JPH0491038A - Production of hydrocarbon - Google Patents

Abstract

PURPOSE:To selectively produce >=2C hydrocarbon by subjecting methane to heat-oxidative coupling using CO2 or steam as an oxidizing agent in the presence of a solid corbon under pressurization. CONSTITUTION:Methane is subjected to oxidative coupling to produce ethane, ethylene, propylene, etc., at 800-900 deg.C and 5-15kg/cm<2> using a solid carbon as a catalyst and using CO2 or steam as an oxidizing agent. The solid carbon includes coal, charcoal produced when coal is distilled, carbon black or active carbon, especially preferably having 500-4000m<2>/g specific surface area. An alkali (earth) metal or compound thereof may be added to the solid carbon. >=2C hydrocarbon can selectively be produced without using an expensive rare earth element as the catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing hydrocarbons useful for producing hydrocarbons having two or more carbon atoms, such as ethane, ethylene, and propylene, from methane.

[Prior art and problems to be solved by the invention] Natural gas contains abundant methane, which is attracting attention as a so-called CI chemical raw material. Synthesizing C2, Cs hydrocarbons such as ethane, ethylene, and propylene using this methane is very important in the development of chemical conversion technology for natural gas.

As a method for producing C2 and C3 hydrocarbons from methane,
A method has been proposed in which methane is subjected to an oxidative coupling reaction in the presence of oxygen and various catalysts. For example, JP-A-61-165340 discloses a catalyst containing a rare earth metal catalyst; JP-A-62-238220 discloses a catalyst containing an alkali metal and a first transition series element; JP-A-205038 proposes a catalyst in which an alkali metal halide is supported on a basic oxide.

When producing ethane, ethylene, etc. by oxidative coupling reaction using these catalysts, methane C2
, the selectivity to C3 hydrocarbons is low.

In particular, in an oxidative coupling reaction in which oxygen coexists, oxygen is converted to water and a large amount of carbon dioxide is produced as a by-product. Furthermore, many of these catalysts contain expensive rare earth elements, and furthermore, their catalytic activity decreases and crystallizes within a short period of time, resulting in high conversion costs.

JP-A-63-222126 proposes a method of oxidative coupling of methane using oxygen without using a catalyst. In this method, methane is heated together with molecular oxygen under pressure, resulting in a combustion reaction and producing large amounts of carbon monoxide and carbon dioxide.

On the other hand, gasification of coal easily proceeds by reaction at 1000° C. or higher using water vapor or a mixed gas of carbon dioxide and oxygen, and is at the stage of practical application. However, the gases obtained are only hydrogen and carbon monoxide, and their value is not necessarily high.

Therefore, an object of the present invention is to provide a method for producing hydrocarbons that can produce hydrocarbons having two or more carbon atoms from methane with high selectivity without using an expensive catalyst.

[Structure of the Invention] In the process of analyzing the coal gasification reaction process, the present inventors discovered that (1) the gasification reaction progresses through intermediates called "surface oxides" that are generated on the carbon surface; (2) A "redox cycle" consisting of repeated oxidation and reduction reactions occurs between the "surface oxides" and carbon, and the amount of produced "surface oxides" increases the gasification reaction of coal. (3) The oxidative coupling reaction of methane proceeds with activated oxygen, but “surface oxides”
The present invention was completed based on the discovery that activated oxygen functions in the same way as activated oxygen in the oxidative coupling reaction of methane. That is, the present invention is a method for producing hydrocarbons having two or more carbon atoms by oxidative coupling by heating methane together with an oxidizing agent under pressure. Provided is a method for producing hydrocarbons by oxidative coupling of methane in the presence of methane.

In the present invention, solid carbon is used as a catalyst. Examples of solid carbon include coal, char produced when coal is carbonized, carbon black, and activated carbon. Among these solid carbons, solid carbon with a large specific surface area, for example, a specific surface area of 500 to 4000 m'/g
Solid carbon is preferred. Further, solid carbon may be impregnated with alkali metals such as potassium and sodium, alkaline earth metals such as calcium and magnesium, or compounds thereof.

In the present invention, carbon dioxide or water vapor, which functions as an oxidizing agent, is used instead of oxygen in order to suppress the generation of carbon oxide. Carbon dioxide and water vapor may be used in combination. Carbon dioxide and water vapor generate carbon-oxygen active species at the solid carbon surface. More specifically, the mechanism of the conventional oxidative coupling reaction of methane using molecular oxygen as an oxidizing agent is as follows. Note that the symbol * indicates activation.

CH4C” 4*(a) 02-20* (b) CH
4+ 20 CH3・+H
O2・ (e) CH3・ + CH3・ →C2H
6(d) CH3.+02→CH302→C01CO2(e) In this oxidative coupling reaction, the reaction proceeds with activated oxygen. The function of the catalyst is to convert this activated oxygen [M+O-] (M indicates a metal catalyst, and 0 is actually a molecular adsorbed oxygen species adsorbed on the metal).
It is explained that the purpose is to generate. In this oxidative coupling reaction, a large amount of carbon monoxide and carbon dioxide are produced as by-products due to the oxidation reaction and combustion reaction of methane by molecular oxygen.

On the other hand, the mechanism of the methane oxidative coupling reaction of the present invention is presumed to be as follows when carbon dioxide is used as the oxidizing agent. In addition, C indicates solid carbon,
C(0) represents a surface oxide on the solid carbon surface.

(+C02→C(0) +CO(A) 2CH4+C(0)-”C2H6+H20+C(B)C
2H6+C(0)→C2H4+H20+C(C)C(C
O) -CO(1)) In the second reaction, the solid carbon functions as a catalyst, and active surface oxygen groups are formed and retained on the surface of the solid carbon by the oxidizing agent carbon dioxide or water vapor. Therefore, methane is actually all converted into hydrocarbons having two or more carbon atoms by the surface precursors on the solid carbon surface, and the selectivity is high.

At the same time, solid carbon is oxidized by surface oxygen,
Provides common gasification products such as carbon monoxide. That is, -carbon oxide is produced by a reaction between solid carbon and an oxidizing agent, similar to the gasification of coal. In this respect, it differs from conventional methods in which carbon monoxide is co-produced through the oxidation reaction of methane.

As is clear from the reaction mechanism described above, in the present invention, ethane, ethylene, etc. can be efficiently produced by simply introducing methane into the gasification process of carbonaceous materials such as coal.

In the methane oxidative coupling reaction of the present invention, the ratio of methane to carbon dioxide or water vapor is about 031 to 5 moles, preferably about 0.25 to 2 moles, per 1 mole of methane. . Note that there is a proportional relationship between the amount of solid carbon and the amount of hydrocarbons having two or more carbon atoms produced.

Furthermore, the conversion rate and selectivity can be controlled by adjusting factors such as solid carbon and reaction temperature.

The lower limit of the reaction temperature is selected in consideration of the conversion rate and selectivity of methane, and the upper limit thereof can be selected in consideration of energy costs and the like. The reaction temperature is, for example, 650 to 1000
℃, preferably about 800 to 900℃. If the reaction temperature is lower than 650°C, methane conversion will hardly proceed;
When the temperature exceeds 00°C, the selectivity does not improve much.

The lower limit of the reaction pressure can be determined by considering the conversion rate and selectivity of methane, and the upper limit can be determined from the viewpoint of the equipment. The reaction pressure is, for example, about 2.5 to 20 kg/c, preferably about 5 to 15 dazzle/c. Pressure is 2.
5) If it is less than cg/c-, the pressurizing effect is small, and 20kg/c-
If it exceeds c-, the yield will not improve much and the high pressure will require a pressure-resistant structure, which is not economical.

[Effects of the Invention] In the method for producing hydrocarbons of the present invention, hydrocarbons having 2 or more carbon atoms can be produced with high selectivity without using expensive rare earth elements as catalysts.

[Examples] The present invention will be described in more detail below based on Examples.

Example 1 An oxidative coupling reaction was carried out using a pressurized flow device. In addition, in order to prevent reactions on the metal surface, the reactor is
It was constructed by inserting a quartz tube into the protective cylinder of the previous type Incoloy H.

Using a fluidized bed pyrolyzer, Yaour
n) Charcoal, Baldurl Charcoal and Taiping 4
Coal chars of different charcoal types were produced by carbonizing each charcoal at a temperature of 900° C. in a nitrogen stream. The obtained char was filled into a quartz tube, and the reaction temperature was 850°C, carbon dioxide - 1:1 (mole ratio), and the gas flow rate was 1.0.
The oxidative coupling reaction was carried out under the conditions of ml/sec and a pressure of 6 k'i/oj. For reference, methane and carbon dioxide were supplied in the same manner as above without filling with char.

The composition of the reaction product was analyzed by gas chromatography. Table 1 shows the results 1.00 seconds after the start of the reaction, along with the amount of char filled.

From Table 1, it is recognized that there is a proportional relationship between the amount of char packed and the amount of C2 compound produced, and the selectivity is high. Furthermore, as a type of char, Yaloon char has high catalytic activity.

Comparative Example 1 When a reaction was carried out in the same manner as in Example 1 except that quartz was filled instead of char, it was confirmed that no C2 compound was generated and the reaction did not proceed.

Comparative Example 2 Using the same equipment as in Example 1, activated carbon (Takeda Pharmaceutical Co., Ltd.
Manufactured by Shirasagi C1 Specific surface area 1200 m'/g, 20
~40 meshes) was charged, and the reaction temperature was 850°C.
, and the pressure was 6 kg/c-, and the reaction was carried out by flowing only methane at a gas flow rate of 1.0 ml/sec. As a result, the production of ethane and ethylene was observed at the beginning of the reaction, probably due to oxygen adsorbed on the activated carbon, but the production decreased over time, and ultimately no C2 compound was detected.

Example 2 Using the activated carbon used in Comparative Example 2, the reaction temperature was 850.90.
The oxidative coupling reaction was carried out under the conditions of 0°C, methane:carbon dioxide-3=1 (molar ratio), mixed gas flow rate of 20 ml/sec, and pressure of 12 kg/C-.

The results are shown in Table 2 along with the amount of activated carbon etc. charged.

Example 3 The same procedure as Example 2 was carried out, except that instead of the activated carbon used in Example 2, solid carbon in which potassium carbonate was supported on the activated carbon by an impregnation method [supported amount: 10 mol/carbon (-) in terms of potassium] was used. An oxidative coupling reaction was carried out in the same manner.

The results are shown in Table 2.

(Hereinafter, blank spaces) From Table 2, similar to Table 1, the selectivity of ethane and ethylene is large.

Example 4 Solid carbon in which Na was supported on the activated carbon used in Comparative Example 2 [
Supported amount: 10 mol/carbon (kg)] in a reaction tube of 100 m
At the reaction temperature shown in Table 3, a mixed gas of methane:nitrogen, water vapor-5 ml/sec: 10 ml/sec, 3.5 ml/sec was flowed to carry out an oxidative coupling reaction. A vaporizer was placed on the upstream side of the reaction tube to supply water vapor to the packed bed of solid carbon, and a pressure-resistant steam trap was placed on the downstream side to condense the water vapor under pressure. The results are shown in Table 3.

Table 3 From Table 3, similar to Table 1 above, the selectivity of ethane and ethylene is large.

Claims (1)

[Claims] A method for producing hydrocarbons with a carbon number of 2 or more by heating methane together with an oxidizing agent under pressure and oxidative coupling, in which methane is oxidized in the presence of solid carbon using carbon dioxide or water vapor as the oxidizing agent. A method for producing hydrocarbons to be coupled.