JP3292311B2 - Purification method of methanol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying methanol, and more particularly to a method for purifying methanol capable of removing oxygen contained as an impurity in methanol to an extremely low concentration. Methanol is used for dry etching of indium oxide film and tin oxide film used as a transparent electrode in liquid crystal devices and solar cells, and as the performance of liquid crystal devices and the like increases, there is a demand for extremely low impurities. .

[0002]

2. Description of the Related Art Generally, as a method of supplying methanol used in the production of semiconductors, methanol vapor generated by placing the bottle in an open end, immersing the bottle in a thermostat and controlling the temperature to an appropriate temperature is used. A method in which the flow rate is controlled by a controller and supplied to the reactor, a method in which methanol is put into a bubbler and bubbled with H ₂ , N ₂ , He or the like and supplied to the reactor are used.
The methanol vapor generated in this way contains, as impurities, oxygen that is mixed in when the raw material methanol is charged into a bottle or bubbler and water that is dissolved in the raw material, etc. It is possible to remove with a dehumidifier such as sieve,
Molecular sieve 3 with low methanol adsorption
It can be removed using A or the like. On the other hand, the oxygen contained in these methanols is usually 10 pp.
m, and it is difficult to remove these oxygens to a low concentration of 0.1 ppm or less by only purging under reduced pressure prior to the use of methanol or purging with an inert gas or the like in the raw material liquid. .

[0003]

As the performance of a liquid crystal device or the like becomes higher, the oxygen content of methanol used in the device becomes 0.1 ppm or less, and furthermore, 0.01 pp.
m or less is desired. In addition, these methanols may be contaminated by impurities such as air during the supply process to the semiconductor manufacturing apparatus such as when connecting bottles or switching pipes, so that the impurities are finally removed immediately before the apparatus such as a reactor. It is desirable. We have:
Firstly, as a catalyst for removing nitrogen and impurity oxygen in an inert gas, an attempt was made to remove oxygen in methanol using a commonly used nickel catalyst or copper catalyst. It has been found that methanol is decomposed, and high-concentration impurities such as hydrogen, carbon monoxide, and carbon dioxide are generated and mixed into a purified gas. As described above, although the demand for high-purity methanol is increasing year by year, there is almost no known technique for efficiently removing oxygen in methanol.

[0004]

Means for Solving the Problems The inventors of the present invention can efficiently remove oxygen contained in methanol to an extremely low concentration and produce methanol which does not generate other impurities due to decomposition of methanol. As a result of intensive studies on the purification method, it has been found that by using a catalyst containing manganese oxide as a main component, impurities such as carbon monoxide and carbon dioxide are not generated, and the oxygen concentration in the methanol-containing gas is reduced to 0.1%. 1 ppm or less, further 0.01 pp
The present invention was completed by finding that it can be removed to m or less. That is, the present invention is a method for purifying methanol, which comprises contacting a crude methanol vapor with a catalyst containing manganese oxide as a main component to remove oxygen contained as an impurity in the crude methanol. The present invention relates to oxygen contained in methanol vapor alone, hydrogen (hydrogen gas base) and methanol vapor (hereinafter collectively referred to as crude methanol) diluted with an inert gas (inert gas base) such as nitrogen or argon. Applied to the removal of

The manganese oxide used in the present invention is a divalent manganese oxide represented by the chemical formula MnO.
There are various methods for obtaining MnO. For example, manganese (II) carbonate, manganese (II) hydroxide, manganese (II) oxalate, manganese (II) acetate and the like are heated in a state where air is shut off, or Alternatively, a method of reducing a higher oxide of manganese with hydrogen or carbon monoxide is a typical production method. MnO may be used as it is, or may be used after being crushed to an appropriate size. However, it is preferable to use MnO supported on a catalyst carrier or the like for the purpose of enhancing contact efficiency. As a method for supporting MnO on a carrier, for example, a carrier powder such as diatomaceous earth, alumina, silica alumina, aluminosilicate and calcium silicate is dispersed in an aqueous solution of a manganese (II) salt, and an alkali is added to the carrier powder. The cake obtained by depositing a manganese (II) component in the mixture and then filtering and washing with water as necessary is dried at 120 to 150 ° C., and then calcined in nitrogen at 300 ° C. or more, and the calcined product is pulverized or Alternatively, inorganic salts such as MnCO ₃ and Mn (OH) ₂ and organic salts of manganese such as MnC ₂ O ₄ and Mn (CH ₃ COO) ₂ are fired in nitrogen, pulverized, and then mixed with heat-resistant cement. And firing again in nitrogen.

[0006] Usually, these are formed into a molded body by extrusion molding, tablet molding, or the like, and can be used as it is or, if necessary, crushed to an appropriate size. As a molding method, a dry method or a wet method can be used, and in that case, a small amount of water, a lubricant, or the like may be used. Note that Mn
The treatment after the treatment with O must be performed in a glove box in a state of not contacting oxygen, such as in an inert gas atmosphere such as nitrogen gas or argon. The content of MnO contained in the catalyst is usually at least 10 wt%, preferably at least 20 wt%. MnO content of 10
If the amount is less than wt%, the deoxygenation ability may decrease, and oxygen may not be sufficiently removed.

In the present invention, the activated catalyst may be filled in a purification column and purified by flowing crude methanol as it is. However, in order to more reliably prevent generation of by-products due to decomposition of methanol and the like. Preferably, the catalyst is pretreated with methanol prior to purification. The pretreatment with methanol is carried out by flowing methanol alone or a mixed gas with an inert gas such as nitrogen or argon at a cylinder linear velocity (LV) of 1 to 10 cm / sec for 1 to 2 hours. The pretreatment is performed at a temperature higher than the temperature at the time of the purification of the crude methanol, and is usually 10 minutes.
0 ° C. or higher, and in order to further enhance the effect of this pretreatment, it is generally preferred that the difference from the temperature at the time of purification of the crude methanol is large,
It is preferable to carry out at a temperature higher by 150 ° C. The above pretreatment may be performed before filling the purification cylinder, or may be performed after the filling. However, if the catalyst is preliminarily filled in the purification cylinder and then subjected to the pretreatment, the methanol is continuously purified. This is convenient.

[0008] Purification of methanol is carried out by passing crude methanol through a purification cylinder filled with the above-mentioned catalyst containing MnO as a main component.
By contact with the catalyst, oxygen contained as an impurity is efficiently removed without causing decomposition of methanol. The oxygen concentration in the crude methanol to which the present invention is applied is usually 100 ppm or less. If the oxygen concentration is higher than this, the calorific value increases, so a heat removal means is required depending on the conditions.

[0009] The amount of methanol is supplied as a filling length of MnO catalyst packed in the purification pipe, can not be indiscriminately particular vary depending on the oxygen concentration and operating conditions, in practice usually is a 1:50 to 5 300 mm You. Fill length is 50
If it is shorter than 1 mm, the oxygen removal rate may decrease, and if it is longer than 1500 mm, the pressure loss may become too large. In addition, the cylinder linear velocity (LV) of crude methanol at the time of purification is usually 100 cm / sec.
c or less, preferably 30 cm / sec or less. The contact temperature between the crude methanol and the MnO catalyst at the time of purification is usually 70 ° C. or lower, and it is preferable to carry out the reaction at room temperature to about 50 ° C. The pressure of the gas at the time of purification is not particularly limited, and the treatment can be performed at normal pressure, reduced pressure, or increased pressure, but is usually 10 kg / cm ² abs or less, preferably 0.1 Kg / cm ² abs or less.
g-5 kg / cm ² abs.

In the present invention, even if a small amount of water is contained in methanol, there is no particular adverse effect on the deoxygenation capacity. Can be removed at the same time. In addition, it is also possible to appropriately combine a water removing step using a dehumidifier such as a molecular sieve as needed with the oxygen removing step using a MnO catalyst, whereby water is reliably removed, and high-purity purified methanol is obtained. be able to.

[0011]

【Example】

Example 1 (Preparation of purification cylinder) A commercially available manganese oxide catalyst was used.
This has a general formula MnOx such as MnO ₂ or Mn ₂ O _3.
It is an extruded product of a mixture of higher oxides represented by (X> 1), which is black. Crush this and 8 ~ 12mes
sieved 63 ml of inner diameter 16.4mm, length 4
Filling length of 300mm in stainless steel purification cylinder of 00mm
(Packing density: 1.6 g / ml). After preheating by flowing nitrogen at a temperature of 300 ° C. and a flow rate of 250 ml / min for 1 hour, carbon monoxide was supplied at normal pressure at a flow rate of 127 ml / m 2.
In (LV = 1 cm / sec), the reduction treatment was carried out by flowing for 3 hours, and then the mixture was switched to nitrogen and cooled to room temperature.
By the way, as a result of reducing the above catalyst in a quartz tube under the same conditions, the color of the catalyst changed to green,
It was confirmed that O ₂ , Mn ₂ O _{3 and the} like were reduced to MnO. Nitrogen-based 5 vol% methanol was added to the above stainless steel purifying cylinder at normal pressure at a temperature of 200 ° C. and a flow rate of 0.
After pretreatment with methanol by flowing at 633 L / min (LV = 5 cm / sec) for 2 hours, the mixture was cooled to room temperature while flowing nitrogen.

(Purification of Methanol) Subsequently, purification of methanol (based on nitrogen) was carried out. A stainless steel bubbler having an inner diameter of 50 mm and a height of 175 mm containing about 50 ml of methanol was immersed in a thermostat set at 15 ° C. to control the methanol pressure, and the oxygen concentration was reduced to 0.01 p.
pm or less by bubbling methanol with purified nitrogen confirmed to be 10 vol.
% Methanol vapor was generated. The concentration of oxygen in the gas containing methanol vapor was measured using a yellow phosphorus emission type oxygen analyzer (measurement lower limit concentration: 0.01 ppm) and found to be 0.17 ppm. This gas was flowed through the purifier at 0.633 L / min (LV = 5 cm / sec), and the oxygen in the outlet gas of the purifier was analyzed by a yellow phosphorus emission type oxygen analyzer. For carbon monoxide, carbon dioxide and hydrocarbons, When analyzed by gas chromatography using FID as a detector (lower limit of measurement: about 0.01 ppm) and hydrogen was analyzed by gas chromatography using TCD as lower detector (lower limit of measurement: about 20 ppm), any impurities were detected. Was not detected, and the concentration was below the lower limit of measurement. Even after 100 minutes from the start of the purification, the oxygen concentration of the outlet gas was 0.01 ppm or less, and no generation of other impurities was observed.

Example 2 (Purification of methanol) Undiluted methanol vapor was purified using the same catalyst as used in Example 1 and using a purifying cylinder pretreated with methanol under the same conditions. About 50 ml of distilled water inside diameter 50mm, height 1
A 75 mm stainless steel bubbler is immersed in a constant temperature bath set at 40 ° C. to control the pressure of methanol vapor generated, and a differential pressure is generated by a vacuum pump installed downstream of the mass flow controller. Flow rate 0.1L /
min. First, 30 mL of undiluted crude methanol was added.
After purging the inside of the purifying cylinder by flowing the purified gas for 0.4 min, the purified nitrogen is added to the crude methanol at 0.4 L / min, which is confirmed to have an oxygen concentration of 0.01 ppm or less, and diluted with the oxygen concentration in the mixed gas. Was measured using a yellow phosphorus emission type oxygen analyzer, and about 0.11 ppm of oxygen was detected. Next, crude methanol (0.1 L / min) was added at 40 ° C.
When the gas was diluted by mixing the purified nitrogen with the methanol at the outlet at 0.4 L / min and analyzing the diluted gas, oxygen was not detected and the generation of impurities such as carbon dioxide and hydrocarbons occurred. Was not seen at all. No impurities were detected in the purified gas even after 100 minutes from the start of the purification.

Comparative Example 1 (Preparation of a purification cylinder) A commercially available nickel catalyst (manufactured by JGC Corporation)
N-111) was used. Its composition is Ni + NiO
45-47 wt% as Ni, Cr 2-3
wt%, Cu 2-3 wt%, diatomaceous earth 27-29 wt% and graphite 4-5 wt%, diameter 5 mm, height 4.5
mm. 8 to 10 me of this nickel catalyst
63 ml of the shredded product was packed in a purification cylinder in the same manner as used in Examples (packing density: 1.0 g / ml). Hydrogen was added under normal pressure at a temperature of 150 ° C and a flow rate of 456 ml / min.
(LV = 3.6 cm / sec) for 3 hours, followed by cooling to room temperature. (Purification of methanol)
The crude methanol was circulated in the same manner as described above, and the outlet gas was analyzed. The oxygen concentration was 0.01 ppm or less.
08 ppm of carbon monoxide and 60 ppm of hydrogen were detected, indicating that methanol was decomposed.

[0015]

According to the present invention, oxygen in methanol which has conventionally been difficult to remove can be reduced to 0.1 ppm or less, more preferably 0.01 ppm, without decomposing methanol.
It was possible to remove to the following extremely low concentrations, and it became possible to obtain ultrahigh-purity methanol vapor.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-61-1005337 (JP, A) JP-A-48-39411 (JP, A) Patent 92839 (JP, C1) Patent 99067 (JP, C1) (58) ) Field surveyed (Int. Cl. ⁷ , DB name) C07C 31/04 C07C 29/88 C07B 63/00 CA (STN)

Claims (4)

(57) [Claims] 1. A method for purifying methanol, comprising contacting a crude methanol vapor with a catalyst containing manganese oxide as a main component to remove oxygen contained as an impurity in the crude methanol. 2. The purification method according to claim 1, wherein the catalyst containing manganese oxide as a main component has been subjected to a pretreatment of contacting with methanol at a temperature higher than the temperature at the time of purification. 3. The purification method according to claim 2, wherein the difference between the pretreatment temperature of the catalyst with methanol and the temperature during purification is 20 to 150 ° C. 4. The amount of manganese oxide contained in the catalyst is 10 watts.
The purification method according to claim 1, which is at least t%.