(654e) Ethylene Glycol Precursor Synthesis Via Formaldehyde Carbonylation Over Solid Acids

The production of ethylene glycol (MEG) from methanol and its derivatives, such as formaldehyde, is potentially attractive, since the carbon needed for such a process can come from synthesis gas, a cheaper carbon source than petroleum-derived ethelyene. Formaldehyde carbonylation using a strong acid catalyst produces glycolic acid (GA) [1-3], which can be esterified and hydrogenated to give MEG. Reaction mixtures of water and formaldehyde pressurized with CO to 240 bar can give yields of 80%[3]. The very high pressures required due to low CO solubility are undesirable, and so methyl formate (MF) has been considered as a source of CO in the liquid phase. MF will decompose to give CO in solution plus methanol. Carbonylation of formaldehyde with MF using heteropoly acid catalysts has been shown to give methyl glycolate (MG) and methyl methoxyacetate (MMAc)[4], which can also be hydrogenated to MEG. In the present study, MG and MMAc were synthesized from formaldehyde and MF mixtures heated to 150°C for 3 h using silicotungstic acid, H4SiW12O40 (SiW12) as the catalyst. Methanol was added to stabilize the formaldehyde. Dimethoxymethane (DMM) and dimethyl ether (DME) were the major byproducts. Up to 30 atm of CO pressure was generated from MF. MG and MMAc yields were limited by the slow release of CO from MF, but the yields of these products could be increased significantly by adding a small amount of gaseous CO. Additionally, carbonylation of DMM as a formaldehyde source was achieved with both MF and gaseous CO. MG and MMAc yields were generally higher with DMM than with formaldehyde, with a greater selectivity for MMAc than MG. A comparison of common heteropoly acids showed that SiW12 had the greatest combined MG and MMAc yield, followed by phosphotungstic acid. Silico- and phosphomolybdic acids were much less active, mainly due to their reduction leading to deactivation.

[1] Loder, D.J. U.S. Patent 2,152,852, 1939. [2] Hendriksen, D.E. Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem. 1983, 28, 176-190. [3] Lee, S.Y.; Kim, J.C.; Lee, J.S.; Kim, Y.G. Ind. Eng. Chem. Res. 1993, 32, 253-259. [4] He, D.; Huang, W.; Liu, J.; Zhu, Q. Catal. Today 1999, 51, 127-134.