WO-2026094839-A1 - METHANE COMBUSTION CATALYST AND METHOD FOR PURIFYING COMBUSTION EXHAUST GAS CONTAINING SULFUR OXIDES

Abstract

The present invention relates to a Pt/SnO 2 -based methane combustion catalyst for combusting methane in a combustion exhaust gas containing sulfur oxides, the methane combustion catalyst being configured such that platinum and/or platinum oxide is supported on a tin oxide-based carrier containing tin oxide as an essential component. In the methane combustion catalyst according to the present invention, the tin oxide-based carrier comprises antimony-doped tin oxide (ATO). At this time, the doping amount of antimony in the tin oxide-based carrier is preferably 0.1-5.0 mass%. In the present invention, the antimony doped in tin oxide improves the ability of the tin oxide to supply oxygen to platinum and the like. As a result, the activity and durability of the methane combustion catalyst can be improved. The Pt/SnO 2 -based methane combustion catalyst is highly active and excellent in durability even without the additional carrying of iridium or without the application of an overcoat layer.

Inventors

• TAKEDA KAZUTAKA
• KATO SHUNSUKE
• TAKANEZAWA HIDENORI

Assignees

• 田中貴金属工業株式会社

Dates

Publication Date

20260507

Application Date

20251027

Priority Date

20241031

Claims (7)

1. A methane combustion catalyst for burning methane in combustion exhaust gas containing sulfur oxides, comprising a tin oxide-based carrier containing tin oxide as an essential component, on which platinum and/or platinum oxides are supported, The methane combustion catalyst is characterized in that the tin oxide-based support consists of antimond-doped tin oxide.
2. The methane combustion catalyst according to claim 1, wherein the amount of antimony doping in the tin oxide-based carrier is 0.1% by mass or more and 5.0% by mass or less, based on the mass of the tin oxide-based carrier.
3. The methane combustion catalyst according to claim 1 or claim 2, wherein the amount of platinum and/or platinum oxide supported on the entire catalyst is 1.0% by mass or more and 10.0% by mass or less, in terms of metallic platinum.
4. The methane combustion catalyst according to claim 1 or claim 2, wherein when the methane combustion catalyst is measured by X-ray photoelectron spectroscopy (XPS), the abundance ratio of metallic platinum R Pt obtained from the platinum 4f spectrum is 70% or more.
5. A methane combustion catalyst according to claim 1 or claim 2, having one of the following forms: granular, pelletized, or tablet-shaped.
6. A methane combustion catalyst according to claim 1 or 2, supported by a support having one of the following shapes: plate, cylindrical, spherical, or honeycomb.
7. In a combustion exhaust gas purification method for oxidizing and removing methane from combustion exhaust gas containing sulfur oxides, A method for purifying combustion exhaust gas, characterized in that the reaction temperature is 300°C or higher and 500°C or lower, and the combustion exhaust gas is brought into contact with the methane combustion catalyst described in claim 1 or claim 2.

Description

Methane combustion catalyst and method for purifying combustion exhaust gas containing sulfur oxides This invention relates to a methane combustion catalyst for oxidizing and removing methane from combustion exhaust gas containing sulfur oxides. More specifically, it relates to a methane combustion catalyst that suppresses catalyst poisoning by sulfur oxides, is low-cost compared to conventional technologies, and possesses high activity and durability. Furthermore, this invention relates to a method for purifying combustion exhaust gas by oxidizing and removing methane using this catalyst. Exhaust gases from engines and boilers that use hydrocarbons such as natural gas, city gas, diesel fuel, and kerosene contain nitrogen oxides (NOx), sulfur oxides ( SO₂ , SOx), carbon monoxide (CO), odorous substances, and particulate matter, as well as unburned hydrocarbons. Since all of these are factors in environmental pollution, exhaust gases are treated with filters and catalytic converters before being released. In particular, methane has been reported to have more than 20 times the greenhouse effect of carbon dioxide, making its removal extremely important from an environmental protection perspective. As a catalyst for oxidizing and removing methane from combustion exhaust gas containing sulfur oxides as described above, a methane combustion catalyst is known in which platinum is supported on a tin oxide support ( SnO2 support) made of tin oxide (Patent Document 1). The reason why tin oxide supports are used in methane combustion catalysts is that inorganic oxides such as alumina supports and zirconia supports, which have been used for a long time as catalysts for hydrocarbon purification, are not effective in oxidizing and removing methane. In particular, for the treatment of exhaust gas containing sulfur oxides, catalysts made of alumina supports and the like suffer from a significant decrease in activity due to catalyst poisoning. Furthermore, improvements have been made to methane combustion catalysts using tin oxide supports, and in particular, the effectiveness of methane combustion catalysts supported with iridium in addition to platinum has been reported (Patent Document 2). This methane combustion catalyst has improved durability against catalyst poisoning by sulfur oxides due to the additional support of iridium. In the following description, methane combustion catalysts supported with platinum or the like on a tin oxide support may be referred to as Pt/ SnO2 catalysts or Pt-Ir/ SnO2 catalysts. These may also be collectively referred to as Pt/ SnO2 system catalysts. The applicant has disclosed a methane combustion catalyst that further improves the activity and durability of conventional Pt/ SnO₂ catalysts (Patent Documents 3 and 4). In making these improvements, the applicant has investigated the activity mechanism of the Pt/ SnO₂ catalyst for methane combustion. According to this investigation, the methane combustion activity of the Pt/ SnO₂ catalyst depends on the platinum being in the oxide state (PtO or PtO₂ ). Furthermore, it is hypothesized that the cause of catalyst poisoning of Pt/ SnO2 catalysts by sulfur oxides lies in the alteration of catalyst particles by sulfur oxides. Specifically, sulfur oxides such as SO2 that fly near the platinum oxide catalyst particles are easily oxidized and reduce the platinum oxide, removing oxygen and becoming SO3, etc., which then desorb. Platinum particles that have been reduced and metallized by sulfur oxides such as SO2 sinter with surrounding metallized platinum particles to form coarse platinum particles with low activity. Catalyst poisoning in Pt/ SnO2 catalysts is caused by the metallization of platinum oxides and sintering of platinum particles as described above, and as long as these processes continue, the catalytic activity will continue to decrease. The catalyst poisoning mechanism described above supports the fact that additional iridium support in Pt/ SnO2 catalysts improves durability. According to the applicant, iridium in the Pt-Ir/ SnO2 catalyst exists as an oxide ( IrO2 ) similar to platinum, and this iridium oxide maintains the oxidation state of platinum by supplying oxygen to the metallized platinum. The iridium oxide is metallized by reduction by oxygen supply to platinum and reduction by sulfur oxides, but it is possible to maintain the iridium oxide state by receiving oxygen supply from the tin oxide support. This cycle of reduction (oxygen supply to platinum) and oxidation (oxygen acceptance from the tin oxide support) of iridium oxide creates a reduction and oxidation cycle in the platinum oxide, and by avoiding the easily sintered metallic platinum state, it contributes to maintaining activity and improving durability. Based on the above considerations, the applicant has disclosed two types of methane combustion catalysts consisting of a Pt/ SnO2 system catalyst that enable improved methane combustion activity and durability (Patent