Investigation of a system of protecting layer for the process of hydrorefining oily distillates of Uzbekistan's petroleum

Article abstract of DOI:10.1134/S1070427207070403

Complex investigation is conducted, directed to development of contacting materials (forcontacts) and catalysts for the protecting layer in the process of hydrorefining petroleum distillates taking into account their specificity and extensively attracting local raw materials. Forcontact FZS-7 is developed which, besides the function of uniform distribution of crude material over the reactor section, diminishes tarring and performs, owing to low nickel content, mild hydrogenation of unsaturated compounds. The proposed kaolin-bset catalyst of the protecting layer with low content of molybdenum oxide works reliably with the residual crude material with high content of iron and displays high enough demetallization activity.

Full text of DOI:10.1134/S1070427207070403

ISSN 1070-4280, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 7, pp. 1207–1212. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © M.P. Yunusov, T.B. Molodozhenyuk, M.M. Ergashev, Sh.B. Dzhalalova, G.A. Gashenko, B.M. Saidulaev 2007, published in
Khimicheskaya Promyshlennost, 2007, Vol. 84, No. 2, pp. 55–61.
TECHNOLOGY OF ORGANIC
AND INORGANIC SUBSTANCES
Investigation of a System of Protecting Layer for the Process
of Hydrorefining Oily Distillates of Uzbekistan’s Petroleum
a
a
a
a
M. P. Yunusov , T. B. Molodozhenyuk , M. M. Ergashev , Sh. B. Dzhalalova ,
a
b
G. A. Gashenko , and B. M. Saidulaev
a
Sultanov Uzbekistan Research Chemical Pharmaceutical Institute, Tashkent, Uzbekistan
b
Fergana’s Petroleum Processing Plant, Fergana, Uzbekistan
Received February 19, 2007
Abstract—Complex investigation is conducted, directed to development of contacting materials (forcontacts) and
catalysts for the protecting layer in the process of hydrorefining petroleum distillates taking into account their speci-
ficity and extensively attracting local raw materials. Forcontact FZS-7 is developed which, besides the function of
uniform distribution of crude material over the reactor section, diminishes tarring and performs, owing to low nickel
content, mild hydrogenation of unsaturated compounds. The proposed kaolin-bset catalyst of the protecting layer
with low content of molybdenum oxide works reliably with the residual crude material with high content of iron and
displays high enough demetallization activity.
DOI: 10.1134/S1070427207070403
Currently in Fergana’s oil refining plant (FORP) is
refined rather heavy hydrocarbon raw material from
various fields in Uzbekistan, which is characterized by
high content of paraffin, sulfur, and tarring compounds
mixed with gas condensate. The refining scheme is
defined by the local conditions: chemical composition
of the petroleum distillates, nomenclature of demand
by market petroleum products, and by technological
potential of the facility for refining petroleum frac-
tions.
Among the targeted processes in FORP a signifi-
cant is producing basic lubricating oils with certain set
of exploitation characteristics. The most problematic
are enhanced colorization, compatibility with addition
agents and low viscosity index. Correction of principal
parameters of basic oils is performed at hydrorefining
on G-24 installation where fractions of deparaffined
distillate and deasphalted residue are treated in sepa-
rate cycles. The tar-asphaltene substances colorizing
petroleum products are mostly removed at deasphalt-
ing, but due to their volatility they contaminate oil dis-
tillates where they are undiserable due to high corro-
sion activity and deactivating effect on alumocobalt-
molybdenum catalyst of hydrorefining. Design of the
currently opertaing installation does not allow regen-
eration of deactivated catalyst directly in the reactor,
therefore when reactor os sealed by deposits the proc-
ess shold be interrupted. From the reactor after cooling
are removed ceramic rings and upper, the most wasted
and damaged part of catalyst. Then fresh catalyst is
loaded and on it the ceramic rings cleaned from edges
and deposits are placed. Thus, the main mass of cata-
lyst is used for long time without regeneration, and raw
material often containing admixture of unsaturated
compounds feeds into the zone of relative high tem-
perature and active catalyst. Unsaturated compounds
initiates formation of sealing products which leads to
faster increase in pressure difference and poisoning of
hydrorefining catalyst. To improve quality of lubricat-
ing oil and the process parameters it is reasonable to
perform multilayer loading of catalytic pacjage with
additional forcontact and protecting catalyst layers.
Successful experimental-industrial testing of kao-
lin-phosphate forcontact (KPC) [1] in the reactor of
Diesel distillate hydrodesulfrization in Fergana petro-
leum plant allowed considering of its application as
front layer in treatment of heavier raw material. How-
ever, testing on a pilot-plant installation showed pro-
gressing grow of tarring components concentration in
oil distillate, in residual fraction in particular, after
contact with KPC under the process parameters analo-
gous to those at the oil hydorefining (Table 1).
1207

YUNUSOV et al.
1208
One probable reason for this observation is accel-
eration of polymerization reactions under the action of
strong Bronsted acid centers [2] at lower hydrogen
pressure compared to hydrodesulfurization of Diesel
fuel. Really, testing the catalytic properties of KPC
forcontact on a flow-type microinstallation in the tem-
perature range 523–573 K revealed its ability of accel-
erating steric isomerization reactions of α-olefins and
double bond migration into molecule followed by oli-
gomerization. Yield of the products of intermolecular
interaction of isomeric hexenes grows with tempera-
ture (Table 2), however, no surface coking was de-
tected in the studied samples. Therefore for lowering
the catalyst surface acidity excess to retard undesired
reactions of to enhance hydrogenating function the
KPC granules were impregnated with nickel com-
pounds followed by thermal treatment. Studying
showed that synthesis at lov pH values leads to dec-
trease in size of both large and small pores while im-
pregnation of KPC by neutral solution increases frac-
tion of pores 12-18 nm in diameter which leads to in-
crease in sorption activity of the sample toward the
largest test-molecules [3].Taking into account the
coarse-pored structure and low specific surface of
KPC, their impregnation conditions were taken to pro-
vide maximumm nickel concentration 1.3–1.5% inthe
granules surface layer at the total NiO content 0.4–
0.5% (sample FZS-7). IR spectrum of scrap from KPC
granule surface showed decrease in the fraction of acid
phosphites correlating with the change in acidity of the
acid centers from pK > 1.5 on the surface to pK < –3
on the internal slice of granule. Modification of the
forcontact with nickel compounds in neutral medium
leads to relative increase in activity toward backbone
isomerization of hex-1-ene and hydrogenation of form-
ing unsaturated compounds.
a
a
Use of nickel salt solution with lower pH at im-
pregnating KPC provides three-fold increase in con-
centration of surface acid centers with pK < –3 and
a
more homogenous distribution of nickel compounds in
the bulk granule (sample FZS-1). This leads to obvious
strengthening of polymerization function in a model
Table 1. Testing protecting layer contacts on a pilot-plant installation. Temperature 523 K, pressure 2 MPa, volume rate 2.0
−1
h , hydrogen to raw material ratio 100:1
Sample
Change in properties of oil fractions on various contacts
Color, CNT Viscosity,
Deposits on contacts, %
Viscosity Iodine number, Sulfur total, Ash resi-−
Cake
Tar
4
units
cSt at 40ºC
index
iodine grams
%
due, %10
per 100 g of oil
Oil distillate fraction III
2
.4
41.6
42.9
43.6
40.2
39.2
87.0
89.3
91.4
90.7
94.3
0.80
0.67
0.65
0.56
0.66
0.43
15
13
9
KPC
FZS-7
FZS-1
AKBM
3.7
2.2
5.2
2.0
0.82
5.8
2.6
1.2
0.8
2.0
1.8
0.48
0.74
12
7
11.2
4.2
0.35
Oil distillate fraction III
4
.5
61.0
62..3
53.6
93.5
96.3
104
0.35
0.91
0.78
0.73
23
17
12
FZS-7
3.8
2.3
0.19
0.03
Did not define
Did not define
AKBM
Residual fraction
0.56
7
.8
343.4
366.2
296.0
89.1
90.1
99.5
1.23
1.18
0.97
63
51
29
FZS-7
7.2
5.2
0.32
11.4
6.9
3.7
4.5
AKBM
0.13
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 7 2007

1
209
INVESTIGATION OF A SYSTEM OF PROTECTING LAYER FOR THE PROCESS
reaction and sharp fall in colorization of oil fractions at
hydrorefining due to intense tarring. On the contrary,
passing residual fraction through FZS-7 layer leads to
decolorizatiun of product by 1-2 TsNT (colorimetric
standard) units. Besides, occurs certain increase in hy-
drocarbon chain branching, probably owing to isomeri-
zation followed by hydrogenation of unsaturated com-
ponents, which leads in some increase in viscosity
(Table 1) and decreases freezing temperature by 1–
2ºC. Appearance of hydrogen sulfide in gas phase to-
gether with practical absence of C –C hydrocarbons
attests proceeding of hydrogenation of the less stable
sulfur compounds in oil fraction without C–C bond
cleavage. Investigation of KPC samples and modified
forcontact FZS-7 after their application to hydrorefin-
ing fraction III of oil distillate under the same condi-
1
5
Table 2. Comparative testing forcontact and catalyst activity in the model reaction of hex-1-ene conversion. Hydrogen
−1
pressure 0.001 MPa, volume rate 0.5–0.05 h
Sample
Vpore, cm3/g
T;K
Yield of reaction products, %
Isomerization
Hydrogena- Oligomeri-
steric
(
Rpore, nm)
Cracking
carcass
0.11
0.63
11.5
19.3
20.3
23.3
0.15
0.76
9.7
tion
0
zation
7.2
0
.14
5÷6; > 10 )
.21
7÷9; > 10 )
.18
6÷8; > 10 )
.31
2÷3; > 10 )
.58
2÷3; 6÷8 > 10 )
.68
4÷5; 7÷8 > 10 )
.68
4÷7; > 10 )
.65
523
573
0
0
56.8
57.4
60.2
37.2
46.6
49.7
55.7
58.0
62.2
11.5
19.0
20.6
55.8
52.3
48.5
44.3
45.9
47.9
20.2
20.3
32.0
15.8
17.3
21.1
KPC
FZS-7
FZS-1
AK
4
0
12.6
13.8
2.1
(
(
(
(
6
23
0.9
0
0
0
523
573
0.3
3.4
7.9
0
4
1.4
1.6
0
3.2
6
23
3.7
0
523
573
7.6
3
0.05
1.0
0
0.9
2.4
0
14.3
20.3
9.0
6
23
0
523
573
4.6
4
0.03
1.5
0
12.2
13.4
9.3
0
7.0
6
23
1.0
0.2
4.5
11.6
0.5
3.7
4.8
2.4
14.8
22.7
3.2
15.4
30.6
10.0
1.4
0
523
573
AB
4
1.0
1.2
3.4
6.8
8.9
0.37
1.4
1.9
1.2
1.5
3.3
14.8
27.1
13.4
23.4
22.3
10.9
13.5
17.3
17.2
19.2
19.9
2.8
(
(
6
23
4.5
0
523
573
1.5
AKB
AKM
AKBM
4
1.5
6
23
2.3
0
523
573
2.5
4
3.7
(
6
23
5.8
0
523
573
1.2
4
1.6
(
4÷8 > 10 )
6
23
2.8
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 7 2007

YUNUSOV et al.
1210
Fig. 1. Changes in metal content: 1 – in residual fraction, 2 – after hydropurification on FZS-7 forcontact, 3 – on AKBM
protecting layer catalyst
tion in a pilot-plant installation revealed decrease in
content of dry cake from 5.76% to 2.6 and of tar-
asphalt substances extractable with benzene-alcohol
mixture from 1.2% to 0.8%. On the FZS-1 forcontact
surface was detected 11.2% of insoluble carbon-
containing compounds. Comparison of decrease in
concentration of metals in starting material and in the
hydrogenizates (Fig. 1)with their distribution in “dry”
cake and in extracts of caked samples allows to con-
clude that the forconacts partially trap alkaline and
alkaline-earth metals, probably in the form of corre-
sponding naphthenates dissolving in hydrocarbons. By
the method of electron-sounding analysis we registered
presence of sodium, potassium and calcium, mainly in
ashed residues of oil fractions and in extracts of used
up forcontact and catalyst of protecting layer (below).
Concentration of typical catalyst poisons in the resid-
ual fraction, the vanadium, nickel and iron organic
metallocomplexes, remains practically unchanged after
passing oil through FZS-7 layer at hydrorefining,
which attest low demetalliation function of this forcon-
tact.
strong Si–O–Al bonds are formed between SiO frag-
4
ments of kaolinit and AlO octahedrons of aluminum
6
hydroxide. Optimal combination of strength and po-
rous characteristics was achieved, in our opinion, with
alumokaolin carrier modified with boric acid (Table 2).
The process of applying active metal from aqueous
solution is significantly affected by state of hydroxyl
shell of carrier, because change in solution pH is de-
fined by dissociation of water molecules at the action
of field strength of dominating aprotic adsorption cen-
ters. Study of acid-base properties of the smples dehy-
droxylated at 823 K showed that introducing kaolin to
psevdobemit composition in strong acid medium en-
hances concentration of coordination-unsaturated alu-
minum ions on the surface of the calcined carrier, but
on the other hand this promotes formation of Bronsted
acid centers typical for alumosilicates [1]. Thus, the
dehydroxylated alumokaolin carrier (AK) surface ears
simultaneously fixed not mutually interacting strong
aprotic and protic acid centers (pK ≤ –5) and weak
a
aprotic basic centers. On immersing the AK sample
into water occurs emphasized alkalization of the me-
dium (pH from 5.9 to 6.8) rather than at the hydration
of aluminum γ-oxide prepared by pseudobemit calcina-
tion at 873–923 K [4], that is, the ratio of primary
(acid) and secondary (basic) Lewis centers is shifted in
To avoid deactivation of cobaltmolybdenum cata-
lyst in the process of work up heavy fractions, we pre-
pared and studied a series of molybdenum-containing
catalysts of protecting layer on the ground of clay min-
erals of Uzbekistan origin with by-products of local
plants for their transformations. When carrier is pre-
pared from bsevdobemit with 25% of kaolin, new very
favor of the latter and surface pK grows to 8.2. This is
a
stipulated by formation of additional basic centers at
the thermal decomposition of doped alkaline-earth
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 7 2007

1
211
INVESTIGATION OF A SYSTEM OF PROTECTING LAYER FOR THE PROCESS
metal hydrocomplexes which in the process of plasti-
cizing of the kaolin – bseudobemit mixture with nitric
acid are washing out from kaolinit interpackage space,
and further at thermal treating they are passed to the
granule surface through capillary canals. De to irregu-
lar distribution of different type OH groups on the alu-
mokaolin carrier surface, before formation of required
monolayer, an “island” polymolybdate film is formed
which contains up to 20% of water soluble molybde-
num in the catalyst composition (AKM). The high con-
ment. Applying of molybdenum oxide does not change
spectrum of distribution by strength of acid centers on
the AKB carrier, but increases concentration of Bron-
sted acid centers on the catalyst surface (AKBM).
Extraction treatment of the prepared catalyst
showed absence of molybdenum water-soluble forms,
although the fraction of active molybdenum extracted
by ammonia is high enough. IR spectrum of AKBM in
KBr pellet registered with reference KBr containing
equivalent amount of AKB for compensation of the
6
+
−1
tent of water soluble mixed structures Mo Td–O–
carrier bands contain bands near 920 cm , which in
6+
Mo
manifests itself as a bend at 33.3 kcm−1 in
conjunction with the data of electron diffuse reflec-
tance spectroscopy evidences that molybdenum ions
are in tetrahedral coordination and its significant part is
in the composition of associates Mo –O–Mo , which
Oh
electronic diffuse reflectance spectrum, attesting weak
enough interaction of active component with the car-
rier.
For strengthening granules and admitting proton-
donor property to surface of hydrorefining catalyst for
facilitating desorption of hydrogenolysis reaction prod-
ucts, to the catalyst compositionis introduced boric
acid. Modifying aluminum oxide with boric acid in the
absence of kaolin leads to formation of carrier (AB)
with high concentration of Bronsted acid centers (–8 <
Td
Td
−
1
are characterized by inflection point at 33.7 kcm .
Clear absorption band in the region of 40.0–43.3 kcm
−
1
is assigned to formation of amorphous alumomolyb-
denborates revealing high catalytic activity in the proc-
ess of hydrocracking of heavy petroleum [5].
Express testing of catalytic properties of the cata-
lyst on a microcatalytic installation of flow type, on the
samples not containing molybdenum in the tempera-
ture range 473 – 673 K predominantly occurs reactions
of stereoisomerization and double bond shift into the
chain of normal acyclic α-olefin. Increase in concen-
tration of acid centers pKa –5.6 leads to increase in the
rate of formation of branced olefins due to backbone
isomerization, but concentration of products of their
hydrogenation decreases.
Hydrogenation of cyclohexene is accompanied
with backbone isomerization with formation of me-
thylcyclopentane and methylcyclopentenes. The same
reaction products: cyclohexane, methylcyclopentane
and various methylcyclopentene were formed bof in
hydrohenation reaction and due to hydrogen redistribu-
tion in the experiments with inert gas. Although in the
second case the products of backbone isomerization
were formed in much less amount, their enhanced con-
centration on the samples with maximum acidity evi-
dences unequivocally the principal role of strong acid
centers in this process. We found that hydrogenating
function of the catalysts correlates with concentration
of water insoluble molybdenum, the maximal activity
showed the catalyst on the carrier with the predominat-
ing strength of acid centers in the range –4.5 < pKa < –
1.5. On the carries with stronger acidity (pKa below –
5) the hydrogenation reaction are less successful and in
the hydrogenizate increases fraction of undesired prod-
ucts of oligomerization.
pK < –4) on its dehydroxylated surface. In the first
a
moment its hydration proceeds presumably by basic
type affording H+ ions to the surrounding medium and
decreasing pH value from 5.9 to 5.6. Then pH grows to
6
.0, which points to the presence of two hydroxyl cen-
ters of two sorts capable of ion exchange, as well as
Lewis acid centers capable of binding active compo-
nent by sorption. Acidification of the medium due to
ion exchange between surface groups of AB carrier
and ammonium para-molybdate water solution shifts
equilibrium to the side of formation in solution of po-
lymolybdate structures, while fraction of water-soluble
oxidomolybdene clusters in the final sample achieves
1
5%.
Modified alumokaolin carrier with optimal B O
2
3
concentration (AKB) the surface alumoborates formed
after calcination at 773 K cover ¼ of monolayer. In
couple with alumosilicate structures they provide for-
mation of bronsted acid centers in the pK range from
a
–
4 to –1.5, regularly distributed on the carrier surface.
At the contact of AKB with water the medium pH be-
gins to change from 5.9 to 5.6, then becomes constant
on 6.3 level, while pH of the carrier surface after hy-
dration becomes equal to 7.2. Intoduction to this sys-
tem of ammonium para-molybdate ammonia solution
results in ion exchange reactions with surface struc-
tures and formation of Mo–O–Al, Mo–O–Si and Al–
O–B–O–Mo bonds fied on the surface at thermal treat-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 7 2007

YUNUSOV et al.
1212
We performed continuously testing of optimal for-
AK – Alumocaolin carrier,
contact samples FZS-7 and of protecting layer catalyst
AKBM on a pilot-plant installation of high pressure
hydrorefining fractions III and resifual fraction af oil
distillates. The forcontact FZS-7 improves characteris-
tics on color and iodine number of oil fraction before
their passing on the catalyst of hydrorefining. Depend-
ing on the process parameter, on the protecting layer
catalyst AKBM stable decreases colorization and sul-
fur content, increases viscosity index at minimal de-
crease in viscosity, and effectively trapped iron and
other metal ions.
AKB – Alumocaolinborate carrier,
AKBM – Molibdenum-containing catalyst on the alu-
mocaolinborate carrier.
REFERENCES
1. Yunusov, M.P., Molodozhenyuk, T.B., and Dzhalalo-
va, Sh.B. Chim. Promyshl., 2005, vol. 82, no. 3,
p. 121.
2
.
Sklyar, V.T., Lebedev, E.V., Zakupra, V.A. Vyshie
olefiny (High olefins), Kiev, Tekhnika, 1964.
3
.
Yunusov, M.P., Molodozhenyuk, T.B., Dzhalalo-
va, Sh.B., Ergashev, M.M., Gashenko, and Saidula-
ev, B.M. International Scientific and Technological
Conference “High technologies, education, perspec-
tives of integration of science and industry”, Tashkent,
Conference proceedings, 2006, p. 112.
ABBREVIATIONS
FORP – Fergana oil refining plant,
G-24 – Installation for hydrorefining oil distillates,
KPC – Caolin-phosphate forcontact,
FZS-1 – Caolin-phosphate forcontact modified with
nickel ions in acid medium,
FZS-7 – Caolin-phosphate forcontact modified with
nickel ions in neutral medium,
4
5
.
.
Nechiporenko, A.P., Vlasov, E.A., and Kudryashov,
A.N. Zh. Prikl. Khim., 1986, vol. 59, no. 3, p. 689.
Rasikov, K.Kh., Vorobiev, V.N., and Abidova, M.F.
On the role op transition metal ion surface species in
oil hydrocrecking. The 6 th Japan-Soviet Catalysis
Seminar Catalysis for Coping with Oil Shortage, 1981,
Osaka, Japan, p. 139.
AB – Alumoborate carrier,
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 7 2007