AROMATIC SOLVENTS

PRIORITY CLAIM

[0001] This application claims the benefit of U.S Provisional Application Serial No. 61/821,596 filed May 9, 2013, and priority to EP 13174733.9 filed July 2, 2013, which are incorporated by reference in their entireties.

FIELD OF THE INVENTION

[0002] This invention relates to a process for regeneration of an at least partially spent catalyst, preferably an at least partially spent aromatic alkylation or transalkylation catalyst, and a process for alkylating an alkylatable aromatic compound using the regenerated catalyst, in which the at least partially spent catalyst is subjected to regeneration using an aromatic solvent.

BACKGROUND OF THE INVENTION

[0003] Zeolite and other porous crystalline molecular sieve catalysts are increasingly being used in low temperature, liquid phase aromatic alkylation processes including ethylbenzene, cumene, and linear polyalkylbenzene synthesis. Operation at lower temperatures improves process economics and, in many cases, product selectivity. However, as in all catalytic processes, the catalyst deactivates with time on stream and needs to be regenerated to recover activity. Although molecular sieve catalysts commonly known for use as liquid phase alkylation and transalkylation catalysts, such as MCM-22 and the related molecular sieves MCM-36, MCM-49 and MCM-56, are uniquely resistant to deactivation by coking, when used in liquid phase alkylation and transalkylation processes, they are susceptible to deactivation as a result of poisons, particularly nitrogen and sulfur compounds, in the feeds. The affinity of these compounds for the active sites in the molecular sieve catalyst can cause rapid deactivation by displacing or neutralizing the acid site.

[0004] There have been numerous studies directed at regeneration of spent alkylation catalysts. U.S. Patent No. 2,541,044 discloses catalytic alkylation with simultaneous restoration of the alkylation catalyst activity by contacting the catalyst with an alkylatable hydrocarbon while interrupting the flow of alkylating agent. U.S. Patent No. 3,148, 155 describes removing metal poisons from cracking catalysts by contacting the poisoned catalyst with an aqueous solution of sulfurous acid, a water-soluble salt of sulfurous acid or a water- soluble salt of hyposulfurous acid. U.S. Patent No. 4,418,235 provides aromatic alkylation in the presence of steam to enhance or preserve zeolite catalyst activity. U.S. Patent No. 4,550,090 discloses a method for displacing high molecular weight poisons from ZSM-5 catalysts, such as those used in dewaxing, by in-situ treatment with more easily desorbed compounds such as ammonia or by treatment with alkali or alkaline metal cations to effect ion exchange. U.S. Patent No. 4,276, 149 describes passivating metal contaminants on zeolite cracking catalysts by contacting with steam for limited periods. U.S. Patent No. 4,678,764 provides reactivation of noble metal-containing zeolites poisoned with sulfur oxides by contacting with aqueous acid solutions, e.g., nitric, carbon, acetic and formic acids. U.S. Patent No. 4,319,057 relates to regenerating molecular sieve dehydration materials with methanol or acetone. U.S. Patent No. 5,425,934 teaches treating zeolites with methanol, ethanol or propanol plus nitric or sulfuric acid for the removal of organic templates. U.S. Patent Nos. 4,365,104 and 4,477,585 disclose enhancing para-selectivity of zeolite alkylation catalysts by treatment with hydrogen sulfide or carbon dioxide. U.S. Patent No. 4,490,570 describes para-selective alkylation of a monoalkylbenzene wherein water in the form of steam can be co-fed with the reactants. U.S. Patent No. 5,077,445 provides a process for liquid-phase synthesis of an alkylbenzene, such as ethylbenzene, using MCM-22 zeolite catalyst hydrated with liquid water. U.S. Patent No. 5, 191, 135 discloses preparing long chain alkyl substituted aromatic compounds by alkylating naphthalenes with C6+ alkylating agent in the presence of large pore size zeolite such as USY and MCM-22 in the presence of 0.5 to 3.0 wt.% co-fed water to increase selectivity to monoalkyl-substituted products. U.S. Patent No. 6,911,568 relates to a process for alkylating an aromatic compound using an alkylation catalyst, in which the spent alkylation catalyst is subjected to regeneration by stripping with a Ci-Cs hydrocarbon. U.S. Patent No. 6,878,654 discloses a process for regenerating a spent aromatics alkylation or trans alkylation catalyst comprising a molecular sieve by contacting the spent catalyst with an oxygen-containing gas and then contacting the catalyst with an aqueous medium. U.S. Patent No. 6,909,026 describes a process for liquid phase aromatics alkylation comprising in-situ catalyst reactivation with at least one polar compound having a dipole moment of at least 0.05 Debyes and selected from the group consisting of acetic acid, formic acid, water, and carbon monoxide.

[0005] There remains a need in the art for a process for regenerating catalysts, preferably liquid phase alkylation or trans alkylation catalysts, contaminated by trace quantities of strongly absorbed poisons, by which activity of the at least partially spent catalysts can be restored to a substantial extent of its fresh state, preferably without any significant decrease in its selectivity. It would be especially desirable to reactivate such catalysts in-situ by treatment with species that are introduced along with the liquid phase. It has now been found that contacting the at least partially spent catalysts with an aromatic solvent, preferably under certain alkylation or transalkylation catalyst reactivation conditions, is an effective way to achieve the above objectives. The process would be particularly efficient and convenient when the aromatic solvent used to contact the at least partially spent catalyst is identical to the alkylation feed, which creates great compatibility between the alkylation reaction and regeneration of the catalyst.

SUMMARY OF THE INVENTION

[0006] In one embodiment, the present invention provides a process for regenerating an at least partially spent catalyst, particularly, an aromatic alkylation catalyst or transalkylation catalyst comprising a molecular sieve, the process comprising the step of contacting the at least partially spent catalyst with an aromatic solvent under catalyst reactivation conditions. Preferably, the aromatic solvent is benzene. Preferably, the catalyst reactivation conditions include at least one of the following: (a) a temperature of about 200°C to about 400°C, and (b) a period of at least 24 hours. Preferably, the molecular sieve of the catalyst is at least one of a MCM-22 family molecular sieve, faujasite, mordenite, zeolite beta, and zeolite Y. Preferably, the process further comprises the step of heating the aromatic solvent treated catalyst under flowing nitrogen under at least one of the following conditions: (a) at a temperature of about 500°C to about 600°C, and (b) at a pressure of about 1 atm (101.3 kPa) to about 5 atm (507 kPa).

[0007] In a further embodiment, the present invention encompasses a process for alkylating an alkylatable aromatic compound comprising the step of contacting the alkylatable aromatic compound and an alkylating agent with a regenerated catalyst comprising a molecular sieve under alkylation or transalkylation conditions. The regenerated catalyst was regenerated by a method comprising the step of contacting an at least partially deactivated or spent catalyst with an aromatic solvent under catalyst regeneration conditions. Preferably, the alkylating agent is ethylene or propylene or polyalkylated aromatic compound and the alkylatable aromatic compound is benzene.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0008] Various specific embodiments, and versions of the present invention will now be described, including preferred embodiments and definitions that are adopted herein. While the following detailed description gives specific preferred embodiments, those skilled in the art will appreciate that these embodiments are exemplary only, and that the present invention can be practiced in other ways. Any reference to the "invention" may refer to one or more, but not necessarily all, of the present inventions defined by the claims. The use of headings is for purposes of convenience only and does not limit the scope of the present invention.

[0009] In one embodiment, the present invention relates to a process for the production of a monoalkylated aromatic compound, particularly ethylbenzene or cumene, by the at least partial liquid phase alkylation of an alkylatable aromatic compound with an alkylating agent in the presence of a regenerated alkylation or transalkylation catalyst. More particularly, in another embodiment, the invention is concerned with a process in which, when the alkylation catalyst has become at least partially spent or deactivated, the catalyst is subjected to an in- situ catalyst regeneration step. The at least partially spent or deactivated catalyst, particularly alkylation or transalkylation catalyst, is contacted with an aromatic solvent under suitable conditions which effectively regenerate the catalyst.

[0010] The term "alkylatable aromatic compound" as used herein means an aromatic compound that may receive an alkyl group. One non-limiting example of an alkylatable aromatic compound is benzene.

[0011] The term "alkylating agent" as used herein means a compound which may donate an alkyl group to an alkylatable aromatic compound. Non-limiting examples of an alkylating agent are ethylene, propylene, and butylene. Another non-limiting example is any poly- alkylated aromatic compound that is capable of donating an alkyl group to an alkylatable aromatic compound.

[0012] The term "aromatic" in reference to the alkylatable compounds which are useful herein is to be understood in accordance with its art-recognized scope which includes alkyl- substituted and unsubstituted mono-and polynuclear compounds. Compounds of an aromatic character which possess a heteroatom are also useful, provided they do not act as catalyst poisons under the reaction conditions selected.

[0013] The term "polyalkylated aromatic compound" as used herein means an aromatic compound that has more than one alkyl substituent. A non-limiting example of a polyalkylated aromatic compound is poly-alkylated benzene, e.g., di-ethylbenzene, tri- ethylbenzene, di-isopropylbenzene, and tri-isopropylbenzene. Substituted aromatic compounds which can be alkylated herein must possess at least one hydrogen atom directly bonded to the aromatic nucleus. The aromatic rings can be substituted with one or more alkyl, aryl, alkaryl, alkoxy, aryloxy, cycloalkyl, halide, and/or other groups which do not interfere with the alkylation reaction.

[0014] Suitable aromatic hydrocarbons include benzene, toluene, xylene, naphthalene, anthracene, naphthacene, perylene, coronene and phenanthrene.

[0015] Generally, the alkyl groups which can be present as substituents on the aromatic compound contain from one to about 22 carbon atoms, for example from about one to eight carbon atoms, and in particular from about one to four carbon atoms.

[0016] Suitable alkyl substituted aromatic compounds include toluene, xylene, isopropylbenzene, normal propylbenzene, alpha-methylnaphthalene, ethylbenzene, cumene, mesitylene, durene, p-cyxene, butylbenzene, pseudocumene, o-diethylbenzene, m- diethylbenzene, p-diethylbenzene, isoainylbenzene, isohexylbenzene, pentaethylbenzene, pentamethylbenzene; 1,2,3,4-tetraethylbenzene; 1,2,3,5-tetramethylbenzene; 1,2,4- triethylbenzene; 1 ,2,3-trimethylbenzene, m-butyltoluene; p-butyltoluene; 3,5-diethyltoluene; o-ethyltoluene; p-ethyltoluene; m-propyltoluene; 4-ethyl-m-xylene; dimethylnaphthalene; ethylnaphthalene; 2,3-imethylanthracene; 9-ethylanthracene; 2-methylanthracene; o- methylanthracene; 9, 10 dimethylphenanthrene; and 3-methyl-phenanthrene. Higher molecular weight alkylaromatic hydrocarbons can also be used as starting materials, and these would include aromatic hydrocarbons such as are produced by the alkylation of aromatic hydrocarbons with olefin oligomers. Such products are frequently referred to in the art as alkylate and include hexylbenzene, nonylbenzene, dodecylbenzene, pentadecylbenzene, hexyltoluene, nonyltoluene, dodecyltoluene, and pentadecyltoluene. Very often alkylate is obtained as a high boiling fraction in which the alkyl group attached to the aromatic nucleus varies in size from about Ce to about C ₁₂ . When cumene or ethylbenzene is the desired product, the present process produces acceptably little by-products such as xylenes. The xylenes made in such instances are less than about 500 ppm.

[0017] Reformate containing substantial quantities of benzene, toluene and/or xylene constitutes a particularly useful feed for the alkylation process of this invention.

[0018] The alkylating agents which are useful in the process of this invention generally include any organic compound having at least one available alkylating group capable of reaction with the alkylatable aromatic compound. Preferably, the alkylating group possesses from 1 to 5 carbon atoms or polyalkylated aromatic compounds. Examples of suitable alkylating agents are olefins such as ethylene, propylene, the butenes and the pentenes; alcohols (inclusive of monoalcohols, dialcohols, and trialcohols) such as methanol, ethanol, the propanols, the butanols and the pentanols; aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde and n-valeraldehyde; and, alkyl halides such as methyl chloride, ethyl chloride, the propyl chlorides, the butyl chlorides and the pentyl chlorides.

[0019] Mixtures of light olefins are especially useful as alkylating agents in the alkylation process of this invention. Accordingly, mixtures of ethylene, propylene, butenes and/or pentenes which are major constituents of a variety of refinery streams, e.g., fuel gas, gas plant off-gas containing ethylene and propylene, naphtha cracker off-gas containing light olefins and refinery FCC propane/propylene streams, are useful aklylating agents herein. For example, a typical FCC light olefin stream possesses the following composition:

[0020] Reaction products which may be obtained from the process of the invention include ethylbenzene from the reaction of benzene with ethylene, cumene from the reaction of benzene with propylene, ethyltoluene from the reaction of toluene with ethylene, cymenes from the reaction of toluene with propylene, and sec-butylbenzene from the reaction of benzene and n-butenes.

[0021] The alkylation process of this invention is conducted such that the organic reactants, i.e., the alkylatable aromatic compound and the alkylating agent, are brought into contact with an alkylation catalyst in a suitable reaction zone such as, for example, in a flow reactor containing a fixed bed of the catalyst composition, under effective alkylation conditions. Such conditions include a temperature of from about 0°C to about 500°C, and preferably between about 50°C to about 250°C, a pressure of from about 0.2 to about 250 atmospheres (about 20 to about 25330 kPa), and preferably from about 5 atmospheres (507 kPa) to about 100 atmospheres (10, 133 kPa), a molar ratio of alkylatable aromatic compound to alkylating agent of from about 0.1 : 1 to about 50: 1, and preferably can be from about 0.5: 1 to about 10: 1, and a feed weight hourly space velocity (WHSV) of between about 0.1 and 500 hr ¹ , preferably between 0.5 and 100 hr ¹ .

[0022] The reactants can be in either the vapor phase or the liquid phase and can be neat, i.e., free from intentional admixture or dilution with other material, or they can be brought into contact with the zeolite catalyst composition with the aid of carrier gases or diluents such as, for example, hydrogen or nitrogen. [0023] When benzene is alkylated with ethylene to produce ethylbenzene, the alkylation reaction may be carried out in the liquid phase. Suitable liquid phase conditions include a temperature between 300°F and 600°F (about 150°C and 316°C), preferably between 400°F and 500°F (about 205°C and 260°C), a pressure up to about 3000 psig (20875 kPa), preferably between 400 and 800 psig (2860 and 5600 kPa), a space velocity between about 0.1 and 20 hr ^"1 , preferably between 1 and 6 hr ^"1 , based on the ethylene feed, and a ratio of the benzene to the ethylene in the alkylation reactor from 1 : 1 to 30: 1 molar, preferably from about 1 : 1 to 10: 1 molar.

[0024] When benzene is alkylated with propylene to produce cumene, the reaction may also take place under liquid phase conditions including a temperature of up to about 250°C, e.g., a temperature up to about 150°C, e.g., a temperature from about 10°C to about 125°C; a pressure of about 250 atmospheres (25,330 kPa) or less, e.g., a pressure from about 1 atmospheres (101.3 kPa) to about 30 atmospheres (3039.8 kPa); and an aromatic hydrocarbon weight hourly space velocity (WHSV) of from about 5 hr ^"1 to about 250 hr ^"1 , preferably from 5 hr ^"1 to 50 hr ^"1 .

[0025] The alkylation catalyst comprises a crystalline molecular sieve preferably selected from MCM-22 family molecular sieves, faujasite, mordenite, zeolite beta (described in detail in U.S. Patent No. 3,308,069), and zeolite Y and USY, both of which are a form of faujasite). The term "MCM-22 family molecular sieve" (or "molecular sieve of the MCM-22 family"), as used herein, includes: (i) molecular sieves made from a common first degree crystalline building block "unit cell having the MWW framework topology". A unit cell is a spatial arrangement of atoms which is tiled in three-dimensional space to describe the crystal as described in the "Atlas of Zeolite Framework Types", Fifth edition, 2001 , the entire content of which is incorporated as reference; (ii) molecular sieves made from a common second degree building block, a 2-dimensional tiling of such MWW framework type unit cells, forming a "monolayer of one unit cell thickness", preferably one c-unit cell thickness; (iii) molecular sieves made from common second degree building blocks, "layers of one or more than one unit cell thickness", wherein the layer of more than one unit cell thickness is made from stacking, packing, or binding at least two monolayers of one unit cell thick of unit cells having the MWW framework topology. The stacking of such second degree building blocks can be in a regular fashion, an irregular fashion, a random fashion, and any combination thereof; or (iv) molecular sieves made by any regular or random 2-dimensional or 3- dimensional combination of unit cells having the MWW framework topology. The MCM-22 family molecular sieves are characterized by having an X-ray diffraction pattern including d- spacing maxima at 12.4±0.25, 3.57±0.07 and 3.42±0.07 Angstroms (either calcined or as- synthesized). The MCM-22 family molecular sieves may also be characterized by having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstroms (either calcined or as-synthesized). The X-ray diffraction data used to characterize the molecular sieve are obtained by standard techniques using the K-alpha doublet of copper as the incident radiation and a diffractometer equipped with a scintillation counter and associated computer as the collection system. The MCM-22 family molecular sieves include, but are not limited to, MCM-22 (described in detail in U.S. Patent No. 4,954,325), MCM-49 (described in detail in U.S. Patent No. 5,236,575), MCM-56 (described in detail in U.S. Patent No. 5,362,697), MCM-36 (described in detail in U.S. Patent No. 5,250,277), PSH-3 (described in detail in U.S. Patent No. 4,439,409), SSZ-25 (described in detail in U.S. Patent No. 4,826,667), ERB-1 (described in detail in European Patent No. 0293032), EMM-10 (described in detail in U.S. Patent No. 8, 110,176), EMM-10-P (described in detail in U.S. Patent No. 7,959,899), EMM-12, EMM- 13, UZM-8 (described in detail in U.S. Patent No. 6,756,030), UZM-8HS (described in detail in U.S. Patent No. 7,713,513), ITQ-1 (described in detail in U.S. Patent No. 6,077,498), ITQ-2 (described in detail in International Patent Publication No. WO97/17290), and ITQ-30 (described in detail in International Patent Publication No. WO2005118476). The molecular sieve can be combined in conventional manner with an oxide binder, such as alumina, such that the final alkylation catalyst contains between 2 and 80 wt.% sieve. Alternatively, the molecular sieve can be used in self-bound form that is without a separate oxide binder.

[0026] As the alkylation process of the invention proceeds, the alkylation catalyst will gradually lose its alkylation activity, such that the reaction temperature required to achieve a given performance parameter, for example conversion of the alkylating agent, will increase. According to the invention, when the alkylation catalyst is referred to as a "spent" catalyst, or has become at least partially deactivated, i.e., alkylation activity of the catalyst has decreased by some predetermined amount, typically 5 to 90%, more preferably 20-80% and, most preferably, 40-70%, compared to the initial alkylation activity of the catalyst, the deactivated catalyst is subjected to the regeneration procedure of the present invention.

[0027] The regeneration procedure of the present invention comprises the step of contacting the at least partially spent catalyst with an aromatic solvent under alkylation or transalkylation catalyst reactivation conditions, preferably in liquid phase. The aromatic solvent may be any suitable solvent having an aromatic moiety and capable of regenerating the catalyst. In one or more embodiments, the aromatic solvent may be selected from the group consisting of benzene, toluene, xylene, naphthalene, anthracene, naphthacene, perylene, coronene, phenanthrene and mixtures thereof. Preferably, the aromatic solvent used is benzene. Preferably, the alkylation or transalkylation catalyst reactivation conditions include at least one of the following: (a) a temperature of about 200°C to about 400°C, preferably about 200°C to about 300°C, and (b) a period of at least 24 hours, typically about 24 hours. The reactivation is conveniently carried out at a pressure between about 1 atm and 50 atm and a WHSV between about 0.01 hr ¹ and 50 hr ¹ . Preferably, the regeneration procedure further comprises the step of heating the aromatic solvent treated catalyst under flowing nitrogen under at least one of the following conditions: (a) at a temperature of about 500°C to about 600°C, preferably about 500°C to about 550°C, and (b) at a pressure of about 1 atm (101.3 kPa) to about 5 atm (507 KPa), typically about 1 atm (101.3 kPa).

[0028] Preferably, after contacting with the flowing nitrogen, the catalyst is optionally washed in water or in a water solution comprised of distilled, deionized or demineralized water, and then calcined at a temperature of about 25 to about 600°C for a period of about 10 minutes to about 48 hours.

[0029] The regeneration procedure of the present invention is found to be effective in restoring at least about 70% of the original activity of the catalyst, as levels of the heteroatom poisons, particularly nitrogen, deposited on the at least partially spent catalyst are significantly reduced, without substantial loss in the monalkylation selectivity of the catalyst.

[0030] The process of contacting with the aromatic solvent of the present invention may be repeated a number of times during the lifetime of the alkylation catalyst and, when it fails to achieve the required increase in catalytic activity, the catalyst can be subjected to a conventional air regeneration.

[0031] The alkylation process of the invention is particularly intended to produce monoalkylated aromatic compounds, such as ethylbenzene and cumene, but the alkylation step will normally produce some polyalkylated aromatic compounds. Thus, the process preferably includes the further steps of separating the polyalkylated aromatic compounds from the alkylation effluent and reacting them with additional aromatic feed in a transalkylation reactor over a suitable transalkylation catalyst. The transalkylation catalyst is preferably a molecular sieve which is selective to the production of the desired monoalkylated species and can, for example, employ the same molecular sieve as the alkylation catalyst, such as MCM-22, MCM-49, MCM-36, MCM-56 and zeolite beta. In addition, the transalkylation catalyst may be ZSM-5, zeolite X, zeolite Y, and mordenite, such as TEA-mordenite. [0032] The transalkylation reaction of the invention is conducted in the liquid phase under suitable conditions such that the polyalkylated aromatic compounds react with the additional aromatic feed to produce additional monoalkylated product. Suitable transalkylation conditions include a temperature of about 100°C to about 260°C, a pressure of about 10 bar to about 50 bar (200-600 kPa), a WHSV of about 1 hr ^"1 to about 10 hr ^"1 on total feed, and a benzene/polyalkylated benzene weight ratio of about 1 : 1 to about 6: 1.

[0033] When the polyalkylated aromatic compounds are polyethylbenzenes and are reacted with benzene to produce ethylbenzene, the transalkylation conditions preferably include a temperature of about 220°C to about 260°C, a pressure of about 20 bar (2000 kPa) to about 30 bar (3000 kPa), a WHSV of about 2 hr ^"1 to about 6 hr ^"1 on total feed and a benzene/PEB weight ratio of about 2: 1 to about 6: 1.

[0034] When the polyalkylated aromatic compounds are polyisopropylbenzenes and are reacted with benzene to produce cumene, the transalkylation conditions preferably include a temperature of about 100°C to about 200°C, a pressure of about 20 bar (2000 kPa) to about 30 bar (3000 kPa), a WHSV of about 1 hr ^"1 to 10 hr ^_1 on total feed and a benzene/PIPB weight ratio of about 1 : 1 to about 6: 1.

[0035] As the transalkylation catalyst becomes at least partially deactivated, it may be subjected to the same regeneration process as described above in relation to the alkylation catalyst.

[0036] Exemplary embodiments can include:

1. A process for regenerating an at least partially spent catalyst comprising a molecular sieve, the process comprising the step of contacting the at least partially spent catalyst with an aromatic solvent under catalyst reactivation conditions to form an aromatic solvent-treated catalyst.

2. The process of paragraph 1, wherein contacting the at least partially spent catalyst with the aromatic solvent is conducted in at least partial liquid phase.

3. The process of paragraph 1 or 2, wherein the aromatic solvent is benzene.

4. The process of any of paragraphs 1 to 3, wherein the catalyst reactivation conditions include at least one of the following: (a) a temperature of about 200°C to about 400°C, and (b) a period of at least 24 hours.

5. The process of any of paragraphs 1 to 4, wherein the molecular sieve of the catalyst is at least one of a MCM-22 family molecular sieve, faujasite, mordenite, zeolite beta, and zeolite Y.

6. The process of paragraph 5, wherein the MCM-22 family molecular sieve is at least one of MCM-22, MCM-49, MCM-56, MCM-36, PSH-3, SSZ-25, ERB-1, EMM- 10, EMM- 10-P, EMM-12, EMM- 13, UZM-8, UZM-8HS, ITQ-1, ITQ-2, and ITQ-30.

7. The process of any of paragraphs 1 to 6, further comprising the step of heating the aromatic solvent treated catalyst under flowing nitrogen under at least one of the following conditions: (a) at a temperature of about 500°C to about 600°C, and (b) at a pressure of about 1 atm (101.3 kPa) to about 5 atm (507 kPa) to form a regenerated catalyst.

8. The process of any of paragraphs 1 to 7, wherein the aromatic solvent treated catalyst has at least 70% of the original catalyst activity.

9. A process for alkylating an aromatic compound comprising the steps of:

(a) contacting an alkylatable aromatic compound and an alkylating agent with a catalyst comprising a molecular sieve under alkylation conditions;

(b) when said alkylation catalyst has become at least partially spent, regenerating the catalyst by the process of claim 1.

10. The process of paragraph 9, wherein the step (a) is conducted in at least partial liquid phase.

11. The process of paragraph 9 or 10, wherein the alkylating agent includes an olefinic group having 1 to 5 carbon atoms, or a polyalkylated aromatic compound.

12. The process of any of paragraphs 9 to 11, wherein the alkylating agent is ethylene or propylene and the alkylatable aromatic compound is benzene.

13. A process for alkylating an aromatic compound comprising the steps of:

(a) contacting an alkylatable aromatic compound and an alkylating agent with a catalyst comprising a molecular sieve under alkylation conditions to produce a mono-alkylaromatic compound;

(b) when said alkylation catalyst has become at least partially deactivated, contacting the catalyst with an aromatic solvent at a temperature of about 200°C to about 300°C for a period of about 24 hours; and

(c) heating the aromatic solvent-treated catalyst of step (b) under flowing nitrogen at a temperature of about 500°C to about 550°C at atmospheric pressure to form a regenerated catalyst,

wherein said alkylatable aromatic compound is benzene, the alkylating agent is ethylene, propylene or polyalkylated aromatic compound, the molecular sieve of the catalyst is MCM- 49, and the steps (a) and (b) are both conducted in at least partial liquid phase.

[0037] The invention will now be more particularly described with reference to the following Examples. In the Examples, catalyst performance is demonstrated by reference to activity and selectivity of the catalyst in benzene alkylation with propylene. Catalyst activity was determined by the intrinsic second order rate constant for the formation of cumene under the reaction conditions (temperature 130°C and pressure 2170 kPa). For a discussion of the determination of the kinetic rate constant, reference is directed to "Heterogeneous Reactions: Analysis, Examples, and Reactor Design, Vol. 2: Fluid-Fluid-Solid Reactions" by L.K. Doraiswamy and M.M. Sharma, John Wiley & Sons, New York (1994) and to "Chemical Reaction Engineering" by O. Levenspiel, Wiley Eastern Limited, New Delhi (1972). Catalyst selectivity was determined by the weight ratio of di-isopropyl benzenes produced to cumene produced (DIPB/IPB) and tri-isopropyl benzenes produced to cumene produced (TrilPB/IPB) under the reaction conditions (temperature 130°C and pressure 2170 kPa). Relative levels of heteroatoms, including carbon, nitrogen and sulfur, deposited on the catalyst are also provided in normalized percentages.

EXAMPLE 1

[0038] Benzene alkylation with propylene was first conducted using an MCM-49 (as described in U.S. Patent No. 5,236,575) catalyst with 80 wt.% MCM-49 crystal and 20 wt.% alumina in 1/20" quadrulobe extrudate form. One gram of the catalyst was charged to an isothermal well-mixed Parr autoclave reactor along with a mixture comprising benzene (156 g) and propylene (28 g). The reaction was carried out at 130°C and 2170 kPa for 4 hours. A small sample of the product was withdrawn at regular intervals and analyzed by gas chromatography. The catalyst performance was assessed by a kinetic activity rate constant based on propylene conversion and cumene selectivity at 100% propylene conversion, and is shown in Table 1.

EXAMPLE 2

[0039] Benzene alkylation with propylene was then conducted using spent MCM-49 catalyst. One gram of this spent catalyst was evaluated for benzene alkylation with propylene in the batch test according to the procedure described in Example 1. Levels of heteroatoms deposited on the spent catalyst were normalized to 100%. Activity and cumene selectivity of this spent catalyst at 100% propylene conversion are listed in Table 1.

EXAMPLE 3

[0040] The spent MCM-49 catalyst from Example 2 was then stripped in-situ in benzene at 200°C for 24 hours in the liquid phase. After stripping, the catalyst was heated under flowing nitrogen at 538°C at atmospheric pressure to remove the volatile benzene. One gram of this regenerated catalyst was evaluated for benzene alkylation with propylene in the batch test according to the procedure described in Example 1. Relative levels of heteroatoms deposited on the spent catalyst, activity and cumene selectivity of this spent catalyst at 100% propylene conversion are listed in Table 1.

EXAMPLE 4

[0041] The spent MCM-49 catalyst from Example 2 was then stripped in-situ in benzene at 300°C for 24 hours in the liquid phase. After stripping, the catalyst was heated under flowing nitrogen at 538°C at atmospheric pressure to remove the volatile benzene. One gram of this regenerated catalyst was evaluated for benzene alkylation with propylene in the batch test according to the procedure described in Example 1. Relative levels of heteroatoms deposited on the spent catalyst, activity and cumene selectivity of this spent catalyst at 100% propylene conversion are listed in Table 1.

EXAMPLE 5

[0042] The spent MCM-49 catalyst from Example 2 was then stripped in-situ in benzene at 400°C for 24 hours in the liquid phase. After stripping, the catalyst was heated under flowing nitrogen at 538°C at atmospheric pressure to remove the volatile benzene. One gram of this regenerated catalyst was evaluated for benzene alkylation with propylene in the batch test according to the procedure described in Example 1. Relative levels of heteroatoms deposited on the spent catalyst, activity and cumene selectivity of this spent catalyst at 100% propylene conversion are listed in Table 1.

EXAMPLE 6

[0043] The spent MCM-49 catalyst from Example 2 was then stripped in-situ in benzene at 538°C at atmospheric pressure to remove the volatile benzene. One gram of this regenerated catalyst was evaluated for benzene alkylation with propylene in the batch test according to the procedure described in Example 1. Relative levels of heteroatoms deposited on the spent catalyst, activity and cumene selectivity of this spent catalyst at 100% propylene conversion are listed in Table 1.

Table 1: Characterization of Spent and Hot Benzene Stripped 80 wt.% MCM-49 / 20 wt.% A1 ₂ 0 ₃ Catalyst

(2nd Order Rate

Constant* 1000)

Normalized

DIPB/IPB

Selectivity (to 100% 107% 126% 162% 87% 0 100% for Fresh

Catalyst)

Normalized Tri- IPB/IPB

Selectivity(to 100% 101% 144% 248% 89% 0 100% for Fresh

Catalyst)

Normalized

Carbon Level (to

- 100% 11 1% 113% 203% 370% 100% for Spent

Catalyst)

Normalized

Nitrogen Level

- 100% 81% 72% 64% 36% (to 100% for

Spent Catalyst)

Normalized

Sulfur Level (to

- 100% 80% 100% 98% 35% 100% for Spent

Catalyst)

[0044] As can be seen from Table 1, hot benzene treatment of the spent alkylation catalyst, particularly at a temperature of about 200°C to about 300°C, was effective in restoring activity of the deactivated MCM-49 extrudate, to up to about 85% of its original activity, as nitrogen content of the spent catalyst was remarkably reduced. At temperature exceeding 300°C, the carbon content of the spent catalyst significantly increased with a corresponding loss in catalyst activity. Monoalkylation selectivity of the spent catalyst was not greatly compromised during the regeneration procedure and may also be even improved when the catalyst is optionally washed in water or in a water solution comprised of distilled, deionized or demineralized water, and then calcined at a temperature of about 25°C to about 600°C for a period of about 10 minutes to about 48 hours.

EXAMPLE 7

[0045] The levels of heteroatoms deposited a the spent MCM-22-based catalyst (65 wt.% MCM-22 as described in U.S. Patent No. 4,954,325 and 35 Wt.% A1 ₂ 0 ₃ were normalized to 100% as listed in Table 2.

EXAMPLE 8

[0046] The spent MCM-22-based catalyst from Example 7 was then stripped in-situ in benzene at 200°C for 24 hours in the liquid phase. After stripping, the catalyst was heated under flowing nitrogen at 538°C at atmospheric pressure to remove the volatile benzene. The relative levels of heteroatoms (as compared to the spent catalyst is Example 7) remaining on the regenerated catalyst is listed in Table 2.

EXAMPLE 9

[0047] The spent MCM-22-based catalyst from Example 2 was then stripped in-situ in benzene at 300°C for 24 hours in the liquid phase. After stripping, the catalyst was heated under flowing nitrogen at 538°C at atmospheric pressure to remove the volatile benzene. The relative levels of heteroatoms (as compared to the spent catalyst is Example 7) remaining on the regenerated catalyst is listed in Table 2.

Table 2: Characterization of Spent and Hot Benzene Stripped 65 wt.% MCM-22 / 35 wt.% A1 ₂ 0 ₃ Catalyst

[0048] As can be seen from Table 2, hot benzene treatment of the spent alkylation catalyst, reduced the carbon levels at a temperature of 200°C and above. Hot benzene treatment also exhibited reduced nitrogen and sulfur levels on the spent MCM-22-based catalyst at temperature of 200°C and above.

EXAMPLE 10

[0049] Spent USY-based catalyst (80 wt.% USY as described in U.S. Patent Nos. 3,293, 192 and 3,449,071 and 20 wt.% A1 ₂ 0 ₃ ) was stripped in-situ in benzene at 200°C for 24 hours in the liquid phase. After stripping, the catalyst was heated under flowing nitrogen at 538°C at atmospheric pressure to remove the volatile benzene. The levels of heteroatoms remaining on the regenerated USY-based catalyst is listed in Table 3.

EXAMPLE 11

[0050] Spent USY-based catalyst was stripped in-situ in benzene at 300°C for 24 hours in the liquid phase. After stripping, the catalyst was heated under flowing nitrogen at 538°C at atmospheric pressure to remove the volatile benzene. The levels of heteroatoms remaining on the regenerated USY-based catalyst is listed in Table 3.

EXAMPLE 12

[0051] Spent USY-based catalyst was stripped in-situ in benzene at 400°C for 24 hours in the liquid phase. After stripping, the catalyst was heated under flowing nitrogen at 538°C at atmospheric pressure to remove the volatile benzene. The levels of heteroatoms remaining on the USY-based catalyst is listed in Table 3.

EXAMPLE 13

[0052] Spent USY-based catalyst was then stripped in-situ in benzene at 538°C at atmospheric pressure to remove the volatile benzene. The levels of heteroatoms remaining on the regenerated USY-based catalyst is listed in Table 3.

Table 3: Characterization of Spent and Hot Benzene Stripped 80 wt.% USY / 20 wt.%

A1 ₂ 0 ₃ Catalyst

"wppm" means parts-per-million by weight.

[0053] As can be seen from Table 3, hot benzene treatment of the spent alkylation catalyst reduced the carbon levels on the regenerated catalyst at 300°C as compared to 200°C; however, the carbon levels increased at 400°C and 500°C, respectively, as compared to 200°C and 300°C. The hot benzene treatment reduced nitrogen levels at 400°C and 500°C, respectively, as compared to 200°C and 300°C. Also, the hot benzene treatment reduced sulfur levels at 500°C as compared to 200°C, 300°C and 400°C.

[0054] All documents described herein are incorporated by reference herein, including any priority documents and/or testing procedures. When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. As is apparent from the foregoing general description and the specific embodiments, while forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited thereby.