Nanoparticle opportunities: Pilot-scale flame synthesis of vanadia/titania catalysts

Major advances in understanding aerosol formation and growth allow now production of nanoparticles with closely controlled characteristics so that some of the early promises of nanotechnology are materialized. The production of flame-made titania particles coated in-situ with vanadia was brought from a microreactor (4 g/h) to a pilot-scale reactor (up to 200 g/h). Corresponding mixtures of titanium- and vanadium-alkoxides were evaporated into a nitrogen or hydrogen stream and fed into a turbulent hydrogen/air or hydrogen/oxygen flame using a commercial burner. By controlling gas flow rates, burner configuration and type of oxidant, particles with a wide range of characteristics were made. Rutile rich (> 85 wt%) to pure anatase (> 99.5 wt%) powders were made by exchanging air with oxygen. Vanadia/titania catalysts were made with UP to 10 wt% V2O5 and were compared to powders made in the flame microreactor. A representative flame-made DeNOx catalyst exhibited twice as much activity as a conventionally prepared reference catalyst for the removal of NO from a model exhaust gas by selective catalytic reduction with ammonia.