Solvent Screening and Process Optimization for Separating Propylene Oxide from Direct Propylene Epoxidation with H₂ and O₂

Abstract

The objective of this study is to develop a separation process of propylene oxide (PO) from direct propylene epoxidation with H2 and O2 via solvent screening followed by process optimization, where PO absorption/concentration/refinery and solvent recovery tower are involved. A comparison of absorption processes among 15 ethers/ketones/esters/aromatics solvents shows that propylene carbonate (PC), diethyl carbonate, and acetophenone are more appropriate absorbents because of their high PO/solvent recovery, absence of reactions/azeotropes, and low energy consumption. Process optimization is further performed for the outlet PO purity requirement, e.g., 99.98% of LyondellBassell. It demonstrates PC to be the most promising solvent, which can afford outlet PO/PC purity and recovery of 99.98%/100% and 99.94%/99.95%. Meanwhile, the solvent recovery tower has lowered stages by 5–14 and energy consumption by 2–3.5 times, respectively. Moreover, the developed separation process is also applicable for inlet components containing propane and acrolein. These results could guide the separation process design of PO from the direct propylene epoxidation with H2 and O2.