KR101829076B1 - Process for recovering monoalkylbenzene - Google Patents

Abstract

The present invention relates to a process for the production of a gas stream comprising contacting a gas stream comprising oxygen and a monoalkylbenzene with a liquid stream comprising a polyalkylbenzene, a compound comprising two phenyl groups linked together via a C ₁ -C ₃ alkylene bridge, Oxygen and monoalkylbenzenes. ≪ RTI ID = 0.0 > [0002] < / RTI > The present invention also relates to a process for preparing an alkylphenyl hydroperoxide comprising the recovery of the monoalkylbenzene.

Description

PROCESS FOR RECOVERING MONOALKYLBENZENE < RTI ID = 0.0 >

The present invention relates to a process for the recovery of monoalkylbenzenes from a gas stream comprising oxygen and monoalkylbenzenes. In addition, the present invention relates to a process for the preparation of alkyl phenyl hydroperoxides comprising the recovery of said monoalkylbenzenes.

Monoalkylbenzenes can be used in the preparation of alkyl phenyl hydroperoxides. For example, ethylbenzene hydroperoxide can be prepared by oxidation of ethylbenzene with oxygen, including gas, e.g., air. Such oxidation methods are well known in the art. Examples of these are described in US5883268. Another known process for preparing alkyl phenyl hydroperoxides is the oxidation of iso-propyl benzene (cumene) or secondary-butyl benzene with the corresponding alkyl phenyl hydroperoxide using oxygen containing gas.

Cumene hydroperoxide can later be decomposed into phenol and acetone. Ethylbenzene hydroperoxide can later be used for the oxidation of alkenes, such as propene, to produce alkene oxides (oxirane or epoxide), such as propylene oxide, and 1-phenylethanol, methylphenylcarbinol. Methylphenylcarbinol can then be dehydrated to styrene. Both styrene and propylene oxide are valuable market products.

Methods for making linkages of styrene monomer ("SM") and propylene oxide ("PO") are known in the art and are commonly referred to as "SM / PO" or "PO / SM" methods. The SM / PO method is described, for example, in WO200005186. In general, the SM / PO method includes the following steps:

(a) reacting ethylene and benzene to form ethylbenzene;

(b) reacting ethylbenzene with oxygen containing gas to form ethylbenzene hydroperoxide;

(c) reacting ethylbenzene hydroperoxide with propene in the presence of an epoxidation catalyst to form propylene oxide and 1-phenylethanol; And

(d) dehydrating 1-phenylethanol with styrene in the presence of a suitable dehydration catalyst.

During the step (b) of oxidizing ethylbenzene to ethylbenzene hydroperoxide, the ethylbenzene does not react. Most ethylbenzene leaves the oxidation reactor as a solvent for ethylbenzene hydroperoxide. However, a significant portion of ethylbenzene also leaves the oxidation reactor as part of the gas stream containing oxygen. The gas stream comprising oxygen and ethylbenzene can be discarded. However, it would be advantageous to recover valuable ethylbenzene from the gas stream containing oxygen and ethylbenzene and then reuse it for some purpose, for example by recycling the recovered ethylbenzene to the oxidation reactor.

 However, in addition to oxygen and monoalkylbenzenes (such as ethylbenzene) and an inert gas such as nitrogen, the gas stream comprising oxygen, nitrogen and monoalkylbenzenes may contain other contaminants such as methane, water, acetaldehyde, propionaldehyde, Methanol, benzene, and toluene. These other contaminants should not be recovered with the monoalkylbenzene from the gas stream. Therefore, the monoalkylbenzene must be efficiently and selectively recovered from a gas stream comprising oxygen and monoalkylbenzene. Also, at the same time, care should be taken to the presence of oxygen, which is a reactive gas in this recovery and is not an inert gas such as nitrogen.

In general, it is known to absorb organic contaminants by contacting the gas stream with a liquid absorbent from a gas stream comprising oxygen and organic contaminants. For example, WO2002102496 discloses a method for recovering combustible components from a gas stream comprising a combustible component and oxygen by selective absorption of the combustible component in a solvent. The process of WO2002102496 is characterized in that, during absorption, the gaseous phase is dispersed on a continuous liquid of solvent. According to WO2002102496, the solvent (absorbent) may be selected from alcohols, aliphatic and aromatic hydrocarbons, and ketones. Further, in Example 1 of WO2002102496, benzene is referred to as a combustible component. Monoalkylbenzenes such as ethylbenzene are not disclosed in WO20010102496.

No. 5,198,000, on the other hand, discloses a process in which ethylbenzene is referred to as one of the organic compounds that can be removed from a gas stream comprising oxygen and organic contaminants. The method of US Pat. No. 5,198,000 is a method of removing volatile organic compounds from a polluted air stream by contacting the polluted air stream with an absorbent to allow the volatile organic compound to be absorbed by the absorbent. Specific absorbents mentioned in US 5 198 000 are motor oil, vegetable oil, corn oil, mineral oil, olive oil, castor oil, coconut oil, palm oil, peanut oil, safflower oil, soybean oil, tucum oil, linseed oil and cottonseed oil. Corn oil is particularly preferred as the liquid absorbent of the invention of US5198000. According to US 5 198 000, the source of the contaminated air stream can be off-gas, flue gas, etc. produced by air stripping.

It is an object of the present invention to provide a process for the recovery of monoalkylbenzenes from a gas stream comprising oxygen and monoalkylbenzenes, wherein monoalkylbenzenes, as discussed above, take into account the inherent reactivity of oxygen in this gas stream, And is efficiently and selectively recovered from the gas stream. In addition, when the absorbent comprising the absorbed monoalkylbenzene is not used as such in another process, e. G. For the production of monoalkylbenzenes, for example by alkylation of benzene, the absorbent is easily separated from the absorbent Should be selected.

Surprisingly, a gas stream comprising oxygen and monoalkylbenzene is contacted with a liquid stream comprising a polyalkylbenzene, a compound comprising two phenyl groups linked together through a C ₁ -C ₃ alkylene bridge, or a mixture thereof, It has been found that monoalkylbenzene can be recovered from the gas stream in an efficient and selective manner.

Accordingly, the present invention is the oxygen and monoalkyl relates to the recovery of mono-alkyl benzene way from the gas stream containing benzene, wherein oxygen and a gas stream containing monoalkyl benzene polyalkyl benzene, C ₁ -C ₃ alkylene bridge With a liquid stream comprising a compound comprising two phenyl groups that are connected to each other via a linker or a mixture thereof.

It is known from the prior art to recover monoalkylbenzenes from a gas stream using liquid polyalkylbenzenes as absorbents as described above. However, as will be discussed further below, it is also possible to use a gas stream containing oxygen in addition to the monoalkylbenzene to be recovered, such as ethylbenzene or cumene, using alkylbenzene hydroperoxide And is not related to the recovery of the monoalkylbenzene from the gaseous effluent of the oxidizing oxidation process.

An example of a prior art process for recovering monoalkylbenzene from a gas stream using liquid polyalkylbenzene as an absorbent is the process described in GB1036589. GB1036589 was filed long ago in 1962 and relates to the production of ethylbenzene from ethylene and benzene. Pure ethylene or ethylene materials containing a certain amount of inert gas may be used according to GB1036589. For example, in Example 1 of GB1036589, the feed gas to the reactor 12 in which ethylene and benzene reacts comprises 6045 parts of ethylene, about 33 mole percent, the remainder being inert gas, particularly methane and ethane. In other words, the oxygen gas is not supplied to the reactor.

No. GB1036589 also discloses that polyethylbenzene formed as a by-product of the reaction of ethylene with benzene can be used to absorb any ethylbenzene from the off-gas from the reactor. For example, in the polyethylbenzene scrubber 47 from Example 1 of GB1036589, 23 parts (0.3 wt%) of benzene, 249 parts (3.6 wt%) of ethylbenzene and 6727 parts (96.1 wt%) of The gas stream containing the inert material (i.e., from the feed gas to the reactor 12) contained 11 parts (0.3 wt%) ethylbenzene, 3275 parts (82.2 wt%) diethylbenzene, and 698 parts (17.5 wt% ) ≪ / RTI > of triethylbenzene in the opposite direction to the liquid polyethylbenzene-enriched stream. The scrubbed gas leaving through the top of the scrubber 47 still contains 40 parts of ethylbenzene so that only 84 wt% of ethylbenzene is absorbed from the gas stream into the liquid polyethylbenzene-rich stream. The liquid stream containing absorbed ethylbenzene leaving through the bottom of the scrubber 47 is recycled to the reactor so that the absorbed ethylbenzene can be recovered as product rather than being discarded.

Furthermore, GB1036589 discloses that the liquid polyethylbenzene-rich stream fed to the polyethylbenzene scrubber 47 is derived from the polyethylbenzene column 42 as an overhead. As mentioned in GB1036589, the lower portion from the column 42 contains hexaethylbenzene, may contain some less fully alkylated ethylbenzene, and is removed via line 44. [ As mentioned above, the overhead stream from column 42 mainly contains diethylbenzene (82.2 wt.%), While the bottom stream from column 42 necessarily contains the feed stream from GB1036589 (page 2, 121-124 Other known high molecular weight by-products formed in the production of ethylbenzene from ethylene and benzene, such as triethylbenzene, tetraethylbenzene, pentaethylbenzene and 1,2-diphenyl Ethane. According to GB1036589, the downstream stream is not used for any purpose and is simply discarded from the process (also evident from page 1, lines 29-31 of GB1036589).

In the process of the present invention, the monoalkylbenzene is recovered from a gas stream comprising oxygen and monoalkylbenzene. As used herein, "monoalkylbenzene" means benzene substituted by a monoalkyl substituent. The alkyl substituent may be a straight or branched C ₁ -C ₆ alkyl group, preferably a straight or branched C ₁ -C ₄ alkyl group, such as ethyl, iso-propyl and secondary-butyl. When the alkyl substituent is iso-propyl, the monoalkylbenzene is also referred to as cumene rather than iso-propylbenzene. Preferably, the monoalkylbenzene is ethylbenzene.

In addition, in the process of the present invention, a gas stream comprising oxygen and monoalkylbenzene must be contacted with a liquid stream comprising:

(I) a polyalkylbenzene or

(Ii) a compound comprising two phenyl groups linked to each other through a C ₁ -C ₃ alkylene bridge or

(Iii) a mixture comprising said polyalkylbenzene and said diphenyl compound mentioned in (i) and (ii), respectively.

As used herein, "polyalkylbenzene" referred to in (i) above means benzene substituted with 2 to 6 alkyl substituents, preferably 3 to 6 alkyl substituents, most preferably 4 to 6 alkyl substituents. Each alkyl substituent may be the same or different. Preferably, each alkyl substituent is the same. Also, preferably, the alkyl substituents are the same as the alkyl substituent of the monoalkylbenzene. The alkyl substituent may be a straight or branched C ₁ -C ₆ alkyl group, preferably a straight or branched C ₁ -C ₄ alkyl group, such as ethyl, iso-propyl and secondary-butyl. The alkyl substituents may be located ortho, meta and / or para to each. Examples of suitable polyalkylbenzenes include 1,2-dialkylbenzenes, 1,3-dialkylbenzenes, 1,4-dialkylbenzenes, 1,2,3-trialkylbenzenes, 1,2,4- , 1,3,5-trialkylbenzene, 1,2,3,4-tetraalkylbenzene, 1,2,4,5-tetraalkylbenzene, pentaalkylbenzene and hexaalkylbenzene, wherein the alkyl group is ethyl, Iso-propyl or secondary-butyl.

The polyalkylbenzene in the liquid stream may be a mixture of various polyalkylbenzenes. Where the liquid stream comprises a polyalkylbenzene, it may comprise a mixture of one or more of the above-mentioned trialkylbenzenes and one or more of the above-mentioned tetraalkylbenzenes. When the monoalkylbenzene is ethylbenzene and the liquid stream comprises polyalkylbenzene, the liquid stream may comprise a mixture of triethylbenzene and tetraethylbenzene, for example the mixture may be triethylbenzene (s) 1,2,3-triethylbenzene, 1,2,4-triethylbenzene and / or 1,3,5-triethylbenzene, and tetraethylbenzene (s) Benzene and / or 1,2,4,5-tetraethylbenzene.

In this method, the liquid stream in contact with the gas stream comprising oxygen and monoalkylbenzene may comprise a compound comprising two phenyl groups linked to each other through the C ₁ -C ₃ alkylene bridge mentioned in (ii) above . Preferably, said C ₁ -C ₃ alkylene bridge is a C ₂ or C ₃ alkylene bridge, most preferably a C ₂ alkylene bridge. Also, apart from being substituted with the two phenyl groups, the C ₁ -C ₃ alkylene bridge may be further substituted with one or more alkyl groups, preferably methyl and / or ethyl.

Suitable compounds comprising two phenyl groups linked together through a C ₁ alkylene bridge, which may be part of a liquid stream in contact with a gas stream comprising oxygen and monoalkylbenzene, according to the present invention are 1,1-diphenyl Ethane, 2,2-diphenylpropane and 2,2-diphenylbutane. Suitable compounds comprising two phenyl groups linked together through a C ₂ alkylene bridge are 1,2-diphenylethane, 1,2-diphenylpropane and 2,3-diphenylbutane. A suitable compound comprising two phenyl groups linked together through a C ₃ alkylene bridge is 1,3-diphenylbutane.

As mentioned in (iii) above, in the present process, the liquid stream in contact with the gas stream comprising oxygen and monoalkylbenzene is a mixture of the polyalkylbenzene mentioned in (i) and (ii) And mixtures thereof. Preferably, the mixture comprises compounds comprising two phenyl groups connected to one another via trialkylbenzene and / or tetraalkylbenzene, preferably tetraalkylbenzene and C ₂ alkylene bridges, for example the mixture is triethylbenzene and / , Tetraethylbenzene and 1,2-diphenylethane. In said mixture, the triethylbenzene may comprise 1,2,3-triethylbenzene, 1,2,4-triethylbenzene and / or 1,3,5-triethylbenzene. In the mixture, the tetraethylbenzene may include 1,2,3,4-tetraethylbenzene and / or 1,2,4,5-tetraethylbenzene. The liquid stream contains 1 to 20% by weight, preferably 3 to 15% by weight, most preferably 5 to 10% by weight of the polyalkylbenzene and 99 to 80% by weight, preferably 97 to 85% by weight, most preferably 95 To 90% by weight of the diphenyl compound.

As mentioned above, in the first step (a) of the so-called SM / PO process, ethylene and benzene react to form ethylbenzene. In the first step, the polyethylbenzene is formed as a by-product as a result of the multiple alkylation of benzene, resulting in a mixture comprising triethylbenzene and tetraethylbenzene. The additional by-product formed in the first step is the 1,2-diphenylethane mentioned above. As evidenced in the examples below, these by-products, which have a relatively high molecular weight relative to ethylbenzene, can be effectively used in the present invention as absorbers for the selective absorption of ethylbenzene from a gas stream comprising oxygen and ethylbenzene. Therefore, apart from efficient and selective absorption of valuable ethylbenzene, polyethylbenzene and 1,2-diphenylethane, as described by the above-mentioned GB1036589, which are usually disused by-products, (B) in which ethylbenzene and oxygen are reacted with ethylbenzene hydroperoxide in another part of the process (i), that is, to recover the starting material ethylbenzene of step (b) as much as possible. Thus, in the present invention, when the liquid stream comprising polyalkylbenzene comprises polyethylbenzene and / or 1,2-diphenylethane, the liquid stream preferably comprises a process for producing ethylbenzene from ethylene and benzene Lt; / RTI >

The amount of oxygen gas in the gas stream comprising oxygen and monoalkylbenzene to be contacted with the liquid stream in the present process is 1 to 10 wt%, preferably 2 to 8 wt%, more preferably 3 to 7 wt% and most preferably 4 To 6% by weight. Also, the amount of monoalkylbenzene in the gas stream may be in the range of 0.1 to 20 wt%, preferably 0.2 to 15 wt%, more preferably 0.5 to 10 wt% and most preferably 1 to 6 wt%. Nitrogen gas may be present in the gas stream in an amount of 70 to 95 wt%, preferably 80 to 90 wt%. Water may be present in the gas stream in an amount of from 1 to 10% by weight, preferably from 1 to 5% by weight. Other contaminants such as methane, acetaldehyde, propionaldehyde, methanol, benzene and toluene may be present in the gas stream in an amount of less than 0.5% by weight, preferably less than 0.1% by weight.

In order to effect efficient transfer of the monoalkylbenzene from the gas stream to the liquid stream comprising polyalkylbenzene, it is preferred that the gas stream and the liquid stream are in contact in opposite directions. However, the same directional operation is also feasible. If the contact occurs in the opposite direction and in the vertical column, preferably feeds the gas stream to the bottom of the column and the liquid stream to the top of the column. However, a horizontal column may also be used, in which case it is desirable to feed the gas stream to the column at various points in the lower portion, and to supply the liquid stream at one point on either the left or right of the length.

In the present invention, when a vertical column is used as an absorber column, the gas phase can be completely dispersed on a continuous liquid using a bubble column. In the latter case, so-called "liquid-filled" columns are problematic in some cases in absorber columns in which sieve plates are not disposed. However, in the present invention, the vertical absorber column does not have to be completely filled with liquid, and a continuous gas phase and a continuous liquid phase can be simultaneously present therein. In fact, it is desirable to operate a column that is not liquid-filled. The plate can be placed in a vertical absorbent column. Examples of suitable sorbent columns are described in "Mass-Transfer Operations ", Robert E. Treybal, McGraw-Hill Book Company, 1980, pages 139-142 and 158-171. A particular suitable sorbent column, including a sheet, is described in Figure 6.8 on page 159 of that document. Which is incorporated herein by reference.

In the present invention, the temperature in the absorbent column may be 20 to 80 캜, preferably 30 to 70 캜, more preferably 40 to 60 캜. Further, in the present invention, the pressure in the sorbent column may be from 0.1 to 10 bar gauge, preferably from 0.5 to 5 bar gauge, more preferably from 1.5 to 3.5 bar gauge.

The method comprises reacting a liquid stream comprising a monoalkylbenzene and a polyalkylbenzene derived from a gas stream, a compound comprising two phenyl groups linked together through a C ₁ -C ₃ alkylene bridge, or mixtures thereof, and a gas comprising oxygen Get the stream. The liquid stream may be used as such in another process, for example in the preparation of monoalkylbenzenes, for example by alkylation of benzene. It is also possible to separate the liquid stream into a portion comprising a monoalkylbenzene and a portion comprising a polyalkylbenzene, a compound comprising two phenyl groups linked to each other through a C ₁ -C ₃ alkylene bridge, or a mixture thereof . The latter portion can then be used again as the liquid absorbent stream in the present process. The separation can be accomplished, for example, in a distillation column under conditions known to those of ordinary skill in the art. As demonstrated in the examples below, ethylbenzene can be advantageously separated at high yields from a liquid fraction comprising absorbed ethylbenzene, triethylbenzene and 1,2-diphenylethane.

As mentioned above, the gas stream comprising oxygen and the monoalkylbenzene may be derived from a process wherein the monoalkylbenzene is oxidized by oxygen with an alkylphenyl hydroperoxide. The present invention therefore also relates to a process for the preparation of alkyl phenyl hydroperoxides comprising the steps of:

(I) reacting a monoalkylbenzene with an alkylphenylhydroperoxide using a gas comprising oxygen as an oxidizing agent;

(Ii) separating the reaction mixture into a liquid stream comprising alkyl phenyl hydroperoxide and monoalkyl benzene and a gas stream comprising oxygen and monoalkyl benzene;

(Ⅲ) liquid comprising poly alkylbenzene, compound, or a mixture thereof containing two phenyl groups connected to each other through a C ₁ -C ₃ alkylene bridge as described above for the separation of a gas stream containing oxygen and monoalkyl benzene Stream, comprising a liquid stream comprising a monoalkylbenzene and polyalkylbenzene derived from a gas stream, a liquid stream comprising a compound comprising two phenyl groups linked together through a C ₁ -C ₃ alkylene bridge, or mixtures thereof, and oxygen Of the gas stream.

Preferably, between steps (ii) and (iii) mentioned above, most of the monoalkylbenzenes contained in the gas stream comprising oxygen and monoalkylbenzene obtained in step (ii) are, for example, Or by cooling with cooling water in a heat exchanger. In this way, the load of ethylbenzene to be absorbed in the next step (iii) is reduced.

The above-mentioned liquid stream obtained in step (ⅲ) are compounds that through the first portion and polyalkyl benzene, C ₁ -C ₃ alkylene bridge, which preferably comprises mono-alkyl benzene containing two phenyl groups connected to each other, or their Lt; RTI ID = 0.0 > a < / RTI > Preferably, said first portion is recycled to said step (i), advantageously such that said monoalkylbenzene is not lost as a valuable starting material in said step (i). Also preferably, said second portion is recycled to said step (iii), advantageously allowing it to be reused as an absorbent.

In the above-mentioned process for producing an alkylphenyl hydroperoxide, as mentioned above in relation to a method for recovering monoalkylbenzene from a gas stream containing oxygen and monoalkylbenzene in general, preferably, the monoalkylbenzene is ethylbenzene , The alkylphenyl hydroperoxide is ethylbenzene hydroperoxide and the polyalkylbenzene comprises triethylbenzene and / or tetraethylbenzene, preferably tetraethylbenzene, and the C ₁ -C ₃ alkylene bridge The compound containing both phenyl groups to be coupled comprises 1,2-diphenylethane. With respect to step (iii) mentioned above, the above discussion of a method for the recovery of monoalkylbenzenes from a gas stream generally comprising oxygen and monoalkylbenzenes is also referred to. The same preferences apply to step (iii) above.

Regarding the above-mentioned steps (i) and (ii) of the process for producing alkylphenyl hydroperoxide, reference is made to WO2006024655 and WO2008058925 which disclose suitable conditions for carrying out steps (i) and (ii) above. WO2006024655 and WO2008058925 are incorporated herein by reference. Other suitable conditions known to those of ordinary skill in the art can also be applied.

The present invention is further demonstrated by the following examples.

Example

In this embodiment, the configuration as shown in Figure 1 is used to recover ethylbenzene (EB) from a gas stream comprising ethylbenzene, oxygen and nitrogen.

With reference to FIG. 1, it can be seen that the amount of methane, acetaldehyde, propionaldehyde, propionaldehyde, propionaldehyde, and propionaldehyde in the amounts of nitrogen (84 wt.%), Oxygen (5 wt.%), Ethylbenzene (4 wt.%) A gas stream containing methanol, benzene and toluene is fed via line 1 to the bottom of column 10 at a flow rate of 106,000 g / h.

Through line 2, a liquid stream comprising triethylbenzene and 1,2-diphenylethane and a trace amount of EB (0.1 wt%) is fed to the top of the column 10. The gas stream and the liquid stream flow through the column 10 in the opposite direction. By this operation, the EB is absorbed into the liquid stream flowing downward from the upwardly flowing gas stream. The temperature in column 10 is 50 占 폚 and the pressure is 2.5 bar gauge. The EB-depleted gas stream leaves the top of the column 10 and is removed as off-gas through line 3. In addition, the EB-rich liquid stream leaves the bottom of the column 10 and passes through the line 4 to the column 11.

In the column 11, which is a distillation column, the EB-rich liquid stream is heated at a bottom temperature of 250 DEG C and an upper pressure of 0.5 bar gauge. The EB-depleted liquid stream leaves the bottom of the column 11 and is sent to a reboiler (not shown in FIG. 1). And recycles the gas stream from the reboiler to the bottom of the column (11). The liquid stream from the reboiler is passed through a heat-exchanger (not shown in FIG. 1), cooled, and recycled to the column 10 via line 2. A make-up stream comprising triethylbenzene (7 wt%) and 1,2-diphenylethane (93 wt%) is fed via line (5) to line (2). To prevent the increase of high molecular weight contaminants in the liquid absorbent stream, a portion of the liquid stream in line 2 is bleed-streamed through line 6 before entering the top of column 10 .

In addition, the gas stream containing EB leaves the top of the column 11 and passes through the line 7 to the cooler 12. The gas stream from the cooler 12 is removed via line 8 as off-gas. Separates the liquid EB stream from the cooler 12 into a first stream recycled to the top of the column 11 and a second stream removed through the line 9. [

In the table below, the flow rates of EB in the streams of each of the lines (1), (2), (3), (5), (6), (8) and (9) , 2-diphenylethane) is mentioned.

From the above table it can be concluded that the liquid stream comprising triethylbenzene and 1,2-diphenylethane is an excellent absorber for absorbing EB from a gas stream comprising ethylbenzene (EB), oxygen and nitrogen. In the EB introduced into the column 10 of Fig. 1 through line 1, 99.6 wt% of EB is absorbed by the absorbent. Also, in the amount of EB introduced, 99.0 wt% of EB is finally recovered through line 9 after separation of the absorbent from EB in column 11.

Claims (11)

Contacting a gas stream comprising oxygen and monoalkylbenzene with a liquid stream comprising a polyalkylbenzene, a compound comprising two phenyl groups linked together through a C ₁ -C ₃ alkylene bridge, or a mixture thereof, A method of recovering monoalkylbenzene from a gas stream comprising alkylbenzene. The process according to claim 1, wherein the monoalkylbenzene is benzene substituted with an alkyl substituent which is a straight chain or branched C ₁ -C ₄ alkyl group. 3. The process of claim 2 wherein the monoalkylbenzene is ethylbenzene and the liquid stream comprises a mixture comprising triethylbenzene, tetraethylbenzene and 1,2-diphenylethane. 4. The process according to claim 3, wherein the liquid stream is derived from ethylene and benzene from a process for the production of ethylbenzene. 5. A process according to any one of claims 1 to 4, wherein the gas stream and the liquid stream are in contact in opposite directions. 6. The method of claim 5, wherein the gas stream is fed to a lower portion of a vertical column and the liquid stream is fed to an upper portion of the column. 5. A process according to any one of claims 1 to 4, wherein the process comprises reacting monoalkylbenzene and polyalkylbenzene derived from the gas stream, a compound comprising two phenyl groups linked to each other through a C ₁ -C ₃ alkylene bridge or causes a gas stream containing a liquid stream and an oxygen-containing mixtures, the two being connected to each other through a fluid stream portion and polyalkyl benzene, C ₁ -C ₃ alkylene bridge containing a monoalkyl benzene A compound containing a phenyl group, or a mixture thereof. (I) reacting a monoalkylbenzene with an alkylphenylhydroperoxide using a gas comprising oxygen as an oxidizing agent;
(Ii) separating the reaction mixture into a liquid stream comprising alkyl phenyl hydroperoxide and monoalkyl benzene and a gas stream comprising oxygen and monoalkyl benzene;
(Iii) reacting a gas stream comprising oxygen and monoalkylbenzene with at least one of a polyalkylbenzene, two phenyl groups linked together through a C ₁ -C ₃ alkylene bridge, Compounds or mixtures thereof to form monoalkylbenzenes and polyalkylbenzenes derived from the gas stream, compounds comprising two phenyl groups linked together through a C ₁ -C ₃ alkylene bridge, or mixtures thereof RTI ID = 0.0 > a < / RTI > liquid stream comprising oxygen and a gas stream comprising oxygen
≪ / RTI > The method of claim 8 wherein the compound, or containing two phenyl groups connected to each other via the part, and polyalkyl benzene, C ₁ -C ₃ alkylene bridge to the liquid stream obtained in step (ⅲ) include monoalkyl benzene Lt; RTI ID = 0.0 > of: < / RTI > 10. The method of claim 9, wherein the moiety comprising the monoalkylbenzene is recycled to step (i). The method according to claim 9, wherein the portion comprising the polyalkylbenzene, the compound comprising two phenyl groups linked to each other through a C ₁ -C ₃ alkylene bridge, or a mixture thereof is recycled to step (iii).

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