JPH0144226B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid oxygen carrier that performs oxidative dehydrogenation of hydrocarbons in the absence of molecular oxygen, and a method for producing the same, in which the oxidation/reduction cycle is performed efficiently. An object of the present invention is to provide a solid oxygen carrier capable of maintaining a high reaction rate and a method for producing the same.

A reaction is already known in which a metal oxide and a hydrocarbon are brought into contact in the absence of molecular oxygen, and the hydrocarbon is oxidized and dehydrogenated by the combined oxygen of the metal oxide. At this time, the metal oxide that participated in the reaction is reduced and becomes a metal or a lower oxide of a metal, so by firing it at a high temperature in the presence of molecular oxygen, the original metal oxide is regenerated, It can be used again for the oxidative dehydrogenation reaction of raw material hydrocarbons. That is, the metal oxide acts as an oxygen carrier that transports molecular oxygen in the form of oxygen bound to the metal and indirectly participates in the oxidative dehydrogenation reaction of hydrocarbons.

A typical example of a reaction using an oxygen carrier is a reaction for producing butadiene from butane or butene as a raw material.

Reactions using an oxygen carrier do not generate explosive gas mixtures as do reactions that bring molecular oxygen into direct contact with hydrocarbons, and if appropriate metal oxides and reaction conditions are selected, carbon monoxide and carbon dioxide can be produced. Combustion reactions that produce carbon can be suppressed to produce useful dehydrogenation reaction products.

However, in the reaction using an oxygen carrier, the oxidative dehydrogenation reaction of the raw material hydrocarbon is carried out by the bound oxygen of the supported metal oxide, so there is a limit to the oxidative dehydrogenation capacity of the oxygen carrier at one time. In order to continue the reaction for a long time, it is necessary to repeat regeneration (oxidation) frequently. Therefore, unless regeneration using molecular oxygen can be carried out efficiently, the reaction rate from the second cycle onwards will decrease. Of course, it is possible to regenerate it to completion by raising the firing temperature and taking a sufficient amount of time, but this increases energy consumption and requires large-capacity regeneration equipment, so it should be done at a lower temperature and in a shorter time. It is industrially advantageous to be able to perform regeneration.

As a result of intensive research into oxygen carriers that can be easily regenerated, the present inventors found that
This has led to the present invention.

(Structure) That is, the first invention relates to the structure of an oxygen carrier, in which a porous carrier supports a metal oxide that can change from an oxidation state to a metal or its lower oxidation state under reaction conditions. In a solid oxygen carrier for oxidative dehydrogenation of hydrocarbons in the absence of the presence of hydrogen, the porous carrier particles have a particle diameter of 20 mm in the radial direction from the surface
A solid oxygen carrier for oxidative dehydrogenation of hydrocarbons, in which 80% or more of the metal oxide is supported on the outer layer portion having a thickness corresponding to By pre-wetting or partially wetting a porous carrier with moisture, impregnating or spraying with an aqueous solution of a salt of a metal that can change from an oxidation state to a metal or its lower oxidation state under reaction conditions, and then drying and oxidizing. The metal oxide is applied to the outer layer portion of the porous carrier particle in a thickness range corresponding to 20% of the particle diameter in the radial direction from the surface of the porous carrier particle.
This is a method for producing a solid oxygen carrier for oxidative dehydrogenation of hydrocarbons in the absence of molecular oxygen, in which 80% or more of the oxygen is supported.

Metals that can be used as oxygen carriers may be metals that can change from an oxidation state to a metal or its lower oxidation state under the reaction conditions, such as metals from group 2 of the periodic table such as Sr and Cd, and metals from the same periodic table such as Sn and Pb. Group 4, Sb,
Group 5 of the same table such as Bi, V, Group 6 of the same table such as Mo, Te, Cr, Group 8 of the same table such as Fe, Co, Ni, Pd, etc.
Metals such as Mn, La, and Cu, or mixtures thereof are targeted.

Although it is possible to use oxides of the above metals as oxygen carriers, porous carriers,
For example, alumina, silica/alumina, titania,
Those supported by magnesia, borya, etc. are better.
This has the advantage that the raw material is easily adsorbed on the oxygen carrier and the reaction rate is improved. Therefore, in the present invention,
Such supported solid oxygen carriers are used.

Common methods for producing oxidation catalysts include drying and firing a dry carrier impregnated with an aqueous solution of the catalyst component, or drying and firing a co-precipitated product of the carrier and catalyst components. In products produced by such a method, the catalyst components are almost uniformly distributed in the carrier.

In general, as catalysts for carrying out oxidation and dehydrogenation reactions of hydrocarbons in the presence of molecular oxygen, catalysts in which the catalytic metal components are uniformly distributed are preferable. In solid oxygen carriers that perform oxidative dehydrogenation of raw material hydrocarbons using the bound oxygen of oxides, the metal oxides present in the center of the particles undergo reduction (reaction with raw material hydrocarbons), oxidation (regeneration with molecular oxygen), ) It was found that the reaction rate was slow for both, and that they were hardly involved in the actual reaction during short cycles.

The present invention was completed based on this recognition.

That is, in the oxygen carrier of the present invention, 80% or more of the metal oxide is supported on the outer layer portion of the carrier particle in a thickness range corresponding to 20% of the particle diameter in the radial direction from the surface of the carrier particle.

Such a solid oxygen carrier for dehydrogenation, in which 80% or more of the metal oxide is supported on the outer layer portion of the porous carrier particle in a thickness range corresponding to 20% of the diameter of the carrier particle in the radial direction from the surface of the porous carrier particle. To manufacture the
The porous carrier is preliminarily moistened or partially moistened with water, impregnated with or sprayed with an aqueous metal salt solution, and then dried and oxidized and calcined. When a wet porous carrier is impregnated or sprayed with an aqueous metal salt solution,
It is difficult for the metal salt aqueous solution to reach the inner layer of the carrier, and most of the metal salt aqueous solution only diffuses and penetrates into the outer layer of the carrier, and by drying and firing, most of the metal oxides are transferred to the outer layer. It will be carried. In order to partially wet the porous carrier, the porous carrier may first be wetted with water and then the surface portion may be dried. Residual moisture then collects in the center of the carrier, so when such a partially wetted carrier is impregnated or sprayed with an aqueous metal salt solution, most of the aqueous metal salt solution impregnated or sprayed later penetrates only to the outer layer of the carrier. First, if the material is dried and fired as it is, most of the generated metal oxides will be present in the outer layer. It is appropriate that the degree of partial wetting is about 50% of the water content at room temperature.

The production of the oxygen carrier according to the present invention and the characteristics of the produced oxygen carrier will be specifically explained with reference to the following Examples, Comparative Examples, and the attached drawings.

Example 1 <Production of solid oxygen carrier> Spherical γ-alumina (12 to 16 meshes, pore volume
0.7ml/g; BET method) 40g was taken, and while stirring at room temperature, 76ml of distilled water was added dropwise through a glass filter to uniformly wet the γ-alumina, and then dried in a desiccator at room temperature. When the weight loss reaches 35g, take it out and partially moisten it.
Made of alumina.

Bismuth nitrate in nitric acid aqueous solution: Bi(NO ₃ ) ₃・5H ₂ O
While stirring a colorless transparent aqueous solution in which 29.1g of
After dropping the above partially wet γ-alumina and impregnating it, it was dried for 1 hour at 120°C in an electric furnace with air circulation, and then at 600°C in a fluidized bath with air circulation.
Firing was carried out for 3 hours.

As a result of performing X-ray diffraction measurements on this fired product using copper's Kα rays as a radiation source, the characteristics of the diffraction peaks near 2θ = 27° and 32° indicate that this is bismuth oxide:
It was confirmed that it was Bi ₂ O ₃ .

This was further analyzed using an X-ray microanalyzer and the results are shown in FIG. From this figure,
For particles with a diameter of 1 mm, 0.1 mm to 0.2 mm from the outer surface
It was found that more Bi was distributed in the thickness range corresponding to 20% of the particle diameter. As a result of integrating the area from the figure, the amount of Bi ₂ O ₃ supported in this outer layer portion was about 80%.

<Reaction> The oxygen carrier 2 c.c. prepared in this way was filled into a stainless steel reaction tube with an inner diameter of 10 mm, placed in a sand fluidized bathtub with a temperature controller (electric heating type), and then heated. The temperature was set at 450°C and the mixture was first treated with water vapor using helium as the diluent gas. In steam treatment, the oxygen carrier immediately after air oxidation is highly active;
Since carbon monoxide and carbon dioxide tend to be produced in large amounts as by-products, reducing the selectivity of the target product, this is a means of suppressing this (see Japanese Patent Application No. 35857-1983).

Next, a reaction test was conducted through 1-butene using helium as a diluent gas. 1-butene is supplied at 0.1 (mole equivalent/mole equivalent) to the oxygen carrier,
The reaction tube outlet gas was directly introduced into gas chromatography to analyze and quantify the reaction products. 1-
The butene reaction rate was 39.8 mol%, the 1,3-butadiene selectivity was 96.5 mol%, and the rest were carbon monoxide and carbon dioxide.

<Regeneration> 1-Butene aeration rate is 0.6 with respect to oxygen carrier
The introduction of raw material gas and helium was stopped at the time when (mole equivalent/mole equivalent) was reached. Thereafter, air was introduced, and after calcining at 500°C for 1 hour, steam treatment was carried out at 450°C in the same manner as described above, and then 1-butene was introduced and the reaction was performed again.

<Reaction> When 1-butene was supplied at 0.1 (mole equivalent/mole equivalent) to the oxygen carrier, the 1-butene reaction rate was 40.5 mol%, which was the same reaction rate as the newly produced oxygen carrier. Ta. The selectivity for 1,3-butadiene was 92.2 mol%, and the rest were carbon monoxide and carbon dioxide.

Comparative Example 1 <Manufacture of oxygen carrier> 40 g of γ-alumina, the same as that used in Example 1
The sample was immersed in 50 ml of a nitric acidic bismuth nitrate aqueous solution (Bi(NO ₃ ) _{3.5H 2} O.66% by weight) without being wetted with water, and then left to dry overnight at room temperature.
This was dried at 120°C for 1 hour under air circulation, then fired at 600°C for 3 hours, and as a result of X-ray diffraction measurement, it was found that bismuth oxide Bi ₂ O ₃ was produced as in Example 1. I confirmed that there is. When this was further analyzed using an X-ray microanalyzer, the results shown in FIG. 2 were obtained. This figure shows that the oxygen carrier prepared by this method has Bi distributed almost uniformly within the particles.

<Reaction> A reaction test was conducted in the same manner as in Example 1 using the oxygen carrier thus prepared. 1-butene to oxygen carrier 0.1
(Mole equivalent/mole equivalent) The analysis results when supplied were a 1-butene reaction rate of 37.0 mol%, a 1,3-butadiene selectivity of 91.5 mol%, and the rest were carbon monoxide and carbon dioxide.

<Regeneration> As in Example 1, the introduction of the reaction raw material gas and helium was stopped when the amount of 1-butene aeration reached 0.6 (mole equivalent/mole equivalent) relative to the oxygen carrier, and the temperature was changed to air and heated to 500°C. It played for an hour.
This was further treated with steam in the same manner as in Example 1.

<Reaction> As a result of further activity test evaluation using 1-butene, the 1-butene reaction rate was 26.5 mol%, which was 37.0% for the newly produced oxygen carrier.
It was significantly lower than the mol%. The 1,3-butadiene selectivity was 90.1 mol%, and the rest were carbon monoxide and carbon dioxide.

If regeneration is performed at 600°C for 3 hours, the reaction rate will return to its original state.

Example 2 <Oxygen carrier production> As in Example 1, 40 g of γ-alumina was partially moistened in advance, and a separately prepared ferric nitrate aqueous solution (90.6% by weight as Fe(NO ₃ ) _{3.9H 2} O) was added. After spraying with a manual sprayer so that the surface is uniformly wet, it is dried in an electric oven at 40℃ with air circulation.
This was again sprayed with the above ferric nitrate aqueous solution, dried again in the electric furnace, and fired at 600° C. for 3 hours under air circulation in the electric furnace. This product was subjected to X-ray diffraction and it was confirmed that Fe ₂ O ₃ was produced. Furthermore, analysis was performed using an X-ray microanalyzer in the same manner as in Example 1, and the results shown in FIG. 3 were obtained. Fe is 0.1 from the outer surface of the particle
It was observed that the particles were more widely distributed at a distance of ~0.2 mm. As a result of integrating the area from the figure, the amount of Fe ₂ O ₃ supported in this outer layer portion was about 80%.

<Reaction> A reaction test using 1-butene was conducted in the same manner as in Example 1, except that the reaction temperature was 400°C. A 1-butene reaction rate of 15.4 mol% and a 1,3-butadiene selectivity of 84.5 mol% were obtained.

<Regeneration and Reaction> The oxygen carrier after the reaction was regenerated with air at 500°C for 1 hour in the same manner as in Example 1, and a reaction test with 1-butene was conducted. As a result, the 1-butene reaction rate was 16.5 mol%. , 1,3-butadiene selectivity
It was confirmed that the activity was 79.5 mol%, which was close to the initial activity.

Comparative Example 2 <Production of Oxygen Carrier> 40 g of γ-alumina was impregnated with 65 ml of ferric nitrate aqueous solution (90.6% by weight as Fe(NO ₃ ) ₃ ·9H ₂ O) without prior wetting treatment. This was dried and fired in the same manner as in Comparative Example 1, and
The results of line diffraction measurement were similar to those in Example 2, and it was confirmed that Fe ₂ O ₃ was produced. The results of analysis using an X-ray microanalyzer are shown in FIG. It can be seen that in the oxygen carrier prepared by this method, Fe is almost uniformly distributed within the particles.

<Reaction> As a result of carrying out the reaction in the same manner as in Example 2, the 1-butene reaction rate was 16.2 mol% and the 1,3-butadiene selectivity was
It was 81.1 mol%.

<Regeneration and reaction> After that, regeneration was performed in the same manner as in Example 2, and further 1
-As a result of a reaction test using butene, the 1-butene reaction rate was 9.5 mol%, which was significantly lower than the previous test. The 1,3-butadiene selectivity was 80.5 mol%.

(Effects) As is clear from Examples 1 and 2, the oxygen carrier of the present invention maintains its original activity even after regeneration. As a result, the oxidative dehydrogenation reaction of hydrocarbons can be continued continuously without raising the firing temperature or lengthening the firing time.

Alternatively, even if the amount of supported metal oxide is reduced,
By centrally supporting it near the surface, the function as an oxygen carrier can be prevented from deteriorating.

[Brief explanation of drawings]

1 to 4 are diagrams showing the component distribution of metal oxides and carriers in the diametrical cross section of the solid oxygen carrier measured by an X-ray microanalyzer, and FIGS. The carriers shown in FIGS. 2 and 4 correspond to the oxygen carriers of Comparative Examples 1 and 2, respectively.
The horizontal axis shows the position in the diametrical cross section of the oxygen carrier (both ends are the particle surfaces), and the vertical axis shows the X-ray intensity.
Furthermore, the broken line in the figure indicates the center position of the particle, and the dotted line indicates the position corresponding to 20% of the particle diameter from the surface.

Claims (1)

[Claims] 1. Oxidative dehydrogenation of hydrocarbons in the absence of molecular oxygen in which a porous carrier supports a metal oxide that can change from its oxidation state to the metal or its lower oxidation state under reaction conditions. In a solid oxygen carrier for carrying out carbonization, 80% or more of the metal oxide is supported on the outer layer portion of the porous carrier particle in a thickness range corresponding to 20% of the particle diameter in the radial direction from the surface of the porous carrier particle. Solid oxygen carrier for oxidative dehydrogenation of hydrogen. 2. A porous carrier is pre-wetted or partially moistened with moisture, and then impregnated or sprayed with an aqueous solution of a metal salt capable of changing from an oxidation state to a metal or its lower oxidation state under reaction conditions, followed by drying and oxidation firing. Carbonization in the absence of molecular oxygen, in which 80% or more of the metal oxide is supported on the outer layer portion of the porous carrier particle having a thickness corresponding to 20% of the particle diameter in the radial direction from the surface of the porous carrier particle. A method for producing a solid oxygen carrier for oxidative dehydrogenation of hydrogen.