Process and plant for producing hydrogen using hydrogen bromide electrolysis

A process for producing hydrogen comprises the following steps: (a) providing a starting mixture containing bromine, water and a sulfur containing compound, (b) reacting the starting mixture provided in step (a) so as to produce a reaction mixture effluent comprising sulfuric acid and hydrogen bromide, (c) separating the reaction mixture effluent obtained in step (b) into one or more hydrogen bromide enriched compositions and into one or more sulfuric acid enriched compositions, wherein at least one hydrogen bromide enriched composition contains at most 1,000 ppm of sulfuric acid, wherein step (c) comprises at least two distillation steps, (d) subjecting at least a portion of the at least one hydrogen bromide enriched composition containing at most 1,000 ppm of sulfuric acid obtained in step (c) to an electrolysis so as to obtain hydrogen and a bromine containing composition, wherein the electrolysis cell is operated at an operational temperature of at least 70 DEG C, and (e) recycling at least a portion of t