Treatment of paraffin naphtha with modified USY zeolite dehydrogenation catalyst

Abstract

The method for processing paraffin naphtha includes contacting a paraffin naphtha feedstock with a catalyst system in a dehydrogenation reactor. The catalyst system includes a framework-substituted ultrastable Y (USY) type zeolite to produce a dehydrogenated product stream. The catalyst system includes a framework-substituted ultrastable Y (USY) type zeolite. The framework-substituted USY type zeolite has a modified USY framework. The modified USY framework includes a USY aluminosilicate framework modified by replacing a portion of the framework aluminum atoms of the USY aluminosilicate framework with a substitution atom, the substitution atom being independently selected from titanium atoms, zirconium atoms, hafnium atoms and combinations thereof. A dehydrogenation catalyst for dehydrogenating paraffin naphtha includes the framework-substituted ultrastable Y (USY) type zeolite.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application serial number 16 / 936,987, filed on July 23, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to processes for upgrading paraffinic naphtha streams and, more particularly, to the dehydrogenation of paraffinic naphtha in the presence of a zeolite catalyst system. Background Art

[0004] Light naphtha is a product of an oil refinery or gas plant containing mainly paraffins having five or six carbon atoms. Converting light naphtha into value-added gasoline blending components has always been a challenge. In conventional refineries, light naphtha is isomerized to produce isomerized products, i.e., gasoline blending components having acceptable octane numbers and high vapor pressures. In petrochemical complexes, light naphtha is steam cracked under severe conditions to produce olefins, such as ethylene, propylene, and butenes. Olefins such as ethylene, propylene, and butenes have higher value than the C5 and C6 hydrocarbons of light naphtha because they are building blocks for other valuable hydrocarbons.

[0005] The inertness of the carbon-carbon and carbon-hydrogen bonds in the hydrocarbon components of light naphtha leads to unfavorable thermodynamics, requires elevated processing temperatures, low selectivity and yield, and high costs for commercial applications. Refiners continue to process larger amounts of light feedstocks, such as shale oil and condensates. In addition, the ever-increasing global gasoline demand can benefit from products derived from light naphtha. Therefore, there is a need for a cost-effective method of converting light naphtha into hydrocarbons suitable as a gasoline blending component or as a structural unit for other valuable hydrocarbons. Summary of the invention

[0006] Exemplary embodiments of the present disclosure relate to a dehydrogenation catalyst for dehydrogenating paraffin naphtha. The dehydrogenation catalyst comprises a framework-substituted ultrastable Y (USY) type zeolite. The framework-substituted USY type zeolite has a modified USY framework. The modified USY framework comprises a USY aluminosilicate framework modified by replacing a portion of the framework aluminum atoms of the USY aluminosilicate framework with a substitution atom, the substitution atom being independently selected from a titanium atom, a zirconium atom, a hafnium atom, and a combination thereof.

[0007] Additional embodiments of the present disclosure relate to methods for processing or dehydrogenating paraffin naphtha. The method comprises contacting a paraffin naphtha feedstock with a catalyst system in a dehydrogenation reactor. The catalyst system comprises a framework-substituted ultrastable Y (USY) type zeolite to produce a dehydrogenated product stream. The framework-substituted USY type zeolite has a modified USY framework. The modified USY framework comprises a USY aluminosilicate framework modified by replacing a portion of the framework aluminum atoms of the USY aluminosilicate framework with a substitution atom, the substitution atom being independently selected from a titanium atom, a zirconium atom, a hafnium atom, and a combination thereof.

[0008] Additional features and advantages of the embodiments of the present disclosure will be set forth in the following detailed description, and in part will be apparent to those skilled in the art from the description, or recognized by practicing the embodiments described herein (including the following detailed description and claims). It should be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and characteristics of the subject matter claimed. DETAILED DESCRIPTION

[0009] Embodiments of the present disclosure include dehydrogenation catalysts and the use of dehydrogenation catalysts for dehydrogenating paraffin naphtha, thereby forming a dehydrogenated product stream, wherein a portion of the paraffin naphtha has been at least partially dehydrogenated. The dehydrogenation catalyst according to an embodiment includes a framework-substituted ultrastable Y (USY) type zeolite having a modified USY framework. The modified USY framework is a USY aluminosilicate framework modified by replacing a portion of the framework aluminum atoms of the USY aluminosilicate framework with a substituting atom. In an embodiment, the substituting atom is independently selected from a titanium atom, a zirconium atom, a hafnium atom, and a combination thereof.

[0010] Reference will now be made in detail to an embodiment of a method of processing a paraffinic naphtha to produce a dehydrogenated product stream, wherein at least a portion of the paraffinic naphtha has been at least partially dehydrogenated.

[0011] According to an embodiment, a method for processing paraffinic naphtha includes contacting a paraffinic naphtha feedstock with a catalyst system in a dehydrogenation reactor to produce a dehydrogenated product stream. The catalyst system includes a framework-substituted ultrastable Y (USY) type zeolite having a modified USY framework. According to the standard definition of a USY aluminosilicate framework, the modified USY framework is an analog of a USY aluminosilicate framework. According to the standard definition, a USY aluminosilicate framework is a lattice constant (UD) of 2.430 nm or more and 2.450 nm or less, a lattice constant (UD) of 600 nm or less, and a lattice constant (UD) of 600 nm or less. 2 / g-900m 2The framework of the aluminosilicate zeolite has a specific surface area of ​​1000 μm / g and a silicon to aluminum molar ratio of 20-100 (calculated based on silicon dioxide (SiO2) and aluminum oxide (Al2O3)).

[0012] Regarding the framework-substituted USY-type zeolite according to an embodiment of the present disclosure, the modified USY framework is a USY aluminosilicate framework modified by replacing a portion of the framework aluminum atoms of the USY aluminosilicate framework with a substituent atom. In an embodiment, the substituent atom is independently selected from titanium atoms, zirconium atoms, hafnium atoms and combinations thereof.

[0013] As used in the present disclosure, the term "Ti-USY" refers to a framework-substituted USY-type zeolite according to an embodiment, wherein the substituting atom is titanium. Similarly, the term "Zr-USY" refers to a framework-substituted USY-type zeolite according to an embodiment, wherein the substituting atom includes zirconium. The term "Hf-USY" refers to a framework-substituted USY-type zeolite according to an embodiment, wherein the substituting atom includes hafnium. The term "(Ti,Zr)-USY" refers to a framework-substituted USY-type zeolite according to an embodiment, wherein the substituting atom includes titanium and zirconium. The term "(Ti,Hf)-USY" refers to a framework-substituted USY-type zeolite according to an embodiment, wherein the substituting atom includes titanium and hafnium. The term "(Zr,Hf)-USY" refers to a framework-substituted USY-type zeolite according to an embodiment, wherein the substituting atom includes zirconium and hafnium. The term "(Ti,Zr,Hf)-USY" refers to a framework-substituted USY-type zeolite according to an embodiment, wherein the substituting atoms include titanium, zirconium, and hafnium.

[0014] The catalyst system of the embodiments, including the framework-substituted USY-type zeolite and its preparation will now be described in more detail. The incorporation of the catalyst system in a process for processing paraffinic naphtha will then be described.

[0015] Catalysts with framework-substituted ultrastable Y (USY) zeolites

[0016] As previously described, in an embodiment of the method for processing paraffin naphtha, the catalyst system includes the framework-substituted USY-type zeolite having a USY aluminosilicate framework, wherein a portion of the framework aluminum atoms are replaced by titanium atoms, zirconium atoms, hafnium atoms, or any combination thereof. The framework-substituted USY-type zeolite may be Ti-USY, Zr-USY, Hf-USY, (Ti, Zr)-USY, (Ti, Hf)-USY, (Zr, Hf)-USY, or (Ti, Zr, Hf)-USY as previously defined. The substituted atoms replace the aluminum atoms that form the ultrastable Y-type zeolite framework, and are therefore used as components of the ultrastable Y-type zeolite framework. The substitution may be verified by analytical techniques, including but not limited to ultraviolet, visible and near-infrared spectrophotometry (UV-Vis-NIR), Fourier transform infrared spectroscopy (FT-IR), or nuclear magnetic resonance spectroscopy (NMR).

[0017] In some embodiments, based on the total mass of the framework-substituted USY zeolite, the framework-substituted USY zeolite includes 0.01 wt% to 5 wt%, or 0.1 wt% to 5 wt%, or 0.2 wt% to 4 wt%, or 0.3 wt% to 3 wt% of substituted atoms calculated on an oxide basis. In the calculation based on oxides, titanium atoms are calculated based on TiO2, zirconium atoms are calculated based on ZrO2, and hafnium atoms are calculated based on HfO2. Titanium, zirconium and hafnium in the framework-substituted USY zeolite can be quantitatively determined by known techniques, such as by X-ray fluorescence analysis, high-frequency plasma emission spectrometry or atomic absorption spectrometry.

[0018] In some embodiments, in addition to the substituted atoms substituted by the aluminum framework, the USY type zeolite substituted by the framework may also include zirconium atoms, titanium atoms, hafnium atoms or any combination thereof, which are connected to the framework of the USY type zeolite substituted by the framework, or are loaded on the framework of the USY type zeolite substituted by the framework, or are combined with the framework of the USY type zeolite substituted by the framework. In such an embodiment, zirconium, titanium or hafnium atoms can be connected as oxide particles (such as titanium dioxide particles, zirconium oxide particles or hafnium dioxide particles). The oxide particles may have a particle diameter of 50nm or less. For the purpose of quantitative analysis, as contemplated herein, based on oxide calculations and based on the total mass of the USY type zeolite substituted by the framework, the amount of the substituted atoms in the USY type zeolite substituted by the framework includes the total amount of titanium, zirconium and hafnium by mass, and titanium, zirconium and hafnium replace the framework aluminum atoms or are connected to the zeolite framework or are loaded on the outside of the zeolite framework or are combined with the zeolite framework. However, it is understood that in all embodiments, at least a portion of the framework aluminum atoms of the USY aluminosilicate framework are substituted by titanium atoms, zirconium atoms, hafnium atoms, or any combination thereof. In an exemplary embodiment, greater than 50%, or greater than 75%, or greater than 90%, or greater than 99% of the titanium, zirconium, and hafnium atoms present in the framework-substituted USY-type zeolite replace the framework aluminum atoms in the zeolite framework, and in particular as particles, not only connected to the zeolite framework, or loaded on the outside of the zeolite framework, or combined with the zeolite framework.

[0019] It will be appreciated by those skilled in the art that when the framework-substituted USY-type zeolite contains a combination of substitution atoms, such as in (Ti,Zr)-USY, (Ti,Hf)-USY, (Zr,Hf)-USY or (Ti,Zr,Hf)-USY, the mass ratio of each type of substitution atom in each zeolite (calculated on an oxide basis) is not limited. Although the reaction described in the method according to the embodiment can be adjusted by adjusting the ratio of titanium / zirconium / hafnium, it will be appreciated that any ratio of titanium / zirconium / hafnium can effectively carry out the method for processing paraffin naphtha according to the present disclosure.

[0020] In a specific non-limiting embodiment, based on the total mass of the framework-substituted USY-type zeolite, calculated on an oxide basis, the framework-substituted USY-type zeolite may include 0.01 wt% to 5 wt% of substituted atoms, and the framework-substituted USY-type zeolite is a (Ti, Zr)-USY zeolite, wherein the substituted atoms include titanium atoms and zirconium atoms.

[0021] According to an embodiment, the framework-substituted USY-type zeolite may exhibit a greater amount of acidity than a comparative unsubstituted USY-type zeolite having the same ratio of silica sites to alumina sites. It should be understood that the ratio of silica sites to alumina sites in the comparative unsubstituted USY-type zeolite is equal to the ratio of silica to alumina measured by conventional techniques. However, with respect to the framework-substituted USY-type zeolite, the ratio of silica sites to alumina sites is calculated so that the number of silica sites is determined by conventional analysis, while the number of alumina sites includes the number of actual alumina sites and the number of framework-substituted alumina sites in which aluminum atoms have been replaced by titanium, zirconium or hafnium.

[0022] Preparation of the framework-substituted USY zeolite

[0023] The framework-substituted USY zeolite in the catalyst system can be prepared by any zeolite preparation method that produces a framework-substituted USY zeolite having a USY aluminosilicate framework, wherein a portion of the framework aluminum atoms are substituted by titanium atoms, zirconium atoms, hafnium atoms, or any combination thereof. In an exemplary preparation technique, the framework-substituted USY zeolite in the catalyst system can be prepared by calcining a USY zeolite at 500° C. to 700° C., wherein the USY zeolite has a lattice constant of 2.430 nm to 2.450 nm, a lattice constant of 600 nm to 700 nm, and a lattice constant of 1.000 nm to 1.000 nm. 2 / g-900m 2 / g of specific surface area and a molar ratio of silica to alumina of 20-100. Then, a suspension containing calcined USY-type zeolite is formed. The suspension may have a liquid / solid mass ratio of 5-15. An inorganic acid or an organic acid is added to the suspension to reduce the pH of the suspension to 1.0-2.0. The pH of the suspension is pre-controlled at 1.0-2.0 to prevent precipitation during mixing of one or more additional solutions. Specifically, one or more additional solutions containing compounds of zirconium, titanium, hafnium or a combination thereof are mixed into the suspension to cause framework substitution at the aluminum site. The suspension is then neutralized with an alkali (e.g., aqueous ammonia) to increase the pH to a range of 7-7.5. The resulting framework-substituted USY-type zeolite may be filtered, washed with water, and dried at a drying temperature of, for example, 80°C-180°C.

[0024] In the framework-substituted USY zeolite, extra-framework aluminum (aluminum atoms that are not part of the zeolite framework) can be removed from the ultra-stable Y-type zeolite raw material to obtain the ultra-stable Y-type zeolite. The extra-framework aluminum can be removed by, for example, dispersing the ultra-stable Y-type zeolite in warm water at 40°C-95°C to prepare a suspension, adding sulfuric acid to the suspension and stirring the suspension for 10 minutes to 3 hours, while maintaining the temperature at 40°C-95°C, thereby dissolving the extra-framework aluminum. After dissolving the extra-framework aluminum, the suspension is filtered, and the residue on the filter is washed with pure water at 40°C-95°C, and dried at 100°C-180°C for 3-30h, thereby obtaining an ultra-stable Y-type zeolite from which the extra-framework aluminum is removed.

[0025] In the preparation of the framework-substituted USY-type zeolite, the ultra-stable Y-type zeolite raw material can be calcined at 500°C-700°C or 550°C-650°C. There is no particular limitation on the calcination time, as long as the framework-substituted USY-type zeolite is obtained. An exemplary calcination time may be 30 minutes to 10 hours. Regarding the calcination atmosphere of the USY-type zeolite raw material, it is preferably carried out in air. The calcined USY-type zeolite raw material is suspended in water at a temperature of 20°C-30°C to form a suspension. Regarding the concentration of the suspension of USY-type zeolite, the liquid / solid mass ratio may be, for example, 5-15, or 8-12.

[0026] Non-limiting examples of inorganic acids used to reduce the pH of the suspension in the preparation of the framework-substituted USY zeolite may include sulfuric acid, nitric acid or hydrochloric acid. Examples of organic acids used to reduce the pH of the suspension in the preparation of the framework-substituted USY zeolite may include carboxylic acids. The amount of inorganic or organic acid is not limited as long as the pH of the suspension can be controlled within the range of 1.0-2.0. Non-limiting example amounts of acid include 0.5-4.0 times or 0.7-3.5 times the molar amount of acid of the molar amount of alumina in the framework-substituted USY zeolite.

[0027] Non-limiting examples of titanium compounds present in the additional solution mixed into the suspension during the preparation of the framework-substituted USY-type zeolite include titanium sulfate, titanium acetate, titanium chloride, titanium nitrate, titanium lactate, and any titanium compound having sufficient solubility in the suspension to allow titanium atoms to replace aluminum atoms in the zeolite framework. In an embodiment, an aqueous solution of a titanium compound prepared by dissolving the titanium compound in water is suitable for use as the titanium compound.

[0028] Non-limiting examples of zirconium compounds present in the additional solution mixed into the suspension during the preparation of the framework-substituted USY-type zeolite include zirconium sulfate, zirconium nitrate, zirconium chloride, and any zirconium compound having sufficient solubility in the suspension to allow zirconium atoms to replace aluminum atoms in the zeolite framework. In an embodiment, an aqueous solution of a zirconium compound prepared by dissolving the zirconium compound in water is suitable for use as the zirconium compound.

[0029] Non-limiting examples of hafnium compounds present in the additional solution mixed into the suspension during the preparation of the framework-substituted USY-type zeolite include hafnium chloride, hafnium nitrate, hafnium fluoride, hafnium bromide, hafnium oxalate, and any hafnium compound having sufficient solubility in the suspension to allow hafnium atoms to replace aluminum atoms in the zeolite framework. In an embodiment, an aqueous solution of a hafnium compound prepared by dissolving the hafnium compound in water is suitable for use as the hafnium compound.

[0030] In the preparation of the framework-substituted USY zeolite, when an aqueous solution of a zirconium compound, a hafnium compound or a titanium compound is mixed with a suspension of an ultrastable Y-type zeolite, the aqueous solution can be gradually added to the suspension. After the aqueous solution is added to the suspension, the solution can be mixed by stirring for 3-5 hours at, for example, room temperature (25°C ± 10°C). In addition, after the mixing is completed, the above-mentioned mixed solution is neutralized by adding an alkali such as ammonia water so that its pH is controlled at 7.0-7.5, thereby obtaining a framework-substituted zeolite in a catalyst.

[0031] It is obvious to a person skilled in the art that when only a zirconium compound (or an aqueous solution thereof) is used as the compound (or an aqueous solution thereof) added to the suspension, the framework-substituted USY-type zeolite used in the catalyst system will be Zr-USY. Similarly, when only a hafnium compound (or an aqueous solution thereof) is used, the USY-type zeolite used in the catalyst system will be Hf-USY. When only a titanium compound (or an aqueous solution thereof) is used, the USY-type zeolite used in the catalyst system will be Ti-USY. When a zirconium compound and a titanium compound (or an aqueous solution thereof) are used, the framework-substituted USY-type zeolite used in the catalyst system will be (Ti, Zr)-USY. When a zirconium compound and a hafnium compound (or an aqueous solution thereof) are used, the framework-substituted USY-type zeolite used in the catalyst system will be (Zr, Hf)-USY. When a zirconium compound, a titanium compound and a hafnium compound (or an aqueous solution thereof) are used, the framework-substituted USY-type zeolite used in the catalyst system will be (Ti, Zr, Hf)-USY.

[0032] The catalyst system according to the method of the embodiment may also include a carrier for the USY-type zeolite substituted by the skeleton. The carrier may include an inorganic oxide other than the USY-type zeolite substituted by the above-mentioned skeleton. The inorganic oxide of the carrier may also include a substance used as a granulator or binder. Any substance contained in any known zeolite catalyst carrier can be used, including as a granulator. Examples of such inorganic oxides include, but are not limited to, alumina, silica, titania, silica-alumina, alumina-titania, alumina-zirconia, alumina-boria, phosphorus-alumina, silica-alumina-boria, phosphorus-alumina-boria, phosphorus-alumina-silica, silica-alumina-titania and silica-alumina-zirconia. In an exemplary embodiment, the catalyst system includes an inorganic oxide selected from alumina and silica-alumina as a carrier. The silica-alumina carrier may be amorphous. In other exemplary embodiments, the catalyst system may include an alumina binder.

[0033] In the embodiment where the catalyst system includes both the framework-substituted USY-type zeolite and the carrier, the weight ratio of the zeolite and the carrier can vary according to the desired catalyst activity level. In an exemplary embodiment, based on the total mass of the catalyst system, the catalyst system may include 1wt% to 80wt%, 10wt% to 80wt% or 20wt% to about 70wt%. Similarly, the catalyst system may include a catalyst carrier having a composition of 20wt% to 92wt%, or 20wt% to 90wt%, or 30wt% to 80wt% based on the total mass of the catalyst system.

[0034] The catalyst system of the method according to the embodiment may also include an active metal component of a single metal or a combination of metals selected from IUPAC Groups 7 to 11 of the periodic table. Examples of active metals include iron, cobalt, nickel, rhodium, palladium, silver, iridium, platinum, gold, chromium, molybdenum and tungsten. Non-limiting examples of combinations of metal components include a combination of molybdenum and tungsten; a combination of cobalt and nickel; and a combination of any one or more of molybdenum, tungsten, cobalt or nickel with a platinum group metal such as platinum, rhodium or palladium. In an exemplary embodiment, the catalyst system may include at least one active phase metal selected from nickel, molybdenum, tungsten, platinum, palladium and a combination thereof. Without being bound by theory, it is believed that the framework substitution of aluminum by titanium, zirconium or hafnium in the framework-substituted USY-type zeolite according to the embodiment can promote a greater amount of active metal distribution on the surface of the zeolite catalyst.

[0035] When a metal component is included in the catalyst system, the catalyst system may contain greater than 0 to about 40 wt% of the metal component, based on the total mass of the catalyst system, the oxide component is calculated on an oxide basis or the metal is calculated on a metal basis. In an exemplary embodiment, based on the total mass of the catalyst system, the catalyst system may include 3 wt% to 30 wt% of a metal component, such as molybdenum, tungsten, cobalt or nickel, calculated on an oxide basis. In other exemplary embodiments, based on the total mass of the catalyst system, the catalyst system may include 0.01 wt% to 2 wt% of a metal component selected from platinum, rhodium or palladium, calculated on an oxide basis.

[0036] Processing of paraffinic naphtha to produce dehydrogenated product streams

[0037] In an embodiment of the method for processing paraffinic naphtha, a paraffinic naphtha feedstock is contacted with a catalyst system in a dehydrogenation reactor to produce a dehydrogenated product stream. The catalyst system has been described in detail in the previous section. A processing method including the catalyst system as an integral component will now be described.

[0038] As used herein, the term "C5 paraffin" refers to an alkane having 5 carbon atoms. Likewise, the term "C6 paraffin" refers to an alkane having 6 carbon atoms.

[0039] As used herein, the term "olefin" refers in some cases to a carbon-carbon double bond or a hydrocarbon containing at least one carbon-carbon double bond. However, in some specific cases, the term "olefin", particularly when stated in the context of the dehydrogenation products of C5 and C6 paraffins, encompasses olefins with five or six carbon atoms (such as 1-pentene, 2-pentene, 1,3-pentadiene, 1,4-pentadiene, 1-hexene, 2-hexene, 3-hexene, 1,3-hexadiene, 1,4-hexadiene, 1,5-hexadiene, 2,4-hexadiene and 1,3,5-hexatriene) and also olefins with less than five carbon atoms (such as ethylene, propylene, 2-methylpropylene, 1-butene, cis-2-butene, trans-2-butene and 1,3-butadiene) produced by cracking C5 and C6 paraffins during dehydrogenation.

[0040] As used herein, the terms "naphthenes" and "cycloalkanes" are equivalent and, in the case of dehydrogenation products of C5 and C6 paraffins, refer to cycloalkanes having six or fewer carbon atoms. In the case of dehydrogenation products of C5 and C6 paraffins, examples of naphthenes and cycloalkanes include cyclopentane, methylcyclopentane, and cyclohexane. Dehydrogenation products of alkanes having seven carbon atoms may include, for example, cycloheptane, methylcyclohexane, and dimethylcyclopentane.

[0041] According to some embodiments, the paraffin naphtha feedstock is a hydrocarbon stream containing alkanes with 2 to 16 carbon atoms. According to other embodiments, the paraffin naphtha feedstock can be a hydrocarbon stream containing alkanes with 2 to 14 carbon atoms, 2 to 12 carbon atoms, 2 to 10 carbon atoms, 3 to 8 carbon atoms, 4 to 7 carbon atoms, 5 to 12 carbon atoms, 5 to 10 carbon atoms, 5 to 7 carbon atoms or 5 to 6 carbon atoms as the main fraction. In other embodiments, based on the gross weight of the paraffin naphtha feedstock, the paraffin naphtha feedstock can contain a total of at least 80wt%, at least 90wt% or at least 95wt% of C5 and C6 alkanes. In some embodiments, the paraffin naphtha feedstock can be a hydrocarbon oil rich in paraffins having a boiling point range of 36°C-175°C and containing alkanes with 5 to 10 carbon atoms or substantially consisting of alkanes with 5 to 10 carbon atoms.

[0042] According to an embodiment, the paraffinic naphtha feedstock is processed by contacting the paraffinic naphtha feedstock with a catalyst system previously described in the present disclosure to cause a reaction such as dehydrogenation. The reaction can be carried out in a reactor as a batch reaction or a continuous reaction. As used in the present disclosure, a "reactor" refers to a container in which one or more reactants can optionally undergo one or more chemical reactions in the presence of one or more catalysts. Similarly, a "dehydrogenation reactor" is any reactor in which dehydrogenation occurs. Examples of reactors include tanks or tubular reactors configured to operate as batch reactors, continuous stirred tank reactors (CSTRs), or plug flow reactors. Exemplary reactors include packed bed reactors, such as fixed bed reactors, ebullating bed reactors, moving bed reactors, and fluidized bed reactors.

[0043] The paraffin naphtha feedstock can be contacted with the previously described catalyst system in any suitable manner based on the configuration of the dehydrogenation reactor so that the catalyst system catalyzes the dehydrogenation of at least a portion of the alkanes in the paraffin naphtha feedstock to produce a dehydrogenated product stream. The dehydrogenated product stream may include dehydrogenated products of C5 and C6 alkanes. The dehydrogenated products of C5 and C6 alkanes may include olefins (1-pentene, 2-pentene, 1,3-pentadiene, 1,4-pentadiene, 1-hexene, 2-hexene, 3-hexene, 1,3-hexadiene, 1,4-hexadiene, 1,5-hexadiene, 2,4-hexadiene and 1,3,5-hexatriene), cycloalkanes (cyclopentane, methylcyclopentane and cyclohexane), aromatic compounds (such as benzene and cyclopentadiene), normal alkanes (normal alkanes) (such as pentane and hexane), isoalkanes (such as 2-methylbutane and 2-methylpentane) and a combination of hydrogen as a byproduct of the dehydrogenation reaction. It should be understood that during dehydrogenation, hydrogen atoms are removed from alkanes to form mixed free radical species, which can lead to further reactions, such as cracking, isomerization, cyclization and aromatization. Therefore, it can be expected that the dehydrogenation product stream includes a mixture of products of this type of further reaction. Examples of such products include but are not necessarily limited to olefins (such as ethylene, propylene, butylene and 1,3-butadiene) less than five carbon atoms, normal alkanes (such as methane, ethane, propane, butane) less than five carbon atoms and isoalkanes (such as 2-methylpropane) less than five carbon atoms.

[0044] In an embodiment of the present disclosure, the dehydrogenated product stream may include greater than 5 wt% olefins having six or fewer carbon atoms, or greater than 10 wt% olefins having six or fewer carbon atoms, or greater than 20 wt% olefins having six or fewer carbon atoms, or greater than 30 wt% olefins having six or fewer carbon atoms, or greater than 40 wt% olefins having six or fewer carbon atoms, or greater than 50 wt% olefins having six or fewer carbon atoms, based on the total weight of the dehydrogenated product stream. It should be understood that when the paraffinic naphtha feedstock is a fraction containing primarily C5 and C6 alkanes, the olefins in the dehydrogenated product stream will include ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, and 1,3-butadiene. Thus, in some embodiments, the dehydrogenated product stream may include greater than 5 wt% olefins, or greater than 10 wt% olefins, or greater than 20 wt% olefins, or greater than 30 wt% olefins, or greater than 40 wt% olefins, or greater than 50 wt% olefins, based on the total weight of the dehydrogenated product stream, wherein the olefins are selected from ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, 1,3-butadiene, and combinations thereof. Without being bound by theory, it is believed that the catalyst system described in accordance with embodiments of the present disclosure has a beneficial selectivity for increasing the weight fraction of olefins in the dehydrogenated product stream relative to the weight fractions of normal alkanes, isoalkanes, cycloalkanes, and aromatic compounds.

[0045] In an embodiment of the method for processing paraffinic naphtha, the dehydrogenation conditions may include a reaction temperature of 300°C to 800°C and a pressure of 0.01 kg / cm 2 -30kg / cm 2 For example, the reaction temperature may be 300°C-700°C, 400°C-700°C, 400°C-650°C, 450°C-650°C, 450°C-600°C, or any sub-range of these. The reaction pressure may be, for example, 0.1 kg / cm 2 -30kg / cm 2 , 1kg / cm 2 -30kg / cm 2 , 1kg / cm 2 -25kg / cm 2 , 1kg / cm 2 -20kg / cm 2 , or any sub-ranges thereof. In an exemplary embodiment, the contacting of the paraffinic naphtha feedstock with the catalyst system may be carried out under the following conditions: a reaction temperature of 450° C. to 600° C.; 1 kg / cm 2 -20kg / cm 2 or 2kg / cm 2 -6kg / cm 2 Reaction pressure; 0.5h -1 -5h -1 A liquid hourly space velocity (LHSV) of 1 to 5; and a molar ratio of hydrogen to hydrocarbon of 1 to 5.

[0046] Without being bound by any particular theory, it is believed that since the dehydrogenation of hydrocarbons is an endothermic reaction and the conversion level is limited by chemical equilibrium, it may be desirable to operate at relatively high temperatures and relatively low hydrogen partial pressures to achieve higher conversions. However, for reactions under harsh conditions, it may be difficult to maintain high activity and selectivity for a long time because undesirable side reactions such as aromatization, cracking, isomerization, coke formation, or a combination thereof may increase. Therefore, reaction conditions may be selected based on maximizing one or more of catalytic activity, catalytic selectivity, and catalyst stability.

[0047] According to one or more embodiments currently described, the catalyst system can have one or more of relatively high activity for the conversion of the previously described reactant chemical species, relatively high selectivity for conversion to linear olefins (e.g., olefins such as ethylene, propylene, 2-methylpropylene, 1-butene, cis-2-butene, trans-2-butene, and 1,3-butadiene), and relatively good stability. As currently described, activity is a measure of the ability of a catalyst to convert a reactant material into a product (a substance having a chemical composition different from that of the reactant material) at a specific temperature, pressure, contact time, and the presence of a diluent such as hydrogen, steam, or nitrogen (if any). In addition, as currently described, selectivity is a measure of the amount of a specific substance in the product in mole percentage relative to the total moles of the reactants converted. As currently described, catalyst stability is a measure of the rate at which activity and selectivity parameters change over time, wherein the smaller the rate change, the more stable the catalyst system.

[0048] According to one or more embodiments, selectivity in olefin production can be achieved by reducing undesirable reactions such as cracking side reactions and isomerization, which can be enhanced by relatively high temperatures and low hydrogen pressures. For the presently described selective dehydrogenation processes, it may be desirable to dehydrogenate a linear hydrocarbon feedstock to produce linear olefins with little or no cracking or isomerization reactions, which tend to produce smaller or branched hydrocarbon chains, respectively. According to one or more embodiments, the isomerization or cracking activity of the presently described dehydrogenation reactions can be maintained at less than 2 mol% of the feedstock, measured as the number of moles of isomerized or cracked hydrocarbons in the product relative to the feedstock.

[0049] In one or more embodiments, the feed stream of paraffin naphtha feedstock can be introduced into the reactor containing the dehydrogenation catalyst system. The feed stream may include reactant materials (such as C5 and C6 normal alkanes) and diluent components. The example of diluent material includes hydrogen, steam, methane, inert gas (such as argon or nitrogen) or a combination thereof. In the absence of restriction, the weight ratio of diluent to reactant material can be 500-5000, such as 500-1000, 1000-2000, 2000-3000, 3000-4000, 4000-5000 or any combination thereof.

[0050] The dehydrogenation product stream leaving the dehydrogenation reactor may include dehydrogenated hydrocarbons, unconverted hydrocarbons that may be identical to the reactant materials, cracked products, byproduct hydrogen and diluent materials from the dehydrogenation reaction. Diluent gases such as hydrogen can be separated from the other parts of the dehydrogenated product stream. These diluent gases can be recycled to be used as diluent materials again, or can be used for other chemical processes. Dehydrogenated hydrocarbons and unconverted hydrocarbons can be separated by downstream separation methods as needed. In some embodiments, unconverted hydrocarbons can then be recycled into the process for subsequent reaction processes.

[0051] In some embodiments, the paraffin naphtha feedstock is brought into the dehydrogenation reactor to contact the catalyst system in a feed stream including a diluent material. In such embodiments, the diluent material in the feed stream may include 5vol% to 30vol% hydrogen, 5vol% to 10vol% hydrogen, 10vol% to 15vol% hydrogen, 15vol% to 20vol% hydrogen, 20vol% to 25vol% hydrogen or 25vol% to 30vol% hydrogen or any combination thereof. In some embodiments, this ratio of hydrogen to other diluents can be used for the dehydrogenation of C5 to C6 hydrocarbons. In some embodiments, the diluent may include hydrogen and an inert gas (such as nitrogen), or may be composed entirely of hydrogen and an inert gas (such as nitrogen). Without being bound by any particular theory, it is believed that the ratio of hydrogen as a diluent increases the selectivity and yield of normal olefins under some reaction conditions. The stability of the catalyst can also be improved using 5vol% to 30vol% hydrogen as a diluent.

[0052] In some embodiments, the method for processing paraffin naphtha feedstock may further include separating the dehydrogenated product stream into at least a dehydrogenated liquid product and a gaseous product. Separation may be accomplished in a suitable device by any conventional vapor-liquid separation method, such as a pressure reducing vessel, a flash tank, a crushing tank, a knock-out drum, a knock-out pot, a compressor suction tank, or a compressor inlet tank. In some embodiments, separation may be achieved by any conventional method for separating a fluid mixture of hydrocarbons with different boiling points, such as by distillation. Then, the method may further include blending the dehydrogenated liquid product into gasoline. The gaseous product may be recovered for use in other refinery processes or as a valuable product.

[0053] Example

[0054] The present invention will be better understood by reference to the following examples, which are provided by way of illustration, and those skilled in the art will recognize that these examples are not meant to be limiting.

[0055] A paraffinic naphtha sample containing C5-C7 hydrocarbons (whose properties and composition are shown in Table 1) was used as a paraffinic naphtha feedstock to demonstrate the dehydrogenation reaction. The experiment was carried out in a pilot plant with a fixed bed reactor. The pilot plant was loaded with 20 cm 3 The catalyst contains Ti, Zr-USY zeolite and platinum as the active phase metal. The pilot plant is at 3kg / cm 2 、LHSV is 4h -1 , a hydrogen to hydrocarbon molar ratio of 3 and reaction temperatures of 475°C, 525°C and 575°C.

[0056] Table 1: Composition of paraffinic naphtha feedstock in exemplary dehydrogenation reactions

[0057]

[0058] Table 2 summarizes the products in the paraffinic naphtha feedstock and the dehydrogenation product stream at three temperatures. The data show that normal alkanes are converted to isoalkanes and olefins over the Ti,Zr-USY zeolite catalyst. The data also show that the olefin content can increase with increasing temperature.

[0059] Table 2: Hydrocarbon composition of the dehydrogenation product stream at different reaction temperatures

[0060]

[0061] Without being bound by theory, it is believed that the acidity of the Ti,Zr-USY zeolite may advantageously benefit the ability of a dehydrogenation system comprising Ti,Zr-USY to produce greater amounts of olefins than would be obtained from a comparative system incorporating an unmodified USY zeolite catalyst having the same silica to alumina ratio.

[0062] Total acidity was determined by pyridine adsorption and desorption at 150° C. for a comparative unmodified USY zeolite (USY-40) having a silica to alumina ratio of 40 and a Ti,Zr-USY zeolite (Ti,Zr-USY-40) having a silica site to alumina site ratio of 40. USY-40 had a total acidity based on 115 micromoles Brunnester acid sites / gram zeolite and 47 micromoles Lewis acid sites / gram zeolite. Ti,Zr-USY-40 had a total acidity based on 149 micromoles Brunnester acid sites / gram zeolite and 107 micromoles Lewis acid sites / gram zeolite.

[0063] The number of strong acid sites in USY-40 and Ti,Zr-USY-40 was determined by pyridine adsorption and desorption at 450° C. USY-40 has strong acid sites based on 27 micromoles of Brunnester acid sites / gram of zeolite and 21 micromoles of Lewis acid sites / gram of zeolite. Ti,Zr-USY-40 has strong acid sites based on 36 micromoles of Brunnester acid sites / gram of zeolite and 37 micromoles of Lewis acid sites / gram of zeolite.

[0064] Project List

[0065] Embodiments of the present disclosure include at least the following items, which are not intended to limit the scope of the present disclosure as a whole or the appended claims.

[0066] Item 1: A method for processing paraffin naphtha, the method comprising: contacting a paraffin naphtha feedstock with a catalyst system in a dehydrogenation reactor to produce a dehydrogenation product stream, the catalyst system comprising a framework-substituted ultrastable Y (USY) type zeolite, wherein the framework-substituted USY type zeolite has a modified USY framework, the modified USY framework comprising a USY aluminosilicate framework modified by replacing a portion of the framework aluminum atoms of the USY aluminosilicate framework with substituent atoms, the substituent atoms being independently selected from titanium atoms, zirconium atoms, hafnium atoms and combinations thereof.

[0067] Item 2: The method according to Item 1, wherein the framework-substituted USY-type zeolite contains 0.01 wt% to 5 wt% of substitution atoms calculated on an oxide basis based on the total mass of the framework-substituted USY-type zeolite.

[0068] Item 3: A method according to Item 1, wherein: based on the total mass of the framework-substituted USY-type zeolite, calculated on an oxide basis, the framework-substituted USY-type zeolite contains 0.01 wt% to 5 wt% of substitutional atoms; and the substitutional atoms include those selected from (a) titanium atoms and zirconium atoms, (b) titanium atoms and hafnium atoms, (c) zirconium atoms and hafnium atoms, and (d) a combination of titanium atoms, zirconium atoms and hafnium atoms.

[0069] Item 4: The method according to Item 1, wherein: based on the total mass of the framework-substituted USY-type zeolite, calculated on an oxide basis, the framework-substituted USY-type zeolite contains 0.01 wt% to 5 wt% of substituted atoms; and the substituted atoms include titanium atoms and zirconium atoms.

[0070] Item 5: A method according to any one of the preceding items, wherein the dehydrogenation product stream contains olefins.

[0071] Item 6: A method according to any one of the preceding items, wherein the dehydrogenated product stream comprises at least 5 wt% olefins based on the total weight of the dehydrogenated product stream.

[0072] Item 7: A method according to any one of the preceding items, wherein the catalyst system further comprises a carrier for the framework-substituted USY-type zeolite, the carrier comprising an inorganic oxide selected from alumina, silica-alumina and a combination thereof.

[0073] Item 8: A method according to any one of the preceding items, wherein the catalyst system further comprises an acidic support, and the acidic support comprises amorphous silica-alumina.

[0074] Item 9: A method according to any one of the preceding items, wherein the catalyst system further comprises at least one active phase metal selected from nickel, molybdenum, tungsten, platinum, palladium and combinations thereof.

[0075] Item 10: A method according to any one of the preceding items, wherein the paraffinic naphtha feedstock comprises a paraffin-rich hydrocarbon oil having a boiling point range of 36°C-175°C.

[0076] Item 11: A method according to any one of the preceding items, wherein the paraffinic naphtha feedstock comprises a paraffin-rich hydrocarbon oil having a carbon number of 5-10.

[0077] Item 12: A method according to any one of the preceding items, wherein the contacting of the paraffin naphtha feedstock with the catalyst system is carried out under the following conditions: a reaction temperature of 450°C to 600°C; a pressure of 1 kg / cm 2 -20kg / cm 2 Reaction pressure; 0.5h -1 -8h -1 A liquid hourly space velocity (LHSV) of 1 to 5; and a molar ratio of hydrogen to hydrocarbon of 1 to 5.

[0078] Item 13: A method according to any one of the preceding items, wherein the catalyst system further comprises an alumina binder.

[0079] Item 14: The method according to any one of the preceding items, further comprising: separating the dehydrogenated product stream into at least a dehydrogenated liquid product and a gas phase product; and blending the dehydrogenated liquid product into gasoline.

[0080] Item 15: A method according to any one of the preceding items, wherein the catalyst system does not contain any zeolite other than the framework-substituted USY-type zeolite.

[0081] Item 16: The method according to any one of the preceding items, wherein the framework-substituted USY-type zeolite contains 0.01 wt% to 5 wt% of substitution atoms, calculated on an oxide basis, based on the total mass of the framework-substituted USY-type zeolite.

[0082] Item 17: A method according to any one of the preceding items, wherein the catalyst system further comprises a carrier for the framework-substituted USY-type zeolite, the carrier comprising an inorganic oxide selected from alumina, silica-alumina and a combination thereof.

[0083] Item 18: A method according to any one of the preceding items, wherein the paraffinic naphtha feedstock comprises a paraffin-rich hydrocarbon oil having a boiling point range of 36°C-175°C.

[0084] Item 19: A method according to any one of the preceding items, wherein the contacting of the paraffin naphtha feedstock with the catalyst system is carried out under the following conditions: a reaction temperature of 450°C to 600°C; a pressure of 1 kg / cm 2 -20kg / cm 2 Reaction pressure; 0.5h -1 -8h -1 A liquid hourly space velocity (LHSV) of 1 to 5; and a molar ratio of hydrogen to hydrocarbon of 1 to 5.

[0085] Item 20: A dehydrogenation catalyst for dehydrogenating paraffin naphtha, the dehydrogenation catalyst comprising a framework-substituted ultrastable Y (USY) type zeolite, wherein the framework-substituted USY type zeolite has a modified USY framework, the modified USY framework comprising a USY aluminosilicate framework modified by replacing a portion of the framework aluminum atoms of the USY aluminosilicate framework with substitution atoms, the substitution atoms being independently selected from titanium atoms, zirconium atoms, hafnium atoms and combinations thereof.

[0086] Item 21: The dehydrogenation catalyst according to Item 20, wherein the framework-substituted USY-type zeolite contains 0.01 wt% to 5 wt% of substitution atoms calculated on an oxide basis based on the total mass of the framework-substituted USY-type zeolite.

[0087] Item 22: A dehydrogenation catalyst according to Item 20, wherein: based on the total mass of the framework-substituted USY-type zeolite, calculated on an oxide basis, the framework-substituted USY-type zeolite contains 0.01 wt% to 5 wt% of substitutional atoms; and the substitutional atoms include those selected from (a) titanium atoms and zirconium atoms, (b) titanium atoms and hafnium atoms, (c) zirconium atoms and hafnium atoms, and (d) a combination of titanium atoms, zirconium atoms and hafnium atoms.

[0088] Item 23: A dehydrogenation catalyst according to Item 20, wherein: based on the total mass of the framework-substituted USY-type zeolite, calculated on an oxide basis, the framework-substituted USY-type zeolite contains 0.01 wt% to 5 wt% of substituted atoms; and the substituted atoms include titanium atoms and zirconium atoms.

[0089] Item 24: The dehydrogenation catalyst according to any one of Items 20 to 23, which is combined with a carrier for the framework-substituted USY-type zeolite, the carrier comprising an inorganic oxide selected from alumina, silica-alumina and a combination thereof.

[0090] Item 25: The dehydrogenation catalyst according to any one of Items 20 to 24, in combination with an acidic support comprising amorphous silica-alumina.

[0091] Item 26: The dehydrogenation catalyst according to any one of Items 20 to 25, which is combined with at least one active phase metal selected from nickel, molybdenum, tungsten, platinum, palladium and combinations thereof.

[0092] Item 27: The dehydrogenation catalyst according to any one of Items 20 to 26, in combination with an alumina binder.

[0093] Item 28: Use of the dehydrogenation catalyst as described in any one of Items 20 to 27 for dehydrogenating paraffin naphtha.

[0094] Item 29: The use according to Item 28, wherein the paraffinic naphtha feedstock comprises a paraffin-rich hydrocarbon oil having a boiling point range of 36°C-175°C.

[0095] Item 30: The use according to Item 28 or Item 29, wherein the paraffinic naphtha feedstock comprises a paraffin-rich hydrocarbon oil having a carbon number of 5-10.

[0096] Item 31: The use according to any one of items 28-30, comprising any additional features of the method for processing paraffinic naphtha according to any one of items 1-19.

[0097] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those of ordinary skill in the art to which the invention belongs. The terms used in the specification of this article are only used to describe specific embodiments and are not intended to be limiting. As used in the specification and the appended claims, the singular forms "a", "an" and "the" are intended to also include plural forms, unless the context clearly indicates otherwise.

[0098] Although specific embodiments have been shown and described herein, it should be understood that various other changes and modifications may be made without departing from the scope of the claimed subject matter. In addition, although various aspects of the claimed subject matter have been described herein, these aspects do not need to be used in combination. Therefore, the appended claims are intended to cover all such changes and modifications within the scope of the claimed subject matter.

Claims

1. A method for processing paraffin naphtha, the method comprising: contacting a paraffinic naphtha feedstock with a catalyst system comprising a framework-substituted ultrastable Y (USY)-type zeolite in a dehydrogenation reactor to produce a dehydrogenated product stream, The framework-substituted USY zeolite has a modified USY framework, wherein the modified USY framework comprises a USY aluminosilicate framework modified by replacing a portion of the framework aluminum atoms of the USY aluminosilicate framework with substitution atoms, wherein the substitution atoms are independently selected from titanium atoms, zirconium atoms, hafnium atoms and combinations thereof.

2. The method according to claim 1, wherein: The framework-substituted USY-type zeolite contains 0.01 wt% to 5 wt% of substitution atoms calculated on an oxide basis, based on the total mass of the framework-substituted USY-type zeolite.

3. The method according to claim 1, wherein: The framework-substituted USY-type zeolite contains 0.01 wt % to 5 wt % of substitution atoms, calculated on an oxide basis, based on the total mass of the framework-substituted USY-type zeolite; and The substituent atom includes an atom selected from (a) a titanium atom and a zirconium atom, (b) a titanium atom and a hafnium atom, (c) a zirconium atom and a hafnium atom, and (d) a combination of a titanium atom, a zirconium atom and a hafnium atom.

4. The method according to claim 1, wherein: The framework-substituted USY-type zeolite contains 0.01 wt % to 5 wt % of substitution atoms, calculated on an oxide basis, based on the total mass of the framework-substituted USY-type zeolite; and The substituent atoms include titanium atoms and zirconium atoms.

5. The method according to any one of claims 1 to 4, wherein: The dehydrogenation product stream contains olefins.

6. The method according to any one of claims 1 to 4, wherein: The dehydrogenated product stream comprises at least 5 wt% olefins, based on the total weight of the dehydrogenated product stream.

7. The method according to any one of claims 1 to 4, wherein: The catalyst system further comprises a support for the framework-substituted USY-type zeolite, wherein the support comprises an inorganic oxide selected from the group consisting of alumina, silica-alumina and combinations thereof.

8. The method according to claim 7, wherein: The support is an acidic support including amorphous silica-alumina.

9. The method according to any one of claims 1 to 4, wherein: The catalyst system further comprises at least one active phase metal selected from the group consisting of nickel, molybdenum, tungsten, platinum, palladium and combinations thereof.

10. The method according to any one of claims 1 to 4, wherein: The paraffinic naphtha feedstock comprises a paraffin-rich hydrocarbon oil having a boiling point range of 36°C to 175°C.

11. The method according to any one of claims 1 to 4, wherein: The paraffinic naphtha feedstock includes a hydrocarbon oil rich in paraffins having a carbon number of 5-10.

12. The method according to any one of claims 1 to 4, wherein: The contacting of the paraffin naphtha feedstock with the catalyst system is carried out under the following conditions: Reaction temperature of 450°C-600°C; 1kg / cm 2 -20kg / cm 2 Response pressure; 0.5h -1 -8h -1 Liquid hourly space velocity (LHSV); and The molar ratio of hydrogen to hydrocarbon is 1-5.

13. The method according to any one of claims 1 to 4, further comprising: separating the dehydrogenated product stream into at least a dehydrogenated liquid product and a vapor phase product; as well as The dehydrogenated liquid product is blended into gasoline.

14. The method according to claim 13, wherein: The catalyst system does not contain any zeolite other than the framework-substituted USY-type zeolite.

15. The method of claim 13, wherein: The paraffin naphtha feedstock comprises a paraffin-rich hydrocarbon oil having a boiling point range of 36° C. to 175° C.; and The contacting of the paraffin naphtha feedstock with the catalyst system is carried out under the following conditions: Reaction temperature of 450°C-600°C; 1kg / cm 2 -20kg / cm 2 Response pressure; 0.5h -1 -8h -1 Liquid hourly space velocity (LHSV); and The molar ratio of hydrogen to hydrocarbon is 1-5.

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