JPH11179378A - Method for decomposing oxygen-containing organic compounds having one carbon atom contained in wastewater - Google Patents

Abstract

(57) Abstract: In a method for decomposing an oxygen-containing organic compound having one carbon atom by a wet oxidation method, the oxygen-containing organic compound is decomposed at a temperature of 100 ° C. or less and at normal pressure without using an oxidizing agent. A method for disassembly is provided. SOLUTION: A wastewater containing an oxygen-containing organic compound having one carbon atom is passed with a oxygen-containing gas at a temperature of 100 ° C. or lower in a reaction vessel equipped with a noble metal-supported activated carbon catalyst layer to oxidatively decompose the oxygen-containing organic compound. A method for decomposing the above oxygen-containing organic compound contained in wastewater.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for treating wastewater containing oxygen-containing organic compounds having one carbon atom such as methanol, formaldehyde, formic acid and formate discharged from various processes at a temperature of 100 ° C. or less and a catalyst in the presence of oxygen. The present invention relates to a method of decomposing and removing by contact.

[0002]

2. Description of the Related Art Oxygen-containing organic compounds having one carbon atom, such as methanol, formaldehyde and formic acid (or a salt thereof), often coexist with other organic compounds having a higher molecular weight, and are subjected to COD treatment or BOD treatment. In many cases, biological treatment is performed collectively in the form of Since such biological treatment can be performed at normal temperature and normal pressure, it is characterized by high stability and easy operation management. However, since it is a biological reaction at room temperature, the reaction rate is slow, the tank volume is large, the space is large, and there are drawbacks in that sludge treatment, which is required for biological treatment, is required. In order to avoid such disadvantages of biological treatment, a wet oxidation method has been proposed. This method promotes the oxidation reaction of an organic compound by using a catalyst or an oxidizing agent, and realizes a more compact apparatus without generation of sludge. However, the methods proposed in JP-B-59-19775, JP-A-49-44556, and the like, require a temperature of 100 ° C. or more,
The device is operated at a temperature of not less than ° C. and under a pressure of several tens of kg / cm ² , and although the device scale is small, operation management is very troublesome. Further, if a non-chlorine oxidizing agent such as ozone or hydrogen peroxide is added, oxidative decomposition of oxygen-containing organic substances can be performed under normal pressure conditions of 100 ° C. or less, but the cost of the oxidizing agent remains unchanged. This is undesirable because it increases the cost of treating wastewater.

[0003]

DISCLOSURE OF THE INVENTION The present invention relates to a method for producing a compound having 1 carbon atom.
An object of the present invention is to provide a method for decomposing two oxygen-containing organic compounds by a wet oxidation method without using an oxidizing agent and decomposing the oxygen-containing organic compound at a temperature of 100 ° C. or lower and at a normal pressure.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, completed the present invention. That is, according to the present invention, a wastewater containing an oxygen-containing organic compound having one carbon atom is passed at a temperature of 100 ° C. or lower together with an oxygen-containing gas at a temperature of 100 ° C. or less in a reaction vessel equipped with a noble metal-supported activated carbon catalyst layer. A method for decomposing the oxygen-containing organic compound contained in wastewater, which is characterized by oxidative decomposition.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a noble metal catalyst supported on activated carbon is used as a catalyst for oxidative decomposition of an oxygen-containing organic compound having one carbon atom (hereinafter simply referred to as a compound to be treated). In this case, the type of activated carbon for supporting the noble metal catalyst does not need to be particularly limited, and may be a general commercial product. To give an example, the raw material of activated carbon is palm,
Any of coal, charcoal, peat, etc. may be used. The physical properties are as follows: the surface area is 500 m ² / g or more, and the pore volume is 0.4 cc / g.
g is preferred, but most commercial activated carbons satisfy this requirement and do not pose a problem.

A noble metal is used as the oxidizing metal supported on the activated carbon. As this noble metal,
Particularly, Pt, Pd, Rh, Ru, Os, and Ir are preferable.
Base metals typified by V, Mn, Cu and the like are inferior in low-temperature activity as compared with the former, and therefore are not suitable for the present invention. If the amount of the noble metal carried is too small, low-temperature oxidation becomes difficult. The value is 0.0 regardless of the type of metal.
It is at least 1 wt%, preferably at least 0.1 wt%. The upper limit is about 1 wt%. Supporting more metal is often ineffective and unnecessary. A method for supporting the catalyst requires a method in which the noble metal is well dispersed as clusters of several tens of degrees. However, this can be easily realized by dissolving a required amount of the water-soluble complex compound of each noble metal in water, impregnating with activated carbon, drying this, and thermally decomposing it in an inert gas.

[0007] The present invention uses a noble metal supported on activated carbon for the catalyst and enables low-temperature oxidation.
A flow-type reactor is used. Under normal pressure, the dissolved amount of oxygen in water is extremely small, so it is necessary to use a flow-type reactor in which gaseous oxygen reaches the vicinity of the active point as the catalyst. The present inventors have determined the particle size and shape of the catalyst,
It has been found that the flow form of the liquid and the gas greatly affects the gas-liquid contact efficiency. It is a well-known fact that too large a catalyst size is not preferable because it reduces the catalyst effectiveness factor. In this regard, it is generally said that reducing the catalyst particle size is preferable because it increases the activity. However, in the case of the present invention, it has been found that as the particle size of the catalyst is reduced, the flow of gas and liquid becomes uneven, and the activity is reduced. It was found that the activity increases when the particle size of the catalyst is reduced as the representative diameter of the catalyst is up to 1 mm. In this case, the representative diameter (d) of the catalyst is expressed by the following equation, where S is the outer surface area of one catalyst particle and V is the volume. The shape of the catalyst is such that the gas and liquid flow as uniformly as possible, and in particular, it is preferable that the catalyst and liquid are not formed. In that respect, spherical and cylindrical shapes are preferred. Simple fragments, saddles, plates, bumps on the surface, double cylinders, etc. should be avoided because they tend to form a thick liquid film or pool and make it difficult to exhibit low-temperature activity.

Next, the present inventors studied a method of flowing drainage water and an oxygen-containing gas through the catalyst layer. In the method of flowing the liquid upward, the rate of oxygen absorption is extremely small, and the liquid is directed downward. I found that it should be washed away. This is considered to be because in the upward flow, the entire catalyst is immersed in water, and the gas passes through it in a bubble state, so that the liquid film through which oxygen should pass is thick and the area of the gas-liquid contact interface is small. It is well known that the gas velocity affects the thickness of the liquid film on the catalyst surface, but in the case of the present invention,
The linear velocity of the gas is preferably maintained at 1.0 cm / sec or more at the superficial velocity. The upper limit is usually 100c
m / sec.

The oxygen-containing organic compound to be treated in the present invention includes methanol, formaldehyde, formic acid and formate, but when the reaction is carried out at a temperature close to the upper limit temperature of 100 ° C. of the present invention. Oxidative degradation of ethanol, halomethanes, ethylene glycol and the like is also possible.

[0010]

Next, the present invention will be described in more detail with reference to examples. Example 1 One liter of a commercially available 0.2 wt% Pt-supported spherical activated carbon catalyst (about 1.5 mm in diameter) was charged into an adiabatic flow reactor. Next, an aqueous solution of sodium formate having a concentration of 1 mol / l was preliminarily heated to 60 ° C. and flowed at a rate of 1 liter / hr from above into the reactor.
It was distributed at a rate of r. At this time, the rise in water temperature due to the heat of combustion of formic acid was canceled by the latent heat of evaporation of water, and the liquid temperature at the outlet of the reactor was 66 ° C. After cooling the effluent, the organic carbon concentration was measured by a TOC densitometer to determine the decomposition rate of Na formate, which was 98.8%.

Example 2 A column of commercially available 0.5 wt% Pd-supported activated carbon (having a diameter of about 1
mm, average length about 2 mm) was charged to the reactor described in Example 1 as 1 liter. Next, from the top in this reactor, 0.1.
A 5 mol / l aqueous methanol solution was added at room temperature (25 ° C.)
Flow at a rate of 1 liter / hr and at the same time 200 Nl of air
/ Hr. At this time, the liquid temperature at the outlet of the reactor was 30 ° C. After the effluent was cooled in a closed flask, the organic carbon concentration was measured with a TOC densitometer, and the conversion of methanol was determined to be 94%.

Example 3 0.2% by weight of Pd and 0.1% in activated carbon having a diameter of 1.6 mm.
One liter of the catalyst supporting 3 wt% of Ru was charged into the reactor described in Example 1. Next, a 0.5 mol / l formalin aqueous solution was preheated to 40 ° C. from above and flowed at a rate of 0.5 liter / hr from above, and air was simultaneously allowed to flow down at a rate of 200 Nl / hr. The reactor outlet liquid temperature at this time was 44 ° C. The effluent was placed in a sealed flask, cooled to room temperature, and the organic carbon concentration was measured with a TOC densitometer to determine the formalin decomposition rate, which was 97.5%.

[0013]

According to the present invention, the oxygen-containing organic compound having one carbon atom contained in the waste water is converted to 100 at normal pressure.
It can be efficiently oxidatively decomposed under a wet condition of not more than ℃.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/72 ZAB C02F 1/72 ZABZ (72) Inventor Hiroaki Nishijima 2-1-1, Tsurumichuo, Tsurumi-ku, Yokohama-shi, Kanagawa Chiyoda (72) Inventor Seiya Hirohama 2-1-1 Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Chiyoda Chemical Works, Ltd.

Claims (4)

[Claims] 1. A wastewater containing an oxygen-containing organic compound having one carbon atom is passed at a temperature of 100 ° C. or lower together with an oxygen-containing gas through a reaction tank equipped with a noble metal-supported activated carbon catalyst layer to oxidize the oxygen-containing organic compound. A method for decomposing the oxygen-containing organic compound contained in wastewater, characterized by decomposing the oxygen-containing organic compound. 2. The method according to claim 1, wherein the noble metal-supported catalyst is a catalyst in which at least one selected from platinum, palladium, ruthenium, rhodium, osmium, and iridium is supported on activated carbon in an amount of 0.01 wt% or more. 3. The method according to claim 2, wherein the shape of the catalyst is spherical or cylindrical, and its representative diameter is 1 mm or more. 4. The method according to any one of claims 1 to 3, wherein the wastewater is caused to flow downward from above in the catalyst layer in the reaction tank.