The environmental problem resulting from the traditional production process of chromic oxide has spawned public concerns all over the world.Integrated in the clean production technology of chromium compounds with sub-molten salt media,the preparation process of chromic oxide through hydrogen reduction of alkali metal chromate salt enables the clean and short-route preparation of chromic oxide.Moreover,the alkali metal hydroxide byproducts can be recycled as reaction media inside the process.To explore the reaction kinetics and mechanisms of the hydrogen reduction process,the reduction of sodium chromate in H2 atmosphere was investigated by using TGA and DSC techniques.The isothermal TGA measurement results showed that in the temperature range from 703 K to 773 K,the hydrogen reduction had only one step of mass loss and the mass loss rate was from 5.91% to 6.36%.The main products of the reaction were NaCrO2 and NaOH,as confirmed by XRD patterns of the reduction products.The non-isothermal TGA measurements of hydrogen reduction was investigated at six different temperature rising rates of 1,5,10,15,20 and 30 K·min-1.According to the Doyle-Ozawa and Kissinger methods,the activation energy was 342.47 kJ·mol-1 and the order of reduction reaction was 0.87.The results in this work will help to enhance the reaction efficiency and optimize the process flow.
