JP2002128716A - Method for producing isopropyl alcohol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing isopropyl alcohol by a vapor phase hydrogenation reaction of acetone, in which an equipment installation cost is reduced and energy can be efficiently utilized. SOLUTION: This method for producing the isopropyl alcohol by subjecting the acetone and hydrogen to the vapor phase reaction is characterized in that an effluent gas from a reactor is brought into contact with the raw material acetone and/or the recovered acetone to vaporize the acetone and thereby to liquefy the produced isopropyl alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing isopropyl alcohol, and more particularly, to an economical method for producing high-purity isopropyl alcohol, for example, by reacting acetone and hydrogen in a gas phase and reducing the energy. About. Isopropyl alcohol is an important intermediate in organic synthesis and an industrially important solvent.

[0002]

2. Description of the Related Art Isopropyl alcohol is used as a general solvent, but is often used as a cleaning agent for IC substrates and a disinfectant, and high purity products are required. As for the product purity, generally, 99.9% by weight or more is commercially available.

A method widely used in recent years for producing isopropyl alcohol is a hydration method of propylene. A method of hydrating an olefin using concentrated sulfuric acid as a catalyst has been known for a long time, but in this case, there is a problem of corrosion by sulfuric acid.

Recently, a gas-liquid mixed phase hydration reaction using a strongly acidic ion exchange resin, a gas phase hydration reaction using a strongly acidic solid acid as a catalyst, and a heteropolyacid,
Hydration by gas phase catalytic reaction using a catalyst supporting an inorganic acid is widely performed.

[0005] As a method for producing isopropyl alcohol, a method of hydrogenating the carbonyl group of acetone has been known for a long time. For example, lithium aluminum hydride,
This is a reduction method using a reagent such as sodium borohydride or a catalytic reduction method using hydrogen gas.

As a method using hydrogen gas, for example,
A method of performing a hydrogenation reaction in the presence of a Raney nickel catalyst in a liquid phase (Japanese Patent Laid-Open No. 3-141235) or a method of performing a gas-phase hydrogenation reaction using a copper oxide / chromium oxide catalyst (Japanese Patent Laid-Open No.
3-41038) has been proposed.

[0007] As to the production process, in the liquid phase hydrogenation reaction method, a reaction is carried out in a trickle bed system (Japanese Patent Laid-Open No. 2-270829), or the inlet of the reaction mixture is circulated to the reactor to improve the reaction yield. (Japanese Patent Laid-Open No. 3-33941) has been proposed.

[0008] Further, regarding a production process in a gas phase hydrogenation reaction method, US Pat. No. 2,456,187 (1948)
Uses a multitubular reactor to separately evaporate acetone and separate the produced isopropyl alcohol, which requires two types of equipment, an acetone evaporator and an isopropyl alcohol separator. However, the circulating hydrogen gas has to be cooled once to separate the isopropyl alcohol, so that the equipment cost is increased and the energy of the circulating hydrogen gas is not effectively utilized.

[0009]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to reduce the number of isopropyl alcohol production facilities in the gas phase hydrogenation reaction of acetone and to produce isopropyl alcohol capable of efficiently utilizing energy. To provide a process.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on reducing the number of manufacturing facilities and efficiently using energy in order to solve the above-mentioned problems. It was found that isopropyl alcohol can be produced economically and efficiently,
The present invention has been completed. That is, the present invention relates to a method for producing isopropyl alcohol by reacting acetone with hydrogen in a gas phase, wherein the isopropyl alcohol produced by contacting a reactor effluent gas with raw material acetone and / or recovered acetone to vaporize acetone is produced. Is a method for producing isopropyl alcohol.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method for producing isopropyl alcohol, which makes effective use of the energy of a gas discharged from a reactor obtained by reacting acetone and hydrogen in a gas phase. The isopropyl alcohol is generally purified by distillation. Product.

The catalyst in the hydrogenation reaction of the present invention is Cu-
Cr-based oxide catalyst, Raney Ni catalyst, Raney Cu catalyst,
Noble metal catalysts such as Pt, Pd, Ru and the like can be mentioned, and those generally used can be applied as they are.

Acetone as a raw material may be crude acetone produced by, for example, a by-product of a cumene phenol plant or direct oxidation of propylene. However, in order to produce high-purity isopropyl alcohol, separation and removal are difficult. Those having a low impurity content are preferable from the viewpoint of product quality.

As hydrogen for hydrogenating the raw material acetone, it is not necessary to use hydrogen having a particularly high purity. For example, hydrogen containing methane generated in an ethylene production plant or hydrogen containing impurities such as ethane and nitrogen may be used. Can be used.

Here, the molar ratio between hydrogen and acetone is usually in the range of 1.1 to 5. If the molar ratio is less than 1.1, not only does the conversion of acetone decrease, but also the selectivity to isopropyl alcohol decreases and the by-products increase. On the other hand, if the molar ratio exceeds 5, the power for recovering unreacted hydrogen and circulating it increases, which is not preferable.

As the reactor used in the present invention, a general packed bed reactor, a multitubular reactor, a moving bed reactor, a suspended bubble column reactor, a stirred tank type suspension reactor and the like are used. Also,
The reaction temperature and pressure are not particularly limited, but generally speaking, in a gas phase reaction, 60-200 ° C., 0.1-1 M
If the Pa-G and pressure are less than 0.1 MPa-G, the reaction rate decreases, and if it exceeds 1 MPa, the pressure resistance of the reactor increases, which is not economical.

In a preferred embodiment of the present invention, the effluent gas of the reactor and the raw material acetone and / or recovered acetone are brought into countercurrent contact with each other, and the distillation and purification are carried out in parallel to mix acetone into liquefied isopropyl alcohol. Can be reduced as much as possible. More preferably, by performing heat exchange with the gas supplied to the reactor and bringing the gas discharged from the reactor into contact with the raw material acetone and / or the recovered acetone, the energy can be more effectively utilized.

In order to further understand the present invention, a detailed description will be given along a process flow with reference to FIG. 1 which is an embodiment. The gas discharged from the reactor 1 from the reactor 1 comprises isopropyl alcohol, unreacted acetone, reaction by-products, unreacted hydrogen and impurities in hydrogen gas such as methane. The reactor effluent gas exchanges heat with the reactor supply gas in the heat exchanger 2 described later, and then reaches the gas-liquid contact device 3 where it contacts the raw material acetone and / or recovered acetone supplied from the upper portion of the device 3. The acetone is vaporized and the isopropyl alcohol produced is liquefied. In this gas-liquid contact device 3, by performing distillation purification at the same time as the contact operation as a preferred embodiment,
It is possible to suppress the entrainment of isopropyl alcohol and reaction by-products in the gaseous phase acetone, and to minimize the incorporation of acetone into the liquid phase isopropyl alcohol,
Equipment costs and energy can be reduced. Here, the reflux amount of the distillation operation is controlled by a condenser (divider) 4 attached to the top of the gas-liquid contact device 3 or separately provided.

Controlled by a condenser (decompressor) 4, a vaporized raw material acetone and a reactor supply gas comprising impurities such as hydrogen gas and methane flowing out from the top of the gas-liquid contacting device 3 are supplied as a circulating gas to a blower and a compressor. After being pressurized by the gas circulating equipment 6, it is circulated to the reactor 1 together with the make-up hydrogen. At this time, preferably, after heat exchange with the gas discharged from the reactor in the heat exchanger 2, the reactor 1
The gas flowing out of the reactor is supplied to the gas-liquid contact device 3, whereby energy efficiency can be further improved.

A part of the distillate gas from the gas-liquid contact device 3 is further cooled by a cooler (knock-out condenser) 5 to condense and separate a liquid substance such as acetone at room temperature. Non-condensable gas such as methane is partially purged out of the system. Although the purge amount is not particularly limited, if the amount is large, hydrogen loss increases, and if the amount is too small, the amount of accumulation in the circulating gas increases, and the equipment cost and power cost of gas circulation increase. . In consideration of these factors, an appropriate circulation amount is determined according to the amount of impurities contained in the hydrogen gas used.
The condensed liquid composed of acetone and others is returned to the condenser (divider) 4 and / or the gas-liquid contact device 3. Here, the cooler 5 may be separated from the gas-liquid contact device 3 and the condenser 4, or may be integrated with the device. On the other hand, a liquid mixture containing isopropyl alcohol as a main component liquefied by the gas-liquid contact device 3 is subjected to a subsequent purification step (not shown).
And purified by distillation to obtain high-purity isopropyl alcohol.

As an example of general distillation purification using acetone and hydrogen as raw materials as in the present application, first, unreacted acetone is separated and recovered. The separated and recovered acetone is supplied to the above-mentioned gas-liquid contact device 3 and / or the condenser (decomposer) 4 to be vaporized and returned to the reactor 1 together with the circulating gas as a reaction raw material. Then, the isopropyl alcohol mixed solution is subsequently subjected to removal of water and further separation of near-boiling compounds and high-boiling compounds to obtain high-purity isopropyl alcohol. Although these distillation operations may be batch distillation, a continuous distillation system including a plurality of reactors is employed efficiently.

[0022]

The present invention will be described in more detail with reference to the following examples. The composition analysis described in the examples was performed using GC-14A manufactured by Shimadzu Corporation (detector: FID, column: DB-WA).
X) Gas chromatography was used to measure He as a carrier gas.

Example 1 A stainless steel reactor having an inner diameter of 27.2 mm and a length of 4000 mm was charged with 1.5 L of a copper oxide / chromium oxide catalyst, and the catalyst was reduced with hydrogen. Subsequently, the reactor effluent gas was circulated to adjust the hydrogen to a predetermined flow rate. In this case, hydrogen was used when 3.7 mol% of methane was contained, and the flow rate was 54 mol / h including methane. Subsequently, 26 mol / h of vaporized acetone was supplied per hour, and the reaction was started at a temperature of 110 ° C. and an inlet pressure of 0.25 MPa-G. Reactor effluent gas passes through a heat exchanger, and then has 1 theoretical plate as a gas-liquid contactor.
It was fed to a zero-stage distillation column. In this distillation column, the raw material acetone supplied from the top of the column was brought into gas-liquid contact to evaporate the acetone, liquefied isopropyl alcohol, and purified by distillation and flowed out from the top and bottom of the column. Tower bottom temperature 75
° C, the top pressure was 0.18 MPa-G, and the reflux ratio was:
It was controlled by a condenser (divider) attached to the top of the tower. In addition, part of the vapor discharged from the top of the tower is cooled to 5 ° C with a knockout condenser (cooler) to remove condensed components such as acetone to prevent methane accumulation in the system, and then discharged outside the system. Was done. Here, the amount of discharge to the outside of the system is such that the molar ratio of hydrogen to methane in the reactor supply gas is 1: 1:
The amount of exhaust gas was controlled to be 1.

The reactor feed gas mainly composed of acetone, hydrogen and methane leaving the distillation column is mixed with make-up hydrogen and heat-exchanged from 35 ° C. to 110 ° C. with the reactor effluent gas in a heat exchanger. After being preheated to 0 ° C, it is recycled to the reactor.

The reaction results at this time were as follows:
% And isopropyl alcohol selectivity was 99%. The temperature at the outlet of the reactor was 130 ° C., which was effectively used as a preheating source for the gas supplied to the reactor and a heat source for a distillation column for evaporating and refining the raw material acetone. Further, isopropyl alcohol in the gas supplied to the reactor was as small as 0.2 mol%, and the acetone concentration in the bottom liquid of the distillation column was 0.15% by weight.

[0026]

The raw material acetone of the present invention is brought into contact with the reactor effluent gas which is a reaction product to vaporize acetone and to liquefy or purify the isopropyl alcohol produced in parallel. By performing the residual heat of the gas supplied to the reactor by heat exchange, the equipment cost and energy can be reduced, which is industrially superior.

[Brief description of the drawings]

FIG. 1 is a flow chart showing one embodiment of the production of isopropyl alcohol to assist the understanding of the present invention.

[Explanation of symbols]

 1. Reactor 2. Heat exchanger 3. Gas-liquid contactor (distillation tower) 4. Condenser (divider) 5. Cooler (knockout condenser) Gas circulation equipment 7. 7. Reactor feed gas line 8. Raw material acetone / recovered acetone supply port Hydrogen supply port 10. Isopropyl alcohol mixture 11. Exhaust gas

Claims (3)

[Claims] 1. A method for producing isopropyl alcohol by reacting acetone and hydrogen in a gas phase, wherein the produced isopropyl alcohol is produced by contacting a reactor effluent gas with raw material acetone and / or recovered acetone to vaporize the acetone. A method for producing isopropyl alcohol, which comprises liquefying. 2. The process according to claim 1, wherein distillation purification is carried out in parallel while bringing the reactor effluent gas and the raw acetone and / or recovered acetone into countercurrent contact. 3. The process according to claim 1, wherein the gas discharged from the reactor after heat exchange with the gas supplied to the reactor is brought into contact with raw acetone and / or recovered acetone.