JPS59199043A - Catalyst for reforming methanol - Google Patents

Abstract

PURPOSE:To obtain a catalyst having high selectivity, activity and durability by depositing Pt, Pd, etc. on a carrier consisting of alumina coated previously with alkali metal oxide. CONSTITUTION:Alumina is previously coated with an alkali metal oxide (e.g. K2O) and at least one metal selected from Pt and Pd is deposited on the obtd. carrier. Preferred concn. of the alkali metal oxide to be deposited on the carrier is 0.01-1.0g (as K2O or Na2O) per 1g alumina. Preferred amt. of Pt or Pd is 0.001-0.1g per 1g alumina. The obtd. catalyst has high selectivity and high activity for a reaction for decomposing methanol to a gas contg. CO and H2, and the durability is also excellent.

Description

[Detailed description of the invention] The present invention relates to a methanol reforming catalyst.

More specifically, the present invention aims to provide a highly active and long-life catalyst at low temperatures that selectively generates hydrogen and carbon monoxide in a method for reforming methanol into a gas containing hydrogen and carbon monoxide. Methanol can be produced on a large scale from coal, natural gas, etc. via synthetic gas, and is easy to transport, so it is of great interest as an energy source to replace petroleum in the future or as a raw material for various chemical industries. is leaning.

One method of using it is to decompose methanol into gas containing hydrogen and carbon monoxide, and use this as a pollution-free fuel for automobiles or as a raw material for producing reduced residue.

On the other hand, hydrogen can be separated from this cracked gas and used as a fuel for fuel cell power generation or as a hydrogen source for hydrogenation of various organic compounds in the oil refining industry.
Carbon oxide can also be used in the carbonylation process of various organic compounds.

Although the decomposition reaction of methanol can occur thermodynamically at relatively low temperatures, the presence of a catalyst is essential in order to carry it out economically.

Traditionally, alumina (
Catalysts have been proposed in which platinum metal elements such as platinum, or base metal elements such as copper, nickel, lithium, zinc, and their oxides are supported on a carrier such as lu2 o3. To date, these catalysts still have many problems, including poor low-temperature activity, lack of heat resistance, and short lifespan.

Among the conventional catalysts mentioned above, for example, 7-At2o.

For catalysts supported with platinum, the following desired reaction ■
as well as methane, carbon dioxide, and water.

There is also the problem that side reactions (2) in which ethers, aldehydes, etc. are produced occur.

Reaction■ CH30HCO+2H2 Reaction■ CH30H+ H2→CH4+ OH+C' from H20C
O→CH4+ C02 CH30H% C1(30CH3+ 3AH20CH3
OF(C+ H2+ H20 Among the above reactions, ■ is the main reaction of methanol decomposition, and at this time, the generated cracked gas has a calorific value equivalent to the endothermic amount of the cracked reaction (approximately 22 to 7/mot). This has the advantage of increasing heat efficiency, leading to improved thermal efficiency.

However, when a side reaction such as reaction (2) occurs, since all of these reactions are exothermic, the calorific value of the by-product decreases by the amount equivalent to the calorific value, which is rather a loss in terms of thermal efficiency.

Furthermore, when this cracked gas is used as a hydrogen source in various processes, water, ethers, etc. produced as by-products in reaction (1) become a factor that makes separation and purification difficult. Of the two reactions, the carbon formation reaction causes deterioration of the catalyst and blockage of the reactor, which impedes long-term stable operation.

Therefore, the present inventors conducted repeated research to solve the above problem fr: By interposing a third substance between the alumina and the active metal, that is, by making the alumina support an alkali metal oxide in advance. It has been found that by converting r -At203, which usually acts as an acidic catalyst, into a basic property and causing a dehydrogenation reaction, the side reaction ratio can be suppressed. That is, in the case of an acidic catalyst, the proton H+, which is the active site of the catalyst, is the OH− of methanol.
2 CH30H→
A dehydration reaction of CH30CHs + H2O occurs to produce ether.

On the other hand, in the case of a basic catalyst, such a dehydration reaction does not occur, but a dehydrogenation reaction of CH30H−+HCH○+H2 occurs, and the aldehyde produced in this reaction subsequently undergoes a reaction of HCHO→H2+ C0. Break it down into parts. Therefore, by allowing the dehydrogenation reaction to occur, it is possible to suppress the side reaction (2) above.

Based on this knowledge, the present inventors conducted various experimental studies, and found that alumina was coated in advance with an alkali metal oxide that has the ability to suppress side reactions, and noble metals such as platinum and palladium were coated on top of this. The present invention was completed based on the discovery that the supported catalyst has extremely excellent activity selectivity in the methanol decomposition reaction.

The method of the present invention is characterized in that a catalyst in which a noble metal such as platinum or palladium is supported on an alumina carrier coated with an alkali metal oxide in advance is used as a methanol decomposition catalyst.

Here, the alkali metal oxide is an oxide of an element in group Ia of the periodic table, for example, 20. Na2O.

Examples include. To coat these with alumina,
It can be easily obtained by immersing alumina in an aqueous alkali metal nitrate solution and then firing it.

The concentration of alkali metal oxide supported on alumina is 20 for alumina 12 or 0.01 for nano.
-0.12, preferably 0.03-0.057, and the amount of Pt, P(i) is 0.001-0.01S', preferably 0.003-0.01S' per 1 g of alumina. 0
．． 011F is preferred.

Next, the method of supporting the noble metal on the support obtained in this way can be any conventionally used method, such as noble metal nitrate or chloride.

A catalyst on which noble metals are supported can be obtained by immersing the carrier in an aqueous solution of a compound such as an ammine complex, calcining it, and then subjecting it to hydrogen reduction treatment.

The catalyst obtained as described above has high selectivity, high activity, and extremely excellent durability for the reaction of decomposing methanol into gases containing hydrogen and carbon monoxide. It has the following.

[Example 1] A pellet consisting of 4zOs with a particle size of 2 to 4 mm was immersed in an aqueous solution of potassium nitrate, dried, and
After firing at ℃ for 3 hours, 20 is 5% by weight based on alumina.
A supported carrier was obtained.

The support thus obtained was immersed in an aqueous solution of tetraammine diplatinum chloride [chemical formula P t (NH3) 4 C1z:], dried, and then calcined at 500°C for 3 hours to give a 0.
Catalyst 1 carrying 5% by weight of platinum was prepared.

This catalyst was reduced at 400° C. for 3 hours in a hydrogen stream, and an activity evaluation test was conducted under the conditions shown in Table 1, yielding the results shown in Table 2.

As a comparative catalyst, platinum was added to a conventional alumina carrier.
．． Table 2 also shows the results of preparing a catalyst supported at 5% by weight and conducting an activity evaluation test at a reaction temperature of 400°C.

Table 1 Table 2 [Example 2] Using the same method as Catalyst 1 prepared in Example 1, the concentrations of K2O were 0.2, 1.0, 3.0, and 5.
0.

Catalysts 2 to 6 were prepared in which platinum was supported in an amount of 0.3% by weight by supporting the platinum in an amount of 10% by weight, immersing it in an aqueous solution of chloroplatinic acid, and performing a hydrogen reduction treatment.

Regarding these catalysts, an activity evaluation test was conducted under the conditions shown in Table 1 except that the reaction temperature was 400° C., and the results shown in Table 3 were obtained.

Table 3 [Example 3] 5% by weight of alumina carrying 20 on a 20 carrier,
Catalysts 7 to 10 supported so that the platinum concentration was 0.1, 0.3, 0.5, and 1% by weight, and Catalyst 11 supported so that the palladium concentration was 0.1 and 0.5% by weight .12 was prepared.

These catalysts were subjected to activity evaluation tests under the same conditions as shown in Table 1, except that the reaction temperature was 400°C, and the results shown in Table 4 were obtained. 7-kt203 pellets were immersed in an aqueous solution of IJum, dried, and fired at 500° C. for 5 hours to obtain a carrier in which Na was supported at a weight ratio of 20 to 5 to alumina.

Catalyst 13 was prepared in which 0.5 weight percent of platinum was supported on this carrier in the same manner as in Example 1, and an activity evaluation test was conducted in the same manner as in Example 1. As a result, the same performance as Catalyst 1 was obtained. Obtained.

[Example 5] Catalyst 1 prepared in Example 1? - Fill a stainless steel reaction tube with 5 cc of methanol at 400°C.
A durability test was conducted for 800 hours with continuous supply of cc/h. As a result, it was confirmed that there was almost no change in methanol reaction rate and cracked gas composition from the initial stage, and that there was no carbon precipitation on the catalyst surface.

[Example 6] A catalyst in which 0.5 weight percent of platinum was supported was prepared in the same manner as in Example 1, except that 7-A-1z O3 b-silicon α-At203 was used in Catalyst 1 of Example 1. As a result of preparing 14 and conducting an activity evaluation test in the same manner as in Example 1,
Performance similar to that of catalyst 1 was obtained.

In the above examples, granular catalysts are described, but
There is no particular limitation on the shape of the catalyst, and it is not to be said that it may be used in a nicham shape, a plate shape, or the like.

Furthermore, although the second embodiment describes the case where methanol is used alone, methanol decomposition may be carried out in the coexistence of a gas containing water vapor, air, etc.

Sub-agent 1) Akira Sub-agent Ryo Hagi Hara -

Claims (1)

[Claims] A methanol reforming catalyst characterized in that one or more metals from the group consisting of platinum and palladium are supported on a carrier in which alumina is coated in advance with an alkali metal oxide.