JPH0947650A - Heat diffusion reaction process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat diffusion reaction process of improved productivity. SOLUTION: A couple of container walls are disposed face to face, and respective container walls are provided with the temperature difference so that one wall is of high temperature and the other wall is of low temperature, and a filler is filled in a reaction space formed between the container walls of a reaction container. Reactive raw material gas is introduced into a reaction space of the reaction container, and the reaction is carried out on the high temperature container wall side, and a formed material of large molecular weight of a plurality of reaction materials to be formed is diffused and moved to the low temperature container wall side key heat diffusion, and exhausted out of the reaction space of the reaction container.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thermal diffusion reaction method.

[0002]

2. Description of the Related Art When a hydrocarbon is reacted in a reaction system having a temperature gradient, hydrocarbon radicals generated on the surface of a high-temperature heating element are immediately separated by a so-called thermal diffusion effect, and a side reaction such as a reverse reaction or a sequential reaction is caused. Suppression has recently been reported. This method has been attracting attention as an interesting method because a product which is thermally unstable and more reactive than the reactants can be obtained with high selectivity.

For example, by this method, a method of efficiently obtaining ethylene from methane using a reaction system having a temperature gradient using a tungsten wire or a carbon rod (supporting a Pt catalyst) as a heat source (high temperature vessel wall), and the like. Has been proposed.

[0004]

However, in these methods, since the heat source is a wire or the like, (i) the heat source also serves as a catalyst, so that the selection of the catalyst is limited, (ii)
The contact surface of the gas deposited in the reaction is small, and the reaction amount is small,
(Iii) Difficulty in controlling convection in the reaction system. Therefore, the present inventor has conducted various studies in order to solve these difficulties, and surprisingly found that the thermal diffusion reaction with significantly improved productivity can be achieved with a simple configuration of filling the reaction space with a filling material. Heading, arrived at the present invention.

[0005]

That is, the gist of the present invention is to arrange a pair of vessel walls facing each other, and each of the vessel walls has a temperature difference such that one is high and the other is low. In addition, in the reaction vessel formed by filling the reaction space formed between the vessel walls with the filler, the reaction raw material gas is introduced into the reaction space of the reaction vessel, and the reaction is performed on the high temperature vessel wall side, A thermal diffusion method is characterized in that a product having a large molecular weight among the obtained plurality of reaction products is diffused and moved to a low temperature vessel wall side by thermal diffusion and is led out from a reaction space of the reaction vessel.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
First, in the reaction container of the present invention, a pair of vessel walls extending in the vertical direction are arranged to face each other, and each vessel wall has a temperature difference such that one is high temperature and the other is low temperature. There is. Examples of such a reaction vessel include one in which two flat plates are opposed to each other and one is kept at a high temperature and the other is kept at a low temperature, and a double tube is formed by two concentric cylinders.

The above-mentioned temperature is determined by the reaction temperature which will be described later, but it is general to select the high temperature side from about 700 to 1400 ° C., and the temperature gradient with the low temperature side is 500 to.
Preferably, the temperature is about 2000 ° C./cm. The heat source is
There is no particular limitation, and a burner using electric power or gas as a fuel is usually used.

For example, in the case of adopting the above-mentioned double pipe type, a high temperature heating gas can be circulated in the inner pipe to make the outer wall of the inner pipe a high temperature side wall. When two flat plates are opposed to each other, they can be on the high and low temperature sides, respectively. These reaction vessels are generally of a so-called vertical type. For example, a reaction raw material gas inlet is provided at an upper part (upper end-middle part) or a lower part (lower end-middle part), and a lower part or an upper part, respectively. An outlet for the reaction product is provided in the section.

In the present invention, it is necessary to fill the reaction space formed between the vessel walls having such a temperature difference with a filler. The filler may be a catalyst or one that is inert to the reaction, but a catalyst is preferably selected. That is, the material, shape, size, etc. of the filler are not particularly limited, but in general, inorganic oxide, metal, etc. molded into a cylindrical shape, a spherical shape, a tablet shape, etc. are used.

For example, a Raschig ring in the form of a tube cut into the same length as the diameter, a Lessing ring in which a partition film is contained therein, and a crushed solid with a controlled particle size can be used. The size of these varies depending on the reaction space, but is generally about 1 mm to 10 mm.

The mode of filling is not particularly limited and may be an appropriate porosity, but is preferably adjusted so as to control the temperature gradient between the vessel walls and natural convection according to the reaction conditions. . Depending on the type of filler, porosity 40
It is usually selected from the range of about 85%. It is possible to further optimize the thermal diffusion rate of the product by using two or more kinds of materials, shapes or sizes of fillers and changing the porosity depending on the location, if necessary. .

In the present invention, the reaction raw material gas is introduced into such a reaction vessel. As the reaction raw material gas, a hydrocarbon or a hydrocarbon-containing gas is generally used. For example, a dehydrogenation reaction of a paraffinic hydrocarbon such as methane or an aromatic hydrocarbon such as ethylbenzene, cumene or t-butylbenzene is suitable. Applied. The above-mentioned introduction of the reaction raw material gas is performed from the upper part to the lower part in the case of producing ethylene from methane, for example, while it is downward in the case of producing aromatic compounds such as benzene, styrene and naphthalene from ethylene. It is preferable to carry out from the part upward.

The rate of introduction varies depending on the intended reaction conditions, but it is preferable that the rate of introduction be such that natural convection in the reaction space is not hindered. The reaction temperature varies depending on the type of reaction and the type of catalyst used, but is selected from at least the thermal decomposition temperature of the reaction raw material gas, and from the range of about 700 to 1400 ° C., the conversion rate of the target reaction product is considered. It is preferable to select it.

For example, the case of producing ethylene and hydrogen from methane will be described. The methane gas introduced into the reaction vessel from the upper portion, for example, the upper end downward, is at a high temperature (for example, when Pt is used as a catalyst). About 1000 ° C., about 1300 ° C. is preferable when W is used) to generate ethylene and hydrogen by the dehydrogenation dimerization reaction by heat from the wall surface of the vessel. 2CH ₄ → CH ₂ = CH ₂ + 2H ₂

In this case, due to the heat diffusion effect, the relatively heavy ethylene diffuses and moves preferentially with respect to methane and hydrogen in the space having the filler on the side of the vessel wall at a low temperature (for example, 30 to 70 ° C.). , Descend to the lower end of the reaction vessel. On the other hand, light hydrogen rises along the hot wall due to the thermal diffusion effect (this hydrogen can also be led out from the upper end), but due to natural convection, it turns down and falls to the lower end of the reaction vessel.

In this way, a reaction product containing unreacted methane is obtained from the lower part such as the lower end of the reaction vessel.
Further, when ethylene gas is introduced as a reaction raw material gas from the lower part, for example, from the lower end part to the upper part, the ethylene gas undergoes a dehydrogenative condensation reaction by the heat from the high temperature wall surface, and an aromatic compound and hydrogen are produced. Then, due to the heat diffusion effect, the aromatic compound preferentially moves to the low temperature side of the vessel wall with respect to hydrogen, is cooled there to become a liquid substance, moves downward by the vessel wall, and is taken out from the lower portion, for example, the lower end portion. . On the other hand, the light reaction gas and the product gas move upward along the hot chamber wall and are taken out from the upper portion, for example, the upper end portion.

[0017]

The present invention will be described in more detail with reference to the following examples. Example 1 A reaction mainly involving dehydrogenation and dimerization of methane was carried out using a thermal diffusion reactor in which a core tube, an inner tube and an outer tube were formed from the inside by three concentric cylinders.

The sizes of the tubes are as follows. (Approximately 100 cm in length) Core tube (Ni-Cr-W-Mo alloy): Inner diameter 17.7 mm, outer diameter 21.7 mm Inner tube (carbon steel): Inner diameter 41.6 mm, outer diameter 48.6 mm Outer tube ( Carbon steel): Inner diameter 93.2 mm, outer diameter 101.6 m
m

A heating gas of about 1000 ° C. was passed through the core tube, while cooling water at room temperature was passed through the annular portion between the inner tube and the outer tube. The annular portion (that is, the reaction space) between the core tube and the inner tube is filled with a porous ceramic ball (silica-alumina system, 4 mmφ) chemically supporting a catalyst (platinum) (porosity 75%), and at room temperature. Raw material gas (methane 100
%) Was circulated from the upper end. Flow velocity (superficial velocity) is 20
m / h, and the reaction product was obtained from the lower end.

The temperature inside the tube was as follows. Inner core tube approx. 1000 ° C Outer core tube surface approx. 970 ° C Inner tube inner surface approx. 50 ° C Inner tube outer surface approx. 30 ° C

The reaction results were a methane conversion rate of 12% and an ethylene / acetylene selectivity of 85% (ethylene 71%, acetylene 14%). For comparison, platinum was supported on the outer surface of the core tube to form a catalyst layer, and the reaction was carried out in the same manner as above without using a filler.
%, Ethylene and acetylene selectivity was 85%.

[0022]

According to the present invention, a thermal diffusion reaction method with improved productivity can be provided.

Claims (1)

[Claims] 1. A reaction formed by arranging a pair of vessel walls facing each other, each of the vessel walls having a temperature difference such that one is at a high temperature and the other is at a low temperature, and is formed between the vessel walls. In a reaction vessel having a space filled with a filler, a reaction raw material gas is introduced into the reaction space of the reaction vessel, the reaction is performed on the side of the high temperature wall, and the molecular weight of a plurality of reaction products obtained is A method for thermal diffusion, characterized in that a large product is diffused and moved to a low temperature vessel wall side by thermal diffusion to be led out from a reaction space of the reaction vessel.