Catalytic system and process for the total hydroconversion of heavy oils

Abstract

A catalytic system characterized in that it comprises: a first catalyst, having a hydrogenating function, consisting of solid particles of which at least 95% by volume having an equivalent diameter smaller than 20 m, containing one or more sulfides of metals of group VI and/or VIII B, possibly prepared starting from an oil-soluble precursor of the same; and a second catalyst, having a cracking function, consisting of solid particles of which at least 90% by volume having an equivalent diameter larger than 5 m and smaller than 5 mm, containing an amorphous silico-aluminate and/or a crystalline silico-aluminate and/or an alumina, the equivalent average diameter of the solid particles of the second catalyst being greater than the equivalent average diameter of the solid particles of the first catalyst. Said catalytic system can be used in a process for the hydroconversion of heavy oils which comprises sending the heavy oil to a hydroprocessing step carried out in one or more slurry reactors, in the presence of hydrogen or a mixture of hydrogen and H.sub.2S, obtaining a stream of products in vapor or liquid-vapor phase, and extracting at the bottom, in continuous or discontinuous, a liquid stream containing non-converted products together with the two catalysts of said catalytic system, said liquid stream extracted then being separated into a clarified primary stream containing the first catalyst, which is at least partially recycled to the hydroprocessing step, and a stream rich in the second catalyst, which is regenerated in a regeneration step and at least partially recycled to the hydroprocessing step.

Claims

1. A catalytic system which can be used for the hydroconversion of heavy oils comprising a mixture of: a first catalyst, having a hydrogenating function, consisting of solid particles of which at least 95% by volume having an equivalent diameter smaller than 20 m, containing one or more sulfides of metals of group VI and/or VIII B; and a second catalyst, having a cracking function, consisting of solid particles of which at least 90% by volume having an equivalent diameter larger than 5 m and smaller than 5 mm, containing an amorphous silico-aluminate and/or a crystalline silico-aluminate and/or an alumina, wherein the equivalent average diameter of the solid particles of the second catalyst is greater than the equivalent average diameter of the solid particles of the first catalyst.

2. The catalytic system according to claim 1, wherein the first catalyst consists of MoS.sub.2 and/or WS.sub.2 and/or FeS.sub.x.

3. The catalytic system according to claim 1, wherein the first catalyst is obtained from an oil-soluble precursor of metals of group VI and/or VIII B.

4. The catalytic system according to claim 1, wherein the crystalline silico-aluminate is selected from zeolites having at least one system of channels with an average diameter higher than 5 Angstroms (large-pore zeolites).

5. The catalytic system according to claim 1, wherein the crystalline silico-aluminate is as MCM-22 zeolite.

6. The catalytic system according to claim 1, wherein at least 90% by volume of the solid particles forming the second catalyst have a diameter larger than 10 m and smaller than 1 mm.

7. The catalytic system according to claim 1, wherein at least 90% by volume of the solid particles forming the second catalyst have a diameter larger than 20 m and smaller than 0.8 mm.

8. The catalytic system according to claim 1, wherein at least 95% by volume of the solid particles forming the second catalyst have a diameter smaller than 5 m.

9. The catalytic system according to claim 1, wherein the equivalent average diameter of the solid particles of the second catalyst is at least 30 m greater than the equivalent average diameter of the solid particles of the first catalyst.

10. The catalytic system according to claim 1, wherein the equivalent average diameter of the solid particles of the second catalyst is at least 50 m greater than the equivalent average diameter of the solid particles of the first catalyst.

11. The catalytic system according to claim 1, wherein the second catalyst is a catalyst for FCC (Fluid Catalytic Cracking).

12. A process for the hydroconversion of heavy oils comprising: feeding the heavy oil to a hydroprocessing step carried out in one or more slurry reactors, using a catalytic system according to claim 1, in the presence of hydrogen or a mixture of hydrogen and H.sub.2S, so obtaining a stream of products in vapour or liquid-vapour phase, and extracting from the bottom of the reactor(s), in continuous or discontinuous, a liquid stream containing non-converted products together with the two catalysts of the catalytic system used, said extracted liquid stream then being separated into a clarified primary stream containing the first catalyst, which is at least partially recycled to the hydroprocessing step, and a stream rich in the second catalyst, which is regenerated in a regeneration step and at least partially recycled to the hydroprocessing step.

13. The process according to claim 12, wherein, before being recycled to the hydroprocessing step, the clarified primary stream is at least partially separated into a clarified secondary stream and a solid stream containing part of the first catalyst, optionally metals present in the heavy oil feed and optionally part of the second catalyst, only said clarified secondary stream being at least partially recycled to the hydroprocessing step.

14. The process according to claim 12, wherein, before being dried, the stream rich in the second catalyst is separated, by addition of a washing solvent, into a liquid stream containing part of the washing solvent and part of the first catalyst, which is recycled to the hydroprocessing step, and into a solid-liquid stream containing part of the solvent and the second catalyst, only said last stream being sent to the regeneration step.

15. The process according to claim 12, wherein the stream rich in the second catalyst is dried before being regenerated in the regeneration step.

16. The process according to claim 12, wherein the hydroprocessing step is carried out at a temperature ranging from 360 to 480 C. and a pressure ranging from 80 to 200 atmospheres.

17. The process according to claim 12, wherein the ratio between the second catalyst and the heavy oil fed to the hydroprocessing step ranges from 1 to 2,000 kg/metric ton.

Description

(1) A preferred embodiment of the present invention is now provided, with the help of FIGS. 1 and 2, which should not be considered as limiting the scope of the invention.

(2) FIG. 1 shows a block scheme of the process.

(3) FIG. 2 shows an example of a process scheme, more detailed with respect to FIG. 1.

(4) The process scheme in FIG. 1 consists of three main sections: a reaction and separation section of the reaction products, a separation section of the solid catalysts and a regeneration section of the second catalyst.

(5) The reaction section (R+S) consists of one or more reactors, all the same, with a parallel configuration if more than one reactor is present, and equipment, process lines and connections between the same which allow the extraction from the reactor(s) and separation of the products (7) from possible liquid or gaseous streams recycled inside the sections, and the extraction from the reactor of a stream containing the two catalysts and the liquid contained in the reactor (11). The extraction of the stream 11 from the reactor can be made in continuous or batch mode.

(6) The following streams are fed in continuous to the reaction section (R+S): the hydrocarbon feedstock (1), a gaseous stream rich in hydrogen (2), the first catalyst (3) or a precursor of the same soluble in the feedstock or in the liquid present in the reactor. All or only some of the different streams can be fed directly to the reactor(s), either totally or only a fraction thereof, mixed before being fed to the reactor(s).

(7) The first catalyst is a solid hydrogenation catalyst dispersed in the reaction medium. The first catalyst forms a slurry system together with the liquid present in the reaction environment.

(8) A stream (15) consisting of the second regenerated catalyst and second fresh catalyst (6), is added to the reaction section. The addition can be made in continuous or batch mode.

(9) The ratio between the stream of catalyst 15 and the hydrocarbon feedstock (cat/oil) can be varied to modulate the effects of catalytic cracking on the overall results of the reaction. It is possible, for example but not exclusively, to vary the productivity, selectivity to products, the characteristics of the distillates and LPG products and residual sulfur and nitrogen content of the liquid products. The products (7) leaving the reaction and separation section, represented, for the sake of simplicity, by a single stream in the scheme, are composed of at least a gaseous stream rich in hydrogen and containing hydrocarbon gases which can be possibly sent to a hydrogen recovery unit, one or more hydrocarbon streams consisting of hydrocarbons liquid under normal conditions and a stream of by-products mainly consisting of hydrogen sulfide, ammonia, water.

(10) Considering only the liquid stream under normal conditions, or the sum of liquid streams under normal conditions, which forms part of the overall stream of products (7) indicated in the scheme, at least 90% by volume is composed of hydrocarbons with a boiling point lower than 380 C.

(11) The stream (11) can be extracted from the reactor in continuous or batch mode. Said stream is sent to the separation section of the solid catalysts (CS). In this section (CS), the second catalyst is separated, obtaining a primary clarified stream and a stream rich in the second catalyst using a suitable technique, or combination of techniques, selected from conventional techniques (sedimentation, filtration, centrifugation, etc.).

(12) The primary clarified stream can be at least partly recycled to the reactor (13), without further separation treatment.

(13) Either all or part of the primary clarified stream can be possibly further separated into a stream containing all or part of the first catalyst (stream rich in the first catalyst) and a secondary clarified stream to be fed to the reactor by means of a second separation treatment, applying conventional techniques or combinations of these (sedimentation, filtration, centrifugation, etc.). In the case of further separation treatment of the primary clarified stream or a part of this, the stream rich in the first catalyst forms the purge stream of the first catalyst (8) and metal contained in the hydrocarbon feedstock fed to the reactor.

(14) The separation operations can be made by mixing to the process streams a suitable solvent (4). The solvent, if used, has the function of improving the separation of the catalysts in the first and/or second separation. The solvent can be a pure organic compound, for example a pure hydrocarbon, or a mixture of suitable organic compounds, for example hydrocarbons. It can also be a stream produced by the process itself or a fraction of the overall stream of products (7). A recovery of the solvent can be carried out in the separation section to generate an internal recycling which limits the consumption of solvent (4). In this case, the stream 4 is a solvent make-up.

(15) In the regeneration section (CR), the stream (12) rich in the second catalyst can be possibly dried, by means of conventional techniques, with a suitable process fluid (14) possibly withdrawn from equipment within the process, before being sent to regeneration. A liquid stream (16) is obtained from the possible drying, which can be sent to the reaction and separation section (R+S) or to the separation section of the catalysts (CS).

(16) In the regeneration section, the second catalyst is regenerated by combustion of the organic compounds deposited on its surface (outer surface of the particles and inner surface of the pores) during the reaction. The combustion is carried out in a regeneration reactor by mixing air (5), possibly heated, with the second catalyst. The combustion eliminates the organic compounds deposited on the second catalyst and produces a gaseous stream (9) mainly composed of CO, CO.sub.2, H.sub.2, H.sub.2O, N.sub.2, SO.sub.2, SO.sub.3, NO.sub.2, NO with the possible entrainment of catalytic solid fines. This stream (9) is treated according to traditional abatement processes of poisons/pollutants common to treatment processes of gaseous effluents from the combustion of organic compounds in general and in particular deposited on solid catalysts.

(17) The regenerated catalyst (17) either partly or totally reacquires its initial activity. An aliquot of the regenerated catalyst can be eliminated (10) to allow the addition of fresh catalyst (6) (catalyst that has not yet been used and regenerated). The ratio of fresh second catalyst/regenerated second catalyst is determined in relation to the activity of the regenerated second catalyst, with respect to the fresh second catalyst, and in relation to the activity to be obtained in the reactor(s) for the conversion of the feedstock.

(18) FIG. 2 indicates an example of a process scheme which illustrates the invention, object of the patent application in question, in greater detail with respect to what is illustrated in FIG. 1.

(19) The feedstock (1) is fed to the reactor (5). A make-up of an oil-soluble precursor of a slurry hydrogenation catalyst, for example an oil-soluble compound of Mo, and/or W, and/or Fe and/or another metal capable of forming a slurry hydrogenation catalyst in a reaction environment, is added to the hydrocarbon stream fed.

(20) A vapour stream (30) leaves the head of the reactor, and passes into the apparatus, or combination of apparatuses (37), and is subsequently cooled in a heat exchanger system (31).

(21) The liquid phase produced (TLP), which represents the total liquid product (33), is separated from the gas phase (34) in one or more gas/liquid separators (32). The apparatus, or combination of apparatuses, (37), is optional, it possibly has the function of controlling the final boiling point of the liquid hydrocarbons produced in the reaction section. This can be obtained for example by washing the vapour stream (30) with a suitable hydrocarbon stream. The fraction of the stream (30) with the highest boiling point is recycled to the reactor together with the washing hydrocarbon stream. If the equipment (37) is not implemented, the control of the final boiling point of the liquid stream produced (33) could be achieved with conventional equipment for the fractionation of hydrocarbon streams. The hydrocarbon fraction with boiling points higher than those desired are then recycled to the reactor (40).

(22) The gaseous stream is treated in a section of the plant (35) suitable for removing the hydrogen sulfide and purging an aliquot of gas (36) to keep the percentage of incondensable hydrocarbons constant in the reaction gas. After being mixed with a stream of make-up H.sub.2 (2), the stream of recycled gas (4) is heated to the desired temperature in an apparatus not illustrated in the drawing before entering the reactor.

(23) A slurry stream (6) containing the first catalyst and second catalyst is extracted from the reactor.

(24) Said current is separated in the separator (7) into a primary clarified stream (13) containing the first catalyst and a stream rich in the second catalyst (9).

(25) The primary clarified stream (13) can be completely recycled (42) to the hydroprocessing reactor (5) or a part of it (14) sent to a further separator (20) in which a secondary clarified stream is separated and recycled (16) to the hydroprocessing reactor (5) and a substantially solid purge stream (15) containing part of the first catalyst and possibly metals contained in the feedstock and possibly part of the second catalyst.

(26) A washing solvent (8) is added to the stream rich in the second catalyst (9) before being sent to an additional solid-liquid separator (12) from which a liquid stream (10) containing the reaction liquid is separated together with a part of the first catalyst and part of the washing solvent which is recycled to the reactor (5) and a solid-liquid stream (11) containing the second catalyst and part of the washing liquid which is dried (19) by means of the drying gas (41).

(27) A stream (17) containing the dried catalyst leaves (19), which is sent to the regenerator (26), in which the catalyst is regenerated with air (24). The regenerated catalyst (27) is recycled, together with the make-up catalyst (29), to the reactor (5) except for a purge (28). A stream of exhausted gas is produced from the regeneration of the catalyst (25).

(28) A stream (18) containing the drying gas and part of the washing solvent also leaves (19), which is cooled in the exchanger (21) and separated in the separator (43) obtaining the drying gas (23) to be recycled to the drying step after heating and a stream containing part of the washing solvent (22) which is recycled to the reactor.

EXAMPLE 1: COMPARATIVE TESTS IN A MICROREACTOR

(29) This example shows how the combined use of two catalysts creates a synergy which allows higher performances than ones obtained with single separate catalysts.

(30) The data provided in Table 1 refer to experimental tests carried out in a plant with a reactor having a total volume of 30 cm.sup.3 (slurry volume in reaction 15 cm.sup.3). The catalytic system was added at the beginning of the test and was maintained in the reactor until the end of the test. The hydrocarbon feedstock was fed in continuous to the reactor by liquid level control. A gaseous stream mainly consisting of hydrogen and incondensable light hydrocarbons, obtained by joining a stream of recycled gas and a stream of make-up H.sub.2, was sent in continuous to the reactor together with the feedstock. The concentration of H.sub.2 in the overall gaseous stream was higher than 97% vol. The flow-rate of the overall gaseous stream to the reactor was 44 Nl/h. The products present in vapour phase were extracted from the head of the reactor. The vapour stream leaving the reactor was cooled and the condensed liquids were collected in a vessel. The tests were carried out at 430 C. and at a partial hydrogen pressure of 125 bar.

(31) Table 1 indicates the characteristics of the feedstock used.

(32) TABLE-US-00001 TABLE 1 characteristics of the feedstock used S wt % 2.56 N wt % 0.58 C wt % 86.0 H wt % 11.4 IBP C. 246 10% C. 359 30% C. 452 50% C. 536 70% C. 620 80% C. 676 Asphaltenes (nC5) wt % 10.8 Ni wppm 32 V wppm 89

(33) Table 2 indicates the results of the tests carried out with three different catalytic systems: the first catalyst alone, the second catalyst alone and the system comprising the two catalysts.

(34) The compositions, dimensions and quantity of the two catalysts are as follows:

(35) First catalyst (Cat-1): molybdenite (MoS.sub.2), obtained from an oil-soluble precursor (Mo-octoate) premixed with fresh feedstock, by heating the mixture to the reaction temperature in the presence of hydrogen. The catalyst is in the form of nanodispersed lamellae. The lamellae are single or stacked with an average stacking degree of less than 4 and have an average equivalent diameter lower than 60 .

(36) The molybdenite is dispersed in the reaction liquid. A fraction or all of the molybdenite can interact with organic solid particles and is deposited on the surface of these. In addition to the dispersed molybdenite, the organic-based solid particles with molybdenite deposited, also participate in the hydrogenating action. Over 95% by volume of the slurry hydrogenation catalyst consists of solid particles with an equivalent diameter lower than 20 m. In the tests indicated in Table 2 carried out in the presence of Cat-1, the quantity of Cat-1 used was obtained with the addition of a quantity of oil-soluble precursor corresponding to 45 g of Mo.

(37) Second catalyst (Cat-2) (weight percentages): 22.8% Si, 25.0% Al, 2.3% La, 0.5% Ti, 0.3% Fe, 0.2% Na, the complement to 100% consisting of O.

(38) Over 90% by volume of the second catalyst consists of solid particles with an equivalent diameter higher than 20 m. In the tests indicated in Table 2 carried out in the presence of Cat-2, the quantity of Cat-2 used was equal to 5.5 g.

(39) TABLE-US-00002 TABLE 2 comparative data with different catalytic systems Cat-1 + Cat-1 Cat-2 Cat-2 Productivity (flow-rate kg/h m.sup.3 130 220 220 feedstock/m.sup.3 reactor) Residual S in the total wppm 3400 9700 2100 liquid product Residual N in the total wppm 2244 382 136 liquid product Fuel Gas wt % 2.5 3.0 2.4 GPL wt % 5.4 6.1 8.9 Light distillates, wt % 11.7 18.7 19.9 C5-170 C. Medium distillates, wt % 57.1 56.4 54.3 170 C.-370 C. Heavy distillates, wt % 22.8 10.1 13.0 370-430 C. coke/insoluble hydrocarbons wt % 0.40 5.78 1.47

(40) The data indicated in Table 2 refer to tests having a duration of 12 hours.

(41) In the example described, it can be observed how the system of the two catalysts allows better results to be obtained with respect to the single systems of separate catalysts as far as the quality of the products is concerned (lower S and N content in the total liquid produced).

(42) Cat-2 alone improves the productivity with respect to Cat-1 alone but increases the formation of coke and/or insoluble organic compounds coke-like. The addition of the hydrogenation catalyst (Cat-1) to Cat-2, not only guarantees a higher quality of the products in terms of residual sulfur and nitrogen, but also reduces the formation of carbonaceous compounds on the cracking catalyst (Cat-2). This allows high catalytic performances of the system to be maintained for a longer period of time.

(43) The separability of the two catalysts, the regeneration of the cracking catalyst and its recycling to the reactor, allow the hydrocracking of heavy feedstocks such as distillation residues, directly to distillates.

EXAMPLE 2: CONTINUOUS TEST IN A PILOT PLANT: PERFORMANCES AND QUALITY OF THE PRODUCTS

(44) The process claimed was also tested on a higher volume reactor. A pilot plant was constructed with a reactor having a total volume of 500 cm.sup.3. The reactor can operate with a slurry volume of 300 cm.sup.3. The pilot plant also allows the addition and extraction of the second catalyst (Cat-2) from the reactor consequently obtaining data representative of the process scheme claimed.

(45) Table 3 indicates the results of a representative test of a set of operative conditions of the process claimed. The data indicated in the present example were obtained at 430 C. and 125 bar of partial hydrogen pressure. During the test, a stream of H.sub.2 having a purity higher than 99% vol. was fed to the reactor at a flow-rate of 50 Nl/h.

(46) The characteristics of the hydrocarbon feedstock fed to the reactor are described in Table 1.

(47) TABLE-US-00003 TABLE 3 Continuous test data in a pilot plant Cat-2/oil g/g 0.10 Cat-2 in the slurry in reaction wt % 35% Mo in the slurry in reaction wppm 4000 Productivity (feedstock(flow-rate/ kg/h m3 136.1 reaction volume) Selectivity to products H.sub.2S wt/wt % 2.5 Fuel Gas wt/wt % 3.6 GPL wt/wt % 15.1 Light distillates (C5-170 C.) wt/wt % 27.6 Medium distillates (170-380 C.) wt/wt % 48.7 Purge/loss in yield wt/wt % 2.5 S in TLP wppm 1550 N in TLP Wppm 110 Overall HDS % 93.7% Overall HDN % 97.5%

(48) In Table 3, it can be observed how the desulfuration and denitrogenation degree are both high. The total liquid obtained (TLP) only contains a few ppm of nitrogen and a very low sulfur fraction. In order to obtain products that respect the specifications relating to the sulfur content, a hydrofinishing treatment which requires a low severity is sufficient.

(49) The results indicated in the example derive from one of the possible configurations (set of operating conditions) the process can have.

(50) The test was set up for converting the feedstock to medium and light distillates. The data refer to steady-state operative conditions of the pilot plant. The experimental test lasted 500 hours. The distribution of the products and productivity can be easily controlled by acting on the operative conditions (cat-2/oil, flow-rate of the gas recycled to the reactor, temperature, total pressure, percentage of catalyst in the slurry present in the reactor, etc.).

(51) FIG. 1 General block scheme of the process

(52) FIG. 2 Example of process scheme