JPH04169552A - Production of isopropyl acetate - Google Patents

Abstract

PURPOSE:To advantageously obtain the title compound by feeding acetic acid and propylene both in a liquid state to a specific catalytic layer of a continuous circulation type fixed bed reactor in a counter flow under a specific condition and recycling the reaction mixture to the catalytic layer at a specific temperature at a specific ratio. CONSTITUTION:A continuous circulation type fixed bed reactor 2 having a catalytic layer 3 packed with a styrene-based (and/or phenol) sulfonic acid type ion exchange resin catalyst wherein an inlet temperature of the catalytic layer is maintained at 80-120 deg.C is charged with acetic acid and propylene both in a liquid state in a counter flow under conditions of a molar ratio A of acetic acid/propylene in a feed flow 1 of 1.0-2.0 and LHSV based on the catalytic layer 3 of acetic acid of 0.1-2.0 and the prepared reaction mixture is cooled to >=70 deg.C, is circulated through an inlet of circulation flow 4 to the catalytic layer 3 in a ratio shown by the formula (X is weight ratio of circulation flow rate/feed flow rate) to give the title compound useful as a solvent, perfume, etc., by using an inexpensive reactor by a liquid-phase reaction efficiently and in readily temperature control in a reaction zone, in high propylene conversion ratio and high productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a continuous process for producing isopropyl acetate by adding propylene to acetic acid in the presence of an acidic ion exchange resin catalyst. Isopropyl acetate produced according to the present invention is a substance useful as a solvent, a fragrance, and the like.

[Prior Art and Problems to be Solved by the Invention] It is well known that when acetic acid and propylene are reacted using an acidic ion exchange resin catalyst, isopropyl acetate is obtained as shown in the following formula.

CHsCOOH+ CHa=CH-CHs -CHsC
OOCH(CHs)z The above esterification reaction is known to include liquid phase reaction, gas phase reaction, and gas-liquid mixed phase reaction, but in gas phase reaction, polymerization of propylene on the catalyst is unavoidable. This is not preferred industrially because it has the disadvantage of shortening the catalyst life. In addition, special public service 1983-
Publication No. 44295 discloses a gas-liquid cocurrent multiphase reaction using liquid acetic acid and gaseous propylene. According to this, since liquid acetic acid moistens the catalyst surface, the catalyst efficiency is increased, and as a result, it becomes possible to use mild reaction conditions.

However, since gaseous propylene passes through the catalyst layer, there is an unavoidable disadvantage that the contact efficiency in that part inevitably decreases. Furthermore, in the case of this gas-liquid multiphase reaction, the propylene that reacts is actually considered to be propylene dissolved in acetic acid, and when the propylene in the liquid phase is consumed by the esterification reaction, gaseous propylene is regenerated. It needs to be dissolved in the liquid phase, which takes time. Therefore, a liquid phase reaction in which both propylene and acetic acid are reacted in a liquid phase is an industrially preferred method.

Regarding the reaction method of the above-mentioned esterification reaction, a continuous method is industrially more advantageous than a batch method. In the case of continuous type reactors, there are continuous seed reactors, fixed bed flow reactors, moving bed reactors, fluidized bed reactors, etc., but when considering the cost and maintenance of the equipment, fixed bed continuous pipes are preferable. type reactors are most preferred. However, when attempting to industrialize the above reaction using a fixed bed continuous tubular reactor, the above reaction is a large exothermic reaction and is inevitably accompanied by a temperature rise in the flow direction.

Therefore, the rate of the reverse reaction in which the produced isopropyl acetate decomposes into acetic acid and propylene increases, and the final conversion rate of propylene cannot be increased by conventional methods.
It has been found that if the temperature rises significantly, the activity of the catalyst, especially the ion exchange resin catalyst, is lost. Therefore, in order to ensure high propylene conversion and catalytic activity, it is necessary to appropriately manage and control the temperature distribution within the reaction zone.

For example, European Patent Publication No. 0054576 discloses a multi-tubular fixed bed reactor. When such a complex reactor is used, it is necessary to provide sufficient pressure resistance, which is not preferable because the construction cost of the reaction equipment increases and maintenance such as catalyst replacement becomes complicated.

Therefore, in order to realize the above-mentioned esterification reaction using a single-tube fixed bed reactor which is advantageous in terms of cost and maintenance, there is a strong need for the development of an inexpensive and easy reaction temperature control method.

[Means for Solving the Problems] That is, the present invention provides a method in which the molar ratio of acetic acid to propylene in the feed stream is in the range of 1.0 to 2.0, and the LHSV of acetic acid to the catalyst layer is in the range of 0.1 to 10. Continuous flow fixed type in which the inlet temperature of the catalyst bed filled with styrene-based sulfonic acid type ion exchange resin and/or phenol sulfonic acid type ion exchange resin catalyst is maintained in the temperature range of 70°C to 102°C under certain conditions. Both acetic acid and propylene are supplied in liquid form and in parallel flow to the bed reactor, the resulting reaction mixture is cooled to a temperature not lower than 70°C, and the mixture is added to the catalyst layer according to the ratio represented by the following formula (I). The present invention relates to a method for producing isopropyl acetate, which is characterized by recycling.

Here, X indicates the circulation ratio, defined as the weight times the circulation flow rate to the feed flow rate, and A indicates the molar ratio of acetic acid to propylene in the feed stream.

The present invention will be further explained below.

The acidic ion exchange resin referred to in the present invention is an ion exchange resin exhibiting acidity, and is a styrene sulfonic acid type resin or a phenol sulfonic acid type resin. Styrenic sulfonic acid type ion exchange resin is a sulfonated resin obtained by copolymerizing styrene and a polyunsaturated compound such as divinylbenzene. Furthermore, the phenolsulfonic acid type ion exchange resin is usually a product obtained by condensing phenolsulfonic acid with pormaldehyde.

As a source of propylene used in the present invention, a hydrocarbon mixture containing about 20% by weight or more of propylene can be used, and such a hydrocarbon mixture can be obtained by catalytically cracking petroleum such as naphtha. A Cs fraction containing propylene is effective.

In the method of the present invention, in order to suppress heat generation due to the reaction, C
s fraction (hereinafter sometimes referred to as rFCC propylene)
It is preferable to use

In addition to hydrocarbons having three carbon atoms such as propylene and propane, this FCC propylene also contains trace amounts of olefins having other than three carbon atoms, heavy metals, sulfur, and the like. Therefore, olefins with a carbon number other than 3 react with acetic acid, producing impurities that reduce the purity of the unreacted raw material acetic acid and the product isopropyl acetate, or heavy metals and sulfur deteriorate the catalyst. There are concerns that this may encourage However, as will be explained in the Examples below, these disadvantages do not occur in the method of the present invention.

The molar ratio of acetic acid/propylene in the feed stream of new raw materials to the catalyst bed (herein simply referred to as "feed stream") is 1.0 to 2.01, more preferably 1.2 to 2.0.
shall be. If the molar ratio is less than 1.0, side reactions such as propylene polymerization will increase, which is economically unfavorable. Also,
When the molar ratio is greater than 2°0, the amount of unreacted acetic acid is large;
This is not preferable because it increases the burden of recovery such as distillation.

Propylene and acetic acid can be fed to the reactor separately or in a mixture as long as the above molar ratio is maintained. Note that the above-mentioned supply flow refers to a flow that does not include the circulation flow described below. Therefore, the acetic acid and propylene in the above molar ratio do not contain components derived from the circulating flow described below.

The supply flow rate to the catalyst layer is determined by the LHSV of acetic acid to the catalyst layer.
preferably 0.1 to 10, more preferably 0.2
It is in the range of ~5. If LHSV is less than 0.1, the production efficiency will be too low, which is not preferable. On the other hand, LHSV is 1
If it is larger than 0, the average residence time in the catalyst layer necessary for the reaction cannot be ensured and the conversion rate becomes low, which is not preferable.

The reaction pressure in the reactor in the present invention may be a pressure sufficient to maintain the reaction system in a liquid phase, for example, 15 kg/cm"
~100kg/cm”, more preferably 15kg/mark 2
It can be appropriately selected from the range of ~50 kg/cm'. If the reaction pressure is lower than 15 kg/cm'', a gas phase will be generated, which is not preferable.
If it is higher than 1", unnecessary pressure-resistant equipment will be provided, which is economically undesirable.

Although the reaction targeted by the present invention is an exothermic reaction, the present inventors believe that temperature control within the reaction zone is important in order to realize this in a flow-through fixed bed reactor that does not require construction costs. discovered and established a method.

That is, the reaction temperature near the inlet of the catalyst layer in the reactor needs to be 70 to 120°C. As mentioned above, the reaction of the present invention is an exothermic reaction, but since the above temperature indicates the temperature near the inlet of the catalyst layer, in order to maintain the temperature within the above range, heating must be carried out as appropriate, taking into account the presence of circulation flow. Or this can be easily achieved by cooling. If the temperature near the inlet of the catalyst layer is lower than 70° C., the reaction rate will be too slow even if the subsequent temperature of the catalyst layer is high, which is not preferable. Furthermore, if the temperature is higher than 120°C, the rate of the reverse reaction in which isopropyl acetate decomposes into acetic acid and propylene increases, which not only makes it impossible to increase the conversion rate of propylene, but also causes many side reactions such as propylene polymerization (which is not preferable).

In the present invention, a specific amount of at least a part of the reaction mixture, which is a reaction product that has passed through the catalyst bed, is circulated to the catalyst bed through an appropriate heat removal equipment such as a heat exchanger, so that It is important to control the temperature. During the circulation, unreacted substances or the desired isopropyl acetate are circulated without being particularly separated from the reaction product flowing out from the reactor.

The temperature of the circulating flow that is circulated to the catalyst bed via appropriate heat removal equipment is naturally lower than the temperature of the reaction product at the outlet of the catalyst bed because it is circulated after being cooled. The temperature does not fall below the temperature near the inlet, i.e. 7
Cool to a temperature not below 0°C. If the catalyst is cooled to a temperature lower than 70° C. and circulated, the temperature of the catalyst layer into which the circulating flow is introduced becomes too low, which is not preferable. More preferably, the temperature is approximately the same as the reaction temperature in the catalyst layer portion to be introduced.

The circulation flow rate required for the reaction temperature control of the present invention varies depending on the amount of heat generated within the reaction region, the allowable temperature rise range, the amount of heat dissipated to the outside of the reaction region, and the like. Additionally, the amount of heat generated within this reaction zone varies depending on the molar ratio of acetic acid to propylene in the feed stream and the feed flow rate.

As a result of intensive research into these complex factors, the present inventors found that the circulation ratio The present invention was completed by discovering that appropriate temperature control is possible if the molar ratio A is equal to or higher than the value expressed by the above formula (I) as a variable.

In particular, it would not be expected that in the reaction of the invention the circulation factor is defined solely by the molar ratio A of acetic acid to propylene in the feed stream.

Although there is no particular upper limit to the circulation rate, a circulation rate greater than necessary increases the burden on equipment, energy, etc. required for circulation (which is undesirable; in practical terms, it is 100 times or less).

In the present invention, there is no particular restriction on the position of the catalyst layer where the circulating flow is introduced. For example, as shown in FIG. 1, the recycle stream can be circulated at a location where it joins the feed stream at the reactor inlet.

However, in order to effectively exhibit the temperature control effect of the circulating flow, it is also possible to circulate the circulating flow to a position in the middle of the catalyst layer, as shown in FIG. 2, for example.

However, in this case, if the volume of the catalyst bed from the position where the circulation flow is introduced to the catalyst bed outlet is V, the position is preferably one where the volume is 1/10 or more of the total volume of the catalyst bed. If it is introduced at a position rearward than this position, the circulating flow will not be sufficiently dispersed within the catalyst layer, making stable temperature control difficult, and thus is not suitable.

Although the method of the present invention has been described using a single stage reactor, it may also be a reactor having two or more stages arranged in series as long as the above-mentioned conditions are met.

In the case of a plurality of series reactors, both the above-mentioned feed stream and the temperature near the catalyst bed inlet refer respectively to the temperature in the first reactor where the reaction initially takes place, and also the temperature at which the above-mentioned circulating flow is circulated. The catalyst layer volume in the description of the position means the total volume of the catalyst layers in a plurality of reactors.

In addition, by appropriately extracting from the reaction mixture and distilling it, the target product, isopropyl acetate, of high purity can be easily obtained.

[Example code] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Here, the composition of the FCC propylene used in the following examples was 76.1% by weight of propylene and 22% by weight of propane.
It is 0% by weight. Furthermore, the molar ratio refers to the molar ratio of acetic acid to propylene, and LHSV is based on the amount of acetic acid supplied.

In the center of a stainless steel cylindrical tube with a length of 2 m and an inner diameter of 10 cm, a catalyst containing Rectit 5PC118 (H- The reactor was filled with 10 liters of mold (trade name), and the remaining space was filled with porcelain Raschig rings to form a fixed bed continuous flow reactor.

This reactor was placed vertically in a constant temperature bath maintained at 85°C.
A device as shown in Figure 1 was created. A constant temperature bath is not shown.

That is, a liquid feed stream 1 consisting of acetic acid and propylene is fed to a reactor 2 and reacts in a catalyst bed 3, and the reaction mixture is withdrawn via a circulation pump. The reaction mixture is cooled via a heat exchanger and a portion thereof is recycled to the circulation inlet 4. The circulating flow is connected to the supply stream 1 at the circulating flow inlet 4.
join with.

Moreover, the reaction mixture is continuously extracted from the reaction mixture outlet 5.

The reactor was fed with a feed stream of acetic acid at an LHSV of 1.0 and a molar ratio of propylene (95 wt% purity) of 1.43 at a reaction pressure of 40 kg/cm2. The circulating stream was cooled to 85° C. via a heat exchanger, circulated at a circulation factor of 12 (calculated circulation factor calculated from the above formula (I): 2.Q), and introduced from the inlet of the catalyst bed. At this time, the temperature distribution inside the catalyst tank was increasing monotonically, and the temperature at the inlet and outlet of the catalyst layer was 8.
5°C and 92°C.

The effluent reaction mixture was analyzed by gas chromatography every 5 hours, and in a steady state with a stable composition, the conversion of propylene was 89.8 mol%, the selectivity to isopropyl acetate was 96.6 mol%, and 1 Even after continuous operation for 0.000 hours, the activity of the catalyst hardly changed, and similar conversion rates and selectivities were obtained.

Examples 2 to 5 In the apparatus of Example 1, the catalyst was Amberlyst-15 (+'!- type, manufactured by Rohm and Haas), which is an acidic ion exchange resin catalyst made by sulfonating a styrene-divinylbenzene copolymer. Product name), F
The reaction was carried out in the same manner as in Example 1, except that CC propylene was used as the raw material propylene, and the catalyst bed inlet temperature, molar ratio, LHSV, reaction pressure, and circulation ratio were changed.

The results obtained are shown in Table 1. No decrease in catalyst activity was observed in either case.

Table 1 Examples 6 and 7 The reaction was carried out in the same manner as in Example 3, except that an apparatus as shown in FIG. 2 was used in which the position at which the circulating flow was introduced into the catalyst bed could be changed. Note that a constant temperature bath is not shown.

That is, in FIG. 2, a liquid feed stream 1 consisting of acetic acid and propylene is fed to a reactor 2, reacts in a catalyst bed 3, and the reaction mixture is withdrawn via a circulation pump.

The reaction mixture is cooled through a heat exchanger, and a portion of the reaction mixture is introduced into the catalyst bed 3 as a recycle stream through a recycle flow inlet 4 located in the middle of the catalyst bed 3 . Moreover, the reaction mixture is continuously extracted from the reaction mixture outlet 5.

The results obtained with the reactor shown in FIG. 2 are shown in Table 2. No decrease in catalyst activity was observed in either case.

Table 2 (Note) Circulation position: Shown as the value obtained by dividing the catalyst bed volume from the circulation flow introduction position to the catalyst bed exit by the total catalyst bed volume.

Comparative Example 1 The reaction was carried out in the same manner as in Example 2, except that the reaction mixture was circulated without being circulated. As a result, the temperature inside the catalyst tank increased rapidly, and the temperature at the outlet reached 180°C or higher. A large amount of sulfur dioxide gas was detected at the outflow of the reactor, so the reaction was stopped and the catalyst layer was examined.The catalyst, which was astringent brown before the reaction, had turned black and had lost most of its acid activity. .

Comparative Examples 2 and 3 Reactions were carried out in the same manner as in Examples 4 and 5, respectively, except that the circulation ratio was changed.

The results obtained are shown in Table 3. In both cases, the catalyst lost its activity within several hours to several minutes.

Table 3 [Effects of the Invention] The method of the present invention realizes an efficient liquid phase reaction in a fixed bed continuous tubular reactor that does not require much equipment cost,
Furthermore, it has become possible to easily manage and control the temperature distribution within the reaction region, and to stably ensure a high conversion rate of propylene and high production efficiency of isopropyl acetate. This also means that the mixed gas of propylene and propane separated from the reaction mixture is economical enough to be disposed of as is, so there is no need to further recover, purify, pressurize, and reuse propylene. This has the effect of significantly reducing equipment costs.

Furthermore, as seen in the examples, the selectivity to inpropyl acetate is sufficiently high, and not only is the variable cost reduced, but it is also easy to purify isopropyl acetate and unreacted acetic acid.

[Brief explanation of the drawing]

FIGS. 1 and 2 are process diagrams including reactors used in Examples. 1...Feed stream 2...Reactor 3...Catalyst layer 4...Circulating flow inlet 5...Reaction mixture outlet Patent applicant Nippon Petrochemical Co., Ltd.

Claims (2)

[Claims] (1) The molar ratio of acetic acid to propylene in the feed stream is 1.
．． LH in the range of 0 to 2.0 and for the acetic acid catalyst layer
Under conditions where the SV is 0.1 to 10, the inlet temperature of the catalyst bed filled with the styrene sulfonic acid type ion exchange resin catalyst and/or the phenolsulfonic acid type ion exchange resin catalyst is set at 70°C to 120°C. Acetic acid and propylene were both fed in liquid form and in parallel flow to a continuous flow fixed bed reactor maintained at a temperature range, and the resulting reaction mixture was
A method for producing isopropyl acetate, characterized in that it is cooled to a temperature not lower than 0°C and circulated through the catalyst layer at a rate expressed by the following formula (I): (7.9A+4.9)/(3.7A^) 2+1.17A-
1)≦X(I) where X indicates the circulation ratio, defined as the weight multiple of the circulation flow rate to the feed flow rate, and A indicates the molar ratio of acetic acid to propylene in the feed stream. 2. The method according to claim 1, characterized in that (2) a feed stream consisting of a C_3 fraction obtained by catalytic cracking of petroleum and acetic acid is used.