Process for producing BTX from a C5—C12 hydrocarbon mixture

Abstract

The invention relates to a process for producing benzene comprising the steps of: (a) providing a hydrocracking feed stream comprising C.sub.5-C.sub.12 hydrocarbons, (b) contacting the hydrocracking feed stream in the presence of hydrogen with a hydrocracking catalyst under process conditions including a temperature of 425-580 C., a pressure of 300-5000 kPa gauge and a Weight Hourly Space Velocity of 3-30 h.sup.1 to produce a hydrocracking product stream comprising BTX and (c) separating the BTX from the hydrocracking product stream, wherein the hydrocracking catalyst comprises a shaped body comprising a zeolite and a binder and a hydrogenation metal deposited on the shaped body, wherein the amount of the hydrogenation metal is 0.010-0.30 wt-% with respect to the total catalyst and wherein the zeolite is ZSM-5 having a silica (SiO.sub.2) to alumina (Al.sub.2O.sub.3) molar ratio of 25-75.

Claims

1. A process for producing benzene comprising the steps of: (a) providing a hydrocracking feed stream comprising C.sub.5-C.sub.12 hydrocarbons, (b) contacting the hydrocracking feed stream in the presence of hydrogen with a hydrocracking catalyst under process conditions including a temperature of 425-580 C., a pressure of 300-5000 kPa gauge and a Weight Hourly Space Velocity of 3-30 h.sup.1 to produce a hydrocracking product stream comprising BTX, and (c) separating the BTX from the hydrocracking product stream, wherein the hydrocracking catalyst comprises a shaped body comprising a zeolite, a binder and a hydrogenation metal deposited on the shaped body, wherein the amount of the hydrogenation metal is 0.035-0.080 wt % with respect to the total catalyst, wherein the zeolite is ZSM-5 having a silica to alumina molar ratio of 25-75, wherein the hydrogenation metal is platinum, and wherein the hydrocracking catalyst comprises less than 0.01 parts tin, less than 0.02 parts lead, less than 0.01 parts bismuth and less than 0.01 parts molybdenum on the basis of 100 parts by weight of the total catalyst.

2. The process according to claim 1, wherein the zeolite has a silica to alumina molar ratio of 30-65.

3. The process according to claim 2, wherein the silica to alumina molar ratio is 35-60.

4. The process according to claim 3, wherein the silica to alumina molar ratio is 40-55.

5. The process according to claim 1, wherein the hydrocracking feed stream comprises a fresh feed stream which is first stage or multi-stage hydro-treated pyrolysis gasoline, straight run naphtha, hydrocracked gasoline, light coker naphtha and coke oven light oil, FCC gasoline, reformate or mixtures thereof.

6. The process according to claim 5, wherein the fresh feed stream has been subjected to hydrogenation, enrichment of mono-aromatic compounds, and/or depentanisation.

7. The process according to claim 5, wherein the hydrocracking feed stream comprises a stream recycled from the hydrocracking product stream.

8. The process according to claim 1, wherein the hydrocracking feed stream is provided by a process which does not involve the step of removing benzene.

9. The process according to claim 1, wherein the hydrocracking feed stream comprises 10-90 wt % of benzene.

10. The process according to claim 1, wherein the amount of the binder in the hydrocracking catalyst is 10-50 wt % with respect to the total catalyst.

11. The process according to claim 1, wherein the hydrocracking catalyst is prepared by depositing the hydrogenation metal on the shaped body by impregnation or ion exchange.

12. The process according to claim 1, wherein the hydrocracking catalyst is an extrudate having an average diameter of 0.1-3 mm.

13. The process according to claim 1, wherein the step (b) is performed at a Weight Hourly Space Velocity of at least 7 h.sup.1.

14. The process according to claim 1, wherein the silica to alumina molar ratio is 40-55.

15. A process for producing benzene comprising the steps of: (a) providing a hydrocracking feed stream comprising C.sub.5-C.sub.12 hydrocarbons, (b) contacting the hydrocracking feed stream in the presence of hydrogen with a hydrocracking catalyst under process conditions including a temperature of 425-580 C., a pressure of 300-5000 kPa gauge and a Weight Hourly Space Velocity of 3-3010 to produce a hydrocracking product stream comprising BTX, and (c) separating the BTX from the hydrocracking product stream, wherein the hydrocracking catalyst comprises a shaped body comprising a zeolite, a binder and a hydrogenation metal deposited on the shaped body, wherein the amount of the hydrogenation metal is 0.035-0.080 wt % with respect to the total catalyst, wherein the zeolite is ZSM-5 having a silica to alumina molar ratio of 25-75, wherein the hydrocracking catalyst comprises less than 0.01 parts molybdenum on the basis of 100 parts by weight of the total catalyst, and wherein the hydrocracking 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 the total catalyst.

16. The process according to claim 15, wherein the amount of the binder in the hydrocracking catalyst is 10-50 wt % with respect to the total catalyst.

17. The process according to claim 15, wherein the zeolite has a silica to alumina molar ratio of 40-55.

Description

EXAMPLES

(1) Preparation of Hydrocracking Catalyst

(2) Catalysts A-D were prepared by using different HZSM-5 extrudates that were made by using NH.sub.4-ZSM-5 zeolite powder having SiO.sub.2/Al.sub.2O.sub.3 ratio of about 23, 30, 50 and 80, and alumina (Al.sub.2O.sub.3) as binder followed by calcination to form HZSM-5 extrudate. The binder content was about 20 wt % based on the total content of the extrudate. Physical properties of the HZSM-5 extrudate are shown below. Cylindrical shape, average diameter 1.6 mm Crush strength (flat plate) 2.2 lb/mm Compacted bulk density 40 lb/ft.sup.3 Surface area, (1-point BET) 375-400 m.sup.2/g

(3) The zeolite extrudates were obtained from Zeolyst International, Inc. and the as-received zeolite extrudates were further calcined at 550 C. in air. The Pt was added into the zeolite extrudates by an ion-exchange method. The Pt ion-exchange was followed by washing and calcinations of the extrudate.

(4) Catalyst A-D

(5) 10.0 g HZSM-5 zeolite extrudates with ZSM-5 having different SiO.sub.2/Al.sub.2O.sub.3 ratios (see Table 1 below) were poured into solution of 4.10 g of 0.005 M H.sub.2PtCl.sub.6.6H.sub.2O and 24.58 g of deionized (DI) H.sub.2O in a 500-ml glass flask. Ion-exchange was made at 60 C. with stirring by magnetic stirrer for 24 h. The extrudates were separated from the solution and rinsed with 500 ml water and the rinsing was repeated 5 times. The rinsed extrudates were further washed by stirring with 300 ml water at room temperature for 15 min and were separated. The catalyst was dried at 90 C. (8 h) and then temperature was ramped at 3 C./min to 280 C. and was held for 6 h.

(6) The compositions of the catalysts are summarized below.

(7) TABLE-US-00001 TABLE 1 catalyst Si, wt % Al, wt % Pt, wt % SiO.sub.2/Al.sub.2O.sub.3 Ratio.sup.1 A 33.65 12.62 0.02 23 B 33.53 13.34 0.02 30 C 35.76 13.15 0.03 55 D 33.54 12.11 0.03 80 .sup.1SiO.sub.2/Al.sub.2O.sub.3 ratio of HZSM-5 powder prior to forming extrudate measured by XRF.

(8) The amounts of the elements in the catalysts were determined by X-ray fluorescence (XRF).

(9) Catalyst Testing

(10) Referring to Examples 1 to 11, catalysts described in this application were tested for hydrocracking reaction using stainless steel tube reactor as described below. 0.10 g catalyst (sized 20-40 mesh) was diluted to 3 ml by premixing with SiC (30 grit) and was loaded in a reactor.

(11) Reactor description: inch tube, 0.028 wall thickness. 1/16 thermocouple with a spacer bar; 121 brass over-sleeve; reactor bed is approx. 5-6 inches in length in center of sleeve.

(12) The catalyst was pre-activated (drying, Pt reduction) by subjecting it to 40 standard cubic centimeters (sccm) of H.sub.2 per minute at 130 C. under 50 psig for 2 hours and subsequently 40 sccm of H.sub.2 (with 50 ppm of H.sub.2S) at 350 C. at 50 psig for 30 min.

(13) The hydrocracking feed stream consisted of 70 wt % benzene, 15 wt % 3-methylpentane and 15 wt % methylcyclopentane. All components of the hydrocracking feed stream are Aldrich regent grade chemicals dried under 4 A molecular sieves overnight.

(14) The hydrocracking feed stream was introduced to the reactor at a temperature of 470 C. and a pressure of 200 psig. The molar ratio of H.sub.2 to the hydrocarbons was 4 to 1, and the H.sub.2S content was 50 ppm based on the total hydrocarbon and H.sub.2 feed.

(15) In all experiments, the WHSV was adjusted to achieve the benzene purity (amount of benzene/amount of benzene plus benzene co-boilers) of 99.82 wt % in the product stream.

Example 1

(16) Catalyst A, weight 0.10 g

(17) Catalyst pretreatment: (a) drying: under 40 sccm H.sub.2 at 50 psig at 130 C. for 2 h; (b) subsequent H.sub.2S treatment: 40 sccm of H.sub.2 (with 50 ppm of H.sub.2S) at 50 psig at 350 C. for 30 min

(18) Hydrocarbon feed composition: 70.0 wt % Benzene, 15.0 wt % 3-methylpentane, 15.0 wt % methylcyclopentane

(19) Hydrocarbon feed rate varied from 41.2 to 49.4 l/min to run at WHSV 20.2 to 24.3 h.sup.1. H.sub.2 (+H.sub.2S) rate: varied to maintain H.sub.2 to HC molar ratio of 4 to 1, and H.sub.2S content 50 ppm based on total feed

(20) Catalyst bed temperature 470 C., pressure 200 psig

Example 2

(21) Catalyst B, weight 0.10 g

(22) Catalyst pretreatment: same as described in example 1

(23) Hydrocarbon feed composition and rate: same as described in example 1.

(24) Hydrocarbon feed rate varied from 30.9 to 47.4 l/min to run at WHSV 15.0 to 23.0 h.sup.1.

(25) H.sub.2 (+H.sub.2S) rate: varied as described in example 1

(26) Catalyst bed temperature 470 C., pressure 200 psig.

Examples 3

(27) Catalyst C, weight 0.10 g

(28) Catalyst pretreatment: same as described in example 1

(29) Hydrocarbon feed composition and rate: same as described in example 1

(30) Hydrocarbon feed rate varied from 18.5 to 20.6 l/min to run at WHSV 9.0 to 10.0 h.sup.1.

(31) H.sub.2 (+H.sub.2S) rate: varied as described in example 1

(32) Catalyst bed temperature 470 C., pressure 200 psig

Example 4

(33) Catalyst D, weight 0.10 g

(34) Catalyst pretreatment: same as described in example 1

(35) Hydrocarbon feed composition and rate: same as described in example 1.

(36) Hydrocarbon feed rate varied from 4.1 to 8.2 l/min to run at WHSV 1.98 to 3.96 h.sup.1.

(37) H.sub.2 (+H.sub.2S) rate: varied as described in example 1

(38) Catalyst bed temperature 470 C., pressure 200 psig

(39) TABLE-US-00002 TABLE 2 wt % C% in effluent Ex- Cata- benzene WHSV, total ample lyst purity h.sup.1 benzene methane light HC.sup.1 aromatics 1 A 99.82 23.3 63.5 1.40 30.08 69.80 2 B 99.82 21.8 64.9 1.39 29.41 70.45 3 C 99.82 9.5 64.6 1.13 29.95 69.90 4 D 99.82 2.8 62.2 1.33 33.3 66.52 .sup.1light HC = C.sub.1-C.sub.5 hydrocarbons

(40) The WHSV obtainable for reaching the purity of benzene of 99.82 wt % decreases as the SiO.sub.2/Al.sub.2O.sub.3 ratio is increased. It can be seen that the methane proportion in the effluent decreases as the SiO.sub.2/Al.sub.2O.sub.3 ratio increases from 23 to 50 and then increases as the ratio increases from 50 to 80. That is, methane in the effluent is the least when the SiO.sub.2/Al.sub.2O.sub.3 ratio is about 50. The SiO.sub.2/Al.sub.2O.sub.3 ratio of 25-75 therefore achieves the desired benzene purity of 99.82 wt % with an optimum benzene and total aromatics and a low methane proportion in the product stream while allowing a high WHSV. Further, the SiO.sub.2/Al.sub.2O.sub.3 ratio of 35-75 achieves a very low methane proportion.

(41) Effect of Pt Content

(42) Catalysts E-K

(43) Catalysts E-Kwere prepared by using the same procedure that was described for catalyst C above but the Pt contents of the catalysts were varied by ion-exchanging the HZSM-5 extrudates (the SiO.sub.2/Al.sub.2O.sub.3 of the zeolite powder was 50) with different amounts of Pt containing solutions. Pt contents of the final catalysts are shown in Table 3. Catalysts were dried and calcined by using the same procedure. These catalysts were used in cracking of the hydrocarbon feedstock in examples 5-13.

(44) TABLE-US-00003 TABLE 3 Catalyst SiO.sub.2/Al.sub.2O.sub.3 Ratio.sup.1 Pt, wt % E 50 0.03 F 50 0.05 G 50 0.067 H 50 0.070 I 50 0.072 J 50 0.15 K 50 0.25 .sup.1SiO.sub.2/Al.sub.2O.sub.3 ratio of HZSM-5 powder prior to forming extrudate measured by XRF.

Example 5

(45) Catalyst E, weight 0.10 g

(46) Catalyst pretreatment: same as described in example 1

(47) Hydrocarbon feed composition and rate: same as described in example 1.

(48) Hydrocarbon feed rate varied from 16.5 to 20.6 l/min to run at WHSV 7.57 to 9.44 h.sup.1.

(49) H.sub.2 (+H.sub.2S) rate: varied as described in example 1

(50) Catalyst bed temperature 470 C., pressure 200 psig

Example 6

(51) Catalyst F, weight 0.10 g

(52) Catalyst pretreatment: same as described in example 1

(53) Hydrocarbon feed composition and rate: same as described in example 1.

(54) Hydrocarbon feed rate varied from 20.6 to 24.7 l/min to run at WHSV 9.91 to 11.89 h.sup.1.

(55) H.sub.2 (+H.sub.2S) rate: varied as described in example 1

(56) Catalyst bed temperature 470 C., pressure 200 psig

Example 7

(57) Catalyst G, weight 0.10 g

(58) Catalyst pretreatment: same as described in example 1

(59) Hydrocarbon feed composition and rate: same as described in example 1.

(60) Hydrocarbon feed rate varied from 20.6 to 24.7 l/min to run at WHSV 10.01 to 12.00 h.sup.1.

(61) H.sub.2 (+H.sub.2S) rate: varied as described in example 1

(62) Catalyst bed temperature 470 C., pressure 200 psig

Example 8

(63) Catalyst H, weight 0.10 g

(64) Catalyst pretreatment: same as described in example 1

(65) Hydrocarbon feed composition and rate: same as described in example 1.

(66) Hydrocarbon feed rate varied from 20.6 to 26.8 l/min to run at WHSV 10.11 to 13.16 h.sup.1.

(67) H.sub.2 (+H.sub.2S) rate: varied as described in example 1

(68) Catalyst bed temperature 470 C., pressure 200 psig

Example 9

(69) Catalyst I, weight 0.10 g

(70) Catalyst pretreatment: same as described in example 1

(71) Hydrocarbon feed composition and rate: same as described in example 1.

(72) Hydrocarbon feed rate varied from 20.6 to 26.8 l/min to run at WHSV 10.11 to 13.16 h.sup.1.

(73) H.sub.2 (+H.sub.2S) rate: varied as described in example 1

(74) Catalyst bed temperature 470 C., pressure 200 psig

Examples 10

(75) Catalyst J, weight 0.10 g

(76) Catalyst pretreatment: same

(77) Hydrocarbon feed composition and rate: same.

(78) Hydrocarbon feed rate varied from l/min to run at 8.92 to 10.99 WHSV to h.sup.1.

(79) H.sub.2 (+H.sub.2S) rate: varied as described in example 1

(80) Catalyst bed temperature 470 C., pressure 200 psig

Examples 11

(81) Catalyst K, weight 0.10 g

(82) Catalyst pretreatment: same

(83) Hydrocarbon feed composition and rate: same.

(84) Hydrocarbon feed rate varied from l/min to run at 7.94 to 9.91 WHSV to h.sup.1.

(85) H.sub.2 (+H.sub.2S) rate: varied as described in example 1

(86) Catalyst bed temperature 470 C., pressure 200 psig

(87) TABLE-US-00004 TABLE 4 wt % C% in effluent Ex- Cata- benzene WHSV, total ample lyst purity h.sup.1 benzene methane light HC.sup.1 aromatics 5 E 99.82 8.00 62.48 1.31 33.21 66.65 6 F 99.82 11.52 60.88 1.15 34.53 65.33 7 G 99.82 12.00 61.52 1.12 33.73 66.13 8 H 99.82 12.12 60.88 1.18 34.26 65.61 9 I 99.82 12.13 60.26 1.19 34.97 64.90 10 J 99.82 8.75 50.46 1.44 44.70 55.18 11 K 99.82 8.23 48.60 1.48 46.15 53.72 .sup.1lights C.sub.1-C.sub.5 hydrocarbons

(88) Based on the hydrocracking test results on Pt/HZSM-5 catalysts the Pt amount of 0.035-0.080 wt % (around 0.05-0.072 wt %) achieves the best balance of the catalyst activity (higher WHSV is preferred for the desired benzene purity), and the contents of methane, lights, benzene and total aromatics.