JPS6021680B2 - Method for producing methane-rich gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a gas substantially enriched in methane by diluting a gas mixture of hydrogen and carbon oxides with steam and contacting a catalyst.

More specifically, the present invention dilutes a raw material gas consisting of oxides of hydrogen and carbon with water vapor, and dilutes it with water vapor, and dilutes it with water vapor, and dilutes it with water vapor. This relates to a method for producing a methane-rich gas by bringing the substance into contact with a methanation catalyst consisting of the following: to carry out a methanation reaction.

With the recent increase in energy demand, there is a large demand for LNG (liquefied natural gas), which is a clean energy source. However, since there is a limit to the stable supply of LNG, processes have been developed to produce SNG (alternative natural gas) from petroleum-based hydrocarbons and coal. When attempting to obtain SNG by gasifying vehicle oil, coal, etc., heavy oil and coal are partially oxidized with oxygen, water, etc. to obtain a gas whose main components are hydrogen and carbon oxides. The gas obtained here is usually a low-calorie gas, and in order to convert it into a high-calorie fuel gas, it must be converted into a gas containing methane as its main component through a methanation reaction. However, there is currently no satisfactory method for converting a low-calorie gas containing hydrogen and carbon oxides as main components into a high-calorie gas containing methane as a main component. The main reason for this is that it is difficult to control the high reaction heat generated in the methanation reaction. The methanation reaction in the methanation method proceeds according to the following reaction formula.
$L+C〇→CH4 10th 2〇 △H=-49-Mother KCa
l Rainbow L + C02 → C ratio + 2 days 20 △H = -39.4K
cal These reactions are very exothermic as shown in △ day, so in order to produce a large amount of methane in an equilibrium manner, the reaction heat must be removed from the reaction system.

For example, if we perform an asthenic equilibrium calculation, C030%,
It can be seen that if a gas containing about 0.70% is reacted adiabatically at 300°C, the reaction will reach an equilibrium state at about 1000°C or higher. However, there are no catalysts that can withstand such high temperatures, and special heat-resistant materials must be used in the reactor. Therefore, in the methanation reaction, it is essential to control the reaction temperature low. Conventionally, various methods have been explored when performing a methanation reaction.

The first method is to circulate part of the methane-rich gas after the methanation reaction and dilute the raw material gas entering the methanation reactor with methane, thereby suppressing heat generation in an equilibrium manner. This process typically requires recycling more than 90% of the product gas to control the reaction temperature, increasing power costs for recycling and the size of the methanation reactor. Furthermore, since methane is circulated, unless the reaction temperature is maintained at 50,000 or less, carbon tends to precipitate, resulting in rapid deterioration of the catalyst.
The next method is to carry out the methanation reaction using the same reactor as the heat exchanger, take the reaction heat out of the system, control the reaction temperature low, and increase the conversion rate of methane. One method for this is to coat the inner wall of the reaction tube with Raney nickel to serve as a catalyst to carry out the methanation reaction. This method has disadvantages in that the reaction provides a high methane yield, the reactor is expensive, and the operation is complicated. Another method is to use a catalyst with a small particle size to form a fluidized bed, and install piping for heat exchange in the fluidized bed.
This method efficiently removes reaction heat by bringing catalyst particles into contact with gas. The disadvantage of this method is that gas bubble formation in the fluidized bed causes poor contact between the catalyst particles and the gas, resulting in poor methane yield. The object of the present invention is to eliminate the drawbacks of the prior art described above, to oxidize hydrogen and carbon by using a new catalyst that allows easy control of reaction temperature and suppresses carbon deposition and sintering. To provide a method for producing a high-calorie gas containing methane as a main component by methanizing a low-calorie gas containing methane as a main component.

The main points of the present invention are: 1) A novel catalyst with excellent methanation ability and long life is used in methanating a raw material gas consisting of hydrogen and carbon oxides.

■As a way to control the extremely large heat generated in the methanation reaction, the raw material gas is diluted with steam. There are two points.
The methanation reaction according to the method of the present invention is carried out at low temperature and high pressure.

More specifically, in order to obtain a highly methanated gas, the ratio of hydrogen to carbon oxide in the raw material gas needs only to be 4 or less in molar ratio. If it is 4 or more, hydrogen will remain and the methane content will decrease accordingly.
Ru.

Furthermore, the ratio of steam dilution to the raw material gas is such that C in the steam/raw material gas is in the range of 3 to 20 (molar ratio), preferably 5 to 20, and is supplied to the methanation reactor filled with the catalyst of the present invention. Then, the reaction is carried out at a reaction pressure of 1 to 10 tm and a reaction temperature of 250 to 500°C to convert it into methane. A low temperature outside this temperature range is unfavorable in terms of activity, and a high temperature causes sintering of the catalyst and reduces the methane yield, so the reaction temperature is preferably within the above range. The most significant feature of the present invention is the methanation catalyst.

Below, the most representative MO among the methanation catalysts of the present invention
-La2Q-AI203 catalyst (form before hydrogen reduction)
I will give a detailed explanation. Ni○-Y203-AI
The 203 catalyst (in its pre-hydrogen reduced form) is obtained by precipitating its precursor from a solution of the respective salts of Ni, Al, and Ni. The function of La in this catalyst is L
a23 intervenes between Ni○ and AI2Q, and not only suppresses the formation of nickel-aluminate precursors, but also
The effect of suppressing carbon precipitation during the methanation reaction and the effect of preventing sintering are also considered, and the catalyst life is shorter than that of conventional Ni0-N203.
Compared to the catalyst, it has been extended to a large extent. Among the methods for producing this catalyst, the most preferred method will be explained.

An aluminum salt, preferably aluminum nitrate, is dissolved in deionized or distilled water. While pouring this aluminum salt solution, an alkaline substance such as sodium hydroxide, potassium hydrcarbonate, sodium carbonate, sodium carbonate aqueous ammonia is added dropwise to substantially completely precipitate the aluminum. The final pH at this time is preferably in the range of 5.0 to 7.0. A solution of a lanthanum salt, preferably lanthanum nitrate, is then added to the solution containing the aluminum precipitate, and a solution of an alkaline substance is then added dropwise while stirring again to substantially completely precipitate the lanthanum. The final pH at this time may be in the range of 6.0 to 8.0. A nickel salt, preferably nickel nitrate, and an alkaline substance are added simultaneously to the solution containing the aluminum and lanthanum precipitates. The final pH at this time is 6.0-8
．． It may be within the range of 0. The temperature of the solution in the above precipitation step is in the range of room temperature to 10,000℃, preferably 70Q
10 qo is good. The resulting nickel, lanthanum, and aluminum precipitates are thoroughly washed with water. When an alkaline substance is used, it is preferable to reduce the content of these components to 0.5 M% or less by washing with water. After washing with water, it was filtered in an oven to obtain a cake-like precipitate. This precipitate can be formed into a catalyst by a conventional catalyst manufacturing method. For example, the precipitate is dried at a temperature of 100 to 40,000, crushed, graphite is added, and the tablet is formed into a tablet.
Calcinate at ~450°C to obtain a complete catalyst. The catalyst of the present invention obtained as described above contains nickel, lanthanum, and aluminum in the form of oxides, and the content ratios are 10 to 95% by weight of nickel oxide and 2% of lanthanum oxide. ~50%, aluminum oxide 3-88%
The catalyst performance is insufficient outside this composition range.

Note that this catalyst needs to be subjected to a reduction treatment to convert nickel oxide into metal nickel before the methanation reaction, and a hydrogen-containing gas is used as the reducing gas, and this reduction treatment is carried out in 1
~10 beats tm, 50,000 for several hours and then for several days. The effects of the present invention are that the temperature rise is suppressed by steam dilution, which prevents sintering of the catalyst, and since there is no carbon precipitation, the life of the catalyst is extended, the methane reactor can be made smaller, and the reactor material is specially designed. It has great industrial effects, such as being economical and not requiring the use of other materials.

According to the method of the present invention, in addition to gases obtained by partial oxidation of coal gas and heavy oils, gases obtained by low-temperature or high-temperature steam decomposition can also be used as the raw material gas.

Hereinafter, the content of the present invention will be explained in more detail with reference to Examples.

Example 1 Dissolve aluminum nitrate 736 in 1 cup of distilled water (liquid A)
Dissolve 133 parts of lanthanum nitrate in 0.3 parts of distilled water (solution B), dissolve 13 parts of nickel nitrate in 1 part of distilled water (solution C)
did.

Add potassium carbonate solution dropwise to solution A and adjust the pH.
was increased to 6.0 to precipitate aluminum. Solution B was added to the solution containing the aluminum precipitate, and a solution of calcium carbonate was added dropwise to raise the pH to 7.5. Solution C and a solution of potassium carbonate were simultaneously added dropwise to the solution containing the lanthanum and aluminum precipitates while adjusting the pH to 7.5, and the pH was finally set to 7.5. The above precipitation operation was carried out at a temperature of 70±10°C.

(The same applies to the following examples). The resulting nickel, lanthanum, and aluminum precipitates were thoroughly washed with distilled water and filtered. This cake-like precipitate is 110 to 130
It was dried at q0 for an hour. The dried precipitate was pulverized to 32 mesh or less, and then molded into a cylinder with a diameter of 6 ribs and a length of 6 ribs using a tablet machine. The molded article was fired at 450 qo for 2 hours to obtain a finished catalyst. This catalyst contains 70% Ni○ and 20%
Contains 10% of 3 and 20% of AI203 (both by weight). The methanation performance of this catalyst was tested by the following method.

The experimental equipment is a flow-type high-pressure reactor, in which the raw material gas is led from a high-pressure cylinder and the water is led to a subheater by a high-pressure pump. After heating, the raw material gas and water are introduced into a reaction tube with an inner diameter of 4.4 ribs and a length of 65 bowers. 0.5-1 in the center of the reaction tube
．． Charge the crushed catalyst for 3 hours. In order to conduct the reaction as adiabatically as possible, the reaction tube was wrapped with alumina cloth to a thickness of about 80 mm. The reaction tube is further kept warm in an electric furnace. The generated gas leaving the reaction tube is cooled, passes through a water trap and a pressure regulator, and its composition is analyzed using a gas chromatograph. Since the methanation reaction is an exothermic reaction, if the reaction is carried out intermittently, a temperature distribution will occur within the catalyst layer. By measuring the temperature distribution, the reaction zone (the distance from the inlet of the catalyst layer to the highest temperature part, that is, the reaction end point) can be determined. A catalyst with good performance has a short reaction zone, and as the catalyst deteriorates, the reaction zone moves toward the outlet side, but a catalyst with good performance has a small reaction zone movement speed. The catalyst reduction conditions and reaction conditions are as follows.

a Reduction conditions Reduction pressure 3 mountains tm reduction temperature
500qC hydrogen gas flow rate 3 dishes h/min reduction time
5 hours or more b Reaction conditions Reaction pressure
3 melon tm reaction temperature
300℃ raw material gas composition ratio 75 ratio hol%
CO and C02 25 hol% ratio 0/C of raw material gas
6. When the methanation reaction between one bait and temple was carried out under the conditions of the mountain hol ratio or higher, the average movement speed of the reaction zone was 0.
．． It was 32 legs/h.

Example 2 For comparison with the present invention, 736 g of aluminum nitrate, 133 g of lanthanum nitrate, and 1364 g of nickel nitrate were dissolved in 2 glasses of water.

A solution of potassium carbonate was added dropwise to this solution, the pH was raised to 7.5, and nickel, lanthanum, and aluminum were simultaneously precipitated. Below the water washing process, the example is divided by 1.
A completed catalyst was obtained in the same manner as above. When this catalyst was subjected to a methanation reaction for one hour under the same experimental conditions as in Example 1, the average moving speed of the reaction zone was 0.78 skin/h. Example 3 For comparison with the present invention, aluminum nitrate 736 and nickel nitrate 1364 were dissolved in water.

A solution of potassium carbonate was passed through the solution while stirring to raise the pH to 7.5, and a precipitate of nickel and aluminum was obtained. The precipitate was washed with water and passed through an oven, and then a solution of 133 parts of lanthanum nitrate dissolved in 0.3 parts of water was added and thoroughly kneaded in a kneader. A completed catalyst was obtained in the same manner as in Example 11 from the drying step onward. When this catalyst was subjected to a methanation reaction for one feeding time under the same experimental conditions as in Example 1, the average moving speed of the reaction zone was 0.98 skin/h. Example 4 In order to compare with the present invention, 736% of aluminum nitrate and 133% of lanthanum nitrate were dissolved in 1 cup of water, and a solution of potassium carbonate was added dropwise to this solution to raise the bait to 6.5%. and precipitated a lantern.

A solution of nickel nitrate 1364 dissolved in 1 cup of water was added to this solution containing aluminum and lanthanum, and a solution of potassium carbonate was added dropwise to raise the pH to 7.5. A finished catalyst was obtained in the same manner as in Example 11 from the water washing step onwards.
When this catalyst was subjected to a methanation reaction for 14 hours under the same experimental conditions as in Example 1, the average moving speed of the reaction zone was 1.3 Cape/h. Comparative Example 1 For comparison with the present invention, 1,650 ml of aluminum nitrate and 2,030 ml of nickel nitrate were dissolved in 3 ml of water.

A solution of potassium carbonate was added dropwise to this solution to adjust the pH to 7.
5 to precipitate nickel and aluminum simultaneously. A finished catalyst was obtained in the same manner as in Example 11 from the water washing step onwards. This catalyst contains Nio in a proportion of 7% and N203 in a proportion of 3%. When this catalyst was subjected to a methanation reaction for one feeding time under the same experimental conditions as in Example 1, the average movement speed of the reaction zone was 2.35 side/h. Example
5 The following five types of catalysts were prepared in the same manner as in Example 1.

a) 9wt% as Ni○, 5wt% as mountain 203
, a catalyst consisting of 5 wt% as AI203, b) Ni
8 skin t% as o, 5wt% as La2Q, AI20
Catalyst consisting of 1% as 3%, c) 70% as Ni○
Catalyst consisting of Wt%, 5~% as La203, 25M% as AI203, d) 6t% as Nio, L
1% as a203, 3mwt% as AI203
a catalyst consisting of e) 4 W% as Ni○, La203
A catalyst consisting of 1 Wt% as AI203 and 50 Wt% as AI203. When the above five types of catalysts were subjected to a methanation reaction for one feeding time under the same experimental conditions as in Example-1,
The average moving speed of the reaction zone is a) 0.48 fences/
h, b) 0.33 mosquitoes/h, c) 0.36 side/h, d) 0
．． 42 legs/h, e) 0.6 legs/h. Example 6 For comparison with the present invention, the following three were prepared in the same manner as in Example 1.
Seed catalysts were prepared.

a) 7 Naka Wt% as Ni○, 1 touch% as Ce02
, a catalyst consisting of 2% as N203, b) 7% as COO, 1OWt% as Ku203, AI203
c) 7 books as Coo
%, 1 touch% as Ce02, 2 cape t as AI203
Catalyst consisting of %. When the above three types of catalysts were subjected to a methanation reaction for one hour under the same experimental conditions as in Example 1, the average movement speed of the reaction zone was a) 0.63 ribs/h, b) respectively. 0.74 fence/h, c) 0.7
It was on the 8th side/h. Note that the product gas compositions in the above Examples and Comparative Examples were all the same in terms of raw material gas and reaction conditions, so the reaction proceeded to the equilibrium state of the methanation reaction, and there was no significant difference.

Claims (1)

[Scope of Claims] 1. By diluting a raw material gas consisting of hydrogen and carbon oxides with steam and bringing it into contact with a catalyst consisting of at least one of nickel and cobalt, one or more rare earth metals and alumina, and methanating it. A method for producing methane-rich gas, characterized by producing methane-rich gas. 2. The method according to claim 1, wherein at least one of the nickel and cobalt is used as an oxide.
A methane-rich gas characterized in that a catalyst consisting of 0 to 95% by weight, 2 to 50% by weight of at least one of the rare earth metals as an oxide, and the balance alumina is brought into contact with the raw material gas. manufacturing method. 3. The method according to claim 1 or 2, wherein the catalyst adds an alkali to a rare earth metal solution containing an aluminum precipitate to precipitate the rare earth metal,
Then, a solution containing at least one of nickel and cobalt and an alkali are added to the liquid containing the precipitate to precipitate the nickel and/or cobalt, and the resulting precipitate is molded and fired. A method for producing methane-rich gas, characterized in that: