UNIST Reveals Green Self-Driving PO System Using H2O2

Abstract

Propylene oxide (PO) is a key industrial chemical, often produced by epoxidizing propylene with H2O2 over titanium silicalite-1. However, current H2O2 production via the anthraquinone process relies on fossil-derived hydrogen, leading to substantial CO2 emissions. Sustainable PO synthesis requires green H2O2 production. Here, we present a fully unassisted, solar- and bias-free system that generates H2O2. This platform enables modular, eco-friendly on-site PO synthesis by coupling formaldehyde oxidation with two-electron O2 reduction under alkaline conditions. Efficient propylene epoxidation under these conditions is achieved using titanium silicalite-1 modified by introducing dinuclear titanium sites with Ti-O-Ti bonds, as revealed by density functional theory and instrumental analyses. The unassisted H2O2 production system is integrated with the modified titanium silicalite-1 to realize continuous PO production (1657 μmolPO cm−2 over 24 h), without electric or solar energy input. This unassisted PO production method can thus be energy-independent, offering a sustainable alternative to conventional processes.

A groundbreaking eco-friendly system capable of producing propylene oxide (PO) without external electricity or sunlight has been developed. PO is a vital raw material used in manufacturing household items such as polyurethane for sofas and mattresses, as well as polyester for textiles and water bottles.

A research team led by Professors Ja Hun Kwak and Ji-Wook Jang from the School of Energy and Chemical Engineering at UNIST, in collaboration with Professor Sung June Cho of Chonnam National University, announced that they have successfully created a self-driven PO production system utilizing in-situ generated hydrogen peroxide (H₂O₂).

Since PO is produced by oxidizing propylene, the process traditionally relies on H₂O₂ supplied from the anthraquinone process, which depends on fossil fuels and results in significant CO₂ emissions. In contrast, the newly developed system generates H₂O₂ autonomously through an electrochemical reaction involving oxygen and formaldehyde, operating spontaneously without external power sources such as electricity or solar energy. This is enabled by the energy difference between the two reactions, allowing the system to function solely on chemical potential.

The produced H₂O₂ reacts with propylene within the system to synthesize PO. The team redesigned the catalyst structure necessary for this oxidation process, overcoming the limitations of conventional zeolite-based catalysts (TS-1), which suffer from reduced activity in alkaline environments-a necessary condition for H₂O₂ formation. This innovation significantly enhances the efficiency of the subsequent propylene oxidation reaction, resulting in improved PO yields.

Figure 1. Schematic of the unassisted catalytic system for propylene epoxidation.

Over a 24-hour period, the system produced 1,657 micromoles (μmol) of PO per square centimeter (cm²), approximately eight times higher than previous eco-friendly H₂O₂-based production methods. Additionally, the process concurrently produces H₂, a clean energy resource.

Economic analyses indicate that this system can reduce the production cost of PO by about 8%, to approximately $2.168 per kilogram, compared to conventional methods. Its simplified design, which omits complex pre-treatment steps and high-temperature, high-pressure equipment, along with the elimination of external energy inputs, significantly lowers capital and operational costs. Moreover, on-site H₂O₂ production minimizes transportation and storage expenses.

Professor Jang stated, "This modular process can be easily installed at various sites, enabling small-scale, customized production and promoting a shift from centralized large-scale manufacturing to decentralized, distributed systems."

Professor Kwak added, "This work represents a significant step forward in overcoming the long-standing limitations of zeolite catalysts, paving the way for a much more sustainable and environmentally friendly chemical industry."

This research was supported by the National Research Foundation of Korea (NRF) through the STEAM program and the Institute for Basic Science (IBS). It also received instrumental support from UNIST's Research Equipment Education and Support Center and the 6D UNIST-PAL beamline at the Pohang Accelerator Laboratory (PALS).

The findings of this research have been published in the online version of Nature Communications on September 30, 2025.

Journal Reference

Kwang Hyun Kim, Seon Woo Hwang, Taehyeon Kim, et al., "Self-driven propylene epoxidation on modified titanium silicalite-1 by in situ generated hydrogen peroxide," Nat. Commun., (2025).