Method for starting up a method for producing kerosene and diesel fuel from hydrocarbon compounds produced by Fischer-Tropsch synthesis

Abstract

Method for starting up a method for producing kerosene and diesel fuel from hydrocarbon compounds produced by Fischer-Tropsch synthesis. The start-up method employs catalytic reaction of Fischer-Tropsch synthesis with a synthesis gas for producing a heavy hydrocarbon fraction and a light hydrocarbon fraction, a reduction (RE) reducing a hydrotreatment catalyst by ensuring contact with a gas comprising hydrogen, bringing the heavy hydrocarbon fraction into contact with the hydrotreatment catalyst (DM). During the step for ensuring contact, the temperature (TEMP) of the catalyst is increased to a temperature of between 260 C. and 360 C. Then, (TR) bringing a mixture comprising the heavy hydrocarbon fraction and the light hydrocarbon fraction into contact with the hydrotreatment catalyst is carried out.

Claims

1. A method for starting up a method for producing kerosene and diesel fuel from hydrocarbon compounds produced by Fischer-Tropsch synthesis, comprising: a) catalytic Fischer-Tropsch synthesis with a synthesis gas to produce a heavy hydrocarbon fraction and a light hydrocarbon fraction, b) reduction of a hydrotreatment catalyst by ensuring contact with a gas comprising hydrogen, and then c) is carried out, c) contacting the heavy hydrocarbon fraction with the hydrotreatment catalyst, d) during c), the temperature of the hydrotreatment catalyst is increased to a temperature of 260 C. to 360 C., and then e) is carried out, e) contacting a mixture comprising the heavy hydrocarbon fraction and the light hydrocarbon fraction with the hydrotreatment catalyst.

2. The method according to claim 1, in which in b), reduction of the hydrotreatment catalyst and a hydrocracking and hydroisomerization catalyst is carried out by contacting with a gas comprising hydrogen, and then c) is carried out, in c), the heavy hydrocarbon fraction is brought into contact with the hydrotreatment catalyst and then with the hydrocracking and hydroisomerization catalyst, in e), the mixture comprising the heavy hydrocarbon fraction and the light hydrocarbon fraction is brought into contact with the hydrotreatment catalyst and then with the hydrocracking and hydroisomerization catalyst.

3. The method according to claim 1, in which b) is carried out at a temperature of 300 C. to 500 C., and then the hydrotreatment catalyst is cooled to a temperature of 120 C. to 170 C., and then c) is carried out.

4. The method according to claim 1, in which at the beginning of d), the heavy hydrocarbon fraction is at a temperature of 100 C. to 250 C. and in which in d), the heavy hydrocarbon fraction is heated gradually for a period of 1 to 20 hours to a temperature of 260 C. to 360 C.

5. The method according to claim 1, in which in e), the light fraction is mixed gradually with the heavy fraction, with the portion of light fraction introduced into the mixture being increased from 0% to 100% by volume of the light fraction obtained from a), over a period of 1 to 20 hours.

6. The method according to claim 1, in which during c), the light hydrocarbon fraction is evacuated from the start-up method.

7. The method according to claim 1, in which the hydrotreatment catalyst comprises at least one metal of group VIIIB or group VIB, and at least one substrate.

8. The method according to claim 7, in which the hydrotreatment catalyst comprises molybdenum and nickel, and a substrate comprising alumina.

9. The method according to claim 2, in which the hydrocracking and hydroisomerization catalyst comprises at least one metal of group VIIIB or group VIB, and at least one substrate.

10. The method according to claim 9, in which the hydrocracking and hydroisomerization catalyst comprises platinum and a substrate a silica-alumina or a zeolite.

11. The method according to claim 1, in which a) is carried out, in the presence of a catalyst comprising a substrate and cobalt or iron, at a total pressure of 0.1 to 15 MPa, at a temperature of 150 to 350 C., and at an hourly volumetric flow rate of 100 to 20,000 volumes of synthesis gas per volume of catalyst and per hour.

12. The method according to claim 1, further comprising: f) after e), continuing to contact the mixture comprising the heavy hydrocarbon fraction and the light hydrocarbon fraction with the hydrotreatment catalyst under the operating conditions for producing kerosene and diesel fuel.

13. The method according to claim 12, in which the contact with the hydrotreatment catalyst is carried out in f) under the following operating conditions: a temperature of 100 to 450 C., a total pressure of 0.5 and to 15 MPa, a hydrogen flow rate such that the volumetric ratio of hydrogen in relation to the hydrocarbon feedstock is 100 to 3,000 Nl/l/h, an hourly volumetric flow rate of 0.1 to 10 h.sup.1.

14. The method according to claim 12, in which in f), the mixture comprising the heavy hydrocarbon fraction and the light hydrocarbon fraction continues to be brought into contact with the hydrotreatment catalyst and then with a hydrocracking and hydroisomerization catalyst, with the contact with the hydrocracking and hydroisomerization catalyst being carried out under the following operating conditions: a temperature of 200 to 450 C., a total pressure of 0.2 to 15 MPa, a hydrogen flow rate such that the volumetric ratio of hydrogen in relation to the hydrocarbon feedstock is 100 to 2,000 Nl/l/h, an hourly volumetric flow rate is 0.1 and to 10 h.sup.1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The example is described with reference to FIG. 1 and to FIG. 2, which represent schematic flows of the process.

(2) Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

(3) In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

(4) The entire disclosures of all applications, patents and publications, cited herein and of corresponding application No. FR 1760011, filed Oct. 24, 2017 are incorporated by reference herein.

EXAMPLES

Example According to the Invention

(5) In step FT, the method produces a heavy fraction circulating in the pipe 3 corresponding to Fischer-Tropsch waxes and a light fraction circulating in the pipe 2 corresponding to Fischer-Tropsch condensates. The feedstock has the following characteristics.

(6) TABLE-US-00001 TABLE 1 Characteristics of the Feedstock Condensates Waxes Density at 15 C. g/cm3 0.7513 0.7613 5.0% C. 68.9 287.1 20.0% C. 128.4 359.2 50.0% C. 217.8 431.4 70.0% C. 272.8 475.2 95.0% C. 368.3 577.7 370 C..sup.+ Compound % by Weight 4 78 Paraffins % by Weight 73 95 Olefins % by Weight 20 4 Oxidized Compounds % by Weight 7 1

(7) In step HDT, an NiMo-type hydrotreatment catalyst on an alumina substrate combined with NiO is used. This catalyst is marketed by Axens under the reference HR945.

(8) After having carried out the reduction step RE, the start-up step DM is carried out. The heavy fraction coming in via the pipe 3 is brought into contact with the hydrotreatment catalyst in the presence of hydrogen.

(9) More specifically, the waxes obtained from the Fischer-Tropsch synthesis step FT are sent in a mixture with a hydrogen stream. The mixture is sent at 150 C. The flow rate of hydrogen is adjusted in such a way as to maintain an H2/HC=600 L/L ratio measured exiting from the unit. During this step, the hydrogen makeup is limited taking into account the very low conversion of olefins and oxidized compounds, present in a very small amount.

(10) Next, the warming-up step TEMP is carried out. The temperature for bringing the hydrotreatment catalyst into contact is increased gradually to the temperature required for the hydrotreatment, 335 C.

(11) Once the target temperature is reached, the transition step TR is carried out. The light hydrocarbon fraction, i.e., the condensates, obtained from the Fischer-Tropsch synthesis FT via the pipe 2, is added in a mixture with the heavy hydrocarbon fraction, i.e., the wax, coming in via the pipe 3. The condensates are injected gradually in such a way as to monitor the increase in the temperature linked to the exothermy of the reaction for hydrogenation of olefins.

(12) The operating conditions of the step HDT are then used to obtain 100% hydrogenation of the olefins in the hydrotreatment section. The conditions are:

(13) P=6.5 MPa (65 bar)

(14) T=335 C.

(15) vvh=1 h1

(16) H2/HC=600 Nl/l/h1 measured exiting from the unit with a fresh H2 makeup on the order of 10% to 20% by volume of the total H2 flow rate (recycled and fresh H2)

(17) The characteristics of the effluent exiting from the hydrotreatment step HDT are listed in Table 2.

(18) TABLE-US-00002 TABLE 2 Characteristics of the Hydrotreated Effluent Density at 15 C. 0.7853 g/cc Sulfur <Detection Limit ppm by Weight Nitrogen <Detection Limit ppm by Weight Oxygen 0 % by Weight n-Paraffins 85.0 % by Weight i-Paraffins 5.68 % by Weight Naphthenes 0 % by Weight Aromatic Compounds 0 % by Weight Olefins 0 % by Weight Simulated Distillation 5 126.4 C. 20 197.8 C. 50 319.7 C. 70 402.5 C. 95 525.3 C. 370 C.+ Compounds 37 % by Weight

(19) The characteristics of the hydrotreated effluent appearing in Table 2 show that the hydrotreatment catalyst does not have any cracking activity. The olefins and the oxidized compounds measured by chromatography are entirely decomposed.

(20) Below, the conversion of the 370 C.+ fraction is defined by the following formula:
Conversion=[(% 370 C.effluent)(% 370 C.feedstock)]/(100% 370 C.feedstock)
with:

(21) % of 370 C.effluents, the fraction by mass of compounds having boiling points lower than 370 C. in the effluents

(22) % of 370 C.feedstock=fraction by mass of compounds having boiling points lower than 370 C. in the hydrocracking feedstock.

(23) During the hydrocracking and hydrotreatment step HCK-HIS, the target conversion of the 370 C.+fraction is 55% by weight. The adequate operating conditions are:

(24) P=6.5 MPa (65 bar)

(25) T catalyst HCK=363 C.

(26) vvh=2 h1

(27) H2/HC=600 L/L

(28) Age of the catalyst: 75 days

(29) The hydrocracking and hydroisomerization catalyst is used in a fixed bed. A Pt-based catalyst marketed by AXENS on a silica-alumina substrate is used.

(30) It is activated by reduction under hydrogen under the following operating conditions: Flow rate of pure hydrogen: 1,000 normal liters per hour and per liter of catalyst, Rise in ambient temperature to 150 C.: 25 C./minute, One-hour plateau at 150 C., Rise from 150 C. to 450 C. at 25 C./minute, Two-hour plateau at 450 C.

(31) Next, the liquid effluent obtained from the hydrocracking and hydroisomerization step HCK-HIS is fractionated. Thus separated are the gasoline fraction, the kerosene fraction, and the diesel fuel fraction. The 370 C.+fraction exiting from the fractionation is recycled to the step HCK-HIS.

(32) Thus, according to the injection mode as well as the temperature for injection of the feedstock according to the invention into the hydrotreatment unit and the hydrocracking and hydroisomerization unit, there are two means making it possible to reduce the poisoning of the hydrotreatment and hydrocracking and hydroisomerization catalysts and thus to preserve the catalytic performance.

(33) The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

(34) From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.