Thermal decarboxylation of demineralized Turkish beypazari lignite by the catalytic effect of Cr²⁺, Fe²⁺, and Co²⁺

Demineralized Beypazari lignite were thermally decarboxylated using Cr²⁺, Fe²⁺, and Co²⁺ as decarboxylation catalysts. Effective loadings of Cr²⁺, Fe²⁺, and Co²⁺ were 2, 5, and 3%, respectively. The calorific values of the demineralized lignite samples increased after the thermal decarboxylation experiments to values about 6, 12, and 15% higher than that of the untreated demineralized sample, when Cr²⁺, Fe²⁺, and Co²⁺, respectively, were used as catalysts. The most effective catalyst, with respect to the lowest activation energy attained, was Cr2+. Decarboxylation temperatures using Cr²⁺, Fe²⁺, and Co²⁺ as catalysts were 150, 100, and 200°C, respectively.