Process for the monoalkylation of aromatic compounds

Abstract

The invention refers to a process for the monoalkylation of aromatic compounds, comprising the step of contacting an aromatic hydrocarbon with an alkylating agent in the presence of a catalyst, wherein said catalyst comprises a FAU-type zeolite exchanged with one or more alkaline or alkaline earth metal cations comprising potassium, cesium and / or calcium and which has a total SiO2 / AI2O3 mole ratio between 10:1 and 80:1.

Description

[0001] PROCESS FOR THE MONOALKYLATION OF AROMATIC COMPOUNDS

[0002] FIELD OF THE INVENTION

[0003] The present invention refers in general to a process for the monoalkylation of aromatic compounds by means of a catalytic alkylation reaction of aromatic compounds. Monoalkylaromatic compounds include linear alkylbenzenes (LAB), which are extensively used as a chemical intermediate to form linear alkylbenzene sulfonates (LAS), substances widely employed in detergents and cleaning products as well as in a variety of other applications including agricultural herbicides, emulsion polymerization, wetting agents, electric cable oil, ink solvents, paints, etc.

[0004] BACKGROUND OF THE INVENTION

[0005] Alkyl aromatic compounds are an important family of substances that are used as raw materials in numerous industrial fields, such as that of plasticizers, polymeric materials, insecticides, in agriculture to prevent the agglomeration of fertilizers, in the manufacture of textiles and fibres, in the leather and hides industry, herbicides, industrial cleaning processes, in the photography industry, in the manufacture of adhesives and in firefighting products such as humidifying agents, in electrochemical processes for the removal of dirt and greases from the surface of a substrate, and in biodegradable detergents, this being the case of the linear mono-alkyl aromatic compounds.

[0006] Monoalkylated aromatic compounds include linear alkylbenzenes (LAB), which are important compounds in industrial applications. For instance, they may be converted by sulfonation into linear alkylbenzene sulfonate (LAS) compounds which are used as surfactants in the manufacture of detergents and other products. In particular, linear alkylbenzenes with long alkyl chains, such as chains having about 8 to about 16 carbons or about 10 to about 14 carbons, are commonly used. However, linear alkylbenzenes with longer chains and with shorter chains also are commercially important as well as branched alkylbenzenes.

[0007] The alkylbenzenes are sometimes referred to as phenylalkanes, and are produced as a commodity in large-scale facilities worldwide with production rates of between 50,000 and 200,000 metric tonnes per year. Linear alkylbenzenes often are made in the petrochemical industry, especially for applications in detergents, by a process which involves dehydrogenating linear paraffins to obtain linear mono-olefins and then carrying out the alkylation of benzene with said mono-olefins in the presence of a catalyst at elevated temperatures. The catalysts can be homogeneous or heterogeneous catalysts such as hydrofluoric acid, aluminum chloride, silica-alumina, or zeolitic catalysts.

[0008] The alkylation reaction is characterized by several parameters including conversion, catalyst deactivation rate, selectivity towards mono-alkylbenzene and isomer distribution.

[0009] Alkylation conversion or, more specifically, fractional conversion can be defined as the fraction of the limiting reactant, in this case the olefin, which is consumed to generate all the products.

[0010] Catalyst deactivation rate can be defined as the ratio between the activity of the catalyst at a considered time and the activity of the catalyst at time zero, wherein the activity of the catalyst is considered in terms of conversion. The deactivation of the catalyst is due to either the poisoning of the active centers and / or to contamination processes.

[0011] Selectivity towards mono-alkylaromatic can be defined as the percentage of monoalkylaromatic with respect to all the reaction products since the reaction also produces by-products lighter than the lightest mono-alkylaromatic of interest, and species whose molecular weights are higher than those of the mono-alkylaromatic compounds produced.

[0012] Isomer distribution can be defined as the distribution of all the positional isomers, such as 2-phenyl, 3-phenyl, 4-phenyl, 5-phenyl, 6-phenyl and the like, as well as branched isomers that result from the alkylation of the aromatic with long chain olefins. Isomer distribution plays a very important role in the tolerance to divalent ions, i.e. , in stability of the end detergents, especially liquid formulations, as well as in their surface activity and in their biodegradation rate.

[0013] Historically, linear alkylbenzenes have been manufactured commercially using Friedel- Crafts condensation employing catalysts such as aluminum chloride, or by using strong acid catalysts such as hydrogen fluoride, for example, to alkylate benzene with olefins. The use of HF acid, however, presents some drawbacks at operational level, as it requires very careful handling and equipment made with special materials due to its high corrosive capacity, which is translated into higher fixed and operating costs, so attempts have been made to develop alternative catalysts based on solids of an acid nature. In the mid 1990s, a solid bed alkylation process, the Detal® process, using a solid non- corrosive acid catalyst (aluminum-magnesium silicate) was introduced (see for instance US 5146026).

[0014] The 2-phenyl isomer content of the product is process dependent. Solid alkylation catalysts, such as those used in the Detal® process, produce products with 2-phenyl isomer content between 25 and 30 %. HF-catalyzed processes typically yield a 2-phenyl isomer content less than 20 %, and AlC typically between 30 and 33 %.

[0015] More recently, zeolite catalysts, such as synthetic faujasites (zeolites X and Y), zeolite L, ZSM-5, ZSM-18, ZSM-20, mordenite and offretite, have also been used to obtain linear alkylbenzenes by alkylation of benzene with olefins. The 2-phenyl isomer content of linear alkylbenzenes obtained using such catalysts depends on the zeolite selected and can vary from about 20 % to 90 %. Most zeolites, with the exception of FAU, produce linear alkylbenzene with 2-phenyl isomer content higher than the previous existing commercial processes.

[0016] In order to meet the desired product properties in the resulting linear alkylbenzene such as 2-phenyl content, the use of a mixture of two or more zeolites as well as the use of different zeolites in separate reaction zones with subsequent blend of the production from each reaction zone have been proposed. The use of two or more catalysts allows to carry out the process with materials of different properties and therefore different catalytic activities. In addition, different catalysts have different rates of decline in their activities.

[0017] A majority of industrial catalytic processes use heterogeneous catalysts nowadays because of their engineering advantages. However, the deactivation of solid catalysts represents a major problem and therefore there are ongoing efforts to develop more active and stable solid acid catalysts for LAB synthesis with major emphasis on zeolites using either batch or flow reactors.

[0018] It is well known that the presence of rare earth elements can strongly affect the strength and density of the acid sites in the zeolitic material, increasing catalytic stability (L. B. Zinner, K. Zinner, M. Ishige and A. S. Araujo, Catalytic activity of lanthanide-doped Y zeolite on the alkylation of benzene with 1 -dodecene model reaction, Journal of Alloys and Compounds, 193, 65-67, 1993). The aluminosilicate exchanged with rare earth elements is an activated crystalline catalyst in which the nuclear structure has been modified because it has chemisorbed or ionically bonded rare earth metal cations. Rare earth cations can be provided starting from the salt of a single metal or preferably from a mixture of salts of different metals such as light rare earth chlorides or didymium chlorides (La, Ce, Pr, Nd). In most applications, rare earth mixtures are preferred because they can be easily obtained commercially and are much more cost-effective than purified rare earth metals. P. B. Venua et al published in the Journal of Catalysts, 4, 81-98, 1966, the potential use of highly acid solid catalysts such as faujasites of the zeolite X and Y type with ion exchange with rare earth metals, denominated REY and REX, for the alkylation of benzene with olefins. A Brazilian patent, P.l. no. 9204326-7 of Deten Quimica S.A. shows the use of a catalyst based on a zeolitic faujasite, specifically zeolite Y, activated with Ca and lanthanides, specifically La, Ce, Nd or Gd. The patent claims a process in a solid-liquid batch reactor operating in complete mixture conditions, with a superacid catalyst, operating at temperatures as low as 80 °C.

[0019] WO 2007 / 104805 discloses a process for obtaining a highly soluble alkyl aromatic sulfonate, with an adjustable 2-phenyl isomer content between 18 % - 70 % by weight, said process comprising the catalytic alkylation of an aromatic compound with a purified alkylating agent, by means of the combination of the following two alkylation processes:

[0020] - an alkylation process with a catalyst producing a raw linear alkyl aromatic compound with a maximum 2-phenyl isomer content of 20 % by weight, wherein said catalyst comprises a FAU type zeolite, between 0.01-0.15 % by weight of at least one of the metals selected from the group consisting of: Li, Na, K, Mg or Ca, and between 0.1-8 % by weight of at least one of the rare earth metals selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm or Eu; and

[0021] - an alkylation process with a catalyst producing a raw linear alkyl aromatic compound with a minimum 2-phenyl isomer content of 20 % by weight, wherein said catalyst comprises a MOR type zeolite, between 0.01 % - 0.2 % by weight of at least one of the metals selected from the group consisting of: Li, Na, K, Mg or Ca, with a maximum of 0.01 % of Na, and between 0-0.5 % by weight of at least one of the metals selected from the group consisting of Ti, Zr, Hf. WO 2009 / 071709 discloses a process for obtaining a linear monoalkylaromatic compound with a 2-phenyl isomer content adjustable between 18% - 70% by weight, through the catalytic alkylation of an aromatic compound with a purified alkylating agent, by means of the combination of the following two alkylation processes:

[0022] - an alkylation process with a catalyst that produces a linear alkylaromatic compound with a maximum content of 2-phenyl isomers of 20 wt %, wherein said catalyst comprises a FAU-type zeolite, between 0.5-2.0 wt % of at least one of the metals selected from the group consisting in: Li, Na, K, Mg or Ca and between 8.0-16.5 wt % of at least one of the rare earth metals selected from the group consisting in La, Ce, Pr, Nd, Pm, Sm or Eu; and

[0023] - an alkylation process with a catalyst that produces a linear alkylaromatic compound with a minimum content of 2-phenyl isomers of 20 wt %, wherein said catalyst comprises a MOR-type zeolite, between 0.01 - 0.02 wt % of at least one of the metals selected from the group consisting in: Li, Na, K, Mg or Ca with a maximum of 0.01 % Na, and between 0.05 wt % of at least one of the metals selected from the group consisting in Ti, Zr, Hf.

[0024] Example 2 of WO 2009 / 071709 refers to the advantages of using a catalyst based on a zeolite Y, with a high content of rare earths (such as La, Ce, Nd and Pd) and sodium, in comparison to a catalyst based on a zeolite Y, with a low content of rare earths (such as La, Ce, Nd and Pd) and sodium, in the process of benzene alkylation with a purified mixture of detergent range olefins / paraffins. Specifically, two catalysts are compared. On one hand, a catalyst (catalyst A) based on a zeolite Y with a total content of 7 % rare earth metals and low sodium (0.1 wt %); and on the other hand, a catalyst (catalyst B) based on a zeolite Y with a content of rare earth metals 71 % higher (12 wt % of rare earth metals) and a content sodium 90 % higher (0.9 wt %). In terms of catalytic activity, the great advantage of catalyst B is that it is capable of keeping comprehensive conversion rates (above 99.5 %) during longer periods of time (30 % more time) with no washing cycles in between. This greater stability of catalyst B when deactivated due to dirt allows extending the duration of reaction cycles and reducing the number of regeneration cycles needed to operate under comprehensive conversion rates with respect to catalyst A. This provides, for the same period of operation time of catalysts A and B, a longer net operation time while the reaction time of catalyst B is taking place (higher productivity of catalyst B), as well as a reduction in the regeneration net costs (lower number of washing cycles throughout said period of time), mainly regarding power consumption.

[0025] WO 2011 / 084180 discloses an alkylation process for the selective alkylation of an aromatic compound, comprising contacting the aromatic compound with an olefin having from 8 to 16 carbon atoms in the presence of a selective zeolite catalyst at reaction conditions, wherein the selective zeolite catalyst comprises a zeolite mixture, the zeolite mixture comprising a first zeolite having a UZM-8 content between 10 and 90 % by weight, a second zeolite comprising a rare earth substituted X or Y zeolite, and comprising an amount between 10 and 90 % by weight; and a rare earth element incorporated into the second zeolitic framework in an amount greater than 16.5 wt %.

[0026] Other patent documents such as WO 2012 / 036967, WO 2012 / 078303 and US 8389787 also relate to processes for alkylation of aryl compounds wherein the catalyst comprises two catalytic materials in order to control 2-phenyl isomer content: a rare earth-containing faujasite and a non-faujasite type zeolite.

[0027] The use of catalytic systems comprising rare earth substituted zeolite catalysts, as those described in the above cited prior art, advantageously provide efficient alkylation processes. However, the growing demand for rare earth elements is creating a number of environmental, geopolitical, social and technical challenges.

[0028] Apart from or in addition to the use of zeolites exchanged with rare earth metals, different strategies have been proposed for coping with the rapid loss of activity of the catalyst during the alkylation reaction of aryl compounds. In US 2004 / 260133 A1 , for instance, the deactivation of the solid catalyst has been addressed by using catalytic reactors with different reaction zones and introducing at the inlet to each reaction zone at least one fraction of the total quantity of olefins necessary for said reaction, solution which allows prolonged reaction cycle durations but however introduces complexity in the process.

[0029] Therefore, there is still a need for a method for monoalkylating aromatic compounds with the required specifications by using more stable catalysts. At the same time, reducing or eliminating the necessity of rare earth elements is also highly desirable.

[0030] BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a process for the alkylation of aryl compounds by using a faujasite (FAU) zeolite catalyst which is exchanged with alkaline and / or alkaline earth metal cations, in particular with potassium (K), cesium (Cs), calcium (Ca) or any combination thereof. This catalyst is more stable against de-activation than analogous zeolites without exchange modification (i.e. raw zeolites), which provides for longer reaction cycles and less frequent washing cycles, while at the same time a higher activity is maintained, which results in lower operating costs. Besides the amount of byproducts formed, such as heavy alkyl benzene (HAB), can be reduced due to the exchange with K, Cs and / or Ca ions. Moreover, while the catalyst may be ion-exchanged with rare earth metals if desired, it has been found that advantageously the catalyst performs well in the absence of or with low amount of any rare earth metal since the quality of the reaction product is maintained, featuring specifications comparable to those obtained under catalysis with rare earth-containing zeolites.

[0031] A first aspect of the invention refers to a process for the monoalkylation of aromatic compounds, comprising the step of contacting an aromatic compound with an alkylating agent in the presence of a catalyst, wherein said catalyst comprises a FAU-type zeolite which is exchanged with one or more alkaline or alkaline earth metal cations comprising potassium, cesium and / or calcium and which has a total SiO^AfeOs mole ratio between 10:1 and 80:1.

[0032] Another aspect of the invention refers to the use of the above-defined zeolite FAU as a catalyst in the production of alkylated aromatic compounds, preferably monoalkylated aromatic compounds.

[0033] These aspects and preferred embodiments thereof are additionally also defined hereinafter in the detailed description and in the claims.

[0034] BRIEF DESCRIPTION OF THE FIGURES

[0035] To better understand the invention, its objects and advantages, the following figures are attached to the specification in which the following is depicted:

[0036] Figure 1 shows a scheme with the reaction cycles of the solid bed alkylation test used herein for assessing catalyst performance. Experiments were carried out in a standard fixed bed reactor with real feed. Experimental conditions consisted of three reaction cycles as follows: a first 24-hour reaction cycle to study the catalyst activity, a second 24-hour reaction cycle to study its regenerability and a third 48-hour reaction cycle to study its stability. Samples were taken every 6 hours in all the cases and after the completion of each cycle a process for regenerating the catalyst was carried out.

[0037] Figure 2 is a graph comparing olefin conversion of one catalyst exchanged with potassium ions according to example 1 of the present invention (herein referred to as catalyst A) and the raw catalyst without being exchanged with any metal cation, i.e. in H form (herein referred to as catalyst REFERENCE).

[0038] Figure 3 is a graph comparing results of the catalytic behavior in terms of heavies selectivity (HAB / LAB content) of three catalysts exchanged with different potassium ion contents according to example 2 of the present invention and the raw catalyst without being exchanged with any metal cation, i.e. in H form. The x axis represents olefin conversions taken at different time points of the trial run.

[0039] Figure 4 is a graph comparing results of the catalytic behavior in terms of heavies selectivity (HAB / LAB content) of three catalysts exchanged with different cesium ion contents according to example 3 of the present invention and the raw catalyst without being exchanged with any metal cation, i.e. in H form. The x axis represents olefin conversions taken at different time points of the trial run.

[0040] Figure 5 is a graph comparing results of the catalytic behavior in terms of heavies selectivity (HAB / LAB content) of a catalyst with cesium and potassium ions according to example 4 of the present invention and the raw catalyst without being exchanged with any metal cation, i.e. in H form. The x axis represents olefin conversions taken at different time points of the trial run.

[0041] Figure 6 is a graph comparing results of the catalytic behavior in terms of heavies selectivity (HAB / LAB content) of two catalysts exchanged with different calcium ion contents according to example 5 of the present invention and the raw catalyst without being exchanged with any metal cation, i.e. in H form. The x axis represents olefin conversions taken at different time points of the trial run.

[0042] DETAILED DESCRIPTION OF THE INVENTION Unless defined otherwise, all technical and scientific terms and expressions used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs.

[0043] The present invention provides a method for monoalkylating aromatic compounds such as benzene by means of a catalytic alkylation reaction of aromatic compounds.

[0044] The catalyst according the present invention is a faujasite. As the skilled practitioner recognizes, faujasite is a type of zeolite for which the abbreviation FAU has been established by the International Zeolite Association. The International Zeolite Association recognizes framework types, classifies them and assigns three-letter codes, and summarizes selected properties and characteristics for the frameworks. In this invention, when we talk of FAU or EMT-FAU type zeolites, we are referring to the group of zeolites with isotopic structures corresponding to the FAU structural type, such as: Y zeolite, Na- X zeolite, siliceous Na-Y, Linde X zeolite, Linde Y zeolite, ZSM-3 zeolite and ZSM-20 zeolite, preferably a Linde zeolite or a Y zeolite.

[0045] In accordance with embodiments of the invention, the catalyst is a zeolite selected from the group consisting of X-type faujasite (FAU-X), Y-type faujasite (FAU-Y), and blends thereof. In a particular embodiment, the catalyst is faujasite Y.

[0046] The faujasite catalyst of the process according to the present invention has a total SiO2 / AhO3 mole ratio between 10:1 and 80:1 , preferably between 15:1 and 60:1 , and more preferably between 20:1 and 40:1 (e.g. 22:1 to 38:1 , 24:1 to 36:1 , 26:1 to 34:1 , 28:1 to 32:1). In a more particular embodiment, the total SiO^AfeOs mole ratio is about 30:1. As the skilled person is aware, total, bulk or overall SiO^AfeOs mole ratio is the silica to alumina (SiC>2 to AI2O3) mole ratio as determined on the basis of the total or overall amount of aluminum and silicon (framework and non-framework) present in the zeolite, that is including all forms of aluminum and silicon present in the bulk composition (but not including any binders or support). Thus, by way of reference, a total SiC^ / AhOs mole ratio of 10:1 corresponds to a total Si / AI mole ratio of 10:2, i.e. 5:1.

[0047] Zeolites exchanged with metal cations are widely employed as catalysts. Such zeolites contain mono-, di-and / or trivalent metal cations, for example cations of alkali metals, alkaline-earth metals, transition metals and / or rare earth metals, incorporated during the synthesis of the zeolite particles and / or inserted subsequently by an ion-exchange technique, e.g. by bringing unexchanged zeolite particles or raw zeolite into contact with a solution of one or more metal salts comprising the cation or cations to be incorporated into the zeolite structure, and subsequently recovering the particles of exchanged zeolite, that is to say zeolite containing a given quantity of metal cations.

[0048] Specifically, the catalyst used in the process of the present invention is a FAU-type zeolite exchanged with one or more alkaline or alkaline earth metal cations selected from K, Cs, and / or Ca ions. Optionally, the zeolite catalyst may be exchanged with additional alkaline or alkaline earth metal cations.

[0049] In a particular embodiment, the zeolite catalyst is exchanged with one or more alkaline or alkaline earth metal cations consisting of K, Cs, and / or Ca ions, i.e. it is exchanged with K, Cs or Ca, or with a combination thereof as sole alkaline or alkaline earth metal cations.

[0050] The total amount of potassium, cesium and / or calcium ions in the zeolite may normally be up to about 10% by weight, more particularly up to about 9%, up to about 8%, up to about 7% up to about 6%, up to about 5%, up to about 4%, up to about 3% or up to about 2% by weight. For instance, the catalyst may comprise from about 0.01% to about 10% by weight of the sum of potassium, cesium and calcium ions. In certain embodiments, the catalyst comprises from about 0.01% or from about 0.02% or from about 0.03% or from about 0.04% or from about 0.05% or from about 0.06% or from about 0.07% or from about 0.08% or from about 0.09% or from about 0.1 % to about 2% or to about 1.9% or to about 1.8% or to about 1 .7% or to about 1.6% or to about 1 .5% or to about 1.4% or to about 1.3% by weight of the sum of potassium, cesium and / or calcium ions. In more particular embodiments, the catalyst comprises from about 0.01 % or from about 0.05% or from about 0.1 % to about 2% or to about 1 .5% or to about 1.3% by weight of the sum of potassium, cesium and / or calcium ions. In even more particular embodiments, the total amount of potassium, cesium and / or calcium ions in the catalyst may range from about 0.1 % to about 1 .3% by weight.

[0051] In a particular embodiment, the catalyst is exchanged with alkaline or alkaline earth metal cations comprising or consisting of potassium ions and the amount of potassium ions in the catalyst is any of the ranges above defined for the total amount or sum of potassium, cesium and / or calcium ions. In a particular embodiment, the catalyst comprises between about 0.15% and about 0.6% or between about 0.21% and about 0.53% by weight of potassium ions. In a more particular embodiment, the catalyst comprises about 0.21%, about 0.35%, about 0.37% or about 0.53% by weight of potassium ions.

[0052] In another particular embodiment, the catalyst is exchanged with alkaline or alkaline earth metal cations comprising or consisting of cesium ions and the amount of cesium ions in the catalyst is any of the ranges above defined for the total amount or sum of potassium, cesium and / or calcium ions. In a particular embodiment, the catalyst comprises between about 0.05% and about 0.6% or between about 0.10% and about 0.50% by weight of cesium ions. In a more particular embodiment, the amount of cesium ions is about 0.10%, about 0.30%, or about 0.50% by weight.

[0053] In another particular embodiment, the catalyst is exchanged with alkaline or alkaline earth metal cations comprising or consisting of calcium ions and the amount of calcium ions in the catalyst is any of the ranges above defined for the total amount or sum of potassium, cesium and / or calcium ions. In a particular embodiment, the catalyst comprises between about 0.05% and about 1.5% or between about 0.10% and about 1.30% by weight of calcium ions. In a more particular embodiment, the amount of calcium ions is about 0.10%, about 0.50% or about 1.30% by weight.

[0054] In a particular embodiment, the catalyst is exchanged with alkaline or alkaline earth metal cations comprising or consisting of K and Cs ions and the amount of K and Cs ions in the catalyst may be as defined above for each of these metals. In a more particular embodiment, the catalyst comprises from 0.01% to 1% by weight of Cs ions and from 0.05% to 1% of K ions, such as from 0.02% to 0.5% by weight of Cs ions and from 0.2% to 0.5% of K ions, for instance about 0.07% by weight of Cs ions and about 0.37% of K ions.

[0055] In a particular embodiment, the catalyst of the process of the present invention maintains its activity over a period of time longer than the corresponding raw catalyst without being exchanged with alkaline and / or alkaline earth metal cations. In a particular embodiment, the activity of the catalyst remains essentially constant over a period of time longer than the corresponding raw catalyst without being exchanged with alkaline and / or alkaline earth metal cations. For the purposes of the present invention, the activity of the catalyst is considered in terms of alkylation conversion, which may be defined as the fraction of the limiting reactant, in this case the alkylating agent (olefin), which is consumed. Therefore, conversion is maintained at a more substantially constant level when using the catalyst proposed herein as compared to the corresponding raw catalyst without being exchanged with alkaline and / or alkaline earth metal cations.

[0056] Further, unlike what is commonly found in the state of the art, the faujasite used in the present invention is highly stable without the need of rare earth metals. A rare-earth element (RE) or rare-earth metal (REM), as defined by the International Union of Pure and Applied Chemistry, is one of a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides, as well as scandium and yttrium. Scandium and yttrium are considered rare-earth elements because they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties, but have different electronic and magnetic properties. The 17 rare-earth elements are cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb), and yttrium (Y).

[0057] In a particular embodiment, the FAU-type zeolite used in the present invention comprises less than 15% by weight of rare earth metals, e.g. less than 14%, less than 13%, less than 12%, less than 11 %, less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, less than 0.5% or less than 0.1 % by weight of rare earth metals. In a particular embodiment, the FAU-type zeolite used in the present invention comprises no rare earth metals.

[0058] The total SiO2 / Al2Os mole ratio, the proportion of alkali metal cations and / or alkaline earth metal cations as well as the proportion of rare earth metals in the catalyst may be obtained by conventional chemical analysis, for instance by inductively coupled plasma- optical emission spectroscopy (ICPOES, Optima 8300 PerkinElmer) after alkaline fusion.

[0059] The catalyst disclosed herein provides high initial conversions (typically, above 98%) and is very stable, allowing longer reaction cycles with less frequent washing cycles. Further, the alkylation is very selective to linear monoalkylaromatic compounds, achieving good product qualities. For instance, it has been found that the reaction product of the process shows a very high content of linear alkylbenzene compounds, typically between 90-99% by weight (more specifically, above 90% by weight), i.e. branched alkylates are typically below 10% by weight, and at the same time the 2-phenyl isomer content may be kept within an appropriate low level (e.g. 15-25% by weight). Heavy alkyl benzene (HAB) content is also normally equal or below about 6% by weight whereas lights production may be controlled satisfactorily as well to amounts close to about 1% by weight.

[0060] The term "alkylate" means an alkylated aromatic hydrocarbon.

[0061] The term "2-aryl content" (e.g. 2-phenyl content when benzene is used as aromatic compound) is defined as the percentage of total alkylate (the alkylate species in which the alkyl chain derived from the olefin employed in the present alkylation process is attached to the aromatic ring) that is comprised of those chemical species in which the attachment of the alkyl chain to the aromatic ring is at the 2-position along the alkyl chain.

[0062] For the purposes of the present invention, the alkylated aromatic compounds obtained in the claimed process may be conveniently analyzed by gas chromatography.

[0063] The process of the present invention involves two reactants, namely aromatic compound and alkylating agent. These reactants can be handled and purified as is generally performed by those of ordinary skill in the art.

[0064] In a particular embodiment of the present invention, the aromatic compound is an aromatic hydrocarbon, preferably selected from the group consisting of: toluene, xylene, cumene, ethylbenzene, benzene and mixtures thereof, but preferably benzene. Thus, the aromatic compound used as starting material in the process of the invention may be either a non-alkylated aromatic (e.g. benzene) or an alkylated aromatic (e.g. ethylbenzene). Thus, as the skilled person will readily appreciate, the process according to the present invention is aimed at the selective monoalkylation (i.e. introduction of one alkyl chain) into the aromatic starting material, regardless of the fact that said aromatic starting material already presents one or more alkyl chains or not. In a preferred embodiment, the present invention is directed to a process for producing monoalkylated aromatic compounds (that is, starting from a non-alkylated aromatic).

[0065] In a particular embodiment of the present invention, the alkylating agent is or comprises a substantially linear (non-branched) olefin. It is preferred that the olefin is monounsaturated. There are two principal kinds of linear mono-olefins: Linear a-olefins or terminal olefins, and linear internal olefins in which the position of the double bond is randomly distributed in the chain. For the purposes of the present invention, either linear terminal olefins, linear internal olefins or a mixture of linear olefins with double bonds at terminal and internal positions can be used. The olefins employed in the practice of this invention normally have from 8 to 30 carbon atoms, typically from 8 to 16 carbon atoms, and more typically from 9 to 14 carbon atoms.

[0066] The olefins can be produced from the dehydrogenation of linear paraffins (which may be extracted from kerosene, derived from ethene by the oligomerization process, or obtained from vegetable oils by hydrotreatment), cracking of paraffins and subsequent oligomerization of smaller olefinic molecules, or other known processes for the production of linear monoolefins. The separation of linear paraffins from a mixture comprising normal paraffins, isoparaffins, and cycloparaffins for dehydrogenation can include the use of known separation processes. Linear olefins can be also separated from a mixture of linear and branched olefins by known processes.

[0067] In a particular embodiment, a purified alkylating agent is obtained in accordance with the teachings of WO 2009 / 071709 by means of a process comprising: i) dehydrogenating a feed of linear paraffins catalytically, producing linear monoolefins, unconverted paraffins and a certain quantity of by-products such as diolefins and non-linear compounds; ii) treating the effluent of step i) in order to hydrogenate selectively the diolefins produced as a by-product at step i) to mono-olefins, thereby obtaining a raw alkylation agent comprising linear mono-olefins, unconverted paraffins and nonlinear compounds; and iii) purifying the raw alkylating agent by separating the non-linear products contained in the step ii) effluent, so that a purified alkylating agent is obtained composed of mono-olefins and paraffins.

[0068] This purification may be carried out by means of non-linear impurity separation techniques familiar to an expert on the matter, such as for example, fractioning and selective adsorption. In the case of selective adsorption, the adsorbent bed may comprise at least one material selected from the group consisting of: zeolites, silica, silica gel, macroporous magnesium silicate, activated alumina, silica-alumina, clays, molecular sieves, cellulose acetate, macroporous polystyrene gel, activated carbon and organoselective polymeric membranes, or the like.

[0069] Therefore, in practice, the alkylating agent is normally a purified alkylating agent consisting of a mixture comprising mono-olefins and paraffins (for simplicity, this mixture is commonly referred to as olefin).

[0070] The olefin compound (or the olefin- pa raff in mixture) and aryl compound are reacted in the presence of a catalyst under reaction conditions. The reaction conditions for alkylation may be selected to minimize isomerization of the alkyl group and minimize polyalkylation of the aryl compound (e.g. benzene), while trying to maximize the consumption of the olefins. The temperature of the alkylation reaction is typically between 50 °C and 200 °C, and preferably between 80 °C and 175 °C. The pressures in the reactor are typically from 1.4 MPa (203 psia) to 7 MPa (1015 psia), and preferably from 2 MPa (290 psia) to 3.5 MPa (507 psia). To minimize polyalkylation, the aromatic compound: olefin mole ratio is typically between 2.5:1 and 70:1 , preferably between 5:1 and 50:1 , and more preferably between 5:1 and 35:1 , such as 10:1 , 15:1 , 20:1 , 25:1 or 30:1. The average residence time in the reactor helps control product quality, and the process is operated at a liquid hourly space velocity (LHSV) from 0.1 IT1to 30 h’1, with a preferred LHSV between 0.3 IT1and 6 h’1.

[0071] In a particular embodiment, the aromatic compound and the olefin are mixed in a mole ratio comprised between 10:1 and 25:1 with a reaction temperature between 100 °C and 150 °C and LHSV between 1 IT1and 6 IT1.

[0072] In a particular embodiment of the present invention, the mixture of the aromatic compound and the alkylating agent comprises a maximum of 15 % or 12.5 % or 10 % or 7.5 % or 5 % or 2.5 % or 1 % or 0.5 % by weight of non-linear compounds.

[0073] In a particular embodiment of the present invention, the mixture of the aromatic compound and the alkylating agent also comprises between 0-1%, 0-0.5% or 0-0.1 % by weight of water.

[0074] In accordance with embodiments of the invention, the alkylation process includes two catalysts: a first catalyst producing lower 2-phenyl isomer content linear alkylbenzene, and a second catalyst component producing higher 2-phenyl isomer content linear alkylbenzene. As used herein, the lower 2-phenyl isomer catalyst would itself produce a 2-phenyl isomer content typically equal or below 25 percent, and corresponds to a FAU- type as previously defined, i.e. which is exchanged with one or more alkaline or alkaline earth metal cations selected from potassium, cesium and / or calcium, which has a total SiO2 / AhO3 mole ratio between 10:1 and 80:1 , and preferably comprises no rare earth metals or a low content thereof.

[0075] As used herein, the higher 2-phenyl isomer content catalyst would itself produce a 2- phenyl isomer content typically greater than 30 percent. The second catalyst is a solid acidic material suitable for production of high 2-phenyl isomer linear alkylbenzene. Typically, the second catalyst component is zeolite selected from the group consisting of UZM-8, Zeolite MWW, Zeolite BEA, Zeolite OFF, Zeolite MOR, Zeolite LTL, Zeolite MTW, BPH / UZM-4, and blends thereof. In the present invention when we talk of MOR type zeolites, we refer to the group of zeolites with isotypical structures corresponding to the MOR structural MOR type, such as: mordenite, Na-D zeolite and Ca-Q zeolite, most preferably to mordenite.

[0076] In a particular embodiment of the present invention, the alkylation reaction is carried out in a reactor with a catalyst arrangement selected from the group consisting of: a fixed bed with a single catalyst, a fixed bed with two different catalysts, completely mixed, at least two different fixed beds each with the same catalyst, at least two different fixed beds each with a different catalyst, a fluidized bed with one or more different catalysts, a slurry reactor with one or more different catalysts.

[0077] In a particular embodiment of the present invention the alkylation reaction is carried out in a reactor configuration which comprises at least one of the reactor configurations selected from the group consisting of: an independent reactor, at least two parallel reactors, at least two series reactors and combinations of these configurations.

[0078] The skilled person knows that numerical values relating to measurements are subject to measurement errors which place limits on their accuracy. Where terms such as "about" or "approximately" are applied to a particular value (e.g. "about 200 °C" or "approximately 200 °C") or to a range (e.g. "about x to approximately y"), the value or range is interpreted as being as accurate as the method used to measure it. Unless explicitly stated otherwise, the general convention in the scientific and technical literature may be applied so that the last digit of numerical values preferably indicates the precision of measurement. Thus, unless other error margins are given, the maximum margin is preferably ascertained by applying the rounding-off convention to the last decimal place. For instance, a value of 3.5 preferably has an error margin of 3.45 to 3.54 and a range of 2% to 10% preferably covers a range of 1 .5% to 10.4%. Said variations of a specified value are understood by the skilled person and are within the context of the present invention. Further, to provide a more concise description, some of the quantitative expressions given herein are not qualified with the term “about”. It is understood that, whether the term “about” is used explicitly or not, every quantity given herein is meant to refer to the actual given value, and it is also meant to refer to the approximation to such given value that would reasonably be inferred based on the ordinary skill in the art, including equivalents and approximations due to the experimental and / or measurement conditions for such given value.

[0079] Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of "about 1 % to about 5 %" should be interpreted to include not only the explicitly recited values of about 1 % to about 5 %, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3 and 4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc. This same principle applies to ranges reciting only one numerical value.

[0080] It should be understood that the scope of the present disclosure includes all the possible combinations of embodiments disclosed herein.

[0081] The following examples are merely illustrative of certain embodiments of the invention and cannot be considered as restricting it in any way.

[0082] Examples

[0083] Example 1 A standard fixed bed reactor was used to assess the performance of different FAU catalysts in the alkylation of benzene with olefins. Experimental conditions consisted of three reaction cycles as follows: a first 24-hour reaction cycle to study the catalyst activity, a second 24-hour reaction cycle to study its regenerability and a third 48-hour reaction cycle to study its stability (see Figure 1 ). Samples were taken every 6 hours in all the cases and after the completion of each cycle a process for regenerating the catalyst was carried out.

[0084] The benzene (Bz) was dried with a molecular sieve to minimize the presence of water, and it was then mixed with olefins (actually, a mixture of mono-olefins and paraffins coming from the dehydrogenation of paraffins, selective hydrogenation of diolefins and purification). The composition of the purified alkylating agent (olefin) is shown in Table 1 :

[0085] Table 1

[0086] The following operation conditions were used in all the alkylation reactions:

[0087] Table 2

[0088] This example shows the advantages of using a zeolite FAU exchanged only with potassium according to the present invention (herein referred to as catalyst A) in comparison with the same catalyst unexchanged, i.e. in acid form (herein referred to as catalyst REFERENCE). Both catalysts were ground and sieved to obtain an equivalent particle size distribution.

[0089] Specifically, catalyst A is a zeolite Y which contains about 0.35% by weight of K, has a total SiO2 / Al2Os mole ratio of about 30:1 and contains no rare earth metals. Catalyst REFERENCE is the raw zeolite of catalyst A but without having been subjected to exchange with K ions.

[0090] As may be appreciated from Figure 2 (comparison of olefin conversion), catalyst A having only about 0.35% by weight of K maintained its activity over a longer period of time than catalyst REFERENCE. Tables 3-5 show the comparative results of the catalytic behavior in a fixed-bed reactor in terms of conversion, monoalkylbenzene selectivity, 2- Ph isomer selectivity, heavies selectivity (HAB / LAB content), non-linear alkylates and lights selectivity.

[0091] Table 3

[0092] Cycles 1 and 2: Standard regeneration every 24 h Cycle 3: Without standard regeneration Table 4

[0093] Table 5

[0094] Example 2

[0095] This example shows the advantages of using a zeolite FAU exchanged with different contents of potassium according to the present invention in comparison with the same catalyst unexchanged, i.e. in acid form. The catalysts were ground and sieved to obtain an equivalent particle size distribution.

[0096] Specifically, the three exchanged catalysts are a zeolite Y which contains about 0.21%, 0.37% or 0.53% by weight of K, has a total SiO^AfeOs mole ratio of about 30:1 and contains no rare earth metals.

[0097] To evaluate the catalysts, a batch reaction system has been used carrying out the reaction as follows:

[0098] Catalyst is activated under a flow of N2 at 160°C overnight. The reactor temperature is decreased to 60°C, in order to add the benzene at a temperature below its boiling point. Then, external olefins cylinder is pre-heated with a resistance. When the reaction temperature in the reactor is achieved, pre-heated olefin with similar composition to that on Table 1 is added, and reactor pressure is set at 20 bar. In that moment we establish the t=0. Reaction samples are taken during the reaction.

[0099] All the catalysts (both exchanged and unexchanged) showed good conversions achieving values higher than 97 % in 60 minutes or less. Besides Figure 3 shows the comparative results of the catalytic behavior in terms of heavies selectivity (HAB / LAB content). As may be appreciated, the exchange with K led to a reduction in heavy alkylbenzene formation at high conversions, which means that the amount of byproducts formed can be reduced by the ion exchange.

[0100] Example 3

[0101] This example shows the advantages of using a zeolite FAU exchanged with different contents of caesium according to the present invention in comparison with the same catalyst unexchanged, i.e. in acid form. The catalysts were ground and sieved to obtain an equivalent particle size distribution. Specifically, the three exchanged catalysts are a zeolite Y which contains about 0.10%, 0.30% or 0.50% by weight of Cs, a total SiO^AfeOs mole ratio of about 30:1 and contains no rare earth metals.

[0102] The catalysts were evaluated in a batch reaction system as described in example 2.

[0103] All the catalysts (both exchanged and unexchanged) showed good conversions achieving values higher than 97 % in 60 minutes or less. Besides Figure 4 shows the comparative results of the catalytic behavior in terms of heavies selectivity (HAB / LAB content). As may be appreciated, the exchange with Cs led to a reduction in heavy alkylbenzene formation at high conversions, which means that the amount of byproducts formed can be reduced by the ion exchange.

[0104] Example 4

[0105] This example shows the advantages of using a zeolite FAU exchanged with caesium and potassium according to the present invention in comparison with the same catalyst unexchanged, i.e. in acid form. The catalysts were ground and sieved to obtain an equivalent particle size distribution.

[0106] Specifically, the exchanged catalyst is a zeolite Y which contains about 0.07% by weight of Cs and 0.37% by weight of K, has a total SiO^AfeOs mole ratio of about 30:1 and contains no rare earth metals. For comparison purposes the results of the catalyst described in Example 2 with a 0.37% by weight of K are also considered and plotted in Figure 5.

[0107] The catalysts were evaluated in a batch reaction system as described in example 2.

[0108] All the catalysts (both exchanged and unexchanged) showed good conversions achieving values higher than 97 % in 60 minutes or less and the catalyst with Cs and K showed even better conversions than the one with K only. Besides Figure 5 shows the comparative results of the catalytic behavior in terms of heavies selectivity (HAB / LAB content). As may be appreciated, the exchange with either K or with Cs and K led to a reduction in heavy alkylbenzene formation at high conversions, which means that the amount of byproducts formed can be reduced by the ion exchange. Example 5

[0109] This example shows the advantages of using a zeolite FAU exchanged with different contents of calcium according to the present invention in comparison with the same catalyst unexchanged, i.e. in acid form. The catalysts were ground and sieved to obtain an equivalent particle size distribution.

[0110] Specifically, the two exchanged catalysts are a zeolite Y which contains about 0.50% or 1.3% by weight of Ca, has a total SiO^AfeOs mole ratio of about 30:1 and contains no rare earth metals.

[0111] The catalysts were evaluated in a batch reaction system as described in example 2.

[0112] All the catalysts (both exchanged and unexchanged) showed good conversions achieving values higher than 97 % in 120 minutes or less. Besides Figure 6 shows the comparative results of the catalytic behavior in terms of heavies selectivity (HAB / LAB content). As may be appreciated, the exchange with Ca led to a reduction in heavy alkylbenzene formation at high conversions, which means that the amount of byproducts formed can be reduced by the ion exchange.

Claims

CLAIMS1. A process for the monoalkylation of aromatic compounds, comprising the step of contacting an aromatic hydrocarbon with an alkylating agent in the presence of a catalyst, wherein said catalyst comprises a FAU-type zeolite which is exchanged with one or more alkaline or alkaline earth metal cations comprising potassium, cesium and / or calcium and which has a total SiO^AfeOs mole ratio between 10:1 and 80:1.

2. The process according to claim 1 , wherein the catalyst maintains its activity over a period of time longer than the analogous raw catalyst unexchanged with alkaline or alkaline earth metal cations.

3. The process according to any one of the preceding claims, wherein the catalyst is based on zeolite FAU-Y.

4. The process according to any one of the preceding claims, wherein the catalyst has a total SiO2 / AhO3 mole ratio between 15:1 and 60:1.

5. The process according to any one of the preceding claims, wherein the catalyst comprises up to about 10% by weight of the sum of potassium, cesium and calcium ions.

6. The process according to any one of the preceding claims, wherein the catalyst comprises from 0.01% to 10% by weight of the sum of potassium, cesium and calcium ions.

7. The process according to any one of the preceding claims, wherein the alkaline or alkaline earth metal cations comprise or consist of potassium.

8. The process according to any one of the preceding claims, wherein the catalyst comprises less than 15% by weight of rare earth metals.

9. The process according to any one of the preceding claims, wherein the alkylating agent is a mixture comprising linear mono-olefins and paraffins having about 8 to about 16 carbons.

10. The process according to any one of the preceding claims, wherein the aromatic compound is benzene.

11. Use of a zeolite FAU as a catalyst in the production of monoalkylated aromatic compounds, wherein said zeolite FAU is exchanged with one or more alkaline or alkaline earth metal cations comprising potassium, cesium and / or calcium and has a total SiO2 / AhO3 mole ratio between 10:1 and 80:1.

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