Process for converting naphtha to paraffins with a hydrocracking feed stream

Abstract

A process for converting petroleum naphtha is disclosed. The process includes contacting a naphtha stream with a catalyst and hydrogen to produce a light paraffin stream. The light paraffin stream is separated into an ethane stream and a propane stream. The ethane stream is thermally cracked to produce ethylene and a pyrolysis gasoline byproduct stream. The pyrolysis gasoline stream is hydrocracked to provide a cracked naphtha stream. The cracked naphtha stream can be contacted with a catalyst and hydrogen and the naphtha stream.

Description

[0001] Priority Statement

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 614,455, filed December 22, 2023, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This field relates to the conversion of naphtha into alkanes. In particular, this field can relate to the conversion of naphtha into pyrolyzed ethane. Background Technology

[0004] Light olefin production is crucial for producing enough plastics to meet global demand. Dehydrogenation is a process by which light alkanes such as ethane and propane are typically dehydrogenated, separately, in the presence of a catalyst, to produce ethylene and propylene. Dehydrogenation can be achieved in the presence of an oxidant such as oxygen or in the absence of an oxidant. Non-oxidative dehydrogenation is an endothermic reaction that requires external heat to drive the reaction. Propane dehydrogenation (PDH) is a widely practiced example of non-oxidative dehydrogenation from propane to propylene. Ethane oxidative dehydrogenation is a newer oxidative method for converting ethane to ethylene, which can be performed at lower temperatures with lower carbon oxide emissions compared to non-oxidative and thermal cracking methods.

[0005] Fluid catalytic cracking (FCC) is another endothermic method that can be fine-tuned to produce large quantities of propylene. However, not every FCC unit can be fine-tuned to produce large quantities of propylene. Moreover, high-propylene FCC units do not recover much ethylene; less than 1% of the global ethylene supply comes from FCC.

[0006] The large quantities of ethylene consumed in the production of plastics and petrochemicals such as polyethylene are produced through the thermal cracking of hydrocarbons. Steam is typically mixed with the feed stream into the cracker to reduce hydrocarbon partial pressure and increase olefin yield, as well as to reduce the formation and deposition of carbonaceous material in the cracking reactor. Therefore, this method is often referred to as steam cracking or pyrolysis.

[0007] Alkanes with a range of carbon numbers can be thermally cracked to produce olefins, including ethane, propane, butane, and naphtha. Ethane and naphtha feedstocks are typical because they yield higher yields of light olefins than propane and butane feedstocks. Ethane feedstocks are used in regions where light hydrocarbon gases are abundant. In regions with limited natural gas resources, naphtha feedstocks are used for steam cracking. Because of their higher production costs compared to ethane steam cracking, naphtha steam cracking has long determined the price of ethylene in the industry. Currently, the world does not produce enough ethane to meet the growing demand for ethylene. Therefore, regions with insufficient ethane supply, such as Asia and Europe, rely primarily on naphtha cracking to supply ethylene. Naphtha steam cracking produces only 30-35% ethylene; the remainder consists of relatively high-value byproducts including propylene, butadiene, and butene-1, and relatively low-value byproducts including pyrolysis oil (pyoil), pyrolysis gasoline (pygas), and fuel gas. Additional pressures on naphtha steam cracking (including minimum production requirements and environmental concerns) have led to government refusal to approve it in some regions, such as China. The ethylene industry needs a more efficient, economical, and environmentally friendly route to light olefins from naphtha feedstock. Summary of the Invention

[0008] A method for converting naphtha into alkanes is disclosed. The method includes contacting a naphtha feed stream with a catalyst and hydrogen to produce a light alkanes feed stream. The light alkanes feed stream can be separated into an ethane feed stream and a propane feed stream. The ethane feed stream is thermally cracked to produce ethylene, propylene, and a pyrolysis gasoline feed stream. The pyrolysis gasoline feed stream is hydrocracked to provide a cracked naphtha feed stream. The cracked naphtha feed stream can be converted together with the naphtha feed stream into ethane and propane feed streams. Appendix picture illustrate

[0009] Appendix picture This is a schematic diagram of a method for converting naphtha according to an exemplary embodiment of the present disclosure. picture .

[0010] definition

[0011] The term "connectivity" refers to the operative permission for fluid flow between enumerated components, which can be characterized as "fluid connectivity".

[0012] The term "downstream connectivity" means that in downstream connectivity, at least a portion of the fluid flowing toward the body can be operatively flowed from the object with which it is fluidly connected.

[0013] The term "upstream connectivity" means that at least a portion of the fluid flowing out of the main body can be operatively directed to an object in fluid communication with it.

[0014] The term "direct connection" means that fluid flow from an upstream component enters a downstream component without passing through any other intermediary container.

[0015] The term "indirect connection" refers to fluid flow from an upstream component entering a downstream component after passing through an intermediary container.

[0016] The term "bypass" means that an object is disconnected from the downstream entity at least within the scope of the bypass.

[0017] As used herein, the terms “major,” “dominant,” or “primary” mean greater than 50%, suitably greater than 75%, and preferably greater than 90%.

[0018] The term "Cx" should be understood as referring to a molecule having the number of carbon atoms indicated by the subscript "x". Similarly, the term "Cx-" refers to a molecule containing less than or equal to x, and preferably x and fewer carbon atoms. The term "Cx+" refers to a molecule having more than or equal to x, and preferably x and more carbon atoms.

[0019] The term "tower" refers to one or more distillation columns used to separate one or more components with different volatility. Unless otherwise specified, each column includes a condenser at the top of the column for condensing a portion of the overhead feed and returning it to the top of the column, and a reboiler at the bottom of the column for vaporizing a portion of the bottom feed and returning it to the bottom of the column. The feed to the column can be preheated. The top pressure is the pressure of the vapor at the top of the column at the vapor outlet. The bottom temperature is the liquid temperature at the bottom outlet. Top and bottom lines refer to the net lines from any downstream reflux or reboiler to the column. A stripping column may omit the reboiler at the bottom of the column, instead providing the heating requirements and separation power for a liquefied inert medium such as steam. Stripping columns typically feed from the top tray and remove the main product from the bottom.

[0020] As used herein, the term "separator" refers to a vessel having an inlet and at least one top vapor outlet and a bottom liquid outlet, and may also have an outlet for an aqueous feed stream from a boot. A flash tank is a type of separator that can be connected downstream to a separator capable of operating at higher pressures. Detailed Implementation

[0021] In the proposed method, C3-C8+ hydrocarbon feedstock is first loaded into a naphtha-to-ethane and propane (NEP) unit to convert naphtha into the desired ethane and propane in the presence of hydrogen. The resulting ethane is then fed into an ethylene production unit, which provides an ethane-to-ethylene yield of over 75%. The resulting propane is fed into a propylene production unit, which provides a propane-to-propylene yield of over 85%. Methane byproducts from the NEP unit and the ethane and propane production units can be used as fuel, including fuel required for the operation of the ethylene and propylene production units at high temperatures. Unconverted or underconverted C4+ components at the reactor outlet can be recycled for further processing into ethane and propane. The NEP method converts liquid feedstocks into ethane and propane, which can significantly improve ethylene and propylene yields. Compared to conventional methods, the NEP method also reduces the proportion of carbon dioxide produced for each petrochemical product. The disclosed NEP method maximizes ethylene and propylene production in combined units including NEP units.

[0022] Go to Appendix picture An embodiment of a method 101 for converting naphtha is disclosed. In one embodiment, method 101 includes a NEP reactor 120, an NEP separation unit 130, an ethane conversion unit 140, and a propane conversion unit 150. Method 101 also includes a hydrocracking unit 110. The naphtha feed stream in line 111 may be combined with the hydrogen feed stream in line 131 to provide the feed stream in line 112. The feed stream in line 112 may be fed into the NEP reactor 120 to contact the NEP catalyst. As described in detail below, the naphtha feed stream in line 111 may be taken from the hydrocracking unit 110. The naphtha feed stream may contain C3 to C8+ hydrocarbons, possibly C3 to C7 hydrocarbons, preferably having a T10 between -10°C and 60°C and a T90 between 70°C and 180°C. In an exemplary embodiment, the naphtha feed stream in line 111 may contain C4 to C7 hydrocarbons. Naphtha feed streams may contain n-chain alkanes, iso-chain alkanes, alkenes, cycloalkanes, and aromatic compounds.

[0023] In one aspect, the naphtha feed stream in line 111 can be heated before being fed into NEP reactor 111. In one embodiment, the naphtha feed stream can be heated to a reaction temperature of 300°C to 600°C, suitably between 325°C and 550°C, and preferably between 350°C and 525°C. Generally, the weight hourly space velocity (WHSV) defined herein as the ratio of the hourly mass flow rate of the feed in line 111 to the total mass of the catalyst in NEP reactor 120 should be at least 0.3 hr. -1 Up to 20 hours -1 Between, appropriately within 0.5hr -1 With 10hr -1 Between, and preferably within 1 hour-1 With 4hr -1 The total pressure should be between 0.1 MPa and 3 MPa (absolute pressure), preferably greater than 1 MPa (absolute pressure). Under these conditions, the C2-C3 yield always exceeds 80% by weight, while the methane yield is less than 16% by weight, suitably less than 14% by weight, and typically less than 12% by weight, and preferably not more than 10% by weight.

[0024] The molar ratio of hydrogen to hydrocarbons is important for the production of ethane and propane. The hydrogen-to-hydrocarbon ratio should be from 0.3 to 15, and preferably from 0.5 to 5. In another embodiment, the molar ratio of hydrogen to hydrocarbons typically does not exceed 5, suitably does not exceed 3, and preferably does not exceed 2. A low hydrogen-to-hydrocarbon ratio promotes the desired reaction kinetics initiated by dehydrogenation. The hydrogen-to-hydrocarbon ratio can be in the range of 50% to 500% of the stoichiometric requirements for converting naphtha molecules to ethane and / or propane, suitably not exceeding 300%, and preferably not exceeding 200%.

[0025] NEP catalysts used to convert naphtha to ethane and propane may contain molecular sieves, including macroporous or mesoporous molecular sieves, that is, 10-membered or 12-membered rings, respectively. Examples of suitable molecular sieves include MFI, MEL, MFI / MEL commensal, MTW, TUN, UZM-39, IMF, UZM-44, UZM-54, MWW, UZM-37, UZM-8, and UZM-8HS. Other suitable molecular sieves include FER, AHT, AEL (SAPO-11), AFO (SAPO-41), MRE, MFS, EUO-1, TON (ZSM-22), MTT (ZSM-23), and UZM-53. Additional molecular sieves with larger pores include FAU, EMT, FAU / EMT commensal, UZM-14, MOR, BEA, UZM-50, MTW, and ZSM-12. Additional examples include MSE and UZM-35.

[0026] MFI is a suitable NEP catalyst. It should be understood that ZSM-5 is an aluminosilicate zeolite of the MFI type belonging to the pentasilicate zeolite family, and possesses Na... n A1 n Si 96 -nO 192· The chemical formula of 16H2O (0 < n < 10). In various embodiments, the ZSM-5 zeolite can have a silica / alumina molar ratio of 20 to 1000, 20 to 800, 20 to 600, 20 to 400, 20 to 200, or 20 to 80. In various embodiments, the ZSM-5 zeolite can have a crystal size in the range of 10 nm to 600 nm, 20 nm to 500 nm, 30 nm to 450 nm, 40 nm to 400 nm, or 50 nm to 300 nm.

[0027] The NEP catalyst can include a bound zeolite. The binder can include oxides of aluminum, silicon, zinc, titanium, zirconium, and mixtures thereof. The binder can include phosphates in the binder or phosphates of the foregoing oxide binder materials. Preferably, the binder is silica. The MFI zeolite can be loaded in a silica-containing binder or an alumina-containing binder (such as aluminum phosphate).

[0028] The MFI zeolite slurry can first be mixed with a binder in the form of a colloidal suspension (sol) and a gelling agent, and then dropped into hot oil to form controlled spheres to produce a calcined support with a diameter of 1 / 8 inch to 1 / 32 inch. Alternatively, the zeolite can be mixed with a silica-containing binder and extruded into an extrudate with a diameter of 1 / 32 to 1 / 4 inch. The extrudate can be washed with ammonia to remove sodium ions from the zeolite, dried, and calcined to remove the organic structure-directing agent (OSDA) from the synthesized zeolite. Optionally, the calcined support can be subjected to ammonium ion exchange using an ammonium nitrate solution to remove residual sodium ions and dried at 110 °C.

[0029] The NEP catalyst includes a metal on the catalyst. The metal can include transition metals. In another example, the metal can include platinum, palladium, iridium, rhenium, ruthenium, and mixtures thereof. The metal can be a noble metal. A modifier metal can also be included on the catalyst. The modifier metal can include tin, germanium, gallium, indium, thallium, zinc, silver, and mixtures thereof. The modifier metal should be more concentrated on the binder than on the zeolite. Each of 0.01 wt% to 5 wt% of the transition metal and the modifier metal can be on the catalyst.

[0030] The metal can be incorporated into the binder by evaporation impregnation. A platinum solution (such as tetraamine platinic nitrate or chloroplatinic acid) can be contacted with the bound spherical or extruded support that has been calcined and ion-exchanged in a rotary evaporator, followed by drying and oxidation.

[0031] The NEP catalyst contains metal on a bonded spherical or extruded support. Preferably, the metal on the binder is greater than the metal on the zeolite. At least 60% by weight, suitably at least 70% by weight, preferably at least 80% by weight, and most preferably at least 90% by weight of metal are on the binder. The zeolite and / or the entire NEP catalyst is steam-oxidized to remove the metal from the zeolite. Steaming is preferably carried out after the metal is added to the catalyst. The dried, impregnated spherical or extruded support can be steam-oxidized in air for a sufficient time to provide the NEP catalyst. Steam oxidation in air at a temperature of 500°C to 650°C and 5 mol% to 30 mol% of steam for 1 to 3 hours may be suitable.

[0032] NEP catalysts must be reduced to activate them for catalyzing the NEP reaction. For example, the catalyst can be reduced in a stream of hydrogen at 500°C to 550°C for 3 hours before contact with the feed.

[0033] Following alkane conversion, a light alkane feed stream is discharged from NEP reactor 120 into effluent line 122. The light alkane feed stream may contain at least 40% by weight ethane or at least 40% by weight propane, or at least 70% by weight, and preferably at least 80% by weight, ethane and propane. The ethane to propane ratio may be in the range of 0.1 to 5. The light alkane feed stream may contain less than 16% by weight, suitably less than 14% by weight, suitably less than 12% by weight, and more preferably less than 10% by weight methane.

[0034] The light alkane stream can be cooled and fed into NEP separation unit 130. NEP separation unit 130 can be a fractionating column or a series of fractionating columns and other separation units that separate the light alkane stream in line 122 into a hydrogen stream in line 131, an ethane stream (primarily ethane) in line 132, a propane stream (primarily propane) in line 133, and a heavy aromatics stream in line 134. NEP separation unit 130 may include a demethanizer that separates the light alkane stream into a gas stream in the top line and a C2+ alkane stream in the bottom line. The gas stream can be sent to a hydrogen purification unit, such as a PSA unit, to recover hydrogen from line 131 for recirculation back to NEP reactor 120 in recirculation line 131. Residual methane from the hydrogen purification unit can be used as fuel gas. The C2+ alkane stream can then be fed into a deethanizer to generate an ethane stream in the deethanizer top line 132 and a C3+ alkane stream in the deethanizer bottom line. The C3+ alkane stream can then be fed into a depropanizer to generate a propane stream in the depropanizer top line 133, and to generate a heavy alkane stream that may contain C4+ hydrocarbons. The NEP separation unit 130 may be in other forms.

[0035] For example, the NEP separation unit 130 may omit the demethanizer, and the light alkane stream in line 122 may be fed to a deethanizer, which generates a C2 stream in the top line of the deethanizer. The C2 stream can be separated in a hydrogen purification unit to recover the hydrogen stream in line 131, while residual ethane and methane from the hydrogen purification unit may include or supplement the ethane stream in line 132. The hydrogen purification unit may include a membrane unit, and the hydrogen recovered from the membrane unit may be further purified in an absorber and then recycled back to the NEP reactor 120 in line 131. In an additional alternative, the C2 stream from the deethanizer may be fed into an ethylene production unit 140, where ethane is converted to ethylene, but methane and hydrogen are inertly passed through for recovery in a downstream ethylene recovery unit.

[0036] The ethane feedstream in line 132 can be fed into ethylene production unit 140, where the ethane in the ethane feedstream is converted into ethylene. In an embodiment, ethylene production unit 140 is a steam cracking unit. The ethane feedstream in line 132 can be cracked under steam in a furnace to produce a cracked feedstream comprising ethylene feedstream 142. The ethane feedstream can be fed into the ethane steam cracking unit in the gas phase. The ethane steam cracking unit can preferably be operated at a temperature of 750°C (1382°F) to 950°C (1742°F). The cracked feedstream leaving the furnace of the ethane steam cracking unit can be in a superheated state. One or more quench towers or other devices known in the art, but preferably oil quench towers and / or water quench towers, can be used to quench or separate the cracked feedstream into multiple cracked feedstreams. The ethane steam cracking unit may also include additional distillation columns, amine scrubbing columns, compressors, expanders, etc., to separate the cracked feed stream into a cracked feed stream rich in individual light olefins, the main component of which is the ethylene feed stream in line 142. Based on the ethane feed stream in line 132, the ethylene feed stream may have an ethylene yield of at least 75% by weight, preferably at least 80% by weight. Among the other components in the cracked feed stream leaving the ethane steam cracker, the ethylene production unit 140 may contain hydrogen, methane, propylene, butene, and pyrolysis gases. Each of these components can be recovered and further processed.

[0037] The ethylene and propylene feed streams from ethylene production unit 140 can be recovered or transported to a polymerization unit, chemical plant, or exported. Based on the ethane feed stream in line 132, product recovery of at least 50% by weight, typically at least 60% by weight, and suitably at least 70% by weight, of valuable ethylene, propylene, and butene products can be achieved from ethane steam cracking unit 140.

[0038] Steam cracking can also produce fewer valuable byproducts, such as pyrolysis gasoline (cracked gas) and fuel oil (cracked oil). Pyrolysis gasoline contains a significant amount of alkanes and aromatic compounds. The resulting alkanes include recoverable or further processed n-alkanes and non-n-alkanes. Aromatic compounds are very stable and difficult to crack in a steam cracker. This method involves recycling the pyrolysis gasoline stream to recover alkanes to improve the yield of the method.

[0039] According to this disclosure, a pyrolysis gasoline feed stream from an ethylene production unit 140 is separated in pipeline 143. In one exemplary embodiment, the pyrolysis gasoline feed stream in pipeline 143 may be hydrocracking to provide a naphtha feed stream.

[0040] The propane feedstream in pipeline 133 can be fed into propylene production unit 150, where the propane in the feedstream is converted into propylene. Propylene production unit 150 can be a propane dehydrogenation (PDH) unit. A PDH catalyst is used in the dehydrogenation reaction process to catalyze the dehydrogenation of propane. Conditions in the dehydrogenation reactor may include a temperature of 500°C to 800°C, a pressure of 40 kPa to 310 kPa (absolute pressure), and a catalyst-to-oil ratio of 5 to 100.

[0041] The dehydrogenation reaction can be carried out in a fluidized manner, where a gas containing reactant alkanes, with or without a fluidized inert gas, is distributed to the reactor in a manner that elevates the dehydrogenation catalyst while simultaneously catalyzing the dehydrogenation of the alkanes. During the catalytic dehydrogenation reaction, coke deposits on the dehydrogenation catalyst, resulting in a decrease in catalyst activity. The dehydrogenation catalyst must then be regenerated in a regenerator. The regenerator combusts the coke from the dehydrogenation catalyst and fuel gas to ensure sufficient enthalpy in the dehydrogenation reactor to promote the endothermic reaction.

[0042] The selected dehydrogenation catalyst should minimize cracking and favor dehydrogenation. Catalysts suitable for this study include active metals that can be dispersed in porous inorganic support materials such as silica, alumina, aluminosilicate, zirconium oxide, or clay. Exemplary embodiments of the catalyst include alumina or silica-alumina containing gallium, noble metals, and alkali or alkaline earth metals.

[0043] The catalyst support comprises a support material, a binder, and optional filler materials to provide physical strength and integrity. The support material may include alumina or silica-alumina. Silica sol or alumina sol may be used as a binder. The alumina or silica-alumina typically comprises alumina with γ, θ, and / or δ phases. The nominal diameter of the catalyst support particles can be from 400 micrometers to 5000 micrometers, with an average diameter of 600 micrometers to 3500 micrometers. Preferably, the surface area of ​​the catalyst support is from 85 m² / g to 140 m² / g.

[0044] Fluidized dehydrogenation catalysts may include a dehydrogenating metal on a support. The dehydrogenating metal may be one or a combination of transition metals. Noble metals may be preferred dehydrogenating metals, such as platinum or palladium. Gallium is an effective metal for the dehydrogenation of alkanes. The metal may be deposited on the catalyst support by impregnation or other suitable methods, or included in the support material or binder during catalyst preparation.

[0045] The acid functionality of the catalyst should be minimized to prevent cracking and facilitate dehydrogenation. Alkali metals and alkaline earth metals can also be included in the catalyst to reduce its acidity. Rare earth metals can be included in the catalyst to control its activity. Metals can be incorporated into the dehydrogenation catalyst at concentrations from 0.001 wt% to 10 wt%. In the case of noble metals, it is preferable to use noble metals at concentrations from 10 parts per million (ppm) to 600 ppm by weight. More preferably, it is preferable to use noble metals at concentrations from 10 ppm to 100 ppm by weight. Platinum is a preferred noble metal. Gallium should be present in the range of 0.3 wt% to 3 wt%, preferably 0.5 wt% to 2 wt%. Alkali metals and alkaline earth metals can be present in the range of 0.05 wt% to 1 wt%.

[0046] The regenerated catalyst can be contacted with the propane feed stream in line 133, and perhaps with a fluidizing gas, to elevate the propane feed stream and dehydrogenation catalyst into the riser during dehydrogenation. Above the riser, spent dehydrogenation catalyst and propylene products can be separated by a centrifugal separator. The propylene product gas can be quenched with a cooling fluid to prevent over-reaction and the generation of undesirable byproducts. Separating propylene products from the PDH effluent stream in line 152 may include quenching contact and fractionation to produce a propylene product feed stream. Unreacted propane can be recycled to the dehydrogenation reactor, and light gases can be recycled as fuel gas to the regenerator for combustion, thereby providing enthalpy for the reaction.

[0047] Propylene production units may also employ catalytic moving bed reactors. The reactor section may comprise several radially flowing reactors in parallel or series, heated by a charge and interstage heaters. Propane feed, possibly with added hydrogen, flows from a screened central tube through an annular dehydrogenation catalyst bed to an outer effluent ring in each dehydrogenation reactor. The flow may be reversed. The dehydrogenation catalyst may comprise noble metals and mixtures thereof, modifiers selected from the group consisting of alkali metals or alkaline earth metals and combinations thereof, components selected from the group consisting of tin, germanium, lead, indium, gallium, thallium and combinations thereof, and porous supports forming catalyst particles. The catalyst support may comprise oil-droplet alumina spheres.

[0048] Dehydrogenation conditions may include temperatures ranging from 400°C to 900°C, pressures from 0.01 atm to 10 atm, and liquid hourly space velocities (LHSVs) from 0.1 hr⁻¹ to 100 hr⁻¹. The pressure in the dehydrogenation reactor should be maintained at the lowest feasible level, consistent with equipment limitations, to maximize the chemical equilibrium advantage. Waste dehydrogenation catalyst in the annular catalyst bed can be removed from the bottom of the bed and transferred to a regenerator for combustion of coke from the catalyst in air at 450°C to 600°C. Noble metals on the catalyst can be redispersed, dried, and returned to the top of the dehydrogenation catalyst bed as regenerated dehydrogenation catalyst via oxyhalogenation.

[0049] The dehydrogenated effluent from propylene production unit 40 is cooled, compressed, and dried, and hydrogen is cryogenically separated from the hydrocarbons, with a net gas purity of 85 mol% to 93 mol%. The hydrocarbon liquid is selectively hydrogenated to convert dienes and acetylene, and the hydrocarbon liquid is fractionated in a deethanerization tower to remove ethane, and propylene is separated from propane in a propane-propylene separation tower to provide polymer-grade propylene. Propane can be recycled as feed to propylene production unit 150.

[0050] The heavy feed stream from NEP separation unit 130 may be taken from the bottom of the propane stripper in line 134. In one aspect, the heavy feed stream in line 134 may contain more than 98% aromatic compounds. According to this disclosure, the heavy feed stream in line 134 may be hydrocracking to provide a naphtha feed stream.

[0051] In one embodiment, the pyrolysis gasoline feed stream in line 143 and the heavy feed stream in line 134 are fed into the hydrocracking reactor of the hydrocracking unit 110. The hydrocracking hydrogen feed stream in line 102 is also fed into the hydrocracking reactor. In one aspect, the hydrocracking hydrogen feed stream in line 102 may be taken from the hydrogen feed stream in line 131. The pyrolysis gasoline feed stream in line 143 and the heavy feed stream in line 134 are fed into a location in the lower half of the hydrocracking reactor. In one embodiment, the pyrolysis gasoline feed stream in line 143 is fed into a location in the lower half of the hydrocracking reactor above the heavy feed stream in line 134.

[0052] In hydrocracking unit 110, the pyrolysis gasoline feed stream in line 143 and the heavy feed stream in line 134 are cracked in the presence of hydrogen into lower molecular weight hydrocarbons comprising a hydrocracking product stream. Another feed stream in line 116 may also be fed into hydrocracking unit 110. Hydrocracking unit 110 may include one or more fixed-bed reactors comprising one or more vessels, single or multiple catalyst beds in each vessel, and various combinations of hydrotreatment catalysts and / or hydrocracking catalysts in one or more vessels. If hydrocracking unit 110 does not include a hydrotreatment reactor, the catalyst bed in the hydrocracking reactor may include a hydrotreatment catalyst for saturating, demetallizing, desulfurizing, or denitrogenating the hydrocarbon feed stream before hydrocracking with a hydrocracking catalyst in a subsequent vessel or a catalyst bed in the hydrocracking unit. The hydrocracking product stream in line 111 is taken from hydrocracking unit 110.

[0053] Hydrocracking catalysts can utilize amorphous silica-alumina or crystalline zeolite cracking substrates, on which Group VIII metal hydride components are deposited. Additional hydride components can be selected from Group VIB to combine with the amorphous silica-alumina or zeolite substrate.

[0054] Zeolite cracking substrates, sometimes referred to in the art as molecular sieves, are typically composed of silica, alumina, and one or more exchangeable cations, such as sodium, magnesium, calcium, and rare earth metals. They are also characterized by relatively uniform pore sizes with diameters between 4 and 14 angstroms. Zeolites with relatively high silica / alumina molar ratios (between 3 and 12) are preferred. Suitable zeolites found in nature include, for example, mordenite, zeolite, flaky zeolite, magnesia-alkali zeolite, cycloid zeolite, chalcogenide, bufosite, and octahedral zeolite. Suitable synthetic zeolites include, for example, B, X, Y, and L crystal types, such as synthetic octahedral zeolite and mordenite. Preferred zeolites are those with pore sizes between 8 and 12 angstroms, where the silica / alumina molar ratio is 4 to 6. An example of a zeolite falling into the preferred group is synthetic Y molecular sieve.

[0055] Naturally occurring zeolites are typically found in sodium, alkaline earth metal, or mixed forms. Synthetic zeolites are almost always prepared in sodium form. In any case, for use as a cracking matrix, it is preferable that most or all of the original zeolite monovalent metals are ion-exchanged with polyvalent metals and / or with ammonium salts, followed by heating to decompose the ammonium ions associated with the zeolite, thereby leaving hydrogen ions and / or exchange sites at their locations, effectively removing cations through further water removal. This property of hydrogen, or "cation-removed" Y zeolite, is described more specifically in US 3,100,006.

[0056] By means of a method, the hydrocracking conditions in the hydrocracking unit 110 may include a temperature of 290°C (550°F) to 468°C (875°F), preferably 343°C (650°F) to 445°C (833°F), a pressure of 4.8 MPa (gauge pressure) (700 psig) to 20.7 MPa (gauge pressure) (3000 psig), and a 0.4 hr -1 to less than 2.5hr 1 The liquid hourly space velocity (LHSV) and 421 Nm 3 / m 3 (2,500 scf / bbl) to 2,527 Nm 3 / m 3 Hydrogen rate in oil (15,000 scf / bbl).

[0057] According to this disclosure, the hydrocracking product stream taken from line 111 is a cracked naphtha stream. The cracked naphtha stream in the line is passed to NEP reactor 120. In one exemplary embodiment, the hydrocracking product stream in line 111 comprises light naphtha having C4 to C7 hydrocarbons. The hydrocracking product stream in line 111 is combined with the hydrogen stream in line 131 to provide the feed stream in line 112. The feed stream in line 112 is fed into NEP reactor 120 and processed as previously described.

[0058] The aforementioned disclosure provides a method for converting naphtha, and this method maximizes the yield.

[0059] Example

[0060] Arab Light crude oil was used as the feedstock for the disclosed method. A comparison was made between a method that recycles the pyrolysis gasoline feedstock to hydrocracking and a method that outputs the pyrolysis gasoline feedstock. The results are listed in the table below:

[0061] surface

[0062]

[0063] The table clearly shows that for the pyrolysis gasoline output method, 4752 kTMA of Arab light feedstock yields 3758 kTMA of light olefins (2200 kTMA ethylene + 1558 kTMA propylene) with a yield of 79.1%. For the method of recycling pyrolysis gasoline back to the hydrocracking unit, the same 4752 kTMA of crude oil yields 3813 kTMA of light olefins (2200 kTMA ethylene + 1613 kTMA propylene) with a yield of 80.2%. No pyrolysis gasoline is output in the recycling method. Therefore, by recycling pyrolysis gasoline (cracked gas) from the ethane steam cracking unit back to the hydrocracking unit, the production of light olefins (ethylene + propylene) is increased.

[0064] Specific implementation plan

[0065] While the following description is presented in conjunction with specific embodiments, it should be understood that the description is intended to be illustrative and not to limit the scope of the foregoing description and the appended claims.

[0066] A first embodiment of this disclosure is a method for converting naphtha, the method comprising: contacting a naphtha feed stream with a catalyst and hydrogen to produce a light alkane feed stream; separating the light alkane feed stream into an ethane feed stream and a propane feed stream; thermally cracking the ethane feed stream to produce a pyrolysis gasoline feed stream; and hydrocracking the pyrolysis gasoline feed stream to provide a cracked naphtha feed stream. An embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, the embodiment further comprising producing an ethylene feed stream by cracking the ethane feed stream. An embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, the embodiment further comprising: separating the light alkane feed stream into an aromatic compound feed stream and hydrocracking the aromatic compound feed stream to provide a cracked naphtha feed stream. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein a pyrolysis gasoline feed stream and an aromatic compound feed stream are hydrocracking in a hydrocracking reactor to produce a cracked naphtha feed stream. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the naphtha feed stream comprises light naphtha having C4 to C7 hydrocarbons. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the step of thermally cracking the ethane feed stream includes charging the ethane feed stream into a steam cracking unit and converting the ethane in the ethane feed stream into ethylene. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the hydrocracking step includes contacting the pyrolysis gasoline feed stream with a hydrocracking catalyst comprising amorphous silica-alumina or crystalline zeolite and a metal hydride component. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, and this embodiment further includes: contacting the cracked naphtha feed stream and the naphtha feed stream with a catalyst and hydrogen to produce a light alkane feed stream. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, and this embodiment further includes: converting propane in the propane feed stream to propylene and charging the propane feed stream into a dehydrogenation unit. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, and this embodiment further includes: hydrocracking a feedstock containing a pyrolysis gasoline feed stream in a hydrocracking reactor to provide a cracked naphtha feed stream.One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, and the embodiment further includes: separating the light alkane stream into a hydrogen stream and recycling the hydrogen stream back to the contact step.

[0067] A second embodiment of this disclosure is a method for converting naphtha, the method comprising: contacting a naphtha feed stream with a catalyst and hydrogen to produce a light alkane feed stream; separating the light alkane feed stream into an ethane feed stream and a propane feed stream; converting ethane in the ethane feed stream into ethylene and a pyrolysis gasoline feed stream; and hydrocracking the feedstock containing the pyrolysis gasoline feed stream in a hydrocracking reactor to provide a cracked naphtha feed stream. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the second embodiment described in this paragraph, further comprising: separating the light alkane feed stream into an aromatic compound feed stream and hydrocracking the aromatic compound feed stream in a hydrocracking reactor to provide a cracked naphtha feed stream. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the second embodiment described in this paragraph, wherein the pyrolysis gasoline feed stream and the aromatic compound feed stream are hydrocracking in a hydrocracking reactor to produce a cracked naphtha feed stream. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding to the second embodiments of this paragraph, wherein the conversion step includes: charging an ethane feed stream into a steam cracking unit. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding to the second embodiments of this paragraph, further comprising: contacting the cracked naphtha feed stream and the naphtha feed stream with a catalyst and hydrogen to produce a light alkane feed stream. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding to the second embodiments of this paragraph, wherein the naphtha feed stream comprises light naphtha having C4 to C8 hydrocarbons.

[0068] A third embodiment of this disclosure is a method for converting naphtha, the method comprising: contacting a naphtha feed stream with a catalyst and hydrogen to produce a light alkane feed stream; separating the light alkane feed stream into an ethane feed stream, a propane feed stream, and an aromatic compound feed stream; converting ethane in the ethane feed stream into an ethylene feed stream; and hydrocracking the aromatic compound feed stream to provide a cracked naphtha feed stream. An embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the third embodiment in this paragraph, further comprising: thermally cracking the ethane feed stream to produce a pyrolysis gasoline feed stream and hydrocracking the pyrolysis gasoline feed stream to provide a cracked naphtha feed stream. An embodiment of this disclosure is one, any, or all of the embodiments described in the preceding embodiments to the third embodiment in this paragraph, further comprising: contacting the aromatic compound feed stream and the pyrolysis gasoline feed stream with a hydrocracking catalyst in a hydrocracking reactor to produce a cracked naphtha feed stream. One embodiment of this disclosure is one, any, or all of the embodiments described in the preceding to the third embodiments of this paragraph, and the embodiment further includes contacting the cracked naphtha feed stream and the naphtha feed stream with a catalyst and hydrogen to produce a light alkane feed stream.

[0069] Although no further detailed description has been provided, it is believed that those skilled in the art can make full use of this disclosure by employing the foregoing description and can readily determine the essential characteristics of this disclosure without departing from the spirit and scope of the invention, and can make various changes and modifications to this disclosure to suit various uses and conditions. Therefore, the foregoing preferred specific embodiments should be understood as illustrative only and not as limiting the remainder of this disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0070] In the foregoing, all temperatures are expressed in degrees Celsius, and all portions and percentages are by weight unless otherwise specified.

Claims

1. A method for converting naphtha, the method comprising: Naphtha feed stream is contacted with catalyst and hydrogen to produce light alkane feed stream; The light alkane stream is separated into an ethane stream and a propane stream; The ethane feed stream is thermally cracked to produce a pyrolytic gasoline feed stream; as well as The pyrolysis gasoline feed stream is hydrocracking to provide a cracked naphtha feed stream.

2. The method according to claim 1, further comprising generating an ethylene stream by cracking the ethane stream.

3. The method according to claim 1, further comprising separating the light alkane feed stream into an aromatic compound feed stream and hydrocracking the aromatic compound feed stream to provide the cracked naphtha feed stream.

4. The method according to claim 3, wherein the pyrolysis gasoline feed stream and the aromatic compound feed stream are hydrocracking in a hydrocracking reactor to produce the cracked naphtha feed stream.

5. The method of claim 1, wherein the naphtha stream comprises light naphtha having C4 to C7 hydrocarbons.

6. The method of claim 1, wherein the step of thermally cracking the ethane feed stream comprises loading the ethane feed stream into a steam cracking unit and converting the ethane in the ethane feed stream into ethylene.

7. The method of claim 1, wherein the hydrocracking step comprises contacting the pyrolysis gasoline feed stream with a hydrocracking catalyst comprising amorphous silica-alumina or crystalline zeolite and a metal hydride component.

8. The method according to claim 1, further comprising contacting the cracked naphtha stream and the naphtha stream with the catalyst and hydrogen to produce the light alkane stream.

9. The method according to claim 8, further comprising converting propane in the propane stream into propylene and loading the propane stream into a dehydrogenation unit.

10. The method of claim 1, further comprising hydrocracking the feedstock containing the pyrolysis gasoline feed stream in a hydrocracking reactor to provide the cracked naphtha feed stream.

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