Revolutionizing titanium production: a comprehensive review of thermochemical and molten salt electrolysis processes

Titanium possesses outstanding properties, including high specific strength, and resistance to high and low temperatures, which have earned it the reputation of being the metal of the future. However, because of the highly reactive nature of titanium, the production processes for metallic titanium are known for their lengthy procedures and high costs, which has led the European Union to classify titanium metal as a critical raw material (CRM) of low category. The founder of the current Kroll process once predicted that metallic titanium could be obtained inexpensively through molten salt electrolysis. Around 2000, electrolytic titanium production experienced a wave of technological advancements. Despite advancements, intermediate and disproportionation reactions in the electrolytic process prevent titanium production via electrolysis from achieving the efficiency and purity required by industrial standards. The development of metallic titanium preparation technologies has gradually diversified into approaches such as thermal reduction, molten salt electrolysis, and titanium alloy preparation. This work provides a comprehensive review of research advances over the past two decades in titanium metal preparation technologies, highlighting the challenges faced by existing methods and proposing potential solutions. It offers useful insights for the development of low-cost titanium preparation technologies.