JPS638811B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a catalyst for producing hydrogen by decomposing and lightening heavy hydrocarbons and using a steam iron reaction. The present inventor first decomposed heavy hydrocarbons such as atmospheric distillation residue oil and vacuum distillation residue oil to make them lighter, and at the same time reduced the iron oxide in the catalyst by the coke that adhered to the catalyst surface during decomposition. proposed a method of generating hydrogen by reacting this reduced iron with steam (Japanese Patent Publications No. 55-104920, No. 56-49790, Japanese Patent Application No.
56−20708). He also proposed a catalyst composition that can be used for this purpose (Japanese Patent Application Laid-Open No. 124542/1983). As a result of further research into the process of the above method and the catalyst used in this process, the present inventors found that a catalyst containing a large amount of SiO ₂ is capable of reacting in a steam iron reaction (H ₂ O + 3FeO → H ₂ + Fe ₃ O ₄ or
H ₂ O + Fe → FeO + H ₂ ) activity is likely to decrease, catalysts containing a certain amount of Cr ₂ O ₃ are less likely to decrease heavy hydrocarbon decomposition activity and steam iron reaction activity, and catalyst composition primary particles It has been found that the average particle size of iron has an effect on the reduction in steam iron reaction activity. The present invention has been made based on this knowledge, and is an improved decomposition and lightening method for decomposing heavy hydrocarbons that is less likely to cause deterioration in the activity of the steam iron reaction, that is, has a long catalyst life. The purpose is to provide a catalyst for producing hydrogen. That is, in the present invention, iron in the oxidized state is 30
~60% _by weight, 0.1 to 8% by weight of _Cr2O3 , 3% by weight or less of _SiO2 , and a heavy hydrocarbon consisting of a catalyst with an average particle size of primary particles of 1μ or less This is a catalyst composition for decomposing and lightening hydrogen and producing hydrogen. The present invention will be explained below. The method for decomposing and lightening heavy hydrocarbons and producing hydrogen to which the catalyst composition of the present invention is applied is to catalytically crack heavy hydrocarbons to lighten them, and at the same time generate hydrogen through a steam iron reaction. However, in this case, the reduction of iron oxide in the catalyst
It utilizes the coke that adheres to the catalyst surface during cracking. A more specific example will be described based on FIG. In the first step 1, a catalyst containing iron (on average, wustite), which has been reduced in the second step 2 described later, is heated in a fluidized bed at a temperature of 450 to 600°C and a pressure of 0 to 15 kg/cm ² G. Heavy hydrocarbons 3 such as atmospheric distillation residue oil, vacuum distillation residue oil, deasphalting residue oil, coal liquefied oil, shale oil, etc., and steam 4 are simultaneously supplied. The reduced iron in the catalyst and steam cause a steam iron reaction, producing hydrogen and oxidizing the iron. On the other hand, heavy hydrocarbons are brought into contact or thermally decomposed by a catalyst to become lighter. When this heavy hydrocarbon is lightened, coke is deposited on the catalyst surface. The generated hydrogen, lightened cracked gas, and cracked oil are discharged from the first step 1 as a product 5 together with unresolved oil or unreacted steam, and are separated and purified. The catalyst with coke attached is transferred to the second
Transferred to process 2. Here, a fluidized bed is formed at a temperature of 700 to 900°C and a pressure of 0 to 15 kg/cm ² G, and an oxygen-containing gas 7 containing an insufficient amount of oxygen to completely burn the coke is supplied. and decoked. The iron oxide (on average, magnetite) in the catalyst is reduced by the attached coke and the generated carbon monoxide gas. The catalyst containing reduced iron is passed through the return pipe 8 to the first step 1 described above.
The waste gas 9 is returned to the second step 2 and subjected to a decomposition reaction and a steam iron reaction, and the exhaust gas 9 is discharged from the second step 2. It should be noted that the decomposition of heavy hydrocarbons and the steam iron reaction in the first step 1 described above are separate processes, that is, the catalyst reduced in the second step 2 is first reacted with steam to perform the steam iron reaction. It goes without saying that the catalyst of the present invention can also be applied to a process in which the oxidized catalyst is brought into contact with heavy hydrocarbons to decompose and lighten them. In addition, in the above process, the iron in the catalyst reacts with the sulfur content of heavy hydrocarbons to form iron sulfide, but in order to remove this, a process for roasting the iron sulfide is also installed. The catalyst of the present invention is applicable. Next, the catalyst of the present invention will be described. The composition of the catalyst in the present invention is in an oxidized state. As described below, the catalyst of the present invention is mostly prepared through a roasting process, so that the unused catalyst is in a completely oxidized state. Therefore, the composition in the present invention refers to the ratio of the new catalyst after catalyst adjustment, or the ratio of the catalyst that has been subjected to the reaction and has been oxidized with coke removed. The reason why the content of iron in the catalyst composition is limited to 30 to 60% by weight as Fe is that if Fe is less than 30% by weight, the amount of hydrogen generated by the steam iron reaction per unit amount of catalyst is small, which is industrially disadvantageous. Moreover, if it exceeds 60% by weight, bogging (fusion or agglomeration phenomenon of catalyst particles) tends to occur, and the number of elements forming the catalyst skeleton decreases, resulting in a high bulk density, which has a negative impact on fluidized bed formation. This is also because the specific surface area decreases, which reduces the decomposition of heavy hydrocarbons and the activity of the steam iron reaction. The reason for limiting Cr ₂ O ₃ to 0.1 to 8% by weight is as follows:
If Cr ₂ O ₃ is less than 0.1% by weight, decomposition of heavy hydrocarbons and steam iron reaction will occur, and iron oxide in the catalyst will be inhibited.
In the process of repeated reduction reactions with CO gas and coke, iron particles grow, and iron sintering occurs on the surface of catalyst particles, resulting in decomposition of heavy hydrocarbons and steam iron reactions, and furthermore, CO gas and coke. This is to prevent the problem of a decrease in the activity of the reduction reaction due to On the other hand, Cr ₂ O ₃ is 8
When the amount exceeds % by weight, the amount of solid solution of Cr ₂ O ₃ and iron increases, and as a result, the number of active centers involved in the steam iron reaction decreases, and the amount of hydrogen generated decreases. SiO ₂ forms a composite oxide with FeO, and this oxide covers the surface of iron oxide particles in the catalyst, significantly inhibiting the steam iron reaction and the reduction reaction of iron oxide. When the SiO ₂ content exceeds 3% by weight, this phenomenon becomes noticeable when the catalyst is repeatedly used over a long period of time. That is, the life of the catalyst is shortened. In addition to the above composition, the average particle diameter of the primary particles constituting the catalyst is required to be 1 μm or less. Since the catalyst of the present invention is preferably used in a fluidized bed process, it is desirable to adjust the average particle size of the catalyst to 40 to 600μ. Incidentally, such catalyst particles are constructed by sintering a large number of even smaller particles. These fine particles are called catalyst-constituting primary particles. For example, what is shown in FIGS. 2 and 3 are secondary electron images of catalyst particles taken using an electron microscope. This figure 2 has a magnification of 40 times, so you can see the size of each catalyst. The length of the white line at the bottom of Figure 2 is
Represents 500μ. Figure 3 shows specific catalyst particles viewed at 1500 times magnification, and these individual particles are the primary particles constituting the catalyst. The length of the white line at the bottom of the photo indicates 5μ. If the average particle diameter of the primary particles constituting the catalyst exceeds 1 μ, Cr ₂ O ₃ and other skeleton-forming components will be unevenly distributed among the particles and will not play a sufficient role in forming the skeleton.
For this reason, repetition of the decomposition of heavy hydrocarbons, the steam iron reaction, and the reduction reaction of iron oxide in the catalyst causes iron particles to grow, causing a decrease in surface area, which is undesirable. In addition, an increase in the particle size of the primary particles means a decrease in the number of primary particles, and since SiO ₂ covers the surface of the iron particles and inactivates them, this negative effect is noticeable. It also becomes. For this reason, as shown in Examples, when a catalyst is used for a long period of time, the amount of hydrogen generated by the steam iron reaction decreases. The average particle size of the primary particles constituting the catalyst can be determined by randomly selecting about 100 particle sizes from the micrographs as described above and measuring them. Next, a method for preparing the catalyst of the present invention will be described. Dissolve iron sulfates, nitrates, chlorides, etc. in water or other iron compounds in acid, add chromate or dichromate to a concentration of 0.1 to 8% by weight after catalyst preparation, or If desired, aluminum salts, calcium salts, magnesium salts, etc. are added and dissolved so that the iron content becomes 30 to 60% by weight as Fe after catalyst preparation. This is precipitated as iron hydroxide with an alkaline solution such as sodium hydroxide, potassium hydroxide, ammonia, etc., and the precipitate is granulated and dried.
It can be prepared by firing at a temperature of 1000-1500°C. In addition, the aforementioned chromate, dichromate, aluminum, calcium, magnesium salts, etc.
It may be used after being dissolved in an alkaline solution. Another method is to use natural iron ores such as laterite, limonite, hematite, siderite, etc., or other iron-containing compounds that satisfy the above composition, or to add Cr ₂ O ₃ of 0.1 to these after preparing the catalyst. A chromium compound is added to the mixture to a concentration of ~8% by weight, and the mixture is ground to an average particle size of 1 μm or less. in this case,
It is difficult to reduce the particle size to 1 μm or less by pulverization using a normal mill, etc., but it is relatively easy to pulverize the particle size to 1 μm or less using a high-pressure air jet pulverizer. By pulverizing the particles to 1 μm or less, the average particle size of the primary particles constituting the catalyst can be reduced to 1 μm or less. It can be prepared by kneading, granulating, drying, and firing the raw materials pulverized in this way at a temperature of 1000 to 1500°C. The catalyst of the present invention as described above has exceptional effects such as being able to stably decompose and lighten heavy hydrocarbons and produce hydrogen through a steam iron reaction over a long period of time. It is industrially useful. Examples and comparative examples of the present invention will be shown below, and the effects of the present invention will be specifically described. Example 1 450g of ferrous sulfate ( _FeSO4.7H2O ) _to 800ml
of distilled water. Next, 35 g of sodium dichromate (Na ₂ Cr ₂ O ₇ 2H ₂ O) and 80 g of sodium hydroxide (NaOH) were dissolved in 1000 ml of distilled water and heated at 40°C.
The above ferrous sulfate solution was added dropwise to the solution while heating and passing nitrogen through the solution. Filter and wash the generated precipitate,
After drying at a temperature of 100°C, it was ground to a particle size of 32 mesh or less. After firing this at a temperature of 1050° C. for 3 hours, the particles were sized to 150 to 32 meshes and used as a catalyst. This catalyst contains 56.1% by weight of iron as Fe, Cr ₂ O ₃
was 5.85% by weight, and SiO ₂ was 0.03% by weight. Further, the specific surface area was 1.2 m ² /g, and the bulk specific gravity was 1.60. Further, the average particle size of the primary particles constituting the catalyst was 0.8μ. Next, using this catalyst, repeated experiments such as decomposition of heavy hydrocarbons and generation of hydrogen by the steam iron method were conducted. The experimental equipment used was a stainless steel fluidized bed reactor with an inner diameter of 52 mm and a height of 1000 mm. Catalyst is supplied from the bottom of this reactor, and the same amount of catalyst as supplied is extracted from a position at a catalyst layer height of 40 cm. First, a catalyst was introduced into the reactor at a rate of 2.5Kg/hr,
The temperature of the catalyst bed was kept at 540°C and the pressure was kept at 0 Kg/cm ² ·G, and Kuwait vacuum distillation residue oil (specific gravity: 1.020,
Remaining coal: 21.1% by weight, sulfur content: 5.3% by weight) 400%
g/hr, steam was supplied at 260 g/hr. Next, the catalyst extracted from the catalyst outlet of the reactor was reintroduced into the reaction system. This operation was repeated three times to obtain more than 15 kg of coke-adhered catalyst. Next, using the same reactor, this coke-covered catalyst was introduced at a rate of 2.5 Kg/hr, and the temperature of the catalyst bed was increased.
830℃, pressure maintained at 0Kg/ ^cm2・G, oxygen concentration
Introducing 10vol% oxygen-containing gas at 600NI/hr,
Reduces iron oxide in the catalyst. After approximately 0.5 hours, the catalyst is removed from the reactor. Next, using this catalyst, the residual oil is decomposed in one pass without repeating the circulation of the catalyst under the above conditions, but from the second time onwards, since the iron oxide in the catalyst has been reduced, A steam iron reaction also occurs at the same time, producing hydrogen. As described above, the decomposition and lightening of the residual oil, the steam iron reaction, and the reduction reaction of iron oxide in the catalyst were repeated. The results are shown in Table 1. Example 2 Fe48.5% by weight, Cr ₂ O ₃ 3.91% by weight, SiO ₂ 1.88
% by weight of laterite ore was crushed into fine particles of 1 μm or less using a high-pressure air jet crushing classifier. This was kneaded, granulated, dried, and fired at 1050°C for 3 hours.
This was sized to 32 mesh to 150 mesh and used as a catalyst. This catalyst contains 57.1% by weight of iron as Fe,
Cr ₂ O ₃ is 4.46% by weight, SiO ₂ is 1.93% by weight, and
The specific surface area was 5.2 m ² /g, and the bulk specific gravity was 1.53. Further, the average particle size of the primary particles constituting this catalyst was 0.9μ. Using this catalyst, decomposition and lightening, steam iron reaction, and iron oxide reduction reaction were repeated in the same manner as in Example 1. The results are shown in Table 1. Example 3 A commercially available catalyst for CO gas shift reaction (G-3A manufactured by Nissan Girdler) was pulverized to 32 meshes or less,
It was fired at 1050°C for 3 hours and sized to 32 to 150 meshes. This catalyst contained 54.7% by weight of iron as Fe, 7.09% by weight of Cr ₂ O ₃ , and 0.10% by weight of SiO ₂ , had a specific surface area of 1.2 m ² /g, and a bulk specific gravity of 1.59. Furthermore, the particle size of the primary particles constituting the catalyst was 0.6μ. Using this catalyst, the same reaction as shown in Example 1 was repeated. The results are shown in Table 1. Comparative Example 1 70 g of sodium hydroxide was dissolved in 1000 ml of distilled water, heated to 40°C, and then an aqueous solution of 450 g of ferrous sulfate (FeSO ₄ 7H ₂ O) dissolved in 850 ml of distilled water was added dropwise while passing nitrogen through the solution. did. The generated precipitate is washed by filtration, dried at 100℃, and ground to 32 mesh or less.
Fired at a temperature of 1050℃. 32 meals of this~
It was sized to 150 mesh and used as a catalyst. The composition is 58.0% by weight of iron as Fe, 0.04% by weight of Cr ₂ O ₃ ,
_SiO2 was 0.04% by weight. Also, the specific surface area is
The particle size was 1.2 m ² /g, the bulk specific gravity was 1.74, and the average particle size of the primary particles constituting the catalyst was 1.5 μ. Using this catalyst, the same reaction as in Example 1 was carried out. The results are shown in Table 2. Comparative Example 2 The amount of sodium dichromate in Example 1 was
The catalyst was prepared in exactly the same manner except that the amount was 75 g. The composition of the catalyst is 50.7% by weight of iron as Fe, Cr ₂ O ₃
12.3% by weight, SiO ₂ 0.05% by weight, specific surface area 1.9
m ² /g and bulk specific gravity of 1.50. Further, the average particle size of the primary particles constituting the catalyst was 1.1 μm. Using this catalyst, the same reaction as in Example 1 was carried out. The results are shown in Table 2. Comparative Example 3 25g of commercially available acidic silica sol (concentration 20%) was added to the precipitate prepared in the same manner as in Example 1.
Kneaded for hours. This was dried at 100℃, crushed to 32 meshes or less, baked at 1050℃ for 3 hours, and then
The particles were sized to a mesh size of 32 to 32 meshes and used as a catalyst. The composition of this catalyst is 55.7% by weight as Fe, Cr ₂ O ₃
4.72 wt%, SiO ₂ 4.18 wt%, specific surface area 2.5
m ² /g, and bulk specific gravity was 1.48. Further, the average particle size of the primary particles constituting the catalyst was 0.9μ. A reaction experiment similar to that in Example 1 was conducted using this catalyst. The results are shown in Table 2. Comparative example 4 Fe 48.5% by weight, Cr ₂ O ₃ 3.91% by weight, SiO ₂ 1.88
% by weight of laterite ore was ground to 10μ or less using a ball mill, kneaded and granulated, dried, and then heated at a temperature of 1050°C for 30 minutes.
The catalyst was calcined for an hour and sized to 32 to 150 mesh. The composition is 55.7% by weight as Fe, 4.72% by weight as Cr ₂ O ₃ and 1.93% by weight as SiO ₂ , and the specific surface area is
The area was 6.7 m ² /g, and the bulk density was 1.69. In addition, the average particle size of the primary particles constituting this catalyst is 9μ
It was hot. A reaction experiment similar to that in Example 1 was conducted using this catalyst. The results are shown in Table 2.

【table】

【table】

【table】

[Table] As is clear from the above results, the catalyst of Comparative Example 1 containing 0.1% by weight or less of Cr ₂ O ₃ has poor decomposition activity for heavy hydrocarbons, and furthermore, the amount of hydrogen generated decreases with repeated use. In addition, the catalyst of Comparative Example 2 in which Cr ₂ O ₃ exceeds 8% by weight decreases the amount of hydrogen generated by repeated use. This seems to be due to the formation of a solid solution between Cr ₂ O ₃ and iron. Furthermore, when the catalyst of Comparative Example 3 containing more than 3% by weight of SiO ₂ is repeatedly used, hydrogen generation is significantly reduced. This seems to be due to the formation of a composite oxide of FeO and SiO ₂ . The catalyst of Comparative Example 4, in which the primary particles constituting the catalyst exceed 1μ, exhibits a decrease in the amount of hydrogen generated by repeated use. This is thought to be because the dispersion of skeleton-forming substances such as Cr ₂ O ₃ decreases, and the skeleton-forming effect decreases.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of one exemplary process to which the catalyst of the present invention can be applied. FIGS. 2 and 3 are photographs used as illustrations, and are secondary electron images of catalyst particles taken using an electron microscope. Figure 2 is 40x, Figure 3
The figure is 1500x magnified.

Claims (1)

[Claims] 1 Iron in oxidized state is 30-60% by weight as Fe,
The composition contains 0.1 to 8% by weight of Cr ₂ O ₃ and 3% by weight or less of SiO ₂ , and the average particle size of the primary particles constituting the catalyst is
A catalyst for decomposition and lightening of heavy hydrocarbons and production of hydrogen, characterized by a particle size of 1μ or less.