Oil refining spent catalysts: A review of possible recycling technologies

• The review paper is focused on recycling technologies of spent FCC catalysts.
• The main way is as admixture in cement and mortar production.
• Spent FCCCs are also used as further catalysts in other processes.
• Few patents are focused on extraction of rare earth from spent FCCCs.
• No industrial processes are available for recovery of rare earths from spent FCCCs.

The aim of this review paper is to analyse the current management of spent fluid catalytic cracking catalysts (FCCCs) and the relevant possible reuse and recycling methods in order to avoid landfilling. FCCCs are used in refining processes for conversion of vacuum gas oil into more valuable gasoline blend components and other products. Every year the worldwide supply is estimated at about 840,000 t (Letzsch, 2014). The main recycling technique found in literature for spent FCCCs entails their use as raw material for concrete and mortar production as partial replacement of sand and cement powder. Other minor applications include their use as catalysts for plastic and biomass pyrolysis and gasification or for production of synthetic fuels. Despite their importance, these processes have not been widely developed at industrial scale. Disposal to landfill or use for concrete blend is still the main choice for the handling of spent catalysts, despite the content of rare earths elements and sometimes other interesting metals like vanadium and nickel that could be recovered. Nevertheless, in the future these catalysts will represent an interesting source for secondary raw materials, considering the scarcity of rare earth elements and shortage of supply, due to the fact that production is concentrated only in few countries. In this perspectives, the recovery of rare earth elements will be of great interest to countries that do not own primary ores. Future research work is expected to lead to economical processes that reach a complete recycling in order to avoid landfilling. This action could be helped by the adoption of new environmental regulations which will heavily charge landfilling as final disposal.