Autothermal reforming catalyst and process of producing fuel gas for fuel cell

Abstract

Autothermal reforming catalysts comprises ruthenium supported on a support containing 5 to 40 percent by mass of a cerium oxide or rare earth element oxide which is composed principally of a cerium oxide, 60 to 95 percent by mass of an aluminum oxide, and 0 to 10 percent by mass in terms of metal of one or more elements selected from the group consisting of an alkaline metal and an alkaline earth metal, the atomic ratio of cerium and rhodium (Ce / Rh) being 1 to 250.

Description

[0001] 1. Field of the Invention[0002] This invention relates to an autothermal reforming catalyst. This invention also relates to a process of producing a fuel gas for a fuel cell wherein hydrocarbons and / or oxygen-containing hydrocarbons are converted to a reformed gas which is composed principally of hydrogen by an autothermal reforming reaction using such a catalyst.[0003] 2. Description of the Prior Art[0004] A known process for producing hydrogen from hydrocarbons or oxygen-containing hydrocarbons is an autothermal reforming method which is the combination of an oxidation reaction and a steam reforming reaction. In this process, hydrocarbons or nitrogen-containing hydrocarbons, steam, and oxygen or air are introduced into a reactor, and a part of the hydrocarbons or oxygen-containing hydrocarbons is subjected to partial or complete combustion. While the reactor is then heated to a predetermined temperature with the heat generated by the combustion, the remaining hydrocarbons o...

AI Technical Summary

Benefits of technology

[0023] No particular limitation is imposed on silica alumina which may, therefore, be in any type of crystallinity form. Needless to mention, an aluminum oxide even containing a small amount of impurities can be used without hindrance.

[0029] The catalyst support used in the present invention contains a cerium oxide or rare earth element oxide which is composed principally of a cerium oxide in an amount of 5 to 40 percent by mass, and preferably 10 to 35 percent by mass. The rare earth metal oxide in an amount of less than 5 percent by mass is insufficient in the effects of suppressing carbon to precipitate, facilitating the activity, and enhancing the heat-resistance under coexistence of oxygen, while that in amount of more than 40 percent by mass reduces the catalyst surface, leading to insufficient catalyst activity.

[0030] The catalyst support used in the present invention contains the aluminum oxide in an amount of 60 to 95 percent by mass, and preferably 65 to 90 percent by mass. The aluminum oxide of less than 60 percent by mass reduces the catalyst surface, leading to insufficient catalyst activity, while that in excess of 95 percent by mass is insufficient in the effects of suppressing carbon to precipitate, facilitating the activity, and enhancing the heat-resistance under coexistence of oxygen.

[0038] In order to enhance the mechanical strength of the catalyst support, a small amount of binder, such as silica and cement may be added thereto.

[0057] The autothermal reforming catalyst of the present invention has an extremely high activity and long working life. However, in the case of continuing the use of the catalyst over a long period of time, if necessary, the catalyst is preferably subjected to a refresh treatment such as reduction under a reduction atmosphere, generally, a hydrogen atmosphere at a temperature of 400 to 1,000.degree. C., and preferably 500 to 700.degree. C.

[0058] The autothermal reforming catalyst of the present invention is not decreased in activity even using ruthenium which has conventionally the tendency to be decreased in activity under an oxygen atmosphere at elevated temperatures, leading to a sufficient working life and can maintain the effect of suppressing carbon to precipitate at a lower steam / carbon ratio. Furthermore, since the catalyst comprises ruthenium which is cheaper among the noble metals, it is advantageous in the industrial use.

Problems solved by technology

The base metal-based catalysts are relatively prone to cause carbon precipitation.

However, these catalysts have a problem that they are expensive.

While ruthenium is relatively cheap, it is prone to de be decreased in activity due to volatilization in the case where oxygen coexists at elevated temperatures such as those at which an autothermal reforming reaction is conducted.

Therefor, there has been demanded a cheap catalyst which hardly cause the carbon to precipitate even under such a condition that the steam / carbon ratio is low in an autothermal reforming reaction so as to be able to produce hydrogen at high efficiency and is excelled in heat resistance under the coexistence of oxygen, but such a catalysts has not been developed yet.