JPS63296842A - Oxidizing palladium catalyst - Google Patents

Abstract

PURPOSE:To enhance the stability of a catalyst and to extend the life thereof, by coating an inorg. carrier with oxide of an element selected from La, Ce, Nd, K or the like and supporting Pd on the formed coating in a dispersed state to form the catalyst. CONSTITUTION:An inorg. carrier is coated with active oxide of one or more element selected from a group consisting of La, Ce, Na, K, Ca, Sr, Ba and Si. Subsequently, Pd and/or palladium oxide are supported on the active oxide coating in a dispersed state to form an oxidizing catalyst. As the inorg. carrier, mullite is pref. used and, as the active oxide, there are alumina, magnesia, titania, zirconia or the like. The pref. addition amount of La, Ce or the like to the active oxide is 5-10wt.%. The obtained oxidizing catalyst can be suitably used in the combustion of various fuels.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a palladium oxidation catalyst that minimizes the deterioration of palladium, which has excellent fuel performance, and greatly extends its life.

(Prior art and its problems) Conventionally, it has been widely practiced to burn hydrocarbon fuel such as methane together with molecular oxygen, typically air, in a combustion device and use the resulting heat as a variety of energy sources.
Therefore, research on these combustions has covered a wide range of areas. In the past, the main goal of research was to obtain combustion gas that did not contain harmful substances such as nitrogen oxides, but in recent years, in addition to this, much effort has been spent on preventing the deterioration of the catalysts used for combustion. It is being healed.

In other words, in conventional combustion devices, palladium catalysts are mainly used, in which active oxides such as alumina, magnesia, titania, and zirconia are coated on an inorganic carrier such as mullite, and palladium or palladium oxide is dispersed and supported on the oxides. When used at high temperatures (e.g., 1200°C or higher), the active oxide in the catalyst deteriorates, i.e., the specific surface area decreases and pores disappear, which causes aggregation and volatilization of palladium, resulting in a decrease in activity. is connected to.

(Object of the invention) The present invention improves the stability of the active oxide by adding another oxide to the active oxide of the conventional palladium catalyst, which lacks high-temperature stability, and as a result palladium The object of the present invention is to provide a palladium oxidation catalyst that improves the stability of the entire catalyst and has a relatively long life even when used at high temperatures.

(Means for Solving the Problems) The present invention provides a catalyst comprising an inorganic carrier coated with an active oxide and palladium and/or palladium oxide dispersedly supported on the active oxide. The oxidation catalyst is stabilized by adding an oxide of at least one element selected from the group consisting of lanthanum, cerium, neodymium, potassium, calcium, strontium, barium, and silicon.

The present invention will be explained in detail below.

The oxidation catalyst used in the method of the present invention has catalyst atoms dispersedly supported on an inorganic carrier coated with an active oxide. It is most preferable to use mullite as the inorganic carrier.

Examples of active oxides include alumina, magnesia, titania, and zirconia. In the present invention, in order to improve the high temperature stability of the active oxide, lanthanum, cerium, neodymium, Oxides such as potassium, calcium, strontium, barium or silicon are added. The amount added is 5 to 1 for the active oxide.
It is desirable that the content be 0% by weight; if it is less than 5%, the addition effect will be insufficient, and if it exceeds 10%, the activity of the active oxide itself may be lost. The reason why the active oxide is stabilized by the addition of these oxides is not clear, but it is believed that when mixed with an active oxide such as alumina, it functions to suppress the reduction in surface area of the active oxide. It is presumed that the stabilizing oxide itself has almost no catalytic activity.

Palladium and/or palladium oxide, which are catalytically active substances, are dispersed and supported on a carrier coated with such an oxide. The supporting method is not particularly limited, and palladium and/or palladium oxide may be deposited on the carrier by binding metal palladium or the like using a binder, or by coating a solution of a palladium compound on the carrier and thermally decomposing the compound. It can be carried.

The oxidation catalyst according to the present invention can be suitably used for combustion of various fuels, such as methane, which is the main component of natural gas, as well as lower aliphatic hydrocarbons such as propane, butane, or mixtures thereof. When using natural gas as a fuel, it may be purified to remove impurities beforehand.

For example, in the combustion of natural gas, the combustion temperature is usually 1000
The palladium oxidation catalyst of the present invention, which has improved high-temperature stability through the addition of lanthanum and the like, can withstand long-term use at such high temperatures, with almost no change in catalyst performance. do not have.

Examples of the present invention will be described below, but the present invention is not limited by these Examples.

(Example) Mullite carrier, 5% by weight of lanthanum oxide and 5% by weight
The coated carrier was coated with alumina containing neodymium oxide of I got a catalyst.

Using 40 g of the catalyst, catalytic combustion of natural gas containing 90% methane was carried out under normal pressure, air flow rate 40 ρ/min, and catalyst inlet gas flow rate 1. m/sec and combustion temperature of 1300"C, the catalyst of this example remained clean for 200 hours.
Combustion gas at 300°C was applied.

(Comparative Example) A mullite carrier was coated with activated alumina, and then the coated carrier was immersed in a palladium nitrate solution, dried, and further treated at 800°C in a hydrogen stream to give 100 g of alumina and 20 g of palladium per carrier 11. A palladium catalyst supported on was obtained.

When this catalyst was used for combustion of natural gas under the same conditions as in the above example, the catalyst of this comparative example became unable to ignite after 20 hours.

(Effect of the invention) The palladium oxidation catalyst according to the present invention improves high temperature stability by adding a stabilizing oxide selected from lanthanum, cerium, etc. to the active oxide consisting of alumina etc. in the palladium catalyst. I try to let them do it.

Therefore, even when the catalyst is used in a combustion reaction at a high temperature of, for example, 1200° C. or higher, deterioration of the active oxide is prevented due to the function of the stabilizing catalyst. The lifespan of is greatly increased,
Its economic contribution is enormous.

Claims (3)

[Claims] (1) A catalyst comprising an inorganic carrier coated with an active oxide and palladium and/or palladium oxide dispersedly supported on the active oxide, wherein the active oxide contains lanthanum,
A palladium oxidation catalyst stabilized by adding an oxide of at least one element selected from the group consisting of cerium, neodymium, potassium, calcium, strontium, barium, and silicon. (2) The active oxide is at least one selected from the group consisting of alumina, magnesia, titania, and zirconia.
The palladium oxidation catalyst according to claim 1, which is an oxide of a species. (3) The amount of stabilizing oxide is 5 to 1 per active oxide.
The palladium catalyst for oxidation according to claim 1 or 2, which has a content of 0% by weight.