Nitric Acid & Other Chemical Catalysts
Nitric acid is a key starting material for the production of fertilizers, helping to boost arability and yield of farmland. Nitric acid is made in three stages. The first step is the oxidation of ammonia gas with air to form nitric oxide. In order to achieve high conversion efficiency, this is normally carried out at pressure over a platinum-rhodium catalyst. The nitric oxide is cooled and further oxidised to form nitrogen oxide, which is then absorbed in water to nitric acid.
Non-fertilizer uses include the production of: explosive-grade ammonium nitrate; adipic acid for making nylon, and toluene diisocyanate for manufacturing polyurethane.
Acetic acid is produced from methanol and carbon monoxide in the Cativa process which relies upon an iridium-ruthenium catalyst to activate methanol carbonylation. There is a huge demand for acetic acid which has a very wide range of applications including cleaning, photography, fumigation, packaging, paints, adhesives and artificial fibres.
Paraxylene and PTA
Platinum is also used in the production of paraxylene (PX), and a palladium catalyst is used in the production of purified terephthalic acid (PTA). PX and PTA are intermediates in the production of polyethylene terephthalate (PET) used for plastics and polyester textiles.