Eco-efficiency improvements in the propylene-to-epichlorohydrin process

BACKGROUND: Epichlorohydrin (ECH) production is an important industrial process, owing to its importance in windmill blade manufacture, but it suffers from several drawbacks such as high energy use, large wastewater production and low atom efficiency. This original study investigates a novel chlorohydrin-free technology with an enhanced separation system for ECH production. Rigorous process simulations were performed in Aspen Plus for the classic and novel processes, and a fair techno-economic and sustainability comparison was made between the new catalytic oxidation route and the classic chlorohydrin process. RESULTS: For the hydrogen peroxide (HP) process route, a novel separation system was developed using methanol as solvent, which enables high purity of ECH. Moreover, allyl chloride (ACH) purification was optimized using thermally coupled distillation to improve the energy efficiency of ACH production. The novel HP process provides 88% higher atom efficiency, about 10% higher yield and a smaller amount of by-products, as well as a 13% increase in production capacity and major savings of 98% in wastewater production, while also achieving lower energy use (<40 MJ kg⁻¹ ECH) and reduced carbon dioxide emission (1.13 kg kg⁻¹ ECH). CONCLUSION: The developed HP process route is feasible and economically viable. Also, it can be partly retrofitted to existing ECH plants based on the chlorohydrin route. As both processes use the same intermediate product, only the ECH part of a classic process would be replaced by the novel route, while keeping the common ACH part. This approach is the most profitable, as only 55% of capital expenditure is required for this modification, while the plant would benefit from all the improvements provided by the novel process.