The AROMAX process for improved selectivity and processing of heavier feedstocks.

Abstract

The present disclosure relates generally to systems, methods, and processes for catalytic hydrocarbon reforming.

Description

[Technical Field]

[0001] The present disclosure relates generally to systems, methods, and processes for catalytic hydrocarbon reforming. [Background technology]

[0002] The catalytic conversion of hydrocarbons to aromatic compounds, known as aromatization or reforming, is an important industrial process. Reforming reactions aim to convert paraffins, naphthenes, and olefins into aromatic compounds and hydrogen. Reforming processes encompass numerous reactions, typically carried out in the presence of a catalyst, such as dehydration cycloreversion, hydrodecyclization, isomerization, hydrogenation, dehydrogenation, hydrocracking, and pyrolysis. Typical reforming processes can be carried out using a variety of reactors containing reforming or "aromatization" catalysts. The catalyst may enhance the reaction rate, the yield of the desired aromatic product(s), and / or the throughput of the desired aromatic compounds. Conventionally, the hydrocarbon feedstock to be reformed is combined with hydrogen before being fed to the first of a series of multiple (e.g., six or seven) reforming reactors. As the feedstock passes through the reactor train, reactions proceed, resulting in the production of aromatic products and hydrogen.

[0003] Given its commercial importance, there is a continuing need for improved systems and methods for catalytic reforming. Summary of the Invention

[0004] The present disclosure relates generally to systems, methods, and processes for catalytic hydrocarbon reforming. In some embodiments, the present disclosure provides a process for operating a reforming reactor system, the process comprising: operating a first reactor series comprising a plurality of reactors, each reactor within the plurality of reactors of the first reactor series comprising a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in a hydrocarbon feedstock to aromatic hydrocarbons, thereby providing a first reactor series effluent comprising aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen; separating hydrogen from the first reactor series effluent, thereby providing a first reactor series effluent with a reduced hydrogen content; and operating a second reactor series comprising a plurality of reactors, each reactor within the plurality of reactors of the second reactor series comprising a catalyst capable of catalyzing the reaction of at least a portion of the unreacted hydrocarbons in the first reactor series effluent with a reduced hydrogen content, In embodiments, the process further includes operating at least one reactor in the plurality of reactors in the first reactor series at a lower severity than at least one reactor in the plurality of reactors in the second reactor series, which may include a lower average catalyst bed temperature, or a reactor endotherm for at least one reactor of the plurality of reactors in the first reactor series that is at least 40° C. lower than the average catalyst bed temperature over the course of operation, or a reactor endotherm for at least one reactor of the plurality of reactors in the second reactor series that is at least 40° C. lower than the average catalyst bed temperature over the course of operation. In related embodiments, the process may involve a catalyst fouling rate in any one reactor of the plurality of reactors in the first reactor series that is less than the catalyst fouling rate in any one reactor of the plurality of reactors in the second reactor series.

[0005] This process, in some embodiments, is referred to herein as C8 +The process may be characterized by a hydrocarbon feedstock containing greater than about 10 volume percent (10 vol.%) of hydrocarbons containing 8 or more carbon atoms, which may be expressed as: In certain embodiments, the process may include a hydrogen-to-hydrocarbon molar ratio in at least one reactor within the plurality of reactors of the second reactor series that is less than the hydrogen-to-hydrocarbon molar ratio in a corresponding reactor of a process employing a reforming reactor system comprising a single reactor series operated without inter-series hydrogen separation, including a hydrogen-to-hydrocarbon molar ratio in the last reactor of the second reactor series that is less than 3:1 at a given conversion, and wherein the hydrogen-to-hydrocarbon molar ratio for the first reactor of the first reactor series is from about 1.5:1 to about 2:1. An additional aspect of the process may be characterized by a hydrogen partial pressure in at least one reactor within the plurality of reactors of the second reactor series that is less than the hydrogen partial pressure in a corresponding reactor of a process employing a reforming reactor system comprising a single reactor series operated without inter-series hydrogen separation as described herein. The process may be further characterized, in embodiments, by a selectivity to benzene, toluene, and xylenes (BTX) in accordance with the present disclosure that is greater than the relative selectivity to BTX provided by an equivalent process employing a reforming reactor system comprising a single reactor train operated without any inter-train hydrogen separation.

[0006] In some embodiments, the process utilizes a catalyst comprising at least one Group VIII metal and a zeolite support, where the Group VIII metal may include platinum (and / or another Group VIII metal such as ruthenium, rhodium, palladium, osmium, or iridium), and the zeolite support may include L-zeolite bound to silicon oxide. Additionally, the catalyst may further comprise at least one halide, such as chloride, fluoride, bromide, iodide, or a combination thereof. The process may further include an effluent of the first reactor series with reduced hydrogen content comprising unconvertible C6 hydrocarbons, and may further include separating the unconvertible C6 hydrocarbons from the effluent of the first reactor series with reduced hydrogen content to produce a second hydrocarbon stream, and introducing the second hydrocarbon stream into the second reactor series via a charge pump, wherein the second hydrocarbon stream may comprise a higher concentration of convertible C6 hydrocarbons than the effluent of the first reactor series with reduced hydrogen content.

[0007] In a further aspect, the process includes heating the second hydrocarbon stream via heat exchange with the effluent of the first reactor series prior to introducing the second hydrocarbon stream into the second reactor series, and heating the second hydrocarbon stream prior to separating hydrogen from the effluent of the first reactor series. In a further embodiment, the process includes separating the second hydrocarbon stream, wherein the C5 - Hydrocarbons are separated from the effluent of the first reactor train, which has a reduced hydrogen content, to form C5 + C5 + From the product C7 + Separate and C 6- To provide the product, C 6- Benzene is extracted from the product to provide a product having a reduced benzene content, and dimethylbutane (DMB) is separated from the product having a reduced benzene content to provide a second hydrocarbon stream.

[0008] In some embodiments, the present disclosure provides a reforming reactor system including a first reactor series comprising a plurality of reactors, wherein each reactor within the plurality of reactors of the first reactor series comprises a catalyst capable of reacting at least a portion of the hydrocarbons in the hydrocarbon feedstock into aromatic hydrocarbons; providing a first reactor series effluent comprising aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen; and further providing a low-pressure separator configured to separate the hydrogen from the first reactor series effluent to produce / provide hydrogen and a first reactor series effluent having a reduced hydrogen content; and providing a second reactor series comprising a plurality of reactors, wherein each reactor in the second reactor series comprises a catalyst capable of reacting at least a portion of the unreacted hydrocarbons in the first reactor series effluent having a reduced hydrogen content into aromatic hydrocarbons.

[0009] In embodiments, the disclosed system may further comprise a catalyst comprising platinum, a silicon oxide-bound L-zeolite support, and at least one halogen, as further disclosed herein, and may additionally comprise an apparatus configured to separate unconvertible C6 hydrocarbons from the effluent of the first reactor series with reduced hydrogen content, capable of producing a second hydrocarbon stream characterized by an increased concentration of convertible C6 hydrocarbons compared to the effluent of the first reactor series with reduced hydrogen content, and characterized by the presence of one or more of: (a) a charge pump operable to introduce the second hydrocarbon stream into the second reactor series; and / or (b) a heat exchange device configured to transfer heat between the second hydrocarbon stream and the effluent of the first reactor series prior to introducing the second hydrocarbon stream into the second reactor series and prior to separating hydrogen from the effluent of the first reactor series via the hydrogen separation device.

[0010] In some aspects, the present disclosure relates to a process for operating a reforming reactor system, comprising operating a plurality of reactors in a reactor series to produce a reactor series effluent comprising aromatic hydrocarbons from a hydrocarbon feedstock comprising hydrocarbons, wherein operating the plurality of reactors comprises: directing a portion of the hydrocarbon feedstock to form an additional feedstock; introducing the additional feedstock into at least one reactor downstream of the first reactor in the reactor series, bypassing the first reactor containing the portion of the hydrocarbon feedstock; and introducing the remaining portion of the hydrocarbon feedstock into the first reactor in the reactor series, wherein each reactor in the plurality of reactors comprises a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in the hydrocarbon feedstock to aromatic hydrocarbons to produce a reactor series effluent. In a further embodiment, each reactor in the reactor series in the disclosed process may be preceded by an associated furnace, and the additional feedstock may be introduced upstream of the furnace preceding the downstream reactor to which the additional feedstock is introduced. and embodiments in which operating the plurality of reactors further comprises introducing an additional feedstock immediately upstream of each furnace associated with each reactor downstream of the first reactor, as well as embodiments in which operating the plurality of reactors further comprises introducing an additional feedstock immediately upstream of each furnace associated with each reactor downstream of the first reactor.

[0011] The process may further include embodiments involving controlling a portion of the additional feedstock introduced into each reactor disposed downstream of the first reactor such that the influent to each reactor of the plurality of reactors has a controlled desired molar ratio of hydrogen to hydrocarbon, the effluent from each reactor of the plurality of reactors has a controlled desired molar ratio of hydrogen to hydrocarbon, or both. In additional aspects, the desired molar ratio of the influents is less than about 3:1, and may further include embodiments in which the ratio is in the range of about 1.5:1 to about 2:1. The process may further be characterized by an aspect in which a portion of the hydrocarbon feedstock is effectively directed upstream of a sulfur removal unit and / or an aspect in which the remainder of the hydrocarbon feedstock is introduced into a sulfur removal unit prior to introduction into the first reactor.

[0012] The process may also include embodiments directed to separating hydrogen from the effluent of the reactor train and, after compressing the separated hydrogen, blending a portion of the separated hydrogen with the remainder of the hydrocarbon feedstock, said blending providing a first reactor feedstock having a hydrogen to hydrocarbon molar ratio in the range of about 1.5:1 to about 2.0:1. In some embodiments, compressing the separated hydrogen and then blending the portion of the separated hydrogen with the remainder of the hydrocarbon feedstock advantageously requires less compressor capacity than an equivalent process employing a reforming reactor system in which all of the hydrocarbon feedstock is introduced into the first reactor of the reactor train. The process may also be directed to reducing catalyst activity, C5 +The process may be further characterized by embodiments in which the selectivity for, or both, are improved compared to an equivalent process in which a portion of the hydrocarbon feedstock is not introduced downstream of the first reactor in the reactor series. Additional non-limiting aspects of the process include removing unconvertible hydrocarbons from the effluent of the reactor series to produce a second hydrocarbon stream and recycling the second hydrocarbon stream to the reactor series as a portion of the hydrocarbon feedstock that bypasses the first reactor, and further including subjecting the entire remaining portion of the hydrocarbon feedstock introduced into the first reactor in the reactor series to a sulfur removal treatment. The process may also include a catalyst comprising at least one Group VIII metal, a zeolite support, and optionally a halogen, including, but not limited to, a catalyst comprising platinum, silicon oxide-bound L-zeolite, and at least one halogen.

[0013] In an aspect, the present disclosure provides a reforming reactor system including a reactor train comprising a plurality of reactors, each reactor comprising a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in a hydrocarbon feedstock to aromatic hydrocarbons to produce a reactor train effluent comprising aromatic hydrocarbons, and a piping arrangement or configuration characterized by a bypass portion of the hydrocarbon feedstock capable of bypassing a first reactor in the reactor train for introduction into at least one reactor downstream of the first reactor in the reactor train, wherein the bypass portion of the hydrocarbon feedstock bypasses the first reactor and the remainder of the hydrocarbon feedstock is introduced into the first reactor. In a further aspect, the system provides a low-pressure separator configured to separate hydrogen from the reactor train effluent, and a compressor configured to compress the separated hydrogen to provide compressed hydrogen such that mixing of the compressed hydrogen with the remainder of the hydrocarbon feedstock results in a molar ratio of hydrogen to hydrocarbons in the feed to the first reactor ranging from about 1.5:1 to about 2.0:1. In an additional embodiment, the piping arrangement may be configured to divert the bypassed portion of the hydrocarbon feedstock upstream of a sulfur removal unit configured to remove sulfur compounds from the remaining portion of the hydrocarbon feedstock.

[0014] The following figures illustrate embodiments of the subject matter disclosed herein. The claimed subject matter may be understood by reference to the following description considered in conjunction with the accompanying figures, in which like reference numerals identify like elements unless otherwise noted. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a reforming system according to certain aspects of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram of a reforming system according to a further aspect of the present disclosure. [Figure 3]1 is a graphical representation of the final hydrogen / hydrocarbon molar ratio as a function of the proportion of hydrocarbon feedstock introduced into a first reforming reactor of a reforming system according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] Reforming or "aromatization" processes, such as the AROMAX® process developed by Chevron Phillips Chemical Company LLC, can selectively convert light C6-C8 naphtha to BTX (benzene, toluene, and xylenes). The feedstock generally contains compounds with six-carbon chains, such as n-hexane, n-heptane, and methylhexane, which can be ring-closed and subsequently used to form benzene, toluene, or xylenes. There are also many species, such as methylpentane, that can be cyclized to methylcyclopentane before opening to form n-hexane. However, a small but potentially significant portion of the feedstock also contains compounds, such as dimethylbutane and trimethylpentane, that must undergo substantial isomerization before aromatization. These compounds are therefore classified as "non-convertible" because they do not become BTX. Unfortunately, these highly branched non-convertibles are highly susceptible to thermal cracking, resulting in the formation of C 5+ Thermal cracking significantly reduces their value, as these species have a high octane number and can be used for mogas (motor gasoline). Longer molecules such as n-octane or nonane may also be readily converted over reforming catalysts (e.g., AROMAX® catalysts). Indeed, longer molecules are more prone to aromatization, and this conversion can be carried out at lower temperatures. However, the resulting aromatics containing methyl, ethyl, and propyl substituents may be thermally cracked to produce fuel gas or benzene, thereby reducing their value.

[0017] It may be beneficial to control the hydrogen partial pressure in the reforming reactor, thus making the hydrogen partial pressure more constant, and / or to reduce the thermal cracking of unconvertible and / or substituted aromatics therein, as described below.

[0018] In accordance with embodiments of the present disclosure, the reforming reaction can be enhanced by staggering the introduction location of the hydrocarbon feedstock and / or through intermediate removal of branched unconvertibles, substituted aromatics, and / or hydrogen. As explained in more detail below, staggering the introduction of the hydrocarbon feedstock, intermediate removal of hydrogen, or both, can operate to reduce hydrogen partial pressure, resulting in improved selectivity and / or reduced undesirable thermal cracking. Additionally, intermediate removal of branched unconvertibles, substituted aromatics, or both can also beneficially reduce thermal cracking.

[0019] As used herein, "convertible" hydrocarbons include hydrocarbons having 6 or 7 carbon atoms without an internal quaternary carbon and hydrocarbons having 6 carbon atoms without two adjacent internal tertiary carbons. Such convertible hydrocarbons may include methylpentane, methylhexane, dimethylpentane, and mixtures thereof. Convertible components may include 2-methylpentane, 3-methylpentane, 2,4-dimethylpentane, 2,3-dimethylpentane, n-hexane, 2-methylhexane, 3-methylhexane, n-heptane, and mixtures thereof. As used herein, "unconvertible" hydrocarbons include highly branched hydrocarbons containing 6 or 7 carbon atoms with an internal quaternary carbon and hydrocarbons having 6 carbon atoms and two adjacent tertiary carbons. Highly branched hydrocarbons include dimethylbutane (DMB), trimethylbutane, dimethylpentane, and mixtures thereof. Highly branched hydrocarbons having 6 or 7 carbon atoms with an internal quaternary carbon may include, for example, 2,2-dimethylbutane, 2,2-dimethylpentane, 3,3-dimethylpentane, 2,2,3-trimethylbutane, and combinations thereof. Highly branched hydrocarbons having 6 carbon atoms and one adjacent internal tertiary carbon atom may include 2,3-dimethylbutane. Highly branched hydrocarbons do not readily convert to aromatic products, but instead tend to convert to light hydrocarbons. As used herein, "unreacted" hydrocarbons refer to convertible hydrocarbons that have passed through the reforming reactor train without being converted to aromatic hydrocarbons.

[0020] The present disclosure provides a reforming system operable to provide consistent hydrogen partial pressure within one or more reforming reactors in a series of one or more reforming reactors and / or to reduce undesirable thermal cracking within such reforming reactors. In an embodiment, the reforming reactor system disclosed herein includes a reactor train including a plurality of reactors, including a first reactor and a last reactor, each reactor in the plurality of reactors including a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in the hydrocarbon feedstock to aromatic hydrocarbons, thereby providing a reactor effluent comprising aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen; and (a) a low-pressure separator configured to separate hydrogen from the effluent of at least one reactor upstream of the last reactor, thereby providing hydrogen and an effluent with a reduced hydrogen content, whereby at least a portion of the effluent with a reduced hydrogen content can be introduced into a reactor downstream of the at least one reactor, or (b) piping configured to allow a bypass portion of the hydrocarbon feedstock to bypass the first reactor in the reactor train and be introduced into a reactor downstream of the at least one reactor, whereby the bypass portion of the hydrocarbon feedstock bypasses the first reactor (wherein the remaining portion of the hydrocarbon feedstock is introduced into the first reactor), or both of (a) and (b).

[0021] In an embodiment, the system of the present disclosure includes a reactor train including a plurality of reactors, including a first reactor and a last reactor, each reactor in the plurality of reactors including a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in the hydrocarbon feedstock into aromatic hydrocarbons, thereby providing a reactor effluent including aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen, and (a) a low-pressure separator configured to separate hydrogen from the effluent of at least one reactor upstream of the last reactor, thereby providing hydrogen and an effluent with a reduced hydrogen content, whereby at least a portion of the effluent with a reduced hydrogen content can be introduced into a reactor downstream of the at least one reactor. Thus, in an embodiment, the system of the present disclosure includes a separator configured for intermediate removal of hydrogen (i.e., downstream of the first reforming reactor in the series and before the final / last reforming reactor). In an embodiment, such a system includes a first reactor series comprising a plurality of reactors, each reactor within the plurality of reactors of the first reactor series comprising a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in the hydrocarbon feedstock to aromatic hydrocarbons, thereby providing a first reactor series effluent comprising aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen; a low-pressure separator configured to separate hydrogen from the first reactor series effluent, thereby providing hydrogen and a first reactor series effluent with a reduced hydrogen content; and a second reactor series comprising a plurality of reactors, each reactor within the plurality of reactors of the second reactor series comprising a catalyst capable of catalyzing the reaction of at least a portion of the unreacted hydrocarbons in the first reactor series effluent with a reduced hydrogen content,

[0022] Such a system is described with reference to Figure 1. Figure 1 is a schematic diagram of a reforming system 100 according to one embodiment of the present disclosure. The system 100 includes six reforming reactors 120A, 120B, 120C, 120D, 120E, and 120F, and a separator 135. While the embodiments of Figures 1 and 2 are shown with six reforming reactors, it should be understood that reforming systems according to the present disclosure may be configured with more or fewer than six reforming reactors. For example, in embodiments, reforming systems according to the present disclosure include seven, eight, or more reforming reactors. In other embodiments, reforming systems according to the present disclosure may include five, four, or three reforming reactors. The reforming systems of the present disclosure may further include one or more furnaces, sulfur removal units, stabilizers, C6 / C7 splitters, extractive distillation units (EDUs), dimethylbutane (DMB) columns, pumps, compressors, and / or heat exchangers, as described in more detail herein below. The reforming system 100 includes furnaces 110A, 110B, 110C, 110D, 110E, and 110F, a stabilizer 140, a C6 / C7 splitter 155, an EDU 170, a DMB column 185, a pump 190, a feed / effluent heat exchanger 107A, an intermediate effluent heat exchanger 107B, and a compressor 138. The various components of the reforming systems described herein may be in fluid communication via appropriate piping, conduits, valves, etc., as shown, for example, in Figures 1 and 2.

[0023] The reforming system disclosed herein includes a series of reforming reactors. As commonly understood, reforming "reactions" typically occur in reforming "reactors." The reforming reactors employed in the systems and methods described herein may be any conventional reactor capable of maintaining a catalyst within the reactor and accepting a continuous flow of hydrocarbons. The catalytic reactor systems described herein may include fixed catalyst bed systems, moving catalyst bed systems, fluidized catalyst bed systems, or combinations thereof. Suitable reactors include, but are not limited to, fixed bed reactors, including radial flow reactors, bubbling bed reactors, and ebullated bed reactors. Feedstock flow may be upward, downward, or radial through the reactor. In various embodiments, the catalytic reactor systems described herein may be operated as adiabatic or isothermal catalytic reactor systems. As used herein, a "hydrocarbon stream" includes hydrocarbons, although components other than hydrogen and carbon-containing molecules (e.g., hydrogen gas) may be present in the stream. In some embodiments, "hydrocarbon" may include individual molecules that contain one or more atoms other than hydrogen and carbon (eg, nitrogen, oxygen, etc.).

[0024] As shown in FIG. 1 , the reforming system 100 generally includes multiple reactors 120A, 120B, 120C, 120D, 120E, and 120F arranged in series with associated furnaces 110A, 110B, 110C, 110D, 110E, and 110F located upstream of each reactor, respectively. A furnace combination coupled to a downstream reactor may be referred to as a "reactor-furnace pair" throughout this specification. The furnaces 110A, 110B, 110C, 110D, 110E, and 110F may include any type of furnace capable of elevating the temperature of reactant streams to achieve the desired inlet temperature to the associated or "paired" downstream reforming reactor. Due to the endothermic nature of the reforming process, the temperature of the feed stream introduced to each reactor may generally need to be elevated to ensure the reforming reaction occurs properly within the reactor.

[0025] A reactor train may include multiple reactor-furnace pairs. In one embodiment, a reactor train includes three or more reactors connected in series. All reactors 120A, 120B, 120C, 120D, 120E, and 120F may be the same size or configuration or may be different. In one embodiment, all reactors 120A, 120B, 120C, 120D, 120E, and 120F are radial flow reactors, in which the hydrocarbon stream passes through the reactor in an inward or outward direction. In one embodiment, the reactors may be sized according to known techniques, and all reactors may be the same size. Alternatively, one or more reactors may be present with different sizes. The reactor train may be referred to as a first reactor train upstream of hydrogen separation and a second reactor train downstream of hydrogen separation. For example, in the embodiment of FIG. 1, the first reactor series S1 includes reforming reactors 120A and 120B with associated furnaces 110A and 110B, respectively, and the second reactor series S2 includes reforming reactors 120C, 120D, 120E, and 120F with associated furnaces 110C, 110D, 110E, and 110F, respectively.

[0026] In the embodiment of FIG. 1 , the first heated furnace 110A is in fluid communication with the first reformer furnace 120A via line 112A, the first reformer reactor 120A is in fluid communication with the second heated furnace 110B via line 115A, the second heated furnace 110B is in fluid communication with the second reformer reactor 120B via line 112B, the second reactor 120B is in fluid communication with the intermediate effluent heat exchanger 107B (described further below) via line 115B, the third heated furnace 110C is in fluid communication with the third reformer reactor 120C via line 112C, the third reformer reactor 120C is in fluid communication with the fourth heated furnace 110B via line 115C. The fourth heated furnace 110D is in fluid communication with the fourth reformer 120D via line 112D, the fourth reformer 120D is in fluid communication with the fifth heated furnace 110E via line 115D, the fifth heated furnace 110E is in fluid communication with the fifth reformer 120E via line 112E, the fifth reforming reactor 120E is in fluid communication with the sixth heated furnace 110F via line 115E, the sixth heated furnace 110F is in fluid communication with the sixth reforming reactor 120F via line 112F, and the sixth reforming reactor 120F is in fluid communication with the feedstock / effluent heat exchanger 107A via line 115F.

[0027] In embodiments, due to component removal between the first and second series of reactors as disclosed herein, one or more reactors in the second series of reactors (i.e., one or more of the reactors downstream of hydrogen separation) may be smaller than the corresponding reactor in a conventional reforming reactor series in which hydrogen and component removal occurs only in the effluent of the final reforming reactor in the system. In embodiments, any one reactor in the plurality of reactors in the second series of reactors (i.e., any one of the reactors downstream of hydrogen separation) has a smaller volume than the corresponding reactor in an equivalent reforming reactor system including a single reactor series operating at the same feed rate without inter-reactor hydrogen separation. As used herein, "interstage," "inter-reactor," and "inter-series" are used to mean between reactors of multiple reforming reactors (e.g., located between the first reactor and the last reactor in a reactor series of a reforming system), as opposed to only downstream of the final reforming reactor in the reforming reactor system.

[0028] In embodiments, the amount of catalyst employed in each reactor of the reforming system is more consistent than the amount of catalyst employed in reforming reactors of a conventional reforming system employing a single series having the same total number of reactors without interstage hydrogen separation. For example, in embodiments, each reactor of the first reactor series and each reactor of the second reactor series comprises a volume percentage of the total volume of catalyst, where the total volume of catalyst includes the sum of the volumes of catalyst in each reactor of the multiple reactors of the first reactor series plus the sum of the volumes of catalyst in each reactor of the multiple reactors of the second reactor series, and the standard deviation of the volume percentage of the total volume of catalyst in the multiple reactors of the first reactor series and the multiple reactors of the second reactor series is less than the standard deviation of the volume percentage of the total volume of catalyst in a process employing an otherwise equivalent reforming reactor system including a single reactor series operated without interstage hydrogen separation. As a non-limiting example, if a conventional reforming system includes six reactors, with the first, second, third, fourth, fifth, and sixth reactors utilizing 10, 10, 10, 20, 20, and 30 volume percent of the total catalyst, respectively, the first through sixth reactors of a system according to the present disclosure may include 15, 15, 15, 15, 20, 20 volume percent of the total catalyst, or any other arrangement that provides a lower standard deviation in volume percent of catalyst between reactors.

[0029] In embodiments, reforming reactors 120A, 120B, 120C, 120D, 120E, and 120F each contain a catalyst for carrying out a reforming process. As known to those skilled in the art, suitable reforming catalysts (also referred to herein as "dehydration cycloreversion" catalysts) are capable of converting at least a portion of the aliphatic, cycloaliphatic, and / or naphthenic hydrocarbons (e.g., non-aromatic hydrocarbons) in a hydrocarbon stream to aromatic hydrocarbons. Any catalyst capable of carrying out the reforming reaction may be used alone or in combination with additional catalytic materials in the reactor. Suitable catalysts may include acidic or non-acidic catalysts. In embodiments, the catalyst is a non-acidic catalyst. In embodiments, the catalyst comprises at least one Group VIII metal and a zeolite support. In embodiments, the Group VIII metal comprises platinum, and the zeolite support comprises L-zeolite bound to silicon oxide. In embodiments, the catalyst further comprises at least one halogen. Suitable non-acidic catalysts may include a non-acidic zeolite support, at least one Group VIII metal, and one or more halides. Suitable halides include chlorides, fluorides, bromides, iodides, or combinations thereof. Suitable Group VIII metals include iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, or combinations thereof. Examples of catalysts suitable for use with the catalytic reactor systems described herein include AROMAX® catalysts available from Chevron Phillips Chemical Company LP (The Woodlands, TX) and catalysts described in U.S. Patent Nos. 6,812,000 and 7,153,801. Each of these catalysts is incorporated herein by reference in its entirety for all purposes not contrary to this disclosure.

[0030] Catalyst supports for use with the disclosed technology can generally include any inorganic oxide. These inorganic oxides may include bound large pore aluminosilicates (zeolites), amorphous inorganic oxides, and mixtures thereof. Large pore aluminosilicates may include, but are not limited to, L-zeolite, Y-zeolite, mordenite, omega zeolite, beta zeolite, and the like. Amorphous inorganic oxides may include, but are not limited to, aluminum oxide, silicon oxide, and titanium oxide. Suitable binders for inorganic oxides may include, but are not limited to, silicon oxide, aluminum oxide, clay, titanium oxide, and magnesium oxide.

[0031] Zeolite materials, both natural and synthetic, are known to have catalytic properties for many hydrocarbon processes. Zeolites are typically ordered, porous, crystalline aluminosilicates with a structure of interconnected voids and channels. The voids and channels throughout the crystalline material can generally be sized to allow for the selective separation of hydrocarbons.

[0032] The term "zeolite" generally refers to a specific group of hydrated crystalline metal aluminosilicates. These zeolites exhibit a network of SiO4 and AlO4 tetrahedra, with aluminum and silicon atoms crosslinked by sharing oxygen atoms into a three-dimensional framework. In the framework, the ratio of oxygen atoms to the sum of aluminum and silicon atoms can be equal to about 2. The framework typically exhibits a negative electron valence, which is balanced by the inclusion of cations, such as metals, alkali metals, alkaline earth metals, or hydrogen, within the crystal.

[0033] Zeolite L catalysts are a subgroup of zeolite catalysts. Typical zeolites L contain a molar ratio of oxides according to the following formula: M 2 / n O·Al2O3·xSiO2·yH2O (1) (where "M" represents at least one exchangeable cation, such as barium, calcium, cerium, lithium, magnesium, potassium, sodium, strontium, and zinc, as well as nonmetallic cations, such as hydronium and ammonium, which may be substituted with other exchangeable cations without causing a substantial change in the basic crystal structure of L-type zeolite.) In the formula, "n" represents the valence of "M," "x" is 2 or greater, and "y" is the number of water molecules contained in the channels or interconnected voids of the zeolite. Bound potassium (K) L-type zeolites, or KL-type zeolites, have been found to be particularly preferred. As used herein, the term "KL zeolite" refers to L-type zeolites in which the predominant metal cation (M) incorporated in the zeolite is potassium. KL zeolites may be cation-exchanged or impregnated with another metal and one or more halides to produce platinum (Pt)-impregnated halide zeolites, or KL-supported platinum halide zeolite catalysts.

[0034] In an embodiment, the at least one Group VIII metal is platinum. In another embodiment, the at least one Group VIII metal is platinum and gold. In an embodiment, the at least one Group VIII metal is platinum and rhenium. The platinum and, optionally, one or more halides may be added to the zeolite support by any suitable method, such as impregnation with a solution of a platinum-containing compound and one or more halide-containing compounds. For example, the platinum-containing compound may be any decomposable platinum-containing compound. Examples of such compounds include, but are not limited to, ammonium tetrachloroplatinate, chloroplatinic acid, diamineplatinum(II) nitrite, bis-(ethylenediamine)platinum(II) chloride, platinum(II) acetylacetonate, diamineplatinum dichloro, platinum(II) chloride, tetraammineplatinum(II) hydroxide, tetraammineplatinum chloride, and tetraammineplatinum(II) nitrate.

[0035] In one embodiment, the catalyst is a large pore zeolite support having a platinum-containing compound and at least one ammonium halide compound. The ammonium halide compound may include one or more compounds represented by the formula N(R)X, where X is a halide, R represents hydrogen or a substituted or unsubstituted carbon chain molecule having 1 to 20 carbons, and each R may be the same or different. In one embodiment, R is selected from the group consisting of methyl, ethyl, propyl, butyl, and combinations thereof, more specifically methyl. Examples of suitable ammonium compounds represented by the formula N(R)X include ammonium chloride, ammonium fluoride, and tetraalkylammonium halides, such as tetramethylammonium chloride, tetramethylammonium fluoride, tetraethylammonium chloride, tetraethylammonium fluoride, tetrapropylammonium chloride, tetrapropylammonium fluoride, tetrabutylammonium chloride, tetrabutylammonium fluoride, methyltriethylammonium chloride, methyltriethylammonium fluoride, and combinations thereof.

[0036] The catalyst may be employed in any conventional type or configuration known in the art. It may be employed in the form of extrudates, tablets, pellets, granules, broken pieces, or various special shapes disposed within a reaction zone (e.g., in a fixed bed) through which the feedstock may be passed in liquid, gas, or mixed phase, either upward or downward, or inward or outward flow.

[0037] In embodiments, the reforming system of the present disclosure further includes a low-pressure splitter configured to separate hydrogen from the effluent of at least one reactor upstream of the last reactor, thereby providing hydrogen and an effluent with reduced hydrogen content, whereby at least a portion of the effluent with reduced hydrogen content may be introduced into a reactor downstream of said at least one reactor. In an embodiment, a system disclosed herein includes a first reactor series comprising a plurality of reactors, each reactor within the plurality of reactors of the first reactor series comprising a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in the hydrocarbon feedstock to aromatic hydrocarbons, thereby providing a first reactor series effluent comprising aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen; a low-pressure separator configured to separate hydrogen from the first reactor series effluent, thereby providing hydrogen and a first reactor series effluent with a reduced hydrogen content, all or a portion of which is fed to a second reactor series, wherein the second reactor series comprises a plurality of reactors, at least one (preferably all) of the reactors within the plurality of reactors of the second reactor series comprising a catalyst capable of catalyzing the reaction of at least a portion of the unreacted hydrocarbons in the first reactor series effluent with a reduced hydrogen content, to aromatic hydrocarbons.

[0038] In certain embodiments, the reforming system 100 includes a separator, such as separator 135. Line 115B fluidly connects the second reforming reactor 120B to the intermediate effluent heat exchanger 107B, where heat exchange with the hydrogen-reduced convertible C6 hydrocarbon recycle in line 195 is effected. Intermediate effluent heat exchanger effluent outlet line 125B fluidly connects the intermediate effluent heat exchanger 107B to the hydrogen separator 135, whereby the heat-exchanged second reforming reactor effluent can be introduced thereto. Feedstock / effluent heat exchanger effluent outlet line 125A fluidly connects the feedstock / effluent heat exchanger 107A to the splitter 135 via the intermediate effluent heat exchanger effluent outlet line 125B, whereby the heat-exchanged sixth reforming reactor effluent can be introduced thereto. The separator 135 may be any separator known in the art operable to separate a hydrogen-containing gas stream from a hydrogen-reduced bottoms stream. In an embodiment, the separator 135 is a low-pressure separator (LPS). A separated hydrogen separator 137 is fluidly connected to the hydrogen separator 135 to remove hydrogen from the hydrogen separator 135. The compressor 138 may be operable to compress the hydrogen-containing gas removed from the hydrogen separator 135. A portion of the compressed hydrogen-containing gas may be removed from the reforming system 100 via a gas outlet line 139B. The hydrogen recycle line 139A may be configured to recycle hydrogen to the reforming reactors of the reactor series (i.e., either the first reactor series, the second reactor series, or both). For example, hydrogen recycle line 139A may branch into a first series hydrogen recycle line 139C, which may introduce a portion of the separated hydrogen into the first reactor series, e.g., via combination with heat-exchanged hydrocarbon feed line 106, and a second series hydrogen recycle line 139D, which may introduce another portion of the separated hydrogen into the second reactor series, e.g., via combination with reduced hydrogen content convertible C hydrocarbon recycle line 195. As a result, hydrogen may be sent back to the fresh hydrocarbon feed stream and the second reactor set, as needed.

[0039] As described hereinabove, a reforming system according to the present disclosure may include one or more heat exchangers. In embodiments, the reforming system of the present disclosure further includes a heat exchange device configured to transfer heat between a second hydrocarbon stream containing a higher concentration of convertible C hydrocarbons than the hydrogen-reduced effluent of the first reactor series and the effluent of the first reactor series prior to introducing the second hydrocarbon stream into the second reactor series and prior to separating hydrogen from the effluent of the first reactor series via the hydrogen separation device. For example, the reforming system 100 includes a feedstock / effluent heat exchanger 107A and an intermediate effluent heat exchanger 107B. The feedstock / effluent heat exchanger 107A is in fluid communication with the final or "last" (the sixth reforming reactor in the embodiment of FIG. 1 ) reforming reactor 120F via line 115F, thereby facilitating heat exchange between the reactor train effluent leaving the reforming reactor 120F via line 115F and the hydrocarbon feed introduced to the feedstock / effluent heat exchanger 107A via the hydrocarbon feed line 105. A heat-exchanged hydrocarbon feed line 106 fluidly connects the feedstock / effluent heat exchanger 107A to the first heated furnace 110A, whereby fresh hydrocarbon feed from the fresh hydrocarbon feed line 105 can be introduced thereto. The feedstock / effluent heat exchanger effluent outlet line 125A is configured to introduce the heat-exchanged reactor train effluent to the separator 135 via combination with the intermediate effluent heat exchanger effluent outlet line 125B.

[0040] The reforming system disclosed herein may further include an apparatus configured to separate unconvertible C6 hydrocarbons from the hydrogen-reduced effluent of the first reactor series to produce a second hydrocarbon stream, the second hydrocarbon stream having a higher concentration of convertible C6 hydrocarbons than the hydrogen-reduced effluent of the first reactor series. Such apparatus may include a stabilizer, a C6 / C7 splitter, an EDU, a DMB column, and / or a charge pump operable to introduce the second hydrocarbon stream into the second reactor series. For example, the reforming system 100 includes a stabilizer 140, a C6 / C7 splitter 155, an EDU 170, a DMB column 185, and a charge pump 195.

[0041] The reforming system of the present disclosure may further include a stabilizer. In the embodiment of FIG. 1 , stabilizer 140 is in fluid communication with hydrogen separator 135 via hydrogen separator bottoms outlet line 136. Stabilizer 140 is operable to separate the hydrogen separator bottoms into a light hydrocarbon stream and a stabilizer bottoms product. In an embodiment, the light hydrocarbon stream comprises LPG. In an embodiment, the light hydrocarbon stream comprises a C 4- In an embodiment, the light hydrocarbon stream comprises a C 4- The stabilizer light hydrocarbon outlet line 145 is configured to remove a top product comprising light hydrocarbons from the stabilizer 140. In an embodiment, the stabilizer bottom product comprises C 5+ Ballast bottoms outlet line 150 is configured to remove the ballast bottoms product from ballast 140. Ballast bottoms outlet line 150 is configured to remove the ballast bottoms product from ballast 140. Ballast bottoms outlet line 150 is configured to remove the ballast bottoms product from ballast 140.

[0042] The reforming system of the present disclosure may further include a C6 / C7 splitter. In the embodiment of FIG. 1, the C6 / C7 splitter 155 is in fluid communication with the stabilizer 140 via the stabilizer bottoms outlet line 150. The C6 / C7 splitter 155 is 6- Hydrocarbons are classified as C 7+ The C7+ outlet line 160 is configured to separate hydrocarbon compounds having seven or more carbon atoms (i.e., C 7+ ) is configured to remove C 6- An outlet line 165 receives hydrocarbon compounds having six or fewer carbon atoms (i.e., C 6- ) is configured to remove the C6 / C7 divider 155. 6- Hydrocarbons as C 7+ It may be any unit known in the art to be operable to separate hydrocarbons.

[0043] The reforming system of the present disclosure may further include an extractive distillation column, also known as an extractive distillation unit (EDU). In the embodiment of FIG. 1, the reforming system 100 includes an EDU 170. The EDU 170 is connected to the C6 / C7 splitter C 6- C so that the product can be introduced into EDU170 6- The EDU 170 is in fluid communication with the C6 / C7 splitter 155 via an outlet line 165. The EDU 170 splits the benzene product into C 6- The benzene product is removed from the EDU 170 via benzene product outlet line 175. Line 180 is operable to separate the remaining hydrocarbons (i.e., C 6- EDU170 is configured to remove the C introduced therein. 6- It may be any extractive distillation unit known in the art to be operable to separate benzene from the product.

[0044] The reforming system of the present disclosure may further include a dimethylbutane (DMB) column. In the embodiment of FIG. 1, the reforming system 100 includes a DMB column 185. The DMB 185 is a C dimethylbutane (DMB) column that is a reduced benzene content product of the EDU 170. 6- The EDU 170 is in fluid communication with the EDU 170 via line 180 so that the product can be introduced into the DMB 185. The DMB 185 contains the C benzene-reduced C 6- The DMB column 185 is operable to separate the dimethylbutane product and the convertible C6 product from the product. The convertible C6 product outlet line 186 is configured to remove the convertible C6 product from the DMB column 185. The line 187 is configured to remove the DMB product from the DMB column 185. The DMB column 185 receives the reduced benzene C6 product introduced thereto. 6- It may be any unit known in the art that is operable to separate DMB from the product, thereby providing a convertible C6 product having reduced DMB content.

[0045] The reforming system of the present disclosure may further include a charge pump. In the embodiment of FIG. 1, the reforming system 100 includes a charge or “inter-series” pump 190. The charge pump 190 is operable to pump at least a portion of a second hydrocarbon stream, having a higher concentration of convertible C6 hydrocarbons than the hydrogen-reduced effluent of the first reactor series, for introduction into the second reforming reactor series. In the embodiment of FIG. 1, the charge pump 190 pumps the convertible C6 product from the DMB column 185 via a conduit through the intermediate effluent heat exchanger 107B to the third furnace 110C.

[0046] As described herein, an embodiment of a reforming system of the present disclosure includes a reactor train including a plurality of reactors, including a first reactor, a last reactor, and at least one intermediate reactor, each reactor comprising a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in a hydrocarbon feedstock to aromatic hydrocarbons, thereby providing a reactor effluent comprising aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen; and piping configured to allow a bypass portion of the hydrocarbon feedstock to bypass the first reactor in the reactor train and be introduced into a reactor downstream of the at least one reactor, thereby bypassing the first reactor (wherein the remaining portion of the hydrocarbon feedstock is introduced into the first reactor). Thus, in an embodiment, the system of the present disclosure includes piping that allows the introduction of the hydrocarbon feedstock into the reforming reactors to be staggered, rather than all of the hydrocarbon feedstock being initially introduced into the first reforming reactor of the system. Such a system is described with reference to FIG. 2, which is a schematic diagram of a reforming system 200 according to one embodiment of the present disclosure. In some embodiments, a system such as system 200 includes six reforming reactors 220A, 220B, 220C, 220D, 220E, and 220F arranged in series, and piping 208, 208A, 208B, 208C, 208D, and 208E configured to stagger the hydrocarbon feed, such that a portion of the hydrocarbon feed bypasses at least the first reforming reactor, while the remaining hydrocarbon feed is introduced into the first reforming reactor. As discussed herein above, while the embodiment of FIG. 2 is shown with six reforming reactors, it should be understood that a reforming system according to the present disclosure may be configured with more or fewer than six reforming reactors. For example, in embodiments, a reforming system according to the present disclosure includes seven, eight, or more reforming reactors. In other embodiments, a reforming system according to the present disclosure may include five, four, or three reforming reactors.

[0047] 1, the reforming system of the present disclosure may further include one or more furnaces, separators, sulfur removers, stabilizers, C6 / C7 splitters, extractive distillation units (EDUs), dimethylbutane (DMB) columns, pumps, compressors, and / or heat exchangers. Reforming system 200 includes furnaces 210A, 210B, 210C, 210D, 210E, and 210F, sulfur remover 209, hydrogen separator 235, stabilizer 240, C6 / C7 splitter 255, EDU 270, first feedstock / effluent heat exchanger 207A, second feedstock / effluent heat exchanger 207B, and compressor 238.

[0048] In the figures, like numbers are used to represent like components. Reforming reactors 220A, 220B, 220C, 220D, 220E and 220F, and associated furnaces 210A, 210B, 210C, 210D, 210E and 210F, hydrogen separator 235, stabilizer 240, C6 / C7 splitter 255, EDU 270, and first feedstock / effluent heat exchanger 207A correspond to reforming reactors 120A, 120B, 120C, 120D, 120E and 120F, and associated furnaces 110A, 110B, 110C, 110D, 110E and 110F, hydrogen separator 135, stabilizer 140, C6 / C7 splitter 155, EDU 170, and first feedstock / effluent heat exchanger 107A described herein above with reference to the embodiment of FIG. 1.

[0049] The reforming system 200 includes a series of six reforming reactors, with hydrogen separation occurring after the final reforming reactor, the sixth reforming reactor 220F. In the reforming system 200, the first furnace 210A is in fluid communication with the first reforming reactor 220A via line 212A, the first reforming reactor 220A is in fluid communication with the second furnace 210B via line 215A, the second furnace 210B is in fluid communication with the second reforming reactor 220B via line 212B, the second reactor 220B is in fluid communication with the third furnace 210C via line 215B, the third furnace 210C is in fluid communication with the third reforming reactor 220C via line 212C, and the third reforming reactor 220C is in fluid communication with the fourth furnace 210D via line 215C. The fourth heater 210D is in fluid communication with the fourth reforming heater 220D via line 212D, the fourth reformer furnace 220D is in fluid communication with the fifth heater 210E via line 215D, the fifth heater 210E is in fluid communication with the fifth reformer furnace 220E via line 212E, the fifth reforming reactor 220E is in fluid communication with the sixth heater 210F via line 215E, the sixth furnace 210F is in fluid communication with the sixth reforming reactor 220F via line 212F, and the sixth reforming reactor 220F is in fluid communication with the second feedstock / effluent heat exchanger 207B via line 215F.

[0050] In an embodiment, each of the reforming reactors 220A, 220B, 220C, 220D, 220E and 220F includes a catalyst for carrying out a reforming process, which may be as described herein above with reference to the embodiment of FIG. 1.

[0051] The reforming system 200 also includes piping configured to allow a bypass portion of the hydrocarbon feedstock to bypass at least the first reforming reactor in the reactor train and to be introduced into at least one reactor downstream of the first reforming reactor. The feedstock may be bypassed at any point upstream of the first furnace or reforming reactor. The feedstock may be bypassed upstream or downstream of the sulfur removal unit 209, described further herein below. In an embodiment, the reforming system 200 includes piping 208 in fluid communication with the hydrogen recycle line 239A and the heat exchanged hydrocarbon feedstock line 206A upstream of the sulfur removal unit 209, and configured to allow a bypass portion of the hydrocarbon feedstock to bypass at least the first reforming reactor in the reactor train and to be introduced into at least one reactor downstream of the first reforming reactor.

[0052] In an embodiment, a portion of the hydrocarbon feedstock is introduced directly upstream of at least one furnace associated with a reforming reactor downstream of the first reforming reactor. For example, a portion of the hydrocarbon feedstock in the heat exchanged hydrocarbon feedstock line 206A may be diverted via lines 208 and 208A to line 215A, whereby the diverted portion of the hydrocarbon feedstock is introduced to a second furnace 210B associated with a second reforming reactor 220B; a portion of the hydrocarbon feedstock in the heat exchanged hydrocarbon feedstock line 206A may be diverted via lines 208 and 208B to line 215B, whereby the diverted portion of the hydrocarbon feedstock is introduced to a third furnace 210C associated with a third reforming reactor 220C; a portion of the hydrocarbon feedstock in the heat exchanged hydrocarbon feedstock line 206A may be diverted via lines 208 and 208C to line 215C, whereby the diverted portion of the hydrocarbon feedstock is introduced to a second furnace 210B associated with a second reforming reactor 220B; a bypassed portion of the hydrocarbon feedstock may be introduced into a fourth heated furnace 210D linked to a fourth reforming reactor 220D; a portion of the hydrocarbon feedstock in the heat exchanged hydrocarbon feedstock line 206A may be diverted via piping 208 and 208D to line 215D whereby a bypassed portion of the hydrocarbon feedstock may be introduced into a fifth heated furnace 210E linked to a fifth reforming reactor 220E; a portion of the heat exchanged hydrocarbon feedstock in the hydrocarbon feedstock line 206A may be diverted via piping 208 and 208E to line 215E whereby a bypassed portion of the hydrocarbon feedstock may be introduced into a sixth heated furnace 210F linked to a sixth reforming reactor 220F; or any combination of the foregoing.

[0053] In an embodiment, system 200 piping 208′ is in fluid communication with heat exchanged hydrocarbon feed line 206A downstream of hydrogen recycle line 239A and is configured to provide a partial or complete bypass portion of the hydrocarbon feed that bypasses at least the first reforming reactor in the reactor train and is introduced into at least one reactor downstream of the first reforming reactor. In an embodiment, system 200 piping 208" is in fluid communication with reduced sulfur content feed line 205B and is configured to provide a partial or complete bypass portion of the hydrocarbon feedstock that bypasses at least the first reforming reactor in the reactor train and is introduced into at least one reactor downstream of the first reforming reactor. In an embodiment, system 200 piping 208''' is in fluid communication with twice heat exchanged hydrocarbon feed line 206B and is configured to provide a partial or complete bypass portion of the hydrocarbon feedstock that bypasses at least the first reforming reactor in the reactor train and is introduced into at least one reactor downstream of the first reforming reactor.

[0054] In an embodiment, the reforming system of the present disclosure includes a sulfur removal unit. The reforming system 200 includes a sulfur removal unit 209. The sulfur removal unit 209 is operable to remove sulfur compounds from the hydrocarbon feedstock introduced thereto via the hydrocarbon feedstock line 206A. In an embodiment, the piping 208 is configured to bypass a bypass portion of the hydrocarbon feedstock upstream of the sulfur removal unit 209, which is configured to remove sulfur compounds from the remaining portion of the hydrocarbon feedstock introduced to the first reforming reactor.

[0055] The sulfur content reduced feedstock line 205B may be in fluid communication with the sulfur removal unit 209 and the second feedstock / effluent heat exchanger 207B. The sulfur removal unit 209 may be any unit known to those skilled in the art to be operable to reduce the amount of sulfur compounds in the hydrocarbon feedstock. Such sulfur compounds may be poisons to the reforming catalyst, and therefore, the sulfur removal unit 209 may reduce the level of such sulfur-containing compounds upstream of the reforming catalyst in the reforming reactor 220. In an embodiment, the sulfur removal unit 209 includes a sulfur converter / adsorber (SCA). In an embodiment, the sulfur removal unit 209 includes one or more vessels that allow the hydrocarbon stream to flow through a sulfur converter containing a Group VIII metal and a sulfur removal system that includes a sulfur adsorber. The sulfur removal system 209 may also function as a precaution or backup in case the upstream hydrocracking system fails or experiences an operational disruption.

[0056] The second feedstock / effluent heat exchanger 207B is fluidly connected to the final or "last" (i.e., the sixth reforming reactor in the embodiment of FIG. 2) reforming reactor 220F via line 215F to facilitate heat exchange between the reactor train effluent exiting the reforming reactor 220F via line 215F and the reduced-sulfur hydrocarbon feed introduced to the second feedstock / effluent heat exchanger 207B via feed line 205B. The twice-heat-exchanged feedstock line 206B fluidly connects the second feedstock / effluent heat exchanger 207B to the first furnace 210A so that fresh hydrocarbon feedstock from the fresh hydrocarbon feedstock 205A can be introduced thereto. The second feedstock / effluent heat exchanger effluent outlet line 225 is configured to introduce the heat-exchanged reactor train effluent to the first feedstock / effluent heat exchanger 207A. Fresh hydrocarbon feed 205A is in fluid communication with first feed / effluent heat exchanger 207A so that a fresh hydrocarbon feed can be introduced thereto and heat can be exchanged between the fresh hydrocarbon feed and the heat-exchanged reactor train effluent introduced thereto via second feed / effluent heat exchanger effluent line 225. Line 230 is configured for removing the twice-heat-exchanged reactor train effluent from first feed / effluent heat exchanger 207A.

[0057] In some embodiments, a reforming system according to the present disclosure, such as reforming system 200, includes a hydrogen separator 235. Line 230 is configured to remove the twice heat-exchanged reactor effluent from first feedstock / effluent heat exchanger 207A and introduce it to hydrogen separator 235. Separated hydrogen outlet 237 is in fluid communication with hydrogen separator 235 for removing hydrogen from hydrogen separator 235, and hydrogen separator bottoms outlet line 236 is in fluid communication with hydrogen separator 235 for removing the reformed reactor product, having a reduced hydrogen content, from hydrogen separator 235.

[0058] The compressor 238 may be operable to compress the hydrogen-containing gas removed from the hydrogen separator 235. A portion of the compressed hydrogen-containing gas may be removed from the reforming system 200 via a gas outlet line 239B. The hydrogen product in line 239B may be further purified to provide hydrogen for use in an industrial process (e.g., a refinery). The hydrogen recycle line 239A may be configured to recycle hydrogen to the reforming reactor of the reactor series. For example, the hydrogen recycle line 239A may be configured so that a portion of the separated hydrogen can be introduced into the first reactor of the series, for example, via combination with the heat-exchanged hydrocarbon feed line 206A. The introduction of hydrogen into the hydrocarbon feed line 206A may be downstream of the location(s) where the hydrocarbon feed is split via piping 208. That is, the line 208 may be connected to the hydrocarbon feed line 206A via the hydrogen recycle line 239A upstream of the location where the hydrogen is subsequently mixed. In this way, the diverted hydrocarbon feedstock contains less hydrogen (i.e., no hydrogen is added), thereby allowing the hydrogen to hydrocarbon molar ratio in one or more reforming reactors downstream of the first reforming reactor to be reduced compared to conventional reforming systems in which the entire hydrocarbon feedstock passes through the first reforming reactor of the system.

[0059] In an embodiment, compressor 238 is configured to compress the separated hydrogen to provide compressed hydrogen such that the combination of the compressed hydrogen introduced into the remainder of the hydrocarbon feedstock in line 206A downstream of piping 208 provides a molar ratio of hydrogen to hydrocarbons in the feedstock in the first reforming reactor 220A in the range of about 1.5:1 to about 2.0:1.

[0060] In an embodiment, the method further includes adjusting the amount of compressed hydrogen mixed via hydrogen recycle line 239A with the remainder of the hydrocarbon feedstock in hydrocarbon feed line 206A downstream of where piping 208 branches off the portion of the hydrocarbon feedstock, such that the mixing provides a hydrocarbon feedstock to first reforming reactor 220A having a molar ratio of hydrogen to hydrocarbon in the range of about 1.5:1 to about 2.0:1.

[0061] As described herein with reference to the embodiment of Figure 1, the disclosed reforming system may further include an apparatus configured to separate one or more components from the reduced-hydrogen content reformed product removed from the hydrogen separator 235 via the hydrogen separator bottoms component outlet line 236. The apparatus configured to separate one or more components from the reduced-hydrogen content reformed product may include one or more of a stabilizer, a C6 / C7 splitter, an EDU, and / or a DMB column. For example, the reforming system 200 may include a stabilizer 240, a C6 / C7 splitter 255, and an EDU 270, which may be units such as those described herein above with reference to the stabilizer 140, the C6 / C7 splitter 155, and the EDU 170 of the embodiment of Figure 1.

[0062] The stabilizer 240 is in fluid communication with the hydrogen separator 235 via a hydrogen separator bottoms outlet line 236. The stabilizer 240 is operable to separate the hydrogen separator bottoms into a light hydrocarbon stream and a stabilizer bottoms product, as described herein above with reference to FIG. 1 . The stabilizer light hydrocarbons outlet line 245 is configured to remove an overhead product comprising light hydrocarbons from the stabilizer 240. The stabilizer bottoms outlet line 250 is configured to remove the stabilizer bottoms product from the stabilizer 240. The C6 / C7 splitter 255 is in fluid communication with the stabilizer 240 via the stabilizer bottoms outlet line 250. The C6 / C7 splitter 255 is configured to separate a C 6- Hydrocarbons as C 7+ It is designed to separate hydrocarbons. 7+ An outlet line 260 is connected to the C6 / C7 splitter 255 to extract hydrocarbon compounds having seven or more carbon atoms (i.e., C7+ ) is configured to remove. 6- An outlet line 265 receives hydrocarbon compounds having six or fewer carbon atoms (i.e., C 6- ) of the C6 / C7 divider. 6- C so that the product can be introduced into EDU270 6- The EDU 270 is in fluid communication with the C6 / C7 splitter 255 via an outlet line 265. The EDU 270 splits the benzene product into C 6- The benzene product is removed from the EDU 270 via benzene product outlet line 275. Line 280 is operable to separate the benzene product from the EDU 270 and to remove the remaining hydrocarbons (i.e., C 6- The remaining hydrocarbons may be introduced into a DMB column such as that depicted in the embodiment of FIG. 1, configured to remove the remaining hydrocarbons (products), or may be directed to an end use such as a mogas pool.

[0063] In embodiments, the hydrocarbon feedstock introduced via hydrocarbon feed line 205A / 206A is a substantially sulfur-free feedstock. In embodiments, all of the fresh feedstock in hydrocarbon feed line 205A / 206A is introduced to a sulfur removal unit (SCA 209). Because sulfur removal generally incorporates hydrogen into the feedstock, in such embodiments, the substantially hydrogen-free hydrocarbon feedstock for introduction into the downstream reactor(s) via line 208 may be obtained by recycling unreacted convertible feedstock obtained from downstream separation, for example, convertible C hydrocarbons obtained from a DMB column as described with reference to FIG. 1. This feedstock is substantially sulfur-free because it has already passed through SCA 209. Alternatively, the SCF beds (i.e., sulfur conversion material) of sulfur converter / adsorber 209 may be located immediately after a naphtha hydrocracker (not shown in the embodiment of FIG. 2) configured to pretreat the hydrocarbon feedstock upstream of reforming system 100 / 200. In such an embodiment, the SCG bed (i.e., sulfur adsorbent) of SCA 209 can be moved to pick up sulfur after the desulfurizer and sulfur adsorber. In such an embodiment, any hydrogen for use in the SCA can be removed overhead of the desulfurizer column.

[0064] It should be understood that the embodiments of Figures 1 and 2 may be combined, i.e., the reforming system of the present disclosure may include both intermediate hydrogen separation in the series (i.e., hydrogen separation upstream of (at least) the final reforming reactor) and piping by which at least a portion of the hydrocarbon feedstock may be introduced into a reforming reactor downstream of the first reforming reactor.

[0065] Also disclosed herein is a method for catalytic reforming of hydrocarbons, the method comprising operating a series of reactors, the series comprising a plurality of reactors, including a first reactor and a last reactor, each reactor in the series comprising a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in a hydrocarbon feedstock to aromatic hydrocarbons, thereby providing a reactor effluent comprising aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen, and adjusting the partial pressure of hydrogen in the series of reactors by: (a) separating hydrogen from the effluent of at least one reactor upstream of the last reactor; (b) directing a portion of the hydrocarbon feedstock to form an additional feedstock and introducing the additional feedstock into at least one reactor downstream of the first reactor in the reactor series, thereby bypassing the first reactor having a portion of the hydrocarbon feedstock and introducing the remaining portion of the hydrocarbon feedstock into the first reactor in the reactor series; and / or by performing both (a) and (b).

[0066] As discussed herein, conventional reforming takes a sulfur-free C6 / C7 feedstock and passes it through a series of six to seven reactors. The product then passes through a feed effluent heat exchanger before proceeding to downstream separation. In the reforming process, highly branched compounds such as dimethylbutane (DMB) are thermally cracked. Larger hydrocarbons are also quickly aromatized and then thermally cracked.

[0067] Operating a reforming catalyst at a low hydrogen partial pressure may be desirable to reduce hydrocracking of the feedstock into fuel gas. However, hydrogen, a product of the aromatization reaction, increases in partial pressure as the feed is converted through the reactor train / series. According to embodiments of the present disclosure, a portion of this undesired hydrogen is removed during the reaction to maintain a more consistent hydrogen partial pressure in the reforming reactor and increase selectivity. In embodiments, branched, unconvertible hydrocarbons and / or substituted aromatics (generally, C 7+ aromatics) can also be removed before they undergo substantial decomposition.

[0068] In an embodiment, the reforming method of the present disclosure therefore includes separating hydrogen from the effluent of at least one reactor upstream of the last reactor to provide hydrogen and an effluent with reduced hydrogen content, and introducing at least a portion of the effluent with reduced hydrogen content into a reactor downstream of the at least one reactor. In an embodiment, the method of the present disclosure includes operating a first reactor series, the first reactor series comprising a plurality of reactors, each reactor within the plurality of reactors comprising a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in a hydrocarbon feedstock to aromatic hydrocarbons, thereby providing a first reactor series effluent comprising aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen; separating hydrogen from the first reactor series effluent, thereby providing hydrogen and a first reactor series effluent with a reduced hydrogen content; and operating a second reactor series, the second reactor series comprising a plurality of reactors, each reactor within the plurality of reactors of the second reactor series comprising a catalyst capable of catalyzing the reaction of at least a portion of the unreacted hydrocarbons in the first reactor series effluent with a reduced hydrogen content, to aromatic hydrocarbons.

[0069] Referring now to FIG. 1 , a description of a reforming method according to the present disclosure, which may provide selectivity enhancement through in-series hydrogen removal, is provided. A hydrocarbon feedstock containing one or more convertible hydrocarbons to be reformed to produce aromatic hydrocarbon(s), is introduced into the reforming system 100 via hydrocarbon feedstock line 105. A variety of feedstocks may be suitable for use in the reforming process, generally including non-aromatic hydrocarbons. For example, the hydrocarbon feedstock may include naphtha boiling range hydrocarbons, including a majority of C6-C7 paraffins. In embodiments, the hydrocarbon feedstock comprises primarily C6 or higher non-aromatic organic compounds. Such feedstocks may include n-hexane and / or n-heptane. In embodiments, the hydrocarbon feedstock introduced via hydrocarbon feedstock inlet line 105 is a mixture of hydrocarbons, including C6-C8 hydrocarbons. In embodiments, the hydrocarbon feedstock may comprise up to about 10 wt %, or up to about 15 wt %, of C5 and lighter hydrocarbons (C5 - In an embodiment, the hydrocarbon feedstock comprises up to about 10 wt% C9 and heavier hydrocarbons (C9 + In embodiments, the utilization of interstage heavy component separation as described herein with reference to the embodiment of FIG. 1 allows for the utilization of heavier hydrocarbon feedstocks. For example, in embodiments, the hydrocarbon feedstock may comprise hydrocarbons containing 8 or more carbon atoms (C8 + ), greater than about 10, 15, 20, or 25 weight percent (wt. %). In such embodiments, upstream equipment traditionally utilized for heavy hydrocarbon removal can be eliminated from the system. For example, in embodiments, the utilization of in-line heavies removal obviates the need for a traditional upstream dehexanizer.

[0070] In embodiments, the hydrocarbon feedstock boils at a temperature within the range of about 70°F (about 21°C) to about 450°F (about 232°C), or within the range of about 120°F (49°C) to about 400°F (204°C). In embodiments, the hydrocarbon feedstock in hydrocarbon feedstock line 105 is a substantially sulfur-free feedstock. In embodiments, the hydrocarbon feedstock stream has a sulfur content of about 200 or less, 100 or less, or 10 or less parts per billion by weight (ppbw), or in the range of about 10 ppbw to about 100 ppbw. Examples of suitable feedstocks include straight-run naphtha from petroleum refineries, or fractions thereof that have been hydrotreated to remove sulfur and other catalyst poisons. Also suitable are synthetic naphtha or naphtha fractions obtained from other sources, such as coal, natural gas, or processes such as the Fischer-Tropsch process, fluid catalytic cracker, and hydrocracker.

[0071] Although not shown in Figures 1 or 2, various upstream hydrocarbon pretreatment steps may be used to prepare the hydrocarbons for the reforming process. For example, hydrotreating may be used to remove catalyst poisons such as sulfur. Contacting the hydrocarbons with a sufficient amount or concentration of nickel (Ni) catalyst, for example, prior to the reforming reaction, may also protect against hydrotreating system failure. In embodiments such as those described below with reference to Figure 2, the reforming system may further include another feedstock / effluent heat exchanger upstream of the sulfur conversion adsorber, which itself is located upstream of feedstock / effluent heat exchanger 107A of Figure 1.

[0072] The hydrocarbon feedstock is introduced into the feedstock / effluent heat exchanger 107A via the hydrocarbon feedstock inlet line 105. Within the feedstock / effluent heat exchanger 107A, heat is transferred between the sixth reforming reactor effluent introduced into the feedstock / effluent heat exchanger 107A via line 115F. The heat-exchanged hydrocarbon feedstock is removed from the feedstock / effluent heat exchanger 107A via the heat-exchanged hydrocarbon feedstock line 106 and introduced into the first furnace 110A. Hydrogen separated in the inter-series hydrogen separator 135 may be introduced together with the heat-exchanged hydrocarbon feedstock via the first reforming reactor series hydrogen recycle line 139C into the heat-exchanged hydrocarbon feedstock line 106. The first furnace 110A increases the temperature of the hydrocarbon feedstock via the first furnace outlet line 112A before introducing the hot feedstock into the first reforming reactor 120A. Reforming of the hydrocarbon feedstock occurs in a first reforming reactor 120A, and the first reforming reactor effluent is removed from the first reforming reactor 120A via a first reforming reactor effluent line 115A and introduced into a second furnace 110B, where the temperature of the effluent is elevated before being introduced into the second reforming reactor 120B via a second furnace effluent line 112B. In the embodiment of Figure 1, the first reactor series includes first and second reforming reactors 120A and 120B, respectively. The effluent of the first reactor series is removed from the second reforming reactor 120B via a second reforming reactor effluent line 115B.

[0073] The effluent of the first reactor train is introduced into the intermediate effluent heat exchanger 107B via the second reforming reactor effluent line 115B, where heat exchange with the hydrogen-reduced convertible C hydrocarbons in the recycle line 195 reduces the temperature of the second reforming reactor effluent and increases the temperature of the hydrogen-reduced convertible C hydrocarbon stream (also referred to herein as the "second hydrocarbon stream"). The cooled first reactor train effluent is removed from the intermediate effluent heat exchanger 107B via the intermediate effluent heat exchanger first reactor train outlet line 125B. The heat-exchanged second reactor train effluent may be combined with the intermediate effluent heat exchanger first reactor train outlet line 125B via the feed / effluent heat exchanger effluent outlet line 125A before introduction into the hydrogen separator 135.

[0074] The hydrogen separator 135 is operated to separate hydrogen from the effluent of the first reactor train. Although shown in the embodiment of Figure 1 as being located after the second reforming reactor, the hydrogen separator 135 may be located at any "inter-reactor" location within the reforming system, such that the splitter 135 is configured to remove hydrogen from a reactor effluent other than (or in addition to) the final reforming reactor effluent. For example, the hydrogen separator 135 may be positioned to separate hydrogen from the first reforming reactor effluent, the second reforming reactor effluent (as shown in the embodiment of Figure 1), the third reforming reactor effluent, the fourth reforming reactor effluent, and / or the fifth reforming reactor effluent, and the hydrogen separator 135 may also be operated to separate hydrogen from the final reforming reactor effluent (e.g., from the sixth reforming reactor effluent according to Figure 1).

[0075] The hydrogen separator 135 operates to separate hydrogen from the entrained feed stream with the net gas removed from the system, thereby providing a reduced-hydrogen content product that is removed from the hydrogen separator 135 via hydrogen separator bottoms outlet line 136. The reduced-hydrogen content product in the hydrogen separator bottoms outlet line 136 may be a liquid product containing about 60 wt% to about 90 wt%, about 65 wt% to about 90 wt%, or about 70 wt% to about 90 wt% aromatics. The hydrogen separated in the hydrogen separator 135 is removed from the hydrogen separator 135 via separated hydrogen outlet line 137. The separated hydrogen may be compressed in a compressor 139. The compressed gas exiting the compressor 138 via compressor outlet line 139 may be utilized throughout the reforming system as desired. As a result, hydrogen is removed in the LPS 135 along with the net gas removed from the system. Alternatively, some hydrogen may be mixed with the fresh hydrocarbon feed stream and sent back to the second series of reactors. For example, in embodiments, a portion of the net gas is removed from the reforming / aromatization system via net gas outlet line 139B. Hydrogen recycle line 139A may be utilized to recycle the separated and compressed hydrogen to the reforming reactors. For example, in the embodiment of FIG. 1, hydrogen recycle line 139A is split into two portions, with a first hydrogen recycle portion being introduced to the first reforming reactor series S1 via first series hydrogen recycle line 139C and a second hydrogen recycle portion being introduced to the second reforming reactor series S2 via second series hydrogen recycle line 139D.

[0076] In embodiments, the reforming reaction occurs under process conditions that thermodynamically favor the dehydration cyclization reaction and limit undesired dehydrocyclization. The reforming reaction can be carried out using any conventional reforming conditions, which, in embodiments, may be adjusted as described herein below. Thus, reforming may be carried out at a reactor inlet temperature ranging from about 600°F (about 316°C) to about 1100°F (about 593°C), from about 650°F (about 343°C) to about 1100°F (about 593°C), from about 700°F (about 371°C) to about 1100°F (about 593°C), from about 800°F (about 427°C) to about 1050°F (about 566°C), or from about 850°F (about 454°C) to about 1050°F (about 566°C). The reforming reaction pressure may range from atmospheric to about 500 psig (3.4 MPa), from about 25 psig (about 0.2 MPa) to about 300 psig (about 2.1 MPa), or from about 30 psig (about 0.2 MPa) to about 100 psig (about 0.7 MPa). The hydrogen to hydrocarbon molar ratio in the reactor stream may be between about 0.1:1 and about 10:1, alternatively between about 0.5:1 and about 5.0:1, or alternatively between about 1:1 and about 3:1. The liquid hourly space velocity (LHSV) of the hydrocarbon feedstock over the aromatization catalyst may be between about 0.50 and about 20, between about 0.50 and about 5.0, or between about 0.50 and about 3.0, based on the catalyst in the reaction zone.

[0077] In embodiments, the first reactor train is operated at a lower severity than the reforming reactors of the second train. For example, the temperature used in the reforming reactors of the first train (i.e., the reforming reactors upstream of the hydrogen separator 135 and intermediate effluent heat exchanger 107B) may be maintained below about 800°F, below about 750°F, or below about 700°F, while the second reactor train (i.e., the reforming reactors downstream of the hydrogen separator 135 and intermediate effluent heat exchanger 107B) may be operated above about 800°F, above about 750°F, or above about 700°F. For example, in embodiments, at least one, more than one, or all of the reactors in the first reactor train are operated at a lower severity than at least one, more than one, or all of the reactors in the second reactor train. Less stringent may include an average catalyst bed temperature or reactor endotherm over the course of operation being at least 20° C., 30° C., or 40° C. less. In embodiments, the catalyst fouling rate in any one reactor, two or more reactors, or all reactors in the plurality of reactors in the first reactor series is less than the catalyst fouling rate in any one reactor, two or more reactors, or all reactors in the plurality of reactors in the second reactor series.

[0078] In embodiments, the reforming reactor of the first reactor train (i.e., the reforming reactor upstream of hydrogen separator 135 and intermediate effluent heat exchanger 107B) operates at a significantly lower temperature than the next reactor train / series, but still operates at a high enough temperature to convert the longer chain hydrocarbons, cyclohexane, and additional longer chain hydrocarbons to aromatics. Without limitation, low temperature operation of the reforming reactor of the first reactor train S1 may help prevent or minimize thermal cracking of the alkylbenzenes produced and other branched molecules in the feedstock.

[0079] In embodiments, the operating conditions of the second series of reforming reactors are more severe. These conditions may include elevated temperature and / or pressure in the second reactor series and / or different process flow rates and / or reactant ratios therein. In embodiments, the weight hourly space velocity is at least about 50%, about 75%, or about 100% greater in the second reactor series relative to the first reactor series. In embodiments, the ratio of hydrogen to hydrocarbon in at least one reactor of the second series of reforming reactors is at least about 10%, about 25%, or about 50% less than the ratio of hydrogen to hydrocarbon in at least one reactor of the first series of reforming reactors.

[0080] The selectivity of the conversion of convertible hydrocarbon components to aromatics is a measure of the effectiveness of the aromatization reaction in converting the convertible hydrocarbon components to the desired, valuable products, aromatics and hydrogen, as opposed to less desirable by-products, such as products from hydrocracking, in the aromatization reactor system(s) 100 / 200. The dehydrocyclization catalyst may be used under reaction conditions effective to achieve a per-pass conversion to aromatics and other hydrocarbons of at least about 50 wt%, about 60 wt%, or about 70 wt%. The yield of desired aromatic products per pass is the per-pass conversion multiplied by the selectivity. As used herein, the term "selectivity" is defined as the percentage of moles of convertible hydrocarbon components converted to aromatics compared to the moles converted to aromatics and other products (e.g., thermal cracking products). Thus, the percent selectivity of a convertible component may be defined as follows: Selectivity = (moles of convertible component converted to aromatics x 100) / (moles of selectively convertible component converted to aromatics and other products). Isomerization of paraffins, the interconversion of paraffins and alkylcyclopentanes having the same number of carbon atoms per molecule, is not considered in determining selectivity.

[0081] The reforming method may further include separating a second hydrocarbon stream from the reduced-hydrogen-content reforming reactor effluent, the second hydrocarbon stream comprising a higher concentration of convertible C6 hydrocarbons than the reduced-hydrogen-content reforming reactor effluent. In embodiments, the reduced-hydrogen-content effluent of the first reactor series comprises unconvertible C6 hydrocarbons, and the method further includes separating the unconvertible C6 hydrocarbons from the reduced-hydrogen-content effluent of the first reactor series to produce a second hydrocarbon stream, and introducing the second hydrocarbon stream into the second reactor series, wherein the second hydrocarbon stream comprises a higher concentration of convertible C6 hydrocarbons than the reduced-hydrogen-content effluent of the first reactor series. Such methods include separating light hydrocarbons (e.g., C6 hydrocarbons) from the reduced-hydrogen-content reformed product removed from the hydrogen separator 135 via the hydrogen separator bottoms outlet line 136. 4- , or LPG), C 7+ , benzene, and / or DMB.

[0082] In embodiments, the methods disclosed herein further include separating light hydrocarbons from the reduced hydrogen content reformed product removed from hydrogen separator 135. For example, in embodiments, the bottoms of LPS 135, including the reduced hydrogen content reformed product, is introduced into stabilizer 140 via hydrogen separator bottoms outlet line 136. Stabilizer 140 is a C 4- As a result, C 5+ To provide the product: C 4- The stream is removed from the stabilizer 140 via stabilizer light hydrocarbon outlet line 145 and 5+ The hydrocarbons are removed from the stabilizer 140 via a stabilizer bottoms outlet line 150. The light hydrocarbon stream may include LPG.

[0083] In embodiments, the methods disclosed herein include extracting C from the reduced hydrogen content reformed product removed from the hydrogen separator 135. 7+For example, in an embodiment, the bottoms from stabilizer 140 are introduced into C6 / C7 splitter 155, which splits the C 7+ The hydrocarbon product stream is separated and is separated from the C6 / C7 splitter 155 to C 7+ Exit line 160 via C 6- removed from the hydrocarbon product stream, which is C 6- C6 / C7 splitter 155 via outlet line 165. 7+ C in the product 7+ The species is C. 7+ The C6 / C7 column 155 is removed from the reforming system via exit line 160, for example, to mogas (motor gasoline pool). 6- Hydrocarbons are C 6- It may be introduced into the EDU 170 via an exit line 165 .

[0084] In embodiments, the methods disclosed herein further include separating benzene from the reduced hydrogen content reformed product removed from hydrogen separator 135. For example, in embodiments, extractive distillation unit 170 is operated to separate benzene from the remaining hydrocarbons. The benzene product is removed from EDU 170 via benzene product outlet line 175. The remaining hydrocarbons with reduced benzene content may be removed from EDU 170 via outlet line 180 for hydrocarbons with reduced benzene content.

[0085] In embodiments, the methods disclosed herein further include separating dimethylbutane from the reduced-hydrogen-content reformed product removed from hydrogen separator 135. For example, in embodiments, the reduced-benzene-content hydrocarbon product in reduced-benzene-content hydrocarbon outlet line 180 is introduced into DMB column 185. DMB 185 is operated to separate DMB, which is removed from DMB column 185 via DMB outlet line 187. The separated DMB is removed from reforming system 100, for example, to mogas. The bottoms component of DMB column 185 may contain almost exclusively convertible C6 species and may be removed from DMB column 185 via convertible C6 product outlet line 186. In embodiments, the convertible C6 product in convertible C6 product outlet line 186 contains at least about 60 wt%, about 70 wt%, about 80 wt%, or about 90 wt% convertible C6 hydrocarbons.

[0086] A second hydrocarbon stream containing a higher concentration of convertible C6 hydrocarbons than the hydrogen-reduced reforming reactor effluent can be introduced into the second series of reforming reactors. For example, in the embodiment of FIG. 1, the convertible C6 product in the convertible C6 product outlet line 186 is sent to the second reactor series S2 via a charge or "interstage" pump 190 and a hydrogen-reduced convertible C6 hydrocarbon recycle line 195. The hydrogen-reduced convertible C6 hydrocarbons in the recycle line 195 can be heat-exchanged in intermediate effluent heat exchanger 107B with the effluent of the first reforming reactor series introduced therein via second reforming reactor effluent outlet line 115B and passed through a third furnace 110C for heating before being introduced into the first reforming reactor of the second series of reforming reactors S2 (i.e., the third reforming reactor 120C in the embodiment of FIG. 1). In certain embodiments, the second hydrocarbon stream introduced into the second reforming reactor train is a C 1 H 2 O 4 ... 5+ Hydrocarbons, C 6- C removed from C6 / C7 splitter 155 via outlet line 165 7+Reduced hydrocarbon content, reduced benzene content C 6- Benzene-reduced C removed from EDU 170 via product outlet line 180 6- The second reforming reactor series S2 may include the stabilizer 140, the C6 / C7 splitter 155, the EDU 170, the DMB column 185, or a combination thereof.

[0087] In embodiments, the second set or series of reforming reactors (S2) may be operated at more severe conditions than the first series of reforming reactors, which may promote the conversion of C compounds to benzene. The hydrogen partial pressure in these reactors may be better controlled by the disclosed systems and methods due to the intermediate removal of hydrogen during the inter-series separation in the hydrogen separator 135 described herein. Branched species (such as DMB) and heavy compounds (C 8+ Because the C6 / C7 splitter 155 is removed prior to the second reforming reactor train (e.g., via DMB column 185 and C6 / C7 splitter 155), thermal cracking to lighter molecules may be significantly less, even under more severe conditions. The reformed effluent from the second train of reforming reactors (i.e., the effluent formed through the third, fourth, fifth, and sixth reforming reactors 120C, 120D, 120E, and 120F and the entrainment furnaces 110C, 110D, 110E, and 110F) is subjected to heat exchange in feed / effluent heat exchanger 107A and combined with the reformed product from the first train of reforming reactors for introduction into hydrogen separator 135.

[0088] In embodiments, the molar ratio of hydrogen to hydrocarbon in at least one reactor of the plurality of reactors in the second reactor train is less than the molar ratio of hydrogen to hydrocarbon in a corresponding reactor of a process employing a reforming reactor system comprising a single reactor train operated without inter-series hydrogen separation. In embodiments, the molar ratio of hydrogen to hydrocarbon in the last reactor of the second reactor train is less than about 3:1 at a constant conversion, and the molar ratio of hydrogen to hydrocarbon in the first reactor of the first reactor train is in the range of about 1.5:1 to about 2:1. In embodiments, the hydrogen partial pressure in at least one reactor of the plurality of reactors in the second reactor train is less than the hydrogen partial pressure in a corresponding reactor of a process employing a reforming reactor system comprising a single reactor train operated without inter-series hydrogen separation.

[0089] In embodiments, interseries hydrogen removal according to the present disclosure provides a selectivity to benzene, toluene, and xylenes (BTX) that is greater than the selectivity to BTX provided by an equivalent process employing a reforming reactor system comprising a single reactor train operated without interseries hydrogen separation.

[0090] In an embodiment, the reforming method includes directing a portion of the hydrocarbon feedstock to form an additional feedstock and introducing the additional feedstock into at least one reactor downstream of the first reactor in the reactor series, thereby bypassing the first reactor with a portion of the hydrocarbon feedstock and introducing the remaining portion of the hydrocarbon feedstock into the first reactor in the reactor series.

[0091] In certain aspects, the reforming methodology and process includes operating a plurality of reactors in a reactor series to produce a reactor series effluent comprising aromatic hydrocarbons from a hydrocarbon feedstock comprising hydrocarbons, wherein operating the plurality of reactors includes directing a portion of the hydrocarbon feedstock to form an additional feedstock and introducing the additional feedstock to at least one reactor downstream of a first reactor in the reactor series, thereby bypassing the first reactor having a portion of the hydrocarbon feedstock and introducing a remaining portion of the hydrocarbon feedstock to the first reactor in the reactor series, wherein each reactor in the plurality of reactors includes a catalyst capable of catalyzing the reaction of at least a portion of the hydrocarbons in the hydrocarbon feedstock to aromatic hydrocarbons, thereby providing an effluent from the reactor series.

[0092] A description of a reforming process according to the present disclosure, which may provide enhanced control of hydrogen partial pressure throughout the reforming reactor train through staggered introduction of the hydrocarbon feedstock, will now be provided with reference to Figure 2. As previously described herein, like numerals are utilized in the figure to represent like equipment.

[0093] A fresh hydrocarbon feedstock containing the hydrocarbons to be reformed is introduced into the first feedstock / effluent heat exchanger 207A via fresh hydrocarbon feed line 205A and its temperature is increased by heat exchange with the reforming reactor effluent in second feedstock / effluent heat exchanger outlet line 225, as described above with reference to FIG. 1. The heat exchanged hydrocarbon feedstock is removed from the first feedstock / effluent heat exchanger 207A via first heat exchanger hydrocarbon feedstock outlet line 206A. Piping 208 / 208' / 208" / 208''' is configured to bypass a portion of the hydrocarbon feedstock so that it can bypass (at least) the first reforming reactor 220A.In a non-limiting example, a portion of the hydrocarbon feedstock may be directed via piping 208 (e.g., 208, 208', 208", and / or 208'") and 208A to a second reforming reactor 220B upstream of the second furnace 210B via mixing with a first reforming reactor effluent removed from the first reforming reactor 220A via a first reforming reactor effluent line 215A, and a portion of the hydrocarbon feedstock may be directed to a second reforming reactor 220B upstream of the second furnace 210B via a second reforming reactor effluent line 215B. The hydrocarbon feedstock may be directed via lines 208 (e.g., 208, 208', 208", and / or 208'") and 208B to a third reforming reactor 220C upstream of the third furnace 210C via mixing with a second reforming reactor effluent removed from the third reforming reactor 220B, and a portion of the hydrocarbon feedstock may be directed via lines 208 (e.g., 208, 208', 208", and / or 208'") and 208B to a fourth furnace 210D via mixing with a third reforming reactor effluent removed from the third reforming reactor 220C via third reforming reactor effluent line 215C. The hydrocarbon feedstock may be introduced into a fourth reforming reactor 220D via conduit 208 (e.g., 208, 208', 208", and / or 208'") and 208C, and a portion of the hydrocarbon feedstock may be introduced into a fifth reforming reactor 220E upstream of the fifth furnace 210E via conduit 208 (e.g., 208, 208', 208", and / or 208'") and 208C, via mixing with a fourth reforming reactor effluent removed from the fourth reforming reactor 220D via a fourth reforming reactor effluent line 215D. 208D, and a portion of the hydrocarbon feedstock may be directed via piping 208 (e.g., 208, 208', 208", and / or 208'") and 208E to the sixth reforming reactor 220F upstream of the sixth furnace 210F via mixing with fifth reforming reactor effluent removed from the fifth reforming reactor 220E via fifth reforming reactor effluent line 215E, or a combination thereof.

[0094] The method may further include controlling a portion of the additional feedstock introduced into each reactor downstream of the first reactor such that the influent to each reactor of the plurality of reactors has a desired molar ratio of hydrogen to hydrocarbon, the effluent from each reactor of the plurality of reactors has a desired molar ratio of hydrogen to hydrocarbon, or both. In embodiments, the desired molar ratio of hydrogen to hydrocarbon in the influent is within the range of about 1.5:1 to about 2:1. In embodiments, the desired molar ratio of hydrogen to hydrocarbon in the effluent is less than about 3:1.

[0095] In an embodiment, the hydrocarbon feedstock is split before adding hydrogen thereto (i.e., line 208 branches off a portion of the hydrocarbon feedstock before adding hydrogen thereto). For example, the hydrocarbon feedstock may be split upstream of the sulfur removal unit 209 but downstream of the first feed effluent heat exchanger 207A. The remaining, unsplit portion of the hydrocarbon feedstock is mixed with hydrogen introduced into the heat-exchanged hydrocarbon feedstock line 206A via hydrogen recycle line 239A and introduced into the sulfur removal unit 209.

[0096] The sulfur removal system 209 may be used to reduce the amount of sulfur in the hydrocarbon stream and may include any suitable sulfur removal system capable of removing sulfur from the hydrocarbon stream. In one embodiment, the sulfur removal system 209 includes one or more vessels that allow the hydrocarbon stream to pass as a fluid through a sulfur conversion material containing a Group VIII metal and a sulfur removal system containing a sulfur sorbent material. The sulfur removal system 209 may also function as a precaution or backup in the event that an upstream hydrocracking system fails or experiences an operational disruption. After passing through the sulfur removal system 209, the hydrocarbon stream may be passed via reduced-sulfur hydrocarbon feed line 205B to a second feedstock / effluent heat exchanger 207B designed to further condition the temperature of the hydrocarbon stream. The hydrocarbon stream may then be passed via line 206B to the reforming reactor portion of the reforming system 200.

[0097] The reduced-sulfur hydrocarbon feedstock containing hydrogen is introduced into the second feedstock / effluent heat exchanger 207B via the reduced-sulfur hydrocarbon feedstock line 205B. Thus, in such an embodiment, the fraction of the feedstock mixed with hydrogen can undergo sulfur removal in the sulfur removal unit 209, heat exchange in the second feedstock / effluent heat exchanger 207B, and temperature increase in the first furnace 210A before being introduced into the first reforming reactor 220A via the first furnace outlet line 212A. As the hydrocarbon feedstock is converted to aromatics in the first reforming reactor 220A, more hydrogen is produced, resulting in an increase in the H / HC molar ratio. The bypassed feedstock without added hydrogen is added to the reformer product in the reactor train. The bypassed feedstock may be added upstream of the furnace(s). The diverted hydrocarbon feedstock may be introduced into the reactor train after each reforming reactor, after one of the reforming reactors downstream of the first reforming reactor, or after multiple reactors downstream of the first reforming reactor and upstream of the last reforming reactor in the system.

[0098] By staggering the injection / introduction point of the hydrocarbon feed, the hydrocarbon feed without added hydrogen can be added in an amount to restore the H2 / HC molar ratio to the desired level. The reactor dimensions can be adjusted to compensate for the increased hydrocarbon load in subsequent reactors. An additional benefit of staggering the hydrocarbon feed is that significantly less hydrogen is recycled with the feed, thereby reducing compressor costs, such as the cost of compressor 238. In existing plants where recycle compressors may be capacity-constrained, staggering the hydrocarbon feed as described herein may allow the bottleneck to be removed.

[0099] As shown in Figure 2, the twice heat exchanged hydrocarbon feed stream exiting the second feed / effluent heat exchanger 207B proceeds through the reactor train in a series flow arrangement. Prior to each reforming reactor 220A, 220B, 220C, 220D, 220E, 220F, the hydrocarbon feed stream passes through an entrained furnace 210A, 210B, 210C, 210D, 210E, 210F, respectively, to raise the temperature of the feed to the desired reactor inlet temperature. Once heated via the upstream furnace, the heated feedstock is introduced into the entrained downstream reforming reactors until the reformed product exits the last reactor in the series as reformed effluent 215F, which passes through the second feedstock / effluent heat exchanger 207B and the first feedstock / effluent heat exchanger 207A where it is cooled by heat exchange with fresh hydrocarbon feedstock in lines 205B and 205A, respectively, before being introduced into the downstream processing unit via line 230.

[0100] The reformer effluent of the last reforming reactor (the sixth reforming reactor 220F in the embodiment of FIG. 2) can be used to increase its temperature via heat exchange with a hydrocarbon feedstock (in the second feedstock / effluent heat exchanger 207B and the first feedstock / effluent heat exchanger 207A in FIG. 2). As described with reference to the embodiment of FIG. 1, hydrogen may be separated from the reformer effluent. For example, the reformer effluent may be introduced into a hydrogen separator 235 via a first feedstock / effluent heat exchanger reformer effluent outlet line 230. In the hydrogen separator 235, hydrogen is separated from the reformer effluent, resulting in an effluent with a reduced hydrogen content. The separated hydrogen is introduced into a compressor 238 via a separated hydrogen outlet line 237, which compresses the net gas removed via the hydrogen separator 235. The compressed gas is removed from the compressor 238 via a compressor outlet line 239. A portion of the compressed gas can be removed from the system via outlet line 239B, and a portion of the hydrogen can be mixed with the hydrocarbon feedstock for introduction into the first reforming reactor 220A via hydrogen recycle line 239A.

[0101] As described with reference to the embodiment of Figure 1, one or more components can be removed from the hydrogen-reduced reformed product. For example, the hydrogen-reduced reformed product can be introduced into stabilizer 240 via hydrogen separator bottoms outlet line 236, thereby removing light hydrocarbons therefrom. The light hydrocarbons can be removed from stabilizer 240 via stabilizer light hydrocarbon outlet line 245, thereby removing C 5+ The reformed product can be removed from the stabilizer 240 via the stabilizer bottoms outlet line 250. 7+ The component is C 5+ The reformed product is introduced from stabilizer 240 via stabilizer bottoms outlet line 250 into C6 / C7 splitter 255 to form a C 5+ It can be removed from the reformed product. 7+ Hydrocarbons are C 7+ C6 / C7 can be removed from the C6 / C7 splitter 255 via an outlet line 260. 6- The reformed product is C 6- Benzene is removed from the C6 / C7 splitter 255 via exit line 265. 6- The C6-reformed product is introduced into the EDU 270 via the product outlet line 265. 6- It can be removed from the modified product.

[0102] The separated benzene product is removed from the EDU 270 via benzene product outlet line 275 to form a C 6- The reformed products are removed from the EDU 270 via EDU outlet line 280. In an embodiment, a C 6- The product is utilized as mogas. In an embodiment, similar to the embodiment of FIG. 1, a C 2 O 4 with reduced benzene content is used. 6-The product is introduced into a DMB column, and DMB is removed therefrom. The resulting DMB-reduced product containing convertible C6 hydrocarbons may be introduced into one or more reforming reactors for further aromatics production therefrom. For example, the convertible C6 hydrocarbons may be introduced into the first reforming reactor 220A via mixing with the hydrocarbon feedstock in line 205B and / or may be introduced into one or more reforming reactors downstream of the first reforming reactor via piping 208. In an embodiment, all of the hydrocarbons in lines 205A / 206A are introduced into the first reforming reactor 220A, and the hydrocarbon feedstock introduced into the one or more reforming reactors downstream of the first reforming reactor comprises the convertible C6 hydrocarbons obtained by hydrogen separation, as well as light hydrocarbons from the hydrogen-reduced reforming product, C 7+ The fresh hydrocarbon feed may include one or more of the following: hydrocarbons, benzene, and / or DMB. In this manner, all of the fresh hydrocarbon feed may be passed to a sulfur removal unit 209 for removing sulfur from the feed stream.

[0103] 1, in embodiments, interseries hydrogen separation may be combined with staggered hydrocarbon feed introduction, as further described with reference to the embodiment of FIG. 2. Thus, for example, hydrogen separation via hydrogen separator 235, light hydrocarbon removal via stabilizer 240, C6 / C7 splitting via C6 / C7 splitter 255, benzene separation via EDU 270, and / or DMB removal via DMB column 185 may be combined to produce hydrogen, light hydrocarbons, C 7+The reactors may be configured and operated to remove hydrocarbons, benzene, and / or DMB from the effluent product of the first stage, first series, or first series of reforming reactors prior to their introduction into the second stage, second series, or second series of reforming reactors. In embodiments, methods including staggered hydrocarbon feedstock introduction as described herein may further include removing unconvertible hydrocarbons from the effluent of the reactor series to produce a second hydrocarbon stream, and recycling the second hydrocarbon stream to the reactor series. The second hydrocarbon stream may be utilized as a portion (or at least a portion) of the hydrocarbon feedstock that bypasses the first reactor.

[0104] Embodiments of the present disclosure provide systems and methods by which the hydrogen partial pressure in one or more reforming reactors can be more consistently maintained through hydrogen removal from the reformed product of a first reactor series upstream of at least one reforming reactor of a second series of reforming reactors. Intermediate hydrogen removal may enhance selectivity. In embodiments, the disclosed systems and methods provide for removal of branched, unconvertible aromatics and / or substituted aromatics between the first and second series of reforming reactors. Through such systems and methods, such branched, unconvertible aromatics and / or substituted aromatics can be removed before undergoing substantial thermal cracking. Intermediate removal of branched compounds may enhance the value of the resulting mogas product. In embodiments, the disclosed systems and methods employ a first series of reforming reactors operated under more severe operating conditions than the second series of reforming reactors. Operating the first and second series of reactors at different conditions may be utilized to maximize selectivity. Additionally, by operating the first reforming reactor train at a lower temperature, it may be possible to reduce or eliminate coatings on the surfaces of piping and equipment that come into contact with the hydrocarbon stream. The reduction or elimination of such protective metallic coatings may represent a significant cost savings in the overall system.

[0105] In embodiments, a dehexanizer is not utilized in the feed preparation portion because interstage heavy component removal according to embodiments of the present disclosure allows the system and method to accommodate heavier feedstocks than conventional reforming systems and methods. In embodiments, the second set or series of reactors (e.g., the third through sixth reforming reactors 120C, 120D, 120E, and 120F in the embodiment of FIG. 1) has fewer flows therethrough, allowing it to be scaled down relative to conventional reactor series in which hydrogen removal occurs solely following introduction to a final reforming reactor. Catalyst consumption may be reduced via the disclosed systems and methods because reduced operating conditions in the first reactor series result in lower deactivation rates, and the second reactor series can be smaller relative to the same reactor in conventional single-series reforming systems and methods.

[0106] The selectivity provided via the systems and methods disclosed herein, including interstage hydrogen removal and component removal, may be higher because pyrolysis precursors are removed prior to the high-temperature reactor of the second reactor train. Selectivity may also be higher because interstage hydrogen removal reduces hydrogen partial pressure. While the hydrogen separator, C6 / C7 splitter, and EDU may be larger to handle the additional flow rate thereto, a charge pump may be utilized to send the convertible C6 hydrocarbons to the second reforming reactor train, and an additional heat exchanger (i.e., interstage effluent heat exchanger 107B) may be utilized to transfer heat to the convertible C6 stream prior to introduction into the second series of reforming reactors, any additional costs may be offset by the enhanced selectivity, reduced catalyst consumption, and the ability to utilize heavier feedstocks and / or less durable equipment within the first reactor train provided via the systems and methods disclosed herein.

[0107] Embodiments of the present disclosure provide systems and methods that can more consistently maintain hydrogen partial pressure in one or more reforming reactors by staggering the introduction of a substantially hydrogen-free hydrocarbon feedstock, thereby bypassing at least a portion of the hydrocarbon feedstock (at least the first reforming reactor). A substantially hydrogen-free hydrocarbon feedstock can be obtained by diverting a portion of the hydrocarbon feedstock upstream of a sulfur removal unit (and before the introduction of hydrogen thereinto), by moving the sulfur removal unit or SCA upstream, and / or by recycling a reduced-hydrogen content reformer product containing convertible C hydrocarbons obtained downstream of a hydrogen separator as the hydrocarbon feedstock. It has been unexpectedly discovered that utilizing multiple feed injection points can significantly improve reforming catalyst performance (e.g., activity and / or C5+ selectivity), provide enhanced C5+ selectivity, and / or reduce (hydrogen) compressor costs and potentially eliminate de-barriers, compared to an equivalent process in which a portion of the hydrocarbon feedstock is not introduced downstream of the first reactor in the reactor series. Utilizing multiple hydrocarbon feed introduction locations may also incur low capital costs to implement. The following examples are provided to further illustrate various exemplary embodiments of the present disclosure. [Example]

[0108] The following examples illustrate embodiments of the present disclosure and are not intended to limit the scope of the specification or claims in any way.

[0109] Example 1 The process of Figure 2 was modeled to determine the molar ratio of hydrogen to hydrocarbon as a function of the hydrocarbon feed rate introduced into the first reforming reactor 220A. An inlet molar ratio of hydrogen to hydrocarbon of 1.46 was used. The extent of reaction was assumed to be the same for all data points. Figure 3 is a graph showing the modeled molar ratio of hydrogen to hydrocarbon exiting the final reforming reactor, the sixth reforming reactor 220F, as a function of the feed rate introduced into the first reforming reactor 220A. As can be seen in Figure 3, staggering the introduction of hydrocarbons so that not all of the hydrocarbon feed is introduced into the first reforming reactor can significantly reduce the final molar ratio of hydrogen to hydrocarbon. While hydrogen production during reforming results in a final molar ratio of hydrogen to hydrocarbon greater than 1.46, feeding substantially hydrogen-free hydrocarbons to the system downstream of the first reforming reactor can significantly reduce the final molar ratio of hydrogen to hydrocarbon exiting the last reforming reactor in the series.

[0110] The specific embodiments disclosed herein are illustrative only, and the disclosure 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 shown herein, other than as described in the following claims. It will therefore be apparent that the specific exemplary embodiments disclosed above may be altered or modified, and all such variations are deemed to be within the scope and spirit of the disclosure. Alternative embodiments resulting from the combination, integration, and / or omission of features of the embodiment(s) are also within the scope of the disclosure. While compositions and methods are described in broader terms such as "having," "comprising," "containing," or "including" various components or steps, compositions and methods can also "consist essentially of" or "consist of" various components and steps. The use of the term "optionally" with respect to any element of a claim means that the element is required, or alternatively, that the element is not required, with either alternative being within the scope of the claim.

[0111] The numerical values ​​and ranges disclosed above may vary somewhat. Whenever a numerical range with a lower and upper limit is disclosed, every numerical value and range falling within that range is specifically disclosed. Specifically, every numerical range disclosed herein (e.g., "about a to about b," or, equivalently, "approximately a to b," or, equivalently, "approximately a to b") is understood to define every numerical value and range encompassed within the broader numerical range. Furthermore, terms in the claims have their plain and ordinary meaning unless explicitly and distinctly defined otherwise in this disclosure.

Claims

1. 1. A process for operating a reforming reactor system, said process comprising: operating a first reactor series, said first reactor series comprising a plurality of reactors, each reactor within the plurality of reactors of said first reactor series comprising a catalyst comprising at least one Group VIII metal, a zeolite support, and at least one halogen, said catalyst being capable of catalyzing the reaction of at least a portion of the hydrocarbons in the hydrocarbon feedstock to aromatic hydrocarbons, thereby providing a first reactor series effluent comprising aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen; separating hydrogen from the effluent of the first reactor series, thereby providing hydrogen and a first reactor series effluent having reduced hydrogen content; and operating a second reactor series, said second reactor series comprising a plurality of reactors, each reactor within said plurality of reactors of said second reactor series comprising a catalyst comprising at least one Group VIII metal, a zeolite support, and at least one halogen, said catalyst being capable of catalyzing the reaction of at least a portion of the unreacted hydrocarbons in the hydrogen-reduced first reactor series effluent to aromatic hydrocarbons; a process for operating said reforming reactor system comprising:

2. further comprising operating at least one reactor in the first series of reactors at a lower severity than at least one reactor in the second series of reactors; wherein the lower stringency is selected from the group including a lower average catalyst bed temperature, a reactor endotherm that is at least 40° C. lower than the average catalyst bed temperature over the course of operation for at least one reactor of the plurality of reactors in the first reactor train, and a reactor endotherm that is at least 40° C. lower than the average catalyst bed temperature over the course of operation for at least one reactor of the plurality of reactors in the second reactor train. The process of claim 1.

3. 3. The process of claim 2, wherein the catalyst fouling rate in any one reactor in the plurality of reactors of the first reactor series is less than the catalyst fouling rate in any one reactor in the plurality of reactors of the second reactor series.

4. The hydrocarbon feedstock is a hydrocarbon containing 8 or more carbon atoms (C ８ ＋ 4. The process of claim 1, wherein the cellulose acetate solution contains more than about 10% by volume of cellulose acetate.

5. 5. The process according to claim 1, wherein the molar ratio of hydrogen to hydrocarbon in at least one reactor in the second series of reactors is less than the molar ratio of hydrogen to hydrocarbon in a corresponding reactor of a process employing a reforming reactor system comprising a single reactor series operated without inter-series hydrogen separation.

6. 6. The process of claim 5, wherein the molar ratio of hydrogen to hydrocarbon in the last reactor of the second reactor series is less than about 3:1 at constant conversion, and wherein the molar ratio of hydrogen to hydrocarbon for the first reactor of the first reactor series is in the range of from about 1.5:1 to about 2:

1.

7. 7. The process according to any one of claims 1 to 6, wherein the hydrogen partial pressure in at least one reactor among the plurality of reactors of the second reactor train is less than the hydrogen partial pressure in the corresponding reactor of a process employing a reforming reactor system comprising a single reactor train operated without inter-train hydrogen separation.

8. 8. The process of any one of claims 1 to 7, wherein the selectivity to benzene, toluene and xylenes (BTX) is greater than the selectivity to BTX provided by an equivalent process employing a reforming reactor system comprising a single reactor train operated without inter-train hydrogen separation.

9. The effluent of the first reactor series with reduced hydrogen content is ６ hydrocarbons, and the process comprises: The non-convertible C ６ separating hydrocarbons from the reduced hydrogen content first reactor series effluent to produce a second hydrocarbon stream; a higher concentration of convertible C than the effluent of the first reactor series with reduced hydrogen content; ６ introducing the second hydrocarbon stream containing hydrocarbons into the second reactor train via a charge pump; and heating said second hydrocarbon stream via heat exchange with the effluent of said first reactor series prior to introducing said second hydrocarbon stream into said second reactor series and prior to separating hydrogen from the effluent of said first reactor series; The process of any one of claims 1 to 8, further comprising:

10. a first reactor series comprising a plurality of reactors, wherein each reactor within the plurality of reactors of said first reactor series comprises a catalyst comprising at least one Group VIII metal, a zeolite support, and at least one halogen, said catalyst being capable of catalyzing the reaction of at least a portion of the hydrocarbons in the hydrocarbon feedstock to aromatic hydrocarbons, thereby providing a first reactor series effluent comprising aromatic hydrocarbons, unreacted hydrocarbons, and hydrogen; a low-pressure separator configured to separate hydrogen from the first reactor train effluent, thereby providing a first reactor train effluent having reduced hydrogen and hydrogen content; and operating a second reactor series comprising a plurality of reactors, each reactor of said second reactor series comprising a catalyst comprising at least one Group VIII metal, a zeolite support, and at least one halogen, capable of catalyzing the reaction of at least a portion of the unreacted hydrocarbons in the hydrogen-reduced first reactor series effluent to aromatic hydrocarbons; 1. A reforming reactor system comprising:

11. Non-convertible C ６ Separating hydrocarbons from the hydrogen-reduced first reactor series effluent to produce a second hydrocarbon stream, wherein the second hydrocarbon stream has a higher concentration of convertible C than the hydrogen-reduced first reactor series effluent. ６ 11. The reforming reactor system of claim 10, further comprising: (a) an apparatus configured to produce a second hydrocarbon stream (comprising a hydrocarbon) from the first reactor series; and (a) a charge pump operable to introduce the second hydrocarbon stream into the second reactor series; (b) a heat exchange device configured to transfer heat between the second hydrocarbon stream and the effluent of the first reactor series prior to introducing the second hydrocarbon stream into the second reactor series and prior to separating hydrogen from the effluent of the first reactor series via the hydrogen separation device, or both (a) and (b).

12. 1. A process for operating a reforming reactor system, said process comprising: operating a plurality of reactors in a reactor train to produce a reactor train effluent comprising aromatic hydrocarbons from a hydrocarbon feedstock comprising hydrocarbons, wherein operating the plurality of reactors comprises directing a portion of the hydrocarbon feedstock to form an additional feedstock, and introducing the additional feedstock into at least one reactor downstream of a first reactor in the reactor train, thereby bypassing the first reactor containing a portion of the hydrocarbon feedstock; and introducing a remaining portion of the hydrocarbon feedstock into a first reactor in the series of reactors, wherein each reactor in the plurality of reactors comprises a catalyst comprising at least one Group VIII metal, a zeolite support, and at least one halogen, the catalyst being capable of catalyzing the reaction of at least a portion of the hydrocarbons in the hydrocarbon feedstock to aromatic hydrocarbons, thereby providing an effluent of the reactor series; 1. A process for operating a reforming reactor system, comprising:

13. 13. The process of claim 12, wherein each reactor in the reactor train is preceded by an entrainment furnace, and wherein the additional feedstock is introduced upstream of the furnace preceding at least one downstream reactor to which the additional feedstock is introduced.

14. 13. The process of claim 12, wherein each reactor in the reactor train is preceded by an entrainment furnace, and operating the plurality of reactors further comprises introducing the additional feedstock immediately upstream of each furnace that entrains each reactor downstream of the first reactor.

15. 15. The process of any of claims 12-14, further comprising controlling the portion of the additional feedstock introduced into each reactor downstream of the first reactor such that the influent to each reactor of the plurality of reactors has a desired molar ratio of hydrogen to hydrocarbon, the effluent from each reactor of the plurality of reactors has a desired molar ratio of hydrogen to hydrocarbon, or both.

16. 16. The process of claim 15, wherein the desired molar ratio of the influents is in the range of about 1.5:1 to about 2:1, the desired molar ratio of the effluents is less than about 3:1, or both.

17. 17. The process of any one of claims 12 to 16, wherein directing a portion of the hydrocarbon feedstock to form the additional feedstock is carried out upstream of a sulfur removal unit, and further comprising introducing the remainder of the hydrocarbon feedstock into the sulfur removal unit prior to introduction into the first reactor.

18. 18. The process of any of claims 12 to 17, further comprising separating hydrogen from the effluent of the reactor train and, after compressing the separated hydrogen, mixing a portion of the separated hydrogen with a remaining portion of the hydrocarbon feedstock such that mixing provides a first reactor feedstock having a molar ratio of hydrogen to hydrocarbon in the range of from about 1.5:1 to about 2.0:

1.

19. 11. The process of claim 10, wherein compressing the separated hydrogen and subsequently combining a portion of the separated hydrogen with the remainder of the hydrocarbon feedstock requires less compressor capacity than an equivalent process employing a reforming reactor system in which all of the hydrocarbon feedstock is introduced into a first reactor in the reactor series.

20. at least one reactor in the first series of multiple reactors is configured to operate at a lower severity than at least one reactor in the second series of multiple reactors; wherein the lower stringency is selected from the group including a lower average catalyst bed temperature, a reactor endotherm that is at least 40° C. lower than the average catalyst bed temperature over the course of operation for at least one reactor of the plurality of reactors in the first reactor train, and a reactor endotherm that is at least 40° C. lower than the average catalyst bed temperature over the course of operation for at least one reactor of the plurality of reactors in the second reactor train.

12. The reforming reactor system according to claim 10 or 11.

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