Patent ID: 8545795

Claim:
Continuous process for the preparation of sodium titanate nanotubes, the process comprising the following steps: a) preparing a reaction mixture comprising a titanium oxide and a solution of sodium hydroxide at a concentration of between 10% and 50% (wt/wt), such that the final TiO 2 concentration in the reaction mixture is between 0.1 and 10% (wt/wt), then transferring the reaction mixture into a feed tank, b) continuously pumping the reaction mixture from the feed tank into two or more reactors interconnected in series via a suitably pressurized system, so that the pumping determines an overall residence time in the two or more reactors, wherein a residence time in each of the two or more reactors is less than 30 minutes, and the overall residence time is less than 90 minutes; c) independently controlling and heating the set of two or more reactors at temperatures between 60 and 180° C. via circulating hot oil or superheated steam passed through a jacket around each of reactor, and monitoring and controlling pressure such that an internal pressure within each reactor is maintained above a flash point; d) continuously removing and cooling a stream leaving the set of two or more reactors, the stream containing a product of the reaction between the titanium oxide and the sodium hydroxide in the form of a suspension; e) separating the product precipitating out by filtration under reduced pressure, decantation or centrifuging, which gives a mother liquor that contains a large amount of sodium hydroxide and can be recycled and used for preparation of a fresh reaction mixture; and f) washing the product precipitating out one or more times with water and optionally with acid solutions or solutions of metal salts in order to promote ion exchange of sodium.