JPH0285224A - Production of dimethyl ether - Google Patents

Abstract

PURPOSE:To prevent deposition of carbon for a long period of time, enhance catalyst activity and depress by-producing of impurities by using alumina catalyst containing oxide of group IIIa metal in production of the subject compound by dehydrating methyl alcohol in vapor phase. CONSTITUTION:In a production of dimethyl ether useful as substitute of fluorocarbon (aerosol propellant) having problem of environmental pollution by dehydrating methyl alcohol in vapor phase, oxide of Sc, Y or La-series in group IIIa elements or Ac-series elements, etc., preferably at least one metal selected from Y, La, Ce, Nd, Sm and Eu is contained in an alumina catalyst in an amount of 0.005-80wt.%, preferably 0.5-20wt.% of total weight of the catalyst. Deposition of carbon is completely prevented for a long period of time by using said catalyst and also catalyst activity at low temperature is enhanced, further, by-production of hydrocarbon such as methane inducing loss of the aimed compound in distillation is steeply reduced, thus the aimed compound is obtained in economically and industrially advantageously.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing dimethyl ether.

More specifically, the present invention relates to a method for producing dimethyl ether by dehydrating methyl alcohol in a gas phase using an alumina catalyst containing a specific metal oxide.

Dimethyl ether is in increasing demand as an aerosol spray agent as a substitute for fluorocarbons, which have become increasingly polluting the environment in recent years.

[Prior art] As a method for producing dimethyl ether by dehydrating methyl alcohol in a gas phase,
Method of dehydration at 375°C 115a tIll (
After CAN 334.121) was developed, 200 to 3
Method of dehydration at 00℃ (J, Chem, Soc, Jap
an, Ind.

Chem, 5ect, 51.138-139.1984
) etc. were also found.

Later, a modified alumina catalyst appeared.

Among them, ■ a silica-alumina catalyst containing an oxide of alkali metal or alkaline earth metal is used, and
Methods carried out under pressure up to psig (USP 3.036
．． 134), using a γ-alumina catalyst containing 00.05 to 2.0% by weight of alkali metal oxide, SV
A method in which the reaction is carried out at 100 to 1000 (1/Hr) and 250 to 450°C, and a method in which dehydration is carried out at 1034 Kpa and 390 "C using an alumina catalyst containing 01 to 20% by weight of silica (Japanese Patent Application Laid-open No. 1983 -42333) is known.

[Problem to be solved by the invention]

Catalysts of production methods (1) and (2) listed in the conventional methods have satisfactory activity, but have the drawback of short catalyst life. This is due to carbon precipitated on the catalyst surface, and the deactivated catalyst must be replaced frequently.Also, the catalyst (2) belongs to the molecular sheet class and has a gas-based space velocity (SV). There are drawbacks such as a very small 0.01 to 2 (1/Hr).

Next, the catalyst (2) is a T-alumina catalyst modified by adding an alkali metal oxide, but even a small amount of addition significantly changes the activity of the original T-alumina catalyst. Quality control is very difficult and it is unsuitable for industrial catalysts. In addition, by incorporating silica in the alumina catalyst 4
In this method, when the purity of silica is low, it leads to a sharp decrease in the activity of the alumina catalyst. Therefore, an expensive silica raw material such as ethyl metasilicate must be used, and the catalyst becomes expensive.

As mentioned above, conventional methods have proposed a modification method in which alkali metal oxides, silica, etc. are added to the alumina catalyst, which causes a decrease in activity due to carbon precipitation. An excellent catalyst that maintains its activity for a long period of time has not been found.

Furthermore, the activity of alumina-based catalysts is higher than that of phosphoric acid-based catalysts.
Although it is relatively stable, its activity is still low, and a large amount of unsaturated hydrocarbons such as propylene and butene, which cause an unpleasant odor in the dimethyl ether product, are produced as by-products.

Increasing the inlet temperature to increase activity leads to increasing the capacity of heat exchangers, heaters, etc.

In addition, this causes carbonaceous matter to precipitate on the catalyst, and
The rapid increase in hydrocarbons such as methane, ethylene and propylene will only reduce resource utilization and increase
lfl'; also leads to increased loss of dimethyl ether during distillation of methyl ether.

The purpose of the present invention is to develop a catalyst that does not deposit carbon over a long period of time, has high activity at low temperatures, and suppresses by-product hydrocarbons, and provides a method for producing dimethyl ether using the catalyst.

[Means and effects for solving the problem] In order to achieve the above object, the present inventors conducted intensive research on catalysts for producing dimethyl ether by dehydrating methyl alcohol, and found that an alumina catalyst selected from Group 3A of the periodic table was used as an alumina catalyst. By containing an oxide of at least one metal,
It not only completely prevents carbon deposition on the alumina catalyst for a long period of time, but also maintains the high activity of the alumina catalyst for a long period of time, and drastically reduces impurities such as methane, ethylene, and propylene produced by decomposition of dimethyl ether. After making this discovery and conducting further research, the present invention was completed. That is, the present invention is characterized in that when methyl alcohol is dehydrated in a gas phase to produce dimethyl ether, an alumina catalyst containing an oxide of at least one metal selected from Group 3A of the Periodic Table is used. This is a manufacturing method.

The present invention will be explained in detail below.

The metal oxide contained in the T-alumina used in the present invention includes scandium, yttrium, lanthanum series elements, actinium series elements, etc. of group 3A of the periodic table, preferably yttrium, lanthanum, cerium, neodymium, samarium, europium, etc. It is an oxide.

A method for preparing an alumina catalyst containing an oxide of a metal selected from Group 3A of the Periodic Table is, for example, (A) high-purity alumina immersed in an aqueous solution of soluble mineral salts such as nitrates of these metals, and immersed in hot water. After evaporating and drying in a bath, 100
1000℃ after drying for a day and night at a temperature of ℃ or higher
The following method involves baking at a high temperature, preferably 400 to 700°C, for several hours.

(B) High purity alumina is suspended in an aqueous solution of soluble mineral salts such as nitrates of these additive metals, and aqueous ammonia is added dropwise to the cloudy solution to adjust the pH of the solution to 8 or higher. A method in which the precipitate is filtered to sufficiently remove the tfL salt, and then dried and calcined as in (A) above.

(C) A method in which an oxide of an additive metal and high-purity alumina are sufficiently mixed in the form of fine particles, and then fired as in (A).

(D) To a sufficiently stirred aqueous solution of soluble mineral salts such as nitrates of added metals, sodium aluminate was added all at once, the pH was adjusted to neutral, and after aging under stirring day and night, the obtained A method in which the slurry I8 liquid is filtered, thoroughly washed until mineral salts are no longer seen, then dried and fired.

etc. can be applied as a catalyst preparation method.

Further, any other catalyst preparation method in which the alumina catalyst contains an oxide of a metal of group 3A of the periodic table may be used as the preparation method.

The amount of added metal oxides is 0.0000000000000000000000000000000000000000000000000000000000 type type type type type type type form type form type form type form type form type form whatever form what form.
0.005 to 80% by weight, preferably 0.5 to 20% by weight.

The high-purity alumina used in the present invention is generally T-alumina, and for example, the content of impurities is 0.3 with silica.
%, less than 0.03% for iron oxides, less than 0.1% for sodium oxides, and a surface area of 100-700 m''7 g is preferably used for catalyst preparation.

The UIM catalyst can usually be used in the form of a powder of about 20 to 200 meshes, but for industrial handling, it is better to mold it into a spherical or cylindrical shape of an appropriate size. for example,
Pore volume with a size of 2 to 101, fa 0 , 2 to 0.9
/! /g, and the apparent density is preferably 0.3 to 1.5 g/mJ2.

The reactor used in the present invention for dimethyl ether synthesis by dehydration of methyl alcohol using an alumina catalyst containing an oxide of at least one metal selected from Group 3A of the Periodic Table can be adiabatic or self-contained depending on the heat transfer method. A heat exchange type, a multi-tube heat exchange type, etc. may be selected.

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

The analysis method is gas chromatography.

Example 1 Pulverized γ-alumina, 60 to 100 mesh 3
8.8g, 3.18g of lanthanum nitrate hexahydrate, 22g of water
The pH of the solution was adjusted to 8.2 by adding dropwise a 5% by weight ammonia aqueous solution.

After this liquid was left at room temperature for 1 hour with stirring, the contents were dried in a water bath at 80°C for 7 times. Then add 1 catalyst
It was dried at 10°C for 24 hours, further calcined at 600''C for 5 hours, sieved into 60-100 mesh sizes, and used for dehydration.

At this time, the content of lanthanum oxide was 3% based on the catalyst.

1.5 g of the above molded catalyst was packed into a quartz heat exchange type fixed bed reactor with an inner diameter of 20 mm, and methyl alcohol gas was introduced into the reactor with both the gas temperature at the inlet of the catalyst layer and the temperature around the outer wall of the catalyst layer maintained at 260°C. W/F=2(g −hr/
mol) (W: catalyst LF: gas flow rate), and the reaction results were investigated.

As a result, the methyl alcohol conversion rate was 72.0%, and the amount of hydrocarbon relative to dimethyl ether was methane: 12 pp11
．． Ethylene: 0.25ppm, Propylene: 0.25p
pm etc.

Comparative Example 1 The reaction was carried out in exactly the same manner as in Example 1, except that the lanthanum oxide-containing T-alumina catalyst was replaced with a T-alumina-free catalyst.

As a result, the methyl alcohol conversion rate was 60.3%, and the amount of hydrocarbons relative to dimethyl ether was 80 ppm for methane.
, ethylene: IPpll, propylene: lppm.

Examples 2 to 9 In Example 1, except that the catalyst layer inlet gas temperature and the catalyst layer outer wall surrounding temperature were both 350°C, and the lanthanum oxide was changed to the metal oxide and content shown in Table 1, The reaction was carried out continuously for 14 days in the same manner as in Example 1,
The reaction results and the coloration of the catalyst due to carbon deposition were observed. The results are shown in Table 1.

As is clear from Table 1, in the T-alumina catalyst containing an oxide of a metal of group 3A of the periodic table, not only is no carbon deposited, but also hydrocarbons, which are impurities in dimethyl ether, are completely eliminated.

Comparative Example 2 The reaction was carried out in exactly the same manner as in Example 2 except that the catalyst was changed to a non-containing T-alumina catalyst. The results are shown in Table 1.

[Effects of the Invention] According to the method for producing dimethyl ether of the present invention, carbon precipitation is prevented by using a T-alumina catalyst containing an oxide of a metal in group 3A of the periodic table as a gas phase dehydration catalyst for methyl alcohol. As it is completely eliminated for a long period of time, the low-temperature activity of the catalyst increases, and furthermore, it becomes possible to drastically reduce by-products of hydrocarbons such as methane, ethylene, and propylene, which are impurities that cause loss of dimethyl ether during distillation.
Therefore, the present invention is a very economical and industrially excellent production method using a gas phase dehydration catalyst that solves the conventional problems.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A method for producing dimethyl ether, which comprises using an alumina catalyst containing an oxide of at least one metal selected from Group 3A of the Periodic Table when producing dimethyl ether by dehydrating methyl alcohol in a gas phase. .