Highly selective synthesis of propylene glycol ether from methanol and propylene oxide catalyzed by basic ionic liquid

BACKGROUND: Propylene glycol ether is expected to be a safe substitute for toxic ethylene glycol ether usually used in industry owing to its negligible toxicity. Although catalysis of solid acids or bases for the synthesis of the ether can avoid separation of catalysts, liquid waste treatment and corrosion problems, it suffers from drawbacks, e.g. lower activity and selectivity to target product, high reaction pressure and temperature. In order to solve these problems, a basic ionic liquid, namely choline hydroxide was prepared and used as a catalyst for synthesis of the ether via atom-economy reaction from propylene oxide and methanol. RESULTS: The ionic liquid showed excellent catalytic performance exhibiting 95.4% conversion of propylene oxide (PO) and 94.6% selectivity to 1-methoxy-2-propanol. It is also an effective catalyst for the reaction of PO with other primary alcohols to yield corresponding ethers. In addition this catalyst can be recovered and reused. CONCLUSION:The high activity and selectivity can probably be ascribed to its basicity and/or the strong polarity and electrostatic field of the reaction medium caused by the ionic liquid. These findings are very rare in synthesis of propylene glycol ether to our knowledge. (C) 2010 Society of Chemical Industry