JPH0673583A - Production of partial-oxidation product of methanol - Google Patents

Abstract

PURPOSE:To produce the partial-oxidation product of methanol from methanol and oxygen by using a fuel-cell system. CONSTITUTION:A mixture of hydrogen, oxygen and methanol is brought into contact with the electrode on both sides of a proton conductor to produce the partial-oxidation product of methanol by a fuel-cell system. This system differs from the conventional fuel-cell system, and a hydrogen donor need not be supplied to one side and oxygen, etc., to the other side. Consequently, the oxygen, hydrogen, methanol, etc., as the raw materials need not be previously separated when the partial-oxidation product of methanol is produced.

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 a novel partial oxide of methanol, such as methyl formate and dimethoxymethane, by applying a fuel cell system using two different types of electrodes.

Methyl formate and dimethoxymethane, which are partial oxides of methanol, are intermediates for the production of acetic acid, formalin and the like, and are industrially extremely important substances.

[0003]

2. Description of the Related Art Conventionally, it has been generally known that formalin, dimethoxymethane (methylal) and methyl formate which are partial oxides of methanol can be obtained by contacting methanol with oxygen in the presence of a catalyst. Formalin is generally produced by using methanol as a raw material, allowing air to exist in the presence of a silver catalyst, and performing a high-temperature reaction at about 500 ° C. On the other hand, methylal has recently been attracting attention as a raw material for producing formalin containing a low concentration of water. For example, JP-A 1-287051 and Chemical Engineering, No. 52
Vol. 4, page 411, it is produced from formaldehyde and methanol using a solid acid catalyst. However,
In this method, formaldehyde is used as a raw material and is not directly produced from methanol, but is an indirect method of producing from methanol via the above-mentioned formalin.

Further, as a method for producing methyl formate, for example, Japanese Patent Publication No. 57-2702 and Japanese Patent Publication No. 57-26502.
In JP-A-54-12315, a copper-zinc system is used as a catalyst to produce hydrogen by dehydrogenating methanol at a reaction temperature of about 300 ° C. Also, JP-A-56-16963
In JP-A-57-128642, methyl formate is obtained by reacting hydrogen and carbon monoxide in the presence of a catalyst such as nickel or copper under high temperature and high pressure conditions.

However, these methylal and methyl formate production methods are harsh such that the reaction conditions are high temperature and high pressure, and cannot be said to be production methods under mild conditions.

In recent years, various attempts have been made to produce electric power at the same time as producing various useful compounds under mild conditions using a fuel cell system. For example, regarding the partial oxidation of methanol using a fuel cell system, Chemis
Try Letters; 1945-1948 (1987), other than those conducted by the present inventors. This method uses a platinum electrode for the anode and cathode as a catalyst electrode, and in addition, by introducing methanol on the anode side and oxygen on the cathode side, dimethoxymethane (methylal), which is a partial oxide of methanol, Manufactures methyl formate, etc. However, in this method, it is necessary to separately supply the substance to be introduced to the anode side with the oxidant (methanol) and the substance to be supplied to the cathode side with the oxidant such as oxygen. It was impossible to mix them, and inevitably it was necessary to separate them in advance in order to carry out the reaction.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a process for producing a partial oxide of methanol by using a fuel cell system under mild conditions without intentionally separating oxygen as a raw material from methanol. It solves the conventional problems such as complexity and large consumption of energy.

[0008]

As a result of intensive studies to solve the above problems, the present inventors have made one electrode (catalyst electrode A) in a fuel cell system a metal and / or a metal compound of this metal, By using a metal different from the metal used for the catalyst electrode A and / or a metal compound of this metal for the other electrode (catalyst electrode B), the oxygen and methanol are intentionally separated as in the conventional fuel cell system. We have found a method for producing a partial oxide of methanol effectively and economically by introducing it into this system without mixing.

That is, the present invention is different from the metal component used for the electrode A composed of a metal and / or a metal compound thereof in one of the electrode chambers separated by the ion conductor and the metal component used for the electrode A in the other electrode chamber. An electrode B made of a metal and / or a metal compound thereof is attached so as to be in contact with an ionic conductor, and the electrodes A and B are short-circuited by a conductor, and a mixture of methanol, oxygen and water is continuously or intermittently supplied to both electrodes. Is a method for producing a partial oxide of methanol, which is characterized in that the partial oxide of methanol is introduced. It is essential that the metal species forming the anode and the metal species forming the cathode are substantially different in the electrode used in the present invention. If the same metal species is used for both electrodes, the yield of the partial oxide of methanol is extremely reduced, and the method of the present invention cannot be substantially carried out.

The electrode used in the method of the present invention is basically prepared from a metal or a metal compound thereof. The metals used for the electrodes or the metals constituting these metal compounds are group 3, group 4, group 5 and group 6 of the periodic table.
It is a metal of group 10, group 7, group 8, group 9, group 10, group 11, and group 12. Specifically, as a Group 3 metal, the element symbol S
Metals represented by c, Y, La, Ac, etc., Group 4 metals are metals represented by element symbols Ti, Zr, Hf, and Group 5 metals are element symbols V, Nb, Ta. Is a metal represented by
Metals represented by Mo and W, Group 7 metals are metals represented by element symbols Mn and Re, and Group 8 metals are metals represented by element symbols Fe, Ru, Os. , Group 9 metals are metals represented by the element symbols Co, Rh, Ir, and group 10 metals are element symbols N
Metals represented by i, Pd, and Pt, Group 11 metals represented by element symbols Cu, Ag, and Au, and Group 12 metals represented by element symbols Zn, Cd, and Hg. It is a metal. Further, in the method of the present invention, when these metals are used in the electrode as a compound of these metals, halides, nitrates, sulfates of these metals,
It is recommended to use as oxide, hydroxide, phosphate and / or ammonium salt. In the method of the present invention, the electrodes A and B are used as electrodes composed of at least one different metal component (metal and / or metal compound). As described above, in the method of the present invention, it is essential that the metal component forming the electrode A and the metal component forming the electrode B be different.

The periodic table used in the method of the present invention is a periodic table based on the International Union of Pure and Applied Chemistry Nomenclature of Inorganic Chemistry (1989).

To facilitate the practice of the method of the present invention, it is recommended to mix the conductive carbonaceous material with the metal component in preparing the electrode. In addition to this, it is also recommended to use a binder to facilitate the formation of the electrode. However, the method of the present invention is not limited to these preparation methods.

Basically, the carbonaceous substance added when preparing the electrode may be any carbonaceous substance having electric conductivity, but as the readily available carbonaceous substance, for example, graphite, activated carbon or carbon black. , Carbon whiskers and the like. In addition, by oxidizing these carbonaceous substances in advance before mixing with the metal, the method of the present invention can be carried out more easily.

The oxidation treatment of the carbonaceous material can be carried out by various methods such as heat treatment using a normal oxygen-containing gas and reagent oxidation treatment using an oxidizing reagent. Examples of the reagent oxidation treatment include nitric acid water heating treatment, permanganic acid aqueous solution treatment, dichromic acid aqueous solution treatment, and hydrogen peroxide water treatment. However, the method of the present invention is not limited to these treatments.

Various kinds of binders can be used for forming the electrode in the method of the present invention, but hot pressing using Teflon resin powder is preferable because of its ease of forming. preferable. Of course,
The method of the present invention is not limited to only these materials and methods.

As the ionic conductor used in the method of the present invention, a protonic acid such as phosphoric acid, sulfuric acid, hydrochloric acid or nitric acid, a solid electrolyte known as a proton conductor such as heteropolyacid, H-montmorillonite or zirconium phosphate, Sr
A perovskite type solid solution having CeO ₃ as a matrix can be used. In addition, a fluoropolymer such as perfluorocarbon is used as a base, and one or more cation exchange groups such as sulfonic acid groups or carboxylic acid groups are introduced into the base,
For example, Nafion (registered trademark of DuPont) can also be used. A liquid such as phosphoric acid may be used by impregnating it with silica wool, or may be sandwiched between ion-permeable filters or membranes.

The methanol used in the method of the present invention does not need to be particularly purified and may have a general reagent purity, and may be a mixture with an organic substance (saturated hydrocarbon etc.) other than methanol. Absent. Furthermore,
In the method of the present invention, a mixture of these raw materials containing methanol, water and oxygen is introduced into both electrode chambers, and at this time, methanol and water are introduced in a liquid state or in a gaseous state. It doesn't matter. When introducing in a liquid state, it may be diluted with a solvent such as methanol and / or water or the like and then introduced. Further, when these mixtures are introduced in a gas state, they may be introduced as a mixture of inert gases such as nitrogen, helium and argon.

According to the method of the present invention, the reaction temperature is usually -2.
It is performed in the range of 0 to 200 ℃, but 0 to 100
More preferably, it is carried out at ℃. If done too cold,
Energy such as cooling is required as the reaction rate decreases,
If it is carried out at an excessively high temperature, the selectivity is lowered and energy such as heating is required, which is not efficient. Further, according to the method of the present invention, the reaction is generally carried out at normal pressure, but it may be carried out under pressure or under reduced pressure if necessary.
Partial oxides of methanol such as methyl formate and dimethoxymethane, which are reaction products, are usually separated and purified by a method such as distillation from a reaction product liquid or gas, distillation after condensation, distillation after gas-liquid separation, and extraction. You can get things.

A conceptual diagram of a fuel cell reactor used for carrying out the method of the present invention is shown in FIG. Electrodes A and B
The electrode chambers 1 and 2 having the are separated by an ion conductor 3 and these two electrodes are short-circuited by a lead wire 4. The electrodes are preferably porous or sheet-shaped, but are not necessarily limited thereto. If necessary, it is possible to apply a voltage between both electrodes. If necessary, electric energy corresponding to the free energy of the reaction can be taken out as electric power from the reaction system.

[0020]

EXAMPLES The method of the present invention will be described in more detail based on the following examples. However, these are exemplary and the method of the present invention is not limited by the examples.

Example 1 Preparation of Electrode (a) Oxidation Treatment of Graphite Graphite powder was dipped in an 8N nitric acid aqueous solution, heated and boiled for 2 hours, washed thoroughly with pure water, and dried to prepare an electrode. used. (B) Preparation of electrode 50 mg of nitric acid-oxidized graphite, 20 mg of each metal powder listed in Table 1 and 5 mg of Teflon powder
21 mm in diameter by hot pressing after mixing well
Each of the circular sheets was used as an electrode.

[0022]

[Table 1] ________________ Added metal powder Catalyst electrode _______________________________________ Iridium electrode I Rhodium electrode II Platinum electrode III Ruthenium electrode IV Palladium electrode V _______________

Example 2 Silica wool in the form of a disk (thickness 1.0 mm, diameter 21
(mm) containing an 85% phosphoric acid aqueous solution as an ion conductor membrane to separate two electrode chambers, and one electrode chamber (electrode chamber 1) was prepared from iridium and graphite (electrode I). Was attached so as to be in contact with the ion conductor membrane. Similarly, the other electrode chamber (electrode chamber 2)
Electrodes prepared from rhodium and graphite (electrode I
I) was installed. After connecting the electrodes I and II with lead wires, the reaction temperature was set to 80 ° C., and methanol (8.3% by volume), oxygen (40.8% by volume) and water vapor (50.
9% by volume) mixed gas was introduced into each electrode chamber at a flow rate of 34.6 ml / min. As a result, an electric current of 7.
0 mA was generated and methyl formate and dimethoxymethane were produced at rates of 1.05 μmol / min and 0.07 μmol / min, respectively. The other product is carbon dioxide,
The selectivity of the partial oxide of methanol was 55%.

Examples 3 to 5 The partial oxidation reaction of methanol was carried out under the same conditions as in Example 2 except that the electrodes attached to the electrode chamber 2 were replaced by electrodes III, IV and V, respectively. The generated current value and the total selectivity of partial oxides (methyl formate and dimethoxymethane) at that time are listed in Table 2.

[0025]

TABLE 2 ______________________________ electrodes generating a current (mA) partial oxide selectivity (%) ______________________________ electrode III 11.49 28.2 electrodes IV 8.28 46.8 electrodes V 8.34 29.0 ______________________________

Examples 6 to 8 Partial oxidation reaction under the same conditions as in Example 2 except that the electrode on the electrode chamber 1 side was changed to the electrode III and the electrodes on the electrode chamber 2 side were changed to the electrodes II, IV and V, respectively. I went. As a result, as shown in Table 3, it was confirmed that a partial oxide of methanol was generated with the generation of current in each combination of electrodes.

[0027]

TABLE 3 ________________________________ electrode chamber 2 generation current (mA) partial oxide selectivity (%) ________________________________ electrode II 2.36 13.8 electrodes IV 1.56 44.3 electrodes V 29.5 10.4 _________________________________

Comparative Example 1 The reaction was carried out under the same conditions as in Example 2 except that the electrode I was used as the electrode in both electrode chambers. As a result, the current is 0.
Only 1 mA was generated, and generation of a partial oxide of methanol was hardly confirmed, and the selectivity of the partial oxide was 0%.

Comparative Example 2 The reaction was carried out under the same conditions as in Example 2 except that the electrode III was used for the electrodes in both electrode chambers. As a result, a current of only 0.2 mA was generated, a partial oxide of methanol was hardly formed, and the selectivity was 0%.

[0030]

According to the present invention, the following effects can be obtained. (1) Under extremely mild conditions, a partial oxide of methanol can be produced with good selectivity. (2) When carrying out the reaction, the energy change of the reaction can be taken out of the reaction system as electric energy (electric power) as necessary, and the electric power can be used as a by-product, which is extremely economical. A partial oxide of methanol can be produced. (3) The reaction can be carried out as a mixture without separating methanol, oxygen and water in advance, and a partial oxide of methanol can be easily produced from a process point of view. The method for producing a partial oxide of methanol has many advantages such as the following.

[Brief description of drawings]

FIG. 1 Schematic diagram of reactor

[Explanation of symbols]

 1 Electrode chamber 2 Electrode chamber 3 Ion conductor 4 Lead wire 5 Electrode A 6 Electrode B

Claims (8)

[Claims] 1. An electrode A composed of a metal and / or a metal compound thereof in one electrode chamber isolated by an ionic conductor, and a metal and / or a metal component different from the metal component used for the electrode A in the other electrode chamber. Electrodes B made of these metal compounds were attached so as to be in contact with the respective ion conductors, electrodes A and B were short-circuited by the conductors, and a mixture of methanol, oxygen and water was introduced into both electrodes continuously or intermittently. And a method for producing a partial oxide of methanol, which comprises contacting. 2. The method according to claim 1, wherein a conductive carbonaceous substance is present on the electrode A and / or the electrode B. 3. The metal constituting the electrode and / or the constituent metal of the metal compound is represented by the third, fourth, fifth, and third elements in the periodic table.
The method according to claim 1, which is a metal selected from the metals of groups 6, 7, 8, 9, 10, 11 and 12. 4. The method according to claim 2, wherein the conductive carbonaceous substance is at least one selected from activated carbon, graphite, carbon black and carbon whiskers. 5. The method according to claim 2, wherein the conductive carbonaceous substance is a carbonaceous substance which has been previously subjected to an oxidation treatment. 6. The carbonaceous substance is heated or brought into contact with or left at room temperature in a solution of at least one selected from an aqueous solution of permanganate, an aqueous solution of nitric acid, an aqueous solution of dichromate and an aqueous solution of sulfuric acid. The method according to claim 5, wherein 7. The electrode A is an electrode composed of iridium and / or an iridium compound, and the electrode B is selected from the group of rhodium, rhodium compounds, platinum, platinum compounds, palladium, palladium compounds, ruthenium and ruthenium compounds. The method according to claim 1, which is an electrode composed of at least one kind. 8. The partial oxide of methanol is formalin,
Methyl formate and / or dimethoxymethane.
The method described.