CA2088402C - Hydrocracking process involving colloidal catalyst formed in situ - Google Patents

Abstract

In a hydrocracking process a feed mixture comprising:
heavy oil containing asphaltenes and sulfur moieties; an oil-soluble, metal-containing compound additive (such as iron pentacarbonyl or molybdenum 2-ethyl hexanoate), which additive is operative to impede coalescence of coke precursors and which forms hydrocracking catalytic particles in situ; and, optionally, a hydrocarbon diluent which is a solvent for asphaltenes and which will assist with dispersion of the additive; is mixed for a prolonged period at low temperature (e.g. 80°C - 190°C) in a first vessel or vessels to disperse the additive without significantly decomposing the additive. Preferably, the product mixture is then digested in a second vessel or vessels by mixing it at an elevated temperature (e.g. 250°C), to decompose the additive. The resulting mixture is then heated to hydrocracking temperature (e.g. 450°C) and introduced into a reactor. A
hydrogen flow, sufficient to maintain mixing in the reactor and efficient (e.g. greater than 98%) stripping of light ends (e.g end point boiling 220°C), is provided. The steps of low temperature mixing to achieve dispersion without additive decomposition, preferably digesting to decompose the additive under mixing conditions, and mixing in the reactor with stripping, combine to yield well dispersed, colloidal catalytic particles which function to impede coke evolution and provide high conversion of the high boiling (504°C+) fraction of the feedstock.

Description

2088~02

2 This invention relates to an improved process for

3 reducing coke formation in hydrocracking of heavy oil, wherein

4~ a mixture of the oil, a solvent for asphaltenes, and an oil-soluble metal compound, which inhibits coalescence of coke 6 precursors and forms catalytic particles in situ, is heated and 7 mixed at moderate temperature in a pre-treatment and is then 8 introduced into the reactor, wherein hydrocracking is conducted 9 with a prolific hydrogen flow to ensure mixing and efficient light end stripping.

12 The present invention was originally developed in 13 connection with hydrocracking of a heavy hydrocarbon feedstock 14 high in content of asphaltenes and sulfur moieties. More particularly, the feedstock tested was vacuum tower bottoms 16 ("VTB") produced from distillation of bitumen. The invention-is 17 not limited in application to such a feedstock; however, it will 18 be described below with specific respect to it, to highlight the 19 problems that required solution.
Bitumen contains a relatively high proportion of 21 asphaltenes. When the bitumen or its vacuum tower bottoms are 22 hydrocracked, the asphaltenes produce coke precursors, from which 23 adherent solid coke evolves. The coke deposits on and adheres 24 to the surfaces of the reactor and downstream equipment. In addition, since part of the feedstock is consumed in the 26 production of coke, the conversion of the feedstock to useful 27 products is reduced.

208~402 -1 The present assignee is an Alberta government research 2 agency which was given a mandate to foster improvements in the 3 upgrading of bitumen and other heavy oils. Realizing the 4 conversion limitation and operating problems that coke deposition inflicts, it initiated a research project to investigate the 6 mechanisms of coke formation and to look for improvements that 7 might be applied commercially.
8 The present processes were generated as a result of 9 this work. The research involved a progression of concepts and experimental discoveries that came together to yield a process 11 characterized by a high order of conversion coupled with reduced 12 deposition of adhesive coke and reduced production of coke.
13 Searches and prosecution of the parents of this 14 application have identified the following relevant prior art:
U.S. 4,294,686 (Fisher et al) teaches that, when liquid 16 hydrogen donor oil is used along with hydrogenation in connection 17 with hydrocracking of bitumen vacuum tower residua, coke 18 deposition is allegedly eliminated.
19 However the present assignee and the assignee of the above cited patent jointly conducted a large scale hydrocracking 21, test on bitumen residue using a liquid hydrogen donor process.
22 This test encountered serious coke production problems. It 23 appears that hydrocracking high asphaltene content feed such as 24 bitumen residue requires more than the presence of liquid hydrogen donor oil alone.
26 U.S. 4,455,218 (Dymock et al) teaches use of Fe(CO)s as 27 a source of catalyst formed in situ for hydrocracking heavy oil 28 in the presence of H2. The reaction is allegedly characterized 29 by elimination of coking.

-1 ~ U.S. 4,485,004 (Fisher et al) teaches hydrocracking heavy 2 oil in the presence of hydrogen, hydrogen donor material, and 3 catalyst comprising particulate Ni or Co on alumina.
4 U.S. 4,134,825 (Bearden et al) teaches forming solid, non-colloidal catalyst in situ in heavy oil using trace amounts of 6 Fe added in the form of an oil-soluble compound such as iron 7 carbonyl. The metal compound is added to the oil and heated to 325-8 415C in contact with hydrogen to convert it to a solid, non-9 colloidal, catalytic form. This catalyst is then used in hydrocracking the oil and it is stated that coke formation is 11 inhibited.
12 U.S. 4,592,827 (Galliasso et al) teaches injecting an 13 oil-soluble, catalyst precursor Mo compound and water into a heavy 14 oil stream moving to a heater, wherein the mixture is heated to a temperature of 230C - 420C to effect decomposition of the Mo 16 compound. The heater product is then introduced into a 17 hydrocracking reactor.

19 In one aspect of the research work underlying the present invention, coke was produced by hydrocracking a mixture of diluent 21 and bitumen vacuum tower bottoms ("VTB") and the coke composition 22 was studied microscopically. It was found that at progressive 23 stages of the evolution of the coke precursors into adherent solid 24 coke, there were present different species of isotropic and anisotropic submicron and micron-sized spheroids. We have 26 identified these species with the following labels:

2088~02 1 ~ - isotropic sphere;
2 - basic isotropic particle;
3 - isotropic agglomerates;
4 - anisotropic spheres;
- basic anisotropic particles;
6 - anisotropic fine mosaic particles;
7 - anisotropic coarse mosaic particles; and 8 - anisotropic agglomerates.
9 It was further experimentally discovered:
- That the evolution of the coke precursors into coke 11 involved a coalescence process from the minute 12 isotropic species to the larger species; and 13 - That if the coalescence process was inhibited with 14 the major portion of the precursors remaining in the isotropic and anisotropic agglomerate states, 16 then the deposition of adherent and solid coke was 17 significantly reduced and even virtually 18 eliminated.
19 These observations led to seeking out and identifying compatible additives that would interfere with the coalescence 21 process and assist in reaching an end where, if any coke was 22 present, it would be present predominantly in the form of 23 agglomerate species, preferably in the isotropic state. It 24 was postulated that a well-dispersed, oil-soluble, metal compound might be used to react in situ with sulfur moieties of the bitumen 26 VTB to produce colloidal, catalytic particles having wetting 27 characteristics that would enable the colloidal particles 1 to collect at the surfaces of the precursor spheroids and inhibit 2 the spheroids from coalescing. Furthermore, it was postulated 3 that an appropriate diluent might advantageously be used to 4 assist in dispersing this additive and in solubilizing the

5~ processor spheroids.

6 It was experimentally discovered that:

7 - if an oil-soluble Mo, Fe, Ni or Co compound

8 additive, for example iron pentacarbonyl or

9 molybdenum 2-ethyl hexanoate, which was decomposable at hydrocracking temperature and 11 which was capable of forming particles in situ 12 that were catalytic with respect to hydrocracking, 13 was mixed with heavy oil (and preferably with a 14 diluent) at a moderate elevated temperature, that was in the range 50 - 300C, preferably 80 - 190C
16 and which was less than the decomposition 17 temperature of the additive, for a period of time 18 sufficient to ensure substantially uniform 19 dispersion of the additive throughout the oil and association of the additive with the asphaltenes;
21 and 22 - if the resultant mixture was heated to 23 hydrocracking temperature and reacted in a 24 reactor;
then the postulated mechanism appeared to take place.
26 Stated otherwise, inclusion of the additive in the 27 reaction mixture undergoing hydrocracking did have the desired 28 effect of reducing the deposition of adherent solid coke, 29 provided that the additive was well dispersed in the manner 1 described. Examination of cooled solid samples after 2 hydrocracking showed that the major portion of coke produced 3 under these conditions was in the form of isotropic agglomerates.
4 It is believed that at reactor temperature this coke would have taken the form of minute spheroids of coke precursor. Chemical 6 analysis of the sample coke indicated that additive metal sulfide 7 was associated therewith in a significant amount and that most 8 of the metal sulphides were colloidal, typically being less than 9 0.1 nanometers in dimension.
In summary, in accordance with the invention an oil-11 soluble, decomposable metal compound of the type described is 12 firstly well dispersed by mixing, preferably with the aid of a 13 diluent, at moderate elevated temperature (e.g. 100C) in the 14 heavy oil and becomes associated with the asphaltenes. When the mixture is then subjected to hydrocracking temperature, colloidal 16 metal sulfide particles are produced which are thought to 17 accumulate at the surfaces of or inside spheroids rich in coke 18 precursors and interfere with their coalescence. Upon completion 19 of hydrocracking the coke precursors are found to be largely transformed into isotropic agglomerates. It is further found 21 that the deposition of adhesive solid coke is significantly 22~ reduced.
23 Subsequent experimental work has shown:
24 - That if the additive is added to the oil at the reactor inlet or at the pre-heater immediately 26 upstream of the reactor, so that prolonged mixing 27 at a proper moderate temperature is not carried 28 out, then hydrocracking is characterized by coke 29 fouling;

`_ 208840~
1 - That if prolonged mixing is done, but at a 2 temperature that is greater than the decomposition 3 temperature of the additive, then the catalytic 4 particles produced are relatively large (e.g. 5 microns to 4mm) and non-colloidal - in this case, 6 coke fouling occurs;
7 - That if bitumen is the oil used, it usually 8 contains sufficient solvent for asphaltenes, so 9 as not to require the addition of diluent or solvent; and 11 - That a preferred procedure involves:
12 - mixing the oil, additive, and preferably an 13 asphaltene solvent, at a temperature in the 14 range 80 - 190C, which temperature is less than the decomposition temperature of the 16 additive, for sufficient time to uniformly 17 disperse the additive, 18 - then digesting the product with mixing at an 19 increased temperature which is greater than the additive decomposition temperature but 21 less than hydrocracking temperature, to 22 decompose the additive while maintaining it 23 in a well dispersed state; and 24 - then heating the mixture to hydrocracking temperature and introducing it into the 26 reactor.

20s~so2 1 The test as to whether the dispersion and digestion 2 steps have been properly conducted for sufficient time, with 3 sufficient agitation and at an appropriate temperature is 4 affirmatively answered if the additive is converted into catalytic metal sulphide particles of colloidal size.
6 When the phrase "decomposition temperature" is used in 7 this specification, it is intended to mean that temperature at 8 which less than about 10% by weight of the additive decomposes 9 during the course of the dispersion step.
Turning now to a second approach that was explored, it 11 was well known that asphaltenes precipitate when pentane is 12 added. Upon considering this known fact, applicants conceived 13 the notion of emphasizing the removal of light ends during 14 hydrocracking to determine the effect on coke formation.
Experimental work was therefore initiated to determine the effect 16 of stripping light ends (Boiling point ("B.P.") <220~C) from the 17 hydrocracking zone. Experimentation showed that coke formation 18 was reduced when light ends were consistently removed during 19 hydrocracking. To improve this, it appeared desirable to apply mixing to the mixture during hydrocracking. Mixing would have 21 the further attribute of maintaining dispersion of the additive 22 metallic component.
23 To further elaborate on the foregoing, it had been 24 noted that coke formation is associated with phase separation.
It was postulated that, if the coke precursors became richly 26 concentrated in a distinct phase, then the coke formation process 27 would proceed rapidly and quantitatively. To impede this, it 28 appeared desirable to strip light ends and reduce phase 29 separation.

Therefore, as a second preferred aspect of the invention, 2 a tube reactor is used, preferably substantially free of internals, 3 and the hydrogen flow through the reactor is prolific and is 4 arranged to achieve mixing throughout the length and breadth of the reaction zone. The prolific hydrogen flow functions to strip light 6 ends from the zone. Preferably, mixing and stripping is 7 accomplished by ensuring that the hydrogen flow is in the range of 8 8,000 - 20,000 SCF/BBL and is sufficient to provide the following 9 Peclet Number ("P.N.") regime in the reactor chamber:
Liquid:
11 axial P.N. = less than 2.0, preferably less than 1.0, most 12 preferably less than about 0.01 13 Gas:
14 axial P.N. = more than 3.0, preferably greater than 5Ø
In another thrust at reducing phase separation, a diluent 16 for solubilizing the asphaltenes was preferably added to the 17 reaction mixture. The diluent (or solvent) was a hydrocarbon 18 fraction having a B.P. of about 220-504C, preferably 220-360C. The 19 solvents used successfully had a high cot~value, as defined in the paper "Oil Sands Composition and Behaviour" by Jean Bichard, (1987) 21 page 2 - 30 published by Alberta Oil Sands Technology and Research 22 Authority, Edmonton, Alberta, Canada.
23 The preferred diluent contained cyclic moieties that are 24 either aromatic or alicyclic but not aliphatic. For example, n-hexane was not a good diluent but cyclohexane, decalin and benzene 26 were good diluents, the last being preferred. However, in the 27 hydrocracker, less expensive than these diluents are the 220C to 28 360C heavy aromatic fraction of the hydrocracker gas-1 oil or the same fraction of coker gas-oil that has not been 2 stabilized.
3 It was hoped that the diluent would in addition 4 function usefully as a liquid hydrogen donor and, in combination with the produced colloidal metal sulfide (which is catalytic in 6 nature) and the plentiful hydrogen, would create a regime that 7 would be favourable to high conversion of the high boiling (e.g.
8 greater than 504C+) fraction and low coke deposition.
9 Experimental runs indicated that when the combination of diluent addition, well dispersed additive addition, and light ends 11 stripping with hydrogen was practised in the context of 12 hydrocracking of heavy oil containing asphaltenes and sulfur 13 moieties, exceptionally high conversion of the high boiling 14 hydrocarbons could be achieved, together with virtually no adhesive coke deposition. When the diluent was omitted from the 16 combination, or the diluent was not a good solvent of asphaltenes 17 or when stripping of light ends was not sufficient, experimental 18 runs showed significant coke deposition. It is to be understood 19 however that diluent addition is only a preferred feature.
In summary then, dispersion is therefore preferably 21 achieved in a distinct step prior to heating to additive 22 decomposition or hydrocracking temperature, by mixing the heavy 23 oil plus additive plus diluent mixture in means such as a 24 continuous flow, stirred tank mixer, the mixture being maintained at a temperature that is in the range 50 - 300C, preferably 80 26 - 190Cj but less than the temperature at which the additive 27 decomposes significantly, the residence time being sufficient to 28 ensure that the additive is substantially uniformly dispersed 29 throughout the mixture. It is preferable also that two or more ~ 2G88~Q2 continuous flow, stirred tank reactors in series be employed for 2 this mixing.
3 Broadly stated, in one aspect the invention comprises 4 a process for preparing a heavy hydrocarbon feedstock for hydrocracking, said feedstock containing asphaltenes and sulfur 6 moieties, comprising: mixing the feedstock and an oil-soluble 7 metal compound additive at a temperature that is in the range 8 50C to 300C and less than the decomposition temperature of the 9 additive, to produce a product mixture; said additive being selected from the group consisting of molybdenum, iron, nickel 11 and cobalt compound additives, said additives being adapted to 12 decompose and react, when heated to hydrocracking temperature, 13 with sulfur moieties in the feedstock to form metal sulfide 14 particles that are catalytic for hydrocracking; said mixing being conducted for sufficient time to cause the additive to be 16 sufficiently dispersed so that the metal sulfide particles formed 17 upon hydrocracking are colloidal in size.
18 In another broad aspect, the invention comprises a 19 process for hydrocracking a heavy hydrocarbon feedstock containing asphaltenes and sulfur moieties, comprising: mixing 21 the feedstock and an oil-soluble metal compound additive at a 22 temperature that is in the range 50C to 300C and less than the 23 decomposition temperature of the additive, to produce a product 24 mixture; said additive being selected from the group consisting of molybdenum, iron, nickel and cobalt compound additives, said 26 additives being adapted to decompose and react, when heated to 27 hydrocracking temperature, with sulfur moieties in the feedstock 28 to form metal sulfide particles that are catalytic for 29 hydrocracking; said mixing being conducted for sufficient time 208~02 1 to cause the additive to be sufficiently dispersed so that the 2 metal sulfide particles formed upon hydrocracking are colloidal 3 in size; then further heating the product mixture to 4 hydrocracking temperature; introducing the heated product mixture into the chamber of a hydrocracking reactor; temporarily 6 retaining the heated product mixture in the chamber, continuously 7 passing sufficient hydrogen through substantially the breadth and 8 length of the chamber contents to maintain mixing of the chamber 9 contents and stripping of light ends, and removing unreacted hydrogen and entrained light ends from the chamber and producing 11 pitch containing colloidal metal sulfide.
12 In still another preferred aspect of the invention, 13 pitch is recycled from the downstream hot separator to the 14 reactor, to improve the conversion. In a more preferred aspect, the separator product, containing heavy distillates and pitch, 16 is distilled to separately recover pitch; in conjunction with 17 this, fresh feed is added to the separator product stream 18 entering the distillation vessel, to reduce the separation of 19 asphaltenes from the pitch. The addition of fresh oil is operative to reduce or prevent the production of adhesive 21 asphaltene lumps, which would otherwise appear in the 22 distillation vessel.

208~402 1 In a preferred embodiment, the invention involves the 2 following units and conditions in the hydrocracking operation, 3 having reference to Figure 44:
4 - Thermal hydrocracker:
operating temperature - 430 - 460C, 6 preferably 450 7 455C;
8 operating pressure - 1500 - 3000 psig, 9 preferably about 2000 psig;
11 - High pressure hot separator:
12 operating temperature - greater than about 13 350C;
14 operating pressure - reactor pressure;
_ Adding 5 - 15% fresh feed (heavy oil) to the 16 underflow from the hot separator;
17 - Low pressure hot separator:
18 operating temperature - l e s s t h a n 19 temperature of hot separator;
21 operating pressure - 100 to 500 psig;
22 - Recycling 0 to 95% pitch from the low pressure 23 hot separator to the reactor.

~ 20~8~02 1~ DESCRIPTION OF THE DRAWINGS
2 Figure 1 is a photographic representation showing the 3 nature of isotropic sphere(s) and basic isotropic particles (b),4 magnified 1650X;
Figure 2 is a photographic representation showing the 6 nature of anisotropic spheres (s) and basic anisotropic particles 7 (b), magnified 1650X;
8 Figure 3 is a photographic representation showing the 9 nature of isotropic agglomerates (g) along with anisotropic solids (a) and iron sulfide particles (S), magnified 1650X.
11 Here, the iron sulfide particles originated from the feedstock.
12 The coke sample studied by the microscope was generated from 13 thermal test without any iron additive (see Figure 17);
14 Figure 4 is a photographic representation showing the nature of anisotropic agglomerates (a), anisotropic fine mosaic 16 (f), and anisotropic coarse mosaic (c), magnified 1650X;
17 Figure 5 is a photographic representation showing 18 anisotropic coke particles having grown via the coalescence of 19 smaller anisotropic spheres (c), magnified 1650X;
Figure 6 is a photographic representation showing 21 isotropic coke particles having grown via the coalescence of 22 smaller isotropic spheres (s), magnified 1650X;
23 Figure 7 is a photographic representation of the 24 reactor baffle after run CF-30 set forth in Example I (Table 2);
Figure 8 is a photographic representation of the 26 reactor baffle after run CF-9 set forth in Example I (Table 2);
27 Figure 9 is a photographic representation of the 28 reactor baffle after run CF-31 set forth in Example I (Table 2);

2~88402 1 Figure 10 is a bar chart setting forth coke composition 2 for runs CF-9, CF-31 and CF-30;
3 Figure 11 is a photographic representation of the 4 reactor baffle after run CF-A3 set forth in Example II (Table 3);
Figure 12 is a bar chart setting forth coke composition 6 for runs CF-A3 and FE-1 set forth in Example III (Table 4);
7 Figure 13 is a photographic representation of the 8 reactor baffle after run FE-1;
9 Figure 14 is a photographic representation of the coke particles from run FE-1, which were mostly isotropic agglomerates 11 (A) associated with iron sulfides. Isotropic spheres (S) were 12 trapped among the agglomerates;
13 Figure 15 is a photographic representation of the coke 14 particles from run FE-1 showing isotropic spheres (S) which were effectively prevented from growing into basic isotropic particles 16 by the iron derivative;
17 Figure 16 is a photographic representation of the 18 reactor baffle after run CF-38 set forth in Example IV;
19 Figure 17 is a plot showing nitrogen flowrate versus coke production for Example V;
21 Figure 18 is a phase diagram for Example V;
22 Figure 19 is a plot showing pressure profiles for runs 23 involving different additives set forth in Example VIII;
24 Figure 20 is a bar plot showing hydrogen consumed for various runs set forth in Example VIII;
26 Figure 21 is a bar chart setting forth coke composition 27 for a number of the runs set forth in Example VIII;

1 Figure 22 is a photographic representation of coke from 2 run CF-40, showing mostly a continuous sheet of basic isotropic 3 particles (B), magnified 1650X - see Example VIII;
4 Figure 23 is a photographic representation of the reactor baffle after run CF-40;
6 Figure 23A is a photographic representation of the 7 reactor coil after run CF-41;
8 Figure 24 is a plot derived from Mossbauer spectroscopy 9 analysis of catalyst produced in accordance with the invention -see Example III (Table 4);
11 Figure 25 is a simplified schematic of a pilot circuit 12 used to carry out the experimental runs reported on in Example 13 IX, with conditions shown thereon;
14 Figure 26 is a plot of pressures recorded between the reactor and separator during run TRU 101 reported on in Example 16 IX;
17 Figure 27 is a plot of pressure differentials taken 18 across the reactor during run TRU 101 of Example IX;
19 Figure 28 is a plot of pressures recorded at the entrance to the reactor during run TRU 101 of Example IX;
21 Figure 29 is a plot of pressure differentials taken 22 across the reactor during run B3-1 of Example IX;
23 Figure 30 is a plot of various pressures taken at 24 different points along the circuit during run B3-1 of Example IX;
Figures 31 and 32 are simplified schematics of the 26 segments of the pilot circuit used to carry out the experimental 27 runs reported on in Example X, with conditions shown thereon;
28 Figure 33 is a simplified schematic of the pilot 29 circuit used to carry out the experimental run carried out in Example XI;

2088~02 1 Figure 34 is a plot of pressure logs for the run of 2 Example XI;
3 Figure 35 is a simplified schematic of the pilot 4 circuit used to carry out the experimental runs reported on in Example XII, with conditions shown thereon;
6 Figure 36 is a plot of differential pressures across 7, the reactor, pressures at the heater, and digester temperature 8 of the circuit used for Example XII;
9 Figures 37(a) to 37(f) is a series of IR spectra demonstrating the effect of change in temperature in the mixing 11 step for Example XIX;
12 Figure 38 shows asphaltene conversion versus pitch 13 conversion for experiments providing pitch conversions between 14 42 and 99% for Example XVII;
Figure 39 is a simplified schematic of the once-16 through pilot circuit used in the first stage of run R 2-1, 17 described in Example XX, with conditions shown thereon;
18 Figure 40 is a simplified schematic of a modified form 19 of the pilot circuit of Figure 39, indicating the recycle of pitch which was practised in the second stage of run R 2-1;
21 Figure 41 is a simplified schematic of a further 22 modified form of the pilot circuit of Figure 40, indicating the 23 recycle of pitch and addition of feed, which was practised in the 24 third stage of run R 2-1;
Figure 42 is a plot of differential pressure across the 26 reactor during run R 2-1;
27 Figure 43 is a plot of pressures taken at different 28 indicated points along the circuit during run R 2-1; and 2088~02 1 Figure 44 is a confocal micrograph depicting a particle 2 from run R 2-1 in a stage of fusion or coalescence of the outer 3 components trapping several particles in the central area. Sub-4 micron size inorganic components of high reflectance are clearly distinguished in several areas of the particle (Reflected mode, 6 647 nm, oil immersion, 2500X).

8 The feedstock to the process is heavy oil. This term 9 is intended to include bitumen, crude oil residues and oils derived from coal-oil co-processing that contain asphaltenes and 11 sulfur moieties. A typical feedstock could be vacuum tower 12 residues derived from Athabasca bitumen.
13 The feedstock is mixed with a catalyst precursor 14 additive and, preferably, a hydrocarbon solvent for asphaltenes.
The additive is an oil-soluble metal compound adapted 16 to decompose at hydrocracking temperature and to react with 17 sulphur moieties in the oil to form, in situ, metal sulphide 18 particles that are catalytic for hydrocracking and which function 19 to impede coalescence of coke precursors. The metal can be selected from the group consisting of Fe, Ni, Co and Mo.
21 Preferred compounds are iron pentacarbonyl and molybdenum 2-22 ethyl hexanoate.
23~ The hydrocarbon solvent for asphaltenes is preferably 24 a recycled stream having a boiling point in the range 220C -504C, preferably 220 - 360C, and preferably having a high cot 26 e value, as defined in the paper previously mentioned "Oil Sands 27 Composition and Behaviour" by Jean Bichard.

1 ~ The preferred amount of additive added is in the range 2 0.0001 - 5 wt.%, based on the weight of the feedstock. Preferably, 3 we use about 0.002 - 0.5 wt. %. Typically, for the specific 4 preferred compounds we use:
molybdenum 2-ethyl hexanoate - 0.01 wt. %
6 molybdenum naphthanate - 0.007 wt. %
7 iron pentacarbonyl - 0.05 wt. %.
8 With respect to the solvent for asphaltenes, some 9 feedstock (e.g. crude Athabasca bitumen) may already contain sufficient solvent so as to not require discrete solvent addition.
11 But in the cases where solvent addition is desirable, the preferred 12 weight ratio of solvent to feedstock is in the range 1:10 to 3:1, 13 preferably 1:4 to 1:1.
14 Mixing can be accomplished in a continuous flow, heated, stirred tank mixer or by pumping the mixture from a tank, through a 16 preheater, and back to the tank. In any event, mixing is conducted 17 in accordance with the following conditions:
18 mixture temperature: within the range 50 - 300C, 19 preferably 80 - 190C, and less than that temperature at which 21 more than about 10 wt. % of the 22 additive is decomposed during the 23 mixing step;

20~8~02 retention time: sufficient to ensure that the 2 additive is substantially 3 uniformly dispersed throughout 4 the oil and is associated substantially at the molecular 6 level with asphaltene.
7 The process has become focused on use of iron 8 pentacarbonyl and molybdenum 2-ethyl hexanoate as the preferred 9 additives.
In the case of the iron pentacarbonyl, a relatively 11 large amount of it needs to be used to achieve satisfactory 12 conversions. However, if too much is used, it tends to form iron 13~ products that build up in the piping and result in blockages and 14 pressure surges. To properly use iron pentacarbonyl, we have 15 found it desirable to first well disperse it in the oil at 16 moderate temperature by mixing and then decompose the additive 17 in a higher temperature digestion step, again under mixing 18 conditions to keep the catalyst precursor dispersed.
19 By way of a typical example, for the case of using iron 20 pentacarbonyl as the additive and 504C+ bitumen vacuum tower 21 residuum as the oil, we use the following conditions:
22 additive amount: 250 ppm (based on oil) 23 solvent: 200 - 504C bitumen 24 fraction solvent/oil ratio: 1:1.2 26 dispersion time: 20 minutes 27 dispersion temperature: 110C

2~88~02 1 dispersion vessel: 1 liter tank with 2 impellor operating at 800 3 rpm 4 digestion time: 60 minutes digestion temperature: 250C
6 digestion vessel: 3.8 liter tank with 7 impellor operating at 8 1000 rpm.
9 By way of a typical example for the case of using molybdenum 2-ethyl hexanoate as the additive with 430C+ bitumen 11 vacuum tower residuum as the oil, we use the following 12 conditions:
13 additive amount: lS0 ppm 14 solvent: 430 - 524C fraction solvent/oil ratio: 1:2 16 dispersion time: 24 hours 17 dispersion temperature: 100C
18 dispersion vessel: 75 litres 19 digestion time: 60 seconds no digestion 21 The mixture is then rapidly heated to about 450C -22 455C and introduced into the hydrocracking reactor. In the 23 reactor, hydrogen is supplied at a rate sufficient to satisfy the 24 Peclet No. regime previously described, to ensure that mixing of the reactor charge occurs and that light ends or volatiles are 26 stripped from the charge.

2088~02 1 By way of an example, we have typically used the 2, following conditions in hydrocracking the mixture produced by the 3 pilot plant when using the mixing treatments previously 4 described:
reactor size: 87" long x 1.77" diameter 6 reactor pressure: 1500 psig 7 reactor temperature: 455C
8 H2 rate: 68 l/min.
9 mixture rate: 2405 g/hr.
distillate flow rate: 1082 g/hr.
11 pitch flow rate: 1322 g/hr.

12["Conversion" is determined by calculating:

13100% (524C+ fraction in 524C+ fraction out) 14(524C+ fraction in) where the 524C+ fraction includes coke but is mineral free.]
16In the case of the Fe(CO)s additive run, pilot plant 17 results based on the typical conditions described showed a 18typical conversion of 90% of the 524C+ fraction. The pitch was 19 analyzed and found to contain colloidal iron sulfide. Coke production was about 1%.
21In the case of the molybdenum 2-ethyl hexanoate run, 22~ pilot plant results based on the typical conditions described 23showed a typical conversion of 90% of the 524C fraction. The 24 pitch contained colloidal molybdenum sulfide. Coke production was about 0.3%.
26The invention as described will now be supported by 27 examples and data developed experimentally.

- 20~40~
EXAMPLES I - V
2 The following examples I - V are included to illustrate 3 some of the features investigated in the early work underlying 4 the present process.
All the tests in examples I - V were performed in a 1 6 litre, baffled, stirred autoclave. The charge, comprising 7 Athabasca vacuum tower bottoms (504C+) as feedstock, solvent 8 (otherwise referred to as "diluent") and additive (if used), was 9 introduced into the autoclave. The autoclave was sealed, purged

10 free of air, pressurized with nitrogen or hydrogen and heated to

11 430C. The reactor was stirred at 800 rpm, wlth a reaction

12 temperature of 430C and a reaction time of 105 minutes.

13 Properties of the Athabasca vacuum tower bottoms (VTB)

14 are given below.
wt. %
16 C 81.76 17 H 9.51 18 S 6.23 19~ N 0.78 API @ 16C: 2.43 21 IBP 504C.
22 Table 1 herebelow provides the composition (wt. %) of 23 diluents used during the experimental procedures.
24 It is noteworthy that according to the relative content 25 of condensed dicycloparaffins and benzocycloparaffins, diluent 26 B has the most hydrogen donor capability and diluent C has the 27 least.

2~8~4~2 2 Diluents 3 Hydrocarbon Type A B C
4 Paraffins 13.02 16.38 13.10 Uncondensed 6 Cycloparaffins 7.32 6.29 5.51 8 Condensed 9 Dicycloparaffins 5.20 13.03 3.80 Condensed 11 Polycycloparaffins 0.49 1.27 0.15 12 Alkylbenzenes 18.07 15.25 11.25 13 Benzocycloparaffins32.29 37.54 20.36 14 Benzodicycloparaffins4.77 3.80 5.53 Naphthalenes 15.86 6.11 19.49 16~ Naphthacycloparaffins1.61 0.26 7.73 17 Fluorenes 0.82 0.00 6.21 18 Phenathrenes/Anthracene 0.61 0.00 6.18 20This example illustrates the effect of different 21 diluents. The autoclave was charged with 109 grams of bitumen 22 and 220 grams of diluent A, B or C. A nitrogen overpressure of 23 0.55 MPa was applied and the contents were thermally cracked at 24430C for 105 minutes.
25The results of the tests are shown in Table 2. The 26 reactor was opened and Figures 7, 8 and 9 show the coke deposited 27on the baffles for experiments CF-30, CF-9 and CF-31, 28 respectively.
29It is noteworthy that experiment CF-31 produced as much coke as experiment CF-9 but that the coke was most easily 31 dislodged from the baffles and reactor surfaces. Moreover, `_ 208~402 1 although experiment CF-31 produced nearly twice as much coke as 2 experiment CF-30, the coke was most easily dislodged. The 3 surfaces of the reactor and baffles of experiment CF-31 were 4 least fouled.
The coke from the three experiments was examined 6 microscopically and the results are shown in Figure 10. It was 7 noted that when the agglomerate content (which was anisotropic) 8~ was relatively high (Experiment CF-31), the coke deposition and 9 adhesion was least intense in spite of the fact that diluent C
had the least hydrogen donor capability.

12 Test conditions: 430C, 105 min., 800 rpm,0.55 MPa 13 initial N2 pressure 14 Diluent to Vacuum Tower Bottoms ratio is 2:1 Experiment No. CF-30 CF-9 CF-31 16 Diluent type B A C
17 Yield (wt. % vacuum tower bottom corrected for diluent) 18 H2 0.21 0.07 0.08 19 C~ - C4 10.3 10.8 14.8 C5 - 200C 42.3 57.1 55.2 21 200 - 360C -8.6 -37.2 -43.5 22 360 - 504C 22.8 26.5 30.6 23 504C+ (coke free) 26.3 33.8 34.6 24 Coke 4.3 7.7 7.7 Conversion to 504C & coke 73.7 66.2 65.4 26 Mass Balance 98.2 97.3 96.9 ` 26 2~8~02 2 This example illustrates the effect of hydrogen 3 overpressure.
4 The experimental conditions and results are shown in Table 3. Experiment CF-A3 is compared with experiment CF-9.
6 Figure 11 shows coke deposition on the baffles for 7 experiment CF-A3. Compared to Experiment CF-9 (Figure 8), the 8 coke yield and deposition of experiment CF-A3 was least.
9 Figure 12 shows results from a microscopic examination of the coke obtained from experiment CF-A3. It is to be compared 11 with those results shown in Figure 10 for experiment CF-9. The 12 results are similar.
13 In both experiments, over 80% of the coke components 14 were of the anisotropic type. The agglomerate concentration for experiment CF-A3 was not significantly more than that of 16 experiment CF-9.
17 This example teaches that abundance of hydrogen alone 18 does not neutralize the adhesiveness of the coke precursors nor 19 does it selectively modify the coke composition.

- 2Q88~2 3 Diluent A A
4 Yield (wt. % VTB), corrected for diluent H2S 0.07 2.2 6 Cl - C4 10.8 11.6 7 Cs - 200C 57.1 44.0 8 200 - 360C -37.2 -18.0 9 360 - 504C 26.5 30.1 504C+ (coke free) 33.8 27.7 11 Coke 7.7 3.1 12 Conversion to 504C & coke66.2 72.3 13 Mass Balance 97.3 98.5 14 Selectivity to Cs - 504C 77.6 Conditions: CF-9: 430C, 105 min., 800 rpm, 0.55 MPa N2 initial 16 pressure, 17 diluent: VTB ratio 2:1 18 Conditions: CF-A3 430C, 105 min., 800 rpm, 6.8 MPa H2 initial 19 pressure diluent: VTB ratio 2:1 22 This example illustrates that coke containing much 23 agglomerate is not adhesive.
24 The results and conditions of experiments CF-A3 and FE-1 are shown in Table 4.
26 Figure 13 shows no coke deposited on the baffles for 27 experiment FE-1. Compared to Experiment CF-A3 (Figure 11), the 28 coke yield and deposition of Experiment FE-1 was least.

20~8402 _ 1 The coke from Experiment FE-1 was observed to be minute 2 particles loosely settled in the bottom of the reactor.

4 Test conditions: 430C, 105 min., diluent/vtb - 2:1, 800 rpm 6 Experiment No. CF-A3 FE-1 7 Diluent A A
8 Gas/Pressure (MPa) H2/6.8 H2/6.8 9 Additive (metal, wt. % VTB) - Fe/0.5 10 Yields on VTB, wt. %, corrected for diluent 11 H2S 1.2 12 Cl - C4 11.6 6.6 13 C5 - 200C 44.0 37.7 14~ 200 - 360C -18.0 -9.1 360 - 504C 30.1 31.2 16 504C+ (coke free) 27.7 31.4 17 Coke 3.1 1.6 18 Figure 12 shows results from a microscopic examination 19 of coke obtained from experiments CF-A3 and FE-1. The results are very different. The coke from experiment FE-1 is over 80%
21 isotropic agglomerate.
22 Figures 14 and 15 for Experiment FE-1 showed that solid 23 particles were all loosely associated with one another. Coke 24 composition showed that over 97% of the components were of the isotropic type - see Figure 12. Isotropic agglomerates accounted 26 for 80% of the coke composition.

2a8~4~2 This data for experiment FE-1 indicated that the 2 adhesiveness of the coke precursors was effectively neutralized 3 by the highly dispersed iron compound. Where isotropic spheres 4 were concentrated (see Figure 15), the isotropic agglomerates 5 effectively prevented the spheres from coalescing into basic 6 isotropic particles.
7 It is noteworthy also, that additive present as iron 8 sulphide amounts to approximately 1/3 the weight of the coke but 9 is not so evident.

EXAMPLE IV
11 This example further illustrates that the choice of 12 diluent is desirable.
13 The experiment CF-38 was done according to the teaching 14 of U.S. 4,455,218 (Dymock et al). The experimental conditions were identical to those shown in Table 4 for experiment FE-1.
16 Whole Athabasca bitumen was used instead of Athabasca VTB and no 17 diluent was added. The whole bitumen contained about 60 wt. %
18 hydrocarbon boiling at temperatures greater than 504C. 0.5%
19 (metal) of iron pentacarbonyl was added on the basis of equivalent 504C+ content in the bitumen.
21 The coke yield was 7.9% (504C+ basis) and this coke 22 adhered very strongly to surfaces of the reactor and baffles.
23 Figure 16 shows the coke deposited on the baffles.

This example illustrates the effect of the rates of 26 continuously removing highly volatile components from the 27 reacting fluids.

_ 2Q~40~
1 The one liter autoclave was fitted with a dip tube for 2 sparging N2 or H2 into the reacting liquid, an outlet permitting 3, continuous flow of product gas, and cold trap condensers to 4 remove volatile products from the gas stream before collecting the latter in a sample bag for analysis. Experiments were 6conducted in the above described reactor at 430C for 105 minutes 7 under 550 kPa pressure both without gas flow and with gas flowing 8 continuously into and out of the reactor. In each experiment, 9110 g of Athabasca 504C+ vacuum tower bottoms (VTB) and 220 g of a diluent were used. Table 5 presented herebelow gives the 11 reaction conditions and experimental results.

13Autoclave Test Results 14 Experiment No. 1 2 3 4 5 6 Diluent Type A A B B B B
16 Nitrogen Flow 17 Rate (1/min) 0.01.89 0.00.21.05 2.16 18 Yield (wt.% VTB):
19 Cl - C4 15.516.5 10.310.08.2 13.8 C5 - 504C 42.338.1 56.556.556.6 51.4 21 504C+ pitch 22 (coke free) 34.638.8 26.327.030.0 29.7 23 Coke 7.93.8 4.33.8 3.4 3.1 24 Condensate recovered from 26 purge gas (wt. ~
27 VTB) -- 47.5 -- 3.1 23.9 39.7 ~ 2088902 2 Simulated Distillation Results of Condensate from Experiment No. 5 3 % Off Temp. C % Off Temp. ~C

Figure 17 shows the amount of coke produced as a 16 function of the rate of flow of nitrogen. As shown for diluents 17 A and B, the amount of coke produced decreased as the rate of 18 flow of nitrogen was increased. At high rates of flow of 19~ nitrogen, the amount of coke produced for the experiment using diluent B (the best hydrogen donor solvent) was not very 21 different from that for the experiment using diluent A (the worst 22 hydrogen donor solvent).
23 It is noteworthy in Table 5, that for those conditions 24 providing the least amount of coke, the amount of condensate recovered from the purge gas was highest. This was true for both 26 diluents A and B.

_ 20~8~02 Table 6 shows results of simulated distillation of the 2 condensate from experiment 5. About 90% of this condensate boils 3 at temperatures less than 220C.
4 This example teaches that coke production is reduced if the low boiling products are removed continuously (stripped) 6 from the reacting fluids. Moreover, it teaches that coke 7 production is reduced if the low boiling products are removed 8 from the diluent.
9 These observations are consistent with the model that has asphaltenes separate as another liquid phase from the 11 reacting fluids. In analogy with the common experiment that has 12 pentane added to bitumen to yield solid asphaltene as a 13 precipitate at room temperature, such an experiment done at high 14 temperature is expected to yield asphaltene as a separate liquid phase. Moreover, it is expected that this separate liquid phase 16 will be rich in the asphaltenes that thermally crack to form 17 coke.
18 This phase separation is shown schematically in Figure 19 18. The three components of this Figure are respectively labelled asphaltenic, aromatic and paraffinic and alicyclic to 21 represent those fractions having boiling points 504C+, 220 22 504C and 220C, respectively. The arrow indicates the evolution 23 of the composition of whole bitumen as might occur for example 24 IV.

EXAMPLE VI
26 This example illustrates the effect of using hydrogen 27 for continuously removing highly volatile components from the 28 reacting fluids.

1 A continuous flow system consisting of a preheater, a 2 2-litre stirred reactor and a product collection system was used.
3 The baffles and stirrer were similar to those of the previous 4 examples. A mixture of Athabasca VTB, diluent A and preheated hydrogen were pumped through the preheater into the bottom of the 6 stirred reactor. Products were removed though a dip tube with 7 its entrance set at 60% of the reactor's height.
8 The experimental conditions and results are shown in 9 Table 7 for experiments 7, 8 and 9. In each experiment the hydrogen flow rate was 12 slpm. In experiment 7, the liquid 11 hourly space velocity is twice that of experiment 8 and of 12 experiment 9. The temperature of the reacting fluids is 20C
13 higher than that of experiment 8.
14 Noteworthy is that the amount of coke produced in experiment 8 was less than that of experiment 7 and that almost 16 no coke at all was produced in experiment 9, in spite of the 17 increased severity of hydrocracking from experiment 7 to 8 to 9.
18 Such a result is expected if one considers that the highly 19 volatile fractions of the reacting fluids are removed with increasing efficiency as conditions are changed from experiment 21 7 to 8 to 9. In experiment 9 the pipe connecting the reactor to 22 the product collection vessel became plugged at the completion 23 of the experiment.
24 In experiment 10, two one-litre reactors were placed in series with the entrances to the dip tubes adjusted at 50% and 26 70% of reactor height. The conditions and results are shown in 27 Table 7.

2 Continuous Bench Unit Test Results 3' Diluent Type : A
4 Pressure : 10 MPa Experiment No. 7 8 9 10 6 Reactor 1 (1) 1.2 1.2 1.2 0.5 7 Reactor 2 (1) -- -- -- 0.7 8 Reaction Temperature 9 (C) 440 440 460 440 Liquid Hourly 11 Space Velocity (hr~l) 1 0.5 0.5 12 Hydrogen FLow rate 13 (slpm) 12 12 12 16 14 VTB Concentration in feed (wt.%) 63.10 65.02 45.53 47.3 16 Conversion (Wt. % VTB
17 to coke and 504C ) 69.0 78.3 98.1 79.8 18 Yield, Wt. % VTB
19 C~ - C4 5.2 7.9 17.3 7.2 C5 - 200C 16.3 19.1 31.4 15.1 21 200C - 360C 23.4 31.1 43.1 24.2 22 360C - 504~C 20.3 18.4 9.3 24.8 23 Coke 4.6 3.1 0.1 4.6 24 504C+ Pitch (coke free) 31.0 21.7 1.9 24.8 26 Total distillate 27 C5 - 504C 60.0 68.6 83.8 64.7 20~8~02 1 It is noteworthy that the conversion was similar to 2 that of experiment 8. This was expected given the different 3 liquid hourly space velocities and different number of reactors.
4 However, the amount of coke produced in experiment 10 was higher than that produced in experiment 8 in spite of the higher rate 6 of flow of hydrogen of experiment 10.
7 This example teaches that hydrogen flow and reactor 8 temperature may be used skilfully to remove (strip) low boiling 9 products from the reacting fluids to reduce the amount of coke that is produced. Moreover it teaches that for one or more 11 hydrocracking reactors in series, a configuration having one 12 reactor only produces the least amount of coke. Moreover, it 13 teaches that if several hydrocracking reactors are placed in 14 series, then least coke is produced if volatile hydrocarbons are removed from the fluids as they pass from one reactor to the 16 next.

18 This example illustrates that by skilful use of reactor 19 configuration, severity of reaction, stripping of volatile components and additive, high conversions of VTB to distillate 21 products can be obtained with acceptable production of coke and 22 minimal fouling of the reactor.
23 The continuous flow system of experiments 7, 8 and 9 24 of Example VI was used. The additive was iron pentacarbonyl.
The conditions and results of experiments 11 and 12 are shown in 26 Table 8.

20884û2 1 The conditions for experiment 12 were much more severe 2 than those of experiment 11. Nevertheless, all surfaces in the 3 reactor, pipes and collection vessel remained free of fouling by 4 coke and the coke that was produced was a fine friable matter S that settled in the product collection vessel.
6 The results of a microscopic examination of the coke 7 produced in experiment 12 are shown in Table 9. 74% of the coke 8 was in the form of agglomerates. 23% of the coke was in the form 9 of isotropic spheres but these spheres were isolated and trapped in a matrix of agglomerates.
11 This example teaches that high conversions with minimal 12 fouling of the reactor may be obtained when the coke that is 13 produced is mostly agglomerates.

2 Experiment No. 11 12 3 Reactor 1 (1) 1.2 1.2 4 Reactor 2 (1) --- ---Reaction 6 Temperature (C) 450 450 7 Liquid Hourly Space 8 Velocity (hr l) 1.05 0.73 9 Hydrogen Flow rate (slpm) 8 12 11 VTB Concentration in Feed 12` (wt. %) 47.5 47.8 13 Catalyst (wt. % of Fe 14 based on VTB) 0.5 0.5

15 Conversion (wt. % VTB

16 to coke and 504C ) 67.8 82.1

17 Yield (wt. % VTB)

18 Cl - C4 19. 1 22.9

19 200 - 350C 19.9 27.6 350 - 504C 21.9 21.1 21 Coke 2.4 2.8 22 504C+ Pitch 23 Coke Free 32.2 17.9 24 Total distillate Cs ~ 504C 60.9 71.6 26 Note that if H2 flow was not increased in experiment 12, one 27 would expect that a 14% increase in conversion should be 28 accompanied by much higher coke yield than the amount recorded.

2 Coke Composition of Run No. 12 3 Vol %
4 Basic Isotropy 3 Isotropic Spheres 23 6 Isotropic Agglomerates 42 7 Basic Anisotropy 0 8 Anisotropic Fine-Mosaic 0 9 Anisotropic Coarse-Mosaic 0 Anisotropic Spheres 0 11 Anisotropic Agglomerates 32 13 This example also compares various additives and 14 various metal compounds.
A series of tests using the following additives:
16 - fine, Alberta coal char, 17 - oil soluble nickel naphthanate, 18 - oil soluble cobalt naphthanate, and 19 - oil soluble molybdenum naphthanate were carried out to compare their relative effectiveness in 21 preventing coke formation and deposition. Iron pentacarbonyl was 22 used as the bench mark for comparison.
23 All tests were performed under common reaction 24 conditions:
0.5 wt. % (metal on vacuum tower bottoms) additive, 26` Athabasca vacuum tower bottoms (33.3%), diluent 27 (66.7%), 6.8 MPa initial hydrogen pressure, 800 rpm 28 stirrer speed, 430C, and 105 minutes reaction time.

_ 20884~2 1 In the case of Alberta coal char, the amount added was 2 equivalent to 4% of the vacuum tower bottoms.
3 Pressure profiles presented in Figure 19 and the 4 hydrogen consumption results presented in Figure 20, showed the following observed order for hydrogen consumption:
6 molybdenum additive (CF-40) 68%
7 nickel additive (CF-41) 39%
8 cobalt additive (CF-41) 27%
9 iron additive (FE-1) 26%
and coal char (CF-43) 21%.
11 Product distributions presented in Table 10 showed the 12 following order of additive for:
13 - vacuum tower bottoms conversion 14 molybdenum > iron > coal > nickel > cobalt - selectivity to Cs - 504CC
16 nickel > iron > cobalt > molybdenum > coal char 17 - coke formation 18 nickel < cobalt < coal char < iron < molybdenum.
19 Figure 21 shows the effectiveness of the various additives in converting the coke precursors to form the non-21 depositing isotropic agglomerate coke particles. Although 22 experiments using additives containing molybdenum consumed the 23 highest amount of hydrogen, over 90% of the coke was basic 24 isotropic particles. In Figure 22, coke from CF-40 appeared as a continuous sheet of basic isotropic particles. The coke from 26 CF-40 was evidently more densely packed than the coke from FE-27 1 using the iron additive (Figures 14 - 15).

`- 2088402 1 As pointed out earlier, it was discovered that, to 2 prevent the coke from depositing on the reactor walls, the 3 additive must selectively transform the coke precursor spheres 4 into isotropic agglomerates. The lack of isotropic agglomerates in coke from experiment CF-40 suggested an explanation for the 6 deposition of adherent coke on the reactor baffles (Figure 23).
7 In contrast, the reactor baffles in experiments with iron 8 pentacarbonyl (Figure 13) did not have any adherent coke.
9 This example teaches that appropriate selection of additive may inhibit coke production and may inhibit deposition 11 of adherent coke when an appropriate diluent is used. Such an 12 additive will maximize the fraction of coke that is in the form, 13 isotropic agglomerate. Oil soluble additives containing iron or 14 cobalt or nickel or combinations of these are preferred.

- 2d8~402 2 Test Conditions: 430C, 6.8 MPa H2 initial pressure, 105 3 min, 800 rpm 4 additive added = metal concentration of 0.5 wt. % VTB
6 Diluent/VTB = 2:1 7 Experiment No. CF-A3 CF-43 FE-1 8 Additive -- Coal char t4%) Fe 9 Diluent type A C A
H2 consumed (wt. %
11' initial H2) 21 21 26 12 Yield, wt. % vacuum 13 tower bottom 14 H2S 2.2 2.3 1.2 C1 ~ C4 11.6 9.8 6.6 16 C5 - 200C 44.0 36.6 37.7 17 200 - 360C -18.0 -7.7 -9.1 18 360 - 504C 30.1 24.4 31.2 19 504C+ (coke free) 27.7 33.0 31.4 Coke 3.1 1.1 1.6 21 Conversion to 504C
22 & coke 72.3 66.2 68.6 23 Selectivity to 24 Cs - 504 C 77.6 80.5 87.0 Mass Balance 98.5 99.0 98.1 208B~02 1 TABLE 10 (Continued) 2 Experiment No. CF-41 CF-42 CF-40 3 Additive Ni Co Mo 4 Diluent type C C C
5' H2 consumed (wt. %
6 initial H2) 39 27 68 7 Yield, wt. % vacuum 8 tower bottom 9 H2S 2.0 1.9 3.3 0 Cl - C4 6.1 8.0 8.5 11 Cs - 200C 34.6 36.4 42.4 12 200 - 360C -2.3 -8.9 -11.8 13 360 - 504C 24.9 27.3 29.6 14 504C+ (coke free) 34.8 35.3 28.2 Coke 0.4 0.9 1.8 16 Conversion to 504C
17 & coke 65.6 64.7 71.8 18 Selectivity to 19 Cs - 504C 87.2 84.7 83.8 Mass Balance 99.6 99.5 98.9 22 These examples as a group support the assertions that:
23 1. Additive dispersion needs to be accomplished at 24 less than decomposition temperature and requires prolonged mixing at moderate elevated temperature 26 to achieve uniform dispersion of the additive 27 through the asphaltenes;
28~ 2. Digestion leading to additive decomposition needs 29 to be accomplished under mixing conditions; and

- 20~84~2 1 3. The combination of the described additive 2 selection, preferred use of solvent, dispersion 3 and digestion steps, and stripping and mixing 4 during hydrocracking, come together to create colloidal catalyst particles which enable high 6 525C+ conversion associated with little adhesive 7 coke formation.
8 Stated otherwise, if the additive is not well 9 distributed at the molecular scale before significant decomposition occurs, then there is a likelihood that relatively 11 large, non-colloidal, micron or larger sized catalyst particles 12 will be produced, accompanied by adherent coke formation and low 13 conversion. In the same vein, if decomposition of the additive 14 takes place without mixing to maintain dispersion, again non-colloidal catalyst can be produced and coke formation and low 16 conversion follow.

18 This example (relating to runs TRU 101 and B 3-1) shows 19 the desirability of properly dispersing the additive by mixing it for a prolonged period at an elevated temperature that is well

21` below the decomposition temperature of the additive; otherwise,

22 when the mixture is subsequently rapidly heated to hydrocracking

23 temperature, severe fouling will occur in the heater or at the

24 reactor inlet and cause plugging, which is characterized by pressure surges in the circuit.
26 Figure 25 shows the circuit used for these tests.
27 Figures 26 - 28 show the pressure logs taken during run TRU 101 28 at points indicated on Figure 25.

2 0 ~ 0 2 1 A mixing and dispersion vessel ("mixer"~ was provided 2 with a pump and return line, so that the feed could be circulated 3 and mixed. Hydrogen from a source was added to the line taking 4 the product from the mixer. The mixture passed through a heater to raise its temperature to hydrocracking temperature. The 6 heater product was then introduced into a hydrocracking reactor.
7 The reactor product was passed through a hot separator to produce 8 pitch.
9 Following were the conditions relating to the first run (TRU 101):
11 (a) Feedstock: Cold Lake crude vacuum bottoms (430C) 12 containing 70% by wt. 525C+ residuum and 300 ppm 13 wt. molybdenum as molybdenum ethyl hexanoate;
14 (b) Dispersion: 24 hours at 135C, later raised to 150C, with mixing and circulation;
16 (c) Hydrogen flow: 14,000 SCF/barrel;
17 (d) Reactor conditions:
18 pressure - 13.6 MPa 19 temperature - 455C.
The mixer was initially operated at 135C for 17.1 21 hours from start. The mixer temperature was then raised to 150C
22 (which was less than the decomposition temperature of the 23 additive). After 25.9 hours from start, a first pressure pulse 24 was observed at PT455, suggesting that minor plugging occurred downstream at the entrance to the hot separator. After 85.3 26 hours from start, a pressure pulse to 16.3 MPa was observed at 27 PT 320, suggesting that minor plugging occurred between PT 320 28 and PT 340. As the plug freed itself, pressure pulses were 29 observed at DP 450, suggesting that the plug was being pushed 20~02 1 through the reactor and downstream to the hot separator. After 2 99 hours from start, the pressure at PT 400 pulsed to 15.2 MPa, 3 suggesting that a plug had formed at the inlet to the reactor.
4 After 108.9 hours from start, the pressure at PT 400 and upstream jumped to 21.6 MPa because a strong plug had formed at the 6 reactor inlet.
7 These results bring up the following observations:
8 - That plugging was not a problem when dispersion 9 was conducted at 135C - but it did become a problem at 150C; and 11~ - That decomposition of the additive was taking 12 place in and adjacent to the heater under non-13 mixing conditions. This led to the formation of 14 large iron particles that plugged the piping.
The same circuit was later used for run B 3-1.
16 Following were the conditions relating to this run:
17 (a) Feedstock: Cold Lake crude vacuum bottoms 18 containing 100 ppm wt. molybdenum as molybdenum 19 ethyl hexanoate dispersed in 200 - 360C gas-oil;
(b) Dispersion: 24 hours at about 105C with mixing 21 and circulation;
22 (c) Hydrogen flow: 14,000 scf/barrel;
23 (d) Reactor conditions:
24 pressure - 13.6 MPa temperature - 450C.

2~88~02 1 The B 3-1 run was continued for 225 hours. It involved 2 the following changes relative to run TRU 101:
3 - the dispersion temperature was lower;
4 - the concentration of additive was considerably reduced; and 6 - the reactor temperature was slightly lower.
7 The pressure logs from run B 3-1 are shown in Figures 8 29 - 30.
9 Smooth, plug-free operation was observed, substantially 10 throughout the test. After about 160 hours the pressure upstream 11 of the separator pulsed briefly to about 19.0 MPa as a plug 12 formed and then broke down. Plugging and fouling of unit 13 surfaces were significantly less severe in run B 3-1 than in run 14 TRU 101.
The runs indicate the desirability of dispersing at a 16 temperature that is significantly less than the decomposition 17 temperature and then heating rapidly to hydrocracking 18 temperature.

This example shows that if the additive is provided in 21 high concentration in oil and if dispersion is practised at a 22 high temperature that exceeds decomposition temperature, then 23 poor results follow.
24 In this test, dispersion and decomposition were carried

25 out in one step at a first site and the mixture product moved to

26 another site for hydrocracking. A concentrate (4% Fe by wt.) was

27' formed at the first site, to facilitate transportation. The two

28 circuits used are shown in Figures 31 and 32.

1 The conditions of the runs are shown in conjunction 2 with the Figures.
3 The results of making several runs with this system 4 were as follows:

8 - feed rate, kg/hr3.420 3.272 2.966 3.121 9 - LHSV 0.97 0.93 0.85 0.89 - reactor temperature, 12 - H2 treat gas rate, 13 1/min 40 40 40 60 14 - additive concen-tration, wt%Fe on 16 524C+ residuum0.49 0.16 0.095 0.12 17 RESU~TS
18 - 525C+ pitch conversion, 19 volume % 57.2 58.1 68.4 67.7 - CCR removal, wt% 24.9 27.4 31.7 33.7 21 - desulfurization, wt% 20.928.7 37.3 35.1 22 Electron microscope analysis of solids from the 23 produced pitch indicated FeSx particles typically having a 24~ diameter of 5~m.
The pitch conversion (57 to 68%) was relatively poor 26 and coke was produced in the reactor circuit.

- 2~884~

2 This example is additive to Example X and shows that 3 if a bitumen/additive is only digested at decomposition 4 temperature, without preliminary low temperature mixing, then poor results follow even if digestion involves mixing.
6 Figure 33 shows the pilot circuit and some conditions 7 used in this experiment. Figure 34 shows the pressure logs from 8 the run.
9 In this test, the following pertained:
- feed: Athabasca bitumen, composition: 45% 220 11 - 524C, 55% 525C+;
12 - feed rate: 2.815 kg/hr.;
13 - additive: iron pentacarbonyl - 33%wt. in 14 llght gas oil;
- additive rate: 32.9 ml/hr.;
16~ - additive concentration: 5000 ppm with respect to 17 525C+ fraction;
18 - hydrogen: 34 standard liters/minute (4000 19 SCF/BBL);
- digester temperature: 250C;
21 - reactor conditions: 450C 10.2 MPa.
22 The estimated pitch conversion was 75%.
23 The pressure drop across the reactor increased slowly 24 during the run and then precipitously after 33 hours. The circuit became inoperable after 36 hours as the pressure recorded 26 at PT23A increased.
27 Examination of material filtered from the product pitch 28 contained iron sulfide particles sized 1 - 2~ .

EXAMPLE XI I
2 This example shows that if appropriate dispersion is 3 conducted at a mild or moderate temperature that is well below 4 additive decomposition temperature and decomposition is conducted with mixing, then good conversion and coke reduction results 6 follow.
7 Figure 35 shows the circuit and conditions used for 8 this run. Figure 36 shows various logs from the run.
9 In this test, bitumen and iron pentacarbonyl were mixed at a temperature of about 100C for about 30 minutes in an 11 impellor-equipped first vessel, to disperse the additive, and 12 then mixed at a temperature of about 250C for about one hour in 13 an impellor-equipped second vessel to decompose the additive 14 while keeping it dispersed.
The following Table 12 sets forth other conditions and 16 the results of the run:

18 Dispersion Vessel Temperature - 100C
19 Digester Temperature - 252C
Fe ppm of 525C+ - 2500 21 Hydrogen Athabasca Reactor Fe(CO)s 525C Days 22 1/min. bitumen TempC LGO/hr conversion 23 kg/hr 24 68.0 2.960 450 11 84 5 68.0 2.960 455 11 87 3 26 55.3 2.405 455 8.9 90 4 27 68 2.960 455 8.9 92 3 2088~02 1 ~ Smooth, plug-free operation was observed for the first 2 100 hours of operation. At that point the pump failed.
3 Following repair, operation of the circuit was fairly smooth, 4 although small fluctuations in pressure drop across the reactor were recorded. Pitch conversion increased slowly from 84% to 92%
6 over a run duration of about 300 hours.
7 Examination showed the iron of the additive to be 8 present in the pitch in the form of colloidal iron sulphide 9 particles.

EXAMPLE XIII
11 This example provides data showing the extent of 12 decomposition of molybdenum naphthanate ("Mo-naph") and 13 molybdenum ethyl hexanoate ("Mo-HEX") at different temperatures.
14 More particularly, infrared spectra of samples of bitumen containing either Mo-naph or Mo-HEX were measured over 16 time at temperatures of 130C, 200C and 300C. In the following 17 table, the % decomposition of each of these catalyst precursors 18 is expressed as a fraction (%) of the respective spectral 19 components that had disappeared by a given time.

- 20~8~Q2 1~ TABLE 13 2Relative Disappearance of Mo-Carboxylates 3in Feed During Heating 4Precursor Sampling Mo-Fraction, wt%a Disappearance, %b 6 Temp., C Time, Min. NAPHC HExd NAPHC HExd 7 130 30f 32.1 32.3 0.0 0.0 8 150 35.4 36.7 0.0 9.8 9 1110 29.9 35.9 10.4 32.2 3030 31.3 37.5 13.9 42.4 11 3990 33.2 37.5 15.1 42.6 12 5820 33.2 38.0 20.9 43.8 13 200 5f 30.6 33.1 0.0 0.0 14 35 30.1 36.4 20.4 33.9 32.4 37.0 22.3 44.8 16 150 36.1 - 31.1 17 240 36.6 - 34.5 18 330 35.5 - 35.9 19 960 - 15.7e _ 65.3 300 Of~g 32.3 33.8 0.0 0.0 21 5 30.8 36.5 50.9 94.6 22 10 33.8 33.1 77.2 97.8 23 20 35.0 - 82.5 24 30 - 34.8 - 96.9 35.5 36.7 84.2 96.2 26 70 36.1 38.4 83.5 96.4 27 a GPC, SX-4/CHCl~; void vol. 100 ml; fr. vol. 25 ml 28 b DRIFTS - carboxylate region

29 c _ 43000 ppm Mo/CLVB
d _ 35000 ppm Mo/CLVB
31 e Product: 16.3% insolubles 32 f Reference sample 33 g Sampled at 100C
34 h Sampled at 260C

2 This example supports the assertion that the catalytic 3 particles produced by the process of the invention are colloidal 4 in size.
A sample of pitch produced in run CFE-1 was examined 6 by X-ray diffraction and Mossbauer spectroscopy.
7 The X-ray diffraction analysis revealed the presence 8 of FeS2.
9 The spectrum from the Mossbauer analysis is shown in Figure 24. The supporting data are set forth in Table 14 below.
11 Notable in the spectrum is the breadth of each of the peaks.
12 Such breadth is indicative of very fine, colloidal particles, 13 typically less than 10 nanometers in dimension.
14 Prior to this test, microscopic examination of samples of pitch obtained from experiments done in accordance with the 16 invention showed no evidence of iron sulphide particles, even 1; though chemical analyses typically showed more than 20% by weight 18 iron sulphide in the pitch. This evidence indicated that the 19 catalyst particles were submicroscopic.

2088~02 2 Channel number: 512 3 Folding point: 257.5 4 Geom. Effect: O
5Results of Fit July 8, 1988 17:16:00 6gO46 CFE-1 deposited 5.0 x 0.1 24/6/88 7 Theory: 4 8Number of Parameters: 26 Number of Iterations: 1 9 Chi : 1.9297 ~ Initial Final Error Check 11 BASELINE4609769 4609769 25.2337 1.000 1.000 12 Total Area0.0266 0.0266 0.0028 1.733 1.729 13 Mag Field 124.956024.9560 0.0250 0.985 0.998 14 Quad Mag 10.1166 0.1166 0.0061 0.986 0.996 Shift Mag 10.58790.5879 0.0031 0.984 1.024 16 Width Out 10.60000.6000 F I X E D
17 3:2:1 corr1.0000 1.0000 F I X E D
18 WNat Mag 10.6000 0.6000 F I X E D
19 Mag Field 228.660328.6603 0.0050 2.034 2.045 Quad Mag 20.0882 0.0882 0.0072 3.743 3.687 21 Shift Mag 20.59850.5985 0.0220 0.695 0.888 22 Width Out 20.60000.6000 F I X E D
23 3:2:1 corr1.000 1.0000 F I X E D
24 Area Mag 20.3342 0.3342 0.0204 1.353 1.385 WNat Mag 20.60000.60000 F I X E D
26 Mag Field 332.000032.0000 F I X E D
27 Quad Mag 3-0.2200 -0.2200 F I X E D
28 Shift Mag 30.26000.26000 F I X E D

1 TABLE 14 (Continued) 2 Width Out 3 0.7500 0.7500 F I X E D
3 3:2:1 corr 1.0000 1.0000 F I X E D
4 Area Mag 3 0.0000 0.0000 F I X E D
WNat Mag 3 0.2600 0.2600 F I X E D
6. Quad Split 1 0.7555 0.7555 0.0218 0.999 0.991 7 Iso Shift 1 0.2700 0.2700 0.0126 0.748 0.755 8 Width 1 0.6000 0.6000 F I X E D
9 Area 1 0.3624 0.3624 0.0121 1.946 1.964 EXAMPLES XV - XIX
11 These examples are based on experimentation using 12 molybdenum naphthanate as the additive or catalyst precursor.
13 In the experiments, vacuum tower bottoms derived from 14 bitumen were used as the feed. ~he characteristics and composition of the feed were as follows:

- 2D8`8~02 2 Distillation Wt. % IBP- 430C
3 IBP - 525C 24.0 4 +525C 76.0 5 Elemental Composition Wt. %
6 Carbon 83.6 7 Hydrogen 9.7 8 Nitrogen 0.8 9 Sulfur 5.9 Oxygen --11 H/C 1.4 12 TLC/FID Class Composition, 13 Hydrocarbons 75.0 14 Asphaltene (includes Preasphaltene) 25.0 The circuit used for the runs reported was that of 16 Figure 25. 300 ppm of molybdenum, as molybdenum naphthanate, was 17 added to the feed tank. The feed was stirred and pumped around 18 the loop at 200C for 3 hours before the experiment. The tests 19 were 12 to 15 hours duration.

EXAMPLE XV
21 This example shows that high conversion of asphaltenes 22. with minimal production of solid coke was achieved when the 23 invention was practised with molybdenum naphthanate as the 24 additive.
An asphaltene-rich feedstock of Cold Lake vacuum 26 residuum, IBP greater than 430C, was charged to a 0.01m3 surge 27 tank. 300 ppm of molybdenum, as molybdenum naphthanate, was 2088~02 added to the tank which was equipped with a stirrer and recycle 2 pump, and mixed therewith under a nitrogen blanket at 200C to 3 form a homogeneous mixture. The mixture was then pumped through 4 the process heater into the reactor. Its temperature was increased to 455C in the process heater. Hydrogen was admixed 6 with the mixture at the entrance to the process heater. The 7 hydrogen was supplied at a rate of 10,000 - 12,000 SCF/BBL and 8 at a pressure of about 2,000 psig. The process heater consisted 9 of a 2.9 mm I.D. 6100 mm long coil immersed in tin at about the hydrocracking temperature.
11 The volume of the hydrocracking reactor was 669 cc.
12 It was a stainless steel cylinder 25 mm I.D. and 1370 mm high.
13 The following conditions applied to the reactor 14 operation:
Volumetric flow of H2/liquid = 10,000 SCF/BBL
16 Liquid Peclet No. = about 0.25 17 Gas Peclet No. = about 6 18 (The Peclet Nos. were determined from tracer studies 19 using Xe133 and Il31 ) The LHSV was 0.4 to 1.0 h 1. It usually required 10 21 12 hours for the reactor to reach steady state operating 22 conditions. The hydrocracking took place at a temperature of 23 455C and pressure of 2000 psig. The reactor effluent comprising 24 a mixture of gases and liquids was fed to a hot separator where gases and liquid were separated.
26 Table 16 provides typical results for the process.

2 Reaction Temperature, C 455 455 3 LHSV, h~1 0.41 1.03 4 Pressure, psig 2000 2000 5 Product Yields wt. % on feed 6 H2S 4.41 3.88 7 C1 ~ C3 8.00 9.01 8 C4 - 195C 20.30 6.88 9 195 - 350C 46.00 39.73 350 - 525C 21.42 35.21 11 +525C 0.11 5.76 12 Coke 0.00 0.86 13 C4 - 525C, vol. % 108.42 96.44 14 Pitch Conversion, wt. % 99.2 91.2 Asphaltene Conversion, wt. % 100.0 84.4 16 HDS, % 82.8 72.7 17 H2 Cons., wt. % of feed 2.5 1.9 18 The above hydrocracking tests were conducted on Cold 19 Lake vacuum bottoms described in Table 15 and the precursor concentration was 300 ppm Mo on feed. After each test, all units 21 of the experimental circuit were opened, examined and found to 22 be free of coke or other fouling.
23 It will be noted that the Mo run was conducted 24 successfully without solvent, even though VTB's were used as the feed.

- 2088~

2 This example supports the assertion that the catalyst 3 from Example XV was colloidal.
4 Hydrocracking residuum was dispersed in methylene chloride and the mixture was injected into a gel permeation 6 column. The molybdenum containing component was found to have 7 an apparent molecular weight range 400 to 3000 with respect to 8 this particular gel permeation column calibrated with respect to 9 polystyrene. This range corresponds to colloidal particles of diameter greater than 0.002 micron but less than 0.01 microns.

12 This example shows the effect of preferential 13 association of catalyst precursor with the asphaltenic fraction 14 of bitumen residue feedstock.
Table 17 shows data from two tests, one with catalyst 16 and one without catalyst. These tests demonstrated the 17 differences on asphaltene conversion and coke yield, in 18 particular. Although the pitch conversions for the two 19 experiments were similar, the asphaltene conversions differed by a factor of 2; the catalyst selectively converted the asphaltene.

_ 2Q88qO~

2 No Catalyst 300 ppm Mo 3 Reactor Temperature; C 455 455 4 LHSV; h h 3.63 3.65 Pressure; psig 2500 2500 6 H2 flow rate; scf/bbl 7900 7800 7 Product Yields wt. % on feed 8 H2S 1.94 2.40 9 Cl - C3 2.59 2.22 0 C4 - 195C 5.16 3.55 11 195C - 350C 22.40 20.20 12 350 - 525C 31.78 35.82 13 +525C 36.25 36.09 14 Coke 6.5 0.79 Pitch Conversion, % 52.9 52.6 16 Asphaltene Conversion, % 23.1 58.5 17 HDS, % 31.8 39.3 18 H2 cons., wt. % of feed 0.42 0.91 19Additional evidence of the effect of catalyst precursor on selective asphaltene conversion and coke suppression is shown 21in Table 18 where the composition of two +525C hydrocracking 22 residua (pitch) are compared.

20~84~2 2 Fraction Pitch I Pitch II
3 Yield % Sulfur % Yield % Sulfur %
4 Maltenes 63.2 3.9 41.5 4.7 Asphaltenes 36.6 5.8 33.4 6.3 6 Preasphaltenes 16.3 6.2 7 Coke 0.2 -- 8.3 6.7 8 Pitch I was derived from a test containing molybdenum 9 naphthanate catalyst precursor. Pitch II was derived from a test not containing molybdenum naphthanate catalyst precursor.
11 Figure 38 shows that asphaltene conversion was favoured 12 by the presence of the catalyst for a broad range of pitch 13 conversion, 42 to 99%. In the presence of catalyst the process 14 units remained clean and free of coke. In the absence of catalyst, the process units became fouled by coke.

17 This example shows that the process operates 18 successfully over a broad range of concentration of precursor in 19 the bitumen residuum.

20~402 2 30 ppm Mo 300 ppm Mo 3 Reaction Temperature 455 455 4 LHSV/ hl 1.03 1.03 Pressure; psig 2000 2000 6 H2 flow rate; scf/bbl 16,400 13,400 7 Product Yields wt. % on feed 8 H2S 2.86 3.88 9 Cl - C3 8.43 9.01 0 C4 - 195C 12.13 6.88 11 195~ - 350C 36.92 39.73 12 350C - 525C 34.37 35.21 13 +525C 5.88 5.76 14~ Coke 0.43 0.86 C4 - 525C 83.42 81.82 16 C4 - 525C; vol. % 100.52 96.44 17 Pitch Conversion, % 91.6 91.2 18 Asphaltene Conversion, % 87.4 84.4 19 HDS, % 53.6 72.7 H2 Cons., wt. % of feed 1.66 1.90 22 This example shows that the catalyst precursor, 23 molybdenum naphthanate, decomposes at temperatures greater than 24 about 300C in the absence or presence of bitumen residuum.

2088~2 1 Figures 37a and 37b show that the catalyst precursor 2 is stable at temperatures less than 250C. Figure 37c shows 3 that the catalyst precursor begins to decompose and polymerize 4 slowly at a temperature of 300C. At higher temperatures the decomposition was more rapid and coke was produced.
6 Figures 37d and 37e show that the catalyst precursor 7 dissolved in bitumen residuum was stable at temperatures less 8 than 250C. Figure 37f shows that the catalyst precursor 9 dissolved in bitumen began to decompose slowly at temperature of 11 Injection of the catalyst precursor into bitumen 12 residuum at 350C produced coke containing molybdenum.

13 EXAMP~E XX
14 In accordance with a preferred embodiment of the invention, the heavy distillate and pitch mixture leaving the 16 hot separator (which treats the reactor product) is subjected to 17 distillation, to produce pitch. Part of this pitch is recycled 18 to the reactor. In so doing the following things are 19 accomplished:
(1) a greater rate of stripping of light ends is 21 obtained without increase of hydrogen flux, the 22 light ends having been removed from the recycle 23 stream. This reduces coke formation and 24 consumption of catalyst;
(2) the active catalyst being in its colloidal form 26 in the recycle stream accumulates in the reactor, 27 to provide a higher steady-state concentration 28 therein than would be obtained without recycle.

2088~02 1 This reduces catalyst consumption by typically 50%
2 from that obtained without recycle; and 3 (3) residence time of pitch is selectively increased 4 thereby increasing overall liquid yield and improved stability of operation.
6 In addition, a small amount of fresh feed is added to 7 this recycle stream, thereby accelerating the mixing of the 8 stream and cooling it before it is mixed with the additive-9 containing feedstock.
This example demonstrates the advantages of practising 11 these preferred features.
12 More particularly, Figures 39 - 41 show the circuits 13 and conditions used in a 3-stage test run (R 2-1) which is now 14 described. The run lasted a total length of 490 hours.
Common conditions of run R 2-1 were as follows:
16 Feed: Cold Lake vacuum bottoms containing 150 ppm 17 molybdenum ethyl hexanoate dispersed in 200 -18 360C gas-oil;
19 Mixing: circulation and mixing for at least 24 hours at 105C under an atmosphere nitrogen blanket 21 was practised, before the feed was processed;
22 Hydrocracking conditions:
23 pressure - 13.6 MPa 24 temperature - about 450C
H2 flow - about 15,000 scf/barrels 26 Distillation:
27 conducted in accordance with ASTM D-1160 28 distillation.

~0884 0~
1 During the first stage, consisting of 96 hours of 2 operation, the test was conducted on a "once through" basis, i.e.
3 without pitch recycle, as shown in Figure 39. In the second 4 stage, unconverted pitch was recycled back to the reactor to contribute 15% by weight of the feed. This second stage process 6 is shown in Figure 40 and lasted for 390 hours. Recycling of 7 unconverted pitch improved fresh feed pitch conversion from 90%
8 (in the first stage) to 98% (in the second stage).
9 Compared to run B 3-1 (Example IX), run R 2-1 never experienced any significant plugging or pressure pulses. This 11 is indicated by the pressure logs set forth in Figures 42 and 43.
12 However, during the distillation of the hot separator 13 product to recover unconverted pitch for recycling, it was noted 14 that significant lumping of pitch (similar to agglomeration) occurred in the distillation pot. These lumps were hard to break 16 up and they adhered strongly to the distillation vessel.
17 ~he lumps were determined to comprise unconverted 18 asphaltene and molybdenum sulfide formed by the additive.
19 In the third stage of the test, involving the last 150 20. hours of the run, a portion of fresh feed was added to the hot 21 separator product, prior to introducing it to the distillation 22 vessel. This arrangement is shown in Figure 41. Also, in this 23 third stage the molybdenum hexanoate concentration was 150 ppm 24 (metal).
25 ` It was determined that, in the second stage, 3164 grams 26 of hot separator product produced 89.4 grams of lumpy solids and 27 28.7 grams of residue adhered strongly to the distillation pot.
28 This was equivalent to 4.1% of the charge.

2û88~02 1 In the third stage, 3200.1 grams of hot separator 2 product plus 601.5 grams of fresh Cold Lake vacuum bottoms 3 produced no lumps and only 6.3 grams of residue adhered to the 4 distillation pot. This was equivalent to 0.2% of the hot separator product.
6 In conclusion then, the test showed:
7 - That the conditions of the process yielded 490 8 hours of operation free of plugging and fouling;
9 - That pitch conversion increased significantly with recycling of unconverted pitch; and 11 - That adding a portion of fresh feed into the 12 distillation unit for pitch separation resulted 13 in reduction of asphaltene separation in the 14 distillation step. In other words, the addition of some fresh feed to the hot recycle pitch 16 accelerated its dispersion in the feed stream to 17 the reactor.
18 At the completion of the test, the reactor and hot separator were 19 opened and all unit surfaces were observed to be clean and free of fouling. Liquid collected from the reactor was filtered. The 21 solid material so obtained was a fine dust consisting of 22 microscopic agglomerates. The solid material so obtained is 23 shown in Figure 44.

Claims (43)

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

1. A process for preparing a heavy hydrocarbon feedstock for hydrocracking, said feedstock containing asphaltenes and sulfur moieties, comprising:
mixing the feedstock and an oil-soluble metal compound additive at a temperature that is in the range 50°C to 300°C and which is less than the decomposition temperature of the additive, to produce a product mixture;
said additive being selected from the group consisting of molybdenum, iron, nickel and cobalt compound additives, said additives being adapted, when heated to hydrocracking temperature, to decompose and react with sulfur moieties in the feedstock to form metal sulfide particles that are catalytic for hydrocracking;
said mixing being conducted for sufficient time to cause the additive to be sufficiently dispersed so that the metal sulfide particles formed upon hydrocracking are colloidal in size.

2. The process as set forth in claim 1 wherein:
mixing is conducted at a temperature in the range of 80°C to 190°C.

3. The process as set forth in claim 2 comprising:
further mixing the product mixture at a temperature greater than the decomposition temperature of the additive and less than hydrocracking temperature for sufficient time to decompose the additive while maintaining it dispersed.

4. The process as set forth in claim 2 wherein:
the additive is provided in an amount between 0.002%
and 5% by weight based on the feedstock.

5. The process as set forth in claim 4 wherein:
the additive is an iron compound.

6. The process as set forth in claim 4 wherein:
the additive is a molybdenum compound.

7. The process as set forth in claim 2 comprising:
mixing a hydrocarbon solvent for asphaltenes with the feedstock and additive during the mixing step.

8. The process as set forth in claim 7 wherein:
the solvent/feedstock weight ratio is in the range 1:10 to 3:1.

9. The process as set forth in claim 3 comprising:
mixing a hydrocarbon solvent for asphaltenes with the feedstock and additive during the mixing step.

10. The process as set forth in claim 9 wherein:
the solvent/feedstock weight ratio is in the range 1:10 to 3:1.

11. The process as set forth in claim 10 wherein:
the additive is provided in amount of between 0.002%
and 5% by weight based on the feedstock.

12. A process for hydrocracking a heavy hydrocarbon feedstock containing asphaltenes and sulfur moieties, comprising:
mixing the feedstock and an oil-soluble metal compound additive at a temperature that is in the range 50°C to 300°C and which is less than the decomposition temperature of the additive, to produce a product mixture;
said additive being selected from the group consisting of molybdenum, iron, nickel and cobalt compound additives, said additives being adapted, when heated to hydrocracking temperature, to decompose and react with sulfur moieties in the feedstock to form metal sulfide particles that are catalytic for hydrocracking;
said mixing being conducted for sufficient time to cause the additive to be sufficiently dispersed so that the metal sulfide particles formed upon hydrocracking are colloidal in size;
then further heating the product mixture to hydrocracking temperature;
introducing the heated product mixture into the chamber of a hydrocracking reactor;
temporarily retaining the heated product mixture in the chamber, continuously passing sufficient hydrogen through substantially the breadth and length of the chamber contents to maintain mixing of the chamber contents and stripping of light ends, and removing unreacted hydrogen and entrained light ends from the chamber and producing a pitch containing product comprising colloidal metal sulfide.

13. The process as set forth in claim 12 wherein:
mixing is conducted at a temperature in the range of 80°C to 190°C.

14. The process as set forth in claim 13 comprising:
before heating to hydrocracking temperature, further mixing the product mixture at a temperature greater than the decomposition temperature of the additive and less than hydrocracking temperature for sufficient time to decompose the additive while maintaining it dispersed.

15. The process as set forth in claim 13 wherein:
the additive is provided in amount of between 0.002%
and 5% by weight based on the feedstock.

16. The process as set forth in claim 15 wherein:
the additive is an iron compound.

17. The process as set forth in claim 15 wherein:
the additive is a molybdenum compound.

18. The process as set forth in claim 13 comprising:
mixing a hydrocarbon solvent for asphaltenes with the feedstock and additive during the mixing step.

19. The process as set forth in claim 18 wherein:
the solvent/feedstock weight ratio is in the range 1:10 to 3:1.

20. The process as set forth in claim 14 comprising:
mixing a hydrocarbon solvent for asphaltenes with the feedstock and additive during the mixing step.

21. The process as set forth in claim 20 wherein:
the solvent/feedstock weight ratio is in the range 1:10 to 3:1.

22. The process as set forth in claim 13 wherein:
sufficient hydrogen is passed through the reactor chamber to maintain the axial Peclet No. for liquid at less than 2.0 and for gas at more than 2Ø

23. The process as set forth in claim 14 wherein:
sufficient hydrogen is passed through the reactor chamber to maintain the axial Peclet No. for liquid at less than 2.0 and for gas at more than 2Ø

24. The process as set forth in claim 15 wherein:
sufficient hydrogen is passed through the reactor chamber to maintain the axial Peclet No. for liquid at less than 2.0 and for gas at more than 2Ø

25. The process as set forth in claim 19 wherein:
sufficient hydrogen is passed through the reactor chamber to maintain the axial Peclet No. for liquid at less than 2.0 and for gas at more than 2Ø

26. The process as set forth in claim 21 wherein:
sufficient hydrogen is passed through the reactor chamber to maintain the axial Peclet No. for liquid at less than 2.0 and for gas at more than 2Ø

27. The process as set forth in claim 22 wherein:
sufficient hydrogen is passed through the reactor chamber to maintain the axial Peclet No. for liquid at less than 2.0 and for gas at more than 2Ø

28. The process as set forth in claim 22 wherein:
the additive is provided in amount of between 0.002%
and 5% by weight based on the feedstock.

29. The process as set forth in claim 23 wherein:
the additive is provided in amount of between 0.002%
and 5% by weight based on the feedstock.

30. The process as set forth in claim 26 wherein:
the additive is provided in amount of between 0.002%
and 5% by weight based on the feedstock.

31. The process as set forth in claim 24 wherein:
the additive is selected from the group consisting of iron and molybdenum compounds.

32. The process as set forth in claim 23 wherein:
the additive is selected from the group consisting of iron and molybdenum compounds.

33. The process as set forth in claim 26 wherein:
the additive is selected from the group consisting of iron and molybdenum compounds.

34. The process as set forth in claim 19 wherein:
the additive is selected from the group consisting of iron and molybdenum compounds.

35. The process as set forth in claim 11 wherein:
the additive is selected from the group consisting of iron and molybdenum compounds.

36. The process as set forth in claim 12 comprising:
recycling part of the produced reactor pitch back to the reactor.

37. The process as set forth in claim 12 comprising:
separating the pitch-containing product to produce a heavy distillate and pitch containing separator product;
distilling the separator product to produce pitch; and recycling part of the distilled pitch back to the reactor.

38. The process as set forth in claim 37 comprising:
adding new feedstock to the separator product prior to distillation.

39. The process as set forth in claim 38 wherein:
mixing is conducted at a temperature in the range of 80°C to 190°C.

40. The process as set forth in claim 39 wherein:
the additive is provided in amount of between 0.002%
and 5% by weight based on the feedstock.

41. The process as set forth in claim 39 comprising:
mixing a hydrocarbon solvent for asphaltenes with the feedstock and additive during the mixing step.

42. The process as set forth in claim 41 wherein:
the solvent/feedstock weight ratio is in the range 1:10 to 3:1.

43. The process as set forth in claim 42 wherein:
sufficient hydrogen is passed through the reactor chamber to maintain the axial Peclet No. for liquid at less than 2.0 and for gas at more than 2Ø