Characterization of FeCo based catalyst for ammonia decomposition

Zofia Lendzion-Bieluń,Rafał Pelka,Łukasz Czekajło,Walerian Arabczyk

doi:10.3390/ecm-1-b007

Abstract

Catalytic ammonia decomposition was studied in order to obtain pure hydrogen for fuel cells, free of COx that are being formed during reforming of hydrocarbons and alcohols. In comparison with hydrogen, ammonia is easy to store and transport, because it is liquid at the temperature of 25 °C under the pressure of 8 atm. In the presented studies a catalytic decomposition of ammonia over fused iron-cobalt catalysts was examined. Catalysts were prepared by alloying iron oxides with an addition of cobalt(II) oxide and promoters (Al2O3, CaO i K2O). Catalysts with various contents of potassium oxide were tested. Chemical composition of the prepared catalysts were determined with an aid of XRF method, whereas phase compositions of the catalysts were established with XRD method. Also the catalysts were characterized by programmed temperature techniques: H2-TPD, TPR. Measurements of the catalysts activity in the ammonia decomposition reaction were carried out in a differential reactor, which enabled to record mass changes and analyze the gas phase. Ammonia decomposition ran at an ambient pressure in the temperature range from 475 to 600oC. In the inlet of the reactor ammonia concentration from 5 to 100 %vol. were tested. On the basis of the analysis of gas sampled from the space above the catalyst bed, nitriding potential P=pNH3/pH23/2 and an ammonia decomposition rate r[mol/gcat ∙s] were calculated. An addition of potassium oxide into iron fused catalysts develops their specific surface areas. An increase in potassium oxide content in the tested catalysts had a beneficial impact on their activity in the ammonia decomposition reaction.

Highlights

Intensive investigations over hydrogen usage as a source for energy production are being conducted currently
Limited availability of noble metals and a relatively low activity of non-noble metals induce to further works on optimization of catalytic systems for ammonia decomposition working at lower temperatures
A series of kinetic measurements of the nitriding process was made for 100% ammonia at a reactor inlet and nitrides reduction with pure hydrogen at 400 oC

Summary

Introduction

Intensive investigations over hydrogen usage as a source for energy production are being conducted currently. Limited availability of noble metals and a relatively low activity of non-noble metals induce to further works on optimization of catalytic systems for ammonia decomposition working at lower temperatures. Both theoretical [5, 9, 11] and experimental studies [12] show that bimetallic systems are promising catalysts for that reaction. In the studies [13] it was presented that an increase in caesium content in ruthenium/nanotubes catalyst had caused an increase in ammonia decomposition degree and an decrease in the activation energy. Distribution of nanocrystallites size in the reduced form of the catalyst, made according to the previously elaborated method based on measurements of the rate of the nitriding reaction of the catalyst, is presented

Experimental

Results and Discussion

Conclusions