JPS6270201A - Production of hydrogen gas - Google Patents

Abstract

PURPOSE:To effectively carry out reaction at a low temperature and efficiently produce hydrogen gas for a long period, by the coexistence of oxygen in a reaction gas on catalytically reacting methanol with steam in the presence of a catalyst. CONSTITUTION:A raw material gas containing methanol, steam and further coexisting oxygen is passed through a catalyst layer in the presence of a previously reduced catalyst, e.g. copper-zinc-aluminum oxide, and catalytically reacted to produce hydrogen gas. The reaction conditions are about 150-400 deg.C reaction temperature, about 1-5mol, based on 1mol methanol, water and about 0.3-5.0hr<-1> liquid hourly space velocity (LHSV) of liquid methanol. The reaction gas composition is about 70-99.5mol% water-methanol mixed gas, about 0.5-3vol% oxygen and the remainder of an inert gas, e.g. nitrogen or helium. Thereby, the hydrogen gas can be effectively produced at a low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for effectively producing hydrogen gas by causing a catalytic reaction between methanol and steam using a catalyst.

BACKGROUND OF THE INVENTION Hydrogen is used in many fields, and its uses are expanding not only to the chemical industry, such as ammonia synthesis, petroleum refining, and hydrodesulfurization, but also to the metallurgical industry and the semiconductor industry.

Recently, hydrogen has also been attracting attention as a new energy source such as fuel cells, and the demand for hydrogen is increasing.

One of the conventionally widely used methods for producing hydrogen gas is to steam reform hydrocarbons such as naphtha or liquefied natural gas (LNG), and convert the resulting hydrogen, carbon oxide, and carbon dioxide into There is a method of producing hydrogen gas by removing -) tungsten carbon and carbon dioxide from a mixed gas containing hydrogen.

This method is 1) The reaction temperature is extremely high, around 900°C.

2) The price of hydrocarbons is unstable, and the supply thereof is also unstable.

For these reasons, it has been said that it is not suitable for medium-scale or small-scale hydrogen gas production.

On the other hand, the method of steam reforming methanol to produce hydrogen gas has a lower reaction temperature of around 300°C than steam reforming of hydrocarbons, and is easy to operate, resulting in stable methanol at a low price. If it is supplied as a hydrogen production method, it is thought that its importance as a hydrogen production method will increase.

Problems to be Solved by the Invention The conditions required for a catalyst for methanol steam reforming reaction are: 1) high activity at low temperatures;

2) Activity deterioration is small.

can be mentioned.

Since this reaction is an endothermic reaction, as the reaction progresses, the gas temperature and the temperature of the catalyst layer decrease, the reaction rate decreases, and there are problems in that even if the amount of catalyst m is increased, the desired conversion rate cannot be obtained. are doing.

Therefore, in order to solve this problem, it is first necessary to efficiently supply heat from the outside and at the same time to improve the low-temperature activation performance of the catalyst.

The next problem is activation deterioration. When the reaction is continued, the activity tends to gradually decrease. The cause of this is said to be that impurities in methanol, such as ethanol, accumulate on the catalyst during the reaction, and the present inventors have also confirmed this fact. Therefore, in order to suppress activity deterioration, it is considered necessary to suppress the accumulation of impurities or to clean the catalyst surface.

Structure of the Invention The present invention aims to provide a method for producing hydrogen from methanol and steam using a catalyst, in which the catalyst can be used effectively even at low temperatures.

That is, the present invention relates to a method for efficiently producing hydrogen gas over a long period of time by allowing oxygen to coexist in the reaction gases of methanol and water vapor, thereby allowing the reaction to occur effectively even at low temperatures.

When a raw material gas containing oxygen is passed through the catalyst layer in the presence of a previously reduced catalyst, the temperature of the catalyst layer increases compared to the case where oxygen is not present, and the methanol conversion activity is significantly improved. This phenomenon is thought to be due to several factors, including 1) partial reoxidation of the reduced catalyst, 2) complete oxidation of some methanol, and 3) complete oxidation of some impurities accumulated on the catalyst surface, but in any case, Even when the reaction gas temperature is low, by following this method, the conversion rate of methanol can be substantially increased and hydrogen can be effectively produced.

On the other hand, regarding the problem of activity deterioration, when oxygen coexists, the activity deterioration tends to be smaller than when oxygen does not coexist, and it is inferred that some cleaning of impurities accumulated on the catalyst surface occurs. be done.

In general, in the case of catalysts used in a reducing atmosphere, such as catalysts for -m carbon shift reactions, repeated oxidation and reduction of the catalyst causes the catalyst to become brittle and powder, which is a major cause of catalyst deterioration or reactor blockage. It is said to be one of the However, in the case of this reaction, such pulverization of the catalyst was not observed even if oxygen was allowed to coexist in the reaction gas, and as shown in the example below, the reaction did not proceed even after 300 hours of continuous reaction. No change in the crushing strength of the catalyst before and after was observed. That is, the present invention was completed by discovering that hydrogen gas can be produced with high activity over a long period of time by allowing oxygen to coexist in the steam reforming reaction of methanol.

The amount of oxygen coexisting in the reaction gas is 0.5% in the reaction gas.
~3% by volume, preferably 1-2% by volume.

Suitable catalysts to be used include copper-zinc-aluminum oxide catalysts and copper-zinc-aluminum-chromium oxide catalysts, which are already known as catalysts for steam reforming reactions of methanol.

As a method for preparing the catalyst, any conventional method such as a coprecipitation method, an impregnation method, a powder mixing method, etc. can be employed.

The reaction conditions for the hydrogen gas production method according to the present invention include a reaction temperature of 150 to 400°C, a ratio of water to methanol of 1 to 5 mol of water to 1 mol of methanol, and a space velocity (LH8V) of liquid methanol of 0.3-5.0
There is a h r-1F.

Although the reaction gas composition is not specified, the water-methanol mixed gas is 70 to 99.5% by volume, preferably 85 to 99.5% by volume, and oxygen is 0.5 to 3% by volume, preferably 1 to 2% by volume.
, and the remainder is made from a mixed gas consisting of inert gases such as nitrogen and helium.

In the method of the present invention, the oxygen concentration in the reaction gas composition can be freely changed within the above range during the reaction. That is, good results can be obtained even if the reaction is carried out by increasing the oxygen concentration intermittently to 2 to 3 volume % and maintaining it in the range of 0.5 to 1.5 volume % during steady state.

Example 1 A mixed aqueous solution of copper nitrate, zinc nitrate, and aluminum nitrate was
The mixture was heated to 0°C and added dropwise to an aqueous sodium carbonate solution (70°C) with stirring to neutralize and coprecipitate the hydroxides of copper, zinc, and aluminum. After thoroughly washing and removing the sodium in the obtained slurry and dehydrating it with a filter press,
A catalyst composition was obtained by drying and firing. The catalyst composition includes copper,
It consists of oxides of zinc and aluminum, and its composition is ff.
1ffi ratio "i" cuo: zno:Aノ203=
The ratio was 5:3:2.

This catalyst composition was pulverized and molded into a 3#Iφ to form a catalyst, and then subjected to a steam reforming reaction of methanol. The reaction conditions are as follows.

Gas inlet temperature 250℃ Reaction gas composition: Water/methanol 90% nitrogen by volume
8% by volume Oxygen 2% by volume LH8V (methanol equivalent) 1.0hr-1 water/
Methanol 1.5 (mol 1 mol) where L
l-1sV is the liquid methanol flow rate (cc/hr) divided by the catalyst volume fil (CC).

In addition, the catalyst was prepared using a hydrogen-nitrogen mixed gas before the reaction.
Pre-reduction was carried out at 0°C. Samples were taken one hour after the start of the reaction, and the activity value was determined to be 96%.

Example 2 A reaction was carried out under the same conditions as in Example 1 except that nitrogen and oxygen in the reaction gas were 9% by volume and 1% by volume, respectively, and the conversion rate of methanol was 93%.

In Comparative Example Example 1, when W accumulation is not allowed to coexist, that is, when nitrogen is 10% by volume, the methanol conversion rate is 8.
It was 6%.

Example 3 A continuous reaction was carried out for 300 hours under the same conditions as in Example 1, and the tendency of activity deterioration was investigated. The results are shown below. For comparison, the same continuous reaction was carried out without oxygen, and the results are also shown in the table below.

Claims (1)

[Claims] (1) A method for producing hydrogen gas, which comprises allowing oxygen to coexist in the reaction gas when producing hydrogen through a catalytic reaction between methanol and steam in the presence of a catalyst.