Vanadium-lithium alumina a potential additive for coke oxidation by CO2 in the presence of O2 during FCC catalyst regeneration

• Spent USY was regenerated in the presence of CO2 and O2 atmospheres.
• Li-V/Al2O3 is effective as an additive up to 1–10 parts of spent USY.
• Coke nature, i.e. produced by hydrocarbon or bio-feed, did not affect catalyst performance.
• CO/CO2 ratio was remarkably increased in the presence of Li-V/Al2O3.
• The catalyst regeneration simultaneously produces CO and mitigates CO2 emissions.

The possibility of performing the regeneration of spent fluid catalytic cracking catalysts in rich CO2 atmosphere can simultaneously reduce greenhouse gas emissions and produce CO for sequential uses. Herein alumina modified by vanadium and lithium was revealed a remarkable catalyst (or additive) for this goal. High CO2 conversion was observed in the presence of helium (for instance at 720 and 800 °C, 39 and 76% of CO2 was converted during the first 5 min of reaction respectively) and it was reduced by less than 5% in the presence of oxygen. Moreover the catalyst works effectively regardless the coke type on spent catalyst, i.e. produced by means of hydrocarbon or bio feed cracking. This catalyst was tested as an additive and works properly up to one part to ten of spent USY. By means of either labeled CO2 or coke (both with carbon 13) it was shown that primary 13CO2 forms 13CO followed by oxygen mobility between alumina and USY promoting coke oxidation. 12CO2 formed in-situ similarly to 13CO2 readily reacts with coke producing CO. These effects improve the coke burning by CO2 and remarkably increase the CO/CO2 ratio even in the presence of O2. Finally these results strongly support that the FCC regeneration step can be kept under auto-thermal condition in CO2 rich atmosphere.

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