JPS6157880B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for steam reforming heavy hydrocarbons. Various proposals have already been made regarding steam reforming of hydrocarbons, and some of them have already been implemented. For example, Special Publication No. 39-29435 has the final boiling point
A process is disclosed for the steam reforming of light hydrocarbons with a boiling point of up to 350°C, preferably between 20 and 220°C, in the presence of a platinum group metal catalyst. However, from the current technical viewpoint, this method also has the following problems. In other words, (a) the raw materials used are limited to relatively light hydrocarbons, making it impossible to cope with the current situation in which the use of heavier raw materials is increasing; and (b) as the raw materials become heavier, (c)
When the water vapor ratio (S/C) is less than 3, there is a marked tendency for carbon to precipitate, causing problems such as a decrease in catalyst activity within a short period of time. As a result of repeated research in search of conditions that enable complete gasification through steam reforming of heavy hydrocarbons, the present inventor found that ruthenium differs from other platinum group metals in steam reforming of heavy hydrocarbons. They discovered that it exhibits a unique behavior and conducted further research to complete the present invention. That is, the present invention has a final boiling point of 650
The present invention provides a method for steam reforming heavy hydrocarbons, which comprises desulfurizing heavy hydrocarbons at temperatures below 0.degree. C. and then gasifying them with steam in the presence of a ruthenium catalyst. The heavy hydrocarbons with a final boiling point of 650°C or lower that are reformed by the method of the present invention include distillation fractions of petroleum and coal oils, and fractions obtained by heat treating and distilling petroleum and coal oils. etc. are exemplified.
In particular, the latter contains many olefins and aromatic components,
Conventionally, it was considered difficult to process, but according to the method of the present invention, it can be easily gasified. Desulfurization methods include methods such as hydrogenation deflowing, alkali cleaning, and solvent desulfurization. For example, in the case of hydrodesulfurization, conventional methods are followed, such as Mo-based, Co-MoO-based, Co-MoO-
Reaction temperature 250-450℃ in the presence of a catalyst such as Al ₂ O ₃ system
The reaction pressure is about 20 to 200 Kg/cm ² G, H ₂ /oil (mole ratio) is about 2 to 20, and LHSV is about 0.2 to 10. In the hydrodesulfurization reaction, hydrogen sulfide removal means are used, such as the combined use of a ZnO-based adsorption desulfurization catalyst. The sulfur content in the heavy hydrocarbon after desulfurization is preferably 10 ppm or less, particularly preferably 1 ppm or less. If the sulfur content in the heavy hydrocarbon cannot be reduced to a predetermined value or less by one desulfurization treatment, the desulfurization treatment may be repeated. The heavy hydrocarbons that have been desulfurized are then subjected to steam reforming. Steam reforming is carried out in the presence of a ruthenium catalyst at a temperature of about 400 to 1000℃ and a pressure of 1 to 50℃.
It is carried out under conditions of approximately Kg/cm ² G and S/C (number of oxygen atoms in water vapor per carbon atom in the raw material) = approximately 0.6 to 10. Ruthenium catalysts include alumina (alpha, beta, gamma, etc.), silica, silica-alumina, magnesia, zirconia, silicon carbide,
It is supported on a known carrier such as silicon nitride or activated carbon. The catalyst may be in any shape such as spheres, pellets, rings, etc. The amount of ruthenium supported on the carrier is preferably about 0.1 to 20% by weight, more preferably 0.5 to 5% by weight. If the reaction temperature is less than 400°C, the amount of catalyst required for complete gasification increases and the tendency for carbon to precipitate increases. On the other hand, if the reaction temperature exceeds 1000°C, sintering of the active metal, crystallization of the carrier, etc. will occur, causing a decrease in catalyst activity. If the reaction pressure is less than 1 Kg/cm ² G, the catalyst activity will not be sufficiently exhibited. On the other hand, if the reaction pressure exceeds 50 Kg/cm ² G, the equipment cost becomes excessive. When the water vapor ratio (S/C) is less than 0.6, carbon precipitation is observed, and even when it exceeds 10, there is no particular improvement in the effect. When heavy hydrocarbons with a final boiling point of 650° C. or lower are desulfurized and then steam reformed by the method of the present invention, the gasification rate is always 100%. Furthermore, since the amount of carbon deposited is extremely small and the catalyst activity is high at low temperatures, the catalyst life is long. Furthermore, the reaction proceeds smoothly even when the S/C is low, which is advantageous. The reason why the method of the present invention can produce such remarkable effects as described above is not clear at present. As is well known, there are still many points that have not been elucidated regarding the selection of catalysts and the mechanisms of catalyst deterioration and regeneration in desulfurization of hydrocarbons, steam reforming, and the like.
Therefore, in the steam reforming as the second step of the present invention, the fact that ruthenium alone can exhibit remarkable effects that are significantly different from other catalysts is completely unexpected even for those skilled in the art. However, it is currently impossible to elucidate the reason. The remarkable effects of the present invention will be clarified by the Examples and Comparative Examples shown below. Examples 1 to 4 A heavy fraction with a sulfur content of 2% by weight obtained by thermally decomposing the vacuum distillation residue of crude oil (final boiling point 500°C, paraffin + naphthene = 63vol%, olefin = 7vol%,
Aromatic compounds (30 vol%) are hydrodesulfurized in the presence of a Co-Mo catalyst to reduce the sulfur content to 0.5 ppm. A reactor with a diameter of 1 inch is filled with 325 ml of a catalyst in which a predetermined amount of ruthenium is supported on spherical alumina with a diameter of 4 mm, and the desulfurized heavy fraction and steam are supplied to the reactor to carry out steam reforming. Table 1 below shows the steam reforming reaction conditions, and Table 2 shows the results 5 hours after the start of the reaction. In either case, almost no tendency for carbon precipitation was observed.

【table】

[Table] Examples 5 to 13 The same heavy hydrocarbons as in Examples 1 to 4 were used in Example 1.
-Desulfurize in the same manner as in 4. Catalyst 325 with 4.0% by weight of ruthenium supported on spherical alumina with a diameter of 4mm
ml is charged into a reactor having a diameter of 1 inch, and the desulfurized hydrocarbons are steam reformed under the conditions shown in Table 3 below. The results at 5 hours after the start of the reaction are shown in the fourth column.
Shown in the table. Almost no tendency for carbon precipitation was observed in any case.

【table】

【table】

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[Table] Comparative Examples 1 to 3 The heavy fraction desulfurized in the same manner as in Examples 1 to 4 using a catalyst in which platinum, palladium, or rhodium was supported instead of ruthenium on alumina having a diameter of 4 mm was Subject to steam reforming under the conditions shown in the table. Both catalysts had extremely low conversion rates and rapidly deteriorated activity, so that they became unusable within a short time.

[Table] Example 14 4% by weight of ruthenium in spherical alumina with a diameter of 4mm
A reactor with a diameter of 1 inch was filled with 650 ml of the supported catalyst, and the heavy fraction desulfurized in the same manner as in Examples 1 to 4 and steam were supplied to the reactor as shown in Table 6 below. Steam reforming is carried out under the following conditions.

[Table] Table 7 below shows the composition of the produced gas, the conversion rate, and the required amount of catalyst after each period of time. The catalytic activity was very stable, and the amount of precipitated carbon did not substantially affect the catalytic activity.

[Table] Comparative Example 4 The heavy fraction with a sulfur content of 2% by weight (final boiling point 500°C) used as the starting material in Examples 1 to 4 was processed in the same reactor as in Example 14 without desulfurization. and steam reforming under the same conditions as in Example 14. In this example, the catalyst activity decreased significantly within a few hours and slippage of the feedstock occurred. Comparative Example 5 A heavy fraction with a sulfur content of 2% by weight (final boiling point 500°C) similar to Examples 1 to 4 was desulfurized to a sulfur content of approximately 100 ppm, and then steam reformed under the same conditions as Example 14. to offer as a pawn. The results are shown in Table 8. Although the catalytic activity of this example is improved compared to the case where desulfurization is not performed (Comparative Example 4), it still deteriorates within a relatively short time and cannot be put to practical use.

【table】

Claims (1)

[Claims] 1. A method for steam reforming heavy hydrocarbons, which comprises desulfurizing heavy hydrocarbons with a final boiling point of 650° C. or lower and then gasifying them with steam in the presence of a ruthenium catalyst.