Technical Field

The present invention relates to a method for
producing unsaturated aldehydes and/or unsaturated acids
from olefins by means of fixed-bed catalytic partial
oxidation in a shell-and-tube heat exchange type reactor, as
well as to a fixed-bed shell-and-tube heat exchange type
reactor used in the above method.
Background Art
A process for producing unsaturated aldehydes and/or
unsaturated acids from olefins is a typical example of
catalytic vapor phase oxidation.
In general, catalytic vapor phase oxidation is
implemented as follows. At least one catalyst in the form of
granules is packed into reaction tubes 11, 12, feed gas 1 is
supplied to a reactor through the reaction tubes and the
feed gas is in contact with the catalyst in the reaction
tubes to perform vapor phase oxidation. Reaction heat
generated during the reaction is removed by heat transfer
with a heat transfer medium, wherein the temperature of the
heat transfer medium is maintained at a predetermined
temperature. Particularly, the heat transfer medium for heat
exchange is provided on the outer surface of the catalytic
tubes to perform heat transfer. A reaction mixture 3
containing a desired product is collected via a duct and
then sent to a purification step. Generally, catalytic vapor
phase oxidation is a highly exothermic reaction. Therefore,
it is very important to control the reaction temperature in
a specific range and to downsize hot spots in the reaction

zone.
To perform the partial oxidation of olefins, a
multimetal oxide containing molybdenum and bismuth or
vanadium or a mixture thereof is used as a catalyst.
Typically, the partial oxidation of olefins may be
exemplified by a process for producing (meth)acrolein or
(meth)acrylic acid by oxidizing propylene or isobutylene, a
process for producing phthalic anhydride by oxidizing
naphthalene or ortho-xylene or a process for producing
maleic anhydride by partially oxidizing benzene, butylene or
butadiene.
Generally, propylene or isobutylene is subjected to
.two-step catalytic vapor phase partial oxidation to form
(meth)acrylic acid as a final product. More particularly, in
the first step 10, propylene or isobutylene is oxidized by
oxygen, diluted inert gas, water vapor and an optional
amount of catalyst to form (meth) acrolein 2 as a main
product. In the second step 20, (meth)acrolein obtained from
the preceding step is oxidized by oxygen, diluted inert gas,
water vapor and an optional amount of catalyst to form
(meth) acrylic acid 3. The catalyst used in the first step is
an oxidation catalyst based on Mo-Bif which oxidizes
propylene or isobutylene to form (meth) acrolein as a main
product. Additionally, a part of (meth)acrolein is further
oxidized on the same catalyst to form acrylic acid
partially. The catalyst used in the second step is an
oxidation catalyst based on Mo-V, which oxidizes
(meth) acrolein-containing mixed gas produced in the first
step, particularly (meth)acrolein, to form (meth)acrylic
acid as a main product.
Reactors for carrying out the above process are
realized in such a manner that each of the above two steps

are implemented in one system or in two different systems
(FIG. 1) (see US Patent No. 4,256,783).
Meanwhile, many attempts are made to increase
productivity of the reactor for producing acrylic acid by
modifying the reactor structure, suggesting an optimized
catalyst for oxidation or improving the operational
conditions.
As mentioned above, vapor phase oxidation of
propylene, isobutylene or (meth)acrolein is an exothermic
reaction. Therefore, it has a problem in that a hot spot (a
point whose temperature is abnormally high or where heat
accumulation is relative high) is generated in a catalytic
bed in the reactor. Such hot spots show a relatively high
temperature compared to other parts of the reactor.
Accordingly, in hot spots, complete oxidation proceeds
rather than partial oxidation, thereby increasing by-
products such as COx, and decreasing the yield of
(meth)acrolein or (meth)acrylic acid. Further, the exposure
of catalyst to high temperature causes rapid inactivation of
catalyst, thereby shortening the lifetime of catalyst. To
solve these problems, a method for inhibiting the generation
of hot spots and equalizing the availability of catalyst
over the whole reactor has been studied to obtain
(meth) acrolein or (meth)acrylic acid with high yield and to
use the catalyst for a long time. In this regard, many
improved catalysts have been continuously suggested.
For example, Japanese Laid-Open Patent Nos. Sho43-
24403 and Sho53-30688 disclose a method for packing a
catalytic bed by diluting a catalyst with an inactive
material in a stepwise manner from the inlet of feed gas to
the outlet of feed gas. However, the above method has a
problem in that it takes too much time and is very difficult

to pack the catalytic bed while varying the dilution ratio
with an inactive material from 100% to 0% gradually. In
addition, Korean Laid-Open Patent No. 1997-0065500 and
Japanese Laid-Open Patent No. Hei9-241209 disclose a method
for packing a catalytic bed by controlling the volume of
finally formed catalyst (secondary particles) in such a
manner that the volume gradually decreases from the inlet to
the outlet. However, the above method has problems in that
when the finally formed catalyst has a relatively large
volume, reaction tubes may be obstructed, and that it is not
possible to obtain a desired level of conversion into
acrolein and yield of acrylic acid, due to insufficient
activity of such large catalyst. Further, Korean Laid-Open
Patent No. 2000-77433 and Japanese Laid-Open Patent No.
2000-336060 disclose a method for using multiple kinds of
catalysts formed by varying the kind and amount of alkali
metals. However, the method has a difficulty in producing
catalysts having different activities at a correct ratio
because the amount of alkali metal used therein is small.
Further, Japanese Laid-Open Patent No. 2003-171340 discloses
a method for using multiple kinds of catalysts formed by
varying particle diameters of silicon/carbon compounds
(carrier). When the catalytic activity is controlled by
varying the particles of SiC, particle size of the SiC (used
as a carrier) can decreases and however, it is difficult to
produce catalysts having different activities by a desired
degree, because such decreased carrier particle size bears
no relation to the primary particle size of a catalytically
active component.
Therefore, there is a continuous need for developing a
method for producing unsaturated aldehydes and/or
unsaturated fatty acids with high yield and using a catalyst

stably, by controlling the temperature of the highest hot
spot efficiently.

Brief Description of the Accompanying Drawings
FIG. 1 is a schematic view showing the structure of a
pilot reactor, wherein the first step and the second step of
reactions are performed individually in a different reactor,
each reactor comprising one catalytic tube, and the
structure of a catalytic bed disposed inside of the
catalytic tube.
Disclosure of the Invention
It is an object of the present invention to provide a
method for producing unsaturated aldehydes and/or
unsaturated fatty acids with high yield while using a
catalyst stably, by controlling the temperature of a hot
spot efficiently, wherein the method is performed in at
least one reaction zone of a first reaction zone 10 for
producing unsaturated aldehydes (for example, (meth)
acrolein) as a main product and a second reaction zone 20
for producing unsaturated acids (for example, (meth)acrylic
acid) as a main product; at least one reaction zone of the
first and the second reaction zones is packed with two or
more catalytic layers, thereby dividing the reaction zone(s)
into two or more reaction regions; and a formed product
(secondary particles) of catalyst packed in each of the
catalytic layers is different in particle size of a
catalytically active component (primary particles) by
controlling the particle size of the catalytically active
component (primary particles) in such a manner that it
gradually decreases from the reaction zone at the inlet of
the reactor to the reaction zone at the outlet of the

reactor.
According to an aspect of the present invention, there
is provided a method for producing unsaturated aldehydes
from olefins by means of fixed-bed catalytic partial
oxidation in a shell-and-tube reactor, characterized in that
the reactor includes a reaction zone for producing
unsaturated aldehydes, comprising two or more catalytic
layers, each of the catalytic layers being packed with a
formed product of catalyst as secondary particles, wherein
the secondary particles in each catalytic layer are formed
of primary particles of a catalytically active component
having a different particle size, and the particle size of
primary particles of the catalytically active component is
controlled so that it decreases from the inlet of the
reactor to the outlet of the reactor.
According to another aspect of the present invention,
there is provided a method for producing unsaturated acids
from unsaturated aldehydes by means of fixed-bed catalytic
partial oxidation in a shell-and-tube reactor, characterized
in that the reactor includes a reaction zone for producing
unsaturated acids, comprising two or more catalytic layers,
each of the catalytic layers being packed with a formed
product of catalyst as secondary particles, wherein the
secondary particles in each catalytic layer are formed of
primary particles of a catalytically active component having
a different particle size, and the particle size of primary
particles of the catalytically active component is
controlled so that it decreases from the inlet of the
reactor to the outlet of the reactor.
According to still another aspect of the present
invention, there is provided a shell-and-tube reactor that
may be used in a method for producing unsaturated aldehydes

and/or unsaturated acids from olefins by means of fixed-bed
catalytic partial oxidation, characterized in that the
reactor includes at least one reaction zone of a first-step
reaction zone for producing unsaturated aldehydes as a main
product and a second-step reaction zone for producing
unsaturated acids as a main product, and at least one
reaction zone of the above reaction zones comprises two or
more catalytic layers, each of the catalytic layers being
packed with a formed product of catalyst as secondary
particles, wherein the secondary particles in each catalytic
layer are formed of primary particles of a catalytically
active component having a different particle size, and the
particle size of primary particles of the catalytically
active component is controlled so that it decreases from the
inlet of the reactor to the outlet of the reactor.
Hereinafter, the present invention will be explained
in detail.
The finally formed product of catalyst packed, in . the
reaction tube of the reactor comprises secondary particles
including the aggregate of a plurality of fine unit
particles (primary particles) formed of a catalytically
active component. For example, the finally formed product of
catalyst includes a formed catalyst (secondary particles)
obtained by binding a plurality of primary particles formed
of a catalytically active component and forming them into a
desired shape, and a supported catalyst (secondary
particles) obtained by supporting a plurality of primary
particles formed of catalytically active component on an
inactive carrier having a desired shape.
According to the present invention, particle size of
primary particles providing a formed product of
catalyst(secondary particle) is controlled instead of

controlling particle size of the formed product of catalyst
itself. Therefore, it is possible to prevent obstruction of
a reaction tube and degradation of catalytic activity caused
by controlling particle size of the formed product of
catalyst according to the prior art.
Preferably, the olefin, unsaturated aldehyde and
unsaturated acid compounds have 3-4 carbon atoms and include
propylene or isobutylene, (meth) acrolein and (meth) acrylic
acid, respectively.
Preferably, the catalytically active component in the
formed product of catalyst used in the first-step reaction
zone for producing unsaturated aldehydes as a main product
is a metal oxide represented by the following formula 1:
[formula 1]

wherein Mo is molybdenum;
A is at least one element selected from the group
consisting of Bi and Cr;
B is at least one element selected from the group
consisting of Fe, Zn, Mn, Nb and Te;
C is at least one element selected from the group
consisting of Co, Rh and Ni;
D is at least one element selected from the group
consisting of W, Si, Al, Zr, Ti, Cr, Ag and Sn;
E is at least one element selected from the group
consisting of P, Te, As, B, Sb, Sn, Nb, Cr, Mn, Zn, Ce and
Pb;
F is at least one element selected from the group
consisting of Na, K, Li, Rb, Cs, Ta, Ca, Mg, Sr, Ba and MgO;
and
each, of a, b, c, d, e, f and g represents the atomic
ratio of each element, with the proviso that when a=10, b is

a number of between 0.01 and 10, c is a number of between
0.01 and 10, d is a number of between 0.0 and 10, e is a
number of between 0.0 and 10, f is a number of between 0 and
20, g is a number of between 0 and 10, and h is a number
defined depending on the oxidation state of each of the
above elements.
Preferably, the catalytically active component in the
formed product of catalyst used in the second-step reaction
zone for producing unsaturated acids as a main product is a
metal oxide represented by the following formula 2:
[formula 2)

wherein Mo is molybdenum;
W is tungsten;
V is vanadium;
A is at least one element selected from the group
consisting of iron (Fe), copper (Cu), bismuth (Bi), chrome
(Cr) , cobalt (Co) and manganese (Mn) ;
B is at least one element selected from the group
consisting of tin (Sn), antimony (Sb) , nickel (Ni), cesium
(Cs) and thallium (T1) ;
C is at least one element selected from the group
consisting of alkali metals and alkaline earth metals;
O is an oxygen atom; and
each of a, b, c, d, e and x represents the atomic
ratio of Mo, W, V, A, B and 0 atoms, with the proviso that
when a=10, 0.5 ≤b ≤ 4, 0.5 ≤c ≤ 5, 0 ≤d ≤ 5, 0 ≤e ≤ 2, 0
≤f ≤ 2, and x is a number defined depending on the
oxidation state of each of the above elements.
The formed product of catalyst to be packed into a
reactor finally may be obtained by forming metal oxide
powder (primary particles) through a extrusion process or

palletizing process and baking the resultant product.
Otherwise, it may be obtained by coating metal oxide
(primary particles) in a liquid or powder state onto an
inactive carrier and baking the resultant product.
The metal oxide used in the present invention as a
catalytically active component (primary particles) may be
applied as an aqueous catalyst solution or suspension by
stirring and mixing aqueous solution of salts of metals
forming the metal oxide. Otherwise, it may be applied as
powder by drying the aqueous catalyst solution or
suspension.
In producing the aqueous catalyst solution or
suspension, there is no particular limitation in salts of
metals forming the metal oxide represented by the above
formula 1 or 2, in the case of molybdenum, bismuth, vanadium
and tungsten. Additionally, in the case of other metal
elements, nitrate, acetate, carbonate, organic acid salts,
ammonium salts, hydroxides and oxides may be used.
Further, there is no particular limitation in
temperature during the baking step in the process for
producing the formed product of catalyst according to the
present invention. Generally, the formed product may be used
after baking it at a temperature lower than 500oC for 5-20
hours. The baking temperature of the formed products in each
of the reaction zones may be the same or different.
According to the present invention, it is possible to
control the particle size and particle size distribution of
the catalytically active component (primary particles) by
optionally carrying out a mechanical pulverization step, or
by adjusting the time or strength in the pulverization step,
for the aqueous catalyst solution or suspension during the
formation thereof or after the formation thereof, or for the

powder obtained by drying the aqueous catalyst solution or
suspension. It is the most preferable to control the
pulverization time.
When the pulverization step is performed in a liquid
phase as in the case of aqueous catalyst solution or
suspension, a homogenizer or ultrasonic homogenizer may be
used. On the other hand, when the pulverization step is
performed in a powder state, a ball mill, attrition mill,
dynamo mill, etc., may be used. Otherwise, a method and
apparatus currently used in controlling particle size
distribution may be used. Preferably, the pulverization rate
of a homogenizer is controlled to 10-10000 rpm.
When primary particles having a relatively small size
are produced, it is preferable to increase the work time and
strength of a particle size distribution controller by 1-3
times gradually, compared to primary particles having a
relatively large size.
Meanwhile, a hot spot is referred to as a point whose
temperature is abnormally high or where heat accumulation is
high, in a catalytic bed. In general, in the case of the
first-step reaction zone, the highest hot spot is generated
at the front part of the first-step reaction zone, enriched
with olefins (propylene, isobytylene) as a main reactant and
molecular oxygen. Similarly, in the case of the second-step
reaction zone, the highest hot spot is generated at the
front part of the second-step reaction zone, enriched with
unsaturated aldehydes (acrolein) and molecular oxygen.
Therefore, the catalytic layer packed with a formed product
of catalyst having the largest primary particle size
preferably includes the hot spot having the highest
temperature. Additionally, the primary particle size of the
formed product of catalyst used in the catalytic layer

including the highest hot spot is preferably 10-150 microns,
more preferably 10-100 microns, and most preferably 10-50
microns.
For example, when two catalytic layers each having a
different size of primary particles of catalytically active
component are packed into a reaction tube, the relatively
large size of primary particles ranges from 10 to 150
microns, preferably from 10 to 100 microns, and more
preferably from 10 to 50 microns, while the relative small
size of primary particles is 10 microns or less and
preferably ranges from 0.01 to 10 microns. In a variant,
when three catalytic layers each having a different size of
primary particles of catalytically active component are
packed into a reaction tube, the largest size of primary
particles ranges from 10 to 150 microns, preferably from 10
to 100 microns, and more preferably from 10 to 50 microns,
the medium primary particle size ranges from 1 to 10
microns, and the smallest size of primary particles is 1
micron or less and preferably ranges from 0.01 to 1 micron.
Carriers for use in forming a catalyst by coating a
catalytically active component on a carrier include inactive
carriers such as alundum, silica-alumina and silicon
carbide. When a catalytically active component in a liquid
phase or powder state is supported on a carrier, it is
preferable that the component is contained in a rotary sugar
coater, planetary swing barrel machine, spherudizer, etc. In
addition, when a catalyst is formed by using only the
catalytically active component powder (primary particles)
without any carrier, conventional catalyst forming processes
including an extrusion process, palletizing process, etc.,
may be used. In this case, preferred shapes of the formed
product of catalyst include cylindrical shapes and hollow

cylindrical shapes. However, when a catalyst is formed by
using only the catalytically active component without any
carrier, the catalytic activity may be excessively high.
Therefore, a formed product of catalyst having a hollow
cylindrical shape is more preferable.
There is no particular limitation in shape of a formed
product of catalyst and in content of catalytically active
component used in the present invention. However, when a
catalytically active component is coated on a carrier, it is
advisable that a catalytically active component is supported
on a spherical carrier in an amount of 20-7 0% and formed
into particles having a size of 3-8 mm in order to
facilitate forming and packing of catalyst. On the other
hand, when a catalytically active component (primary
particles) is directly formed into a formed products of
catalyst (secondary particles) without carrier through an
extrusion process or pelletizing process, it is "advisable
that the catalyst has a cylindrical shape having a diameter
of 3-8 mm in which a cavity having a diameter of about 0.5-5
mm is perforated so that the content of catalytically active
component can be 20-70%.
A plurality of formed products of catalyst having
different sizes of primary particles, obtained according to
the presence/absence of a pulverization step and conditions
in the pulverization step are packed into each of the zones
formed by dividing a reaction tube in a reactor in multiple
zones. The more the primary particle size of catalytically
active component decreases, the more the reactivity
increases (while the selectivity and stability decrease).
Therefore, when a catalytic layer having a relatively
largest size of catalytically active component is packed in
the vicinity of the front part of each inlet of the first

and the second reaction zones in which the highest hot spot
is formed, it is possible to reduce heat generation, to
prevent excessive heat accumulation and to inhibit undesired
byproduct formation. Additionally, when catalysts having
relatively small primary particle sizes are packed
sequentially from the next of the hot spot to the rear end
of the reaction tube in such a manner that the primary
particle size decrease, it is possible to increase the
catalytic activity at the rear end of the reaction tube,
thereby increasing the overall yield of a desired product
and producing a desired final product stably for a long
time. More particularly, it is preferable that a catalyst
having the largest primary particle size is used in the
vicinity of the hot spot and a catalyst having a relatively
small primary particle size is used in a part following the
vicinity of the hot spot. According to the present
invention, the primary particle size of a catalytically
active component decreases gradually from the inlet of the
reactor to the outlet of the reactor. In other words, the
catalytic activity increases gradually from the inlet to the
outlet.
Theoretically, when the number of reaction zones
increases, the reaction zones being divided through the use
of different catalytic layers in the first step and the
second step depending on the exothermic temperature
distribution of the reactor, it is possible to control the
reaction heat more easily. However, it is not possible to
increase the number of reaction zones infinitely when viewed
from a commercial point of view. Therefore, in order to
satisfy the effect of the present invention to a desired
degree, it is preferable to use two or three reaction zones.
Meanwhile, each catalytic layer may be packed to any height

capable of controlling the heat generation of the reactor
efficiently. The packing height of the catalytic layer
having the largest primary particle size of catalytically
active component preferably includes the highest hot spot.
More particularly, the above-mentioned packing height,
starting from the inlet, is 10-50%, preferably 10-30% of the
total height of the catalytic bed.
Since methods for packing a catalyst into a commercial
reactor are generally known, a packing method suitable for a
given reactor can be used. Additionally, it is preferable to
pack a predetermined amount of catalyst separately for each
reaction tube.
For example, in order to perform oxidation in a
reactor according to the present invention, a feed gas 1
including 1-10 volume% of a feed compound such as propylene,
1-15 volume% of oxygen, 5-60 volume% of water vapor and 20-
80 volume% of an inert gas is introduced onto a catalyst at
a temperature ranging from 200°C to 350°C, under a pressure
of between atmospheric pressure and 3 atm, at a space
velocity of 500-4000 hr-1 (STP) .
Mode for Carrying Out the Invention
Reference will now be made in detail to the preferred
embodiments of the present invention. It is to be understood
that the following examples are illustrative only and the
present invention is not limited thereto.
Example 1
(Preparation of Catalyst 1)
To a 50L glass reactor equipped with a conventional
branch type agitator and homogenizer, 40L of distilled water
was introduced and then heated. At 90°C, 10,000 g of
ammonium molybdate was dissolved therein to form solution

(1) . To 2500 ml of distilled water, 6600 g of cobalt
nitrate, 4120 g of bismuth nitrate, 2750 g of iron nitrate,
185 g of cerium nitrate and 28.63 g of potassium nitrate
were added and then mixed thoroughly to form solution (2) .
Solution (1) was mixed with solution (2) slowly by using the
homogenizer. After both solutions were completely mixed, the
homogenizer was further operated for 30 minutes
continuously. The resultant suspension was collected and the
particle size distribution of precipitate was determined.
The precipitate comprised 90% or more of particles having a
size of 10-50 microns with no particles having a size
greater than 100 microns.
After the suspension obtained as described above was
dried for 12 hours or more, the resultant powder was
pulverized and formed into ring-shaped pellets having an
inner diameter of 2 mm, outer diameter of 6 mm and a length
of 6 mm. The pellets were baked at 450°C under air for 5
hours and then checked for catalytic activity.
The resultant catalytically active component had the
composition of: (Catalyst 1),
excluding oxygen.
(Preparation of Catalyst 2)
The process described in the above Preparation of
Catalyst 1 was repeated to provide Catalyst 2, except that
the homogenizer was used for 60 minutes. The resultant
suspension was collected and the particle size distribution
of precipitate was determined. The precipitate comprised 93%
or more of particles having a size of 10 microns or less.
The resultant catalytically active component had the
composition of: (Catalyst 2),
excluding oxygen.
(Oxidation)

To a stainless steel reactor having an inner diameter
of 1 inch, Catalyst 1 was packed to the height of 300 mm and
Catalyst 2 was packed to the height of 600 ram, from the
inlet of the reaction gas toward the outlet. Then, a mixed
gas containing 8 volume% of propylene, 14 volume% of oxygen,
18 volume% of water vapor and 60 volume% of inert gas was
subjected to oxidation at the space velocity of 1600 hr-1 and
at the reaction temperature of 280°C. The results are shown
in the following Table 2.
Comparative Example 1
Oxidation in Example 1 was repeated, except that
Catalyst 1 was packed alone to the height of 900 mm instead
of using Catalyst 1 together with Catalyst 2. The results
are shown in the following Table 2.
Comparative Example 2
Oxidation in Example 1 was repeated, except that
Catalyst 2 was packed alone to the height of 900 mm instead
of using Catalyst 1 together with Catalyst 2. The results
are shown in the following Table 2.
Comparative Example 3
(Preparation of Catalyst 3)
The process described in the above Preparation of
Catalyst 1 was repeated to provide Catalyst 3, except that
the homogenizer was not used. The resultant suspension was
collected and the particle size distribution of precipitate
was determined. The precipitate comprised no particles
having a size of 100 microns or less. The resultant
catalytically active component had the composition of:
(Catalyst 3), excluding oxygen.
(Oxidation)
Oxidation in Example 1 was repeated, except that
Catalyst 3 was packed alone to the height of 900 mm instead

of using Catalyst 1 together with Catalyst 2. The results
are shown in the following Table 2.
Example 2
(Preparation of Catalyst 4)
To a 50 L glass reactor equipped with a conventional
branch type agitator and homogenizer, 30 L of distilled
water was introduced and then heated. After reaching the
boiling point, 2960 g of ammonium paratungstate, 10000 g of
ammonium molybdate and 2320 g of ammonium metavanadate were
introduced thereto, in turn. Then, the mixture was heated so
as to maintain the boiling state, while agitating the
mixture until it was completely dissolved. Next, an aqueous
solution containing 1370 g of copper nitrate, 1650 g of
nickel nitrate and 960 g of strontium nitrate in 2.6 L of
water was added to the mixed aqueous solution containing the
above three kinds of ammonium salts, while the homogenizer
was rotated at 4000 rpm. After both aqueous solutions were
completely mixed, the homogenizer was further operated for
30 minutes. The resultant suspension was collected and the
particle size distribution of precipitate was determined.
The precipitate comprised 80% or more of particles having a
size of 10-50 microns with no particles having a size
greater than 100 microns.
The suspension obtained as described above was sprayed
onto a silica-alumina carrier having a diameter of 5 mm
disposed in a sugar coater through a spray nozzle to coat
the carrier. At the same time, the coated carrier was dried
with hot air at 100 °C to obtain a catalyst supported on a
carrier. The resultant catalyst supported on a carrier was
baked at 4 50°C for 5 hours under air flow to provide a
finally formed product of catalyst (Catalyst 4). After
baking, the amount of the coated catalyst powder was 30 wt%

based on the total weight of the carrier and the catalyst
powder. The resultant catalytically active component had the
composition of: excluding oxygen.
(Preparation of Catalyst 5)
The process described in the above Preparation of
Catalyst 4 was repeated to provide Catalyst 5, except that
the homogenizer was used for 1 hour. The resultant
suspension was collected and the particle size distribution
of precipitate was determined. The precipitate comprised 80%
or more of particles having a . size of 10 microns or less.
The resultant catalytically active component had the
composition of: excluding oxygen.
(Oxidation)
To a stainless steel reactor having an inner diameter
of 1 inch, Catalyst 4 was packed to the height of 1000 mm
and Catalyst 5 was packed to the height of 2000 mm, when
viewed from the inlet of the reaction gas toward the outlet.
Then, a mixed gas containing 7 volume% of acrolein, 13
volume% of oxygen, 20 volume% of water vapor and 60 volume%
of inert gas was subjected to oxidation at the space,
velocity of 1800 hr-1 and at the reaction temperature of
250°C.
Comparative Example 4
Oxidation in Example 2 was repeated, except that
Catalyst 4 was packed alone to the height of 3000 mm.
Comparative Example 5
Oxidation in Example 2 was repeated, except that
Catalyst 5 was packed alone to the height of 3000 mm.
Comparative Example 6
(Preparation of Catalyst 6)
The process described in the above Preparation of
Catalyst 4 in Example 2 was repeated to provide Catalyst 6,

except that the homogenizer was not used. The resultant
suspension was collected and the particle size distribution
of precipitate was determined. The precipitate comprised no
particles having a size of 100 microns or less. The
resultant catalytically active component had the composition
of: excluding oxygen.
(Oxidation)
Oxidation in Example 2 was repeated, except that
Catalyst 6 was packed alone to the height of 3000 mm instead
of using Catalyst 4 together with Catalyst 5.
Example 3
(Preparation of Catalyst 7)
To a 50 L glass reactor equipped with a conventional
branch type agitator and homogenizer, 30 L of distilled
water was introduced and then heated. After reaching the
boiling point, 2960 g of ammonium paratungstate, 10000 g of
ammonium molybdate and 2320 g of ammonium metavanadate were
introduced thereto, in turn. Then, the mixture was heated so
as to maintain the boiling state, while agitating the
mixture until it was completely dissolved. Next, an aqueous
solution containing 2740 g of copper nitrate, 2400 g of
niobium nitrate and 960 g of strontium nitrate in 2.6 L of
water was added to the mixed aqueous solution containing the
above three kinds of ammonium salts, while the homogenizer
was rotated at 4000 rpm. After both aqueous solutions were
completely mixed, the homogenizer was further operated for
30 minutes. The resultant suspension was collected and the
particle size distribution of precipitate was determined.
The precipitate comprised 80% or more of particles having a
size of 10-50 microns with no particles having a size
greater than 100 microns.
After the suspension obtained as described above was

dried for 12 hours or more, the resultant powder was
pulverized and formed into ring-shaped pellets having an
inner diameter of 4 mm, outer diameter of 6 mm and a length
of 6 mm. The pellets were baked at 4 50°C under air for 5
hours to provide a finally formed product of catalyst
(Catalyst 7) . The resultant catalytically active component
had the composition of: excluding
oxygen.
(Preparation of Catalyst 8)
The process described in the above Preparation of
Catalyst 7 was repeated to provide Catalyst 8, except that
the homogenizer was used for 1 hour. The resultant
suspension was collected and the particle size distribution
of precipitate was determined. The precipitate comprised 80%
or more of particles having a size of 10 microns or less.
The resultant catalytically active component had the
composition of: excluding oxygen.
(Oxidation)
To a stainless steel reactor having an inner diameter
of-1 inch, Catalyst 7 was packed to the height of 300 mm and
Catalyst 8 was packed to the height of 600 mm, when viewed
from the inlet of the reaction gas toward the outlet. Then,
a mixed gas containing 7 volume% of acrolein, 13 volume% of
oxygen, 20 volume% of water vapor and 60 volume% of inert
gas was subjected to oxidation at the space velocity of 1800
hr-1 and at the reaction temperature of 250°C.
Comparative Example 7
Oxidation in Example 3 was repeated, except that
Catalyst 7 was packed alone to the height of 900 mm.
Comparative Example 8
Oxidation in Example 3 was repeated, except that
Catalyst 8 was packed alone to the height of 900 mm.

Comparative Example 9
(Preparation of Catalyst 9)
The process described in the above Preparation of
Catalyst 7 in Example 3 was repeated to provide Catalyst 6,
except that the homogenizer was not used. The resultant
suspension was collected and the particle size distribution
of precipitate was determined. The precipitate comprised no
particles having a size of 100 microns or less. The
resultant catalytically active component had the composition
of: excluding oxygen.
(Oxidation)
Oxidation in Example 3 was repeated, except that
Catalyst 9 was packed alone to the height of 900 mm instead
of using Catalyst 7 together with Catalyst 8.
The following Table 1 shows the particle size and
particle size distribution of primary particles formed of
catalytically active component in the finally formed product
of catalyst obtained from the above Examples and Comparative
Examples.
[Table 1]



The following Table 2 shows the results obtained from
the oxidation of propylene performed by using each of the
reactors packed with the catalysts according to Example 1
and Comparative Examples 1, 2 and 3. Further, the following
Table 3 shows the results obtained from the oxidation of
acrolein performed by using the catalysts according to
Examples 2 and 3 and Comparative Examples 4-9.
In Tables 2 and 3, the reactant (propylene or
acrolein) conversion ratio, selectivity and yield are
calculated based on the following mathematical formulae 1-6.
[mathematical formula 1]
propylene conversion ratio(%) = [moles of reacted
propylene/moles of supplied propylene] X 100
[mathematical formula 2]
selectivity(%) to acrolein + acrylic acid = [moles of
produced acrolein and acrylic acid/moles of reacted
propylene] X 100
[mathematical formula 3]
yield(%) of acrolein + acrylic acid = [moles of
produced acrolein and acrylic acid/moles of supplied
propylene] X 100
[mathematical formula 4]

acrolein conversion ratio (%) = [moles of reacted
acrolein/moles of supplied acrolein] X 100
[mathematical formula 5]
selectivity(%) to acrylic acid = [moles of produced
acrylic acid/moles of reacted acrolein] X 100
[mathematical formula 6]
yield(%) of acrylic acid = [moles of produced acrylic
acid/moles of supplied acrolein] X 100.
FTable 21



As shown in Tables 2 and 3, Examples 1, 2 and 3 using
two kinds of formed catalysts having different primary
particle size of catalytically active component to perform
oxidation provide excellent reactant (propylene or acrolein)
conversion ratio and selectivity and yield to a desired
product compared to Comparative Examples 1-9 using a formed
catalyst having the same primary particle size of
catalytically active component, respectively.
Industrial Applicability
As can be seen from the foregoing, according to the
present invention using two kinds of catalysts having a
different particle size of catalytically active component,
it is possible to efficiently control the temperature of the
highest hot spot in a reactor, to use a catalyst stably and
to produce unsaturated aldehydes and/or unsaturated fatty
acids with high yield. Additionally, it is possible to
produce unsaturated aldehydes and/or unsaturated fatty acids
in a stable manner even under a high concentration of
starting materials, high space velocity and high load,

thereby improving the productivity significantly.

WE CLAIM:
1. A shell-and-tube reactor that may be used in a the method for producing unsaturated
aldehydes (2) and/or unsaturated acids (3) from olefins (1) by means of fixed-bed catalytic partial
oxidation, wherein the reactor comprises at least one reaction zone of a first-step reaction zone (11)
for producing unsaturated aldehydes (2) as a main product and a second-step reaction zone (21) for
producing unsaturated acids (3) as a main product, and at least one reaction zone of the reaction
zones comprises two or more catalytic layers, each of the catalytic layers being packed with a
formed product of catalyst as secondary particles;; wherein the secondary particles in each catalytic
layer are formed of primary particles of a catalytically active component having a different particle
size, and the particle size of primary particles of the catalytically active component is controlled so
that it decreases from an inlet of the reactor to an outlet of the reactor.
2. The reactor as claimed in claim 1, wherein the catalytically active component is obtained
by agitating and mixing a solution of salts of metals forming a metal oxide to form an aqueous
catalyst solution or suspension; and carrying out a pulverization step during or after the formation
of the aqueous catalyst solution or suspension in order to control the primary particle size of the
catalytically active component.
3. The reactor as claimed in claim 1, wherein the catalytically active component is obtained
by agitating and mixing a solution of salts of metals forming a metal oxide to form an aqueous
catalyst solution or suspension; and drying the aqueous catalyst solution or suspension to obtain
powder and pulverizing the powder to control the primary particle size of the catalytically active
component.
4. The reactor as claimed in claim 1, wherein the formed product of catalyst is a formed
catalyst obtained by binding a plurality of primary particles formed of a catalytically active
component and forming them into a desired shape, or a supported catalyst obtained by supporting a
plurality of primary particles formed of a catalytically active component on an inactive carrier
having a desired shape.
5. The reactor as claimed in claim 1, wherein the catalytic bed is packed in two catalytic
layers, including a first layer having a catalytically active component with a primary particle size of
10-150 microns and a second layer having a catalytically active component with a primary particle
size of 10 microns or less.

6. The reactor as claimed in claim 1, wherein the catalytic bed is packed in three catalytic
layers, including a first layer having a catalytically active component with a primary particle size of
10-150 microns, a second layer having a catalytically active component with a primary particle size
of 1-10 microns, and a third layer having a catalytically active component with a primary particle
size of 1 micron or less.

The invention discloses a shell-and-tube reactor that may be used in a the method for producing
unsaturated aldehydes (2) and/or unsaturated acids (3) from olefins (1) by means of fixed-bed
catalytic partial oxidation, wherein the reactor includes at least one reaction zone of a first-step
reaction zone (11) for producing unsaturated aldehydes (2) as a main product and a second-step
reaction zone (21) for producing unsaturated acids (3) as a main product, and at least one reaction
zone of the reaction zones comprises two or more catalytic layers, each of the catalytic layers being
packed with a formed product of catalyst as secondary particles ; wherein the secondary particles in
each catalytic layer are formed of primary particles of a catalytically active component having a
different particle size, and the particle size of primary particles of the catalytically active component
is controlled so that it decreases from an inlet of the reactor to an outlet of the reactor.