Abstract: There is provided a process for producing a catalyst to convert carbon monoxide in a gas into carbon dioxide. The process comprises causing activated carbon to absorb an aqueous solution of chloroplatinic acid, reducing the absorbed chloroplatinic acid to platinum with a reducing agent, and decomposing an excess of the reducing agent with hydrogen peroxide. The catalyst contains at least 6 mg of platinum per gram of activated carbon.

Abstract: A reduction catalyst is disclosed. This catalyst comprises a naturally-occurring inorganic material which is a tuff consisting essentially of SiO.sub.2, Al.sub.2 O.sub.3 and H.sub.2 O containing 1-10% by weight of an alkali metal oxide and an alkaline earth metal oxide and has an X-ray diffraction pattern as shown in Table A or Table B. It is produced by depositing of the tuff metal ions selected from the group consisting of a metal belonging to Ib Group, IIb Group and VIII Group of Periodic Table, chromium, vanadium and manganese, followed by heat treatment, and repeating the same using different metal ions on each occasion. The catalyst is useful as a reduction catalyst for nitrogen oxides.