Polysulfide-assisted urea synthesis from carbon monoxide and ammonia in water

Abstract

Efficient conversion of carbon monoxide into urea in an aqueous ammonia solution was demonstrated through coupling with the elemental sulfur reduction to polysulfides. This reaction starts with a simple mixture of carbon monoxide, ammonia, elemental sulfur, and a small amount of hydrogen sulfide for polysulfide formation, enabling an almost complete conversion of 1 atm of carbon monoxide to urea (95–100% yield) within 216, 64, and 32 h at 35 °C, 50 °C, and 65 °C, respectively. Polysulfides control the overall reaction rate while suppressing the accumulation of a by-product, hydrogen sulfide, to less than 1 Pa. These functions follow simple kinetic and thermodynamic theories, enabling prediction-based reaction control. This operational merit, together with the superiority of water as a green solvent, suggests that our demonstrated urea synthesis is a promising option for sulfur utilization beneficial for agricultural production.

Supercritical CO2 as the carbon source and reaction medium for methanethiol synthesis in primordial subseafloor

“…The generated CO, as well as the CO delivered through the scCO2 flux (Fig. 1C), is also useful for various abiotic reactions (74,75).…”

“…Indeed, the 7-day reaction without H2 under otherwise identical condition resulted in the precipitation of MoS2 in a yellow-colored aqueous solution. The color was indicative of polysulfides, dissolved sulfur chains (Sn 2-; n = 2-8) formed as a result of the reaction of H2S with elemental sulfur (S 0 ) (74,75). Additionally, the formation of S 0 was confirmed by the X-ray diffraction (XRD) measurement of MoS2 formed in the absence of H2 (SI Appendix, Fig.…”