Sustainable Ammonia and Advanced Symbiotic Fertilizer Production Using Catalytic Multi-Reaction Reactors with Nonthermal Plasma and Simultaneous Reactive Separation

Abstract

The theoretical bases of a novel intensified catalytic multi-reaction-zone reactor (M-RZR) system are described. The M-RZR with two reaction zones (RZ-1 and RZ-2) was used for ammonia synthesis. In the catalytic nonthermal plasma reaction zone (RZ-1), ammonia was synthesized and it was immediately sequestrated by a highly porous polymeric solid acid absorbent in the ammonia neutralization reaction zone (RZ-2). The solid acid was a sulfonated cross-linked porous polystyrene foam known as polyHIPE polymer (s-PHP, HIPE = high internal phase emulsion). The s-PHP and its neutralized version (sn-PHP) were previously developed as an advanced symbiotic fertilizer (or synthetic root system) for agro-process intensification for the enhancement (50-300%) of crop yield and nitrogen fixation especially under water and nutrient stress. In this first ever "proof-of-concept" study of the M-RZR system, without any attempt for optimization, it was shown that the ammonia conversion per pass reached ca. 40% and ammonia concentration was ca. 20 vol %. The energy cost of ammonia was 0.76 MJ/g NH<inf>3</inf> which was 2 times smaller than optimized systems in which the ammonia concentration in the product stream was ca. 1.5 vol %. Direct conversion of hydrogen enhanced clean syngas (a<inf>1</inf>CO + a<inf>2</inf>CO<inf>2</inf> + a<inf>3</inf>H<inf>2</inf> + a<inf>4</inf>N<inf>2</inf> + a<inf>5</inf>CH<inf>4</inf>) to ammonia and its reversible sequestration by CO<inf>2</inf> to form solid ammonium carbamate/carbonate was demonstrated. This method is not only useful for direct conversion of syngas to ammonium carbonate/urea fertilizers but also for obtaining anhydrous ammonia for fuel applications. The reactive in situ air separation was also demonstrated for the generation of nitrogen for ammonia synthesis and oxygen for the gasification of biomass as a sustainable source of hydrogen. © 2017 American Chemical Society.