BACKGROUND OF THE INVENTION

[0001] This application relates to methods and systems for the conversion of hydrocarbon feedstocks, in particular, naphtha feedstocks, into product streams containing a high yield of high- octane gasoline. In particular, this application relates to improving the selectivity for isomerization over cracking, leading to an overall improved product yield compared to conventional reforming catalysts, particularly when used in combination with other reforming catalysts.

[0002] Naphtha reforming has been an important refining process for decades, generating hydrogen, chemicals feedstock (benzene, toluene, xylenes, which are also known as BTX), and high-octane gasoline. A typical naphtha feedstock will contain paraffins, olefins, naphthenes, aromatics, and isomers thereof. To reform a typical naphtha feedstock into gasoline and/or BTX, a reforming catalyst converts these molecules into aromatic hydrocarbons. Gasoline may additionally include isoparaffins; however, isoparaffins contribute much less than aromatics to the octane number of gasoline and do not contribute to BTX yield at all. A gasoline fraction typically derives even less contribution to its octane number from paraffins and naphthenes.

[0003] To carry out the necessary reforming reactions, reforming catalysts typically include a metal (e.g., platinum) to dehydrogenate and an acid function to dehydrocyclize. However, the paraffin dehydrocyclization reaction to generate aromatic hydrocarbons is not particularly favored by conventional reforming catalysts and conversion is often slow and/or incomplete.

[0004] Zeolitic catalysts have been investigated for their use in reforming, though in a limited manner. Advantageously, zeolitic catalysts may be modified to resist coking and, due to their permanent acid functionality, do not require the addition of chloride to the system. However, much of the catalytic activity in zeolitic catalysts takes place in the pores of the zeolite. Thus, the selectivity and activity of the catalyst are highly dependent on the mass diffusion of the hydrocarbons from the feedstock into and out of the pores of the catalyst. Larger molecules are difficult to convert, as their size excludes them from entering the pore. Consequently, zeolitic catalysts (e.g., Pt/Re zeolites) are best suited for reforming feedstocks that are limited to smaller hydrocarbons that easily diffuse in and out of the pores of the zeolite. However, smaller hydrocarbons, such as C1-C5 hydrocarbons, are also not desirable in a feedstock, as these are not readily converted to aromatics. Thus, presently, the preferred feedstock for a zeolitic catalyst is generally limited to C6-C7 feedstock (as opposed to a full-range C4-C12 feedstock). A C6-C7 feedstock, in turn, produces a hydrocarbon product stream limited to primarily benzene and toluene products. [0005] What is needed is a reforming system that can effectively convert full-range (C4-C12) hydrocarbon feedstocks with widely varying dispositions, in particular, having a significant paraffinic fraction, into a hydrocarbon product stream characterized by a high octane number.

SUMMARY OF THE INVENTION

[0006] This application relates to the methods and systems for the conversion of a hydrocarbon feedstock, in particular, naphtha feedstock, into a hydrocarbon product stream containing a high yield of high-octane gasoline. In particular, this application relates to improving how the selectivity for isomerization over cracking may be achieved, leading to an overall improved product yield compared to conventional reforming catalysts, particularly when used in combination with other reforming catalysts.

[0007] Provided herein are methods for treating a precursor zeolite having a bulk silica-to- alumina ratio and a framework silica-to-alumina ratio with one or more of acid, steam, and a combination thereof under conditions effective to prepare a modified zeolite having a framework silica-to-alumina ratio of about 40: 1 to about 1000: 1 and a bulk silica-to-alumina ratio of about 40: 1 to about 500: 1 ; and contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced isomerization activity as compared to the precursor zeolite. The modified zeolitic catalyst may then be used to convert a hydrocarbon feed stream into a product stream comprising high octane gasoline, for example, by contacting a hydrocarbon feed stream with the modified zeolitic catalyst under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream comprising one or more of a C5+ fraction.

[0008] Also provided herein are systems for converting hydrocarbons comprising: a hydrocarbon feed stream inlet configured and arranged to receive a hydrocarbon feed stream; at least one reactor comprising at least one catalyst bed, the catalyst bed comprising at least one modified zeolitic catalyst, wherein the modified zeolitic catalyst comprises a transition metal and a modified zeolite characterized by one or more of the following: a bulk silica-to-alumina ratio of about 40:1 to about 500; 1 and a framework silica-to-alumina ratio of about 40: 1 to about 1000: 1;

and a hydrocarbon product stream outlet configured and arranged to receive a hydrocarbon product stream. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] This application relates to the methods and systems for the conversion of a hydrocarbon feedstock, in particular, naphtha feedstock, into a hydrocarbon product stream containing a high yield of high-octane gasoline. In particular, selectivity for isomerization over cracking may be achieved, leading to an overall improved product yield compared to conventional reforming catalysts, particularly when used in combination with other reforming catalysts.

[0010] FIG. 1 depicts an example of a system described herein for converting a hydrocarbon feed stream.

[0011] FIG. 2 provides data illustrating the effect of steam treating for one hour at various temperatures on the acidity (collidine uptake) of several modified zeolitic catalysts disclosed herein, as is discussed in the Examples.

[0012] FIG. 3 provides data illustrating that at the same C5+ fraction yield, a hydrocarbon product stream derived from a modified zeolitic catalyst having extra-framework alumina has a higher octane number than a hydrocarbon product stream derived from Pt/Re chlorided alumina, as is discussed in the Examples.

[0013] FIG. 4 provides data illustrating that at the same C5 + Ce cyclic hydrocarbon yield, a hydrocarbon product stream derived from a modified zeolitic catalyst having extra-framework alumina has a higher octane, as is discussed in the Examples.

[0014] FIG. 5 provides data illustrating the effect of extra-framework alumina resulting from steaming a zeolitic catalyst precursor on C4 isomerization of a hydrocarbon product stream.

[0015] FIG. 6 provides data illustrating that the enhanced C5+ yield derived from paraffin isomerization derived from extra-framework alumina may be reversed by acid washing a modified zeolitic catalyst, as is discussed in the Examples.

[0016] FIG. 7 provides data illustrating that the enhanced isomerization derived from extra framework alumina may be reversed by acid washing a modified zeolitic catalyst, as is discussed in the Examples.

DETAILED DESCRIPTION

[0017] This application relates to the methods and systems for the conversion of hydrocarbon feedstocks, in particular, naphtha feedstocks, into product streams containing a high yield of high- octane gasoline. In particular, this application relates to improving how the selectivity for isomerization over cracking, leading to an overall improved product yield compared to conventional reforming catalysts, particularly when used in combination with other reforming catalysts. [0018] To facilitate an understanding of the present invention, a number of terms and phrases are defined below.

[0019] To facilitate an understanding of the present invention, a number of terms and phrases are defined below and in the following text.

[0020] For purposes of this disclosure and the claims hereto, the numbering scheme for the Periodic Table Groups is according to the IUPAC Periodic Table of Elements (Dec 1, 2018).

[0021] As used in the present disclosure and claims, the singular forms“a,”“an,” and“the” include plural forms unless the context clearly dictates otherwise.

[0022] The term“and/or” as used in a phrase such as“A and/or B” herein is intended to include “A and B”,“A or B”,“A”, and“B”.

[0023] Alpha value is an approximate indication of the catalytic cracking activity of a catalyst compared to a standard catalyst and gives the relative rate constant (rate of normal hexane conversion per volume of catalyst per unit time). It is based on the activity of silica- alumina cracking catalyst having an alpha value of 1 (Rate Constant = 0.016 s-1). The alpha test is described in U.S. Pat. No. 3,354,078; in the Journal of Catalysis, 4, 527 (1965); 6, 278 (1966); and 61, 395 (1980), each incorporated herein by reference with respect to its disclosure of how to carry out the alpha test. The experimental conditions of the test used herein include a constant temperature of 1000°F (537.8°C) and a variable flow rate as described in detail in the Journal of Catalysis, 61, 395 (1965). The effluent product stream may be analyzed by vapor chromatography.

[0024] Collidine uptake can be determined as the micromoles of collidine absorbed per gram of sample that is dried under nitrogen flow at 200°C for 60 minutes on a Thermogravimetric Analyzer (Model Q5000), manufactured by TA Instruments, New Castle, Delaware). After drying the sample, the collidine can be sparged over the sample. The collidine uptake can then be calculated from the following formula: (weight of sample after sparging with collidine - weight of dried sample x 106 ÷ (molecular weight of collidine x weight of dried sample). As used herein, “collidine uptake” refers to an uptake calculated after sparging the sample for 60 minutes at a collidine partial pressure of 3 torr (~ 400 kPa).

[0025] As used herein, and unless otherwise specified, the term“hydrocarbon” means a class of compounds containing hydrogen bound to carbon, and encompasses saturated hydrocarbons, unsaturated hydrocarbons, and mixtures thereof, including mixtures of hydrocarbons having different values of n.

[0026] As used herein, and unless otherwise specified, the term“Cn” means hydrocarbon(s) having n carbon atom(s) per molecule, wherein n is a positive integer. As used herein, and unless otherwise specified, the term“Cn+” refers to a hydrocarbon composition defined by hydrocarbons having“n” or more carbon atoms, where“n” is an integer greater than 0. This includes paraffins, olefins, cyclic hydrocarbons, and aromatics and isomers thereof. Similarly, the term“Cn-” refers to a hydrocarbon composition defined by hydrocarbons having“n” or fewer carbon atoms, wherein “n” is an integer greater than 0. This includes paraffins, olefins, cyclic hydrocarbons, aromatics, and isomers thereof.

[0027] As used herein, and unless otherwise specified, liquid petroleum gas (“LPG”) refers to a hydrocarbon composition, for example, a fraction of the hydrocarbon product stream, comprising propane and butane (including n-butane and iso-butane).

[0028] As used herein, and unless otherwise specified, the term “aromatic” refers to unsaturated cyclic hydrocarbons having a delocalized conjugated p system and having from six to thirty carbon atoms (e.g., aromatic C6-C30 hydrocarbon). Examples of suitable aromatics include, but are not limited to benzene, toluene, xylenes, mesitylene, ethylbenzenes, cumene, naphthalene, methylnaphthalene, dimethylnaphthalenes, ethylnaphthalenes, acenaphthalene, anthracene, phenanthrene, tetraphene, naphthacene, benzanthracenes, fluoranthrene, pyrene, chrysene, triphenylene, and the like, and combinations thereof. Additionally, an aromatic may comprise one or more heteroatoms. Examples of heteroatoms include, but are not limited to, nitrogen, oxygen, and/or sulfur. Aromatics with one or more heteroatom include, but are not limited to thiophene, benzothiophene, oxazole, thiazole and the like, and combinations thereof. An aromatic may comprise monocyclic, bicyclic, tricyclic, and/or polycyclic rings (in any embodiment, at least monocyclic rings, only monocyclic and bicyclic rings, or only monocyclic rings) and may be fused rings. As used herein, the plural use of“xylenes” and grammatical variations thereof is used to convey that the xylene may be any isomer of xylene, including m-xylene, o-xylene, p-xylene, or any blend thereof.

[0029] As used herein“An” where n is an integer, refers to an aromatic hydrocarbon comprising“n” number of carbons in the aromatic ring. For example, an As fraction includes all aromatics having eight carbons in the aromatic ring structure. Likewise, At, refers to aromatic hydrocarbon having six carbons in the aromatic ring structure.

[0030] As used herein, the term“olefin,” alternatively referred to as“alkene,” and grammatical derivatives thereof, refers to an unsaturated hydrocarbon chain of two to about twelve carbon atoms in length containing at least one carbon-to-carbon double bond. An olefin may be straight chain or branched chain. Non-limiting examples include ethylene, propylene, butylene, and pentene. “Olefin” is intended to embrace all structural isomeric forms of olefins. [0031] As used herein, and unless otherwise specified, the term“paraffin,” alternatively referred to as“alkane,” and grammatical derivatives thereof, refers to a saturated hydrocarbon chain of one to about thirty carbon atoms in length, such as, but not limited to methane, ethane, propane and butane. A paraffin may be straight-chain, cyclic or branched-chain.“Paraffin” is intended to embrace all structural isomeric forms of paraffins. The term“acyclic paraffin” refers to straight-chain or branched-chain paraffins. The term“isoparaffin” refers to branched-chain paraffins and the term“n-paraffin” or“normal paraffin” refers to straight-chain paraffins.

[0032] As used herein, the term“full-range naphtha” and grammatical derivatives thereof, refers to a middle boiling range hydrocarbon fraction or fractions, typically including three or more hydrocarbons (e.g., between four and twelve carbon atoms), which are major components of gasoline, and having a boiling range characterized by a T5-T95 range of 10°C to 232°C, where T5 defines the temperature at which 5% of the hydrocarbon composition boils and T95 defines the temperature at which 95% of the hydrocarbon composition boils. Boiling range may be determined by simulated distillation (“SimDis”) according to ASTM D2887-18. Full-range naphtha comprises “light” naphtha and“heavy” naphtha. Light naphtha is a lighter fraction of full-range naphtha having a T95 boiling point less than about 90°C. The fraction of full-range naphtha having a T5 boiling point greater than about 90°C is considered heavy naphtha. Unless otherwise specified, full-range naphtha refers to a composition comprising both heavy and light naphtha.

[0033] Unless otherwise specified,“naphtha,” (and grammatical variations thereof) refers to a composition that falls within the boiling point range boundaries of full-range naphtha and may have the same T5-T95 range as full-range naphtha or may have different T5 and/or T95 temperatures than full-range naphtha. Naphtha may comprise full-range naphtha, light naphtha, heavy naphtha, or any other contemplated fraction defined by a subset of hydrocarbons having, for example, a defined T5 and/or T95 temperature, a defined molecular weight range, a defined number of hydrocarbons, and the like. Naphtha may include paraffins, olefins, naphthenes, and/or aromatics.

[0034] As used herein,“feedstock” and“feed” (and grammatical derivatives thereof) are used interchangeably and both refer to a composition that is fed into a reforming reactor. A feedstock may optionally have been pre-treated to modify its disposition.

[0035] As used herein,“reactor,” and grammatical derivatives thereof, refers to a vessel comprising one or more catalyst beds. A reactor inlet refers to a conduit that conveys a hydrocarbon stream to that reactor. Unless specified otherwise, all reactor temperatures refer to an equivalent isothermal (El) temperature. Experiments in the Examples are performed in an isothermal reactor having a defined inlet temperature. Commercial reactors, however, are typically adiabatic and reactor temperature is controlled in a different manner. In adiabatic reactors, a temperature profiled may be specified that results in an average temperature across the entire reactor equivalent to a specified isothermal reactor temperature.

[0036] As used herein, the term“straight run naphtha” (also termed“virgin naphtha”) refers to petroleum naphtha obtained directly from fractional distillation. As used herein, the term“fluid catalytic cracker (FCC) naphtha” refers to naphtha produced by the well-known process of fluid catalytic cracking. The term“FCC naphtha” is intended to encompass one or more of light cut naphtha (LCN), intermediate cut naphtha (ICN), and heavy cut naphtha (HCN). As used herein, the term“coker naphtha” refers to naphtha produced by the well-known process of coking in one or more coker units or cokers. Coker naphtha generally includes more sulfur and/or nitrogen than straight run naphtha. As used herein, the term“delayed coker naphtha” refers to naphtha produced by the well-known process of delayed coking. As used herein, the term“fluid coker naphtha” refers to naphtha produced by the well-known process of fluid coking. As used herein, the term “hydrocrackate” refers to a naphtha cut of a hydrocracker byproduct. As used herein, the term “hydrotreated naphtha” refers to naphtha produced by the well-known process of hydrotreating. As used herein, the term“steam cracker naphtha (SCN)” refers to naphtha produced by the well- known process of steam cracking.

[0037] A common method for characterizing the octane number of a composition is to use Research Octane Number (RON). As used herein, “octane number” and“RON” are used interchangeably, and both refer to the RON of the C5+ fraction of a hydrocarbon product stream. Although various methods are available for determining RON, in the claims below, references to Research Octane Number (RON) correspond to RON determined as described in Ghosh, P. et al. (2006)“Development of Detailed Gasoline Composition-Based Octane Model,” Ind. Eng. Chem. Res., 45(1), pp 337-345. As used herein,“high octane” is meant to describe a hydrocarbon composition having a RON of at least about 80, at least about 85, at least about 90, at least about 95, at least about 99, or about 100; or in a range of about 80 to about 100, about 90 to about 100, or about 95 to about 100. RON is used herein, particularly in the Examples, as a surrogate for conversion. In any reforming reaction, a higher RON can be achieved by pushing the reaction forward with more severe operating conditions or longer run times. However, in doing so, the yield of desirable products in a hydrocarbon product stream is sacrificed. Thus, advantages are realized here in the simultaneous production of a hydrocarbon product stream having a high yield of desirable products (e.g., C5+ hydrocarbons, aromatics) and that desirable fraction having a high octane-rating (RON).

[0038] The relative paraffin, aromatic, and naphthene content of a hydrocarbon feedstock may be described by its N+2A value, which is the naphthene content (wt. %) plus twice the aromatic content (wt. %). A higher N+2A value will have more naphthenes and aromatics where as a lower N+2A number will have more paraffins.

[0039] As used herein, the term“conditions effective to” refers to conditions to which a hydrocarbon feed stream may be subjected that results in a hydrocarbon product stream having a desired yield and/or octane number. Conditions may include temperature, pressure, reaction time, and the like, which are conditions known to those of ordinary skill in the art with benefit of this disclosure.

[0040] Advantages of the modified zeolitic catalysts described herein are apparent in an increased yield of desired products or product fractions in a hydrocarbon product stream derived from a modified zeolitic catalyst. As used herein, and unless otherwise specified,“percent yield” or“yield” is the total weight of the specified product divided by the total weight of the hydrocarbon feed stream and converted to a percent.

[0041] As used herein, the term“coke,” and grammatical derivatives thereof, refers to carbonaceous material that deposits on the surface, including within the pores, of a catalyst (e.g., a modified zeolitic catalyst). Formation of coke on a catalyst’s surface decreases the availability of active sites for the reforming reactions to take place. Thus, as coke builds up over time, the quality of a resulting hydrocarbon product stream may decrease. Measures of hydrocarbon product stream quality (e.g. , octane number, yield) are used herein as an indirect measure of coke formation on a modified zeolitic catalyst.

[0042] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the present specification and associated claims are to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the embodiments of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0043] One or more illustrative embodiments incorporating the invention embodiments described herein are presented herein. Not all features of a physical implementation are described or shown in this application for the sake of clarity. It is understood that in the development of a physical embodiment incorporating the embodiments of the present invention, numerous implementation-specific decisions must be made to achieve the developer's goals, such as compliance with system-related, business-related, government-related and other constraints, which vary by implementation and from time to time. While a developer’s efforts might be time- consuming, such efforts would be, nevertheless, a routine undertaking for those of ordinary skill in the art and having benefit of this disclosure.

[0044] While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methods may also“consist essentially of’ or“consist of’ the various components and steps.

Methods and Systems for Converting Hydrocarbons

[0045] Methods and systems for converting hydrocarbons are provided herein that utilize a modified zeolitic catalyst to convert a hydrocarbon feed stream to a hydrocarbon product stream. The isomerization activity of a modified zeolitic catalyst may be tuned by adding extra-framework metal oxides. Additionally, in any embodiment, a modified zeolitic catalyst prepared as disclosed herein may display reduced cracking activity. Thus, use of a modified zeolitic catalyst as disclosed herein may be particularly beneficial converting residual unreacted paraffins in a hydrocarbon stream to isoparaffins to boost product stream octane number.

Methods and Systems for Converting Hydrocarbons

[0046] Methods and systems for converting hydrocarbons are provided herein that utilize one or more modified zeolitic catalysts to convert a hydrocarbon feed stream to a hydrocarbon product stream. Advantageously, and surprisingly, a modified zeolitic catalyst may display enhanced isomerization activity over other undesired reforming reactions (e.g., dealkylation, cracking). This may be particularly useful where paraffm-to-aromatic conversion is incomplete and conversion of remaining paraffins to isoparaffins can boost the hydrocarbon product stream’s octane number. The isomerization activity of zeolitic catalyst may be tuned by adjusting its framework and/or bulk silica-to-alumina ratio. By using the systems and methods disclosed herein, a hydrocarbon feed stream comprising paraffins (which are typically viewed as undesirable) may be more fully converted to highly valuable products.

[0047] Provided herein are methods for treating a precursor zeolite having a bulk silica-to- alumina ratio and a framework silica-to-alumina ratio with one or more of acid, steam, and a combination thereof under conditions effective to prepare a modified zeolite having a framework silica-to-alumina ratio of about 40: 1 to about 1000: 1 and a bulk silica-to-alumina ratio of about 40: 1 to about 500: 1 ; and contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced isomerization activity as compared to the precursor zeolite. The modified zeolitic catalyst may then be used to convert a hydrocarbon feed stream into a product stream comprising high octane gasoline, for example, by contacting a hydrocarbon feed stream with the modified zeolitic catalyst under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream comprising one or more of a C5+ fraction.

[0048] Also provided herein are systems for converting hydrocarbons comprising: a hydrocarbon feed stream inlet configured and arranged to receive a hydrocarbon feed stream; at least one reactor comprising at least one catalyst bed, the catalyst bed comprising at least one modified zeolitic catalyst, wherein the modified zeolitic catalyst comprises a transition metal and a modified zeolite characterized by one or more of the following: a bulk silica-to-alumina ratio of about 40:1 to about 500; 1 and a framework silica-to-alumina ratio of about 40: 1 to about 1000: 1; and a hydrocarbon product stream outlet configured and arranged to receive a hydrocarbon product stream.

Modified Zeolitic Catalysts for Use in the Disclosed Methods and Systems

[0049] The modified zeolitic catalysts for use in the methods and systems described herein includes a modified zeolite and at least one transition metal.

[0050] A modified zeolitic catalyst as disclosed herein may be prepared from a zeolite, herein referred to as a“precursor zeolite” or a“zeolite.” As used herein,“precursor zeolite,”“zeolite,” or “zeolitic” (and grammatical variations thereof) are defined to refer to a crystalline material having a porous framework structure built from tetrahedral atoms connected by bridging oxygen atoms. A precursor zeolite is modified to produce a modified zeolite as described herein, which is subsequently converted to a modified zeolitic catalyst disclosed herein. Thus, the modified zeolites are precursor zeolites that have been treated in such a way that the one or more of the bulk silica- to-alumina ratio and framework silica-to-alumina ratio is increased relative to the precursor zeolite bulk silica-to-alumina ratio and framework silica-to-alumina ratio.

[0051] Examples of known zeolite frameworks are given in the“Atlas of Zeolite Frameworks” published on behalf of the Structure Commission of the International Zeolite Association”, 6th revised edition, Ch. Baerlocher, L.B. McCusker, D.H. Olson, eds., Elsevier, New York (2007) and the corresponding web site, http://www.iza-structure.org/databases, each which is incorporated by reference herein with respect to its disclosure of zeolitic frameworks and methods for their preparation. Under this definition, a zeolite can refer to aluminosilicates having a zeolitic framework type as well as crystalline structures containing oxides of heteroatoms different from silicon and aluminum. Such heteroatoms can include any heteroatom generally known to be suitable for inclusion in a zeolitic framework, such as gallium, boron, germanium, phosphorus, zinc, antimony, tin, and/or other transition metals that can substitute for silicon and/or aluminum in a zeolitic framework. A zeolite may be referred to by the number of tetrahedral atoms (exclusive of oxygen atoms) that define pore openings in the zeolite. For example, a precursor zeolite may be an 8-member ring zeolite, a 10-member ring zeolite, or a 12-member ring zeolite. Preferably, a precursor zeolite is a 12-member ring zeolite. A precursor zeolite may be a three-dimensional zeolite. Examples of suitable precursor zeolites include zeolites having a FAU, LTL, BEA, MAZ, MTW, MEI, MOR, or EMT-FAU intermediate framework structure. Examples of suitable precursor zeolites having an FAU framework structure include, but are not limited to, USY (or dehydrated USY), Na-X (or dehydrated Na-X), LZ-210, Li-LSX, zeolite X, and zeolite Y. Examples of suitable precursor zeolites having an LTL framework structure include, but are not limited to, zeolite L, gallosillicate L, LZ-212 and perlialite. Examples of suitable precursor zeolites having a BEA framework structure include, but are not limited, to Beta, Al-rich Beta, CIT-6, and pure silica Beta. Examples of suitable precursor zeolites having an MAZ framework structure include, but are not limited to, mazzite, LZ-202, and ZSM-4. Examples of suitable precursor zeolites having an MTW framework structure include, but are not limited to, ZSM-12, CZH-5, NU-13, TPZ-12, Theta-3, and VS-12. Examples of suitable precursor zeolites having an MEI framework structure include, but are not limited to, ZSM-18 and ECR-40. Examples of suitable precursor zeolites having an MOR framework structure include, but are not limited to, Ca-Q, LZ- 211, mordenite, and Na-D. Examples of suitable precursor zeolites having an EMT-FAU intermediate structure include, but are not limited to, CSZ-1, ECR-30, ECR-32, ZSM-20, and ZSM-3. A precursor zeolite may be a zeolite L, zeolite Y, or USY. A person of ordinary skill in the art knows how to make the aforementioned frameworks.

[0052] Zeolites, being an aluminosilicate material, have a framework silica-to-alumina ratio and bulk silica-to-alumina ratio. As used herein,“bulk silica-to-alumina ratio” refers to the silica- to-alumina ratio of a zeolite inclusive of alumina within and outside the framework (extra framework alumina). As used herein,“framework silica-to-alumina ratio” refers to the silica-to- alumina ratio of a zeolite of tetrahedrally coordinated alumina within the framework and exclusive of alumina outside the framework (extra-framework alumina, which is typically octahedrally coordinated). The bulk silica-to-alumina ratio, framework silica-to-alumina ratio, and extra framework metal oxide content, unless otherwise indicated, are measured on a modified zeolitic catalyst (defined below) after all modifications, for example, after steaming, silicone selectivation, and/or acid/base washing of a precursor zeolite. Framework silica-to-alumina ratio may be measured by solid state NMR. Bulk silica-to alumina ratio may be measured by any elemental analysis technique, for example, inductively coupled plasma atomic emission spectroscopy or inductively coupled plasma mass spectrometry.

[0053] Processes for producing modified zeolites include, for example, steaming a precursor zeolite. In such processes, a precursor zeolite may be steamed in an atmosphere comprising steam at a temperature of about 750°F (398.9°C) to about 3000°F (1649°C), about 1000°F (537.8°C) to about 2000°F (1093°C), or about 1500°F (815.6°C) to about 1800°F (982.2°C). The atmosphere can include as little as about 1 vol. % water and up to about 100 vol. % water. A precursor zeolite can be exposed to steam for any convenient period of time, such as about 10 minutes to about 48 hours. In particularly useful examples, a precursor zeolite is steamed for about 1 hour to about 5 hours at a temperature of about 1500°F (815.6°C) to about 1800°F (982.2°C), which includes about 1500°F (815.6°C), about 1600°F (871.1°C), about 1700°F (926.7°C), and about 1800°F (982.2°C).

[0054] A precursor zeolite may be steamed multiple times, if desired, to produce a modified zeolite. If steamed multiple times, each steam treatment can occur with other steps performed between steam treatments, for example, acid washing. Typical acid leaching conditions can include using a suitable acid, such oxalic acid, citric acid, or nitric acid, in concentrations ranging from about 0.1 molar up to about 10 molar, preferably about 1 molar, at a temperature ranging from about 20°C up to about 100°C.

[0055] Advantageously, a modified zeolitic catalyst may favor isomerization over other undesired reforming reactions such as, but not limited to, cracking and dealkylation. Enhanced selectivity for isomerization may be imparted to a modified zeolitic catalyst by adjusting the framework and/or bulk silica-to-alumina ratio of the precursor zeolite from which the modified zeolitic catalyst is derived. A modified zeolite suitable for preparing a modified zeolitic catalyst may have a high bulk silica-to-alumina ratio, for example, at least about 40: 1 ( e.g ., about 40: 1 to about 500: 1), or at least about 80: 1 (e.g., about 80: 1 to about 500: 1). A modified zeolite useful for the preparation of the modified zeolitic catalysts described herein may have a high framework silica-to-alumina ratio, for example, at least about 40: 1 (e.g., about 40: 1 to about 1000: 1), at least about 80: 1 (e.g., about 80: 1 to about 1000: 1), or at least about 500: 1 (e.g., about 500: 1 to about 1000: 1).

[0056] A modified zeolite may include an extra-framework metal oxide component. Metal oxides may be present in the modified zeolite at about 0.05 wt. % to about 5 wt. % based on the weight of modified zeolitic catalyst prepared therefrom. Suitable extra-framework metal oxides include, but are not limited to, alumina, titania, gallia, zirconia, boron oxide, tungsten oxide, niobium oxide, and combinations thereof. Preferably, the metal oxide is alumina. A modified zeolite may be contacted with one or more metal oxides or metal oxide precursors to incorporate the metal oxide into the zeolitic extra-framework space. This may be achieved, for example, the steaming and/or acid washing a precursor zeolite under conditions effective to extract framework alumina into the extra-framework space. In such instances, this may be more readily achieved by starting with a precursor zeolite having a lower framework silica-to-alumina ratio (i.e., a higher framework alumina content).

[0057] An extra-framework metal oxide component may alternatively or additionally be imparted to a modified zeolite by contacting the modified zeolite with a solution containing the metal oxide or a metal oxide precursor that may be converted to an oxide upon calcination at a concentration suitable to achieve the desired metal oxide content. For example, when incorporating alumina, aluminum nitrate, trimethyl alumina, or alumina binders (followed by steaming) may be used. A modified zeolitic catalyst may contain about 0.05 wt. % to about 5 wt. %, based on the total weight of the modified zeolitic catalyst derived from the modified zeolite. In any embodiment, a precursor zeolite may be steamed and/or acid washed under conditions effective to remove framework and extra-framework metal oxides and a preferred amount of metal oxide may be doped back into the modified zeolite to achieve a desired extra-framework metal oxide content. In such instances, this may be more readily achieved by starting with a precursor zeolite having a higher framework silica-to-alumina ratio (i.e.. a lower framework alumina content).

[0058] The presence of extra-framework metal oxides decreases collidine uptake of a modified zeolitic catalyst. While not wishing to be bound by theory, it is believed that reduction of framework alumina of the zeolitic catalyst precursor increases the selectivity for dehydrocyclization and the presence of extra-framework alumina provides enhanced isomerization functionality to a modified zeolitic catalyst. It is believed that the acid functionality derived from extra-framework metal oxides contribute less to cracking and hydrocarbon dealkylation than framework metal oxides. This may be due to steps and comers present on small metal oxide crystals trapped in the zeolite cavities or on the external surface of the zeolite. Thus, a modified zeolitic catalyst, prepared from a modified zeolite having a high framework silica-to-alumina ratio as well as an extra-framework metal oxide component, may achieve both dehydrocyclization and isomerization while minimizing cracking and dealkylation.

[0059] A modified zeolite may be treated with a source of one or more transition metals to form a modified zeolitic catalyst described herein. A modified zeolitic catalyst may include at least about 0.01 wt. %, at least about 0.05 wt. %, at least about 0.25 wt. %, at least about 1 wt. %, at least about 2.5 wt. %, at least about 5 wt. %, at least about 10 wt. %, or in a range from about 0.01 wt. % to about 10 wt. %, about 0.01 wt. % to about 5.0 wt. %, 0.01 wt. % to 2.5 wt. %, about 0.01 wt. % to about 1 wt. %, about 0.01 wt. % to about 0.25 wt. %, about 0.01 wt. % to about 0.05 wt. %, about 0.05 wt. % to about 10 wt. %, about 0.05 wt. % to about 5.0 wt. %, about 0.05 wt. % to about 2.5 wt. %, about 0.05 wt. % to about 1 wt. %, about 0.05 wt. % to about 0.25 wt. %, about 0.25 wt. % to 10 wt. %, about 0.25 wt. % to about 5 wt. %, about 0.25 wt. % to about 1 wt. %, about 1 wt. % to about 10 wt. %, about 1 wt. % to about 5 wt. %, about 1 wt. % to about 2.5 wt. %, about 2.5 wt. % to about 10 wt. %, about 2.5 wt. % to about 5 wt. %, or about 5 wt. % to about 10 wt. % transition metal, based on the total weight of the modified zeolitic catalyst. For example, a modified zeolitic catalyst may include about 0.9 wt. % of a transition metal. The transition metal may be a Group 10 transition metal, for example, nickel (Ni), palladium (Pd), platinum (Pt), or a combination thereof. Suitable sources of platinum include, but are not limited to, tetraamine platinum (II) nitrate, tetraamine platinum hydroxide, chloroplatinic acid, and the like. Typical methods for incorporation of a metal include impregnation (such as by incipient wetness), ion exchange, deposition by precipitation, and any other convenient method for depositing a metal.

[0060] Optionally, a modified zeolite or a zeolitic catalyst precursor may be combined with a support or binder material (both are referred to as a“binder” herein) to form a modified zeolitic catalyst. A modified zeolitic catalyst may include from about 1 wt. % to about 10 wt. %, about 1 wt. % to about 20 wt. %, about 1 wt. % to about 30 wt. %, about 1 wt. % to about 40 wt. %, about

1 wt. % to about 50 wt. %, about 1 wt. % to about 60 wt. %, about 1 wt. % to about 70 wt. %, about

1 wt. % to about 80 wt. %, about 1 wt. % to about 90 wt. %, about 1 wt. % to about 99 wt. %, about

10 wt. % to about 20 wt. %, about 10 wt. % to about 30 wt. %, about 10 wt. % to about 40 wt. %, about 10 wt. % to about 50 wt. %, about 10 wt. % to about 60 wt. %, about 10 wt. % to about 70 wt. %, about 10 wt. % to about 80 wt. %, about 10 wt. % to about 90 wt. %, about 10 wt. % to about 99 wt. %, about 20 wt. % to about 30 wt. %, about 20 wt. % to about 40 wt. %, about 20 wt. % to about 50 wt. %, about 20 wt. % to about 60 wt. %, about 20 wt. % to about 70 wt. %, about 20 wt. % to about 80 wt. %, about 20 wt. % to about 90 wt. %, about 20 wt. % to about 99 wt. %, about 30 wt. % to about 40 wt. %, about 30 wt. % to about 50 wt. %, about 30 wt. % to about 60 wt. %, about 30 wt. % to about 70 wt. %, about 30 wt. % to about 80 wt. %, about 30 wt. % to about 90 wt. %, about 30 wt. % to about 99 wt. %, about 40 wt. % to about 50 wt. %, about 40 wt. % to about 60 wt. %, about 40 wt. % to about 70 wt. %, about 40 wt. % to about 80 wt. %, about 40 wt. % to about 90 wt. %, about 40 wt. % to about 99 wt. %, about 50 wt. % to about 60 wt. %, about 50 wt. % to about 70 wt. %, about 50 wt. % to about 80 wt. %, about 50 wt. % to about 90 wt. %, about 50 wt. % to about 99 wt. %, about 60 wt. % to about 70 wt. %, about 60 wt. % to about 80 wt. %, about 60 wt. % to about 90 wt. %, about 60 wt. % to about 99 wt. %, about 70 wt. % to about 80 wt. %, about 70 wt. % to about 90 wt. %, about 70 wt. % to about 99 wt. %, about 80 wt. % to about 90 wt. %, about 80 wt. % to about 99 wt. %, or about 90 wt. % to about 99 wt. % binder based on total weight of the modified zeolitic catalyst. A suitable modified zeolite-to- binder ratio may be about 10: 1, about 4: 1, about 2: 1, about 1 : 1, about 1 :2, about 1 :4, or about 1 : 10. [0061] Optionally, one or more promoters may be present in a modified zeolitic catalyst described herein. For example, a modified zeolitic catalyst may include at least about 0.005 wt. % to about 10 wt. %, about 0.005 wt. % to about 5 wt. %, about 0.005 wt. % to about 1 wt. %, about 0.005 wt. % to about 0.5 wt. %, about 0.005 wt. % to about 0.01 wt. %, about 0.01 wt. % to about 10 wt. %, about 0.01 wt. % to about 5 wt. %, about 0.01 wt. % to about 1 wt. %, about 0.01 wt. % to about 0.5 wt. %, about 0.5 wt. % to about 10 wt. %, about 0.5 wt. % to about 5 wt. %, about 0.5 wt. % to about 1 wt. %, about 1 wt. % to about 10 wt. %, about 1 wt. % to about 5 wt. %, or about 5 wt. % to about 10 wt. % of a promoter based on total weight of the modified zeolitic catalyst. The promoter may be a Group 3 metal, a Group 4 metal, a Group 5 metal, a Group 6 metal, a Group 7 metal, a Group 8 metal, a Group 9 metal, a Group 10 metal, a Group 11 metal, a Group 13 metal, and a Group 14 metal. Examples of promoters include, but are not limited to, scandium (Sc), tin (Sn), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), palladium (Pd), gallium (Ga), iridium (Ir), indium (In), germanium (Ge), rhodium (Rh), ruthenium (Ru), and copper (Cu). Promoters may be incorporated from about 0.005 wt. % to about 15 wt. % by any method well known in the art, for example, impregnation, Muller addition, ion exchange, and/or the like.

[0062] Optionally, the modified zeolite in a modified zeolitic catalyst may be present at least partly in hydrogen form. This can readily be achieved, for example, by ion exchange to convert the modified zeolite to the ammonium form, followed by calcination in air or an inert atmosphere at a temperature from about 400°C to about 1000°C to convert the ammonium form to the active hydrogen form. If an organic structure-directing agent is used in the synthesis of a zeolite, additional calcination may be desirable to remove the organic structure-directing agent.

[0063] Optionally, a modified zeolitic catalyst may include one or more selectivating agents to introduce diffusional limitations to a modified zeolitic catalyst. Silicone selectivation can be performed with any suitable silicone oil or from an organic silica source such as tetraethyl orthosilicate (TEOS). As used herein, a selectivating agent refers to an agent that prevents unwanted activity derived from sites on the modified zeolite’s external surface.

[0064] A zeolitic catalyst precursor may be calcined, reduced (e.g., in Eh) and/or sulfided by methods well known in the art to yield a modified zeolitic catalyst. Sulfidation can be performed by any convenient method, such as gas phase sulfidation or liquid phase sulfidation.

[0065] As used herein, modified zeolitic catalyst, and grammatical variations thereof, refers to a catalyst prepared from a precursor zeolite by adjusting the acidity of a precursor zeolite to form a modified zeolite. A precursor zeolite’s acidity is multi-faceted, and may be indicated by one or more of its alpha value, collidine uptake, Bronsted acid site density, ratio of Bronsted-to-Lewis acid sites, and ammonia adsorption/desorption. Structurally, these properties may be influenced by one or more of the framework sibca-to-alumina ratio, bulk silica-to-alumina ratio, and an extra framework metal oxide component, among others. Changing any of these structural components, likewise, may change the precursor zeolite’s acidity. As used herein, a modified zeolitic catalyst may have an acidity, as measured by alpha value, of less than about 2 or less than about 1, for example, in a range of about 0 to about 3, about 0 to about 2, or about 0 to about 1. A modified zeolitic catalyst may have an acidity, as measured by collidine uptake, of less than about 40 pmol/g, less than about 35 pmol/g, less about 30 pmol/g, less than about 25 pmol/g, less than 20 pmol/g, less than about 15 pmol/g, or less than about 10 pmol/g; ranges include about 0 pmol/g to about 10 pmol/g, about 0 pmol/g to about 15 pmol/g, about 0 pmol/g to about 20 pmol/g, about 0 pmol/g to about 25 pmol/g, about 0 pmol/g to about 30 pmol/g, about 0 pmol/g to about 35 pmol/g, about 0 pmol/g to about 40 pmol/g, about 10 pmol/g to about 15 pmol/g; about 10 pmol/g to about 20 pmol/g; about 10 pmol/g to about 25 pmol/g; about 10 pmol/g to about 30 pmol/g; about 10 pmol/g to about 35 pmol/g; and about 10 pmol/g to about 40 pmol/g. Preferably, a modified zeolitic catalyst has a collidine uptake of less than about 40 pmol/g. In any embodiment, a modified zeolitic catalyst may have a collidine uptake of between about 10 pmol/g and 40 pmol/g.

[0066] Particular embodiments of modified zeolitic catalysts suitable for use in the methods and systems described herein include:

• aUSY precursor zeobte (with an alpha of2.2 and a colbdine uptake of l0.9 pmol/g) steam-treated for 1 hour at 1500°F (815.6°C), bound with silica at a ratio of 80:20 zeolite: silica, impregnated with 0.9% Pt;

• aUSY precursor zeobte (with an alpha of2.2 and a colbdine uptake of l0.9 pmol/g) steam-treated for 1 hour at 1500°F (815.6°C) + 0.9 wt. % Pt, bound with silica at a ratio of 80:20 zeolite: silica, impregnated with 0.9% Pt;

• a USY precursor zeolite (with an alpha of 12 and a collidine uptake of 99.6 pmol/g) steam-treated for 5 hours at 1500°F (815.6°C) + 0.9 wt. % Pt, bound with silica at a ratio of 80:20 zeolite: silica, impregnated with 0.9% Pt;

• a USY precursor zeolite (with an alpha of 12 and a collidine uptake of 99.6 pmol/g) steam-treated for 1 hour at 1600°F (871.1°C) + 0.9 wt. % Pt, bound with silica at a ratio of 80:20 zeolite: silica, impregnated with 0.9% Pt; and

• a USY precursor zeolite (with an alpha of 12 and a collidine uptake of 99.6 pmol/g) steam-treated for 1 hour at 1700°F (926.7°C) + 0.9 wt. % Pt, bound with silica at a ratio of 80:20 zeolite: silica, impregnated with 0.9% Pt.

Methods and Systems of Converting Hydrocarbons [0067] Methods and systems are provided herein that utilize at least one modified zeolitic catalyst for converting a hydrocarbon feed stream to a hydrocarbon product stream. A hydrocarbon feed stream may be contacted with a modified zeolitic catalyst comprising a modified zeolite, a transition metal, and optionally a binder under conditions effective to convert a hydrocarbon feed stream to a hydrocarbon product stream comprising high-octane gasoline. The methods described herein may further comprise providing hydrogen to the at least one reactor in which the contacting is carried out.

Systems for Converting Hydrocarbons

[0068] A system for performing the above-described method is also provided herein. A system may include, but is not limited to, a hydrocarbon feed stream, a hydrocarbon product stream, and at least one reactor in which the hydrocarbon feed stream may be contacted with one or more of the modified zeolitic catalysts as described herein under conditions effective to convert the hydrocarbon feed stream to the hydrocarbon product stream. The at least one reactor has a hydrocarbon feed inlet constructed and arranged to receive the hydrocarbon feed stream and a hydrocarbon product outlet constructed and arranged to provide the hydrocarbon product stream. A system for converting a hydrocarbon feed stream may be part of a reforming unit. In any embodiment, a reforming unit may be further capable of regenerating a modified zeolitic catalyst. For example, the reforming unit may be a cyclic reforming unit or a semi-regenerative reforming unit.

Example Systems

[0069] An example reforming system suitable for use with the methods disclosed herein is shown in FIG. 1. The reforming system 100 includes a pre-treatment stage 102, a post-treatment separator 104, a heater 106, a reactor 108, a separation stage 110, and a compressor 112 for compressing a recycled hydrogen stream 111. A hydrocarbon feed stream 101 may be conveyed to a pre-treatment stage 102 to modify the disposition of the hydrocarbon feed stream 101 for compatibility with downstream processes. For example, the pre-treatment stage 102 may modify the sulfur content, nitrogen content, and/or remove water from the hydrocarbon feed stream 101.

[0070] The pre-treatment stage effluent 103 comprising a treated hydrocarbon feed stream may then be conveyed to a post-treatment separator 104 to isolate the treated hydrocarbon feed stream from a waste stream 116, which may include water, ammonia, hydrogen sulfide, and the like. The post-treatment separator effluent 107 comprising a treated hydrocarbon feed stream may then be conveyed together with hydrogen joining from the recycled compressed hydrogen stream 113 to a heater 106 to warm the hydrocarbon feed stream. The heated hydrocarbon feed stream 107 may then be conveyed to a reactor 108. The reactor 108 comprises at least one catalyst bed 120. At least one of the catalyst beds 120 in reactor 108 comprises one or more of a modified zeolitic catalyst as described herein. After being conveyed through the reactor 108, the reactor effluent 109 comprising a hydrocarbon product stream may be conveyed to a separation stage 110, which isolates valuable fractions of the hydrocarbon product stream. The separation stage may include one or more separation processes, each of which may be, for example, extraction, distillation, membrane separation, aromatic/saturate separation, or any combination thereof.

[0071] For example, hydrogen 111 may be isolated from the hydrocarbon product stream. The hydrocarbon product stream may be separated into two or more fractions 114, 115, including, but not limited to, a C4- fraction, an LPG fraction, a C5+ fraction, a C7+ fraction, an aromatic fraction, or any combination thereof. Optionally, an aromatics fraction may be further separated to isolate one or more of benzene, toluene, xylenes, or heavier aromatics. In another example, a C5+ fraction may be separated to isolate low vapor pressure, high-octane gasoline. The hydrogen 111 may be collected for commercial sale or may be recycled back to the system, passing through a compressor 112 and joining the hydrocarbon feed stream at any location upstream of the reactor 108. For example, FIG. 1 depicts the compressed recycled hydrogen stream 113 joining the post-treatment separator effluent 107. Alternatively, the recycled hydrogen stream 113 may be reintroduced into the system with the hydrocarbon feed stream 101, the post-treatment effluent 103, or with heated hydrocarbon feed stream 107. It may also be fed directly into the reactor 108. In any embodiment, the recycled hydrogen stream 113 may not be entirely derived from recycled hydrogen. For example, the recycled hydrogen stream 113 may be supplemented with hydrogen from another source (e.g, commercially available hydrogen or hydrogen from another reforming unit).

[0072] In any embodiment, the pre-treatment stage 102 may not be present. In such embodiments, the hydrocarbon feed stream 101, together with a hydrogen stream 113, is directly conveyed to the heater 106 then to the reactor 108. In any embodiment, a reactor may contain multiple catalyst beds, for example, in a stacked bed configuration. In any embodiment, a reforming system may comprise two or more reactors, each comprising one or more catalyst beds. In such cases, the system may include one or more conduits to fluidly connect the two or more reactors to each other. A conduit connecting two reactors may further comprise a heater.

Hydrocarbon Feed Streams

[0073] The methods and systems described herein may be suitable for converting a hydrocarbon feed stream comprising naphtha feedstock, a fraction thereof (e.g., light naphtha, heavy naphtha), or a feedstock comprising C6-C8 hydrocarbons. A suitable hydrocarbon feed stream may have a boiling range characterized by a T5-T95 range of about 10°C to about 232°C. Examples of suitable full-range naphtha (or naphtha fractions) include hydrotreated naphtha, fluid catalytic cracker (FCC) naphtha, straight run naphtha, coker naphtha, delayed coker naphtha, fluid coker naphtha, and any blend thereof. A hydrocarbon feed stream comprising C6-C8 hydrocarbons may include v paraffins, C6-C8 naphthenes, G,-Cs aromatics, or combinations thereof.

[0074] Advantageously, the modified zeolitic catalysts as described herein are efficient at catalyzing the conversion of paraffins to isoparaffins. Thus, a modified zeolitic catalyst may be particularly advantaged for converting hydrocarbon feed streams with a high paraffin content and/or a low N+2A value. A hydrocarbon feed stream may comprise C4-C12 paraffins, for example, butane, pentane, hexane, heptane, and/or octane. A hydrocarbon feed stream may comprise at least about 30 wt. %, at least about 45 wt. %, at least about 50 wt. %, at least about 60 wt. %, at least about 70 wt. %, at least about 80 wt. %, at least about 90 wt. %, at least about 95 wt. %, at least about 99 wt. % or about 100 wt. %; or in a range of about 45 wt. % to about 100 wt. %, about 50 wt. % to about 100 wt. %, about 60 wt. % to about 100 wt. %, about 70 wt. % to about 100 wt. %, about 90 wt. % to about 100 wt. % or about 95 wt. % to about 100 wt. % C4-C12 paraffins, based on total weight of the hydrocarbon feed stream. A hydrocarbon feed stream may be characterized by an N+2A value of less than about 90 (i.e.. about 0 to about 90), less than about 80 (i.e.. about 0 to about 80), less than about 70 (i.e.. about 0 to about 70), less than about 60 (i.e.. about 0 to about 60), less than about 50 (i.e., about 0 to about 50), or less than about 40 (i.e., about 0 to about 40).

[0075] Alternatively, the majority of a suitable hydrocarbon feed stream may comprise G,-Cs hydrocarbons, for example, hexane, heptane, and/or octane. A hydrocarbon feed stream may comprise at least about 60 wt. %, at least about 70 wt. %, at least about 80 wt. %, at least about 90 wt. %, at least about 95 wt. %, at least about 99 wt. % or about 100 wt. %; or in a range of about 45 wt. % to about 100 wt. %, about 50 wt. % to about 100 wt. %, about 60 wt. % to about 100 wt. %, about 70 wt. % to about 100 wt. %, about 90 wt. % to about 100 wt. % or about 95 wt. % to about 100 wt. % G,-Cs hydrocarbons, based on total weight of the hydrocarbon feed stream. In any embodiment, a hydrocarbon feed stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) C6-Cs paraffins or may comprise all G,-Cs paraffins (e.g., greater than about 99 wt. % or about 100 wt. %). In any embodiment, a hydrocarbon feed stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) hexane or may comprise all hexane (e.g., greater than about 99 wt. % or about 100 wt. %). In any embodiment, a hydrocarbon feed stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) heptane or may comprise all heptane (e.g., greater than about 99 wt. % or about 100 wt. %). [0076] The modified zeolitic catalyst as provided herein may be resistant to the presence of nitrogen. For example, a modified zeolitic catalyst may be contacted with a hydrocarbon feed containing up to 1000 ppm basic nitrogen without significant detrimental effects to the modified zeolitic catalyst’s activity. In addition to being resistant to nitrogen, a modified zeolitic catalyst as described herein may also be tolerant of sulfur in a hydrocarbon feed stream, particularly when rhenium is absent from said modified zeolitic catalyst. Whereas the presence of sulfur in a hydrocarbon feed stream typically drives down product stream yield when using a chlorided alumina catalyst, a modified zeolitic catalyst as disclosed herein does not suffer the same effects. For example, a modified zeolitic catalyst may be compatible with a feedstock having no measurable sulfur content to about 10 ppm sulfur, including about 0.5 ppm to about 10 ppm, about 1 ppm to about 10 ppm, and about 1.5 ppm to about 10 ppm.

[0077] Thus, a modified zeolitic catalyst as provided herein may provide particular advantages to cyclic reforming units and semi-regenerative reforming units as these types of units typically require more frequent offline catalyst regeneration than (more expensive) reforming units such as continuous catalyst regeneration reforming units.

Reactors

[0078] In the methods and systems described herein, a hydrocarbon feed stream may be contacted with one or more modified zeolitic catalysts as described herein under conditions effective to convert a hydrocarbon feed stream to a hydrocarbon product stream. The contacting may be performed in one or more reactors, each comprising at least one catalyst bed. At least one of catalyst beds includes a modified zeolitic catalyst as described herein. The one or more catalyst beds may be fixed beds or moving beds. The one or more catalyst beds may be contained within a single reactor or may be in separate reactors.

[0079] The reaction conditions for converting a hydrocarbon feed stream to a hydrocarbon product stream may be any suitable conditions known in the art. For example, the one or more reactors may each, independently, be held at a pressure of about 15 psig (103 kPa) to about 1500 psig (10340 kPa) and/or an Fkihydrocarbon ratio (FkiHC ratio) of about 0.1 : 1 to about 10: 1. The combined one or more reactors may have a weight hourly space velocity (WHSV) of about 0.1 hours-1 to about 15 hours-1. The one or more reactors may each, independently, be held at an El temperature of about 400°C to about 750°C. For example, a reactor may be held at an El temperature of about 500°C, a pressure of about 350 psig (2410 kPa), a WHSV of about 0.1 hours ¹ to about 15 hours ¹ , and/or an H2:HC ratio of about 5: 1.

Hydrocarbon Product Streams [0080] When a hydrocarbon feed stream comprises naphtha (or a fraction thereof), the hydrocarbon product stream derived therefrom may comprise, consist essentially of, or consist of aromatic and isoparaffmic hydrocarbons (i.e.. upgraded naphtha). A hydrocarbon product stream or fractions thereof (e.g., the C5+ fraction) may be characterized by a higher octane number than the hydrocarbon feed stream from which it is derived. For example, the C5+ fraction of a hydrocarbon product stream may be characterized by an octane number of at least about 80, at least about 85, at least about 90, at least about 95, at least about 99, or about 100; or in a range of about 80 to about 100, about 90 to about 100 or about 95 to about 100. A hydrocarbon product stream or fractions thereof may be further blended with other streams, such as a gasoline source.

[0081] When a hydrocarbon feed stream comprises C4-C12 hydrocarbons, the hydrocarbon product stream derived therefrom may comprise C4-C12 aromatics. A hydrocarbon product stream may include at least about 30 wt. %, at least about 50 wt. %, at least about 70 wt. %, at least about 90 wt. %, at least about 99 wt. % or about 100 wt. %; or in a range of about 30 wt. % to about 100 wt. %, about 50 wt. % to about 100 wt. %, about 70 wt. % to about 100 wt. %, about 30 wt. % to about 90 wt. % or about 50 wt. % to about 70 wt. % C4-C12 aromatics.

[0082] When a hydrocarbon feed stream comprises C6-C8 hydrocarbons, the hydrocarbon product stream derived therefrom may comprise C6-C8 aromatics. A hydrocarbon product stream may include at least about 30 wt. %, at least about 50 wt. %, at least about 70 wt. %, at least about 90 wt. %, at least about 99 wt. % or about 100 wt. %; or in a range of about 30 wt. % to about 100 wt. %, about 50 wt. % to about 100 wt. %, about 70 wt. % to about 100 wt. %, about 30 wt. % to about 90 wt. % or about 50 wt. % to about 70 wt. % C6-C8 aromatics. A hydrocarbon product stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) benzene or may comprise all benzene (e.g., greater than about 99 wt. % or about 100 wt. %). Alternatively, a hydrocarbon product stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) toluene or may comprise substantially all toluene (e.g., greater than about 99 wt. % or about 100 wt. %). Alternatively, a hydrocarbon product stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) Cs aromatics (e.g., ethylbenzene, xylenes) or may comprise substantially all Cs aromatics (e.g., greater than about 99 wt. % or about 100 wt. %).

[0083] Further, whereas chlorided alumina catalysts produce C9+ aromatics, which have limited commercial value compared to C6-Cs aromatics, a modified zeobtic catalyst as described herein tends to yield more valuable C6-Cs aromatics. Additionally, when compared to product streams yielded from chlorided alumina, the modified zeobtic catalysts described herein may yield a higher C5+ fraction at the same octane number due to the conversion of paraffins to isoparaffins rather than to smaller hydrocarbons through cracking. \

Example Embodiments

[0084] One nonlimiting example embodiment includes a method of preparing a modified zeolitic catalyst comprising: treating a precursor zeolite having a bulk silica-to-alumina ratio and a framework silica-to-alumina ratio with one or more of acid, steam, and a combination thereof under conditions effective to prepare a modified zeolite having a framework silica-to-alumina ratio of about 40: 1 to about 1000: 1 and a bulk silica-to-alumina ratio of about 40: 1 to about 500: 1; and contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced isomerization activity as compared to the precursor zeolite. Optionally, the embodiment may be combined with one or more of the following Elements: Element 1 : the method further comprising contacting the modified zeolite with a metal oxide under conditions effective to prepare a modified zeolitic catalyst having extra-framework metal oxides; Element 2: the method wherein treating comprises steaming at a temperature of between about 750°F (398.9°C) to about 3000°F (1649°C) for a period of about 1 hour to about 5 hours; Element 3: the method wherein, wherein treating comprises steaming at a temperature of between about 1500°F (815.6°C) to about 3000°F (1649°C) for a period of about 1 hour to about 5 hours; Element 4: the method wherein the modified zeolite is characterized by one or more of the following: a bulk silica-to-alumina ratio of about 80: 1 to about 500: 1 and a framework silica-to-alumina ratio of about 80: 1 to 1000: 1; Element 5: the method wherein the framework silica-to-alumina ratio of the modified zeolite is about 500: 1 to about 1000: 1 ; Element 6: the method wherein the precursor zeolite is one or more of a 12-member ring zeolite, a 12-member ring three-dimensional zeolite, a zeolite having an FAU or BEA intermediate framework structure, a Beta zeolite, a Y zeolite, an L zeolite, an USY zeolite, and combinations thereof; Element 7: the method wherein the precursor zeolite is a USY zeolite; Element 8: the method wherein the modified zeolitic catalyst is characterized by an alpha value of not more than about 3; Element 9: the method wherein the modified zeolitic catalyst is characterized by a collidine uptake of not more than about 40 pmoles/g; Element 10: the method wherein the modified zeolitic catalyst is characterized by a collidine uptake of about 10 pmoles/g to about 40 pmoles/g; Element 11 : the method wherein the modified zeolitic catalyst comprises about 0.05 wt. % to about 5 wt. % extra-framework metal oxide; Element 12: the method wherein the metal oxide is one or more of the following compounds: titania, alumina, zirconia, gallia, niobium oxide, boron oxide, and tungsten oxide; Element 13: the method wherein the transition metal comprises at least one of the following: platinum, palladium, and nickel; Element 14: the method, further comprising: contacting a hydrocarbon feed stream with the modified zeolitic catalyst under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream comprising one or more of a C5+ fraction; Element 15: Element 14 and wherein the C5+ fraction has a RON of at least about 95; Element 16: Element 14 and wherein the hydrocarbon feed stream comprises one or more of full-range naphtha, hydrotreated naphtha, virgin naphtha, intermediate cracked naphtha, fluid catalytic cracker naphtha, straight run naphtha, coker naphtha, delayed coker naphtha, steam cracker naphtha, fluid coker naphtha, hydrocrackate, and blends thereof; Element 17: Element 14 and wherein the hydrocarbon product stream comprises at least about 80 wt. % of a C5+ fraction; Element 18: Element 14 and wherein the conditions effective to comprise one or more of the following conditions: a reactor El temperature of at least about 450°C, a reactor WHSV of at least about 5 hours ¹ , aH2:HC ratio of at least about 2.5: 1, a reactor pressure of about 215 psig (1480 kPa), or any combination thereof; Element 19: Element 14 and wherein the conditions comprise one or more of the following conditions: an El temperature of at least about 500°C, a pressure of not more than about 215 psig (1480 kPa), a WHSV of not more than about 5 hours ¹ , and an H2:HC ratio of not more than about 2.5: 1; and Element 20: Element 14 and wherein the hydrocarbon feed stream is characterized by an N+2A value of less than about 90. Examples of combinations include, but are not limited to, Element 1 in combination with one or more of Elements 3-20; Element 2 in combination with one or more of Elements 3-20; Element 3 in combination with one or more of Elements 4-20; Element 4 in combination with one or more of Elements 5-20; Element 5 in combination with one or more of Elements 6-20; Element 6 in combination with one or more of Elements 7-20; Element 7 in combination with one or more of Elements 8-20; Element 8 in combination with Element 20 and one or more of Elements 9-27; Element 9 in combination with one or more of Elements 10-20; Element 10 in combination with one or more of Elements 11-20; Element 11 in combination with one or more of Elements 12-20; Element 11 in combination with one or more of Elements 12-20; Element 12 in combination with one or more of Elements 13-20; Element 13 in combination with one or more of Elements 14-20; Element 14 in combination with one or more of Elements 16-20; Element 15 in combination with one or more of Elements 16-20; Element 16 in combination with one or more of Elements 17-20; Element 17 in combination with one or more of Elements 18-20; Element 18 in combination with one or more of Elements 19-20; Element 19 in combination with Element 20; Element 3 in combination with Element 14;

[0085] Another nonlimiting example embodiment includes a system comprising: a hydrocarbon feed stream inlet configured and arranged to receive a hydrocarbon feed stream; at least one reactor comprising at least one catalyst bed, the catalyst bed comprising at least one modified zeolitic catalyst, wherein the modified zeolitic catalyst comprises a transition metal and a modified zeolite characterized by one or more of the following: a bulk silica-to-alumina ratio of about 40: 1 to about 500; 1 and a framework silica-to-alumina ratio of about 40: 1 to about 1000: 1 ; and a hydrocarbon product stream outlet configured and arranged to receive a hydrocarbon product stream. Optionally the embodiment may include one or more of the following Elements: Element 21 : the system wherein the catalyst bed is a fixed bed; Element 22: the system wherein the modified zeolite is characterized by one or more of the following: a bulk silica-to-alumina ratio of about 80: 1 to about 500: 1 and a framework silica-to-alumina ratio of about 80: 1 to 1000: 1.; Element 23: the system wherein the modified zeolite is characterized by a framework silica-to-alumina ratio of about 500: 1 to about 1000: 1. Examples of combinations include, but are not limited to, Element 21 in combination with one or more of Elements 22 and 23; and Element 22 in combination with Element 23.

[0086] To facilitate a better understanding of the present invention, the following examples of preferred or representative embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.

EXAMPLES

Example 1: Catalyst Preparation.

[0087] Modified Zeobtic Catalysts: A USY precursor zeolite with FAU framework having a bulk silica-to-alumina ratio of at least 60 is extruded with silica (binder) at a ratio of 80:20 (zeolite to silica) and then steamed at about 1500°F (815.6°C) to about 1800°F (982.2°C) for about 1 hour to about 5 hours to generate a zeobtic catalyst precursor. The zeobtic catalyst precursor is then impregnated with 0.9% platinum, reduced in Eh, and sulfided in 10 wt. % FES. Where indicated in particular examples, in addition to platinum, the zeobtic catalyst precursor is impregnated with extra-framework alumina by treating with aluminum nitrate.

[0088] Pt/Re Chlorided Alumina Catalysts: Pt/Re chlorided alumina catalysts are prepared by loading 1 wt. % chlorine onto extruded Pt/Re on aluminum oxide having a large surface area followed by reducing in EE and sulfiding in 10 wt. % FES.

Example 2: Properties of Modified Zeolitic Catalysts.

[0089] Data herein will be illustrated for different modified zeolitic catalysts prepared in a variety of methods. The starting zeolite, referred to as either USY A or USY B, has properties as shown in Table 1 below. Table 1 also reports the effects on alpha value and collidine uptake after extruding each with 80:20 zeolite: silica followed by steaming for 1 hour at either 1500°F (815.6°C) or 1700°F (926.7°C).

Table 1

[0090] FIG. 2 provides data illustrating the effect of steam treating for one hour at various temperatures on the collidine uptake of modified zeolitic catalysts prepared by steaming a either a USY A precursor zeolite or a USY B precursor zeolite extruded with silica at an 80:20 zeolite: silica ratio.

Example 3: The Hydrocarbon Feed Stream.

[0091] To illustrate the activity of example modified zeolitic catalysts as described herein, a hydrocarbon feed stream having naphtha range boiling fraction is conveyed through a catalyst bed having a modified zeolitic catalyst prepared as described in Example 1. The hydrocarbon feed stream is n-heptane or a feedstock having the properties disclosed in Table 2 below.

Table 2

[0092] The hydrocarbon feed stream as described in Table 2 is pre-treated by passing it through molecular sieve material to remove water and through a sulfur adsorbent to adjust sulfur content to about 0.6 ppm.

Example 4: Reactor Conditions.

[0093] All catalysts are tested either in an isothermal 16-channel fixed bed unit (< 1 cc catalyst) or in a fixed-bed isothermal microunit (1-5 cc catalyst). The reactor was operated at a temperature of between about 450°C and about 525°C, a pressure of between about 125 psig (860 kPa) and about 350 psig (2410 kPa), an PkiHC ratio of between about 1.25: 1 and about 5: 1, and a WHSV of between about 1 hour ¹ and about 10 hour ¹ . In the following examples, specific conditions within these ranges are indicated.

Example 5: Characterizing the Hydrocarbon Product Stream.

[0094] The hydrocarbon product stream is analyzed by gas chromatography. Octane is calculated according to the model described by Ghosh, P. et al. (2006)“Development of Detailed Gasoline Composition-Based Octane Model.” Ind. Eng. Chem. Res., 45(1), pp. 337-345.

Example 6: Improved Aromatic Yield.

[0095] FIG. 3 provides data illustrating the effect of extra-framework alumina on hydrocarbon product stream octane number. The hydrocarbon feed stream is naphtha as described in Table 3 and the reactor is operated at a 5.5: 1 H2:HC ratio, 350 psig (2410 kPa), a WHSV of 1 hour ¹ to 5 hour ¹ and a temperature of 500°C.

[0096] Platinum impregnation of modified zeolites is carried out using either tetraamine platinum nitrate (“PtNCb”) or tetraamine platinum hydroxide (“PtOH”). The modified zeolitic catalysts depicted in FIG. 3 are prepared as follows:

• USY A, extruded with 80:20 zeolite: silica, impregnated with 0.9% Pt (PtOH), steamed 1 hour at 1500°F (815.6°C), impregnated with 0.5 wt. % alumina;

• USY B, extruded with 80:20 zeolite: silica, impregnated with 0.9% Pt (PtOH), steamed 1 hour at 1700°F (926.7°C);

• USY A, extruded with 80:20 zeolite: silica, impregnated with 0.9% Pt (PtN03), steamed 1 hour at 1500°F (815.6°C).

[0097] In addition to the modified zeolitic catalyst intentionally impregnated with extra- framework alumina, the modified zeolitic catalyst prepared from the USY B precursor zeolite and steamed 1700°F (926.7°C) has an extra-framework alumina component, as the USY B precursor zeolite is more aluminous than the USY A precursor zeolite. At equal C5+ fraction yields, the modified zeolitic catalysts having extra-framework alumina appear to produce a hydrocarbon product stream having a higher octane number than the hydrocarbon product stream derived from the modified zeolitic catalyst prepared from the USY A precursor zeolite. Further, it is possible that addition of 0.5 wt. % extra-framework alumina may be more than necessary to achieve the desired enhanced isomerization. For example, 0.25 wt. %, 0.1 wt. %, 0.075 wt. %, or 0.05 wt. % extra-framework alumina may be sufficient to achieved desired isomerization activity.

[0098] FIG. 4 provides data similar data, illustrating that at the same C5 + Ce cyclic hydrocarbon yield, a hydrocarbon product stream derived from a modified zeolitic catalyst prepared from a modified zeolite having extra-framework alumina appears to have a higher octane number. The modified zeolitic catalysts, hydrocarbon feed stream, and reaction conditions are the same as described with respect to FIG. 3. The improved hydrocarbon product stream octane number at identical cyclic hydrocarbon yields suggests that improved octane is not due to paraffin dehydrocyclization, but rather paraffin isomerization.

Example 7: Isomerization Selectivity.

[0099] FIG. 5 provides data illustrating the effect of extra-framework alumina on the isomerization of C4 hydrocarbons. The modified zeolitic catalysts, hydrocarbon feed stream, and reaction conditions are the same as described with respect to FIGS. 3 and 4. At the same C4 fraction yield, a hydrocarbon product stream derived from a modified zeolitic catalyst prepared from a modified zeolite having extra-framework alumina appears to exhibits a higher ratio of isomerized to normal paraffins (iC4/nC4).

[0100] FIG. 6 illustrates that the enhanced isomerization imparted to a modified zeolitic catalyst by the presence of extra-framework alumina may be removed by acid washing with oxalic acid. In FIG. 6, the reactor conditions and hydrocarbon feed stream are the same as described with respect to FIGS. 3-5. It appears that the modified zeolitic catalyst treated with oxalic acid generates a hydrocarbon product stream having a lower C5+ fraction yield when the RON reaches industrially relevant levels (e.g., 95). The modified zeolitic catalysts depicted in FIG. 6 are prepared as follows:

• USY A, extruded with 80:20 zeolite: silica, impregnated with 0.9% Pt, steamed 1 hour at 1500°F (815.6°C);

• USY B, extruded with 80:20 zeolite: silica, impregnated with 0.9% Pt, steamed 1 hour at 1600°F (871.1°C);

• USY B, extruded with 80:20 zeolite: silica, impregnated with 0.9% Pt, steamed 1 hour at 1700°F (926.7°C);

• USY B, extruded with 80:20 zeolite: silica, impregnated with 0.9% Pt, steamed 5 hours at 1500°F (815.6°C), and washed with oxalic acid.

[0101] FIG. 7 further illustrates that the enhanced isomerization imparted by the presence of extra-framework alumina may be reversed by acid washing. In FIG. 7, the reactor conditions, hydrocarbon feed stream, and modified zeolitic catalysts are the same as described with respect to FIG. 6.

[0102] Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. The invention illustratively described herein suitably may be practiced in the absence of any element that is not specifically described herein and/or any optional element described herein.