FR2475569A1 - Upgrading of heavy oils by visbreaking and deasphalting - with visbreaking effected in presence of hydrogen and steam - Google Patents

Abstract

Upgrading of asphaltene-contg. hydrocarbon feeds is carried out by (a) visbreaking the feed in the presence of H2 and steam, (b) deasphalting at least part of the effluent with a solvent, and (c) removing the solvent from the solvent-rich phase and recovering a hydrocarbon fraction with a low content of asphaltenes and other impurities. Step (a) is pref. effected at 350-510 deg.C and 20-200 (esp. 30-70) bar with a residence time of 0.1-30 min. The water feed wt. ratio is pref. 0.002-0.3 and the H2 feed vol. ratio is pref. 50-2000. Step (b) is pref. effected with a 4-7C hydrocarbon solvent (esp. pentane) using a solvent/feed vol. ratio of 1-10 (esp. 1.5-4). The prods. are suitable for use as hydrocracking, hydrofining or catalytic cracking feedstocks. Hydrovisbreaking in the presence of steam increases the middle distillate yield when the prod. is hydrocracked, reduces the asphaltene yield and improves the yield and quality of the malthene fraction.

Description

 The present invention relates to a method and more specifically to an arrangement of processes for the conversion of hydrocarbon feeds containing asphaltenes and other metalliferous compounds into more valuable products. The process arrangement which is the subject of the invention more particularly comprises a thermal hydrotreatment of the asphaltenic fillers associated with pentane or light gasoline deasphalting in order to prepare, with high yields, fillers of suitable composition for subsequent hydrodesulfurization.

The asphaltenic fillers whose treatment is the subject of the invention are the residues of atmospheric distillation or vacuum distillation of conventional crudes; they are also heavy oils with a density greater than 0.950, containing from 5 to 30% of atmospheric distillates, such as Boscan crude or heavy oils from the Orinoco belt in Venezuela or from the Athabasca to
Canada. Finally, it is generally all hydrocarbon feeds containing asphaltenic compounds and soluble or suspended metals, including the charges arising from the pyrolysis of the oil shale or the liquefaction of the coal.

 When these asphaltenic fillers are heavy oils or distillation residues of conventional crude oils, they are characterized not only by a high content of asphaltenes but also by a high content of resins, metals, especially nickel and vanadium, sulfur compounds and nitrogen compounds; they are also characterized by a high viscosity which can cause handling problems, in particular with regard to their pumping and transport by oil pipelines.

 The direct hydrotreatment of these fillers to reduce the sulfur, nitrogen and metal impurities content causes problems that become economically insurmountable when the content of metals, nickel and vanadium, becomes too high, for example greater than 100 parts per million by weight. (ppm). In fact, the metals, on the one hand, and a fraction of the asphaltenic carbon, remain fixed on the catalyst, obstructing the pores, destroying the activity of the active centers and creating losses of charges. This results in the need to renew the catalyst load at a rate which is all the more frequent as the metal and asphaltene contents are higher.

It is then necessary to separate the asphaltenic charge into two fractions: a fraction composed mainly of asphaltenes and containing most of the metals and the complementary fraction sometimes referred to as maltenes and containing the resins and the oil. The separation operation commonly described in the prior art is the precipitation of asphaltenes by the addition to asphaltenic oil of adequate amounts of light hydrocarbons under suitable conditions. When not targeting the production of lubricating oils but selective precipitation of asphaltenes, the preferred solvents are hydrocarbons containing from 4 to 7 carbon atoms, pentane being the most frequently mentioned.

This deasphalting operation must be carried out as selectively as possible so as to obtain a maximum yield of the maltenic fraction, which is likely to have a better recovery. The yield of maltenes obviously depends on the asphalthen content of the treated feedstock and the nature of these asphaltenes; the selectivity of the operation depends on the operating conditions, temperature, pressure, residence time in the mixer settler, but it depends mainly on the nature of the precipitation solvent and the solvent / charge ratio used. In the case of pentane, this ratio is high, usually greater than 4; this is also one of the key points of the process, economically, since all of the solvent must be recovered by selective vaporization from mixtures maltène-solvent and asphaltene-solvent, which requires a high energy consumption.

OBJECT OF THE INVENTION
The object of the invention is to increase the yields of the deasphalting operation of an asphaltenic oil by subjecting this oil to a prior hydrolysis treatment in the presence of water vapor under pressure conditions. moderate.

 Another object of the invention is to make possible the precipitation of asphaltenes using a much lower solvent rate, 1.5 to 4, than that which would be used for other deasphalting without this prior treatment.

 A last object of the invention, is that the hydropyrolysis (hydrovisbreaking) preliminary is carried out in the presence of water vapor but also in that it can be conducted under pressure conditions and lower residence time that in the processes of the same type forming part of the prior art.

DESCRIPTION OF THE PRIOR ART
Numerous patents relate to the integration of visbreaking or hydroviscoreduction type thermal pretreatment with solvent deasphalting of asphaltenic fillers.

 U.S. Patent Nos. 2,914,457, 3,053,750 and 3,132,088 disclose a visbreaking operation performed upstream of a deasphalting operation, but this is a conventional visbreaking treatment, it is i.e. without adding hydrogen. US Pat. No. 2,943,048 falls within the same category with regard to thermal pretreatment, but in this case the de-pilling is carried out by precipitation with heptane in the presence of hydrochloric acid or chlorinated organic compounds.

 US Pat. No. 2,975,121 describes the combination of a hydrogen treatment of an asphaltenic charge and a deasphalting operation, the heat treatment being carried out at pressures of between approximately 140 and 350 bar, for residence time between 1 and 60 minutes.

 No. 3,338,818 also recommends hydrovisbreaking prior to the deasphalting operation; the hydrovisbreaking unit is itself integrated in the distillation unit which is fed by the raw load and by the effluents of the visbreaking unit. Hydrogen gas from the purge of the hydrovisbreaking unit is also used as a stripping agent in the distillation unit. One of the essential characteristics of the process is that a hydrogenated, paraffinic heavy fraction is recycled at the inlet of the hydrovisbreaking at a rate of at least 1 volume per 10 volumes of fresh feedstock.

 US Patent 3,796,653 also claims the combination of hydrogen pretreatment and deasphalting; the essential characteristic is that the hydrogen used contains from 5 to 30 mol% of hydrogen sulphide, resulting in a deeper transformation of the hydrotreated feedstock and, consequently, lower asphaltene yields in the subsequent deasphalting operation. ; this pre-treatment with hydrogen takes place under pressure conditions of between 70 and 210 bars with H2 / hydrocarbon volume ratios of between 168.5 and 5055 m3 / m3.

DESCRIPTION OF THE INVENTION
The subject of the invention relates to the combination of hydrovisbreaking of asphaltenic fillers and solvent deasphalting with a view to purifying the fillers and rendering them capable of undergoing subsequent catalytic treatments, such as hydrocracking, hydrorefining or catalytic cracking.

 An essential feature of this arrangement is that, at the inlet of the hydrovisbreaking unit, water is added to the feedstock, preferably from 0.2 to 30% water by weight, so that the operation takes place, not only under hydrogen pressure but also under water vapor pressure. The fact of carrying out the operation under partial pressure of water vapor makes it possible, surprisingly, not only to increase the yield of middle distillates in a subsequent hydrocracking operation, but especially to reduce the asphaltenes yields at the end of the process. The maltenic fraction obtained contains less metals than can be obtained without prior hydrovisbreaking and even when the hydrovisbreaking operation is carried out in the absence of water vapor.

 FIG. 1 gives, by way of example, a brief description of the process arrangement as recommended in the invention. The asphaltenic feedstock from line 1 is mixed with hydrogen and water from lines 2 and 3 respectively. Hydrogen is a mixture of recycle hydrogen and make-up hydrogen injected at 4 into the reactor. unit. The water is a mixture of recycle water and make-up water injected into the unit. The ternary mixture composed of the charge> of pressurized hydrogen gas and water, after preheating in an exchange system not shown in the diagram, is injected into the visbreaking furnace 6.The hydropyrolysis operation takes place at pressures of 20 to 200 bar, preferably at relatively moderate pressures between 30 and 70 bar, at temperatures between 3500C and 510 C and preferably between 420 "C and 490 C with a ratio volu 3 hydrogen / hydrocarbons in 3 mique hydrogen / hydrocarbons in m3 of hydrogen gas per m of liquid charge between 50 and 2000 and preferably between 200 and 600. The amount of water added in kg of liquid water per 100 kg of liquid charge is between 0.2 and 30 and preferably between 2 and 10. Depending on the charges processed and the desired conversion rate, the residence time corresponding to the visbreaking operation is usually between 0.1 minute and 30 minutes. For residence times greater than 2 minutes, it is advantageous, in order to avoid too rapid coking of the tubes of the oven, to allow the reaction to continue in a ripening chamber 7, where the reaction continues during the set time, at a temperature close to the outlet temperature of the oven. This grinding chamber can operate with a rising current or with a downward flow of reagents present. At the exit of the furnace, or at the exit of the ripening chamber if the duration of the residence time justifies its use, the mixture is hardened. by injection of water (line 8) at a temperature which varies from 150 ° C. to 3000 ° C. depending on the pressure applied, to then be sent to the hot separator 9, where a mixture comprising hydrogen gas, the vapor form, is separated off in vapor form; light gasoline and water, on the one hand, and on the other hand a liquid fraction sent through the pipe 10 to the deasphalting unit 11. The steam fraction from 9 is cooled and condensed in the condenser 12 before to arrive at the cold separator 13.De this cold separator is separated a gaseous fraction containing essentially hydrogen gas, which escapes the line 14 to be largely recycled via the pipe 2; it is purged through line 15. The liquid fraction settles in two phases in the separator 13; the aqueous phase is partly recycled to hydrovisbreaking, via line 3, and partially purged (line 28) while the hydrocarbon phase is introduced into a second decanter 15 where are separated the last traces of water before being recycled, the gasoline being withdrawn via line 16. This second decanter may optionally be replaced by a distillation column in the case where it is desired to selectively obtain the C5 cut used as the preferred solvent in the deasphalting operation.

 As for the heavy fraction, withdrawn from the separator 9 via the pipe 10, it is mixed in line (17) with the deasphalting solvent from the evaporators 20 and 21 (lines 19 and 18) where the solvent-maltene and solvent phases are separated. -asphaltènes. the end of the precipitation and the settling of the asphaltenes takes place in the deasphalting column 11 which is, for example, a single column, a column with rotating disks or a system of the mixer-settler type. the asphaltenic phase is withdrawn in liquid form via line 22 to evaporator 21 from which a vapor phase is separated, recondensed at 23 before being recycled, and a liquid asphaltic phase sent to storage (line 25). The maltenic phase is withdrawn through line 24 to the evaporator 20 where the solvent is separated in vapor form, recondensed at 26 and recycled while the maltenic fraction is sent to storage via line 27. Given the quantities As the solvent is used, it will generally be advantageous to carry out the separation of the solvent from the maltenic phase in 2 stages and hence to use instead of the evaporator 20 a series of 2 evaporators.

 The deasphalting column preferably operates between 30 and 70 bar at a temperature preferably between 120 and 2500C. In fact, the precise operating conditions depend essentially on the asphaltenic charge resulting from the hydrovisbreaking after separation of the light fractions and depend mainly on the nature of the solvent used. Generally speaking, the conditions of pressure and of temperature are chosen so as to be able to carry out the operation in the liquid phase and to be able to evacuate the phaltenic phase in liquid form. The preferred solvents are hydrocarbons with 4 to 7 carbon atoms. , alone or as a mixture, but in order to optimize the selectivity and to obtain the highest possible yields in the maltenic phase, it is preferable to use as the solvent the hydrocarbons containing 5 carbon atoms alone or as a mixture, for example pentane, isopentane, light-weight species. direct distillation or from cracking of heavier fractions, such as the hydrovisbreaking of the asphaltenic charge forming part of the process arrangement described in the present invention. One of the essential characteristics of the deasphalting unit, as it is integrated in the process arrangement described in the invention, relates to the volume ratio solvent / asphaltenic charge that must be used to obtain good selectivity While without pretreatment, this ratio must be greater than 4 and preferably greater than 5 so that the maltenic fraction can be easily treated in a subsequent hydrotreatment, the pretreatment of hydrovisbreaking in the presence of water causes such changes in the charge. that to obtain the same performance selectivity in the deasphalting, solvent / charge ratios lower than 4 and more generally between 1.5 and 4 are sufficient; this is due to the fact that the pretreatment as recommended here not only decreases the weight content of asphaltenes observed in hydrovisbreaking without water but also decreases the H / c ratio of these same asphaltenes, making them less soluble in the maltenic phase.

 The solvent / charge ratio may therefore be chosen from 1 to 10 and preferably from 1.5 to 4, by volume.

EXAMPLES
The following examples are presented to illustrate the feature of the process arrangement which is the subject of the present invention both in terms of yields and in terms of the quality of the maltenic phase obtained at the end. the deasphalting operation. Two examples corresponding to two asphaltenic fillers are presented, but it is understood that the scope of the process arrangement described in the present invention is not limited to these two fillers alone, to the operating conditions applied and to the nature of the solvent used.

 The hydrovisbreaking and deasphalting tests are carried out continuously. The visbreaking unit is constituted by an oven having a heating section and a curing section and whose treatment capacity is between 2 and 10 liters of load per hour. For tests requiring a residence time greater than 1 micron, the biphasic mixture leaving the furnace was introduced into a 5-liter capacity vessel operating as an upflow. After the hydrovisbreaking tests, the light fraction and the water were separated from a residue sent to deasphalting.

 The deasphalting unit consists of a column with baffles.

 The unit can operate under pressure and the temperature of the operation is set so that the asphaltenic phase can be withdrawn in liquid form. The two phases obtained are separated and the solvent is distilled off and / or stripped.

EXAMPLE 1
The treated feedstock consists of a vacuum residue of the Aramco type, the characteristics of which are shown in Table 1.

 A first test A is performed without prior hydrovisbreaking with a solvent ratio equal to 5; a second test B is carried out under the same conditions, but with a solvent ratio equal to 3.

The operating conditions, the yields of asphaltenes and maltenes, as well as the characteristics of these products are presented in Table 2; a third test (C) involves prior hydrovisbreaking under the operating conditions reported in Table 2; a fourth test (D) also involves a prior hydrovisbreaking but in the presence of water vapor, the amount of water added corresponding to 10% of the weight of the treated residue. In these two last tests, the effluents at the exit of the pretreatment were separated into two fractions, namely a fraction distilling below 21,000 and a fraction distilling above 210 C which constituted the deasphalting charge; in the latter two cases, the loperation was carried out with a solvent (pentane) level equal to 3, that is to say, significantly lower than the solvent levels generally recommended in the prior art. The results obtained are gathered in FIG. Table 2; it can be seen that simple hydrovisbreaking and even more hydrovisbreaking in the presence of water vapor leads not only to a decrease in the asphaltenic fraction but above all to an improvement in the quality of the malthene products obtained, which are lighter and have a lower lower metal content than maltenic products obtained in the absence of pre-treatment.

EXAMPLE 2
The load used is a raw Boscan head (350+ load).

The characteristics of the load are presented in Table 1.

 4 tests of a series identical to the series in the first example were carried out; the operating conditions and the properties of the products obtained are presented in Table 3.

Once again, the integration of hydrovisbreaking and even more hydrovisbreaking in the presence of water vapor improves the yields and quality of maltenic products.

TABLE 1
CHARGES CHARGES

<tb><SEP> Residual <SEP> under <SEP> empty <SEP> Raw <SEP> and left
<tb><SEP> Aramco <SEP> Boscan
<tb> Initial <SEP> Point <SEP> of <SEP> Distillation <SEP> 525 <SEP> 350
<tb><SEP> Oc
<tb> Yield <SEP> on <SEP> gross <SEP> 21
<tb><SEP> (X <SEP> weight)
<tb> Density <SEP> d20 <SEP> 1,003 <SEP> 1,037
<tb> Viscosity <SEP> to <SEP> 100 C <SEP> (Cst) <SEP> 340 <SEP> 5 <SEP> 200
<tb> Asphaltenes <SEP> (% <SEP> weight) <SEP> 4.2 <SEP> 15.3
<tb> Carbon <SEP> Conradson <SEP> (% <SEP> weight) <SEP> 16.4 <SEP> 18
<tb> Metals <SEP> (Ni <SEP> + <SEP> V) <SEP> (ppm) <SEP> 80 <SEP> 1 <SEP> 400
<tb> Sulfur <SEP> (% <SEP> Weight) <SEP> 4.05 <SEP> 5.9
<tb> Nitrogen <SEP> (ppm) <SEP> 2 <SEP> 900 <SEP> 7 <SEP> 900
<tb> Flow <SEP> Point <SEP> (C) <SEP> 20
<Tb>
TABLE 2
TREATMENT OF THE ARAMCO VACUUM RESIDUE

<tb><SEP> A <SEP> B <SEP> C <SEP> D
<tb> Hydrovisbreaking <SEP> No <SEP> No <SEP> Yes <SEP> Yes
<tb><SEP> T <SEP> (OC) <SEP> 480 "<SEP> 480 C <SEP>
<tb> Time <SEP> of <SEP> residence <SEP> (min) <SEP> 0.5 <SEP> 0.5
<tb> Pressure <SEP> (bars) <SEP> 50 <SEP> 50
<tb> Flow rate <SEP> H2 <SEP> (m3 / m3) <SEP> 500 <SEP> 500
<tb> Water <SEP> (Kg / Kg <SEP> load) <SEP> 0,1
<tb> Deasphalting <SEP> of <SEP> the <SEP> fraction
<tb><SEP> 2100C +
<tb><SEP> T <SEP> (OC) <SEP> 195 <SEP> 200 <SEP> 195 <SEP> 195
<tb> Solvent / load <SEP> (m / m) <SEP> 5 <SEP> 3 <SEP> 3 <SEP> 3 <SEP>
<tb> Yield <SEP> (% <SEP> weight) <SEP> in <SEP> 210- C <SEP> 5 <SEP> 6
<tb><SEP>"<SEP> in <SEP> fraction <SEP> maltenic <SEP> 85.5 <SEP> 85.5 <SEP> 82 <SEP> 83
<tb><SEP> in <SEP> in <SEP> fraction <SEP> asphalted
<tb> nick <SEP> 14.5 <SEP> 14.5 <SEP> 13 <SEP> 11
<tb> Fraction <SEP> maltenic
<tb><SEP> Sulfur <SEP> (Z <SEP> weight) <SEP> 3.68 <SEP> 3.76 <SEP> 3.60 <SEP> 3.60
<tb> Metals <SEP> (Ni <SEP> + <SEP> V) <SEP> (ppm) <SEP> 30 <SEP> 40 <SEP> 25 <SEP> 21
<tb> Fraction <SEP> (210-3500C) <SEP>% <SEP> Weight <SEP> 0 <SEP> 0 <SEP> 10 <SEP> 12
<tb> Asphalt fraction <SEP>
<tb><SEP> Sulfur <SEP> (Z <SEP> weight) <SEP> 6.23 <SEP> 5.76 <SEP> 6.1 <SEP> 6.8
<tb> Metals <SEP> (ppm) <SEP> 375 <SEP> 316 <SEP> 458 <SEP> 569
<tb> Point <SEP> of <SEP> softening <SEP> 161 <SEP> 155 <SEP> 160 <SEP> 165
<Tb>
TABLE 3
TREATMENT OF RAW BOSCAN

<tb><SEP> A <SEP> B <SEP> C <SEP> C
<tb> Hydrovisbreaking <SEP> No <SEP> No <SEP> Yes <SEP> Yes
<tb><SEP> T <SEP> (C) <SEP> 470 C <SEP> 470 C <SEP>
<tb> Time <SEP> of <SEP> residence <SEP> (min) <SEP> 0.5 <SEP> 0.5
<tb> Pressure <SEP> (bars) <SEP> 60 <SEP> 60
<tb> Flow rate <SEP> 112 <SEP> (m3 / m3) <SEP> 600 <SEP> 500
<tb> Water <SEP> (Kg / Kg <SEP> load) <SEP> O <SEP> 0,1
<tb> Deasphalting <SEP> of <SEP> the <SEP> fraction
<tb><SEP> 210 C + <SEP>
<tb><SEP> T <SEP> (C) <SEP> 195 <SEP> 200 <SEP> 195 <SEP> 195
<tb> Solvent / filler <SEP> (m / m) <SEP> 5 <SEP> 3 <SEP> 3 <SEP> 3
<tb> Yield <SEP> (% <SEP> weight) in <SEP> fraction
<tb><SEP> 210-C <SEP> 0 <SEP> 0 <SEP> 4 <SEP> 5
<tb><SEP> in <SEP> fraction <SEP> maltenic <SEP> 63 <SEP> 65 <SEP> 64 <SEP> 64
<tb><SEP>"<SEP> in <SEP> fraction <SEP> Asphaltene <SEP> 37 <SEP> 35 <SEP> 32 <SEP> 31
<tb> Fraction <SEP> maltenic
<tb><SEP> Sulfur <SEP> (% <SEP> weight) <SEP> 5.30 <SEP> 5.50 <SEP> 5.20 <SEP> 5.25
<tb> Metals <SEP> Ni + <SEP> V <SEP> (ppm) <SEP> 295 <SEP> 380 <SEQ> 280. <SEP> 250
<tb> Fraction <SEP> (210-350 C) <SEP> (% <SEP> weight) <SEP> O <SEP> O <SEP> 9 <SEP> 11
<tb> Asphalt fraction <SEP>
<tb><SEP> Sulfur <SEP> Z <SEP> Weight <SEP> 6.9 <SEP> 6.65 <SEP> 6.75 <SEP> 7.0
<tb> Metals <SEP> ppm <SEP> 3.280 <SEP> 3.300 <SEP>3; 815 <SEP> 4.260 <SEP>
<tb> Point <SEP> of <SEP> softening <SEP> 170 <SEP> 160 <SEP> 170 <SEP> 175
<Tb>

Claims (1)

1.- A process for converting a hydrocarbon feed containing asphaltenes, characterized in that it comprises the following steps a) the hydrocarbon feedstock is reacted with hydro gene and steam the water under visbreaking conditions, b) at least part of the first stage effluent is deasphalted with a deasphalting solvent in a disassembling zone, and a solvent rich and poor phase is collected separately. asphaltenes and a solvent-poor phase rich in asphaltenes, and  c) the solvent is removed from the solvent-rich phase, and  collects a cut of hydrocarbons low in asphaltenes and  very impurities. 2. Method according to claim 1, wherein the weight ratio  water / hydrocarbon feed is 0.002: 1 to 0.3: 1. 3. The process according to claim 1, wherein the conditions of  visbreaking include a pressure of 20 to 200 bar, a  temperature of 350 to 5100C and a ratio hydrogen / hy  hydrocarbons from 50 to 2000 m3 / m3. 4. The process according to claim 3, wherein the pressure is  30 to 70 bars. 5. Method according to one of claims 1 to 4, wherein the time  of residence of step (a) is from 0.1 minute to 30 minutes. 6. A process according to one of claims 1 to 5, wherein the soil  of deasphalting is selected from hydrocarbons having  4 to 7 carbon atoms or mixtures thereof, used in connection with  solvent / hydrocarbon feed from 1: 1 to 10: 1. 7. The process according to claim 6, wherein the solvent /  Hydrocarbon load is 1.5: 1 to 4: 1. 8. A process according to one of claims 1 to 7, wherein the soil  is a hydrocarbon having 5 carbon atoms.