Patent Description:
The composition of the crude phenols obtained from coal tar is very complicated. For example, the phenols mixture extracted from the fraction with boiling range from <NUM> to <NUM> of one heavy coal tar contained <NUM> types of phenols, most of which have concentrations lower than <NUM> wt% of the whole coal tar, as disclosed <NPL>. Some of these phenols also have very similar boiling points. This makes their separation and purification extremely difficult. In addition, only certain phenols, such as phenol, cresols, xylenols, naphthols and possibly methylnaphthols, have high volumes, have been widely used, and are therefore of economic interest. <CIT> and <CIT> describe a process for making phenol and xylenes from a coal-derived phenol-containing stream. Transalkylation of alkylphenols with benzene/toluene is used to make phenol and alkylbenzenes. The cresol and xylenols in the stream are converted to phenol, and the alkylbenzenes are converted to xylenes. <CIT> discloses a process for making cresols and optionally xylenes.

Transalkylation of propylphenol and benzene/toluene to phenol and alkylbenzenes using different zeolites, including HZSM-<NUM>, HBeta, and HMOR, was described in "<NPL>).

The transalkylation reaction of <NUM>,<NUM>-xylenol and phenol to make cresols occurred using different zeolite catalysts including HZSM-<NUM>, HBeta, and HMOR, was described in "<NPL>. Therefore, there is a need for a method of producing cresol, and optionally xylene, from lower value longer chain alkylphenols in low and medium temperature coal tars.

The Figure illustrates one embodiment of a process according to the present invention.

The process of the disclosure provides a method of producing cresols and optionally xylenes.

The undesirable longer-chain alkylphenols in coal-derived feed streams can be converted to valuable products including, but not limited to, phenol, cresols, and xylenes by transalkylation. The alkylphenols in the coal-derived feed stream can be transalkylated with a reactant (e.g., benzene and/or toluene) to transfer the longer-chain alkyl group (for example, ethyl, propyl, butyl, etc.) to obtain phenol and alkylbenzenes (ethylbenzene, propylbenzene, ethyltoluene, etc.) as products. However, it has been determined that, in some cases, alkylphenols with methyl groups (such as cresols, xylenols, and trimethylphenols) can also be transalkylated with an aromatic compound, but not as easily as longer-chain alkyl groups.

Therefore, new processes have been developed which convert longer chain alkylphenols having two or more carbon atoms, as well as alkylphenols with methyl groups, into cresols. In some processes, xylenes may also be produced.

The process of the disclosure involves transalkylating the longer-chain alkylphenols (i.e., having an alkyl chain with <NUM> or more carbon atoms) with an aromatic solvent such as benzene and/or toluene in a first transalkylation reaction zone to obtain a reaction mixture comprising phenol, cresol, xylenol, trimethylphenol, and alkylbenzenes. Some xylenols and trimethylphenols can also convert under transalkylation to form cresols/phenol in the first transalkylation reaction zone. The remaining xylenols and trimethylphenols are reacted with phenol in a second transalkylation reactor to obtain the desired cresols. The aromatic solvent and alkylbenzene products from the first transalkylation reactor may be sent to an aromatic processing section to produce p-xylene. Unused aromatic solvent may be recycled to the first transalkylation reactor.

By using consecutive transalkylation reactors, the alkylphenols contained in the coal tar feed can be converted to more valuable cresols, and optionally xylenes.

The source of the alkylphenol stream can be a coal-derived feed stream, such as low temperature coal tar, medium temperature coal tar, high temperature coal tar, cresylic acid, or a crude phenolic mixture containing phenol, alkylphenols (methylphenols (cresols), ethylphenols, dimethylphenols (xylenols), propylphenols, butylphenols, methylethylphenols, trimethylphenols etc.), as well as heavier alkylphenols (such as indanols and naphthols). Coal tar is derived from the process of dry distillation and gasification of coal and is classified based on the temperature used for this process (<NUM>-<NUM> (low temperature), <NUM>-<NUM> (medium temperature), and greater than <NUM> (high temperature)). Cresylic acid is a generic term referring to combinations of phenol and alkylphenols, and it can be obtained from either coal or petroleum processing, for example. A crude phenolic mixture can be obtained by the processing of coal tar oils and the purification of phenol containing waste from coke ovens, low temperature carbonization, and hydrogenation plants, for example. The composition of the feed stream will vary depending on its source.

The coal-derived feed stream can be separated into various streams. Suitable separation processes include, but are not limited to, distillation, extraction, solvent extraction, acid and base extraction, adsorption, extractive distillation, crystallization, supercritical fluid extraction, chelation, eutectic reaction, or membrane separation. The crude alkylphenol stream may have a boiling point of about <NUM> or less. For example, the crude alkylphenol stream may comprise a portion of a low or medium temperature coal tar distillate stream having a boiling point of about <NUM> or less.

The separation effluent can optionally be treated to remove contaminants such as nitrogen, sulfur, and other elements. The treated fraction of the effluent can be used as the starting alkylphenol stream for the present process. Other methods of providing the alkylphenol stream could also be used. Optionally, phenol and cresols can be separated from the alkylphenol stream at this step.

The alkylphenol stream from the coal-derived feed stream comprises a complex mixture of alkylphenols comprising one or more methylphenols (cresols), ethylphenols, dimethylphenols (xylenols), trimethylphenols, propylphenols, butylphenols, methylethylphenols, etc.), as well as heavier alkylphenols (such as indanols and napthols).

The alkylphenol stream is transalkylated with benzene or toluene. Transalkylation is a chemical reaction resulting in transfer of an alkyl group from one organic compound to another. In the first transalkylation process, the alkylphenol stream and an aromatic reactant stream comprising one or more of benzene and toluene are provided to the first transalkylation reaction zone. The alkylphenol is transalkylated with benzene and/or toluene to form phenol and/or cresols and alkylbenzene and/or alkyltoluene. Catalysts, particularly zeolite catalysts, are often used to effect the reaction. If desired, the transalkylation catalyst may be metal stabilized using a noble metal or base metal, and may contain suitable binder or matrix material such as inorganic oxides and other suitable materials. The feed is usually heated to reaction temperature and then passed through a reaction zone, which may comprise one or more individual reactors or multiple catalyst beds in a single reactor. Passage of the combined feed through the reaction zone produces an effluent stream comprising unconverted feed and product monoalkylated hydrocarbons.

The transalkylation reaction may take place in any conventional or otherwise convenient manner and may comprise a batch or continuous type of operation, with continuous operation being preferred. The transalkylation catalyst is usefully disposed as a fixed bed in a reaction zone of a vertical tubular reactor, with the alkylaromatic feed stock charged through the bed in an upflow or downflow manner.

Any suitable transalkylation reaction conditions can be used. The transalkylation reaction conditions will depend on the particular reactor type use, as is known in the art. For the transalkylation of alkylphenol with benzene and/or toluene, the temperature is typically in the range of <NUM>-<NUM>, or <NUM>-<NUM>. The transalkylation zone is typically operated at pressures ranging from about <NUM> MPa(g) to <NUM> MPa(g), or <NUM> MPa(g) to <NUM> MPa(g). The WHSV is generally in the range of <NUM> to <NUM> hr-<NUM>, or <NUM> to <NUM> hr-<NUM>.

The catalyst is typically selected to have relatively high stability at a high activity level. Suitable transalkylation catalysts include, but are not limited to zeolites, acidic clay, silica alumina, acidic resins, mixed metal oxides, and the like, as are known in the art.

The molar ratio of benzene and toluene to alkylphenols may be in the range of <NUM>-<NUM>.

The first transalkylation effluent stream may comprise one or more of cresol, phenol, xylenol, trimethylphenol, alkylbenzenes (e.g., xylene, ethylbenzene, and heavy alkylbenzenes (defined as alkylbenzenes containing <NUM> or more carbon atoms)), and alkylphenols having an alkyl chain of <NUM> or more carbon atoms.

The first transalkylation effluent stream is sent to the first transalkylation separation zone to be separated into a transalkylated alkylphenol stream comprising cresol, phenol, xylenol, trimethylphenol, and alkylphenols having an alkyl chain of <NUM> or more carbon atoms, and an aromatic stream comprising benzene, toluene, xylenes, ethylbenzene, and heavy alkylbenzenes.

The transalkylated alkylphenol stream is sent to a second transalkylation reaction zone where xylenols and trimethylphenols are transalkylated with phenol to produce cresol.

Any suitable second transalkylation reaction conditions can be used. The second transalkylation reaction conditions will depend on the particular reactor type use, as is known in the art. For the transalkylation of alkylphenol with phenol, the temperature is typically in the range of <NUM>-<NUM>, or <NUM>-<NUM>. The transalkylation zone is typically operated at pressures ranging from about <NUM> MPa(g) to <NUM> MPa(g), or <NUM> MPa(g) to <NUM> MPa(g). The WHSV is generally in the range of <NUM> to <NUM> hr-<NUM>, or <NUM> to <NUM> hr-<NUM>.

The catalyst is typically selected to have relatively high stability at a high activity level. Suitable transalkylation catalysts include, but are not limited to zeolites, acidic clay, silica alumina, acidic resins, mixed metal oxides, and the like as are known in the art.

The molar ratio of phenol to xylenol/trimethylphenol may be in the range of <NUM> to <NUM>.

The second transalkylation effluent stream comprises cresol, xylenol, trimethylphenol, and unconverted phenol. The second transalkylation effluent stream can be separated into a cresol stream comprising cresol, and a recycle phenol stream comprising xylenol, trimethyl phenol, and unconverted phenol. The cresol stream which is a mixture of cresols can be recovered.

The first and/or second transalkylation processes can be performed in any suitable reactor type, including but not limited to, fixed bed reactors, moving bed reactors, ebullated bed reactors, fluidized bed reactors, continuous catalyst regeneration (CCR) reactors, semi-regenerative reactors, batch reactors, continuous stirred tank (CSTR) reactors, and slurry bed reactors, or combinations thereof.

The cresol stream can be isomerized in a cresol isomerization reaction zone to form a mixed cresol stream. The mixed cresol stream can be separated to recover a specific cresol, such as m-cresol, and a second mixed cresol stream comprising o-cresol and p-cresol. The second mixed cresol stream can then be recycled back to the cresol isomerization reaction zone.

The cresol isomerization reaction conditions typically include a temperature in the range of <NUM> to <NUM>, or <NUM> to <NUM>. The cresol isomerization zone is typically operated at pressures ranging from about <NUM> MPa(g) to <NUM> MPa(g), or <NUM> MPa(g) to <NUM> MPa(g). The WHSV is generally in the range of <NUM> to <NUM> hr-<NUM>, or <NUM> to <NUM> hr-<NUM>.

Any suitable cresol isomerization catalyst can be used. The cresol isomerization catalyst is typically selected to have relatively high stability at a high activity level. Suitable cresol isomerization catalysts include, but are not limited to zeolites, acidic clay, silica alumina, acidic resins, mixed metal oxides, and the like, as are known in the art.

The transalkylated alkylphenol stream can optionally be sent to a phenolic separation zone before it is sent to the second transalkylation reaction zone. The unconverted alkylphenols having an alkyl chain of <NUM> or more carbon atoms can be separated into a recycle stream and recycled to the first transalkylation reaction zone.

The aromatic stream from the first transalkylation reaction zone can be sent to an aromatic separation zone where it is separated into one or more of a recycle stream comprising one or more of benzene and toluene, a heavy alkylbenzene stream comprising heavy alkylbenzenes, and a mixed xylene stream comprising xylenes and ethylbenzene. The recycle stream from the aromatic separation zone can be recycled to the first transalkylation reaction zone.

The mixed xylene stream can be sent to a xylene separation zone to be separated into a second xylene stream comprising ethylbenzene, o-xylene and m-xylene, and a p-xylene stream comprising p-xylene. The p-xylene stream can be recovered. The second xylene stream can be isomerized in a xylene isomerization reaction zone to form an isomerized xylene stream. The isomerized xylene stream can be recycled to the aromatic separation zone.

The xylene isomerization reaction conditions include a temperature is typically in the range of <NUM> to <NUM>, or <NUM> to <NUM>. The xylene isomerization zone is typically operated at pressures ranging from about <NUM> MPa(g) to <NUM> MPa(g), or <NUM> MPa(g) to <NUM> MPa(g). The WHSV is generally in the range of <NUM> to 200hr-<NUM>, or <NUM> to <NUM> hr-<NUM>.

Any suitable xylene isomerization catalyst can be used. Suitable xylene isomerization catalysts include, but are not limited to homogeneous catalysts, such as BF3-HF, and heterogeneous catalysts, such as amorphous silica alumina, zeolites or metal promoted zeolites. The catalyst is typically selected to have relatively high stability at a high activity level.

The heavy alkylbenzene stream can be sent to a heavy alkylbenzene dealkylation reaction zone and/or a heavy alkylbenzene transalkylation reaction zone to make benzene, toluene, and xylenes as the main products. The treated heavy alkylbenzene stream can be sent to the aromatic separation zone.

The heavy alkylbenzene dealkylation reaction conditions include a temperature is typically in the range of <NUM> to <NUM>, or <NUM> to <NUM>. The heavy alkylbenzene dealkylation zone is typically operated at pressures ranging from about <NUM> MPa(g) to <NUM> MPa(g), or <NUM> MPa(g) to <NUM> MPa(g). The WHSV is generally in the range of <NUM> to <NUM> hr-<NUM>, or <NUM> to <NUM> hr-<NUM>. Any suitable heavy alkylbenzene dealkylation catalyst can be used. The catalyst is typically selected to have relatively high stability at a high activity level. Suitable heavy alkylbenzene dealkylation catalysts include, but are not limited to zeolites, acidic clay, silica alumina, acidic resins, mixed metal oxides, and the like, as are known in the art.

The heavy alkylbenzene transalkylation reaction conditions include a temperature is typically in the range of <NUM> to <NUM>, or <NUM> to <NUM>. The heavy alkylbenzene transalkylation is typically operated at pressures ranging from about _ <NUM> MPa(g) to <NUM> MPa(g), or <NUM> MPa(g) to <NUM> MPa(g). The WHSV is generally in the range of <NUM> to <NUM> hr-<NUM>, or <NUM> to <NUM> hr-<NUM>. Any suitable heavy alkylbenzene transalkylation catalyst can be used. The catalyst is typically selected to have relatively high stability at a high activity level. Suitable heavy alkylbenzene transalkylation catalysts include, but are not limited to zeolites, acidic clay, silica alumina, acidic resins, mixed metal oxides, and the like as are known in the art.

One aspect of the invention is a process for producing cresol. In one embodiment, the process comprises: providing an alkylphenol stream comprising alkylphenol; transalkylating the alkylphenol stream and a reactant stream comprising one or more of benzene and toluene in a first transalkylation reaction zone under first transalkylation reaction conditions in the presence of a first transalkylation catalyst to produce a first transalkylation effluent stream comprising at least one of phenol, cresol, xylenol, trimethylphenol, benzene, toluene, xylenes, ethylbenzene, heavy alkylbenzenes, and alkylphenol having an alkyl chain of <NUM> or more carbon atoms; separating the first transalkylation effluent stream in a first transalkylation separation zone into a transalkylated alkylphenol stream comprising at least one of the phenol, the cresol, the xylenol, the trimethylphenol, and the alkylphenol having the alkyl chain of <NUM> or more carbon atoms, and an aromatic stream comprising benzene, toluene, xylenes, ethylbenzene, and heavy alkylbenzenes; transalkylating at least a portion of the transalkylated alkylphenol stream with phenol in a second transalkylation reaction zone under second transalkylation reaction conditions in the presence of a second transalkylation catalyst to produce a second transalkylation effluent stream comprising cresol, and at least one of the unconverted phenol, xylenol, and trimethylphenol; and recovering a cresol stream comprising the cresol.

In some embodiments, the process of the invention further comprises separating the transalkylated alkylphenol stream in a phenolic separation zone into a first phenolic stream comprising the phenol, the cresol, the xylenol, and the trimethylphenol, and a second stream comprising the alkylphenols having the alkyl chain of <NUM> or more carbon atoms; and recycling the second stream to the first transalkylation reaction zone; wherein the at least a portion of the transalkylated alkylphenol stream comprises the first phenolic stream.

In some embodiments, recovering the cresol stream comprises separating the second transalkylation effluent stream in a second transalkylation separation zone into the cresol stream and a recycle phenol stream comprising the phenol, the xylenol, and the trimethylphenol; and recycling the recycle phenol stream to the phenolic separation zone located between the first and second transalkylation reaction zone.

In some embodiments, the process further comprises separating the aromatic stream in an aromatic separation zone into at least a recycle stream comprising one or more of benzene and toluene, a heavy alkylbenzene stream comprising the heavy alkylbenzene, and a mixed xylene stream comprising the xylene and ethylbenzene; separating the mixed xylene stream in a xylene separation zone into a second xylene stream comprising ethylbenzene, o-xylene and m-xylene, and a p-xylene stream comprising p-xylene; isomerizing the second xylene stream in a xylene isomerization reaction zone under xylene isomerization reaction conditions in the presence of a xylene isomerization catalyst to form a xylene isomerization effluent stream comprising mixed xylenes; recycling the xylene isomerization effluent stream to the aromatic separation zone; and recovering the p-xylene stream.

In some embodiments, the process further comprises at least one of: dealkylating the heavy alkylbenzene stream in a dealkylation reaction zone under dealkylation conditions in the presence of a dealkylation catalyst; and transalkylating the heavy alkylbenzene stream in a transalkylation reaction zone under transalkylation conditions in the presence of a transalkylation catalyst to form a treated heavy alkylbenzene effluent stream.

In some embodiments, the process further comprises recycling the treated heavy alkylbenzene effluent stream to the aromatic separation zone; and recycling the recycle stream from the aromatic separation zone to the first transalkylation reaction zone.

In some embodiments, the process further comprises isomerizing the cresol stream in a cresol isomerization reaction zone under cresol isomerization reaction conditions in the presence of a cresol isomerization catalyst to form a cresol isomerization effluent stream comprising mixed cresol; and recovering a m-cresol stream from the mixed cresol isomerization effluent stream.

In some embodiments, the process further comprises recycling the mixed cresol stream to the cresol isomerization reaction zone.

In some embodiments, the process further comprises separating a feed stream comprising alkylphenol into at least the alkylphenol stream comprising alkylphenols and a cresol stream comprising cresols; and introducing the cresol stream into the cresol isomerization zone.

In some embodiments, the process further comprises: treating the alkylphenol stream for removal contaminants such as nitrogen, sulfur, and other elements before introducing the alkylphenol stream into the first transalkylation zone.

In some embodiments, providing the alkylphenol stream comprises: providing a coal-derived feed stream to a first separation zone; and separating the coal-derived feed stream in the first separation zone into the alkylphenol stream and at least one of a first phenol stream comprising phenol and a first cresol stream comprising cresol.

In some embodiments, separating the coal-derived feed stream comprises separating the coal-derived feed stream by one or more of distillation, extraction, solvent extraction, acid and base extraction, adsorption, extractive distillation, crystallization, supercritical fluid extraction, chelation, eutectic reaction, or membrane separation.

In some embodiments, the coal-derived feed stream comprises a portion of a low temperature coal tar stream, a medium temperature coal tar stream, a high temperature coal tar stream, a cresylic acid stream, or a crude phenolic mixture.

In some embodiments, the first transalkylation reaction conditions or the second transalkylation reaction conditions or both comprise one or more of: a temperature in a range of <NUM> to <NUM>; a pressure in a range of <NUM> MPa(g) to <NUM> MPa(g); and a WHSV in a range of <NUM> to <NUM> hr-<NUM>.

In some embodiments, the process further comprises; introducing a phenol stream comprising phenol into the second transalkylation reaction zone.

In some embodiments, transalkylating the alkylphenol stream and the reactant stream takes place in the presence of hydrogen, nitrogen, or a combination thereof in the first transalkylation reaction zone.

In some embodiments, transalkylating the at least the portion of the transalkylated alkylphenol stream with the phenol takes place in the presence of hydrogen, nitrogen, steam or a combination thereof in the second transalkylation reaction zone.

In some embodiments, the first transalkylation catalyst comprises a heterogeneous acid catalyst, wherein the second transalkylation catalyst comprises a heterogeneous acid catalyst, or both.

In some embodiments, at least one of the first transalkylation reaction zone and the second transalkylation reaction zone comprises a fixed bed reactor, a moving bed reactor, an ebullated bed reactor, a fluidized bed reactor, a continuous catalyst regeneration (CCR) reactor, a semi-regenerative reactor, a batch reactor, a continuous stirred tank (CSTR) reactor, a slurry reactor, or combinations thereof.

In some embodiments, the process further comprises separating a feed stream comprising alkylphenol into at least the alkylphenol stream comprising alkylphenols and a phenol stream comprising phenols; and introducing the phenol stream into the second transalkylation zone.

The Figure is an illustration one embodiment a process <NUM> according to the present invention.

The coal-derived feed stream <NUM> is sent to a first separation zone <NUM>, such as a distillation column. The coal-derived feed stream <NUM> may be filtered and have water removed before being sent to the first separation zone <NUM> (not shown). The coal-derived feed stream is separated into stream <NUM> of hydrocarbons having a boiling point less than about <NUM> and stream <NUM> of hydrocarbons having a boiling point greater than about <NUM>.

The phenolic compounds are found in stream <NUM>. Stream <NUM> is sent to a second separation zone <NUM>, such as an extraction zone, where it is separated into a fraction <NUM> containing the alkylphenol compounds and stream <NUM> containing the non-phenolic and heavy phenolic compounds.

The fraction <NUM> is sent to treating zone <NUM> to remove the contaminants forming an alkylphenol stream <NUM> comprising alkylphenol. Optionally, phenol and cresols can be separated at this point in a third separation zone <NUM> and be sent to the second transalkylation reaction zone (stream <NUM> comprising phenol) and cresol separation zone (stream <NUM> comprising cresol), respectively.

The alkylphenol stream <NUM> is sent to the first transalkylation reaction zone <NUM> along with a reactant stream <NUM> comprising benzene and/or toluene. The first transalkylation reaction zone <NUM> contains a first transalkylation catalyst. The first transalkylation effluent stream <NUM> comprising phenol, cresol, xylenol, trimethylphenol, benzene, toluene, xylene, ethylbenzene, heavy alkylbenzene, and unconverted alkylphenol having an alkyl chain of <NUM> or more carbon atoms.

The first transalkylation effluent stream <NUM> is sent to a first transalkylation separation zone <NUM> where it is separated into a transalkylated alkylphenol stream <NUM> and an aromatic stream <NUM>. The transalkylated alkylphenol stream <NUM> comprises phenol, cresol, xylenol, trimethylphenol, and the unconverted alkylphenol having an alkyl chain having <NUM> or more carbon atoms. The aromatic stream <NUM> comprises benzene, toluene, xylene, ethylbenzene, and heavy alkylbenzene.

The transalkylated alkylphenol stream <NUM> is sent to a phenolic separation zone <NUM> where it is separated into a first phenolic stream <NUM> and a second stream <NUM>. The first phenolic stream <NUM> comprises phenol, cresol, xylenol, and trimethylphenol.

The second stream <NUM> comprises unconverted alkylphenol having an alkyl chain having <NUM> or more carbon atoms, such as ethylphenol, propylphenol, and butylphenol. The second stream <NUM> is recycled to the first transalkylation reaction zone <NUM>.

The first phenolic stream <NUM> is sent to a second transalkylation reaction zone <NUM> along with an optional phenol stream <NUM>, and optionally phenol from stream <NUM>. The second transalkylation reaction zone <NUM> comprises a second transalkylation catalyst. The second transalkylation effluent stream <NUM> comprises cresol, and unconverted phenol, xylenol, and trimethylphenol.

The second transalkylation effluent stream <NUM> is sent to a second transalkylation separation zone <NUM> where it is separated into a cresol stream <NUM> comprising cresol and a recycle phenol stream <NUM> comprising the unconverted phenol, xylenol, trimethylphenol. The recycle phenol stream <NUM> is recycled to the phenolic separation zone <NUM>.

Cresol stream <NUM> can be recovered. Optionally, cresol stream <NUM> can be sent to a cresol isomerization reaction zone <NUM> to obtain a cresol product stream <NUM>. The cresol product stream <NUM> and optionally cresol stream <NUM> can be separated in a cresol separation zone <NUM> to obtain a stream <NUM> comprising a specific cresol, such as m-cresol, and a mixed cresol stream <NUM> comprising the remaining cresols. Optionally the mixed cresol stream <NUM> can be recycled back to the cresol isomerization reaction zone <NUM>.

The aromatic stream <NUM> from the first transalkylation separation zone <NUM>, which comprises benzene, toluene, xylene, ethylbenzene, and heavy alkylbenzene, is sent to an aromatic separation zone <NUM>. The aromatic stream <NUM> is separated into a recycle stream <NUM>, a heavy alkylbenzene stream <NUM>, and a mixed xylene stream <NUM>.

The recycle stream <NUM>, which comprises benzene and/or toluene, can be recycled to the first transalkylation reaction zone <NUM>.

The heavy alkylbenzene stream <NUM>, which comprises heavy alkylbenzene, can be sent to a dealkylation and/or transalkylation reaction zone <NUM>. The treated heavy alkylbenzene stream <NUM> is sent to the aromatic separation zone <NUM>.

The mixed xylene stream <NUM>, which comprises a mixture of xylenes, may be sent to a xylene isomerization zone <NUM>. The xylene isomerization effluent <NUM> is sent to a xylene separation zone <NUM> where it is separated into a p-xylene stream <NUM> and a second mixed xylene stream <NUM>. The second mixed xylene stream <NUM>, which comprises o-xylene, m-xylene, and ethylbenzene, is sent to the aromatic separation zone <NUM>. The p-xylene stream <NUM> can be recovered.

As used herein, the term "zone" can refer to an area including one or more equipment items and/or one or more sub-zones. Equipment items can include one or more reactors or reactor vessels, heaters, exchangers, pipes, pumps, compressors, and controllers, columns, and the like. Additionally, an equipment item, such as a reactor, dryer, or vessel, can further include one or more zones or sub-zones.

As depicted, process flow lines in the figures can be referred to, interchangeably, as, e.g., lines, pipes, branches, distributors, streams, effluents, feeds, products, portions, catalysts, withdrawals, recycles, suctions, discharges, and caustics.

Claim 1:
A process for producing cresol comprising:
providing an alkylphenol stream comprising alkylphenol;
transalkylating the alkylphenol stream and a reactant stream comprising one or more of benzene and toluene in a first transalkylation reaction zone under first transalkylation reaction conditions in the presence of a first transalkylation catalyst to produce a first transalkylation effluent stream comprising at least one of phenol, cresol, xylenol, trimethylphenol, benzene, toluene, xylenes, ethylbenzene, heavy alkylbenzenes, and alkylphenol having an alkyl chain of <NUM> or more carbon atoms;
separating the first transalkylation effluent stream in a first transalkylation separation zone into a transalkylated alkylphenol stream comprising at least one of the phenol, the cresol, the xylenol, the trimethylphenol, and the alkylphenol having the alkyl chain of <NUM> or more carbon atoms, and an aromatic stream comprising benzene, toluene, xylenes, ethylbenzene, and heavy alkylbenzenes;
transalkylating at least a portion of the transalkylated alkylphenol stream with phenol in a second transalkylation reaction zone under second transalkylation reaction conditions in the presence of a second transalkylation catalyst to produce a second transalkylation effluent stream comprising cresol, and at least one of the unconverted phenol, xylenol, and trimethylphenol; and
recovering a cresol stream comprising the cresol.