Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2 ~
SPECIFIC~TION
A method for pretreating a catalyst slurry and a
method for the continuous partial hydrogenation
of monocyclic aromatic hydrocarbons using the
pretreated catalyst slurry
Technical Field
The present invention relates to a me~hod for
pretreating a catalyst slurry and a method for the
continuous partial hydrogenation of monocyclic aromatic
hydrocarbons usiny the pretreated catalyst slurry.
More particularly, the present invention is concerned
with a method for pretreating a catalyst slurry in
which a slurry containing a ruthenium catalyst is
heat-treated, and a method in which the partial hydrog-
enation of monocyclic aromatic hydrocarbons is carried
out using the pretreated catalyst slurry to thereby
efficiently, ,stably and continuously produce and recov-
er corresponding cycloolefins, especi.ally cyclohexenes.
Cyclohexenes are hi.ghly valuahle i.n the commerce as
intermediates :Eor the manufacture oE organic chemical
engineering products, and particularly, they are impor-
tant as intermediates for the production of polyamides
and lysines.
- 2 - 2 ~
Background Art
Various methods have been proposed for producing
cyclohexenes using as starting materials monocyclic
aromatic hydrocarbons. For example, it has been pro-
posed to use (1) a method using water, an alkali agent
and a catalyst composition containing a member selected
from the Group VIII elements of the Periodic Table
[Japanese Patent Publication (Kokoku) No. 5~-
22850/1981]. Further, it has been proposed to use (2)
a method in which a reaction is carried out in the
presence of a ruthenium catalyst and a neutral or an
acidic aqueous solution containing a salt of a cation
of at least one member selected from the group consist-
ing of Group IA and Group IIA metals of the Periodic
Table and manganese [Japanese Patent Publication
(Kokoku) No. 57-7607/1982~. Still furtherl it has been
proposed to use (3) a method in which a reaction is
carried out Ln the presence oE a ru(herl.i.um catcllyst
dispersed in si.lica gel derived from a hydrolysis
product of a si.licon alkoxide, and water [Japanese
Pa-tent Publicati.on (Kokoku) No. 60-59215/1985]. Still
fur-ther, i-t has been proposed to use (43 a method in
which a reaction is carried out in the presence of a
~5 catalyst comprising ruthenium supported on barium
- 3 - 2~a4~4
sulfate, water and an additive rJapanese Laid-Open
Patent Application (Kokai) No. 61-40226/1986]. Still
further, it has been proposed to use (5) a method in
which a reaction is carried out in the presence of a
catalyst comprising ruthenium supported on a compound
containing a rare earth element, water and an alkali
agent [Japanese Patent Publication (Kokoku) No. 1-
29174/1989]. Still further, it has been proposed to
use (6) a method in which a reaction is carried out in
the presence of metallic ruthenium particulates, zirco-
nium oxide or hafnium oxide, and water [Japanese Laid-
Open Patent Application (Kokai) No. 62-81332/1987].
Still further, it has been proposed to use (7) a method
in which a reaction is carried out in the presence of a
ruthenium catalyst using as a starting material a
monocyclic aromatic hydrocarbon which substantially
does not contain a sulfur compound [Japanese Laid-Open
Patent Application (Kokai) No. 60-255738/1985]. Still
further, it has been proposed to use (8) a method in
which a reaction is carried out in the presence of a
ruthenium catalyst and water in an atmosphere which
does not cause iron to be deposited on the catalyst
[Japanese Laid-Open Patent Application (Kokai) No. 62-
67033/1987~. In all of these methods, catalyst slur-
ries prepared by dispersing or dissolving a ruthenium
- 4 -
catalyst and various types of additives in water are
brought into contact with monocycl.ic aromatic hydrocar-
bons and hydrogen by mixing in a liquid phase, thereby
obtaining cycloolefins.
When a practical process for continuously produc-
ing cycloolefins is designed accorcling to these conven-
tional methods, it is requisite to effect complete
separation between a catalyst slurry comprised of a
ruthenium catalyst and water (hereinbelow frequently
referred to simply as "aqueous phase") and an oil phase
containing a partial. hydrogenation reaction produc-t and
an unreacted monocyclic aromatic hydrocarbon (hereinbe-
low frequently referred to simply as "oil phase~).
With such a process, if components of the aqueous
phase, for example, excess amounts of a catalyst and/or
an additive (such as a solid material, an alkaline
material, or an acidic material which is added for
improvement and stabilization of reaction performance)
get mixed into the oil phase, problems, such a5 clog-
ging of process pipes or corrosi.on of conventionally
used apparatus materials, would occur due to the mixed
components. Such problems can he solved to a certain
extent by provid:ing, for example, a :Eiltering device or
a washing clevice for removing the mixed components.
l~owever, in the commercial practice, facilities and
- 5 ~ a ~ ~ ~
operations therefor are inevitably accompanied with
difficulties. Further, in a continuous partial hydrog-
enation reaction as well, it is apparent that when
excess amounts of a catalyst and/or an additive get
mixed, and even when gradually get mixed into the oil
phase, and flow away, some measures and facilities must
be provided for ~eeping the reaction system stable for
a prolonged period of time.
Accordingly, from a commercial viewpoint, means
for preventing components of the aqueous phase from
excessively getting mixed into the oil phase is strong
ly desired.
The term, "excess" used herein means an amount in
excess of the solubility of components of the aqueous
phase in an oil phase under partial hydrogenation
reaction conditions or phase separation conditions (for
example, the temperatures employed, and the composition
of the oil phase generally comprising a reaction
product and an unreacted startlng mater:i.al). As a
practical mat:ter, however, probl.ems arise when excess
amounts of several times the solubility get mixed.
Therefore, more specifically, the term "excess" used
herein means several or more times the solubility. For
example, according to the study of the present inven-
tors, when a partial hydrogenation reaction of benzene
- 6 2~
is conducted at a hydrogen pressure of 50 kg/cm2G and
at 150 ~C using as an aqueous phase a catalyst and an
1~ % hy weight agueous ZnSO4-7~2O solution (which is an
additive to be added for improvement and stabilization
of a reaction yield) to thereby obtain a reaction
mixture comprised of 50 mole % of benzene and 50 mole %
of a mixture of cyclohexene and cyclohexane, the solu-
bility of water in the oil phase is about 1 ~ by
weight, and the solubility of ~nSO4 in the oil phase is
1 ppm or less (the solubility thereof in water dis-
solved in the oil phase is 100 ppm or less). In this
instance, the meaning of "excess" is several times, for
example, two or three times the above-mentioned solu-
bility of about 1 % by weight with respect to water and
1 ppm with respect to ZnSO~. In addition, it is noted
when the above-mentioned excess mixing of water and
ZnSO4 occurs, the mixing of solid components of the
aqueous phase into the oil phase is also observed in
most cases.
E'rom thi.s viewpoint, a revie~w i.s made of the
conventional technologies. For example, with respect
to the above--described prior art methods (1) to (6),
although there is a description regarding a continuous
reaction according to a liquid phase suspension method,
only a batch reaction is conducted in the Examples
.. : ~ . ,
- 7 ~
thereof and there is no description regarding an at-
tempt to almost completely separate a ca~alyst slurry
from an oil phase, which separation is aimed at by the
present invention.
Further, the above-described prior art methods (5)
to (8) are the methods developed by the present inven-
tors themselves. Especially in the methods (7) and
(8), the partial hydrogenation reaction of monocyclic
aromatic hydrocarbons is continuously carried out using
a catalyst slurry comprised of a ruthenium catalyst and
water. In the prior art methods (7) and (8), continu-
ous reaction was actually performed, and partial hy-
drogenation reaction was successfully performed over a
period of 100 to 500 hours at relatively stable reac-
tion performance. However, there is no description
regarding materials having gotten mixed into the col-
lected oil phase and the amounts thereof, and no study
has been conducted with respect to almost complete
separation of the catalyst sl.urry from the oil
phase, which separation is aimed at by the present
invention.
Disclosure of Invention
The present inventors have carried out continuous
partial hydrogenation reactions using various types of
catalyst slurries with respect to monocyclic aromatic
- 8 ~ 2~53~
hydrocarbons which were continuously flowed and fed to
a reaction zone, and have made detailed investigations
not only on reaction performance but also on the sepa-
ration between an aqueous phase and an oil phase. As a
result, the present inventors have found that when such
a reaction comprising a flow step (flow reaction) is
easily started, a portion of the components of the
catalyst slurry which should be essentially retained in
the aqueous phase gets mixed into the oil phase and
flowed away, thereby causing adverse effects on the
subsequent process operations and materials. Further,
the present inventors have determined that this phenome-
non rather generally occurs although the occurrence of
this phenomenon depends on the difference of the compo-
nents of the catalyst slurry. Still further, it has
been found that this phenomenon cannot be recognized by
only observing a reaction mixture after conducting an
ordinary batch reaction, and that in some cases, this
phenomenon is observed in a continuous reaction al-
though the oil phase appears to be clearly separated
from the aqueous phase after the batch reaction. Still
further, the present inventors have found that in order
to prevent the phenomenon, it is not sufficient to only
provide a stationary separating vessel having a suffi-
cient size for separating most of the catalyst slurry
_
from the oil phase.
The present inventors have extensively and inten-
sively studied with a view toward avoiding such a
phenomenon, to thereby complete the present invention.
According to one aspect of the present invention, there
is provided a method Eor pretreating a catalyst slurry
for use in the continuous partial hydrogenation of
monocyclic aromatic hydrocarbons by the reaction with a
hydrogen gas, which comprises heat-treating a catalyst
slurry comprised mainly of a ruthenium catalyst and
water, while agitating, at a temperature of from 60 to
180 ~C for at least lO minutes, prior to the use of the
catalyst slurry in the continuous partial hydrogenation
of the aromatic hydrocarbon.
]5 In another aspect of the present invention, there
is provided a method for the continuous partial hydrog-
enation of monocyclic aromatic hydrocarbons, which
comprises: (1) continuously feeding a monocyclic
aromatic hydrocarbon and a hydrogen gas to a reaction
zone to effect a contact thereof with a catalyst slurry
comprised mainly of a ruthenium catalyst and w~ter and
perform a partial hydrogenation reaction of the aromat-
ic hydrocarbon, the catalyst slurry having been heat-
treated at a temperature of from 60 to 180 ~C for at
least 10 minutes while agitating, thereby obtaining a
- l o ~ 3 ~ 4 ~-~
reaction mixture comprising an oil phase comprised
mainly of a partial hydrogenation reaction product and
the unreacted aromatic hydrocarbon and an aqueous phase
comprised of the catalyst slurry and (2) continuously
introducing the reaction mixture to an oil phase-
aqueous phase separation zone to separate the oil phase
from the aqueous phase.
When the pretreatment of the present invention is
carried out under suitable conditions, the desired
activity and selectivity of the catalyst with respect
to the partial hydrogenation reaction of monocyclic
aromatic hydrocarbons can be stably obtained as from
immediately after the start of the flow reaction.
Further, an improvement of the selectivity itself is
sometimes attained.
Hereinbelow, the particular embodiments of the
present invention will be described. The catalyst
slurry comprised of a ruthenium catalyst and water to
be used in the present invention comprises as essential
components a ruthenium catalyst and water. ~n addi-
tion, the catalyst slurry may further comprise various
types of additives, as described hereinbelow.
Examples of ruthenium catalysts include metallic
ruthenium particulates and ruthenium supported on
various carriers, for example, rare earth element
I 1 2 ~
compounds, oxides and hydroxides of Ti, Zr, Hf, Nb, Ta,
Cr, Fe, Co, Al, Ga and Si, hydrates of such oxides and
hydroxides, and water insoluble salts, such as barium
sulfate. The ruthenium catalyst may contain catalyst
components other than ruthenium, such as Cu, Fe, Zn and
Ag. To improve reaction performance and effect reac-
tion stabilization, the following additi~es can be
added to the ruthenium catalyst. The additives include
a variety of soluble and insoluble materials, such as
salts of a Group IA metal, a group IIA metal, Zn and
Co, various a]kali agents (reagents for alkalinization,
such as NaOH and ammonia), oxides and hydroxides of Ti r
Zr, Hf, Nb Ta, Cr, Fe, Co, A1, Ga and Si, hydrates of
such oxides and hydroxides, and activated carbon.
Especially, a method in which metallic ruthenium
particulates and, as a solid additive, an oxide or a
hydroxide of Ti, Zr, Hf, Nb, Ta, Cr, Fe, Co, Al, Ga, Si
or a hydrate thereof are used with an aqueous solution
of a Zn salt (for example, the above-mentioned prior
art method (6)) can be preferably employed because the
selectivity and yield are high in the preparation of
cycloolefins by partial hydrogenation reaction.
The amount of catalyst to be used depends on the
form of the catalyst. When rne-tallic ruthenium particu-
lates are used, the catalyst is used in an amount of
- 12 ~ 5~
from l x lO-5 to 0.1 part by weight, preferably from l
x 10-4 to 5 x 10-2 part by weight, per part by weight
of coexisting water. When a catalyst comprised of
ruthenium supported on a carrier is used, the catalyst is
used in an amount of from 1 x 10-4 to 0.3 part by
weight, preferably from 1 x 10-3 to 0.1 part by weight,
per part by weight of coexisting water. Further, when
a solid additive is used in addition to the catalyst
itself, the total amount of the catalyst and the solid
additive other than the catalyst, that is, the slurrv
concentration, is in the range of from 1 x 10-3 to 0.3
part by weight, preferably from 1 x 10-2 to 0.1 part by
weight, per part by weight of coexisting water. When
the additive is soluble in water, the amount thereof
can be chosen in the range of from several parts per
million to solubility.
Examples of monocyclic aromatic hydrocarbons to be
fed to a partial hydrogenation reaction zone include
benzene, toluene, xylenes, and lower alkylbenzenes w:ith
an alkyl group having 2 to 4 carbon atoms. The partial
hydrogenation reaction is generally conducted at a
temperature of from lO0 to 200 ~C under a hydrogen
pressure of from 10 to 100 kg/cm2G. The time for
contact of the monocyclic aromatic hydrocarbon with the
catalyst is generally in the range of from about 1
_ 13 _ 2~3~
minute to 10 hours. The reaction mixture to be with-
drawn as an oil phase i.5 a mixture of a cyclohexene, a
cyclohexane and an unreacted starting material. The
method for separating the desired reaction product from
the unreacted material is not limited, and any one of
the conventional methods can be employed. For example,
separation can be performed by distillation.
The pretreatment of a catalyst slurry according to
the method of the present invention is conducted in a
condition such that oil phase components, such as a
monocyclic aromatic hydrocarbon as a starting material,
are not present. However, a small amount of oil phase
components can be present as long as it is soluble in
the aqueous phase under pretreatment conditions.
Further, the pretreatment of the present invention is
carried out for the catalyst slurry which is for the
first time to be used for a partial hydrogenation
reaction. The pretreatment according to the present
invention is not necessarily required Eor the catalyst
slurry which has once been pre~reated and which has
already been used in the partial hydrogenation reaction
and then cooled for reuse in a partial hydrogenation
reaction.
The gaseous phase under which the pretreatment of
the present invention is performed may be comprised of
14 ~ 2~t7A~ ~
steam, hydrogen, air or nitrogen. The type of the gas
is not especially limited as long as it does not have
an adverse effect on the catalyst. Generally, however,
a hydrogen or a nitrogen atmosphere is preferred.
Moreover, when the pretreatment is conducted in the
presence of hydrogen, that is, in the presence of
hydrogen dissolved in the catalyst slurry, the desired
activity and selectivity of the catalyst for the par-
tial hydrogenation reaction of monocyclic aromatic
hydrocarbons can be stably ensured as from immediately
after the start of flow reaction, and in some cases an
improvement of the selectivity itself is attained.
Therefore, the above-mentioned method for the pretreat~
ment is advantageous. In such a method, the pretreat-
ment is conducted at a hydrogen pressure of from 1 to
100 kg/cm2G, preferably under the same pressure as that
in the partial hydrogenation reaction.
The pretreating method of the present invention is
conducted at a temperature of from 60 to 180 ~C. When
the temperature is lower than 60 ~C, an extremely
pro].onged period of time is undesirably required for
the pretreatment, or the effects aimed at by the
present invention cannot be obtained. On the other
hand, when the temperature is higher than 180 ~C,
denaturi~ation of the catalyst itself sometimes occurs
- 15 - 2~
to disadvantages. It is preferred that the pretreat-
ment be conducted at a temperature of from 100 to
150 ~C.
In the present invention, it is requisite to
conduct the pretreatment for a period of at least 10
minutes under the above-described conditions. A pre-
ferred treating period varies depending on the types of
components of the catalyst slurry and the treatment
temperature. Generally, however, the treating period
is at least 10 minutes, generally in the range of from
several hours to several days.
The reason why in a continuous partial hydrogena-
tion reaction, a complete separation is attained be-
tween an aqueous phase (a catalyst aqueous phase) and
an oil phase by the pretreatment of the catalyst slurry
according to the present invention, so that the compo-
nents of the catalyst slurry are inhibited from getting
mixed into the oil phase, has not yet been elucidated.
However, it is presumed as follows: Even in a compound
generally known as a hydrophll;c compound, a lipophilic
surface is partially formed thereon as viewed micro-
scopically, which lipophilic surface is likely to cause
the compound to get mixed into the oil phase. However,
this lipophilic surface would be changed to a hydro-
philic surface by the pretreatment of the present
_ 16 - 2~A~4
invention.
By virtue of the present invention, a desired
partial hydrogenation reaction product can be continu-
ously obtained without suffering from the excess mixing
of the components of the catalyst slurry into the oil
phase and, hence, the operations, facilities and the
like which are required for separation can be stream-
lined on an industrial scale. The method of the
present invention is highly valuable in the commerce.
Best mode for Carrying Out the Invention
The present invention will now be further illus-
trated in more detail with reference to the following
Examples which should not be construed to be limiting
the scope of the present invention.
The preparation methods of the catalyst slurries
employed in Examples 1, 2 and 4 hereinbelow are the
same as those described in the Examples of U.S. Patent
No. 4,734,536, and the preparation method of the cata-
lyst slurry employed in Example 3 hereinbelow is the
same as that described in the Example of U.S. Patent
No. 4,678,861.
Example 1
A catalyst slurry comprised of 2.5 g of a metallic
ruthenium particulate catalyst (average crystallite
size, 55 ~) containing 7.4 % by weight of zinc, which
;. . - . ~.. , , ,........ ,,, ~ .. ..
. . : ,. - :. . :~:- . : .. :
.,, i ~'' ''i:: , : ;,., : ' '' ' .'
,:.,. ., , - ;:,- -. .; ~ , : . -
., ~ . . .: . .~ ,, - ;,. . . .:
: ,~
,:: :, ::: , :
.: , , -:: ' , . '
,
- 17 - 2055~4
ruthenium catalyst had been obtained by reducing
Ru(OH)3 having contained zinc hydroxide, 15 g of ZrO2
powder (average particle size, 0.35 ~), and 1,400 ml of
an 18 ~i aqueous solution of ZnSO4-7H2O containing
250 mg of ZnSO4-3Zn(OH)2, was charged into a continuous
flow reaction apparatus having an inner capacity of 3
liters which was provided therein with an about 100 ml
stationary vessel for oil phase-aqueous phase separa-
tion (equipped with an inlet for a reaction mixture, an
~ outlet for an aqueous phase, and an outlet for an oil
phase) and had Teflon coating applied at portions to be
brought into contact with the liquid.
Next, the gaseous phase was replaced by a hydrogen
gas, and the temperature was elevated~to 150 ~C over a
period of one hour while~agieating the~catalyst slurry.
Subsequently, hydrogen was introduced to attain a total
ineernal pressure of 50 kg/cm2G, which was kept for 20
hours. Thus, pretreatment of the catalyst slurry was
performed. Thereafter, benzene~was fed at a rate of 2
liter/hr, and the partial hydrogenation reaction of
benzene was continuously carried out while maintaining
a temperature of 150 ~C and a hydrogen pressure of
50 kg/cm2G.
The aqueous phase discharged from the stationary
vessel for oil phase-aqueous phase separation was
-~
. : , , , ,: :, ~. ~, ., - .. : , . - .
., : . , ,, . . . . :
, ~ , : .. , . . . .: ~
- : . , . . i ; .. ... ~, ~
. - -. . . .. .
:.
. ; , . : ~ , : , ~ , :. ," .
- 18 - 2055~
recycled to the reaction system, while the oil phase
discharged was cooled and passed through a polypropyl-
ene microporous filter. The water contents precipitat-
ed from the oil phase due to the occurrence of a super-
saturat.ed state caused by the cooling and the compo-
nents of the catalyst slurry excessively mixed into the
oil phase, were aggreqated and filtered to thereby
separate the same from the oil phase. Thus, the oil
phase as a reaction product was continuously withdrawn.
On the other hand, the separated and collected water
and water-soluble components were appropriately recy-
cled to the reaction apparatus. These operations were
continuously carried on for 500 hours, thereby obtain-
ing a partial hydrogenation reaction mixture comprised
of benzene, cyclohexene and cyclohexane.
An aliquot of the separated and collected water
was taken out, and the amount of the water-soluble
cc onent (ZnS04 and the like) of the catalyot slurry
contained in the collected water was analyzed to find
that the cohtent of this component was as small as 10 -
30 ppm in terms of the amount of Zn by weight relative
to the weight of the separated and collected water.
After the completion of flow reaction, ehe microporous
filter was taken out, and the deposition of 001id
materials thereon was examined. ~he amount of white
; . : .. - : . : ,. .
19 - 2 0 ~
Zr~2 deposited was only of a trace. From the above, it
is apparent that the amount of components of the cata-
lyst slurry which got mixed into the oil phase during
the flow reaction was extremely small, so that substan-
tially no material got mixed into the oil phase, except
only the water, the amount of which corresponded to the
solubility of water in the oil phase at 150 ~C.
Example 2
Substantially the same procedure as in Example 1
was repeated to perform a continuous reaction for 200
hours, except that the pretreatment operation of the
catalyst slurry was conducted by elevating the tempera-
ture to 80 ~C over a period of 30 minutes, and the
pretreatment was continued for 48 hours at the same
temperature. The content of Zn in the water separated
and collected during the continuous reaction was 10-50
ppm by weight. Further, the amount of white ZrO2
deposited on the microporous filter was of a trace, and
the amount of c~ nents of the catalyst getting mixed
into the oil phase during the flow reaction was ex-
tremely small. From the above, it is apparent that
substantially no material got mixed into the oil phase,
except the water, the amount of which corresponded to
the solubility of water in the oil phase at 150 ~C.
Comparative Example 1
~ , , . .' ~' ' ' ,' '
.. . . .
..
-- 2 0
Substantially the same procedure as in ~xample l
was repeated to perform a continuous reaction for 200
hours, except that the pretreatment of the catalyst
slurry was not carried out, and that in the process of
temperature elevation to 150 ~C, feeding of benzene was
started at the time when the temperature reached 100 ~C
by heating for five minutes. The content of Zn in the
water separated and collected during the continuous
reaction was 80-600 ppm by weight. Abou-t 1.0 g of a
mixture of white ZrO2 and the ruthenium catalyst was
deposited on the microporous filter. From the above,
it is apparent that the components of t:he catalyst
slurry excessively got mixed into the oi.l phase.
Example 3
Pretreatment of a catalyst slurry and a partial
hydrogenation reaction of benzene were carried out in
substantially the same manner as in Example 1, except
that a catalyst slurry comprised of 70 g of a hydroge-
nating catalyst composed of 1 % of rutheni.um supported
on lanthanum hydroxide, 700 mg of z:irlc ox.ide, 35 g of
sodium hydroxide and 1400 ml of water used. During the
reaction, an aliquot of the separated and collected
water was taken out, and the amount of components of
the catalyst slurry which was contaLned therein was
analyzed. The amount of Na was as small as 30 to 70
- 21 - 205~
ppm by weight, and the amount of Zn was less than 0.2
ppm by weight, relative to the weight of the separated
and collected water. After the completion of the flow
reaction, the microporous filter was taken out and
ex~ ined to determine solid components deposited there-
on. Only a trace amount of hydrogenating catalyst was
observed.
Comparative Example 2
Substantially the same procedure as in Comparative
Example 1 was repeated to perform a continuous reac-
tion, except that the same catalyst slurry as used in
Example 3 was used. The amount of Na contained in the
water separated and collected during the continuous
reaction was 150-500 ppm by weight, and the amount of
Zn contained therein was 0.5-2 ppm by weight. After
the completion of the flow reaction, deposition of
about 2.5 g of the hydrogenating catalyst was observed
on the microporous filter.
Example 4
Substantially the same procedure as in Example 1
was repeated to perform a continuous reaction, except
that the gaseous phase was replaced by nitrogen at
atmospheric pressure in the pretreatment of the cata-
lyst slurry. The amount of Zn contained in the water
separated and collected during the continuous reaction
... . . ~. : :' ' '.
i ~ . ~' , :' ,
- 22 ~ 5 ~ ~ ~
was 10-60 ppm. Only a trace amount of white ZrO2 was
deposited on the microporous filter. From khe above, it
is apparent that the amount of components of the c~ta-
lyst slurry which got mixed into the oil phase during
the flow reaction was extremely small. The selectivity
for cyclohoxene immediately after the start of the flow
reaction was about 3% lower than that obtained in
Example 1.
Industrial Applicability
sy virtue of the present invention, the continuous
partial hydrogenation of monocyclic aromatic hydrocar-
bons can be efficiently attained. In -the present
invention, partial hydrogenation reaction products can
be efficiently obtained without suffering from the
excess mixing of the components of the catalyst slurry
into an oil phase containing the partial hydrogenation
reaction products, and operations and facilities re-
quired for separation can be simplified. The partial
hydrogenation products oE monocyclic aromatic hydrocar-
bons efficiently obtained by the present inventi.on are
highly valuable as i.ntermediates for the manufacture of
organochemical industrial products, and par-ticularly,
they are important as intermediates for the production
of polyamides and lysines.
