JPH03188032A - Preparation of propylene - Google Patents

Abstract

PURPOSE:To prepare highly pure propylene in a high yield by feeding a raw material mixture containing isopropanol into a reactor having a solid catalyst layer filled with a catalyst and homogeneously heating the catalyst layer with a thermal medium. CONSTITUTION:A raw material containing isopropanol is fed into a reactor having a solid catalyst layer filled with a catalyst, preferably gamma-alumina catalyst, and having an inner diameter of 0.5-10cm and a catalyst layer height of 1-30m and the catalyst layer is homogeneously heated with a thermal medium at 200-400 deg.C to prepare propylene in high yield, efficiency and purity. When the isopropanol prepared by hydrogenating acetone by-produced on the preparation of phenol by a cumene method is utilized as the raw material, the by-produced acetone can be effectively utilized profitably.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing propylene, and particularly to a method for obtaining high-purity propylene in high yield through a dehydration reaction of isopropanol.

<Prior Art> As a classical method for producing olefins, a method is known in which alcohols are subjected to a dehydration reaction in the presence of a strong acid such as sulfuric acid. In recent years, olefins have been mainly produced by naphtha cranking, but in order to diversify the raw materials for producing olefins and obtain high-purity olefins, methods have been developed to obtain olefins by dehydrating alcohols. For example, various methods have been proposed, such as a method for producing ethylene by dehydrating ethanol, and a method for producing high-purity isobutylene by dehydrating tertiary-butanol. In these methods, the use of various catalysts has been investigated,
Methods using solid acid catalysts such as silica alumina and ion exchange resins have been proposed because they are easier to handle than strong acids and there are fewer restrictions on the material of the reactor. Also,
Since the dehydration reaction is accompanied by a large endotherm, it is necessary to carry out the reaction at a high temperature, and various methods of the reaction have been studied.

For example, in the production of ethylene, there is a method using an adiabatic reactor (Japanese Patent Publication No. 59-19927), a method using a combination of an isothermal reactor and an adiabatic reactor (Japanese Patent Publication No. 64-34).
No. 929), etc. have been proposed.

On the other hand, conventionally, most of the acetone produced as a by-product in the production of phenol by the cumene method has been used as a raw material for the synthesis of methyl methacrylate. However, in recent years, the manufacturing method of methyl methacrylate has been converted to a method that uses other synthetic raw materials, and as a countermeasure for the surplus of this by-product acetone, a way to effectively utilize it is being sought. A method of producing propylene by subjecting it to a dehydration reaction is currently being considered.

<Problems to be Solved by the Invention> As described above, when a strong acid is used for the dehydration reaction, it is inconvenient to handle and the material of the reactor is limited. Furthermore, the produced olefins react in the presence of these strong acids, and are, for example, polymerized and converted into high-molecular compounds, or isomerized and converted into other compounds other than olefins. There is also the problem that the yield of olefins is reduced, so the use of strong acids is not preferred.

On the other hand, as a method using a solid acid catalyst, methods using an adiabatic reactor and a combination of an isothermal reactor and an adiabatic reactor have been proposed as described above. When these methods are applied to the dehydration reaction of isopropanol, since this dehydration reaction involves a large endothermic reaction, in the method using an adiabatic reactor, it is necessary to extremely heat the reaction mixture in the preheating section. . However, isopropanol has poor thermal stability and is prone to thermal decomposition at temperatures above 400°C, so isopropanol is thermally decomposed into acetone.
It decomposes in the catalyst and becomes heavy, leading to a decrease in yield and activity of the catalyst, and there is a fear that high purity propylene cannot be obtained. Furthermore, isopropanol itself causes coking in the preheating section, causing clogging and causing serious problems in the reaction.

Accordingly, an object of the present invention is to provide a method capable of producing high-yield, high-purity propylene from isopropanol.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the present invention supplies a raw material mixture containing isopropanol to a reactor having a fixed catalyst bed filled with a catalyst, and uses a heating medium to dry the catalyst bed. 200~4
The present invention provides a method for producing propylene, which is characterized by uniformly heating to 00° C. and carrying out a fixed bed gas phase reaction.

Further, it is preferable that the catalyst is a γ-alumina catalyst.

Furthermore, in the method of the present invention, the inner diameter of the reactor is 0.
．． 5 to 10 cm, and the height of the fixed catalyst layer is 1 to 30 m.
It is preferable that

Isopropanol, which is the main component of the raw material mixture used in the method of the present invention, may be produced by any method and is not particularly limited.

In particular, it is industrially advantageous to use isopropanol obtained by hydrogenating acetone by-produced in the production of phenol by the cumene method by an appropriate method.

The amount of isopropanol fed to the reactor is typically LHS
0.1 to 1 Ohr-' in V, preferably O, S to 3h
It is about r-'.

In addition to isopropanol, the raw material mixture used in the present invention is a gaseous material inert to the dehydration reaction of isopropanol, in order to quickly discharge from the reaction system a reaction product containing propylene generated by the dehydration reaction of isopropanol. May contain substances. Examples of such gaseous substances include nitrogen, helium, argon, and the like. Further, the gaseous substances include substances that are liquid before being supplied to the reactor but become gaseous under the reaction conditions in the reactor. Examples of such substances include pentane and hexane.

If this gaseous substance is mixed with isopropanol and fed to the reactor, the amount used is usually 1
The range is preferably from 0.05 to 10 moles.
If too much gaseous material is used, a large amount of inert gas will need to be separated from the reaction product mixture of propylene and water and recycled to the reactor, increasing the cost of separation and circulation. resulting in economic disadvantage.

The catalyst used in the fixed catalyst layer in the present invention is not particularly limited as long as it is a solid catalyst that causes isopropanol to undergo a dehydration reaction. Examples include alumina catalysts, silica alumina catalysts, magnesia catalysts, zeolite catalysts, activated clay, etc., and titanium oxide (Ti02
Also included are catalysts supported on metals such as J and zirconium oxide (zroz). In the present invention, a γ-alumina catalyst is particularly preferred among alumina catalysts.

These may be used alone or in combination of two or more.

The form of the catalyst used is not particularly limited as long as it can form a fixed catalyst layer. Examples include tablet type, ring type, spherical type, cylindrical extrusion type, trefoil extrusion type, granule type, etc., which have high catalyst strength,
A spherical type, a tablet type, and an extrusion type are preferable because they enable uniform filling into a reaction tube.

The height of the fixed catalyst layer formed by filling the reactor with this catalyst is determined by the height of the fixed catalyst layer, as described later, because the smaller the inner diameter of the reactor, the more desirable it is. , 1 to 30 m, preferably 2 to 20 m.

The reactor used in the method of the present invention is not particularly limited as long as it has a structure that can be heated uniformly from the outside using a heating medium. For example, external heating methods include passing a heating medium through a jacket placed outside the reaction tube, or immersing the reaction tube in a constant temperature bath filled with heating medium; Examples include internal heating methods such as heating with a heater; composite heating methods that combine external heating and internal heating.

Moreover, this reactor may have a preheating section configured integrally or separately from the reactor.

The inner diameter of this reactor is preferably thin from the point of view of thermal efficiency of heating, but from the point of view of productivity and catalyst filling efficiency, it is desirable that the inner diameter of this reactor is 0.
5 to 10 cm is preferred, particularly 2 to 8 cm.

Further, this reactor may be composed of a single reaction tube having the above-mentioned inner diameter, or may be constructed by connecting a plurality of reaction tubes in parallel. When the reactor is composed of a plurality of reaction tubes, it may be heated with a common heating medium, or each reaction tube may be heated individually.

The temperature of heating with a heating medium is 200 to 400°C, and in particular when using isopropanol obtained by hydrogenating acetone as the raw material, it contains trace amounts of impurities, so the temperature should be 350°C or less. is preferable.

Furthermore, in the case of a structure in which the reactor is integrated with the preheating section, the heating temperature in the preheating section may be the same as the heating temperature of the reactor.

Further, even when the preheating section is configured separately from the reactor, the temperature of the preheating section is preferably 350° C. or lower in order to suppress decomposition of isopropanol.

The heating medium used for heating is not particularly limited as long as it can uniformly heat the reactor. For example, molten salt,
Examples include hot oil, electric heater steam, and flame. Examples of hot oil include Dowsome A
, Mobile Team 600. Examples include JRCS Hitherm #101 Therm-S 300 and Therm-S 600.
In addition, as the molten salt, for example, Neo S-5AL
Examples include T (manufactured by Souken Kagaku ■).

The pressure in the reactor may be any pressure that brings the inside of the reaction system into a gas phase state, and may be reduced pressure, normal pressure, or increased pressure, and is not particularly limited.
It is preferable to keep it below ATM.

The reaction is carried out in a continuous manner.

The direction of flow of the reaction mixture may be either upward flow or downward flow.

<Example> Hereinafter, the present invention will be specifically explained by giving examples and comparative examples of the present invention.

(Example 1) Inner diameter 38.4 mm, length 4 with external preheating device connected
The middle part of an 800 mm vertical tubular reactor made of 5U3316 with a heating jacket was filled with 5000 mJZ of spherical γ-alumina catalyst with a particle diameter of 3 mm to form a catalyst layer with a height of 4300 mm. Adjust the temperature of the preheating device to 190t,
320℃ Neo 5K-5ALT (
(manufactured by Souken Kagaku ■) is distributed uniformly throughout the reactor.
It was heated to 0°C and the internal pressure was 18 kg/c+a'G.
After the isopropanol was preheated to 190°C through a preheating device, it was heated to 5000 m12/hr (LH3V 1, O
The reaction was carried out by feeding from the top of the reactor at a flow rate of hr-'). The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid reaction mixture and a gaseous product. The amount of liquid reaction mixture and gaseous products in the gas-liquid mixture discharged from the bottom of the reactor after 8 hours have passed after starting the supply of isopropanol from the top of the reactor is the average amount per hour. and 1180 g/hr.

It was 16101/hr. At this time, the temperature of the catalyst layer population was 186°C, and the temperature of the catalyst layer outlet was 311°C.

The resulting liquid reaction mixture and gaseous products were analyzed by gas chromatography to determine the reaction results of the Improper Tool dehydration reaction.

As a result, the conversion rate of isopropanol was 99.3 moA%.
The propylene selectivity was 99.5moJZ%, the selectivity for acetone as a by-product was 0.1moβ%, and the selectivity for diisopropyl ether was 0.06fflo11%. Also, the purity of propylene in the gaseous product is 9
It was 9.8 moI 1%.

(Example 2) In a reactor with the same configuration as Example 1, the temperature of the preheating device was 300°C, the temperature of the heating section was 330°C, and the internal pressure was 18°C.
It was adjusted to kg/c112G. After preheating isopropanol to 300°C through a preheating device, 7500°C
The reaction was carried out by feeding from the top of the reactor at a flow rate of m12/hr (LH3V1.5hr-'). The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid reaction mixture and a gaseous product. 8 hours after the start of isopropanol supply from the top of the reactor, the temperature of the catalyst layer was 3.
The temperature at the outlet of the catalyst layer was 319°C. At this time, the resulting liquid reaction mixture and gaseous products were analyzed by gas chromatography to determine the reaction results of the isopropanol dehydration reaction. As a result, the conversion rate of isopropanol was 99.3110J! %, propylene selectivity 99.7moj! %, the selectivity of acetone, which is a by-product, was 0.07 mon%, and the selectivity of diisopropyl ether was 0.09 LeoJZ%.

(Example 3) In a reactor having the same configuration as Example 1, the temperature of the preheating device was adjusted to 300°C, the temperature of the heat medium flowing through the heating jacket part was adjusted to 330°C, and the internal pressure was adjusted to 18 kg/cm2G. Isopropanol (purity = 97.3%) obtained by hydrogenating acetone produced as a by-product in the phenol production process using the cumene method is passed through a preheating device to preheat it, and then
500ml/hr (LH5V 1.5hr
-') was fed from the top of the reactor and reacted.
The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid reaction mixture and a gaseous product. Eight hours after the start of supply of isopropanol from the top of the reactor, the temperature of the catalyst layer was 300°C, and the temperature of the catalyst bed outlet was 319°C. At this time, the resulting liquid reaction mixture and gaseous products were analyzed by gas chromatography to determine the reaction results of the isopropanol dehydration reaction. As a result, the conversion rate of isopropanol was 99.2a+oJZ%,
The selectivity for propylene was 99.6 mou%, the selectivity for acetone as a by-product was 0.03 moIL%, and the selectivity for diisopropyl ether was 0.02 moJ2%.

(Comparative Example 1) Connected to preheating device, inner diameter 25.4 mm, length 4000 mm
1500 mJZ of spherical γ-alumina with a particle size of 3 mm was filled approximately in the middle of a vertical tubular reactor made of 5US316' with a diameter of 3 mm to form a catalyst layer with a height of 1300 mm. The temperature of the preheating device was adjusted to 250°C, and the catalyst layer was heated to 4°C using an electric furnace.
Heat to 10℃ and internal pressure 18 kg/c+n'G
And so. After preheating isopropanol through a preheating device, it is heated at 1500 L1℃/hr (LH3V1 h
The reaction was carried out by feeding from the top of the reactor at a flow rate of r-'). The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid reaction mixture and a gaseous product. Eight hours after the start of supply of isopropanol from the top of the reactor, the temperature of the catalyst bed population was 282°C, and the temperature of the catalyst bed outlet was 390°C.
'C. At this time, the resulting liquid reaction mixture and gaseous products were analyzed by gas chromatography to determine the reaction results of the isopropanol dehydration reaction.
As a result, the conversion rate of isopropanol was 99.6moj2
%, propylene selectivity was 90.6 moj2%, and acetone was produced as a by-product at 4.3 IIlOIL%. Furthermore, the liquid reaction mixture contained 2.8% by weight of a yellow oil that was a product of the polymerization reaction that occurred in the reactor. The propylene content in the obtained gaseous product was 97.5 mo1%.

<Effects of the Invention> According to the method of the present invention, isopropanol can be dehydrated to produce highly purified propylene with high yield and efficiency. Furthermore, if isopropanol obtained by hydrogenating acetone, which is a by-product in the phenol production process by the cumene method, is used, it is advantageous because it provides a way to effectively utilize this by-product acetone.

Claims (4)

[Claims] (1) A raw material mixture containing isopropanol is supplied to a reactor having a fixed catalyst bed filled with a catalyst, and the catalyst bed is uniformly heated to 200 to 400°C using a heating medium to perform a fixed bed gas phase reaction. A method for producing propylene, the method comprising: (2) The method for producing propylene according to claim 1, wherein the catalyst is a γ-alumina catalyst. (3) The method for producing propylene according to claim 1 or 2, wherein the inner diameter of the reactor is 0.5 to 10 cm, and the height of the fixed catalyst layer is 1 to 30 m. (4) The method for producing propylene according to any one of claims 1 to 3, wherein the isopropanol is obtained by hydrogenating acetone, which is a by-product when producing phenol using the cumene method.