The XRD pattern for the zeolite sample was prepared, using a D8 Advance Model XRD system (Broker Co, Germany). The
resulting pattern is shown in Figure1.To identify the synthesized sample, its XRD spectrum was compared with the reference
sample spectrum, which showed good agreement. The pattern of peaks for Y-zeolite is shown in figure 1.
Figure 1. XRD pattern of Na-Y zeolite.
The Na-Y zeolite in natural form, has small adsorption power, and for this reason, its improved forms are used in the process of
adsorption. To improve the Na-Y zeolite adsorption power, the Na cations are exchanged with the cation from the ion exchange
metals. In this work, the ions were exchanged, using the solid-state ion exchange (SSIE) method. In this method, the acidic form of
the zeolite, ie, H-Y zeolite is reacted with the metal salt at elevated temperature. Conventional industrial methods were implied to
convert the Na-Y zeolite to H-Y zeolite [14].
3.2.
Sulfur adsorption process:
The sample of petroleum cut was desulfurized in a batch reactor. The absorbent zeolite and the sample were placed in the reactor
with a ratio of 1 to 10 g per ml and stirred by magnetic container for a fixed period of time. The mixture was filtered and the amount
of sulfur content in the desulfurized sample was measured. The test was repeated with various sample/absorbent ratios.
3.3.
The effect of time:
4
Authors /American Journal of Oil and Chemical Technologies 5 (2014) 45-47
The sulfur content of the sample HSRG with the reactor residence time was also measured, and the resulting curve is shown in
figure 2. As it is evident from the curve, most of the amount of sulfur is adsorbed in the first 45 minutes of the experiment, where
the capacity of adsorption of sulfur in the sample by zeolite is o.92 mg of sulfur per g of adsorbent. Most of the adsorption was
achieved in the initial minutes of the process, for example, adsorption rates after 5 and 10 minutes were 0.70 and 077 mg of sulfur
per g of adsorbent, respectively, while the corresponding figure, after 2 hours, reached 0.95. Eventually, the process approached the
equilibrium condition, after 4 hours.
140
sulfur content (ppm S)
Sulfur content (ppm S)
120
100
80
60
40
20
0
0
0.5
1
1.5
2
2.5
Time (h)
3
3.5
4
4.5
Figure 2. Effect of gasoline residence time in the batch stirring reactor.
3.4.
The effect of temperature:
Sulfur Content (ppm S)
The effect of temperature on the adsorption process of HSRG sample, by zeolite Ni-Y, was also studied and the results are presented
in figure 3. It is noticed that, as the temperature is increased, the removal of sulfur content from the sample is decreased. For
example, when the temperature is raised from 25oC (room temperature) to 60oC, the sulfur content adsorbed by the zeolite, reduces
from 0.92 to 0.77 mg of sulfur per g of adsorbent, which may be attributed to the exothermic nature of the reaction.
160
Adsorption capacity (mg(S)/g)
140
Sulfur content (ppm S)
120
100
80
60
40
20
0
20
30
40
Temperature (C)
50
60
70
Figure 3. Effect of temperature on the sulfur content of the HSRG sample after use of Ni-Y zeolite.
5
Authors /American Journal of Oil and Chemical Technologies 5 (2014) 45-47
4.
Conclusions:
The experimental results show that Ni-Y zeolite has a higher selectivity in removing the sulfur content from a petroleum
cut(HSRG), than other zeolites.
Desulfrization of light petroleum cuts by Ni-Y zeolite, at ambient conditions, can be achieved with formation of complexation. The
process of adsorption by Ni-Y zeolite, depends on two main factors, namely the time and temperature. In this work, most of the
sulfur content of the sample was adsorbed within 45 minutes of the test, and 0.92 mg of sulfur (96.8% of total removed) per g of
adsorbent was adsorbed. Temperature increase has an adverse effect on the adsorption of sulfur by Ni-Y zeolite, and a increase of
35oC, causes the adsorption rate to be reduced by 16.3%. It also can be concluded that with introduction of the ion exchange metals
in the zeolite structures, their adsorption power improves in removing the aromatic and sulfur components in the organic liquid
mixtures. This may hopefully leads to enhanced transport fuels, and better observation of environmental standards.
5.
Acknowledgements:
The authors wish to thank Young Researchers Club of Omidiyeh Islamic Azad University and Isfahan Refinery for their support in
this project.
6.
References:
[1] Herna´ndez-Maldonado, A. J.; Yang, R. T. Desulfurization of Diesel Fuels via π-Complexation with Nickel(II)-Exchanged Xand Y-zeolites. Ind. Eng. Chem. Res. 2004, 43, 1081.
[2] Herna´ndez-Maldonado, A.J. R.T. Yang, J. Am. Chem. Soc. 126 (2004) 992.
[3] Xue, M.; Chitrakar, R.; Sakane, K.; Hirotsu, T.; Ooi, K.; Yoshimura, Y.; Toba, M.; Feng, Q. Preparation of Cerium-Loaded YZeolites for Removal of Organic Sulfur Compounds from Hydrodesulfurizated Gasoline and Diesel Oil. J. Colloid Interface Sci.
2006, 298, 535.
[4] Song, C. An Overview of New Approaches to Deep Desulfurization for Ultra-Clean Gasoline, Diesel Fuel and Jet Fuel. Catal.
Today 2003, 86, 211.
[5] Velu, Ma, X.; S.; Kim, J. H.; Song, C. Deep Desulfurization of Gasoline by Selective Adsorption over Solid Adsorbents and
Impact of Analytical Methods on ppm-Level Sulfur Quantification for Fuel Cell Applications. Appl. Catal. B: EnViron. 2005, 56,
137.
[6] Velu, S.; Ma, X.; Song, C. Selective Adsorption for Removing Sulfur from Jet Fuel over Zeolite-Based Adsorbents. Ind. Eng.
Chem. Res. 2003, 42, 5293.
[7]Velu, S.; Song, C.; Engelhard, M. H.; Chin, Y. H. Adsorptive Removal of Organic Sulfur Compounds from Jet Fuel over KExchanged NiY Zeolites Prepared by Impregnation and Ion Exchange. Ind. Eng. Chem. Res. 2005, 44, 5740.
[8] Dastanian, M.; Azad, F.S. Desulfurization of Gasoline over Nanoporous Nickel-Loaded Y-Type Zeolite at Ambient Conditions.
Res. 2010, 43, 113.
[9] King DL, Li L. Removal of sulfur components from low sulfur gasoline using copper exchanged zeolite Y at ambient
temperature. Catal Today 2006;116:526–9.
[10] Herna´ndez-Maldonado, A. J.; Yang, R. T. Desulfurization of Liquid Fuels by Adsorption via π Complexation with Cu(I)-Y
and Ag-Y Zeolites. Ind. Eng. Chem. Res. 2003, 42, 123.
[11) Yang, R. T.; Herna´ndez-Maldonado, A. J.; Yang, F. H. Desulfurization of Transportation Fuels with Zeolites under Ambient
Conditions. Science 2003, 301, 79.
[12] Yang, R. T.; Takahashi, A.; Yang, F. H. New Sorbents for
Desulfurization of Liquid Fuels by π-Complexation. Ind. Eng. Chem. Res. 2001, 40, 6236.
[13] Herna´ndez-Maldonado, A. J.; Yang, F. H.; Qi, G.; Yang, R. T.
Desulfurization of Transportation Fuels by π-Complexation Sorbents: Cu(I)-, Ni(II)-, and Zn(II)-zeolites. Appl. Catal. B: EnViron.
2005, 56, 111.
[14] Baerlocher, Ch.; McCusker, L. B.; Olson, D. H. Atlas of Zeolite Framework Types, 6th ed.; Elsevier: New York, 2007.
6
Authors /American Journal of Oil and Chemical Technologies 5 (2014) 45-47
7