Converting gaseous urea (deriv.) into carbon di:oxide and ammonia - by contacting with catalyst in presence of water vapour

摘要

Process for converting into ammonia and carbon dioxide of gaseous urea and gaseous cpds. with one or more N atoms and one or more C atoms which can be formed (in)directly from urea, comprises contacting one or more of these cpds. in the presence of water vapour with a catalyst. Pref. catalyst is chosen from active carbon, oxide cpds. and phosphates of boron and aluminium. Pref. oxide cpds. are SiO2, ZnO, TiO2, MgO, Al2O3 and mixts. and/or cpds. of these. The water vapour is used in at least an amt. sufficient to convert all the carbon present in the hydrolysable cpds. into CO2. The process is pref. carried out at 100-500 deg.C esp. 120-420 deg.C with a contact time between the catalyst and the gas mixt. of at least 0.01 sec., esp. 0.1-20 sec. Process is cheap and simple to operate and is esp. useful for treating vapour mixts. obtd. during the concn. of aq. urea solns. and contg. e.g. large amts. of water vapour, small amts. of CO2 and NH3 and cyanic acid and isocyanic acid obtd. by the hydrolysis of urea. The resulting CO2 and NH3 contg. stream can be recycled to the low pressure part of a urea prodn. process.