Process for producing BTX from a C5-C12 hydrocarbon mixture

Abstract

The present invention relates to a process for producing chemical grade BTX from a mixed feedstream comprising C5-C12 hydrocarbons by contacting said feedstream in the presence of hydrogen with a catalyst having hydrocracking/hydrodesulphurization activity. Particularly, a process for producing BTX from a feedstream comprising C5-C12 hydrocarbons is provided comprising the steps of: (a) contacting said feedstream in the presence of hydrogen with a combined hydrocracking/hydrodesulphurization catalyst to produce a hydrocracking product stream comprising BTX; and (b) separating the BTX from the hydrocracking product stream. The hydrocracking/hydrodesulphurization catalyst comprises 0.1-1 wt-% hydrogenation metal in relation to the total catalyst weight. The hydrocracking/hydrodesulphurization catalyst further comprises a zeolite having a pore size of 5-8 and a silica (SiO.sub.2) to alumina (Al.sub.2O.sub.3) molar ratio of 5-200. The hydrocracking/hydrodesulphurization conditions include a temperature of 450-580 C., a pressure of 300-5000 kPa gauge and a Weight Hourly Space Velocity of 0.1-10 h.sup.1.

Claims

1. Process for producing BTX comprising: (a) contacting a feedstream comprising C5-C12 hydrocarbons in the presence of hydrogen with a hydrocracking/hydrodesulphurisation catalyst comprising 0.1-1 wt-% hydrogenation metal in relation to the total catalyst weight and a zeolite having a pore size of 5-8 and a silica (SiO.sub.2) to alumina (Al.sub.2O.sub.3) molar ratio of 5-200 under process conditions comprising a temperature of 450-580 C., a pressure of 300-5000 kPa gauge and a Weight Hourly Space Velocity of 0.1-10 h.sup.1 to produce a hydrocracking product stream comprising BTX; and (b) separating the BTX from the hydrocracking product stream; wherein the hydrocracking/hydrodesulphurisation catalyst comprises less than 0.01 parts tin, less than 0.02 parts lead, and less than 0.01 parts bismuth (on the basis of 100 parts by weight of total catalyst); and wherein the feedstream comprises benzene.

2. The process according to claim 1, wherein the hydrocracking product stream further comprises less than 5 wt-% of methane.

3. The process according to claim 1, wherein the hydrocracking product stream further comprises less than 1 wt-% of non-aromatic C6+ hydrocarbons.

4. The process according to claim 1, wherein the hydrocracking/hydrodesulphurisation conditions include a temperature of 470-550 C., a pressure of 600-3000 kPa gauge and a Weight Hourly Space Velocity of 0.2-6 h.sup.1.

5. The process according to claim 1, wherein the hydrogenation metal comprises an element selected from Group 10 of the periodic table of Elements.

6. The process according to claim 1, wherein the hydrogenation metal is platinum.

7. The process according to claim 1, wherein the hydrocracking/hydrodesulphurisation catalyst comprises a mixture of ZSM-5 and Pt-modified alumina (Pt/Al.sub.2O.sub.3) wherein the weight ratio of ZSM-5:Pt/Al.sub.2O.sub.3 is between 5:1 and 1:5.

8. The process according to claim 1 wherein the feedstream further comprises 10-300 wppm of sulphur and the hydrocracking product stream comprises less than 5 wppm of sulphur.

9. The process according to claim 1, wherein the molar ratio of hydrogen to hydrocarbon species (H.sub.2/HC molar ratio) in the reactor feed is between 1:1 and 4:1.

10. The process according to claim 1, wherein the feedstream comprises pyrolysis gasoline, straight run naphtha, light coker naphtha and coke oven light oil or mixtures thereof.

11. The process according to claim 1, wherein the BTX is separated from the hydrocracking product stream by gas-liquid separation or distillation.

12. The process according to claim 1, further comprising performing hydrodealkylation by contacting said BTX with hydrogen to produce a hydrodealkylation product stream comprising benzene and fuel gas.

13. The process according to claim 12, wherein the hydrodealkylation is performed in the absence of a hydrodealkylation catalyst under hydrodealkylation conditions including a temperature of 600-800 C., a pressure of 3-10 MPa gauge and a reaction time of 15-45 seconds; or wherein the hydrodealkylation is performed in the presence of a hydrodealkylation catalyst selected from the group consisting of supported chromium oxide catalyst, supported molybdenum oxide catalyst, platinum on silica or alumina and platinum oxide on silica or alumina under hydrodealkylation conditions including a temperature of 500-650 C., a pressure of 3.5-7 MPa gauge and a Weight Hourly Space Velocity of 0.5-2 h.sup.1.

14. The process according to claim 2, wherein the hydrocracking product stream comprises less than 4 wt-% methane.

15. The process according to claim 4, wherein the hydrocracking/hydrodesulphurisation conditions include a temperature of 470-550 C., a pressure of 1000-2000 kPa gauge and a Weight Hourly Space Velocity of 0.4-2 h.sup.1.

16. The process according to claim 7, wherein the hydrocracking/hydrodesulphurisation catalyst comprises a mixture of ZSM-5 and Pt-modified alumina (Pt/Al.sub.2O.sub.3) wherein the weight ratio of ZSM-5:Pt/Al.sub.2O.sub.3 is between 3:1 and 1:3.

17. The process according to claim 1, wherein the separating of the BTX from the hydrocracking product stream is performed without solvent extraction.

18. Process for producing BTX comprising: (a) contacting a feedstream comprising C5-C12 hydrocarbons in the presence of hydrogen with a hydrocracking/hydrodesulphurisation catalyst comprising greater than 0.5 to 1 wt-% hydrogenation metal in relation to the total catalyst weight and a zeolite having a pore size of 5-8 and a silica (SiO.sub.2) to alumina (Al.sub.2O.sub.3) molar ratio of 5-200 under process conditions comprising a temperature of 450-580 C., a pressure of 300-5000 kPa gauge and a Weight Hourly Space Velocity of 0.1-10 h.sup.1 to produce a hydrocracking product stream comprising BTX; and (b) separating the BTX from the hydrocracking product stream; wherein the hydrocracking/hydrodesulphurisation catalyst comprises less than 0.01 parts tin, less than 0.02 parts lead, and less than 0.01 parts bismuth (on the basis of 100 parts by weight of total catalyst); and wherein the feedstream comprises benzene.

19. Process for producing BTX comprising: (a) contacting a feedstream comprising C5-C12 hydrocarbons in the presence of hydrogen with a hydrocracking/hydrodesulphurisation catalyst comprising 0.1-1 wt-% hydrogenation metal in relation to the total catalyst weight and a zeolite having a pore size of 5-8 and a silica (SiO.sub.2) to alumina (Al.sub.2O.sub.3) molar ratio of 5-200 under process conditions comprising a temperature of 450-580 C., a pressure of 300-5000 kPa gauge and a Weight Hourly Space Velocity of 0.1-10 h.sup.1 to produce a hydrocracking product stream comprising BTX; and (b) separating the BTX from the hydrocracking product stream; wherein the hydrocracking/hydrodesulphurisation catalyst comprises less than 0.005 parts tin, less than 0.01 parts lead, and less than 0.005 parts bismuth (on the basis of 100 parts by weight of total catalyst), and wherein the feedstream comprises benzene.

20. The process according to claim 19, wherein the hydrocracking/hydrodesulphurisation catalyst is free of tin, bismuth, and lead.

Description

Example 1 Preparation OF Hydrocracking/Hydrodesulphurisation Catalyst

(1) A hydrocracking/hydrodesulphurisation catalyst has been prepared as follows.

(2) Commercially available MFI type zeolite in the hydrogen form having a Si to Al molar ratio of about 100:1 was mixed with an alumina binder at a zeolite to binder weight ratio of about 9:1. The subsequent mixture was formed into spherical particles of approximately 1.6 mm diameter to provide bound zeolite particles.

(3) Commercially available platinum-modified gamma-alumina particles (spheres of about 1.6 mm diameter) comprising 0.75 wt-% platinum were obtained. The platinum-modified gamma-alumina particles were having a total surface area of about 200 m.sup.2/g (measured by standard nitrogen BET method), a pore volume of approximately 0.7 cc/g and a mean pore diameter of approximately 20 nm.

(4) Subsequently, the bound zeolite particles and the platinum-modified gamma-alumina articles were homogeneously mixed at a 1:1 weight ratio to provide the hydrocracking/hydrodesulphurisation catalyst composition.

Example 2 Hydrocracking/Hydrodesulphurisation of Pyrolysis Gasoline

(5) Reaction tests were carried out using a 12 mm (inner diameter) stainless steel reactor tube containing a catalyst bed comprising 4 g of the hydrocracking/hydrodesulphurisation catalyst composition prepared in Example 1. At the start of the experiment the mixed catalyst bed was dried (to remove any adsorbed water) in situ in the test reactor at 140 C. under flowing hydrogen (100 ml/minute at 40 to 60 psig operating pressure) for a minimum of 2 hours. After this, the hydrogen flow and pressure were maintained whilst the reactor temperature was raised to the desired test temperature (typically 500 C.) and held at this temperature for a minimum of 2 hours prior to the introduction of hydrocarbon feed. During these conditioning phases any Pt oxide present in the calcined catalyst is believed to be reduced to Pt metal. The reactor was operated at a temperature of 450-550 C., at a pressure of 100-400 psig (690-2760 kPa) and a weight hourly space velocity of 2-4 hr.sup.1. (WHSV is defined as hourly mass of hydrocarbon liquid fed to the reactor/mass of catalyst in the reactor).

(6) In each case the molar ratio of hydrogen to hydrocarbons in the reactor feed was maintained at a molar-ratio of about 4:1. The typical composition of the pyrolysis gasoline used for these tests is shown in Table 1 as provided herein below:

(7) TABLE-US-00001 TABLE 1 Component wt-% (By GC) Total C6-C8 alkanes 16.54 C6 alkanes 13.17 C7 alkanes 3.25 C8 alkanes 0.12 Total Aromatics 75.36 BTX 74.85 C9 + aromatics 0.51 Trimethyl Benzene 0.03 EMBzs 0.21 C10 + aromatics 0.08 Minors (unidentified) 8.10

(8) During the tests the reactor product stream (hydrocracking product stream) was analysed via an online gas chromatograph fitted with a flame ionisation detector and calibrated to allow the identification and quantification of the hydrocarbon species. (Measured by using a Shimadzu GC-2014 fitted with a DB1 Column60 m long; 0.32 mm internal diameter with 5.00 m film thickness. Analysis test method conditions: oven 50 C. hold 3 min, ramp 5 C. per min to 250 C. hold for 5 min. Helium carrier gas column flow 3.37 ml/minute; Total flow 107.4 ml/minute; Split ratio 30:1; Linear velocity 40.0 cm/second; Inlet pressure 25.8 psi.)

(9) The hydrocracking product stream for the experiments carried out at each set of operating conditions are shown in table 2 as provided herein below.

(10) Accordingly, it was found that a feedstream comprising a highly complex mixture of C5+ hydrocarbons can be converted into a hydrocracking product stream comprising LPG, an intermediate aromatic stream and less than 5 wt-% of methane by using the hydrocracking/hydrodesulphurisation process of the present invention.

(11) TABLE-US-00002 TABLE 2 H.sub.2:HC Pressure Total Cyclo- (molar WHSV (kPa Temp Ben- Tol- Aro- Eth- Pro- bu- Total Pen- hex- 2- 3- hex- ratio) (hr.sup.1) gauge) ( C.) zene uene matics EB CH.sub.4 ane pane tanes LPG tane ane MCP MP MP ane 4 3 2760 450 43.7 20.3 73.47 3.7 0.5 3.4 12 5.6 21 0.37 0.2 0.3 0.36 0.31 0.49 (400 psig) 500 45.4 22.1 74.12 1.6 1.6 6.7 12.4 3.6 22.7 0.1 0.0 0.1 0.04 0.03 0.19 525 47.3 23.1 76.74 1.3 2.1 7.5 10.4 2.2 20.1 0.05 0.0 0.046 0.02 0.01 0.00 550 46.9 23.7 76.48 0.9 3.8 7.8 10.5 0.8 19.1 0.01 0.0 0 0.00 0.00 0.01 4 3 2070 450 45.6 21 78.21 5 0.3 2.4 8.7 4.4 15.5 0.38 0.4 0.3 0.39 0.41 0.31 (300 psig) 500 47.6 22.3 77.88 2.1 0.9 5.2 10.2 3.6 19 0.15 0.0 0.1 0.09 0.08 0.07 525 48.2 23.1 77.92 1.3 1.6 6.6 10 2.6 19.2 0.06 0.0 0.1 0.02 0.02 0.00 550 47.9 24.1 78.46 1 2.6 8.5 8.5 1.4 18.4 0.02 0.0 0 0.00 0.00 0.00 4 3 1380 450 47.4 20.7 76.74 3 0.3 3 9.9 4.8 17.7 0.39 0.4 0.3 0.43 0.40 0.31 (200 psig) 500 49 21.5 77.1 1.6 0.8 5.3 10.8 3.5 19.6 0.16 0.1 0.1 0.10 0.11 0.10 525 48.8 22.7 77.88 1.1 1.2 6.8 10.1 2.6 19.5 0.08 0.01 0.077 0.04 0.04 0.01 550 49 23.2 77.84 0.7 2.1 8.4 9.2 1.7 19.3 0.02 0.007 0.03 0.01 0.01 0.00 4 3 690 450 47.1 20.3 78.3 4.4 0.2 2.3 7.7 3.2 13.2 0.36 1 0.6 0.48 0.52 0.67 (100 psig) 500 49.1 21.5 77.89 1.7 0.5 5.1 9.6 3.1 17.8 0.19 0.3 0.2 0.20 0.19 0.18 550 49.9 22.8 78.14 0.5 1.4 7.9 9.2 1.9 19 0.04 0 0 0.02 0.02 0.01 4 4 1380 500 47.7 21.1 78.17 2.7 0.6 4.3 9.5 3.5 17.3 0.21 0.0 0.2 0.20 0.20 0.21 2 (200 psig) 48.7 22.7 77.71 1.2 0.9 5.8 10.6 3.3 19.7 0.11 0.0 0.1 0.07 0.06 0.01 Total Aromatics includes ethylbenzene as well as xylenes, C9 aromatics and C10 aromatics detected in the reactor products. EB means ethylbenzene, MCP means methylcyclopentane, 2MP means 2-methylpentane and 3-MP means 3-methylpentane.

Example 3 Influence of H2/Hydrocarbon Molar Ratio on Benzene Purity

(12) Reaction tests were carried out using the same catalyst and the same experimental setup as described in Example 2. The hydrocracking/hydrodesulphurisation process was carried out at a temperature of 495 C., a pressure of about 1380 kPa gauge (200 psig) and a WHSV of 1 hr.sup.1 (based on the weight of liquid feed) throughout the experiment using a plant derived pyrolysis gasoline with a composition as shown in the Table 3 below.

(13) TABLE-US-00003 TABLE 3 Component wt-% (By GC) Total C6-C8 alkanes 13.14 C6 alkanes 12.25 C7 alkanes 0.81 C8 alkanes 0.08 Total Aromatics 72.89 BTX 71.78 C9 + aromatics 0.98 Trimethyl Benzene 0.07 EMBzs 0.48 C10 + aromatics 0.13 Minors (unidentified) 13.97

(14) Accordingly, it was found that a higher benzene purity in the product stream can be obtained by selecting a relatively low H.sub.2/HC molar ratio; see Table 4.

(15) TABLE-US-00004 TABLE 4 H2:HC Cyclo Total Benzene molar Hex- hex- co- ben- purity ratio 2-MP 3-MP ane MCP ane boilers zene (wt-%) 4:1 0.006 0.004 0.004 0.038 0.024 0.076 42.26 99.82 3:1 0.004 0.002 0.002 0.019 0.01 0.037 41.77 99.91 2:1 0.002 0.001 0.001 0.006 0.003 0.022 40.03 99.94 1.5:1.sup. 0.002 0.001 0.001 0.002 0.001 0.007 38.28 99.98