Method for producing aromatic alcohol

Aromatic alcohol is produced by reducing aromatic hydroperoxide with hydrogen in a liquid phase, using a Pt catalyst solely or a catalyst containing Pt and at least one element selected from the group consisting Pb, Sn, Cu, As, Sb, In, Se and Bi in a fixed bed reactor.

BACKGROUND OF THE INVENTION 
This invention relates to a process for the production of aromatic alcohols 
using improved catalysts. 
Aromatic alcohols are useful as intermediates for various types of organic 
compounds and as solvents, and are advantageously produced industrially by 
the reduction of aromatic hydroperoxides. 
Japanese Patent Publication No.26961/1964 and U.S. Pat. No.2,491,926 
disclose methods of producing .alpha.-cumyl alcohol by reducing cumene 
hydroperoxide or dicumyl peroxide dissolved in cumene with hydrogen in the 
presence of hydrogenation catalysts such as Pd, Ni, etc. Such reactions 
are accompanied by the evolution of heat; therefore, use of a solvent is 
recommended for mitigating reaction heat and for lowering side reactions 
as much as possible. As said solvents, water-immiscible solvents such as 
hydrocarbons are employed. However, deactivation of the catalyst is 
recognized to occur unexpectedly soon when said solvents are used, so, a 
method of employing a lower aliphatic alcohol is disclosed by Japanese 
Patent Laid-open No. 69527/1980. Further, in order to obtain aromatic 
alcohols in good yield a method is disclosed in Japanese Patent Laid open 
No.174737/1985, wherein said reduction is conducted in coexistence with 
amines or some compounds capable of being converted to amines during said 
hydrogenation reaction. 
However, in the hydrogenation method described in said Patent Laid-open, a 
complex process is necessary for the separation of desired aromatic 
alcohols from aliphatic alcohols, amines, etc. having different properties 
from those of the aromatic alcohols. In addition, a complex structure of 
equipment is needed for the separation of the produced alcohols and a 
suspended catalyst, and therefore, the method mentioned above can not be 
advantageously employed for industrial mass production thereof. 
Japanese Patent Laid-Open No.16843/1984 discloses, when reducing aromatic 
hydroperoxide with hydrogen gas in the presence of a catalyst containing 
Pd, a method wherein a feed liquid containing aromatic hydroperoxide is 
allowed to pass downstream in a fixed bed reactor. Japanese Patent 
Laid-open No. 110639/1984 discloses, when reducing aromatic hydroperoxide 
with hydrogen, a method wherein a Pd catalyst with Pd surface area of at 
least 200m.sup.2 /g Pd is employed in the form of a fixed bed. 
It is described that in the hydrogenation method in said patent Laid-open 
elution of the Pd was barely found, and that the desired aromatic alcohols 
can be rather effectively obtained. The operating time reported in said 
patent Laid-open was only 720 hours (30 days), whereas, the present 
inventors conducted an even longer time of operation to find a completely 
deactivated catalyst at the 70th day of operation (refer to COMATIVE 
EXAMPLE 2 below). In addition, when we measured the concentrations of Pd 
in the liquid produced by passing aromatic hydroperoxide solutions having 
concentrations changed over the Pd catalyst, we recognized a proportional 
relationship between both concentrations as shown in the next TABLE 1. 
TABLE 1 
______________________________________ 
Concentration of metal in solution 
Concentration of cumene 
produced (concentrated 200 times) 
hydroperoxide in feed 
(weight by ppm) 
(weight by %) Pd(0.3%)/.gamma.-alumina catalyst 
______________________________________ 
2.0 7 
4.0 14 
8.3 32 
16.1 46 
______________________________________ 
Test liquids were passed at 60.degree. C., and at a LHSV of 6/hour. 
That is, as not insignificant quantities of Pd were eluted with aromatic 
hydroperoxide, the use of a Pd catalyst results in the problem of the 
inevitable deactivation of the catalyst. 
When using a supported Ni catalyst, the catalyst has a disadvantage in 
spite of having a capacity to reduce aromatic hydroperoxide with hydrogen, 
of giving a low yield of the desired aromatic alcohols because of many 
side-reactions (refer to COMATIVE EXAMPLE 3 below). 
It is an object of the present invention, therefore, to provide a method 
improved with respect to the catalysts of producing aromatic alcohols 
wherein no problems such as stated above will occur. 
SUMMARY OF THE INVENTION 
This invention in outline, relates to a method of producing aromatic 
alcohols, that is, a method of manufacturing aromatic alcohols by reducing 
aromatic hydroperoxides with hydrogen in liquid phase which comprises 
using a Pt catalyst exclusively or using both a catalyst containing Pt and 
at least one element selected from the group consisting of Pb, Sn, Cu, As, 
Sb. In, Se and Bi in a fixed bed reactor. 
The present inventors, as a result of earnest investigations conducted to 
overcome said problems, have found that by using a Pt catalyst in a fixed 
bed reactor in a method of reducing aromatic hydroperoxides with hydrogen 
in liquid phase, the catalyst will not be deactivated, but rather will 
achieve high and stable activity even during long periods of use. 
Also even though a liquid containing aromatic hydroperoxide was passed over 
a supported Pt catalyst in accordance with the conditions in TABLE 1, the 
Pt concentration (after 200-fold concentration) of &he produced liquid did 
not exceed the limit of detection (1 wt.ppm) and no Pt was found in the 
production liquid, and it was confirmed that the elution of Pt due to 
aromatic hydroperoxide hardly occured when a Pt catalyst was used, to 
complete the present invention. 
However, even though the use of a Pt catalyst in a fixed bed reactor may 
stabilize higher activity, it was determined that as far as slight amounts 
of impurities were concerned, a part of the produced aromatic alcohol was 
further converted by aromatic ring hydrogenation to alcohol having a 
cyclohexane ring (refer to EXAMPLE 12 below). The quantity of this product 
obtained by aromatic ring hydrogenation is very small, but the boiling 
point thereof is very near to that of the aromatic alcohol making said 
product difficult to be removed, resulting in the problem of lowered 
product purity. Therefore, it is required to develop a catalyst which has 
long stable hydrogenation activity with less aromatic ring hydrogenation, 
when producing aromatic alcohols by reducing aromatic hydroperoxides. 
The present inventors, for solving said problem, have earnestly conducted 
investigations and as a result, found that a stable higher activity can be 
obtained by use of said combined catalyst without accompanying aromatic 
ring hydrogenation.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will be concretely illustrated below. 
(Aromatic hydroperoxides) 
As examples of aromatic hydroperoxides to be subjected to the hydrogenation 
reaction in this invention, alpha phenylethyl hydroperoxide, cumene 
hydroperoxide, cymene hydroperoxide, o,m- or o,p-diisopropylbenzene 
monohydroperoxide, o,m- or o,p-diisopropylbenzene dihydroperoxide, 
isopropylnaphthalene hydroperoxide, etc., and compositions which contain 
at least one member selected from the group consisting thereof can be 
given. 
(Hydrogen) 
The amount of hydrogen to be fed to the hydrogenation reaction system in 
this invention is 1-50 times as much as the amount theoretically required, 
preferably 1-30 times and most preferably 1-20 times. Excess feeding of 
hydrogen causes loss thereof, and requires an undue scale of equipment in 
recovery and circulating systems, and sometimes gives rise to unnecessary 
side-reactions. 
(Catalyst) 
The catalyst components used in the process of producing aromatic alcohols 
according to this invention are usually supported on suitable carriers. 
The Pt metal supporting ratios thereof, in regardless of using Pt only or 
using Pt combined catalysts, are generally 0.01-5 wt. %, preferably 0.03-3 
wt. %, wherein the ratio of the elements other than Pt is usually 0.001-3 
wt. %, preferably 0.005-2 wt. %. 
As for the carriers, heat-resistant inorganic compounds, for example, 
synthetic gels such as alumina, silica, etc., or natural inorganic 
carriers such as diatomaceous earth, porous clay, carbon, etc. can be 
given. 
(Reaction mode) 
As for the reaction modes in the process of producing aromatic alcohols 
according to this invention, as shown in Japanese patent Laid-open 
No.73709/1979, batch process, continuous process or any other suitable 
process which is well known as a hydrogenation method for organic peroxide 
can be embodied. However, when a catalyst is employed in a form of 
suspended bed, a catalyst removal process is needed, making its apparatus 
complicated: therefore, a fixed bed is preferable. In a fixed bed, when an 
upflow is used, the catalyst is liable to become fluidized to cause 
deactivation; therefore, a downflow is more preferable. 
As for solvents used for diluting the aromatic hydroperoxides in the method 
of producing aromatic alcohol according to this invention, any solvent 
which is capable of dissolving aromatic hydroperoxides along with the 
products obtained therefrom can be used, and for example, aliphatic 
hydrocarbons, aromatic hydrocarbons and aromatic alcohols can be given. 
For instance, in a process of manufacturing cumene hydroperoxide, cumene 
is present in said process as a solvent, and it can be used as a solvent 
as it is in a hydrogenation of cumene hydroperoxide in the process of the 
present invention. In addition it is also a preferable method to recycle 
cumyl alcohol as shown in a following formula, which is obtained by the 
hydrogenation of cumene hydroperoxide, to be used as a solvent. 
##STR1## 
(Concentration of aromatic hydroperoxide) 
In the hydrogenation reaction using a catalyst in the process of producing 
aromatic alcohols according to this invention, it is desirable to control 
the concentration of aromatic hydroperoxide in the feed liquid supplied to 
the reactor to at most 25 wt. %. preferably 0.01-15wt, and most preferably 
0.1-10 wt. %. When said concentration is more than 25 wt. %, a 
considerable amount of heat is evolved, causing some problems such as hard 
control of reaction temperature, depression of high activity, formation of 
side reactions, etc. 
(Reaction temperature) 
The hydrogenation reaction, in the method of producing aromatic alcohols 
according to this invention, is usually conducted in a temperature range 
of 20.degree.-120.degree. C., preferably 30 -120.degree. C., and most 
preferably 40.degree.-20.degree. C. Too high a reaction temperature is not 
desirable, because side reactions such as a decomposition reaction of the 
aromatic hydroperoxide itself or the like will violently take place. On 
the other hand too low a reaction temperature will produce problems such 
as decreased reaction rate, etc. 
(Reaction pressure) 
The total pressure in the hydrogenation reaction in the method of preparing 
aromatic alcohols according to this invention, ranges usually from normal 
pressures to a certain high pressure, preferably from normal pressures to 
50 kg/cm.sup.2 G and most preferably from normal pressures to 30 
kg/cm.sup.2 G. As the hydrogenation reaction proceeds easily, excess 
reaction pressure just entails excessive apparatus costs for no real 
effect, and causes problems such as subsequent hydrogenation reaction of 
the produced liquid and solvent. 
EXAMPLES 
This invention will be further illustrated in detail with reference to the 
following examples. In the examples, % is meant to be weight % unless 
notified to the contrary. 
CATALYST PREATION EHAMPLE-1 
After impregnating a 0.8-1.3% aqueous solution of hydrogen 
hexachloroplatinate (IV) (hexahydrate) into pellet type .gamma.-alumina 
with dimensions of 3 mm.phi..times.3 mm, the resultant pellets were dried 
at 110.degree. C. for 12 hours. 
Then, the dried pellets were reduced in a hydrogen stream at 400.degree. C. 
for 16 hours to obtain a supported Pt catalyst having a composition of 
Pt(0.3-0.5%)/.gamma.-Al.sub.2 O.sub.3. 
EXAMPLE-1 
A 200 ml autoclave equipped with inlet pipes for raw material and hydrogen 
and an outlet pipe for liquid products and a basket type of stirrer filled 
with 0.8 g of catalyst containing 0.3% Pt prepared according to CATALYST 
PREATION EXAMPLE-1 was maintained at 60.degree. C. 1.2L/hour of 
solution of 3.7% cumenehydroperoxide (hereinafter abbreviated as CHP) in 
cumene and 12L/hour of hydrogen were fed therein continuously, while the 
hydrogenation products were continuously collected through the outlet pipe 
to keep the content in the autoclave at about 80 ml. At this time the 
hydrogen pressure was kept at 7.5 kg/cm.sup.2 -G and the stirrer was 
rotated at 750 rpm. The reaction rate of hydrogenation of CHP after 8 
hours from the start of feed is shown in TABLE 2 below. 
EXAMPLE-2 
The procedure of EXAMPLE-1 was repeated except that the catalyst containing 
0.5% of Pt was used and the concentration of CHP and feed rate of hydrogen 
were increased to 8.0% and 27L/Hours respectively. The results are shown 
in TABLE 2. 
TABLE 2 
______________________________________ 
Reaction rate of hydrogen- 
CHP Concentration 
ation 
EXAMPLE [%] [mol/kg Pt .multidot. hour] 
______________________________________ 
1 3.7 19,000 
2 8.0 17,800 
______________________________________ 
EXAMPLE-3 
One liter of catalyst containing 0.3% of Pt prepared according to CATALYST 
PREATION EXAMPLE-1 was charged in a stainless steel tube with an inner 
diameter of 27.2 mm equipped with a thermowell tube having an outer 
diameter of 6 mm. keeping the temperature at the entrance of the catalyst 
layer at 45.degree. C.; 7.2L/hr. of liquid having a composition of 3.5% 
CHP, 77.0% cumyl alcohol and 19.5% cumene; and 72L/hr. of hydrogen at a 
pressure of 8 kg/cm.sup.2 G were continuously fed thereto. The conversion 
of CHP after 8 hours from the start of feed was 99.9%, and the conversions 
after 20 and 150 days were 99.7% and 99.9% respectively to obtain stable 
activity. All the yields of cumyl alcohol based on the amount of CHP fed 
were 99%. 
CATALYST PREATION EXAMPLE-2 
After impregnating a 0.8% aqueous solution of hydrogen hexachloroplatinate 
(IV) (hexahydrate) into pellet type .gamma.-alumina with dimensions of 3 
mm.phi..times.3 mm, the resultant pellets were dried at 110.degree. C. for 
12 hours. 
Then, the dried pellets were reduced in a hydrogen stream at 400.degree. C. 
for 16 hours. 
Further impregnating a 0.1% aqueous solution of lead nitrate into the 
reduced Pt catalyst and after drying it at 110.degree. C. for 12 hours it 
was reduced in a hydrogen stream at 400.degree. C. for 16 hours to obtain 
a catalyst having a composition of Pt(0.3%)-Pb(0.03%)/.gamma.-Al.sub.2 
O.sub.3. 
EXAMPLE-4 
The procedure of EXAMPLE-1 was repeated except that the catalyst prepared 
according to CATALYST PREATION EXAMPLE-2 and a 3.5% CHP solution in 
cumene were used. The results are shown in TABLE 3 below. 
In addition, the procedure of EXAMPLE-3 was repeated except that the 
catalyst prepared according to CATALYST PREATION EXAMPLE-2 was used. 
The conversion of CHP and selectivity to cumyl alcohol and 
2-cyclohexyl-2-propanol (nuclear hydrogenation product of cumyl alcohol) 
after 8 hours from the start of feed are shown in TABLE 3 together with 
other examples. 
CATALYST PREATION EXAMPLES 3-9 
Except for using in place of the aqueous solution of lead nitrate in 
CATALYST PREATION EXAMPLE-2, 0.1-1.0% solutions of stannous chloride 
(CATALYST PREATION EXAMPLE-3), cupric chloride (CATALYST PREATION 
EXAMPLE-4), arsenic trichloride [dioxane solution] (CATALYST PREATION 
EXAMPLE-5), antimony trichloride (CATALYST PREATION EXAMPLE-6), indium 
chloride (CATALYST PREATION EXAMPLE-7), selenium monochloride [benzene 
solution] (CATALYST PREATION EXAMPLE-8), and bismuth nitrate (CATALYST 
PREATION EXAMPLE-9) were used to prepare catalysts according to &he 
method described in CATALYST PREATlON EXAMPLE-2, comprising 0.3% of PT, 
0.3% of Sn and In or 0.03% of Cu, As, Sb, Se and Bi respectively supported 
on .gamma.-alumina. 
EXAMPLE 5-11 
The procedure of EXAMPLE-4 was repeated except that the catalysts prepared 
in CATALYST PREATION EXAMPLES 3 through 9 were used. The results are 
shown in TABLE 3 below. 
EXAMPLE-12 
The procedure of EXAMPLE-4 was repeated except that the catalyst containing 
0.3% Pt prepared according to CATALYST PREATION EXAMPLE-1 was used. The 
results are shown in TABLE 3. 
COMATIVE EXAMPLE-1 
The procedure of EXAMPLE-4 was repeated except that the catalyst of 
Pt(0.3%)-Ag(0.03%)/.gamma.-alumina prepared according to CATALYST 
PREATION EXAMPLE-2 using silver nitrate in place of lead nitrate was 
used. The results are shown in TABLE 3. 
TABLE 3 
__________________________________________________________________________ 
Autoclave is used 
Fixed bed downflow type reactor is used 
Reaction rate of 
Selectivity 
Selectivity to 
hydrogenation 
Convertion 
to cumyl 
2-cyclohexyl- 
Additive 
[mol/kg of CHP alcohol 
2-propanol 
EXAMPLE element 
catalyst .multidot. hr] 
[%] [%] [%] 
__________________________________________________________________________ 
EXAMPLE 4 
Pb 61.8 99.9 99.0 0.34 
EXAMPLE 5 
Sn 58.1 99.9 99.2 0.01 
EXAMPLE 6 
Cu 57.5 99.8 99.1 0.26 
EXAMPLE 7 
As 61.0 99.8 99.1 0.18 
EXAMPLE 8 
Sb 57.7 99.9 99.2 0.02 
EXAMPLE 9 
In 59.5 99.9 99.2 0.02 
EXAMPLE 10 
Se 61.9 99.9 99.1 0.11 
EXAMPLE 11 
Bi 61.3 99.8 99.0 0.24 
EXAMPLE 12 
-- 61.6 99.8 98.7 1.04 
COMA- 
Ag 0.9 2.0 97.0 0.01 
TIVE 
EXAMPLE 1 
__________________________________________________________________________ 
COMATIVE EXAMPLE-2 
After impregnation of a 0.6% aqueous solution of palladium chloride into 
pellet type .gamma.-alumina with dimensions of 3 mm.phi..times.3 mm, the 
pellets were dried at 110.degree. C. for 12 hours. 
Then, the dried pellets were reduced in a hydrogen stream of 400.degree. C. 
for 16 hours to obtain a supported Pd catalyst having a composition of Pd 
(0.3%)/.gamma.0Al.sub.2 O.sub.3. 
The procedure of EXAMPLE-3 was repeated except that the Pd catalyst 
obtained in such a manner was used. The conversions of CHP after 8 hours 
and 20 days from the start of feed were 99.9% and 100% respectively, and 
the conversions after 40 and 70 days were 98.8% and 97.1% respectively, 
catalytic activity significantly decreasing. 
COMATIVE EXAMPLE-3 
The procedure of EXAMPLE 3 was repeated except that the commercially 
available Ni catalyst [Trade name: Ni-3266E by Harshaw Co.] was used and 
the Ni catalyst was pretreated in a hydrogen stream at 250.degree. C. for 
4 hours prior to feed. The conversion of CHP after 8 hours from the start 
of feed was 97%, the yield of cumyl alcohol was as low as 81% and 
by-products as acetophenone, .alpha.-methylstyrene, 1-phenylethanol, etc. 
were found. 
As can be understood from the above, the manufacturing methods according to 
this invention permit stable hydrogenation of aromatic hydroperoxide with 
a high conversion rate as well as the production of corresponding aromatic 
alcohol with selectivity.