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Carbon-supported iron complexes were investigated as electrocatalysts for the reduction of nitric oxide (NO) in a H-2-NO fuel cell conceived for the production of hydroxylamine (NH2OH) with concomitant generation of electricity. Two types of iron complexes with tetradentate ligands, namely bis(salicylidene)ethylenediimine (Salen) and phthalocyanine (Pc), supported on activated carbon or graphite were prepared and evaluated as electrocatalysts, either without further treatment or after pyrolysis at 700 degrees C. The performance in the reduction of NO of gas diffusion cathodes based on these electrocatalysts was investigated in an electrochemical half cell (3-electrode configuration) using linear sweep voltammetry (LSV). The most promising electrocatalysts were studied further by chronoamperometric experiments in a H-2-NO fuel cell, which allowed comparison in terms of power output and hydroxylamine production. Depending on the concentration of the NO feed (6 or 18%), the best electrocatalytic performance was delivered either by FePc or FeSalen. The gas diffusion electrode based on FeSalen supported on activated carbon with 0.3 wt% Fe-loading provided the highest current density (86 A/m(2)) and the best current efficiency (43%) towards the desired NH2OH when operating at the higher NO concentration (18%). Moreover, FeSalen offers the advantage of being cheaper than FePc. The experimental work was complemented by density functional theory (DFT) calculations, which allowed to shed more light on the reaction mechanism for the reduction of nitric oxide at the atomistic level.

NOx emissions have been limited in many countries because of their adverse impact on the environment. Different strategies to reduce the amount of NOx realized into the environment from combustion devices have been developed but the main technique to prevent NOx formation in accordance with the limit level of the regulation at a lower cost is flue gas recirculation (FGR). This paper presents the result of a series of laboratory tests to determine the emissions of nitrogen oxides and carbon monoxide from a standard natural gas fired burner applied very often in metallurgical practice. There was a marked effect on the NOx and CO emissions by varying the excess air and the quantity of recirculating flue gases in the combustion air. Significant reductions in the NOx and CO emissions of approximately 80% and 70%, respectively, were achieved by external flue gas recirculation.

In many countries NOx emissions are limited because of their adverse impact on the environment. Different methods to reduce the amount of NOx released into the environment from combustion devices have been developed. The main technique to prevent NOx formation in accordance with the regulation limit at a reasonable cost is flue-gas recirculation (FGR). This paper presents the results of laboratory tests to determine the emissions of nitrogen oxides from a standard natural-gas-fired burner. There was a marked effect on the NOx emissions by varving the excess air and the quantity of recirculated flue gases in the combustion air. A significant reduction in the NOx, by approximately 80 %, was achieved by external flue-gas recirculation. The results obtained from the measurements were compared with those obtained from a calculation of the equilibrium compositions and the adiabatic flame temperature of the combustion products related to the quantity of supplied combustion air and recirculated flue gases. V številnih državah je emisija NOx omejena zaradi škodljivega vpliva na okolje. Razvite so bile različne metode za zmanjšanje NOx, emitiranega v okolje iz zgorevnih naprav, in najvažnejša metoda za preprečenje tvorbe NOx, skladno s predpisi in za sprejemljivo ceno je recirkulacija zgorevnih plinov (FGR). V tem članku predstavljamo rezultate serije laboratorijskih preizkusov, namenjenih ugotavljanju emisije dušikovih oksidov iz standardiziranega gorilnika za zemeljski plin. Emisija NOx je močno odvisna od prebitka zraka in od količine recirkuliranih zgorevnih plinov v zraku za zgorevanje. Pomembno zmanjšanje NOx, približno 80 %, je bilo doseženo z eksterno recirkulacijo zgorevnih plinov. Eksperimentalno določene vrednosti so bile primerjane s tistimi, ki so bile izračunane na osnovi ravnotežne sestave in adiabatske temperature plamena v odvisnosti od količine zgorevnega zraka in recirkuliranih zgorevnih plinov.