WO2012074194A2

WO2012074194A2 - Method for preparing alpha methyl styrene

Info

Publication number: WO2012074194A2
Application number: PCT/KR2011/007488
Authority: WO
Inventors: Seung-Back Ha; Suk-Joon Yoo; Dong-Hyun Cho
Original assignee: Lg Chem, Ltd.
Priority date: 2010-12-01
Filing date: 2011-10-10
Publication date: 2012-06-07
Also published as: KR20120059875A; CN103052611B; CN103052611A; JP5635696B2; JP2013535484A; WO2012074194A3; KR101403517B1

Abstract

This disclosure relates to a method of preparing alpha methyl styrene that may lower explosion risk during a hydrogenation reaction of cumene hydroperxoide due to increase in concentration, improve selectivity to 90% or more to increase the amount to cumyl alcohol thus selectively increasing the amount of alpha methyl styrene, and control the amount of cumene hydroperoxide to control the production amount of alpha methyl styrene according to market demand, through a selective hydrogenation process of cumene hydroperoxide obtained by oxidation of cumene during a phenol preparation process under maximally stabilized conditions of low concentration and temperature.

Description

[TITLE OF THE INVENTION]

METHOD FOR PREPARING ALPHA METHYL STYRENE

[TECHNICAL FIELD]

This disclosure relates to a method of preparing alpha methyl styrene for selectively increasing production of alpha methyl styrene.

[BACKGROUND OF ART]

Alpha-methyl styrene (AMS) is variously used as an additive in the preparation of a specific copolymer such as ABS and novel polymer. And, it may be used as an intermediate in the preparation of unsaturated AMS dimer. The dimer is used as a molecular weight control agent in the preparation of a copolymer such as acrylonitrile-butadiene-styrene resin and styrene-butadiene rubber. The hydrogenated form of the AMS dimer may have an industrial value as an ingredient of a lubricant composition.

The AMS is produced as a by-product of a phenol preparation process, and in general, phenol and AMS are prepared through an oxidation and dehydration processes using cumene as raw material. Fig. 1 is a process flow diagram schematically showing the conventional phenol preparation process.

Referring to Fig. 1 , according to the conventional method, cumene is oxidized in the presence of oxygen in an oxidation reactor (1) to which cumene is supplied so as to prepare a stream of about 24 wt% of cumene hydroperoxide (CHP) and a small amount of converted cumyl alcohol (CA), which is transferred to a receiver (2), and then, the stream containing about 24 wt% of CHP is concentrated in a stripper (3). And then, the stream containing concentrated CHP and CA is passed through a receiver (4) and supplied to a cleavage reactor (5) so as to dehydrate in the presence of an acid catalyst, thereby producing phenol and acetone from CHP and producing alpha methyl styrene (AMS) from CA. However, according to the above method, only 0.035 mol% of CA is produced per 1 mole of CHP in the oxidation process of cumene, and thus, AMS production amount in the phenol preparation process is limited by a very small amount of cumyl alcohol produced by the cumene oxidation process. Thus, studies for selectively increasing AMS production have been progressed, and a method of increasing AMS production by selectively converting a part of CHP coming from the stripper into CA before the cleavage reactor has been suggested. However, this method has decreased process efficiency due to low conversion rate and selectivity, and has a problem in terms of safety due to use of highly concentrated CHP.

Further, a method of converting AMS into cumene again has been disclosed for recycling into an oxidation reactor instead of increasing AMS production (US Patent No. 5,905,178). And, there has been an attempt to minimize AMS production (US Patent No. 5,530,166), but studies on increasing AMS production are insufficient.

[SUMMARY OF THE INVENTION]

Accordingly, the present invention provides a method of preparing alpha methyl styrene using additives such as ABS, and the like, for the purpose of selectively increasing production of AMS which has been considered as a by-product in a phenol preparation process, through a selective hydrogenation process of cumene hydroperoxide to cumyl alcohol.

The present invention also provides a method of preparing alpha methyl styrene that may control the production amount of AMS according to market demand by controlling the amount of cumene hydroperoxide stream introduced in a hydrogenation process.

The present invention also provides a method of preparing alpha methyl styrene that may stably prepare cumyl alcohol by progressing hydrogenation of low concentration of cumene hydroperoxide stream to exclude a possibility of ignition of cumene hydroperoxide, thus ultimately increasing production of AMS.

The present invention provides a method of preparing alpha methyl styrene comprising:

(a) oxidizing cumene to prepare a cumene hydroperoxide stream;

(b) separating at least of the cumene hydroperoxide stream without concentration and selectively hydrogenating it in the presence of a noble metal catalyst so as to prepare cumyl alcohol; and (c) concentrating the reactant including the cumyl alcohol and dehydrating it in the presence of an acid catalyst so as to prepare a product including alpha methyl styrene.

In the step (b), the cumene hydroperoxide stream may be used in the hydrogenation reaction in the concentration of about 5 to 25 wt%. And, in the step (b), about 5 to 50 wt% of the cumene hydroperoxide stream may be separated and used in the hydrogenation reaction. The cumene hydroperoxide streatm further comprises cumyl alcohol.

According to the method of the present invention, selectivity of the hydrogenation reaction may be 95% or more, and conversion rate of cumene hydroperoxide may be about 95% or more.

And, in the step (b), a part of the cumene hydroperoxide stream is subjected to a hydrogen reaction, and in the step (c), the product including cumyl alcohol may further comprise cumene hydroperoxide stream which is not subjected to a hydrogenation reaction. And, in the step (c), the product including alpha methyl styrene may further comprise phenol and acetone. And, the product including cumyl alcohol may be concentrated to a concentration of 80 to 82 wt% and used in the dehydration reaction. The method may further comprise neutralizing the product including alpha methyl styrene and distilling it, after the step (c), in order to obtain alpha methyl styrene, phenol and acetone.

[BRIEF DESCRIPTION OF THE DRAWINGS]

Fig. 1 is a process flow diagram schematically showing the conventional phenol preparation process.

Fig. 2 schematically shows a phenol process flow diagram for producing alpha methyl styrene according to the present invention.

[DESCRIPTION OF THE MARKS]

1, 10: oxidation reactor

2, 4, 20, 50: receiver

30: catalytic hydrogenation reactor 3, 40: stripper

5, 60: cleavage reactor

6, 70: neutralizer reactor

7, 80: distillation apparatus

[DETAILED DESCRIPTION OF THE EMBODIMENTS]

Hereinafter, a method of preparing alpha methyl styrene according to specific embodiments will be explained.

In a general phenol process, about 24 ~ 25 wt% of a cumene hydroperoxide (CHP) solution prepared through 3 oxidation reactors are passed through a stripper and concentrated into a CHP solution of about 80 ~ 82 wt%, and then, passed through a cleavage reactor and produced into phenol, acetone and AMS.

However, cumene hydroperoxide is explodable when mixed with air, and has an ignition point of about 57 to 79 ^°C . Further, there are risks of explosion and fire when it contacts with organic material, acid, base and metal ingredients. And, it has been reported that as the concentration of cumene hydroperoxide increases, a runway reaction temperature decreases and thus a risk of explosion increases (Thermochimica acta, 501, 2010, 65-71). Accordingly, there is a need for a method of stably performing a phenol process without using high concentration of cumene hydroperoxide.

Thus, it is very important that a conversion process of cumene hydroperoxide should be performed under maximum stabilized conditions, i.e., lower concentration of cumene hydroperoxide and low temperature.

In the existing oxidation process of cumene, only about 0.035 mole% of cumyl alcohol is produced per 1 mole of cumene hydroperoxide, and thus there is a limitation in increasing production of alpha methyl styrene.

Accordingly, the present invention provides a process of producing cumyl alcohol under stabilized condition using low concentration of cumene hydroperoxide. The present invention also provides a method of increasing production of cumyl alcohol through a hydrogenation process of cumene hydroperoxide into cumyl alcohol, and then, dehydrating the cumyl alcohol to ultimately increase production of alpha methyl styrene.

According to one preferred embodiment of the invention, provided is a method of preparing alpha methyl styrene comprising: (a) oxidizing cumene to prepare a cumene hydroperoxide stream; (b) separating at least of the cumene hydroperoxide stream without concentration and selectively hydrogenizing it in the presence of a noble metal catalyst so as to prepare cumyl alcohol; and, (c) concentrating the reactant including the cumyl alcohol and dehydrating it in the presence of an acid catalyst so as to prepare a product including alpha methyl styrene.

According to the method of the present invention, since a part of cumene hydroperoxide obtained after the oxidation of cumene is separated in a low concentration state before concentration and used in a catalytic hydrogenation process instead of concentrating a cumene hydroperoxide stream obtained by the oxidation of cumene in a stripper and then progressing a dehydration reaction in a cleavage reactor, selectivity and conversion rate into cumyl alcohol may be improved.

Therefore, since the present invention converts cumene hydroperoxide into cumyl alcohol in a low concentration stability-secured area during the production process, more excellent results may be exhibited than the existing process. Specifically, the present invention does not use a cumene hydroperoxide stream which is passed through a stripper and enters into a cleavage reactor as a reactant of a hydrogenation reaction, but use cumene hydroperoxide after oxidation of cumene, thus securing stability of the process.

According to the present invention, a cumene hydroperoxied stream of the concentration of 5 to 25 wt% is produced through the (a) step. And, a small amount of cumyl alcohol may be included in the stream through the oxidation of cumene.

The oxidation conditions of the step (a) are not specifically limited, and it may be progressed under general conditions. For example, the oxidation of cumene may be progressed by the auto-oxidation by oxygen containing gas such as air or concentrated oxygen air, and the like. The oxidation reaction may be performed using an additive such as alkali or without an additive. The oxidation reaction temperature may be commonly about 50~200^°C , and the reaction pressure may be about 5MPa. As the additives, an alkali metal compound such as NaOH, OH; an alkali earth metal compound; an alkali metal carbonate such as Na₂C0₃, NaHC0₃; ammonia; alkali metal ammonium carbonate, and the like may be used.

In the step (a), the oxidation of cumene may be progressed through a plurality of oxidation reactors, preferably 3 oxidation reactors commonly used in a phenol process. And, the step (a) may comprise oxidizing a cumene containing stream having a cumene concentration of about 80% or more, preferably about 98% or more in the presence of an oxygen containing stream so as to form a cumene hydroperoxide containing stream.

Further, a common initiator may be used to promote the oxidation of cumene, and for example, an organic hydroperoxide such as cumene hydroperoxide, t-butyl hydroperoxide, and the like, a peroxy type free radical initiator, or an azo type free radical initiator, and the like may be used.

In the step (b), the cumene hydroperoxide stream obtained in the step (a) is hydrogenated to increase the content of cumyl alcohol.

For this, in the step (b), a part of the cumene hydroperoxide stream is hydrogenated. It is preferable to separate about 5 to 50 wt% of the cumene hydroperoxide stream to hydrogenate it.

The noble metal catalyst used in the hydrogenation reaction may include at least one selected from the group consisting of gold, silver, platinum, palladium, iridium, ruthenium, rhenium, rhodium, and osmium. The noble metal catalyst may further include a support selected from the group consisting of alumina, silica, clay, carbon, zirconia, titania, a mseoporous molecular sieve, and a combination thereof.

The noble metal catalyst may be used in an amount of about 1 to 15 parts by weight, preferably about 2 to 12 parts by weight, more preferably about 5 to 10 parts by weight, based on 100 parts by weight of the cumene hydroperoxide stream. If the amount of the noble metal catalyst is less than 1 part by weight, conversion rate may be decreased, and if it exceeds about 15 parts by weight, selectivity may be lowered.

The hydrogenation may be preferably conducted at a temperature of from about 40 to 80 ^°C , hydrogen flow rate of about 1 : 1 to about 1 :10 according to mole ratio to CHP, for about 1 to 5 hours. And, the hydrogenation reaction may be conducted under common fluid space velocity condition.

Further, the hydrogenation reaction may be conducted by adding about 1 to 10 moles of hydrogen per 1 mole of cumene hydroperoxide. If the mole of hydrogen is less than about 1 mole, conversion rate and selectivity may be decreased, and if it exceeds about 10 moles, excessive amount of hydrogen should be recycled thus unfavorable in terms of economical feasibility.

Since the present invention progresses a hydrogen process of cumene hydroperoxide at low concentration and low temperature as in the step (b), a risk of explosion at a runway reaction temperature of cumene hydroperoxide may be reduced to increase conversion rate into cumyl alcohol under maximum stabilized conditions.

And, high concentration of cumene hydroperoxide may be converted into cumyl alcohol to increase the content of cumyl alcohol, and increase the content of alpha methyl styrene in the subsequent step. Preferably, selectivity of the hydrogenation reaction may be about 90% or more, more preferably about 95% or more. Specifically, in a conventional catalyst reduction, conversion rate is about 20 to 35%, selectivity is about

80%, and maximum yield is about 40%, while the catalyst hydrogenation of the present invention may obtain cumyl alcohol with conversion rate of about 95% or more, selectivity of about 95% or more and yield of about 90% or more. And, cumene that is mixed with cumene hydroperoxide may also be partly converted into cumyl alcohol during a hydrogenation process, and thus additional yield improvement may be expected.

The step (c) prepares alpha methyl styrene using cumyl alcohol. In the step (c), the reactant including cumyl alcohol may further comprise a cumene hydroperoxide stream that is not hydro genated. Thus, the product including alpha methyl styrene may further comprise phenol and acetone through a dehydration reaction of the reactant. Preferably, the cumene hydroperoxide stream in the reactant may be contacted with an acid catalyst, and then, dehydrated to produce phenol and acetone. And, the cumyl alcohol in the reactant may be contacted with an acid catalyst, and then, dehydrated to produce alpha methyl styrene. And, a small amount of acetophenone, cumene and heavy compounds may be further included in the product.

Further, the reactant including cumyl alcohol may be concentrated into a concentration of about 80 to 82 wt% and used in the dehydration reaction.

If necessary, to minimize production of heavy compounds, a mixture of the remaining stream other than the cumene hydroperoxide stream used in the hydrogenation reaction of the step (b) and the cumyl alcohol obtained in the step (b) may be diluted before conducting the step (c).

In the step (c), the acid catalyst may be preferably a liquid or solid acid catalyst. The liquid acid catalyst may include sulfuric acid or nitric acid, preferably sulfuric acid. The solid acid catalyst may include a metal oxide modified by Group 6 metal oxide, sulfated transition metal oxide, mixed metal oxide of cerium oxide and Group 4 metal oxide, or a combination thereof.

The method of the present invention may further comprise neutralizing the product including alpha methyl styrene and distilling it, after the (c) step. Through the process, alpha methyl styrene, phenol and acetone may be separated.

The distillation conditions are not specifically limited, and it may be conducted by a common method. In the neutralization step, the kind and content of the neutralization agent are not specifically limited. Hereinafter, a method of preparing alpha methyl styrene according to one preferred embodiment of the invention will be explained in detail referring to drawings. Fig. 2 schematically shows a phenol process flow diagram for producing alpha methyl styrene of the invention.

Referring to Fig. 2, the method of the present invention may be progressed with passing an oxidation reactor (10) for progressing the oxidation of cumene; a catalytic hydrogenation reactor (30) for hydrogenating a part of cumene hydroperoxide stream obtained after the oxidation; a stripper (40) for concentrating cumyl alcohol obtained by the hydrogenation reaction and remaining cumene hydroperoxide stream that is not used in the hydrogenation reaction; a cleavage reactor (60) for progressing a dehydration reaction of the mixture concentrated in the stripper; a neutralizer reactor (70) for progressing neutralization of the product obtained by the dehydration reaction; and, a distillation apparatus for separating the product (80). Further, a receiver (20, 50) may be equipped between the oxidation reactor (10) and the stripper (40), and between the stripper (40) and the cleavage reactor (60).

Specifically, the present invention prepares cumene hydroperoxide of low concentration and cumyl alcohol by the oxidation of cumene, hydrogenates at least a part of the cumene hydroperoxide without concentration so as to prepare cumyl alcohol, mixes remainder of cumene hydroperoxide that is not used in the hydrogenation reaction and cumyl alcohol obtained by the hydrogenation reaction so as to prepare a reactant including cumyl alcohol, and dehydrates the reactant in the presence of an acid catalyst, thereby obtaining a product including alpha methyl styrene with increased productivity. Since the product may also include phenol and acetone, the product may be neutralized and distilled to obtain AMS with increased productivity together with phenol and acetone. Therefore, through a selective hydrogenation process of cumene hydroperoxide, conversion rate of cumene hydroperoxide into cumyl alcohol may be improved and the content may be increased, and ultimately, the amount of alpha methyl styrene may be increased.

Specifically, according to the present invention, cumene is supplied to the oxidation reactor (10) and the oxidation reaction of cumene is progressed in the presence of oxygen. Through the oxidation of cumene, a cumene hydroperoxide stream of concentration of about 5 to 25 wt%, preferably about 10 to 25 wt%, more preferably about 20 to 25 wt% is produced, wherein cumyl alcohol is included.

Then, a part of the stream is separated and transferred to a receiver (20), and then, supplied to the hydrogenation reactor (30) so as to progress a hydrogenation reaction. The cumene hydroperoxide stream of low concentration transferred to the receiver (20) is supplied top-down or bottom-up of the catalytic hydrogenation reactor (30) so as to prepare cumyl alcohol by a hydrogenation reaction. The reactor used in the hydrogenation reaction may include a CSTR reactor (Continuous stirred-tank reactor), but any reactor commonly used in a hydrogenation reaction may be used without limitation. For example, it is preferable that a catalyst is filled in the catalyst hydrogen reactor, and hydrogen is introduced to progress the reaction with maintaining the internal temperature. And, the reactant of concentrated cumene hydroperoxide stream may be introduced top-down of the reactor using a pump.

After the hydrogenation reaction is completed, prepared cumyl alcohol is supplied to the receiver (20) again, and thereby transferred to the stripper (40). And, a CHP stream of concentration of 5 to 25 wt% that is not hydrogenated is directly transferred to the stripper (40).

Thereby, the stripper (40) includes a mixture of streams of cumyl alcohol obtained by the hydrogenation reaction, and cumyl alcohol and cumene hydroperoxide, which are not used in the hydrogenation reaction.

And then, the mixture is concentrated to a concentration of about 80 to 82 wt% in the stripper (40), passed through the receiver (50) and transferred to the cleavage reactor (60).

And then, the mixture is continuously dehydrated in the cleavage reactor (60) so that the acid catalyst may decompose the cumene hydroperoxide into phenol and acetone, and dehydrate the cumyl alcohol into AMS.

And, the mixture of phenol, acetone and AMS produced in the cleavage reactor (60) is transferred to a neutralizer reactor (70), and a neutralization agent is introduced therein to progress a neutralization reaction.

Finally, the product is transferred to the distillation apparatus (80) to separate into phenol, aceton and AMS through distillation.

The conditions of reactors used in each reaction step are not specifically limited, and any commonly known reactors may be used. And, each reactor may be connected and installed through a separate transfer line. And, finally separated phenol, acetone and AMS may be collected in a collection receiver through a separately connected and installed outlet.

The present invention may produce cumyl alcohol in a stabilized state without a risk of explosion of cumene hydroperoxide, by progressing a hydrogenation reaction of cumene hydroperoxide obtained by the oxidation of cumene under maximum stabilized conditions of low concentration and low temperature. In addition, the present invention may increase AMS production in a phenol plant by converting cumene hydroperoxide into cumyl alcohol with high selectivity through a hydrogen process, and control AMS production according to market demand by controlling the amount of cumene hydroperoxide stream introduced in a hydrogen process.

Hereinafter, the present invention will be explained in detail with reference to the following Examples. However, these examples are only to illustrate the invention, and the scope of the invention is not limited thereto. [Examples 1 and 2]

Alpha methyl styrene was prepared according to the process flow diagram of

Fig. 2.

First, oxidation of cumene was progressed with an oxidizer under the following conditions using 3 oxidation reactors in a phenol process to prepare a stream including cumene hydroperoxide (CHP) of concentration of 25 wt%.

(1) Condition of introducing first oxidizer

supply (CHP 0.4% + cumene 99.6%) 1 ml/min, 02: 100 ml/min, pressure: 3bar, reaction temperature: 100 ^°C

(2) Condition of introducing second oxidizer

supply (CHP 8.42% + cumene 91.58%) 1 ml/min, 02: 100 ml/min, pressure:

3bar, reaction temperature: 96 ^°C

(3) Condition of introducing third oxidizer

supply (CHP 16.27% + cumene 83.73%) 1 ml/min, 02: 100 ml/min, pressure: 3bar, reaction temperature: 94 ^°C

The concentration of CHP stream was changed from 8.4 to 24 wt% while passing through 3 oxidation reactors as shown in the following Table 1.

Then, 25 wt% of the stream of low concentration was separated and transferred to a receiver (20), and then, supplied to a catalytic hydrogenation reactor (30).

The hydrogenation reactor was filled with a catalyst Pd/C, hydrogen was introduced and the reaction was progressed while maintaining internal temperature. And, the reactant of cumene hydroperoxide stream of 25 wt% concentration was introduced top-down of the reactor using a pressurization pump. The hydrogenation reaction was progressed under conditions of 150 g of cumene hydroperoxide (CHP) of 25 wt% concentration, 1 g of 1 wt% Pd/C, and hydrogen flow rate of 150 cc/min. And, the mole ratio of the cumene hydroperoxide stream and the introduced hydrogen was maintained 1 :8. The hydrogen reaction was progressed respectively for 7 hours and 3 hours in Examples 1 and 2. As the result, final product with cumene hydroperoxide (CHP) conversion rate of 99.97%, CA increase rate of 960.5%, and CA concentration of 25% was obtained.

After the reaction was completed, conversion rate of cumene hydroperoxied into cumyl alcohol was analyzed with liquid chromatography, and the result was shown in Table 2.

After the hydrogenation reaction is completed, prepared cumyl alcohol is supplied to the receiver (20), and transferred to the stripper (40). Thereby, the stripper (40) is filled with a mixture of cumyl alcohol obtained by the hydrogenation reaction, and a stream including cumyl alcohol and cumene hydroperoxide which are not used in the hydrogen reaction.

Then, the mixture is concentrated in the stripper (40), passed through a receiver (50) and transferred to a cleavage reactor (60), and the remainder is directly transferred to the cleavage reactor.

And then, an acid catalyst is introduced in the cleavage reactor (60), and the mixture is continuously dehydrated so that the acid catalyst decomposes cumene hydroperoxide into phenol and acetone, and dehydrates cumyl alcohol into AMS.

Into the cleavage reactor, 100 g of feedstock (CHP 72 wt%, CA 8 wt%, cumene 20 wt%) and 1 g of H₂S0₄ were introduced to progress the reaction. And, the reaction temperature was maintained 65 ^°C , and raised to 1 10^°C after conversion until the concentration of CHP became less than 1%, so as to convert CA into AMS.

The mixture of phenol, acetone and AMS produced in the cleavage reactor (60) was transferred to a neutralizer reactor (70), and a neutralization agent was introduced to progress a neutralization reaction. After neutralization, the product was transferred to a distillation reactor (80), and separated into phenol, AMS and acetone through distillation.

By the above reaction, yield for conversion from CHP into phenol was 99.36%, yield for conversion from CHP into aceton was 98.30%, and yield for conversion from CA into AMS was 82.45%.

[Table 1 ]

The above Table 1 shows that most of CHP was decomposed into phenol and acetone and the concentration decreased from 82 wt% to 1 wt% in the 1^st cleavage reactor, and 1 wt% of CHP decreased to 1 wt% or less in the 2^nd cleavage reactor.

[Comparative Examples 1 and 2]

150 g of the prepared cumene hydroperoxide of concentration of 25 wt% and 1 g of Co/Al/P0₄ (Co: 7wt%, Al: 25wt%, P: 3wt%) catalyst were used to progress a reduction reaction without hydrogen to prepare cumyl alcohol. The reaction times were respectively 7 hours and 3 hours in Comparative Examples 1 and 2. Other conditions were the same as Example 1, and the reaction was progressed to prepare AMS. Conversion rate of cumene hydroperoxide and increase rate of cumyl alcohol are shown in Table. 2

[Comparative Examples 3 and 4] 50 g of cumene hydroperoxide of concentration of 80 wt%, which was passed through the oxidation of cumene and concentrated through a stripper, was diluted in 100 g of acetone, and subjected to a reduction reaction using catalysts of Table 2 without progressing a hydrogenation reaction so as to prepare cumyl alcohol. Conversion rate of cumene hydroperoxide and increase rate of cumyl alcohol are shown in Table 2.

[Table 2]

CA increase

960.5 479.6 57.5 39 225.2 321.9 rate (%)

As shown in the above Table 2, Examples 1 and 2 of the present invention exhibit excellent conversion rate of cumene hydroperoxide (CHP) and increased production of cumyl alcohol compared to Comparative Examples 1 and 2, by using 25 wt% of the CHP solution passed through the oxidation reactor as a feedstock of the hydrogenation reaction. Further, in the preparation of phenol, acetone and alpha methyl styrene through dehydration using cumyl alcohol, Examples 1 and 2 of the present invention exhibit 100 to 1200% increased AMS production compared to Comparative Examples 1-4.

[Experimental Example]

After the addition of CHP was completed in the hydrogenation process of Example 1, the composition of the reactant solution was analyzed over time. According to the analysis, CHP conversion rate and CA increase rate in the catalytic hydrogenation process were measured by the following method, and the results are shown in Table 3. [Equation 1]

CHP conversion rate(%) = (CHP feedstock(wt%)-CHP product(wt%))/(CHP feedstock(wt%))

[Equation 2]

CA increase rate(%) = (CA product(wt%)-CA feedstock(wt%))/(CA feedstock(wt%))

[Table 3]

AMS 0 0.001 0.001 0.001 0.001 0.001 0.001 0.001

Phenol 0 0 0 0 0 0 0 0

Acetone 0 0 0 0 0 0 0 0

DCP 0 0 0 0 0 0 0 0

CHP

conversion 10.59 28.12 46.18 64.31 85.43 99.97 99.97 rate(%)

CA increase

178.52 330.68 479.58 649.85 816.72 937.64 960.50 rate(%)

Claims

[CLAIMS]

1. A method of preparing alpha methyl styrene comprising:

(a) oxidizing cumene to prepare a cumene hydroperoxide stream;

(b) separating at least a part of the cumene hydroperoxide stream without concentration and selectively hydrogenating it in the presence of a noble metal catalyst so as to prepare cumyl alcohol; and

(c) concentrating the reactant including the cumyl alcohol and dehydrating it in the presence of an acid catalyst so as to prepare a product including alpha methyl styrene.

2. The method according to claim 1, wherein in the step (b), the cumene hydroperoxide stream is used in the hydrogenation reaction in the concentration of 5 to 25 wt%.

3. The method according to claim 1, wherein in step (b), 5 to 50 wt% of the cumene hydroperoxide stream is separated and used in the hydrogenation reaction.

4. The method according to claim 1 , wherein the noble metal catalyst includes at least one selected from the group consisting of gold, silver, platinum, palladium, iridium, ruthenium, rhenium, rhodium and osmium.

5. The method according to claim 4, wherein the noble metal catalyst further comprises a support selected from the group consisting of alumina, silica, clay, carbon, zirconia, titania, a mseoporous molecular sieve, and a combination thereof.

6. The method according to claim 1, wherein the noble metal catalyst is used in an amount of 1 to 15 parts by weight, based on 100 parts by weight of the cumene hydroperoxide stream.

The method according to claim 1, wherein the hydrogenation reaction is conducted at a temperature of 40 to 80 ^°C , at a hydrogen flow rate of 1 :1 to 1 : 10 according to the mole ratio to cumene hydroperoxide (CHP) for 1 to 5 hours.

8. The method according to claim 1, wherein the hydrogen reaction has selectivity of 95% or more.

9. The method according to claim 1, wherein in conversion rate of the cumene hydroperoxide is 95% or more.

10. The method according to claim 1, wherein the cumene hydroperoxide stream further comprises cumyl alcohol.

11. The method according to claim 1 , wherein the acid catalyst is a liquid or solid acid catalyst.

12. The method according to claim 1 1, wherein the liquid acid catalyst is hydrochloric acid, sulfuric acid or nitric acid, and the solid acid catalyst is selected from the group consisting of Group 4 metal oxide modified by Group 6 metal oxide, sulfated transition metal oxide, mixed metal oxide of cerium oxide and Group 4 metal oxide, and a combination thereof.

13. The method according to claim 1, wherein in the step (b), a part of the cumene hydroperoxide stream is subjected to a hydrogenation reaction, and in the step (c), the reactant including the cumyl alcohol further comprises a cumene hydroperoxide stream which is not subjected to a hydrogenation reaction.

14. The method according to claim 1 , wherein in the step (c), the product including alpha methyl styrene further comprises phenol and acetone.

15. The method according to claim 1, wherein the reactant including cumyl alcohol is concentrated to a concentration of 80 to 82 wt% and used in the dehydration reaction.

16. The method according to claim 1, wherein the method further comprises neutralizing the product including alpha methyl styrene and distilling it, after the (c) step.