Bottom-up design of the operating window for direct urea synthesis from first-principles molecular thermodynamics
Year: 2026
Type: preprint
Abstract: Urea, among the most widely utilized foods for crops, is mass-produced via the carbon-and energy-intensive Bosch–Meiser process. However, its operating condition is settled empirically, vulnerable to undersampling and suboptimal production, and its molecular mechanism is not well understood. Here we present a bottom-up design of the operating condition driven by first-principles molecular modeling. Using a machine learning force field trained on first-principles calculations of urea and relevant species, we explored the free energy surface of the reaction space from reactant to product across temperatures. We found a strong thermodynamic preference for acyl substitution over competing pathways, with a free energy minimum around 420 K arising from the balance between carbamic acid’s protonation ratio and solvation number, which respectively increase and decrease with temperature. And we confirmed that the optimal condition originates from near-critical behavior, showing a fixed ratio to the critical temperature below unity. The maximum-yield temperatures of simulation and experiment correspond when scaled to their critical temperatures, suggesting this combined approach for engineering the operating condition.
Source: ChemRxiv
Authors: Minwoo Kim, Seungtae Kim, Ji Woong Yu, Won Bo Lee
Institutions: Seoul National University, Ajou University
Language: English
Subfield: Physical and Theoretical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7213446749