FR2617498A1 - PROCESS FOR THERMOCATALYTIC HYDROCONVERSION OF HYDROCARBON HEAVY LOAD - Google Patents

Abstract

The process comprises three stages in the presence of hydrogen: a thermal first reaction (M), a catalytic second reaction (R1, R2) carried out with catalysts of decreasing particle size and relatively low acidity and a catalytic third reaction (R3, R4) carried out with a catalyst of relatively high acidity. Application to the treatment of hydrocarbon feedstocks containing resins and/or asphaltenes, for the purpose of converting them into less heavy fractions.

Description

The invention relates to the treatment of heavy petroleum products,

  containing resins and / or asphaltenes, for the purpose of converting them into less heavy, more easily transportable or treatable fractions

  by the usual processes of refining.

  By "asphaltenes" is meant a substance insoluble in n-pentane.

STATE OF THE ART

  The combination of a thermal hydroconversion with a catalytic hydrotreatment has already been described in the prior art; thus the US patent. No. 4,017,379 proposes a two-step process, in the first stage of which the heavy hydrocarbon oil is subjected to thermal cracking at a temperature of 400 to 800 ° C and a hydrogen pressure of about 1 to 200 bar and in the the second stage of which the product of the first stage is subjected as such to catalytic hydrotreatment at a temperature of 350 to 500 ° C and a hydrogen pressure of about 50 to 300 bar. However, this process has proved to be a problem because the catalyst tends to poison and degrade relatively quickly, causing its too frequent change. No. 4,530,753 and 4,530,754 also recommend the coupling of a thermal step with a catalytic step. The thermal step is carried out at a temperature of 400 to 530 C under a pressure of about 0 to 200 bar, while the catalytic hydrotreatment is carried out at a temperature of 350 to 450 C under a temperature of

  hydrogen pressure of about 50 to 250 bar.

  The method of US 4,530,753 claims to avoid rapid deactivation of the catalyst by use of a particular carrier; that of US 4,530,754

  is supposed to lead to a product of good thermal stability.

  U.S. Patent No. 4,510,042, incorporated herein by reference, claims to associate a thermal hydroconversion step with subsequent steps (a) of hydrodemetallization on a low acid catalyst such as

  described in US Pat. Nos. 4,499,203 and 4,552,650 and (b)

  desulfurization. Although the processes of the prior art, in particular that of US Pat. No. 4,510,042, make it possible to obtain fairly satisfactory results, it is still possible to improve them by further increasing the

  operating time of the catalysts.

SUMMARY OF THE INVENTION

  The object of the present invention is to describe a process for the conversion of heavy petroleum products, containing resins and / or asphaltenes, which overcomes the drawbacks of the prior art

  and can especially work for long periods of time.

  This process can therefore be considered as an improvement of the

  process described in US Patent 4,510,042.

  This process is characterized in that: a) in a first step, a mixture of the feedstock and hydrogen is passed into a thermal reaction zone at a temperature of 400 to 460 ° C and a pressure of 5 to 20 ° C. MPa, b) in a second step, at least a portion of the effluent from step (a) is passed through hydrogen with at least two separate catalyst beds, the first bed being formed of particles of average equivalent diameter of 2.5 to 6 mm and the second bed of particles of average equivalent diameter of 0.5 to 2.5 mm, these two catalyst beds each containing an alumina support and

  at least one metal or metal compound of group VIA and / or VIII.

  Preferably, the acidity of the alumina support, determined by adsorption of ammonia at 0.4 bar and 320 ° C., is less than Joules per gram and its surface area is between 10 and 180 m 2 / g, c) in a third step, the effluent from step (b) is passed with hydrogen through at least one catalyst bed containing an alumina support and at least one metal or group VI A metal compound and / or VIII. Preferably, the acidity of said alumina support, determined by adsorption of ammonia at 0.4 bar and 3205 ° C., is greater than 30 Joules per gram and its surface

between 150 and 350 m2 / g.

  The process is particularly suitable for the treatment of heavy loads having a density of 910 to 1050 kg / m 3 and a kinematic viscosity at 400 ° C of 0.5 to 8 cst (mm / s). that is, whose viscosity at 100 C is included

  between 50 and 30000 cst (mm / s): heavy oils, extra-

  heavy oils, shale oils, atmospheric residues and vacuum residues of conventional crude oils, deasphalted oils from propane precipitation, butanes, pentanes or light gasoline from the asphaltic phase contained in the aforementioned , this same asphaltic phase eventually

  diluted to lower the yiscosity, meet these criteria.

  These fillers usually contain at least 2% by weight

insolubles with n-pentane.

  During the thermal hydroconversion stage, the viscosity at 400 C will be substantially lowered and, for example, divided by a factor of between 2 and 3. On values determined at 1000 ° C the viscosity is more commonly measured the reduction factor. desired viscosity may be between 5 and 50 and preferably between 10 and 30. If the production of light products and the viscosity reduction that accompanies it undoubtedly have a positive influence on the performance of the subsequent catalytic step, it is it is preferable not to cross during the thermal hydroconversion stage a certain threshold of severity above which the charge exhibits a tendency to flocculation which causes unacceptable losses of pressure in the catalytic bed rather quickly. This propensity for flocculation of the product resulting from the thermal step deserves special attention insofar as it makes it possible to assess whether the heat-cracked filler will tend to flocculate or not to flocculate in contact with the catalytic bed with the gradual and rapid appearance of a load loss prohibitive to the smooth running of the process. A simple and effective method to assess this tendency to flocculation is to determine the flocculation threshold in a series of tests where five volumes of a mixture of isooctane and orthoxylene are added to a volume of hydrocarbon feedstock. the proportions vary from one trial to another. The flocculation threshold which characterizes the passage of a colloidal solution of asphaltenes and resins to a micron suspension of these same entities, is determined either by light scattering (flocculometer), or more simply by a spot test; this latter test is based on the fact that the flocculated particles diffuse less rapidly than the surrounding liquid when the mixture is placed on a filter paper; a uniform spot will indicate the absence of particles in suspension while the appearance of a darker zone in the middle of the spot will reveal the presence of flocculated asphaltenes and will make it possible to appreciate the threshold of flocculation. It is quite possible to relate this threshold (S.F.) to

  the volume fraction of xylene in the xylene-isoctane mixture: S.F.

  corresponds to the minimum amount of xylene in the solvent necessary to avoid the appearance of the dark zone of flocculation in the middle of the spot: SF =% O.xylene by volume According to this definition the value of SF will vary from 0 to 10, and the higher the SF value, the more the product will tend to flocculate under the influence of the most varied parameters: dilution of the charge by a light cut, increase of temperature, pressure, contact with solid bodies, such as catalysts likely to to initiate flocculation. It is sometimes customary to designate the value of S.F. as merit at the task. In the hydroconversion process which is the subject of the invention, the severity of the thermal step is preferably such that the product resulting from this step has a flocculation threshold (or merit at the spot) of less than 7, 5 and preferably less than 6. Above 7.5, any modification of the reaction medium or of the surrounding medium may cause an onset of flocculation with deposition of the flocculate on the catalytic bed, increase of the pressure drop and eventually ,

reactor obstruction ..

  This hydrothermal step is most often slightly endothermic even if there is a slight consumption of hydrogen (0.3 to

0.6%).

  Controlling the severity of the thermal step by controlling the value of S.F. is therefore a preferred condition for the process according to the invention to be able to work during economically interesting operating cycles. This is not a sufficient condition; to take full advantage of the previous thermal step, it is also necessary that the catalytic steps are carried out with the catalysts whose characteristics are given in the

this description.

  The catalyst used in the second stage of the process, in the form of at least two beds of different particle sizes, advantageously has an area of between 100 and 180 m 2 / g, preferably 120 to 160 m 2 / g, and the acidity of its alumina support, determined by the ammonia adsorption test at 0.4 bar and 320 C, is preferably less than 30 Joules / g, for example 20 to 28 Joules / g. The average equivalent diameter of the catalyst particles of the first bed (or first beds) is 2.5 to 6 mm, preferably 3 to 5 mm, and that of the catalyst particles of the last bed (or of the last beds) is 0.5 to 2.5 mm, preferably 1 to 2 mm. The catalyst of the first type represents usefully 10 to 40%, that of the second type 60 to 90% of the total amount, by weight, of catalyst

  used in the second stage of the process.

  This catalyst comprises alumina and at least one metal or group metal compound of group VI A (Mo, W) and / or VIII (Fe, Ni, Co). The active agents are preferably in the form of sulphides, in particular a

  mixture of molybdenum sulphide and nickel sulphide.

  The metal content of the catalysts is advantageously from 3 to 25% by weight. For example, the molybdenum content may be between 6 and 16% and preferably between 8 and 12% and the nickel content between

  1.5 and 5% and preferably between 2 and 4%.

  The pore volume of the catalyst will usefully be 0.7 to 1.2 cm / g and the pore volume with a diameter larger than 0.1 micron will be

  preferably greater than 0.3 cm3 / g.

  All catalysts on alumina as support and having these general characteristics will advantageously be used in the process according to the invention, but among all these catalysts, catalysts prepared from an alumina support of acicular structure, type bugs of chestnut, or sea urchins, as they have been described in the French patent

  No. 2,538,814 and its equivalent US 4,510,042.

  According to a preferred embodiment of the method, the second step is carried out with a succession of beds using 3 different catalysts:

26 1 7498

  10 to 30% by weight of the total; particles of 3.6 to 4.5 mm 2nd bed 10 to 30% by weight of the total; particles of 2.5 to 3.5 mm 1 + 2nd bed: 20 to 40% by weight of the total 3rd bed: the complement to 100%, ie 60-80%; particles 0.7 to 2 mm The second stage of the process is carried out at 350-440 ° C., preferably at 380 ° -420 ° C., and 40-200 bar; the space velocity is preferably 0.2 to 2 vvh and the volume ratio hydrogen gas / charge

  hydrocarbon liquid preferably 300 to 3000.

  The third step is implemented in the general operating conditions that those of the second step. Thus, the catalyst is of the same kind as regards the metals present and their proportions, but the catalyst very advantageously has a specific surface area of 150 to 350 m 2 / g, preferably 160 to 300 m 2 / g, and the support an acidity of adsorption of ammonia, in the aforementioned test, greater than 30 Joules per gram, preferably 32 to Joules per gram. The pore volume of the catalyst is, for example, 0.4 to 1 cm 3 / g, the pore volume with a diameter greater than 0.15 micrometer is preferably less than 0.1 cm 3 / g and the pore volume of diameter less than 10 nm is preferably less than 0.2 cm / g. The particle size (equivalent diameter) may be, for example, 0.5 to 3 mm. By equivalent mean diameter, we mean the diameter of the sphere which would have the same V / S ratio as the

  considered particle of which V is the volume and S the external surface.

  The attached figure allows to define more precisely the characteristics of the method according to the invention. The fresh feedstock is introduced under pressure (1) into unit o, after preheating (3), it is mixed (4) with pressurized hydrogen gas, makeup gas mixture (2) and recycle gas ( 29). The heating of the mixture is continued in exchangers and in an oven (5) and the mixture is then injected via line (6) into the maturator (M) via the distribution device D. The reaction mixture exits via line (7) before

  to cross successively the reactors (R, R2, R3 and R4).

  to cross successively the reactors (R1, R2, R3 and R4).

  Q1, Q'l, Q2, Q3 and Q4 denote the quenching devices that equip the various reactors. The quenching fluid arrives through lines (8), (11), (14), (17). It can be injected in line or preferably at the top of the reactors (9), (12), (15), (18) just above the homogenization and fluid distribution devices (D1, D1, D2 , D3, D4). The fluids flow up and down the catalytic beds and are transferred from one reactor to another by the lines

(10), (13), (16).

  At the outlet of the last reactor, the effluents are sent via the line (19) through the cooler (20) into the hot separator (SI); the liquid fraction exits the line (21) to be charged to the distillation tower (D). Distilled fractions such as (27a) and (27b) and a residue (27c) are collected. The gaseous fraction that leaves (S1) via the line (22) is first cooled in (23) and enters the line (24) in the cold separator (S2) which separates a liquid fraction also sent by the line ( 25) to the distillation and a gaseous fraction which through the line (26) is directed towards the compressor (C) and then by the line (28) to the purification step (P) involving an amine treatment and optionally a gas oil washing of hydrogen gas. This purification step can also be placed upstream of the recycling compressor. The hydrogen gas purified and reconcentrated with hydrogen can be partly mixed with the make-up gas by the line (29) or partly be

  redistributed to the various quenching devices by line (30).

  The thermal hydroconversion step can be carried out in the single oven at very high temperatures of between 430 and 460 ° C., for a residence time in the oven preferably ranging from 20 seconds to 60 seconds. This thermal conversion step is preferably carried out in a vertical maturator; the residence time of the liquid phase in this maturing agent will be, for example, between 30 minutes and 30 minutes, the temperatures applied will preferably be less than 440.degree. C., advantageously between 400 and 440.degree. The report

2 6 1 7498

  H2 / HC expressed in m of TPN hydrogen gas per m of TPN liquid charge will advantageously be between 100 and 800 and preferably between 200 and 600 and the total pressure may advantageously be between 5 and 20 MPa and preferably between 12 and 17. MPa. In practice, the operating conditions will be selected according to the load to be treated and, very usefully, the flocculation threshold at the outlet of the M maturator will be less than 7.5 and preferably less than 6 to avoid the problems that could result, regarding the bed

  catalytic, a tendency of the charge to flocculate.

  At the exit of the maturator, the effluents are usefully cooled, preferably with cold hydrogen, so as to lower their temperature below 380 C. The temperature in the first reactor will preferably be less than 435 C. The speed overall spatial density will preferably be between 0.8 and 2 h. In the reactor R2 also containing a demetallization catalyst, the applied temperatures will remain below 440 C and will preferably be between 390 C and 430 C; the space velocities will preferably be between 0.8 and 2 h. In the reactors R3 and R4 containing conventional hydrorefining catalysts, the space velocities will also preferably be between 0.8 and 2 h -1 in each of the reactors; As for the temperatures they will remain usefully between 370 C and 430 C and preferably between 380 C and 420 C. One of the original features of the process consists in effect to operate in the first two reactors (second stage of the process) at an average temperature and a maximum temperature of 10 to 15 C higher than in the last two reactors R3 and R4 (third stage of the process). Like Ql, the other quenchs Q'i, Q2, Q3, Q4 will preferably be made with cold hydrogen gas but the implementation of a liquid fluid, charge or fraction resulting from the

  distillation, may also be carried out.

26 17498

  In the reactors Ri, R2, R3, R4, the pressure applied is

  preferably related to that of the maturator M to the losses of load close.

  To minimize these pressure drops, the reactors R3 and R4 may advantageously be arranged in parallel rather than in series as shown in the figure. For the feeds where the content of metals (Ni, V, Fe, Na) and pollutants (C, SiO 2, Al 2 O 3) is greater than 250 ppm by weight, resulting in a cycle time of the catalysts of the reactor R 1 being less than 6 months, can install in parallel two identical reactors Rl and R'l one pending, the other in operation and possibly two sets of reactors (Ri + R2) and (R'l + R'2) one waiting, the other in operation so that the unit, as a whole,

  can walk without stopping for a year.

EXAMPLE 1

  In a pilot plant with a two-liter reactor and four 7-liter reactors (see attached figure), a Safaniya vacuum residue is treated, the characteristics of which are shown in Table 1. The system operates almost adiabatically that is to say that the effluent is cooled at the outlet of the various reactors by injection of a quantity of hydrogen gas recycling close to 120 liter / liter. The height of each catalytic reactor is 5 m. The operation takes place at 14.5 MPa of total pressure, measured in the maturator, and the pressure drop in the unit determined between the outlet and the inlet of the recycle compressor is around 0.75 MPa. the space velocities and hydrogen gas flows applied during the test series. A sampling loop at the exit of the maturator makes it possible to extract samples having undergone the only thermal conversion and to determine their threshold of flocculation. The tests are carried out at high severity in the thermal step so that the behavior of the various catalyst arrangements can be compared rapidly. The conditions of

2 6 1 7 4 98

  it temperature and residence time applied in the maturator and the

  various reactors are shown in Table 3. The amounts of.

  catalyst are the same in all reactors. For each catalyst arrangement, the time required to multiply the initial pressure drop by a factor of 2 as well as the performances after 200 hours of operation and at the end of the test is measured for each catalyst arrangement. The conversion shown is the conversion to weight percent of the residual 520 C fraction of the feedstock. Booster heaters make it possible to keep the various temperatures constant from one test to another. The characteristics of catalysts are shown in

table 2.

  The supports of the catalysts A, B, C and F are of the acicular type (US-4,510,042). The supports of the catalysts D and E are of the gamma type

cubic (non-acicular).

  Catalysts A, B and C are identical, apart from the grain size; this last difference leads to slight variations in

  the distribution of porosities, non-significant variations.

  Examination of the results clearly shows the advantage of using the catalyst arrangement of the test 1, as recommended in the description of the invention. In all the other tests, the increase in pressure drop appears much faster even in the test 2 where the catalyst remains a catalyst of low acidity having little propensity to accelerate the formation of coke. Large surface catalysts on cubic gamma alumina more acidic and smaller particle size have shorter cycles. The comparison of tests 1 and 5 shows the need to have a function

  hydrogenating on the top catalyst of the first reactor.

2 6 1 7 4 9 8

EXAMPLE 2

  The BOSCAN atmospheric residue is treated, the characteristics of which are shown in Table 1. The operating conditions applied are the same as in Table 3, except for the temperatures in the maturation which are equal to 432 C at the inlet and

  4180 C at the exit for a merit (S.F.) of the adjacent effluent of 7.

  The results obtained are shown in Table 4; the conversion shown is the conversion to weight percent of the residual fraction 500 C + of the load. This second example again illustrates the advantages provided by the recommendations of the invention namely a good scaling in the first reactor catalysts decreasing particle sizes, all having a low acidity, a surface less than 160 m 2 / g and a low propensity to train

coke.

EXAMPLE 3

  The RSV Safaniyah described in Table 1 is treated at increasing severities of the thermal step. All the tests are carried out at a conversion close to 50% by offsetting the decreases in severity in the thermal step by a slight increase in temperatures in the catalytic stages; all tests are performed at temperature

  constant. The results are shown in Table-5.

EXAMPLE 4

  4a (invention): the vacuum treatment Safaniya (Table 1) is applied to the processing treatment of Example 1. The effluent then passes into the reactors R1 to R4 containing: R1: 50% Catalyst A followed by 50% Catalyst C R2: 100% catalyst C R3 and R4: 100% each catalyst E. 4b: for comparison, to show the influence of the particle size, the test 4a is repeated identically except that Ri and R2 contain each of 100% catalyst A, R3 and R4 being the same as

test 4a.

  4c: likewise, test 4a is repeated identically excepted. that R1 and R2 each contain 100% catalyst C, R3 and R4 being the same as

test 4a.

  The average temperature is 400 C (R1 and R2) and 385 C (R3 and R4). The residence time is 1 hour in each reactor and the

  H2 / HC ratio is 700 1/1 in each reactor.

  The results are shown in Table 6.

TABLE 1

CHARACTERISTICS OF CHARGES

  Vacuum residue | Atmospheric residue

SAFANIYA BOSCAN

  Density (kg / m3) 1034 1033 IV (mm2 / s at 1000 ° C) 5100 4285 IV (mm2 / s at 400 ° C) 2,4 3,2 IS% weight 5,4 5,65 insoluble n-pentane {( % wt.) 23, 1 24.4 metals (V-Ni-Fe-Na) ppm 220 1500 Conradson ICarbone (wt% 20.2 20.3 jDistillate ss / void (500 C-) wt% O 17

V = kinematic viscosity.

  TABLE 2: CATALYST CHARACTERISTICS

| I CATALYSEURI A B | C J D E | F

  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ I _ _ _ _ I _ _ _ _ I _ _ _ _ I_ _ _ _ I

  SUPPORT-Nature A 20 3 A1203 A1203 JA1203 (ec) | A1203 (yc) l A1203 Laciculairacicularandacicular structureI not | non acicular Acicular acicular acicular acidity (joules / g) 24 23 25 35 41 24 equivalent diameter (cm) 0.42 0.28 0.18 0.125 0.125 0.4 balls balls balls extruded. extruded. ball

CATALYST I

  surface (m / g) 142 138 147 239 219 157 Total porous ivolume I (cm3 / g) 0.96 0.93 0.93 0.91 0.91 0.98 Porous ivolume> lem j 0.22 | 0,18 0,17 | 0,03 | 0,03 | 0.2 i Porous ivolume> O, lwmj 0.34 | 0.33 | 0.32 | 0.11 | 0.08 | 0.36 | pore volume <10 nm J 0.07 0.09 0.11 0.18 0.13 0.04 IM O3% by weight | 14.2 14.3 14.3 15 14.8 0 INiO% wt. 2.9 | 3.1 3.0 3.2 3.1 0 Ideneness of bed J 0.55 0.57 0.57 0.57 0.56 0.51

  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __II _ _ _ _ _ _ I _ _ _ _ _ _ I _ _ _ _ _ _ I _ _ _ _ _ _ I _ _ _ _ _ _ C

o oD

TABLE 3

  THERMOCATALYTIC HYDROCONVERSION OF ATMOSPHERIC RESIDUE SAFANIYA

OPERATING CONDITIONS

T I iI

I IMATURATEIR1 | R2 1 R3 I R4 1

  I stay (h) I 0.33 - 1 11 1

H2 / HC (1/1) 550 I 670 790 810 930

  T entry C 437 I 385 400 380 380 T exit o C 426 I 405 415 390 390 SF (merit) 7.0 I I I

I, T T T T

  RESULTS TEST 1 1 TEST 2 IESSAI S3-TEST 41TEST 51

I II

  Reactor loading I I I I I I

1 1__ _ _ _1 1 1 1 -

I- | 20% AI0% to 120% FI

  R1 30% B | 0% B 1100% D1100% EI 30% BI

I 50% CI 100% CI I I 50% CI

R2 C C D E C I

R3 E - E E E I

R4 E E E E

i -

  t- A P X 2 (hours) I I I I I I (end of test) 1224 888 624 528 480

I I I I I I I

  | Co. 1200 hours | 55 | 52 | 53 | 55 | 56 | Conversion

152000C (%) I I I I 1 1 I

  520 C (%) end of test 51 48 51 52 l 50 1200 hours 1 96,1 I 97,4 I 97,91 97, 81 93 |

HDM (%) I I I I I I I I

  | | Ifin test | 95.3 | 95.8.94,31 92.91 91 |

I I I I I I I I I I I

11200 hours | 91 92 94 95 89

HDS (%) I

  | | Ifin test | 89 | 89 | 87 | 84 | 86 |

  I _ _ _ I _ _ _ I _ _ I _ _ _ _ _ _ _

TABLE 4

  THERMOCATALYTIC HYDROCONVERSION OF A BOSCAN ATMOSPHERIC RESIDUE

  t RESULTS t TEST 1 TEST 2 TEST 3 I Loading t reactors% A

R1 30% B 100% C 1 00% D

| 50% C 5 C

R2 C C D

R3 E E E

R4 E E E

  t-> ibP X 2 (hours) 864 744 648 (end of test) Conversion 200 hours. 67% 63% 69% 5000c + (%) t 1t0 () end of test | 66% 66% 63% 1200 hours 97, 5 98.0 | 99.0

HDM (%) |

  | 1th of test 97.0 96.5 1 94.0 | 1200 hours | 91.0 92.0 1 94.0

HDS (%) |

| | Ifin test | 88.5 88.0 | 89.0

26 1 7498

TABLE 5

T. I T

  I | | TEST 1 of l | I | EXAMPLE 1 SF output 5.5 6.5 7 thermal step

  _ _ _ _ _ _ I._ _ _ I _ _ _ _ _ _ _ _

Average maturation T 424 427 432

I

  T average R1 403 400 395 oC R2 412 410 407

R3 385 385 385

R4 385 385 385

  t-p P X 2 (hrs) 6100 2760 1224 (end of test)

| I I I +

  json inj200 hours | 55 1 54 1 55 lConversion,

15200C +) I I

  I '' Ifin test | 53 i 52 51 1200 hours | 98.6 | 97.2 | 96.1

HDM (%) |

  | I | end of test 91,6 93,9 95,3 | | 1200 hours | 93 92 91

HDS (%)

{tifin test 84 I 87 89

  I _ _ _ _ _ I _ _ _ _ _ _ I _ _ _ _ _ _ _ I _ _ _ _ _ _ _ _

TALBEAU 6

I I t. I TEST 4a TEST 4b TEST 4c

CATALYSTS A + C + E TO C + E

  t-> AP X 2 (hours) (end of test) 1088 1016 888 4 r 1 i I I Conver1200 hours 53 52 53 Conversion,

1.0 520 C + (% /) i 1j20 C () Iof test | 49 I 48 48 1200 hours 95.2 94.4 97.4

HDM (%)

End of test 94.4 93.6 95.6

hours | 90 | 89 92.

HDS (%) |

| | Test end 88 1 87 | 89

  I _ _ _ _ _ I I _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ I, 1 _ _ _ _, _ I

Claims (8)

  1. A process for converting a hydrocarbon heavy load, comprising the following successive steps: a) in a first step, a mixture of the feedstock and hydrogen is passed into a thermal reaction zone, at a temperature of 400.degree. at 460 ° C. and at a pressure of 5 to 20 ° NPa, b) in a second step, at least a portion of the effluent from step (a) is passed with hydrogen through at least two successive successive beds of catalyst, the first bed being formed of particles of average equivalent diameter of 2.5 to 6 mm and the second bed of particles of average equivalent diameter of 0.5 to 2.5 mm, these two catalyst beds containing each a carrier of alumina and at least one metal or metal compound of the VIA group and / or VIII.   c) in a third step, the effluent of step (b) is passed, with hydrogen, through at least one bed of catalyst containing an alumina support and at least one metal or compound of group VI A and / or VIII metal.   2. A process according to claim 1, wherein the operating conditions of the first stage are mutually adapted to provide a hydrocarbon effluent having a flocculation threshold at most   7.5, and preferably less than 6.   3. A process according to claim 1 or 2, wherein the surface of the catalyst beds of step (b) is from 100 to 180 m 2 / g and the acidity of the support of the catalysts of said beds is less than 30 Joules per gram, and the catalyst surface of step (c) is from 150 to 350 m 2 / g and the acidity of the support of said catalyst is greater than 26 17498   Joules per gram, said acidities being determined by adsorption of ammonia at 0.4 bar and 320 C. 4. A process according to claim 1 or 2, wherein the surface of the catalyst beds of step (b) is from 120 to 160 m 2 / g and the acidity of the support of the catalysts of said beds is from 20 to 28 Joules per gram, and the catalyst surface of step (c) is from 160 to 300 m 2 / g and the acidity of the support of said catalyst from 32 to 50 J. per gram, said acidities being determined by adsorption of ammonia at 0.4 bar and 320 C.   5. Method according to one of claims 1 to 4, wherein the   porous volume of the catalyst of step (b) is 0.7 to 1.2 cm3 / g, that of the catalyst of step (c) is 0.4 to 1 cm / g and the volume of pores of diameter wider than 0.1 micrometer is greater than 3 3   0.3 cm3 / g for the catalyst of step (b) and less than 0.15 cm3 / g for the catalyst of step (c);   6. A process according to one of claims 1 to 5, wherein the   The catalyst particles of step (b) have an average diameter of 3 to 1 mm for the first bed and 1 to 2 mm for the last bed.   7.- Method according to one of claims 1 to 6, wherein one operates   in step (b) with 3 successive beds of catalyst, the mean equivalent diameter of the particles being from 3.6 to 4.5 mm for the first bed, from 2.5 to 3.5 mm for the second bed and from 0.7 to 2 mm for the third bed.   8. A process according to one of claims 1 to 7, wherein the   the average temperature of step (b) is at least 10 C greater than   the average temperature of step (c).