METHOD FOR CONVERTING HEAVY HYDROCARBON FEEDSTOCKS

Abstract

The invention concerns a process for the conversion of a heavy hydrocarbon feed, said process comprising the following steps: a) a step for hydroconversion of the heavy hydrocarbon feed in the presence of hydrogen in at least one or more three-phase reactors disposed in series or in parallel, containing at least one hydroconversion catalyst, so as to obtain a liquid effluent with a reduced Conradson carbon, metals, sulphur and nitrogen content, b) one or more optional steps for separating the effluent obtained from step a) in order to obtain at least one light liquid fraction boiling at a temperature of less than 350 C. and a heavy liquid fraction boiling at a temperature of more than 350 C., c) a step for hydroconversion of the liquid effluent obtained from the hydroconversion step a) in the case in which the separation step b) is not carried out, or of the heavy liquid fraction obtained from the separation step b) when said step b) is carried out, in the presence of hydrogen in at least one or more three-phase reactors disposed in series or in parallel and containing at least one hydroconversion catalyst, in which process the overall hourly space velocity employed is in the range 0.05 to 0.18 h.sup.1.

Claims

1. A process for the conversion of a heavy hydrocarbon feed, said process comprising the following steps: a) a step for hydroconversion of the heavy hydrocarbon feed in the presence of hydrogen in at least one or more three-phase reactors disposed in series or in parallel, containing at least one hydroconversion catalyst, the hydroconversion step a) being carried out under an absolute pressure in the range 2 to 35 MPa, a temperature in the range 300 C. to 550 C., and under a quantity of hydrogen mixed with the feed in the range 50 to 5000 normal cubic metres (Nm.sup.3) per cubic metre (m.sup.3) of feed, in a manner such as to obtain a liquid effluent with a reduced Conradson carbon, metals, sulphur and nitrogen content, b) one or more optional steps for separating the effluent obtained from step a) in order to obtain at least one light liquid fraction boiling at a temperature of less than 350 C. and a heavy liquid fraction boiling at a temperature of more than 350 C., c) a step for hydroconversion of the liquid effluent obtained from the hydroconversion step a) in the case in which the separation step b) is not carried out, or of the heavy liquid fraction obtained from the separation step b) when said step b) is carried out, in the presence of hydrogen in at least one or more three-phase reactors disposed in series or in parallel, containing at least one hydroconversion catalyst, the hydroconversion step c) being carried out under an absolute pressure in the range 2 to 38 MPa, at a temperature in the range 300 C. to 550 C., and under a quantity of hydrogen in the range 50 to 5000 normal cubic metres (Nm.sup.3) per cubic metre (m.sup.3) of liquid feed under standard temperature and pressure conditions, in which process the overall hourly space velocity employed is in the range 0.05 to 0.18 h.sup.1.

2. The process as claimed in claim 1, in which the overall hourly space velocity employed is in the range 0.05 h.sup.1 to 0.09 h.sup.1.

3. The process as claimed in claim 1, in which at least a portion of the effluent obtained from the hydroconversion step c) undergoes one or more steps d) for fractionation in order to separate the effluents with different cut points.

4. The process as claimed in claim 1, in which the feed contains hydrocarbon fractions wherein at least 80% by weight have a boiling temperature of more than 300 C., atmospheric residues and/or vacuum residues, atmospheric residues and/or vacuum residues obtained from hydrotreatment, hydrocracking and/or hydroconversion, fresh or refined vacuum distillates, cuts from a cracking unit such as FCC, coking or visbreaking, aromatic cuts extracted from a lubricant production unit, deasphalted oils obtained from a deasphalting unit, asphalts obtained from a deasphalting unit or similar hydrocarbon feeds, or a combination of these fresh feeds and/or refined effluents, or residues or distillates obtained from the direct liquefaction of coal, or residues or distillates obtained from coal pyrolysis or from shale oils, or in fact a residual fraction obtained from the direct liquefaction of lignocellulosic biomass alone or as a mixture with coal and/or a fresh and/or refined oil fraction.

5. The process as claimed in claim 1, in which step a) or step c) is carried out at an absolute pressure in the range 5 to 25 MPa, at a temperature in the range 350 C. to 500 C.

6. The process as claimed in claim 1, in which each reactor in step a) and/or step c) may contain one or more supported catalysts and/or one or more unsupported catalysts.

7. The process as claimed in claim 1, in which the hydroconversion catalyst of step a) or step c) is a catalyst comprising an alumina support and at least one metal from group VIII selected from nickel and cobalt, said element from group VIII being used in association with at least one metal from group VIB selected from molybdenum and tungsten.

8. The process as claimed in claim 1, in which the quantity of nickel in the hydroconversion catalyst of step a) is in the range 0.5% to 10%, expressed as the weight of nickel oxide (NiO), and the molybdenum content is in the range 1% to 30%, expressed as the weight of molybdenum trioxide (MoO.sub.3).

9. The process as claimed in claim 1, in which the separation step b) is carried out using one or more flash drums in series.

10. The process as claimed in claim 3, in which the light liquid fraction separated in step b) is sent to the fractionation step d).

Description

DESCRIPTION OF THE FIGURES

[0049] FIG. 1 diagrammatically represents the process in accordance with the invention in the case in which the separation step b) is carried out.

[0050] The feed is sent via the line 1 to a hydroconversion section A operating at a high hydrogen pressure and preferably in ebullated bed mode.

[0051] (A) represents the step a) for hydroconversion of the feed 1 in the presence of hydrogen, with the hydrogen arriving via the conduit 2. The hydroconversion step a) may be composed of one or more reactors disposed in parallel and/or in series.

[0052] The effluent from the hydroconversion section A is sent to the separation section B via the conduit 3.

[0053] The heavy liquid fraction obtained from the separation section B is sent to the hydroconversion step c) represented by the section C via the conduit 5, while the light effluent is extracted from the separation B via the conduit 4. Part or all of this latter may be sent to the fractionation section D via the conduit 42 and/or partially and/or completely directed towards another unitary operation via the conduit 41.

[0054] The hydroconversion step c), C, is composed of one or more reactors disposed in parallel and/or in series. The conduit 6 represents the injection of hydrogen into the hydroconversion step c). The entirety of the effluent from the hydroconversion step c), C, may be sent to the fractionation section D via the conduit 7 for fractionation into a plurality of cuts. In this process layout, only two cuts are shown, a light cut 8 and a heavy cut 9.

[0055] FIG. 2 illustrates the invention in a preferred embodiment.

[0056] The feed is sent via the conduit 1 to the hydroconversion step a) (section A) which is composed of a plurality of reactors disposed in series and/or in parallel and preferably composed of two reactors operating in ebullated bed mode (A.sub.1 and A.sub.2) disposed in parallel and operating under hydrogen (conduits 21 and 22 respectively).

[0057] The effluents obtained from the hydroconversion section A are combined and sent via the conduit 3 to the separation section B. In the separation section B, the conditions are generally selected in a manner such as to obtain two liquid fractions, a fraction termed a light fraction 4 and a fraction termed a heavy fraction 5, using any separation means known to the person skilled in the art, preferably without intermediate atmospheric distillation and vacuum columns, preferably by stripping, more preferably by a concatenation of flash drums and yet more preferably via a single flash drum.

[0058] The heavy liquid fraction leaving the separation section is then sent via the conduit 5 to the hydroconversion section C composed of one or more reactors disposed in parallel and/or in series and preferably composed of a single reactor with a high hydrogen pressure 6 operating in ebullated bed mode.

[0059] In the fractionation section D, the conditions are generally selected in a manner such as to obtain at least two liquid fractions, a fraction termed a light fraction 8, and a fraction termed a heavy fraction 9, preferably with the aid of a series of atmospheric and vacuum distillation columns.

[0060] The following examples illustrate the invention without limiting its scope.

EXAMPLES

Feed

[0061] The heavy feed was a vacuum residue (VR) from an Oural crude the principal characteristics of which are presented in Table 1 below.

TABLE-US-00001 TABLE 1 Composition of feed for the process Feed for step A Feed VR Oural Density 1.0165 Viscosity at100 C. cSt 880 Conradson Carbon % by wt 17.0 C7 Asphaltenes % by wt 5.5 C5 Asphaltenes % by wt 10.9 Nickel + Vanadium ppm 254 Nitrogen ppm 6150 Sulphur % by wt 2.715

[0062] This heavy VR feed was used as the fresh feed for all of the various examples.

Example 1 (Comparative)

[0063] Conventional process layout at high hourly space velocity (overall HSV=0.3 h.sup.1) and at high temperature

[0064] This example illustrates the prior art in a process layout with two ebullated bed reactors disposed in series, operated at high hourly space velocity (HSV) and at a high temperature and with a separation section.

Section a) Hydroconversion

[0065] The fresh feed of Table 1 was sent in its entirety to a section A for hydroconversion in the presence of hydrogen. Said section comprised a three-phase reactor containing a NiMo/alumina hydroconversion catalyst with a NiO content of 4% by weight and a MoO.sub.3 content of 9% by weight, the percentages being expressed with respect to the total mass of catalyst. The section functioned in ebullated bed mode with an upflow of liquid and gas.

[0066] The conditions applied in the hydroconversion section A are shown in Table 2.

TABLE-US-00002 TABLE 2 Operating conditions Section A P, total MPa 16 Temperature C. 430 Quantity of hydrogen Nm.sup.3/m.sup.3 640

[0067] These operating conditions allowed a liquid effluent with a reduced Conradson carbon, metals and sulphur content to be obtained.

Separation Section

[0068] The hydroconverted liquid effluent was then sent to a separation section B composed of a single gas/liquid separator operating at the pressure and temperature of the reactors of the first hydroconversion section A. A fraction termed a light fraction and a fraction termed the heavy fraction were then separated. The light fraction was mainly composed of molecules with a boiling point of below 350 C. and the fraction termed the heavy fraction was mainly composed of molecules of hydrocarbons boiling at a temperature of more than 350 C.

Section c) for Hydroconversion

[0069] The characterization of the heavy fraction sent to the second hydroconversion section C is presented in Table 3.

TABLE-US-00003 TABLE 3 Composition of the feed for section b) for hydroconversion in ebullated bed mode, C Feed for step C Feed Heavy fraction Density 0.9742 Conradson carbon % by wt 11.9 C.sub.7 Asphaltenes % by wt 5.2 C.sub.5 Asphaltenes % by wt 5.2 Nickel + Vanadium ppm 104.4 Nitrogen ppm 5890 Sulphur % by wt 1.2601

[0070] In this reference process layout, the heavy fraction 5 was sent alone and in its entirety to a second hydroconversion section C in the presence of hydrogen, 6. Said section comprised a three-phase reactor containing a NiMo/alumina hydroconversion catalyst with a NiO content of 4% by weight and a MoO.sub.3 content of 9% by weight, the percentages being expressed with respect to the total mass of catalyst. The section functioned in ebullated bed mode with an upflow of liquid and of gas.

[0071] The conditions applied to the hydroconversion section C are presented in Table 4.

TABLE-US-00004 TABLE 4 Operating conditions Section C P, total MPa 15.6 Temperature C. 430 Quantity of hydrogen Nm.sup.3/m.sup.3 420

Fractionation Section

[0072] The effluent from the hydroconversion section C was sent to a fractionation section D composed of an atmospheric distillation from which a light fraction 8 boiling at a temperature essentially below 350 C. and an unconverted heavy atmospheric residue fraction AR boiling at a temperature essentially higher than 350 C. were recovered; the yields with respect to the fresh feed and the quality are given in Table 5 below.

TABLE-US-00005 TABLE 5 Yields and Qualities of effluents from the fractionation section Unconverted atmospheric Fraction residue Yield with respect to % by wt 58.4 fresh feed (1) Density 0.9678 Conradson carbon % by wt 9.55 C.sub.7 Asphaltenes % by wt 4.0 Nickel + Vanadium ppm 41.5 Nitrogen ppm 5885 Sulphur % by wt 0.7849 Sediments (IP-375) % by wt 0.54

Overall Performances

[0073] With this conventional process layout, for an overall hourly space velocity (HSV) of 0.3 h.sup.1, the total conversion of the heavy 540 C.+ cut was 75.4% by weight and the sediments content (IP-375) in the unconverted residual heavy cut AR was 0.54% by wt.

Example 2 (in Accordance with the Invention)

[0074] Process layout in accordance with the invention with low hourly space velocity (overall HSV=0.089 h.sup.1) and low temperature

[0075] In this example, the present invention is illustrated in a process layout with two ebullated bed reactors disposed in series, operated at a low hourly space velocity (HSV) and at a low temperature and with a separation section.

Hydroconversion Section a)

[0076] The fresh feed of Table 1 was sent in its entirety to a section A for hydroconversion in the presence of hydrogen, said section comprising a three-phase reactor containing a NiMo/alumina hydroconversion catalyst with a NiO content of 4% by weight and a MoO.sub.3 content of 9% by weight, the percentages being expressed with respect to the total mass of catalyst. The section functioned in ebullated bed mode with an upflow of liquid and gas.

[0077] The conditions applied in the hydroconversion section A are shown in Table 6.

TABLE-US-00006 TABLE 6 Operating conditions Section A P, total MPa 16 Temperature C. 410 Quantity of hydrogen Nm.sup.3/m.sup.3 1000

[0078] These operating conditions allowed a liquid effluent with a reduced Conradson carbon, metals and sulphur content to be obtained.

Separation Section

[0079] The hydroconverted liquid effluent was then sent to an interposed separation section B composed of a single gas/liquid separator operating at the pressure and temperature of the reactors of the first hydroconversion section. A fraction termed a light fraction and a fraction termed the heavy fraction were then separated. The light fraction was mainly composed of molecules with a boiling point of below 350 C. and the fraction termed the heavy fraction was mainly composed of molecules of hydrocarbons boiling at a temperature of more than 350 C.

Section c) for Hydroconversion

[0080] The characterization of the heavy fraction sent to the second hydroconversion section C is presented in Table 7.

TABLE-US-00007 TABLE 7 Composition of the feed for the ebullated bed hydroconversion section (C) Feed for step C Feed Heavy fraction Density 0.9665 Conradson carbon % by wt 10.57 C.sub.7 Asphaltenes % by wt 3.6 C.sub.5 Asphaltenes % by wt 4.2 Nickel + Vanadium ppm 65.7 Nitrogen ppm 5680 Sulphur % by wt 1.030

[0081] In this process layout in accordance with the present invention, the heavy fraction 5 was sent alone and in its entirety to a second hydroconversion section C in the presence of hydrogen, 6, said section comprising a three-phase reactor containing a NiMo/alumina hydroconversion catalyst with a NiO content of 4% by weight and a MoO.sub.3 content of 9% by weight, the percentages being expressed with respect to the total mass of catalyst. The section functioned in ebullated bed mode with an upflow of liquid and of gas.

[0082] The conditions applied to the hydroconversion section C are presented in Table 8.

TABLE-US-00008 TABLE 8 Operating conditions Section C P, total MPa 15.6 Temperature C. 410 Quantity of hydrogen Nm.sup.3/m.sup.3 560

Fractionation Section

[0083] The effluent from the hydroconversion section C was sent to a fractionation section D composed of an atmospheric distillation from which a light fraction 8 boiling at a temperature essentially below 350 C. and an unconverted heavy atmospheric residue fraction AR boiling at a temperature essentially higher than 350 C. were recovered; the yields with respect to the fresh feed and the quality are given in Table 9 below.

TABLE-US-00009 TABLE 9 Yields and Qualities of effluents from the fractionation section Unconverted atmospheric Fraction residue Yield with respect to % by wt 54.0 fresh feed (1) Density 0.9590 Conradson carbon % by wt 7.42 C.sub.7 Asphaltenes % by wt 2.1 Nickel + Vanadium ppm 10.3 Nitrogen ppm 5305 Sulphur % by wt 0.4684 Sediments (IP-375) % by wt 0.15

Overall Performance

[0084] With this process layout in accordance with the invention with an overall HSV=0.089 h.sup.1, the total conversion of the heavy 540 C.+ cut was 75.3% by weight and the sediments content (IP-375) in the unconverted heavy residual AR cut was only 0.15% by weight. Compared with the conventional process layout dealt with in Example 1, the purification performance was higher for an almost identical level of conversion of the heavy 540 C.+ cut. The stability of the liquid effluents from conversion was very substantially improved.