JPS583961B2 - Method for thermochemically producing hydrogen from hydrogen sulfide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for the multistage thermal decomposition of hydrogen sulfide to obtain hydrogen.

Unlike fossil fuels such as oil and coal, hydrogen does not produce harmful gas by-products such as sulfur dioxide and carbon monoxide when it is burned, so there is a great deal of interest in its use as a clean fuel. There is.

By the way, currently, hydrodesulfurization treatment is dominantly carried out for desulfurization of crude oil, heavy oil, and various petroleum fractions, and in this process, a considerable amount of hydrogen is consumed, and as a result, a considerable amount of hydrogen sulfide is produced. is a by-product.

Moreover, the amount of by-products tends to increase year by year as oil refinery equipment becomes larger, oil consumption increases, and regulations on sulfur dioxide gas emission concentration become stricter.

Since this hydrogen sulfide has no particular utility value by itself, it is strongly desired to convert it into other valuable substances.

However, although several methods have been proposed for the effective use of this by-product hydrogen sulfide, the only industrially meaningful methods are the Claus method and the modified Claus method. In these methods, the hydrogen atoms in hydrogen sulfide are discarded in the form of water, so the hydrogen gas used in the desulfurization treatment is not recovered, which is extremely disadvantageous from an economic point of view.

As a method to overcome these disadvantages, a method has been proposed in which hydrogen sulfide is directly thermally decomposed in the presence of a catalyst to produce hydrogen together with sulfur, but in the case of this direct thermal decomposition, the equilibrium constant is extremely small. Therefore, in order to accelerate the reaction, it is necessary to return the generated sulfur to room temperature and extract it from the reaction system.
The basic problem is that heat loss is large.

The present inventors have completed the present invention as a result of intensive research to overcome such problems associated with direct thermal decomposition of hydrogen sulfide.

That is, according to the present invention, in thermally decomposing hydrogen sulfide in multiple stages, (a) a step of reacting hydrogen sulfide with iodine to generate hydrogen iodide and sulfur; A step of reacting an aromatic compound to generate a hydrogenated aromatic compound and iodine; (c) a step of dehydrogenating the hydrogenated aromatic compound to generate hydrogen and regenerating the aromatic compound. A characterized method for producing hydrogen is provided.

To carry out the method of the present invention, hydrogen sulfide and iodine are first reacted in the presence of excess water to produce hydrogen iodide and sulfur.

(H2S+12-2HI+S) In this case, the reaction temperature is 2
The temperature is 5 to 400°C, preferably 25 to 200°C, and the reaction pressure is 1 to 15k9/Cm2, preferably 3 to 10kg.
/cm2, and the amount of iodine used relative to hydrogen sulfide is 1 to 10 mol, preferably 3 to 5 mol, per 1 mol of hydrogen sulfide.

In addition, the water present in the reaction system has the effect of dissolving hydrogen iodide, which is a product, and removing it from the reaction system, and the amount of water is in excess of the iodine used, usually 2 to 10 times the mole. Preferably it is 3 to 5 times the mole.

In this way, hydrogen iodide is generated according to the amount of iodine used, but this hydrogen iodide can be easily separated from the reaction system by cooling to room temperature and solvent extraction using water as a medium. can.

The hydrogen iodide thus produced is then reacted with an aromatic compound to obtain the corresponding hydrogenated aromatic compound and iodine.

(Ar+HI→H-Ar+1/2■2, where Ar is an aromatic compound and H-Ar is a hydrogenated aromatic compound) In this case, the reaction temperature is 25 to 300℃, preferably 50 to
200℃, reaction pressure 1-200kg/cm2,
It is preferably 5 to 100 kg/cm2, and the amount of aromatic compound used is usually 3 to 20 times, preferably 6 to 10 times, by mole relative to hydrogen iodide.

As the aromatic compound, benzene, toluene, xylene, etc. can be used, and in any case, various substituents such as alkyl groups, Those having an alkoxy group etc. are also included.

When these aromatic compounds are reacted with hydrogen iodide,
No iodination reaction occurs, but a hydrogenation reaction.

Moreover, this reaction is carried out in the presence of a hydrogenation catalyst.

As the hydrogenation catalyst, it is preferable to use a catalyst that is not easily poisoned by iodine or hydrogen iodide, especially a ruthenium catalyst (containing metal, hydroxide, oxide, organic acid, or inorganic acid salt).

The generated hydrogenated aromatic compound can be more easily separated by adsorbing iodine on activated carbon, starch, etc. and separating and removing the iodine from the reaction system.

Finally, the hydrogenated aromatic compound thus produced is dehydrogenated by a conventional method to regenerate the aromatic compound, which is recycled to the hydrogenation step.

The method of the present invention is advantageous in terms of thermal energy because each reaction step can be carried out at a relatively low temperature, and since the amount of heat required to separate the reaction products is small, heat loss is also extremely small.

Furthermore, since the reaction temperature involving iodine is 200° C. or lower, there is no particular difficulty in selecting reaction equipment.

Moreover, since the process of the invention is carried out as a completely closed system and the raw material consumed is essentially only hydrogen sulfide, it does not pose any pollution problems and is very economically advantageous.

Next, the present invention will be explained in more detail with reference to Examples.

Example A: Reaction of H2S+■2→2HI+S 7QCC of water and 10.0 gr. of iodine with an internal volume of 150
Fill a CC flow-through quartz reaction tube with 300cc of hydrogen sulfide.
When the reaction was carried out for 24 hours at a flow rate of /min and 50°C, 77.0 mmole of hydrogen iodide was produced.

The generated sulfur was separated by a filtration method.

The conversion rate of iodine to hydrogen iodide calculated from the amount of hydrogen iodide produced was 98%, indicating that the reaction progressed almost quantitatively.

B: Reaction of 6HI+C6H6→C6H12+3■2 (1
) Hydroiodic acid, which is an aqueous solution of hydrogen iodide (HI concentration 5
7%, specific gravity 1.7) 40ml (HI: 3.03 x 10-
1 mol) and benzene 4.4 ml (4.95 x 10-2 mol) were placed in a Hastelloy autoclave with an internal volume of 100 ml together with 0.66 g of ruthenium hydroxide as a catalyst, and the mixture was heated at 150°C and under the conditions of 10 kg/cm2. When the reaction was carried out for 2 hours, cyclohexane was obtained with a yield of 100% based on benzene.

(2) Ruthenium supported on barium sulfate (supported amount 5
The above B-(1) except that 1 g (% by weight) is used as a catalyst.
When the reaction was carried out in the same manner as above, cyclohexane was obtained with a yield of 100% based on benzene.

C: C6H12 → C6H6 + 3H2 reaction Using a flow-type glass reactor, 5 g of catalyst with pt1% supported on A1203 was packed and the feeding rate of cyclohexane was 0.02C.
C/min-m2 (cat・surface area
) at a reaction temperature of 300° C. and a pressure of 1 atmosphere, the concentration of cyclohexane in the outlet gas was at a trace level, and the conversion rate of cyclohexane to benzene was approximately 100%.

Claims (1)

[Claims] 1. In thermally decomposing hydrogen sulfide, (a) a step of reacting hydrogen sulfide with iodine to produce hydrogen iodide and sulfur; (b) reacting the produced hydrogen iodide with an aromatic compound. (c) dehydrogenating the hydrogenated aromatic compound to generate hydrogen and regenerating the aromatic compound. Method. 2. The method according to claim 1, wherein the step (a) of reacting hydrogen sulfide and iodine is carried out in the presence of water. 3. The method according to claim 1 or 2, wherein the step of reacting hydrogen iodide with an aromatic compound is carried out in the presence of a ruthenium catalyst.