CC BY
6UOT 66.097.3
Aliyeva A.A.
Associate Professor, Doctor of Philosophy in Chemical Sciences,
Faculty of Chemical Technology, Department of Petrochemical Technology and Industrial Ecology, Azerbaijan State Oil and Industry University, Baku, Republic of Azerbaijan Mustafayev E.M. Master Student, Azerbaijan State Oil and Industry University, Baku, Republic of Azerbaijan Алиева А. А.
доцент, доктор философии по химическим наукам, химико-технологический факультет, Азербайджанский государственный университет нефти и промышленности,
Баку, Азербайджанская Республика Мустафаев Э.М. магистрант,
Азербайджанский государственный университет нефти и промышленности,
Баку, Азербайджанская Республика E-mail: [email protected]
Gasoline components on the base of composite catalysts Компоненты бензина на основе композитных катализаторов
Abstract: The article is devoted to the study of the natural gasoline conversion into high-octane components on the composite catalysts based on zeolite. The conversion of natural gasoline has been studied on the composite catalysts which components are Co(Ni) H-zeolite (MOR) and zirconium dioxide modified with the SO4 - anion. Co-MOR/(SO42-)ZrO2, Ni-MOR/(SO42~)ZrO2 are effective catalysts in order to increase the resources of iso-C5-C6 hydrocarbons.
Аннотация: Статья посвящена исследованию процесса конверсии природного бензина в высокооктановые компоненты на композитных катализаторах на основе цеолита. Конверсия
природного бензина была исследована на композитных катализаторах, компонентами которых являются Co(Ni) H-цеолит (MOR) и диоксид циркония, модифицированный анионом SO42. Co-MOR/(SO42-)ZrO2, Ni-MOR/(SO42~)ZrO2 являются эффективными катализаторами для увеличения ресурсов углеводородов iso-Cs-C6.
Keywords: natural gasoline; high-octane components; composite catalysts; conversion; isomerization; zeolite.
Ключевые слова: природный бензин; высокооктановые компоненты; композитные катализаторы; конверсия; изомеризация; цеолит.
Introduction. The current level of requirements for the quality of motor fuels is determined not only by the need to ensure operational characteristics, but also by improvement of the environmental features of vehicles. In most regions of the world strict regulations have been imposed in order to drive the demand for increased clean fuels. Therefore gasoline composition has undergone changes in terms of using C5-C7 isomerization processes. These environmental regulations for gasoline production are clean fuel initiatives which include lead phase out, reduction of benzene, aromatics and olefin hydrocarbons and addition of oxygen containing additives to gasoline [3, 4].
In order to improve the anti-knock characteristics of modern gasolines with a limited content of aromatic hydrocarbons the C5-C6 isomerization of alkanes plays an important role. However their processing has become difficult due to the need of separation of these hydrocarbons from light fractions of straight-run gasoline (natural gasoline) and the staged isolation of iso-pentane and isohexanes. The presence of C7+ residues in the feed serves as an additional factor complicating the process of isomerization of C5-C6 alkanes due to their decomposition into undesirable C4-hydrocarbons.
Studies of the natural gasoline conversion on the composite catalysts consisting of sulfated zirconium oxide and H-zeolite (where the zeolite is HMOR) showed the possibility of eliminating the noted disadvantages.
Experimental Part
The object of the study was composite catalysts the components of which were Me (Co,Ni) H-zeolite (HMOR) and zirconium dioxide (SZ) modified with the SO42-anion. HMOR-17 modification carried out by ion-impregnation method introducing of the marked elements from solutions of CoSO4^O, NKNO3V6H2O, ZrO(NO3)2 2H2O salts and sulfotation of (NH4)2SO4 taken in prescribed amounts [2].
The resulting samples of anion-modified zirconium dioxides were molded using a binder component-oxide hydrogel aluminum, taken at the rate of 5 g per 100 g of dry catalyst mass. Then modified mordenite is thoroughly mixed with hydrogel aluminium, dried, crushed into cylindrical catalyst pellets and calcinated.
The prepared catalyst used in the main studies of natural gasoline conversions contains 65% (wt.) H-zeolite, 15% (wt.) SZ and the rest is a binder. The reaction products are analyzed on "Autosystem XL" gas chromatography. All hydrocarbon products are identified and the octane characteristics are calculated.
Results and Discussion
Isomerization process is used in order to meet octane demand for gasoline and plays a significant role in the production of clean fuels, premium gasoline grades. Mordenite catalysts for the isomerization of n-alkanes are the most active zeolite catalysts [4].
Conversion of natural gasoline is accomplished over
the Co-MOR/(SO42-)ZrO2
and Ni-MOR/(SO4 -)ZrO2 composite catalytic systems. The results of studying the conversion of natural gasoline in the temperature range between 180-200°C showed that Co/MOR/SZ catalyst has a positive effect on the increasing of iso-C5-C6 alkanes (Table 1).
Table 1 — Conversion of natural gasoline over the Co/MOR/SZ catalyst
Duration of
Temperature,°C
Distribution of reaction products, % (mass.)
experiment, min. C4- «0 O 0 s C5 40 O 0 s C6 iso-C7 C7+
5.5 25.2 19.2 18 8.4 5,4 18,3
30 180 1,9 32 20 28,8 3,3 1,52 12,48
45 1,54 32 23 26,7 3,6 0,87 12,29
30 200 1,6 34 20 25,4 3,3 3,2 12,5
45 1,8 36 21 23,5 3,2 2,5 12,05
As can be seen from data presented in table 1 the formation C6 isomers decreases, while iso-C5 increases. As a result of promotion the used catalyst stabilizes its isomerization activity. With an increase in temperature from 180 to 200°C the noted pattern of natural gasoline components conversions becomes more distinct, as the content of iso-C5 in natural gasoline by the 45th minute reaches 36% and the content of iso-C6 slightly reduces. The yield of n-pentane practically remained stable for a given time interval. It should also be noted that the content of n-C6 remains constant (3.63.2%), while the content of higher molecular weight components C7+ is independent of temperature. These data show that in the process of contacting natural gasoline with Co/MOR/SZ the overall activity of the catalyst does not decrease, however the catalyst functions responsible for shifting the distribution of products change. Taking into account the conversion of higher molecular weight hydrocarbons and the formation of lower molecular weight pentanes, it can be assumed that this catalytic system has a high hydrogenating ability which leads to hydrocracking.
Comparative experiments were carried out with a sample in which cobalt was replaced by a more easily reduced nickel. The results of studying the conversion of natural gasoline over the Ni/MOR/SZ catalyst at 150-200°C are presented in table 2.
Table 2 — Effect of the temperature and duration of experiment on the catalytic conversion of natural gasoline over the Ni/MOR/SZ, uH2 = 30 ml/min
Temperature, °C Time, min Composition of reaction product, % (mass)
C4- iso-C5 n-C5 iso-C6 n-C6 C7+
5,5 25,2 19,2 18 8,4 23,7
150 30 2,8 32 21 25,4 4,5 2,5
60 2,6 32,1 22 25,0 4,5 2,2
180 30 1,9 32 20 28,8 3,3 1,50
60 1,8 39 21 22,7 3,1 2,5
200 30 1,4 41 21 20,5 3,2 2,6
60 0,1 24 38,4 22,1 3,3 2,5
Table 3 — Effect of the duration of experiment on the composition of the natural gasoline conversion products, Ni/MOR/SZ, T = 180°C; um = 80 ml / min
Time, min Composition of reaction product, % (mass)
C- iso-C5 n-C5 iso-C6 n-C6 iso-C7 C7+
5,5 25,2 19,2 18 8,4 5,4 18,3
30 1,9 35 20,1 25,5 3,5 1,6 12,4
60 1,7 38,5 20,8 24,5 3,3 1,7 12,1
90 1,7 37,0 20,7 24,0 3,2 1,1 12,0
120 1,8 37,0 21,0 21,6 3,3 1,2 12,1
As can be seen in table 2 all components of the natural gasoline experience quantitative changes. The content of iso-C5, n-C5 and iso-C6 components increases, while the content of other components decreases. It should also be especially noted the decrease in the concentration of C4, C6 and C7+ hydrocarbons. Changes in the distribution of hydrocarbons before and after contact with the catalyst depend on temperature and process.
Increasing the temperature up to 200°C has a more significant effect on the composition of the reaction products. In the first 30 minute of the experiment the conversion products of natural gasoline are enriched in the iso-C5 component but with
the duration of the experiment its content sharply declines. This change is not related to catalyst deactivation. The amount of returned C7+ in the reaction product during this period of time decreases and the sum of hydrocarbons iso-C5, n-C5 and iso-C6 rise.
The effect of increasing the ratio of hydrogen to natural gasoline on the stability of the process has been shown in table 3. From the comparison of table 2 and 3 can be seen that an increase in the linear rate of hydrogen supply by 2.6 times does not affect the conversion of the heptane component of natural gasoline, but stabilizes the yield of iso-C5 iso-C6 hydrocarbons.
In general the presented results show that unlike massive SZ catalysts [4, 5], the Ni/MOR/SZ composite sample is able to involve in the process the heptane component of straight-run gasoline and thereby significantly increase the resources of higher octane iso-C5, n-C5 and iso -C6 components in one pass of natural gasoline over the catalyst.
Tables present that contact of natural gasoline with composite catalyst, which comprises of the properties of anion-modified zirconium and H-zeolite leads to significant changes in the distribution of hydrocarbons. Furthermore the most important changes are: a) consumption (conversion) of C7+; b) reduction of C4-alkanes; c) accumulation of C5-C6 alkanes including high-octane iso-pentane and dimethylbutanes.
Conclusions
The conversion of natural gasoline over the composite catalysts which components are H-zeolite and zirconium dioxide can open the new avenue for the production of high octane gasoline components. Moreover the conversion of a complex mixture of hydrocarbons over the composite catalyst enables to open a wide range of opportunities for transfer of straight-run gasoline from high-temperature dehydrocyclization to low-temperature isomerization.
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