Note: Descriptions are shown in the official language in which they were submitted.
~ACXGROUND OF THE INVEN~ION
The hydrode~ulfurization of petroleum distillate hydro-
c~rbons employing a ca~aly~ cpmprising a supported hydrogena~ing
aomponent which is at least one member of,the group con6isting of
Group VI-B and Group VlII metals in a fo~m capable of promoting
hydro~enating reactions is well-known in the art. Especial~y
e'ffective catalysts for the purpose of such hydrodesulfurization
reaction~ are those comprising molybdenum and two members of the
iron group metals. Preferred cat,alysts of thi~ class are those
containing nickel, cobalt and molyb,denum but other combinations
of iron group metals and molybdenum such as iron-molybdenum-cobalt,
nickel-molybdenum-iron, as well as combinations of ~ickel and
molybdenum, cobalt and molybdenum, nickel and tungsten or ,other
Group VI-B or Group VIII metal~ taken singly or in combination are
sui~able, Th~ hydrogenating or desulfurizing components of such
oataly~t are employed in the sulfided or unsulfided form with the
~ulfided form being preferred.
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~ ~ogg658
Although the desulfuri~ation processes of the prior art
employing the above-identified catalyst compositions have been
useful in the substantial desulfurization of petroleum distillates,
improved desulfurization activity is required to satisfy anti-
pollution standards being urged upon manufacturers of petroleum
products. Therefore, it is desired that an improved petroleum
distillate desulfurization process be provided as measured by the
improved activity of the hydrodesulfurization catalyst.
SUMMARY OF THE INVENTION
An improved petroleum distillate catalytic desulfurization
process is obtained by employing a catalyst composition comprising a
Group VI-B hydrogenating component and at least one iron group
hydrogenating component on alumina, the hydrogenating components
; being in the sulfided form, and wherein from 5 to 20 volume percent
of the catalyst pores have a radius in the range of 100 to 300 A.
DESCRIPTION OF THE INVENTION
The invention is applicable to the desulfurization of
petroleum distillates. As employed in the description of this
invention, the term "petroleum distillates" refers to those petroleum
crude oil fractions having an initial boiling point above 300F.
(148.9C.) at atmospheric pressure and containing less than 2.0
weight percent asphaltenes. Petroleum distillates obtained by con-
ventional fractionation, extraction, and/or catalytic and thermal
processes from crude oils normally will contain in excess of 0.7
weight percent sulfur with sulfur concentrations as high as 6.0
weight percent being conventional. The process of this invention
is directed to the desulfurization of these sulfur-containing
petroleum distillates.
:10996S8
The catalyst employed in the desulfurization of the
sulfur-containing petroleum distillates comprises a Group VI-B
hydrogenating metal and at least one iron group hydrogenating
metal on alumina, the hydrogenating metals being in the sulfided
form. The total concentration of the hydrogenating metals is in
the range of 8 - 25 weight percent of the catalyst composite. The
weight ratio of the sum of the iron group metals to the Group VI-s
metal is in the range of 0.2 - 0.5, preferably 0.25 - 0.40. When
nickel and cobalt are utilized, the weight ratio of nickel to cobalt
is in the range of 0.1 - 2.S, preferably 0.2 - 2Ø
In addition to alumina, the carrier or support can contain
a minor contaminating proportion (less than a total of 5.0 weight
percent) of one or more refractory metal oxides, other than alumina,
~uch a~, ~ilica, thoria, boria, titania, magnesia, zirconia, etc.
The pore volume of the catalyst is in the range of 0.3
to 0.7 cc per gram and the surface area of the catalyst composite
should be in the range of 150 to 350 square meters per gram,
preferably 175 to 300 square meters per gram. The pore radius of
the catalyst composite, as employed in this application, is
determined by multiplying the pore volume by 2 x 104 and dividing
the result by the suxface area. The pore volume distribution is
determined by nitrogen adsorption using the method described by
E. V. Ballou, O. K. Kollen, in Analytical Chemistry, Volume 32,
page 532, 1960.
:~,alss6ss
In addition to the above characteristics, the catalyst
compc)sites of this invention have a pore voiume distribution such
that from 5 to 20 volume percent of the pores have a radius in the
range from 100 to 300 A. Preferably, the percent of the pores
having a radius in the range of 100 to 300 A is in the range of
S to 15 volume percent.
The catalyst composites of this invention can be prepared
by methods known in the art. Typically, the alumina support having
the required pore volume distribution, is dried and calcined at a
temperature in the range from 800 to 1,600F. (426.7 to 853.4C.)
in an oxygen-containing atmosphere, such as air, for a period
ranging from 1 to 24 hours.
In preparation of a nickel-cobalt-molybdenum-on-alumina
catalygt composite, for example, extruded calcined alumina pellets
can be impregnated with an ammonium monomolybdate solution so as to
obtain a catalyst composite containing from 5.0 to 15.0 weight
percent of the molybdenum. The impregnated alumina can then be
dried at, for example, a temperature of 250F. (121C.) for 24 hours.
The alumina support impregnated with molybdenum can
thereafter be contacted with an aqueous solution of nickel nitrate
and cobalt nitrate to provide a catalyst composite containing the
desired concentrations of molybdenum, nickel,-and cobalt. The wet
catalyst composite can then be dried in a second drying stage,
followed by calcining under conditions previously described.
i(3996S~
The catalyst composition can then be subjected to a
presulfiding step for conversion of the hydrogenation metals to
the sulfided form. This procedure can comprise treating the
calcined catalyst composite with hydrogen sulfide or preferably
a mixture of hydrogen and hydrogen sulfide at a temperature
normally in the range from about 300 to 750F. (149 to 399C.)
or more and at a pressure ranging from atmospheric to 3,000 psig
(211 kg/cm2). When employing a mixture of hydrogen and a hydrogen
sulfide as a presulfiding gaseous mixture, the concentration of
hydrogen sulfide will normally range from about 5 to about 20
percent by volume.
Other methods can be employed to presulfide the catalyst
composite. For example, the catalyst composition can be contacted
with a mercaptan or carbon disulfide contained in an inert solvent
or contained in the petroleum distillate feed to the hydrodesulfur-
ization process. Normally, the concentration of the mercaptan or
carbon disulfide in the solvent or feed will be in the range of
0.001 to 3.0 weight percent.
It is also within the scope of this invention to convert
the hydrogenation metals to the sulfided form by employing the
sulfur contained in the petroleum distillate feed. A suitable
method is described in U. S. Letters Patent 3,948,763, w~s~-~s
.~-inaorporatod he~ein by ro~enGo thoroto. As descri~ed in the
subject patent, the catalyst composite is sulfided with the sulfur-
containing petroleum distillate at a temperature in excess of 660F.
(349C.) and thereafter the desulfurization process is conducted at
a temperature less than 650F. (343C.).
109965~
The desulfurization reactions are effected by contacting
the defined catalyst with the petroleum distillate feed in the
pre~ence of uncombined hydrogen pressures in the range of about
200 to 4,000 psig ~14 to 280 kg/cm ). Hydrogen gas is circulated
through the reactor at a rate between about 400 to 12 ! 000 standard
cubic feet (scf) per barrel of feed (7.12 to 213.6 SCM/100 L).
The hydrogen purity of the circulating gas can vary from about 60
to 100 volume percent.
The hydrodesulfurization reaction can be conducted in the
liquid or vapor phase and at a liquid hourly space velocity in the
range of 0.25 to 10. Total reaction zone pressures in the range of
200 to 4,000 psig (14 to 280 kg/cm2), preferabl~ in the range of
300 to 1,000 p~ig (21 to 70 kg/cm2) are maintained in the desulfur-
lzation zone. The hydrodesulfurization reactions effected pursuant
to the process of this invention are conducted at a temperature that
is maintained, after the relevantly rapid elevation of temperature
upon start-up, in the range of about 550 to 800F. (287.8 to
426.7C.).
The following examples are presented to demonstrate the
objects and advantages of the invention. It is not intended,
however, to limit the invention to the specific embodiment presented
therein.
~(~99658
EXAMPLE I
In this Example, the criticality of employing a catalyst
composite having from 5 to 20 percent of the volume of pores with
a radius in the range of 100 to 300 A is demonstrated for catalyst
composites comprising 1.0 weight percent nickel, 3.0 weight percent
cobalt, and 12.0 weight percent molybdenum on alumina. 23.4 percent
of the volume of pores of Catalyst A had a radius in the range of
100 to 300 A, 18.7 volume percent of the pores of Catalyst B had a
radius in the range of 100 to 300 A, and 9.6 volume percent of the
pores of Catalyst C had a radius in the ran~e of 100 to 300 A. The
surface area, average pore radius, pore volume and pore size distribu-
tion for each of the named catalysts are presented below in Table I:
TABLE I
Catalyst A Catalyst B Catalyst C
Surface Area: m2/g204.6 182.5 246.2
Pore Volume: cc/g0.46 0.39 0.46
Avg. Pore Radius ~2V/A): A 45.1 42.7 37.3
Pore Size Distribution:
% of Pore Volume
250-300 A Radius 0.8 0.7 0.6
- 200-250 1.6 1.4 1.1
: 150-200 2.6 2.8 1.8
100-150 18.4 13.8 6.1
90-100 6.7 5.2 2.6
80- 90 8.4 6.9 4.2
70- 80 8.5 8.0 7.8
60- 70 8.9 9.3 10.1
50- 60 8.5 9.5 11.3
45- 50 4.9 5.6 .6.9
40- 45 4.6 6.3 7.3
35- 40 5.1 5.6 7.5
30- 35 4.2 6.0 7.6
25- 30 5.5 6.7 8.5
20- 25 5.7 5.7 8.1
15- 20 5.7 6.6 8.2
10- 15 0.1 0.0 0.4
7- 10 0.0 0.0 0-0
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lW9658
Each of the catalysts was separately employed in the hydro-
desulfurization of a Kuwait vacuum gas oil which was characterized
as follows:
Gravity: API 24.1
Sulfur: wt. % 2.60
Nitrogen: wt. ~ 0.069
Aniline Pt.: F. (C) 174 (79.1)
ASTM Distillation: ASTM D 1160
Method, F. (C)
5~ 637 (336~
682 (361)
750 (399)
810 (432)
887 (475)
go 961 (516)
EP 1,011 (544)
The hydrodeaulfurization conditions employed in each of the runs
comprised a hydrogen partial pressure of 650 pounds per square inch
(45.50 kg/cm ), a liquid hourly space velocity of 2.0 and a
desulfurization temperature of 720F. (382.2C.). The relative
desulfurization activity of each of the aatalysts was determined by
the following relationship:
k = L (l/S - l/So)
where:
k = second order desulfurization rate constant
for the catalyst.
L = liquid hourly space velocity
S = sulfur in the product, weight percent
SO = sulfur in the feed, weight percent
Employing the above relationship, it was determined that for each
run conducted for a period of at least 18 hours and at most 36 hours
the rate constant (k) was 1.5, 1.7, and 2.2, respectively. Therefore,
by reducing the percent volume of pores having a radius in the range
of 100 to 300 A to below 20 the activity of Catalyst B was 13 percent
higher and by reducing the volume of pores to the preferred range
(5 to 15 percent) the activity of Catalyst C was improved by 46
percent when compared to the activity of Catalyst A.
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~(~99~$8
EXAMPLE II
In this Example, the criticality of employing a catalyst
composite having from 5 to 20 percent of the volume of pores with
a radius in the range of 100 to 300 A is demonstrated for catalyst
composites comprising 2.5 weight percent nickel, 1.25 weight percent
cobalt, and 11.0 weight percent molybdenum on alumina. 25.0 percent
of the volume of pores of Catalyst D had a radius in the range of
100 to 300 A and 9.3 volume percent of the pores of Catalyst E had
a radius in the range of 100 to 300 A. The surface area, average
pore radius, pore volume and pore size distribution for each of the
named catalysts are presented below in Table II.
TABLE II
Cataly8t D Catalyst E
Surface Area: m2/g214.4 286.8
Pore Volume: cc/g 0.51 0.44
Avg. Pore Radius (2V/A): A 47.4 30.7
Pore Size Distribution:
% of Pore Volume
250-300 A Radius 0.8 0.9
200-250 1.7 1.4
150-200 4.6 2.3
100-lS0 19.1 4.7
90-100 6.5 1.5
80- 90 8.5 2.3
70- 80 8.9 2.9
60- 70 8.7 4.7
50- 60 8.5 6.3
45- 50 4.7 4.6
40- 45 4.5 S.9
35- 40 4.6 8.0
30- 35 4.2 9.5
25- 30 4.5 13.8
20- 25 4.8 15.2
15- 20 5.4 14.3
10- 15 0.0 1.7
7- 10 -
_ g _
~(999658
Each of Catalysts D and E was separately employed in the
hydrodesulfurization of the Kuwait vacuum gas oil of Example I
employing the hydrodesulfurization conditions in each of the runs
set forth in Example I. Utilizing the method for determining
desulfurization activity of the catalysts described in Example I,
the rate constant for the run utilizing Catalyst D was 1.1 and the
rate constant for the run employing Catalyst E was 1.4. Therefore,
by reducing the percent volume of pores having a radius in the range
of 100 to 300 A to below 20 the activity of Catalyst E was 27
percent greater than the activity of Catalyst D.
Although the invention has been described with reference
to specific embodiments, references, and details, various modifica-
tions and changes will be apparent to one skilled in the art and
are contemplated to be embraced in this invention.
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