NaA zeolite membrane for recovery of ammonia
Ammonia is made in a system that includes a conversion reactor for performing a Haber-Bosch process. Effluent streams from the conversion reactor, which include an ammonia component and excess hydrogen and nitrogen reactants, are fed to a membrane separator that includes NaA zeolite membranes disposed on one or more hollow porous supports. The NaA zeolite membranes are highly selective for the ammonia component, allowing the ammonia to be collected from a lumen of the membranes as a product and enriching the excess hydrogen and nitrogen reactants for reuse in the conversion reactor. These systems and the methods of their use are effective to replace and/or modify the energy-intensive condensation/recycling steps in the traditional Haber-Bosch process used to condense NH3 from the exiting stream of the reactor. The selective removal of ammonia by high quality NaA membranes helps to shift the ammonia evolution reaction.
1 . A method of making ammonia, comprising:
feeding a reactants stream to a conversion reactor, the reactants stream including an H 2 component and an N 2 component;
evolving a reactant product stream from the conversion reactor, the reactant product stream including ammonia;
feeding the reactant product stream to a membrane separator;
selectively transporting ammonia from the reactant product stream through a membrane layer on the membrane separator to an outlet stream; and
collecting the ammonia component as a product from the outlet stream,
wherein the membrane separator includes:
one or more porous supports, the porous supports having zeolite nanocrystals seeded into pores of the supports, and heated to above about 200° C., thereby coating a surface of the supports to form a membrane-coated surface, the membrane-coated surface comprising the membrane layer disposed on the one or more porous supports, the membrane layer including NaA zeolite, wherein the zeolite nanocrystals have a particle size between about 50 nm and about 250 nm, and
wherein the membrane separator provides NH 3 /H 2 and NH 2 /N 2 selectivities of at least about 1,220 and 10,000, respectively, at a temperature of 200° C. and a pressure of 34.5 bar.
2 . The method according to claim 1 , wherein the membrane layer is generally annularly shaped with an outer surface and an inner lumen, wherein the membrane-coated surface is the outer surface, and the outlet stream is in fluid communication with the inner lumen.
3 . The method according to claim 1 , wherein the reactant product stream is fed at a temperature below about 200° C.
4 . The method according to claim 1 , wherein the reactant product stream is fed at a pressure between about 40 psig and about 510 psig.
5 . The method according to claim 1 , wherein the reactant product stream includes reaction products from a Haber-Bosch reaction.
6 . The method according to claim 5 , wherein the Haber-Bosch reaction is performed in the conversion reactor, and any H 2 component or N 2 component is recycled to the conversion reactor.
7 . The method according to claim 1 , wherein the pores of the support are between about 100 nm and about 500 nm.
8 . The method according to claim 1 , wherein the one or more porous supports include hollow ceramic fibers.