JPS5831976B2 - Catalyst for methane production and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-resistant catalyst for methane synthesis that can efficiently produce methane and advantageously utilize the large heat of reaction, and a method for producing the same.

The methane synthesis reaction is a reaction that involves the generation of a large amount of reaction heat, and it is very important from the economical point of view of the methane synthesis process to effectively utilize the reaction heat as an energy source.

In order to effectively recover and utilize this reaction heat, it is preferable to carry out the reaction at as high a temperature as possible, but conventional nickel-based catalysts, which exhibit high activity and high selectivity for methane synthesis reactions, are not particularly effective at high temperatures. There were drawbacks such as severe deterioration of activity.

Therefore, in the methane synthesis reactions using nickel-based catalysts that have been proposed so far, it has been necessary to constantly remove the reaction heat and pay special attention to temperature control of the catalyst bed in order to avoid high-temperature reactions.

The present inventors have overcome the shortcomings of these conventional methods and developed a highly heat-resistant catalyst that can effectively utilize the reaction heat as an energy source to efficiently synthesize methane at high temperatures. As a result of intensive research, it was discovered that a nickel-molybdenum alloy-molybdenum carbide catalyst has excellent heat resistance.

Such a methane synthesis catalyst with good heat resistance must maintain sufficient activity to initiate the methane synthesis reaction at low humidity even after a long period of high-temperature reaction.

The importance of developing activity even at low temperatures can be understood by considering that the reaction must start when synthesis gas is introduced into the catalyst bed in an adiabatic reaction tube.

Once the reaction starts, the catalyst bed temperature increases due to the reaction heat, so that the reaction gas easily reaches an equilibrium composition.

The temperature of the produced gas at this time is determined by the amounts of reacted hydrogen and carbon monoxide, but in an adiabatic reaction tube, this temperature is equal to the catalyst temperature at the outlet of the catalyst bed.

This means that the reaction gas temperature cannot exceed the maximum usable temperature of the catalyst.

Therefore, the amount of meta7, convertible hydrogen, and carbon oxide is determined by the temperature range between the catalyst's activation temperature and the maximum usable temperature, and therefore, the concentration thereof in the raw material gas is determined.

The catalyst of the present invention consists of a nickel-molybdenum alloy and molybdenum carbide supported on a porous carrier.

In this case, any common porous carrier can be used.

Examples include alumina, silica, silica-alumina, boria, titania, alumina-boria, zirconia, lanthanum oxide, and compounds or mixtures thereof.

The nickel content in the catalyst is 1 to 50% by weight as NiO, preferably 3 to 30% by weight, and the molybdenum content is 1 to 40% by weight as MoO3, preferably 5 to 30% by weight.
It is heavy.

The nickel component and molybdenum component in the catalyst of the present invention act in the state of forming an alloy, but they must be well mixed with the molybdenum carbide particles, or they must be in a well (C-supported state) on the molybdenum carbide particles. There is.

For this purpose, nickel and molybdenum must exist as a compound or be well mixed in the oxide state, and when reduced with hydrogen, they form a nickel-molybdenum alloy or a nickel-molybdenum intermetallic compound. Preferably, they are in a mixed state.

By treating these well-mixed conditions under high pressure using a mixed gas containing hydrogen and carbon oxide, a catalyst with good heat resistance in which nickel-molybdenum alloy particles are well dispersed between molybdenum carbide particles is produced. become.

There is no particular difficulty in producing the catalyst of the present invention. First, a catalyst in which a compound of nickel oxide and molybdenum oxide or a good mixture thereof is supported on a carrier is prepared, and then this catalyst is After treatment with hydrogen gas at a temperature of 900°C, treatment with a reducing gas containing -carbon oxide and hydrogen at a humidity of 500-800°C or without hydrogen treatment at a temperature of 500-800°C with hydrogen and - It may be treated with a gas containing carbon oxide.

In reality, a methane production equipment is filled with a catalyst supported with a compound of nickel oxide and molybdenum oxide or a good mixture thereof, and hydrogen gas is heated to 400 to 900°C.
The raw material gas for methane production may be passed through the reactor under reaction conditions, or the raw material gas for methane production may be passed directly under reaction conditions after filling the catalyst without being subjected to hydrogen treatment.

The reaction for synthesizing methane using the catalyst of the present invention is carried out at a reaction humidity of 300 to 700°C, a reaction pressure of 50 to 100°C, and a reaction pressure of 9/cr.
11, and a distribution method is adopted as the reaction method.

The composition of the reaction raw material gas is usually 10 to 75 vol of hydrogen.
The amount of carbon oxide is 3 to 25 v□l, and lower hydrocarbons such as methane and ethane may be mixed in this raw material gas.

Next, the present invention will be explained in more detail based on examples.

Example The composition of nickel nitrate, ammonium paramolybdate, and various carriers was determined by a kneading method.

:MoO3:Support=20:25:55 (weight φ) Catalyst 2yd was packed into a reaction tube and heated at 700°C.
After treatment for 15 hours in a hydrogen atmosphere at normal pressure, hydrogen 45
While flowing a raw material gas consisting of steamed rice, 15% carbon oxide, and 40% methane to 80% under high pressure of 9/Cm, 6%
Carbonization treatment was carried out at 500 ℃ overnight.

It was confirmed by X-ray analysis that in this state, the nickel and molybdenum components in the catalyst had changed to a nickel-molybdenum alloy and molybdenum carbide.

Using this series catalyst, 650℃, 80 to 9/Cn1, S■
Table 1 shows the methane synthesis activity expressed as the concentration of methane in the produced gas at 400° C. after the reaction was carried out for 10 days under the condition of 15,000 hr'.

For side comparison, a commercially available nickel catalyst for methane synthesis, which exhibits high activity in methane synthesis reactions at low temperatures, was filled in the same reaction tube as in the example, and after hydrogen treatment at 400°,
Cm2, S■ = 15000hr4 and hydrogen 45tl), -
The reaction was carried out using a raw material gas containing 15 parts of carbon oxide and 40 parts of methane.

As a result, the methane concentration in the produced gas at 400'C immediately after the hydrogen treatment was 97φ, but after being used for the reaction overnight at 650°, this value drastically decreased to 42%.

The methane concentration in the raw material gas is 40%, so 6500
By allowing the reaction to take place for one day, the catalyst was effectively disqualified.

As is clear from the results shown in the Examples and Comparative Examples, the nickel-molybdenum alloy-molybdenum carbide catalyst prepared as described above maintains high methane synthesis activity at low temperatures even after being used for a long period at high temperatures of 6500 °C. It can be seen that it is excellent as a heat-resistant catalyst.

Claims (1)

[Scope of Claims] 1. A heat-resistant methane production catalyst for producing methane from a mixed gas containing carbon monoxide and hydrogen, which is made of an N-type molybdenum alloy and molybdenum carbide supported on a porous carrier. 2 A compound or a good mixture of nickel oxide and molybdenum oxide supported on a porous carrier is heated at a temperature of 400 to 90°C.
After treatment with hydrogen at 0 °C, treatment with a gas containing hydrogen and -carbon oxides at a temperature of 500-800 °C, or without hydrogen treatment, vortex 1i containing hydrogen and -carbon oxides at a temperature of 500-800 °C. A method for producing a heat-resistant methane production catalyst for producing methane from a mixed gas containing carbon monoxide and hydrogen, characterized by processing with a gas.