HK1075883A - Production of alkyl aromatic compounds - Google Patents

Description

Preparation of alkylaromatics

Background

Catalytic reactions utilizing aromatics and olefins in the presence of acidic zeolite catalysts have been used in a number of improved chemical processes to produce alkylaromatics such as cumene and ethylbenzene. From the beginning of the 90 s of the 20 th century, Mobil/Badger, Dow/Kellogg, UOP and others have developed new zeolite-based cumene processes. These cumene processes achieve alkylation of benzene and propylene in the liquid phase in the presence of a solid acidic zeolite catalyst. The process developed by CDTech achieves alkylation of benzene and propylene in a mixed phase within a catalytic distillation column having distillation apparatus and a zeolite catalyst stack. Catalysts that can be used for the alkylation of benzene and propylene and the transalkylation of benzene and polyisopropylbenzene in the liquid phase include: beta zeolite, Y zeolite, omega zeolite, ZSM-5, ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68, faujasite, mordenite, porous crystalline magnesium silicate, and tungstate modified zirconia, all of which are well known in the art.

MCM-22 and its use for catalytic synthesis of alkylaromatics are described, for example, in U.S. Pat. nos. 4,954,325(Rubin), 4,992,606(Kushnerick), 5,077,445(Le), 5,334,795(Chu), and 5,900,520(Mazzone), which are incorporated herein by reference in their entirety. MCM-36 and its use for the synthesis of alkylaromatics is described in U.S. Pat. Nos. 5,250,277(Kresge), 5,292,698(Chu), and 5,258,565(Kresge), which are incorporated herein by reference in their entirety. MCM-49 and its use for the synthesis of alkylaromatics is described in U.S. Pat. Nos. 5,236,575(Bennett), 5,493,065(Cheng), and 5,371,310(Bennett), which are incorporated herein by reference in their entirety. MCM-56 and its use for the catalytic synthesis of alkylaromatics is described in U.S. Pat. Nos. 5,362,697(Fung), 5,453,554(Cheng), 5,536,894(Degnan), 5,557,024(Cheng), and 6,051,521(Cheng), which are incorporated herein by reference in their entirety. MCM-58 and its use for making alkylaromatics is described in U.S. Pat. Nos. 5,437,855(Valyocsik) and 5,569,805(Beck), which are incorporated herein by reference in their entirety. MCM-68 and its use for making alkylaromatics is described in U.S. Pat. No. 6,049,018(Calabro), which is incorporated herein by reference.

Catalytic synthesis of alkylaromatics using tungstate modified zirconia is described in U.S. Pat. No. 5,563,311(Chang), which is incorporated herein by reference. One method of liquid phase alkylation or transalkylation using zeolite beta is described in U.S. patent No. 5,081,323(Innes), which is incorporated herein by reference. Processes for producing cumene from zeolite Y are described in U.S. patent nos. 5,160,497 (junguin) and 5,240,889(West), which are incorporated herein by reference. Further, U.S. Pat. Nos. 5,030,786(Shamshoum), 5,980,859(Gajda) and European patent 0,467,007(Butler), which are incorporated herein by reference, describe processes for preparing alkylaromatics using beta, Y and omega zeolites. U.S. Pat. Nos. 5,522,984(Gajda), 5,672,799(Perego), 5,980,859(Gajda) and 6,162,416(Gajda), which are incorporated herein by reference, describe processes for the production of cumene from beta zeolite. Processes for the preparation of, for example, cumene and ethylbenzene using mordenite are described in U.S. patent No. 5,198,595(Lee), which is incorporated herein by reference. A process for making ethylbenzene using a regioselective zeolite catalyst is described in U.S. patent No. 5,689,025(Abichandani), which is incorporated herein by reference.

In the first zeolite-based ethylbenzene production developed by Mobil and Badger in the early 80 s of the 20 th century, benzene was vapor phase alkylated with ethylene and vapor phase transalkylation was performed with benzene and polyethylbenzene. The alkylation and transalkylation steps of this early process were carried out in the presence of a solid acidic ZSM-5 catalyst. The process for making ethylbenzene using ZSM-5 is described in U.S. Pat. No. 5,157,185(Chu), which is incorporated herein by reference.

At the end of the 80 s and 90 s of the 20 th century, UOP/Lummus, Mobil/Badger and others developed several liquid phase zeolite-based ethylbenzene processes. Alkylation of benzene with ethylene and transalkylation of benzene and polyethylbenzene are carried out in the liquid phase in the presence of a solid acidic zeolite catalyst. Catalysts useful for the alkylation of ethylene and benzene and the transalkylation of benzene and polyethylbenzene in a liquid phase process include: beta zeolite, Y zeolite, omega zeolite, ZSM-5, ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68, faujasite, mordenite, porous crystalline magnesium silicate, and tungstate modified zirconia. The process developed by CDTech achieves alkylation of benzene and propylene in a mixed phase within a catalytic distillation column having a distillation apparatus and a zeolite catalyst stack. Processes for the preparation of ethylbenzene using intermediate pore size zeolites are described in U.S. Pat. Nos. 3,751,504(Keown), 4,547,605(Kresge), and 4,016,218(Haag), which are incorporated herein by reference. U.S. Pat. Nos. 4,169,111(Wight) and 4,459,426(Inwood), which are incorporated herein by reference, disclose processes for preparing ethylbenzene using large pore size zeolites such as Y zeolite. The synthesis of zeolite ZSM-12 is described in U.S. Pat. No. 5,021,141(Rubin), which is incorporated herein by reference. The process for making ethylbenzene using zeolite ZSM-12 is described in U.S. patent No. 5,907,073(Kumar), which is incorporated herein by reference. The use of mordenite for the preparation of ethylbenzene is described in U.S. patent No. 5,430,211(Pogue), which is incorporated herein by reference. Liquid phase synthesis of ethylbenzene using zeolite beta is described in U.S. Pat. Nos. 4,891,458(Innes) and 6,060,632(Takamatsu), which are incorporated herein by reference. U.S. Pat. Nos. 4,849,569(Smith), 4,950,834(Arganbright), 5,086,193(Sy), 5,113,031(Sy), and 5,215,725(Sy), which are incorporated herein by reference, teach various catalytic distillation systems for the production of alkylated aromatic compounds including ethylbenzene and cumene.

U.S. patent No. 5,902,917(Collins), which is incorporated herein by reference, teaches a process for producing alkylaromatic compounds, particularly ethylbenzene and cumene, in which a feedstock is first fed to a transalkylation zone and all of the effluent from the transalkylation zone is then poured directly into an alkylation zone along with an olefin alkylating agent, particularly ethylene or propylene.

U.S. patent No. 6,096,935(Schulz), which is incorporated herein by reference, teaches a process for producing alkylated aromatics using a transalkylation reaction zone and an alkylation reaction zone. The effluent from the transalkylation reaction zone is passed through an alkylation reaction zone where the effluent from the transalkylation reaction zone is alkylated to the desired alkylated aromatic compound. The processes for producing ethyl and isopropyl aromatics using a transalkylation reaction zone and an alkylation reaction zone are taught in further detail in U.S. patent nos. 6,232,515 and 6,281,399(Schulz), which are incorporated herein by reference.

U.S. Pat. No. 6,479,721(Gadja), which is incorporated herein by reference, teaches a process for the alkylation of aromatic compounds with olefins using a solid catalyst wherein the ratio of olefins and/or the maximum olefin concentration in the alkylation catalyst bed is maintained below an upper limit, thereby reducing the catalyst deactivation rate and reducing the formation of diphenyl alkanes.

PCT published application WO02062734(Chen), incorporated herein by reference, teaches a process for producing monoalkylated aromatic products such as ethylbenzene and cumene utilizing a series of alkylation zones and transalkylation zones or reaction zones combining alkylation and transalkylation. This invention claims to minimize the amount of excess aromatic material used and needed to be recovered and recycled, thereby reducing the cost of the product.

U.S. Pat. No. 6,313,362(Green), which is incorporated herein by reference, teaches a process for the alkylation of aromatic compounds wherein the alkylation product is contacted with a purification medium in a liquid phase pre-reaction step to remove impurities and form a purified stream. The purified stream may then be further processed using liquid phase transalkylation to convert the polyalkylated aromatic compounds to monoalkylated aromatic compounds. The process may use a large pore molecular sieve catalyst such as MCM-22 as the purification medium for the pre-reaction step because such catalysts have high activity for alkylation, strong retention of catalyst poisons, and low activity for oligomerization under pre-reactant conditions. The process is said to remove olefins, diolefins, styrene, oxygenated organic compounds, sulfur-containing compounds, nitrogen-containing compounds, oligomeric compounds, and the like.

U.S. Pat. No. 4,358,362(Smith), which is incorporated herein by reference, teaches a method of enhancing the catalytic activity of a zeolite catalyst by contacting a feedstream containing catalytically harmful impurities with a zeolitized adsorbent. The invention can be used in a variety of processes including wax removal, for example, the method of the invention can be used to reduce the initial equilibrium (lineout) temperature by 100 ° F.

Japanese patents JP4198139 and 717536(Hidekichi), incorporated herein by reference, teach a process for the production of alkylbenzenes comprising the step of pretreating the benzene to reduce base compounds prior to alkylation of the benzene with an acidic catalyst. Removal of the base material from benzene is accomplished by contacting the benzene feed stream with clay, zeolites, activated carbon, silica gel, alumina, and ion exchange resins.

Patent No. 4,973,790(Beech) incorporated herein by referenceTeaches an oligomerization of C from catalytically cracked heavy petroleum oils₂To C₁₀A process for producing olefins. The oligomerization of olefins is accomplished by zeolites having shape selectivity to gasoline and distillate products in the presence of added hydrogen. A water wash or guard bed is employed in the feed pretreatment step to remove basic nitrogen compounds present in the light olefin refinery stream, thereby increasing catalyst life.

U.S. patent No. 5,053,579(Beech), which is incorporated herein by reference, teaches a process for upgrading unstable olefins, naphtha and diolefins, such as coker gasoline fractions. This patent teaches oligomerizing olefins to gasoline and refinery products over a zeolite catalyst. Hydrogen is added and a feedstock pretreatment is performed to remove basic nitrogen compounds, thereby increasing the life of the catalyst. Water washing of the coker gasoline fraction is the preferred method for removing basic nitrogen compounds.

One method of making Linear Alkylbenzenes (LABs) is taught in U.S. patent No. 5,245,094(Kocal), which is incorporated herein by reference. Olefin feedstocks resulting from the dehydrogenation of paraffins are treated to reduce the aromatics content therein, thereby increasing catalyst life and product linearity.

There are several publications that discuss the positive and negative effects of zeolite catalysts and moisture content of the feedstock. For example, U.S. patent No. 5,030,094(Shamshoum), which is incorporated herein by reference, discloses a process for producing ethylbenzene in which the catalyst life is increased by reducing the concentration of water in the feed to the reactor. In contrast, U.S. Pat. No. 5,240,889(West), which is incorporated herein by reference, teaches a catalyst composition for use in alkylation and transalkylation reactions for the production of ethylbenzene and cumene. But in this patent it is taught that increasing the water content of the catalyst increases the life of the catalyst.

U.S. patent No. 5,300,722(Amundsen), which is incorporated herein by reference, teaches a process for the alkylation of aromatic compounds without oxygen. In this process, an aromatic hydrocarbon is contacted with an alkylating agent under liquid phase alkylation conditions in a reaction vessel in the absence of oxygen and in the presence of a silicon-containing molecular sieve catalyst. The absence of oxygen is said to significantly increase the catalyst life.

U.S. patent No. 5,744,686(Gajda), which is incorporated herein by reference, teaches a process for removing nitrogen-containing compounds from an aromatic hydrocarbon stream by contacting the aromatic hydrocarbon stream with a selective adsorbent having an average pore size of less than about 5.5 angstroms. The selective adsorbent is a non-acidic molecular sieve selected from the group consisting of closed-cell 4A zeolite, 5A zeolite, hydrophobic silicalite (silicalite), F-hydrophobic silicalite, ZSM-5, and mixtures thereof. One embodiment taught in this patent includes the use of a combination of a fractionation zone and an adsorption zone.

U.S. patent No. 5,744,686 is a continuation of U.S. patent No. 5,744,686, U.S. patent No. 5,942,650(Gajda), incorporated herein by reference, and is used for the alkylation, and isomerization and disproportionation of aromatics with ethylene or propylene. The pore size of the catalyst used for these reactions is at least 6 angstroms.

One process for producing alkylated benzenes or mixtures of alkylated benzenes is taught in U.S. patent No. 6,297,417(Samson), which is incorporated herein by reference. The process comprises contacting the feed benzene with a solid acid such as an acidic clay or an acidic zeolite in a pretreatment zone at a temperature in the range of 130 ℃ to 300 ℃. This patent teaches that this pretreatment step increases the life of the catalyst used for alkylation and transalkylation.

U.S. patent No. 6,355,851(Wu), which is incorporated herein by reference, teaches a zeolite catalyzed cumene synthesis process in which benzene and propylene feedstocks are pretreated to remove catalyst poisons. The benzene feed is pretreated under pressure by contact with a bed of "hot" clay at a temperature of about 200 to 500 c and then subjected to distillation to separate benzene from the higher molecular weight species formed from the olefin poisons during the hot clay treatment. The benzene feed is also subjected to a "cold" clay treatment in which the benzene distillate is contacted with clay at ambient temperature. The propylene feed is pretreated by contact with alumina to remove traces of sodium-containing compounds as well as moisture, by contact with molecular sieves to remove water, and by contact with two modified aluminas to remove catalyst poisons. The pretreated propylene and benzene feedstocks are then reacted in the presence of a zeolite catalyst to produce cumene without causing a rapid decrease in catalyst activity.

PCT published application WO0107383, incorporated herein by reference, teaches a process for purifying an olefin-containing feedstream in a polymerization or alkylation step, characterized by passing the feedstream through an adsorbent layer.

PCT published application WO0214240(Venkat), incorporated herein by reference, teaches a process for removing polar impurities from an aromatic feedstock by contacting the feedstock at a temperature of less than 130 ℃ with a molecular sieve having a pore size greater than 5.6 angstroms.

However, none of these prior art teachings teach a complete and consistently effective method for removing deleterious substances from hydrocarbon feedstocks used in alkylation and/or transalkylation processes, thereby avoiding the destruction of the preferred acidic zeolite catalysts in such reactions. The limitations and deficiencies of the prior art are overcome in whole or in part by the improved integrated process of the present invention.

Object of the Invention

Accordingly, it is a primary object of the present invention to provide an improved method, process, and related apparatus for pretreating a hydrocarbon feedstock prior to contact with an alkylation and/or transalkylation acidic zeolite catalyst bed to remove or substantially reduce impurities in said feedstock that may adversely affect the performance, service, or life of the catalyst bed.

It is a general object of the present invention to provide a pretreated hydrocarbon feedstock which is substantially free of impurities which could damage downstream catalyst beds used in alkylation, transalkylation and similar processes.

It is another general object of the present invention to provide one or a series of pretreatment steps for purifying one or more hydrocarbon feed streams prior to downstream catalytic process steps.

It is a particular object of the present invention to provide a process or apparatus for treating an olefin or aromatic feedstock to remove organic or inorganic nitrogen compounds from the preparation of a catalytic alkylation or transalkylation process.

It is another particular object of the present invention to provide a process for pretreating a hydrocarbon feedstock comprising one or a combination of distillation, extraction and/or adsorption steps to remove or substantially reduce impurities that may be toxic to downstream catalytic beds.

It is yet another specific object of the present invention to provide an in-line guard bed packed with a suitable adsorbent for pretreating a hydrocarbon feedstream to remove or substantially reduce nitrogen compounds prior to contacting the feedstream with the catalyst bed.

Other objects and advantages of the invention will in part be obvious and will in part appear hereinafter. Accordingly, the present invention includes, but is not limited to, methods, processes and related apparatus involving several steps and various components, and the relationship and order of one or more such steps and components with respect to each other, as exemplified in the following description. Various modifications and alterations to the methods and apparatus described herein will be apparent to those skilled in the art, and it is intended that all such modifications and alterations be within the scope of the present invention.

Summary of The Invention

Although many commercial successes have been achieved in the production of alkylaromatics such as cumene and ethylbenzene in the presence of acidic zeolite catalysts, the susceptibility of acidic zeolite catalysts to deactivation severely limits the run length of the catalyst and the life of the catalyst. In accordance with the present invention, it has now been found that nitrogen-containing impurities in one or both feedstocks neutralize the acidic active sites on the acidic zeolite catalyst thereby reducing the catalytic activity and the ability to effect the desired reaction. The long term accumulation of these nitrogen-containing impurities on the catalyst gradually reduces the catalytic activity to an unacceptable level for plant performance, requiring plant shutdown to reactivate, regenerate, or replace the catalyst.

The cost of a plant shutdown typically includes not only the cost of operating to restore plant operation to a desired or commercially acceptable level, but also the loss of profit to the manufacturer in selling the product that would have been produced during the plant shutdown. Frequent activation or regeneration of poisoned catalysts can also reduce catalyst life in some cases. In this case, additional costs for replacing the catalyst also occur.

It has been found that pretreatment of one or both feedstocks to remove nitrogen-containing compounds and/or other impurities (which are present in an amount sufficient to adversely affect the performance of the acidic zeolite catalyst) with a pretreatment process or combination of processes of the invention prior to alkylation and/or transalkylation, while simultaneously subjecting the adsorbent used in the adsorption pretreatment to regeneration treatment, is the most effective way to minimize costs while minimizing detrimental impurities in the feedstock.

Detailed description of the preferred embodiments

A. Distillation pretreatment process

Some impurities that negatively impact the performance of the acidic zeolite catalyst may have very high or very low volatility compared to the feedstock, which can typically be better removed by a distillation process. Two such examples are solvents used for extracting benzene: n-formyl morpholine (NFM) and n-methyl pyrrolidone (NMP). Both NFM and NMP have been found to be toxic to acidic zeolite catalysts. These solvents have a very high boiling point compared to benzene and can therefore be separated from benzene economically and efficiently by distillation. Another example is ammonia, which is highly volatile compared to propylene and can therefore be economically and efficiently separated from propylene by distillation.

In some cases, both impurities lighter (more volatile) than the feedstock (e.g., nitrogen-containing compounds) and impurities heavier (less volatile) than the feedstock can be removed by distillation in a single distillation column, or alternatively, in a series of distillation columns. When a single column operation is employed, light impurities are removed from at or near the top of the column, heavy impurities are removed from at or near the bottom of the column, and pretreated feedstock is recovered from the middle portion of the column as a side draw.

Some impurities, including nitrogen-containing compounds, can also be removed from the feedstock by distillation in the same distillation apparatus, while other light and/or heavy impurities can also be removed. In some cases, heavy nitrogen compounds and/or other heavy impurities may be removed at or near the bottom of the column, while pretreated purified feedstock may be recovered at or near the top of the column. In other cases, light nitrogen compounds and/or other light impurities may be removed at or near the top of the column, while pretreated purified feedstock may be recovered at or near the bottom of the column. In other cases, light nitrogen compounds and/or other light impurities may be removed at or near the top of the column, heavy nitrogen compounds and/or other heavy impurities may be removed at or near the bottom of the column, and the pretreated purified feedstock is recovered from the middle portion of the column as a side draw.

B. Extraction pretreatment process

Some of the feed impurities can be optimally removed from the feed by an extraction process in which a suitable extractant is used to separate impurities from the feed that are preferentially soluble in the extractant. For example, ammonia, which is known to be toxic to many zeolite catalysts, has a higher solubility in water than propylene, and thus can be easily removed from propylene by washing with water, which may or may not be acidified.

C. Selective adsorption pretreatment process

Some feedstock impurities can be optimally removed from the feedstock by a selective adsorption pretreatment process using a suitable, preferably regenerable, adsorbent. Suitable regenerable adsorbents suitable for the purposes of the present invention which have been found to be effective for several regenerations in situ include: acid clays, zeolite catalysts, molecular sieves, activated alumina, activated carbon, silica gel, and ion exchange resins. After a period of use, the adsorbent will gradually lose at least a portion of its activity and effectiveness, varying with changes in the nature of the adsorbent, the nature of the feedstock being treated and the impurities contained therein, the concentration of impurities in the feedstock, and the temperature and pressure conditions. In some cases, the activity or effectiveness of the adsorbent will be reduced to the point where continued use thereof has been deemed to no longer be practicable or commercially or both. Such spent adsorbent is defined herein as "spent adsorbent" which may be discarded or replaced, and which may alternatively be regenerated in accordance with the present invention. It has been found that certain spent adsorbents can be effectively regenerated multiple times in situ by removing adsorbed impurities under suitable conditions. It has now been found that effective regeneration of certain adsorbents can be achieved by exposing the adsorbent to a substantially inert gas stream (i.e., inert with respect to the adsorbent) at elevated temperatures, such as nitrogen, air, natural gas, liquefied petroleum gas, methane, ethane, propane, butane, pentane, or water vapor; or exposure to a substantially inert liquid stream such as liquefied petroleum gas, ethane, propane, butane, pentane, hexane, benzene, toluene, or xylene. It has further been found that some adsorbents can also be regenerated by replacing the adsorbed impurities with other compounds which adsorb onto the adsorbent more strongly than the initially adsorbed impurities. Typically, water or a mixture containing a high concentration of water is typically employed for effective preferential displacement of adsorbed impurities from the adsorbent, since water is strongly adsorbed on most of the foregoing adsorbents. Certain adsorbents may also be regenerated using acid treatment methods such as scrubbing with an acid mixture stream.

D. Embodiments of the invention

The first embodiment of the present invention is: only the olefins in the alkylation and/or transalkylation process are pretreated if the aromatic feedstock employed in the process is deemed to be substantially free of impurities that are detrimental to the zeolite catalyst used in one or more catalyst beds in the reaction zone of the process. According to the invention, the pretreatment of the olefin feed may be carried out as it enters the process, or together with other pretreatment and/or purification steps, or alternatively after other pretreatment and/or upstream purification steps have been completed, but before contact with the catalytic bed. The foregoing additional pretreatment and/or upstream purification steps employed serve to reduce other impurities in the feedstock which may have a negative impact on the performance of the zeolite catalyst, the purity of the desired alkyl aromatic product, or other characteristics or product quality characteristics in the process.

Another embodiment of the present invention is: only the aromatic feedstock in the alkylation and/or transalkylation process is pretreated if the olefin feedstock employed in the process is deemed to be substantially free of impurities that are detrimental to the zeolite catalyst used in one or more catalyst beds in the reaction zone of the process. According to the invention, the pretreatment of the aromatic feedstock may be carried out as it enters the process, or together with other pretreatment and/or purification steps, or alternatively after other pretreatment and/or upstream purification steps have been completed, but before contact with the catalytic bed. The foregoing additional pretreatment and/or upstream purification steps employed serve to reduce other impurities in the feedstock which may have a negative impact on the performance of the zeolite catalyst, the purity of the desired alkyl aromatic product, or other characteristics or product quality characteristics in the process.

The aromatic feed stream may also be pretreated in accordance with the present invention along with other streams in the process or after pretreatment and/or purification of the aromatic feedstock along with other streams in the process by other pretreatment and/or purification steps. The foregoing other pretreatment and/or purification steps employed serve to reduce other impurities in the feedstock which may have a negative impact on the performance of the zeolite catalyst, the purity of the desired alkyl aromatic product, or other characteristics or product quality characteristics in the process.

Yet another embodiment of the present invention is: both the olefin feedstock and the aromatic feedstock in the alkylation and/or transalkylation process are pretreated if both the olefin feedstock and the aromatic feedstock employed in the known process contain or are prone to contain impurities that are detrimental to the zeolite catalyst used in one or more of the catalyst beds in the reaction zone of the process. In this embodiment of the invention, the pretreatment of the olefin feed may be carried out according to the invention as it enters the process, or together with other pretreatment and/or purification steps, or optionally after other pretreatment and/or upstream purification steps have been completed, but before contact with the catalytic bed. The foregoing additional pretreatment and/or upstream purification steps employed serve to reduce other impurities in the feedstock which may have a negative impact on the performance of the zeolite catalyst, the purity of the desired alkyl aromatic product, or other characteristics or product quality characteristics in the process. Also in this embodiment of the invention, the pretreatment of the aromatic feedstock may be carried out according to the invention as it enters the process, or together with other pretreatment and/or purification steps, or alternatively after other pretreatment and/or upstream purification steps have been completed, but before contact with the catalytic bed. The foregoing additional pretreatment and/or upstream purification steps employed serve to reduce other impurities in the feedstock which may have a negative impact on the performance of the zeolite catalyst, the purity of the desired alkyl aromatic product, or other characteristics or product quality characteristics in the process.

The aromatic feed stream may also be pretreated in accordance with this embodiment of the invention along with other streams in the process, or after pretreatment and/or purification of the aromatic feed along with other streams in the process by other pretreatment and/or purification steps. The foregoing additional pretreatment and/or purification steps are employed to reduce other impurities in the feedstock which may have a negative impact on the performance of the zeolite catalyst, the purity of the desired alkyl aromatic product, or other characteristics or product quality characteristics in the process.

Under the appropriate circumstances, any two, or even all three of the distillation, extraction, and selective adsorbent feed pretreatment processes of the present invention can be combined with each other and adsorbent regeneration steps described herein, and used in any convenient sequence or order, thereby enabling a highly efficient, highly effective, tailored integrated process employing a wide range of operating parameters that can meet the processing requirements of different feeds containing different possible impurities.

Although some prior art processes suggest removing at least some of the nitrogen-containing compounds by contacting the feedstock to be purified with a selective adsorbent, they do not address the advantages of using regenerable adsorbents; there is no teaching of in situ regeneration of spent adsorbents using a variety of suitable and effective methods; the effectiveness of multiple in situ regeneration methods in successfully restoring adsorption activity, successfully restoring at least some of the lowest acceptable adsorption capacity of a spent adsorbent, has not been demonstrated as in the present invention; nor does it emphasize the importance of reliable multiple adsorption regenerations on process effectiveness. Since almost all selective adsorbents used in the prior art processes have a limited adsorption capacity, the following problems are very critical: that is, the adsorbent used in the pretreatment process can be regenerated in situ multiple times sufficiently to restore its original adsorption effectiveness and to restore at least some minimum acceptable adsorption capacity, thereby enabling it to be successfully reused several times. We have found that the regenerability of the adsorbent tends to be a determining factor in determining whether a selective adsorbent feed pretreatment process is economically viable. If a spent adsorbent cannot be regenerated several times sufficiently to restore its original adsorption effectiveness and to restore at least some minimum acceptable adsorption capacity so that it can be reused with its original adsorption effectiveness, it needs to be removed from the process vessel and replaced with fresh adsorbent once it is spent. The material costs of periodically using a fresh charge of adsorbent, the labor costs required to purchase, transport, store, and fill the fresh adsorbent into a process vessel, as well as the labor costs of removing, storing, transporting, and processing spent adsorbent, etc., will rapidly increase and make the prior art pretreatment processes generally economically undesirable.

Furthermore, the prior art does not teach a variety of suitable alternative pretreatment processes for removing different impurities from different feedstocks, nor does it teach that such processes can generally be combined and integrated with, and/or used in conjunction with, other pretreatment and/or purification steps for reducing other impurities in the feedstock that may have a negative impact on the catalyst used for alkylation/transalkylation, the purity of the desired alkylaromatic product, or other characteristics in the production of total alkylaromatics or product quality characteristics. By being used concurrently with and/or in conjunction with other pretreatment and/or purification steps, capital and operating costs for removing nitrogen compounds and/or other impurities can be significantly reduced and/or minimized. For example, ammonia impurities in a propylene feed can be easily removed from the feed by adding several trays to a distillation column used to purify the propylene feed. In this case, the cost of such ammonia removal from propylene is minimal, since the cost of adding several trays is minimal and essentially no additional operating costs are required.

The following examples provide illustrative embodiments of the present invention.

Example 1

A propylene feed containing 20ppm by weight of ammonia was pretreated in accordance with one embodiment of the invention by feeding it at a rate of 72g per hour to a guard bed containing 20.3g of Selexsorb CD supplied by Alcoa. The guard bed was maintained at 30 ℃. When 78g of propylene had passed through the guard bed, the treated propylene sample was found to contain only 0.03ppm by weight of ammonia, thereby indicating the effectiveness of the guard bed in reducing the ammonia content of the propylene feed.

Example 2

The same guard bed and the same propylene feed containing 20ppm by weight of ammonia as in example 1 above were used in this example. In this example the propylene flow rate was slightly reduced to 71g per hour and the guard bed temperature was increased to 57 ℃. When 77g of propylene had been treated, a sample of the effluent was taken. The ammonia content in this effluent sample was found to be only 0.01ppm by weight ammonia, thereby illustrating the continued effectiveness of the guard bed in removing ammonia from the feed.

Example 3

According to another embodiment of the present invention, a propylene feed containing about 110ppm by weight of moisture (water) and 1.3ppm by weight of ammonia was pretreated by feeding at a flow rate of 90g per hour to two guard beds in series prepared according to the present invention. The first guard bed contained 60g of 3A molecular sieve supplied by PQ corp. for the purpose of removing moisture from the propylene stream. The second guard bed contained 10g of 13X molecular sieves supplied by Grace Davison for the purpose of removing ammonia from the propylene stream. Both guard beds were maintained at 35 ℃.

Effluent samples were periodically taken from the second guard bed to determine the ammonia content in the pretreated propylene stream. Even after more than 99kg of propylene was treated, the ammonia content of the pretreated propylene stream was still below the lower detection limit of 0.01ppm by weight.

Example 4

According to another embodiment of the invention, a benzene feedstock containing about 15ppm by weight of moisture and 7ppm by weight of NFM was pretreated by feeding the feedstock to a guard bed containing 13X molecular sieves (supplied by Aldrich Chemical Co., Ltd.) prepared in accordance with the present invention. The benzene flow rate was 110g per hour and the guard bed was maintained at ambient temperature conditions of about 25 ℃.

Effluent samples were taken periodically from the guard bed to determine NFM content in the pretreated stream. The NFM content of the pretreated benzene stream was less than 0.03ppm by weight after 10kg of benzene had been treated.

Example 5

According to another embodiment of the invention, a benzene feedstock containing about 15ppm by weight of moisture and 7ppm by weight of NMP was pretreated by feeding the feedstock to a guard bed containing 10g of 13X molecular sieve prepared in accordance with the present invention at a flow rate of 110g per hour. The guard bed was maintained at ambient temperature conditions of about 25 c.

Effluent samples were periodically taken from the guard bed to determine the NMP content in the pretreated stream. When 10kg of benzene had been treated, the NMP content in the pretreated benzene stream was less than 0.01ppm by weight.

Example 6

According to another embodiment of the invention, a benzene feedstock containing about 25ppm by weight of moisture and 35ppm by weight of NFM is pretreated by feeding the feedstock to a guard bed containing 10g of 13X molecular sieve (supplied by PQ Corp) made in accordance with the present invention at a flow rate of 110g per hour. The guard bed was maintained at about 110 ℃.

Effluent samples were taken periodically from the guard bed to determine NFM content in the pretreated stream. When 5kg of benzene had been treated, the NFM content in the pretreated benzene stream was less than 0.01ppm by weight. The plant was then operated continuously until the NFM level broke through, and the content of this component in the pretreated benzene stream was found to exceed 0.05ppm by weight. The unit was then shut down and the spent adsorbent was regenerated at 235 c for 24 hours under a continuous nitrogen purge.

At this time, the regenerated adsorbent was cooled, and the nitrogen purge was terminated. The adsorbent recovers its adsorption effectiveness at 110 ℃ on benzene feedstock containing 20 to 25ppm by weight of moisture and 35ppm by weight of NFM at a flow rate of 110g per hour. Periodic analysis of effluent samples again confirmed that after 5kg of benzene had been treated, the NFM content in the pretreated benzene stream remained below 0.01ppm by weight. The plant was then operated continuously until the NFM level had mutated, and the content of this component in the pretreated benzene stream was found to exceed 0.05ppm by weight. The apparatus was then shut down and the spent adsorbent was regenerated at 235 c for 24 hours under a continuous nitrogen purge, followed by cooling of the regenerated adsorbent and termination of the nitrogen purge. The adsorbent then regains its effectiveness at 110 ℃ in adsorbing benzene feed containing 20-25 ppm by weight moisture and 35ppm by weight NFM at a flow rate of 110g per hour. Effluent samples were periodically analyzed to again determine that after 5kg of benzene had been treated, the NFM content in the pretreated benzene stream remained below 0.01ppm by weight.

In summary, the regenerable adsorbent used in this example was regenerated twice in situ in the presence of nitrogen at elevated temperature in accordance with the present invention. The adsorption effectiveness of the regenerated adsorbent was found to be fully restored after each regeneration, and thus effluent samples were found to contain NFM levels below 0.01ppm by weight. In addition, it has been found that the regenerated sorbent is capable of pretreating at least 5kg of a benzene feedstock containing 20 to 25ppm by weight of moisture and 35ppm by weight of NFM. Thus, this example demonstrates the effectiveness of multiple regenerations using elevated temperature nitrogen gas to restore adsorption effectiveness and to restore the spent adsorbent to at least its minimum acceptable adsorption capacity to enable its use in removing NFM and other nitrogen-containing impurities from the feedstock.

Example 7

According to another embodiment of the invention, a benzene feedstock containing about 50ppm by weight of moisture and 35ppm by weight of NFM is pretreated by feeding the feedstock to a flow rate of 110g per hour containing 10g of 13X molecular sieve made in accordance with the present invention. The guard bed was maintained at about 110 ℃.

Effluent samples were taken periodically from the guard bed to determine NFM content in the pretreated stream. When 5kg of benzene had been treated, the NFM content in the pretreated benzene stream was less than 0.01ppm by weight. The plant was then operated continuously until the NFM level had mutated, and the content of this component in the pretreated benzene stream was found to exceed 0.05ppm by weight. The unit was then shut down and the spent adsorbent was regenerated at 200 c for 16 hours under continuous steam purge conditions. The regenerated adsorbent was then dried under a nitrogen purge for 4 hours.

After cooling the regenerated adsorbent and terminating the nitrogen purge, the adsorbent returned to its adsorption effectiveness at 110 ℃ on benzene feed containing 50ppm by weight of moisture and 35ppm by weight of NFM at a flow rate of 110g per hour. Effluent samples were periodically analyzed to determine that the NFM content in the pretreated benzene stream was less than 0.01ppm by weight after 5kg of benzene had been treated. The plant was then operated continuously until the NFM level broke through, and the content of this component in the pretreated benzene stream was found to exceed 0.05ppm by weight. The unit was then shut down and the spent adsorbent was regenerated again at 200 c under a continuous steam purge and then dried under a nitrogen purge.

After cooling the regenerated adsorbent and terminating the nitrogen purge, the adsorbent returned to its adsorption effectiveness at 110 ℃ on benzene feed containing 50ppm by weight of moisture and 35ppm by weight of NFM at a flow rate of 110g per hour. Effluent samples were periodically analyzed to determine that when 5kg of benzene had been treated, the NFM content in the pretreated benzene stream was less than 0.01ppm by weight.

The plant was then operated continuously until the NFM level broke through, and the content of this component in the pretreated benzene stream was found to exceed 0.05ppm by weight. The adsorbent was then regenerated with steam a third time under approximately the same conditions as before, dried with nitrogen and cooled in nitrogen to restore adsorption effectiveness. It was again determined that when regenerated the adsorbent was able to pretreat more than 5kg of benzene containing 50ppm by weight of moisture and 35ppm by weight of NFM while the NFM level in the effluent remained below 0.01ppm by weight.

In summary, the regenerable adsorbent used in this example was regenerated in situ three times in the presence of nitrogen at elevated temperature in accordance with the present invention. The adsorption effectiveness of the regenerated adsorbent was found to be fully restored after each regeneration, and thus effluent samples were found to contain NFM levels below 0.01ppm by weight. In addition, it has been found that the regenerated sorbent is capable of pretreating at least 5kg of a benzene feedstock containing 50ppm by weight of moisture and 35ppm by weight of NFM. Thus, this example demonstrates the effectiveness of multiple regenerations using elevated temperature steam to restore adsorption effectiveness and to restore at least a minimum acceptable adsorption capacity to the spent adsorbent to enable its use in removing NFM and other nitrogen-containing impurities from the feedstock.

Example 8

A batch of MCM-22 type catalyst was loaded into a pilot plant alkylation reactor and tested for cumene synthesis. Between 5,603 hours and 5,630 hours of catalyst use, the benzene charge rate was about 65g per hour and the propylene charge rate was about 29g per hour. The reactor temperature was 128 ℃ and the propylene conversion was steadily greater than 99.99%.

At 5,631 hours, the pure benzene feed was replaced with a benzene feed made by adding 50ppm of NMP. Meanwhile, a guard bed of the present invention containing 22.5g of 13X molecular sieve was placed upstream of the alkylation reactor of the pilot plant to pretreat the benzene feed to remove NMP. The guard bed was maintained at an ambient temperature of about 25 ℃. No NMP was detected in the benzene feed at the exit of the guard bed and the catalyst in the alkylation reactor remained stable during this time. The conversion of propylene remained above 99.99%. This example shows the effectiveness of a guard bed prepared and operated in accordance with this method of the present invention for removing NMP from a benzene feedstock to prevent catalyst deactivation.

At 5,652 hours of use, the 13X molecular sieve guard bed was bypassed and the NMP-containing benzene feed was charged to the reactor without pretreatment according to the process of the present invention. The temperature profile in the reactor changes very rapidly, indicating that catalyst poisoning is occurring. The NMP-containing benzene feed was then replaced with a pure benzene feed. At 5,676 hours of use, the propylene conversion was found to have dropped below 99.98%, indicating that the catalyst bed was damaged or deactivated due to catalyst poisoning by NMP.

It will be apparent to those skilled in the art that other variations and modifications in the above-described apparatus and process for pretreating one or more hydrocarbon feedstocks charged to an alkylation and/or transalkylation reactor to remove materials toxic to the alkylation and/or transalkylation catalyst do not depart from the scope of the invention herein disclosed, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

Claims (54)

1. An improved process for producing a desired alkylaromatic compound by reacting an olefinic feedstock and an aromatic feedstock in the presence of an acidic zeolite catalyst in a reaction zone, wherein the olefinic feedstock or the aromatic feedstock or both contains at least one impurity in an amount sufficient to adversely affect the performance of the acidic zeolite catalyst, the improvement comprising performing steps (a) through (f) in any order, followed by step (g), wherein:

(a) treating the olefin feed to the reaction zone by distillation to substantially separate and remove the relatively more volatile nitrogen impurities or the relatively less volatile nitrogen impurities, or both, from the olefin feed if present in the olefin feed to the reaction zone in an amount sufficient to adversely affect the performance of the acidic zeolite catalyst and where such impurities are not substantially separable by other treatment means;

(b) treating the aromatic feedstock for the reaction zone by distillation to substantially separate and remove any relatively high volatility nitrogen impurities or relatively low volatility nitrogen impurities, or both, present in the aromatic feedstock for the reaction zone in an amount sufficient to adversely affect the performance of the acidic zeolite catalyst and not substantially separable therefrom by other treatment means;

(c) treating the hydrocarbon feedstock for the reaction zone by extraction with a suitable extractant to substantially separate impurities from the hydrocarbon feedstock if present in the olefin feedstock for the reaction zone in an amount sufficient to adversely affect the performance of the acidic zeolite catalyst and where the nitrogen impurities are preferentially soluble in the suitable extractant are not substantially separable by other treatment methods;

(d) treating the aromatic feedstock for the reaction zone by extraction with a suitable extractant to substantially separate and remove nitrogen impurities from the aromatic feedstock for the reaction zone if such impurities are present in the aromatic feedstock for the reaction zone in an amount sufficient to adversely affect the performance of the acidic zeolite catalyst and are not sufficiently separable herein by other treatment methods;

(e) treating said hydrocarbon feedstock for said reaction zone by selective adsorption with a regenerable adsorbent to substantially remove nitrogen impurities therefrom and periodically regenerating said adsorbent in situ, if nitrogen impurities are present in said olefin feedstock for said reaction zone in an amount sufficient to adversely affect the performance of said acidic zeolite catalyst and are not substantially removed therefrom by other treatment means;

(f) treating the aromatic feedstock for the reaction zone by selective adsorption with a regenerable adsorbent to substantially remove nitrogen impurities therefrom and periodically regenerating the adsorbent in situ if nitrogen impurities are present in the aromatic feedstock for the reaction zone in an amount sufficient to adversely affect the performance of the acidic zeolite catalyst and are not substantially removed by other treatment methods;

(g) passing the pretreated olefinic feedstock and the aromatic feedstock to a reaction zone, wherein if the olefinic feedstock contains at least one nitrogen impurity, the olefinic feedstock is pretreated according to one or more of steps (a), (c) or (e); if the aromatic feedstock contains at least one nitrogen impurity, the olefin feedstock is pretreated in accordance with one or more of steps (b), (d) or (f).

2. The process of claim 1, wherein the olefin feed is pretreated as it enters the process, or with or after other pretreatment and/or purification steps, but before entering the reaction zone.

3. The process of claim 1, wherein said olefin feedstock pretreatment comprises at least one distillation step.

4. The process of claim 1, wherein the olefin feed pretreatment comprises at least one distillation step wherein at least one nitrogen impurity is removed at or near the top of the distillation column and the pretreated olefin feed is recovered at or near the bottom of the distillation column.

5. The process of claim 1, wherein the olefin feed pretreatment comprises at least one distillation step wherein at least one nitrogen impurity is removed at or near the bottom of the distillation column and the pretreated olefin feed is recovered at or near the top of the distillation column.

6. The process of claim 1 wherein said olefin feed pretreatment comprises at least one distillation step wherein at least one light nitrogen-containing compound and/or other light impurities is removed at or near the top of the distillation column, at least one heavy nitrogen-containing compound and/or other heavy impurities is removed at or near the bottom of the distillation column, and the pretreated olefin feed is recovered as a side draw.

7. The process of claim 1, wherein said olefin feed pretreatment comprises at least one extraction step.

8. The process of claim 1, wherein said olefin feed pretreatment comprises at least one extraction step wherein said olefin feed is extracted with water and/or acidified water.

9. The process of claim 1, wherein said olefin feedstock pretreatment comprises at least one selective adsorption step with at least one regenerable adsorbent, wherein said adsorbent is selected from the group consisting of acidic clays, zeolite catalysts, molecular sieves, alumina, silica, activated alumina, activated carbon, silica gel, and ion exchange resins.

10. The process of claim 1, wherein the olefin feedstock pretreatment comprises at least one selective adsorption step with a regenerable adsorbent, further wherein the regeneration of the spent adsorbent comprises exposing the spent adsorbent to a stream of a substantially inert gas selected from the group consisting of nitrogen, air, natural gas, liquefied petroleum gas, methane, ethane, propane, butane, pentane, water vapor, and mixtures thereof, at an elevated temperature.

11. The process of claim 1, wherein said olefin feedstock pretreatment comprises at least one selective adsorption step with a regenerable adsorbent, further wherein the regeneration of the spent adsorbent comprises exposing the spent adsorbent to a stream of a substantially inert liquid selected from the group consisting of liquefied petroleum gas, ethane, propane, butane, pentane, hexane, benzene, toluene, ethylbenzene, xylenes, and mixtures thereof, at an elevated temperature.

12. The process of claim 1, wherein said pretreatment of the olefin feedstock comprises at least one selective adsorption step with a regenerable adsorbent, further wherein the regeneration of the spent adsorbent comprises the step of replacing adsorbed impurities with other compounds that adsorb more strongly preferentially on the adsorbent than the impurities.

13. The process of claim 1, wherein said olefin feedstock pretreatment comprises at least one selective adsorption step with a regenerable adsorbent, further wherein regeneration of said spent adsorbent comprises an acidification treatment step.

14. The process of claim 1 wherein the aromatic feedstock is pretreated as it enters the process, or with or after other pretreatment and/or purification steps, but before entering the reaction zone.

15. The process of claim 1 wherein the aromatic feedstock is pretreated in conjunction with other streams in the process or after pretreatment and/or purification of the aromatic feedstock in conjunction with other streams in the process by other pretreatment and/or purification steps.

16. The process of claim 1 wherein said aromatic feedstock pretreatment comprises at least one distillation step.

17. The process of claim 1 wherein said aromatic feedstock pretreatment comprises at least one distillation step wherein at least one nitrogen impurity is removed at or near the top of the distillation column and the pretreated aromatic feedstock is recovered at or near the bottom of the distillation column.

18. The process of claim 1 wherein said aromatic feedstock pretreatment comprises at least one distillation step wherein at least one nitrogen impurity is removed at or near the bottom of the distillation column and the pretreated aromatic feedstock is recovered at or near the top of the distillation column.

19. The process of claim 1 wherein said aromatic feedstock pretreatment comprises at least one distillation step wherein at least one light nitrogen-containing compound and/or other light impurities are removed at or near the top of the distillation column, at least one heavy nitrogen-containing compound and/or other heavy impurities are removed at or near the bottom of the distillation column, and the pretreated aromatic feedstock is recovered as a side draw.

20. The process of claim 1 wherein said aromatic feedstock pretreatment comprises at least one extraction step.

21. The process of claim 1 wherein said aromatic feedstock pretreatment comprises at least one extraction step wherein said aromatic feedstock is extracted with water and/or acidified water.

22. The process of claim 1, wherein said aromatic feedstock pretreatment comprises at least one selective adsorption step with at least one regenerable adsorbent, wherein said adsorbent is selected from the group consisting of acidic clays, zeolite catalysts, molecular sieves, alumina, silica, activated alumina, activated carbon, silica gel, and ion exchange resins.

23. The process of claim 1, wherein the pretreatment of the aromatic feedstock comprises at least one selective adsorption step with a regenerable adsorbent, and further wherein the regeneration of the spent adsorbent comprises exposing the spent adsorbent to a stream of a substantially inert gas selected from the group consisting of nitrogen, air, natural gas, liquefied petroleum gas, methane, ethane, propane, butane, pentane, steam, or mixtures thereof, at an elevated temperature.

24. The process of claim 1, wherein the pretreatment of the aromatic feedstock comprises at least one selective adsorption step with a regenerable adsorbent, and further wherein the regeneration of the spent adsorbent comprises exposing the spent adsorbent to a stream of a substantially inert liquid selected from the group consisting of liquefied petroleum gas, ethane, propane, butane, pentane, hexane, benzene, toluene, ethylbenzene, xylene, or mixtures thereof, at an elevated temperature.

25. The process of claim 1 wherein said aromatic feedstock pretreatment comprises at least one selective adsorption step with a regenerable adsorbent, and further wherein said regeneration of said spent adsorbent comprises the step of replacing adsorbed impurities with other compounds that adsorb more strongly preferentially on the adsorbent than the impurities.

26. The process of claim 1, wherein the aromatic feedstock pretreatment comprises at least one selective adsorption step using a regenerable adsorbent, further wherein the regeneration of the spent adsorbent comprises an acidification step.

27. The process of any of claims 1-26, wherein the olefin feedstock comprises olefins having from 2 to 4 carbon atoms.

28. The process of any of claims 1-26, wherein the olefinic feedstock comprises at least one member selected from the group consisting of ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, isobutene, and mixtures thereof.

29. The process of any of claims 1-26, wherein the aromatic feedstock comprises at least one member selected from the group consisting of benzene, toluene, ethylbenzene, xylenes, isopropylbenzene, n-propylbenzene, butylbenzene, and mixtures thereof.

30. The process of any one of claims 1-26, wherein the aromatic feedstock comprises benzene.

31. The method of any one of claims 1-26, wherein the desired alkyl aromatic compound comprises at least one member selected from the group consisting of: ethylbenzene, cumene, n-propylbenzene, butylbenzene, diethylbenzene, diisopropylbenzene, dibutylbenzene, ethyltoluene, cymene, butyltoluene, ethylcumene, butylethylbenzene, butylcumene and mixtures thereof.

32. The method of any one of claims 1-26, wherein the desired alkyl aromatic compound comprises at least one member selected from the group consisting of: ethylbenzene, cumene, mixtures of diethylbenzene isomers, p-diethylbenzene, m-diethylbenzene, mixtures of diisopropylbenzene isomers, p-diisopropylbenzene, m-diisopropylbenzene, and mixtures thereof.

33. The process of any one of claims 1 to 26 wherein said reaction zone comprises one or more acidic zeolite catalysts.

34. The process of any one of claims 1 to 26 wherein said reaction zone comprises one or more acidic zeolite catalysts selected from the group consisting of beta zeolite, Y zeolite, ZSM-5, ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68, faujasite, mordenite, zirconium phosphate, and porous crystalline magnesium silicate.

35. A process for producing a desired alkylaromatic from an olefin feedstock and an aromatic feedstock using an acidic zeolite catalyst, wherein:

(a) pretreating an aromatic feedstock or an olefinic feedstock with one or more pretreatment steps comprising at least one selected from distillation, extraction, and selective adsorption to remove or substantially reduce nitrogen-containing compounds that deactivate acidic zeolite catalysts used in reaction zones in the plant;

(b) a selective adsorption step using at least one regenerable adsorbent selected from the group consisting of: zeolites, zeolite catalysts, molecular sieves, silicates, alumina, activated carbon, silica gel, and ion exchange resins;

(c) regenerating the spent adsorbent at least twice in situ, said regeneration being accomplished by at least one of the following steps: (i) exposing the spent adsorbent to a flow of inert gas or inert liquid at elevated temperature, (ii) replacing the adsorbed impurities with other compounds that adsorb more strongly preferentially on the adsorbent than the impurities, and (iii) acid treatment;

(d) the treated aromatic and/or olefinic feedstock is then reacted in a reaction zone to produce the desired alkylaromatic compound; and

(e) the distillation zone is utilized to separate the desired alkylaromatic compound, recover unreacted starting materials and recoverable byproducts, and purge non-recoverable byproducts.

36. The process of claim 35, wherein the pretreatment of the feedstock is carried out as the feedstock enters the process, or together with or after other pretreatment and/or purification steps, but before entering the reaction zone.

37. The method of claim 35, wherein the feedstock is pretreated after being treated with other streams in the process or pretreated and/or purified with other streams in the process by other pretreatment and/or purification steps.

38. The process of claim 35, wherein the pretreatment of the at least one feedstock comprises at least one selective adsorption step with a regenerable adsorbent, further wherein the regeneration of the spent adsorbent comprises exposing the spent adsorbent to a stream of a substantially inert gas selected from nitrogen, air, natural gas, liquefied petroleum gas, methane, ethane, propane, butane, pentane, water vapor, or mixtures thereof, at an elevated temperature.

39. The process of claim 35, wherein the pretreatment of the at least one feedstock comprises at least one selective adsorption step with a regenerable adsorbent, further wherein the regeneration of the spent adsorbent comprises exposing the spent adsorbent to a stream of a substantially inert liquid selected from liquefied petroleum gas, ethane, propane, butane, pentane, hexane, benzene, toluene, xylene, or mixtures thereof, at an elevated temperature.

40. The process of claim 35, wherein the pretreatment of the at least one feedstock comprises at least one distillation step.

41. The process of claim 35, wherein the pretreatment of the at least one feedstock comprises at least one distillation step wherein at least one nitrogen impurity is removed at or near the top of the distillation column and the pretreated feedstock is recovered at or near the bottom of the column.

42. The process of claim 35, wherein the pretreatment of the at least one feedstock comprises at least one distillation step wherein at least one nitrogen impurity is removed at or near the bottom of the distillation column and the pretreated feedstock is recovered at or near the top of the column.

43. The process of claim 35, wherein the pretreatment of at least one feedstock comprises at least one distillation step wherein at least one light nitrogen-containing compound and/or other light impurities is removed at or near the top of the distillation column, at least one heavy nitrogen-containing compound and/or other heavy impurities is removed at or near the bottom of the distillation column, and the pretreated feedstock is recovered as a side draw.

44. The method of claim 35, wherein the pretreatment of the at least one feedstock comprises at least one extraction step.

45. The process of claim 35 wherein the pretreatment of at least one of the feedstocks comprises at least one extraction step wherein the aromatic feedstock is extracted with water and/or acidified water.

46. The process of any of claims 35-45, wherein the olefin feedstock comprises olefins having from 2 to 4 carbon atoms.

47. The process of any of claims 35-45, wherein the olefinic feedstock is selected from the group consisting of ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, isobutene, and mixtures thereof.

48. The process of any one of claims 35-45, wherein the aromatic feedstock is selected from the group consisting of benzene, toluene, ethylbenzene, xylenes, isopropylbenzenes, n-propylbenzenes, butylbenzenes, and mixtures thereof.

49. The process of any one of claims 35-45, wherein the aromatic feedstock is benzene.

50. The method of any one of claims 35-45, wherein the desired alkyl aromatic compound comprises at least one member selected from the group consisting of: ethylbenzene, cumene, n-propylbenzene, butylbenzene, diethylbenzene, diisopropylbenzene, dibutylbenzene, ethyltoluene, cymene, butyltoluene, ethylcumene, butylethylbenzene, butylcumene and mixtures thereof.

51. The method of any one of claims 35-45, wherein the desired alkyl aromatic compound comprises at least one member selected from the group consisting of: ethylbenzene, cumene, mixtures of diethylbenzene isomers, p-diethylbenzene, m-diethylbenzene, mixtures of diisopropylbenzene isomers, p-diisopropylbenzene, m-diisopropylbenzene, and mixtures thereof.

52. The process of any one of claims 35 to 45, wherein the reaction zone comprises one or more acidic zeolite catalysts.

53. The process of any one of claims 35 to 45 wherein said reaction zone comprises one or more acidic zeolite catalysts selected from the group consisting of beta zeolite, Y zeolite, ZSM-5, ZSM-12, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM-68, faujasite, mordenite, zirconium phosphate, and porous crystalline magnesium silicate.

54. A process for producing a desired alkylaromatic from an aromatic feedstock and an olefin feedstock using an acidic zeolite catalyst, wherein:

(a) pretreating the aromatic feedstock and the olefinic feedstock with a pretreatment process comprising at least one pretreatment step selected from the group consisting of distillation, extraction, and selective adsorption to remove or substantially reduce nitrogen compounds that deactivate the acidic zeolite catalyst used in the reaction zone of the plant;

(b) a selective adsorption step using at least one regenerable adsorbent selected from the group consisting of: zeolites, zeolite catalysts, molecular sieves, silicates, alumina, activated carbon, silica gel, and ion exchange resins;

(c) regenerating the spent adsorbent at least twice in situ, said regeneration being accomplished by at least one of the following steps: (i) exposing the spent adsorbent to a flow of inert gas or inert liquid at elevated temperature, (ii) replacing the adsorbed impurities with other compounds that preferentially adsorb onto the adsorbent more strongly than the impurities, and (iii) acid treatment;

(d) the treated aromatic and/or olefinic feedstock is then reacted in a reaction zone to produce the desired alkylaromatic compound; and

(e) the distillation zone is utilized to separate the desired alkylaromatic compound, recover unreacted starting materials and recoverable byproducts, and purge non-recoverable byproducts.