JPS6251938B2 - - Google Patents

Description

Detailed Description of the Invention (Purpose and Background) The present invention relates to an oxidative dehydrogenation reaction of hydrocarbons, in which the by-products of various oxygen-containing hydrocarbon compounds, carbon monoxide, and carbon dioxide are suppressed. The purpose of the present invention is to provide a method that can increase the selectivity of a target product and perform stable continuous operation over a long period of time.

In order to produce useful compounds by oxidative dehydrogenation of hydrocarbon raw materials, a method is generally used in which the raw material gas is brought into contact with a catalyst at high temperature together with a molecular oxygen-containing gas, such as air, to carry out an oxidative dehydrogenation reaction. ing. A typical example is a method of producing butadiene by bringing butane or butene into contact with a metal oxide catalyst together with air to carry out an oxidative dehydrogenation reaction using molecular oxygen.

However, such a method has the disadvantage that various oxygen-containing hydrocarbon compounds are produced as by-products, which complicates the purification process. Additionally, since flammable hydrocarbon gas and molecular oxygen coexist, there is a built-in risk of explosion due to operational errors.

In contrast, in the absence of molecular oxygen-containing gas,
When hydrocarbon raw material gas is brought into contact with metal oxide,
It is known that the oxidative dehydrogenation reaction of hydrocarbon raw materials is carried out by the bound oxygen of metal oxides.

For example, as a means to investigate the reaction characteristics of various catalysts (metal oxides) in the production of butadiene by oxidative dehydrogenation of butene, we used helium as a carrier gas and butene as a carrier gas. ―Bi, Mo―Sb, Mo―
It has been reported that butadiene was produced when it was brought into contact with As at high temperatures (Echigotani et al., Chemical Society of Japan 1978 Annual Meeting). This indicates that butadiene is produced through oxidative dehydrogenation of butene by the bound oxygen of a metal oxide, but no specific method for its practical application is suggested.

That is, the metal oxide that participated in the reaction is reduced to a metal or a lower oxide of a metal, so
Its oxidative dehydrogenation ability has its own limits, and it is difficult to use it industrially unless you consider regenerating it into the original metal oxide and using it again in the oxidative dehydrogenation reaction of hydrocarbons. . Regeneration is carried out by high-temperature calcination in the presence of molecular oxygen, thus allowing the metal oxide to carry molecular oxygen in the form of metal-bound oxygen and indirectly participate in the oxidative dehydrogenation reaction of the hydrocarbons. It will act as an oxygen carrier.

Practical oxygen carriers not only have excellent reaction rate and selectivity, but also reduce metal oxides (reaction with raw material hydrocarbons) and oxidize (regeneration with molecular oxygen) easily and quickly. At the same time, it must have sufficient mechanical strength to withstand frequent cycles of reduction and oxidation.

In other words, a fixed bed or fluidized bed (moving bed) system can be considered as an apparatus for carrying out such a reaction continuously, but in order to make a continuous process using a fixed bed, it is necessary to use a reaction column. It is necessary to install two reactors and use them alternately for reaction and regeneration, and in reactions using oxygen carriers, this switching must be done frequently, making the operation somewhat complicated.

On the other hand, in the case of a fluidized bed (moving bed) method,
Operation is simplified because a completely continuous process can be achieved by providing separate reaction and regeneration columns and circulating the oxygen carrier between them. However, in this case, the oxygen carrier not only circulates between the reaction tower and the regeneration tower, but also actively moves within each of the reaction tower and regeneration tower in the fluidized bed.
Must have sufficient strength against wear.

From this point of view, metal oxides themselves have a remarkable tendency to become pulverized during use, and although they have excellent initial activity, they have the drawback of being difficult to regenerate. Therefore, the present inventors attempted to use a metal oxide supported on a porous carrier.

Metal oxides supported on porous carriers are
It has the advantage that mechanical strength (compressive strength, filling strength, abrasion strength) can be adjusted as desired. However, in order for it to be put to practical use as an oxygen carrier, it must not only have both reactivity and selectivity, but also be easy to regenerate. Requiring a high temperature for regeneration means that it consumes a lot of energy, and requiring a long time means that the regeneration equipment needs to be large-sized, both of which have a large impact on the economic efficiency of the process.

The present inventors have discovered that in order to meet these requirements, the porous carrier used must satisfy certain conditions, and have completed the present invention based on this finding.

(Structure) The present invention involves the oxidation of bismuth by contacting a hydrocarbon gas with an oxygen carrier in which a bismuth oxide is supported on a porous carrier having a specific surface area of 40 to 300 m ² /g in the absence of a molecular oxygen-containing gas. This is a method for oxidative dehydrogenation of hydrocarbon gas, which involves oxidative dehydrogenation of hydrocarbons using bound oxygen.

At the start of the reaction with hydrocarbon gas, all of the bismuth oxides do not need to be completely bismuth oxides with the highest valence, and at the end of the reaction, the lower bismuth oxides produced are It is not necessary that all the oxides are completely the lowest valence oxide of bismuth. In short, it may be used in a state where the amount of bound oxygen increases or decreases before and after the reaction.

Such bismuth oxide has a specific surface area of 40~
It is supported on a porous carrier of 300 m ² /g. Porous carriers include, for example, alumina, silica, silica-alumina, titania, magnesia, borya,
Sepiolite etc. can be used. However, if a specific surface area of 300 m ² /g or more is used, although the reaction rate is high, by-products are produced in large quantities and the target product is hardly obtained. On the contrary, the specific surface area is 40
If it is less than m ² /g, although there are few by-products and the selectivity of the target product is high, the reaction rate is significantly lowered, so it is also not practical. The reaction for producing butadiene from butene will be described in more detail below as a representative example.

The supported oxygen carrier is easily prepared by impregnating or spraying a porous carrier having a desired specific surface area with an aqueous bismuth salt solution, followed by drying and calcination (decomposition of the metal salt).

The supported oxygen carrier thus prepared is contacted with the starting butene in the absence of molecular oxygen.

As the raw material, 1-butene, 2-butene alone or a mixture thereof, or a gas containing them is used.

The reaction temperature for producing butadiene by oxidative dehydrogenation of butene is approximately 300 to 600°C, preferably 350 to 550°C,
The reaction pressure is about normal pressure.

In order to quickly oxidize and regenerate bismuth or its lower oxides produced by reacting with the raw material butene using oxygen-containing gas (air), the firing temperature is higher than the temperature of the butadiene production reaction. Usually 400, depending on the type of metal.
Perform at ~700°C.

Freshly prepared oxygen carriers or freshly regenerated oxygen carriers have a strong initial activity and are susceptible to reactions that produce carbon monoxide and carbon dioxide, so they must be treated with steam or reducing gas before reacting with feedstock hydrocarbons. It is desirable to do so.

As the reducing gas, carbon monoxide (CO), hydrogen, lower hydrocarbon gases such as CH ₄ , C ₂ H ₆ , or a mixture thereof such as synthesis gas, COG gas, etc. can be used. .

Further, water vapor and reducing gas may be diluted with an inert gas such as nitrogen.

If the degree of treatment with water vapor or reducing gas is too low, the effect will naturally be small, and if it is too high, the activity of the oxygen carrier will decrease, so ultimately it is necessary to find the optimal value experimentally, but it is effective for the time being. In order to increase the amount of water vapor or reducing gas, it is preferable to use 0.01 (mole equivalent/mole equivalent) or more of water vapor or reducing gas per oxygen carrier. The treatment temperature varies depending on the oxygen carrier, but is preferably about 200 to 500°C.

The effects of the present invention will be shown below with reference to Examples.

Example 1 First, γ-alumina was prepared. Prepare 4.1 kg of 5% by weight (as Al ₂ O ₃ ) sodium aluminate aqueous solution in a stainless steel container with an internal volume of 10, and add
10.5 g of a 50% by weight aqueous glyconic acid solution was added and stirred. To this was added an 8.4% by weight aqueous aluminum sulfate solution in a short period of time until the pH reached 9.5.
The amount added at this time was 4.2 kg. The obtained prepared liquid was a white slurry liquid, and after being left overnight, the cake was filtered under reduced pressure using an aspirator and washed with 0.2% aqueous ammonia. After washing, the cake was dried at 110°C for 14 hours, and then baked in an electric furnace at 600°C for 3 hours. The product thus obtained is γ-alumina, with a specific surface area of 260
m ² /g.

These γ-alumina particles are sieved to give 12 to 16
40 g of mesh was taken and impregnated with 48 ml of a nitric acidic bismuth nitrate: Bi(NO ₃ ) ₃ .5H ₂ O aqueous solution (55.4% by weight as Bi(NO ₃ ) ₃ ) under reduced pressure. It was then dried for 30 minutes at 130°C in a stream of air. The obtained dry product (white particles) is further placed in an air stream,
A solid oxygen carrier (Bi ₂ O ₃ supported amount: 41.1% by weight) was prepared by firing at 600° C. for 3 hours. Take 2 c.c. of this solid oxygen carrier, fill it in a stainless steel reaction tube (inner diameter of the filled part 10 mm), place it in a sand fluidized bath with a temperature controller, and maintain the reaction temperature at 450 at normal pressure.
After steam treatment at 0.degree. C. while passing helium gas as a carrier gas, 1-butene was passed through an oxygen carrier at a ratio of 0.1 (mole equivalent/mole equivalent). The reaction tube outlet gas was introduced into gas chromatography for quantitative analysis. The 1-butene reaction rate is
The selectivity for 1,3-butadiene was 38.5 mol% and 91.5 mol%. Other carbon monoxide and carbon dioxide were produced.

1-Butene aeration rate relative to oxygen carrier
When it reaches 0.6 (mole equivalent/mole equivalent), 1-
The supply of butene and helium was stopped, air was introduced, the temperature was calcined at 600°C for 3 hours, the temperature was lowered to 450°C, the steam treatment was carried out in the same manner as above, and then 1-butene was introduced and the reaction test was carried out in the same manner as above. I went there. As a result, the 1-butene reaction rate was 37.0 mol%, the 1,3-butadiene selectivity was 91.5 mol%, and the others were carbon monoxide and carbon dioxide.

Example 2 The dried product at the γ-alumina production stage prepared in Example 1 was fired at 1100° C. for 9 hours in an electric furnace. This product had a specific surface area of 81 m ² /g. 20g of this fired product was taken and treated with a nitric acidic bismuth nitrate aqueous solution (Bi) in the same manner as shown in Example 1.
( _NO3 ) ₃ as 55.4% by weight) impregnated with 24ml, 130℃
Dry in an electric oven for 30 minutes, then dry in air at 600℃.
(Bi ₂ O ₃ supported amount: 38.6% by weight) for 3 hours.
This was taken at 2c.c. and heated to 450°C using the same reactor as shown in Example 1 using 1-butene as a raw material gas.
A reaction test was conducted in the same manner as in Example 1.
The 1-butene reaction rate was 34.5 mol%, and the 1,3-butadiene selectivity was 86.5 mol%. Other carbon monoxide and carbon dioxide were produced.

Further, in the same manner as in Example 1, the oxygen carrier used for the oxidative dehydrogenation of butene was oxidized in air and then subjected to steam treatment to repeat the reaction, and stable results were continuously obtained.

Example 3 Commercially available titania with a specific surface area of 45 m ² /g (particle size 12
~16 mesh) Take 40g of bismuth nitrate:Bi
(NO ₃ ) ₃・9H ₂ O: 29.11g in 20ml of 8N nitric acid aqueous solution
The solution was impregnated under reduced pressure at room temperature, and then dried at 150°C for 30 minutes. This was further calcined at 600℃ for 3 hours under air circulation (Bi ₂ O ₃ loading rate
38.6% by weight). 2 c.c. was taken, installed in the same apparatus as shown in Example 1, and a reaction test was conducted at 450°C using 1-butene as a raw material in the same manner as in Example 1. Reaction rate 35.4 mol%,
The 1,3-butadiene selectivity was 77.5 mol%, and carbon monoxide and carbon dioxide were also produced.

Further, in the same manner as in Example 1, the oxygen carrier used for the oxidative dehydrogenation of butene was oxidized in air and then subjected to steam treatment to repeat the reaction, and stable results were continuously obtained.

Comparative Example 1 40 g (12 to 16 meshes) of commercially available silica/alumina (press molded product) with a specific surface area of 396 m ² /g
Then, a nitric acidic bismuth nitrate aqueous solution (55.4% by weight as Bi(NO ₃ ) ₃ ) was prepared in the same manner as in Example 1.
After impregnating 48ml and drying at 130℃ for 30 minutes,
It was baked at ℃ for 3 hours. Take 2c.c. of this, install it in the same equipment as shown in Example 1, and heat it at 450℃.
As a result of carrying out the reaction using 1-butene as a raw material in the same manner as in Example 1, the 1-butene reaction rate was 45.9 mol%, but the 1,3-butadiene selectivity was
1.4 mol%, and 98.2 mol% was carbon monoxide and carbon dioxide. In addition, 0.4 mol% of bentenes was produced.

Comparative Example 2 38.3 g of commercially available diatomaceous earth (particle size 12 to 16 mesh) having a specific surface area of 5.0 m ² /g was taken and converted into a nitric acidic bismuth nitrate aqueous solution (Bi(NO ₃ ) ₃ ) in the same manner as in Example 1. 55.4% by weight) was impregnated, dried at 130°C for 30 minutes, and then calcined at 600°C for 3 hours to obtain an oxygen carrier with a Bi ₂ O ₃ loading rate of 41.1% by weight.

Take 2c.c. of this, install it in the same equipment as shown in Example 1, and use 1-butene as a raw material at 450°C.
As a result of conducting a reaction test in the same manner as in Example 1,
The 1-butene reaction rate was 5.0 mol%, the 1,3-butadiene selectivity was 95.6 mol%, and carbon monoxide and carbon dioxide were produced at 4.4 mol%. Although the selectivity to 1,3-butadiene was high, the reaction rate was low and the butadiene yield was low.

Claims (1)

[Claims] 1. Oxidation of bismuth by contacting hydrocarbon gas with an oxygen carrier in which bismuth oxide is supported on a porous carrier with a specific surface area of 40 to 300 m ² /g in the absence of molecular oxygen-containing gas. A method for oxidative dehydrogenation of hydrocarbon gas, which comprises oxidative dehydrogenation of hydrocarbons using bound oxygen. 2. In the absence of a molecular oxygen-containing gas, hydrocarbon gas is brought into contact with an oxygen carrier made of a porous carrier with a specific surface area of 40 to 300 m ² /g supporting bismuth oxide to generate hydrocarbons due to the bound oxygen of the bismuth oxide. By carrying out an oxidative dehydrogenation reaction of the gas and oxidizing bismuth or a lower oxide of bismuth produced at the same time with molecular oxygen to regenerate an oxygen carrier and use it again for contacting hydrocarbon gas. The oxidative dehydrogenation method according to claim 1. 3. The method according to claim 1 or 2, wherein the hydrocarbon gas is butene.