Mineral oils: processes and products – Refining – Sulfur removal
Reexamination Certificate
2001-02-23
2003-05-27
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Refining
Sulfur removal
C208S213000, C208S21600R, C208S217000, C208S25100H, C208S25400R, C208S108000, C585S259000, C585S260000, C585S265000, C585S274000, C585S276000
Reexamination Certificate
active
06569318
ABSTRACT:
It is known that the catalysts for conversion of hydrocarbons and in particular for hydrotreatment of residues are deactivated by metal deposits, such as vanadium sulfide and nickel sulfide, and by coke deposits. It is also known that coke deposits are increased when the acidity of the catalyst increases.
The applicant discovered, surprisingly, that the use of catalysts of controlled acidity and/or the monitoring of the concatenation of the catalysts to use the most acidic catalyst second leads to quite better performance levels. The invention therefore relates to a process for hydrocarbon conversion, for example, hydrotreatment, and more particularly hydrodesulfurization of residues that were previously partially demetallized, consisting in moving a partially demetallized residue onto at least one catalyst of controlled acidity.
These catalysts are characterized in that their acidity is limited and/or that the ratio between their performance level in a hydrogenation reaction is to a large extent greater than their performance level in an acidity test reaction. In the case where two catalysts that have controlled, but different acidity are used in one or more reactors, it is recommended to concatenate them in the following way:
if a single one of the two catalysts contains cobalt, it is preferable to position the latter upstream from the second catalyst that does not contain cobalt,
if both or neither of the two contain cobalt, it is preferable to use as a second the more acidic catalyst or the catalyst with the smallest hydrogenation/acidity ratio.
The acidity and the performance level of hydrogenation are evaluated by a catalytic test of a mixture of model molecules: the hydrogenation of toluene and the isomerization of cyclohexane. According to this test that is described below and under these measuring conditions, the level of activity in isomerization of cyclohexane should be limited to 0.10 and/or the ratio of hydrogenating activity/isomerizing activity should be greater than 10.
The catalytic test that makes it possible to monitor the acidity of the catalysts is carried out according to the following operating procedure:
The catalysts are sulfurized in situ under dynamic conditions in the tubular traversed fixed-bed reactor of a catatest-type pilot unit (manufacturer Vinci Technologies), whereby the fluids circulate from top to bottom. The hydrogenating and isomerizing activities are measured immediately after the pressurized sulfurization without reexposure to air with the hydrocarbon feedstock that was used to sulfurize the catalysts.
The sulfurization and test feedstock consists of 5.8% dimethyl disulfide (DMDS), 20% toluene and 74.2% cyclohexane by weight. The stabilized catalytic activities of equal volumes of catalysts thus are measured in the hydrogenation reaction of the toluene. The follow-up to the isomerization of the cyclohexane, diluting toluene, makes it possible to estimate the acidity of the catalysts.
The conditions for measuring activity are as follows (taking into consideration total vaporization and the ideal gas law):
Total pressure:
6.0
MPa
Toluene pressure:
0.38
MPa
Cyclohexane pressure:
1.55
MPa
Hydrogen pressure:
3.64
MPa
H
2
S pressure:
0.22
MPa
Catalyst volume:
40
cc
Feedstock flow rate:
80
cc/h
Hourly volumetric flow rate:
2
l/l/h
−1
Hydrogen flow rate:
36
l/h
Sulfurization and test temperature
350° C. (3° C./min)
Sampling of the liquid effluent is analyzed by gas phase chromatography. The determination of molar concentrations in unconverted toluene (T) and concentrations of hydrogenation products: methyl cyclohexane (MCC6), ethyl cyclopentane (EtCC5) and dimethyl cyclopentane (DMCC5) make it possible to calculate a hydrogenation rate of toluene X
HYD
defined by:
X
HYD
(%)=100 * (
MCC
6
+EtCC
5
+DMCC
5)/(
T+MCC
6
+EtCC
5
+DMCC
5)
The cyclohexane isomerization rate X
ISO
is calculated in the same way from concentrations of unconverted cyclohexane and its reaction product, methyl cyclopentane. Whereby the hydrogenation reaction of toluene and isomerization of the cyclohexane are first order reaction under our test conditions, and the reactor acts like an ideal piston reactor, hydrogenating activity A
HYD
and isomerizing activity A
ISO
of the catalysts are calculated by applying the formula:
Ai
=ln(100/(100−
X
i
)).
The ratio of hydrogenating activity to isomerizing activity H/A is equal to A
HYD
/A
ISO
.
The hydrodesulfurization processes of this invention can be applied to, for example, petroleum fractions such as the crude petroleums of degree API that are less than 20, the extracts of asphaltic sands and oil shales, atmospheric residues, vacuum residues, asphalts, deasphalted oils, deasphalted vacuum residues, deasphalted crudes, heavy fuels, atmospheric distillates and vacuum distillates or else with hydrocarbons other than the carbon liquefiers.
The hydrorefining and hydroconversion reactions of these hydrocarbon feedstocks (hydrotreatments) can be carried out in a reactor that contains the catalyst that is arranged in a fixed bed. Another application of the invention is the use of these same catalysts in an effervescent bed, particularly within the framework of hydrotreatments.
In the fixed-bed or effervescent-bed processes, the hydrotreatments that are intended to eliminate the impurities such as sulfur, nitrogen, and metals and to lower the mean boiling point of these hydrocarbons are usually used at a temperature of about 320 to about 470° C., preferably about 350 to 450° C., under a partial hydrogen pressure of about 3 MPa (mega Pascal) to about 30 MPa, preferably 5 to 20 MPa, at a volumetric flow rate of about 0.1 to about 6 volumes of feedstock per volume of catalyst and per hour, preferably 0.2 to 2 volumes per volume of catalyst and per hour, whereby the ratio of gaseous hydrogen to liquid hydrocarbon feedstock is between 100 and 5000 normal cubic meters per cubic meter (Nm
3
/m
3
), preferably between 200 and 1500 (Nm
3
/m
3
).
The catalysts of this invention generally have the following composition:
at least one metal of group VIB: 5 and 40% by weight of oxide, preferably molybdenum or tungsten,
at least one metal of group VIII: 0.1 to 10% by weight of oxide, preferably iron, cobalt and nickel,
at least one porous oxide substrate such as aluminas or silica-aluminas. It is preferred to use substrates that contain alumina: 40 to 94.6% by weight of an oxide substrate relative to the total mass of the catalyst,
optionally at least one dopant that is selected from the group that consists of phosphorus, boron, silicon and halogens; 0 to 10% by weight overall of P
2
O
5
, SiO
2
, B
2
O
3
, and/or halogens.
The catalysts according to the invention can be prepared by any suitable methods, in particular by the methods that are described in French Patents No. 97/07149, 87/09 359, 96/15 622 or else 96/13 797. As an example and without limiting the scope, the first catalyst, which can be of NiCoMo type without a dopant, can be prepared by impregnation of an alumina by an aqueous solution that contains a molybdenum precursor, a cobalt precursor and a nickel precursor. The second catalyst, which can be of NiMoP type, can be prepared, as an example, by co-impregnation of an alumina by an aqueous solution that contains a molybdenum precursor, a nickel precursor and a phosphorus precursor.
The optional metals and dopants can be introduced at any moment of the preparation, in particular by impregnation on a substrate that is already formed or introduced during the synthesis of the substrate.
The catalysts that are described in this invention are shaped in the form of grains of different shapes and sizes. They are used in general in the form of cylindrical extrudates or multilobar extrudates, such as bilobar, trilobar, or multilobar extrudates of straight or twisted shape, but they can optionally be produced and used in the form of crushed powder, tablets, rings, balls, wheels. They have a specific surface area that is measured by nitrogen adsorption according to the BET method (Brunauer, Em
Guibard Isabelle
Harle Virginie
Kasztelan Slavik
Kressmann Stephane
Morel Frederic
Griffin Walter D.
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
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