ITMI20071303A1 - PROCEDURE FOR THE CONVERSION OF HEAVY DISTILLED HYDROCARBURIC CHARGES WITH HYDROGEN AUTOPRODUCTION - Google Patents

Description

DESCRIPTION of the industrial invention

Description

The present invention relates to a high productivity process for the total conversion to distillates only, without the simultaneous production of fuel oil or coke, of heavy feedstocks, including heavy crude oils with a high content of metals, distillation residues, heavy oils from from catalytic treatments, "visbreaker tars", "thermal tars", bitumen from "oil sands" possibly obtained from mining, liquids from different rank coals and other high-boiling hydrocarbon fillers known as "black oils", also including hydrogenating treatments in where self-produced hydrogen is used in the process itself.

The conversion of heavy fillers into liquid products can be carried out essentially through two ways: one of the thermal type, the other based on hydrogenating treatments. The growing demand for high quality distillate products and the parallel reduction in the demand for by-products such as coke and fuel oil, pushes to find new integrated processes that allow the complete conversion of heavy feedstocks.

Thermal processes, mainly coking and visbreaking, have undoubted advantages since they allow to feed charges with a high level of pollutants. However, the high production of coke and tar is such as to severely limit their validity in certain contexts. In addition, the poor quality of the distillates involves severe hydrogenating treatments to favor the removal of heteroatoms and lead to specification of the products.

Visbreaking allows to obtain very low yields for distillates and with poor quality products, obtaining, on the other hand, high quantities of tar.

Coking, in addition to having higher investment costs, also produces low quality distillates and high quantities of coke.

As regards the hydrogenating processes, they consist in treating the feedstock in the presence of hydrogen and suitable catalysts, pursuing various objectives:

• Demolish the asphaltenic structures with high molecular weight and favor the removal of Ni and V (hydrodemetallation, HDM) and, at the same time, reduce the asphaltenes content in the feed.

• Remove S and N through hydrogenation and hydrogenolysis reactions (respectively hydrodesulfurization, HDS and hydrodeazotation, HDN).

• Reduce CCR (Conradson Carbon Residue) by means of Hydrocracking (HC) and Hydrodearomatization (HDA) reactions.

• Transforming high molecular weight molecules into light molecules (distillates) through Hydrocracking (HC) reactions.

The hydroconversion technologies currently used use fixed bed or boiled bed reactors and employ catalysts generally consisting of one or more transition metals (Mo, W, Ni, Co, etc.) supported on silica and / or alumina, or other support. oxidic.

Fixed bed technologies, even in the most advanced versions, have severe limitations both in terms of flexibility on the feedstock (as the presence of high concentrations of metals and other pollutants would imply too frequent regeneration cycles of the catalyst), and because they do not allow you to convert heavy charges to levels above 30-40%. As a consequence of said limitations, fixed bed hydroconversion technologies are completely inadequate to configure total conversion schemes of heavy charges to distillates.

To obviate these limitations at least in part, the ebullient bed processes have been developed in which the catalytic bed, despite being confined to a certain portion of the reactor, is mobile and can expand due to the flow of the reactants in the liquid and gaseous phase. This allows the reactor to be equipped with mechanical devices to remove the exhausted catalyst and feed the fresh catalyst continuously without interrupting the run. Due to this possibility of continuously replacing the exhausted catalyst, the ebullated bed technologies can process heavy fillers with a metal content up to 1200 ppm Ni + V. However, while benefiting from the improvements allowed by the continuous regeneration of the catalyst, the ebullient bed technology allows to obtain conversion levels to distillates up to a maximum of 60%. It is possible to bring the conversion to Γ80% by operating at high severity and with the recycling of a portion of the products, however, encountering problems of stability of the fuel oil produced due to the separation of the unconverted asphaltene phase that remains, also in this case. , the heart of the problem. For these reasons also the ebullated bed technology, however entailing a significant production of fuel oil, does not lend itself to the implementation of total conversion processes to distillates.

As an alternative to hydroconversion processes based on the use of catalysts supported on a fixed bed or on a boiled bed, processes have been proposed which use catalysts homogeneously dispersed in the reaction medium (slurry). These slurry processes are characterized by the presence of catalyst particles having very small average dimensions and uniformly dispersed in the hydrocarbon phase. Consequently, the activity of the catalyst is hardly affected by the presence of metals or carbon residues resulting from the degradation of asphaltenes.

Compared to thermal processes, residue hydroconversion technologies also have limitations linked to high investment costs. Furthermore, they require quite high hydrogen consumption. The latter element is a very critical factor, especially in certain contexts where the availability of natural gas is limited. Consequently, it may be important to produce hydrogen from alternative sources, for example through the gasification of byproducts such as coke, residues, tar, asphaltenes, etc.

For all the above reasons, the realization of integrated processes in which it is possible to use by-products of low value for the production of hydrogen for internal use represents an advantageous solution from all points of view. Deasphalting, a liquid-liquid extraction treatment based on the use of paraffins, allows to separate a variable portion of DAO, deasphalted oil, which can have such qualitative characteristics (in terms of metal content, carbon residue, etc.) as to facilitate it. the subsequent conversion. This process offers several advantages compared to coking: significantly lower investment costs, the possibility of modulating yield and quality of DAO and asphaltenes according to needs, production of a by-product (the same asphaltenes) that can be fed in liquid form to the gasification process.

As known, deasphalting does not produce distillates: it is therefore necessary to subject the DAO to subsequent cracking treatments.

Recently, a process for the primary upgrading of heavy hydrocarbons that combines distillation, solvent deasphalting and thermal cracking to produce a partially upgraded synthetic crude oil substantially free of metals and asphaltenes has been claimed in US-6274003 by Ormat Industries. In the upgrading process the feed is first distilled to produce a lighter fraction, substantially free of asphaltenes, and a residue containing metals and asphaltenes.

A part of the distilled fraction passes to a hydrotreating unit, while the residual fraction is de-asphalted, to produce an oil (DAO) and an asphaltene residue. The DAO and possibly a part of the hydrotreated product (which acts as a hydrogen donor diluent) are combined and sent to a thermal cracking: the cracking product returns to the distillation column, from which the fractions that go to make up the partially upgraded syncrude.

In subsequent patents of the same owner (W003060042, US-6702936, US200401 18745, EP1465967) the process scheme is improved by claiming the use of a treatment which also includes the gasification of asphaltenes to produce synthesis gas, the treatment of synthesis gas, with production of hydrogen and hydroprocessing of distillates.

Patent application IT-2004A002446 claims a conversion process of heavy fillers which allows their total transformation ("zero residue refinery"). In this application IT-2004A002446 a process is described more precisely which involves the use of the following units: solvent deasphalting (SDA), hydroconversion of the DAO with catalysts in the slurry phase, distillation. The residue derived from the hydrotreatment stream, together with the catalyst in the slurry phase contained therein, is recycled to the hydrotreatment section. The asphaltene stream can be sent to a gasification section (POx) in order to obtain a mixture of H2 and CO.

We have surprisingly found that, by subjecting the DAO obtained from the deasphalting of the distillation residue of the heavy charge to hydrocracking in the presence of low concentrations of dispersed catalysts, it is possible to obtain high yields in distillates with excellent control over the formation of coke and gases. In this way it is not necessary to recycle the unconverted residue to the hydrocracking section. This residue can thus be recycled directly to the initial fractionation column or to the deasphalting zone from which, in addition to the asphaltenes present in the feed, any by-products formed in the hydrocracking phase can be removed and thus used, self-producing at the same time the necessary hydrogen. to the hydrogenating treatments envisaged by sending the asphaltenic stream to a gasification section. By comparing this solution with the one that provides a thermal cracking stage for the DAO conversion, it is possible to optimize the selectivity of the process, maximizing the yield to distillates and minimizing the production of coke and gas. Compared to the solution claimed in patent application IT-2004A002446, which provides for the use of high concentrations of catalyst and its recycling together with the distillation residue derived from hydrotreatment, the new solution proposed here allows to use minimum concentrations of catalyst, which it can be used only once, greatly simplifying the scheme; even at low concentrations of catalyst, its formulation allows optimal hydrogenation of the feed by preventing or minimizing the formation of coke. Sending the hydrotreatment residue to the deasphalting section allows for the recovery of additional amounts of DAO to be converted and, at the same time, for the gasification of the most concentrated fraction in pollutants (metals derived from the feed, together with traces of catalyst).

The process, object of the present invention, for the conversion of heavy charges comprises the following steps:

• sending the heavy charge to a first distillation zone (DI) having one or more atmospheric and / or vacuum distillation stages through which one or more light fractions are separated from the distillation residue;

• sending the fraction consisting of the distillation residue of the first distillation zone (D I) to a deasphalting zone (SDA) in the presence of solvents, obtaining two streams, one consisting of deasphalted oil (DAO), the other containing asphaltenes;

• sending the stream containing asphaltenes to a gasification zone (POx) in order to obtain a mixture of H2 and CO;

• mixing of the deasphalted oil stream (DAO) with a suitable hydrogenation catalyst and sending the mixture obtained to a hydrocracking zone (HCK) in which the self-produced hydrogen is introduced into the gasification zone (POx) after being separated into a gas separation zone (GS) from the mixture containing CO;

• sending the effluent stream from the hydrocracking zone to a second distillation zone (D2) consisting of one or more flash stages and / or one or more atmospheric distillation stages through which the different fractions coming from the hydrocracking reaction are separated from the distillation residue which is recycled to the first distillation zone (DI) and / or to the deasphalting zone (SDA).

The heavy feedstocks treated can be of different nature: they can be chosen from heavy crude oils, distillation residues, "heavy oils" from catalytic treatments, for example "unconverted oils" from fixed or boiled bed hydrotreatment, "heavy cycle oils" from catalytic cracking treatments, "thermal tars" (coming for example from visbreaking or similar thermal processes), bitumen from "oil sands", different types of carbon and any other high-boiling charge of hydrocarbon origin generally known in the art with the name of " black oils ".

The choice of sending the recycle of the distillation residue of the second distillation zone to the first distillation zone (DI) and / or to the deasphalting zone (SDA) is influenced by how the second distillation zone is carried out: it will be preferable to send completely or at least in part this residue to the deasphalting zone (SDA) if said second zone consists of one or more atmospheric distillation stages.

The first distillation zone (DI) can preferably be constituted by one or more atmospheric distillation stages or by one or more distillation stages and a vacuum stage.

Possibly the heavier fraction of the light fractions separated in the first distillation zone can be, at least in part, sent to the hydrocracking zone (HCK).

Gasification can be carried out by feeding to the gasifier the stream containing asphaltenes together with oxygen and steam which react under exothermic conditions at a temperature of over 1300 ° C and a pressure between 30 and 80 bar to produce mainly H2 and CO. The hydrogen produced can then be used in the hydrogenation section.

The separation of H2 from the H2 and CO mixture obtained from gasification can preferably be carried out by means of molecular sieves.

Part of the syngas stream, i.e. a mixture of H2 and CO, obtained from gasification, can be further valorised as fuel for the generation of steam or by combustion with combined cycles (IGCC) or be transformed into paraffinic hydrocarbons by Fischer-Tropsch synthesis or even be converted into methanol, dimethylether, formaldehyde and more generally in all that series of products derivable from the chemistry of Cl.

Furthermore, the H2e CO mixture obtained in the gasification zone (POx) before being sent to the separation zone (GS) is sent to a water-gas-shift zone (WGS) to generate hydrogen by reaction with water. The same paraffinic hydrocarbons obtained via Fischer-Tropsch can be mixed with the various cuts obtained from the distillation or flash stage, improving their compositional characteristics.

The distillation stages are preferably carried out under reduced pressure at a pressure ranging from 0.001 to 0.5 MPa, preferably from 0.1 to 0.3 MPa.

The distillation stages are preferably carried out under reduced pressure at a pressure ranging from 0.001 to 0.5 MPa, preferably from 0.1 to 0.3 MPa.

The deasphalting step (SDA), carried out by extraction with a solvent, hydrocarbon or not, is generally carried out at temperatures between 40 and 200 ° C and at a pressure between 0, 1 and 7 MPa.

It can also be formed by one or more sections operating with the same solvent or with different solvents; the recovery of the solvent can be carried out in subcritical or supercritical conditions in several stages, thus allowing a further fractionation between deasphalted oil and resins.

It is advisable that the solvent of this deasphalting stage be selected from light paraffins having from 3 to 6 carbon atoms, preferably having from 4 to 5 carbon atoms, or a mixture thereof.

The hydrocracking (HCK) step is carried out in the presence of catalysts in the slurry phase preferably at temperatures between 380 and 480 ° C, more preferably between 420 and 470 ° C, and at a pressure between 2 and 20 MPa, more preferably between 10 and 18 MPa.

The hydrogen is fed to the hydrocracking reactor, which can operate both in down-flow and, preferably, up-flow mode. This gas can be fed into different sections of the reactor.

The catalyst precursors used can be selected from those obtainable from easily decomposable oil-soluble precursors (metal naphthenates, metal derivatives of phosphonic acids, metal-carbonyls, etc.) or from preformed compounds based on one or more transition metals such as Ni, Co , Ru, W and Mo: the latter is preferred due to its higher catalytic activity.

The concentration of the catalyst, defined on the basis of the concentration of the metal or metals present in the hydrocracking reactor, is between 50 and 5000 ppm, preferably between 50 and 900 ppm.

The process claimed therein allows the production of a 'Tight syncrude' (atmospheric and vacuum distillates) completely de-asphalted and demetallated and also upgraded in terms of density, viscosity, CCR sulfur content.

An embodiment of the present invention is now provided with the aid of the attached figure 1 which however is not to be considered a limitation of the scope of the invention itself.

In fig. 1 the heavy charge (1) is fractionated in a first distillation zone (DI) from which the light fractions (2) and (3) are separated from the distillation residue (4).

The first distillation residue (4) is sent to a deasphalting unit (SDA), an operation which is carried out by extraction with a solvent (8).

Two streams are obtained from the deasphalting unit (SDA): one (9) consisting of deasphalted oil also called "deasphalted oil" (DAO), the other containing asphaltenes (10).

The stream consisting of deasphalted oil (9), freed from the solvent used for extraction, is sent from a hydrocracking area (HCK).

The stream containing asphaltenes (10) is sent to a gasification section (POx) in order to obtain syngas or a gaseous mixture H2 and CO (11) which is sent to a separation zone (GS) through which a substantially constituted stream separates CO (12) and a stream substantially constituted by H2 (13) which is sent to the hydrocracking stage thus supplying the necessary quantity of hydrogen.

The outgoing stream (16) from the hydrocracking stage (HCK) is sent to a second distillation zone (D2).

In the second distillation zone (D2), consisting of a distillation column possibly preceded by a flash, the lighter fractions (D2i, D22, D2 ..., D2n) are separated from the heavier bottom (19) which is recycled (20) to the first distillation zone (DI) and / or (21) to the deasphalting zone (SDA).

Eventually at least part (22) of the heavier light fraction (3) separated in the first distillation zone (DI) can be sent to the hydrocracking zone (HCK).

Some examples are reported below with the aim of better illustrating the invention, it being understood that it must not be considered or limited by them.

Example 1: Preparation of a deasphalted oil.

<■> Charge: 250 g atmospheric residue

<■> Deasphalting agent: about 2.5 1 of n-pentane

<■> Temperature: 180 ° C

<■> Pressure: 16 atm

The residue and a volume of npentane equal to 8-10 times the volume of residue are loaded into an autoclave. The mixture of filler and solvent is heated up to the temperature of 180 ° C, with stirring (800 rpm) by means of a mechanical impeller for a period of 30 min. At the end of the operation, the decantation and separation takes place between the two phases, the asphaltenic one that settles on the bottom of the autoclave, and that of the deasphalted oil diluted in the solvent. Decanting takes about two hours. By means of an appropriate recovery system, the DAO-solvent phase is transferred to a second tank. The DAO-pentane phase is then recovered, after which the solvent is eliminated by evaporation.

The yield obtained by applying the procedure described is equal to 89.8% wt of desfalted oil with respect to the starting residue.

Example 2: Hydrocracking of deasphalted oil with n-pentane.

The test was conducted using a 30 cm stirred micro-autoclave in accordance with the following general operating procedure:

about 10 g of the feed is introduced into the reactor, to which the catalyst precursor is added;

the system is pressurized with hydrogen and brought to temperature by means of an electrically heated oven;

during the reaction the system is kept stirred by a swinging capillary system operating at a rotation speed of 900 rpm; moreover, the total pressure is kept constant by means of an automatic system for replenishing the consumed hydrogen;

- once the test is completed, the quenching of the reaction is carried out; the autoclave is then depressurized and the gases collected in a sampling bag; the gaseous samples are subsequently sent for gas chromatography analysis;

the solids are separated from the products present in the reactor by filtration; liquid products are analyzed to determine: distillate yields, sulfur content, nitrogen content, carbon residue and metal content.

The reaction was carried out by feeding the charge produced in example 1 under the operating conditions indicated in Table 1. The product distribution data are shown in Table 2.

Example 3: Thermal cracking of deasphalted oil with npentane.

The test was conducted according to the operating procedure shown in example 2, without adding catalyst and replacing hydrogen with nitrogen. The reaction was carried out by feeding the charge produced in example 1 under the operating conditions indicated in Table 1. The product distribution data are shown in Table 2.

Table 1: Operating conditions

Table 2: Product distribution

Claims (17)

CLAIMS 1. Process for the conversion of heavy fillers selected from heavy and extra-heavy crude oils, distillation residues from crude oil or from catalytic treatments, "visbreaker tars", "thermal tars", bitumen from "oil sands", liquids from carbon different rank and other high boiling fillers of hydrocarbon origin known as "black oils", comprising the following stages: • sending the heavy charge to a first distillation zone (DI) having one or more atmospheric and / or vacuum distillation stages through which one or more light fractions are separated from the distillation residue; • sending the fraction consisting of the distillation residue of the first distillation zone (D I) to a deasphalting zone (DSA) in the presence of solvents, obtaining two streams, one consisting of deasphalted oil (DAO), the other containing asphaltenes; • sending the stream containing asphaltenes to a gasification zone (POx) in order to obtain a mixture of H2 and CO; • mixing of the deasphalted oil stream (DAO) with a suitable hydrogenation catalyst and sending the mixture obtained to a hydrocracking zone (HCK) in which the self-produced hydrogen is introduced into the gasification zone (POx) after being separated into a gas separation zone (GS) from the mixture containing CO; • sending the effluent stream from the hydrocracking zone to a second distillation zone (D2) consisting of one or more flash stages and / or one or more atmospheric distillation stages through which the different fractions coming from the hydrocracking reaction are separated from the distillation residue which is recycled to the first distillation zone (DI) and / or to the deasphalting zone (SDA). 2. Process according to claim 1 where the gasification is carried out by feeding to the gasifier the stream containing asphaltenes together with oxygen and steam which react under exothermic conditions at a temperature of over 1300 ° C and a pressure of between 30 and 80 bar to mainly produce H2 and CO. 3. Process as per claim 1 where the H2e CO mixture obtained in the gasification zone (POx) before being sent to the separation zone (GS) is sent to a water-gas-shift zone (WGS) to generate hydrogen by means of reaction with water. 4. Process according to claim 1 where the first distillation zone (DI) consists of one or more atmospheric distillation stages. 5. Process according to claim 1 where the first distillation zone (DI) consists of one or more distillation stages and a vacuum stage. 6. Process according to claim 1 where the heavier fraction of the light fractions separated in the first distillation zone is at least partially sent to the hydrocracking zone (HCK). 7. Process according to claim 1 wherein the distillation stages are carried out at a reduced pressure comprised between 0.001 and 0.5 MPa. 8. Process according to claim 7 wherein the distillation stages are carried out at a reduced pressure of between 0.01 and 0.3 MPa. 9. Process according to claim 1 wherein the deasphalting step (SDA) is carried out at temperatures between 40 and 200 ° C and at a pressure between 0.1 and 7 MPa. 10. Process according to at least one of claims 1 to 9 wherein the solvent of the deasphalting step (SDA) is a light paraffin or a mixture of light paraffins having a number of carbon atoms ranging from 3 to 6. 11. Process according to claim 10 wherein the deasphalting solvent is a light paraffin or a mixture of light paraffins having a number of carbon atoms from 4 to 5. 12. Process according to claim 1 wherein the deasphalting step (SDA) is carried out with recovery of the solvent in the supercritical phase. 13. Process according to claim 1 where the hydrocracking step (HCK) is carried out at temperatures between 380 and 480 ° C, preferably between 420 and 470 ° C, and at a pressure of between 2 and 20 MPa, preferably between 10 and 18 MPa . 14. Process according to at least one of claims 1 to 13 where the hydrogenation catalyst for hydrocracking is an easily decomposable precursor or a preformed compound based on one or more transition metals. 15. Process according to claim 14 where the transition metal is molybdenum. 16. Process according to claim 1 where the concentration of the catalyst in the hydrocracking reactor, defined on the basis of the concentration of the metal or metals present, is between 50 and 5000 ppm. 17. Process according to claim 15 where the concentration of the catalyst in the hydrocracking reactor is between 50 and 900 ppm.