Iron supported catalyst comprising a Ca-deficient hydroxyapatite for waste gas treatment

A catalyst composition for catalytic reduction of NOx compounds, comprising Fe deposited on a porous support comprising at least 60 wt % of a calcium-deficient hydroxyapatite having a Ca/P molar ratio of less than 1.67. The support preferably has a specific BET surface area of at least 110 m2/g and a pore volume of at least 0.5 cm3/g, both measured after heat treatment at 200°C. The catalyst composition may be brought into contact in a fixed or fluidized bed or by injection with a NOx-containing waste gas stream at a temperature of at least 100°C and preferably at most 600°C to carry out, in the presence of 02, a reduction by NH3 of at least a portion of the NOx. The process may further include injecting an alkali sorbent into the waste gas stream to remove other contaminants such as heavy metals and/or acid gases with the alkali sorbent. A blend comprising the alkali sorbent and the deNOx catalyst may be formed to treat the waste gas stream. The ammonia may be injected into the waste gas or may be included in the alkali sorbent and/or the deNOx catalyst.