Development of Selective Conversion Process of Fuel Nitrogen to N_2 with Metal Nanoparticles

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1.Nanoscale FeOOH particles, precipitated onto low rank coals from an aqueous solution of FeCl_3 by using Ca(OH)_2, are reduced into metallic iron with the size of 20-30nm during fluidized bed pyrolysis, and metal nanoparticles promote efficient conversion of fuel nitrogen to N_2. There are two formation routes of N_2, secondary decomposition reactions of volatile nitrogen (tar, HCN,and NH_3) and conversion reactions of char nitrogen, and the latter is the main route with more highly-dispersed iron.2.When 15 coals with different ranks are pyrolyzed at 1000ﾟC with a fixed bed reactor, some low rank coals show extremely high conversion of fuel nitrogen to N_2,50-60%. Demineralization of these coals with HCl washing, XRD analyzes of low and high temperature ashes, and ICP analysis of HCl leachate lead to the conclusion that the presence of Fe-containing minerals in ion-exchangeable forms is the key factor determining for remarkable N_2 formation.3.The XPS and TEM-EDX measurements of the cahrs after pyrolysis reveal that such minerals are transformed into iron metal particles with the size of <approximately equal> 10nm, and that the mineral-derived iron show much higher activity for selective conversion of char nitrogen to N_2 than the externally-added iron. It is likely that iron-catalyzed solid phase reactions proceed through formation of interstitial iron nitrides and subsequent decomposition into N_2.4.Pyrolysis of these low rank coals with a free-fall type reactor is also carried out from a practical point of view, and it is suggested that tarry materials with pyrrolic and pyridinic nitrogen forms are converted to N_2 on the surface of the mineral-derived fine iron. When these compounds are passed over iron metal particles with the size of 20nm supported on pure carbon to verify this possibility, the conversion to N_2 take place exclusively.