JPS5845286B2 - Methyl alcohol reforming catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst for reforming methyl alcohol used for reforming methyl alcohol into a gas rich in hydrogen and carbon oxides.

Carbon monoxide, hydrocarbons, which are harmful substances in the exhaust of internal combustion engines,
It is known that one means of reducing nitrogen oxides is to add hydrogen, which has the property of burning stably at a leaner air-fuel ratio, in order to operate the fuel at a leaner air-fuel ratio.

One way to make the hydrogen to be added is to decompose methyl alcohol.

This method uses heat from the exhaust gas of an internal combustion engine to decompose methyl alcohol.

As is well known, the exhaust gas heat of an internal combustion engine varies from a temperature close to room temperature to around 800°C.
There is a need for an efficient catalyst that can be reformed over a wide temperature range of ~800°C.

As this type of catalyst, conventionally, γ-alumina (hereinafter referred to as γ-A 203) was mixed with copper (hereinafter referred to as Cu) in a hydrogen atmosphere.
and/or a catalyst supporting nickel (hereinafter referred to as Ni) is used.

However, conventional Cu catalysts can sufficiently reform methyl alcohol over a relatively wide temperature range in their initial state, but when used at around 700°C for more than 100 hours, the temperature range in which methyl alcohol can be sufficiently reformed is limited to the initial state. There is a problem that it deteriorates compared to .

The inventor conducted various studies to solve the above problem and found the following.

In other words, the Cu catalyst in which Cu is supported on γ-AI203 has the property of sufficiently decomposing methyl alcohol from a temperature of 200°C, but it is heat resistant only up to a temperature of 600°C, and for this reason, the lowest modification of methyl alcohol is possible. The quality temperature will rise considerably compared to the initial stage.

The Ni catalyst, in which Ni is supported on γ-A I 20 a, has a considerably high temperature of 450°C or higher at which it can sufficiently decompose methyl alcohol, but it is heat resistant up to about 950°C.

In addition, with a Cu-Ni catalyst in which Cu and Ni are mixed and supported on γ-A■203, from 250°C
Methyl alcohol can be reformed for more than 200 hours at temperatures up to 'c.

However, the target temperature range of 200 to 800°C is still not fully satisfied.

The inventors found that the initial minimum reforming temperature of the Cu catalyst was 200°C.
In view of the fact that the Ni catalyst is heat resistant up to approximately 950°C, we conducted numerous experiments to obtain a catalyst that has the advantages of the properties of the Cu catalyst and the properties of the Ni catalyst. The invention is Cu: 36-62% by weight, Ni: 8-3
2% by weight and Cr: 18-41% by weight (total of 1
00% by weight) is supported on γ-A1203 in an amount of 16% or more by weight.

According to the present invention, although the reason is not clear, the presence of Cr can suppress the heat-induced melting phenomenon of Ni and Cu particles and prevent a decrease in the catalytic active areas of Ni and Cu. Combined with the fact that the composition is limited to the above composition range, methyl alcohol can be modified over a wide temperature range from 200 to 800 degrees Celsius, even if it is used for a long time at a high temperature of 800 degrees Celsius. can do.

The present invention will be explained below with reference to Examples.

Example Cu(NO3)2.6H20, Ni(NO3)2.6H
Eleven types of solutions prepared using 20°Cr(NOa)2.9HO at the proportions shown in Table 1 were prepared.

A granular carrier of γ-A1203 (
A surface area of 10 m”/El) is immersed for 30 minutes.

After soaking, dry at a temperature of 100-180℃,
Bake at 00°C for 60 to 90 minutes.

Then, this process (from immersion to calcination) was repeated once again to coat the surface of the γ-Al 203 support with CuO, NiO
, CrO.

After that, 2oo'c@later hydrogen reduction to CuO, NiO
, CrO is reduced to Cu, Ni, Cr: Cu-Ni-C
r Obtain catalyst.

Next, in order to examine the heat resistance of the catalyst thus prepared, it was left in an electric furnace at 800° C. for 24 hours, and the minimum reforming temperature of methyl alcohol thereafter is shown in Table 1.

As can be understood from Table 1, the catalyst with a minimum reforming temperature of methyl alcohol of 200°C or less after the heat resistance test is 716
．． 8, 9, 10, and 11 catalysts.

Incidentally, the initial minimum reforming temperature of methyl alcohol before the heat resistance test was 200°C.

From this, the catalyst of /I68,9,10.11 is 20
It can be seen that methyl alcohol can be modified over a temperature range of 0°C to 800°C.

FIG. 1 shows the composition range in which the minimum reforming temperature of methyl alcohol is 200° C. after the heat resistance test.

The area surrounded by the curve in FIG. 1 is the composition range where the minimum reforming temperature is 200°C.

Note that the numbers in FIG. 1 correspond to the catalyst numbers in Table 1.

Based on the results in Table 1 and the results in Figure 1, the present inventors have determined that Cu
- After examining the composition range of the catalyst metal of Ni-Cr,
Cu is 36-62% by weight, Ni is 8-32% by weight, C"
is 18 to 41% by weight.

However, Cu + N i + Cr is ioo weight %.

Next, the present inventors investigated the relationship between the amount of the Cu-Ni-Cr catalytic metal relative to the γ-A l 20a support and the minimum reforming temperature of methyl alcohol after the above durability test.

The results are shown in FIG. In this Figure 2, the vertical axis shows the minimum reforming temperature of methyl alcohol, and the horizontal axis shows the γ-A
Amount of catalyst metal supported on 1203 carrier 101i+ G)
shows.

The number of each curve in FIG. 2 corresponds to the catalyst number in Table 1.

In this Figure 2, if we focus on the catalysts whose minimum reforming temperature is 200°C or less in Table 1, that is, the catalysts A8, 9, 10, and 11, we can see that in order to make the minimum reforming temperature 200°C, it is necessary to ,10
For this catalyst, it is necessary to support the catalytic metal of Cu-Ni-Cr on 100 g of γ-A1203 support by about 28.9 or more (about 28.9% or more for the γ-A1203 support in terms of weight □).
8%).

Further, for catalysts A9 and 11, a supported amount of about 169 or more is required.

As mentioned above, within the composition range of the catalyst metal of Cu-Ni-Cr to obtain the reforming temperature range of 200°C to 800°C, that is, Cu: 36 to 62% by weight, Ni: 8 to 32% by weight.
, Cr: It was confirmed that the amount of the catalyst metal selected within the composition range of 18-41% by weight on the γ-Al 203 support was approximately 16g (16% by weight).

In the present invention, methyl alcohol is modified according to the reaction formula shown below.

CHOHHO21502+0.6ON2→1.65H2
+0.75 CO+0.10 CH4+0. l 5H,
,0+0. l 5 CO2 + 0.60 N2 In the present invention, the minimum temperature for obtaining about 1.570 cc of reformed gas excluding nitrogen gas from 1 cc of methyl alcohol in the above reaction formula was defined as the minimum reforming temperature.

In the Cu-Ni-Cr catalyst in the above example,
The carrier is γ-A1□03, and this γ-A l 2Q.

The reason for using it is that it has a large surface area and high catalytic activity.

However, as is well known, γ-A1□03 has a crystal transformation point, and at a temperature of about 900° C., it transforms into α-A1203 and its surface area decreases.

For this reason, it is expected that the minimum reforming temperature of methyl alcohol will vary widely.

Therefore, there is a need for a carrier whose surface area hardly decreases even when it is transformed into α-A1203.

As a result of various experiments, the present inventors discovered the following carrier.

That is, Ba, Sr, La, Ce. r-Al2O3 is immersed in an O, l-0.5 molar solution (nitrate of each metal) containing one or more metals selected from Si, and then heated at 600 °C to 900 °C for 2 to This is a carrier obtained by firing for 5 hours.

The carrier obtained in this way contains γ-Al as the main component.
20 s, but Bad obtained by firing.

It contains one or more metal oxides selected from La2O3, Si02zCeO, and SroQ.

In this carrier, BaO, SrO, etc.
Although the reason is not clear, it was possible to prevent the surface area of the carrier from decreasing when γ-A1203 is attached to α-A 120 s.

Incidentally, a catalyst having a composition of /16.10 shown in Table 1 of Example 1 was supported on the above carrier, and this catalyst was
When the minimum reforming temperature was measured after being placed in an electric furnace at 00° C. for 24 hours, good results were obtained as shown in FIG.

In other words, when using a carrier in which γ-A1203 contains BaO and a carrier in which γ-A1203 contains SrO, the minimum reforming temperature is the initial value of 200°C, and the durability time is 24 hours (as described above). Even after the lapse of time under these conditions, the temperature only rises to about 205°C.

Furthermore, when a carrier containing SiO2 in γ-A I 20 s is used, the minimum reforming temperature only rises to about 210° C. after 24 hours of durability.

In addition, when 7-Al2O3 has 3 L a 203, the temperature is about 223 °C, and γ-A l 20 s has Ce
In the case of containing O, the minimum reforming temperature only increased to about 233°C, and in both cases, the increase in the minimum reforming temperature was small, and good results were obtained.

When ordinary γ-A1□03 was used to support a catalyst metal of the same composition and a heat resistance test was conducted under the same conditions, the minimum reforming temperature rose to about 300'C as shown by the broken line in FIG.

From this, γ-A containing each of the above metal oxides
When using 1203 as a carrier, normal γ-A1
It can be seen that the increase in the minimum reforming temperature is very small compared to the case where No. 203 is used.

Note that the concentration of the solution in which γ-A1203 is immersed is 0.1 to
Although the concentration is 0.5 molar, it is not limited to this concentration, and a preferable concentration range can be determined by experiment.

The above-mentioned catalyst is a catalyst with a so-called granular structure using granular γ-A1□03, but it is not limited to a granular structure. Ceramic honeycomb structure, metal honeycomb structure with γ-alumina attached to the metal surface by thermal spraying,
A metal linear structure in which γ-alumina is attached to a thin metal wire may also be used.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams used to explain the present invention.
The figure shows a Cu-Ni-C catalyst in which the minimum reforming temperature of methyl alcohol is 200°C or less in a Cu Ni Cr-based catalyst.
Figure 2 is a characteristic diagram showing the composition range of r; Figure 2 is a % characteristic diagram showing the relationship between the amount of catalyst metal supported on Cu-Ni-Cr and the reforming temperature of methyl alcohol on the γ-A1203 carrier;
FIG. 3 shows the characteristics showing the relationship between the minimum reforming temperature and the type of γ-A1203 carrier.

Claims (1)

[Scope of Claims] 1. A catalyst used for reforming methyl alcohol into a hydrogen-rich gas, in which 16% or more by volume of a catalyst metal having the following composition is supported on γ-alumina. A methyl alcohol reforming catalyst characterized by: (a) Cu 36-62% by weight, Ni 8-32% by weight, C
r18-41% by weight. However, Cu+Ni+Cr=100% by weight. 2. In a catalyst used for reforming methyl alcohol into a hydrogen-rich gas, 16% or more by volume of a catalytic metal having the following composition is supported on γ-alumina, and BaO is added to this γ-alumina. , La2O3,5i
n2. A catalyst for reforming methyl alcohol, characterized in that it contains one or more metal oxides selected from CeO and SrO. (a) Cu 36-62% by weight, Ni 8-32% by weight, C
r18-41% by weight. However, Cu+Ni+Cr=100% by weight.