Integrated Process For Production Of High Octane Gasoline, High Aromatic Naphtha And High Cetane Diesel From High Aromatic Middle Distillate Range Streams (United States Patent Application 20150267130 Indian Oil Corporation Ltd.)

Integrated Process For Production Of High Octane Gasoline, High Aromatic Naphtha And High Cetane Diesel From High Aromatic Middle Distillate Range Streams (United States Patent Application 20150267130 Indian Oil Corporation Ltd.)
September 24, 2015
Applicant: Indian Oil Corporation Ltd., Mumbai, India
Abstract
An integrated process for production of ultra low sulfur products of high octane gasoline, high aromatic naphtha and high Cetane Diesel from high aromatic middle distillate range streams from any cracker units such as Light Cycle Oil (LCO) stream of Fluid catalytic cracking (FCC) units and comprising of subjecting the feed boiling between 200 to 400.degree. C. and having at least 30 wt % multi-ring aromatics content subjected to hydrotreating for removal of heteroatoms like sulfur and nitrogen and at a pressure sufficient only for saturation of one ring of multi-ring aromatics. The effluent from hydrotreating is subjected to hydrocracking at same pressure of hydrotreating step above for selective opening of saturated ring of multi-ring aromatics. The effluent from hydrocracking is separated in CUT-1 boiling between 35 to 70.degree. C., CUT-2 boiling between 70 to 200.degree. C. in which the monoaromatics and alkylated monoaromatics are concentrated and CUT-3 boiling above 200.degree. C. in which concentration of saturates i.e. paraffins and naphthenes significantly increased. The CUT-3 is selectively oxidized in selective oxidation step in presence of catalyst, an oxidizing agent and operating conditions such that it results in diesel product with more enhanced Cetane.
BACKGROUND OF THE INVENTION
[0002] Low value high aromatic middle distillate range streams from any cracker units such as Light Cycle Oil (LCO) stream of Fluid catalytic cracking (FCC) units, because of high Sulphur, Nitrogen and Aromatic content; are very low value streams. Historically, these streams were being used as blend stocks in middle distillate and as cutter stock in fuel oil. Because of growing environmental consciousness the emission norms are getting stringent and at the same time the demand for high quality ultra low sulphur diesel (ULSD) is increasing rapidly. Therefore, these streams can no longer be used directly as diesel pool blending stocks. Further, the worldwide demand of Fuel oil is also declining sharply hence another conventional usage of these types of low value high aromatic streams as cutter stock has also become significantly low. Presently, in most of the refineries, these streams are being blended and hydrotreated along with diesel hydrotreater (DHDT) feed. In some refineries, these are also hydrocracked along with Vacuum Gas Oil (VGO) in a high pressure hydrocracker. But hydrotreating these streams for Diesel pool blending stock is inefficient means of utilizing costly hydrogen since hydrotreating only removes sulphur but cetane number remains much below the limit of Euro-III/IV/V diesel pool Cetane specification. Hydrocracking these streams along with VGO in conventional high pressure hydrocrackers improve diesel yield, but at the same time also increases naphtha generation substantially. Moreover, processing these streams in VGO hydrocracker also reduce throughput of VGO. Consequently, with both these options actual potential of high aromatics middle distillate range streams remains underutilized.
[0003] The middle distillate range streams of cracker units such as LCO stream of FCC units are rich in aromatic compounds. Depending upon the severity of the operating conditions the total aromatics in these types of streams vary from 50 to 90 wt %, in which mono-aromatic compounds are only 20-30 wt %, whereas di-aromatics are 50-70 wt % and the rest 5-10 wt % are polycyclic aromatic type of compounds. However, the poly-aromatic types of compounds present in these types of streams rarely have more than 3 rings.
[0004] The middle distillate range streams boiling between 150 and 400.degree. C. are often considered as low value streams owing to their high aromaticity and high sulfur and nitrogen levels, since these streams are difficult to accommodate in diesel pool. Examples of such streams are light cycle oil (LCO) from FCC and Coker Gas Oil from Delayed Coker units. These low value streams in refineries have very low cetane values, thus accommodating them in diesel pool requires higher consumptions of costly hydrogen. Merely hydrotreating them to improve their qualities is very inefficient means of utilizing hydrogen. The judicious use of hydrotreating, hydrocracking with ring opening functionality in staged manner is required. For example, only hydrotreating these streams may result in diesel range product with poor cetane and hydrotreating with conventional hydrocracking in existing hydrocrackers may result in high yield losses in terms of lighter products of light naphtha and heavy naphtha of inferior quality with medium quality diesel range product. Further, these streams constitute high levels of aromatics which are valuable in some fields of art. If they are converted to utilizable compounds, they can be very good feed stock for petrochemical products. Therefore, it is preferable to convert these aromatics in more valuable and usable compounds and use rest of the portion rich in naphthenes and paraffins as diesel can be a viable and economical option for refiners.
[0005] Different techniques of conversion of highly aromatic, low value middle distillate streams of cracker units into high value, high octane motor gasoline, and USLD have been described in many patents, such as U.S. Pat. No. 8,404,103 described the technique of conversion of highly aromatic feeds such as LCO into low sulphur diesel and high octane naphtha using mild hydrotreating and hydrocracking reactions. In this patent it has been claimed that the octane quality of the gasoline or naphtha fraction can be improved by allowing slippage of organic nitrogen to hydrocracker reactor by optimizing the operating condition of the hydrotreater. The patent also claims to obtain naphtha having at least 50 wt % mono aromatics concentration with RON value at least 85 and diesel with sulphur concentration less than 10 ppmw.
[0006] The U.S. Pat. No. 8,066,867 claims to develop process for converting LCO into low sulphur diesel and high octane naphtha using mild hydrotreating and hydrocracking reaction. The patent also claims to produce naphtha with RON value at least 85 units and diesel with sulphur content less than 10 wt-ppm.
[0007] The U.S. Pat. No. 7,837,860 describes an integrated process for hydrodesulfurization of middle distillate streams and hydrocracking of highly aromatic hydrocarbon streams such as LCO for production of low sulphur diesel and high octane naphtha.
[0008] The U.S. Pat. No. 7,384,542 describes about the invention of process for production of low sulphur diesel and high octane naphtha form highly aromatic and substantially dealkylated streams like LCO. The process claims to produce mono-cyclic aromatic compounds having boiling points in the range of naphtha.
[0009] The U.S. Pat. No. 4,990,239 of Mobil Oil Corporation describes their invention for production of Gasoline and distillate fuels from Light Cycle Oil. The patent claims to produce Gasoline with RON value at least 87 units and low sulphur diesel with cetane value at least 30. Another patent, U.S. Pat. No. 4,985,134 from the same assignee claims to produce gasoline and diesel fuel of cetane number at least 35 from LCO.
[0010] U.S. Pat. No. 4,828,676 discloses a process for production of ultra high octane gasoline from Aromatic distillates using hydrocracking reaction. In their process, they have disclosed to use iron as one of the components in the catalyst for ring opening purpose.
[0011] Some patents are also available where highly aromatics and dealkylated streams like LCO has been converted into Petrochemical feed stocks and xylenes. The U.S. Pat. No. 7,368,619 discussed about the process where diesel and aromatic compounds including xylene have been produced from LCO. The U.S. Pat. No. 7,271,303 claims to develop a process for producing diesel and aromatic compounds integrating hydrocracking and catalytic reforming. Another patent U.S. Pat. No. 7,265,252 discloses production of Xylene from LCO by selective hydrocracking reaction.
[0012] The common shortcoming in all of the above discussed inventions is the property of ULSD which is produced as one of the streams during the process. Although diesel produced in the process is low in sulphur but the other properties such as Cetane Number remains much lower than that required for EURO-III/IV/V diesel pool. Therefore, for complete upgradation of these types of high aromatic middle distillate range cracker streams, the cetane of the ULSD produced during the process also needs to be improved.
[0013] The U.S. Pat. No. 4,723,963 of Exxon Research and Engineering Company discussed about invention on selective oxidation of aromatic compounds for improve of cetane rating of middle distillate. The patent claims that oxidation of aromatics particularly alkylaromatics and hydroaromatics at benzylic position improves the cetane rating of the fuel. The patent has also disclosed the cetane rating of different aromatic compounds normally present in middle distillate range fuels and their corresponding oxidized compounds.
[0014] U.S. Pat. No. 7,501,054 and U.S. Pat. No. 7,501,374 discuss about the invention of process and catalyst for upgrading diesel fuel by introducing oxygen. The patent also discloses a process to convert alkyl-naphthene-aromatics compound to alkyl ketones.
[0015] It is therefore, important to develop an integrated process of interest that can upgrade these types of high aromatic content middle distillate range streams of cracker units into value added products keeping view that all potential are utilized to their limits.
SUMMARY OF THE INVENTION
[0016] Accordingly, the present invention provides an integrated process for production of High Octane Gasoline, High Aromatic Naphtha and High Cetane Diesel, the process comprising: [0017] a. subjecting a feed to hydrotreating step at a predetermined pressure to obtain a first effluent having a substantially reduced quantity of hetero-atoms compared to the feed, the feed comprising at least 30 wt % multi-ring aromatics and having boiling point between 200 to 400.degree. C., wherein the predetermined pressure is capable to saturate one or more rings of multi-ring aromatics and to remains unsaturated one or more rings of the multi-ring aromatics; [0018] b. subjecting the first effluent to a hydrocracking step at the predetermined pressure to obtain a second effluent, the hydrocracking step resulting in selective opening of at least one saturated ring of the multi-ring aromatics; [0019] c. separating the second effluent into a CUT-1, a CUT-2 and a CUT-3, with the CUT-1 having a boiling point between 35 to 70.degree. C., the CUT-2 having boiling point between 70 to 200.degree. C. and comprising an enhanced concentration of mono aromatics and alkylated mono aromatics and the CUT-3 having boiling point above 200.degree. C. and comprising an enhanced concentration of saturates; and [0020] d. subjecting at least a part of the CUT-3 to a selective oxidation step to in presence of catalyst, an oxidizing agent to obtain diesel range product with enhanced cetane number.
[0021] In one of the embodiment, the present invention provides an integrated process for production of High Octane Gasoline, High Aromatic Naphtha and High Cetane Diesel, the process comprising: [0022] a. subjecting a feed to hydrotreating step at a predetermined pressure to obtain a first effluent having a substantially reduced quantity of hetero-atoms compared to the feed, the feed comprising at least 30 wt % multi-ring aromatics and having boiling point between 200 to 400.degree. C., wherein the predetermined pressure is capable to saturate one or more rings of multi-ring aromatics and to remains unsaturated one or more rings of the multi-ring aromatics; [0023] b. separating the first effluent into a first part and a second part; [0024] c. subjecting the first part of the first effluent to a hydrocracking step at the predetermined pressure to obtain a second effluent, the hydrocracking step resulting in selective opening a saturated ring of the multi-ring aromatics; [0025] d. combining the second part of the first effluent with the second effluent to obtain a third effluent; [0026] e. separating the third effluent into a CUT-1, a CUT-2 and a CUT-3, with the CUT-1 having a boiling point between 35 to 70.degree. C., the CUT-2 having boiling point between 70 to 200.degree. C. and comprising an enhanced concentration of mono aromatics and alkylated mono aromatics and the CUT-3 having boiling point above 200.degree. C. and comprising an enhanced concentration of saturates; and [0027] f. subjecting at least a part of the CUT-3 to a selective oxidation step to in presence of catalyst, an oxidizing agent to obtain diesel range product with enhanced cetane number.
[0028] According to the present invention, wherein a remaining part of the CUT-3 is mixed with the first part of the first effluent and subjected to the hydrocracking step at the predetermined pressure to obtain the second effluent.
[0029] In one of the embodiment, the present invention provides an integrated process for production of ultra low sulfur products of high octane Gasoline, high aromatic Naphtha and high Cetane Diesel and the process comprising: [0030] a. a feed comprising at least 30 wt % multi-ring aromatics and having boiling point between 200 to 400.degree. C.; [0031] b. the feed is subjected to hydrotreating step for removal of heteroatoms and at a pressure sufficient only for saturation of one ring of multi-ring aromatics to obtain a first effluent; [0032] c. the effluent from hydrotreating step along with effluent from hydrocracking step below (d) is separated in CUT-1 boiling between 35 to 70.degree. C., CUT-2 boiling between 70 to 200.degree. C. in which the monoaromatics and alkylated monoaromatics are concentrated and CUT-3 boiling above 200.degree. C. in which concentration of saturates is significantly increased; [0033] d. part of the CUT-3 from above (c) is subjected to hydrocracking at same pressure of hydrotreating step above for selective opening of saturated ring of multi-ring aromatics; and [0034] e. the CUT-3 from above (c) is selectively oxidized in selective oxidation step in presence of catalyst system, an oxidizing agent and operating conditions in order to obtain diesel product with more enhanced cetane.
[0035] According to one embodiment of the present invention, the part of the CUT-3 is sent as feed to hydrocracking step and remaining part is recovered and sent to selective oxidation step.
[0036] According to another embodiment of the present invention, the part of the CUT-3 which is sent to the hydrocracking step is in the range of 30 to 70 wt % of totally CUT-3.
[0037] In one of the embodiment, the present invention provides an integrated process for production of ultra low sulfur products of high octane Gasoline, high aromatic Naphtha and high Cetane Diesel and the process comprising: [0038] a. a feed comprising at least 30 wt % multi-ring aromatics and having boiling point between 200 to 400.degree. C.; [0039] b. the feed is subjected to hydrotreating for removal of heteroatoms and at a pressure sufficient only for saturation of one ring of multi-ring aromatics to obtain a first effluent; [0040] c. the first effluent from hydrotreating is subjected to hydrocracking at same pressure of hydrotreating step above for selective opening of saturated ring of multi-ring aromatics to obtain a second effluent; [0041] d. the second effluent from hydrocracking is separated in CUT-1 boiling between 35 to 70.degree. C., CUT-2 boiling between 70 to 200.degree. C. in which the monoaromatics and alkylated monoaromatics are concentrated and CUT-3 boiling above 200.degree. C. in which concentration of saturates significantly increased; [0042] e. the CUT-3 from above (d) is further subjected to hydrotreating for producing product of sulfur content of below 10 ppm; [0043] f. the CUT-3 from above (e) after hydrotreating is selectively oxidized in selective oxidation step to in presence of catalyst, an oxidizing agent and operating conditions in order to obtain diesel product with more enhanced cetane.
[0044] In yet another embodiment of the present invention, the CUT-3 after selective oxidation Step (f) is having cetane number of at least 42.
[0045] In yet another embodiment of the present invention, the CUT-1 corresponds to ultra-low sulfur products of high octane Gasoline and octane number of the CUT-1 is at least 84 and sulphur content of the CUT-1 is below 50 ppmw. In one of the embodiment the CUT-1 corresponds to ultra-low sulfur products of high octane Gasoline and octane number of the CUT 1 is in the range of 84 to 90 units and sulphur content of the CUT 1 is in the range of 5 to 50 ppmw.
[0046] In yet another embodiment of the present invention, the CUT-2 corresponds to high aromatic Naphtha and octane number of the CUT-2 is at least 90 and sulphur content of the CUT-2 is below 50 ppmw. In one of the embodiment CUT-2 corresponds to high aromatic Naphtha and octane number of the CUT-2 is in the range of 90 to 105 units and sulphur content of the CUT-2 is in the range of 5 to 50 ppmw.
[0047] In yet another embodiment of the present invention, the feed is a high aromatic middle distillate.
[0048] In yet another embodiment of the present invention, the feed is diesel range hydrocarbon feedstock selected from (a) mineral petroleum oil; (b) Light Cycle Oil stream of FCC unit; (c) gas oil stream of delayed coker unit; (d) pyrolysis oil; (e) thermally cracked bio-sources or mixtures thereof.
[0049] In yet another embodiment of the present invention, the hydrotreating step is carried out at a pressure of about 25 to 75 barg and temperature of about 280 to 450.degree. C. and at a LHSV of 0.1 to 5.0 h.sup.-1.
[0050] In yet another embodiment of the present invention, the hydrocracking step is carried out at a same pressure as that of hydrotreating step.
[0051] In yet another embodiment of the present invention, the hydrocracking step is carried out at a temperature of 300 to 450.degree. C. and at a LHSV of 0.1 to 5.0 h.sup.-1.
[0052] In yet another embodiment of the present invention, the hydrocracking step is carried out at a conversion level that gives combined yield of CUT 1 and CUT 2 of above of about at least 30 wt %.
[0053] In yet another embodiment of the present invention, the CUT-2 is having monoaromatics and alkylated monoaromatics concentration more than 30 wt %.
[0054] In yet another embodiment of the present invention, the CUT-3 before oxidation step is having cetane number not more than 40. In one of the embodiment the CUT-3 before oxidation step is having cetane number in the range of 30 to 37.
[0055] In yet another embodiment of the present invention, the CUT-3 before oxidizing step is rich in a benzocycloparaffins and at least in the range of 10 to 30 wt % and in no case less than 10 wt %. In one of the embodiment benzocycloparaffins in the CUT-3 is more than 20 wt %. In another embodiment CUT-3 also includes paraffins, naphthenes, benzodicyclyparaffins, alkylaromatics, aromatics, diaromatics, triaromatics, etc. In one of the preferred embodiment benzocycloparaffins is naphtho-benzenes.
[0056] In yet another embodiment of the present invention, the CUT-3 stream is oxidized with oxidizing agent at a temperature in the range of 35 to 250.degree. C., pressure in the range of 1 to 50 barg and reaction time of oxidation in the range of 0.1 to 36 hrs.
[0057] In yet another embodiment of the present invention, the oxidizing agent is selected from organic, inorganic, molecular oxygen or oxygen containing gases, ozone or ozone containing gas and mixtures thereof.
[0058] In yet another embodiment of the present invention, the oxidation product of the CUT-3 is partially recycled to selective oxidation step during oxidation step to increase the yield & selectivity of oxidized compounds in product and ratio of recycle feed to feed is between 1 to 20 vol/vol.
[0059] In yet another embodiment of the present invention, the cetane improvement of the CUT-3 after selective oxidation is between 2 to 15 units more than that the CUT-3.
[0060] In yet another embodiment of the present invention, the selective oxidation step is carried out over a catalyst selected from mixture of metal oxide and salts of organometallic oxide.
[0061] In yet another embodiment of the present invention, the catalyst for selective oxidation step comprises: [0062] a. a metal oxide, the metal of which selected from Fe, Cr, Cu and Co or their mixture impregnated on inert support; [0063] b. organometallic catalyst comprises salts of metal phthalocyanines impregnated on inert support material and the metal of organometallic complex is selected from Co, Fe and Cr.
[0064] In yet another embodiment of the present invention, the salts of metal phthalocyanines are selected from nitride, nitrate, chloride, sulfide, sulfate, sulfonate, amide or mixtures thereof.
[0065] In yet another embodiment of the present invention, the support material of catalyst for selective oxidation step is selected from activated charcoal, silica, silica/alumina, alumina or a mixture thereof.
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