Process for the production of hydrogen by catalyzed hydrolysis of a complex hydride, and facility with semi continuous reactor for carrying out the method
The present invention relates to a process for producing a continuous flow of hydrogen by catalyzed hydrolysis of a complex hydride, which comprises at least adding continuously and at constant rate a fuel solution to a reactor comprising a complex hydride stabilized on a hydroxide on a cobalt boride catalyst that is added in excess inside said reactor. Sodium borohydride is preferably used, the hydroxide is sodium hydroxide and the catalyst is supported on nickel foam. Parameters and optimal conditions to achieve continuous production of hydrogen have been determined, which is essential in the operation of fuel cells. A facility comprising a semi continuous reactor designed to perform the above process, which needs no refrigeration is also an object of the present invention, as well as a washing and reactivation process of a catalyst of the type used in the process mentioned above.
1. Process for producing a continuous flow of hydrogen by catalyzed hydrolysis of a complex hydride, characterized in that it comprises at least the following step:
adding at a constant rate to a semi continuous reactor a fuel solution comprising a complex hydride stabilized on a hydroxide, over a cobalt boride catalyst that is added in excess to said reactor, the complex hydride being present at the fuel solution at a concentration comprised between 7% and 21% w/w including both limits, the addition of said fuel solution over the catalyst being carried out at a rate comprised between 1.5 ml/min and 5 ml/min including both limits, the excess amount of the catalyst being comprised between 408 mg and 725 mg including both limits, and the temperature being comprised between 42° C. and 65° C. including both limits.
2. Process according to claim 1 , characterized in that the complex hydride is present in the fuel solution in a concentration comprised between 9% and 19% w/w including both limits, the addition of said fuel solution over the catalyst is carried out at a rate comprised between 2.5 ml/min and 4 ml/min including both limits, the excess amount of catalyst is comprised between 458 and 675 mg including both limits, and the temperature is comprised between 47° C. and 60° C. including both limits.
3. Process according to claim 1 , characterized in that the complex hydride is sodium borohydride.
4. Process according to claim 1 , characterized in that the solution that acts as fuel with which the complex hydride is stabilized is sodium hydroxide.
5. Process according to claim 4 , characterized in that the solution is sodium hydroxide 4.5% by weight of the solution.
6. Process according to claim 1 , characterized in that the cobalt boride catalyst is supported on nickel foam.
7. Process according to claim 1 , characterized in that it comprises, prior to the addition of the fuel solution over the catalyst, the step of stabilizing the complex hydride in the fuel solution comprising the hydroxide.
8. Process according to claim 1 , characterized in that the process comprises extracting from the semi continuous reactor the hydrogen stream obtained by hydrolysis and directing it to the washing means.
9. Process according to claim 1 , characterized in that it comprises directing the hydrogen stream obtained by hydrolysis to a fuel cell continuously and at constant rate.
10. Process according to claim 9 , characterized in that the fuel cell is PEM.
11. Process according to claim 1 , wherein it further comprises washing and reactivating the cobalt boride catalyst used in the process, according to the following steps:
extracting from the semi continuous reactor the cobalt boride catalyst used in the hydrolysis and washing it at least twice with purified water,
immersing the catalyst in a solution comprising the complex hydride used at a ratio comprised between 8 w/w and 14 w/w for a time comprised between 5 and 10 minutes; and
washing again the catalyst in purified water at least once.