MXPA97010346A - Process of transformation of a gasoleo cutting to produce a fuel with high indicede cetano, desaromatico and desulfur - Google Patents

Abstract

The present invention relates to a process for converting a gasoil cut into a fuel with a high degree of cetane, dearomatized, comprising at least one first stage called desulphurisation and deep denitrogenation in which the gasoil cut is passed. and the hydrogen on a catalyst comprising a mineral support, at least one metal or metal compound of group VIB, at least one metal or metal compound of group VIII and of phosphorus or at least one phosphorus compound and at least one second step subsequent to the aromatization, in which the desulfurized and denitrogenated product exiting the first stage and the hydrogen are passed over a catalyst comprising a mineral support, and at least one noble metal or noble metal compound of group VI

Description

PROCEDURE DB TRANSFORMATION DI ÜN COURT DK GASÓLEO TO PRODUCE ON FUEL WITH HIGH INDEX OF CETAN, DBSAROMATIZED AND DESULFURATED Field of the Invention The present invention relates to the domain of fuels for internal combustion engines. It relates more particularly to the manufacture of a fuel for compression ignition engines. In this domain, the invention relates to a process for transforming a gas oil cut to produce a fuel with a high cetane number, dearomatized and desulfurized.

Background of the Invention At present, diesel cuts when they come from the direct distillation of crude oil or when they have left the catalytic fractionation process, still contain non-negligible amounts of aromatics, nitrogen compounds and sulfur compounds. In the legislative framework of most industrial countries, the fuel usable in engines must contain a R £ £ 0.26522 amount of sulfur less than about 500 parts per million by weight (ppm). In certain countries, norms of a maximum content of aromatic substances and nitrogen are not yet imposed. It has however been found that several countries or states, for example Sweden and California, contemplate limiting the content of aromatic substances to a value below 20% by volume, even less than 10% by volume and certain experts also think that this content could be limited to 5% in volume. In Sweden in particular, certain classes of diesel fuel must already meet very severe specifications. Thus, in this country the diesel fuel of class II must not contain more than 50 ppm of sulfur and not more than 10% by volume of aromatic compounds and that of class I not more than 10 ppm of sulfur and 5% by volume. volume of aromatic compounds. Currently in Sweden, class III diesel fuel must contain less than 500 ppm of sulfur and less than 25% by volume of the aromatics. Similar limits have to be respected in the same way in California for this type of fuel. During this time, motorists of several countries are exerting pressure so that the legislation obliges the oil tankers to produce and sell a fuel whose cetane index has a minimum value. Currently, French legislation requires a minimum cetane number of 49, but it is foreseeable that in the near future this minimum rate will be at least 50 (as is already the case for the class I fuel in Sweden) and probably also from at least 55 and more likely between 55 and 70. Numerous specialists seriously contemplate the possibility of having in the future a standard that imposes a lower nitrogen content for example at approximately 200 ppm and even certainly below 100 ppm. In fact, a reduced nitrogen content allows a better stability of the products and in general will also be sought by both the seller of the product and the manufacturer. It is necessary to prepare a reliable and efficient procedure that allows obtaining, from the conventional diesel cuts of direct distillation or that come from the catalytic fractionation (LCO cut) or from another conversion process (coking, visbreaking (reduction of the viscosity), hydroconversion of the waste, etc.) a product having improved characteristics as regards both the cetane number and the contents of aromatic, sulfur and nitrogen substances. It is particularly important, and this is one of the advantages of the process of the present invention, to produce the minimum of gaseous hydrocarbon compounds and to be able to have a directly and integrally assessable effluent provided that the fuel cut is of very high quality. On the other hand, the process of the present invention allows a production over an important period of time without having to regenerate the catalysts used, which have the advantage of being very stable over time.

DETAILED DESCRIPTION OF THE INVENTION In its broadest formulation, the present invention thus relates to a process for converting a gas oil cut to produce a fuel with a high cetane index, dearomatized and desulfurized in at least two successive stages. It also refers to the fuel obtained by said process. More precisely, the present invention relates to a process for converting a gas oil cut into a fuel with a high cetane ratio, dearomatized and desulfurized, which comprises the following steps: a) at least one first stage called desulphurization and deep denitrogenation in which said gasoil and hydrogen cut is passed over a catalyst comprising a mineral support, at least one metal or metal compound of group VIB of the classification periodically of the elements and a quantity expressed by weight of the metal with respect to the weight of the spent or finished catalyst of about 0.5 to 40%, at least one metal or metal compound of group VIII of said periodic classification in an amount expressed by weight of the metal with respect to the weight of the spent or finished catalyst of about 0.1 to 30% and of the phosphorus or at least one phosphorus compound of a quantity expressed by weight of phosphorus pentoxide with respect to the weight of the support of about 0.001 to 20% and b) at least one second subsequent step called "desaromatization" in which at least part, and preferably all, of the product leaving the first stage is passed, at least in part, and preferably completely desulfurized and denitrogenated and of hydrogen on a catalyst comprising, on a mineral support, at least one noble metal or noble metal compound of group VIII in an amount expressed by weight of metal with respect to the weight of the spent or finished catalyst of about 0.01 to 20%, and preferably at least one halogen.

Advantageously, according to the process, the hydrogen is introduced at the level of each of the first and second stages, and is eventually recycled at the level of the first and second stages, independently of each other, which means that there is no common gas management out of those stages. Preferably, according to the process, the effluent exiting the first stage is subjected to a steam separation of the water so that at least part of the gas phase separates, which could be treated and possibly recycled at least in part at the level of said stage. At least a part of the product from the separation is subjected to the second stage of the process according to the invention. The effluent leaving the last stage, preferably being separated from the steam, passes vigorously to a coalescing device and is eventually dried. In a preferred embodiment of the invention, the operating conditions of steps a) and b) are chosen as a function of the characteristics of the load, which may be a direct gas distillation cut, a gasoil cut that comes from the catalytic fractionation. or a gasoil cut that comes from the coking or visbreaking (reduction of the viscosity) of the waste or a mixture of two or more of these cuts so that a product containing less than 100 ppm of sulfur and less is obtained of 200 ppm, or better than 50 ppm of nitrogen and the conditions of step b) are chosen so as to obtain a product containing less than 10% by volume of the aromatic compounds. These conditions could be made more severe so that after the second stage a fuel containing less than 5% by volume of the aromatic compounds is obtained, less than 50 ppm even less than 10 ppm of sulfur, less than 20 ppm, even less of 10 ppm of nitrogen and having a cetane number of at least 50 and likewise at least 55 and more frequently between 55 and 60. To obtain such results the conditions of step a) comprising a temperature of about 300 ° C at approximately 450 ° C, a pressure of about 2 MPa at about 20 MPa and an overall hourly space velocity of the liquid charge of about 0.1 to about 10 and preferably 0.1 to 4 and that of step b) a temperature of about 200 ° C at 400 ° C, a total pressure of about 2 MPa at about 20 MPa and a global spatial velocity per hour of the liquid charge of about 0.5 to about 10.

When it is desired to remain in a relatively low pressure range in order to obtain excellent results, it is possible to carry out a first step a) under conditions which allow to reduce the sulfur content of the product to a value of approximately 500 to 800 ppm then send this product to a subsequent stage a2) in which the conditions will be chosen to reset the sulfur content to a lower value of about 100 ppm, preferably less than about 50 ppm and the product output from this step a2) is then sent to the stage b). In this embodiment the conditions of step a2) are identical even, preferably milder than when a given load is operated in a single step a), because the product sent to this stage a2) already has a strongly reduced content of sulfur. In this embodiment, the catalyst of step a) can be a conventional catalyst of the prior art such as for example that described in the text of the patent applications in the name of the applicant FR-A-2197966 and FR-A -2538813 and that of step a2) is that described above for step a). Without going outside the scope of the present invention, the same catalyst is used in steps a) and a2). In these steps a), al), a2) the catalyst support can be chosen from the group consisting of alumina, silica, silica-aluminas, zeolites, titanium oxide, magnesia, zirconia, argils and mixtures of at least two of these mineral compounds. Alumina is very commonly used. In a preferred embodiment of the invention, the catalyst in these steps a), al), a2) will comprise, deposited on the support, at least one metal or a metal compound, advantageously selected from the group consisting of molybdenum and tungsten and at least one metal or metal compound advantageously selected from the group consisting of nickel, cobalt and iron. Very often this catalyst comprises molybdenum or a molybdenum compound and at least one metal or a metal compound selected from the group consisting of nickel and cobalt. In a particular and preferred form of the invention the catalyst of these steps a), al), a2) will comprise the boron or at least one boron compound preferably in a quantity expressed by weight of trioxide with respect to the weight of the lower support or equal to 10%, and preferably deposited on the support. The amount of the metal or metal compound of group VIB (Mo is preferred) expressed by weight of the metal with respect to the weight of the spent or finished catalyst will preferably be about 2 to 30% and more often about 5 to 25% and that of the metal or metal compound of group VIII (Ni or Co are preferred) will preferably be about 0.5 to 15% and more frequently about 1 to 10%. A catalyst containing Ni, Mo, P is preferably used, the proportions of these elements have been described above, or better Ni, Mo, P, B. A particularly advantageous catalyst is that described in patent EP-297,949 whose teaching is included in this description. This catalyst comprises; a) a support comprising a porous mineral matrix of boron or a compound of boron and phosphorus or a phosphorus compound, and b) at least one metal or metal compound of group VIB of the periodic classification of the elements and at least one a metal or metal compound of group VIII of said classification, in which the sum of the amounts of boron and phosphorus, expressed respectively in the weight of boron trioxide (B203) and of phosphorus pentoxide (P2O5) with respect to the weight of the support is about 5 to 15%, preferably about 6 to 12% and advantageously about 8 to 11.5%, the atomic ratio of boron to phosphorus (B / P) is about 1.05: 1, at 2 : 1 and preferably from about 1.1: 1 to 1.8: 1. Advantageously at least 40% and preferably at least 50% of the total pore volume of the spent or finished catalyst is contained in the pores of average diameter greater than 13 nanometers. The catalyst preferably has a total pore volume between 0.38 and 0.51 cm3xg_1. The amount of the metal or group VIB metals contained in the catalyst is usually such that the atomic ratio of the phosphorus to the metal or metals of group VIB (P / VIB) is from about 0.5: 1 to 1.5: 1 and from Preference from about 0.7: 1 to 0.9: 1. The respective amounts of the metal or of the metals of group VIB and of the metal or of the metals of group VIII contained in the catalyst are usually such that the atomic ratio of the metal or of the metals of group VIII on the metal or metals of the group VIB (VIII / VIB) is from about 0.3: 1 to 0.7: 1 and preferably from about 0.3: 1 to about 0.45: 1. The amount by weight of the metals contained in the spent or finished catalyst expressed by weight of the metal with respect to the weight of the spent or finished catalyst is usually, for the metal or metals of the VIB group of about 2 to 30% and preferably about 5 to 25%, and for the metal or metals - of the group VIII of about 0.1 to 15% and more particularly about 0.1 to 5 % and preferably from about 0.15 to 3% in the case of noble metals of group VIII (Pt, Pd, Ru, Rh, Os, Ir) and from about 0.5 to 15% and preferably from about 1 to 10% in the case of non-noble metals of group VIII (Fe, Co, Ni). In step b) the mineral support can be chosen from the group consisting of alumina, silica, silica-aluminas, zeolites, titanium oxide, magnesia, boron oxide and mixtures of at least two of these mineral compounds This support will preferably comprise at least one halogen chosen from the group consisting of chlorine, fluorine, iodine and bromine and preferably chlorine and fluorine. In an advantageous embodiment, this support will comprise chlorine and fluorine. The amount of the halogen will more often be from about 0.5 to about 15% by weight with respect to the weight of the support. The most frequently used support is alumina. The halogen is usually introduced onto the support from the halides of the corresponding acid and the noble metal, preferably platinum or palladium, from, for example, aqueous solutions of its salts or compounds such as, for example, hexachloroplatinic acid in the case of platinum.

The amount of the noble metal (Pt or Pd is preferred) of this catalyst of step b) will preferably be from about 0.01 to 10%, frequently from about 0.01 to 5% and more frequently from about 0.03 to 3% expressed in weight of the metal with respect to the weight of the spent or finished catalyst. A particularly advantageous catalyst is described in patent FR-2,240,905 whose teaching is included. It comprises a noble metal, aluminum, a halogen, and has been prepared by mixing the aluminous support with a noble metal compound and a reducer of the formula AlXyR3_y where y equals 1.3 / 2 or 2, X is a halogen and R is a monovalent hydrocarbon radical. Another catalyst which is very convenient is that described in US Pat. No. 4,225,461. It comprises a noble metal and a halogen and has been prepared in a particular manner. The following examples illustrate the invention without limiting what is provided.

Example 1 A direct distillation gas oil cut is available. Its characteristics are reported on table No. 1. Its sulfur content is 1.44 %. This gasoil cut is treated according to a scheme in 2 stages: a first stage on a catalyst containing, in the form of the oxide, about 3% nickel, 16. 5% molybdenum and 6% P205 on alumina. This first stage contemplates the desulfurization and deep denitrogenation of the gasoil cut - a second stage on a catalyst containing approximately 0.6% platinum on alumina. This second stage essentially contemplates the deep desaromatization of the effluent of the first stage, but also allows the sulfur content to be further reduced.

The first stage is carried out in a pilot idrotreatment unit. It carries two reactors in series that can contain up to 20 1 of the fixed bed catalyst. The unit carries a hydrogen recycling compressor. The cooling of the fluids is descending in each one of the reactors. The unit has a column in the line of separation or steam distillation that allows to separate or distill the effluent of the reaction that is completely free of H2S and NH3 formed in the course of the reaction. 5 1 of the same catalyst is loaded in each of the reactors in this pilot unit. In this unit, a desulphurization and a deep denitrogenation of said gasoil cut is carried out applying the following operating conditions: - WH = 1.5 h "1 - total pressure = 50 bar (10 bar = 1 MPa) - Recycling of H2 = 400 normal liters of H2 / liter of load (NI / l) - Temperature = 340 ° C This produces a product that is deeply desulfurized (sulfur content less than 50 ppm) and very deeply denitrogenated (nitrogen content less than 6 ppm). Its characteristics are reported in Table No. 1. The material balance is reported in table 2.

The effluent is preserved for the pilot tests of the second stage. The second stage is carried out in a pilot unit of smaller size carrying a 1 1 reactor with a rising fluid outlet. The unit does not carry a recycling compressor. This unit is loaded with 1 1 of the fixed-bed catalyst. The operating conditions are the following: - WH = 6 h "1 - Total pressure = 50 bar - H2 flow rate = 400 NI H2 / 1 load - Temperature = 300 ° C This produces a product that is deeply de-aromatized (aromatic content less than 5%) and has a very strong cetane index (65). Its detailed characteristics are reported on table No. 1. The material balance is reported in the table 2. The formation of the gas in the course of the operation is not detected. The integrity of the effluent can be evaluated as long as the fuel cut is of very good quality.

Table No. 1 Analysis of the load and effluent of the 1 / a. and 2 / stages (D86 meaning according to ASTM-D86 method) Table No. 2: Material Balance 1 / a. and 2 / a. stages Example 2 A catalytic fractionation gas oil (LCO) cut is available. Its characteristics are reported on table No. 3. Its sulfur content is 1.56%. This gasoil cut is treated according to a 2-stage scheme: a first step on a catalyst containing, in the form of the oxide, about 3% nickel, 16.5% molybdenum and 6% P205 on alumina. This first stage contemplates the desulfurization and deep denitrogenation of the gasoil cut. - a second stage on a catalyst containing approximately 0.6% platinum on alumina. This second stage contemplates essentially the deep desaromatización of the effluent of the first stage, but also allows to lower still the content of sulfur and nitrogen.

The first stage is carried out in a pilot hydrotreating unit. It has two reactors in series that can contain up to 20 1 of catalyst. The unit carries a hydrogen recycling compressor. The output of the fluids is descending in each of the reactors. The unit has a column in the line of separation or steam distillation that allows to separate or distil the effluent of the reaction that is thus completely free of H2S and NH3 formed in the course of the reaction. 5 1 of the same catalyst is loaded in each of the reactors in this pilot unit. A deep desulfurization and denitrogenation of said gasoil cut is carried out in this unit applying the following operating conditions: - WH = 1 h "1 - total pressure = 80 bar (10 bar = 1 MPa) - Recycling of H2 = 400 NI H2 / 1 load - Temperature = 375 ° C This produces a product that is deeply desulphurized (sulfur content below 50 ppm) and very denitrogenated (nitrogen content less than 6 ppm). Its characteristics are reported on Table No. 3. The material balance is reported in table 4. The effluent is conserved for the pilot tests of the second stage. The second stage is carried out in a pilot unit of very small size that carries a 1 1 reactor, with the rising output of the fluids. The unit does not carry a recycling compressor. This unit is loaded with 1 1 of the catalyst. The operating conditions are the following: - WH = 4 h_1 Total pressure = 50 bar - H2 flow rate = 400 1 H2 / 1 load - Temperature «300 ° C This produces a product that is deeply de-aromatized (content of aromatic substances less than 5%) and that has a cetane index of the engine of 54. Its detailed characteristics are reported on table No. 3. The balance of materials is reported in table 4. Gas formation has not been detected in the course of the operation. The integrity of the effluent can be evaluated as long as there is a very high quality fuel cut.

Table no. 3 Analysis of the load and effluent of the 1st and 2nd stages Table 4 Material Balance 1 / a. and 2 / a. Stages Example 3 The same load as the one mentioned in Example 2 is treated, under the same conditions of WH, total pressure, H2 recycling and temperature in each of the stages, the only difference is that in the 1 / a. A catalyst containing, in the form of the oxide, about 3% of nickel, 15% of molybdenum, 6% of P205 and 3.5% of B203 on alumina and in 2 / a is used. stage a catalyst containing approximately 0.6% platinum, 1% chlorine and 1% fluorine on alumina. The material balance of each of these stages is the same as that given in example 2, table 4. The analysis of the effluent of the first stage and the second stage is reported in the table given below.

This example shows very well the effect of the use of a catalyst containing boron in the first stage and also shows the influence of the use of a catalyst containing both the chlorine and the fluorine of the 2 / a. stage.

It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property

Claims (14)

1. A process for transforming a gasoil cut into a fuel with a high cetane index, dearomatized and desulfurized, characterized in that it comprises the following stages with the introduction of hydrogen and the eventual recycling of the hydrogen at the level of each of the first and second stages independently between them: a) at least one first stage called desulphurization and deep denitrogenation in which the gasoil and hydrogen cutting is passed over a catalyst comprising a mineral support, at least one metal or metal compound of group VIB of the classification periodically of the elements in a quantity expressed by weight of the metal with respect to the spent or finished catalyst of about 0.5 to 40%, at least one metal or metal compound of group VIII of said periodic classification in an amount expressed by weight of the metal with with respect to the weight of the spent or finished catalyst of approximately 0.1 to 30% and of the phosphorus or at least one compound of the phosphorus in an amount expressed by weight of the phosphorus pentoxide with respect to the weight of the support from about 0.001 to 20% and b) at least a second subsequent stage called "desaromatización" in which at least a part of the product from the separation or distillation is passed steam of the effluent obtained at the outlet of the first stage, product that is at least partly desulfurized and denitrogenated, and hydrogen on a catalyst comprising, on a mineral support at least one noble metal or noble metal compound of group VIII in a quantity expressed by weight of the metal with respect to the weight of the spent or finished catalyst of approximately 0.01 to 20%.

2. The method according to claim 1, characterized in that the operating conditions of step a) are chosen so as to obtain a product containing less than 100 ppm of sulfur and less than 200 ppm of nitrogen and the conditions of step b ) are chosen so as to obtain a product containing at least 10% by volume of the aromatic compounds.

3. The method according to claims and or 2, characterized in that the operating conditions e 1 a. stage a) comprise a temperature of 300 ° C to 450 ° C, a total pressure of 2 MPa at 20 MPa and an overall space velocity per hour of the liquid charge of 0.1 to 10 h and that of the stage Da b) a temperature of 200 C at 400 ° C, a total pressure of 2 MPa at 20 MPa and an overall speed per hour, of the liquid load of 0.5 to 10 h

4. The process according to claims 1 to 3, characterized in that the catalyst of stage a) comprises at least one metal or a metal compound selected from the group consisting of molybdenum or tungsten and at least one metal or a metal compound chosen from the group consisting of nickel, cobalt and iron.

5. The process according to one of claims 1 to 4, characterized in that the catalyst of stage a) comprises the molybdenum or a molybdenum compound in a quantity expressed by weight of the metal with respect to the weight of the spent or finished catalyst of approximately 2. at 30% and a metal or a metal compound selected from the group consisting of nickel and cobalt in a quantity expressed by weight of the metal with respect to the weight of the catalyst exhausts or terminates from about 0.5 to 15%.

6. The process according to one of claims 1 to 5, characterized in that the metal of the GVHI is nickel and the metal of the GV1I is molybdenum.

7. The process according to one of claims 1 to 6, characterized in that the catalyst of step a) further comprises the boron or at least one boron compound in a quantity expressed by weight of boron trioxide with respect to the weight of the support, less than or equal to 10%.

8. The process according to one of claims 1 to 7, characterized in that the support of the catalysts used in step a) and in step b) are chosen independently of one another from the group consisting of alumina, silica, silicates, aluminas, zeolites, titanium oxide, magnesia, boron oxide, zirconia, argils and mixtures of at least two of these mineral compounds.

9. The process according to one of claims 1 to 8, characterized in that the catalyst support of step b) comprises at least one halogen.

10, The procedure in accordance with one of p and claims 1 to 9, characterized in that the catalyst support of step b) comprises a halogen amount of from about 0.5 to about 15% by weight with respect to the weight of the support.

11. The process according to claim 9 or 10, characterized in that the catalyst support of step b) comprises at least one halogen selected from the group consisting of chlorine and fluorine.

12. The process according to one of claims 9 to 11, characterized in that the catalyst support of stage b) comprises chlorine and fluorine.

13. The process according to one of claims 1 to 12, characterized in that the catalyst of step b) comprises at least one metal or a metal compound selected from the group consisting of palladium and platinum in a quantity expressed by weight of the metal with respect to the weight of the spent catalyst of approximately 0.1 to 10%.

14. The fuel obtained in accordance with the third step of any of claims 1 to 13.