METHOD FOR OBTAINING HYDROCARBON SOLVENTS WITH BOILING POINT ABOVE 300 ?C AND POUR POINT LOWER THAN OR EQUAL TO -25 ?C

Abstract

A method for producing hydrocarbon solvents having a sulfur content of less than 10 ppm, aromatic hydrocarbon content of less than 500 ppm, an initial boiling point higher than or equal to 300? C. and final boiling point lower than or equal to 500? C., for a fraction interval of a maximum of 100? C., and pour point lower than ?25? C. according to the standard ASTM D5950, comprising of the following steps of: dewaxing of a hydrocarbon fraction having initial boiling point higher than 300? C. derived from the distillation of a gas oil fraction, hydrodearomatisation of all or part of the dewaxed effluent, in the presence of a catalyst comprising nickel on an alumina base, at a pressure ranging from 60 to 200 bar and a temperature ranging from 80? C. to 250? C., recovery of the dewaxed and dearomatised fraction, distillation in fractions of the dewaxed and dearomatised fraction, recovery of at least one 300? C.+ fraction having pour point lower than ?25? C., this fraction having a distillation interval lower than 100? C.

Claims

1. A (300? C.+) hydrocarbon fraction having pour point lower than ?25? C., initial boiling point higher than 300? C. and final boiling point lower than or equal to 500? C., with fraction interval lower than 100? C., having a sulfur content of less than 10 ppm and with content of aromatic hydrocarbons less than 500 ppm, obtained by a method comprising the following steps: dewaxing of a hydrocarbon fraction having initial boiling point higher than 300? C. derived from the distillation of a gas oil fraction obtained by any crude oil refining process, and recovery of all or part of the dewaxed effluent, the step of dewaxing comprising at least one first section for mild cracking in the presence of a silicalite-based catalyst, having silica/alumina ratio greater than 130, comprising 0% to 10% by weight of at least one metal from group VIII, and possibly 0% to 10% by weight of a metal from Group VI; hydrodearomatisation of all or part of the dewaxed effluent, in the presence of a catalyst comprising nickel on an alumina base, at a pressure ranging from 60 to 200 bar and a temperature ranging from 80? C. to 250? C., and said dewaxed effluent being possibly previously desulphurised in advance if its sulfur content is greater than 15 ppm, recovery of the dewaxed fraction, possibly desulphurised, and dearomatised, distillation (DA1) in fractions of the said dewaxed and dearomatised fraction, and finally recovery of at least one 300? C.+ fraction having pour point lower than ?25? C. that is usable as solvent, this fraction having a distillation interval lower than 100? C., characterised in that said hydrocarbon fraction contains more than 30% by weight of naphthenic compounds, and less than 10% by weight of normal paraffins, and the mono naphthenic compounds represent more than 20% by weight of the naphthenic compounds.

2. A hydrocarbon fraction according to claim 1, containing less than 5% by weight of normal paraffins.

3. A hydrocarbon fraction according to claim 1, characterised in that it has a pour point that is lower than ?30? C., a kinematic viscosity at 40? C. less than or equal to 15 mm.sup.2/g, preferably ranging from 5 mm.sup.2/g to 10 mm.sup.2/g and an aniline point below 120? C.

4. A hydrocarbon fraction according to claim 1, characterised in it comprises less than 35% by weight of hydrocarbons having a chain length of more than 22 carbon atoms, and more than 65% by weight of hydrocarbons having a chain length of less than 22 carbon atoms.

5. A hydrocarbon fraction according to claim 1, as a solvent in applications related to phytosanitary products, inks and sealant putty or even as a fluid for metal working.

Description

[0068] In order to describe the invention in a more precise manner, figures representing the different forms of implementation of the invention have been provided in support of this description.

[0069] FIG. 1 represents the system of the invention for which two separate reactors (R1) and (R2) are shown respectively for the steps of dewaxing and dearomatisation.

[0070] FIG. 2 represents the system of the invention for which a single reactor is shown containing two separate sections (SR1) and (SR2) respectively for the steps of dewaxing and dearomatisation, with one cavity (30) separating these said sections.

[0071] FIG. 3 represents the sections for mild cracking and hydrotreating contained in the dewaxing reactor R1 or SR1 in the FIGS. 1 and 2.

[0072] In FIG. 1, a feed stock of gas oil (GO) derived from any process for refining crude oil is introduced through the pipe line (10) into the separator enabling a fractional distillation DF referenced (1) where it is separated into two fractions, one light fraction (Cl) discharged from the fractional distillation unit DF via the pipe line (12) and a heavy fraction CL discharged from the fractional distillation unit DF via the pipe line (11).

[0073] This heavy fraction CL is sent to the dewaxing reactor R1 referenced (2) fed in parallel by the hydrogen arriving via the pipe lines (31), and then (32). All of the dewaxed effluent is directed through the pipe line (14) into an atmospheric distillation unit DA2 referenced (5). Two, three or four effluents are distilled according to the choice of recovery process contemplated, only the dewaxed fraction CDP discharged via the pipe line (15) is sent to the step of dearomatisation.

[0074] For example, the dewaxed effluent may be distilled in the distillation unit DA2 in two dewaxed fractions, three dewaxed fractions or four dewaxed fractions; [0075] one hydrocarbon fraction of C1 to C4 also called fuel gas is discharged through the pipe line (21) and a hydrocarbon fraction of more than 5 carbon atoms (or C5+) is discharged through the pipe line (15) to the dearomatisation reactor R2 referenced as (3), [0076] or one hydrocarbon fraction of C1 to C4 discharged through the pipe line (21) and two hydrocarbon fractions, one of C5 distilling at 150? C. (or C5-150) discharged through the pipe line (22) and the other distilling above 150? C. (or 150? C.+) is discharged through the pipe line (15) to the dearomatisation reactor R2 referenced as (3), [0077] or one hydrocarbon fraction of C1 to C4 discharged through the pipe line (21) and three hydrocarbon fractions, the first one of C5 distilling at 150? C. (or C5-150) discharged through the pipe line (22), the second distilling from 150? C. to 300? C. (or 150-300) is discharged through the pipe line (23) and the third distilling above 300? C. (or 300? C.+) discharged through the pipe line (15) to the dearomatisation reactor R2 referenced as (3).

[0078] The dewaxed fraction CDP discharged through the pipe line (15) is sent through the pipe line (16) into the reactor R2 referenced as (3) fed in parallel by the hydrogen coming from the pipe line (31) through the pipe line (33).

[0079] The dewaxed and dearomatised effluent is recovered upon being output from the reactor R2 (3) through the pipe line (17) and directed to a distillation unit DA1 referenced as (4) in order to be distilled therein into at least four fractions: [0080] the 300? C.+ fraction or fractions recovered through the pipe line (18), [0081] the (150-300) fraction discharged through the pipe line (27), [0082] the (C5-150) fraction discharged through the pipe line (26), [0083] and the C1-C4 fraction or fuel gas discharged through the pipe line (25).

[0084] In a certain mode of implementation, the light fraction recovered through the pipe line (12) upon being output from the DF separator (1) may be introduced in whole or part through the pipe line (24) into the CDP effluent before its entry into the reactor R2 (3).

[0085] In addition, the (C5-150) fractions upon being output from the distillation units DA1 and DA2 may advantageously be mixed together with the (150-300) fractions with all or part of the light fraction Cl in the pipe line (12) and upon being output from the distillation unit DA1 (4).

[0086] In some preferred embodiments, the heavy fraction CL upon being output from the DF separator (11) is only partially sent to the reactor R1 (2), a part of the said fraction sent through the pipe line (20) being mixed with the CDP dewaxed effluent.

[0087] Similarly, if the content of aromatic hydrocarbons is too high in the 300? C.+ fraction or if the viscosity of the CDP effluent is insufficient, a part of the 300? C.+ fraction upon being output from the distillation unit DA1 (4) is recycled via the pipe line (28) into the pipe line (16) directing the CDP effluent into the reactor R2 (3).

[0088] FIG. 2 differs from FIG. 1 in that one single reactor (5) is shown for the steps of dewaxing and dearomatisation containing two sections, one for dewaxing SR1 referenced as (2) and one section for dearomatisation SR2 referenced as (3), these two sections being separated by a cavity (30). In this figure, a feed stock of gas oil (GO) derived from any process for refining crude oil is introduced through the pipe line (10) into the DF separator referenced as (1) where it is separated into two fractions, one light fraction (Cl) discharged from DF (1) through the pipe line (12) and one heavy fraction CL discharged from DF (1) through the pipe line (11).

[0089] The heavy fraction CL is sent to the section SR1 (2) of the reactor (5) fed in parallel by the hydrogen coming in through the pipe lines (31), and then (32) in order to be dewaxed therein. All of the dewaxed fraction is sent to the section SR2 (3), possibly after being mixed in the cavity (30) separating the two sections with the additional hydrogen arriving from the pipe line (33). This injection of hydrogen is useful to the dearomatisation reaction but also serves the function of adjusting the inlet temperature of the feed stock or dewaxed fraction in the section SR2 (3) by quenching (or quench) thereby enabling the lowering of the inlet temperature of the section SR2 (3).

[0090] In a particular embodiment of the invention, it is also possible to inject all or part of the light fraction (Cl) through the pipe line (24) into the cavity (30) in order for it to be dearomatised like the dewaxed heavy fraction (CL). The quantity of hydrogen will be adjusted accordingly as well as the inlet temperature in the section SR2 (3).

[0091] As in FIG. 1, the dearomatised and dewaxed effluent is recovered upon being output from the reactor (5) through the pipe line (17) and directed to a distillation unit DA1 referenced as (4) in order to be distilled therein into at least four fractions: [0092] the 300? C.+ fraction or fractions recovered through the pipe line (18), [0093] the (150-300) fraction discharged through the pipe line (27), [0094] the (C5-150) fraction discharged through the pipe line (26), [0095] and the C1-C4 fraction or fuel gas discharged through the pipe line (25).

[0096] Similarly, if the content of aromatic hydrocarbons is too high in the 300? C.+ fraction or fractions, a part of the 300? C.+ fraction upon being output from the distillation unit DA1 (4) is recycled via the pipe line (28) into the cavity (30) of the reactor (5) in order to be dearomatised therein once again, in section SR2 of the said reactor (5).

[0097] FIG. 3 represents a fraction from the dewaxing reactor (2) in FIG. 1 or from the dewaxing section SR1 (2) of the reactor (5). This fraction presents the distribution in layers of the catalysts for dewaxing (S1) and hydrotreating (S2). S1 is preferably selected from the catalysts for hydrodewaxing with mild cracking, that are silicalite based supporting possibly nickel and possibly tungsten, such as KF1102 marketed by ALBEMARLE. S2 is a conventional hydrotreating catalyst based on a support of metal oxide, alumina, silica, silica/alumina, supporting metals from group (VIII), of the types including nickel, cobalt, molybdenum, tungsten, and preferably nickel/molybdenum-, nickel/cobalt-, and cobalt/molybdenum type combinations. S2 may be KF647 also sold by ALBEMARLE. In a preferred embodiment of the invention, the first and third layers are filled with the dewaxing catalyst S1 and constitute the largest volumes (31% and 46% volume). The second and fourth layers are only filled with S2 each occupying a volume of 11.5%. In this FIG. 3, the heavy fraction (CL) to be dewaxed is introduced into the reactor (2) of FIG. 1 through the pipe line (13), the hydrogen is injected through the pipe line (32) and the dewaxed effluent is recovered through the pipe line (14).

[0098] The performance of the present invention will now be illustrated in the following section of the present description, however these examples are not intended to limit the scope thereof.

EXAMPLE 1

[0099] This present example describes the preparation of a dewaxed and dearomatised fraction according to the invention, having an initial boiling point higher than 300? C. and whose pour point is below ?30? C.

[0100] The process is operated as described in FIG. 1 using in the dewaxing reactor (2) the catalysts described here above for FIG. 3. In the dearomatisation reactor, a nickel on alumina catalyst is used, the amount of nickel being greater than 10% by weight and the specific surface area being greater than 140 mm2/g.

[0101] The reaction temperature in the dewaxing reactor is 305? C. under a pressure of 30 barg, with a defined Hourly Space Velocity (HSV) corresponding to the ratio of flow rate of the feed stock volume (m3/h) over the catalyst volume (m3/h) of 1 h.sup.?1 and a hydrogen/feed stock ratio of 250 Nl (NL:normal litre) of hydrogen per litre of hydrocarbon feed stock. In the dearomatisation reactor, the temperature is 245? C., under a pressure of 160 barg, a hydrogen/feed stock ratio of 250 Nl of hydrogen per litre of hydrocarbon feed stock and an HSV of 0.4 h.sup.?1. The characteristics of the products from the beginning to the end of the reaction chain are shown in Table 1 here below.

TABLE-US-00001 TABLE 1 GO before DF (Gas Oils before 300? C. + Fraction Fractional Before After After R2 Characteristics Distillation R1 (2) DA2 and DA1 % by weight 17.5 9.8 13.8 127 ppm Aromatic Hydrocarbons % by weight 21.5 27.7 6.3 4.5 n-paraffins % by weight 35 38.4 42.7 47.1 Isoparaffins % by weight 25.8 24.1 34.4 48.3 Total Naphthenes % by weight Mono 20.8 23.2 35.8 naphthenes % by weight olefins 0.52 0.35 0.7 <0.05 ASTM D2710 (gBr.sub.2/100 g sample) % by weight Saturated <0.09 0 <0.1 <0.1 Hydrocarbons <C9 Viscosity at 40? C. 4.5 7.7 8.7 8.7 (mm.sup.2/g), ASTM D445 Sulfur (ppm) ASTM 2 2.4 3.9 <1 D5453 Nitrogen (ppm) by <0.5 <0.5 <0.5 <0.5 Chemiluminescence Distillation Fraction 236- 296.8- 327.9- 314- (? C.) ASTM D86 365 369.3 371.4 367.3 Pour Point (? C.) ?4 +12 ?40 ?40 ASTM D5950 with reference to D97 (3 degree points) Aniline Point (? C.) 98.7 ASTM D-611

[0102] Thus it is found that by the method of the invention, it is possible to obtain hydrocarbon fluids free of aromatic hydrocarbons and all kinds of pollutants, which may be used as solvents, with distillation fraction at a temperature above 300? C. and whose pour point is well below ?30? C. It should be noted that the amount of naphthenes is significantly greater than 40% by weight in these hydrocarbons, the amount of mononaphthenes is significantly greater than 20% by weight. The said pollutants correspond in particular to the olefins, sulfur compounds and nitrogen compounds.

EXAMPLE 2

[0103] This example compares the characteristics of the products obtained in Example 1 referenced as X with those of the products obtained from hydrodewaxing mainly by isomerisation of gasoil fractions or a hydrocracked and hydrodearomatised gas oil. These products resulting from the prior art are respectively referenced as T1 and T2.

[0104] The comparative characteristics are presented in Table 2 here below.

TABLE-US-00002 TABLE 2 Characteristics X T1 T2 ppm by weight of 127 264 70 Aromatic Hydrocarbons % by weight n- 4.5 0.1 16 paraffins % by weight 47.1 74.2 59.9 Isoparaffins, % by weight Total 48.3 24.8 24.1 Naphthenes % by weight Mono 35.8 18.9 22.4 naphthenes Sulfur (ppm) by UV <1 <1 <1 method Viscosity at 40? C. 8.7 10.3 6.1 (mm2/g), ASTM D445 Distillation Fraction 314-367 334-378 305-347 (? C.) ASTM D86 Pour Point (? C.), ?40 ?35 0 ASTM D5950 with reference to D97 (3 degree points) Aniline Point (? C.) 98.7 108 101 ASTM D6 11

[0105] It should be noted that with respect to the fraction with boiling above 300? C., the dewaxing provides the ability to reduce the pour point to lower than ?30? C. It should also be noted that comparatively between the fractions X and T1, the content of mono naphthenes is very different, for X this is greater than 20% and even greater than 30% by weight, while that it remains significantly lower than 20% by weight for T1. The reduction of the aniline point for the fraction X indicates an improvement of the solvent power.