GB1563276A - Process for conversion of hydrocarbons - Google Patents

Description

(54) PROCESS FOR THE CONVERSION OF HYDROCARBONS (71) We, SHELL INTERNATION ALE RESEARCH MAATSHAPPIJ B.V., a company organised under the laws of the Netherlands, of 30 Carel van Bylandtlaan, The Hague, The Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a process for the reparation of one or more light hydrocarbon oil distillates from a hydrocarbon oil residue obtained by vacuum distillation or from an asphalt obtained in the deasphalting of this residue.

In the atmospheric distillation of crude mineral oil, as applied on a large scale in refineries in the reparation of light hydrocarbon oil distillates, a residual oil its obtained as by-product. To increase the yield of light hydrocarbon oil distillates from the crude - oil concerned, a heavy hydrocarbon oil distillate can be separated from the residual oil mentioned by vacuum distillation, which hydrocarbon oil distillate can be converted in a relatively simple way, for instance by catalytic cracking or hydrocracking, into one or more light hydrocarbon oil distillates. Just as in the atmospheric distillation, a residual oil is obtained as by-product in the vacuum distillation.In some cases this residual oil is suitable for use as the starting material for the preparation of residual lubricating oil, but usually the residual oil, which as a rule has a total vanadium and nickel content of more than 100 ppmw and a Ramsbottom Carbon Test value (RCT) of more than 15%w, is only suitable for use as a fuel oil component.

In view of the increasing demand for light hydrocarbon oil distillates attempts were made in the past to convert the vacuum residues into light distillates, for instance by catalytic cracking or hydrocracking. The use of the vacuum residues as produced as the feed for these processes has such serious drawbacks that their application on a commercial scale is out of the question.

Thus, the principal drawbacks of, for instance, catalytic cracking of the vacuum residues are that a very high catalyst consumption occurs and that because of the very high coke and gas production only a low yield of the desired light distillates is obtained. Hydrocracking of the vacuum residues involves a very rapid catalyst deactivation and/or a very high gas production and/or a very high hydrogen consumption.

To increase the yield of light hydrocarbon oil distillates from the crude oil concerned, one might consider deasphalting the vacuum residues mentioned and thus separating a deasphalted oil, which may be converted, for instance by catalytic cracking or hydrocracking, into one or more light hydrocarbon oil distillates. A drawback of this route is, however, that deasphalting of the vacuum residues yields asphalt as a by-product. Apart from the use for engineering purposes, for instance in road-building, and as a component for refinery fuel, the applicability of this material is limited. Conversion of the asphalt into light hydrocarbon oil distillates via the above-mentioned catalytic cracking or hydrocracking processes cannot be considered in view of the very high metal content and the very high RCT of this material.Application of other conversion processes such as coking, thermal cracking and gasification in combination with hydrocarbon synthesis is rather unattractive in view of the low yield of desired light hydrocarbon oil distillates and/or the high costs attending the process.

In view of the above and considering the fact that in the processing of crude mineral oil into light hydrocarbon oil distillates via atmospheric distillation, vacuum distillation combined with conversion of the vacuum distillate and possible deasphalting, combined with conversion of the deasphalted oil, considerable quantities of vacuum residue and/or asphalt are obtained as by-products, it will be clear that there is an urgent need for a process which offers the possibility of converting these vacuum residues and asphalt in an economically justifiable way -into light hydrocarbon oil distillates such as gasolines.

Since catalytic cracking has proved in practice to be an excellent process for the conversion of heavy hydrocarbon oil distillates such as gas oils into light hydrocarbon oil distillates such as gasolines, we have carried out an investigation to find out how far use can be made of catalytic cracking in the conversion of the above-mentioned vacuum residues and asphalt. It has been found that by a proper combination of catalytic cracking as the main process with a twostage catalytic hydrotreatment as a supplementary process, a process can be realized that is highly suitable for this purpose. The present patent application relates to such a process.

In the process according to the invention a hydrocarbon residue obtained by vacuum distillation and having a total vanadium and nickel content of more than 100 ppmw and an RCT of more than 15%w, or an asphalt obtained in the deasphalting of this residue, is subjected to a two-stage catalytic hydrotreatment under such conditions in the first stage that the liquid reaction product of the first stage, which is used as the feed for the second stage, has a total vanadium and nickel content that is less than 10% of that of the feed to the first stage and that the said liquid reaction product has a total vanadium and nickel content of less than 100 ppmw and under such conditions in the second stage that after separation of the desired light hydrocarbon oil distillates from the liquid reaction product of the second stage by atmospheric distillation and use of the distillation residue as the feed or as a'feed component for the catalytic cracking unit, the fresh feed for the catalytic cracking unit has an RCT of less than 3%w and a nickel content and a total vanadium and nickel content of less than 4 and 10 ppmw, respectively.The first stage of the catalytic hydrotreatment should be carried out in the presence of a catalyst which contains more than 80%w silica and the second stage in the presence of a catalyst which contains at least one metal selected from nickel and cobalt, and, in addition, at least one metal selected from molybdenum and tungsten, on a carrier, which carrier contains more than 40%w alumina. The desired light hydrocarbon oils are separated from the cracked product by atmospheric distillation.

In the process according to the invention catalytic cracking is used as the main process. In this process a considerable proportion of the heavy feed is converted into the desired light distillates. By atmospheric distillation one or more light distillates are separated from the cracked product as end products. To increase the yield of light distillates it is preferred to recycle at least part of the residue obtained in the atmospheric distillation of the cracked product to the catalytic cracking unit. When, in the process according to the invention, part of the said residue is recycled to the catalytic cracking unit it is preferred to choose for this purpose a fraction separated from the residue by distillation.If at least part of the said residue is recycled to the catalytic cracking unit, this liquid is preferably subjected to a catalytic hydrotreatment before it is subjected to catalytic cracking again. In the catalytic cracking process, which is preferably carried out in the presence of a zeolitic catalyst, coke is deposited on the catalyst.

This coke is removed from the catalyst by burning off during a catalyst regeneration step that is combined with the catalytic cracking, whereby a waste gas is obtained substantially consisting of a mixture of carbon monoxide and carbon dioxide.

Catalytic cracking is preferably carried out at an average temperature of from 400 to 550"C, a pressure of from 1 to 10 bar, a space velocity of from 0.25 to 4 kg.kg-'.h-l and a rate of catalyst replenishment of from 0.1 to 5 tonnes of catalyst per 1000 tonnes feed. There is particular preference for the catalytic cracking being carried out at an average temperature of from 450 to 5250C, a pressure of from 1.5 to 7.5 bar, a space velocity of from 0.5 to 2.5 kg.kgl.h-' and a rate of catalyst replenishment of from 0.2 to 2 tonnes of catalyst per 1000 tonnes of feed.

In the process according to the invention the feed for the catalytic cracking unit is subjected to a two-stage catalytic hydrotreatment as a supplementary process. The first stage serves substantially to reduce the metal content of the feed in the manner indicated. During the first stage the RCT of the feed also decreases. The second stage serves to reduce the RCT and the metal content of the feed in the manner indicated.

In the process according to the invention the two-stage catalytic hydrotreatment is preferably carried out at an average temperature of from 375 to 4500 C, a hydrogen partial pressure of from 75 to 300 bar, a space velocity of from 0.1 to 1.5 kg.l-'.h-' and a hydrogen/feed ratio of from 250 to 2000 Nl.kg-'. There is particular preference for carrying out the two stages at an average temperature of from 390 to 4300 C, a hydrogen partial pressure of from 100 to 275 bar, a space velocity of from 0.2 to 1.0 kg.l-'.h-' and a hydrogen/feed ratio of from 500 to 1500 Nl.kg-'. In the first stage a catalyst is applied which contains more than 80%w silica.Catalysts consisting entirely of silica as well as catalysts comprising one or more metals having hydrogenation activity, in particular a combination of nickel and vanadium on a carrier substantially consisting of silica, are eligible for this purpose. Very suitable catalysts for use in the first stage are catalysts that meet certain specific requirements with regard to their porosity and particle size and that are described in Netherlands patent application No.

7309387. The first stage is preferably carried out in the presence of a quantity of H2S corresponding to an H2S content of the gas at the reactor inlet of more than 10%v. To this end a sufficient quantity of H2S from an external source may be continuously added to the feed of the first stage. However, from an economic point of view it is more attractive to utilize as much as possible of the H2S present in the exit gases of the first and the second stage. With this in mind the following embodiments for the first stage may be considered.

a) Application of gas recirculation to the first stage, as much H2S as possible being left in the recycle gas until the desired H2S concentration is reached.

Subsequently, a certain proportion of H2S can be continuously removed from the recycle gas to maintain the desired H2S concentration.

b) Especially when a high H2S concentration is desired it may take a considerable time before the H2S concentration in the recycle gas has reached the desired value. This situation may be dealt with by adding to the gas during this time H2S from an external source and reducing the added quantity of H2S as the process advances. This additional quantity of H2S may originate, for instance, from the second stage.

c) Instead of gas recirculation in the first stage, or in combination with it, exit gas from the second stage may be used as the feed gas for the first stage.

In the second stage of the catalytic hydrotreatment a catalyst is applied which contains at least one metal chosen from nickel and cobalt and, in addition, at least one metal chosen from molybdenum and tungsten on a carrier, which contains more than 40%w of alumina. Very suitable catalysts for application in the second stage are catalysts comprising the metal combination nickel/molybdenum or cobalt/molybdenum on alumina as the carrier. The second stage is preferably carried out in the presence of a quantity of H2S corresponding with an H2S content of the gas at the inlet of the reactor of less than 5%v. This means that, when in the second stage gas recirculation is applied, at least part of the H2S has to be removed from the exit gas of the second stage before this gas is recycled.An attractive embodiment of the two-stage catalytic hydrotreatment in which the said H2S concentration in both stages is taken into account is the following. The exit gas from the second stage is divided into two portions. One portion is used as feed gas for the first stage together with exit gas from the first stage. The second portion, after removal of at least part of the H2S, is used as feed gas for the second stage together with fresh hydrogen.

An attractive embodiment of the first stage of the catalytic hydrotreatment is one in which the hydrocarbon oil to be treated is passed through a vertically disposed catalyst bed, after which during operation fresh catalyst is periodically introduced at the top of the bed and spent catalyst is withdrawn at the bottom thereof (processing in bunker flow operation). Another attractive embodiment for the first stage is one in which several reactors containing a fixed catalyst bed are present, which reactors are alternately used for the catalytic hydrotreatment, while the catalytic hydrotreatment is carried out in one or more of these reactors, the catalyst in the other reactors is renewed (processing in fixed-bed swing operation). The second stage of the catalytic hydrotreatment is preferably carried out over a conventional fixed catalyst bed.

If in the process according to the invention the two-stage catalytic hydrotreatment is applied to an asphalt, this asphalt has been obtained by deasphalting a vacuum residue. Deasphalting of the vacuum residue is preferably carried out at elevated temperature and pressure and in the presence of an excess of a lower hydrocarbon such as propane, butane or pentane as the solvent.

The process according to the invention is very suitable to be used as part of a more extensive process for the preparation of light hydrocarbon oil distillates from atmospheric distillation residues. Such processes may be carried out as follows. An atmospheric distillation residue is separated by vacuum distillation into a vacuum distillate and a vacuum residue. The desired light hydrocarbon oil distillates are prepared from the vacuum distillate by catalytic cracking or hydrocracking and from the vacuum residue according to the invention.

If desired, the vacuum residue may be separated by deasphalting into a deasphalted oil and asphalt. The desired light hydrocarbon oil distillates are then prepared from the vacuum distillate and from the deasphalted oil by catalytic cracking and/or hydrocracking and from the asphalt according to the invention. If in the preparation of light distillates from atmospheric residues use is made of catalytic cracking for the conversion of the vacuum distillate and/or of the deasphalted oil, this catalytic cracking is preferably carried out in the same catalytic cracking unit in which the conversion of the product of the twostage hydrotreatment took place.If in the preparation of light distillates from atmospheric residues a vacuum distillate as well as a deasphalted oil has to be processed, these two materials are preferably processed in the same way, either by catalytic cracking or by hydrocracking.

If in the preparation of light distillates from atmospheric residues use is made of catalytic cracking for the conversion of the vacuum distillate and/or of the deasphalted oil, these materials are preferably first subjected to a catalytic hydrotreatment.

This treatment, like the aforementioned catalytic hydrotreatment which is preferably applied to the part of the catalytically cracked product to be recirculated, if desired, to the catalytic cracking unit, aims chiefly at reducing the metal content of the feed to the catalytic cracking unit and thus limiting the catalyst consumption in the cracking unit and further aims at saturating the feed for the catalytic cracking unit with hydrogen and thus at decreasing coke deposition on the cracking catalyst and increasing the yield of the desired product. The catalytic hydrotreatment of the residue to be recirculated to the catalytic cracking unit as well as the catalytic hydrotreatment of the vacuum distillate or the deasphalted oil can very suitably be carried out in the same unit.

Three process schemes for the conversion of atmospheric distillation residues into light hydrocarbon oil distillates will be elucidated hereinafter in more detail with reference to the appended figures.

Process scheme I (Fig. 1).

The process is carried out in an apparatus comprising successively a vacuum distillation section (1), a first catalytic hydrotreating section (2), a second catalytic hydrotreating section (3), a first atmospheric distillation section (4), a catalytic cracking section (5) and a second atmospheric distillation section (6). A hydrocarbon oil residue (7) obtained by atmospheric distillation is separated by vacuum distillation into a vacuum distillate (8) and a vacuum residue (9). The residue (9), together with a hydrogen stream (10), is subjected to the first stage of a two-stage catalytic hydrotreatment. After separation of a gas stream (11), substantially consisting of C4- hydrocarbons and H2S, from the hydrotreated product, the liquid reaction product (12), together with a hydrogen stream (13), is subjected to the second stage of the catalytic hydrotreatment.After separation of a gas stream (14), substantially consisting of C4- hydrocarbons and H2S, from the hydrotreated product, the liquid reaction product (15) is separated by atmospheric distillation into a gasoline fraction (16) and a residue (17). The residue (17) is mixed with the vacuum distillate (8) to form the fresh feed stream (18) for the catalytic cracking unit. The fresh feed stream (18) is mixed with the middle distillate fraction (19) obtained in the atmospheric distillation of the cracked product (20) referred to hereinafter, and the mixture is catalytically cracked In the regeneration of the catalyst in the catalytic cracking unit a waste gas (21) is obtained substantially consisting of a mixture of carbon monoxide and carbon dioxide.The catalytically cracked product (20) is separated by atmospheric distillation into a C4- fraction (22), a gasoline fraction (23), a middle distillate fraction (19) and a residue (24) being a mixture of heavy cycle oil and slurry oil.

Process scheme II (Fig. 2).

The process is carried out in an apparatus comprising successively a vacuum distillation section (1), a first catalytic hydrotreating section (2), a second catalytic hydrotreating section (3), first atmospheric distillation section (4), a third catalytic hydrotreating section (5), a catalytic cracking section (6) and a second atmospheric distillation section (7). A hydrocarbon oil residue (8) obtained by atmospheric distillation is separated by vacuum distillation into a vacuum distillate (9) and a vacuum residue (10). The residue (10), together with a hydrogen stream (11), is subjected to the first stage of a two-stage catalytic hydrotreatment.After separation of a gas stream (12), substantially consisting of C4- hydrocarbons and H2S, from the hydrotreated product, the liquid reaction product (13), together with a hydrogen stream (14), is subjected to the second stage of the catalytic hydrotreatment. After separation of a gas stream (15), substantially consisting of C4- hydrocarbons and H2S, from the hydrotreated product, the liquid reaction product (16) is separated by atmospheric distillation into a gasoline fraction (17), a middle distillate fraction (18) and a residue (19). The vacuum distillate (9), together with a hydrocarbon stream (20), is subjected to a catalytic hydrotreatment.

After separation of a gas stream (21), substantially consisting of H2S, from the hydrotreated product, the reaction product (22) is mixed with the residue (19) to form the fresh feed stream (23) which is cracked in the catalytic cracking unit. In the regeneration of the catalyst in the catalytic cracking unit a waste gas (24) is obtained substantially consisting of a mixture of carbon monoxide and carbon dioxide. The catalytically cracked product (25) is separated by atmospheric distillation into a C4- fraction (26), a gasoline fraction (27), a middle distillate fraction (28) and a residue (29) being a mixture of heavy cycle oil and slurry oil.

Process scheme III (Fig. 3).

The process is carried out in an apparatus comprising successively a vacuum distillation section (1), a deasphalting section (2), a first catalytic hydrotreating section (3), a second catalytic hydrotreating section (4), a first atmospheric distillation section (5), a hydrocracking section (6), a second atmospheric distillation section (7), a catalytic cracking section (8) and a third atmospheric distillation section (9). A hydrocarbon oil residue (10) obtained by atmospheric distillation is separated by vacuum distillation into a vacuum distillate (11) and a vacuum residue (12). The residue (12) is separated by deasphalting into a deasphalting oil (13) and asphalt (14). The asphalt (14), together with a hydrogen stream (15), is subjected to the first stage of a two-stage catalytic hydrotreatment.After separation of a gas stream (16), substantially consisting of C - hydrocarbons and H2S, from the hydrotreated product, the liquid reaction product (17), together with a hydrogen stream (18), is subjected to the second stage of the catalytic hydrotreatment. After separation of a gas stream (19), substantially consisting of C4- hydrocarbons and H2S, from the hydrotreated product, the liquid reaction product (20) is separated by atmospheric distillation into a gasoline fraction (21), a middle distillate fraction (22) and a residue (23). The vacuum distillate (11) is mixed with the deasphalted oil (13) and the mixture (24), together with a hydrogen stream (25), is subjected to hydrocracking.

After separation of a gas stream (26), substantially consisting of C4- hydrocarbons and H2S, from the hydrocracked product, the liquid product (27) is separated by atmospheric distillation into a gasoline fraction (28), a middle distillate fraction (29) and a residue (30). The residues (23) and (30) are mixed and the mixture (31) is catalytically cracked. In the regeneration of the catalyst in the catalytic cracking unit a waste gas (32) is obtained substantially consisting of a mixture of carbon monoxide and carbon dioxide. The catalytically cracked product (33) is separated by atmospheric distillation into a C4- fraction (34), a gasoline fraction (35), a middle distillate fraction (36) and a residue (37) being a mixture of heavy cycle oil and slurry oil.

The present application also comprises apparatus for carrying out the process according to the invention as schematically shown in Figs. 1--3.

The invention will now be elucidated with reference to the following examples.

The process according to the invention was applied to an atmospheric distillation residue of a crude oil from the Middle East.

The atmospheric distillation residue has an initial boiling point of 3700 C, a sulphur content of 3.85%w, an RCT of 8.4%w, a C6 asphaltenes content of 6.0%w, a V content of 46 ppmw and a Ni content of 14 ppmw.

The process was carried out according to process schemes I-Ill. In the different sections the following conditions were applied.

In all the process schemes a Ni/V/SiO2 catalyst containing per 100 pbw silica, 0.5 pbw nickel and 2 pbw vanadium, was used for the first stage of the two-stage catalytic hydrotreatment and a Ni/Mo/Al2O3 catalyst containing per 100 pbw alumina, 4 pbw nickel and 11 pbw molybdenum, for the second stage. The two stages of the twostage catalytic hydrotreatment were carried out under the conditions given in the table.

TABLE I II III ist 2nd 1st 2nd Ist 2nd Scheme No. stage stage stage stage stage stage Average temp., C 420 425 420 425 420 430 PH23 bar 150 150 180 180 220 220 PH2S, bar 20 < 1 20 < 1 30 < 2 Space velocity, kg.r'.h'' 0.6 0.4 0.7 0.35 0.4 0.3 H2/feed ratio, Nl.kg-t 750 1000 750 1000 1000 1000 The catalytic hydrotreatment of the vacuum distillate (9) included in process scheme II was carried out at an average temperature of 380"C, a PH2 of 35 bar, a space velocity of 0.5 I.l-'.h-' and a hydrogen/oil ratio of 1000 Nl.kg-' and with application of a nickel-molybdenum catalyst on alumina as the carrier.The deasphalting included in process scheme III was carried out at 1200C with liquid butane as the solvent and with application of a solvent/oil weight ratio of 4:1. The hydrocracking of the vacuum distillate/deasphalted oil mixture (24) included in process scheme III was carried out in two stages, the total reaction product from the first stage being used as the feed for the second stage. The first stage of the hydrocracking was carried out at an average temperature of 389"C, a P,, of 120 bar, a space velocity of 0.45 kg.l-'.h-' and a H2/oil ratio of 1000 Nl.kg-' and with application of nickel-molybdenum catalyst containing fluorine on alimina as the carrier.The second stage of the hydrocracking was carried out at an average temperature of 370"C, a H2 of 120 bar, a space velocity of 1.0 kg.l-'.h-' and a Hoil ratio of 100 Nl.kg-' and with application of a nickeltungsten catalyst on faujasite as the carrier.

In all process schemes the catalytic cracking was carried out at a temperature of 4900 C, a pressure of 2.2 bar, a space velocity of 2 kg.kg-1.h-1 and a rate of catalyst replenishment varying from 0.5 to 1.0 tonne of catalyst per 1000 tonnes of oil and with application of a zeolitic cracking catalyst.

Example I.

This example was carried out according to process scheme I. With 100 pbw of the 370"C+ atmospheric distillation residue (7) as the starting material the following quantities of the various streams having the properties mentioned were obtained: 56.0 pbw 370-520 C vacuum distillate (8), 44.0 pbw 520"C+ residue (9) with an RCT of 18.7%w, a V content of 105 ppmw and a Ni content of 32 ppmw, 0.5 pbw hydrogen (10), 1.4 pbw C4- fraction + H2S (11), 43.1 pbw liquid product (12) with a V + Ni content of 8 ppmw, 1.0 pbw hydrogen (13), 2.5 pbw C4- fraction + H2S (14), 41.6 pbw liquid product (15) with an RCT of 5.4%wand a V + Ni content of 3.5 ppmw, 5.4 pbw C5-2000C gasoline fraction (16), 36.2 pbw 200"C+ residue (17) with an RCT of 6.2%w and a V + Ni content of 4.1 ppmw, 92.2 pbw of the mixture (18) with an RCT of 2.6%w and a V + Ni content of 1.7 ppmw ppmw and a Ni content of 1.4 ppmw, 21.8 pbw C4- fraction (22), 53.4 pbw C5-2000C gasoline fraction (23), 15.5 pbw 20e3700C middle distillate fraction (19), and 10.6 pbw 370"C+ residue (24).

Example II.

This example was carried out according to process scheme II. With 100 pbw of the 370"C+ atmospheric distillation residue (8) as the starting material the following quantities of the various streams having the properties mentioned were obtained: 56.0 pbw 370-520 C vacuum distillate (9), 44.0 pbw 520 C+ residue (10) with an RCT of 18.7%w, a V content of 105 ppmw and a Ni content of 32 ppmw, 0.4 pbw hydrogen (11), 1.2 pbw C4- fraction + H2S (12), 43.2 pbw liquid product (13) with an RCT of 13.0%w and a V + Ni content of 6.6 ppmw, 1.3 pbw hydrogen (14), 3.0 pbw C4- fraction + H2S (15), 41.5 pbw liquid product (16), 5.5 pbw C6-2000C gasoline fraction (17), 6.4 pbw 20-3700C middle distillate fraction (18), 29.6 pbw 3700C residue (19) with an RCT of 5.8%w, a Ni content of 3.5 ppmw and a V + Ni content of 3.9 ppmw, 0.4 pbw hydrogen (20), 1.4 pbw H2S (21), 84.6 pbw of the mixture (23) with an RCT of 2.3%w, a Ni content of 1.2 ppmw and a V + Ni content of 1.3 ppmw, 16.3 pbw C4- fraction (26), 44.6 pbw C5-2000C gasoline fraction (27), 14.1 pbw 200--3750C middle distillate fraction (28), and 4.6 pbw 370"C+ residue (29).

Example III.

This example was carried out according to process scheme III. With 100 pbw of the 370"C+ atmospheric distillation residue (10) as the starting material the following quantities of the various streams having the properties mentioned were obtained: 56.0 pbw 37(w5200C vacuum distillate (it), 44.0 pbw 520"C+ residue (12) with an RCT of 18.7%w, a V content of 105 ppmw and a Ni content of 32 ppmw, 23.0 pbw deasphalted oil (13), 21.0 pbw asphalt (14) with an RCT of 50%w, a V content of 210 ppmw and a Ni content of 65 ppmw, 0.3 pbw hydrogen (15), 1.0 pbw C4- fraction + H2S (16), 20.3 pbw liquid product (17) with an RCT of 26.low and a V + Ni content of 17 ppmw, 0.9 pbw hydrogen (18), 1.7 pbw C4- fraction + H2S (19), 19.5 pbw liquid product (20), 2.5 pbw C6-2000C gasoline fraction (21), 4.7 pbw200-3700C middle distillate fraction (22), 12.3 pbw 370 C+ residue (23) with an RCT of 5.2%w and a V + Ni content of 9.2 ppmw, 79.0 pbw of the mixture (24) with an RCT of 1.4%w, a V content of 1.5 ppmw, a Ni content of 0.5 ppmw and a sulphur content of 3.1 %w, 2.8 pbw hydrogen (25), 6.0 pbw C4- fraction + H2S (26), 75.8 pbw liquid product (27), 34.1 pbw C,--2000C gasoline fraction (28), 24.1 pbw 20e370"C middle distillate fraction (29), 17.6 pbw 370"C+ residue (30), 29.9 pbw of the mixture (31) with an RCT of 2.l%w, a V+Ni content of 3.8 ppmw and a Ni content of 3.1 ppmw, 5.7 pbw C4- fraction (34), 15.7 pbw C5-2000C gasoline fraction (35), 5.0 pbw 200--370"C middle distillate fraction (36), and 1.7 pbw 3700C+ residue (37).

WHAT WE CLAIM IS: 1. A process for the preparation of one or more light hydrocarbon oil distillates, characterized in that the preparation is carried out, starting from a hydrocarbon oil residue obtained by vacuum distillation and having a total vanadium and nickel content of more than 100 ppmw and an RCT of more than 15%w or from an asphalt obtained in the deasphalting of this residue, by catalytic cracking as the main process in combination with a two-stage catalytic hydrotreatment as a supplementary process, that the catalyst in the first stage of the hydrotreatment contains more than 80%w silica, that the catalyst in the second stage of the hydrotreatment contains at least one metal selected from nickel and cobalt, and, in addition, at least one metal selected from molybdenum and tungsten on a carrier, which carrier contains more than 40%w alumina, that the vacuum residue of the asphalt is subjected to the two-stage catalytic hydrotreatment under such conditions in the first stage that the liquid reaction product of the first stage, which is used as the feed for the second stage, has a total vanadium and nickel content that is less than 10% of that of the feed to the first stage and that the said reaction product has a total vanadium and nickel content of less than 100 ppmw and under such conditions in the second stage that after separation of the desired light hydrocarbon oil distillates from the reaction product of the second stage by atmospheric distillation and use of the distillation residue obtained as the feed or as a feed component for the catalytic cracking unit, the fresh feed to the catalytic cracking unit has an RCT of less than 3%w and a nickel content and a total vanadium and nickel content of less than 4 and 10 ppmw, respectively, and that the desired light hydrocarbon oils are separated from the catalytically cracked product by atmospheric distillation.

2. A process according to claim 1, characterized in that at least part and preferably a distillate fraction of the residue

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (15)

**WARNING** start of CLMS field may overlap end of DESC **. 0.4 pbw hydrogen (11), 1.2 pbw C4- fraction + H2S (12), 43.2 pbw liquid product (13) with an RCT of 13.0%w and a V + Ni content of 6.6 ppmw, 1.3 pbw hydrogen (14), 3.0 pbw C4- fraction + H2S (15), 41.5 pbw liquid product (16), 5.5 pbw C6-2000C gasoline fraction (17), 6.4 pbw 20-3700C middle distillate fraction (18), 29.6 pbw 3700C residue (19) with an RCT of 5.8%w, a Ni content of 3.5 ppmw and a V + Ni content of 3.9 ppmw, 0.4 pbw hydrogen (20), 1.4 pbw H2S (21), 84.6 pbw of the mixture (23) with an RCT of 2.3%w, a Ni content of 1.2 ppmw and a V + Ni content of 1.3 ppmw, 16.3 pbw C4- fraction (26), 44.6 pbw C5-2000C gasoline fraction (27), 14.1 pbw 200--3750C middle distillate fraction (28), and 4.6 pbw 370"C+ residue (29). Example III. This example was carried out according to process scheme III. With 100 pbw of the 370"C+ atmospheric distillation residue (10) as the starting material the following quantities of the various streams having the properties mentioned were obtained: 56.0 pbw 37(w5200C vacuum distillate (it), 44.0 pbw 520"C+ residue (12) with an RCT of 18.7%w, a V content of 105 ppmw and a Ni content of 32 ppmw, 23.0 pbw deasphalted oil (13), 21.0 pbw asphalt (14) with an RCT of 50%w, a V content of 210 ppmw and a Ni content of 65 ppmw, 0.3 pbw hydrogen (15), 1.0 pbw C4- fraction + H2S (16), 20.3 pbw liquid product (17) with an RCT of 26.low and a V + Ni content of 17 ppmw, 0.9 pbw hydrogen (18), 1.7 pbw C4- fraction + H2S (19), 19.5 pbw liquid product (20), 2.5 pbw C6-2000C gasoline fraction (21), 4.7 pbw200-3700C middle distillate fraction (22), 12.3 pbw 370 C+ residue (23) with an RCT of 5.2%w and a V + Ni content of 9.2 ppmw, 79.0 pbw of the mixture (24) with an RCT of 1.4%w, a V content of 1.5 ppmw, a Ni content of 0.5 ppmw and a sulphur content of 3.1 %w, 2.8 pbw hydrogen (25), 6.0 pbw C4- fraction + H2S (26), 75.8 pbw liquid product (27), 34.1 pbw C,--2000C gasoline fraction (28), 24.1 pbw 20e370"C middle distillate fraction (29), 17.6 pbw 370"C+ residue (30), 29.9 pbw of the mixture (31) with an RCT of 2.l%w, a V+Ni content of 3.8 ppmw and a Ni content of 3.1 ppmw, 5.7 pbw C4- fraction (34), 15.7 pbw C5-2000C gasoline fraction (35), 5.0 pbw 200--370"C middle distillate fraction (36), and 1.7 pbw 3700C+ residue (37). WHAT WE CLAIM IS:

1. A process for the preparation of one or more light hydrocarbon oil distillates, characterized in that the preparation is carried out, starting from a hydrocarbon oil residue obtained by vacuum distillation and having a total vanadium and nickel content of more than 100 ppmw and an RCT of more than 15%w or from an asphalt obtained in the deasphalting of this residue, by catalytic cracking as the main process in combination with a two-stage catalytic hydrotreatment as a supplementary process, that the catalyst in the first stage of the hydrotreatment contains more than 80%w silica, that the catalyst in the second stage of the hydrotreatment contains at least one metal selected from nickel and cobalt, and, in addition, at least one metal selected from molybdenum and tungsten on a carrier, which carrier contains more than 40%w alumina, that the vacuum residue of the asphalt is subjected to the two-stage catalytic hydrotreatment under such conditions in the first stage that the liquid reaction product of the first stage, which is used as the feed for the second stage, has a total vanadium and nickel content that is less than 10% of that of the feed to the first stage and that the said reaction product has a total vanadium and nickel content of less than 100 ppmw and under such conditions in the second stage that after separation of the desired light hydrocarbon oil distillates from the reaction product of the second stage by atmospheric distillation and use of the distillation residue obtained as the feed or as a feed component for the catalytic cracking unit, the fresh feed to the catalytic cracking unit has an RCT of less than 3%w and a nickel content and a total vanadium and nickel content of less than 4 and 10 ppmw, respectively, and that the desired light hydrocarbon oils are separated from the catalytically cracked product by atmospheric distillation.

2. A process according to claim 1, characterized in that at least part and preferably a distillate fraction of the residue

obtained after atmospheric distillation of the product prepared by catalytic cracking is recycled to the catalytic cracking unit.

3. A process according to claim 2, characterized in that the fraction of the product prepared by catalytic cracking which is recycled to the catalytic cracking unit is subjected to a catalytic hydrotreatment.

4. A process according to any one of claims 1--3, characterized in that the catalytic cracking is carried out at an average temperature of from 400 to 550"C and preferably of from 450 to 5250C, a pressure of from 1 to 10 bar and preferably of from 1.5 to 7.5 bar, a space velocity of from 0.25 to 4 kg.kgl-'.h-' and preferably of from 0.5 to 2.5 kg.kgl-'.h-' and a rate of catalyst replenishment of from 0.1 to 5 tonnes of catalyst per 1000 tonnes of feed and preferably of from 0.2 to 2 tonnes of catalyst per 1000 tonnes of feed.

5. A process according to any one of claims 1-4, characterized in that the twostage catalytic hydrotreatment is carried out at an average temperature of from 375 to 450"C and preferably of from 390 to 4300 C, a hydrogen partial pressure of from 75 to 300 bar and preferably of from 100 to 275 bar, a space velocity of from 0.1 to 1.5 kg.l-'.h- and preferably of from 0.2 to 1.0 kg. l-' .h-' and a hydrogen/feed ratio of from 250 to 2000 Nl.kg-' and preferably of from 500 to 1500 Nl.kg-'.

6. A process according to any one of claims 1--5, characterized in that in the first stage of the two-stage catalytic hydrotreatment a catalyst is used containing the metal combination nickel-vanadium on silica as the carrier.

7. A process according to any one of claims 16, characterized in that the first stage of the two-stage catalytic hydrotreatment is carried out in the presence of a quantity of H2S corresponding with an H2S content of the gas at the reactor inlet of more than 10%v.

8. A process according to any one of claims 16, characterized in that in the second stage of the two-stage catalytic hydrotreatment a catalyst is used containing the metal combination nickel-molybdenum or cobalt-molybdenum or cobaltmolybdenum on alumina as the carrier.

9. A process according to any one of claims 1-8, characterized in that the second stage of the two-stage catalytic hydrotreatment is carried out in the presence of a quantity of H2S corresponding with an H2S content of the gas at the reactor inlet of less than 5%v.

10. A process according to any one of claims 1--9, characterized in that the first stage of the two-stage catalytic hydrotreatment is carried out- according to the bunker flow principle or to the fixed-bed swing principle and the second stage over a conventional fixed catalyst bed.

11. A process according to any one of claims 1--10, characterized in that it is used for the preparation of one or more light hydrocarbon oil distillates from a hydrocarbon oil residue obtained by atmospheric distillation, that the atmospheric residue is separated by vacuum distillation into a vacuum distillate and a vacuum residue, that the vacuum residue is separated further - if desired -- into a deasphalted oil and asphalt and that the vacuum distillate and - if present -- the deasphalted oil are converted into the desired light hydrocarbon oil distillates by catalytic cracking and-or hydrocracking.

12. A process according to claim 11, characterized in that the catalytic cracking of the vacuum distillate and/or the deasphalted oil is carried out in the same catalytic cracking unit in which the conversion of. the product of the two-stage catalytic hydrotreatment takes place, preferably after catalytic hydrotreatment of the said vacuum distillate and/or deasphalted oil.

13. A process for the preparation of one or more light hydrocarbon oil distillates, as claimed in claim 1, substantially as described hereinbefore with reference to the examples.

14. Light hydrocarbon oil distillates, characterized in that these have been prepared according to a process as described in claim 13.

15. Plant for carrying out a process according to claim 13, characterized in that this plant is substantially equal to one of the plants shown schematically in Figs. 1--3.