CA1088016A

CA1088016A - Process for the desulphurization of hydrocarbon oils

Info

Publication number: CA1088016A
Application number: CA239,854A
Authority: CA
Inventors: Jakob Van Klinken; Karel M. A. Pronk
Original assignee: Shell Canada Ltd
Current assignee: Shell Canada Ltd
Priority date: 1975-02-21
Filing date: 1975-11-18
Publication date: 1980-10-21
Also published as: ZA757935B; SE403490B; FR2301588B1; AU8777875A; NL188659B; AU497062B2; NL7502071A; DE2557913C2; IT1051698B; JPS5197603A; BE836991A; DE2557913A1; NL188659C; FR2301588A1; JPS613836B2; SE7514534L; GB1525508A

Abstract

A B S T R A C T
A process for the catalytic hydrodesulphurization of heavy hydrocarbon oils, in which process a heavy hydrocarbon oil consisting at least partly of a deasphalted oil is contacted at elevated temperature, a hydrogen partial pressure below 90 bar and in the presence of a quantity of water corresponding with a water vapour partial pressure during the process of 0.1-10 bar, with a catalyst which contains nickel and/or cobalt and in addition molybdenum and/or tungsten supported on a carrier.

Description

108~ 6

- 2 -The invention relates to a process for the catalytic hydrodesulphurization of heavy hydrocarbons.
Heavy hydrocarbon oils such as residues obtained in the distillation of crude petroleum oils at atmospheric pressure (known as long residues) generally contain a considerablequantity of sulphur compounds. In order to reduce the sulphur content of the heavy oils they may be subjected to a catalytic hydrodesulphurization treatment. This treatment is carried out by contacting the heavy oil, together with hydrogen, at elevated temperature and pressure with a desulphurization catalyst. Suitable catalysts for this purpose are those which contain nickel and/or cobalt and in addition molybdenum and/or tungsten supported on a carrier. One drawback to this direct desulphurization route is that a fairly rapid deactivation of the catalyst generally occurs. This catalyst deactivation is caused because the above-mentioned heavy hydrocarbon oils generally contain a considerable quantity of asphaltenes and metal compounds such as nickel and vanadium compounds, a considerable proportion of which metal compounds are present bound to the asphaltenes in the oil. These compounds are deposited on the catalyst during the desulphurization process, as result of which the catalyst deactivates rapidly. It has been found that the catalyst deactivation which occurs in the hydrodesulphurization of heavy hydrocarbon oils by the direct route can be partly 1~8~1)1~i compensated by carrying out the process in the presence of a quantity of water corresponding with a water vapour partial pressure in the process of 0.5-30 bar. It has further been found that the favourable effect of steam on the catalyst activity in the hydrodesulphurization of the present heavy oils occurs both if the process is carried out at high pressure (PH ~ 90 bar) and if the process takes place at low pressure (PH < 90 bar).
In order to avoid the above-mentioned catalyst deactivation caused by the deposition of asphaltenes and metal compounds, the heavy oil can be deasphalted before being subjected to the catalytic hydrodesulphuriz-ation treatment. This indirect desulphurization route, which is applied in practice inter alia for the desulphurization of long residues, is effected by first separating the long residue by distillation at reduced pressure into a distillate fraction and a residual fraction, subsequently deasphalting the residual fraction and mixing the deasphalted oil with the distillate fraction, and finally desulphurizing the resultant mixture. If desired, for example when the heavy oil contains too few light components, the distillation at reduced pressure may be omitted and the deasphalting treatment may be directly applied to the heavy oil to be d~ulphurized. Just as in the direct desulphurization route, catalysts which contain nickel and/or cobalt and in addition molybdenum and/or tungsten supported on a carrier have also been found very suitable for application in the indirect desulphurization route.
It has now been found that for the desulphurization at hydrogen partial pressures below 90 bar of heavy hydrocarbon oils which consist at least partly of deasphalted oils, the activity of catalysts which contain nickel and/or cobalt and in an addition molybdenum and/or tungsten supported on a carrier can be considerably increased by carrying out the process in the presence of a quantity of water corresponding with a water vapour partial pressure in the process of 0.1-10 bar.
This discovery may be regarded as surprising for two reasons.
In the first place it has been determined that the presence bf steam in the hydrodesulphurization of hydrocarbon oil distillates with the application of the present catalysts has no effect at all on their activity. This is the case both if the process is carried out at high pressure (PH ~ 90 bar) and if the process takes place at low pressure (PH ~ 90 bar). In the second place, it has been determined that the favourable effect of steam in the hydrodesulphurization of heavy oils consisting at least partly of deasphalted oils with the application of the present catalysts does not ; occur if the process is carried out at high pressure.
The present invention therefore relates to a process for the catalytic hydrodesulphurization of heavy hydrocarbon oils, in which process a heavy hydrocarbon oil consisting of a mixture of a distillate obtained in the distillation at reduced pressure of a long residue with a deasphalted short residue is contacted at elevated temperature, a hydrogen partial pressure below 90 bar and in the presence of a quantity of water corres-ponding with a water vapour partial pressure during the process of 0.1-10 bar, with a catalyst which contains nickel, cobalt or a mixture thereof and in addition molybdenum, tungsten or a mixture thereof supported on a carrier.
In the process according to the invention the feed used must be a heavy hydrocarbon oil consisting at least partly of deasphalted oil, for ~ - 4 --80~6 example a deasphalted distillation residue of a crude oil. This distillation residue may have been obtained both from distillation at atmospheric pressure (long residue) and from distillation at reduced pressure (short residue). Although in the process according to the invention it is in principle possible to start from a feed consisting entirely of a deasphalted oil, for example a deasphalted long or short residue, the feed chosen is preferably a mixture of a distillate obtained in the distillation at reduced pressure of a long residue and a deasphalted short residue. A very suitable feed for the process according to the invention can be prepared by separating a long residue by distillation at reduced pressure into a distillate and a short residue, deasphalting the short residue and mixing the distillate with the deasphalted oil, preferably in production ratio. If in the process according to the invention use is made of a distillate obtained from the distillation at reduced pressure lt!~38~6 of a long residue as one of the components making up the feed, a flashed distillate of a long residue is preferably chosen for this purpose. ~ r In the process according to the invention the feed should consist at least partly of a deaaphalted oil. Deasphalting of the oil is preferably carried out at elevated temperature and pressure and in the presence of an excess of a lower hydrocarbon as solvent, such as propane, butane or pentane or a mixture thereof.
According to the invention the hydrodesulphurization is carried out in the presence of a quantity of water corresponding with a water vapour partial pressure during the process of 0.1-10 bar. The quantity of water used should preferably correspond with a water vapour partial pressure during the process of 0.5-7.5 bar.
The requisite quantity of water can be added to the gas and/or liquid stream which is passed over the catalyst.
The water may be added as such, for example to the heavy oil to be desulphurized, or steam can be added to the hydrogen stream which is supplied to the process. If desired, instead of water, a compound can be added, such as a lower alcohol, from which water is formed under the prevailing reaction conditions.
The catalysts which are suitable to be used in the process according to the invention contain nickel and/or cobalt and in addition molybdenum and/or tungsten supported on a carrier. Preferably, catalysts are used which contain 0.5-20 parts by weight and in particular 1~8~

0.5-10 parts by weight of nickel and/or cobalt and 2.5-60 parts by weight and in particular 25-30 parts by weight of molybdenum and/or tungsten per 100 parts by weight of carrier. The atomic ratio between the nickel and/or cobalt on the one hand and the molybdenum and/or tungsten on the other may vary within wide limits, but is preferably between 0.1 and 5. Examples of very suitable metal combinations for the present catalysts are nickel/tungsten, nickel/molybdenum, cobalt/molybdenum and nickel/cobalt/molybdenwn.
The metals may be present on the carrier in metallic form or in the form of their oxides or sulphides. It is preferred to use the catalysts in the form of their sulphides. Very suitable carriers for the present catalysts are oxides of elements from Groups II, III and IV of the Periodic System, such as silica, alumina, magnesia and zirconia, or mixtures of the said oxides such as silica-alumina, silica-magnesia, alumina-magnesia and silica-zirconia. It is preferred to use aluminas and silica-aluminas as carrier for the present catalysts.
The preparation of the present catalysts is preferably carried out by single-stage or multi-stage coimpregnation of a carrier with an aqueous solution which contains one or more nickel and/or cobalt compounds and one or more molybdenum and/or tungsten compounds, followed by drying and calcining of the composition. During drying of the compositions, which is generally carried out at temperatures between 100 and 150C, physically 10880~;

bound water is removed from the compositions; during the calcining of the compositions, which is generally effected by heating the compositions to a final temperature between 450 and 550C and maintanining the compositions for some time at this final temperature, decomposition of the metal salts with formation of the corresponding metal oxides takes place. As nickel and cobalt compounds, frequent use is made of the nitrates in preparing the present catalysts. As molybdenum and tungsten compounds, ammonium molybdate and tungstate are generally used.
It has been found that during the calcining of the present compositions, considerable heat effects ;
may occur which can adversely affect the activity of the ultimate catalysts. In order to prepare catalysts having a high activity it is therefore important to minimize these heat effects during the calcining. One of the causes of strong heat effects during the calcining is the combined decomposition of nitrates and ammonium compounds. The heat effects connected with this decomposition may be avoided by using formiates of nickel or cobalt instead of nitrates during the preparation of the catalysts.
Another possibility to minimize the heat effects occurring during the calcining is to carry out the calcining very carefully, for example by applying a low rate of heating up, by carrying out heating in steps, etc.
Local overheating of the composition during the calcining, ~ !
with all its adverse effects on the activity of the ultimate catalysts, can be largely avoided by ensuring i~88~16 proper heat removal during the calcining, for example by passing, while calcining is taking place, a gas stream at high speed over the material to be calcined and by calcining the material in a comparatively thin layer.
The catalytic hydrodesulphurization of heavy hydrocarbon oils according to the invention is preferably carried out by passing the hydrocarbon oil together with hydrogen at elevated temperature and a hydrogen partial pressure below 90 bar in an upward, downward or radial direction through one or more vertically arranged fixed catalyst beds. The hydrocarbon oil to be desulphurized may be entirely or partly saturated with hydrogen, and in addition to the hydrogen phase and the catalyst phase a hydrogen-containing gas phase may be present in the reactor. The hydrodesulphurization according to the invention may be carried out in a single reactor, containing one or more catalysts beds, or in two or more reactors.
An attractive manner of introducing steam when using several catalyst beds in the process according to the invention, consists of adding steam between two or more of the catalyst beds.
The reaction conditions used during the hydrodesulphurization according to the invention may vary within wide limits, provided that the hydrogen partial pressure is less than 90 bar. The hydrodesulphurization is preferably carried out at a temperature of 300-450C, hydrogen partial pressure of 10-75 bar, a space velocity of -- 10 -- ' ~

0.1-10 parts by weight of feed per part by volu~e of catalyst per hour and a hydrogen/feed ratio of 150-2000 NlH2 per kg of feed. Particular preference is given to a temperature of 325-425C, a hydrogen partial pressure of 20-60 bar, a space velocity of 0.2-5 parts by weight of feed per part by volume of catalyst per hour and a hydrogen/feed ratio of 250-1500 NlH2 per kg of feed.
As has been mentioned above, the process according to the invention is suitable inter alia to be applied 10 to deasphalted oils produced after deasphalting of distillation residues obtained from the distillation at atmospheric or reduced pressure of crude petroleum.
The process according to the invention is also very suitable to be applied to deasphalted crude petroleum 15 and to deasphalted oils obtained after the deasphalting of distillation residues deriving from the distillation of products prepared by thermal or catalytic cracking of heavy hydrocarbon oils. Where the above-mentioned deasphalted oils are used as feed for the process according 20 to the invention, these oils can~be used as such or mixed with distillate oils.
The end product of the process according to the invention is a heavy hydrocarbon oil with a low sulphur content, which is very suitable to serve inter alia 25 as feed for a catalytic conversion process for the preparation of light hydrocarbon oils such as gasoline and kerosine. Examples of such conversion processes 10~8()16 are catalytic cracking and hydrocracking. Another very suitable application of the desulphurized heavy hydrocarbon oils prepared according to the invention is their use as residual fuel oil with low sulphur content or their use as low-sulphur blending component for the preparation of residual fuel oils. In the latter application, the other components in the blend may be both distillate and residual components. A very suitable blending component for the low-sulphur heavy hydrocarbonril for the preparation of a residual fuel oil is the asphalt obtained in the preparation of the deasphalted oil which serves as feed for the process according to the invention.
The invention will now be elucidated with reference to the following example.
EXAMPLE
The influence of steam on the activity of the present catalysts for the hydrodesulphurization of various hydrocarbon oils was investigated for two catalysts ( catalysts I and II) and three hydrocarbon oils (feeds A, B and C) in a catalyst testing test. In this test the oil, together with hydrogen, was passed in downward direction through a vertically arranged cylindrical reactor in which a fixed bed of the catalyst concerned was present in the form of 1.5 mm extrudates. The experiments were carried out at a water vapour partial pressure varylng from 0-20 bar, which was obtained by adding various quantities of water to the feeds. The composition 1~8t~016 of the catalysts, which were used in the form of their sulphides, is shown below.
CATALYST I
Co/Mo/A12O3, containing 4.3 parts by weight of cobalt and 10.9 parts by weight of molybdenum per 100 parts by weight of alumina carrier.
CATALYST II
Ni/Mo/A1203, containing 4.3 parts by weight of cobalt and 10.9 parts by weight of molybdenum per 100 parts by weight of alumina carrier.
The three hydrocarbon oils which were used in the present experiment may be described as follows.
FEED A
Hydrocarbon oil with a sulphur content of 3.24 % by weight and a total vanadium and nickel content of 5 ppmw`, which oil had been obtained as follows starting from a long residue of a Middle East crude oil.
100 Parts by weight of this long residue were separated by flashing into 47 parts by weight of flashed distillate and 53 parts by weight of short residue.
The short residue was deasphalted with n-butane as solvent at an average temperature of 125C, a pressure of 40 bar and a solvent/oil weight ratio of 4:1. In this manner 33 parts by weight of deasphalted oil and 20 parts by weight of asphalt were obtained from the short residue. The flashed distillate was mixed in production ratio with the deasphalted oil into 80 parts by weight of a heavy hydrocarbon oil which was used as feed A.

1~18~)16 FEED B
Hydrocarbon oil with sulphur content of 3.9~ by weight, a total vanadium and nickel content of 62 ppmw and a C5 asphaltene content of 6.4% by weight, which oil had been obtained as long residue in the distillation at atmospheric pressure of a Middle East crude oil.
FEED C
Hydrocarbon oil with a sulphur content of 2.6%
by weight, which oil had been obtained as distillate in the flashing of a long residue of a Middle East crude oil.
A total of 12 desulphurization experiments we~e carried out. Experiments 1-4 with feed A were carried out at a temperature of 395C, a space velocity of 0.8 kg of feed per kg of catalyst per hour and an H2/feed ratio of 1000 NlH2 per kg of feed.
Experiments 5-8 with feed B were carried out at a temperature of 420C, a space velocity of 4.35 kg of feed per kg of catalyst per hour and an H2/feed ratio of 250 NlH2 per kg of feed.
Experiments 9-12 with feed C were carried out at a temperature of 350C, a space velocity of 2 kg of feed per kg of catalysti per hour and an H2/feed ratio of 4000 Nl/H2 per kg of feed.
The results of the desulphurization experiments are shown in the table.

108E~ 6 Table --Exp. Feed Catalyst PH bar PH O,bar Sulphur in product No. No. No. 2 2 % b~ weight __________ ________ ________ ________ ___ ____ _________ 1 A I 35 ~ 0.20 2 A I 35 5 0.14

3 AII 95 - 0.06

4 AII 95 5 o.o6

5 BII 70 - 2.5*) B II 70 10 1.8*) 7 BII 150 - 1.4*) 8 BII 150 20 1.1*) 9 C I 70 - 0.21 10 C I 70 7 0.21 11 C I 150 - 0.11 12 C I 150 10 0.11 ==_===========_==============================_==================
*) These figures indicate the average sulphur content ln product, measured over the entire lifetime of the catalyst.
Of the experiments 1-12 shown in the table only experiment 2 (low pressure/use of steam/feed consisting partly of deasphalted oil) is an experiment according to the invention. The other experiments are included for the sake of comparison.
The results shown in the table clearly demonstrate that the use of steam in the hydrodesulphurization of hydrocarbon oils using the present catalysts:
ta) in the case of hydrocarbon residues, has a favourable effect on catalyst activity, both at high and low pressure (compare experiments 5-8)c (b) in the case of hydrocarbon oil distillates, has no effect on catalyst activity, neither at high nor low pressure (compare experiments 9-12).
(ç) in the case of hydrocarbon oils consisting at least partly of deasphalted oi], has a favourable effect on catalyst activity at low pressure, but no effect on catalyst activity at high pressure (compare experiments 1-4).

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the catalytic hydrodesulphurization of heavy hydrocarbon oils, in which process a heavy hydrocarbon oil consisting of a mixture of a distillate obtained in the distillation at reduced pressure of a long residue with a deasphalted short residue is contacted at elevated temperature, a hydrogen partial pressure below 90 bar and in the presence of a quantity of water corresponding with a water vapour partial pressure during the process of 0.1-10 bar, with a catalyst which contains nickel, cobalt or a mixture thereof and in addition molybdenum, tungsten or a mixture thereof supported on a carrier.

2. A process as claimed in claim 1, wherein the heavy hydrocarbon oil is prepared by separating a long residue by distillation at reduced pressure into a distillate and a short residue, deasphalting the short residue and mixing the distillate with the deasphalted oil.

3. A process according to claim 2 wherein the distillate and the short residue are mixed in the ratio in which they are produced.

4. A process as claimed in claim 2, wherein the heavy hydrocarbon oil consists partly of a flashed distillate of a long residue.

5. A process as claimed in claim 1, wherein the quantity of water used corresponds with a water vapour partial pressure during the process of 0.5-7.5 bar.

6. A process as claimed in claim 5, wherein the catalyst contains from 0.5 to 20 parts by weight of nickel, cobalt or a mixture thereof and 2.5-60 parts by weight of molybdenum, tungsten or a mixture thereof per 100 parts by weight of carrier.

7. A process according to claim 6 wherein the catalyst contains from 0.5 to 10 parts by weight of nickel, cobalt or a mixture thereof and from 2.5 to 60 parts by weight of molybdenum, tungsten or a mixture thereof per 100 parts by weight of carrier.

8. A process as claimed in claim 6, wherein in the catalyst the atomic ratio between nickel, cobalt or a mixture thereof on the one hand and molybdenum, tungsten or a mixture thereof on the other is between 0.1 and 5.

9. A process as claimed in claim 8, wherein in the catalyst the metals are present in the form of their sulphides.

10. A process as claimed in claim 9, wherein the carrier is alumina or silica-alumina.

11. A process as claimed in claim 8, which is carried out at a temperature from 300 to 450°C, a hydrogen partial pressure from 10 to 75 bar, a space velocity from 0.1 to 10 parts by weight of feed per part by volume of catalyst per hour and a hydrogen/feed ratio from 150 to 2000 NLH2 per kg of feed.

12. A process according to claim 11 which is carried out at a temperature from 325 to 425°C, a hydrogen partial pressure from 20 to 60 bar, a space velocity from 0.2 to 5 parts by weight of feed per part by volume of catalyst per hour and a hydrogen/feed ratio from 250 to 1500 NLH2 per kg of feed.

13. A process according to claim 1, 8 or 11 further including the catalytic cracking or hydrocracking of the resultant desulphurized hydro-carbon oil.

14. A process according to claim 1, 8 or 11 further including blending the resultant desulphurized heavy hydrocarbon oil, as a blending component, with one or more distillate or residual oil components.

15. A process according to claim 1, 8 or 11 further including blending the resultant desulphurized heavy hydrocarbon oil, as a blending component, with an asphalt obtained in the preparation of the deasphalted oil present in the heavy oil to be desulphurized.