FR2906813A1 - Heavy petroleum feed e.g. vacuum residue, hydroconverting method for producing petrol, involves de-asphalting vacuum residue to obtain de-asphalted oil, and recycling totality of oil by hydroconversion - Google Patents

Abstract

The method involves subjecting a feed directly to a hydroconversion in presence of a supported or dispersed catalyst. Effluent is subjected to an atmospheric distillation followed by vacuum distillation to obtain a vacuum residue. Totality of the residue is de-asphalted, and de-asphalted oil is obtained, where the oil contains 1 percentage of asphaltenes. Totality of the de-asphalted oil is recycled by hydroconversion.

Description

This application relates to a process for hydroconversion of charges

  Heavy oil residues to produce especially gasoline, diesel or VGO (vacuum gas oil).

  Such processes already exist, but they still leave an unconverted fraction which has only a small value in comparison with converted products such as gasoline, middle distillates or even VGO (vacuum gas oil or vacuum gas oil). In a conventional scheme, a solvent deasphalting step (SDA) is added to the unconverted residue, whether it is an atmospheric residue (AR) or a vacuum residue (VR). A deasphalted oil (DAO) is then recovered which can be marketed as such, but with a relatively low market value. It is possible to crack this DAO for example in a catalytic cracking unit (FCC) or other conversion unit. The disadvantage is then low production of poor quality middle distillates or requiring expensive investments to improve its properties. For example, US Pat. No. 6,017,441 describes a method in which the heavy charge (such as a vacuum residue) is subjected to ebullated bed hydroconversion in the presence of a catalyst containing at least one GVIII metal, preferably also at least one metal of GVI B, at a pressure of 5-35 MPa and 350-450 C. The effluent obtained is fractionated by atmospheric distillation and distillation under vacuum. The vacuum residue obtained is sent at least partly into a deasphalting unit. It is possible to recycle part of said residue to the hydroconversion unit. The DAO obtained after deasphalting is sent to a bubbling bed hydrotreatment, preferably mixed with at least a portion of the vacuum distillates obtained by vacuum distillation. This unit operates in milder conditions than the hydroconversion unit. By distillation of the effluent from the hydrotreatment, the gasoline and diesel fractions are recovered; the resulting residue is sent to a catalytic cracking unit (FCC). We have now looked for a process for the production of gasoline and diesel with improved yields while maintaining and good qualities of products, with a simpler and more economical process.

The invention relates to a process in which the DAO is recycled entirely in the hydroconversion unit of the residue itself. Given the high reactivity of the DAO (consequence of its low content of asphaltene) relative to the starting residue, we thus achieve a total extinction of the DAO thanks to a strong pass conversion of the DAO. Until now, it was considered that the recycling of all the DAO would lead to too high asphalt contents due to the production of asphaltenes during the hydroconversion reaction. However, under the conditions of the process, the increase in this content is reduced.

With the process according to the invention, it has been found that a very good load could be produced for catalytic cracking (FCC) which is VGO and whose quality is much higher than that of the prior art; this stems from the fact that the prior art feed still contained poorly separated DAO which made it more refractory to the FCC. Thus, in the method of the invention, the VGO can be sent directly to the FCC and without pre-treatment. More specifically, the invention relates to a heavy-charge conversion process having a boiling point higher than 340 ° C. for at least 80% of the feedstock, a Conradson carbon content of at least 5% by weight, an asphaltenes content of at least 1 wt.%, a sulfur content of at least 0.5 wt.%, a metal content of at least 20 ppm, wherein: said feedstock is directly subjected to a hydroconversion stage; the presence of a supported or dispersed catalyst, the conversion being at least 30% by weight, the effluent obtained is subjected to an atmospheric distillation followed by distillation under vacuum, a residue under vacuum is obtained, - the totality said residue is deasphalted, a deasphalted oil is obtained which contains less than 1% by weight of asphaltenes - and all of said deasphalted oil is recycled to the hydroconversion stage.

The invention is explained with reference to FIG. The feedstock is of the residue type, it generally has a Conradson carbon content of at least 5 wt.% And generally at least 10 wt.%, An asphaltene content (C7 / 5 of the standard IP-143) of minus 1%, often at least 2% and very often at least 5% wt, and can even equal or exceed 24% wt. Their sulfur content is generally at least 0.5%, often at least 1% and often at least 2% or even up to 4% or even 10% wt. The amounts of metals they contain are generally at least 5 ppm, often at least 50 ppm and typically 100 ppm or at least 200 ppm wt. Such feedstocks are crude oils that are partially topped, e.g. deessentials, atmospheric residues, vacuum residues, atmospheric or vacuum residues derived from the distillation of crude oils (SR), or from a primary conversion process of an atmospheric or vacuum residue (such as a visbreaking, a hydroconversion ...), or atmospheric or vacuum residues from conventional light to medium or heavy crude oils (eg Middle East, Urals, West Africa ...) or extra heavy crude oils eg. an API less than 15 (raw from Venezuela, Canada ...). It is also possible to include the coals or cokes advantageously introduced in suspension. The fillers are generally characterized by a boiling point above 340 ° C. for at least 80% by weight of the filler, and preferably for at least 90% by weight of the filler. Their initial boiling point is generally at least 300 ° C. The process is particularly applicable to heavy feeds having a boiling point above 500 ° C., or even 5 ° C. for at least 80% by weight of the feedstock. preferably at least 90% of the charge. They generally have (fresh feeds) a viscosity of less than 100000cSt at 100 ° C, or even less than 40,000 cSt, and preferably less than 20,000 cSt at 100 ° C. They must generally be converted to produce finished products such as gasoline and LPG, lower boiling point. The charge arriving via line 1 is sent to the hydroconversion unit 2 which operates as a bubbling bed.

To this feed is added via line 3 the DAO from the deasphalting unit which will be described later. The hydroconversion step therefore allows a partial conversion of the residue into lighter products than the feedstock (gas, gasoline, middle distillates, VGO vacuum distillates) leaving a certain amount of unconverted residue; it can be carried out according to various methods, such as the following commercial processes: fixed-bed hydroconversion processes preferably followed by a visbreaking unit (Hybrid, preferably followed by a visbreaking unit, Unibon ...) which operate with moderate pass conversions typically of less than 50 wt.% but at least 20 wt.% or at least 30 wt. Semi-continuous supported bed hydroconversion processes with supported catalyst which operate with moderate pass conversions typically of less than 50 wt% but at least 20 wt% or at least 30 wt%. ebullated bed processes advantageously operating with semi-continuous catalyst booster (H-OH, LC-Fining, etc.) which operate with high pass conversions, generally at least 60% by weight. This type of process is preferred. Slurry hydroconversion processes (HDHPLUS, EST ...) which operate with generally high pass conversions of at least 50 wt% or at least 60 wt% and preferably at least 80 wt%. or their associations.

The conversion is defined as the ratio (% wt residue in the feed -% residue in the product) /% residue in the feed, for the same point of load-product cut; typically this cutting point is between 450 and 550 C, and often about 500 C; in this definition, the residue being the fraction boiling from this cutting point (such as 500 C + for example).

For bubbling bed processes, at least one supported catalyst suitable for bubbling bed processes is generally used; such catalysts are known to those skilled in the art. This catalyst is generally a catalyst comprising a support, generally amorphous, which is preferably an alumina, and at least one group VIII metal (for example nickel and / or cobalt), most often in combination with at least one Group VIB metal (eg molybdenum). For example, a catalyst comprising from 0.5 to 10% by weight of nickel and preferably from 1 to 5% by weight of nickel (expressed as nickel oxide NiO) and from 1 to 30% by weight of molybdenum of preferably from 5 to 20% by weight of molybdenum (expressed as molybdenum oxide MoO3) on a support, for example an alumina support. This catalyst is most often in the form of extruded or ball. The mechanical strength of the supports is high. This step is usually carried out under an absolute pressure of 5 to 35 MPa and most often 10 to 25 MPa at a temperature of about 300 to about 500 C and often about 350 to 450 C. The VVH of the liquid and the hydrogen partial pressure are selected according to the characteristics of the batch to be treated and the desired conversion. Most often the VVH of the liquid is from about 0.1 to about 5 hours and preferably from about 0.15 to about 2 hours. The used catalyst is partly replaced in semi-continuous by fresh catalyst according to the methods known to those skilled in the art. In this step, a catalyst is advantageously used, ensuring both the demetallization and the desulphurization, under conditions making it possible to obtain a liquid feed with reduced content of metals, Conradson carbon and sulfur and making it possible to obtain a high conversion.

In fixed bed processes, generally, at least one fixed bed of supported hydroconversion catalyst is used. These catalysts are known to those skilled in the art. The operation is usually carried out under an absolute pressure of from 5 to 35 MPa and most often from 10 to 20 MPa at a temperature of approximately 300 to 500 ° C. and often of approximately 350 to 450 ° C. The VVH and the partial pressure of hydrogen are chosen according to the characteristics of the batch to be treated and the desired conversion. Most often, the VVH is in a range of from about 0.1 to about 5 hours and preferably about 0.15 to about 2. The amount of hydrogen blended with the filler is usually from about 100 to about 1000 normal cubic meters (Nm3) per cubic meter (m3) of liquid feed and most often 25 from about 500 to about 3000 Nm3 / m3. The ideal catalyst must have a high hydrogenating power so as to achieve a deep refining, and to obtain a significant lowering of sulfur, Conradson carbon and asphaltenes content. For example, one of the catalysts described by the Applicant in EP-B-113297 and EP-B-113284 may be used. Preferably, a bed of a hydrodemetallization catalyst is placed upstream (with respect to the circulation of the charge) of this bed. In the case where the zones are distinct (different reactors), it will be possible to operate the 2nd reactor at a relatively low temperature, ie substantially lower than the temperature of the hydrodemetallization zone, which goes in the direction of a deep hydrogenation. and a limitation of coking. The present invention would not depart from the scope of the present invention by using the same catalyst in the two zones, or by grouping these two zones together to form only one in which the hydrodemetallization would be carried out. hydrodesulfurization simultaneously or successively with a single catalyst or with several different catalysts.

In this step it is also possible to use at least one catalyst, providing both demetallization and desulphurization, under conditions which make it possible to obtain a low-content liquid feed of metals, Conradson carbon and sulfur. It is also possible to use at least two catalysts, one of which mainly provides the demetallization and the other mainly of the desulfurization under conditions which make it possible to obtain a low-content liquid feed of metals, Conradson carbon and sulfur. With regard to processes operating in slurry, ie in the presence of a circulating dispersed catalytic phase, they generally operate under a total pressure of 1 to 50 MPa, preferably 2-30 MPa, with a partial pressure of hydrogen ranging from 1 to 50 MPa, preferably 2 to 30 MPa, with a temperature of 300 to 600 C, preferably 400 to 470 C, the contact taking place for a certain time necessary for the conversion of the residue, from 5 minutes to 20 hours, preferably between 1 and 10 hours. The catalysts are well known to those skilled in the art, and are obtained from the thermal decomposition of catalytic precursors (eg, molybdenum naphthenate, etc.). The effluent obtained at the end of the hydroconversion stage (exiting via line 4) is distilled in the atmospheric column 5 and then the atmospheric residue (line 6) is distilled in the vacuum column 7.

In the zone 5 of atmospheric distillation, the conditions are generally chosen so that the cutting point for the residue is from about 300 to about 400 ° C. and preferably from about 340 to about 380 ° C. light gases (line 16), distillates and a residue. The distillates [gasoline fraction (line 8) and diesel fraction (line 309)] thus obtained are generally intended for the corresponding fuel pools. Before being sent, the gas oil produced by the process according to the invention is hydrotreated in a subsequent unit 14, under the operating conditions and with the catalysts usually used and known to those skilled in the art, so as to bring the content in sulfur to market specifications, which is less than 10 ppm sulfur, and to improve the index of 2906813 7 cetane. Before being sent to the gasoline pool, the gasoline fraction is generally processed by reforming (not shown in the figure). The atmospheric residue (line 6) is sent to vacuum distillation.

In the vacuum distillation zone 7, the conditions are generally chosen such that the cutting point for the residue is from about 450 to 600 ° C and most often from about 500 to 550 ° C. Vacuum distillate fractions (VGO) obtained exit through line (s) 10 and the residue under vacuum through line 11. The VGO is advantageously sent at least partly into a catalytic cracking unit 15. The residue under Vacuum is sent to the deasphalting unit 12. The deasphalting step using a solvent is carried out under conditions well known to those skilled in the art.

It is possible to use, for example, processes such as Solvahl, Rose, etc. Deasphalting is usually carried out at a temperature of 60 to 250 ° C. with at least one hydrocarbon solvent containing from 3 to 7 carbon atoms, optionally with at least one addition additive. Useful solvents and additives are widely described.

It is also possible and advantageous to carry out the recovery of the solvent according to the opticritic process, that is to say using a solvent under non-supercritical conditions. This process makes it possible in particular to significantly improve the overall economy of the process. This deasphalting can be done in a mixer-settler or in an extraction column.

In the context of the present invention the technique (eg the Solvahl process) using at least one extraction column and advantageously only one is preferred. Advantageously, as in the Solvahl process with a single extraction column, the solvent / feed-in ratios in SDA are low, between 4/1 and 6/1. This allows in addition excellent extraction of metals and asphaltenes, to have only very small amounts of solvent in the DAO. The deasphalting unit produces a DAO (deasphalted oil) substantially free of asphaltenes and an asphalt (line 13) concentrating most of the impurities from the residue and which is drawn off. The management of the solvent, which is known to those skilled in the art, has not been shown. The yield of DAO can vary from less than 50 wt% to more than 90 wt%. DAO has an asphaltene content reduced to less than 1% in general (C7 measurement), preferably less than 0.5%, most often less than 0.05% by weight measured in insoluble C7 and even more preferably less than 0.3% by weight measured in insoluble C5 and less than 0.05% by weight measured in insoluble C7. This low asphaltenes content makes it possible to dilute the feedstock to be treated and to lower the operating conditions of hydroconversion, compared to a process without recycling.

This low asphaltenes content makes it possible, according to the invention, to recycle all of the DAO in hydroconversion, which leads to a maximum recovery of the middle distillate load, and advantageously while maintaining acceptable catalyst life times. The asphaltenes concentrated in the hydroconversion residue are found in the asphalt, which is then advantageously eliminated; in this way the recycled effluent (DAO) behaves as a diluent of the asphaltenes of the feed which improves the hydroconversion. Thus the total conversion is at least 20% or at least 30% wt, and in the case of bubbling beds at least 60% or even at least 80%, and in the case of slurry, the most often at least 80%.

Example The feed is an extra heavy crude vacuum residue (RV) from the state of Alberta in Canada. Its properties are as follows: Athabasca VR Density 1.07 Viscosity at 100 C cSt 30640 Conradson Carbon% s% 21.9 C7 Asphaltene wt% 14.9 Nickel ppm 137 Vanadium ppm 337 Nitrogen ppm 6000 Sulfur wt% 5.4 2906813 9 The results obtained in 3 tests are compared: - (1) in hydroconversion alone, that is to say: hydroconversion, atmospheric distillation and vacuum distillation of the atmospheric residue; there is neither deasphalting nor recycling - (2) in the process according to FIG. 1 but in the absence of recycling of the DAO, that is to say: hydroconversion, atmospheric distillation then vacuum distillation of the atmospheric residue , deasphalting - (3) in the process according to the invention and according to FIG. 1, that is to say with a recycling of all the DAO; In these tests, a boiling bed hydroconversion is carried out with a NiMo / alumina catalyst at a pressure of 13 MPa of hydrogen and a temperature of 440 ° C .; the deasphalting is carried out according to the Solvahl process with pentane. The table below indicates the yields obtained in% by weight with respect to a base of 15 100 of VC: (1) interesting conversions are obtained in light products but there remains 27.3% unconverted residue. Even operating the hydroconversion unit in liquid recycle mode, it is not possible to significantly increase this conversion level due to the highly refractory nature of this unconverted residue. (2) yields of light products do not increase, simply the unconverted RV is separated into 18.8% of CAD and 8.5% of asphalt. (3) in this case the DAO is converted into light fractions and the amount of asphalt increases only slightly compared to the previous scheme, from 8.5 to 9.4% wt. Hydrogen consumption logically rises from 2.5 to 3.1% wt, since DAO has to be converted. On the other hand, there is a clear improvement in the yields of high value-added products. In particular, gasoline increased from 6.7% to 10% by weight, and the diesel produced rose from 29.1% to 35.8% by weight. RV (1) RV HCK (2) HCK + SDA (3) HCK + SDA load Without SDA and without Without recycling With recycling recycling H2S + NH3: 5.3 5.3 5.7 Gas: 4.0 4.0 5.2 Petrol: 6.7 6.7 10.0 Diesel: 29.1 29.1 35.8 VGO: 30.2 30.2 36.9 Remaining VR 27.3 0.0 0.0 DAO 0.0 18.8 0.0 SDA Purge 0.0 8.5 9.4 Total 102.5 102.5 103.1 H2 Consumption 2.5 2.5 3.1 Thus, contrary to the preconceived idea of the person skilled in the art, it is possible to recycle in total a DAO containing little asphaltenes. Until now, it was not thought that this recycling would lead to such a significant improvement in efficiency (+ 23% for diesel and + 49% for gasoline compared to a one-shot process) because the refractoriness of DAO was considered crippling. It has been shown here that the refractory compounds are removed by deasphalting. The invention thus makes it possible to obtain gasoline and diesel fractions (after hydrotreatment) with very good yields with good product qualities with a more economical process since it has made it possible to reduce the number of units (one unit). less hydrotreatment compared to the prior art. 15

Claims (7)

  1. Heavy load conversion process having a boiling point greater than 340 C for at least 80 wt% of the feed, a Conradson carbon content of at least 5 wt%, an asphaltene content of at least 1 % wt, a sulfur content of at least 0.5 wt%, a metal content of at least 20 ppm, wherein: said feed is directly subjected to a hydroconversion step in the presence of a catalyst supported or dispersed, the conversion being at least 30% wt, the effluent obtained is subjected to an atmospheric distillation followed by a vacuum distillation, a residue under vacuum is obtained characterized in that - all of said residue is deasphalted, a deasphalted oil is obtained which contains less than 1 wt.% of asphaltenes and all of said deasphalted oil is recycled to the hydroconversion stage.   2. A process according to claim 1 wherein the filler has a boiling point above 500 C for at least 80 wt.% Of the filler and a viscosity of less than 100,000 cSt at 100 C.   3. Method according to one of claims 1 or 2 wherein the hydroconversion stage operates in a bubbling bed with a pass conversion of at least 60% by weight.   4. Method according to one of claims 1 to 2 wherein the hydroconversion step operates in a fixed bed with a pass conversion greater than or equal to 20% by weight and less than 50% by weight.   5. Method according to one of claims 1 to 2 wherein the hydroconversion step operates in a moving bed with a pass conversion of greater than or equal to 20% by weight and less than 50% by weight.   6. Method according to one of claims 1 to 2 wherein the hydroconversion step 25 operates in slurry with a pass conversion of at least 50 wt%.   7. The method of claim 6 wherein the hydroconversion step operates in slurry at a temperature of 400-470 C and with a total conversion of at least 80 wt%.