BACKGROUND [0002] Large-scale refinery production separates crude oil into many fractions one of which is known as virgin naphtha. Virgin naphtha is often reformed to make aromatic naphtha or reformate for motor gasoline blending and chemicals recovery. The fractionation process is often a complex distillation that primarily relies on the difference in the boiling points of the components of the reformate for separation into various fractions. Many of these fractions may contain naphthalene. Consequently, there exists a need for aromatic fluids having a reduced naphthalene concentration and a process for producing aromatic fluids having a reduced concentration of naphthalene. These processes permit naphthalene-containing aromatic fluid to be converted into products with enhanced value and to recover by-products for recycling.

The reduction of naphthalene in aromatic fluids results in better low temperature performance, reduction of odor, and reduction of volatility.

[0003] Japanese Patent Application No. 49-49947 discloses a method of selective hydrogenation of naphthalene to tetrahydronaphthalene by hydrogenating in the presence of one or more supported oxides or sulfides of metals of Group VIII or Group VIB and hydrogen containing hydrogen sulfide or a gas containing hydrogen.

[0004] "Selective Hydrogenation of Naphthalene and Alkylnaphthalenes on a Palladium Catalyst", Inst. Geol. Razrab. , Moscow, U. S. S. R. , (1972), discloses a method of selectively hydrogenating naphthalene to tetrahydronaphthalene in the presence of a 0.5% palladium on alumina catalyst in sulfidated form at a temperature from 400 °C to 500 °C and a pressure of 25 atm. to 100 atm. The article discloses that at lower temperature or higher pressures decalins or decahydronaphthalene are favored.

[0005]"Selective Hydrogenation of Naphthalene to Tetralin", Inst. Goryuch. Iskop, Moscow, U. S. S. R. , (1982), discloses a method of selectively hydrogenating naphthalene to tetrahydronaphthalene in the presence of an aluminum-palladium sulfide catalyst in the presence of a maximum of 0.15% sulfur at a pressure of 5.0 MPa and a temperature of 260 °C.

[0006]"Hydrogenation of Naphthalene to Tetralin in the Presence of a Palladium Catalyst", Inst. Goryuch. Iskop, Moscow, U. S. S. R. , (1972), discloses a method of selectively hydrogenating naphthalene to tetrahydronaphthalene in the presence of a palladium on aluminum oxide in sulfated form in the presence of no more than 0.25% sulfur compounds at a temperature of 200 °C to 280 °C.

[0007] "Selectivity in Platinum Metal Catalyzed Hydrogenations", Engelhard Industries, Technical Bulletin, (1965), discloses that a palladium catalyst in a hydrogenation of naphthalene reaction spontaneously stops at the formation of tetrahydronaphthalene.

[0008] U. S. Application Publication No. 20040006251 discloses the selective transalkylation of naphthalene.

[0009] It is desirable to develop new processes for the reduction of aromatic content in hydrocarbon fluid stream.

SUMMARY OF THE INVENTION [0010] The present invention provides processes for reducing the aromatic content of a hydrocarbon fluid containing a polycyclic aromatic compound. The hydrocarbon fluid comprises at least one aromatic compound, typically a mixture of two or more aromatic compounds.

[0011] One embodiment of the present invention provides a process for reducing the aromatic content of a hydrocarbon fluid containing a polycyclic aromatic compound the process comprising a transalkylation step and a hydrogenation step.

[0012] One embodiment of the present invention provides a process for reducing naphthalene concentration in a hydrocarbon fluid, the process comprising contacting the hydrocarbon fluid and an alkylating agent with a transalkylation catalyst under transalkylation conditions to form a transalkylated product stream, and contacting the transalkylated product stream and hydrogen with a hydrogenation catalyst under hydrogenation conditions to form a hydrogenated product stream.

[0013] One embodiment of the present invention provides a process for reducing naphthalene concentration in a hydrocarbon fluid, the process comprising contacting the hydrocarbon fluid and hydrogen with a hydrogenation catalyst under hydrogenation conditions to form a hydrogenated product stream, and contacting the hydrogenated product stream and an alkylating agent with a transalkylation catalyst under transalkylation conditions to form a transalkylated product stream.

BRIEF DESCRIPTION OF THE DRAWINGS [0014] Fig. 1 shows a single reactor process with two catalyst beds.

[0015] Fig. 2 shows a single reactor process with one catalyst bed.

[0016] Fig. 3 shows a two-reactor in series process with H2 co-feed to the hydrogenation reactor.

[0017] Fig. 4 shows a two-reactor in series process with Ha co-feed to both the transalkylation and hydrogenation reactors.

[0018] Fig. 5 shows a two-reactor in series process with H2 co-feed to the hydrogenation reactor.

[0019] Fig. 6 shows a catalytic distillation process.

DETAILED DESCRIPTION OF THE INVENTION [0020] The present invention is directed to processes for reducing the aromatic content of a hydrocarbon fluid containing a polycyclic aromatic compound.

[0021] One embodiment of the present invention provides a process for reducing the aromatic content of a hydrocarbon fluid containing a polycyclic aromatic compound the process comprising a transalkylation step and a hydrogenation step.

[0022] One embodiment of the present invention provides a process for reducing naphthalene concentration in a hydrocarbon fluid, the process comprising contacting the hydrocarbon fluid and an alkylating agent with a transalkylation catalyst under transalkylation conditions to form a transalkylated product stream, and contacting the transalkylated product stream and hydrogen with a hydrogenation catalyst under hydrogenation conditions to form a hydrogenated product stream.

[0023] One embodiment of the present invention provides a process for reducing naphthalene concentration in a hydrocarbon fluid, the process comprising contacting the hydrocarbon fluid and hydrogen with a hydrogenation catalyst under hydrogenation conditions to form a hydrogenated product stream, and contacting the hydrogenated product stream and an alkylating agent with a transalkylation catalyst under transalkylation conditions to form a transalkylated product stream.

[0024] In one embodiment the hydrocarbon fluid is exemplified by, but is, not limited to, Aromatic 150 and Aromatic 200 Fluids sold by ExxonMobil Chemical Company.

[0025] The elemental groups herein referred to are based on the CAS version of the Periodic Table of the Elements.

[0026] Reducing the aromatic content of a hydrocarbon fluid containing a polycyclic aromatic compound encompasses reducing at least one aromatic ring of the polycyclic aromatic compound, i. e. , the aromatic ring content of the polycyclic aromatic compound is reduced.

Feedstock [0027] In one embodiment the hydrocarbon fluid containing a polycyclic aromatic compound useful in this process can be derived from a substantially dealkylated feedstock. The type of hydrocarbon fluid feedstock useful in one embodiment of the present invention comprises one or more fused-ring polycyclic aromatic compounds, although assemblies of two or more cyclic compounds, either single ring cyclics or aromatics or fused compounds may also be present. In one embodiment according to the present invention the hydrocarbon fluid comprises 1,2, 4-trimethylbenzene ; 1,2, 3- trimethylbenzene; m-cymene; a mixture of alkylbenzene compounds having from 1 to 4 alkyl substituents, each alkyl substituent having from 1 to 4 carbon atoms and the alkylbenzene compounds have a total number of carbon atoms ranging from 10 to 12; naphthalene ; and methylnaphthalene.

10028] The polycyclic aromatic compound is typically obtained from catalytic reforming operations but may also be obtained from cracking operations, e. g. fluidized bed catalytic cracking (FCC) or moving bed Thermofor catalytic cracking (TCC).

Typically, these feed stocks have a hydrogen content of no greater than about 12.5 wt.

% and API gravity no greater than 25 and an aromatic content no less than 50 wt. %.

100291 A substantially dealkylated feedstock is a product that was formerly an alkyl aromatic compound, or mixture of alkyl aromatic compounds, that contained bulky relatively large alkyl group side chains affixed to the aromatic moiety. The dealkylated product is the aromatic compound having substantially no bulky side chain alkyl group. Representative examples of the aromatic compound include phenanthrene, anthracene, dibenzothiophene, fluoroanthene, fluorene, benzothiophene, acenaphthene, biphenyl or naphthalene.

[0030] During acid catalyzed cracking and similar reactions, prior dealkylation generally will remove side chains of greater than 5 carbon atoms while leaving behind primarily methyl or ethyl groups on the aromatic compounds. Thus, for purposes of this invention, the polycyclic aromatic compounds can include substantially dealkylated aromatic compounds which contain small alkyl groups, such as methyl and sometimes ethyl and the like, remaining as side chains, but with relatively few large alkyl groups, e. g. the C3 to C9 groups.

[0031] In one embodiment, the hydrocarbon fluid comprises a mixture of polycyclic compounds, dealkylated or substantially dealkylated, which would be found in a refinery by-product stream. Alternatively, the hydrocarbon fluid comprises a relatively pure feed consisting essentially of one type of polycyclic aromatic compound.

[0032] Representative examples of suitable hydrocarbon fluids include, but are not limited to, refinery by-product derived feedstocks including reformate, light cycle oils and heavy cycle oils from catalytic cracking or pyrolysis processes. Other examples of suitable feedstocks include the liquid product from a delayed or fluid bed coking process, such as a coker gas oil, an aromatics-rich fraction produced by lubricant refining, e. g. , furfural extraction. Other sources of suitable feedstocks include a heavy crude fraction obtained by crude fractional distillation.

[0033] Specifically, the polycyclic aromatic compound contemplated contains, but is not limited to, at least 2 cyclic groups and up to at least 5 cyclic groups. It can be a hydrocarbon containing up to 5 or more benzene rings in any arrangement including fixed benzene rings in linear arrangement. It can be almost entirely or predominantly carbocyclic and can include or be part of a heterocyclic system in which at least one of the cyclic elements of the molecule contains at least one heteroatom such as sulfur, nitrogen and/or oxygen.

[0034] In one embodiment according to the present invention the hydrocarbon fluid may be Aromatic 150 or Aromatic 200 fluids sold by ExxonMobil Chemical Company.

Aromatic 150 fluid comprises approximately fifty components with some of the principle components comprising about 1.7 wt. % of 1,2, 4-trimethylbenzene; about 3.0 wt. % of 1,2, 3-trimethylbenzene and meta-cumene; a mixture of about 81. 6 wt. % Cl0 to C12 benzene compounds, having one or more substituents selected from methyl, ethyl, propyl, and butyl; about 8.6 wt. % naphthalene; and about 0.3 wt. % methylnaphthalene. The weight % is based on the total weight of the fluid.

10035] Alternatively, the Aromatic 150 fluid may be distilled at atmospheric pressure to remove about 60 wt. % of the lighter components to leave an Aromatic 150 fluid concentrate that is about 40 wt. % of the total material prior to distillation. The Aromatic 150 fluid concentrate comprises about 20.4 wt. % naphthalene. The weight % is based on the total weight of the fluid.

[0036] Aromatic 200 fluid comprises approximately 25 to 30 components with some of the principle components comprising naphthalene (10 wt%) ; various alkylnaphthalenes (75 wt%), including 2-methylnaphthalene (26 wt%), 1- methylnaphthalene (13 wt%), 2-ethylnaphthalene (2 wt%), dimethyl naphthalenes (18 wt%), and trimethyl naphthalenes (7 wt%) ; and the remaining 15 wt% comprises primarily alkylbenzenes, as determined by gas chromatographic analysis. The weight % is based on the total weight of the fluid.

I0037] In one embodiment of the present invention the hydrocarbon fluid includes, but is not limited to, Aromatic 150; Aromatic 200; aromatic refinery by-product derived feedstocks including, but not limited to, reformate, light cycle oils and heavy cycle oils from catalytic cracking or pyrolysis processes; the liquid product from a delayed or fluid bed coking process, such as a coker gas oil; an aromatics-rich fraction produced by lubricant refining, e. g. , furfural extraction; heavy crude fraction obtained by crude fractional distillation; coal tar ; and asphaltenes. In another embodiment of the present invention the hydrocarbon fluid includes any feedstock which comprises naphthalene and alkyl-benzenes ; alternatively the hydrocarbon fluid comprises at least 0.2 wt. % naphthalene; alternatively the hydrocarbon fluid comprises from about 0.2 wt% to about 50 wt% naphthalene; alternatively the hydrocarbon fluid comprises from about 0.5 wt% to about 35 wt% naphthalene; alternatively the hydrocarbon fluid comprises from about 1 wt% to about 30 wt% naphthalene; alternatively the hydrocarbon fluid comprises from about 5 wt% to about 15 wt% naphthalene; alternatively the hydrocarbon fluid comprises from about 8 wt% to about 12 wt% naphthalene. The weight % is based on the total weight of the hydrocarbon fluid.

Hydrogenation [0038] One embodiment of the present invention provides a process for reducing the aromatic content of a hydrocarbon fluid containing a polycyclic aromatic compound by a combination of transalkylation and hydrogenation.

[0039] In one embodiment of the present invention, when hydrogenation occurs first, at least a portion of the polycyclic aromatic compound is hydrogenated to form a hydrogenated product stream, which is a reaction product where at least a portion of the polycyclic aromatic compound has been at least partially hydrogenated. At least a portion of the hydrogenated product stream is transalkylated. The hydrogenation catalyst includes, but is not limited to, a Group VIII metal based catalyst, which may be supported or unsupported. The support used could be those known in the art such as alumina, silica, carbon, silica-alumina, clay, zirconia, titania, microporous materials, with pore mouths large enough to allow reactant accessibility to the metal sites, such as molecular sieves, including crystalline zeolites (aluminosilicates), aluminophosphates (AlPOs), metalloaluminophosphates (MeAPOs), and silicoaluminophosphates (SAPOs), and mesoporous materials of the MCM-41 family.

Preferred supports are those such as alumina, carbon, or silica, including, but not limited to, supports whose Bronsted acidity has been reduced by inorganic or organic base compounds. The catalyst may be chosen from, but is not limited to, palladium on an alumina support, palladium on a carbon support, and palladium on a silica support.

Examples of supported catalysts include, but are not limited to, from about a 0.01 wt% to 25 wt% palladium catalyst on an alumina support, alternatively from about a 0.1 wt% to 5 wt% palladium catalyst on an alumina support, alternatively from about a 0.1 wt% to 1.2 wt% palladium catalyst on an alumina support, alternatively from about a 0.5 wt% palladium catalyst on an alumina support; alternatively about a 0.01 wt% to 25 wt% palladium catalyst on a carbon support, alternatively from about a 0.1 wt% to 5 wt% palladium catalyst on a carbon support, alternatively from about a 0.1 wt% to 1.2 wt% palladium catalyst on a carbon support, alternatively from about a 1.0 wt% palladium catalyst on a carbon support ; or alternatively about a 0.01 wt% to 25 wt% palladium catalyst on a silica support, alternatively from about a 0.1 wt% to 5 wt% palladium catalyst on a silica support, alternatively from about a 0.1 wt% to 1.2 wt% palladium catalyst on a silica support, alternatively from about a 0.5 wt% palladium catalyst on a silica support. The weight % is based on the total weight of the catalyst.

[0040] In one embodiment of the present invention, when transalkylation occurs first, the transalkylated product stream, which is a reaction product where at least a portion of the polycyclic aromatic compound has been transalkylated to have at least one alkyl-group, is hydrogenated over a hydrogenation catalyst including, but not limited to, a Group VIII metal based catalyst, which may be supported or unsupported. The support used could be those known in the art such as alumina, silica, carbon, silica- alumina, clay, zirconia, titania, microporous materials, with pore mouths large enough to allow reactant accessibility to the metal sites, such as molecular sieves, including crystalline zeolites (aluminosilicates), aluminophosphates (AlPOs), metalloaluminophosphates (MeAPOs), and silicoaluminophosphates (SAPOs), and mesoporous materials of the MCM-41 family. Preferred supports are those such as alumina, carbon, or silica, including, but not limited to, supports whose Bronsted acidity has been reduced by inorganic or organic base compounds. The catalyst may be chosen from, but is not limited to, palladium on an alumina support, palladium on a carbon support, and palladium on a. silica support. Examples of supported catalysts include, but are not limited to, from about a 0.01 wt% to 25 wt% palladium catalyst on an alumina support, alternatively from about a 0.1 wt% to 5 wt% palladium catalyst on an alumina support, alternatively from about a 0.1 wt% to 1.2 wt% palladium catalyst on an alumina support, alternatively from about a 0.5 wt% palladium catalyst on an alumina support; alternatively about a 0.01 wt% to 25 wt% palladium catalyst on a carbon support, alternatively from about a 0.1 wt% to 5 wt% palladium catalyst on a carbon support, alternatively from about a 0.1 wt% to 1.2 wt% palladium catalyst on a carbon support, alternatively from about a 1.0 wt% palladium catalyst on a carbon support ; or alternatively about a 0.01 wt% to 25 wt% palladium catalyst on a silica support, alternatively from about a 0.1 wt% to 5 wt% palladium catalyst on a silica support, alternatively from about a 0.1 wt% to 1.2 wt% palladium catalyst on a silica support, alternatively from about a 0.5 wt% palladium catalyst on a silica support. The weight % is based on the total weight of the catalyst.

[0041] The hydrogenation process may occur at typical hydrogenation conditions, which include a typical temperature range from about 50 °C. to 250 °C., alternatively from about 75 °C. to 200 °C., alternatively from about 85 °C. to 150 °C., alternatively from about 90 °C to 125 °C, alternatively at about 100 °C ; and a typical pressure range from about 100 psig to 3500 psig, alternatively from about 125 psig to 2000 psig, alternatively from about 150 psig to 1000 psig, alternatively from about 200 psig to 500 psig, alternatively from about 250 psig to 400 psig, alternatively at about 300 psig.

[0042] In one embodiment of the present invention, a transalkylation catalyst capable of hydrogenation under transalkylation conditions may be used to achieve the hydrogenation. These types of transalkylation catalysts include, but are not limited to, a bi-functional metal-containing solid acid catalyst and a physical mixture of solid acids and metal-containing catalysts. The bi-functional metal containing solid acid catalyst includes, but is not limited to, nickel, palladium, platinum, rhodium, ruthenium, their salts, their oxides, and their alloys on acidic solid supports, including, but not limited to, a zeolite bound extrudate and an acidic metal oxide. When the hydrogenation and transalkylation processes are conducted in a single reactor, either with a single catalyst bed or multiple catalyst beds, the processes may occur at a typical temperature range from about 50 °C. to 300 °C., alternatively from about 75 °C. to 250 °C., alternatively from about 90 °C to 150 °C, alternatively at about 100 °C.

Pressures may typically range from about 1 psig to 3500 psig, alternatively from about 100 psig to 1000 psig, alternatively from 200 psig to 1000 psig, alternatively from about 250 psig to about 500 psig, alternatively at about 300 psig.

Transalkylation [0043] The polycyclic aromatic compound is contacted with an aromatic transalkylating agent, typically, an alkyl-substituted monocyclic aromatic compound.

The alkyl-substituted monocyclic aromatic compound has from one to four short chain alkyl substituents. Preferably, the short chain alkyl substituent contains from 1 to 2 carbon atoms, i. e. , methyl and ethyl substituents. Most preferably the short chain hydrocarbon is ethyl, in which instance the monocyclic aromatic compound is a transethylating agent. Representative examples of transalkylating agents include ethylbenzene; toluene; ortho-, meta-, or para-xylene (e. g. o-, m-or p-xylene); ortho-, meta-, or para-methylbenzene; and mixtures thereof.

[0044] The source of monocyclic aromatic compound comprises a reformate fraction or any other ethyl substituted monocyclic aromatic-rich feed. Specific examples include a reformate from a swing bed or moving bed reformer. Although useful sources of these monocyclic aromatic compounds include a reformate fraction, other useful sources include, but are not limited to, pyrolysis gasoline, coker naphtha, methanol-to-gasoline, or other zeolite catalyst olefin or oxygenate conversion process wherein significant aromatics product is obtained. Another source of monocyclic aromatic compound is the heavy side product of various aromatics conversion processes (e. g. , toluene disproportionation and xylene isomerization).

[0045] Another advantage to using the monocyclic aromatic compound as a transalkylating agent, instead of alkylating with an alcohol or alkylhalide, is the resulting conversion of the monocyclic aromatic compound to a gasoline boiling range product when the monocyclic aromatic compound is an ethylalkylbenzene or to benzene when the monocyclic aromatic compound is ethylbenzene. The polyalkylated alkylating agents, having both an ethyl substituent and at least one methyl substituent, are typically not entirely dealkylated by the reaction. The ethyl substituent is selectively transferred preferentially versus the transfer of a methyl substituent when the ethyl substituent and the methyl substituent are on the same mononuclear aromatic compound. The ethyl substituent is also selectively transferred from ethylbenzene in a mixture also containing methyl-or polymethylbenzene compounds.

[0046] The transalkylation of a polycyclic aromatic compound, such as naphthalene, with an alkylsubstituted monocyclic aromatic compound, such as ethylbenzene, is an equilibrium reaction. The optimal temperature for a particular catalyst, naphthalene- containing feed and alkylating agent may be determined by routine testing.

[0047] The equilibrium of the transalkylation is affected by the ratio of the alkylsubstituted monocyclic aromatic compound to naphthalene-containing aromatic compound containing fluid. A higher mono-alkylsubstituted benzene to naphthalene ratio increases the equilibrium concentration of the substituted naphthalene and benzene in the transalkylation. By controlling the ratio of mono-alkylsubstituted benzene to naphthalene-containing aromatic compound containing fluid, while holding other parameters constant, the concentration of naphthalene in the transalkylation product mixture may be minimized and the concentration of benzene maximized.

[0048] A larger naphthalene to alkylsubstituted benzene ratio increases the equilibrium concentration of benzene formed during the transalkylation. In one embodiment according to the present invention, the hydrocarbon fluid is contacted with an acidic catalyst in the presence of an alkylsubstituted benzene containing fluid, wherein the ratio of the naphthalene to alkylsubstituted benzene ranges from about 1 : 1 to preferably about 1: 10.

[0049] The transalkylation catalyst used in the process of this invention includes, but is not limited to, an acid catalyst. The classes of suitable catalysts include crystalline metallosilicates, such as zeolites, including molecular sieves. Other acidic oxides may also be suitable. These solid catalysts are useful in fluid and fixed bed catalysis, and, being heterogeneous to the reactants, are readily separable therefrom.

[0050] The choice of transalkylation catalyst most useful for this process is dependent upon the feedstock and, in some cases, the product desired. For example, with the larger polycyclic aromatic compounds that contain over about 2 aromatic rings, the pore size of the catalyst must be sufficiently large since the pore size constraints of the zeolite can hinder admittance of these bulky molecules. Thus, the preferred transalkylation catalysts for this embodiment of the invention are the large pore zeolitic behaving catalytic materials, including H+Beta, MCM-22, MCM-49, Mordenite, USY, and acidic mixed-metal oxides such as WOx/Zr, wherein x is 2 to 3.

The zeolitic catalytic materials are exemplified by those that in their aluminosilicate form would have a Constraint Index ranging from up to about 2, preferably from about 0.2 to 2 and more preferably, less than 1. The acidic mixed-metal oxides may contain other additives such as the iron oxides.

[00511 Reference is here made to U. S. Pat. No. 4,784, 745 for a definition of Constraint Index and a description of how this value is measured. The preferred catalytic materials having the appropriate functionality include mordenite, zeolite beta, faujasites such as zeolite Y, and Ultra Stable Y (USY).

[0052] Other zeolitic catalytic materials are useful in this process particularly with feeds that are predominantly composed of polycyclic systems having two rings, such as naphthalene and alkyl-substituted naphthalenes such as monoethylnaphthalene. A particular class of catalytic materials having the appropriate functionality, in any embodiment disclosed herein, includes, but is not limited to, those having the topology of ZSM-5, ZSM-11, ZSM-12, ZSM-50 and MCM-22. These zeolites are described in the following patent and patent applications which are fully incorporated by reference : ZSM-5 in U. S. Patent No. 3,702, 886 ; ZSM-11 in U. S. Patent No. 3,709, 979; ZSM-12 in U. S. Patent No. 3,832, 449; ZSM-50 in U. S. Serial No. 705,822, filed February 26, 1985 MCM-22 in U. S. Patent No. 4,956, 514; zeolite beta in U. S. Patent No.

3, 308, 069; and MCM-49 in U. S. Patent No. 5,236, 575.

[0053] The catalytic materials described are exemplary of the topology and pore structure of suitable acid-acting refractory solids; useful catalysts are not confined to the aluminosilicates, and other refractory solid materials which have the desired acid activity, pore structure and topology may also be used. The crystalline zeolites have a porous framework. The framework typically comprises primarily silicon tetrahedrally coordinated and interconnected with oxygen bridges. Other framework components, for example, may include Group IIIA elements of the Periodic Table, e. g. aluminum, boron and gallium. Other elements such as phosphorus and iron may be included as framework components. Aluminum phosphates and silico-aluminum phosphates are specifically contemplated. The zeolite designations referred to above, for example, define the topology only and do not restrict the compositions of the zeolitic-behaving catalytic components.

[0054] The transalkylation catalyst should have sufficient acid activity and selectivity to promote the alkylation/transalkylation reactions at reasonable temperatures and catalyst space velocities. Transalkylation is specifically defined herein as the transfer of one or more lower alkyl groups, such as ethyl, from the alkyl substituted monocyclic aromatic compound to the polycyclic aromatic compound, such as naphthalene.

[0055] The active component of the transalkylation catalyst, e. g. , the zeolite, will typically be used in combination with a binder or substrate because the particle sizes of the pure zeolitic behaving materials are often too small and lead to an excessive pressure drop in a catalyst bed. This binder or substrate, which is preferably used in this service, is suitably any refractory binder material. Examples of these materials are well known and typically include silica, silica-alumina, silica-zirconia, silica-titania, alumina, Titania or zirconia. The catalyst may be in the form of a powder or extrudate. The catalyst comprises the zeolite as an active component in the range of 0 to 100 wt% and a binder in the range of from 0 wt% to about 40 wt%. In another embodiment the transalkylation catalyst comprises a self bound extrudate zeolite, such as, but not limited to, MCM-22. The weight % is based on the total weight of the catalyst.

[0056] The particle size and the nature of the transalkylation catalyst will usually be determined by the type of process which is being carried out, such as: a down-flow, liquid phase, fixed bed process ; an up-flow, fixed bed, liquid phase process; an ebullating, fixed fluidized bed liquid or gas phase process ; or a liquid or gas phase, transport, fluidized bed process, as noted above, with the fixed-bed type of operation preferred.

[0057] The lower limits on transalkylation catalyst activity and on reactive conditions are sufficient to convert at least about 20 % and preferably at least about 50 % of the polycyclic aromatic compounds in the feed to an alkylated, hydrogenated compound.

Conversion of the polycyclic aromatic compounds refers to the addition of molecular weight (e. g. ethyl) side chains. The total number of moles of polycyclic aromatic compounds in the product will normally be about the same as the total moles of polycyclic aromatic compounds in the feed to the reactor. The degree of alkylation of the naphthalene, i. e. , the degree of naphthalene reduction, ranges from about 40 to 95%, preferably from at least about 50%.

[0058] With most transalkylation catalysts, the following transalkylation conditions can be used in any of the embodiments disclosed herein. Temperatures may typically range from about 250 °C to 600 °C (482 °F to 1100 °F), alternatively from about 270 °C to 350 °C, alternatively at about 275 °C. Although fluidized, fixed or moving bed reactors can be used, the relative ratios of feed to transalkylation catalyst, as applied to fixed beds will be provided. Weight hourly space velocities (WHSV) of from about 0.5 to 15, more specifically from about 0.5 to about 5 will usually give good results.

Pressures may typically range from atmospheric, or even subatmospheric to relatively high pressures and will typically range from about 1 to about 1000 psig, alternatively from, about 250 psig to about 500 psig, alternatively at about 300 psig.

[0059] The transalkylation catalyst life may be prolonged by removing contaminants such as water and oxygenates. Any solid drying agent known to those skilled in the art may be used to reduce the water concentration in the alkylation or transalkylation feedstream, such as those disclosed in U. S. Patent No. 6,297, 417, which is fully incorporated by reference. Non-limiting examples of suitable drying agents include aluminas, silicas, silica-aluminas, and zeolites. The aluminas, silicas, and silica- aluminas may be crystalline or amorphous. Zeolites are crystalline microporous aluminosilicates that have framework structures formally constructed from (Si04) and (A104) tetrahedra that share vertices. Each framework topology contains a regular array of pores, channels, and/or cages that vary in size, shape, and dimensionality.

Examples of suitable zeolites include erionite, chabazite, rho, gismondine, Linde 13X, Linde type A (LTA) molecular sieves, such as 3A, 4A, and 5A. A description of these zeolites, their structures, properties, and methods of synthesis can be found in the following references: Zeolite Molecular Sieves, Donald W. Breck, John Wiley & Sons, 1974; Atlas of Zeolite Structure Types, 3rd ed. , W. M. Meier and D. H. Olson, Butterworth-Heinemann, 1992; and Handbook of Molecular Sieves, R. Szostak, Chapman & Hall, New York, 1992 ; which are incorporated herein by reference. Many of the suitable aluminas, silicas, silica-aluminas, and zeolites are commercially available. The preferred drying agents comprise LTA zeolites, including 3A, 4A, and 5A, in addition to Linde zeolite 13X and Selexsorb CDOTM brand alumina.

[0060] Benzene and substituted benzenes can also contain oxygen and organic oxygenates. The equilibrium concentration of molecular oxygen which is dissolved in unsubstituted benzene at about 23 °C. is about 300 ppm by weight, as measured by an oxygen analyzer, such as an Orbisphere Oxygen Analyzer Model 26083 or any other conventional method of oxygen analysis."Organic oxygenates"are defined as organic compounds which comprise carbon, hydrogen, and oxygen. Non-limiting examples of organic oxygenates, which may be found in benzene and substituted benzenes, include organic hydroperoxides, ketones, aldehydes, and phenols. The organic oxygenates may be natural impurities in the aromatic hydrocarbon as it is obtained from coal tar, or from a gasoline refinery, or from a benzene extraction unit, or a hydrodealkylation unit typically present at naphtha steam cracker facilities. Alternatively, the organic oxygenates may be produced by the reaction of oxygen with hydrocarbons present in the feed. In addition to oxygen and oxygenates, aromatic hydrocarbons may also contain small amounts of other impurities, including nitrogen-containing organic compounds, typically for example, traces of extraction solvents, such as N- methylpyrrolidone.

[0061] The lifetime of any alkylation/transalkylation catalyst can be increased by the above-described process to remove water and/or organic oxygenates.

Transalkylation/Hydrogenation Combination [0062] In one embodiment according to the present invention, the transalkylation of the polycyclic aromatic compounds followed by hydrogenation will provide a mixture of products comprising partially or fully hydrogenated derivatives including partially hydrogenated derivatives, some of which have the alkyl substituent on the aromatic ring of the partially hydrogenated derivative and some of which have the alkyl substituent on the non-aromatic ring of the partially hydrogenated derivative. Fully hydrogenated derivatives of polycyclic aromatic compounds have substantially no aromatic rings remaining, e. g. , naphthalene fully hydrogenated to decahydronaphthalene. A partially hydrogenated polycyclic aromatic compound retains at least one aromatic ring, e. g. , naphthalene partially hydrogenated to tetrahydronaphthalene or anthracene partially hydrogenated to 1,2, 3,4- tetrahydroanthracene or phenanthrene partially hydrogenated to 9,10- dihydrophenanthrene.

[0063] In another embodiment according to the present invention, when hydrogenation of the polycyclic aromatic compound occurs prior to the transalkylation, then a portion of the hydrogenated polycyclic aromatic compound is partially hydrogenated, i. e. , at least one aromatic ring remains in the partially hydrogenated polycyclic aromatic compound.

[0064] In another embodiment according to the present invention when hydrogenation and transalkylation occur concurrently, then the transalkylation occurs prior to full hydrogenation of the polycyclic aromatic compound. The transalkylation may occur on the unhydrogenated polycyclic aromatic compound or on a partially hydrogenated polycyclic aromatic compound. Partial hydrogenation may occur prior to transalkylation. A transalkylated polycyclic aromatic compound may be subsequently partially or fully hydrogenated.

[0065] In one embodiment according to the present invention, the transalkylation of naphthalene followed by hydrogenation will provide a mixture of products comprising tetrahydronaphthalene derivatives including alkylated tetrahydronaphthalene compounds some of which have the alkyl substituent on the aromatic ring of the tetrahydronaphthalene derivative and some of which have the alkyl substituent on the non-aromatic ring of the tetrahydronaphthalene derivative.

[0066] In another embodiment according to the present invention, the hydrogenation of naphthalene followed by alkylation will provide a mixture of products comprising tetrahydronaphthalene derivatives in which the alkyl substituent is on the aromatic ring of the tetrahydronaphthalene derivative. It is understood by one of ordinary skill in the art that transalkylation can alkylate more than one alkyl group on the tetrahydronaphthalene derivative.

[0067] In another embodiment according to the present invention, the transalkylation reaction and the hydrogenation occur concurrently in the same reactor, which will provide a mixture of products as described in the preceding two paragraphs.

Reduction of Aromatic Content [0068] In another embodiment, conversion of the polycyclic aromatic compound via the transalkylation/hydrogenation combination process is greater than from 50%, alternatively greater than from 70%, alternatively greater than from 80%, alternatively greater than from 85%, alternatively greater than from 90%, alternatively greater than from 95%, alternatively greater than from 99%. In another embodiment, the reduction of aromatic content in the hydrocarbon fluid via the transalkylation/hydrogenation combination process is greater than from 95%, alternatively greater than from 99%.

The polycyclic aromatic compound is converted to an alkylated, hydrogenated compound as described in paragraphs [0062] through [0066].

Reactor Configurations [0069] Figure 1 discloses a single-reactor process with two catalyst beds for the hydrogenation/transalkylation combination process. The hydrogen feed 1 and the hydrocarbon fluid feed 2 are co-fed via inlet feed 3 into the reactor 4. Within the reactor 4 are a transalkylation catalyst bed 5, containing a transalkylation catalyst, and a hydrogenation catalyst bed 6, containing a hydrogenation catalyst. The reaction products exit the reactor 4 via outlet stream 7.

[0070] Figure 2 discloses a single-reactor process with one catalyst bed for the hydrogenation/transalkylation combination process. The hydrogen feed 1 and the hydrocarbon fluid feed 2 are co-fed via inlet feed 3 into the reactor 8. Within the reactor 8 is a catalyst bed 9, containing either a bi-functional metal-containing solid acid catalyst or a mixture of solid acid and metal-containing catalysts. The reaction products exit the reactor 8 via outlet stream 24.

[0071] Figure 3 discloses a two-reactor in series process with hydrogen co-feed to the hydrogenation reactor only. The hydrocarbon fluid feed 10 is fed into the transalkylation reactor 11, which contains a transalkylation catalyst. The hydrogen feed 12 is introduced into the transalkylated product stream feed 13, which is fed into the hydrogenation reactor 14, which contains a hydrogenation catalyst. The final reaction products exit the hydrogenation reactor 14 via outlet stream 15.

[0072] Figure 4 discloses a two-reactor in series process with hydrogen co-feed to both the transalkylation and hydrogenation reactors. The hydrogen feed 1 and the hydrocarbon fluid feed 2 are co-fed via inlet feed 3 into the transalkylation reactor 11, containing a transalkylation catalyst. The transalkylated product stream feed 13 is fed into the hydrogenation reactor 14, which contains a hydrogenation catalyst. The final reaction products exit the hydrogenation reactor 14 via outlet stream 25.

[0073] Figure 5 discloses a two-reactor in series process with hydrogen co-feed to the hydrogenation reactor. The hydrogen feed 1 and the hydrocarbon fluid feed 2 are co- fed via inlet feed 3 into the hydrogenation reactor 14, containing a hydrogenation catalyst. The hydrogenated product stream feed 26 is fed into the transalkylation reactor 11, which contains a transalkylation catalyst. The final reaction products exit the transalkylation reactor 11 via outlet stream 27.

[0074] Figure 6 discloses a catalytic distillation process. The hydrogen and hydrocarbon fluid feed 16 are fed into the distillation column 19 and are contacted with the transalkylation catalyst 17. After transalkylation, the transalkylated product stream and heavier components 21, flow downward and exit the distillation column 19 via the bottoms takeoff 23. The lighter components 20, including the unreacted hydrocarbonfluid stream, flow upward to the hydrogenation catalyst 18. After hydrogenation, the hydrogenated product stream and lighter components exit the distillation column 19 via the overhead takeoff 22.

EXAMPLES Test Methods [0075] Samples of reaction mixtures were withdrawn at regular time intervals and analyzed by gas chromatography (GC) (non-polar HP-1 column, 30 m, crosslinked methylsiloxane) and GC-Mass Spectrometry (GC/MS), using the same column. A Hewlett Packard HP 6890 Series GC System and GC/MS System were utilized.

[0076] Fluorescent Indicator Adsorption (FIA) was measured by ASTM method D- 1319.

[0077] The weight % of the metal of the catalyst is based on the total weight of the catalyst. The weight % of the components of the hydrocarbon fluid are based on the total weight % of the hydrocarbon fluid.

Examples 1 & 2-Transalkylation/Hydrogenation Combination Process [0078] Transalkylation experiments were conducted in a fixed-bed reactor containing 2.0 g MCM-22/alumina extrudates (65/35,20-40 mesh). Feed contained naphthalene, ethyltoluene, trimethylbenzenes, and other polysubstituted alkylbenzenes. The catalyst was dried under dry nitrogen flow at 350 °C for 1 hour prior to feed introduction. The transalkylation reaction conditions were at 275 °C and 300 psig with a WHSV of from 1 to 2.

[0079] The transalkylation products were hydrogenated over a 0.5 wt. % palladium on alumina catalyst in a 300 ml autoclave at 100 °C and 300 psig with a 10 to 1 liquid to catalyst weight ratio. Hydrogen pressure was kept at 300 psig during hydrogenation.

Gas chromatography and mass spectrometry were used to analyze products from both steps. Products were divided into three fractions based on boiling points: components with boiling points less than naphthalene, naphthalene, and components with boiling points higher than naphthalene. The results of both examples are shown in Table 1.

Table 1: Transalkylation/Hydrogenation Results Example 1 2 Transalkylation Step Catalyst MCM-22/AI203 (65/35) MCM-22/AI203 (65/35) Pressure (psig) 300 300 Temperature (°C) 275 300 WHSV 2 1 Naphthalene Conversion 52. 70% 72.20% Selective Hydrogenation Step Catalyst 0. 5 Pd/AI203 0. 5% Pd/AI203 Pressure (psig) 300 300 Temperature (°C) 100 100 Reaction Time (h) 4 4 Naphthalene Conversion 99. 00% 98.80% Composition Data Feed Product Feed Product Boiling Point Less than Naphthalene 82. 0 wt. % 82.6 wt. % 82.0 wt. % 79.4 wt. % Naphthalene 12. 1 wt. % 0.05 wt. % 12.6 wt. % 0.04 wt. % Boiling Point Higher than Naphthalene 5. 9 wt. % 17.36 wt. % 5.5 wt. % 20.6 wt. % Total Naphthalene Reduction 99. 6% 99.7% Changes in Naphthalene and Plus Fraction-0. 6% 2. 5% Examples 3,4, 5,6, 7,8, 9,10, & 11-Transalkylation Step Alone [0080] Transalkylation experiments, Examples 3 through 8, were conducted similarly to Examples 1 and 2, above. The feed contained naphthalene, ethyltoluenes, trimethylbenzenes, and other polysubstituted alkylbenzenes. The results are shown in Table 2 below.

Table 2: Results of Transalkylation Step. Example 3 4 5 6 7 8 Catalyst MCM-22 MCM-22/Beta/AIzO3 Mordenite/Al203 USY/AI203 WOx/ZrO2 Al203 Pressure (psig) 300 300 300 300 300 300 Temperature (°C) 275 275 275 275 275 275 WHSV 2 2 2 2 2 2 Naphthalene in Feed 13. 40 wt. % 12.10 wt. % 10.30 wt. % 12.50 wt. % 12.60 wt. % 12. 00 wt. % Naphthalene in Product 4. 40 wt. % 5. 70 wt. % 4. 20 wt. % 5.40 wt. % 3.90 wt. % 9.40 wt. % Naphthalene Reduction 67. 50 wt. % 53. 10 wt. % 59. 40 wt. % 56. 80 wt. % 68. 90 wt. % 22.00 wt. % Naphthalene and Plus 19. 3 wt. % 18.00 wt. % 16.50 wt. % 17.90 wt. % 18.10 wt. % 18.00 wt. % Fraction in Feed Naphthalene and Plus 19.7 wt. % 22.00 wt. % 20.50 wt. % 21. 50 wt. % 21.40 wt. % 19.20 wt. % Fraction in Product Changes in Naphthalene and 0. 40% 4. 00% 4.00% 3. 60% Plus Fraction 10081] The following transalkylation reactions, Examples 9,10, and 11, were conducted in Swagelok@ stainless steel mini-reactors, having internal volumes of 13 cc, that were heated to about 275 °C by placing the mini-reactor into a silicone oil bath preheated to 275 °C. The catalyst to Aromatic 150 fluid ratio was about 0.1 gram/gram. The reaction time is about five hours from the time the mini-reactor was placed into the preheated silicone oil bath to removal of the mini-reactor from the preheated silicone oil bath. The reaction mixture was not stirred. The reactor contents were cooled to room temperature by submersing the reactor into water. After the reactor contents were cooled to room temperature, the liquid phase was separated from the solid catalyst by decanting the liquid from the solids. No solvent was added. The liquid phase was analyzed by gas chromatography using a Hewlett-Packard 6890 with a 30-meter non-polar HP-1 (cross-linked methylsiloxane) column. The starting temperature of the gas chromatograph column oven was 10 °C and it was programmed to heat to 300 °C at a rate of 5 °C per minute. A response factor of 1 was used for all components. The results are shown in Table 3 below.

Table 3 Naphthalene Reduction In Aromatic 150 Fluid Under Conditions in Example 9 Catalyst Description % Naphthalene Removed Valfor C-80613 H+ zeolite beta, 89. 8 powder 65% MCM-22,35% A1203 binder 68. 1 65% MCM-22, 35% A1203 binder 70. 8 80% MCM-22,20% A1203 58. 5 binder 100% MCM-22,0% A1203 binder 73.9 100% MCM-22,0% A1203 binder 70. 3 40% MCM-22,40% Mordenite, 56.4 20% A1203 binder 65% Tosoh 360 HUA USY, 35% 68. 6 A1203 binder 65% Beta, 35% A1203 binder 39. 6 [0082] The general procedure of Example 9 was used except that the Aromatic Fluid 150 concentrate containing about 20.4 wt. % naphthalene was heated in the presence of H+BETA catalyst for 5 hours at about 275 °C. Approximately 82% of the naphthalene was converted to ethylnaphthalene.

[0083] The general procedure of Example 9 was used except that the Aromatic Fluid 150 concentrate containing about 20.4 wt. % naphthalene was heated in the presence of MCM-22 catalyst, as a powder, for 5 hours at about 275 °C. Approximately 74% of the naphthalene was converted to ethylnaphthalene.

Example 12,13, 14,15, & 16-Hydrogenation Step Alone [0084] Example 12, hydrogenation of an aromatic fluid containing 26.5 wt% naphthalene, was conducted similarly to Examples 1 and 2, above. The results are shown in Table 4 below. There was a yield loss of 24.6%.

Table 4: Results of Hydrogenation Step. Example 12 Catalyst 0. 5% Pd/AI203 Temperature (°C) 100 Pressure (psig) 300 Reaction Time (h) 4 Naphthalene in Feed 26. 50 wt. % Naphthalene in Product 0. 09 wt. % Naphthalene Reduction 99. 70% Naphthalene and Plus Fraction In Feed 39.60 wt. % Naphthalene and Plus Fraction in Product 15. 00 wt. % Changes in Naphthalene and Plus Fraction-24.60% [0085] The hydrogenation process of Examples 13,14, and 15 was conducted in a 300cc Eze-seal autoclave from Autoclave Engineers equipped with a Robinson- Mahoney catalyst basket was utilized for the batch experiments. The catalyst basket was first charged with the palladium catalyst and the basket was then inserted into the body of the autoclave. The autoclave was sealed and charged with a mixture of 1,2, 4- trimethylbenzene and naphthalene concentrate. The naphthalene concentrate was generated by distillation of the lighter boiling components of Aromatic 150 Fluid and contained naphthalene (55.4 wt. %) and polyalkylbenzenes (balance). The resulting feed composition in the reactor contained 1,2, 4-trimethylbenzene (48.8 wt. %), polyalkylbenzenes from Aromatic 150 Fluid (24.3 wt. %) and naphthalene (26.9 wt.

%). The contents of the autoclave were purged with hydrogen then pressurized to approximately 250 psig with hydrogen. The stirred mixture was then heated to 100 °C, at 100 °C, the pressure was adjusted to approximately 300 psig H2 and maintained at approximately 300 psig H2 for 4 hours. The feed to catalyst ratio was 10 to 1 (g/g).

GC and GC/MS samples were removed to monitor the reaction.

[0086] Two different catalysts were tested: a commercial 0.5 wt. % palladium catalyst on alumina, 3.2 mm pellets obtained from Aldrich Chemical Co. Catalog No. 20,574- 5, and a commercial 1 wt. % palladium catalyst on carbon, 4 to 8 mesh obtained from Aldrich Chemical Co. Catalog No. 20, 575-3. The results are shown in Table 5 for the palladium on alumina catalyst and in Table 6 for the palladium on carbon catalyst.

Table 5. Pd/Al203 Catalyst: Composition of reaction products vs. reaction time Reaction Time (h) Feed O. Sh lh 2h 3h 4h Composition (wt%) 1,2, 4-trimethylbenzene 48. 7 48. 2 48.2 48.0 48.2 48.2 A-150 Polyalkylbenzenes 24. 8 24.4 24.2 26.1 26.2 26.2 Naphthalene 26. 5 23.4 19.7 8.6 1.4 0.09 Tetrahydronaphtlialene 0. 0 4.0 7.9 17.2 24.1 25.1 Decahydronaphthalene (cis & trans) 0.00 0. 00 0. 01 0. 01 0. 04 0.33 Conversion (%) 99.70 Selectivity (%) 98. 70 Table 6. Pd/C Catalyst: Composition of reaction product vs. reaction time Reaction Time (h) Feed 0. 25h 0. 5h lh 2h Composition (wt%) 1,2, 4-trimethylbenzene 48.6 48.7 48.9 48.8 48.7 Polyalkylbenzenes from A150 24. 5 24.1 25.9 25.7 25.8 Naphthalene 26. 9 16.1 7.7 0.1 0.1 Tetraliydronaphthalene 0. 0 11.2 17.5 25.4 24.9 Decahydronaphthalene (cis & trans) 0. 00 0.01 0.01 0.06 0.67 Conversion (%) 99.60 Selectivity (%) 99.80 [0087] The above procedure was followed, except the reactants were a combination of Aromatic 200 Fluid containing naphthalene (10.3 wt. %), 2-methylnaphthalene (26.3 wt. %), and 1-methylnaphthalene (12.9 wt. %). No 1,2, 4-trimethylbenzene was added.

The reactants were reacted with the 0.5 wt. % palladium catalyst on alumina as described above. The results are shown in Table 7 below.

Table 7. Pd/A1203 Catalyst: Composition of reaction products vs. reaction time Reaction Time (h) Feed 1h 3h Sh 8h Composition (wt%) Naphthalene 10. 3 8.1 4.6 2.1 0. 34 1-Methylnaphthalene 12. 9 12.4 11.4 10 7.5 2-Methylnaphthalene 26. 2 25.5 23.6 21.4 17. 4 Tetrahydronaphthalene 0. 0 2.3 5.5 8. 1 9.8 Conversion (°/0) 96.70 [0088] The hydrogenation process of Example 16 was conducted in the following manner. A commercial 0.3 wt. % palladium on alumina catalyst was placed in an isothermal fixed-bed reactor of a continuous flow hydrotreater. Aromatic 150 Fluid containing 10.1 wt. % naphthalene and >99 vol% total aromatic was processed at 99- 107 °C at 300 psig and a hydrogen to naphthalene molar ratio of 5. The liquid hourly space velocity (LHSV) varied from 1.0 to 6.0 hr-1. The results are shown in Table 8 below.

Table 8 : Pd/AI203 Catalyst : Composition of reaction products vs. LHSV LHSV (1/h4) Feed 1 2 4 6 Naphthalene, wt% 10.1 0 01 <0.01 <0.01 0 02 Tetrahyrdonaphthalene, wt% 0.6 10 5 10.7 10.5 11 3 Conversion (%) 99 8 Aromatics, FIA vol% >99 >99 >99 [0089] The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects as illustrative only and not restrictive. Specifically, the invention includes three or more reactors in series in any order, and three or more catalyst beds in any order in the same reactor or in different reactors. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.