Process configuration for production of petrochemical feed-stocks

Abstract

The invention relates to a process configuration for production of light olefins and aromatics from residual hydrocarbon streams. In this configuration a high severity catalytic cracking process is employed for producing higher yields of lighter olefins and various boiling fractions. C4 stream separated from gaseous product is subjected to metathesis and aromatized to form mono aromatics.

Claims

1. An integrated process for producing light olefins and aromatics from residual hydrocarbon streams, the process comprising: a) subjecting the residual hydrocarbon streams to catalytic cracking to produce a catalytically cracked effluent, wherein the catalytically cracked effluent is fractionated into a C3-C4 stream, light cracked naphtha, heavy cracked naphtha, light cycle oil, and clarified oil; b) separating the C3-C4 stream into a propylene containing stream and a butylene and pentene containing stream; c) subjecting the butylene and pentene containing stream to metathesis and to a separation to produce propylene and hexenes, wherein the hexenes is aromatized to produce benzene and alkyl substituted benzenes and an unconverted stream; d) selectively hydrogenating the light cracked naphtha to produce a selectively hydrogenated stream comprising olefins and saturates; e) subjecting the selectively hydrogenated stream to extractive distillation using a solvent to form an extract stream containing aromatics along with sulfur compounds and a raffinate stream containing olefins and hydrotreating the extract stream to obtain a hydrotreated extract stream; f) combining the heavy cracked naphtha along with liquid hydrocarbon streams boiling in the range of C5-210° C. from a delayed coker unit in a circulating fluidized bed reactor from step (i) for fractionation into a dry gas, a C3-C4 stream, a C5-70° C. stream, a 70-170° C. stream, a 170° C.+ stream, and a 200° C.+ stream; g) hydrotreating the light cycle oil to produce an intermediate stream, wherein the intermediate stream comprises di aromatics or poly aromatics; h) hydrocracking the intermediate stream to produce a hydrocracked stream, and fractionating the hydrocracked stream into additional products; and i) hydrotreating the clarified oil to produce a hydrotreated stream, wherein hydrotreated stream is fed to the delayed coker unit to produce lighter products and needle coke, wherein the lighter products are gases, liquid hydrocarbon streams boiling in a range of C5-210° C., and diesel; wherein the process yields light olefins in a range of 11-15 weight % and aromatics in a range of 15-21 weight %, and wherein in the weight % is with reference to the residual hydrocarbon stream streams.

2. The process as claimed in claim 1, wherein the unconverted stream, rich in higher olefins with a good octane number and the 170° C.+ stream are routed to a gasoline pool.

3. The process as claimed in claim 1, wherein the hydrotreating of step g) removes hetero atoms and selectively saturates the poly aromatics to di aromatics and the di aromatics to mono aromatics.

4. The process as claimed in claim 1, wherein the 200° C.+ stream and the diesel stream are blended into a diesel pool.

5. The process as claimed in claim 1, wherein the 200° C.+ stream has a cetane number in a range of 30-42 and the diesel stream has a cetane number in a range of 22-30.

6. The process as claimed in claim 1, wherein the unconverted stream has an octane number in a range of 90-93 and the 170° C.+ stream has an octane number in a range of 90-95.

7. The process as claimed in claim 1, wherein the hydrocracked stream is fractionated into dry gas, C3-C4 stream, liquid hydrocarbon streams boiling in a range of C5-70° C., 70-170° C. rich in mono aromatics and alkyl substituted mono aromatics and 200° C.+.

8. The process as claimed in claim 1, wherein the solvent used for the extractive distillation is general selective solvents or a combination of solvents for aromatics extraction.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 illustrates conventional FCC main fractionator and utilization of streams; and

(2) FIG. 2 illustrates process of the present invention.

DESCRIPTION OF THE INVENTION

(3) Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such steps of the process, features of the product, referred to or indicated in this specification, individually or collectively, and any and all combinations of any or more of such steps or features. The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purposes of exemplification only. Functionally-equivalent products and methods are clearly within the scope of the disclosure, as described herein.

(4) In the conventional FCC (FIG. 1) gas con section, FCC reactor effluent (1) is fractionated into different cuts in a FCC main fractionator (2). The hot vapors from the reactor enter the bottom section of the column. These vapors are fractionated to produce the following products: DG and LPG (3), Light naphtha to treatment and blending to gasoline pool (4), Heavy naphtha to DHDT/HGU unit (5), Light cycle oil to DHDT (6), Clarified oil to Fuel oil (7). These streams undergo treatment before being blended into the finished products.

(5) According to the main feature, in the present invention, these streams are further subjected to different types of new catalytic processes which convert them further into more additional valuable products such as light olefins, BTX, high octane gasoline and high cetane diesel along with premium grade petroleum coke.

(6) In one embodiment, the present invention provides an integrated process for producing light olefins and aromatics from residual hydrocarbon streams comprising:

(7) a) subjecting a residual hydrocarbon stream (10) to catalytic cracking to produce a catalytically cracked effluent, wherein the catalytically cracked effluent is fractionated into a C3-C4 stream (12), light cracked naphtha (13), heavy cracked naphtha (14), light cycle oil (15), and clarified oil (16),

(8) b) separating the C3-C4 stream (12) into a propylene containing stream (18) and a butylene and pentene containing stream (19),

(9) c) subjecting the butylene and pentene containing stream (19) to metathesis and separation to produce propylene (21) and hexenes (22), wherein hexenes (22) is aromatized to produce benzene and alkyl substituted benzenes (24) and an unconverted stream (25),

(10) d) selectively hydrogenating the light cracked naphtha (13) to produce a selectively hydrogenated stream comprising olefins and saturates (27),

(11) e) subjecting the selectively hydrogenated stream (27) to extractive distillation using a solvent to form an extract stream (30) containing aromatics along with sulfur compounds and a raffinate stream (29) containing olefins and hydrotreating the extract stream (30) to obtain stream (32),

(12) f) combining the heavy cracked naphtha (14) along with liquid hydrocarbon streams boiling in the range of C5-210° C. (52) from a delayed coker unit (50) in a circulating fluidized bed reactor for fractionation into dry gas (34), C3-C4 stream (35), liquid hydrocarbon streams boiling in the range of C5-70° C. (36), 70-170° C. (37) and 170° C.+ (38),

(13) g) hydrotreating the light cycle oil (15) to produce an intermediate stream (40),

(14) h) hydrocracking the intermediate stream (40) to produce a hydrocracked stream (42) which is fractionated into additional products,

(15) i) hydrotreating the clarified oil (16) to produce a hydrotreated stream (49), wherein the hydrotreated stream (49) is fed to a delayed coker unit (50) to produce lighter products and needle coke (54), wherein the lighter products are gases (51), liquid hydrocarbon streams boiling in the range of C5-210° C. (52), and diesel (53)

(16) wherein the process yields light olefins in a range of 11-15 weight % and aromatics in a range of 21-30 weight % in stream (52)

(17) wherein in the weight % is with reference to the residual hydrocarbon stream.

(18) In another embodiment, the stream (25) rich in higher olefins with good octane number and stream (38) are routed to gasoline pool (55).

(19) In a further embodiment, the present invention provides that the hydrotreating of step g) removes hetero atoms and selectively saturates the poly aromatics to di aromatics and di aromatics to mono aromatics.

(20) In yet another embodiment, the stream (47) and stream (53) are blended into a diesel pool (56).

(21) In a preferred embodiment, the stream (47) has a cetane number in a range of 30-42 and stream (53) has a cetane number in a range of 22-30.

(22) In yet another preferred embodiment, the stream (25) has an octane number in a range of 90-93 and stream (38) has an octane number in a range of 90-95.

(23) In one embodiment, stream (42) is fractionated into dry gas (43), C3-C4 stream (44), liquid hydrocarbon streams boiling in the range of C5-70° C. (45), 70-170° C. (46) rich in mono aromatics and alkyl substituted mono aromatics and 200° C.+ (47).

(24) In an embodiment of the present invention, the general selective solvents such as ethylene glycol, sulfolane, dimethylsulfoxide, etc., or a combination of solvents are used for extractive distillation.

(25) In a preferred embodiment, the present invention provides a system for producing light olefins and aromatics from residual hydrocarbon streams, comprising:

(26) (a) a high severity catalytic cracking unit (11) for cracking C3-C4 stream (12) and fractionating the catalytically cracked effluent, wherein the high severity catalytic cracking unit is in communication with a propylene splitter unit (17), a metathesis reactor and separation unit (20), hydrotreater (48), hydrotreater (39), and a circulating fluidized bed reactor (33),

(27) (b) a propylene splitter unit (17)

(28) (c) a metathesis reactor and separation unit (20) to produce propylene (21) and hexenes (22) by metathesis,

(29) (d) an aromatizing reactor unit (23) to aromatize hexenes (22),

(30) (e) a selective hydrogenation unit (26) to convert all the di-olefins responsible for gum formation and fouling present in light cracked naphtha (13) to olefins and saturates forming part of a selectively hydrogenated stream (27),

(31) (f) an extractive distillation column (28) for producing an extract stream (30) and a raffinate stream (29) from the selectively hydrogenated stream (27),

(32) (g) hydrotreaters (31), (39) and (48), wherein hydrotreater (31) is downstream of an extractive distillation column (28) and hydrotreaters (39) and (48) are downstream of the high severity catalytic cracking unit, and wherein hydrotreater (39) removes hetero atoms and selectively saturates poly aromatics to di aromatics and di aromatics to mono aromatics from light cycle oil (15) and hydrotreater (48) removes sulfur and metals from clarified oil (16) to make a desirable feed stock for producing needle coke,

(33) (h) a circulating fluidized bed reactor (33) for treating the combined stream of heavy cracked naphtha (14) and liquid hydrocarbon streams boiling in the range of C5-210° C. (52) and fractionating the reactor effluent,

(34) (i) a mild hydrocracking unit (41) for selective ring opening of di or poly aromatics in intermediate stream (40) to produce a hydrocracked stream (42),

(35) (j) a delayed coker unit (50) for thermally cracking stream (49) to produce and fractionate lighter products and needle coke (54).

(36) In another embodiment, the high severity catalytic cracking unit (11) operates at a pressure in a range of 1.5 to 2 kg/cm.sup.2 (g) and temperature in a range of 540 to 600° C.

(37) In yet another embodiment, the hydrotreaters (31), (39) and (48) operate at a pressure in a range of 30 to 120 kg/cm.sup.2 (g) and temperature in a range of 300 to 400° C.

(38) In a further embodiment, the hydrocracking unit (41) operates at a pressure in a range of 80 to 130 kg/cm.sup.2 (g) and temperature in a range of 250 to 420° C.

(39) Description of Process Flow Scheme

(40) As shown in FIG. 2, high severity catalytic cracking unit (11) is fed with residual hydrocarbon stream (10) and the reactor effluent is fractionated into various product streams such as C3-C4 stream (12), liquid hydrocarbon streams boiling in the range of C5-70° C. and 70-170° C. (13), 170-210° C. (14), 210-370° C. (15) and 370° C..sup.+. The stream 12 sent to propylene splitter unit (17) where propylene is separated from stream 12 into stream 18 which contains 99.7 wt % C.sub.3s and stream (19) containing mostly C.sub.4 and C.sub.5s. Stream (19) with 99.7% C4's is fed to a metathesis reactor and separation unit (20). Unit (20) produces propylene (21) and hexenes (22) by metathesis from stream (19) containing butenes and pentanes. Stream (22) is fed to aromatizing reactor unit (23) where the hexenes (22) along with higher olefins are aromatized to benzene and alkyl substituted benzenes (24). The unconverted stream (25) rich in higher olefins like hexenes, heptenes and octenes with good octane number will be routed to gasoline pool (55). The light naphtha stream (13) comprising 30 wt % olefins, 5 wt % di olefins and 40 wt % aromatics are fed to a selective hydrogenation unit (26). In this unit, all the di olefins which are the sources for gum formation and fouling are converted to olefins and saturates. The selectively hydrogenated stream (27) is sent to an extractive distillation column (28). The solvent extracts the aromatics along with sulfur compounds as stream (30) whereas olefins rich stream (29) is the raffinate in an extraction column operating at a temperature range of 30-180° C. After solvent recovery, stream (30) is hydrotreated and directed to an aromatics plant with 99% rich in aromatics. The stream (14) along with (52) is fed to (33) which is typically a circulating fluidized bed reactor. The reactor effluent is fractionated into various product streams such as dry gas (34), C3-C4 stream (35), liquid hydrocarbon streams boiling in the range of C5-70° C. (36), 70-170° C. (37) and 170° C.+ (38). The stream (15) is fed to a hydrotreater unit (39) to remove the hetero atoms such as sulfur and to selectively saturate the poly aromatics to di aromatics and di aromatics to mono aromatics. Effluent from unit (39), stream (40) is processed in mild hydrocracking unit (41) for selective ring opening of di/poly aromatics. Stream (42) is fractionated to various products such as dry gas (43), C3-C4 stream (44), liquid hydrocarbon streams boiling in the range of C5-70° C. (45), 70-170° C. (46) which is rich in mono aromatics and alkyl substituted mono aromatics and 200° C..sup.+ (47) having a good cetane number of 42 which is blended into diesel pool (56). The stream (16) is subjected to hydrotreating in unit (48) to remove the sulfur and metals to make a desirable feed stock for producing needle coke. Stream (49) is fed to delayed coker unit (50) for thermally cracking the feedstock to produce lighter products along with needle coke (54). The lighter products are fractionated into various products such as gases (51), liquid hydrocarbon streams boiling in the range of C5-210° C. (52), and 210-370° C. (53) diesel stream which can be routed to diesel pool (56).

(41) Technical Advantages of the Invention:

(42) The present invention has the following advantage over the prior arts: 1. The present invention produces high amount of propylene and mono-aromatics from high boiling hydrocarbon streams. 2. The present invention also produces gasoline with high octane number and diesel with high cetane number which can be blended directly into its pools. 3. This invention further produces saturated LPG for use as fuel to automobiles and premium quality petroleum needle coke for manufacturing of electrodes in arc furnaces in the steel industry.

(43) From the above process flow scheme, it can be seen that the process configuration of current invention converts the streams from high severity FCC unit into propylene, aromatics and octane rich gasoline, cetane rich diesel along with premium quality petroleum coke.

Examples

(44) The disclosure will now be illustrated with working examples, which is intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice of the disclosed methods, the exemplary methods, devices, and materials are described herein. It is to be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may vary.

(45) The yields of the processes are established in pilot plants experiments and simulation of the entire configuration is carried out in AspenHYSYS software. The typical yields of high severity FCC unit which is the starting unit in this configuration are shown in Table-1. Typical yields of conversion process units in the above configuration are shown in Table-2, 3, 4, respectively.

(46) TABLE-US-00001 TABLE 1 True boiling point (TBP) yields of high severity catalytic cracking unit (11) Products Wt % Dry gas (w/o inert) 10.91 LPG 44.15 LCN (C5-70° C.) 9.19 MCN (70-170° C.) 17.14 HCN (170-210° C.) 2.69 LCO (210-340° C.) 7.88 CLO (340° C.+) 2.24 Coke 5.8

(47) TABLE-US-00002 TABLE 2 Yields of conversion unit-33 Products Wt % Dry gas 7.33 LPG 43.88 Benzene rich cut (70-90° C.) 5.80 Benzene lean cut (C5-70° C. and 40.89 90-210° C.) Coke 2.10

(48) TABLE-US-00003 TABLE 3 Yields of conversion unit-41 Products Wt % Dry gas  1.5 LPG  8.0 Light Naphtha (C5-100° C.) 15.0 Heavy Naphtha (100-200° C.) 55.0 Diesel (200+° C.) 20.5

(49) TABLE-US-00004 TABLE 4 Yields of conversion unit-50 Products Wt % Dry gas  8.7 LPG  2.6 Naphtha  5.1 Gas oil 33.0 Needle coke 50.6

(50) The comparison of typical yields obtained from Fig-1 and Fig-2 process are given in Table 5.

(51) TABLE-US-00005 TABLE 5 Product Yields, wt % FIG. 1 FIG. 2 Dry Gas 2.48 7.02 LPG 24.53 42.0 Propylene 9.77 17.4 Gasoline (C5-210) 50.98 35.19 LCO (210-340) 9.73 7.59 CLO (340+) 7.97 2.16 Coke 4.31 6.0

(52) Table 5 shows that further processing of the stream obtained from unit no (11) by using the present configuration as described in the present invention produces light olefins, mono aromatics, gasoline with octane number in the range of 90-95, diesel with cetane number in the range of 30-42 along with the needle coke. The process leads to an increase in the yield of dry gas, LPG, propylene and coke and reduction in the yields of gasoline, light cycle oil and clarified oil.

(53) Light cycle oil (15) undergoes conversion in unit (39) to an intermediate (40) and the change in quality in the typical temperature range of 300 to 400° C. and pressure range of 30 to 120 kg/cm′ (g) is given in Table 6. Table 6 demonstrates that hydrotreatment of the light cycle oil (15) reduces the sulfur content, increases the content of saturates and mono aromatics, while reducing the content of di aromatics and poly aromatics.

(54) TABLE-US-00006 TABLE 6 Stream No-15 Stream No-40 Sulfur, ppm 9500 6.2 Saturates, wt % 24 34 Mono Aromatics 39.6 51.5 Di Aromatics 36.1 14.4 Poly Aromatics 0.3 0.1

(55) The typical yields of the unit (39) in the typical temperature range of 300 to 400° C. and pressure range of 30 to 120 kg/cm.sup.2 (g) is given in Table 7.

(56) TABLE-US-00007 TABLE 7 Product Yields Wt % H.sub.2S 1.54 NH.sub.3 0.04 Fuel gas 0.85 Naphtha 1.3 Diesel 98.7

(57) The reactor temperature and pressure ranges are very critical in achieving the desired result of decreasing sulfur, di aromatics and poly aromatics content in the feed which forms the desired feed to the hydrocracking unit (41). The yield and product quality from the hydrocracking unit (41) depends on the quality of intermediate stream (40). However, if the temperature in the hydrotreatment unit (39) is decreased to 290° C. and the pressure is 35 kg/cm.sup.2, the conversion of di aromatics to mono aromatics, poly aromatics to di aromatics and sulfur compounds to H.sub.2S decreases. The composition of intermediate stream (40) at 290° C. and 25 kg/cm.sup.2 is given in Table 8.

(58) TABLE-US-00008 TABLE 8 Stream No-15 Stream No-40 Sulfur, ppm 9500 3610 Saturates, wt % 24 27.0 Mono Aromatics 39.6 46.8 Di Aromatics 36.1 26.0 Poly Aromatics 0.3 0.19

(59) When the temperature in unit (39) is decreased to 290° C. and pressure is reduced to 25 kg/cm.sup.2 conversion of di aromatics to mono aromatics, poly aromatics to di aromatics and sulfur compounds to H.sub.2S decreases.

(60) TABLE-US-00009 TABLE 9 Product Yields Wt % H.sub.2S 1.2 NH.sub.3 0.034 Fuel gas 0.662 Naphtha 1.20 Diesel 99.212

(61) Similarly, when the temperature in unit (39) is increased to 400° C. and pressure is increased to 125 kg/cm.sup.2 (g), desired yield of the products is not obtained.

(62) TABLE-US-00010 TABLE 10 Product Yields Wt % H.sub.2S 1.66 NH.sub.3 0.041 Fuel gas 0.98 Naphtha 1.7 Diesel 98.34

(63) Similarly, the conversion of sulfur compounds to H.sub.2S decreases from 99% to around 60% below pressure of 30 kg/cm.sup.2 (g) and below temperature of 300° C. in hydrotreatment unit (31) and hydrotreatment unit (48).

(64) If the temperature and pressure in a high severity catalytic cracking unit (11) are varied to 520° C. and 1.4 kg/cm.sup.2 (g) respectively, the yield of light cycle oil and clarified oil increases, while lower yields of dry gas and LPG are obtained.

(65) TABLE-US-00011 TABLE 11 Product Yields Wt % Dry Gas 3.75 LPG 32.53 LCN (C5-70) 15.50 MCN (70-170) 18.52 HCN (170-210) 1.38 LCO (210-340) 16.79 CLO (340+) 6.34 Coke 5.2

(66) If the temperature and pressure in a high severity catalytic cracking unit (11) are varied to 600° C. and 1.4 kg/cm.sup.2 (g) respectively, the yields of LCN, MCN, HCN and CLO clarified oil decreases while higher yields of dry gas and LPG are obtained as shown in Table-12.

(67) TABLE-US-00012 TABLE 12 Product Yields Wt % Dry Gas 12.68 LPG 45.88 LCN (C5-70) 8.57 MCN (70-170) 15.10 HCN (170-210) 2.34 LCO (210-340) 7.51 CLO (340+) 2.21 Coke 5.72

(68) The typical yields of the unit (41) at temperature of 70° C. and 240 kg/cm.sup.2 (g) are given in Table-13.

(69) TABLE-US-00013 TABLE 13 Products Wt % Dry gas 1.1 LPG 5.0 Light Naphtha (C5-100° C.) 8.0 Heavy Naphtha (100-200° C.) 47.0 Diesel (200+° C.) 38.9

(70) The typical yields of the unit (41) at temperature of 135° C. and 425 kg/cm.sup.2 (g) are given in Table-14.

(71) TABLE-US-00014 TABLE 14 Products Wt % Dry gas  2.2 LPG 10.5 Light Naphtha (C5-100° C.) 24.0 Heavy Naphtha (100-200° C.) 52.0 Diesel (200+° C.) 11.3

(72) On increasing the temperature and pressure beyond the ranges the yield and quality of heavy naphtha cut (100-200° C.) which is the good petrochemical feed stock decreases.