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Comparison of catalysts based on individual alkali and alkaline earth metals with their composites used for steam gasification of coal
Authors Zubek Katarzyna Czerski Grzegorz Porada Stanisław Journal Energy & Fuels Year Vol. Number Pages 2018 32 5 5684?5692 Impact Factor 2.835 DOI Abstract in the main language of the article One-component catalysts based on alkali and alkaline earth metals (sodium, potassium, and calcium) as well as their composites were applied to the surface of coal samples used in the gasification process. The aim of this work was to compare the impact of these catalysts on the steam gasification of coal by analyzing the results of catalytic and noncatalytic measurements. The use of composites was intended to check whether it is possible to accomplish the synergistic effects (an effect arising between two or more substances interacting together to produce an effect greater than the sum of their individual effects) and overcome the shortcomings of individual metal catalysts. Measurements of steam gasification were conducted by a thermovolumetric method under isothermal conditions at an elevated pressure of 1 × 106 Pa and at four temperatures ranging from 1073 to 1273 K. On the basis of the obtained results, curves of the formation rate of gasification products were developed and yields of main products (hydrogen and carbon monoxide) were evaluated. The influence of the temperature and type of catalyst on the kinetics of H2 and CO formation was determined, and kinetic parameters (activation energy and pre-exponential factor) were calculated on the basis of three models (isoconversional method, grain model, and random pore model). The obtained results showed the effectiveness of the catalysts tested, especially at low temperatures (1073-1173 K). In this temperature range, the one-component catalyst based on Na (3 wt %) was the most effective. Other single-component catalysts (3 wt % K and 3 wt % Ca) were less catalytically active at 1073 K than composite catalysts consisting of 1 wt % Na and 1 wt % K or 1 wt % Na, 1 wt % K, and 1 wt % Ca, although the former composite contained a smaller amount of catalytically active material. These results indicate that at low temperatures the type of catalyst is more important than the quantity. However, the addition of a catalyst, regardless of type, caused a decrease in the activation energy of CO and H2 formation reactions by nearly half in comparison with that seen for the noncatalytic process. Keywords in the main language Title in the additional language Abstract in the additional language Keywords in the additional language | 
